JPH05315680A - Solid-state laser - Google Patents

Abstract

PURPOSE:To facilitate manufacturing a low-cost, small-sized, integrated multiple wavelength laser, which produces low-noise, high-power output and is easy to adjust. CONSTITUTION:A solid-state laser comprises a cylindrical laser medium 13 having a vertical axis, a spherical nonlinear element 14 having the same center as the laser medium 13, an optical resonator consisting of a reflecting mirror composed of coatings 15 and 16 applied to the input and output surfaces of the nonlinear element 14, a device 17 for rotating the optical resonator, and a semiconductor laser 19 for pumping the laser medium 13. This solid-state laser is capable of producing a laser beam at different frequencies by the rotation of the optical resonator, while the conventional condenser and input and output mirrors are eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state laser device which excites a solid-state laser medium with a semiconductor laser to cause laser oscillation.

[0002]

2. Description of the Related Art In LD-pumped solid-state lasers, miniaturization, high output, low noise, multi-wavelength, and easy adjustment have been made, respectively. Was difficult to bring.

An example of a conventional multiwavelength solid state laser device is shown in FIG.
Shown in.

A conventional solid-state laser device 70 shown in FIG. 7 has a pumping semiconductor laser 72, a laser medium 74 pumped by the semiconductor laser 72, and a multi-wavelength laser for converting the wavelength of oscillation light from the laser medium 74. A nonlinear KTP crystal (KTiOPO ₄ ) 76, a turntable 78 for rotating the KTP crystal 76, and a resonator structure composed of a pair of input / output mirrors 80 and 82 arranged on both sides of the laser medium 74 and the KTP crystal 76. , A lens system 85 that collects the oscillation light 84 of the semiconductor laser 72, and the like.

Here, the oscillation wavelength of the semiconductor laser 72 is 808 nm, and the laser medium 74 is an Nd: YAG crystal. The input mirror 80 is provided with a coating 86 so as to have high reflection for wavelengths of 1064 nm and 532 nm and high transmission for wavelength of 808 nm, and the output mirror 82 has high reflection for wavelengths near 1064 nm, 5
The coating 87 is applied so as to be non-reflective for wavelengths near 32 nm and 459 nm.

As is well known, the fundamental wave (near infrared light) generated by a solid-state laser travels in a nonlinear optical crystal to transfer energy to a second harmonic (green light) and a sum frequency (blue light). To be done. At this time, when the phase velocity of the fundamental wave and the phase velocity of the second harmonic and the sum frequency satisfy certain conditions, the energy is efficiently transferred,
This condition is called a phase matching condition. The KTP crystal for green light and the KTP crystal for blue light have different light traveling directions with respect to the crystal axes when the phase matching condition is satisfied. Therefore,
With respect to one KTP crystal 76, the crystal plane is cut so that the fundamental wave is incident in the directions satisfying the respective phase matching conditions.

As shown in FIG. 7, the KTP crystal 76 is installed on a turntable 78, rotates in the resonator, and the traveling direction of the fundamental wave in the resonator is the direction of the KTP crystal 76 for generating green light. , Or a wavelength of 532 when arranged so as to match the direction for generating blue light of the KTP crystal 76.
nm green light 88 or blue light 89 having a wavelength of 459 nm is generated.

[0008]

However, in the case of the above-mentioned multi-wavelength solid-state laser device, the fundamental wave is directed to one nonlinear optical crystal in the direction satisfying the phase matching conditions of the second harmonic and the sum frequency. It is extremely difficult to precisely cut the crystal plane so that the second harmonic or the sum frequency is weak due to a slight phase mismatch with the vertically incident fundamental wave or refraction to the non-normally incident fundamental wave. Or, it often happens that it cannot oscillate.

Further, since the input / output mirror is used, it is not suitable for downsizing and high output of the laser device.

