CN111061064B - Double-beam optical trap beam auxiliary alignment device and method - Google Patents
Double-beam optical trap beam auxiliary alignment device and method Download PDFInfo
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Abstract
The invention discloses a double-beam optical trap beam auxiliary alignment device and a method. The plane reflector is horizontal and the reflecting surface is upward, one of the planes of the right-angle sides at the other side is fixedly arranged on one half side of the plane reflector in a close and contact manner, and the plane where the hypotenuse of the pair of triangular prisms is plated with a semi-transparent and semi-reflective film; the pair of four-quadrant position detectors are horizontally arranged on the same plane and are positioned above the plane reflecting mirror and the pair of triangular prisms. The invention can simply and effectively assist the optical adjustment of the optical trap light beam, improve the optical trap performance and provide an efficient, rapid and convenient consistent adjustment scheme for an optical power suspension system taking the optical trap as a core component.
Description
Technical Field
The invention relates to a light beam alignment device and a light beam alignment method of an instrument and a sensing system using a light force suspension system as a measurement basis, belonging to the technical field of optical precision measurement, in particular to a double-light beam optical trap light beam auxiliary alignment device and a double-light beam optical trap light beam auxiliary alignment method.
Background
The optical trap is a core optical path and key in an optical suspension system, the optical suspension system is a new subject established on the basis of laser control, laser cooling, laser capture and other technologies, micro-nano particles (typically micro-nano spheres) are suspended through the optical force action of laser beams, and the particles are supported by the optical force to replace a mechanical support structure; thereby isolating the interaction between the particles and the environment and avoiding the interference of various environmental factors, such as vibration, heat conduction and the like, on the motion of the particles; at the moment, the micro-nano particles are used as a medium in measurement and sensing to realize high-precision measurement, and the anti-interference performance is better, namely the core competitiveness of an optical force system taking an optical trap as a core. Meanwhile, by selecting micro-nano spheres with special defects, such as diamond spheres with color centers, various modern physical effects can be researched and verified on a micro scale.
The suspended particles in the optical force suspension system are micro-nano particles, an optical trap is formed near the focus of the light which is transmitted in the opposite directions through two beams of light, the particles are captured by utilizing the gradient force and the scattering force in the optical trap, no mechanical contact exists between the suspended particles and the external environment, and the suspended particles are stabilized at the position with the lowest central energy of the optical trap.
The micro-nano balls captured by the laser can be processed according to the harmonic oscillator, and for the harmonic oscillator in the free state, the harmonic oscillator is in a random motion state even when the harmonic oscillator is not in external contact due to internal thermal motion, and the strength of the motion state is generally described by adopting equivalent temperature. In an optical suspension system, a set of laser cooling system is usually adopted to perform feedback control on the motion of the micro-nano balls captured by laser, so as to reduce the random motion amplitude, and the process is called laser cooling. The typical laser cooling system comprises a small ball position information sensing unit, an electrical information processing system and a feedback system, wherein the cooling light can adopt a wavelength different from that of the capture light, and the capture and particle cooling can be simultaneously realized by adopting the same optical path. According to the current technology, the displacement of the random movement of the particles can be controlled to picometers (pm: 10) by the laser cooling technology-12Meters), equivalent temperature is close to milli-kelvin (10)-3On).
In addition, the micro-nano small balls are very small in size, can be arranged in a container in advance, are matched with corresponding releasing devices such as high-energy laser emitting and ultrasonic emitting modes, are released when in application, and are captured by laser. In addition, the typically adopted micro-nano balls are silicon materials, and the diameter is between 100nm and 10 um; other specialty materials may be used as pellets depending on the needs of the study.
The optical suspension system is a research hotspot at present and is also a very good research platform, various sensors with ultra-high precision can be developed by utilizing the system, and a microminiaturized sensor can also be developed, but the premise is to solve a series of technical problems in the optical suspension system, wherein the alignment problem of an optical trap is one of key links influencing the performance of the optical suspension system.
The optical trap utilizes two capture light beams which are opposite and have coincident focal points to form a capture area of micro-nano particles (small balls) near the focal point, and the alignment adjustment precision of the two light beams determines the optical field distribution condition of the optical trap area, thereby influencing the capture performance. The position and angle errors of two opposite beams can be decomposed into two aspects, namely beam central line nonparallel and beam central line dislocation deviation. The unparallel of the central line of the light beam can cause the direction change of the gradient force and the scattering force in the light trap, so that the trapping stability of the light trap for trapping micro-nano particles is reduced, and the dislocation of the central line of the light beam can cause the rotation of the particles and influence the measurement precision. In order to obtain a capture result, the optical path of the optical trap needs to be finely adjusted, and the two errors are reduced as much as possible, so that the two light beams are strictly parallel, and the transmission center lines coincide.
