JP2001210899A - Semiconductor laser exciting solid-state laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser exciting solid-state laser device which is easy to assemble, adjust each position, and maintain optical parts, and stably operates with respect to a temperature change. SOLUTION: A solid laser device is constituted by an exciting unit 10 and a resonator unit 20. The exciting unit 10 is constituted by a semiconductor laser 11 for emitting excited lights, a condensing optical system 15 for condensing the excited lights, a semiconductor laser holder 12 for holding the semiconductor laser 11, an optical system holder 16 for holding the condensing optical system 15, and the like. The resonator unit 20 is constituted by a laser medium 23 for emitting emitted lights by exciting by the excited lights condensed by the condensing optical system 15, a nonlinear optical element 22 for converting the emitted lights in wavelength, a resonator holder 21 for integrally holding the laser medium 23 and the nonlinear optical element 22, and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser-excited solid-state device for arranging a laser medium and a nonlinear optical element in a resonator and exciting the laser medium with a semiconductor laser to generate fundamental oscillation light and nonlinear light. The present invention relates to a laser device.

[0002]

2. Description of the Related Art As a related prior art, US Pat.
No. 731795 describes a semiconductor laser-pumped solid-state laser device in which a laser diode, a lens, a laser medium, a nonlinear optical element, and an output coupler are linearly arranged. Processing is performed according to the shape of each optical component including the heat sink to be held, and each optical component is integrally held without a position adjustment mechanism.

In order to make the optical axis of the excitation light source coincide with the optical axis of the laser resonator and realize efficient laser oscillation, it is necessary to ensure the dimensional accuracy of each optical component and the processing accuracy of the block on the order of μm. is there. For this reason, such mount structures have strict accuracy control, lower production yield,
It is not practical in practice.

In this mounting structure, the laser oscillation becomes unstable because the optical axis shifts and the resonator length change due to the thermal deformation of the block and each optical component.

Furthermore, in this mounting structure, the component shape needs to be rotationally symmetric about the optical axis. Although a relatively low output laser diode can be accommodated in a round package, the optical axis of the laser diode generally does not always coincide with the symmetry axis of the round package. Output 1
In order to ensure sufficient heat dissipation with a laser diode exceeding 00 mW, a round package is not sufficient and is often directly mounted on a heat dissipation block.

Another prior art is disclosed in Japanese Patent No. 268288.
No. 1 discloses a single transverse mode pumped laser in which a semiconductor laser and a laser gain material are butt-connected to each other. Referring to FIG. 1 and the like, the pumping semiconductor laser 18 is fixed to a mounting member 22 made of copper. The mounting member 22 is screwed or fixed to a block 23 made of copper or the like, and the laser gain medium 12 and the optically transparent rod 15 are fixed to the block 23 by an adhesive.

[0007] The mounting member 22 and the block 23 are mounted on a thermoelectric cooler 24 and maintained at a desired temperature. The hot surface of the thermoelectric cooler 24 is mounted on a heat sink 25 to perform heat exchange. A temperature controller 27 mounted within the block 23 and responsive to the output of the temperature sensor 26
Maintains the cold surface of the thermoelectric cooler 24 at a desired temperature.

[0008]

However, in order to realize efficient laser oscillation, it is necessary to match the optical axis of the excitation light with the optical axis of the laser resonator with high precision. Does not describe a specific optical axis adjustment method. Therefore, as a method of optical axis adjustment assumed from such a structure, the semiconductor laser 18 is fixed first,
When the optical transparent rod 15 is gripped by some position and angle adjustment mechanism, and the adhesive is injected into the gap between the block 23 and the semiconductor laser 18 is operated to monitor the laser oscillation state, the optical transparent rod 15 is It is considered that the position was adjusted to the optimal position. At this time, there is a possibility that the gap between the optically transparent rod 15 and the block 23 becomes large. If the gap is wide, heat transfer becomes poor and the laser oscillation operation becomes unstable. Further, when the thickness of the adhesive entering the gap increases, the effect of the adhesive over time deteriorates, and the long-term stability decreases.

