JP2015138938A - Laser oscillator, and wavelength switching device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser oscillator arranged to be able to switch two of fundamental waves of laser light such as RGB.SOLUTION: A laser oscillator comprises: a first reflection mirror which reflects light of a first wavelength; a second reflection mirror which reflects light of the first wavelength and light of a second wavelength; a laser medium which is set on an optical axis of light travelling back and forth between the first and second reflection mirrors; a wavelength-conversion element which performs a second harmonics conversion of light amplified by the laser medium to output to the second reflection mirror; VBG which is provided on a light reflection plane of the first reflection mirror and reflects light of the second wavelength according to the incident angle of light incident from the laser medium; and an angle-adjustment mechanism which holds the first reflection mirror, and drives the first reflection mirror so that the reflection plane of the first reflection mirror and VBG form a perpendicular or particular angle with respect to the optical axis.

Description

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

  In a device that displays a color image, such as a projector device or a projection television, light sources of three colors R (red), G (green), and B (blue) are required as light sources. As these light sources, semiconductor lasers are expected as efficient light sources, but at present, green semiconductor lasers are still under development.

  As another means for obtaining these three primary color lights, there is a laser oscillator. The laser oscillator excites a laser medium using a semiconductor laser that outputs high energy, for example, a semiconductor laser of 808 nm band, selects a wavelength of light output from the laser medium, amplifies the wavelength-selected light, and then a laser. Oscillates as light.

  Specifically, the laser oscillator includes, for example, a laser medium such as Nd: YVO4, a semiconductor laser that excites the laser medium, and a total reflection mirror and a partial reflection mirror that are provided to face each other with the laser medium interposed therebetween. And a resonator. The laser oscillator excites a laser medium with a laser beam of a semiconductor laser, and selects one of wavelengths of 900 nm band, 1 μm band, and 1.3 μm band output from the laser medium by a total reflection mirror. Wavelength selection is realized by using a total reflection mirror that reflects only light of a specific wavelength. The laser oscillator amplifies the wavelength-selected light by reciprocating it through a laser medium using a resonator, and outputs the amplified light from a partially reflecting mirror. The total reflection mirror can reflect light having a specific wavelength incident perpendicularly to the reflection surface with a reflection efficiency close to 100%.

  When one of the three primary color lights, for example, light having a wavelength of 671 nm (R) is obtained by a laser oscillator, the laser oscillator converts the amplified light having a fundamental wave of 1342 nm into a second harmonic wave (SHG) by a wavelength conversion element. : Second Harmonic Generation). Similarly, light having wavelengths of 532 nm (G) and 457 nm (B) is also obtained by converting the light of 1064 nm and 914 nm to the second harmonic, respectively, for the other wavelengths of light of 532 nm (G) and 457 nm (B). Can be obtained (for example, see Patent Document 1).

  However, in the technique described in Patent Document 1, it is necessary to select and amplify one light among the fundamental waves (1342 nm, 1064 nm, and 914 nm) output from the laser medium. The total reflection mirror required for obtaining is different. Therefore, it is necessary to prepare three laser oscillators or replace the total reflection mirror. Therefore, the number of parts increases and the manufacturing cost increases. Therefore, a technique for switching the three primary color lights with one laser oscillator is desired.

  As a technique for switching the wavelength of laser light, a technique is disclosed in which a diffraction grating is used instead of a total reflection mirror, and the light is switched to light having a desired wavelength by changing the angle of the diffraction grating. (For example, patent document 2). A diffraction grating is a glass substrate or the like that has grooves, and can separate wavelengths by utilizing a light diffraction phenomenon. Further, the diffraction grating can change the direction of the reflected light by changing the angle at which the light is incident. The technique of the above-mentioned patent document 2 utilizes this property, changes the incident angle of light by changing the installation angle of the diffraction grating, and switches the wavelength by specularly reflecting light of a specific wavelength to the laser medium.

JP, 2012-98495, A JP 2003-69146 A

  However, when a diffraction grating is used as in the technique of Patent Document 2, the absolute diffraction efficiency is generally as low as about 70% and the loss is large. When this diffraction grating is applied to a laser oscillator that converts the fundamental wave to the second harmonic by using the wavelength conversion element as in Patent Document 1, the laser does not oscillate because the loss of light at the second harmonic conversion is large. . In a laser oscillator that performs second harmonic conversion, the diffraction grating for wavelength selection needs to have an absolute diffraction efficiency (about 90% or more) equivalent to that of a total reflection mirror.

  Here, it is conceivable to use a volume Bragg grating (hereinafter referred to as VBG) which is a kind of diffraction grating. VBG is a kind of diffraction grating in which phase patterns having different refractive indexes are formed inside glass. The VBG can reflect light having a specific wavelength incident at a specific angle with an efficiency close to 100%. However, VBG can switch the reflection or transmission of light of a specific wavelength by changing the incident angle of light. However, by changing the incident angle of light, VBG has a wide wavelength band such as the fundamental wave of RGB. There is a problem that switching (for example, switching between the 900 nm band and the 1300 nm band) cannot be performed.

  In order to solve the above problems, a wavelength switching device and a laser oscillator according to the present invention provide a laser oscillator capable of switching two of fundamental wave laser beams such as RGB.

  The laser oscillator of the present invention includes a first reflection mirror that selectively reflects light of a first wavelength, a second reflection mirror that reflects light of the first wavelength and the second wavelength, and the first reflection. A laser medium that is disposed on an optical axis of light traveling back and forth between the mirror and the second reflection mirror, amplifies the light, and second harmonic conversion of the light amplified by the laser medium, And a wavelength conversion element that outputs to the second reflection mirror, wherein the second wavelength is provided on a light reflection surface of the first reflection mirror according to an incident angle of light incident from the laser medium. A volume Bragg grating that selectively reflects light, and holding the first reflecting mirror, and the reflecting surfaces of the first reflecting mirror and the volume Bragg grating are perpendicular to the optical axis or Specific corner An angle adjusting mechanism for driving the first reflecting mirror so as to form the first reflecting mirror and the reflecting surface of the volume Bragg grating with respect to the optical axis by the angle adjusting mechanism. When vertical, the volume Bragg grating transmits light perpendicular to the reflecting surface, and the first reflecting mirror transmits the first wavelength of light transmitted through the volume Bragg grating. When the light is selected and reflected by the laser medium, and the angle adjustment mechanism makes the first reflecting mirror and the reflecting surface of the volume Bragg grating have a specific angle with respect to the optical axis, The volume Bragg grating selects the light of the second wavelength from the light incident on the reflecting surface at a specific angle, and the laser The first reflection mirror reflects light other than the second wavelength transmitted through the volume Bragg grating in a direction different from the optical axis. Thus, it is not incident on the laser medium.

