JPH06188489A - Assembling method for optical resonator - Google Patents

Abstract

PURPOSE:To provide an optical resonator and the assembling method of the optical resonator, which can secure high positioning accuracy and can maintain the high positioning accuracy. CONSTITUTION:Spacers 17, 18 and 19 are inserted. A first mirror 13, optical elements 14 and 15 and a second mirror 16 are held at the intervals determined with the spacers 17, 18 and 19. Then, the side surfaces of the first mirror 13, the optical elements 14 and 15 and the second mirror 16 are bonded to a holding stage 21 with a specified bonding agent. Then, the spacers 17, 18 and 19 are removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an externally excited SHG (Second Hamonic Generation) having an internal resonator structure, for example.
) It relates to an optical resonator applied to a laser or the like, and further to a method for assembling this optical resonator.

[0002]

2. Description of the Related Art Conventionally, in an externally pumped SHG laser having an internal cavity structure, it is possible to efficiently generate a laser beam of a short wavelength by exciting a resonator section with a laser beam generated by a pumping light source. It has become.

That is, as shown in FIG. 10, in this type of externally pumped SHG laser 1, a laser light source 2 generates a laser light L0 having a predetermined wavelength λ0, and this laser light L1 is passed through a lens 3 to a resonator. Lead to 4. Resonator 4 here
Arranges the mirrors 5 and 6 having wavelength selectivity in parallel, and arranges the laser crystal 7 and the SHG crystal 8 between the mirrors 5 and 6. As a result, in the resonator 4, the laser light L0 is guided through the mirror 5 to the laser crystal 7,
The laser crystal 7 is excited by the laser light L0 to generate a laser light L1 having a predetermined wavelength λ1 and irradiates the SHG crystal 8 with the laser light L1.

When the laser beam L1 having the wavelength λ1 is incident on the SHG crystal 8, a second harmonic of the laser beam L1 is generated, which causes the externally pumped SHG laser 1 to have the wavelength λ2 (that is, the laser beam). A laser beam L2 having a short wavelength of (1/2 wavelength of L1) is generated. In order to efficiently generate the laser beam L2 having the wavelength λ2, the laser beam L2 is used in the SHG laser 1.
The wavelength λ0 of 0 is selected as the wavelength of the absorption line of the laser crystal 7, whereby the laser crystal 7 can be efficiently excited.

Further, in the SHG laser 1, the mirror surfaces 5M and 6M of the mirrors 5 and 6 are formed of a vapor deposition film having a predetermined film thickness, so that the transmittance and the reflectance are respectively different at the wavelength λ0 and the wavelengths λ1 and λ2. The mirror 5 is formed to have a high reflectance, and the mirror 6 is formed to have a high reflectance and a high reflectance at the wavelength λ1 and the wavelength λ2, respectively. As a result, in the SHG laser 1, the laser light L0 having the wavelength λ0 is efficiently transmitted through the mirror 5 and the laser crystal 7 is transmitted.
On the other hand, the generated laser light L2 having the wavelength λ2 can be efficiently transmitted through the mirror 6 and output to the outside.

In the SHG laser 1, the wavelength λ
With respect to the laser light L1 of 0, a resonator is formed by the mirrors 5 and 6 and is confined between the mirrors 5 and 6, whereby the laser light L2 (that is, SHG light) of the predetermined wavelength λ2 is efficiently formed as a whole. You can do it.

[0007]

By the way, in the SHG laser 1 which forms a resonator in this way, the efficiency greatly varies depending not only on the processing accuracy of each optical element itself but also on the assembly accuracy.

That is, in the SHG laser 1, by forming an optical resonator between the mirror 5 and the mirror 6,
The optical elements 5 to 5 are highly accurately arranged so that the surfaces of the elements 5 to 8 which are perpendicular to the optical axis of the laser beam L0 are parallel to each other.
8 need to be positioned. Furthermore, in the SHG laser 1, it is necessary to maintain this positioning accuracy after assembly. Particularly, in the optical elements 5 to 8 of this type, it is difficult to maintain the positioning accuracy with respect to the change of the ambient temperature because the thermal expansion coefficients are different.

