JPH08179175A - Holder for optical member and fixing method therefor - Google Patents

Abstract

PURPOSE: To prevent stray light from being generated with light overflowing from the optical member by forming a groove, which extends nearby the optical path of a light beam along the optical path to the overall length of the holder, in a surface for fitting optical member. CONSTITUTION: The holder 20 has the flat optical member-fitting surface 20a and fixes LN crystal 15 while overlapping the top surface 15a of the LN crystal 15 along the passing direction of the laser beam 18 on the fitting surface 20a. In this fitting surface 20a, the groove 20b is formed which extends nearby and along the optical path of the laser beam 18 to the overall length of the holder 20. The LN crystal 15 is fixed to the holder 20 by adhering a part of the fitted surface 20a positioned outside both sides of the groove 20b to the crystal surface 15a with an adhesive. When the groove 20b is thus formed, since the excess part of the laser beam 18 passes through the groove 20b as it is, even if the LN crystal 15 is not thick enough or if the skirt part of the laser beam 18 overflows from the LN crystal 15 because of insufficient optical axis adjustment, stray light is prevented from being generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a holder for fixing an optical member such as an optical crystal through which a light beam passes.

The present invention also relates to a method of fixing the above-mentioned optical member to a holder.

[0003]

2. Description of the Related Art As disclosed in, for example, Japanese Patent Laid-Open No. 62-189783, there is known a solid-state laser device for exciting a solid-state laser crystal doped with a rare earth element such as neodymium with a semiconductor laser or the like. In this type of solid-state laser device, in order to obtain a laser beam of a shorter wavelength, a nonlinear optical crystal (crystal of a nonlinear optical material) is arranged in the resonator so that the solid-state laser beam becomes a second harmonic wave or the like. Wavelength conversion is also widely performed.

By the way, in the above-mentioned solid-state laser device, in order to fix a small solid-state laser crystal or a nonlinear optical crystal at a predetermined position, these crystals are fixed to a holder with an adhesive or the like, and the holder is fixed. The method of fixing to a reference plate or the like is often applied. Such a fixing method is widely applied to optical devices other than the solid-state laser device and also to fixing optical members other than the optical crystal.

Conventionally, as one of the holders, one shown in FIG. 2 is known. The holder 1 has a flat optical member mounting surface 1a, and the optical member 3 is mounted with the surface 3a of the optical member 3 through which the light beam 2 passes along the light beam passing direction being aligned with the mounting surface 1a. It is something that is fixed. The fixing is performed by, for example, adhering the optical member surface 3a and the mounting surface 1a.

[0006]

The above-mentioned conventional holder has a simpler structure as compared with, for example, one that grips two side end portions of an optical member, but on the other hand, it may generate stray light. . That is, when the optical member is not sufficiently thick or when the optical axis adjustment is insufficient, the portion near the center of the light beam passes through the optical member, but the peripheral end portion of the light beam (the so-called "skirt"). Part) may protrude from the optical member. Then, the protruding portion of this light beam is diffusely reflected on the boundary surface between the optical member and the holder, and the diffusely reflected light becomes stray light.

The portion of the light beam protruding from the optical member as described above is, if it is a Gaussian beam,
In most cases, it is a portion with a low intensity outside the 1 / e ² diameter (the beam diameter where the optical power in the beam cross section becomes 1 / e ^{2 of the} maximum value), and the stray light is also considerably weak. But,
Nevertheless, such stray light often adversely affects optical equipment.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical member holder that does not generate stray light due to light protruding from the optical member, and a method for fixing the optical member. To do.

[0009]

An optical member holder according to the present invention has a flat optical member mounting surface, and has a flat optical member mounting surface along the light beam passing direction of the optical member through which the light beam passes. In an optical member holder for fixing the optical member in a state where the surface is aligned with the mounting surface, a groove extending along the optical path in the vicinity of the optical path of the light beam is provided on the optical member mounting surface along the optical path. It is characterized by being formed.

Preferably, in this optical member holder, the length in the optical axis direction is equal to or less than the length of the optical member in the same direction as described in claim 2.

Further, in this optical member holder, the optical member mounting surface is preferably mirror-polished as described in claim 3.

On the other hand, the method of fixing an optical member according to the present invention is
According to a fourth aspect of the present invention, the surface of the optical member along the light beam passing direction is adhered to the optical member mounting surface of the optical member holder according to the present invention with an adhesive.