Further, there is a problem that an air layer exists between the nonlinear optical element and the solid-state laser medium, and the relative position between the nonlinear optical element and the solid-state laser medium changes due to air vibration, resulting in unstable output. there were.

The present invention has been made to solve the above-mentioned problems, and first of all, a solid-state laser device having a special structure is first provided to provide a multi-wavelength laser device which can be easily manufactured and adjusted. A first object is to provide a small-sized and high-output multi-wavelength laser device, and a second object is to provide a multi-wavelength laser device that can obtain stable output with less noise. As the third purpose,
Further, the final object is to realize the above-mentioned objects in a single structure by combining them, and consequently to provide a low-cost multi-wavelength laser device.

[0012]

In order to achieve these objects, a solid-state laser device of the present invention comprises a cylindrical laser medium excited by light, a spherical nonlinear element surrounding the laser medium as a center, and An optical resonator including a non-linear element, and rotating means for rotating the non-linear element,
The solid-state laser device is characterized by satisfying the phase matching conditions of the harmonic and the sum frequency at two certain rotation angles and generating multi-wavelength laser light.

In order to achieve the above object, the solid-state laser device of the present invention includes a spherical laser medium excited by light, a cylindrical nonlinear element surrounded by the center of the laser medium, and the laser medium. An optical resonator including the optical resonator and rotating means for rotating the laser medium are provided, and the phase matching conditions of the second harmonic and the sum frequency are satisfied at two certain rotation angles, and laser light of multiple wavelengths is generated. And a solid-state laser device.

In order to achieve the above object, the solid-state laser device of the present invention comprises a spherical non-linear element which surrounds a cylindrical laser medium excited by light as a center, and the non-linear element in which the laser medium is in close contact. An optical resonator comprising spherical surfaces coated on the entrance surface and the exit surface, and a solid object characterized by rotating the optical resonator and satisfying a phase matching condition of a second harmonic and a sum frequency at two rotation angles. It is equipped with a laser device.

In order to achieve the above object, the solid-state laser device of the present invention comprises a spherical laser medium excited by light, a cylindrical nonlinear element surrounded by the center of the laser medium, and the nonlinear element. An optical resonator formed of spherical surfaces coated on the incident surface and the emitting surface of the laser medium, which are brought into close contact with each other, and the optical resonator are rotated to satisfy the second harmonic and sum frequency phase matching conditions at two rotation angles. The solid-state laser device is provided.

In the solid-state laser device, a translucent heat conductor may be inserted in the resonator.

Further, in the solid-state laser device, a resonator having a plurality of resonator structures may be used.

In the solid-state laser device, a semiconductor laser may be used for pumping.

[0019]

In the solid-state laser device of the present invention having the above-described structure, first, a cylindrical laser medium is excited by light, and the generated fundamental wave light is wavelength-controlled by a spherical non-linear element surrounding the laser medium as a center. The converted second harmonic wave and the sum frequency are generated by traveling in the direction of different phase matching conditions in the rotating non-linear crystal, and are amplified in the optical resonator including the non-linear element. Generates laser light.

Secondly, in a nonlinear crystal in which a fundamental wave is excited by a light which is excited in a spherical laser medium, the generated fundamental wave light is wavelength-converted by a cylindrical nonlinear element surrounded by the center of the laser medium, and the fundamental wave rotates. The second harmonic wave and the sum frequency are generated by advancing in the directions of different phase matching conditions, and are amplified in the optical resonator including the laser medium to generate multi-wavelength laser light.

Thirdly, in the solid-state laser device according to the first operation, the cylindrical laser medium is excited by light, and the generated fundamental wave light is brought into close contact with the laser medium as a center. The wavelength is converted by the non-linear element, and the second harmonic and the sum frequency are generated by traveling in the directions of different phase matching conditions in the non-linear crystal in which the fundamental wave rotates, and the incident surface and the exit surface of the non-linear element are coated. The laser is amplified in the optical resonator having the spherical surface to generate multi-wavelength laser light, and the input / output mirror and the condenser lens system are omitted, and the size can be reduced. Further, the relative position between the nonlinear optical element and the solid-state laser medium does not change, and the output is stable.

