JPH11330601A - Light intensity modulated laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light intensity modulated laser device which is stabilized in output power and output position at the same time and restrained from becoming large in size as a whole, even if it is composed of a solid-state laser device and a modulation device. SOLUTION: A light intensity modulated laser device has a structure where a laser beam L2 is projected from a solid-state laser device 2 using an exciting light L2 outputted from an exciting light source 1, the laser beam L2 is made to penetrate through a light intensity modulation device 3 so as to be intensity- modulated into an intensity-modulated laser beam L3, and the laser beam L3 is outputted from the light intensity modulated device 3. A photodetector 4 measures the average intensity of the laser beam L3, receiving a part of the laser beam L3, and the exciting light source 1 is controlled in output by a control 5 on the basis of the measurement result so as to lessen a variation in the output of the solid-state laser device 2. Furthermore, at least a resonator of the solid-state laser device 2 is provided onto an invar material base plate B1, and the resonator is kept at a constant temperature by a temperature controlling means 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of solid-state laser devices, and more particularly to a solid-state laser device capable of emitting intensity-modulated laser light.

[0002]

2. Description of the Related Art Intensity modulated laser light is used for various purposes. For example, there is a distance measurement using the laser light. As a method of measuring the distance, a method is generally used in which the intensity-modulated laser light is emitted toward a target, and the distance is calculated by measuring the phase difference between the reflected light and the emitted light with a detector. .

On the other hand, a laser beam having high monochromaticity and good coherence is useful as a laser beam used for distance measurement. In particular, a solid-state laser device that uses a semiconductor laser as an excitation light source can emit laser light with good monochromaticity and coherence and is compact, so that it is the most suitable laser device for distance measurement.

[0004] Therefore, it is preferable to use a solid-state laser device excited by a semiconductor laser to emit intensity-modulated laser light and use it for distance measurement. However, a solid-state laser device having an intensity modulation function is not commercially available, and if such a laser device is desired, a commercially available CW laser device and a modulation element are separately purchased, and these are purchased. You need to combine them yourself.

[0005]

However, when an existing device is combined by itself as described above, the stability with respect to the output amount (such as the average intensity) and the stability with respect to the output position (such as the direction of the optical axis) are reduced. There are the following problems:

[0006] Regarding the stability regarding the output amount, a configuration for stabilizing each element such as a laser device and a modulation element is provided. However, since the stability of the combined apparatus as a whole is determined by the stability of each element, it is not possible to demand a higher stability than the individual elements for the entire apparatus.

With respect to the stability of the output position, for example, a configuration is conceivable in which a position detector is provided to monitor a part of the output light, and based on the output light, the emission direction is finely adjusted and stabilized. However, in such a configuration, the size of the entire device is increased due to the attachment of the position detector, the fine movement device, the control device, and the like. When a position detector is used, the position detector is also used for detecting an output amount in order to suppress the size of the entire apparatus as much as possible and to prevent a large amount of monitoring light from being output light. become. However, the position detector has a lower detection accuracy of the output amount than the dedicated light detection element, and the accuracy of the stability regarding the output amount is deteriorated. That is, it is difficult to stabilize the output amount and the output position at the same time while suppressing an increase in the size of the entire apparatus.

Further, as an incidental problem, when an existing device (a device sold as a finished product) is purchased and combined, for example, in a solid-state laser device, its components and the like are already fixed at predetermined positions. However, there is also a problem that the degree of freedom of combination is low, for example, it is not possible to freely change the arrangement according to the design, and the whole apparatus becomes large.

An object of the present invention is to provide a light intensity capable of simultaneously stabilizing an output amount and an output position and suppressing an increase in the size of the entire device, while having a configuration in which a solid-state laser device and a modulation element are combined. An object of the present invention is to provide a modulation laser device.

[0010]

The light intensity modulation laser device according to the present invention has the following features. (1) It has a solid-state laser device, its excitation light source, a light intensity modulation element, a photodetector, and a control unit, and laser light from the solid-state laser device passes through the light intensity modulation element and is intensity-modulated. Is configured to be output from the device as a laser beam, the photodetector receives a part of the intensity-modulated laser beam, measures the average intensity of the light, and the control unit determines a result of the measurement. The output of the excitation light source is controlled so that the output fluctuation is reduced based on the above, at least the resonator portion of the solid-state laser device, on a single base plate made of Invar material, directly or from the Invar material A light intensity modulation laser device provided through a holding member, and provided with a temperature adjusting means capable of keeping at least the resonator portion at a constant temperature.

