WO2022207900A1

WO2022207900A1 - System for cutting a fabric into portions by generating oblong gas bubbles

Info

Publication number: WO2022207900A1
Application number: PCT/EP2022/058743
Authority: WO
Inventors: Fabrizio Romano; Cyril MAUCLAIR; Emmanuel Baubeau
Original assignee: Keranova
Priority date: 2021-04-01
Filing date: 2022-04-01
Publication date: 2022-10-06
Also published as: FR3121349A1; FR3121349B1

Abstract

The invention relates to a cutting apparatus that includes a femtosecond laser source (10) for emitting a Gaussian laser beam, a shaping system (30) for modulating the Gaussian laser beam, an optical scanner (40) for moving the modulated laser beam, and an optical focusing system (50) for focusing the modulated laser beam. The cutting apparatus is characterised in that a processing device further comprises a control unit (60) for controlling the femtosecond laser source (10), the shaping system (30), the optical scanner (40) and the optical focusing system (50), in order to produce horizontal and vertical cutting planes on the basis of oblong gas bubbles.

Description

SYSTEM FOR CUTTING A FABRIC INTO PORTIONS BY GENERATION OF

OBLONG GAS BUBBLES

TECHNICAL AREA

The present invention relates to the technical field of surgical operations carried out using a femtosecond laser, and more particularly that of ophthalmological surgery, in particular for applications for cutting out corneas or lenses.

The invention relates to a device for cutting a human or animal tissue, such as a cornea or a lens, by means of a femtosecond laser source.

By femtosecond laser source, we mean a light source capable of emitting a laser beam in the form of ultra-short pulses, the duration of which is between

1 femtosecond and 100 picoseconds, preferably between 1 and 1000 femtoseconds, in particular of the order of a hundred femtoseconds.

PRIOR ART

1. Generation of horizontal cutting planes The femtosecond laser source is an instrument capable of cutting the corneal tissue, for example, by focusing a laser beam in the stroma of the cornea, and by producing a succession of small adjacent gas bubbles.

More precisely, during the focusing of the laser beam in the cornea, a plasma is generated by non-linear ionization when the intensity of the laser exceeds a threshold value, called optical breakdown threshold. A gas bubble then forms, causing a very localized disruption of the surrounding tissues. Thus, the volume actually ablated by the laser beam is very small compared to the disrupted zone.

The area cut by the laser beam at each pulse is very small, on the order of a micron or ten microns depending on the power and the focusing of the beam. Thus, a corneal lamellar cut can only be obtained by making a series of contiguous impacts over the entire surface of the area to be cut.

We know from document WO 2016/055539 a device for cutting ocular tissue

2 (human or animal) from a femtosecond laser source 1 . This cutting device is shown in Figure 1. The cutting device makes it possible, from a laser beam 11 coming from a femtosecond laser source 1, to generate a plurality of simultaneous laser impact points in a focal plane 101 of the cutting device. As illustrated in Figure 2, each point of impact forms a respective gas bubble 102. To simultaneously generate a plurality of impact points, the cutting device comprises a spatial light modulator 3 (known by the acronym SLM, from the acronym “Spatial Light Modulator”). A phase mask is applied to the SLM 3. This phase mask makes it possible to modulate the phase of the wavefront of the laser beam 11 coming from the femtosecond laser source 1 . The phase modulation of the wave front makes it possible to delay or advance the phase of the various points of the surface of the beam compared to the initial wave front so that each of these points carries out a constructive interference in N distinct points in the focal plane 101 of the cutting device. This redistribution of energy at a plurality of impact points only takes place in a single plane (ie the focal plane of the cutting device) and not all along the propagation path of the modulated laser beam. Thus, the phase modulation of the wavefront makes it possible to generate a single modulated laser beam 31 which forms a plurality of impact points only in the focal plane 101: the modulated laser beam 31 is unique throughout its path of spread.

To cut a lens on a surface of 1 mm ² , approximately 10,000 points of impact must be made very close to each other. Simultaneously generating multiple impact points reduces the time required to cut a lens surface by increasing the area treated with a single laser shot and reducing the number of round trips required to produce multiple adjacent rows of points .

The plurality of simultaneously generated impact points constitutes a pattern. By moving 103 this pattern in the focal plane 101 of the cutting device, it is possible to form a horizontal cutting plane 104 comprising a multitude of gas bubbles 102 (cf. FIG. 3). To move the pattern in the focal plane 101, the cutting device comprises a scanning device 4, composed of controllable galvanometric mirrors, and/or plates allowing the movement of optical elements, such as mirrors or lenses. This scanning device 4—positioned downstream of the SLM 3—allows the modulated laser beam 31 to be moved along a trajectory back and forth along a succession of segments constituting a beam displacement path. Forming thus a horizontal cutting plane 104 comprising a multitude of gas bubbles 102 (cf. FIG. 4).

When the multitude of gas bubbles 102 has been formed in the focal plane 101 of the cutting device, the portion of lens located above the horizontal cutting plane can be separated from the portion of lens located below the cutting plane. horizontal cutting by picking up the existing tissue bridges 105 between the gas bubbles 102 using a tool.

During cataract surgery, a stack 106 of horizontal cutting planes 104 is formed by moving the focal plane of the cutting device (cf. FIG. 5). To move the focal plane 101, the cutting device comprises an optical focusing device 5 - positioned downstream of the scanning device 4 - composed in particular of one (or more) motorized lens(es) to allow its ( their) translational movement along the optical path of the laser beam modulated by the SLM 3 and deflected by the scanning device 4.

By moving the focal plane 101 to different positions along the optical path of the laser beam, and by repeating, for each position of the focal plane, the steps:

- generating a pattern of stitch points, and

- displacement of the pattern of impact points, it is possible to obtain a stack 106 of horizontal cutting planes 104. The different slices of lens defined by these horizontal cutting planes 104 can then be separated from each other by a practitioner dissecting the lens using a tool.

Even if this technique is very effective, an object of the present invention is to propose, from the cutting device described in WO 2016/055539, a new technical solution to limit the number of tissue bridges present in each cutting plane. in order to facilitate the dissection operations of the lens C by the practitioner.

2. Generation of vertical cutting planes In addition to the horizontal cutting planes 104, it is desirable to produce vertical cutting planes 107 in the lens. These vertical planes 107 are produced between two successive horizontal planes (production of a lower horizontal cutting plane 104a then production of the vertical cutting planes 107 then production of an upper horizontal cutting plane 104b). This makes it possible to subdivide the lens C into cubes 108 that can be aspirated by a suction cannula 109 during cataract surgery for example (cf. FIG. 7) unlike current systems which require an ultrasonic phacoemulsifier.

At the present time, a vertical cutting plane 107 is obtained by producing lines of superimposed gas bubbles in the lens C. To produce a vertical cutting plane, the laser beam from the laser source is not not phase modulated. With each pulse of the femtosecond laser source, a single point of impact is formed. This point of impact produces a gas bubble. By moving the laser beam using the scanning device, it is possible to move the point of impact in the focal plane of the cutting device. This makes it possible to produce a succession of small adjacent gas bubbles, which then form a cutting line in the focal plane of the cutting device. By moving the focal plane - with the aid of the focusing device - to different positions along the optical path of the laser beam, it is possible to overlap the lines of gas bubbles in order to obtain a vertical cutting plane.

Since such a vertical cutting plane is produced "point by point", the operation of forming the various vertical cutting planes is slow. Indeed, at present, the points of impact are made at an average speed of 300,000 impacts/second. To cut "point by point" a lens on an area of approximately 65mm ² , taking into account the times during which the laser stops producing pulses at the end of the segment to allow the mirrors to position themselves on the next segment, it is necessary on average 15 seconds.