  The wavelength switching device of the present invention includes a first reflecting mirror that selects light of a first wavelength from light output from a laser medium that amplifies light and reflects the light to the laser medium, and the first reflecting mirror. A volume Bragg grating that is provided on the light reflecting surface of the light beam and selectively reflects light of the second wavelength according to an incident angle of light incident from the laser medium, and holds the first reflecting mirror, The angle at which the first reflecting mirror and the volume Bragg grating are driven to drive the first reflecting mirror so that the reflecting surface forms a perpendicular or specific angle with respect to the optical axis of the light output from the laser medium. An adjustment mechanism, and when the angle adjustment mechanism makes the reflection surfaces of the first reflection mirror and the volume Bragg grating perpendicular to the optical axis, The Bragg grating transmits light perpendicularly incident on the reflecting surface, and the first reflecting mirror selects the light having the first wavelength from the light transmitted through the volume Bragg grating, and When the reflecting surface of the first reflecting mirror and the volume Bragg grating is set to a specific angle with respect to the optical axis by the angle adjusting mechanism, the volume Bragg grating is reflected by the laser medium. The light having the second wavelength out of the light incident on the reflection surface at a specific angle is selected and reflected by the laser medium, and the light having a wavelength other than the second wavelength is transmitted. The light other than the second wavelength transmitted through the volume Bragg grating is reflected in a direction different from the optical axis so as not to enter the laser medium.

  The laser oscillator of the present invention is a volume that selectively reflects light of the second wavelength on the reflecting surface of the first reflecting mirror that reflects light of the first wavelength according to the incident angle of light incident from the laser medium. A Bragg grating is provided, and the first reflecting mirror and the reflecting surface of the volume Bragg grating are first or perpendicularly formed with respect to the optical axis of the light output from the laser medium by the angle adjusting mechanism. For example, it is possible to switch between two of the laser beams such as RGB fundamental waves.

1 is a configuration diagram of a laser oscillator according to Embodiment 1. FIG. An example in which the wavelength switching device according to the first embodiment selects light of the second wavelength. An example in which the wavelength switching device according to the first embodiment selects light of the first wavelength. An example in which the wavelength switching device according to the first embodiment oscillates by selecting light of the first wavelength. The example which the laser oscillator which concerns on Embodiment 1 selects and oscillates the light of the 2nd wavelength. FIG. 3 is a configuration diagram of a laser oscillator according to a second embodiment. An example in which the laser oscillator according to the second embodiment selects light of the first wavelength. Example in which the laser oscillator according to the second embodiment selects light of the second wavelength The laser oscillator which concerns on Embodiment 2 selects the light of the 3rd wavelength. FIG. 6 is a configuration diagram of a laser oscillator according to a third embodiment. 9 shows an example in which the laser oscillator according to the third embodiment oscillates light of the first wavelength. An example in which the laser oscillator according to the third embodiment oscillates light of the second wavelength.

Embodiment 1
Hereinafter, the configuration of the laser oscillator according to the first embodiment will be described with reference to FIGS.

  In FIG. 1, the laser oscillator includes a wavelength switching device 1, a laser medium 5, a semiconductor laser 6, a wavelength conversion element 7, and a partial reflection mirror 8 (second reflection mirror).

  The semiconductor laser 6 is an excitation light source for the laser medium 5 and outputs excitation light having a shorter wavelength so that the two energy levels of the first wavelength and the second wavelength can be excited. The semiconductor laser 6 makes the oscillated excitation light incident on the laser medium 5. For example, when the laser medium 5 is Nd: YVO4, the oscillation wavelength is set to 808 nm.

  The laser medium 5 receives the excitation light output from the semiconductor laser 6 and outputs light including the first wavelength light λ1 and the second wavelength light λ2. The laser medium 5 is a material having a gain with respect to the light λ1 having the first wavelength and the light λ2 having the second wavelength, the light reflecting surface 2b (hereinafter referred to as a second surface) of the VBG2 and the end surface 5a, and It arrange | positions so that the light-incidence surface 7a of the wavelength conversion element 7 mentioned later and the end surface 5b may face each other.

  The wavelength conversion element 7 performs second harmonic conversion on the light output from the laser medium 5. Further, the wavelength conversion element 7 is disposed so as to face the end face 5 b of the laser medium 5. Further, the wavelength conversion element 7 is divided into a wavelength conversion region 7A for converting the first wavelength light λ1 into the second harmonic and a wavelength conversion region 7B for converting the wavelength λ2 of the second wavelength.

  The second reflecting mirror 8 reflects a part of the first wavelength light λ 1 and the second wavelength light λ 2 to the laser medium 5. The second reflecting mirror 8 is provided on the second surface 7 b of the wavelength conversion element 7. That is, in the present embodiment, the second reflecting mirror 8 is provided with a reflecting surface perpendicular to the optical axis of the light output from the laser medium 5.

  The wavelength switching device 1 selects the first wavelength light λ <b> 1 or the second wavelength light λ <b> 2 from the light output from the laser medium 5 and reflects it to the laser medium 5. The wavelength switching device 1 includes a VBG 2, a total reflection mirror 3 (first reflection mirror), and an angle adjustment mechanism 4. In the following description, the second reflecting mirror 8 and the wavelength switching device 1 are assumed to be resonators.

  Hereinafter, the configuration of the wavelength switching device 1 will be described in detail.

  VBG2 is obtained by periodically changing the refractive index of glass to form a diffraction grating. For this reason, this VBG 2 is light having the second wavelength when the second surface 2b is at a specific angle (for example, the first angle θ1) with respect to the optical axis of the light output from the laser medium 5. Is selected and reflected to the laser medium 5 and transmits light of other wavelengths. In the following description, it is defined as regular reflection that the VBG 2, the first reflection mirror 3, and the second reflection mirror 8 select predetermined light from the light output from the laser medium and reflect it to the laser medium. .

