JP2014197633A - Laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To output light beams which have a plurality of slightly different wavelengths only by mounting one solid-state laser element.SOLUTION: A laser device includes: a wavelength converting element 4 which refracts a fundamental wave output from a solid-state laser element 3 double so as to reduce light with a wavelength of 1,047 nm as a fundamental wave more as the light with the wavelength of 1,047 nm has larger intensity; and a wavelength converting element 5 which reduces light with a wavelength of 1,053 nm as a fundamental wave more as the light with the wavelength of 1,053 nm has larger intensity. The solid-state laser element 3 has an "a" axis and a "c" axis in a plane perpendicular to an optical axis, and the "a" axis and "c" axis of the solid-state laser element 3 and "a" axes and "c" axes of the wavelength converting elements 4, 5 are inclined.

Description

  The present invention relates to a laser device used for a light source such as a projector device.

For example, in a device that displays a color image, such as a projector device or a projection television, three colors R (red), G (green), and B (blue) are required as light sources.
In recent years, as these light sources, laser light in the 900 nm band, 1 μm band, and 1.3 μm band is oscillated as fundamental laser light, and a nonlinear material is used to convert the fundamental laser light to second harmonic conversion (SHG: Second). A wavelength conversion laser device (laser oscillator) for converting into Harmonic Generation) light has been developed.

For example, Patent Document 1 below discloses a wavelength conversion laser device including a semiconductor laser element, a solid-state laser element, and a wavelength conversion element.
In this wavelength conversion laser device, when the semiconductor laser element oscillates the excitation light, the solid-state laser element generates the fundamental wave by absorbing the excitation light oscillated from the semiconductor laser element, and the wavelength conversion element is generated from the solid-state laser element. The wavelength of the generated fundamental wave is converted to generate a second harmonic of the fundamental wave.

When a solid-state laser element is used as a laser medium for generating a fundamental wave as in this wavelength conversion laser device, the wavelength spectrum width of the fundamental wave becomes very narrow, and therefore the wavelength of the second harmonic of the fundamental wave. The spectral width is also very narrow.
This feature means that coherency is high and has various merits, but when used for a light source such as a display, there is a demerit that speckle noise increases due to strong interference.
As one method for reducing speckle noise, there is a method for reducing coherency by mixing light of a plurality of wavelengths.
In order to obtain light of a plurality of wavelengths with the laser device as described above, it is only necessary to generate fundamental waves of a plurality of wavelengths and convert the wavelengths of the respective fundamental waves.

FIG. 6 is a block diagram showing a conventional wavelength conversion laser device.
In FIG. 6, a semiconductor laser 101 is a light source that oscillates excitation light, and a lens 102 is an optical component that condenses the excitation light oscillated by the semiconductor laser 101 onto a solid-state laser element 103.
The solid-state laser element 103 is a laser medium that absorbs the excitation light collected by the lens 102 and generates laser light having a wavelength A that is a fundamental wave, and the solid-state laser element 104 absorbs the excitation light and emits a fundamental wave. This is a laser medium that generates a laser beam having the wavelength B.
The wavelength conversion element 105 is an optical component that performs wavelength conversion of the laser beams having the wavelengths A and B generated by the solid-state laser elements 103 and 104 and outputs two wavelength conversion lights.
The wavelength conversion laser apparatus of FIG. 6 is an apparatus that outputs two wavelength-converted lights, but the same apparatus is also disclosed in Patent Document 2 below.

Thus, if two solid-state laser elements 103 and 104 are mounted as laser media, two wavelength-converted lights can be output, so that speckle noise can be reduced.
Here, as a countermeasure against speckle of the green light source, when considering a plurality of wavelengths, it is necessary to extract a plurality of slightly different wavelengths around 532 nm which is green. Therefore, it is necessary to prepare a material that oscillates light having a plurality of slightly different wavelengths near 1064 nm as a laser medium that generates a fundamental wave.
However, there is almost no laser medium that oscillates light having a wavelength near 1064 nm, except for Nd: YVO4. In reality, it is not possible to oscillate light having a plurality of wavelengths slightly different near 1064 nm. Have difficulty.

WO2006 / 103767 pamphlet JP 2006-66436 A (FIG. 1)

  Since the conventional laser device is configured as described above, if two solid-state laser elements are mounted as a laser medium, two wavelength-converted lights can be output, but two solid-state laser elements are mounted. As a result, there is a problem in that the apparatus is increased in size and cost.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a laser device that can output light having a plurality of slightly different wavelengths by mounting only one solid-state laser element. And

  The laser device according to the present invention includes a semiconductor laser that oscillates excitation light, a first optical axis that has a gain with respect to light of a first wavelength, and a second that has a gain with respect to light of a second wavelength. It is composed of a crystal having an optical axis, and enters excitation light oscillated by a semiconductor laser from one end face, absorbs the excitation light, and outputs light of the first and second wavelengths from the other end face. The solid laser element has one end face facing the other end face of the solid laser element, and the light output from the other end face of the solid laser element is birefringent so that the intensity of the light of the first wavelength increases. The first optical element for reducing the light of the first wavelength, and one end face thereof faces the other end face of the first optical element, and the light output from the other end face of the first optical element The higher the intensity of light of the second wavelength by birefringence, A second optical element that reduces light of the second wavelength, a first reflecting mirror that is disposed on one end face side of the solid-state laser element and reflects light of the first and second wavelengths, A second reflecting mirror that is disposed on the other end face side of the optical element and reflects light of the first and second wavelengths, and the optical axis of the solid-state laser element is in a plane perpendicular to the optical axis, The optical axis and the optical axis of the first and second optical elements are inclined.

