JP3153486B2 - Temperature control device for optical element and laser oscillator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a temperature control device for controlling the temperature of an optical element such as a nonlinear optical crystal, and a laser oscillator having the temperature control device.

[0002]

2. Description of the Related Art Conventionally, when a fundamental oscillation light of a laser is converted into light having high utility such as a second harmonic, a nonlinear optical crystal or the like, which is a kind of optical element, is often installed in a laser oscillator. Is done. Since the nonlinear optical crystal has a high conversion efficiency at a predetermined temperature, the temperature is often controlled when the nonlinear optical crystal is used.

In general, when controlling the temperature of an optical element in a laser oscillator, when the temperature is lower than 80 ° C., the amount of heat generated and the amount of heat absorbed by a Peltier element that is in thermal contact with a support supporting the optical element are controlled. This is done by: On the other hand, 80
Temperature control at a temperature of not less than ° C. is conventionally performed by another temperature control method. FIG. 1 shows the prior art at a temperature of 80 ° C. or higher. The support 11 of the optical element is made of, for example, copper, and has a through hole 11a. The optical element 12 is inserted into the through hole 11a. The temperature of the optical element is controlled by controlling the amount of heat generated by the resistance heating element 10 such as tungsten wound close to the support 11.

The reason why the temperature control method is different at the boundary of 80 ° C. is that a solder material that melts at about 80 ° C. is used for joining the components of the Peltier element.

[0005]

The resistance heating element generates less heat than the Peltier element, and it takes time to heat the optical element. The resistance heating element itself does not have a cooling function. Therefore, when the resistance heating element is used for temperature control, the temperature is controlled only by controlling the amount of heat generated. Considerably worse than if you had. For this reason, when the heat capacity of the object whose temperature is to be controlled is large, overshoot up and down with respect to the desired temperature is often repeated, and it takes a long time to stabilize at the desired temperature. Further, when the temperature changes due to the influence of disturbance or the like, it takes a long time to return to the original temperature again. Further, when the optical element is replaced, it is necessary to cool the device. However, in natural cooling, it takes time for the temperature to decrease, and forced cooling by another mechanism is required for cooling in a short time.

When the temperature of the optical element is controlled by the resistance heating element, the temperature controllability is specifically limited to about 0.5 ° C., so that the controllability is low and the temperature stability is almost the same. Therefore, when controlling the temperature of the optical element incorporated in the laser device with a resistance heating element that requires high temperature controllability of about 0.1 ° C., the output of laser oscillation and the oscillation wavelength may fluctuate. High in nature. In addition, a temperature control device using a resistance heating element is relatively large because a large amount of resistance heating element is required in order to obtain a large amount of heat required to enhance the temperature controllability and the like, and is relatively large. Difficult to incorporate into laser oscillator.

On the other hand, a Peltier element can switch between heating and cooling depending on the direction of current flow and generate a large amount of heat. Therefore, a temperature control device using a Peltier element can reach a desired temperature in a short time. It is excellent in temperature controllability and temperature stability, and has good responsiveness to temperature fluctuations due to disturbances and the like. Further, since the temperature control device using the Peltier element can be easily miniaturized, it can be installed in a narrow laser oscillator.

However, as described above, a Peltier element using a solder material cannot withstand a temperature of 80 ° C. or higher. In view of the above circumstances, the present invention provides a small-sized temperature control device that can control the temperature of an optical element at a high temperature, and has excellent temperature controllability and temperature stability, and a laser oscillator with excellent output stability. The purpose is to provide.

[0009]

According to a first aspect of the present invention, there is provided a temperature control apparatus comprising: a support on which an optical element is supported;
And a Peltier element having a plurality of components joined by a brazing material having a temperature of more than 0 ° C. and controlling the temperature of the optical element supported by the support by controlling the temperature of the support. I do.

A second temperature control device according to the present invention includes a holder having a support portion on which an optical element is supported at a central portion and having heat transfer portions extending from both sides of the support portion.
A resistance heating element fixed to one of the heat transfer portions of the holder,
A Peltier element fixed to the other heat transfer section of the holder.

A first laser oscillator according to the present invention is a laser oscillator comprising: an optical element disposed on an optical axis in an optical resonator; and a temperature control device for controlling a temperature of the optical element. A control device is supported by the support on which the optical element is supported, and has a plurality of components joined by a brazing material having a melting point exceeding 200 ° C. and controlling the temperature of the support. And a Peltier element for controlling the temperature of the optical element.

A second laser oscillator according to the present invention is a laser oscillator comprising: an optical element disposed on an optical axis in an optical resonator; and a temperature control device for controlling a temperature of the optical element. A control device includes a holder having a support portion at the center portion for supporting the optical element and having heat transfer portions extending from both sides of the support portion, and a resistive heat fixed to one of the heat transfer portions of the holder. And a Peltier element fixed to the other heat transfer portion of the holder.