As another method, an optical transparent rod 15 is first used.
Is fixed to the block 23, and the mounting member 22 to which the semiconductor laser 18 is fixed is temporarily fixed to the block 23.
It is also conceivable to adjust the semiconductor laser 18 to the optimum position by positioning the mounting member 22 while monitoring the laser oscillation state by operating the laser beam. In this case, the distance between the semiconductor laser 18 and the laser gain medium 12 is about several tens μm due to the butt connection, and the two are extremely close to each other. Therefore, when the position of the mounting member 22 is adjusted or fixed, the semiconductor laser 18 and the laser gain medium 12 are separated. It is likely to be damaged by contact. Therefore, the adjustment method of moving one of the butt-connected members causes a reduction in manufacturing yield.

An object of the present invention is to provide a semiconductor laser-pumped solid-state laser device which can easily assemble, adjust the position of, and maintain optical components and can operate stably with respect to temperature changes.

[0011]

SUMMARY OF THE INVENTION The present invention provides a semiconductor laser that emits excitation light, a light-collecting element that collects the excitation light,
A laser medium provided in a resonator and excited by condensed excitation light to generate oscillating light, a reflection mirror unit forming the resonator, a laser holding member for holding a semiconductor laser, and a light holding element An excitation unit comprising a light-collecting element holding member, a resonator unit integrally holding the laser medium and the reflection mirror means, a fixing means for fixing the relative positions of the excitation unit and the resonator unit, and an excitation unit. And a base member to which any one of the unit and the resonator unit is attached.

According to the present invention, the semiconductor laser and the condensing element are formed as a single unit, and the laser medium and the reflecting mirror are formed as a single unit, so that the assembly and position adjustment of parts for each unit can be performed. It can be completed and mass production in unit units becomes possible.

Further, when assembling and adjusting the position of the entire apparatus, it is sufficient to assemble and adjust the position of the excitation unit and the resonator unit. Therefore, the number of parts to be assembled and adjusted can be reduced, and the simplification and yield of manufacturing can be reduced. Can be improved. Further, if any trouble occurs in a part in the manufacturing process, it is possible to quickly cope with the problem only by replacing the defective unit without disassembling all parts. The normal part of the defective unit can be used in the unit manufacturing process by disassembling the unit, so that the part can be reused and the part loss can be reduced.

According to the present invention, the excitation unit has a sliding surface substantially perpendicular to the optical axis of the excitation light, and the resonator unit has a sliding surface substantially perpendicular to the optical axis of the resonator. The fixing means is characterized in that the excitation unit and the resonator unit are fastened to the respective sliding surfaces in a direction perpendicular to the sliding surface.

According to the present invention, when the optical axes of the excitation light and the resonator are aligned, the sliding surface can be smoothly moved relatively in the surface direction, so that fine adjustment of the position is facilitated. Each optical axis can be accurately and quickly matched. Here, the sliding surfaces of the excitation unit and the resonator unit may be in direct contact with each other, or may be, for example, a thin plate made of a material having a sliding effect and having high heat conductivity, such as a copper foil or a copper plate.

Further, the fixing means applies a slight deformation to the excitation unit and the resonator unit in the optical axis direction by tightening the excitation unit and the resonator unit to each sliding surface in a vertical direction with variable pressing force. The relative distance can be finely adjusted on the order of μm.

Here, it is particularly effective when the reflection mirror means has a curved surface. In a linear resonator with a curved mirror, there is only one optical axis of the resonator, which coincides with the normal at a particular point on the curved mirror. for that reason,
By sliding the excitation unit and the resonator unit in a plane perpendicular to the optical axis, the optical axis of the excitation light can easily match the optical axis of the resonator.

Further, the present invention has a temperature control element for controlling the temperature of the base member, and a window for accommodating the excitation unit, the resonator unit, the base member and the temperature control element, and for taking out the oscillation light to the outside. It is provided with a housing member.

According to the present invention, the temperature of the optical components such as the semiconductor laser and the laser medium can be controlled collectively by the temperature control element controlling the temperature of the base member. Therefore, the size and weight of the entire apparatus can be reduced as compared with the case where a temperature control element is prepared for each optical component. Further, since the temperatures of the semiconductor laser and the laser medium are easily matched, the entire temperature can be managed by one temperature sensor, and the temperature can be easily adjusted.