  According to the present invention, the first optical element that birefringes the light output from the solid-state laser element and decreases the light of the first wavelength as the intensity of the light of the first wavelength is increased. And a second optical element that decreases the light of the second wavelength as the intensity of the light of the second wavelength is increased by birefringing the light output from the optical element, and the optical axis in the solid-state laser element Is in a plane perpendicular to the optical axis, and the optical axis and the optical axis of the first and second optical elements are inclined, so only by mounting one solid-state laser element, There is an effect that light having a plurality of slightly different wavelengths can be output.

It is a top view which shows the structure of the laser apparatus by Embodiment 1 of this invention. It is a perspective view which shows the principle of operation of the laser apparatus by Embodiment 1 of this invention. It is a top view which shows the structure of the laser apparatus by Embodiment 2 of this invention. It is a perspective view which shows the principle of operation of the laser apparatus by Embodiment 2 of this invention. It is a top view which shows the structure of the laser apparatus by Embodiment 3 of this invention. It is a block diagram which shows the conventional wavelength conversion laser apparatus.

Embodiment 1 FIG.
FIG. 1 is a top view showing a configuration of a laser apparatus according to Embodiment 1 of the present invention, and FIG. 2 is a perspective view showing an operation principle of the laser apparatus according to Embodiment 1 of the present invention.
1 and 2, a semiconductor laser 1 is a light source that oscillates excitation light.
The lens 2 is an optical component that focuses the excitation light oscillated by the semiconductor laser 1 onto the solid-state laser element 3.

For example, the solid-state laser element 3 has a gain for the a-axis (first optical axis) having a gain with respect to light having a wavelength of 1047 nm (first wavelength) and the light having a wavelength of 1053 nm (second wavelength). It is composed of a crystal having a c-axis (second optical axis) and has excitation light collected by the lens 2 from one end face 3a, absorbs the excitation light, and is a fundamental wave. The laser medium outputs light having a wavelength of 1047 nm and light having a wavelength of 1053 nm from the other end face 3b.
As a material of the solid-state laser element 3, for example, a YLF material (Nd: YLF) to which Nd is added can be used.
This Nd: YLF material is characterized in that the gain peak wavelength in the a-axis direction of the crystal axis is around 1047 nm and the gain peak wavelength in the c-axis direction of the crystal axis is around 1053 nm.
In the example of FIG. 1, the wavelength of the excitation light oscillated from the semiconductor laser 1 is around 792 nm so that the Nd: YLF material that is the solid-state laser element 3 can be excited.

The wavelength conversion element 4 has one end face 4 a facing the other end face 3 b of the solid-state laser element 3, and birefringes the fundamental wave output from the end face 3 b of the solid-state laser element 3, so that the fundamental wave having a wavelength of 1047 nm is obtained. This is a first optical element that reduces light having a wavelength of 1047 nm as the intensity of light increases.
That is, since the wavelength conversion element 4 is formed of polarization inversion using, for example, LiNbO3 to which MgO is added (the polarization direction of polarization inversion is perpendicular to the paper surface of FIG. 1), the wavelength conversion element 4 has a wavelength of 1047 nm. The light is converted into SHG light (second harmonic light).
The c-axis that is the optical axis of the wavelength conversion element 4 is arranged so as to be perpendicular to the paper surface of FIG. 1, and the c-axis that is the optical axis of the solid-state laser element 3 is the same as the paper surface of FIG. Since they are arranged at an angle of 45 ° with respect to the horizontal plane, the c-axis of the wavelength conversion element 4 and the c-axis of the solid-state laser element 3 have an inclination of 45 °.
Here, an example in which the material of the wavelength conversion element 4 is LiNbO3 to which MgO is added is shown, but this is only an example, and for example, LiTaO3 to which MgO is added may be used.

One end face 5a of the wavelength conversion element 5 faces the other end face 4b of the wavelength conversion element 4, and the fundamental wave output from the end face 4b of the wavelength conversion element 4 is birefringent to generate a fundamental wave having a wavelength of 1053 nm. The second optical element reduces the light having a wavelength of 1053 nm as the intensity of light increases.
That is, since the wavelength conversion element 5 is formed of polarization inversion using, for example, LiNbO3 to which MgO is added (the polarization direction of polarization inversion is perpendicular to the paper surface of FIG. 1), the wavelength conversion element 5 has a wavelength of 1053 nm. The light is converted into SHG light (second harmonic light).
The c-axis that is the optical axis of the wavelength conversion element 5 is arranged so as to be perpendicular to the paper surface of FIG. 1, and the c-axis that is the optical axis of the solid-state laser element 3 is the same as that of the paper surface of FIG. Since the wavelength conversion element 5 and the solid-state laser element 3 are inclined by 45 ° from the horizontal plane, the c-axis of the wavelength conversion element 5 and the solid laser element 3 have an inclination of 45 °.
Here, an example in which the material of the wavelength conversion element 5 is LiNbO3 to which MgO is added is shown, but this is only an example, and for example, LiTaO3 to which MgO is added may be used.