(2) The solid-state laser device, the excitation light source, the light intensity modulation element, the light detector, and the optical system provided therebetween are provided on one base plate made of Invar material. The intensity-modulated laser device according to (1).

(3) The above-mentioned (1), wherein the solid-state laser device, the excitation light source, the light intensity modulation element, the photodetector, and the optical system provided therebetween are provided with a temperature adjusting means so as to maintain a constant temperature. The intensity-modulated laser device according to (1).

(4) The intensity-modulated laser device according to the above (1), wherein the temperature adjusting means uses an element which generates or absorbs heat by the Peltier effect.

(5) A cover for locally covering the resonator portion is further provided, and the cover is formed so that light can enter and exit the resonator portion, and the inside of the cover has a constant temperature. The intensity-modulated laser device according to (1).

(6) The temperature adjusting means utilizes an element which generates or absorbs heat by the Peltier effect, wherein the element comprises an upper surface of the cover and a lower surface of a base plate made of Invar material. The intensity-modulated laser device according to the above (5), which is provided in (5).

In the present invention, the term "resonator portion" refers to a solid-state laser device included in the light intensity modulation laser device of the present invention, which is provided between the mirrors in addition to the pair of mirrors that normally constitute the resonator. It contains all the components such as the laser active medium obtained.

[0017]

As described in the description of the prior art, the light intensity modulation laser device is mainly used for distance measurement. In such a case, since it is a precise measurement work of measuring the phase difference of the sine waveform output light with a detector, positional fluctuations such as a shift in the optical axis of the output light must be particularly suppressed. No. The present inventors have focused on a solid-state laser portion, particularly a resonator portion, among the elements constituting the light intensity modulation laser device, and have a configuration in which at least this portion is provided on a single base plate. Invar material was used as the material for. Hereinafter, a base plate made of Invar material,
It is called "Invar base plate". According to this configuration, even if there is a temperature change around the device or the device itself, at least the positional relationship between components constituting the resonator portion hardly changes, and the output is stabilized.

In the present invention, at least the resonator portion is kept at a constant temperature while using the Invar base plate. This configuration not only stabilizes the temperature of the resonator part itself, but also limits the temperature range in which the Invar base plate used for this part can exhibit its special thermal expansion coefficient characteristics most. , And the stability of the positional relationship between the parts is determined.

Further, in the present invention, a special control is performed in order to further reduce and stabilize the output fluctuation in terms of intensity. In the control, a part of the intensity-modulated laser light (hereinafter referred to as “intensity-modulated light”), which is the output light, is made incident on the photodetector, and the average intensity is measured. This is control for stabilizing the intensity modulated light (output light). In order to stabilize fluctuations in this control, the technique itself of the operation performed on the numerical value is feedback control, that is, so-called APC (Auto Power Control). However, an important feature unique to this control is that, as shown in FIG. 1, a part L31 of the intensity-modulated light L3 is taken as a sample, the average intensity of the light is measured, and the measurement result is
The point is that feedback control is performed by going back to the excitation light source 1 beyond the light intensity modulation element and further beyond the solid-state laser device. With this configuration, it is possible to control so that the total output fluctuation, which is a sum of unstable operations of elements (such as a solid-state laser device and a light intensity modulation element) that may cause output fluctuation, is always kept constant. Become. Therefore, high stability, which is not restricted by the stability of individual elements, can be easily obtained as a whole device including the solid-state laser device and the light intensity modulation element.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a light intensity modulation laser device according to the present invention comprises a solid-state laser device 2 and its excitation light source 1, light intensity modulation element 3, photodetector 4, control unit 5, inversion unit. It has a material base plate B1 and a temperature adjusting means 6 as main components. The excitation light source 1 emits excitation light L1, and the excitation light causes the solid-state laser device 2 to emit laser light L2. The laser light L2 passes through the light intensity modulation element 3 and is converted into intensity modulated light L3.