Further, by housing the excitation unit, the resonator unit, the base member and the temperature control element in the housing member, the influence of disturbances such as dust, humidity and air flow can be eliminated, and the laser operation can be stabilized.

Further, the present invention is characterized in that a nonlinear optical element for wavelength-converting the oscillating light is provided in the resonator, and further held in the resonator unit.

According to the present invention, the laser medium and the nonlinear optical element are held by the same resonator unit, so that the positional fluctuation between the laser medium and the nonlinear optical element becomes extremely small, and the laser operation can be stabilized. .

Further, the present invention is characterized in that the reflection mirror means is provided on the excitation light incident surface of the laser medium.

According to the present invention, since the reflection mirror means constituting the resonator and the laser medium are integrated, there is no need to align the optical axes of the resonator and the laser medium. for that reason,
It is easy to assemble the optical parts, and the optical axis deviation due to vibration or the like can be eliminated.

Further, the present invention is characterized in that the reflection mirror means is provided on the nonlinear light emitting surface of the nonlinear optical element.

According to the present invention, since the reflection mirror means and the nonlinear optical element constituting the resonator are integrated, the optical axis alignment of the resonator and the nonlinear optical element becomes unnecessary. Therefore, assembling of the device becomes easy, and furthermore, the optical axis shift due to vibration or the like can be eliminated.

[0027]

FIG. 1 is a block diagram showing an embodiment of the present invention. Package 1 as a housing member
Is formed by sealing a hollow cap 1b on a metal substrate 1a. A window member 7 for extracting the laser output light to the outside is attached to a side surface of the cap 1b.

A Peltier element 2 as a temperature control element is mounted on the upper surface of the substrate 1a, and a metal base plate 3 is mounted on the Peltier element 2. The Peltier element 2 absorbs heat of the base plate 3. To the substrate 1a. Peltier device 2
Are lead-through terminals (not shown) provided on the substrate 1a.
And the Peltier element 2 is driven by an external temperature controller.

A small hole is formed in the end face of the base plate 3, and a thermistor 6 as a temperature sensor is mounted in the small hole. The lead wire of the thermistor 6 is connected to a through terminal (not shown) provided on the substrate 1b, and the sensor output of the thermistor 6 is supplied to an external temperature controller. The temperature controller monitors the sensor output and controls the drive current of the Peltier element 2 so that the temperature of the base plate 3 becomes constant.

The solid-state laser device includes an excitation unit 10 and a resonator unit 20, as shown in the plan view of FIG. The excitation unit 10 includes a semiconductor laser 11 that emits excitation light, a condensing optical system 15 that condenses the excitation light,
The semiconductor laser 11 includes, for example, a semiconductor laser holder 12 that holds the semiconductor laser 11 in a C-mount system, an optical system holder 16 that holds a condensing optical system 15, and the like.

The semiconductor laser holder 12 and the optical system holder 16 are formed of a heat conductive material such as copper in a rectangular parallelepiped shape, and both have a sliding surface substantially perpendicular to the optical axis of the excitation light. 12 is fixed to the optical system holder 16 by fastening a set screw 12a. The optical system holder 16 is fixed to the base plate 3 by fastening a set screw 16a.

The condensing optical system 15 includes a fiber lens 13
And an axially symmetric condenser lens 14. Since the beam divergence angle of the semiconductor laser 11 is greatly different in the orthogonal direction, the fiber lens 13 condenses in the direction of the larger divergence angle and converts it into parallel light, thereby eliminating astigmatism and improving light use efficiency. And the condenser lens 14 has a function of adjusting the diameter of a beam incident on the resonator unit 20.

As shown in FIG. 5, the resonator unit 20 includes a laser medium 23 which is excited by the excitation light condensed by the condensing optical system 15 to generate oscillation light, and a non-linear optical system which converts the oscillation light into a wavelength. Resonator holder 2 integrally holding element 22, laser medium 23 and nonlinear optical element 22
1 and the like.