At present, in the optical trap optical path adjustment, the main condition mode is manual adjustment by manpower, the optical path adjustment error is judged by using a card and observing light spots through human eyes, and then the angle of an incident reflector of an optical trap light beam incident optical path is adjusted, so that the angle effect of the optical trap light beam is adjusted. The adjustment precision of the double-beam optical trap optical path adjustment mode depends on observation of human eyes, and is low in reliability, poor in repeatability, dependent on subjective judgment of an observer, poor in precision, time-consuming and labor-consuming, so that the efficiency is low in application and the consistency is poor.
The double-beam optical trap is the core constitution of the optical suspension system, determines the measuring effect of the precision measuring system taking the optical suspension system as the measuring scheme, and aims at the current situation that the double-beam adjusting process in the existing double-beam optical trap mainly depends on the judgment of human eyes, which causes the large alignment error of the optical trap light beam, the difficult adjustment, the low efficiency and the low precision, an objective optical trap adjusting device and method with good repeatability and high consistency are urgently needed to improve the alignment precision of the optical trap light path adjustment and the performance of the optical trap, thereby promoting the application of the optical suspension system in the precision measuring field.
Disclosure of Invention
Aiming at the technical current situation of the double-beam optical trap, the light path adjustment of two light beams of the existing double-beam optical trap depends on the judgment of people, the consistency is poor, and the precision is not high, the invention provides the auxiliary alignment device and the method for the double-beam optical trap light beams.
The invention provides an auxiliary adjusting device and an adjusting method for the core structure of the optical power suspension system, is expected to promote the development of the optical power suspension technical field and promote the popularization and application of the optical power suspension system in various precision measurement fields.
The technical scheme adopted by the invention is as follows:
a dual-beam optical trap beam auxiliary alignment device comprises: the double-beam optical trap comprises a left beam and a right beam, the two beams are respectively reflected by respective adjusting mechanisms and then are incident to the same position in a coaxial parallel and opposite direction mode to form the optical trap, and when the double-beam optical trap is used, the beam auxiliary alignment device is arranged at the center of the optical trap and comprises a pair of right-angle prisms, a plane mirror and a pair of four-quadrant position detectors, wherein the right-angle prisms, the plane mirror and the four-quadrant position detectors are completely the same in shape and size; the cross sections of the right-angle prisms are right-angled isosceles triangles, the right-angle prisms are completely connected in a close fit manner by the plane of the right-angle side at one side and are arranged in parallel by the plane of the right-angle side at the other side to form a parallelogram prism, the plane reflector is horizontally arranged, the reflecting surface is upward, one of the planes of the right-angle sides at the other side of the right-angle prisms is fixedly arranged in a close fit manner on one half side of the plane reflector, and the plane of the hypotenuse of the right-angle prisms is plated with a semi-transparent and semi-reflective film; the pair of four-quadrant position detectors are horizontally arranged on the same plane and are arranged above the plane mirror and the pair of right-angle prisms.
The device is used for respectively acquiring the offset directions of the two correlation beams of the optical trap to serve for adjusting the direction of the optical path adjusting mechanism, and the signals of the four quadrants of the two correlation beams on the four-quadrant position detector QPD are consistent, so that the central lines of the two correlation beams are parallel, the transmission optical axes are overlapped and the directions are opposite.
The sensitive surfaces of the pair of four-quadrant position detectors are perpendicular to the plane where the two right-angle sides of the pair of right-angle prisms are connected in a close fit mode, the sensitive surfaces of the pair of four-quadrant position detectors are respectively arranged right above the plane where the two right-angle sides of the pair of right-angle prisms which are parallel to each other are arranged, and the sensitive surfaces of the pair of four-quadrant position detectors receive light beams which are converted after parallel incident light is reflected by the plane where the hypotenuse of the right-.
Each four-quadrant position detector is positioned so that the light beam incident on the detector is completely on the sensitive surface of the detector.
The adjusting mechanism is a moving platform provided with an incidence reflector. The adjusting mechanism has angle and linear adjusting functions, and a six-degree-of-freedom adjusting table can be adopted typically.
For the left light beam, the light beam is incident to the adjusting mechanism to be reflected, and then is directly reflected to the sensitive surfaces of the pair of four-quadrant position detectors through the planes where the two bevel edges of the pair of right-angle prisms are located respectively after being reflected; and for the right light beam, the light beam is incident to the adjusting mechanism to be reflected, then is respectively reflected to the plane reflecting mirror through the planes where the two bevel edges of the pair of right-angle prisms are located, is reflected by the plane reflecting mirror, then is respectively transmitted by the pair of right-angle prisms, and then is incident to the sensitive surfaces of the pair of four-quadrant position detectors.