First, a configuration using an invar base plate will be described. In the present invention, at least the resonator portion is provided on one Invar base plate B1. The extent to which other portions in addition to the resonator portion are provided on one Invar base plate is optional. In the example of FIG. 1, from the excitation light source 1 to the output side mirror 2b of the solid-state laser, that is, the excitation light source 1, necessary optical systems such as a collimator lens and a focus lens, and a resonator portion (the input side mirror 2a,
The laser active medium 2c and the output side mirror 2b) are provided on one Invar base plate.

On the other hand, in the present invention, from the excitation light source to the light intensity modulating element, the last slit, and the photodetector,
Providing all components on a single base plate is a preferred embodiment regardless of the material of the base plate. Thus, the positional fluctuation in the optical axis direction and the direction perpendicular to the optical axis is suppressed to some extent, and the output is more stabilized. Further, the entire individual devices can be compactly assembled.

From these points, the following embodiment is preferable for the configuration using the base plate. A mode in which all components of the device are provided on one Invar base plate. One base plate (b) made of a material other than the Invar material
1) is set to a size in which all components can be arranged,
A mode in which an invar material base plate is further provided thereon, and at least a resonator portion is arranged on the invar material base plate. In this embodiment, the invar base plate may be fitted into the base plate b1.

All the components of the device may be provided directly on the base plate or via a holding member.
Since components such as a mirror and a laser active medium of the resonator are different from each other in size, they are usually arranged on the same optical axis via a holding member. When a holding member is used for mounting the resonator portion and other elements on the Invar base plate, the material of the holding member is an Invar material. Accordingly, the positional relationship between the components is not easily affected by the thermal expansion not only in the positional relationship in the optical axis direction of the beam but also in the direction perpendicular to the optical axis direction of the beam.

The invar material is an alloy having a characteristic (invar characteristic) in which a change in length is very small at a temperature near room temperature. That is, while the coefficient of thermal expansion of a normal metal shows a linear increase near room temperature, the coefficient of thermal expansion of an Invar material draws a special curve that is almost flat near room temperature. As the invar material, a Fe—Ni alloy (Fe64.6, Ni3
5.4 [mol%]), Super Invar (Fe64.
2, Ni 31.0, Co 4.8), stainless invar (Fe 37.3, Co 52.3, Cr 10.4),
Fe-B type, Cr-Fe-Mn type, Mn-Ge type, and the like. Among them, Super Invar is
In particular, the coefficient of thermal expansion is small (± 0.1 [1
0 ^-6 K ^-1 ]), particularly preferable materials for the base plate and the holding member.

Next, the temperature adjustment will be described. As shown in FIG. 1, in the present invention, at least the resonator portion is adjusted to a constant temperature by the temperature adjusting means 6. As a result, at least the resonator portion is kept at a constant temperature without depending on the fluctuation of the environmental temperature or the like, and the pointing of the laser is stabilized.

The temperature to be kept constant by the temperature adjusting means is 10 to 40 when the structure in which all the components are formed on one base plate is taken into consideration due to the operating temperature of the semiconductor laser as the excitation light source. ° C, and it is preferable to control the temperature so that the oscillation wavelength of the semiconductor laser matches the absorption wavelength of the laser active medium. When only the resonator portion is formed on one base, the temperature may be set to an arbitrary temperature within a range where the laser active medium normally emits light.
In the case where the fundamental wave is converted to visible light and emitted by inserting the HG element, the temperature must be controlled so that the SHG element operates stably, that is, the phase matching is maintained. Is required.

The temperature adjusting means may be of any type as long as it can adjust the temperature of the target portion (ie, at least the resonator portion) to be adjusted to a constant temperature. Although the temperature adjusting means 6 is schematically shown by a dashed line in FIG. 1, specifically, a part for actually exchanging heat such as heating and cooling and a target part by controlling this are kept at a constant temperature. And a control unit for keeping the The control unit is omitted in the figure. Any type of heating device / cooling device may be used alone or in combination for the portion that exchanges heat. However, a device that generates or absorbs heat by the Peltier effect (Peltier device) is small. It is preferable because of its simple configuration.

The temperature range to be adjusted is at least the resonator portion. However, if the temperature of the entire portion where the invar base plate is used is adjusted, the invar characteristic can be fully utilized. In this case, it is a preferable mode to adjust the temperature of the resonator portion and other elements from the lower surface side of the invar material base plate through the invar material base plate.
This facilitates uniform temperature adjustment for each component on the Invar base plate. For example, when a Peltier element is applied, a configuration in which the Peltier element is laid on the lower surface of the base plate may be used.