To remedy this drawback, and starting from the cutting device according to WO 2016/055539, the inventors have tried to produce vertical cutting planes by implementing the principle of reduction of the points of impact from each pulse of the laser source. In particular, the inventors determined a phase mask to be applied to the SLM to generate several simultaneous impact points 111 at different depths Z1, Z2, Z3 from a single modulated laser beam (cf. FIG. 8). For example, from a pattern composed of three (four, five, etc.) impact points 111 a, 111 b, 111 c generated simultaneously at different depths Z1, Z2, Z3, it is theoretically possible, in moving the pattern along a displacement segment by means of the scanning device, to simultaneously generate three (four, five, etc.) lines of superimposed gas bubbles, which decreases by the corresponding factor the time required for the formation of a vertical cutting plane. However, the inventors discovered that the alignment of the simultaneously generated impact points 111 was not sufficient, so that the lines of gas bubbles were not perfectly superimposed. This misalignment makes it difficult for the lens cubes to detach.

The inventors have therefore developed a new cutting device including a shaping system (to modulate the phase of the wave front of a Gaussian laser beam) and a control unit configured to apply to the shaping system, a axiconic modulation setpoint. This makes it possible to produce a modulated laser beam of the Bessel type (from the Gaussian laser beam) having an impact point making it possible to generate an oblong gas bubble in the tissue and thus cut it to a much greater depth than a beam. Gaussian.

Another object of the present invention is to propose a solution to the problem of forming vertical cutting planes in an ocular tissue (such as a cornea or a lens) from the cutting device described in WO 2016/055539.

DISCLOSURE OF THE INVENTION

To this end, the invention proposes an apparatus for cutting human or animal tissue, said apparatus including a femtosecond laser source configured to emit a Gaussian laser beam in the form of pulses and a device for processing the Gaussian laser beam, the device processing device being disposed downstream of the femtosecond laser source, the processing device comprising:

- a shaping system positioned on the trajectory of the Gaussian laser beam, to modulate the phase of the wavefront of the Gaussian laser beam, the shaping system being configured to produce a modulated laser beam from the Gaussian laser beam ,

- an optical scanning scanner arranged downstream of the shaping system to move the modulated laser beam,

- a focusing optical system downstream of the shaping system, for focusing the modulated laser beam in a focal plane of the cutting device and for moving the focal plane of the cutting device to a plurality of positions along an optical axis of propagation of the modulated laser beam, noteworthy in that the processing device further comprises a control unit for controlling the femtosecond laser source, the shaping system, the optical scanning scanner, and the system focusing optics, in order to produce at least one horizontal cutting plane extending perpendicular to the optical axis, the control unit being configured to:

- apply to the shaping system, a parabolic modulation instruction in order to produce a modulated laser beam of the "Focal Line" type from the Gaussian laser beam, said modulated laser beam of the "Focal Line" type having an impact point slender in a direction perpendicular to the optical axis, the slender point of impact having, in the focal plane, a width and a length greater than the width, said slender point of impact making it possible to generate an oblong gas bubble in the fabric and thus cut it over a length greater than a Gaussian beam,

- drive the scanning optical scanner to move the slender point of impact of the "Focal Line" type modulated laser beam along a moving optical path to successively form a plurality of adjacent oblong gas bubbles, said gas bubbles constituting the horizontal cutting plane.

In the context of the present invention, the term "horizontal cutting plane" means a plane located in the tissue to be treated and extending perpendicular to the optical axis of propagation of the laser beam from the cutting device.

In the context of the present invention, the term "vertical cutting plane" means a plane located in the tissue to be treated and extending parallel to an optical axis of propagation of the laser beam from the cutting device.

In the context of the present invention, the term “point of impact” means an area of the laser beam included in its focal plane in which the intensity of said laser beam is sufficient to generate a gas bubble in a tissue.

In the context of the present invention, the term "adjacent impact points" means two impact points arranged facing each other and not separated by another impact point.

“Neighboring impact points” means two points of a group of adjacent points between which the distance is minimum.

In the context of the present invention, the term “pattern” means a plurality of laser impact points generated simultaneously in a plane of focus of the cutting device. Thus, the invention makes it possible to modify the intensity profile of the laser beam in the focal plane, in such a way as to be able to improve the quality or even the speed of the cutting depending on the profile chosen. This intensity profile modification is obtained by modulating the phase of the laser beam.

The optical phase modulation is achieved by means of a phase mask. The energy of the incident laser beam is conserved after modulation, and the shaping of the beam is achieved by acting on its wavefront. The phase of an electromagnetic wave represents the instantaneous situation of the amplitude of an electromagnetic wave. The phase depends on both time and space. In the case of the spatial shaping of a laser beam, only the variations in phase space are considered.

The wave front is defined as the surface of the points of a beam having an equivalent phase (i.e. the surface made up of the points whose travel times from the source that emitted the beam are equal). The modification of the spatial phase of a beam therefore passes through the modification of its wavefront.

This technique makes it possible to carry out the cutting operation in a faster and more efficient way because it uses a point of impact making it possible to generate an oblong gas bubble whose length is greater than that of a bubble obtained at from an impact point generated by a Gaussian laser beam.

Preferred but non-limiting aspects of the cutting apparatus are as follows:

- the shaping system may comprise a spatial light modulator, the control unit being configured to apply a parabolic phase mask emulating a cylindrical lens on the spatial light modulator;

- the parabolic phase mask can be a two-dimensional image to be displayed on the spatial light modulator to cause an unequal spatial phase shift of the Gaussian laser beam, the value (fi) of each pixel of the two-dimensional image being defined by the following formula:

<|)i(x,y)=kx ² where:

• "07" represents the value of a pixel of the two-dimensional image,

• “x” is the abscissa of the pixel of the two-dimensional image,

• "y" is the ordinate of the pixel of the two-dimensional image, and

• “k” is a positive coefficient; - the parabolic phase mask can be a two-dimensional image to be displayed on the spatial light modulator to cause an unequal spatial phase shift of the Gaussian laser beam, the value f2 of each pixel of the two-dimensional image being defined by the following formula: f ₂ (c,g) = kx ² + ly ² where:

• "0 _{2 >>} represents the value of a pixel of the two-dimensional image,

• “x” is the abscissa of the pixel of the two-dimensional image,

• "y" is the ordinate of the pixel of the two-dimensional image,

• “k” is a positive coefficient, and

• “l” is a positive coefficient;

- the displacement path may comprise at least one segment, the parabolic phase mask being determined so that the length of each slender point of impact extends parallel to said and at least one segment;

- the control unit can also be configured to control the femtosecond laser source, the shaping system, the optical scanning scanner, and the optical focusing system, in order to produce at least one vertical cutting plane extending parallel to the optic axis;

- the control unit can be configured for:

• apply to the shaping system, an axiconic modulation instruction in order to produce a modulated laser beam of the Bessel type from the Gaussian laser beam, said modulated laser beam of the Bessel type having an elongated point of impact in a direction parallel to the optical axis, the elongated point of impact having a width and a depth greater than the width, said elongated point of impact making it possible to generate an oblong gas bubble in the tissue and thus to cut it to a depth greater than a Gaussian beam,

driving the scanning optical scanner to move the elongated point of impact of the Bessel-type modulated laser beam along another optical path of movement to successively form a plurality of adjacent gas bubbles, said gas bubbles constituting the plane vertical cutting; - the object focal plane of the focusing system can be positioned at a non-zero distance from the image focal plane of the shaping system, so that the elongated point of impact of the Bessel-type modulated laser beam comprises: o a focused ring in the focal plane of the cutting device, o a line of concentration of the rays of the Bessel-type modulated laser beam extending outside the focal plane of the cutting device, said line making it possible to form the oblong gas bubble , the ring having an intensity lower than the intensity of the line not allowing the formation of a gas bubble;

- the control unit can be programmed to control the optical focusing system so that the focal plane of the cutting device extends, along the optical axis, above the desired position for the cutting plane vertical ;

- the control unit can be programmed to control the optical focusing system so that the focal plane of the cutting device extends, along the optical axis, below the desired position for the cutting plane vertical ;

- the cutting device can be adapted to successively produce horizontal and vertical cutting planes so as to form cubes of fabric: o the control unit controlling the femtosecond laser source, the shaping system, the optical scanner scanning, and the optical focusing system to produce an initial horizontal cutting plane, then o the control unit controlling the femtosecond laser source, the shaping system, the optical scanning scanner, and the optical focusing system to produce at least one vertical cutting plane located above, along the optical axis, the initial horizontal cutting plane, then o the control unit controlling the femtosecond laser source, the shaping system, the optical scanner scanning, and the optical focusing system to produce a final horizontal cutting plane above, along the optical axis, said and at least one vertical cutting plane.