  The first reflecting mirror 3 selects the light λ1 having the first wavelength when the reflecting surface of the first reflecting mirror 3 is perpendicular to the optical axis of the light output from the laser medium 5. It is regularly reflected and other light is transmitted. Further, when the reflection surface has an angle of θ1 with respect to the optical axis of the light output from the laser medium 5, the design is such that all the light is reflected or transmitted in a direction different from the laser medium 5. Is done.

  The angle adjustment mechanism 4 switches the angle of the VBG 2 between the first angle θ1 and the vertical by holding and driving the first reflection mirror 3.

  The laser medium 5 is a material having a gain with respect to the light λ1 having the first wavelength and the light λ2 having the second wavelength, and is disposed so as to face the second surface 2b of the VBG2. In the following description, the angles of the VBG 2, the first reflecting mirror 3, or the second reflecting mirror 8 adjusted by the angle adjusting mechanism 4 are the same as the reflecting surface 2 b of the VBG 2 and the reflecting surface of the first reflecting mirror 3. It is defined as the angle formed by the optical axis.

  Next, the operation of the wavelength switching device according to the first embodiment will be described with reference to FIGS. FIG. 2 is an example in which the wavelength switching device according to the first embodiment selects light of the second wavelength. FIG. 3 is an example in which the wavelength switching device according to the first embodiment selects light of the first wavelength. In the description of the operation of the laser oscillator according to the first embodiment, a case where the first wavelength light λ1 and the second wavelength light λ2 are mixed and incident from the second surface 2b of the VBG 2 will be described as an example.

  In FIG. 2, when the angle of the VBG 2 and the first reflecting mirror 3 is set to the first angle θ1 by the angle adjusting mechanism 4, the VBG 2 regularly reflects the light λ2 having the second wavelength. At this time, the light λ 1 having the first wavelength passes through the VBG 2 and enters the first reflection mirror 3. Since the first reflecting mirror 3 is designed to have the best reflection characteristics when the light is incident perpendicularly to the reflecting surface, the first reflecting mirror 3 is different from the same path as the incident light of the first wavelength light λ1. Reflect in the direction. As described above, when the angle of the VBG 2 and the first reflection mirror 3 is set to the first angle θ1 by the angle adjustment mechanism 4, the wavelength switching device 1 regularly reflects the light λ2 having the second wavelength.

  On the other hand, in FIG. 3, when the angle of the second surface 2 b of the VBG 2 is made perpendicular to the optical axis of the light output from the laser medium 5 by the angle adjusting mechanism 4, the first wavelength light λ 1 and the second wavelength Both light λ2 passes through VBG2 and enters the first reflecting mirror 3 perpendicularly. The first reflecting mirror 3 transmits the light λ2 having the second wavelength and regularly reflects the light λ1 having the first wavelength. Thus, when the angle of the VBG 2 and the first reflection mirror 3 is made vertical by the angle adjustment mechanism 4, the wavelength switching device 1 regularly reflects the light λ1 having the first wavelength.

  As described above, when the angle of VBG2 is the first angle θ1, the wavelength switching device 1 specularly reflects the light λ2 of the second wavelength, and specularly reflects the light λ1 of the first wavelength when the angle is vertical. The wavelength to be selected can be switched simply by adjusting the angles of the VBG 2 and the first reflecting mirror 3. The first wavelength and the second wavelength are not particularly limited as long as the wavelengths can be reflected and transmitted by the VBG 2 and the first reflection mirror 3.

  Next, the operation of the laser oscillator according to the first embodiment will be described with reference to FIGS. FIG. 4 shows an example in which the wavelength switching device according to the first embodiment selects and oscillates light of the first wavelength. FIG. 5 shows an example in which the laser oscillator according to the first embodiment oscillates by selecting light of the second wavelength.

  In FIG. 4, the laser medium 5 outputs the light having the first wavelength and the light having the second wavelength, which are fundamental waves, from the end faces 5a and 5b.

  When the excitation light oscillated by the semiconductor laser 6 enters from the side surface 5c of the laser medium 5 and is absorbed by the laser medium 5, the laser medium 5 is excited, and the fundamental wavelength light λ1 and the second wavelength light λ1. Light including the light λ2 is output from the end faces 5a and 5b.

  When the angle of the VBG 2 is made vertical by the angle adjustment mechanism 4, the wavelength switching device 1 reflects the light λ 1 having the first wavelength and transmits the light λ 2 having the second wavelength. On the other hand, the second reflecting mirror 8 reflects the light λ1 having the first wavelength and the light λ2 having the second wavelength. At this time, the light λ1 of the first wavelength has a smaller optical loss in the resonator than the light λ2 of the second wavelength, and therefore the oscillation threshold is reduced, and the light λ1 of the first wavelength oscillates. That is, the light λ1 having the first wavelength is amplified with high efficiency between the VBG 2 and the second reflecting mirror 8 and oscillates.

  Specifically, the first wavelength light λ 1 output from the end face 5 a is reflected by the wavelength switching device 1, further amplified by the laser medium 5, and incident on the wavelength conversion element 7. Further, the light λ1 having the first wavelength is converted into the second harmonic in the wavelength conversion region 7A, and laser light λ1a having a wavelength that is half the first wavelength is generated.

  The first wavelength light λ1 remaining without being converted is reflected by the second reflecting mirror 8, passes through the wavelength conversion region 7B, and is converted again to the second harmonic in the wavelength conversion region 7A.

  Further, the first wavelength light λ <b> 1 remaining without being converted returns to the laser medium 5. Wavelength converted light is output from the second reflection mirror 8 by allowing the second reflection mirror 8 to transmit light λ1a having a wavelength that is half the first wavelength.

  On the other hand, in FIG. 5, when the excitation light oscillated by the semiconductor laser 6 enters from the side surface 5 c of the laser medium 5 and is absorbed by the laser medium 5, the laser medium 5 is excited and light of the first wavelength that is the fundamental wave. Light including λ1 and light λ2 of the second wavelength is output from the end faces 5a and 5b.

  When the angle of the VBG 2 is set to the first angle θ1 by the angle adjusting mechanism 4, the wavelength switching device 1 regularly reflects the light λ2 of the second wavelength to the laser medium 5 and the light λ1 of the first wavelength as described above. Is reflected or reflected in a direction not incident on the laser medium 5.