[0013]

Embodiments of the present invention will be described below. FIG. 2 is a front view (a) and a side view (b) showing an embodiment of the first temperature control device of the present invention. A through-hole 21a having a rectangular cross section is formed in a copper support 21, and an LBO crystal 22, which is a kind of nonlinear optical crystal, is inserted as an optical element. Support 2
1 is a hole 2 having a diameter of about 1 mm close to the LBO crystal 22;
1b is opened and the thermocouple 23 is inserted.
Further, one surface of the Peltier device 20 is fixed to the support 21. The Peltier element 20 is composed of a plurality of semiconductor components 20a and heat transfer plates 20 made of a brazing material mainly composed of AuSn.
b has a joined structure. The other surface of the Peltier device 20 is fixed to the substrate 27 of the laser device. Although a single-stage Peltier device is shown in FIG. 2, a multi-stage Peltier device may be used if necessary. A Teflon cover 24 is attached to the outside of the support 21.

When the Peltier element 20 is energized in an appropriate direction, the surface in contact with the support 21 generates heat and the support 21 is heated, and the LBO crystal 22 inside the support is heated by heat conduction.
Is heated. Based on the temperature data detected by the thermocouple 23, the amount of current flowing through the Peltier element 20 and the current supply time are controlled, or the direction of the current supply is reversed, thereby controlling the temperature of the LBO crystal 22. The effect of disturbance is reduced by the cover 24 to stabilize the temperature.

The L inserted in the through hole 21a of the support 21
In order to bring the BO crystal 22 into a phase matching state with respect to the Nd: YAG laser beam having a wavelength of 1064 nm, the LBO crystal 22 is heated and controlled to a phase matching temperature of about 140 ° C. In this case, the temperature controllability is as high as 0.01 ° C. or less,
When the Nd: YAG laser beam 25 having a wavelength of 1064 nm is irradiated, the LBO crystal 22 stably generates a second harmonic 26 having a wavelength of 532 nm.

The first temperature control device of the present invention comprises, for example, A
Heating to 200 ° C. is made possible by using a recently developed and practically used Peltier element using a brazing material such as uSn that does not melt to a high temperature exceeding 200 ° C. However, it is difficult to control the temperature of 200 ° C. or more with the first temperature control device of the present invention. On the other hand, in recent years, the wavelength band used by lasers has expanded, and it has become necessary to thermally remove defects generated in optical elements. Therefore, it is strongly required to use optical elements at a high temperature exceeding 200 ° C. ing. What has responded to the above situation is a second temperature control device of the present invention.

FIG. 3 is a front view (a), a side view (b) and a graph (c) showing a temperature gradient of an embodiment of the second temperature control device of the present invention. A resistance heating wire 310 is wound as a resistance heating element around one of the heat transfer portions 341 of the copper holder 340, and one surface of the Peltier element 320 is bonded to the other heat transfer portion 342. The other surface of the Peltier element 320 is fixed to the substrate 360 of the laser device. Although a single-stage Peltier element is shown in FIG. 3, a multi-stage Peltier element may be used if necessary, as in the embodiment shown in FIG. A through-hole 343 a having a rectangular cross section is formed in
Is opened, and the optical element 330 is inserted.
The support portion 343 has a diameter of 1 m close to the optical element 330.
A hole 343b of about m is opened, and a thermocouple 350 is inserted.

A constant amount of current is applied to the resistance heating wire 310 so that the temperature in the vicinity of the optical element 330 rises to, for example, a temperature exceeding 200 ° C. The heat generated by the resistance heating wire 310 travels through the heat transfer section 341 and reaches the support section 343, and reaches the optical element 330 inserted into the through hole 343a. Further, this heat reaches the Peltier element 320 through the heat transfer section 342. Resistance heating wire 3
While the heat generated at 10 is transmitted to the Peltier element 320,
Since the heat is removed by radiation cooling or the like, the holder 34
When the position on the holder 340 is plotted on the vertical axis and the temperature is plotted on the horizontal axis, the temperature becomes higher on the side of the resistance heating wire 310 and lower on the side of the Peltier element 320 as shown in the graph of FIG. A gradient occurs. Therefore, the temperature of the optical element 330 becomes 20
Even if the temperature exceeds 0 ° C., the temperature of the Peltier element 320 becomes lower than the melting point of the bonding material by devising the shape of the holder 340, so that the Peltier element itself is safe.

The holder 340 can be heated by the Peltier element 330 up to a temperature lower than the melting point of the Peltier element 330. Once the heating is completed, the calorific value of the resistance heating wire 310 is lost while the heat is transferred to the Peltier element 330. Since it is only necessary to compensate for the heat generated, the resistance heating wire 310 can be made relatively small, and the entire apparatus can be downsized even if the resistance heating wire is used.

