JPS61208002A - Light transmission device - Google Patents

Abstract

PURPOSE:To obtain stable laser light of which the distribution of the refractive index in the plane direction of light-transmittable substrates disposed to face each other is made uniform by insulating and holding the heat at the periphery of the substrates and passing a cooling medium in the spacing between the opposed surfaces of the substrates. CONSTITUTION:The cooling medium from a supply pipe 18 is stored in a pocket 20 and passes evenly through the spacing from respective square grooves 25 to cool the opposed surfaces of an output mirror 14 and a light transmittable body 15. The heat which is generated by the passage of the laser light outputted during laser oscillation and diffused to the entire part of the mirror 14 and the body 15 is less radiated from the boundary face at the periphery as the circumference is held by a spacer consisting of a heat insulating material. The temp. distribution within the plane of the output mirror is small and the temp. gradient between the mirror 14 and the body 15 is small. The gradient of the refractive index is thereby decreased to a small level and therefore such an inconvenience as to converge the laser light is prevented even if the laser light is transmitted.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a light transmission device.

[Technical background of the invention and its problems]

In the case of an optical resonator in a laser oscillator, which is a light transmission device, total reflection is provided on both sides of the excitation part (1) facing each other! (2) and an output mirror (3).

When the output of the laser beam (4) emitted from the output mirror (3) is increased, its directivity changes in the direction of convergence as shown by the broken line in the figure. When the laser beam is transmitted through the output mirror (3), absorption occurs inside the output mirror (3), resulting in a temperature rise. This may cause the refractive index to increase or
This phenomenon is thought to be caused by a convex lens effect caused by thermal expansion of the transparent part. In order to alleviate the above-mentioned phenomenon, a nozzle (5) for ejecting cooling gas has been provided, and cooling gas is forcibly blown onto the surface of the output mirror (3) from this nozzle (5). However, the sprayed surface was not uniformly cooled, and the above phenomenon could not be sufficiently alleviated.

In addition, in the case of a transmission window, there is a problem that the laser light may change its optical path or move as a convergent beam due to deformation.

[Purpose of the invention]

The present invention provides a light transmitting device in which the light refraction effect due to temperature rise in the transmitting portion is reduced.

[Summary of the invention]

At least two light transmitting bodies are arranged to face each other with a gap between them, and a cooling medium is allowed to flow through the gap.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below based on drawings showing embodiments.

Taking an optical resonator in a laser as an example, in order to simplify the explanation, only the configuration on the output mirror side will be shown and explained with reference to FIGS. 1 to 4. That is, the above configuration can be roughly divided into each having a transmission hole αC in the center.

(Pol) (A holder α2 consisting of two members combined into a container shape by 1υ, and a first substrate disposed in parallel with a gap α3 coaxially with the transmission hole α0 within this holder) ! IC14) and a light transmitting body (l!9) which is the second substrate.
and.

These output mirrors a4), spacers (16a) and (16b) that individually hold both sides of the outer peripheral part of the light transmitting body α9 and airtightly abut both of them against the transmitting hole α1, and the holding body (I3) It is composed of a supply pipe and a discharge pipe α9, which are connected to each other via a connecting body αD.The above structure is explained in more detail. These also form the holes formed at the time of merging, and the supply pipe (18, σ
It is connected to 1. Spacer (16a), (16b)
is made of a thermally insulating material and is divided into two halves, and when combined, the outer shape is rectangular and has a space on the inside with the same diameter as the through hole αQ, and this space side Km
A groove shaped like this is formed. The output mirror α4 and the light transmitting body α4 are fitted into the grooves. Also.

These spacers (16a) and (16b) are attached to the holding body HI.
It is fitted into the stepped portion C24). Further, the opposing surfaces of the spacers (16a) and (16b) are provided with pockets (4) and a large number of square grooves (c) that expose the surfaces of the output mirror and the light transmitting body in the CD direction. , these square grooves have pockets tn, a1) and gaps (
13. The supply pipe 18 is connected to a cooling medium generator such as cooling air (not shown), and the discharge pipe (1ω) is connected to return the discharged medium to the cooling medium generator, thereby creating a circulation flow path. On the other hand, the surface of the output mirror I opposite to the surface facing the light transmitting body a5 is coated with a dielectric multilayer film.

With the above configuration, the cooling medium supplied from the supply pipe α barrel is collected in the pocket (A) and passes through the gaps from each square groove (G) evenly to the output mirror 4. The opposite surface of the light transmitting body (IS) is cooled. Therefore, during laser oscillation.

