JPH08222785A - Solid state laser equipment - Google Patents

Abstract

PURPOSE: To stabilize output without dependence on the change of state due to deterioration or the like of a semiconductor laser, by installing a circuit for controlling the wavelength of a first laser light by controlling the temperature of a cooling.heating element, and keeping the wavelength constant. CONSTITUTION: A cooling.heating element for cooling and heating a semiconductor laser 10, a beam splitter 20 for leading out a part of the reflected light from dichroic coating 24, photodetectors 30, 32 for receiving the led-out reflected light and detecting the intensity, and a circuit 33 for controlling the wavelength of the first laser light 11 by controlling the temperature of the cooling.heating element in the manner in which the outputs from the photodetectors 30, 32 become minimum are installed. By controlling the wavelength of the first laser light 11, the output of the semiconductor laser 10 is stabilized, and the wavelength can be made to coincide with the absorption peak of solid state laser medium 21. Thereby laser output of high stability and high efficiency can be obtained.

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 for generating a laser beam used in the fields of optical information processing, optical applied measurement control, printing / plate making, and medical fields.

[0002]

2. Description of the Related Art Conventionally, in order to stabilize the output of a semiconductor laser-excited all-solid-state laser device, Japanese Patent Laid-Open No. 4-3450 has been proposed.
As disclosed in Japanese Patent No. 78, a method is known in which a part of the semiconductor laser light is monitored by an external light receiver and the drive current of the semiconductor laser is changed so that the laser output becomes constant. This method is effective when the temperature of the semiconductor laser is constant, but when the temperature of the semiconductor laser changes due to a change in ambient temperature or when the driving current increases due to deterioration of the semiconductor laser, the semiconductor laser Since the wavelength of light changes and deviates from the absorption peak of the solid-state laser medium, there is a problem that even if the output is controlled to be constant, the output of the all-solid-state laser light fluctuates. Therefore, in order to stabilize the output of the all-solid-state laser, it is necessary to stabilize the output of the semiconductor laser and also keep the wavelength constant.

[0003]

SUMMARY OF THE INVENTION The present invention provides an all-solid-state laser with stable output that does not depend on state changes due to deterioration of the semiconductor laser and the like by stabilizing the output of the semiconductor laser light and making the wavelength constant. The purpose is to provide.

[0004]

To achieve the above object, the present invention provides a semiconductor laser that emits a first laser beam as excitation light, a pair of resonator mirrors, and the first laser beam. A laser medium that emits a second laser beam, and functions as a reflection film for the first laser beam on the opposite side of the semiconductor laser in the laser medium, and for the second laser beam. In a solid-state laser device having a dichroic coating functioning as a non-reflective film, a cooling / heating element for cooling / heating the semiconductor laser, and a beam for extracting a part of reflected light from the dichroic coating. A splitter and a light receiver that receives the reflected light that has been taken out and detects its intensity,
A solid-state laser device comprising: a circuit for controlling the wavelength of the first laser light by controlling the temperature of the cooling / heating element so that the output from the light receiver becomes minimum. In particular, means for extracting a part of the first laser light before entering the laser medium, and a second light receiver for receiving a part of the extracted first laser light and detecting the intensity thereof. It is preferable to further include a circuit for controlling the current of the semiconductor laser so that the output of the second light receiver becomes constant.

[0005]

In the semiconductor laser, the bandgap and the refractive index of the light emitting region change due to changes in temperature or current, and the oscillation wavelength thereof changes. A semiconductor laser used for an all-solid-state laser is generally of a multi-mode type, and in most cases the oscillation wavelength is wider than the absorption spectrum of the solid-state laser medium. Therefore, even a slight change in the oscillation wavelength of the semiconductor laser changes the amount of light absorbed by the solid-state laser medium, resulting in a change in the output of the all-solid-state laser. In order to avoid the output fluctuation caused by this, it is only necessary to fix the oscillation wavelength of the semiconductor laser to the absorption peak of the solid-state laser medium, and for that purpose, the drive current and the temperature of the semiconductor laser may be simultaneously controlled. In order to make the output of the semiconductor laser constant, a part of the output may be monitored by the light receiver, and the drive current value may be changed so that the monitor output becomes constant. In order to match the oscillation wavelength of the semiconductor laser with the absorption peak of the solid-state laser medium, the output of the semiconductor laser should be minimized while the output of the semiconductor laser is stabilized. Good. That is, a part of the transmitted light may be monitored by the light receiver, and the temperature may be controlled so that the monitor output is minimized. In this way, the oscillation wavelength can be made to coincide with the absorption peak of the solid-state laser medium while the output of the semiconductor laser is stabilized.

[0006]

EXAMPLE A solid-state laser medium containing N with a Nd concentration of 1% will be described below.
An embodiment of the present invention using a d: YAG laser will be described with reference to the drawings. FIG. 1 is a diagram for explaining the configuration of an all-solid-state laser that is an embodiment of the present invention.