BRIEF DESCRIPTION OF THE DRAWINGS Other characteristics and advantages of the invention will emerge clearly from the description which is made of it below, by way of indication and in no way limiting, with reference to the appended figures, in which:

- Figure 1 is a schematic representation of a cutting device described in WO 2016/055539;

- Figure 2 is a schematic representation of gas bubbles created by points of impact in a focal plane of the cutting device of Figure 1,

- Figure 3 is a schematic representation of gas bubbles created successively by moving the points of impact in the focal plane of the cutting device of Figure 1,

- Figure 4 is a schematic representation of a horizontal cutting plane obtained using the cutting device of Figure 1,

- Figure 5 is a schematic representation of a stack of horizontal cutting planes obtained using the cutting device of Figure 1,

- Figure 6 is a schematic representation of horizontal and vertical cutting planes,

- Figure 7 is a schematic representation of a patient's eye,

- Figure 8 is a schematic representation of impact points formed simultaneously using an SLM of the cutting device of Figure 1,

- Figure 9 is a schematic representation of a cutting device according to the invention,

- Figure 10a is a representation of a slender point of impact of a "Focal Line" type beam,

- Figure 10b schematically illustrates a first example of parabolic-type phase modulation,

- Figure 10c schematically illustrates a second example of parabolic type modulation,

- Figure 11 illustrates examples of parabolic phase masks,

- Figure 12a is an image of a Bessel type beam along a longitudinal profile,

- figure 12b is an image of the Bessel type beam according to a transverse profile,

- Figure 13 is a schematic representation illustrating the focusing of a non-diffracting Bessel type beam, - figure 14a is an image of a first phase mask making it possible to emulate the behavior of a negative axicon on an SLM of the cutting device according to the invention,

- figure 14b is an image of a second phase mask making it possible to emulate the behavior of a positive axicon on the SLM of the cutting device according to the invention,

- Figure 15a is a schematic representation of a Bessel type beam along a longitudinal profile,

- Figure 15b is a schematic representation of the Bessel type beam according to a transverse profile,

- Figure 16 is a partial assembly diagram of the cutting device,

- figure 17 is a schematic representation of a Bessel beam,

- figure 18a is a schematic representation of a parasitic tissue bridge of a tissue cut from a Gaussian laser beam,

- Figure 18b is a schematic representation of a parasitic tissue bridge of a tissue cut from a "Focal Line" type laser beam,

- Figure 19 is a schematic representation illustrating the formation of a vertical cutting plane from a Gaussian laser beam on the one hand and a Bessel laser beam on the other hand.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to a system for cutting human tissue using a femtosecond laser. In the rest of the description, the invention will be described, by way of example, for the cutting of a lens of a human or animal eye.

1. Cutting device

Referring to Figure 9, there is illustrated an embodiment of the cutting device according to the invention. This can be arranged between a femtosecond laser source 10 and a target to be treated 2.

The femtosecond laser source 10 is capable of emitting a Gaussian laser beam in the form of pulses. By way of example, the femtosecond laser source 10 emits light of 1030 nm wavelength, in the form of 400 femtosecond pulses. The femtosecond laser source 10 has a power of 20 W and a frequency of 500 kHz. The target 2 is for example a human or animal tissue to be cut, such as a cornea or a lens.

The cutting device comprises: a shaping system 30 positioned on the path of the laser beam 110 coming from the femtosecond laser 10, an optical scanning scanner 40 downstream of the shaping system 30, an optical focusing system 50 downstream of the scanning optical scanner 40, and a control unit 60.

The shaping system 30 makes it possible to modulate the phase of the laser beam 110 coming from the femtosecond laser source 10. This shaping system 30 is advantageously a programmable component.

The scanning optical scanner 40 makes it possible to direct the phase-modulated laser beam 310 coming from the shaping system 30 to move the cutting pattern along a path of movement predefined by the user in the focal plane 101 of the cutting system.

The focusing optical system 50 makes it possible to move the focal plane 101 - corresponding to the cutting plane - of the modulated and deflected laser beam 410.

The control unit 60 makes it possible to control the shaping system 30, the optical scanning scanner 40 and the optical focusing system 50.

This cutting device is suitable for forming horizontal and vertical cutting planes. Depending on the type of cutting plane desired (vertical or horizontal), the control unit 60:

- configures the shaping system to modulate the laser beam 110 according to the desired aspect for the points of impact, and

- controls the scanning optical scanner 40 and the optical focusing system 50 to generate the desired cutting plan.

As will be described in more detail below, the inventors have developed an original configuration solution of the cutting device for the formation of horizontal and vertical cutting planes.

2. Elements of the cutting device 2.1. shaping system The spatial shaping system 30 of the laser beam makes it possible to vary the wave surface of the laser beam 110 according to the shape desired for the point(s) of impact of the modulated laser beam.

The shaping system 30 preferably comprises a spatial light modulator, known by the acronym SLM, from the English acronym “Spatial Light Modulator”. The SLM makes it possible to modulate the final energy distribution of the laser beam 110 coming from the laser source 10. The SLM is a device consisting of a layer of liquid crystals with controlled orientation making it possible to dynamically shape the front of wave, and therefore the phase of the laser beam 110. The liquid crystal layer of an SLM is organized as a grid (or matrix) of pixels. The optical thickness of each pixel is electrically controlled by orientation of the liquid crystal molecules belonging to the surface corresponding to the pixel. The SLM exploits the principle of anisotropy of liquid crystals, i.e. the modification of the index of liquid crystals, according to their spatial orientation. The orientation of liquid crystals can be achieved using an electric field. Thus, the modification of the index of the liquid crystals modifies the wavefront of the laser beam.

In a known way, the SLM implements a phase mask, i.e. a map determining how the phase of the laser beam 110 must be modified to obtain a given amplitude distribution. The phase mask is a two-dimensional image, each point of which is associated with a respective pixel of the SLM. This phase mask makes it possible to control the index of each liquid crystal of the SLM by converting the value associated with each point of the mask - represented in gray levels between 0 and 255 (therefore from black to white) - into a command value - represented in a phase between 0 and 2TT. Thus, the phase mask is a modulation instruction displayed on the SLM to cause in reflection an unequal spatial phase shift of the laser beam 110 illuminating the SLM. Of course, those skilled in the art will appreciate that the gray level range may vary depending on the model of SLM used. For example in some cases, the gray level range can be between 0 and 220. A more precise quantification of the addressing level also leads to larger value ranges, for example 1024 levels on 10 bits.

Different phase masks can be applied to the SLM depending on the type of clipping plane that the user wishes to achieve, namely:

- either a vertical cutting plane, - or a horizontal cutting plane.