Fourthly, in the solid-state laser device according to the second operation, the spherical laser medium is excited by light, and the generated fundamental wave light is brought into close contact with the laser medium as a center. The second harmonic and the sum frequency are generated by the wavelength conversion by the non-linear element, and the fundamental wave travels in the directions of different phase matching conditions in the rotating non-linear crystal, and the incident surface and the emitting surface of the laser medium are coated. The laser is amplified in the optical resonator having the spherical surface to generate multi-wavelength laser light, and the input / output mirror and the condenser lens system are omitted, and the size can be reduced. Further, the relative position between the nonlinear optical element and the solid-state laser medium does not change, and the output is stable.

Fifth, in the solid-state laser device described in the above action, it is possible to provide a multi-wavelength laser of high quality output by inserting the intra-cavity translucent heat conductor to prevent the thermal effect.

Sixth, with the above-mentioned plurality of structures, it is possible to increase the output of the multi-wavelength laser.

Seventh, by using a semiconductor laser for pumping, a multi-wavelength laser having advantages such as small size, light weight, long life, high conversion efficiency and low cost can be provided.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

First, FIG. 1 shows a block diagram of a solid-state laser device 10 according to a first embodiment of the present invention.

The laser device 10 of the present embodiment has a cylindrical solid-state laser medium 13 which intersects the optical axis 11 and has a central axis in the vertical direction, and a spherical non-linear element which is in close contact with the solid-state laser medium 13 as a center. 14 KTiOPO ₄ (hereinafter KT
Abbreviated as P. ), An optical resonator comprising a reflection mirror having coatings 15 and 16 on the entrance surface and the exit surface of the nonlinear element 14, and a rotation device 17 for rotating the optical resonator.
And the solid-state laser medium 1 arranged on the optical axis 11.
And a semiconductor laser 19 for exciting the laser beam 3.

Here, the wavelength of the semiconductor laser 19 is set to 80
The thickness was set to 8 nm, and Nd: YAG crystal was used as the laser medium 13. The coating 15 has high reflection at a wavelength of 1064 nm and high transmission at a wavelength of 808 nm. The coating 16 has high reflection at a wavelength of 1064 nm and a wavelength of 532.
It has high transmission for nm and 459 nm.

As described in the prior art, K for green light
The TP crystal and the KTP crystal for blue light have different light traveling directions with respect to the crystal axis when the phase matching condition is satisfied. That is, in order to generate the second harmonic that becomes green light,
When the x, y, and z axes are the crystal axes of KTP, the phase matching condition is satisfied when the fundamental wave is incident in a direction parallel to the xy plane and at a certain angle (hereinafter, G direction) from the x axis. Highest conversion efficiency to light. On the other hand, in order to generate the sum frequency that becomes the blue light, the conversion efficiency to the blue light is highest when the fundamental wave is incident in the direction parallel to the y axis (hereinafter, B direction). The KTP crystal 21 for both green light and blue light used in the present embodiment has a KTP crystal 21 having planes perpendicular to the two incident directions, and the KTP crystal 21 has a plane parallel to the z axis as shown in FIG. A spherical KTP crystal 14 that has been subjected to spherical polishing so that it rotates can be coaxially inserted into the inside of the cylindrical YAG crystal 13.

The spherical coating surfaces 15 and 16 on both sides of the non-linear element 14 form an optical resonator similar to the input / output mirrors 86 and 87 in the solid-state laser device 70 of the conventional example. The spherical surface of the end surface on the semiconductor laser 19 side has a focusing function equivalent to that of the focusing lens system 85 in the conventional solid-state laser device 70. Therefore, the condensing lens system 85 and the input / output mirrors 86, 87 can be omitted from the conventional example by the coating surfaces 15, 16 on both sides of the input / output light of the spherical nonlinear element 14, and the solid-state laser device can be made more compact. Can be converted.