Secondly, a double-beam optical trap beam auxiliary alignment method: by adopting the device, the device is parallelly placed in the light path of the light trap and is fixed, the plane reflector and the light beam required by the double-beam light trap are parallel in advance, and the light path is adjusted as follows:
firstly, adjusting a left light path:
closing the right light beam or blocking the right light beam to enable only the left light beam to be incident into the light trap, enabling the left light beam to be incident into the adjusting mechanism to be reflected, and directly reflecting the left light beam onto the sensitive surfaces of the pair of four-quadrant position detectors through the planes where the two bevel edges of the pair of right-angle prisms are located respectively after reflection;
the pair of four-quadrant position detectors convert light beams incident on four quadrants of the respective photosensitive surfaces into electric signals, the central positions of the light beams are obtained according to the sizes of the electric signals of the four quadrants, and then the pitch angle, the roll angle and the horizontal position posture of an incident plane mirror of the adjusting mechanism of the left light beam are adjusted, so that the light beams of the left light beam incident on the pair of four-quadrant position detectors are converged to the centers of the four quadrants of the photosensitive surfaces, and the sizes of the electric signals output by the respective four quadrants of the photosensitive surfaces of the pair of four-quadrant position detectors are the same;
then adjust the right side light path:
closing the left light beam or blocking the left light beam to enable only the right light beam to be incident in the light trap, enabling the right light beam to be incident on an incident plane mirror of the adjusting mechanism to be reflected, respectively reflecting the right light beam to the plane reflecting mirror through planes where two bevel edges of the pair of right-angle prisms are located after reflection, and respectively transmitting the right light beam to be incident on the sensitive surfaces of the pair of four-quadrant position detectors after being reflected by the plane reflecting mirror;
the pair of four-quadrant position detectors convert light beams incident on four quadrants of the respective photosensitive surfaces into electric signals, the central positions of the light beams are obtained according to the sizes of the electric signals of the four quadrants, and then the pitch angle, the roll angle and the horizontal position posture of an incident plane mirror of the adjusting mechanism of the right light beam are adjusted, so that the light beams of the right light beam incident on the pair of four-quadrant position detectors are converged to the centers of the four quadrants of the photosensitive surfaces, and the sizes of the electric signals output by the respective four quadrants of the photosensitive surfaces of the pair of four-quadrant position detectors are the same;
through the two steps, under the condition that the left light beam and the right light beam are respectively closed at the other side, the centers of the light beams are converged to the centers of the two four-quadrant position detectors, at the moment, the device is removed, the left light beam and the right light beam are simultaneously opened, and as the two light beams are respectively focused at the centers of the two four-quadrant position detectors at fixed positions, the central lines of the two light beams are superposed, the propagation directions are opposite and parallel, and a double-light-beam light trap area is formed at the middle position.
The position of the four-quadrant position detector is fixed.
The invention relates to a four-Quadrant Photodetector (QPD) which is a photodetector, and the typical structure is that in a circular area of a detection center, the four quadrants are divided into A, B, C, D four detection photosensitive surfaces by taking a circle center as the center and according to a plane, and each photosensitive surface outputs an electric signal corresponding to the intensity of an optical signal.
As shown in fig. 1, the central position of the light beam can be known according to A, B, C, D, which shows the magnitude of the output electric signals of the four detecting photosurfaces: the dotted circles indicate the incident positions of the light beams, at this time, the signals of B and D are respectively greater than A, C, which indicates that the centers of the light beams are in the left half plane, i.e., the areas of B and D, and the signals of A, B are respectively greater than C, D, which indicates that the centers of the light beams are in the upper half plane, i.e., the areas of a and B, and the positions of the centers of the light beams in the quadrant B can be known by combining the above information. Meanwhile, the light path is adjusted according to the relative size information of the signals of the four quadrants, the incident angle of the light beam is changed, and finally the A, B, C, D output signals are the same, so that the center of the light beam is positioned at the center of the four-quadrant photodetector and does not deflect to any quadrant, which is the basic principle of the QPD detection position. The QPD employs a four-quadrant photodetector, and determines the center position of the light beam by comparing the outputs of several quadrants, and the positional information accuracy is very high, better than micron-scale.
The invention uses a pair of QPDs placed at different positions in the optical path, and adjusts the light beam to make the light beam center on the pair of QPDs coincide with the center position of the QPD, and determines a straight line according to the principle of two points, wherein the direction of the light beam is the straight line determined by the center positions of the pair of QPDs. In practical applications, a part of the light is extracted by reflection through a prism or a reflector for detection, and a central straight line of the light beam is determined by a connecting line of central points of a mirror image of the QPD relative to the incident reflection surface of the light beam.