For the realization of a horizontal cutting plane, the phase mask used (hereinafter referred to as "parabolic phase mask") makes it possible to apply a phase modulation to expand or contract the energy of the laser beam according to a single direction. More specifically, the application of a parabolic phase mask makes it possible to lengthen or compress the profile of the laser beam in a single direction to obtain a slender point of impact substantially in the shape of a linear segment. A modulated laser beam of the “Focal Line” type is thus obtained. For the realization of a vertical cutting plane, the phase mask used (hereinafter referred to as "conical linear phase mask") allows to apply a linear phase modulation with rotational symmetry. A modulated laser beam of the “Bessel” type is thus obtained.

2.1.1. Horizontal cutting plane

With regard to the cutting of a horizontal plane, the inventors propose to modulate the phase of the laser beam 110 coming from the femtosecond laser source 10 so as to produce, downstream of the shaping system 30, a modulated laser beam 310 of the “Focal Line” type.

2.1.1.1. "Focal Line" type beam

A "Focal Line" type beam can be mathematically defined as a beam whose distribution of the electric field (E) follows this relationship:

_( x ² + y ²ⁿ \

E x,y) = E ₀ e ^wyn )

Where

- Eo is the maximum amplitude of the electric field,

- w _x and w _y are the half-widths in 1/e ² of the distribution of the electric field according to the directions x and y with w _x < w _y ,

- x, y are the transverse horizontal and vertical coordinates,

- n is a positive integer.

This relation is defined in an XY plane transverse to the direction z of propagation of the laser wave, for an isotropic medium. Z and time dependencies are neglected for simplicity. As illustrated in Figure 10a, the corresponding profile is in the form of a line 200 of intensity:

- of length "L" equal to 2wy in the direction y, and

- of width "/ >> equal to 2wx according to x.

The uniformity of the intensity line depends on the integer n, defining the order of the super-Gaussian envelope along the y axis. The larger n is, the more constant the intensity distribution along the y-axis.

Figure 10a shows the simulated intensity distribution for such a beam in the case where n=4 and wy=5 ^* wx.

2.1.1.2. Parabolic phase mask to form a modulated laser beam of "Focal Line" type

There are different techniques for generating a “Focal Line” type beam from a Gaussian laser beam. These techniques generally involve the implementation of a phase modulation of the parabolic or uniaxial curvature type.

With reference to FIGS. 10b and 10c, an example of parabolic-type phase modulation has been illustrated making it possible to form a beam of the “Focal Line” type in the focal plane from a cylindrical lens placed on the path of a beam collimated Gaussian laser:

- Figure 10b illustrates the formation of a "Focal Line" type beam by dilation of a collimated Gaussian laser beam,

- Figure 10c illustrates the formation of a "Focal Line" type beam by compression of a collimated Gaussian laser beam.

More precisely, FIG. 10b illustrates an example of parabolic-type phase modulation using a cylindrical lens with a concave plane 210. The use of such a lens makes it possible to “expand” the laser beam 110 (of dimensions 2 ^* wx, 2 ^* wy) along a transverse axis x so as to obtain an oblong laser beam (of dimensions 4 ^* wx and 2 ^* wy) in the focal plane: the dispersion of the laser beam 110 occurs only along the axis defined by the curvature of the cylindrical lens (x-axis) without influencing the width of the transverse intensity distribution along the other transverse axis (y-axis).

FIG. 10c illustrates an example of parabolic-type phase modulation using a cylindrical lens with a convex plane 220. The use of such a lens makes it possible to “contract” the laser beam 110 (of dimensions 2 ^* wx, 2 ^* wy) along a transverse axis x so as to obtain an oblong laser beam (of dimensions wx and 2 ^* wy) in the focal plane: the focusing of the laser beam 110 occurs only along the axis defined by the curvature of the cylindrical lens (axis x) without influencing the width of the transverse intensity distribution along the other transverse axis (y-axis). Thus in the case of FIG. 10c, when passing through the cylindrical lens 220 with a convex plane and focal length f, the half-width of the collimated laser beam passes from 2 ^* wx, 2 ^* wy to wx, 2 ^* wy at the focus of this one.

The use of a cylindrical lens therefore makes it possible, by modulating the phase of a Gaussian beam, to form a "Focal Line" type beam at the focus of the lens. The dimensions of this focal line can be adjusted according to the power of dispersion (respectively focusing) of the lens. This length increases (respectively this width decreases) quasi-linearly with f, within the framework of the paraxial approximation.

The inventors for their part propose using the shaping system 30 including the SLM to generate the “Focal Line” type beam in order to avoid the use of an optical/mechanical element.

To this end, a parabolic phase mask (making it possible to emulate a cylindrical lens) is applied to the SLM by the control unit 60. The SLM then allows a phase modulation of the Gaussian laser beam 110 coming from the femtosecond laser source 10 .

Thus by using the same SLM, it becomes possible to achieve:

- a horizontal cutting plane made up of oblong impact points, then

- vertical cutting planes in Bessel beam mode, without changing optical elements and therefore considerably reducing the time of the surgical procedure, compatible with an application on the patient's eyeball of less than 3 minutes.

Two examples of parabolic phase masks are shown in Figure 11. When one of the first and second parabolic phase masks 221, 222 is applied to the shaping system 30, the shaping system 30 is capable of imprinting the phase profile of a cylindrical lens on the beam. input Gaussian laser 110 to obtain a modulated laser beam of the "Focal Line" type 310 at the output of the shaping system 30.

The first parabolic phase mask 221 is defined by the following relation:

<|)i(x)=kx ² where :

- “fi(c)” represents a set point value applied to the pixel of the SLM with abscissa “x” whatever its ordinate “y” (i.e. invariant along y),

“k” a positive coefficient, and

- " >> the abscissa corresponding to a pixel of the SLM.

The second parabolic phase mask 222 is defined by the following relationship: f ₂ (c) = kx ² + ly ² where:

- “f _å (c)” represents a set point value applied to the pixel of the SLM with abscissa “x” and ordinate “y”,

“k” a positive coefficient,

- "/ >> is a positive coefficient,

- "x" the abscissa corresponding to an SLM pixel,

"y" the ordinate corresponding to a pixel of the SLM.

When one of the first and second parabolic phase masks illustrated in FIG. 11 is applied to the SLM, the shaping system makes it possible to form a modulated laser beam of the "Focal Line" type (in the focal plane) from of the Gaussian laser beam 110 coming from the femtosecond laser source 10. A modulated laser beam is thus obtained having a spatial distribution of intensity in beams of the “focal line” type:

- extending in a plane transverse to the direction z of propagation of the laser wave (i.e. horizontal focal plane), and

- having a first dimension (i.e. length) greater than a second dimension (i.e. width).

In other words, the phase modulation of the laser beam 110 coming from the femtosecond laser from the shaping system 30 on which a parabolic phase mask is applied makes it possible to obtain a modulated laser beam 310 having a point of elongated impact in the focal plane of the cutting device, said elongated point of impact making it possible to generate an oblong gas bubble in said focal plane of the cutting device.

The choice of the gray level values of the points of the parabolic phase mask makes it possible to optimize the first and second dimensions (ie length and width) of the “Focal line” type beam, and therefore the volume in which its energy is deposited. The parabolic phase mask to be applied to the shaping system 30 to form a modulated laser beam of the "focal line" type can be calculated:

- using a partition algorithm (Vellekoop and Mosk, 2008),

- or any other algorithm known to those skilled in the art, such as for example an iterative algorithm based on the Fourier transform, such as an “IFTA” type algorithm, acronym for the English expression “Itérative Fourrier Transform Algorithm” .

In the context of producing horizontal planes of gas bubbles, for example for surgery on the anterior segment of the eye, the "Focal Line" type beam makes it possible to generate a continuous photo-disruption plane by lateral displacement of the distribution of laser intensity within the tissue to be cut using the optical scanning scanner 40 illustrated in FIG. 9, as will be described in more detail below.