Next, a process of generating green light and blue light will be described step by step.

First, when the rotating device 17 is rotated so that the direction of green light generation of the spherical KTP crystal 14 coincides with the traveling direction of the fundamental wave, the laser light 23 from the semiconductor laser 19 is collected on the spherical surface 15. The light is transmitted through the input side portion of the KTP crystal 14 and absorbed by the YAG crystal 13. The YAG crystal 13 excited by the incident light 23 is 106
The light of 4 nm is amplified, and a light field is generated in the resonator formed by the coated spherical surfaces 15 and 16. A part of the 1064 nm laser light is converted into the second harmonic by passing through the output side portion of the KTP crystal 14 and becomes a green laser light 25 of 532 nm, which passes through the coating 16 and is output to the outside.

Next, the rotary table 17 is rotated to rotate the spherical KTP.
When the B direction for generating blue light of the crystal 14 coincides with the traveling direction of the fundamental wave, the laser light 23 from the semiconductor laser 19
Is condensed by the spherical surface 15, is transmitted through the input side portion of the KTP crystal 14, and is absorbed by the YAG crystal 13. This incident light 23
The YAG crystal 13 excited by the light amplifies the 1064 nm light, and a light field is generated in the resonator formed by the coating spherical surfaces 15 and 16. At this time, in the output side portion of the KTP crystal 14, the laser light of 1064 nm and the laser light of 808 nm are frequency-converted, and the sum frequency is 459 nm.
The blue laser light 27 is generated. The blue laser light 27 passes through the coating 16 and is output to the outside.

When green light is generated, the pumping light 23 from the semiconductor laser 19 may have a wavelength that is easily absorbed by the Nd: YAG crystal of the laser medium 13, but when blue light is generated, it is pumped at 808 nm because of phase matching. Light produces the sum frequency most efficiently. Since the wavelength of 808 nm is also near the absorption peak of the Nd: YAG crystal, if it is fixed at this wavelength, it is not necessary to readjust the wavelength of the semiconductor laser,
Green light and blue light can be converted simply by rotating the KTP spherical crystal 14.

FIG. 3 is a block diagram of the solid-state laser device 30 of the second embodiment of the present invention.

The laser device 30 of this embodiment has a cylindrical non-linear element 3 which intersects the optical axis 31 and has a central axis in the vertical direction.
KTP of No. 2, a spherical solid-state laser medium 33 adhered to the non-linear element 32 as a center, and an optical resonator including a reflecting mirror having coatings 35 and 36 on the incident surface and the emitting surface of the solid-state laser medium 33. A rotation device 37 for rotating the optical resonator, and a semiconductor laser 3 for exciting the solid-state laser medium 33 arranged on the optical axis 31.
9 and 9.

Here, as in the first embodiment, the wavelength of the semiconductor laser 39 is set to 808 nm and the Nd: YAG crystal is used as the laser medium 33. The coating 35 is
High reflection is obtained at a wavelength of 1064 nm, and high transmission is obtained at a wavelength of 808 nm. The coating 36 is highly reflective for the wavelength 1064 nm and highly transmissive for the wavelengths 532 nm and 459 nm.

As described in the first embodiment, G direction and B direction
Planes perpendicular to the two incident directions
As the P crystal has, the KTP crystal 32 for both green light and blue light used in this embodiment has a cylindrical shape that rotates along a rotation axis that coincides with the z axis as shown in FIG. 4, and has a hollow outside. In order to perform mirror coating on the cylindrical laser medium 41, the spherical laser medium 41 was subjected to spherical polishing and then adhered thereto.

