JPH10303491A - Ld-excited wavelength converting solid laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an LD-excited wavelength converting solid laser device where the temperature of a nonlinear optical element can be set without regard to an LD beam whereby stable output can be obtained at all times. SOLUTION: This laser device is of such a structure that it accommodates a nonlinear optical element 5 within a resonator and that it oscillates the SH waves of fundamental waves induced and emitted from a solid laser medium 3 and outputs them to outside through an output mirror 6, and here an etalon 4 which has an action to reduce noise is inserted between the solid laser medium 3 and the nonlinear optical element 5. In this case, coating which permeates the fundamental waves from the solid laser medium 3 and shows a high reflectance to the LD beam from the semiconductor laser 1 is applied to the end face of the etalon 4, whereby the LD beam does not strike the nonlinear optical element 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a low-noise LD-pumped wavelength conversion solid-state laser device in which an etalon is inserted in an optical resonator.

[0002]

2. Description of the Related Art Output light from a semiconductor laser (hereinafter referred to as LD)
The solid-state laser medium is condensed and irradiated to a solid-state laser medium, and a fundamental wave stimulated and emitted from the solid-state laser medium is irradiated to a nonlinear optical crystal housed in an optical resonator to produce a second light.
2. Description of the Related Art There is known a wavelength conversion solid-state laser device that generates a harmonic, oscillates a second harmonic (hereinafter, referred to as an SH wave) in an optical resonator, and outputs the same to an outside through an output mirror.

In this type of LD-pumped wavelength-converting solid-state laser device, an etalon having the function of reducing the number of longitudinal modes and removing noise due to longitudinal mode competition is inserted between the solid-state laser medium and the nonlinear optical element. There is a low-noise laser device.

Incidentally, in a nonlinear optical element such as KNbO ₃ used in an LD-pumped wavelength conversion solid-state laser device, the phase matching condition changes depending on the temperature. Therefore, in order to always obtain a stable output, the temperature of the nonlinear optical element must be kept constant. Need to be controlled.

[0005] The temperature control of the nonlinear optical element includes:
Conventionally, as shown in FIG. 3, a thermometer 31 is embedded in a base plate 30 on which a solid-state laser medium 23, an etalon 24, a nonlinear optical element 25, an output mirror 26 and the like are mounted, and based on a temperature detection value K thereof, The driving current (L
D current) and a drive current of a Peltier element for temperature control (not shown).

[0006]

By the way, in the temperature control system shown in FIG. 3, since the thermometer 31 is not directly attached to the nonlinear optical element 25, even if the value of K is controlled to be constant, the LD is controlled. The temperature of the nonlinear optical element 25 changes due to light irradiation, and a temperature difference occurs between the temperature and the temperature detected by the thermometer 31. In addition, thermometer 31
Even if the laser light is directly attached to the nonlinear optical element 25, if the LD light changes even slightly, the influence of the change is directly received, and it is impossible to control the temperature.

From the above, conventionally, there has been a problem that the output of the nonlinear optical element becomes unstable because the temperature of the nonlinear optical element changes due to the irradiation of the LD light to the nonlinear optical element and the phase matching condition is deteriorated. .

The present invention has been made in view of such circumstances, and is capable of setting the temperature of a nonlinear optical element irrespective of the LD light, thereby always obtaining a stable output.
An object of the present invention is to provide an excitation wavelength conversion solid-state laser device.

[0009]

The structure for achieving the above object will be described with reference to FIG. 1 showing an embodiment. Excites the solid-state laser medium 3 with the LD light, accommodates the nonlinear optical element 5 in the optical resonator including the solid-state laser medium 3, and converts the SH wave of the fundamental wave induced and emitted from the solid-state laser medium 3 into light. In a laser device configured to oscillate in a resonator and output to the outside via an output mirror 6, and in which an etalon 4 is inserted between the solid-state laser medium 3 and the nonlinear optical element 5, The end face is characterized by being provided with a coating that highly transmits the fundamental wave from the solid-state laser medium 3 and has a high reflectance with respect to the LD light from the semiconductor laser 1.

According to the LD-pumped wavelength-converting solid-state laser device of the present invention having the above-described structure, the LD light from the semiconductor laser 1 is reflected by the etalon 4 and is not irradiated on the nonlinear optical element 5. , And the temperature detected by the thermometer is not different.

Therefore, the temperature of the nonlinear optical element 5 is determined only by the temperature control system as shown in FIGS. 1 and 2, and the phase matching condition is not deteriorated. You can get the output.

[0012]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a view taken in the direction of arrow A in FIG. Output light from the semiconductor laser 1 is applied to a solid-state laser medium (Nd: YAG) 3 via a collimator lens 2a and a focus lens 2b. On one surface of the solid-state laser medium 3, a high-reflection coating film 3a that transmits the LD light from the semiconductor laser 1 and reflects the fundamental wave and the SH wave stimulatedly emitted from the solid-state laser medium 3 with high reflectance. Is formed,
An optical resonator is formed between the high reflection coating film 3a and the output mirror 6.

An etalon 4 and a nonlinear optical element (KNbO ₃ ) 5 for generating an SH wave are inserted into the optical resonator to remove noise due to longitudinal mode competition. The fundamental wave stimulated and emitted by exciting the solid-state laser medium 4 with the output light is applied to the nonlinear optical element 5 to generate a second harmonic. The output mirror 6 mainly transmits the SH wave, and the SH wave is output to the outside of the optical resonator via the output mirror 6.

The SH wave output to the outside of the optical resonator is separated into actual output light and monitor light by a beam splitter 7 disposed close to an output mirror 6, and the monitor light is guided to a photodetector 8. The intensity is detected. This detection result is fed back to the LD / temperature controller driver 9,
The LD current is controlled so as to keep the SH wave output constant.