  On the other hand, the second reflecting mirror 8 regularly reflects the first wavelength light λ 1 and the second wavelength light λ 2 to the laser medium 5. At this time, the light λ2 of the second wavelength has a smaller optical loss in the resonator than the light λ1 of the first wavelength, so that the oscillation threshold is reduced and the light λ2 of the second wavelength oscillates. That is, the light λ2 having the second wavelength is amplified with high efficiency between the VBG 2 and the second reflection mirror 8 and oscillates.

  Specifically, the second wavelength light λ <b> 2 output from the end face 5 a is reflected by the wavelength switching device 1, further amplified by the laser medium 5, and incident on the wavelength conversion element 7. The light λ2 having the second wavelength is converted into the second harmonic in the wavelength conversion region 7B, and laser light λ2a having a wavelength half that of the second wavelength is generated.

  The second wavelength light λ2 remaining without being converted is reflected by the second reflecting mirror 8 and converted again into the second harmonic in the wavelength conversion region 7B. Further, the second wavelength light λ <b> 2 remaining without being converted passes through the wavelength conversion region 7 </ b> A and returns to the laser medium 5. By allowing the second reflection mirror 8 to transmit the generated laser light λ2a having a half wavelength of the second wavelength, the wavelength-converted light λ2a is output from the second reflection mirror 8.

  As described above, when the angle of the VBG 2 and the first reflecting mirror 3 is set to the first angle θ1, the laser light λ2a having a half wavelength of the second wavelength is oscillated, and when the angle is set to be vertical, the wavelength is half the first wavelength. The laser light λ1a can be oscillated, and the oscillation wavelength of the laser oscillator can be switched only by adjusting the angles of the VBG 2 and the first reflection mirror 3.

  As an example of the laser medium 5 according to the present embodiment, it is conceivable to use, for example, an Nd: YVO4 material having gains at wavelengths of 914 nm, 1064 nm, and 1342 nm. In this case, the first wavelength can be 914 nm and the second wavelength can be 1064 nm, for example. Further, based on the above principle, light having a wavelength of 457 nm, which is the second harmonic of 914 nm, and light having a wavelength of 532 nm, which is the second harmonic of 1064 nm, can be switched only by adjusting the angle of VBG2. As a result, among the three primary colors, blue (457 nm) and green (532 nm) can be switched and oscillated by one laser oscillator. The wavelengths of the two fundamental waves to be oscillated may be, for example, 914 nm and 1342 nm. In this case, blue (457 nm) and red (671 nm) light is obtained. The same applies to the following embodiments.

  Moreover, since VBG2 which concerns on this Embodiment has good wavelength selectivity, it is possible to switch reflection or permeation | transmission with respect to the light of a wavelength difference of 1 nm or less. The laser oscillator according to the present embodiment does not need to limit the light to be oscillated to the three primary colors using this property, and uses 1064 nm and 1086 nm as the fundamental wave, for example, slightly at 532 nm and 543 nm. It is also possible to switch green light of different wavelengths. The same applies to the following embodiments.

  Furthermore, the type of the laser medium 5 according to the present embodiment is not particularly limited as long as it is a material having gains at a plurality of wavelengths. The same applies to the following embodiments.

  In the description of the laser oscillator according to the present embodiment, the side pumping method in which the semiconductor laser 6 is incident from the side surface 5c of the laser medium 5 is shown as an example. it can. In that case, for example, the semiconductor laser 6 is arranged on the first surface 2a side of the VBG 2 so that the excitation light output from the semiconductor laser 6 is transmitted through the first reflection mirror 3 and VBG 2 and is incident from the end surface 5a. Just design. The same applies to the following embodiments.

  In the description of the laser oscillator according to the present embodiment, the first reflection mirror 3 is provided on the first surface 2a of the VBG 2. However, the same effect can be obtained by providing the first reflection mirror 3 on the second surface 2b. In that case, the first reflecting mirror 3 transmits the light of the second wavelength reflected by the VBG 2. The same applies to the following embodiments.

  Further, in the present embodiment, an example in which laser light is extracted using the VBG 2 and the first reflection mirror 3 as a total reflection mirror and the second reflection mirror 8 as a partial reflection mirror has been described. However, the VBG 2 and the first reflection mirror are illustrated. Of course, it is possible to configure 3 as a partial reflection mirror and the second reflection mirror 8 as a total reflection mirror. In this case, the VBG 2 and the total reflection mirror need to transmit the wavelength converted light. The same applies to the following embodiments.

  As the wavelength conversion element 7, for example, it is conceivable to use a Mg-added LiNbO3 material or a Mg-added LiTaO3 material in which polarization inversion is formed. In this case, as shown in FIG. 1, by forming two different polarization inversion periods in one wavelength conversion element 7, the first wavelength light λ1 is wavelength-converted to generate light having a wavelength of λ1a. The one wavelength conversion element and the second wavelength conversion element that converts the wavelength of the light λ2 having the second wavelength to generate light having the wavelength λ2a can be integrated. Further, the same effect can be obtained by arranging the two wavelength conversion elements 7 individually, changing the order of arrangement, or making each element using different materials. Moreover, it is good also as an external wavelength conversion system which arrange | positions the wavelength conversion element 7 outside the wavelength switching apparatus 1 and the 2nd reflective mirror 8. FIG. The same applies to the following embodiments.

  As described above, the laser oscillator according to the first embodiment selects the first reflection mirror 3 that selects the light having the first wavelength from the light incident perpendicularly to the reflection surface and reflects the light to the laser medium 5; Of the light incident at a specific angle with respect to the reflection surface, VBG2 that selectively reflects light of the second wavelength and the reflection surfaces of the first reflection mirror 3 and VBG2 are perpendicular to the optical axis or specific Since the angle adjusting mechanism 4 that drives the first reflecting mirror 3 to form an angle is provided, it is possible to switch between two laser beams such as RGB.

  In the laser oscillator according to the present embodiment, since the wavelength switching device 1 is configured by combining the VBG 2 and the first reflection mirror 3, the VBG 2 and the first reflection mirror 3 independently emit light having different wavelengths. Reflection can be performed with high efficiency, and even when the wavelength conversion element 7 is used, laser light can be oscillated with little loss of light.

Embodiment 2. FIG.
Hereinafter, the laser oscillator according to the second embodiment will be described with reference to FIGS. The laser oscillator according to the second embodiment is characterized in that light of three wavelengths is switched by providing the wavelength switching device of the laser oscillator described in FIG.

