JP2003115628A - Laser apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser apparatus in which the shifting amount of a laser oscillation wavelength due to a temperature change can be suppressed and which has a single longitudinal mode low noise output. SOLUTION: A laser medium 14 generates a laser beam by the excitation beam 11 of a semiconductor laser 71a so that a resonator is provided between a resonator mirror 13 and an output mirror 16 to bring about a laser oscillation. An etalon 15 is provided in the resonator to set the laser oscillation to the single longitudinal mode. An optical element and a resonator block 18 are expanded and contracted by the heat generated by a temperature change of an environment, the excitation beam, and a laser oscillation beam during operation. Even though a resonator block 12 is expanded, the expansions of both cancel each other so that the effective operational length of the resonator is not changed, because the resonator mirror 13 and the output mirror 16 are mounted at the inside of the block 12 and an output mirror block 17 and hence the laser oscillation wavelength is not shifted as well.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser device, and more particularly to an internal resonance type laser device using a laser medium excited by a semiconductor laser.

[0002]

2. Description of the Related Art A method of using a semiconductor laser (LD) as an excitation light source has become widespread as a method of realizing high efficiency of a solid-state laser. By using the LD, it is possible to efficiently excite the absorption peak of the solid-state laser crystal,
Further, since the current-light output efficiency of the LD itself is high, there is an advantage that extra energy is not required. A semiconductor laser (LD) pumped solid-state laser device is widely used not only for research but also industrially because of its features such as low power, small size, long life, and easy handling. FIG. 9 shows a conventional LD pumped solid state laser device. Here, in order to realize a blue laser, an LD pumped solid-state laser using a semiconductor laser 71 (LD), an Nd: YAG crystal 73 as a solid-state laser medium, and a KNbO ₃ (KN) crystal 74 as a nonlinear optical crystal for wavelength conversion. The device will be described. In this device, the excitation light (809
nm) passes through the condenser lens 72 and is condensed on the Nd: YAG crystal 73 (solid-state laser medium). The fundamental wave 76 (946 nm) output by the Nd: YAG crystal 73 is
The concave surface of the surface 73a of the Nd: YAG crystal 73 and the concave surface of the surface 78a of the output mirror 78 are confined in a resonator constituted by applying a high-reflection coating to the fundamental wave 76 (946 nm), and laser oscillation occurs. By inserting a KNbO ₃ (KN) crystal 74 (non-linear optical crystal) for wavelength conversion into this resonator, the fundamental wave 76 (946 nm) is generated from the KNbO ₃ (KN) crystal 74 for wavelength conversion to the second harmonic. Wave 77
(473 nm). The output mirror 78 reflects the fundamental wave 76 (946 nm) and outputs the second harmonic wave 77 (473).
nm) is coated so that
The second harmonic wave 77 (473 nm) from the KNbO ₃ (KN) crystal 74 for wavelength conversion passes through the output mirror 78 and is output to the outside. The etalon 75 is inserted to suppress the generation of noise such as output instability and mode hop caused by longitudinal mode competition when the second harmonic is generated in the resonator, and the oscillation longitudinal mode is set to a single value. The wavelength has been changed.