In order to more effectively control the temperature of elements (particularly, the resonator portion) provided on the Invar material base plate, a cover for locally covering the resonator portion is further provided, and the cover and the Invar material base are provided. The plate surrounds the resonator part as much as possible. According to this embodiment, only the temperature inside the cover needs to be intensively controlled.

The cover is formed so that light can enter and exit the resonator portion. That is, since the excitation light and the laser light emitted from the resonator portion enter and exit the cover, at least the entry and exit portions are formed using a material that is transparent to the light that enters and exits. And an embodiment in which the entrance and exit portions are formed as through holes.

When the cover is provided, it is preferable that the temperature adjusting means (particularly, the Peltier element) is attached to the upper surface of the cover and the lower surface of the Invar base plate. Thereby, the temperature can be effectively adjusted by sandwiching the space in the cover from above and below. If necessary, a temperature adjusting means may be further provided on the side of the cover. When the temperature adjusting means is attached to the cover, the portion is preferably made of a material having good thermal conductivity, or a part of the cover may be constituted by a Peltier element or the like.

Next, a description will be given of a configuration for stabilizing output fluctuations in terms of intensity. As shown in FIG. 1, of the intensity-modulated light L3, a part of the light L31 is received by the photodetector 4 and the average intensity is measured, and the rest is output as intensity-modulated light L32 (output light) to the outside. Is output. Photodetector 4
The controller 5 calculates the fluctuation of the intensity-modulated light L31 (= the fluctuation of the intensity-modulated light L32) based on the result of the measurement of the average intensity, and operates the excitation light source 1 so that the fluctuation becomes smaller. The magnitude of the output of the light L1 is controlled.

In the above-described control, the technique pertaining to the numerical operation itself for stabilizing the output fluctuation of the apparatus may use a feedback control technique. For example, as shown in FIG. 1, a target value S1 of the output to be stabilized is given as a constant to the control unit 5 in advance, and a deviation between this S1 and the measurement result S2 of the output from the photodetector is obtained. And a method of controlling the excitation light source such that the already occurring fluctuations are corrected. In the case of using the feedback control method, known control devices and techniques themselves may be used.

A control section for controlling the excitation light source;
The processing of the measurement result from the photodetector may be performed at an optimum time interval or may be performed continuously. The measurement of the average intensity of the light-intensity-modulated light L31 in the photodetector may be in accordance with the processing in the control unit.

As the solid-state laser device and its excitation light source, it is preferable to use a solid-state laser device using a semiconductor laser element as an excitation light source. The laser active medium of the solid-state laser device may be a YAG crystal doped with Nd or Tm, or a YVO crystal doped with Nd or Er.
A laser active medium for a general solid-state laser device such as _four crystals can be used. Since YVO ₄ oscillates with linearly polarized light, it is preferable in that the polarization direction can be easily matched with an AOM crystal described later.

In the case of using a laser active medium doped with a rare earth element (or as a direct compound), an excitation light source should be selected so as to emit excitation light having a wavelength appropriate for the type of the rare earth element. In particular, the combination of using a Nd-doped YVO ₄ crystal as a laser active medium of a solid-state laser device and using a semiconductor laser element that emits laser light having a wavelength of around 810 nm as an excitation light source constitutes an inexpensive and compact solid-state laser device. Is preferred.

Examples of the light intensity modulation element include an acousto-optic modulation element (AOM) and an electro-optic modulation element (EOM). For the purpose of distance measurement, a modulation frequency of about several tens of MHz is useful, and both AOM and EOM can be used. However, using AOM is cheaper and preferable.

The AOM is a known element made of a substance exhibiting an acousto-optic effect. The AOM inclines the AOM at an appropriate angle (Bragg angle) with respect to the optical axis of the incident laser beam, and applies the intensity of the ultrasonic wave to be applied. Is modulated at the desired frequency,
The intensity-modulated laser light is refracted as zero-order light and first-order light (first-order diffracted light), and is output in two directions at an angle.
Crystals used for AOM have a polarization direction in which diffraction effectively occurs. Usually, it is more advantageous to make this polarization direction and the polarization direction of the incident laser light uniform.