The reflecting mirror 6 is coated on the end surface 3a of the solid-state laser element 3, and the reflecting mirror 6 transmits the excitation light (Nd: excitation light having an YLF excitation wavelength) oscillated by the semiconductor laser 1, while having a wavelength that is a fundamental wave. It is an optical component having a characteristic of reflecting light of 1047 nm and a wavelength of 1053 nm. The reflecting mirror 6 constitutes a first reflecting mirror.
The reflecting mirror 7 is coated on the end face 3b of the solid-state laser element 3, and the reflecting mirror 7 transmits the light having the fundamental wavelength of 1047 nm and the wavelength of 1053 nm, while passing the excitation light (Nd: excitation light having the YLF excitation wavelength). It is an optical component having the property of reflecting.

The reflecting mirror 8 is coated on the end face 4a of the wavelength conversion element 4, and the reflecting mirror 8 transmits light having a wavelength of 1047 nm and a wavelength of 1053 nm that are fundamental waves, and reflects SHG light that is light of the second harmonic. It is an optical component having characteristics.
The light transmissive component 9 is coated on the end face 4b of the wavelength conversion element 4, and the light transmissive component 9 has a characteristic of transmitting light having a fundamental wavelength of 1047 nm, light having a wavelength of 1053 nm, and SHG light having a second harmonic. It is an optical component.

The light transmissive component 10 is coated on the end face 5a of the wavelength conversion element 5, and the light transmissive component 10 has a characteristic of transmitting light having a fundamental wavelength of 1047 nm, light having a wavelength of 1053 nm, and SHG light having a second harmonic. It is an optical component.
The reflecting mirror 11 is coated on the end face 5b of the wavelength conversion element 5. The reflecting mirror 11 transmits SHG light that is second harmonic light, while reflecting light having wavelengths of 1047 nm and 1053 nm that are fundamental waves. It is an optical component having characteristics. The reflecting mirror 11 constitutes a second reflecting mirror.

Next, the operation will be described.
The lens 2 focuses the excitation light on the solid-state laser element 3 when the semiconductor laser 1 oscillates excitation light having a wavelength of around 792 nm.
The solid-state laser element 3 receives the excitation light condensed by the lens 2 from the end face 3a, absorbs the excitation light, and generates light having a fundamental wavelength of 1047 nm and light having a fundamental wavelength of 1053 nm. Output from the end face 3b.

When the wavelength conversion element 4 receives two fundamental waves outputted from the end face 4b of the solid-state laser element 3 from the end face 4a, the wavelength conversion element 4 birefrings the fundamental wave, and the intensity of light having a fundamental wavelength of 1047 nm increases. , Decrease the light of wavelength 1047 nm.
That is, the wavelength conversion element 4 is arranged so that the c-axis that is the optical axis is perpendicular to the paper surface of FIG. 1, and the polarization is inverted so that SHG light is generated from the light having the wavelength of 1047 nm that is the fundamental wave. Is formed. The polarization direction of the polarization inversion is perpendicular to the paper surface of FIG.
As a result, the wavelength conversion element 4 can perform wavelength conversion on a component in a direction perpendicular to the paper surface of FIG. 1 in the optical electric field of light having a wavelength of 1047 nm, and the wavelength 523. Converted to 5 nm light.

  The end face 4b of the wavelength conversion element 4 is coated with a light transmission component 9, and the end face 5a of the wavelength conversion element 5 is coated with a light transmission component 10, but the light transmission components 9 and 10 have a wavelength that is a fundamental wave. Since it has a characteristic of transmitting light having a wavelength of 523.5 nm which is 1047 nm and wavelength of 1053 nm and SHG light, light having a wavelength of 1047 nm, wavelength of 1053 nm which is a fundamental wave and light having a wavelength of 523.5 nm which is SHG light. Passes through the end face 4 b of the wavelength conversion element 4 and the end face 5 a of the wavelength conversion element 5 and enters the wavelength conversion element 5.

When the wavelength conversion element 5 receives two fundamental waves and SHG light output from the end face 4b of the wavelength conversion element 4 from the end face 5a, the wavelength conversion element 5 birefrings the fundamental wave, and the intensity of light having a wavelength of 1053 nm, which is the fundamental wave. Is larger, the light having a wavelength of 1053 nm is decreased.
That is, the wavelength conversion element 5 is arranged so that the c-axis, which is an optical axis, is perpendicular to the paper surface of FIG. 1, and the polarization is inverted so that SHG light is generated from light having a wavelength of 1053 nm, which is the fundamental wave. Is formed. The polarization direction of the polarization inversion is perpendicular to the paper surface of FIG.
As a result, the wavelength conversion element 5 can convert the wavelength of the component in the direction perpendicular to the paper surface of FIG. 1 in the optical electric field of the light having the wavelength of 1053 nm, and the light having the wavelength of 1053 nm is the SHG light. Converted to 5 nm light.