As described above, the nonlinear optical crystal (KNbO
Research and development of a visible light laser using a second harmonic wave 77 using a ₃ (KN) crystal 74) have been actively conducted. Among them, there is a great demand for low-noise output laser light. Normally, in the generation of the internal resonator type second harmonic wave 77, noise due to longitudinal mode competition, mode hopping, or the like occurs. To suppress the occurrence. As the simplest method, a method of inserting an etalon 75 into a resonator and unifying the oscillation longitudinal mode (single wavelength) has been tried for a long time. When the etalon 75 is used by inserting it in the resonator, the thickness of the etalon 75 is designed so that the solid-state laser medium (Nd: YAG crystal 7
It is necessary to consider the gain width of 3) and the longitudinal mode interval determined by the resonator. The optimized etalon 75 is
The temperature of the etalon 75 is kept constant so that the transmission peak position does not move. However, even if the temperature of only the etalon 75 is adjusted, the environmental temperature change in which the laser resonator is placed, the optical element used in the laser resonator, or the like causes excitation light or laser light that causes laser oscillation (basic Wave 76)
As a result, the temperature changes in some way and the effective resonator length changes. This change in the effective resonator length means a shift in the laser oscillation wavelength, and if the laser oscillation wavelength changes, it will move to the transmission peak position of the etalon 75, and the transmission of the etalon 75 with the temperature kept constant. The peak and the laser oscillation wavelength deviate from each other, and stable laser oscillation cannot be performed with low noise. In the worst case, mode hop or noise occurs. Therefore, as shown in FIG. 9, the holder 79 and the holder 80 are fixed to the reference plate 81 so as to form an integrated resonator, and Nd: YAG is attached to the holder 80.
Crystal 73 (solid-state laser medium), KNbO ₃ (KN) crystal 7
4 (non-linear optical crystal), etalon 75, output mirror 78
The semiconductor laser 71 and the condenser lens 72 are fixed to the holder 79, and the heat generated in the excitation section and the resonance section is cooled by the Peltier element 82 of the electronic cooling element via the reference plate 81, and the heat sink 83 is attached. The method of radiation is used. Further, in order to maintain the single longitudinal mode, the fundamental wave 7 leaking from the output mirror 78 side outside the laser resonator.
While monitoring the longitudinal mode of No. 6, the signal is fed back and the position of the output mirror 78 is controlled by a piezoelectric element or the like to adjust the resonator length, and the etalon transmission peak and the laser oscillation wavelength are tuned.

[0004]

The conventional laser device is constructed as described above. However, in the device shown in FIG. 9, the solid laser medium (Nd: YAG crystal 73) and the output mirror 78 are the holders. It is attached to the outside of 80.
When mounting in such a state, expansion and contraction of the resonator block due to temperature changes such as environment, excitation light and oscillated fundamental wave 76
Due to the heat generated by the optical components, the optical component expands and contracts, and even when cooled, the temperature difference between the respective parts causes a change in the effective working length of the solid-state laser medium (Nd: YAG crystal 73), and the holder 80 expands and contracts the output mirror 78. The effective action length of the cavity length changes due to the movement of the surface 78a. Therefore, there is a problem that the laser oscillation wavelength shifts and stable laser oscillation with low noise cannot be performed. In addition, the solid-state laser medium (Nd: YAG crystal 7
Although it has been attempted to devise only the mounting position of 3) and cooling of the etalon 75, the entire resonator must be designed in consideration of the arrangement of the optical components, the mounting block mounting the optical components, and the cooling of the whole. There is a problem that does not happen. on the other hand,
There is a system in which a longitudinal mode detector is provided outside the resonator and the signal is fed back to stabilize the laser oscillation wavelength, but there is a device for measuring the longitudinal mode outside the laser resonator (for example, Fabry-Perot interferometer). ), A circuit for feeding back the signal, a piezoelectric element for driving the position of the output mirror 78 by the signal, and a large measuring device and a control system such as a driving circuit for the piezoelectric element. This impairs the advantages of the LD-pumped solid-state laser, such as ease of handling and small size.

The present invention has been made in view of such circumstances, and the components of the resonator block and the optical element are formed by the change of the ambient temperature and the heat generation of the optical element due to the excitation light or the laser fundamental wave. An object of the present invention is to provide a laser device that can suppress the shift amount of the laser oscillation wavelength even if it expands and contracts, is small and easy to handle, and has a single longitudinal mode and low noise output.

[0006]

In order to achieve the above object, a laser device of the present invention is a laser device in which a laser medium is excited by excitation light to cause laser oscillation in a laser resonator, the laser resonator being configured. Each element to be mounted is fixed so as to suppress or prevent the wavelength shift due to the effective change of the resonator length due to the temperature change.

Further, the laser device of the present invention is a laser device in which a laser medium is excited by excitation light and oscillates in a laser resonator, so that the mounting of the laser medium constituting the laser resonator is effective by changing the temperature. It is configured to be fixed in a direction to suppress or prevent a wavelength shift due to a change in the cavity length.