In the above configuration, the focus lens 2
b, the solid-state laser medium 3, the etalon 4, the nonlinear optical element 5, the output mirror 6, and the beam splitter 7 are fixed on a common base plate 10. This base plate 10 includes
A thermometer 11 is embedded at a position directly below the etalon 4, and a Peltier element 12 for temperature control, to which a heat radiating plate 13 is thermally connected, is arranged on a lower surface side of the base plate 10.

The temperature detection value K of the thermometer 11 is fed back to the LD / temperature controller driver 9 so that the temperature of the base plate 10, that is, the temperature of the nonlinear optical element 5 is kept constant.
The drive current of the Peltier device 12 is controlled.

In this embodiment, the output wavelength of the semiconductor laser 1 is 809 nm, and the solid-state laser medium 3 is Nd: YAG and the laser fundamental wave is 946 nm.
m, the SH wave (nonlinear optical element: KNbO ₃ ) of 47
The etalon 4 used in the LD-excitation wavelength conversion solid-state laser device having such a specification has the following structure.

That is, in this embodiment, the thickness of the etalon 4 is set to 0.3 mm, and the reflectance at both end surfaces is
The coating is applied so that the fundamental wave is 10% at a wavelength of 946 nm and the LD light from the semiconductor laser 1 is at least 90% at a wavelength of 809 nm.

By applying such a coating, the laser beam from the semiconductor laser 1 can be emitted without losing the original etalon effect.
D light can be highly reflected. As a result, the influence of the LD light does not reach the nonlinear optical element 5, and the difference between the actual temperature of the nonlinear optical element 5 and the value K detected by the thermometer 11 disappears.

Therefore, the temperature of the nonlinear optical element 5 is set to
Regardless of light, the temperature control system shown in FIGS.
1, the Peltier element 12 and the temperature controller driver 9) alone, and the phase matching condition of the nonlinear optical element 5 does not deteriorate. As a result, always stable S
H wave output can be obtained.

If the temperature of the nonlinear optical element can be determined irrespective of the LD light, the SH wave can be expected to increase in addition to the stabilization of the SH wave. A specific example will be described below.

First, in the conventional method, as shown in FIG. 3, an SH wave is separated by a beam splitter 27, monitor light is detected by a photodetector 28, and its output is fed back to an LD / temperature controller driver 29. , LD current (LD output power) (hereinafter APC (Automatic
Power Control) function), of course, LD
Since the current and the output of the SH wave must be in a proportional relationship, the temperature of the nonlinear optical element 25, that is, the base plate 30
Is required to be set when the LD current is maximized.

For example, assuming that the maximum current is 1.4 A (ampere) and the current at the time of executing the APC function is about 1.2 A, when LD current is 1.4 A → SH wave output is K = 37.
LD current that reaches a maximum at 0 ° C .;
Consider the case where the maximum occurs at 0 ° C. (However, when the current is large, in the conventional method, the nonlinear optical element needs to be heated and the set temperature of K needs to be lowered.) The temperature of K is set to 38.0 ° C. and the AP is set.
When the C function is activated, a current of 1.2 A is supplied in a normal environment. However, if the output tends to decrease due to a change in the environment, the current increases. Here, the output is restored at the moment when the current is increased, but when the output is decreased again due to the temperature rise of the nonlinear optical element, the current further increases. , And the output remains reduced. Further, if the cycle of the increase and decrease of the current coincides with the cycle of the change of the temperature of the nonlinear optical element, and the phase is shifted by a half cycle, the output may oscillate.

Therefore, the set temperature of K needs to be 37.0 ° C. even when 1.2 A is supplied, and the output is lower than the optimum case. On the other hand, when the temperature of the nonlinear optical element can be set irrespective of the light of the LD (the current of the LD) as in the present invention, the temperature can always be set to the optimum temperature, and the same current can be set when the APC function is executed. As for the value, a larger output can be obtained.

[0025]

As described above, according to the LD pumping wavelength conversion solid-state laser device of the present invention, the fundamental wave from the solid-state laser medium is applied to the end face of the etalon inserted between the solid-state laser medium and the nonlinear optical element. Is applied, and a coating showing high reflectivity for LD light from the semiconductor laser is applied, so that the LD light is not irradiated to the nonlinear optical element, and the temperature of the nonlinear optical element is determined regardless of the LD light. can do. As a result, a stable SH wave output can always be obtained.

[Brief description of the drawings]

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

FIG. 2 is a view taken in the direction of arrow A in FIG. 1;

FIG. 3 is a configuration diagram showing an example of a conventional LD-pumped wavelength conversion solid-state laser device.

[Explanation of symbols]

 Reference Signs List 1 semiconductor laser 2a collimator lens 2b focus lens 3 solid-state laser medium 3a high reflection coating film 4 etalon 5 nonlinear optical element 6 output mirror 7 beam splitter 8 photodetector 9 LD / temperature controller driver 10 base plate 11 thermometer 12 Peltier element 13 Heat sink

Claims (1)

[Claims] 1. A solid-state laser medium is excited by output light from a semiconductor laser, and a nonlinear optical element is accommodated in an optical resonator including the solid-state laser medium, and a fundamental wave stimulatedly emitted from the solid-state laser medium is provided. A laser device configured to oscillate the second harmonic in the optical resonator and output it to the outside via an output mirror, and wherein an etalon is inserted between the solid-state laser medium and the nonlinear optical element. The end face of the etalon is coated with a coating that transmits a fundamental wave from a solid-state laser medium at a high level and has a high reflectivity to light from a semiconductor laser. Laser device.