When the output of the Peltier element 320 is controlled based on the temperature data detected by the thermocouple 350, the temperature gradient is controlled, and the temperature of the optical element 330 is controlled indirectly. As a result, a high temperature controllability of about 0.1 ° C. is obtained by taking advantage of the high temperature controllability of the Peltier element. FIG. 4 is a diagram showing one embodiment of the first laser oscillator of the present invention.

The laser oscillator 40 is an Nd: YAG laser oscillator, and includes four resonance mirrors 41, 42, 43,
44 and Nd: YAG between mirrors 43 and 44
The crystal 45 has a so-called Z-type resonator.
A temperature control device 48 shown in FIG. 2 is installed on the optical axis between the mirrors 41 and 42, and an LBO crystal, which is a kind of nonlinear optical crystal, is inserted in a support of the temperature control device 48.

The Nd: YAG crystal 47 is optically excited by the oscillation light of the semiconductor laser element 45 via the lens 46 and the mirror 43. The fundamental oscillation light 49 having a wavelength of 1064 nm generated in the Nd: YAG crystal 47 is wavelength-converted by the LBO crystal inserted in the support of the temperature control device.
A second harmonic 50 having a wavelength of 532 nm is generated. The second harmonic 50 is taken out of the resonator through the mirror 42. The temperature of the LBO crystal is adjusted to a temperature of about 140 ° C., which is the phase matching temperature, and the temperature of the LBO crystal is controlled under high temperature controllability.
2 nm laser light is generated.

FIG. 5 is a diagram showing an embodiment of the second laser oscillator of the present invention. The laser oscillator 60 is an Ar laser oscillator, and includes two resonance mirrors 61 and 62.
And a laser tube 63 disposed between them and enclosing Ar gas to excite and emit light by discharge. A temperature control device 64 shown in FIG. 3 is installed on the optical axis in the resonator, and a BBO crystal, which is a kind of nonlinear optical crystal, is inserted into a holder of the temperature control device 64.

The wavelength 488 nm generated from the laser tube 63
Is incident on a BBO crystal whose temperature is controlled to a high temperature of 250 ° C., so that the BBO crystal generates a second harmonic wave 66 having a wavelength of 244 nm. The second harmonic 66 is taken out of the resonator through the mirror 61. Since the second harmonic 66 having a wavelength of 244 nm is ultraviolet light, a defect occurs inside the BBO crystal. However, the second harmonic 66 is generated by the second harmonic because the BBO crystal is maintained at the high temperature as described above. Defects inside the crystal are removed, and the reliability of laser oscillation is improved. At the same time, stable output due to high temperature controllability and wavelength 244nm
Laser light is generated.

[0025]

According to the first temperature control device of the present invention,
Even when the temperature is as high as 80 ° C. or more, the temperature of the optical element can be heated and controlled with high temperature controllability and high stability using a small device. According to the second temperature control device of the present invention, 20
Even at a high temperature of 0 ° C. or higher, the temperature of the optical element can be heated and controlled with high temperature controllability and high stability.

According to the first and second laser oscillators of the present invention, a stable laser output can be obtained. In particular, according to the second laser oscillator of the present invention, the reliability of laser oscillation is also improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a conventional technique for controlling the temperature of an optical element.

FIG. 2 is a front view (a) and a side view (b) showing one embodiment of the first temperature control device of the present invention.

FIG. 3 is a front view (a), a side view (b), and a graph (c) showing a temperature gradient of an embodiment of the second temperature control device of the present invention.

FIG. 4 is a diagram showing one embodiment of a first laser oscillator of the present invention.

FIG. 5 is a diagram showing one embodiment of a second laser oscillator of the present invention.

[Explanation of symbols]

 20,320 Peltier element 20a Semiconductor component 20b Heat transfer plate 11,21 Support body 12,22,330 Optical element 310 Resistance heating wire 340 Holder 341,342 Heat transfer part 343 Support part 40,60 Laser oscillator 41,42,43, 44,61,62 Mirror for resonance 48,64 Temperature control device

Claims (2)

(57) [Claims] 1. A supporting portion for supporting an optical element is provided at a center portion.
Extending from both sides of the supporting portion.
A temperature control device comprising: a holder having a heating portion; a resistance heating element fixed to one of the holders ; and a Peltier element fixed to the other heat transfer portion of the holder. . 2. An optical element disposed on an optical axis in an optical resonator.
And a temperature control device for controlling the temperature of the optical element.
In the laser oscillator, the temperature control device includes a holder having a support portion in which the optical element is supported at a central portion and having heat transfer portions extending from both sides of the support portion, and a heat transfer portion of one of the holders. a resistance heating element secured to the part, the laser oscillator characterized in that with a Peltier element which is fixed to the other of the heat transfer portion of the holder.