As one of the methods for ensuring and maintaining such positioning accuracy, a method of directly adhering the entrance and exit surfaces of the optical elements 5 to 8 with an adhesive is conceivable. However, in the case of this method, the internal loss of the resonator increases due to the adhesive, and eventually the SHG light cannot be efficiently emitted. Further, the adhesive itself cannot guarantee the light resistance to the laser beams L1, L2, and L3, and the transparent adhesive is required, so that the adhesive itself can be selected only slightly. Further, there is a drawback that the internal strain generated by directly applying the adhesive cannot be completely removed.

On the other hand, a method of holding each of the optical elements 5 to 8 by using a mechanical means can be considered. In this case, the mirrors 5 and 6 are held by mechanical means so as to be pressed from both sides, but it is difficult to maintain the positioning accuracy. That is, in the case of holding by the mechanical means in this way, once the position is displaced, the original state cannot be restored, and thus it becomes impossible to completely prevent the change over time.
Further, in the case where the elements are held so as to be pressed from both sides, when the temperature changes, the pressing force changes between the facing surfaces of the respective elements, which eventually causes interference between the elements. Further, there is a problem that the photoelasticity of the optical element changes due to this pressing force, and in this case, the characteristics of the SHG laser 1 itself such as noise level and output power change.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an assembling method of an optical resonator which can easily secure high positioning accuracy and can maintain the high positioning accuracy. .

[0012]

According to the present invention, the above object is to dispose a first optical element and a second mirror with a predetermined optical element interposed therebetween, and the first mirror, the optical element, After a spacer is inserted between the second mirrors and the space between them is maintained at a space determined by the spacer, the side faces of the first mirror, the optical element, and the second mirror are held by an adhesive. Adhered to a table, the first mirror, the optical element,
Optical resonance, in which the second mirror is held on the holding table at the interval, and then the spacer is removed to hold the first mirror, the optical element, and the second mirror through the space of the interval. This is achieved by the method of assembling the container.

[0013] Preferably, as the adhesive, an adhesive having elasticity that changes into rubber when fixed is used.

Further, preferably, when the spacer is inserted between the first mirror, the optical element and the second mirror and the space between them is maintained at a space determined by the spacer, One mirror is applied to a predetermined reference member, and the first mirror, the optical element, and the second mirror are pressed against the reference member, so that the space between them is maintained at the space determined by the spacer. You can

Further, preferably, one surface of the first mirror is convex, and the reference member is the first mirror.
A concave portion may be formed corresponding to the convex surface of the mirror, and the spherical surface may be pressed against the concave portion for positioning.

Further, preferably, the optical element is a laser crystal which is excited by excitation light to generate laser light of a predetermined wavelength, and an SHG which receives the laser light and generates a second harmonic of the laser light. A crystal, the first mirror transmits the excitation light incident from the outside and guides it to the laser crystal, reflects the laser light and the second harmonic, and the second mirror is The second harmonic may be transmitted and emitted to the outside, and the excitation light, the laser light, and the second harmonic may be reflected.

[0017]

According to the above-described structure, the first mirror, the optical element, and the second mirror can be held on the holding table at a highly accurate interval determined by the spacer by a simple operation, and by removing the spacer. The interference between the first mirror, the optical element, and the second mirror can be prevented, and an adhesive having elasticity can be applied to restore the original holding position.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below in detail with reference to the accompanying drawings. The examples described below are
Since it is a preferred specific example of the present invention, various technically preferable limitations are attached, but the scope of the present invention is, unless otherwise stated to limit the present invention, in the following description.
It is not limited to these modes.

FIG. 1 is a schematic sectional view showing an embodiment of an externally pumped SHG laser according to the present invention.

In the figure, the SHG laser 10 generates a laser light L0 having a wavelength of 820 [nm] by a laser light source 11, and emits this laser light L0 to a resonator 12 via a lens 3. In the resonator 12, 1/4 which is the first mirror
A laser crystal 1 is transmitted by the laser beam L0 after passing through the wave plate 13.
4 is excited, and the laser beam L1 obtained as a result is incident on the SHG crystal 16 which also functions as a second mirror through a predetermined optical glass (BK7) 15 corresponding to an air space.
As a result, in the resonator 12, the SHG crystal 16 generates the second harmonic L2 of the laser light L1, and the second harmonic L2 is emitted to the outside.