A curved surface portion is formed on the excitation light incident surface of the laser medium 23 by photolithography technology or the like, and a coating having a high reflectance with respect to the wavelength of the oscillating light of the laser medium 23 is applied to form the resonator. A curved mirror 24 constituting one of them is formed.

On the other hand, the non-linear light emitting surface of the non-linear optical element 22 is formed in a planar shape, and similarly, by applying a coating having a high reflectance with respect to the wavelength of the oscillating light of the laser medium 23, the other side of the resonator is provided. A mirror 25 is formed.

As described above, the resonator mirror is connected to the laser medium 23.
In addition, by forming the optical axis integrally with the nonlinear optical element 22, the optical axis alignment is simplified, and as a result, the assembly of optical components is facilitated, and the optical axis shift due to vibration or the like can be eliminated.

The resonator holder 21 is formed of a heat conductive material such as copper in the shape of a rectangular parallelepiped, has a sliding surface 26 substantially perpendicular to the optical axis of the resonator, and the optical system holder 16 is also formed of the resonator. The resonator holder 21 has a sliding surface substantially perpendicular to the optical axis, and is fixed to the optical system holder 16 by fastening a set screw 30. A washer 35 for preventing loosening is attached to the head of the set screw 30.

Next, the procedure for assembling and adjusting the positions of components will be described. First, the semiconductor laser holder 12 on which the semiconductor laser 11 and the fiber lens 13 are mounted is temporarily fixed to the optical system holder 16 with a set screw 12a. It slides and is fully tightened with the set screw 12a.
Next, the condenser lens 14 is placed, the position and the optical axis are adjusted, and an adhesive is applied and fixed. Thus, the excitation unit 10 is completed.

Next, with respect to the resonator unit 20, the resonator holder 21 is set on another optical bench, the laser medium 23 and the non-linear optical element 22 are placed, and the position and the optical axis are adjusted. Apply and fix. Thus, the resonator unit 20 is completed.

Next, the resonator unit 20 is connected to the excitation unit 1.
The optical unit holder 16 is temporarily fixed to the optical system holder 16 with a set screw 30, and the resonator unit 20 is slid in the vertical direction of the optical axis while keeping the optical unit holder 16 in close contact with the optical system holder 16 so that the excitation light optical axis of the excitation unit 10 is After the resonator optical axis of the resonator unit 20 is made to coincide with the optical axis of the resonator, the screw is fully tightened with a set screw 30. At this time, by adjusting the pressing force by tightening the set screw 30, the position of the resonator can be finely adjusted on the order of μm within the sliding surface. Thus, the basic configuration of the solid-state laser device is completed.

Next, the optical system holder 16 is mounted on the base plate 3, and the optical system holder 16 is temporarily fixed with a set screw 16 a, and the optical system holder 16 is positioned so that the optical axis of the solid-state laser device passes through the window member 7. After the adjustment, the screw is fully tightened with the set screw 16a.

After the units are assembled and adjusted in this way, by assembling and adjusting the units, the number of parts to be assembled and adjusted can be reduced, and the manufacturing can be simplified and the yield can be improved.

The sliding surfaces of the semiconductor laser holder 12 and the optical system holder 16, the sliding surfaces of the optical system holder 16 and the resonator holder 21, and the sliding surfaces of the optical system holder 16 and the base plate 3 are in direct contact. However, adhesion and thermal bonding can be improved by interposing a shim made of a material having good adhesion and heat conductivity such as copper foil.

FIG. 3 is a plan view showing another configuration example of the excitation unit 10. The condensing optical system 15 includes a GRIN lens 17 whose refractive index changes according to a predetermined function according to the distance from the optical axis.
The excitation light incident surface is formed as a single body, and is formed on a cylindrical surface exhibiting one-way light collecting property.

FIG. 4 is a plan view showing still another example of the configuration of the excitation unit 10. The condensing optical system 15 is composed of axially symmetric condensing lenses 18 and 19, and forms a zoom optical system in which the beam diameter can be easily adjusted.