The heat generated by the passage of the output laser beam and diffused throughout the output mirror αX and the light transmitting body α4 is cooled down evenly, so even if a temperature gradient occurs in the thickness direction, there is no temperature gradient in the surface direction. becomes significantly smaller. As a result, both the output mirror σ and the light transmitting body haze were kept extremely flat, and the phenomenon of focusing the laser beam was sufficiently reduced.

ti, even if deformation occurs due to the temperature gradient in the thickness direction mentioned above, in the case of a transmission window structure in which light transmitting bodies are opposed to each other rather than in combination with an output mirror, the thermal deformation will be as shown in Fig. 5. Since it can be made symmetrical by arranging the light transmitting body (l!9), parallel movement of the laser beam (4) can be prevented.

When applied as a transmission window for a carbon dioxide laser oscillator with an output of IKW or more, it is advantageous to have a thinner light transmitting body provided facing each other because absorption of laser light is smaller. When there is a pressure difference on both sides, mechanical strength is required, so the thickness of the light transmitting member on the vacuum side must be sufficiently thick.

〔Effect of the invention〕

As detailed above, the structure is such that the cooling medium flows evenly through the gap between the optically transparent substrates placed opposite each other, so for example, in the laser optical resonator or transmission window, the laser beam may be focused or moved in parallel. K has been eliminated and stable laser light can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an embodiment of the present invention, FIG. 2 is a side view, and FIG. 3 is a sectional view taken along the line ■-■ in FIG.
Figures 4 and 4 are cross-sectional views taken along the ff-ff line in Figure 2;
The figure is a block diagram of main parts showing another embodiment of the present invention, and FIG. 6 is a block diagram showing a conventional example. Mouse...Permeation hole (I...Holding body (IS...
Gap (14)...Output mirror (is-...Light transmitter (16a), (16b)-xH-"J-α
υ...Supply pipe αt...Discharge pipe (c)...Square
Groove Figure 1 Figure 2 Figure 3 Figure 1i4 Figure 5 Procedural amendment (suspect) 1. Indication of the incident Japanese Patent Application No. 60-48271 2. Name of the invention Light transmitting device 3. Person making the amendment Relationship between patent applicant (307) Toshiba Corporation 4, agent 1-1 Shibaura-chome, Minato-ku, Tokyo 105 Tokyo Co., Ltd. Head Office Office Full text of the specification 6, details of amendments as shown in the appendix 1, Title of the invention: Light transmitting device 2, claims: a first light transmitting substrate; at least one or more second light transmitting second substrates facing the first substrate with a gap therebetween; A light transmitting device comprising: a holding means for thermally insulating and holding the two, with the gap serving as a passage for a cooling medium; and a cooling means for supplying the cooling medium to the gap. 3. Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a light transmitting device. [Technical background of the invention and its problems] In the case of an optical resonator in a laser oscillator ζ, which is the main part of a light transmission device, total reflection mirrors (2) are provided on both sides of an excitation part (1) to face each other. and an output mirror (3). When the output of the laser beam (4) emitted from the output mirror (3) is increased, its directivity changes in the direction of convergence as shown by the broken line in the figure. In this phenomenon, when the laser beam passes through the output tube (3), absorption occurs inside the output tube (3), resulting in a temperature rise. This increases the refractive index and
This phenomenon is thought to be caused by a convex lens effect caused by thermal expansion of the transparent part. In order to alleviate the above phenomenon, a nozzle (5) for ejecting cooling gas has been provided, and the cooling gas is forcibly blown onto the surface of the output mirror (3) from this nozzle (5). However, the sprayed surface was not uniformly cooled, and the above phenomenon could not be sufficiently alleviated. Further, in the case of a transmission window, there is a problem in that the laser beam is deformed and the optical path of the convergent beam or the like changes or moves. [Object of the Invention] The present invention provides a light transmitting device in which the light refraction effect due to temperature rise in the transmitting portion is reduced. [Summary of the Invention] At least two light transmitting bodies are arranged to face each other with a gap between them, and a cooling medium is allowed to flow through the gap. [Embodiments of the Invention] The present invention will be explained below based on drawings showing embodiments. Taking an optical resonator in a laser as an example, in order to simplify the explanation, the explanation will be given with reference to FIGS. 1 to 4, which show only the configuration on the output mirror side. That is, the above configuration can be roughly divided into two holes each having a transmission hole in the center. A holder (12) consisting of two members combined into a container shape by a transparent hole (11), and an output which is a first substrate disposed parallel to the transparent hole coaxially with a gap α in this holder. The mirror I and the light transmitting body α9 which is the second substrate. These output *ff411. Both sides of the outer peripheral part of the light transmitting body (L!9) are individually held and both are brought into airtight contact with the four parts of the above-mentioned transmission hole. spacers (16a), (16b),