The end face 5b of the wavelength conversion element 5 is coated with a reflecting mirror 11. The reflecting mirror 11 has a characteristic of transmitting SHG light and reflecting light having wavelengths of 1047 nm and 1053 nm, which are fundamental waves. Therefore, the light having a wavelength of 523.5 nm which is SHG light converted by the wavelength conversion element 4 and the light having a wavelength of 526.5 nm which is SHG light converted by the wavelength conversion element 5 are the end face 5b of the wavelength conversion element 5. Is transmitted to the outside.
Note that light having a wavelength of 1047 nm and a wavelength of 1053 nm, which are fundamental waves, are reflected by the end face 5 b of the wavelength conversion element 5, and thus return to the wavelength conversion element 4.

The laser apparatus of FIG. 1 is characterized in that the c-axis of the solid-state laser element 3 is disposed with an inclination of 45 ° from the horizontal plane of the paper of FIG. 1 with the optical axis that is the traveling direction of the fundamental wave as the center ( (See FIG. 2).
Although FIG. 1 shows an example in which the tilt angle is 45 °, two fundamental waves (lights having a wavelength of 1047 nm and a wavelength of 1053 nm) have an electric field component whose wavelength is converted by the wavelength conversion elements 4 and 5. As long as the angle becomes, it can be tilted any number of times. When an Nd: YLF material is used as the material of the solid-state laser element 3, the tilt angle may be tilted to an angle other than n × 90 ° (n: integer).

Hereinafter, the principle of wavelength conversion by the wavelength conversion elements 4 and 5 will be described.
When the intensity of the excitation light oscillated from the semiconductor laser 1 is increased, the active ions in the solid-state laser element 3 are excited and an inversion distribution is formed.
As a result, the fundamental wave having a wavelength of 1047 nm having a high gain travels in the solid-state laser element 3 as linearly polarized light polarized in the a-axis direction of the solid-state laser element 3.
Thereafter, the polarization direction is inclined with respect to the optical axis of the wavelength conversion element 4, and the fundamental wave is incident on the wavelength conversion element 4.
Since LiNbO3 to which MgO, which is the material of the wavelength conversion element 4 is added, has birefringence, the polarization direction of the fundamental wave having a wavelength of 1047 nm rotates while traveling in the wavelength conversion elements 4 and 5.
At this time, the vertical component of the optical electric field of the fundamental wave with a wavelength of 1047 nm contributes to SHG conversion, and is converted into SHG light with a wavelength of 523.5 nm having a photon energy twice that of the light with a wavelength of 1047 nm in the wavelength conversion element 4. Will be.

By the conversion to SHG light, light having a wavelength of 1047 nm, which is a fundamental wave, is reduced (light loss is generated). The conversion efficiency to SHG light increases in proportion to the square of the light intensity of the fundamental wave due to its nonlinearity. This is because the increase in the optical loss increases as the light intensity of the fundamental wave increases. Means.
Therefore, as the intensity of light having a wavelength of 1047 nm increases, the resonator loss of light having a wavelength of 1047 nm increases, and the threshold gain for laser oscillation increases. As a result, the number of excitation ions that give a gain to light having a wavelength of 1047 nm increases, and the number of excitation ions that give a gain to light having a wavelength of 1053 nm that is in thermal equilibrium with the light also increases, so that light having a wavelength of 1053 nm can be oscillated.
At this time, since the gain of light having a wavelength of 1053 nm is generated in the c-axis direction of the solid-state laser element 3, it oscillates as linearly polarized light polarized in the c-axis direction.

The polarization direction of the fundamental wave having a wavelength of 1053 nm is rotated while traveling in the wavelength conversion elements 4 and 5, similarly to the fundamental wave having a wavelength of 1047 nm.
At this time, the vertical component of the optical electric field of the fundamental wave with a wavelength of 1053 nm contributes to SHG conversion, and is converted into SHG light with a wavelength of 526.5 nm having photon energy twice that of the light with wavelength of 1053 nm in the wavelength conversion element 5. Will be.
Also in this case, light loss due to conversion to SHG light occurs by the same mechanism. That is, as the intensity of light having a wavelength of 1053 nm increases, a resonator loss proportional to the square of the light intensity occurs.

As described above, as the light intensity of the fundamental wave of one wavelength increases, the optical loss increases, the gain necessary to oscillate the fundamental wave increases, and the number of ions in the steady state increases. Since the phenomenon that the gain with respect to the other wavelength increases and oscillation becomes easier occurs, the two fundamental waves compete with each other.
The number of upper level ions N1 that gives a threshold gain for light having a wavelength of 1047 nm and the number of upper level ions N2 that gives a threshold gain for light having a wavelength of 1053 nm are determined by the light intensity of each fundamental wave. However, steady oscillation occurs at each light intensity such that the number of upper level ions N1 and the number of upper level ions N2 satisfy the thermal equilibrium condition.