By using the auxiliary adjusting device in the invention, the light beam transmission central lines of the left and right two beams of captured light of the double-beam light trap are respectively adjusted to be superposed with the central point of the QPD by adjusting the light path, so that the superposition of the propagation directions of the superposed two captured light beams can be realized, and the adjustment of the angle and the dislocation of the two captured light beams can be realized. Which is the main working principle of the present invention.
In the invention, the angle and the position of the optical path are adjusted according to the signal detected by QPD, and the function can be realized by a displacement table and an angle adjusting bracket. The adopted adjusting bracket at least needs to satisfy the angle adjustment of 2 orthogonal directions and the position adjustment of 2 directions. As a typical example, a six-degree-of-freedom stage or frame may be used, with which the plane mirror fixed thereto is adjusted, thereby achieving adjustment of the angle/displacement.
The invention has the beneficial effects that:
the invention provides a method for realizing alignment light path adjustment of double light beams of an optical trap by using an optical auxiliary adjusting device composed of optical devices such as a triangular prism and the like for the first time.
The method utilizes the precision position detection performance of QPD, replaces subjective observation and judgment of people, is accurate and reliable, has high repeatability, can adjust the relative direction and position of the double beams of the double-beam optical trap at high precision, is favorable for obtaining the high-performance optical trap, improves the capturing effect of micro-nano balls, and is favorable for technical development and application of the optical suspension system in the precision measurement field and other scientific research fields.
Drawings
FIG. 1 is a schematic diagram of the arrangement of the detection photosensitive surfaces of a four-quadrant photodetector;
FIG. 2 is a schematic diagram of a dual beam optical trap;
FIG. 3 is a diagram of an optical path assisted adjustment mechanism for a dual beam optical trap;
FIG. 4 is a schematic diagram of left beam angle and direction adjustment using the optical path adjustment device;
fig. 5 is a schematic diagram of right beam angle and direction adjustment using the optical path adjusting device.
In the figure: the device comprises triangular prisms (1, 2), a plane mirror (3), a pair of four-quadrant position detectors QPD (4, 5) and an adjusting mechanism (6).
Detailed Description
The invention is further illustrated by the following examples in conjunction with the accompanying drawings:
fig. 2 is a schematic diagram of a dual-beam optical trap, which mainly includes two lenses L1 and L2, and two parallel lights incident from left to right. Two parallel beams of light are generally output by the same laser in two perpendicular polarization states, and a typical laser is a 1064nm laser. The focal points of the two lenses L1 and L2 are superposed, and two beams of flat light which enter from left to right are respectively focused on the focal point position of the center, so that an optical trap region is formed at the focal point, the center of the optical trap is a stable point, and the optical trap region has the functions of capturing and suspending micro-nano balls positioned in the optical trap region. After the micro-nano small ball is captured, the micro-nano small ball is supported by the optical force of a light trap and is not mechanically supported in the environment, and the interference of the micro-nano small ball by air can be further eliminated by pumping vacuum, so that the small ball and the environment are isolated, and a high-performance research platform can be provided for the field of precision measurement. As shown in fig. 2, the two light beams are reflected by respective lenses L1 and L2 and then incident on the same spot in a parallel and opposite manner to form a light trap, and a small ball (blue circle) is captured by the light trap. The black dotted line in the figure indicates the beam center position and the transmission direction of the left and right two light beams.
When the micro-nano ball leaves the capture center, two optical trap forces of scattering force and gradient force are applied to the captured micro-nano ball in the laser capture optical trap, and the resultant direction of the scattering force and the gradient force points to the center of the optical trap, so that when the micro-ball deviates from the optical trap, the optical trap pulls the micro-nano ball back to the center of the optical trap. Wherein the scattering force is a force generated by the micro-nano spheres deviating from the center in the horizontal direction (laser incidence direction), and the gradient force is a force generated by the micro-nano spheres deviating from the center in the vertical direction. The scattering and gradient forces behave like springs in physics.
Under the theoretical assumption, the optical path system of the optical trap is adjusted to ensure that the focal points of the left and right beams are superposed, the transmission directions are parallel, the beams are transmitted in opposite directions, the power centers of the two beams are mutually overlapped, the lowest potential energy point in the optical trap, namely the stable point, is at the center of the optical trap, and the scattering force and the gradient force field to the captured small ball are symmetrically distributed, so that the small ball is in the most stable state. At the moment, the micro-nano balls which are captured and suspended are utilized to realize the precise measurement of various physical quantities, and the highest measurement precision can be obtained.