FIG. 6 is a configuration diagram showing another example of the resonator unit 20. The excitation light incident surface of the laser medium 23 is formed in a planar shape, and a mirror 28 constituting one of the resonators is formed by applying a coating having a high reflectance to the wavelength of the oscillation light of the laser medium 23.

On the other hand, a curved surface portion is formed on the non-linear light emitting surface of the non-linear optical element 22 by photolithography technology or the like, and a coating having a high reflectivity with respect to the wavelength of the oscillation light of the laser medium 23 is provided. Curved mirror 27 is formed.

As described above, the resonator mirror is connected to the laser medium 23.
In addition, by forming the optical axis integrally with the nonlinear optical element 22, the optical axis alignment is simplified, and as a result, the assembly of optical components is facilitated, and the optical axis shift due to vibration or the like can be eliminated.

In the above description, the excitation unit 10 is mounted on the base plate 3 and the resonator unit 20 is mounted on the excitation unit 10. However, the resonator unit 20 is mounted on the base plate 3, Resonator unit 20
A configuration in which the excitation unit 10 is attached to the device is also possible.

[0050]

Next, a specific example of the structure will be described. An Nd: YVO ₄ crystal is used as the laser medium 23, a KTP (KTiOPO ₄ ) crystal is used as the nonlinear optical element 22, and a semiconductor laser element 11 that emits excitation light having a wavelength of 809 nm is used.

On the surface of the laser medium 23 on the excitation light incident side, a wavelength of 1064 nm, which is the oscillation wavelength of the laser medium 23, is used.
Is applied with a reflectance of 99.9% or more and a transmittance of 95% or more with respect to the wavelength of 809 nm of the excitation light. Opposite surfaces of the laser medium 23 and the nonlinear optical element 22 have a wavelength of 1064 n
m is coated so that the transmittance is 99.9% or more. The output side surface of the nonlinear optical element 22 is provided with a coating having a reflectance of 99.9% or more for a wavelength of 1064 nm and a transmittance of 95% or more for a wavelength of 532 nm. Thus, the laser medium 23
Is formed between the incident side surface of the non-linear optical element 22 and the exit side surface of the nonlinear optical element 22.

The wavelength of 809 nm from the semiconductor laser device 11
Is excited to excite the laser medium 23, laser oscillation having a wavelength of 1064 nm occurs in the resonator, and this oscillation light is wavelength-converted by the nonlinear optical element 22, and is nonlinearly converted into a nonlinear light having a wavelength of 532 nm, which is the second harmonic 8. Green light is generated.

Next, another configuration example will be described. Laser medium 2
3, a Nd: YAG crystal is used as the nonlinear optical element 22, a KN (KNbO ₃ ) crystal is used as the nonlinear optical element 22, and a semiconductor laser element 11 that emits excitation light having a wavelength of 809 nm is used.

The surface of the laser medium 23 on the excitation light incident side has a reflectivity of 99.9% or more with respect to a wavelength of 946 nm, which is an oscillation wavelength of the laser medium 23, and a wavelength of 809 nm with respect to the excitation light. A coating having a transmittance of 95% or more is provided. Opposite surfaces of the laser medium 23 and the nonlinear optical element 22 are coated with a coating having a transmittance of 99.9% or more at a wavelength of 946 nm. The output surface of the nonlinear optical element 22 is coated with a coating having a reflectance of 99.9% or more at a wavelength of 946 nm and a transmittance of 95% or more at a wavelength of 473 nm. Thus, a resonator is formed between the incident surface of the laser medium 23 and the emission surface of the nonlinear optical element 22.

The wavelength of 809 nm from the semiconductor laser device 11
When the laser beam 23 is excited to excite the laser medium 23, laser oscillation with a wavelength of 946 nm occurs in the resonator, and this oscillation light is wavelength-converted by the nonlinear optical element 22, and the second
Non-linear blue-green light having a wavelength of 473 nm, which is the harmonic 8, is generated.

The nonlinear light thus obtained travels along the optical axis, passes through the window member 7 and is extracted to the outside, and is used for applications such as optical recording, optical communication, and measurement, and other short wavelength laser light sources. You.