In such a state, as the light intensity of the fundamental wave increases, the optical loss with respect to the fundamental wave increases. That is, the fundamental wave is a fundamental wave such as the solid-state laser element 3 and the wavelength conversion elements 4 and 5. This can only occur in a system that circulates both optical elements that cause optical loss.
Therefore, by a resonator having a solid-state laser element 3 having gains at two different wavelengths and an optical element that gives optical loss such as wavelength conversion for both wavelengths, and a fundamental wave including both elements This can be realized in a configuration that oscillates.

  As is apparent from the above, according to the first embodiment, the fundamental wave output from the solid-state laser element 3 is birefringent, and the intensity of the fundamental wave light having a wavelength of 1047 nm increases. The wavelength conversion element 4 for reducing the wavelength 1053 nm and the wavelength conversion element 5 for reducing the light of the wavelength 1053 nm as the intensity of the fundamental wave having a wavelength of 1053 nm increases by birefringing the fundamental wave output from the wavelength conversion element 4. The a-axis and c-axis of the solid-state laser element 3 are in a plane perpendicular to the optical axis, and the a-axis and c-axis of the solid-state laser element 3 and the a-axis and c-axis of the wavelength conversion elements 4 and 5 are inclined. Since it is configured so that light having a plurality of slightly different wavelengths (SHG light having a wavelength of 523.5 nm and SHG light having a wavelength of 526.5 nm) can be output by mounting only one solid-state laser element 3. The effect that can be Unlikely to.

In the first embodiment, the optical axis of the solid-state laser element 3 is tilted. By tilting the optical axis of the solid-state laser element 3, the wavelength conversion elements 4 and 5 can convert the wavelengths of the two fundamental waves. I have to.
When the optical axis is not inclined, for example, when the a-axis of the solid-state laser element 3 is arranged vertically, the fundamental wave with a wavelength of 1053 nm that oscillates in the c-axis direction of the solid-state laser element 3 has a vertical electric field component. For this reason, the wavelength conversion element 5 does not perform wavelength conversion.
When the wavelength conversion element 5 does not perform wavelength conversion, the optical loss with respect to the fundamental wave with the wavelength of 1053 nm does not increase in proportion to the square of the light intensity, so that the threshold gain of the fundamental wave with the wavelength of 1047 nm does not increase. Oscillation with a fundamental wave of 1047 nm is stopped.
In that case, only a fundamental wave with a wavelength of 1053 nm and light with a wavelength of 526.5 nm, which is the SHG light, can be output. This problem can be solved by rotating the polarized light using the wave plate, but by tilting the optical axis of the solid-state laser element 3 as in the first embodiment, without using the wave plate, Simultaneous oscillation of two fundamental waves can be realized.

In the first embodiment, an example in which a YLF material (Nd: YLF) to which Nd is added is used as the material of the solid-state laser element 3 is described. However, if the material has a plurality of gain wavelengths, Nd: It goes without saying that the same function can be realized even if a material other than YLF is used.
Further, even if the polarization directions having the gain peak are not orthogonal to each other, the competition between the fundamental waves as described above occurs, so that oscillation at a plurality of wavelengths is possible.

In the first embodiment, the wavelength conversion element 4 and the wavelength conversion element 5 are separately manufactured and arranged so that the directions of polarization inversion are the same direction, but one material (LiNbO3 or The wavelength conversion element 4 and the wavelength conversion element 5 may be integrally formed by forming polarization inversions in LiTaO3).
In this way, if the wavelength conversion element 4 and the wavelength conversion element 5 are integrally manufactured at the same time, they can be manufactured inexpensively and easily.

Embodiment 2. FIG.
FIG. 3 is a top view showing a configuration of a laser device according to Embodiment 2 of the present invention, and FIG. 4 is a perspective view showing an operation principle of the laser device according to Embodiment 2 of the present invention.
3 and FIG. 4, the same reference numerals as those in FIG. 1 and FIG.
The wavelength conversion element 20 is an optical element that has one end face 20 a facing the other end face 3 b of the solid-state laser element 3 and birefringes a fundamental wave output from the end face 3 b of the solid-state laser element 3.
That is, the wavelength conversion element 20 is formed of polarization reversal using, for example, LiNbO3 to which MgO is added (the polarization direction of the polarization reversal is perpendicular to the paper surface of FIG. 3). It is divided into areas 23.