2.1.2. Vertical cutting plane

With regard to the cutting of a vertical plane, the inventors propose to modulate the phase of the laser beam 110 coming from the femtosecond laser source 10 so as to produce, downstream of the shaping system 30, a modulated laser beam 310 non-diffracting Bessel type.

A Bessel laser beam is said to be "non-diffracting" because it has the property of keeping a constant profile along the optical axis of propagation of the laser beam (hereinafter referred to as "optical axis"), contrary to the behavior of a Gaussian laser beam (such as the laser beam 110 coming from the femtosecond laser source 10) which disperses when it is focused.

As will be described in more detail below, a Bessel type laser beam makes it possible to form an elongated point of impact along the z direction of propagation of the laser wave.

2.1.2. 1. Bessel bundle

A perfect zero-order Bessel beam can be mathematically defined as a beam whose electric field (E) is formally described by the zero-order Bessel function of the first kind Jo:

E(r, f, z) AoJo(k _r r)e ^jk _z ^z where:

- Ao is the amplitude of the electric field, - k _z and kr are the longitudinal and radial wave vectors,

- z, r, and f are the longitudinal, radial, and azimuthal components.

The profile of the Bessel beam is represented by a central peak of maximum intensity surrounded by concentric rings of lower intensity, as illustrated in Figures 12a and 12b which are respectively front and side views of a Bessel beam. Bessel relative to its optical axis.

We observe in FIGS. 12a, 12b a propagation with a constant profile over a distance of nearly 100 μm (image 312, FIG. 12b) with a diameter of the focusing spot (image 311, FIG. 12a) of less than 1 μm. In comparison, a Gaussian beam typically exhibits a constant propagation profile over 20 µm with a focus spot diameter of 1 µm.

Referring to Figure 13, the formation of the Bessel beam 313 results from the interference of plane waves whose wave vectors form a conical surface. In theory, the transverse extension of the ring structure is infinite, as well as the non-diffractive propagation distance.

In practice, the experimental Bessel beam has a finite non-diffractive propagation distance ZB along the optical axis due to the finite propagation observed in optics and the limited amount of energy. This finite non-diffractive propagation distance ZB defines a non-diffraction zone ZND.

It is assumed that ZB » ZR, ZR being the Rayleigh distance of the usual Gaussian beam of similar transverse size. In other words, the depth (i.e. dimension along a direction parallel to the optical axis of propagation of the laser beam) of each point of elongated impact of a Bessel beam is much greater than the depth of each point d impact with a Gaussian laser beam (such as the laser beam from the femtosecond laser source).

Thus, the use of a Bessel beam makes it possible to cut a much greater depth of tissue than with a Gaussian beam. In particular, from a single elongated point of impact of a Bessel beam, it is possible to cut a tissue over a depth equivalent to that of four superimposed points of impact of a Gaussian beam. The displacement, by the scanning optical scanner, of the elongated impact point of a Bessel beam makes it possible to generate a perfectly vertical vertical cutting plane four times faster than with a Gaussian beam impact point. Due to its specific formation based on a conical wavefront, the Bessel beam exhibits remarkable self-regeneration properties, which means that the beam can regenerate itself within the ZND non-diffraction zone after any obstacle in its path. This makes it possible to ensure the quality of the cutting of the vertical planes by guaranteeing the formation of an extended gas bubble with each firing of the laser source 10, even when part of the modulated laser beam 310 is masked by an obstacle.

The generation of a plurality of impact points at different depths from a multipoint modulated laser beam does not allow obtaining a vertical cutting plane of equivalent quality to that of a vertical cutting plane obtained at from a Bessel bundle. Indeed, with a multipoint modulated laser beam allowing the generation of several impact points along the optical axis, imperfections in the phase modulation generate uncontrolled light at a focal plane of the optical focusing system. . This uncontrolled light interferes with the desired impact point pattern. It is therefore impossible to precisely control the relative intensities of the impact points in the case of a multipoint modulated laser beam allowing the generation of several impact points along the optical axis.

Thus, due to the self-regeneration capabilities of the Bessel beam, the elongated point of impact resulting from a Bessel beam has a significant advantage compared to the points of simultaneous impacts formed along the optical axis by a multipoint modulated laser beam.

2.1.2.2. Tapered linear phase mask to form a Bessel-like modulated laser beam

There are different techniques to generate a Bessel beam from a Gaussian laser beam. These techniques typically involve axiconic phase modulation.

In particular, the Bessel beam can be obtained by using a conical lens known as an “axicon”. The conical lens can be concave/hollow (we speak of "negative axicon") or convex/domed (we speak of "positive axicon").

The inventors propose for their part to use the shaping system 30 including the SLM to generate the Bessel beam in order to avoid the use of an optical/mechanical element. For this purpose, a conical linear phase mask (allowing to emulate an axicon) is applied to the SLM by the control unit 60. The SLM then allows a conical phase modulation of the Gaussian laser beam 110 coming from the femtosecond laser source 10. Thus by using the same SLM, it becomes possible to produce a horizontal cutting plane in multipoint, then vertical cutting planes in Bessel beam mode without changing optical elements and therefore considerably reducing the time of the surgical procedure, compatible with an application on the eyeball of the patient less than 3 minutes. Two examples of such phase masks are illustrated in Figures 14a and 14b. When one of the first and second phase masks is applied to the SLM, the SLM is able to imprint the phase profile of an axicon on the input Gaussian laser beam 110 to obtain a modulated Bessel type laser beam 310 at the output of the shaping system 30.

Referring to Figure 14a, the first conical linear phase mask (referenced

314) emulates the behavior of a negative axicon (i.e. concave axicon). Referring to Figure 14b, the second conical linear phase mask (referenced

315) emulates the behavior of a positive axicon (i.e. convex axicon). These first and second phase masks each have a symmetry of revolution around a central point of symmetry, the level of gray of each pixel varying according to the distance between said pixel and the central point of symmetry.

When one of the phase masks illustrated in FIGS. 14a and 14b is applied to the SLM, the shaping system 30 makes it possible to form a modulated laser beam of the Bessel type 310 (at the output of the shaping system 30) at from the Gaussian laser beam 110 coming from the femtosecond laser source 10 (at the input of the shaping system 30). One thus obtains a modulated laser beam having a spatial distribution of intensity in Bessel beam

With reference to FIGS. 15a and 15b, this Bessel-type modulated laser beam comprises, in a plane transverse to the optical axis:

- a central spot 313a of maximum intensity, and

- several concentric rings 313b, 313c, 313d of decreasing intensity as a function of the radial distance from the optical axis.

This Bessel beam 313 extends over a depth L along the optical axis A-A' (ie in the non-diffraction zone ZND of the Bessel beam). The choice of the grayscale values of the points of the conical linear phase mask makes it possible to optimize the depth L of the Bessel beam 313 and therefore the volume in which its energy is deposited.

The conical linear phase mask to be applied to the SLM of the shaping system to form a modulated Bessel laser beam can be calculated:

- using a partition algorithm (Vellekoop and Mosk, 2008),

- or any other algorithm known to those skilled in the art.

2.1.2.3. Assembly of the cutting device in the context of the cutting of a fabric from a modulated laser beam of the Bessel type

Figure 16 shows an assembly diagram of the cutting device. This assembly diagram is partial in that it does not show the femtosecond laser source, and the optical scanning scanner. Furthermore in this figure 16, the optical focusing system 50 (as a whole) is represented by an equivalent lens 51, it being understood for those skilled in the art that the optical focusing system 50 does not consist solely of a fixed lens .