  In the present embodiment, the wavelength switching device 1 is described as the first wavelength switching device 1, VBG 2 is described as the first VBG 2, and the angle adjustment mechanism 4 is described as the first angle adjustment mechanism 4.

  In the present embodiment, in addition to the first wavelength and the second wavelength, the semiconductor laser 5 outputs short-wavelength excitation light that can excite energy levels of three wavelengths including the third wavelength.

  The laser medium 5 receives the excitation light output from the semiconductor laser 6 and outputs light including the light λ3 having the third wavelength in addition to the light λ1 having the first wavelength and the light λ2 having the second wavelength. Therefore, the laser medium 5 uses a material having a gain with respect to the first wavelength light λ1, the second wavelength light λ2, and the third wavelength light λ3.

  Further, the wavelength conversion element 7 includes a third wavelength in addition to the wavelength conversion region 7A for converting the first wavelength light λ1 to the second harmonic and the wavelength conversion region 7B for converting the second wavelength light λ2 to the second harmonic. The light λ3 is divided into a wavelength conversion region 7C for wavelength conversion.

  Hereinafter, the configuration of the laser oscillator according to the second embodiment will be described with reference to FIG. FIG. 6 is a configuration diagram of a laser oscillator according to the second embodiment. Note that portions corresponding to the configuration of the laser oscillator of the first embodiment are denoted by the same reference numerals as those in FIG. 1 and description thereof is omitted.

  In FIG. 6, the laser oscillator further includes a wavelength switching device 10 (second wavelength switching device).

  The second wavelength switching device 10 selects the first wavelength light λ <b> 1 or the second wavelength light λ <b> 2 and the third wavelength light λ <b> 3 from the light output from the laser medium 5 and reflects it to the wavelength conversion element 7. To do. The second wavelength switching device 10 includes a second VBG 11, a second reflection mirror 8, and a second angle adjustment mechanism 13, and a second wavelength with respect to the optical axis of the light output from the laser medium 5. When the angle formed between the VBG 11 and the reflecting surface of the second reflecting mirror 8 is the second angle θ2, the first wavelength light λ1 is reflected, and when the angle is vertical, the second wavelength light λ2 and the third wavelength light are reflected. Reflects λ3.

  Hereinafter, the configuration of the second wavelength switching device 10 will be described in detail.

  The second VBG 11 has a first wavelength when the light reflecting surface 11a (hereinafter referred to as a third surface) is at a second angle θ2 with respect to the optical axis of the light output from the laser medium 5. Is selected and reflected to the laser medium 5, and transmits light of other wavelengths.

  The second reflection mirror 8 is provided on the fourth surface 11b of the second VBG 11 in the present embodiment. In addition, the second reflection mirror 8 has the second wavelength light λ 2 and the second wavelength when the reflection surface of the second reflection mirror 8 is perpendicular to the optical axis of the light output from the laser medium 5. Three-wavelength light λ3 is reflected by the laser medium 5 and other light is transmitted. Further, the second reflection mirror 8 transmits all light to the laser medium 5 when the reflection surface is at the second angle θ2 with respect to the optical axis of the light output from the laser medium 5. Are designed to reflect or transmit in different directions.

  The second angle adjustment mechanism 13 holds and drives the second reflecting mirror 8, thereby outputting the angles of the reflecting surface of the second reflecting mirror 8 and the reflecting surface 11 a of the second VBG 11 from the laser medium 5. Is switched to the second angle θ2 or perpendicular to the optical axis of the emitted light. In the following description, the first and second wavelength switching devices are assumed to be resonators.

  Next, the operation of the wavelength switching device according to the second embodiment will be described with reference to FIGS.

  FIG. 7 shows an example in which the laser oscillator according to the second embodiment selects light of the first wavelength. FIG. 8 shows an example in which the laser oscillator according to the second embodiment selects light of the second wavelength. FIG. 9 shows an example in which the laser oscillator according to the second embodiment selects light of the third wavelength. In the description of the operation of the laser oscillator according to the second embodiment, the second surface of the first VBG 2 is a mixture of the first wavelength light λ1, the second wavelength light λ2, and the third wavelength light λ3. 2b and the case where it injects into the 3rd surface 11a of 2nd VBG11 is demonstrated as an example.

  Next, an example of oscillating the light λ1 having the first wavelength will be described with reference to FIG.

  In FIG. 7, the laser medium 5 outputs the first wavelength light λ1, the second wavelength light λ2, and the third wavelength light λ3, which are fundamental waves, from the end faces 5a and 5b.

  When the angle of the first VBG 2 is made vertical by the first angle adjustment mechanism 4, the first wavelength switching device 1 reflects the light λ 1 of the first wavelength and the light λ 3 of the third wavelength to the laser medium 5, The second wavelength light λ2 is transmitted.

  Specifically, the first VBG 2 transmits the light output from the end face 5a, that is, the first wavelength light λ1, the second wavelength light λ2, and the third wavelength light λ3. Further, the first wavelength light λ 1 and the third wavelength light λ 3 transmitted by the first VBG 2 are reflected by the first reflecting mirror 3 to the laser medium 5.

  Furthermore, the first wavelength light λ 1 reflected by the first wavelength switching device 1 is amplified by the laser medium 5 and enters the wavelength conversion element 7.

  Part of the light λ1 having the first wavelength incident on the wavelength conversion element 7 is converted into the second harmonic in the wavelength conversion region 7A, and laser light λ1a having a wavelength half the first wavelength is generated.

  The first wavelength light λ1 remaining without being converted is transmitted through the wavelength conversion regions 7B and 7C.

  By the second angle adjustment mechanism 13, the second wavelength switching device 10 in which the angle of the second VBG 11 is set to the second angle θ2, the light λ1 of the first wavelength remaining without being converted by the wavelength conversion element 7 is used. Select and reflect to the wavelength conversion element 7.

  Specifically, the second VBG 11 reflects the light λ1 having the first wavelength to the wavelength conversion element 7, and transmits the other light, that is, the light λ2 having the second wavelength and the light λ3 having the third wavelength. . Further, the second wavelength light λ2 and the third wavelength light λ3 transmitted by the second VBG 11 are reflected by the second reflection mirror 8 in a direction different from the direction in which the wavelength conversion element 7 and the laser medium 5 are installed. Or it is transparent. Therefore, the third wavelength light λ3 reflected by the first wavelength switching device 1 is not confined in the resonator, and thus is not amplified and does not oscillate.