[0013]

In the optical member holder of the present invention, since the groove as described above is formed on the optical member mounting surface, even if a part of the light beam protrudes from the optical member, the light beam The protruding part of the part passes through this groove as it is. Therefore, this protruding light will not be irregularly reflected at the boundary surface between the optical member and the holder,
Alternatively, the degree is reduced, and the generation of stray light is prevented.

If the generation of stray light can be prevented in this way, the tolerance of the optical axis adjustment can be increased even if the thickness of the optical member such as an optical crystal cannot be made sufficiently large.

If the tolerance of the optical axis adjustment can be increased in this way, various holders having different heights are prepared in order to adjust the holder height to absorb variations in the optical axis, for example. In such a case, the type (height) of the holder to be prepared can be reduced.

In order to fix the optical member to the optical member holder having the above-mentioned structure, it is convenient to apply the above-mentioned method of the present invention and adhere the both members with an adhesive.

When the optical member is adhered to the optical member holder as described above, the adhesive is likely to seep out of the adhering surface.
In the conventional holder for optical members, the adhesive applied to the surface 3a of the optical member and / or the mounting surface 1a shown in FIG. 2 seeps out to the shaded portion in FIG. May be attached to the beam passing portion of the. In such a case, the adhesive has an adverse effect on the light beam 2 such as light loss, and therefore it is necessary to carefully wipe off the exuded adhesive.

On the other hand, when the optical member holder according to the present invention having the above-described structure is used, the adhesive is not applied to the groove portion of the optical member mounting surface, so that even if the adhesive oozes out, it does not fail. This occurs at a portion outside the groove, that is, at a position apart from the beam passage portion on the end surface of the optical member. Therefore, in this case, it is possible to prevent the adhesive from adhering to the beam passage portion of the end surface of the optical member,
It is possible to eliminate or simplify the adhesive wiping work.

As described above, when the length of the optical member holder in the optical axis direction is equal to or less than the length of the optical member in the same direction, it is easier to wipe off the exuded adhesive. Becomes The reason will be described later in detail with reference to embodiments.

If the optical member mounting surface of the optical member holder is mirror-polished, the adhesive can easily spread uniformly and widely. Therefore, the adhesive layer can be made thinner to prevent the above-mentioned seepage. It can be eliminated or reduced.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the embodiments shown in the drawings. FIG. 3 shows a laser diode pumping solid-state laser to which an optical member holder 20 according to an embodiment of the present invention is applied, and FIG. 1 shows the optical member holder 20 in detail.

First, a laser diode pumped solid-state laser will be briefly described with reference to FIG. This laser diode pumped solid-state laser is a semiconductor laser 11 that emits a laser beam 10 as excitation light.
And a gradient index lens 12 that collects the laser beam 10 that is divergent light, and a YAG crystal (hereinafter referred to as NAG) that is a solid-state laser medium doped with neodymium (Nd).
(d: YAG crystal) 13 and this Nd: YAG crystal
It has a resonator mirror 14 arranged on the front side of 13 (right side in the figure).

The resonator mirror 14 and Nd: YAG
Between the crystal 13 and the Nd: YAG crystal 13 side, LiNbO ₃ crystal having a periodic domain inversion structure (hereinafter, referred to as
An LN crystal) 15 and an etalon 16 are arranged.

The semiconductor laser 11 has a wavelength of 809 nm.
A laser beam that emits a laser beam 10 is used. N
Neodymium ions are excited in the d: YAG crystal 13 by the incident laser beam 10 to emit a laser beam 18 having a wavelength of 946 nm. This laser beam 18 has a wavelength of ½, that is, LN crystal 15 which is a non-linear optical material.
Converted to the second harmonic of 473 nm 19
Is emitted from the resonator mirror 14.

The LN crystal 15 is adhesively fixed to a holder 20 according to the invention, the other solid-state laser components are also fixed to respective holders (not shown), and these holders are fixed to a reference plate (not shown). Hereinafter, the holder 20 will be described in detail with reference to FIG.

The holder 20 has a flat optical member mounting surface 20.
a, and the surface 15a of the LN crystal 15 along the passage direction of the laser beam 18 is aligned with this mounting surface 20a.
Fix N crystal 15. The optical member mounting surface 20a is provided with a groove 20b extending in the vicinity of the optical path of the laser beam 18 along the optical path and over the entire length of the holder. LN crystal 15
Is fixed to the holder 20 by adhering the portions of the mounting surface 20a located on the outer sides of the groove 20b to the crystal surface 15a with an adhesive.