Further, the laser device of the present invention is a laser device in which a laser medium is excited by excitation light to cause laser oscillation in a laser resonator. In the laser device, a resonator mirror or an output mirror constituting the laser resonator, or both of them. The mounting is configured so as to be fixed in such a direction as to suppress or prevent the wavelength shift caused by the effective change in the cavity length due to the change in temperature.

Further, the laser device of the present invention is a laser device in which a laser medium is excited by excitation light to cause laser oscillation in the laser resonator, so that each element constituting the laser resonator is attached effectively by a temperature change. It is configured to be fixed via a resonator change suppressing component that leads or suppresses a wavelength shift due to a change in the resonator length.

Further, in the laser device of the present invention, in the laser device in which the laser medium is excited by the excitation light and oscillates in the laser resonator, the laser medium constituting the laser resonator or the resonator mirror and the output mirror are attached. Is configured to be fixed via a resonator change suppressing component that leads or suppresses a wavelength shift associated with an effective resonator length change due to a temperature change.

The laser device of the present invention is characterized in that the laser medium is a solid laser crystal. The laser device of the present invention is characterized in that the excitation light source is a semiconductor laser. The laser device of the present invention is provided with a non-linear optical crystal in the resonator for wavelength conversion.

The laser device of the present invention is configured as described above, and uses a semiconductor laser (LD) as an excitation light source, at least one resonator mirror and an output mirror, and a laser medium which is a solid laser crystal for oscillating laser light. , An etalon provided in the resonator, a resonator block having cooling means for fixing them, the resonator mirror or the output mirror, or both, and when the laser medium is attached to the resonator block, Environmental temperature change, excitation L
When the optical element and the resonator block expand and contract due to heat generated by D or the fundamental wave, the optical element and the resonator change suppressing component are attached in such a direction as to prevent the laser oscillation wavelength from shifting. Here, in the resonator mirror or the output mirror, the end surface of the laser medium can also play the role. Further, when the effect of suppressing the wavelength shift is small with only the resonator mirror or the output mirror, or both, it is also possible to fix the resonator mirror, the output mirror, or both via a resonator change suppressing component having a larger suppressing effect. it can. As described above, by attaching the optical element and the resonator change suppressing component, the wavelength of laser oscillation does not shift,
A stable laser output can be obtained.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a laser device of the present invention will be described with reference to FIGS. FIG. 1 is a view showing a cross section of a laser device by exciting a semiconductor laser 71a of the laser device of the present invention. FIG. 2 is a diagram showing changes in effective working length of each component of the laser device of the present invention. The line of the arrow shown in FIG. 2 does not show the length, but shows the range of change within the arrow line. (The same applies to FIGS. 4 and 6 below.) This laser device includes a semiconductor laser (LD) 71a that outputs pumping light (809 nm) and a laser medium provided with pumping light 11 in a resonator. Condensing lens 72a for condensing on the end face
And a resonator mirror coating 13a forming a resonator
And a laser medium 14 (for example, Nd: YAG crystal or the like) that is excited by excitation light and that oscillates within the resonator (fundamental wave: 946 nm). , Provided in the resonator to unify the oscillation longitudinal mode (single wavelength)
Etalon 15, a resonator mirror block 12 in which a resonator mirror 13 is adhesively fixed on a surface 13b, and an output mirror block 1 in which an output mirror 16 is adhesively fixed on a surface 16b.
7, a resonator mirror block 12, a laser medium 14, an etalon 15, and an output mirror block 17 are bonded and fixed to each other, and a Peltier element 19 for cooling the resonator block 18.

In the present laser device, the ambient temperature changes, and the semiconductor laser 71a for excitation and its excitation light 11 are used.
Alternatively, even if the optical element and the resonator block 18 expand and contract due to heat generated by the fundamental wave, etc., and the temperature refractive index of the optical element changes, the effective operating length of the resonator changes (resonator length). The resonator mirror 13 or the output mirror 16 or both are formed so as to suppress or prevent the shift of the laser oscillation wavelength and are fixed to the resonator block 18 so that the effective action length change 26) becomes as small as possible. It is characterized by that.