  In addition, wavelength-converted light is output from the 2nd reflective mirror 8 by making the 2nd reflective mirror 8 permeate | transmit with respect to the laser beam (lambda) 1a of the half wavelength of the generated 1st wavelength.

  The light λ1 having the first wavelength reflected by the second wavelength switching device 10 is transmitted through the wavelength conversion regions 7B and 7C, and part of the light is converted again into the second harmonic in the wavelength conversion region 7A.

  As described above, the first wavelength switching device 1 reflects the first wavelength light λ1 and the third wavelength light λ3 to the laser medium 5, and the second wavelength switching device 10 selects the first wavelength light λ1. Therefore, the light λ1 having the first wavelength is amplified and oscillated. That is, since the optical loss in the resonator is smaller with respect to the light λ1 having the first wavelength, the oscillation threshold value is reduced, and the light λ1 having the first wavelength oscillates.

  An example in which the light λ2 having the second wavelength is oscillated will be described with reference to FIG. In FIG. 8, the semiconductor laser 6 enters the excitation light from the side surface 5 c of the laser medium 5 and absorbs it in the laser medium 5. The laser medium 5 is excited by the excitation light, and outputs the first wavelength light λ1, the second wavelength light λ2, and the third wavelength light λ3, which are fundamental waves, from the end faces 5a and 5b.

  When the first angle adjusting mechanism 4 sets the angle of the first VBG 2 to the first angle θ1, the first wavelength switching device 1 selects the light λ2 having the second wavelength from the light output from the end face 5a. Then, it is reflected by the laser medium 5.

  Specifically, the light λ <b> 2 having the second wavelength is selected by the first VBG 2 from the light output from the end surface 5 a and reflected to the laser medium 5. At this time, the first VBG 2 transmits light having a wavelength other than the second wavelength, that is, light λ1 having the first wavelength and light λ3 having the third wavelength. Further, the first wavelength light λ1 and the third wavelength light λ3 transmitted by the first VBG 2 are reflected or transmitted by the first reflection mirror 3 in a direction different from the direction in which the laser medium 5 is installed. .

  Further, the second wavelength light λ <b> 2 reflected by the first wavelength switching device 1 is amplified by the laser medium 5 and enters the wavelength conversion element 7.

  The light λ2 having the second wavelength incident on the wavelength conversion element 7 is transmitted through the wavelength conversion region 7A, converted to the second harmonic in the wavelength conversion region 7B, and generates light λ2a having a wavelength half that of the second wavelength.

  The second wavelength light λ2 remaining without being converted passes through the wavelength conversion region 7C.

  By the second angle adjusting mechanism 13, the second wavelength switching device 10 in which the angle of the second VBG 11 is vertical is transmitted through the wavelength conversion region 7C and the second wavelength light λ2 that has not been subjected to the second harmonic conversion. To reflect.

  Specifically, the second VBG 11 transmits the first wavelength light λ1, the second wavelength light λ2, and the third wavelength light λ3. Of the light transmitted through the second VBG 11, the second wavelength light λ <b> 2 and the third wavelength light λ <b> 3 are reflected to the wavelength conversion element 7 by the second reflection mirror 8. Furthermore, the first wavelength light λ <b> 1 transmitted through the second VBG 11 is transmitted by the second reflection mirror 8. The laser beam λ2a is output from the second reflection mirror 8 by allowing the second reflection mirror 8 to transmit the laser beam λ2a having a half wavelength of the second wavelength.

  In addition, a part of the reflected light λ2 having the second wavelength is transmitted through the wavelength conversion region 7C and converted again into the second harmonic in the wavelength conversion region 7B.

  The second wavelength light λ <b> 2 remaining without being converted in the wavelength conversion region 7 </ b> B returns to the laser medium 5, is amplified, and is incident on the first wavelength switching device 1 again.

  In this way, the first wavelength switching device 1 reflects the second wavelength light λ2 and reflects it to the laser medium 5, and the second wavelength switching device 10 reflects the second wavelength light λ2 and the third wavelength light λ3. Is selected and reflected, the second wavelength light λ2 is amplified and oscillated. That is, since the optical loss in the resonator is smaller with respect to the light λ2 of the second wavelength, the oscillation threshold is reduced, and the light λ2 of the second wavelength is laser-oscillated. Note that the third wavelength light λ3 is not confined in the resonator by the first wavelength switching device 1, and therefore is not amplified and does not oscillate.

  Next, an example in which the third wavelength light λ3 is oscillated will be described with reference to FIG.

  In FIG. 9, as in the wavelength switching device described with reference to FIGS. 7 and 8, from the laser medium 5, the first wavelength light λ1, the second wavelength light λ2, and the third wavelength light λ3, which are fundamental waves, are transmitted to the end face 5a. And 5b.

  When the angle of the first VBG 2 is made vertical by the first angle adjustment mechanism 4, the first wavelength switching device 1 reflects the light λ 1 of the first wavelength and the light λ 3 of the third wavelength to the laser medium 5, The light λ2 having the second wavelength is transmitted.

  Specifically, the first VBG 2 transmits the light output from the end face 5a, that is, the first wavelength light λ1, the second wavelength light λ2, and the third wavelength light λ3. The first wavelength light λ1 and the third wavelength light λ3 transmitted by the first VBG 2 are reflected by the first reflecting mirror 3 to the laser medium 5, and the second wavelength light λ2 is transmitted. Therefore, the light λ2 having the second wavelength is not amplified by the laser medium 5 and does not oscillate.

  The third wavelength light λ 3 reflected by the first wavelength switching device 1 is amplified by the laser medium 5 and enters the wavelength conversion element 7.

  In addition, the third wavelength light λ3 incident on the wavelength conversion element 7 is transmitted through the wavelength conversion regions 7A and 7B, a part of which is second harmonic converted in the wavelength conversion region 7C, and has a wavelength half that of the third wavelength. Laser light λ3a is generated.

  The third wavelength light λ 3 remaining without being converted enters the second wavelength switching device 10.