The region 21 of the wavelength conversion element 20 is a first optical element that birefringes the fundamental wave output from the end face 3b of the solid-state laser element 3 and reduces the light with a wavelength of 1047 nm as the intensity of the light with a wavelength of 1047 nm increases. Thus, a polarization inversion having a period that generates SHG light from light having a wavelength of 1047 nm is formed.
The region 22 of the wavelength conversion element 20 is a second optical element that birefringes the fundamental wave output from the end face 3b of the solid-state laser element 3 and reduces the light at the wavelength 1053 nm as the intensity of the light at the wavelength 1053 nm increases. Thus, a polarization inversion having a period for generating SHG light from light having a wavelength of 1053 nm is formed.
The region 23 of the wavelength conversion element 20 is a third optical element that reduces the light with the wavelength 1047 nm and the light with the wavelength 1053 nm as the intensity of the light with the wavelength 1047 nm and the light with the wavelength 1053 nm increases. Polarization reversal is generated so as to generate sum frequency conversion (SFG) light.
Although FIG. 3 shows an example in which the region 21, the region 22, and the region 23 are integrally formed, it is needless to say that the region 21, the region 22, and the region 23 may be separately manufactured.

The c-axis, which is the optical axis of the wavelength conversion element 20 (the optical axes of the regions 21, 22 and 23), is disposed so as to be perpendicular to the paper surface of FIG. Since the c-axis, which is the optical axis, is inclined by 45 ° from the horizontal plane of the paper of FIG. 3, the c-axis of the wavelength conversion element 20 and the c-axis of the solid-state laser element 3 are inclined by 45 °.
Here, an example in which the material of the wavelength conversion element 20 is LiNbO3 to which MgO is added is shown, but this is only an example, and for example, LiTaO3 to which MgO is added may be used.

The reflecting mirror 24 is coated on the end face 20a of the solid-state laser element 20, and the reflecting mirror 24 transmits the excitation light (Nd: excitation light having an YLF excitation wavelength) oscillated by the semiconductor laser 1, while having a wavelength that is a fundamental wave. It is an optical component having a characteristic of reflecting light of 1047 nm and a wavelength of 1053 nm. The reflecting mirror 24 constitutes a first reflecting mirror.
The reflecting mirror 25 is coated on the end face 20b of the wavelength conversion element 20, and the reflecting mirror 25 transmits SHG light and SFG light which are second harmonic light, while light having wavelengths of 1047 nm and 1053 nm which are fundamental waves. Is an optical component having a characteristic of reflecting light. The reflecting mirror 25 constitutes a second reflecting mirror.

Also in the case of the second embodiment, a fundamental wave with a wavelength of 1047 nm and a fundamental wave with a wavelength of 1053 nm are generated simultaneously by the same principle as in the first embodiment.
In the region 21 of the wavelength conversion element 20, the vertical component of the optical field of the fundamental wave having a wavelength of 1047 nm is wavelength-converted, and SHG light having a wavelength of 523.5 nm is generated.
In the region 22 of the wavelength conversion element 20, the vertical component of the optical field of the fundamental wave having a wavelength of 1053 nm is wavelength-converted, and SHG light having a wavelength of 526.5 nm is generated.
The fundamental wave having a wavelength of 1047 nm and the fundamental wave having a wavelength of 1053 nm have different wave numbers. However, since the sum frequency conversion portion in the region 23 of the wavelength conversion element 20 has birefringence, the wave number of the wavelength 1047 nm and the wave number of the wavelength 1053 nm. SFG light having a wavelength of 525.0 nm is generated by placing them in a condition where they are equal, that is, in an arrangement that allows phase matching.
At this time, it is the vertical components of the optical fields of the two fundamental waves that contribute to the wavelength conversion to the sum frequency.
Thereby, three wavelength conversion lights (light with a wavelength of 523.5 nm, light with a wavelength of 526.5 nm, light with a wavelength of 525.0 nm) are transmitted through the end face 20b of the wavelength conversion element 20 and output to the outside.

  Here, in the SFG light, for each of the two fundamental waves, a component that matches the polarization inversion direction of the SFG conversion region contributes to the conversion. Therefore, if the configuration as in the second embodiment is adopted, both of the two fundamental waves have components having a polarization direction perpendicular to the paper surface of FIG. 3, so that SFG conversion can be performed with high efficiency. .

In the second embodiment, the polarization inversion directions in the regions 21, 22, and 23 in the wavelength conversion element 20 are all directions perpendicular to the paper surface of FIG. 3, and each wavelength is changed only by changing the period of the polarization inversion. It is possible to provide a conversion function. Therefore, the three regions can be manufactured by a single process, and can be manufactured inexpensively and easily.
However, this does not mean that the two wavelength conversion element portions and the sum frequency conversion element portion must be made of the same material.
Further, even if the arrangement order of the three optical element portions is changed, light that is wavelength-converted with respect to the corresponding fundamental wave is generated, so that it is obvious that the arrangement is not limited to the configuration example of FIG. is there.
In the first and second embodiments, the example in which the optical axis of the solid-state laser element 3 is tilted is shown. However, the same function can be realized even if the optical axis of the wavelength conversion element is tilted. Obviously.

Embodiment 3 FIG.
In the third embodiment, a laser device in which the solid-state laser element 3 and the wavelength conversion element 20 have a waveguide structure will be described.
FIG. 5 is a top view showing a configuration of a laser apparatus according to Embodiment 3 of the present invention. In FIG. 5, the same reference numerals as those in FIGS.
In the third embodiment, the laser device of the second embodiment described above has a waveguide structure. However, the laser device of the first embodiment may have a waveguide structure.