The laser resonator is usually made of a material having a small expansion coefficient. Further, the temperature is kept constant by the Peltier element 19 or the like so that the temperature does not change significantly (the resonator block effective action length change 25) with respect to the environmental temperature change. Similarly, the laser medium 14 and the optical elements (resonator mirror 13, etalon 15, output mirror 16, etc.) need not only the ambient temperature but also the excitation light 1 for causing laser oscillation.
Expansion due to temperature change due to 1 or once oscillated fundamental wave
Due to the influence of the change in the refractive index, the effective cavity length changes (laser medium effective action length change 22, resonator mirror effective action length change 21, etalon effective action length change 23, output mirror effective action length change 24 Since the oscillation wavelength shifts, these are also controlled by the Peltier element 19 or the like so that the temperature becomes constant like the resonator. In particular, in order to suppress the fluctuation of the transmission peak position of the etalon 15, the temperature is often adjusted separately from other optical elements. However, it is impossible to suppress the temperature change of the laser medium 14 and the optical elements (the resonator mirror 13, the etalon 15, the output mirror 16, etc.) only by the Peltier element 19. Therefore, it is necessary to devise the mounting positions and materials of the optical elements (resonator mirror 13, etalon 15, output mirror 16, etc.) to suppress or prevent wavelength shift due to temperature change.

Usually, the resonator block 18 and the like used in the laser device have a positive linear expansion coefficient. In addition, the optical element also has many positive values for both the coefficient of linear expansion and the change in refractive index with temperature. The resonator block is kept constant by a temperature measuring element such as a thermistor against a change in environmental temperature. But,
There is a thermal slope between the actual measurement and the part that determines the cavity length. Therefore, there are some parts that cannot be controlled against changes in the environmental temperature. The extension of the resonator block 18 due to the environmental temperature change is set to dLb / dt. On the other hand, the resonator mirror 13 and the output mirror 16 also change in length due to environmental temperature changes and temperature changes due to the excitation light and the fundamental wave. The change amount of the resonator mirror 13 with respect to the temperature is dLc / dt, and the change amount of the output mirror 16 is dLo / d.
t. Similarly, the laser medium 14 is also affected by environmental temperature changes and temperature changes due to the excitation light 11 and the fundamental wave. The length change due to expansion is dLl / dt, and the length change due to the refractive index change is dLn / dt. If the resonator block 18 is a frame that determines the laser resonator length,
By attaching the extensions of the resonator mirror 13 and the output mirror 16 to the resonator block 18 so as to shorten the resonator length, the extension of the resonator block 18 due to the temperature, the extension of the laser medium 14 and the extension of the etalon 15 are performed. It is possible to suppress the wavelength shift to the long wavelength side. That is, the change in the effective operating length of the resonator 26 (for an increase of 1 ° C.) = DLb
/ Dt + (dLl / dt + dLn / dt)-(dLc /
dt + dLo / dt). The former term is a direction to extend the cavity length, and the latter term is a factor to shorten it. If this suppression force is small, you can attach it through another material,
Greater suppression can be obtained. In a solid-state laser device or the like, there is a temperature rise in the laser medium due to the excitation light 11 or the laser oscillation light itself, which is caused by the resonator block 18
Often not the same as the temperature. The selection and thickness of these optical elements and other materials are optimized in consideration of the effective elongation of the resonator length with respect to temperature. Of these, not only the environmental temperature but also the temperature rise due to the excitation light 11 and the temperature rise due to the laser light oscillated by the laser are naturally taken into consideration.