  By the second angle adjustment mechanism 13, the second wavelength switching device 10 that makes the angle of the second VBG 11 vertical selects the wavelength λ 3 of the third wavelength that remains without being converted by the wavelength conversion element 7, and the wavelength Reflected to the conversion element 7.

  Specifically, the second VBG 11 transmits the first wavelength light λ1, the second wavelength light λ2, and the third wavelength light λ3. Of the light transmitted through the second VBG 11, the second wavelength light λ <b> 2 and the third wavelength light λ <b> 3 are reflected to the wavelength conversion element 7 by the second reflection mirror 8. Further, the first wavelength light transmitted through the second VBG 11 is transmitted by the second reflecting mirror. Therefore, the light λ1 having the first wavelength reflected by the first wavelength switching device 1 is not confined in the resonator, and thus is not amplified and does not oscillate.

  Note that wavelength converted light is output from the second reflection mirror 8 by allowing the second reflection mirror 8 to transmit the generated laser light λ3a having a half wavelength of the third wavelength.

  The third wavelength light λ3 reflected by the second wavelength switching device 10 is partly converted again into the second harmonic in the wavelength conversion region 7C.

  Thus, the first wavelength switching device 1 reflects the first wavelength light λ1 and the third wavelength light λ3 to the laser medium 5, and the second wavelength switching device 10 reflects the second wavelength light λ2 and the third wavelength light λ3. Since the light λ3 having the wavelength is selected and reflected, the light λ3 having the third wavelength is amplified and oscillated. That is, since the optical loss in the resonator is smaller with respect to the light λ3 having the third wavelength, the oscillation threshold is reduced, and the light λ3 having the third wavelength is laser-oscillated.

  In the description of the present embodiment, the first wavelength switching device 1 and the second wavelength switching device 10 have the first angle θ1 with respect to the optical axis of the light output from the laser medium 5 on the reflecting surface. And the second angle θ2, the first VBG2 selects the second wavelength light λ2 and reflects it to the laser medium 5, and the second VBG11 reflects the first wavelength light λ1. It was. At this time, the first angle θ1 and the second angle θ2 may be specific angles, and are not limited to the first angle θ1 and the second angle θ2. For example, the first VBG 2 has a second wavelength when the second angle 2 is formed by the first angle adjusting mechanism 4 with respect to the optical axis of the light output from the laser medium 5. The light λ2 may be reflected. The second VBG 11 has a first wavelength when the third surface 11a forms the third angle θ3 with respect to the optical axis of the light output from the laser medium 5 by the second angle adjustment mechanism 10. The light λ1 may be reflected.

  As described above, the laser oscillator according to the second embodiment includes the first wavelength switching device 1, the second VBG 11, and the second reflection mirror 8 that are configured by the first VBG 2 and the first reflection mirror 3. Since the resonator is configured by the second wavelength switching device 10 configured as described above, it is possible to switch the three light components of the RGB fundamental wave.

Embodiment 3 FIG.
The laser oscillator according to the third embodiment is characterized in that in the laser oscillator according to the first embodiment, the light of the fundamental wavelength is switched except for the wavelength conversion element. Hereinafter, the laser oscillator according to the third embodiment will be described with reference to FIGS.

  FIG. 10 is a configuration diagram of a laser oscillator according to the third embodiment of the present invention. Note that portions corresponding to the configuration of the laser oscillator of the first embodiment are denoted by the same reference numerals as those in FIG. 1 and description thereof is omitted.

  In FIG. 10, the laser oscillator includes a wavelength switching device 1, a laser medium 5, a semiconductor laser 6, and a second reflection mirror 8.

  The wavelength switching device 1 includes a VBG 2, a first reflection mirror 3, and an angle adjustment mechanism 4, and the VBG 2 and the first reflection mirror 3 with respect to the optical axis of light output from the laser medium 5. When the reflecting surface forms the first angle θ1, the second wavelength light λ2 is reflected, and when the reflecting surface is vertical, the first wavelength light λ1 is reflected.

  The laser medium 5 is a material having a gain with respect to the light λ1 having the first wavelength and the light λ2 having the second wavelength, and is disposed so as to face the second surface 2b of the VBG2.

  The semiconductor laser 6 is an excitation light source for the laser medium 5 and oscillates excitation light having a shorter wavelength so that two energy levels of the first wavelength and the second wavelength can be excited. The semiconductor laser 6 is arranged so that the oscillated excitation light can enter the laser medium 5. The end surface 5b of the laser medium 5 is provided with a second reflecting mirror 8 that reflects the light λ1 having the first wavelength and the light λ2 having the second wavelength.

  Next, the operation of the laser oscillator according to the third embodiment will be described with reference to FIGS. FIG. 11 shows an example in which the laser oscillator according to the third embodiment of the present invention oscillates light of the first wavelength.

  In FIG. 11, when the excitation light oscillated by the semiconductor laser 6 enters from the side surface 5c of the laser medium 5 and is absorbed by the laser medium 5, the laser medium 5 is excited, and the first wavelength light λ1 that is the fundamental wave The light λ2 having the second wavelength is output from the end faces 5a and 5b.

  When the angle of the VBG 2 is made vertical by the angle adjustment mechanism 4, the wavelength switching device 1 reflects the light λ 1 having the first wavelength to the laser medium 5 and transmits the light λ 2 having the second wavelength.

  On the other hand, the second reflection mirror 8 reflects the light λ1 having the first wavelength and the light λ2 having the second wavelength. At this time, since the optical loss in the resonator is smaller with respect to the light λ1 having the first wavelength, the oscillation threshold value is reduced, and the light λ1 having the first wavelength oscillates. By allowing the second reflection mirror 8 to partially transmit the first wavelength light λ 1, the first wavelength light λ 1 is output from the second reflection mirror 8.

  Next, an operation in which the laser oscillator according to the third embodiment oscillates light of the second wavelength will be described with reference to FIG.

  FIG. 12 shows an example in which the laser oscillator according to the third embodiment oscillates light of the second wavelength.

  In FIG. 12, when the excitation light oscillated by the semiconductor laser 6 enters from the side surface 5c of the laser medium 5 and is absorbed by the laser medium 5, the laser medium 5 is excited, and the first wavelength light λ1 that is the fundamental wave The light λ2 having the second wavelength is output from the end faces 5a and 5b.