Therefore, in the quarter-wave plate 13, the total thickness is selected to be 0, 5 [mm], and one surface on the laser light source 11 side is formed into a spherical surface, and the mirror surface 13M is formed on this spherical surface. To form. Further, the quarter wavelength plate 13 is provided with a predetermined coating (HR coat) so that the laser light L0 of the laser light source 11 can be efficiently transmitted and the laser light L1 and the SHG light L2 of the laser crystal 14 can be efficiently reflected. A mirror surface 13M is formed.

On the other hand, in the laser crystal 14,
A Nd: YAG crystal having a thickness of 1 and 5 [mm] is selected, and a laser beam L0 having a wavelength of 1064 [nm] is generated thereby. SHG
As the crystal 16, KTiPO4 crystal having a thickness of 2, 5 [mm] is selected, and a mirror surface 16M is formed on the emitting surface.

The mirror surface 16M is formed by a predetermined coating (AR coating) so that the laser light L0 of the laser light source 11 and the laser light L1 of the laser crystal 14 can be efficiently reflected and the SHG light L2 can be efficiently transmitted. To be done. Accordingly, in the resonator 12, the laser light source 11
Laser beam L0 efficiently excites laser crystal 14 to emit laser beam L2, and SHG having a wavelength of 532 [nm], which is the second harmonic of laser beam L1.
The light L2 can be emitted efficiently.

In this resonator 12, as shown in FIG. 2, spacers 17, 18, and 19 are inserted in order to sequentially make a quarter.
Wave plate 13, laser crystal 14, optical glass 15, SHG
The crystal 16 is pressed against the abutting jig 20, and in this state, the quarter-wave plate 13, the laser crystal 14, the optical glass 15, and the SHG crystal 16 are bonded to the substrate 21, and then the spacer 1
It is designed to be assembled by removing 7 to 19.

That is, in the resonator 12, as shown in FIG.
After pressing 3 and then the spacer 17, the laser crystal 14 and the spacer 18 are pressed as shown in FIG. Further, as shown in FIG. 5, after pressing the optical glass 15 and the spacer 19, the SHG crystal 16 is pressed as shown in FIG. 6, and in this state, the 1/4 wavelength plate 13, the laser crystal 14, and the optical crystal 14 are pressed onto the substrate 21. Glass 15, SHG crystal 1
The side of 6 is pressed and bonded.

Further, in the resonator 12, when the adhesive is fixed, the spacer 17 is formed as shown in FIGS.
.About.19 are pulled out, the fitting jig 20 is removed, and then the laser light source 11 and the lens 3 are combined to form the SHG laser 10 as a whole. Here, the spacers 11 to 13 are formed to have a small thickness and maintain sufficient parallelism.

Thus, in the optical element forming the resonator, the smoothness sufficient to form the laser oscillator,
By being polished with the surface accuracy, the resonator 12 can be assembled by a simple assembling operation in which the spacers 17 to 19 are inserted and pressed against the abutting jig 20 to be adhered. At this time, the parallelism between the optical elements can be secured. Furthermore, the side surfaces of the quarter-wave plate 13, the laser crystal 14, the optical glass 15, and the SHG crystal 16 are adhered and held to the substrate 21, so that various adhesives are applied as necessary to secure sufficient strength. can do.

With respect to this point, in this embodiment, 1 /
Four-wave plate 13, laser crystal 14, optical glass 15, SH
The side surface of the G crystal 16 is adhered to the substrate 21. As a result, in the resonator 12, residual stress due to adhesion can be reduced, and when the parallelism between the optical elements 13 to 16 is disturbed when the spacers 17 to 19 are pulled out, the optical stress is further increased due to temperature change. Even when the elements 13 to 16 expand, the elasticity of the adhesive can restore the original state, and the deterioration of the characteristics due to the change over time can be reduced.

Further, by pulling out and holding the spacers 17 to 19, it is possible to prevent interference between the elements A to D even when the ambient temperature changes, and to obtain the resonator 12 whose change with time is small. be able to.