Next, the operation of the present laser device shown in FIG. 1 will be described. Excitation light 11 (809 nm) output from the semiconductor laser 71a is condensed by the condenser lens 72a, and is transmitted through the resonator mirror coating 13a of the resonator mirror 13 having a high transmittance for the excitation light 11, Laser medium 14 (Nd: YA) provided in the resonator
Exciting the end face of (G crystal, etc.). The fundamental wave (946 nm) output from the excited laser medium 14 is fixed on the resonator mirror block 12 by the surface 13b, and the resonator mirror coating 13a of the resonator mirror 13 is fixed on the output mirror block 17 by the surface 16b. The laser is oscillated by being confined in the resonator formed between the output mirror coatings 16a of the output mirror 16 thus formed. The resonator mirror coating 13a and the output mirror coating 16a are
A highly reflective coating for the fundamental wave (946 nm) is provided on the concave surface. Then, the etalon 15 is inserted to make the oscillation longitudinal mode into a single wavelength in order to suppress generation of noise due to longitudinal mode competition in the resonator and mode hop. Also, the resonator mirror 13 and the output mirror 1
Reference numeral 6 is adhesively fixed to the resonator mirror block 12 and the output mirror block 17, and is fixed to the resonator block 18. Although not shown here, the laser medium 1
Similarly, the etalon 15 and the etalon 15 are fixed to the resonator block 18 by blocks. This resonator block 18 is
It is fixed to the Peltier element 19 in order to keep the temperature constant, whereby the optical element and the laser medium 14 are kept at a constant temperature through each block. The etalon 15 may be controlled at this temperature, but it is more stable to adjust the temperature individually.

Next, regarding the present laser device shown in FIG.
The effective elongation of each part will be described when the temperature of each element changes due to the environmental temperature, the excitation light, the fundamental wave generated by laser oscillation, or the like. Here, it is assumed that the temperature changes in the positive direction and the expansion coefficient / refractive index change is positive. Mount the resonator mirror 13 on the surface 1 with respect to the resonator mirror block 12.
3b is attached to the output mirror block 17 by attaching the output mirror 16 to the surface 16b. The resonator length effective action length change 26 is extended by the laser medium effective laser action length change 22, the etalon effective action length change 23, and the resonator block effective action length change 25. Further, the elongation of each mirror block (12, 17) was neglected on the assumption that it is very small compared to the change 25 of the effective action length of the resonator block. Now attach each mirror (13, 16) to surface 1
3b and the surface 16b, the mirrors 13 and 16 extend in a direction to shorten the cavity length effective action length change 26 due to the temperature change. The extension is referred to as a resonator mirror effective action length change 21 and an output mirror effective action length change 24.
Resonance length effective action length change 26 of actual extension amount (for increase of 1 ° C.) = (Resonator block effective action length change 25
+ Laser medium effective action length change 22 + etalon effective action length change 23)-(cavity mirror effective action length change 21
+ Output mirror effective length change 24). here,
(Cavity block effective action length change 25 + Laser medium effective action length change 22 + Etalon effective action length change 23)
When (resonator mirror effective action length change 21 + output mirror effective action length change 24) becomes almost the same size, the change in resonator length effective action length change 26 becomes small, and the transmission peak of etalon 15 becomes It is possible to prevent the occurrence of noise by reducing the deviation. Up to now, it was general to use an element whose expansion of each element due to temperature is small, but as in the present invention, it is possible to suppress the change of the resonator length by positively utilizing the expansion. .

FIG. 3 is a diagram showing a second embodiment of the laser device of the present invention. The laser resonator has a laser medium 34 having an end surface having a resonator mirror coating 33a that highly transmits the excitation light 31 and highly reflects the oscillated laser light,
Output mirror coating 36a for highly reflecting an oscillating laser
And an output mirror 36 that has been subjected to
Laser medium 34 passes through the cavity mirror coating 33a
Is irradiated. An etalon 35 is inserted in the resonator to achieve a single longitudinal mode. In addition, the laser medium 34
The surface 33 b of the output mirror 36 and the surface 36 b of the output mirror 36 are bonded to the resonator mirror block 32 and the output mirror block 37, respectively, and fixed to the resonator block 38. Although not shown here, the etalon 35 is similarly fixed to the resonator block 38 by a block. This resonator block 38 has a Peltier element 3 for keeping the temperature constant.
The optical element and the laser medium 34 are maintained at a constant temperature through each block. Etalon 35
The temperature may be controlled at this temperature, but individual temperature adjustment is more stable.

FIG. 4 shows a laser device having the structure shown in FIG.
It is a figure which shows the effective action length change of each element / block by environmental temperature change and excitation light / laser oscillation light. The change of the effective action length of the laser medium due to the change of the environmental temperature or the excitation light / laser oscillation light is 42, and the change of the etalon effective action length is 4
3. If the output mirror effective action length change is 44 and the resonator block effective action length change is 45, the actual extension amount of the resonator length effective action length change 46 = (45 + 43) − (42
+44) ... (1).