In order to make a part of the intensity-modulated light passing through the light-intensity modulation element incident on the photodetector, it may be divided into a photodetector and an output using a beam splitter or the like. When the AOM is used as the light intensity modulation element, the laser light is separated into the zero-order light and the primary light and emitted as described above. The present invention proposes a configuration in which one of the two emitted lights is used for a photodetector and the other is used as output light. With this configuration, it is not necessary to use a beam splitter or the like to split the laser light as described above, and light loss in the splitting element can be reduced.

When the AOM is used, only one of the 0th-order light and the 1st-order light is conventionally used for output and the other is discarded wastefully. It is preferable because it can be used effectively. Further, since the intensities of the 0th-order light and the 1st-order light do not change so much, the amount of light incident on the photodetector can be much larger than in the case of using a beam splitter or the like. The accuracy of the measurement of the intensity or the accuracy of the measurement of the position fluctuation of the output optical axis described later is improved.

The EOM is a known element made of a substance exhibiting an electro-optic effect. When an electric signal is applied to the EOM, a laser beam intensity-modulated at the frequency of the electric signal is generated similarly to the action of a sound wave on the AOM. can get.

The solid-state laser device of the present invention may be further provided with a configuration capable of converting the wavelength of the output laser light (ie, the fundamental wavelength at which laser oscillation occurs in the resonator) depending on the application. As a method of wavelength conversion, a second harmonic generation, higher harmonic generation, a method using optical parametric oscillation, and the like can be mentioned.

For example, when the laser beam to be output requires light in the visible region, for example, when used in an atmosphere containing moisture, the fundamental oscillation wavelength of the solid-state laser device is set to near-infrared. Preferably, the laser beam is used as a fundamental wave and the second harmonic is generated.

To generate the second harmonic, a second harmonic generation element (SHG element) is provided in the resonator of the solid-state laser device.
Is preferable, whereby a small-sized laser device capable of emitting a high-output visible laser beam can be easily formed. As the SHG element, KTiOP
O ₄ crystal and LiNbO ₃ crystal (PPLN: periodically poled Lithium Niobat)
e), a similarly poled LiTaO ₃ crystal (PPL
T) can be used. An element using a Z-cut LiNbO ₃ or LiTaO ₃ crystal having periodic polarization inversion has a high conversion efficiency due to quasi-phase matching, and these crystals do not rotate in the polarization direction.
This is preferable because the alignment of the polarization direction with the M crystal can be maintained and high efficiency can be achieved. It is further preferable to use a Z-cut PPLN or PPLT doped with an impurity such as Mg because light damage resistance can be improved.

The photodetector may be any device, such as a photodiode, that receives light-intensity-modulated light and outputs an electric signal corresponding to the average intensity.

In order to effectively input the laser light emitted from the solid-state laser device to the light intensity modulation element, an appropriate focusing optical system should be selected. For example, as a simple and preferable structure, (the divergence angle of the laser light emitted from the solid-state laser device), and (the distance between the output-side mirror of the solid-state laser device and the modulation element) is determined by one A condenser lens can be used.

[0048]

EXAMPLE 1 In this example, the light intensity modulation laser device shown in FIG. 2 was actually manufactured. In FIG. 2, the control unit and the wiring system are omitted.

[Configuration of the Entire Apparatus] A Nd: YVO ₄ laser apparatus (basic oscillation wavelength 1064 nm) is constructed by pumping a semiconductor laser (wavelength: 810 nm), and a green laser beam (green) is obtained by disposing an SHG element inside the resonator. 532 nm), and the green laser light is modulated by AOM at a modulation frequency of 80 MHz.
The configuration is such that the signal is output after being subjected to intensity modulation of z. Each component is attached to a holding member (excluding a structural part having a fine movement function) B2 made of Invar material, and they are fixed on one Invar material base plate B1.
Super Invar was used for all Invar materials.

The temperature adjusting means has a structure in which a Peltier element is laid on the lower surface of the base plate B1, and a lowermost base plate is provided therebelow. The configuration of the control for stabilizing the fluctuation in the intensity of the output is such that the primary light from the AOM is output from the device,
The zero-order light is received by the photodetector, the average intensity is measured, and the output of the semiconductor laser is feedback-controlled based on the average intensity.