However, in the actual optical path adjustment process, the adjustment condition of the optical path is judged by using a color card to observe through naked eyes, the angles of two beams of incident light are adjusted, and the parallelism and the staggering degree of two opposite beams of light are judged by people. The precision of the light path adjustment depends on the judgment of people, the consistency is poor, the precision is not high, the efficiency is low, and the problems that two opposite light beams have a certain included angle in actual adjustment or the central lines of the two light beams are parallel to each other, but the two light beams are staggered in space and the focuses are not coincident are easily caused. Under the condition, the goodness of fit of light intensity distribution and theoretical distribution in the optical trap is influenced, and further the scattering force and gradient force distribution of the optical trap are influenced, so that the stability of the capturing performance of the optical trap on the small ball is reduced, the reliability is reduced, and under the extreme condition, a plurality of stable points exist in the optical trap, so that the stable point of the small ball cannot be accurately determined, and the application performance of the optical suspension system is influenced.
As shown in fig. 2, the dual-beam optical trap includes two left and right beams, which are reflected by the respective adjusting mechanisms 6 and then enter the same position in a coaxial parallel and opposite manner to form the optical trap.
As shown in fig. 3, the device can be used to assist in accurately adjusting the transmission directions of two beams of the dual-beam optical trap, and improve the beam alignment and adjustment accuracy.
As shown in fig. 3, the beam assisted alignment device is arranged at the center of the optical trap during use and comprises a pair of right-angle prisms 1 and 2 with identical shapes and sizes, a plane mirror 3 and a pair of four-quadrant position detectors 4 and 5; the sections of the right-angle prisms 1 and 2 are right-angle isosceles triangles, namely the base angles of the triangles are 45 degrees, the right-angle prisms 1 and 2 are completely attached to each other by the plane of the right-angle side of one side of each right-angle prism 1 and 2, and are arranged in parallel by the plane of the right-angle side of the other side of each right-angle prism to form a parallelogram prism, the plane reflector 3 is horizontally arranged, the reflecting surface is upward, one of the planes of the right-angle sides of the right-angle prisms 1 and 2 is fixedly attached to one half side of the plane reflector 3, and the planes of the hypotenuses of the right-angle prisms 1 and 2 are plated with semi-transparent and semi-reflective films and are; the pair of four-quadrant position detectors 4 and 5 are horizontally arranged on the same plane and arranged above the plane mirror 3 and the pair of right-angle prisms 1 and 2, and the two four-quadrant position detectors of the pair of four-quadrant position detectors QPD4 and 5 are respectively positioned right above the two right-angle prisms of the pair of right-angle prisms 1 and 2.
In the specific implementation, the planes of the right-angle sides of a pair of right- angle prisms 1 and 2 are mutually adhered to form a parallelogram prism; and then the plane of the other right-angle side of one right- angle prism 1, 2 of the parallelogram prism is adhered to the plane reflector and is adhered to the half part of one side, so that the two right-angle prisms and the plane reflector are fixedly connected into a whole to be manufactured into a whole. The optical transparent adhesive can be used in the adhesion, and the transmission and reflection of light are not influenced.
The sensitive surfaces of the pair of four- quadrant position detectors 4 and 5 are perpendicular to the plane where the two right-angle sides of the pair of right- angle prisms 1 and 2 are connected in a close fit manner, the sensitive surfaces of the pair of four- quadrant position detectors 4 and 5 are respectively corresponding to the right above the plane where the two right-angle sides of the pair of right- angle prisms 1 and 2 are parallel to each other, and the sensitive surfaces receive light beams which are reflected by the plane where the hypotenuses of the right- angle prisms 1 and 2 pass through and then are turned over.
Each four- quadrant position detector 4, 5 is positioned such that the incident light beam is completely on its sensitive surface, otherwise the up-down position of the four- quadrant position detector 4, 5 is adjusted until the sensitive surface of the four- quadrant position detector 4, 5 can accommodate the entire incident light beam detection. And meanwhile, the distance between the four-quadrant position detector and the right-angle prism is also adjusted, and the size of an incident light beam range of the four-quadrant position detector is smaller than that of a QPD photosensitive surface.
For the left light beam, the light beam enters the adjusting mechanism 6 to be reflected, and then is directly reflected to the sensitive surfaces of the pair of four- quadrant position detectors 4 and 5 through the planes of two bevel edges of the pair of right- angle prisms 1 and 2 respectively;
for the right light beam, the light beam enters the adjusting mechanism 6 to be reflected, then is respectively reflected to the plane reflecting mirror 3 through the planes where the two hypotenuses of the pair of right- angle prisms 1 and 2 are located, and then is reflected by the plane reflecting mirror 3, then is respectively transmitted by the pair of right- angle prisms 1 and 2 and then enters the sensitive surfaces of the pair of four- quadrant position detectors 4 and 5.