FIG. 5 is a diagram showing a laser resonator that does not exhibit the effects of the present invention, for comparison with FIG. The symbols are the same as in FIG. However, the mounting position of the laser medium 34 is on the surface 33c, and the mounting position of the output mirror 36 is on the surface direction of the output mirror coating 36a.

For comparison with FIG. 4, FIG. 6 shows changes in the ambient temperature of the laser resonator and the pumping light which do not exhibit the effects of the present invention.
FIG. 7 is a diagram showing changes in effective action length of each element / block due to laser oscillation light. Change the effective action length of the laser medium by 4
2a, the etalon effective action length change is 43a, the output mirror effective action length change is 44a, and the resonator block effective action length change is 45a. Cavity length effective action length change of actual extension amount due to environmental temperature change and excitation light / laser oscillation light 46a = (42a + 45a + 43a + 44a) ...
It becomes (2). Since the same element has the same effective action length change, the difference is obtained from (1) and (2), and the effective action length change Δ = 46a−46 = 2 × (42a + 4).
4a). Therefore, it can be seen that the effect of the present invention on the effective resonator length is effective. In this embodiment, the effective action length is increased by the laser medium 34. However, in actual use, if the change in the refractive index is positive, the effective action length is increased by the temperature rise and the resonator length is extended. To work.
This is the same regardless of the mounting method.

FIG. 7 is a diagram showing a third embodiment of the laser device of the present invention. Similar to the second embodiment, the laser resonator has a laser medium 54 having an end face having a surface 53b provided with a resonator mirror coating 53a that highly transmits the pumping light 51 and highly reflects the oscillating laser light, and an oscillating laser. Output mirror 5 with an output mirror coating 56a that highly reflects light
6, the excitation light is irradiated onto the laser medium 54 through the resonator mirror coating 53a. An etalon 55 and a nonlinear optical crystal 50 (for example, KNbO ₃ (KN) crystal) for generating the second harmonic of the fundamental wave are inserted in the resonator. Non-linear optical crystal 5 for wavelength conversion in this resonator
By inserting 0 (KNbO ₃ (KN) crystal), the fundamental wave (946 nm) generated in the laser medium 54 is converted into the nonlinear optical crystal 50 (KNbO ₃ (KN) crystal) for wavelength conversion.
To induce the second harmonic (473 nm). The output mirror 56 is provided with an output mirror coating 56a so as to reflect the fundamental wave (946 nm) and transmit the second harmonic (473 nm), and KNbO ₃ (K
The second harmonic (473 nm) from the (N) crystal passes through the output mirror 56 and is output to the outside. In addition, an etalon 55 is inserted in the resonator to achieve a single longitudinal mode. The laser medium 54 and the output mirror 56 are bonded to the resonator mirror block 52 and the output mirror block 57, respectively, and fixed to the resonator block 58. Although not shown here, the nonlinear optical crystal 50 and the etalon 5
Similarly, 5 is fixed to the resonator block 58 by a block. This resonator block 58 is fixed to a Peltier element 59 in order to keep the temperature constant, whereby the optical element and the laser medium 54 are kept at a constant temperature through each block. The etalon 55 may be controlled at this temperature, but individual temperature adjustment is more stable.

Here, the change in the effective action length of the laser medium is L
54, output mirror effective length change L56, nonlinear optical crystal effective length change L50, etalon effective length change L55, resonator block effective length change L
58, the actual effective length change ΔL of the resonator is ΔL = (L50 + L55 + L58) − (L54
+ L56) ... (3), and becomes (L50 + L55 + L
58) and (L54 + L56) are almost the same value,
The change in the resonator length becomes small, the deviation from the transmission peak of the etalon 55 becomes small, and mode hops and noise generation can be prevented.