It is composed of a supply pipe α frame and a discharge pipe 0, which are connected to the holder (2) via a connecting body aη. To explain the above structure in more detail, the holder (1) is combined to form pockets (E) and Ql at the top and bottom in the figure. These also communicate with the supply pipe end, α, through the holes formed at the time of joining. Spacer (16a), (
16b) is made of a thermally insulating material and is divided into two parts, and when combined, the outer shape is rectangular and has a space on the inside with the same diameter as the through hole α1, and an annular shape on the side of this space. A concave groove is formed. The output mirror←4 and the light transmitting body haze are fitted into this groove. Also. These spacers (16a) and (16b) are fitted into a stepped portion 01 formed on the holder α. Further, the opposing surfaces of the spacers (16a) and (16b) are provided with pockets (A) and a large number of square grooves (C) that expose the surfaces of the output mirror I and the light transmitting body α9 in the direction (21). These square grooves serve as flow paths that communicate the pocket (to), Ql) and the gap αj. The above-mentioned supply pipe α is connected to a cooling medium generating device such as cooling air (not shown), and the discharge pipe α is connected to return the discharged medium to the cooling medium generating device. is configured to form a On the other hand, the light transmitting body of the output mirror a (the surface opposite to the surface facing the US is coated with a dielectric multilayer film. With the above configuration, the cooling medium supplied from the supply pipe barrel a is (a) The output mirror I and the light transmitting body (19) are cooled by passing through the gap from each square groove (c) on an average basis. Therefore, during laser oscillation. The heat generated by passing through the output mirror and diffused throughout the light transmitting body (is) is held by a spacer made of a thermally insulating material, so the heat dissipated from the boundary surface around the output mirror is small. The temperature distribution within the mirror has a small temperature gradient due to thermal diffusion, and the cooling is averaged from the opposing surfaces of the output mirror α and the light transmitting body 9.
1st. A temperature gradient in the second substrate is formed in the thickness direction, and even if this temperature gradient is created in the thickness direction, the temperature gradient in one surface direction is extremely small. This allows the output mirror (1
Xun. Both light-transmitting materials have small in-plane temperature gradients, so the gradient of refractive index can be kept small, and therefore, even when laser light is transmitted through them, it is possible to prevent disadvantageous phenomena such as convergence of laser light. . Furthermore, even if deformation occurs due to the temperature gradient in the thickness direction, in the case of a transparent window structure in which light transmitting bodies are opposed to each other, rather than in combination with an output mirror, the thermal deformation will occur as shown in Figure 5. Since it can be made symmetrical by arranging the light transmitting body α$, convergence and parallel movement of the laser beam (4) can be prevented. Note that when applied as a transmission window for a carbon dioxide laser oscillator with an output of more than IKW, for example, an output of more than 10KW, it is advantageous if the thickness of the light transmitting body provided oppositely is thinner, since absorption of laser light is smaller. When there is a pressure difference on both sides, as in the case of a vacuum container window, mechanical strength is required, so the thickness of the light transmitting member on the vacuum side must be sufficiently thick. In addition, in the above embodiment, heat radiation from the surroundings was prevented by holding the substrate such as the output mirror with a thermally insulating holding means. It may also be configured to hold parts. [Effects of the Invention] As described in detail above, the peripheries of the light-transmitting substrates placed opposite each other are held insulated, and the cooling medium is allowed to flow through the gap between the opposing sides, thereby reducing refraction in the plane direction of the substrates. Since the ratio distribution has been made uniform, the phenomenon of convergence or parallel movement of laser light due to the laser's optical resonator or transmission window has been eliminated, making it possible to obtain stable laser light. 4. Brief description of the drawings Figure 1 is a front view showing an embodiment of the present invention, Figure 2 is a side view, and Figure 3 is a sectional view taken along the line ■-■ in Figure 1.
FIG. 4 is a sectional view taken along line ff-IV in FIG. 2, FIG. 5 is a block diagram of main parts showing another embodiment of the present invention, and FIG. 6 is a block diagram showing a conventional example. α1...Transmission hole @...Holder←Holder...Gap α荀...Output mirror α [with]...Light transmitting body (16M), (16b)...Heat insulation spacer Nishiki...supply pipe a9...discharge/outlet pipe (c)/
・Corner groove

Claims (1)

[Claims] a light-transmitting first substrate; at least one or more second light-transmitting second substrates facing the first substrate with a gap therebetween; the gap serves as a passage for a cooling medium to hold the two; 1. A light transmitting device comprising: a holding means for holding a cooling medium; and a cooling means for supplying a cooling medium to the gap.