Referring to Figure 16, the Bessel beam is formed just after the conical phase modulation plane, i.e., just after the SLM of the shaping system 30. The SLM simulating a conical lens (axicon negative or positive), the central spot of maximum intensity of the Bessel beam forms in the focal plane image 32 of the SLM.

The equivalent lens 51 of the focusing optical system 50 is arranged downstream of the shaping system 30, and is arranged so that the object focal plane 52 of the equivalent lens extends at a non-zero distance from the image focal plane 32 of the shaping system 30 along the optical axis.

Thus, the object focal plane 52 of the equivalent lens 51 of the optical focusing system 50 extends outside the non-diffraction zone ZND of the Bessel beam, so that at the output of the cutting system, a point d elongated impact as shown in Figure 17 is obtained. This elongated point of impact is composed of:

- a Bessel ring 33a focused on the image focal plane 53 of the equivalent lens 51 (corresponding to the focal plane of the cutting device),

- a line 33b of concentration of the rays of the Bessel beam - corresponding to the image of the non-diffraction zone ZND - said line 33b forming outside the image focal plane 53 of the equivalent lens 51 . In the context of the present invention, it is the concentration line 33b of the elongated point of impact which is used to produce the vertical cutting plane (the energy contained in the Bessel ring is not sufficient to form a gas bubble). The ray concentration line 33b can form either before or after the ring 33a, depending on the sign of the phase modulation. In other words, the position of line 33b relative to ring 33a depends on the type of axicon (positive or negative) emulated thanks to the conical linear phase mask.

As Bessel's ZND non-diffraction zone (i.e. line 33b) is moved outside the focal plane of the cutting system, no interference occurs with unmodulated light. This allows better control of the intensity profile without energy losses due to beam filtering.

2.2. Scanning optical scanner

The optical scanning scanner 40 makes it possible to deflect the modulated laser beam (“Focal Line” or “Bessel” type) 310 so as to move the point(s) of impact into a plurality of positions 43a-43c in the cutting plane.

The 40 Scanning Optical Scanner includes:

- an inlet orifice to receive the phase modulated laser beam 31 coming from the shaping unit 30,

- one (or more) optical mirror(s) pivoting around at least two axes to deflect the phase modulated laser beam 310, and

- an exit orifice to send the deflected modulated laser beam 410 to the focusing optical system 50.

The optical scanner 40 used is for example an IntelliScan III scanning head from SCANLAB AG.

The entry and exit orifices of such an optical scanner 40 have a diameter of the order of 10 to 20 millimeters, and the attainable scanning speeds are of the order of 1 m/s to 10 m/s.

The mirror(s) is (are) connected to one (or more) motor(s) to allow their pivoting. This (these) motor(s) for pivoting the mirror(s) is (are) advantageously controlled by the unit of the control unit 60 which will be described in more detail below. The control unit 60 is programmed to control the scanning optical scanner 40 so as to move the point of impact along a path of movement contained in the cutting plane.

In the case of a horizontal clipping plane, the motion path includes a plurality of clipping segments. The displacement path can advantageously have the shape of a slot.

In the case of a vertical clipping plane, the motion path includes a segment. In this case, the control unit 60 can be configured to command the optical scanner 40 to move back and forth from the elongated point of impact of Bessel to cut the cutting plane over its entire depth. For example, if the optical scanner 40 starts the segment from the left, it will start this segment from the right on the way back, then from the left, then from the right and so on over the entire height of the cutting plane.

Advantageously, the control unit 60 can be programmed to activate the femtosecond laser 10 when the scanning speed of the optical scanner 40 is greater than a threshold value. This makes it possible to synchronize the emission of the laser beam 110 with the scanning of the optical scanning scanner 40. More precisely, the control unit 60 activates the femtosecond laser 10 when the pivoting speed of the mirror(s) of the optical scanner 40 is constant. This makes it possible to improve the cutting quality by producing a homogeneous surfacing of the cutting plane.

2.3. Focusing optical system

The optical focusing system 50 makes it possible to move the focal plane of the cutting device according to the type of cutting plane to be produced.

The focusing optical system 50 comprises:

- an inlet orifice to receive the phase-modulated and deflected laser beam coming from the optical scanning scanner 40,

- one (or more) motorized lens(es) to allow its (their) translational movement along the optical path of the modulated and deflected laser beam, and

- an exit orifice to send the focused laser beam towards the tissue to be treated. The lens(es) used with the focusing optical system 50 can be f-theta lenses or telecentric lenses. Both f-theta and telecentric lenses achieve a plane of focus over the entire XY field, unlike standard lenses for which it is curved. This guarantees a size of constant focused beam over the entire field. For f-theta lenses, the position of the beam is directly proportional to the angle applied by the scanner while the beam is always normal to the sample for telecentric lenses.

The control unit 60 is programmed to control the movement of the lens(es) of the optical focusing system 50 so as to move the focal plane of the cutting device according to the type of cutting plane to be achieve.

In the case of a horizontal cutting plane, the cutting plane corresponds to the focal plane of the cutting device. The control unit 60 controls the movement of the lens(es) of the optical focusing system 50 to focus the modulated and deflected laser beam 410 to a desired depth corresponding to the depth of the cutting plane to be produced.

In the case of a horizontal cutting plane, the cutting plane coincides with the focal plane of the cutting device.

In the case of a vertical cutting plane, the cutting plane can be located:

- below the focal plane of the cutting device in the case where the conical linear phase mask used allows the SLM to emulate a positive axicon (the Bessel ring 33a is located above the concentration line 33b used to make the cut), in this case the control unit 60 controls the optical focusing system 50 to focus the modulated and deflected laser beam 410 to a desired depth greater than the depth of the cutting plane to be made (so that the concentration line 33b of the elongated point of impact is located at the depth of the cutting plane to be produced),

- above the focal plane of the cutting device in the case where the conical linear phase mask used allows the SLM to emulate a negative axicon (the Bessel ring 33a is located below the concentration line 33b used to make the cut) in this case the control unit 60 controls the optical focusing system 50 to focus the modulated and deflected laser beam 410 at a desired depth less than the depth of the cutting plane to be made (so that the concentration line 33b of the elongated point of impact is located at the depth of the cutting plane to be produced).

Finally, the control unit 60 can be programmed to drive the optical scanning scanner 40 so as to vary the area cut in the focal plane between two successive cutting planes. This makes it possible to vary the shape of the volume finally cut according to the intended application. Preferably, the distance between two successive cutting planes is between 2 μm and 500 miti, and in particular:

- between 2 and 20 pm to treat a volume requiring high precision, for example in refractive surgery, preferably with a spacing of between 5 and 10 pm, or

- between 20 and 500pm to treat a volume that does not require great precision, such as for example to destroy the central part of a lens nucleus, preferably with a spacing between 50 and 300pm.

Of course, this distance can vary in a volume composed of a stack of cutting planes.

2.4. Control unit

As indicated previously, the control unit 60 makes it possible to control the various elements constituting the cutting device, namely the femtosecond laser source 10, the shaping system 30, the optical scanning scanner 40 and the optical system of focus 50.

The control unit 60 is connected to these different elements via one (or more) communication bus allowing:

- the transmission of control signals such as

• the activation signal to the femtosecond laser source 10,

• the phase mask to the shaping system 30,

• the scanning speed at the 40 scan optical scanner,

• the position of the scanning optical scanner 40 along the path of movement,

• the depth of cut to the optical focusing system 50.

- the reception of measurement data from the various elements of the system such as

• the scanning speed reached by the optical scanner, or

• the position of the focusing optical system, etc.;

The control unit 60 may be composed of one (or more) workstation(s), and/or one (or more) computer(s) or may be of any other type known to those skilled in the art. job. The control unit 60 can for example comprise a mobile phone, an electronic tablet (such as an IPAD®), a personal assistant (or "PDA", acronym for the English expression "Personal Digital Assistant"), etc. In all cases, the control unit 60 comprises a processor programmed to allow the control of the femtosecond laser source 10, of the shaping system 30, of the optical scanning scanner 40, of the optical focusing system 50, etc.