In the process of adjusting the light path, the auxiliary adjusting device is horizontally placed in the double-beam light trap and removed after the adjustment is finished. Adjusting the device and making the left captured light beam enter from the oblique side of the triangular prism 1, respectively irradiating the two quadrant photoelectric position detectors QPD1 and QPD2 through the oblique side reflection of the two triangular prisms, and roughly adjusting the angle of the incident light beam to make the light beam converge on the range of the photosensitive surface of the QPD1 and QPD 2; the captured light on the right enters from the oblique sides of the triangular prisms 2, is reflected by the oblique sides of the two triangular prisms respectively, then irradiates two quadrant photoelectric position detectors QPD1 and QPD2 through secondary reflection of a plane mirror, and is converged within the range of the photosensitive surfaces of the QPDs 1 and QPD2 by roughly adjusting the angle of the incident light beam on the right.
Fig. 4 is a schematic diagram of left beam angle and direction adjustment using the optical path adjusting means. The black and dashed arrows in the figure indicate the direction of transmission of the incident beam at the beam center before and after modulation, respectively. The incident light is incident into the light trap through a plane mirror fixed on the adjusting mechanism. The adjustment and translation of the spatial angle of the light beam incident into the optical trap are realized by utilizing the three-dimensional adjustment function of an adjusting mechanism such as a six-degree-of-freedom adjusting platform.
In the figure, the dotted line indicates the case when the adjusting mechanism is at the position P1, in which case the light beam incident into the light trap has a certain angular deviation in the paper surface, and in this case, the light beam is transmitted to the inclined surface of the triangular prism 1, then is partially reflected on the transflective film on the inclined surface, and is irradiated on the QPD1, and the light beam on the QPD1 is shown as a dotted circle; meanwhile, the light beams are partially transmitted on the transflective film, transmitted to the inclined plane of the triangular prism 2 through the light-transmitting adhesion surfaces of the two triangular prisms, and reflected to the QPD2 through the transflective film thereon, wherein the light beams on the QPD2 are shown as a dashed box. From the operating principles of QPD1 and QPD2, the transmitted light beam entering the optical trap has angular deviation, and at this time, the four quadrants of QPD1 and QPD2 change, and the signal can accurately reflect the angular deviation. As can be seen, the center is located in the B, D quadrant, so that the deviation of light can be known by analyzing the currents in the A, B, C, D quadrants of the two QPDs, thereby providing adjustment information for the adjustment mechanism to adjust the direction of incident light.
If the deflection direction of the incident beam is not in the plane of the paper but deviates from the paper around the paper, then the center of the beams obtained by the two QPDs changes up and down, and the center of the beam is in A, B quadrant or C, D quadrant according to the positive and negative of the angle with the paper, so that the included angle with the paper can be determined according to the signal magnitude in A, B quadrant and C, D quadrant, and the angle adjustment is performed by using the adjusting mechanism, which is similar to the nature shown in the figure.
By reading the four quadrant signal of A, B, C, D in QPD, as shown by A1、B1、C1、D1And A2、B2、C2、D2The angle and deviation of the incident light can be adjusted according to the adjusting mechanism. As shown in P2 in the figure, the angle of the incident light beam entering the optical trap region is adjusted by the adjustment function of the adjustment mechanism, so that the direction of the input light is changed from the dotted line direction to the solid line direction, before the optical path propagation path is adjusted similarly, the incident light beam is reflected on the inclined planes of the two triangular prisms and enters the QPD1 and QPD2, respectively, and when the angle and the deviation are adjusted to zero, the illumination region on the QPD is evenly distributed on the A, B, C, D quadrants, and the four quadrant signal outputs are the same, for QPD1, QPD2 means a1、B1、C1、D1The signals are identical, A2、B2、C2、D2The same is true for the signal. The beam center of the beam input is thus determined to be at the center of QPD1 and QPD2, the direction of the input beam at that time being uniquely determined by the center of QPD1 and QPD 2.
Fig. 5 is a schematic diagram of right beam angle and direction adjustment using a path adjustment device. The black and dashed arrows in the figure indicate the direction of travel of the incident beam at the beam center before and after adjustment, respectively. The incident light is incident into the light trap through a plane mirror fixed on the adjusting mechanism. The adjustment and translation of the spatial angle of the light beam incident into the light trap are realized by utilizing the three-dimensional adjustment function of the adjustment mechanism.