In the above description, an example of the short wavelength light source including the laser medium 23 and the nonlinear optical element 22 has been described. However, the present invention is also applicable to a fundamental wave laser light source using only the laser medium 23 without the nonlinear optical element 22. Is applicable.

[0058]

As described above in detail, according to the present invention, the semiconductor laser and the condensing element are constituted as a single unit, and the laser medium and the reflection mirror means are constituted as a single unit. Assembly and position adjustment of parts can be completed, and mass production in unit units becomes possible.

Further, in assembling and adjusting the position of the entire apparatus, it is sufficient to assemble and adjust the position of the excitation unit and the resonator unit. Therefore, the number of parts to be assembled and adjusted can be reduced, and the simplification of the production and the yield can be reduced. Can be improved.

Further, since the excitation unit and the resonator unit have a sliding surface substantially perpendicular to the optical axis,
When aligning the optical axes of the excitation light and the resonator, the sliding surface can be moved relatively smoothly in the surface direction, so that fine adjustment of the position is easy and each optical axis can be adjusted with high accuracy and speed. Can be matched.

Further, by controlling the temperature of the base member by the temperature control element, the temperature of optical components such as a semiconductor laser and a laser medium can be controlled collectively.

Further, by holding the laser medium and the nonlinear optical element in the same resonator unit, positional fluctuation between the laser medium and the nonlinear optical element becomes extremely small, and the laser operation can be stabilized.

In this manner, a compact and compact semiconductor laser-pumped solid-state laser device which is easy to assemble, adjust the position and maintain optical components, operates stably with respect to temperature changes, and can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention.

FIG. 2 is a plan view of the excitation unit 10 as viewed from above.

FIG. 3 is a plan view showing another configuration example of the excitation unit 10.

FIG. 4 is a plan view showing still another configuration example of the excitation unit 10.

FIG. 5 is a configuration diagram of the resonator unit 20 of FIG.

FIG. 6 is a configuration diagram showing another example of the resonator unit 20.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Package 2 Peltier element 3 Base plate 6 Thermistor 7 Window member 8 Second harmonic 10 Excitation unit 11 Semiconductor laser 12 Semiconductor laser holder 12a, 16a, 30 Set screw 15 Condensing optical system 16 Optical system holder 20 Resonator unit 21 Resonance Holder 22 nonlinear optical element 23 laser medium 24, 27 curved mirror 25, 28 mirror

Claims (6)

[Claims] 1. A semiconductor laser that emits excitation light, a condensing element that condenses the excitation light, and a laser medium that is provided in a resonator and that is excited by the condensed excitation light to generate oscillating light. A reflection mirror means forming a resonator; an excitation unit comprising a laser holding member for holding a semiconductor laser and a light-collecting element holding member for holding a light-collecting element; and a laser medium and a reflection mirror means. A semiconductor laser comprising: a resonator unit to be held; fixing means for fixing the relative positions of the excitation unit and the resonator unit; and a base member to which one of the excitation unit and the resonator unit is attached. Excitation solid-state laser device. 2. The excitation unit has a sliding surface substantially perpendicular to the optical axis of the excitation light, the resonator unit has a sliding surface substantially perpendicular to the optical axis of the resonator, and a fixing means. 2. The semiconductor laser-excited solid-state laser device according to claim 1, wherein the pumping unit and the resonator unit are fastened to each sliding surface in a direction perpendicular to the sliding surface. A temperature control element for controlling the temperature of the base member; a housing member containing the excitation unit, the resonator unit, the base member and the temperature control element, and having a window for taking out oscillation light to the outside; The solid-state laser device according to claim 1, wherein the semiconductor laser-excited solid-state laser device is provided. 4. The semiconductor laser pump according to claim 1, wherein a nonlinear optical element for converting the wavelength of the oscillated light is provided in the resonator, and further held by the resonator unit. Solid state laser device. 5. The semiconductor laser-excited solid-state laser device according to claim 1, wherein the reflection mirror means is provided on an excitation light incident surface of the laser medium. 6. The semiconductor laser-pumped solid-state laser device according to claim 4, wherein the reflection mirror means is provided on the nonlinear light emitting surface of the nonlinear optical element.