The spherical coating surfaces 35 and 36 on both sides of the laser medium 33 form an optical resonator as in the first embodiment, and the spherical surface of the end surface of the laser medium 33 on the semiconductor laser 39 side is: It has a focusing function equivalent to that of the focusing lens system 85 in the conventional solid-state laser device 70. Therefore,
Due to the coating surfaces 35 and 36 on both sides of the input / output light of the spherical laser medium 33, the focusing lens system 8 is different from the conventional example.
5 and the input / output mirrors 86 and 87 can be omitted,
Similar to the first embodiment, the solid-state laser device can be further downsized.

Next, the process of generating green light and blue light will be described step by step.

First, when the rotating device 37 is rotated so that the direction of the green light generation of the cylindrical KTP crystal 32 coincides with the traveling direction of the fundamental wave, the laser light 43 from the semiconductor laser 39 is spherical surface 35. The light is collected, transmitted through the KTP crystal 32, and absorbed by the YAG crystal 33. The YAG crystal 33 excited by the incident light 43 amplifies the 1064 nm light, and a light field is generated in the resonator formed by the coating spherical surfaces 35 and 36. A part of the 1064 nm laser light is converted into the second harmonic by passing through the KTP crystal 32, becomes a green laser light 45 of 532 nm, passes through the coating 36, and is output to the outside.

Next, the rotating device 37 is rotated to form a cylindrical K
When the B direction for blue light generation of the TP crystal 32 coincides with the traveling direction of the fundamental wave, the laser light 43 from the semiconductor laser 39 is condensed by the spherical surface 35 and transmitted through the KTP crystal 32, and Y
It is absorbed by the AG crystal 33. The YAG crystal 33 excited by the incident light 43 amplifies 1064 nm light,
A light field is created in the resonator consisting of the coated spheres 35, 36. At this time, in the KTP crystal 32, 1064 nm
And the laser light of 808 nm are up-converted to generate the blue laser light 47 of 459 nm which is the sum frequency. This blue laser light 47 is coated 3
6 is transmitted and is output to the outside.

Since the wavelength of 808 nm is also near the absorption peak of the Nd: YAG crystal, if the wavelength is fixed to this wavelength, it is not necessary to readjust the wavelength of the semiconductor laser 39 and only the rotating device 37 is rotated. , Green light and blue light can be converted.

In the first and second embodiments,
Although the laser mediums 13 and 33 and the nonlinear elements 14 and 32 are arranged in close contact with each other, they are arranged between the laser medium 51 and the nonlinear element 53 like the solid-state laser device 50 of the third embodiment shown in FIG. By inserting the translucent heat conductor 55 to remove the thermal effect, it is possible to provide a solid-state laser device with higher beam quality. In this case, the translucent heat conductor 55 may be arranged in a cylindrical shape at the center of the laser medium 51 and the non-linear element 53, or the laser medium 51 and the non-linear element 5 may be arranged.
It may be arranged on the outside of 3 by spherical polishing.

According to FIG. 5, the laser light 58 from the semiconductor laser 57 arranged on the optical axis 56 is condensed on the spherical surface 59 and absorbed by the laser medium 51. The laser medium 51 excited by the incident light 58 amplifies the 1064 nm light, and a light field is generated in the resonator formed by the coating spherical surfaces 59 and 60. Similar to the first and second embodiments, when the rotating device 61 is rotated, it is 1064 nm at two certain angles.
Part of the laser light of is converted into the second harmonic wave or the sum frequency by passing through the KTP crystal 53, and the green laser light 62 of 532 nm or the blue laser light 63 of 459 nm.
Then, it passes through the coating 60 and is output to the outside.

Here, as in the first embodiment, the wavelength of the semiconductor laser 57 is set to 808 nm, and the laser medium 51 is an Nd: YAG crystal. The coating 59 is
High reflection is obtained at a wavelength of 1064 nm, and high transmission is obtained at a wavelength of 808 nm. The coating 60 is highly reflective for the wavelength 1064 nm and highly transmissive for the wavelengths 532 nm and 459 nm.