In the figure, the solid arrow indicates the case when the adjusting mechanism is at the position P3, in which the light beam incident into the light trap has a certain angle error on the paper surface, in this case, the light beam is transmitted to the inclined surface of the triangular prism 2, then is partially reflected on the transflective film on the inclined surface, and is reflected by the plane mirror and then irradiates on the QPD2, and the light beam on the QPD2 is as indicated by the solid circle on the QPD; meanwhile, the light beams are partially projected on the semi-reflective and semi-transparent film of the triangular prism 2, transmitted to the inclined plane of the triangular prism 1 through the light-transmitting adhesion surfaces of the two triangular prisms, reflected by the semi-reflective and semi-transparent film on the triangular prism, and transmitted to the QPD1 through the reflection of the plane mirror, and the light beams on the QPD1 are shown as a real-time wire frame. From the signals of the QPDs 1 and 2, if there is an angular deviation of the transmitted light, the signals of the QPDs 1 and 2 can accurately respond, as can be seen from the figure, the center of the signal is located in the B, D quadrant, so that the deviation of the light can be known according to the currents of the A, B, C, D four quadrants.
By reading the four quadrant signal of A, B, C, D in QPD, as shown by A1、B1、C1、D1And A2、B2、C2、D2The angle and deviation of the incident light can be adjusted according to the adjusting mechanism. As shown in the figure, the deflection of incident light causes A, B, C, D signals output by four quadrants on two QPDs to have different magnitudes, and according to the relative magnitudes of the signals of the four quadrants on the two QPDs, the incident light path angle and position of the light beam input to the optical trap are adjusted by the adjusting mechanism until the irradiation area on the QPD is evenly distributed on A, B, C, D four quadrants, at which time the four quadrant signals output are the same, and for QPD1, QPD2 means A1、B1、C1、D1The signals are identical, A2、B2、C2、D2The signal is also oneAnd (5) sampling. The beam center of the beam input is thus determined to be at the center of QPD1 and QPD2, the direction of the input beam being uniquely determined by the centers of QPD1 and QPD 2.
The adjustment process is practically similar to that in the left optical path, and the light beam in the right beam adjustment needs to pass through the primary reflection of the plane mirror before reaching the QPD, and the reflection does not affect the QPD under the premise of adopting a 45-degree triangular prism.
And it can be proved that in this case, in the case where the adjustment is performed so that the centers of the two beams on the upper surface of the QPD and the two QPD centers coincide with each other, after the adjustment device is removed, the beam transmission directions of the two beams are opposite, and the optical paths coincide with each other, thereby achieving the intended target.
Therefore, the device and the method are simple and sensitive in alignment, can effectively assist optical adjustment of the optical trap light beam, improve the performance of the optical trap, and provide an efficient, quick and convenient consistent adjustment scheme for an optical power suspension system taking the optical trap as a core component.
Claims (6)
1. The utility model provides a dual beam optical trap light beam assists aligning device, dual beam optical trap include two light beams about, two light beams incide same department with coaxial parallel and opposite direction mode formation optical trap after the respective guiding mechanism (6) reflection respectively which characterized in that: when in use, the beam auxiliary alignment device is arranged at the center of the optical trap and comprises a pair of right-angle prisms (1, 2) with identical shapes and sizes, a plane mirror (3) and a pair of four-quadrant position detectors (4, 5); the cross sections of the right-angle prisms (1 and 2) are right-angle isosceles triangles, the planes of the right-angle sides on one side of the right-angle prisms (1 and 2) are completely attached and connected, the planes of the right-angle sides on the other side of the right-angle prisms are arranged in parallel to form a parallelogram prism, the plane reflector (3) is horizontally arranged, the reflecting surface faces upwards, one of the planes of the right-angle sides on the other side of the right-angle prisms (1 and 2) is fixedly attached and arranged on one half side of the plane reflector (3), and the plane of the hypotenuse of the right-angle prisms (1 and 2) is plated with a semi-transparent and semi-reflective film; a pair of four-quadrant position detectors (4 and 5) are horizontally arranged on the same plane and are arranged above a plane reflector (3) and a pair of right-angle prisms (1 and 2), the sensitive surfaces of the pair of four-quadrant position detectors (4 and 5) are vertical to the plane where two right-angle sides of the pair of right-angle prisms (1 and 2) are connected in a close contact manner, and the transmission center lines of two light beams are coincided with the straight lines determined by the centers of the four-quadrant position detectors (4 and 5) respectively, so that the angle adjustment and the dislocation adjustment of the two light beams are realized; for the left light beam, the light beam enters the adjusting mechanism (6) to be reflected, and then is directly reflected to the sensitive surfaces of the four-quadrant position detectors (4 and 5) through the planes of two bevel edges of the right-angle prisms (1 and 2) respectively; for the right light beam, the light beam enters the adjusting mechanism (6) to be reflected, the light beam is reflected by the planes where the two hypotenuses of the pair of right-angle prisms (1 and 2) are located and then reflected to the plane reflecting mirror (3), and the light beam is reflected by the plane reflecting mirror (3), then transmitted by the pair of right-angle prisms (1 and 2) and enters the sensitive surfaces of the pair of four-quadrant position detectors (4 and 5).