FIG. 8 is a diagram showing a fourth embodiment of the laser apparatus of the present invention. Similar to the second embodiment, the laser resonator highly reflects the pumping light 61 and the laser medium 64 having an end face with the surface having the resonator mirror coating 63a for highly reflecting the oscillating laser light and the oscillating laser. The output mirror 66 is provided with the output mirror coating 66a, and the excitation light 61 is irradiated onto the laser medium 64 through the resonator mirror coating 63a. A nonlinear optical crystal 60 for generating the second harmonic of the fundamental wave is inserted in the resonator. In addition, an etalon 65 is inserted in the resonator to achieve a single longitudinal mode. Further, the laser medium 64 and the output mirror 66 are bonded to the resonator mirror block 62 and the output mirror block 67, respectively, and the resonator block 68
It is fixed to. Although not shown here, the nonlinear optical crystal 60 and the etalon 65 are similarly fixed to the resonator block 68 by blocks. This resonator block 68 is fixed to a Peltier element 69 in order to keep the temperature constant, whereby the optical element and the laser medium 64 are kept at a constant temperature through each block. Here, when the effective resonator length due to the ambient temperature or the excitation light / laser oscillation light changes, and the suppression amount is small in the laser medium 64 or the optical element, a resonator having a large effect of suppressing the resonator change is newly added. By attaching the change suppressing component 62a, a greater effect can be brought about. In this embodiment, the laser medium 6
Although it is adhered only to the resonator mirror coating 63a on the four end faces, it can be naturally attached to the output mirror 66 side.

In practice, the laser medium 64 contains Nd: YV.
O ₄ , thickness 1 mm, output mirror 66 BK 7, thickness 3 m
m, nonlinear optical crystal 60 with KTP, thickness 2 mm, etalon 65 with synthetic quartz, thickness 0.5 mm, resonator block 6
8 uses Super Invar, and the resonator length is 25 mm. Further, aluminum and a thickness of 2 mm are used for the resonator change suppressing component 62a having a large effect of suppressing the resonator change. When the temperature of each element changes by 1 ° C., the change in effective thickness is about −21 nm for Nd: YVO ₄ and about 70 n for KTP.
m, BK7 is about 44 nm, etalon (synthetic quartz) 65 is about 7 nm, resonator block (super invar) 56 is about 3 nm, and resonator change suppressing component 62a is about 50 nm. Here, in Nd: YVO ₄ , the increase in the effective action length (increase in the resonator length) due to the change in the refractive index is
The negative value is shown because it is larger than the reduction of the cavity length due to expansion. Therefore, from the above formula (3), ΔL = 7 nm. This means that if the laser oscillation wavelength is 1064 nm,
It is about 1/100 wavelength or less and can be said to be very stable against temperature changes and temperature changes due to excitation light and fundamental waves.

As described above, as shown in the embodiment, by positively utilizing the temperature change and incorporating the effective action length change in the resonator, a single vertical length is obtained without a large control system or drive system. Laser oscillation can be performed in a mode. In these embodiments, the resonator block 68 and each element block are shown individually, but it goes without saying that the integral type is more rigid and stable. In addition, in these embodiments, the laser medium 64
It is assumed that the temperature of the nonlinear optical crystal 60 is the same as the temperature of the resonator block 68, but in reality, it may be slightly different because it is affected by the excitation light 61 and the laser oscillation light. Also in this case, the optimum design can be performed by measuring the variation in advance or performing simulation.

[0028]

The laser device of the present invention is configured as described above, and includes at least one resonator mirror and an output mirror, a solid laser medium that oscillates a laser beam by pumping a semiconductor laser (LD), and a single longitudinal mirror. The etalon to be turned into a mode is mounted on the resonator block, and its resonator mirror or output mirror, or both, or the laser medium and the resonator change suppression component generate heat due to environmental temperature change or excitation light or laser oscillation light. Since the optical element and the resonator block are mounted so as to reduce the change in the effective working length even if they expand or contract, the laser oscillation wavelength does not shift and a stable laser output with low noise is obtained. be able to. In single longitudinal mode oscillation of a laser device, use a large measurement system, control system, and drive system by devising the adhesion of optical elements (including the laser medium and parts that promote the effect) as described above. Without
A small-sized, inexpensive laser device with low noise output becomes possible.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a laser device of the present invention.

FIG. 2 is a diagram for explaining changes in effective operating length of the device according to the embodiment of FIG.