When the groove 20b as described above is formed on the optical member mounting surface 20a of the holder 20, the LN crystal 15 is not sufficiently thick or the optical axis adjustment is insufficient. Even if the "hem" of the laser beam 18 protrudes from the LN crystal 15, the protruding portion of the laser beam 18 passes through the groove 20b as it is. Therefore, this protruding light is not diffusely reflected at the boundary surface between the LN crystal 15 and the holder 20, and stray light is prevented from being generated.
The depth and width of the groove 20b are set to be sufficiently large so that the protruding portion of the laser beam 18 does not hit the holder 20.

Here, of course, no adhesive is applied to the groove 20b portion, so that even if the adhesive seeps out to the end face 15b side of the LN crystal 15, it will always come from the laser beam passage portion of this crystal end face 15b. It will occur at a distant place (hatched portion in Fig. 1). Therefore, in this case, the adhesive can be prevented from adhering to the laser beam passage portion of the LN crystal end face 15b, and the operation of wiping the adhesive becomes unnecessary or simplified.

In this embodiment, the length of the holder 20 in the optical axis direction is aligned with the length of the LN crystal 15 in the same direction.
The length of the holder 20 may be larger than the length of the LN crystal 15 as shown by the one-dot chain line in FIG. 1, but it may be equal to or longer than the length of the LN crystal 15 as described above. The shorter the length, the easier it is to wipe off the oozing adhesive. Hereinafter, the reason will be described with reference to FIG.

FIG. 4 shows the side shapes of the LN crystal 15 and the holder 20. If the holder 20 is longer than the LN crystal 15 as shown by the one-dot chain line in the figure, the leached adhesive will collect in the corner indicated by the arrow A. It is difficult to clean the adhesive accumulated in such a part,
The work has to be carried out particularly carefully because it may extend toward the center of the N crystal end face 15b and contaminate the laser beam passage portion of the end face 15b.

On the other hand, if the length of the holder 20 is equal to or less than the length of the LN crystal 15, the end face 20c of the holder 20 is aligned with the LN crystal end face 15b as shown by the solid line in FIG. It can be placed inside 15b. When the end surface 20c of the holder 20 is inside the LN crystal end surface 15b, the leached adhesive collects in the corner indicated by arrow B. Even if the adhesive accumulated in such a portion extends to the center side of the LN crystal 15, it does not cause a problem because it does not contaminate the laser beam passage portion of the LN crystal end face 15b.

On the other hand, when the end face 20c of the holder 20 is aligned with the LN crystal end face 15b, the leached adhesive will collect in the portion indicated by the arrow C. In this way, the adhesive that accumulates on the flat part is different from when it accumulates on the corners.
Easy to work and easy to wipe.

In this embodiment, the optical member mounting surface 20a of the holder 20 is mirror-polished. By doing this, the adhesive can easily spread uniformly and widely, so the adhesive layer can be made thinner to prevent the above-mentioned seepage,
Or it can be kept low.

Although the embodiment constituted as the one for fixing the non-linear optical crystal in the solid-state laser has been described above, the present invention is applicable to an optical device other than such a solid-state laser, and an optical member other than the non-linear optical crystal. Of course, the same can be applied to the case of fixing.

[Brief description of drawings]

FIG. 1 is a perspective view showing an optical member holder according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a conventional optical member holder.

FIG. 3 is a side view showing a solid-state laser using the holder for optical members of the above-mentioned embodiment.

FIG. 4 is an explanatory diagram for explaining seepage of an adhesive in an optical member holder.

[Explanation of symbols]

 1 Optical member holder 2 Optical beam 3 Optical member 10 Laser beam (excitation light) 11 Semiconductor laser 12 Condensing lens 13 Nd: YAG crystal 14 Resonator mirror 15 LN crystal with periodic domain inversion structure 16 Etalon 18 Solid-state laser beam 19 Second harmonic 20 Holder for optical components

Claims (4)

[Claims] 1. An optical member holder having a flat optical member mounting surface, and fixing the optical member with the surface of the optical member through which the light beam passes along the light beam passing direction being aligned with this mounting surface. The optical member holder according to claim 1, wherein a groove extending near the optical path of the light beam along the optical path and over the entire length of the holder is formed on the optical member mounting surface. 2. The optical member holder according to claim 1, wherein the length in the optical axis direction is equal to or less than the length in the same direction of the optical member. 3. The optical member holder according to claim 1, wherein the optical member mounting surface is mirror-polished. 4. A method for fixing an optical member, characterized in that a surface of the optical member along the light beam passing direction is adhered to the optical member mounting surface of the optical member holder according to claim 1 with an adhesive.