2. The dual-beam optical trap beam assist alignment device of claim 1, wherein:
the sensitive surfaces of the pair of four-quadrant position detectors (4 and 5) are respectively and correspondingly arranged right above the plane where the two mutually parallel right-angle sides of the pair of right-angle prisms (1 and 2) are positioned, and the sensitive surfaces receive light beams which are reflected by the plane where the oblique sides of the parallel incident light beams of the right-angle prisms (1 and 2) are positioned and then are turned.
3. The dual-beam optical trap beam assist alignment device of claim 1, wherein:
each four-quadrant position detector (4, 5) is positioned such that the beam incident on itself is entirely on its sensitive surface.
4. The dual-beam optical trap beam assist alignment device of claim 1, wherein:
the adjusting mechanism (6) is a moving platform provided with an incidence reflector.
5. The dual-beam optical trap beam-assisted alignment method applied to the device of claim 1, characterized in that: using the apparatus of claim 1, the apparatus is placed in parallel into the optical trap path and fixed;
the optical path is adjusted as follows:
firstly, adjusting a left light path:
closing the right light beam or blocking the right light beam to enable only the left light beam to be incident into the light trap, reflecting the left light beam incident into the adjusting mechanism (6), and directly reflecting the left light beam to the sensitive surfaces of the pair of four-quadrant position detectors (4 and 5) through planes where two bevel edges of the pair of right-angle prisms (1 and 2) are located respectively after reflection;
the pair of four-quadrant position detectors (4 and 5) convert light beams incident on four quadrants of the respective photosensitive surfaces into electric signals, the central positions of the light beams are obtained according to the sizes of the electric signals of the four quadrants, and then the pitch angle, the roll angle and the horizontal position posture of an incident plane mirror of the adjusting mechanism (6) of the left light beam are adjusted, so that the light beams incident on the pair of four-quadrant position detectors (4 and 5) of the left light beam are converged to the centers of the four quadrants of the photosensitive surfaces, and the sizes of the electric signals output by the respective four quadrants of the photosensitive surfaces of the pair of four-quadrant position detectors (4 and 5) are the same;
then adjust the right side light path:
closing the left light beam or blocking the left light beam to enable only the right light beam to be incident in the light trap, enabling the right light beam to be incident on an incident plane mirror of the adjusting mechanism (6) to be reflected, respectively reflecting the planes where two bevel edges of the pair of right-angle prisms (1 and 2) are located to the plane reflecting mirror (3) after reflection, respectively transmitting the planes through the pair of right-angle prisms (1 and 2) after reflection by the plane reflecting mirror (3), and then incident on the sensitive surfaces of the pair of four-quadrant position detectors (4 and 5);
the pair of four-quadrant position detectors (4 and 5) convert light beams incident on four quadrants of the respective photosensitive surfaces into electric signals, the central positions of the light beams are obtained according to the sizes of the electric signals of the four quadrants, and then the pitch angle, the roll angle and the horizontal position posture of an incident plane mirror of the adjusting mechanism (6) of the right light beam are adjusted, so that the light beams incident on the pair of four-quadrant position detectors (4 and 5) of the right light beam are converged to the centers of the four quadrants of the photosensitive surfaces, and the sizes of the electric signals output by the respective four quadrants of the photosensitive surfaces of the pair of four-quadrant position detectors (4 and 5) are the same;
after light path adjustment, under the condition that the light beams on the left side and the right side are respectively closed, the centers of the light beams are converged to the centers of the two four-quadrant position detectors (4 and 5), at the moment, the device is removed, the light beams on the left side and the right side are simultaneously opened, at the moment, the central lines of the two light beams are superposed, the propagation directions are opposite and parallel, and a double-light-beam light trap area is formed at the middle position.
6. The dual-beam optical trap beam assist alignment method of claim 5, wherein:
the four-quadrant position detectors (4 and 5) are fixed in position.
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| CN101598741A (en) * | 2009-07-27 | 2009-12-09 | 浙江大学 | Utilize the four-beam fiber-optic trap device for measuring acceleration |
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