As shown in FIG. 6, the multi-wavelength laser can be increased in output by using a plurality of the devices of the first embodiment. In this case, the used KTP crystal 64 for both green light and blue light is made into several spherical KTP crystals 65 which are spherically polished so as to rotate along a rotation axis coincident with the z axis as shown in FIG. Is a cylindrical YAG crystal 6
6 was inserted coaxially and brought into close contact. This method can be applied to the second and third embodiments.

Although Nd: YAG is used as the solid-state laser medium in this embodiment, other solid-state laser medium such as Nd: YVO ₄ may be used. In addition, K
Although TP is used, other nonlinear optical material such as an organic nonlinear optical element may be used. Besides, various modifications can be made without departing from the spirit of the present invention.

[0050]

As is apparent from the above description, the solid-state laser device of the present invention has a structure in which a cylindrical laser medium is inserted in the center of a spherical nonlinear element, or vice versa. A multi-wavelength laser having advantages such as smaller size, lighter weight, longer life, higher conversion efficiency, and lower cost can be provided by adopting a structure in which a cylindrical non-linear element is inserted in the central part of. Furthermore, with the plurality of the above configurations, it is possible to increase the output of the multi-wavelength laser.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a solid-state laser device according to a first embodiment.

FIG. 2 is a configuration diagram of a spherically polished non-linear element and a cylindrical laser medium inserted in the central portion of the first embodiment.

FIG. 3 is a configuration diagram of a solid-state laser device according to a second embodiment.

FIG. 4 is a configuration diagram of a spherically polished laser medium and a cylindrical non-linear element inserted in the central portion of the second embodiment.

FIG. 5 is a configuration diagram of a solid-state laser device according to a third embodiment.

FIG. 6 is a configuration diagram of each element in which the device of the first embodiment is made plural.

FIG. 7 is a configuration diagram of a conventional solid-state laser device.

[Explanation of symbols]

 13 Nd: YAG crystal 14 Second harmonic generation KTP 19 Semiconductor laser 32 Second harmonic generation KTP 33 Nd: YAG crystal 51 Nd: YAG crystal 53 Second harmonic generation KTP 55 Translucent thermal conductor

Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location H01S 3/108 8934-4M

Claims (7)

[Claims] 1. A cylindrical laser medium that is excited by light, a spherical nonlinear element that surrounds the laser medium as a center, an optical resonator that includes the nonlinear element, and a rotating unit that rotates the nonlinear element. , A solid-state laser device that satisfies the phase matching conditions of the second harmonic and the sum frequency with a certain two rotation angles and generates laser light of multiple wavelengths. 2. A spherical laser medium excited by light, a cylindrical nonlinear element surrounded by the center of the laser medium, an optical resonator including the laser medium, and a rotating means for rotating the laser medium. And a phase matching condition of the second harmonic and the sum frequency are satisfied at a certain two rotation angles, and a multi-wavelength laser beam is generated. 3. The solid-state laser device according to claim 1, wherein an optical resonator having spherical surfaces coated on the entrance surface and the exit surface of the nonlinear element, which are in close contact with the laser medium, and the optical resonator are rotated. A solid-state laser device, comprising: a rotating means, satisfying a phase matching condition of a second harmonic and a sum frequency with a certain two rotation angles and generating laser light of multiple wavelengths. 4. The solid-state laser device according to claim 2, wherein an optical resonator having a spherical surface coated on the entrance surface and the exit surface of the laser medium, which is in close contact with the nonlinear element, and the optical resonator are rotated. A solid-state laser device, comprising: a rotating means, satisfying a phase matching condition of a second harmonic and a sum frequency with a certain two rotation angles and generating laser light of multiple wavelengths. 5. The solid-state laser device according to claim 1, wherein a translucent heat conductor is inserted in the resonator. 6. The solid-state laser device according to claim 1, further comprising a resonator having a plurality of resonator structures. 7. The solid-state laser device according to claim 1, wherein a semiconductor laser is used for pumping.