Advantageously, the control unit 60 is programmed to vary the shape of the modulated laser beam between two successive cutting planes, in particular between a horizontal cutting plane and a vertical cutting plane.

2.5. Principle of operation

We will now describe in more detail the principle of operation of the cutting device with reference to the destruction of a lens in the context of a cataract operation.

To partition the lens into cubes suitable for aspiration by a suction cannula, horizontal and vertical cutting planes are formed starting with the horizontal cutting plane deepest in the lens and stacking the vertical cutting planes and successive horizontals to the most superficial horizontal cutting plane in the lens.

In a first step, the deepest horizontal cutting plane is made. The control unit 60:

- applies a parabolic phase mask to the shaping system 30 to produce a modulated laser beam of the "Focal Line" type,

- controls the movement of the focusing system 50 to make the focal plane of the cutting device coincide with the desired deepest cutting plane,

- activates the femtosecond laser source 10, and

- Controls the displacement of the optical scanning scanner 40 along the optical path (for example in crenel).

A succession of shots are made in the focal plane of the cutting device. With each shot, a slender point of impact (ie whose length is greater than the width) focuses in the focal plane. This slender point of impact forms an oblong gas bubble in a direction transverse to the axis of propagation z of the modulated laser beam. 40-scan optical scanner allows the point of impact to be moved slender in the focal plane between each shot. When the entire surface of the horizontal cutting plane is covered with gas bubbles, the horizontal cutting plane is finalized.

In a second step, several adjacent vertical cutting planes are made with the cutting device. For each vertical cutting plane, the control unit 60:

- applies a conical linear phase mask to the shaping system 30 to produce a modulated laser beam of the “Bessel” type,

- controls the movement of the focusing system 50 to position the line of concentration 33b of the elongated point of impact in the cutting plane (the focusing plane being above or below the cutting plane depending on whether the axicon emulated on the shaping system 30 is a positive axicon or a negative axicon),

- activates the femtosecond laser source 10, and

- controls the displacement of the scanning optical scanner 40 along the optical path (for example a segment).

A succession of shots are made. With each shot, an elongated point of impact is formed, this elongated point of impact including:

- a low intensity ring 33a located in the focal plane of the cutting device,

- a high intensity concentration line 33b located on/under the focal plane of the cutting device.

Each elongated point of impact forms an oblong gas bubble along the optical axis of propagation of the modulated laser beam. The optical scanner allows the elongated point of impact to be moved under/over the focal plane between each shot. When the entire path of travel is covered with gas bubbles, the vertical cutting plane is finalized.

If the depth of focus line 33b is less than the desired depth for the vertical cutting plane, then control unit 60 can control scanning optical scanner 40 and focusing optical system 50 to move back and forth the point of impact elongated along the optical path by varying the depth of the focal plane of the cutter between outward and return.

Several vertical cutting planes are thus obtained above the initial horizontal cutting plane. In a third step, an upper horizontal plane is made to cap the vertical cutting planes. This horizontal cutting plane is produced using the same method as that described with reference to the first step.

In this way, crystallin cubes defined between the horizontal and vertical planes produced in the first, second and third steps are obtained.

These can be repeated to make a stack of crystalline cubes.

3. Conclusions

3. 1. Advantage associated with the generation of a "Focal Line" type beam The production of a horizontal cutting plane from a "Focal Line" type modulated laser beam makes it possible to maximize the chances of a photo -disruption of the fabric 2 with respect to a horizontal cutting plane produced from a Gaussian laser beam making it possible to generate one (or more) point(s) of circular impact(s).

Indeed, the principle of photodisruption of tissue 2 by ultrashort laser pulses depends on nonlinear absorption mechanisms that are highly dependent on the optical and physical properties of the irradiated tissue.

However, the irradiated fabric 2 can locally present inhomogeneous optical and physical properties, so that an area 21 of the fabric 2 can be less absorbent locally, and prevent the formation of a gas bubble when it is irradiated.

In the case of irradiation by a Gaussian beam making it possible to generate one (or more) point(s) of circular impact(s), this phenomenon can leave a parasitic tissue bridge 22 of size P1 equal to twice the separation of the points impact, as shown in Figure 18a. This large size of the parasitic tissue bridge 22 can make it difficult for the practitioner to subsequently dissect the tissue using a tool.

In the case of beam irradiation of the “Focal Line” type making it possible to generate a slender point of impact (i.e. whose length is greater than the width), the tissue bridge 22 is strictly circumscribed to the less absorbent zone 21, as shown in Figure 18b. This makes it possible to reduce the size P2 of the parasitic tissue bridge 22, and therefore to facilitate the operation of dissection of the tissue 2 subsequently carried out by the practitioner using a tool.

3.2. Advantages associated with using a Bessel type beam As mentioned previously, it is possible to cut a much greater depth of tissue with a Bessel beam, which makes it possible to generate a cutting plan much faster than with a Gaussian beam.

As an indication, figure 19 makes it possible to compare the time required to produce a vertical cutting plan:

- from a Gaussian beam on the one hand (images 610a to 61 Of),

- from a Bessel beam on the other hand (images 620a to 620c).

In the case of the use of a Gaussian beam generating a single circular point of impact moved by the optical scanning scanner, it is necessary to perform four return trips to form gas bubbles which are superimposed to constitute the plane cutting. The time required for the realization of the vertical cutting plan can be formulated as follows:

T1 = (8 x t1 ) + (7 x t2)

Where :

- T1 corresponds to the total cutting time,

- t1 corresponds to the travel time of a line,

- t2 corresponds to the time it takes to perform a U-turn.

Assuming t1 ^« t2 = t, then the cutting time of the plane is equal to 15 t in the case of a Gaussian beam.

In the case of the use of a beam of Bessel, only a round trip is necessary to constitute the cutting plan. The time required for the realization of the vertical cutting plan can be formulated as follows:

T2 = (2 x t1 ) + (1 x t2)

Where :

- T2 corresponds to the total cutting time

- t1 corresponds to the travel time of a line

- t2 corresponds to the time it takes to complete a half-turn

Assuming t1 ^« t2 = t, then the cutting time of the plane is equal to 3 t in the case of a Bessel beam.

The use of an SLM to shape a Gaussian beam according to an axiconic modulation setpoint to obtain a Bessel modulus laser beam generating an elongated point of impact therefore makes it possible to reduce by a factor of five the time required to produce of a vertical cutting plane. 3.3. General conclusion

Thus, the invention makes it possible to have an effective three-dimensional cutting tool, unlike current tools which can only produce two-dimensional cutting planes (vertical cuts in quarters or sticks without the possibility of combining them with horizontal cuts in a acceptable time).

In particular, the cutting apparatus is configured to perform a surgical cutting operation in a rapid and efficient manner. The SLM makes it possible to dynamically shape the wavefront of the laser beam from the femtosecond laser source since it is digitally configurable:

- the horizontal cutting planes are made using a multipoint phase mask,

- the vertical cutting planes are made using a conical linear phase mask.

The change of phase mask being carried out in a few milliseconds, the sequence of successively horizontal then vertical cutting planes and so on, is done extremely quickly without having to mobilize optical/mechanical elements, which gives this invention its character. single lens enabling a lens to be cut into 10,000 to 20,000 cubes in a time of the order of 30 seconds, whereas it would take between 5 and 10 minutes for current systems to do the equivalent, which is of course unacceptable from the point of view of for patient comfort and safety.