[Structure of Each Part] The semiconductor laser device 1 serving as an excitation light source has an oscillation wavelength of 810 nm and a continuous oscillation (CW).
And the maximum output is 500 mW. Semiconductor laser element 1
The temperature was controlled at 25.0 ° C. using a Peltier device 1a. The excitation light L1 is transmitted through an optical system (a collimating lens p).
1. The focus lens p2) is configured to be incident on the laser crystal 2a of the solid-state laser device 2.

Laser crystal 2a of solid laser device 2
Is YVO with a-axis cut, Nd 1.0at%, thickness 1mm
_Four crystals were obtained. Both end faces before and after the laser crystal 2a are parallel planes. Of the two end faces, the end face on the side on which the excitation light L1 is incident is coated with non-reflection for the excitation light wavelength of 810 nm and high reflection for the oscillation wavelength of 1064 nm. The structure also serves as the mirror on the input side. In addition, an emission wavelength of 1064 n
m was applied with a non-reflective coat.

The SHG element 2b arranged in the resonator of the solid-state laser device 2 is a Mg-doped Z-cut periodically poled LiNbO ₃ crystal having a reversal period of 7.0 μm, a length of 5 mm, a thickness of 0.5 mm, The anti-reflection coating for 1064 nm and 532 nm was applied to both end surfaces.

As shown in FIG. 2, an etalon 2c (made of quartz, 0.3 mm in thickness)
mm, reflectivity of 78.8%) to make the longitudinal mode of the laser beam uniform.

The mirror 2e on the output side of the resonator is a mirror provided with a concave surface having a radius of curvature of 50 mm, a high reflection coating for an oscillation wavelength of 1064 nm, and a non-reflection coating for the second harmonic light of 532 nm. By attaching to the holder 2f, the transverse mode of the output laser was adjusted. The resonator length was 20 mm. The solid-state laser device 2 configured as described above had a maximum output of about 15 mW with respect to 532 nm (green) laser light, and the longitudinal mode of the laser light was a single mode.

Of the output light from the solid-state laser device 2, the fundamental oscillation wavelength light is converted into a fundamental wave cut filter P3.
, And the green laser light L2 is focused on the AOM by the focusing lens p4 (focal length f = 12.0 mm).

The AOM used had a center frequency of 350 MHz and a bandwidth of 150 MHz. The AOM is mounted on an angle-variable table, and has a configuration in which the incident angle of the laser beam L2 can be changed by adjusting the AOM. In addition, the polarization direction of the laser light L2 and the polarization direction of the AOM are configured to be uniform. With the ultrasonic wave applied to the AOM, the angle of the AOM was adjusted so that the incident angle became the Bragg angle.
The zero-order light emitted on the optical axis extension of the incident light L2 and the first-order light emitted in a direction at an angle to the zero-order light were obtained.

As shown in FIG. 2, a jig p5 having a pinhole for output and a reflection surface for light detection is provided on the emission side of the AOM, and the zero-order light from the AOM is supplied to the photodetector 4. It is configured to be incident and output primary light.

[Evaluation of Output Fluctuation in Strength]
As the photodetector 4, a photodiode for visible light was used. A control unit (not shown) calculates a deviation between a measurement result (signal) of the average intensity of the zero-order light by the photodetector 4 and a target value of the average intensity to be kept constant, so that the deviation becomes small. When the current value supplied to the semiconductor laser 1 as the excitation light source was controlled (that is, to return to the target value even if the fluctuation occurred), the output fluctuation could be suppressed to within ± 0.1%. Numerical operation itself for stabilization applied feedback control.

[Basic Performance of Apparatus Without Controlling Position Fluctuation] The intensity of the primary light serving as output light was 10 mW. When the AOM ultrasonic wave was modulated at a frequency of 80 MHz while monitoring the intensity of the primary light, it was observed that the intensity of the primary light was modulated at 80 MHz. At this time, the degree of modulation was 100%, and the average intensity was 5 m.
It became W. When the emission light of this laser device, that is, the emission position of the first-order diffracted light, was monitored in a state where the control for stabilizing the beam position fluctuation in the present invention was not performed, ± 300 μm considered to be due to external fluctuations
A change in the rad position was observed.