Further, in this embodiment, in the fitting jig 20, as shown in FIG.
A circular through-hole 21A is formed at the corresponding position of the quarter-wave plate 13 corresponding to the four-wave plate 13, whereby a quarter-hole is formed on the basis of the through-hole 20A.
The optical axis can be easily aligned by pressing the wave plate 13. Thus, by inserting a spacer between each optical element and pressing it against the abutting jig, and after adhering the optical element to the substrate in this state, the spacer can be pulled out to easily assemble the resonator with high accuracy. Therefore, the positioning accuracy can be maintained after the assembling.

In the above embodiments, the case where the mirror surface is formed on the end face of the SHG crystal has been described, but the present invention is not limited to this, and is also applied to the case where the SHG crystal and the mirror are formed separately. can do.

Further, in the above-mentioned embodiments, the case where the silicone type adhesive is applied has been described, but the present invention is not limited to this, and various adhesives having elasticity which changes into rubber like when fixed are applied. Thus, the optical element can be restored to the original holding position, and a normal UV-curable adhesive or the like can be widely applied within a practically sufficient range.

[0033]

As described above, according to the optical resonator and the method of assembling the optical resonator according to the present invention, it is possible to easily secure high positioning accuracy and maintain this high positioning accuracy.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of an optical resonator according to an assembly method of the present invention.

FIG. 2 is a perspective view showing an entire assembling work of the optical resonator shown in FIG.

FIG. 3 is a perspective view showing a first work procedure of the assembly work of FIG.

FIG. 4 is a perspective view showing a second work procedure of the assembling work of FIG. 2;

5 is a perspective view showing a third work procedure of the assembly work of FIG. 2. FIG.

FIG. 6 is a perspective view showing a fourth work procedure of the assembly work of FIG. 2;

7 is a perspective view showing a fifth work procedure of the assembling work of FIG. 2. FIG.

8 is a perspective view showing a sixth work procedure of the assembling work of FIG. 2. FIG.

FIG. 9 is a perspective view showing a backing plate.

FIG. 10 is a schematic sectional view showing an SHG laser.

[Explanation of symbols]

 1, 10 SHG laser 2, 11 Laser light source 4, 14 Resonator 5, 6 Mirror 7, 14 Laser crystal 8, 16 SHG crystal 13 1/4 wavelength plate 15 Optical glass 17, 18, 19 Spacer 20 Fixing jig 21 board

Claims (5)

[Claims] 1. A first and a second mirror are arranged with a predetermined optical element interposed therebetween, and a spacer is interposed between the first mirror, the optical element and the second mirror to provide a space therebetween. After maintaining the spacing of the first mirror, the optical element, and the side surface of the second mirror to the holding table with an adhesive, the first mirror, the optical element, The second mirror is held on the holding table at the interval, and then the spacer is removed to hold the first mirror, the optical element, and the second mirror via the space of the interval. And an optical resonator assembling method. 2. The method for assembling an optical resonator according to claim 1, wherein the adhesive has an elasticity that changes into a rubber when fixed. 3. The first mirror, when the spacer is inserted between the first mirror, the optical element, and the second mirror, and the space between them is maintained at a space determined by the spacer. To a predetermined reference member and press the first mirror, the optical element, and the second mirror against the reference member so that the space between them is maintained at the space determined by the spacer. The method for assembling the optical resonator according to claim 1 or 2, characterized in that. 4. The one surface of the first mirror is formed as a convex surface, and the reference member is formed with a concave portion corresponding to the convex surface of the first mirror, and the spherical surface is pressed against the concave portion. The optical resonator assembling method according to claim 3, wherein the optical resonator is positioned. 5. The optical element includes a laser crystal that is excited by excitation light to generate laser light of a predetermined wavelength, and an SH that receives the laser light and generates a second harmonic of the laser light.
G crystal, the first mirror transmits the excitation light incident from the outside and guides it to the laser crystal, reflects the laser light and the second harmonic, and the second mirror, 5. The optical resonator according to claim 1, wherein the second harmonic is transmitted and emitted to the outside, and the excitation light, the laser light, and the second harmonic are reflected. Assembly method.