In the solid-state laser device of this embodiment, as shown in FIG. 1, a semiconductor laser 1 having an output of 1 W and a wavelength of 810 nm is used.
The first laser light 11 output from 0 is split into the first reference light 12 and the excitation light 13 by the beam splitter 20. The reference light 12 is the semiconductor laser 1
The incident light is incident on the second photodetector 30 for monitoring the output of 0, and the output is input to the current control circuit 31 of the semiconductor laser. The current control circuit 31 controls the current value of the semiconductor laser 10 so that the output from the second light receiver 30 becomes constant.

On the other hand, the excitation light 13 has a wavelength of 810 nm and is A
After passing through the resonator mirror 23 having R and 1064 nm with HR coating, it is incident on the Nd: YAG crystal 21 having a length of 10 mm to excite Nd ions. Nd: YAG
At the incident end face of the excitation light of the crystal, wavelengths of 810 nm and 106
AR coating is applied at 4 nm, and the output end face is
The dichroic coating film 24 is AR at 1064 nm and HR at 810 nm. The excitation light is reflected by the HR coating 24 on the emission end face, part of it is reflected as the second reference light 14 by the beam splitter 20, and is incident on the first light receiver 32. Then, the output of the light receiver 32 is input to a circuit 33 for controlling the wavelength of the first laser light, and the temperature control element 3 is controlled by the circuit 33 so that the output of the light receiver 32 is minimized.
4 is driven to control the temperature of the semiconductor laser.
As a result, the oscillation wavelength of the semiconductor laser can be made to coincide with the absorption peak of the Nd: YAG crystal by adjusting the temperature so that the reflected light from the Nd: YAG crystal becomes the weakest. Then, the output mirror 22 having a transmittance of 5% at the wavelength of 1064 nm and the HR at the wavelength of 1064 nm of the Nd: YAG crystal.
A stable second laser beam 15 having a wavelength of 1064 nm is generated from the laser resonator formed between the coating surface and the laser cavity. The actual output value was 250 mW.

In this embodiment, only the case of Nd: YAG crystal is described, but other materials doped with Nd (Y
Even if LF, YVO4, GGG, glass, etc.) is used, there is no problem if a semiconductor laser matched to the absorption peak is used. Further, if the same coating as that applied to the resonator mirror 23 is applied to the incident end face of the Nd: YAG crystal 21 for the excitation light, the resonator mirror 23 can be omitted, and an SHG crystal such as KTP is provided in the resonator. It can be easily inferred that it will function as a short-wavelength light source by inserting it. Furthermore, by locking the wavelength of the first laser light without using the second photodetector and the current control circuit of the semiconductor laser, the same effect can be obtained in increasing the efficiency of the output light with respect to the pumping input.

[0010]

As described above, according to the solid-state laser device of the present invention, the excitation light supplied from the semiconductor laser to the pair of resonator mirrors is received by the laser medium to emit the second laser light. In the solid-state laser device on the opposite side of the semiconductor laser in the laser medium, which is provided with a dichroic coating that functions as a reflection film for the excitation light and as a non-reflection film for the second laser light,
A part of the reflected light from the dichroic coating is taken out by the beam splitter, the light is received by the light receiver, and the temperature of the semiconductor laser is controlled by the cooling / heating element so that the intensity becomes the minimum. By controlling, the output of the semiconductor laser as the pumping light can be stabilized and the wavelength can be matched with the absorption peak of the solid-state laser medium, so that the laser output with high stability and high efficiency can be obtained. Further, by extracting a part of the excitation light before entering the laser medium, receiving the light, and controlling the current of the semiconductor laser so that the intensity thereof becomes constant, the output of the semiconductor laser is further stabilized.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining the configuration of a solid-state laser device that is an embodiment of the present invention.

[Explanation of symbols]

 10 Semiconductor Laser 11 First Laser Light (Excitation Light) 12 First Reference Light 13 Excitation Light 14 Second Reference Light 15 Second Laser Light 20 Beam Splitter 21 Solid Laser Medium 22 Output Mirror 23 Resonator Mirror 24 Dichroic Coating film 30 Second light receiver 31 Current control circuit for semiconductor laser 32 First light receiver 33 Circuit for controlling wavelength of first laser light 34 Temperature control element

Claims (2)

[Claims] 1. A semiconductor laser that emits a first laser light as excitation light, a pair of resonator mirrors, and a laser medium that receives the first laser light and emits a second laser light, A solid-state laser device provided with a dichroic coating on the opposite side of the semiconductor laser in the laser medium, which functions as a reflection film for the first laser light and as a non-reflection film for the second laser light. In the above, a cooling / heating element for cooling / heating the semiconductor laser, a beam splitter for extracting a part of the reflected light from the dichroic coating, and a strength of the extracted reflected light by receiving the reflected light. The wavelength of the first laser light is controlled by controlling the temperature of the light receiving device to be detected and the temperature of the cooling / heating element so that the output from the light receiving device becomes minimum. Solid state laser device and having a road. 2. A means for extracting a part of the first laser light before entering the laser medium, and a second means for receiving a part of the extracted first laser light and detecting the intensity thereof. The solid-state laser device according to claim 1, further comprising a light receiver, and a circuit that controls a current of the semiconductor laser so that an output of the second light receiver is constant.