[Effects of Temperature Adjusting Means] Next, the base B1
The temperature of the thermistor attached to the base B1 was adjusted to 20.0 ° C. using the lower Peltier device. At this time, when the fluctuation of the beam position was monitored, ± 1
It was confirmed to be within 00 μrad.

Example 2 In this example, the excitation light source / resonator portion of the device manufactured in Example 1 was further covered with a cover, and a Peltier element / fin was attached to the upper surface of the cover. With this configuration, the temperature of the entire apparatus is adjusted by the Peltier element under the base B1, and the inside of the cover is particularly adjusted.
In this embodiment, the temperature is adjusted from two directions, that is, the lower part of the base B1 and the upper surface of the cover.

An aluminum plate was used as a material for the cover, and a rectangular parallelepiped lid was formed to cover the area C shown by the dashed line in FIG. An emission window was opened in the side wall of the cover and a quartz plate with a 532 nm anti-reflection coating was fitted so that the laser beam L2 emitted from the resonator portion could pass through the cover. Further, a Peltier element is attached to the upper surface of the cover, and further, aluminum fins for assisting the heat release of the Peltier element are mounted thereon.

[Effects of Temperature Adjusting Means] First, the base B1
Using two Peltier devices on the bottom and the top of the cover,
The temperature was adjusted to 5.0 ° C., and the beam emission position of the emitted light (first-order diffracted light) was monitored.
It was confirmed that the fluctuation of the beam position was within ± 100 μrad. From this state, the ambient temperature is set to 20 ° C to 4 ° C.
When the beam emission position was monitored by changing the temperature to 0 ° C., the beam position variation was kept within ± 100 μrad. From this, it was found that the temperature adjusting means of this embodiment stably stabilizes the temperature of the laser device against fluctuations in ambient temperature, and as a result, stabilizes fluctuations in the beam emission position.

[0065]

As described above, the light intensity modulation laser device of the present invention operates the excitation light source of the solid-state laser device based on the fluctuation of the average intensity of the final output light after the intensity modulation element. Therefore, the output characteristics are more stable than the configuration of the conventional combination. In addition, the accumulation of the control devices provided for each component can be omitted, and the size can be reduced. Further, since the temperature is adjusted using the Invar base plate, the positional fluctuation of the output light can be further stabilized with a simple structure.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a configuration of a main part of a light intensity modulation laser device according to the present invention.

FIG. 2 is a diagram schematically showing a configuration of a light intensity modulation laser device manufactured in an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Excitation light source 2 Solid-state laser device 3 Light intensity modulation element 4 Photodetector 5 Control part 6 Temperature control means B1 Invar material base plate L1 Excitation light L2 Laser light from solid-state laser device L3 Intensity-modulated laser light

Claims (6)

[Claims] A solid-state laser device, an excitation light source for the solid-state laser device, a light intensity modulation element, a photodetector, and a control unit. The device is configured to be output from the apparatus as modulated laser light, the photodetector receives a part of the intensity-modulated laser light, measures an average intensity of the light, and the control unit performs the measurement. Controlling the output of the excitation light source such that the output fluctuation is reduced based on the result of the above, wherein at least the resonator portion of the solid-state laser device is directly or indirectly mounted on one base plate made of Invar material. A light intensity modulation laser device provided via a holding member made of a material and provided with a temperature adjusting means capable of keeping at least the resonator portion at a constant temperature. 2. A solid-state laser device, an excitation light source, a light intensity modulation element, a photodetector, and an optical system provided therebetween are provided on a single base plate made of Invar material. 2. The intensity-modulated laser device according to 1. 3. The solid-state laser device, an excitation light source, a light intensity modulation element, a photodetector, and an optical system provided therebetween are provided with a temperature adjusting means so as to maintain a constant temperature. Intensity modulated laser device. 4. The intensity-modulated laser device according to claim 1, wherein the temperature adjusting means uses an element that generates or absorbs heat by the Peltier effect. 5. A cover for locally covering the resonator portion, wherein the cover is formed so that light can enter and exit the resonator portion, and the inside of the cover has a constant temperature. 2. The intensity-modulated laser device according to 1. 6. The temperature adjusting means uses an element which generates or absorbs heat by the Peltier effect, wherein the element is provided on an upper surface of the cover and a lower surface of a base plate made of Invar material. The intensity-modulated laser device according to claim 5, which is provided.