  When the angle of the VBG 2 is set to the first angle θ 1 by the angle adjusting mechanism 4, the wavelength switching device 1 reflects the light λ 2 of the second wavelength to the laser medium 5 and transmits the light λ 1 of the first wavelength or the laser medium 5. Reflects to areas other than where.

  On the other hand, the light λ 1 having the first wavelength and the light λ 2 having the second wavelength are reflected to the laser medium 5 by the second reflecting mirror 8. At this time, since the optical loss in the resonator is smaller with respect to the light λ2 having the second wavelength, the oscillation threshold is reduced, and the light λ2 having the second wavelength is laser-oscillated. By allowing the second reflection mirror 8 to partially transmit the second wavelength light λ <b> 2, the second wavelength light λ <b> 2 is output from the second reflection mirror 8.

  As described above, when the angle of the wavelength switching device 1 is made vertical, the first wavelength light λ1 is oscillated, and when the wavelength switching device 1 is set to the first angle θ1, the second wavelength light λ2 is oscillated. Therefore, it is possible to switch the oscillation wavelength of the laser oscillator by simply adjusting the angles of the VBG 2 and the first reflection mirror 3, and to obtain light of a desired fundamental wave.

  In the laser oscillator according to the second embodiment, a laser oscillator that switches the fundamental wave of three wavelengths can be configured by removing the wavelength conversion element 7.

1 wavelength switching device (first wavelength switching device), 2 volume Bragg grating (first VBG), 3 first reflection mirror (total reflection mirror), 4 first angle adjusting mechanism, 5 laser medium, 6 Semiconductor laser, 7 Wavelength conversion element, 8 Second reflection mirror (partial reflection mirror), 10 Second wavelength switching device, 11 Second volume Bragg grating (second VBG) 13 Second angle adjustment mechanism

Claims (3)

A first reflecting mirror that selectively reflects light of the first wavelength;
A second reflecting mirror that reflects light of the first wavelength and the second wavelength;
A laser medium installed on the optical axis of light reciprocating between the first reflecting mirror and the second reflecting mirror, and amplifying the light;
In a laser oscillator comprising: a wavelength conversion element that performs second harmonic conversion on the light amplified by the laser medium and outputs the converted light to the second reflection mirror;
A volume Bragg grating that is provided on a light reflecting surface of the first reflecting mirror and selectively reflects light of the second wavelength according to an incident angle of light incident from the laser medium;
The first reflecting mirror is held, and the first reflecting mirror and the reflecting surface of the volume Bragg grating are driven perpendicularly or at a specific angle with respect to the optical axis. An angle adjustment mechanism for
When the angle adjusting mechanism makes the first reflecting mirror and the reflecting surface of the volume Bragg grating perpendicular to the optical axis, the volume Bragg grating is incident perpendicularly to the reflecting surface. Transmitting light, and the first reflecting mirror selects light of the first wavelength from light transmitted through the volume Bragg grating and reflects it to the laser medium;
When the angle adjustment mechanism causes the reflection surface of the first reflection mirror and the volume Bragg grating to have a specific angle with respect to the optical axis, the volume Bragg grating is specific to the reflection surface. Of the light incident at an angle, the light having the second wavelength is selected and reflected by the laser medium, and the light having a wavelength other than the second wavelength is transmitted. The first reflecting mirror has the volume Bragg grating. A laser oscillator characterized in that light other than the transmitted second wavelength is reflected in a direction different from the optical axis and is not incident on the laser medium. The first reflection mirror and the second reflection mirror further select and reflect light of a third wavelength,
The laser oscillator is
A second volume Bragg grating that is provided on a light reflecting surface of the second reflecting mirror and selectively reflects light of the first wavelength according to an incident angle of light incident from the laser medium;
The second reflection mirror is held, and the second reflection mirror and the reflection surface of the second volume Bragg grating form the second reflection mirror so as to form a perpendicular or specific angle with respect to the optical axis. A second angle adjusting mechanism for driving the mirror,
When the angle adjustment mechanism causes the reflection surfaces of the first reflection mirror and the volume Bragg grating to be perpendicular to the optical axis, the first reflection mirror causes the volume Bragg grating to Select the light of the first wavelength and the light of the third wavelength among the transmitted light and reflect it to the laser medium,
When the second angle adjustment mechanism makes the reflection surfaces of the second reflection mirror and the second volume Bragg grating perpendicular to the optical axis, the second reflection mirror is Selecting the light of the second wavelength and the light of the third wavelength from the light transmitted through the second volume Bragg grating and reflecting it to the laser medium;
When the second angle adjusting mechanism causes the second reflecting mirror and the reflecting surface of the second volume Bragg grating to have a specific angle with respect to the optical axis, the second volume Bragg The grating selects light of the first wavelength from light incident on the reflecting surface at a specific angle, reflects the light to the laser medium, transmits light of the wavelength other than the first wavelength, and transmits the second reflection mirror. 2. The laser according to claim 1, wherein light having a wavelength other than the second wavelength transmitted through the second volume Bragg grating is reflected in a direction different from the optical axis and is not incident on the laser medium. Oscillator. A first reflection mirror that selects light of a first wavelength from light output from a laser medium that amplifies the light and reflects the light to the laser medium;
A volume Bragg grating that is provided on a light reflecting surface of the first reflecting mirror and selectively reflects light of a second wavelength according to an incident angle of light incident from the laser medium;
The first reflection mirror is held, and the reflection surface of the first reflection mirror and the volume Bragg grating forms a perpendicular or specific angle with respect to the optical axis of the light output from the laser medium. An angle adjustment mechanism for driving the first reflection mirror,
When the angle adjusting mechanism makes the first reflecting mirror and the reflecting surface of the volume Bragg grating perpendicular to the optical axis, the volume Bragg grating is incident perpendicularly to the reflecting surface. Transmitting light, and the first reflecting mirror selects light of the first wavelength from light transmitted through the volume Bragg grating and reflects it to the laser medium;
When the angle adjustment mechanism causes the reflection surface of the first reflection mirror and the volume Bragg grating to have a specific angle with respect to the optical axis, the volume Bragg grating is specific to the reflection surface. Of the light incident at an angle, the light having the second wavelength is selected and reflected by the laser medium, and the light having a wavelength other than the second wavelength is transmitted. The first reflecting mirror has the volume Bragg grating. The wavelength switching device, wherein the transmitted light other than the second wavelength is reflected in a direction different from the optical axis and is not incident on the laser medium.

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