The solid-state laser element 3 of the third embodiment has a waveguide type structure, and Nd: YLF is used as the material of the waveguide 31 through which light propagates.
On the lower and upper surfaces of the waveguide 31, SiO 2 films 32 and 33 having a refractive index smaller than that of the waveguide 31 are formed as cladding layers.
The waveguide thickness is, for example, 100 μm, and the thicknesses of the two cladding layers are, for example, 1 μm. Further, a substrate 34 for holding the waveguide 31 and the SiO 2 films 32 and 33 is bonded to the solid-state laser element 3, and the material of the substrate 34 is a glass material having a thermal expansion coefficient close to that of the waveguide 31. Is used. Further, the thickness of the substrate 34 is set to about 1 mm so that handling is easy.

In front of the waveguide type solid-state laser element 3, a waveguide type wavelength conversion element 20 having the same waveguide structure is disposed.
As a material of the waveguides 41, 42, and 43 of the wavelength conversion element 20, MgO-added LiNbO3 in which polarization inversion is formed is used.
That is, as in the second embodiment, the wavelength conversion element 20 converts the SHG light from the region 21 in which the polarization inversion has been formed so as to generate SHG light from the light having a wavelength of 1047 nm and the light having the wavelength of 1053 nm. A region 22 in which polarization inversion having a period to be generated is formed and a region 23 in which polarization inversion to generate SFG light having a wavelength of 1047 nm and a wavelength of 1053 nm are integrally formed.

The direction of polarization inversion of all the regions 21, 22, and 23 is a direction horizontal to the paper surface of FIG. 5 and the thin plate direction of the waveguides 41, 42, and 43.
On the lower and upper surfaces of the waveguides 41, 42, 43, SiO2 films 44, 45 having a refractive index smaller than that of the waveguides 41, 42, 43 are formed as cladding layers.
The waveguide thickness is, for example, 100 μm, and the thicknesses of the two cladding layers are, for example, 1 μm. Further, a substrate 46 for holding the waveguides 41, 42, 43 and the SiO 2 films 44, 45 is bonded to the wavelength conversion element 20, and the material of the substrate 46 is the waveguides 41, 42, 43 and A glass material having a similar coefficient of thermal expansion is used. Further, the thickness of the substrate 46 is set to about 1 mm so that handling is easy.

  In the case of the third embodiment, similarly to the second embodiment, three wavelength conversion lights (light with a wavelength of 523.5 nm, light with a wavelength of 526.5 nm, and light with a wavelength of 525.0 nm) are converted into a wavelength conversion element. 20 is transmitted through the end face 20b to the outside.

When the shape of the solid-state laser element 3 and the wavelength conversion element 20 is a bulk shape, the vertical component and the horizontal component of the electric field of light traveling inside the element have a correlation, and at the time of wavelength conversion, only the vertical component is converted. Therefore, the polarization state reflected by the end face 20b of the wavelength conversion element 20 and returning to the solid-state laser element 3 depends on the wavelength conversion efficiency, and the oscillation state becomes unstable. The problem is known.
When the shape of the solid-state laser element 3 and the wavelength conversion element 20 is a waveguide type, the mode of light traveling inside the elements is separated into two modes, a TE mode and a TM mode. Will contribute to the conversion and suffer losses. At this time, since the TE mode circulates in the resonator without receiving a loss due to wavelength conversion, it plays a very important role in stably oscillating the fundamental wave. From such a principle, if the shape of the solid-state laser element 3 is a waveguide type, an advantage that cannot be obtained by the bulk type that the oscillation of the fundamental wave is stabilized is obtained.

In the first to third embodiments, an example in which the laser medium that generates the fundamental wave for performing the SHG conversion is the solid-state laser element 3, but instead of the solid-state laser element 3, a gain medium having a plurality of gain wavelengths ( For example, a similar function can be realized using a gas laser, a dye laser, a semiconductor laser, or the like.
In addition, if an element whose light loss increases as the light intensity increases instead of the wavelength conversion element, similar multi-wavelength oscillation is possible.

  In the present invention, within the scope of the invention, any combination of the embodiments, or any modification of any component in each embodiment, or omission of any component in each embodiment is possible. .

  DESCRIPTION OF SYMBOLS 1 Semiconductor laser, 2 Lens, 3 Solid state laser element, 3a One end surface of the solid state laser element 3, 3b The other end surface of the solid state laser element 3, 4 Wavelength conversion element (1st optical element), 4a of the wavelength conversion element 4 One end face, 4b The other end face of the wavelength conversion element 4, 5 Wavelength conversion element (second optical element), 5a One end face of the wavelength conversion element 5, 5b The other end face of the wavelength conversion element 5, 6 Reflector ( First reflecting mirror), 7, 8 Reflecting mirror, 9, 10 Light transmitting component, 11 Reflecting mirror (second reflecting mirror), 20 Wavelength converting element, 20a One end face of wavelength converting element 20, 20b Wavelength converting element The other end face of 20, 21 region (first optical element), 22 region (second optical element), 23 region (third optical element), 24 reflecting mirror (first reflecting mirror), 25 reflecting mirror (Second reflecting mirror), 31 Waveguide , 32, 33 SiO2 film, 34 substrate, 41, 42, 43 waveguide, 44 and 45 SiO2 films, 46 a substrate, 101 a semiconductor laser, 102 lens, 103, 104 solid-state laser element, 105 wavelength conversion element.