FIG. 3 is a diagram showing another embodiment of the laser device of the present invention.

FIG. 4 is a diagram for explaining changes in effective operating length of the device according to the embodiment of FIG.

FIG. 5 is a diagram showing a laser device that does not consider a change in effective working length.

FIG. 6 is a diagram for explaining changes in effective operating length of elements of the laser device in FIG.

FIG. 7 is a diagram showing another embodiment of the laser device of the present invention.

FIG. 8 is a diagram showing another embodiment of the laser device of the present invention.

FIG. 9 is a diagram showing a conventional laser device.

[Explanation of symbols]

11, 31, 51, 61 ... Excitation light 12, 32, 52, 62 ... Resonator mirror block 13 ... Resonator mirror 13a, 33a, 53a, 63a ... Resonator mirror coating 13b, 33b, 33c, 53b, 63b ... Surface 14, 34, 54, 64 ... Laser medium 15, 35, 55, 65 ... Etalon 16, 36, 56, 66 ... Output mirror 16a, 36a, 56a, 66a ... Output mirror coating 16b, 36b, 56b, 66b ... Surface 17 , 37, 57, 67 ... Output mirror block 18, 38, 58, 68 ... Resonator block 19, 39, 59, 69 ... Peltier element 21 ... Resonator mirror effective action length change 22, 42, 42a ... Laser medium execution Action length change 23, 43, 43a ... Etalon effective action length change 24, 44, 44a ... Output mirror effective action length change 2 , 45, 45a ... Resonator block effective action length change 26, 46, 46a ... Resonator length effective action length change 62a ... Resonator change suppressing component 71, 71a ... Semiconductor laser 72, 72a ... Condenser lens 73 ... Nd : YAG crystal 73a, 78a ... surface 74 ... KNbO ₃ (KN) crystal 75 ... etalon 76 ... fundamental 77 ... second harmonic 78 ... output mirror 79, 80 ... holder 81 ... reference plate 82 ... Peltier element 83 ... heat sink

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Claims (8)

[Claims] 1. In a laser device in which a laser medium is excited by pumping light to oscillate a laser in a laser resonator, each element constituting the laser resonator is attached along with an effective change in resonator length due to a temperature change. A laser device characterized by being configured so as to be fixed in a direction in which a wavelength shift is suppressed or prevented. 2. In a laser device in which a laser medium is excited by pumping light and oscillates in a laser resonator, mounting of the laser medium constituting the laser resonator is accompanied by a change in effective resonator length due to temperature change. A laser device characterized by being configured so as to be fixed in a direction in which a wavelength shift is suppressed or prevented. 3. A laser device in which a laser medium is excited by excitation light to cause laser oscillation in a laser resonator, wherein a resonator mirror or an output mirror constituting the laser resonator,
Alternatively, the laser device is characterized in that both of them are fixed so as to suppress or prevent a wavelength shift caused by an effective change in the cavity length due to a change in temperature. 4. A laser device in which a laser medium is excited by pumping light to oscillate a laser in a laser resonator, wherein each element constituting the laser resonator is attached in accordance with a change in effective resonator length due to a temperature change. A laser device characterized in that the laser device is configured to be fixed via a resonator change suppressing component that leads to a direction in which a wavelength shift is suppressed or blocked. 5. In a laser device in which a laser medium is excited by excitation light and oscillates in a laser resonator, mounting of the laser medium or the resonator mirror and the output mirror forming the laser resonator is effective by changing the temperature. A laser device characterized in that the laser device is configured to be fixed via a resonator change suppressing component that guides in a direction of suppressing or preventing a wavelength shift due to a change in the resonator length. 6. The laser device according to claim 1, claim 2, claim 3, claim 4, or claim 5, wherein the laser medium is a solid-state laser crystal. 7. The laser device according to claim 1, claim 2, claim 3, claim 4, claim 5 or claim 6, wherein the pumping light source is a semiconductor laser. 8. A laser device according to claim 1, claim 2, claim 3, claim 4, claim 5, claim 6 or claim 7, wherein a nonlinear optical crystal is provided in the resonator for wavelength conversion. A laser device characterized in that