In conclusion, the cutting device described above has many advantages, in particular due to the dynamic reconfigurability of the shaping system which makes it possible in particular: i) to switch from the cutting of a horizontal plane using a "Focal Line" type beam (via the application of a parabolic phase mask on the SLM) to the cutting of a vertical plane using a "Bessel" type beam (via the application of a conical linear phase mask), ii) to adjust the dimensions (length and width) of the points of impact

^■ the "Focal Line" type beam on the one hand, and

^■ the “Bessel” type beam on the other hand, without complicating the optical assembly, that is to say without adding an optical element in the cutting device, iii) to control the uniformity of the intensity distribution and also to prevent the formation of unwanted hot spots along the optical axis. The invention has been described for operations of cutting a lens in the field of ophthalmological surgery, but it is obvious that it can be used for other type of operation in ophthalmological surgery without departing from the scope of the 'invention. For example, the invention finds an application in corneal refractive surgery, such as the treatment of ametropia, in particular myopia, hypermetropia, astigmatism, in the treatment of loss of accommodation, in particular presbyopia. The invention also finds an application in the treatment of cataracts with incision of the cornea, cutting of the anterior capsule of the lens, and fragmentation of the lens. Finally, more generally, the invention relates to all clinical or experimental applications on the cornea or the lens of a human or animal eye. Even more generally, the invention relates to the broad field of laser surgery and finds an advantageous application when it comes to cutting and more particularly vaporizing human or animal soft tissues with a high water content.

The reader will have understood that many modifications can be made to the invention described above without materially departing from the new teachings and advantages described here.

Claims

1. Apparatus for cutting human or animal tissue, said apparatus including a femtosecond laser source (10) configured to emit a Gaussian laser beam (110) in the form of pulses and a device for processing the Gaussian laser beam, the device processing device being disposed downstream of the femtosecond laser source (10), the processing device comprising:

- a shaping system (30) positioned on the trajectory of the Gaussian laser beam, to modulate the phase of the wavefront of the Gaussian laser beam, the shaping system (30) being configured to produce a modulated laser beam from the Gaussian laser beam,

- an optical scanning scanner (40) arranged downstream of the shaping system to move the modulated laser beam,

- an optical focusing system (50) downstream of the shaping system (30), for focusing the modulated laser beam in a focal plane of the cutting device and for moving the focal plane of the cutting device a plurality of positions along an optical axis (A-A') of propagation of the modulated laser beam, characterized in that the processing device further comprises a control unit (60) for controlling the femtosecond laser source (10 ), the shaping system (30), the scanning optical scanner (40), and the focusing optical system (50), in order to produce at least one horizontal cutting plane extending perpendicular to the optical axis (A-A'), the control unit (60) being configured for:

- applying to the shaping system (30), a parabolic modulation instruction in order to produce a modulated laser beam of the "Focal Line" type from the Gaussian laser beam, said modulated laser beam of the "Focal Line" type having a point of slender impact in a direction perpendicular to the optical axis, the slender point of impact having, in the focal plane, a width and a length greater than the width, said slender point of impact making it possible to generate a gas bubble oblong in the fabric and thus cut it to a length greater than a Gaussian beam,

- drive the scanning optical scanner to move the slender point of impact of the "Focal Line" type modulated laser beam along an optical path displacement to successively form a plurality of oblong adjacent gas bubbles, said gas bubbles constituting the horizontal cutting plane.

2. Cutting apparatus according to claim 1, wherein the shaping system (30) comprises a spatial light modulator (SLM), the control unit (60) being configured to apply a parabolic phase mask (221 , 222) emulating a cylindrical lens on the Spatial Light Modulator (SLM).

3. Cutting apparatus according to claim 2, wherein the parabolic phase mask is a two-dimensional image to be displayed on the spatial light modulator (SLM) to cause an unequal spatial phase shift of the Gaussian laser beam (110), the value (fi ) of each pixel of the two-dimensional image being defined by the following formula:

<|)i(x,y)=kx ² where:

• "07" represents the value of a pixel of the two-dimensional image,

• “x” is the abscissa of the pixel of the two-dimensional image,

• "y" is the ordinate of the pixel of the two-dimensional image, and

• “k” is a positive coefficient.

4. Cutting apparatus according to claim 2, wherein the parabolic phase mask is a two-dimensional image to be displayed on the spatial light modulator (SLM) to cause an unequal spatial phase shift of the Gaussian laser beam (110), the value (F2 ) of each pixel of the two-dimensional image being defined by the following formula:

02(x,y) = kx ² + ly ² where:

• "0 _{2 >>} represents the value of a pixel of the two-dimensional image,

• “x” is the abscissa of the pixel of the two-dimensional image,

• "y" is the ordinate of the pixel of the two-dimensional image,

• “k” is a positive coefficient, and • “l” is a positive coefficient.

5. Cutting apparatus according to any one of claims 2 to 4, wherein the path of movement comprises at least one segment, the parabolic phase mask (221, 222) being determined so that the length of each point of elongated impact extends parallel to said and at least one segment.

6. Cutting device according to any one of claims 1 to 5, in which the control unit (60) is further configured to control the femtosecond laser source (10), the shaping system (30), the scanning optical scanner (40), and the focusing optical system (50), in order to produce at least one vertical cutting plane extending parallel to the optical axis (A-A').

7. Cutting apparatus according to claim 6, wherein the control unit (60) is configured to:

- applying to the shaping system (30), an axiconic modulation setpoint in order to produce a modulated laser beam of the Bessel type from the Gaussian laser beam, said modulated laser beam of the Bessel type having an elongated point of impact according to a direction parallel to the optical axis, the elongated point of impact having a width and a depth greater than the width, said elongated point of impact making it possible to generate an oblong gas bubble in the tissue and thus cut it to a greater depth larger than a Gaussian beam,

- driving the scanning optical scanner to move the elongated point of impact of the Bessel-type modulated laser beam along another optical path of movement to successively form a plurality of adjacent gas bubbles, said gas bubbles constituting the plane vertical cutting.

8. Cutting device according to claim 7, in which the object focal plane of the focusing system (50) is positioned at a non-zero distance from the image focal plane of the shaping system (30), so that the point d The elongated impact of the Bessel-type modulated laser beam includes: o a ring (33a) focused in the focal plane of the cutting device, o a line (33b) of concentration of the rays of the modulated laser beam of the Bessel type extending outside the focal plane of the cutting device, said line (33b) making it possible to form the oblong gas bubble, the ring (33a) having an intensity lower than the intensity of the line (33b) not allowing the formation of a gas bubble.

9. Cutting device according to any one of claims 7 or 8, in which the control unit (60) is programmed to drive the focusing optical system (50) so that the focal plane of the cutting device extends, along the optical axis (A-A'), above the desired position for the vertical cutting plane.

10. Cutting device according to any one of claims 7 or 8, in which the control unit (60) is programmed to drive the optical focusing system (50) so that the focal plane of the cutting device extends, along the optical axis (A-A'), below the desired position for the vertical cutting plane.

11. Cutting device according to any one of claims 6 to 10, which is adapted to successively produce horizontal and vertical cutting planes so as to form cubes of fabric:

- the control unit controlling the femtosecond laser source (10), the shaping system (30), the optical scanning scanner (40), and the optical focusing system (50) to produce a horizontal cutting plane initial, then

- the control unit controlling the femtosecond laser source (10), the shaping system (30), the optical scanning scanner (40), and the optical focusing system (50) to produce at least one vertical cutout located above, along the optical axis (A-A'), of the initial horizontal cutting plane, then

- the control unit controlling the femtosecond laser source (10), the shaping system (30), the optical scanning scanner (40), and the optical focusing system (50) to produce a horizontal cutting plane final above, along the optical axis (A-A'), of said and at least one vertical cutting plane.