Claims (13)

A semiconductor laser that oscillates excitation light; and
The semiconductor device includes a crystal having a first optical axis having a gain with respect to light having a first wavelength and a second optical axis having a gain with respect to light having a second wavelength. A solid-state laser element that receives excitation light oscillated by a laser, absorbs the excitation light, and outputs light of the first and second wavelengths from the other end face;
One end face is opposite to the other end face of the solid-state laser element, the birefringence of the light output from the other end face of the solid-state laser element, the greater the intensity of the light of the first wavelength, A first optical element for reducing light of a first wavelength;
One end face faces the other end face of the first optical element, the light output from the other end face of the first optical element is birefringent, and the intensity of the light of the second wavelength is increased. A second optical element that reduces the light of the second wavelength as it is larger;
A first reflector that is disposed on one end face side of the solid-state laser element and reflects the light of the first and second wavelengths;
A second reflecting mirror disposed on the other end face side of the second optical element and reflecting the light of the first and second wavelengths,
An optical axis of the solid-state laser element is in a plane perpendicular to the optical axis, and the optical axis of the optical axis and the first and second optical elements are inclined.   The first optical element is a wavelength conversion element that converts the wavelength of the first wavelength light, and the second optical element is a wavelength conversion element that converts the wavelength of the second wavelength light. The laser device according to claim 1, wherein the light after wavelength conversion by the optical element is transmitted through the second reflecting mirror.   3. The laser device according to claim 2, wherein the light after wavelength conversion by the first and second optical elements is second harmonic light.   3. The laser device according to claim 2, wherein the first and second optical elements are optical parts in which polarization inversion is formed using LiNbO3 or LiTaO3 as a material.   5. The laser device according to claim 4, wherein polarization inversion is formed in one material, and the first and second optical elements are integrally formed.   2. The laser device according to claim 1, wherein the first reflecting mirror is coated on one end face of the solid-state laser element, and the second reflecting mirror is coated on the other end face of the second optical element. A semiconductor laser that oscillates excitation light; and
The semiconductor device includes a crystal having a first optical axis having a gain with respect to light having a first wavelength and a second optical axis having a gain with respect to light having a second wavelength. A solid-state laser element that receives excitation light oscillated by a laser, absorbs the excitation light, and outputs light of the first and second wavelengths from the other end face;
One end face is opposite to the other end face of the solid-state laser element, the birefringence of the light output from the other end face of the solid-state laser element, the greater the intensity of the light of the first wavelength, A first optical element for reducing light of a first wavelength;
One end face faces the other end face of the first optical element, the light output from the other end face of the first optical element is birefringent, and the intensity of the light of the second wavelength is increased. A second optical element that reduces the light of the second wavelength as it is larger;
One end face is opposite to the other end face of the second optical element, and the light output from the other end face of the second optical element is birefringent to generate light of the first and second wavelengths. A third optical element that reduces the light of the first and second wavelengths as the intensity of
A first reflector that is disposed on one end face side of the solid-state laser element and reflects the light of the first and second wavelengths;
A second reflecting mirror disposed on the other end face side of the third optical element and reflecting the light of the first and second wavelengths,
An optical axis in the solid-state laser element is in a plane perpendicular to the optical axis, and the optical axis and the optical axes in the first, second and third optical elements are inclined. apparatus.   The first optical element is a wavelength conversion element that converts the wavelength of the first wavelength light, the second optical element is a wavelength conversion element that converts the wavelength of the second wavelength light, and the third optical element is the first optical element. And a wavelength conversion element that generates light of a third wavelength from light of the second wavelength, the light after wavelength conversion by the first and second optical elements and the first light generated by the third optical element. 8. The laser device according to claim 7, wherein light having a wavelength of 3 is transmitted through the second reflecting mirror. The light after wavelength conversion by the first and second optical elements is second harmonic light,
The laser device according to claim 8, wherein the light having the third wavelength generated by the third optical element is light having a sum frequency of the first wavelength and the second wavelength.   9. The laser device according to claim 8, wherein the first, second, and third optical elements are optical components in which polarization inversion is formed using LiNbO3 or LiTaO3 as a material.   11. The laser device according to claim 10, wherein polarization inversion is formed in one material, and the first, second and third optical elements are integrally formed.   8. The laser device according to claim 7, wherein the first reflecting mirror is coated on one end face of the solid-state laser element, and the second reflecting mirror is coated on the other end face of the third optical element.   The laser device according to any one of claims 1 to 12, wherein the solid-state laser element and the optical element have a waveguide structure.

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