WO2014192040A1 - Optical element supporting body, wavelength conversion apparatus, and method for manufacturing optical element supporting body - Google Patents

Abstract

This optical element supporting body is provided with: an optical element having two parallel surfaces; a holder that is provided with a pair of holding sections; a molten metal sheet, which is provided between at least one surface of the two parallel surfaces of the optical element, and the holding section of the holder; and a pressing member, which applies pressure to the holder in the direction of sandwiching the optical element and the metal sheet. This wavelength conversion apparatus is characterized in: being provided with the optical element supporting body, a wavelength conversion crystal that converts a wavelength of laser light, and a housing, which has the optical element supporting body and the wavelength conversion crystal disposed therein, and which has the inside thereof in an airtight state; converting the wavelength of the laser light by means of the wavelength conversion crystal; and separating, by means of the optical element, a part of laser output light from laser output light outputted from the wavelength conversion crystal.

Description

Optical element support, wavelength conversion device, and method of manufacturing optical element support

The present invention relates to an optical element support, a wavelength conversion device, and a method for manufacturing an optical element support.

A conventional wavelength conversion device converts the wavelength of laser light using a wavelength conversion crystal and separates the wavelength of the laser light after wavelength conversion, thereby extracting only the target wavelength. In the laser light output from the wavelength conversion crystal, the target short wavelength laser light after the conversion and the laser light of the wavelength before the conversion are propagated on substantially the same optical axis. In order to perform spectroscopy when the beam diameter is not large enough, the dichroic mirror with a coating (a coating that selects reflection or antireflection depending on the wavelength) emits too much laser light and the coating deteriorates. Therefore, a sufficient life as a laser device cannot be obtained. Thus, by using a Perran blocker prism that enters and exits at a Brewster angle, it becomes possible to separate wavelengths with an optical element without a coating. As means for fixing an optical element such as a prism, there is means for pressing and fixing two parallel surfaces with a fastener or the like (see, for example, Patent Document 1).

US Patent 5,694,257 (3rd page, Fig. 2)

In the conventional wavelength conversion device, an optical element such as a prism is pressed and fixed with a fastener or the like. Therefore, the prism is displaced when an external force exceeding the frictional force of the surface pressed by transportation or the like is applied. There was a problem.

In the optical element support according to the present invention, the molten metal sheet is interposed between at least one of the two parallel surfaces of the optical element and the holding portion of the holder, and the pressing member is the optical element and the metal sheet. The pressure is applied to the holder in the direction of sandwiching.

In this invention, since the optical element and the holder are fixed with a metal sheet, the optical element is not displaced even when an external force of transportation is applied, and a wavelength conversion device that does not require optical path adjustment after manufacturing is provided. realizable.

It is a figure which shows the wavelength converter in Embodiment 1 of this invention. It is a side view which fixed the prism in the optical element support body in Embodiment 1 of this invention.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a wavelength converter according to Embodiment 1 for carrying out the present invention. The wavelength conversion device 1 includes a second harmonic generation (SHG) crystal 4, a third harmonic generation (THG) crystal 5, and an antireflection coating, which will be described later, in the housing 2. The optical element support body 8 comprised from the prism 9 which is a non-optical element, the holder which supports this prism 9, etc., and the damper 6 are provided. Furthermore, the inside of the housing 2 is filled with clean air, oxygen gas, or inert gas, and is kept airtight. The configuration of the optical element support 8 will be described later. The wavelength converter 1 receives a fundamental laser beam L0 having a frequency ω from a laser oscillator (not shown) and outputs a third harmonic laser beam L2.

Next, the operation of the wavelength conversion device 1 will be described. The fundamental laser beam L0 having the frequency ω passes through the incident window 3 and enters the SHG crystal 4 when entering the wavelength conversion device 1. The SHG crystal 4 transmits part of the incident fundamental wave laser light L0 and converts the remaining part of the wavelength into the second harmonic laser light L1 that is the second harmonic of the double frequency. Accordingly, the first mixed laser beam M1 output from the SHG crystal 4 includes the fundamental laser beam L0 and the second harmonic laser beam L1. Next, the first mixed laser beam M 1 is incident on the THG crystal 5. The THG crystal 5 transmits part of the incident first mixed laser light M1, and the remaining part of the fundamental laser light L0 and the second harmonic laser light L1 is three times the fundamental laser light. Wavelength-converted to a third harmonic laser beam L2, which is the third harmonic of the frequency of, and output. The output second mixed laser beam M2 includes a fundamental laser beam L0, a second harmonic laser beam L1, and a third harmonic laser beam L2.

The laser beam M2 enters the prism 9, and is split into the fundamental laser beam L0, the second harmonic laser beam L1, and the third harmonic laser beam L2. The fundamental laser beam L0 and the second harmonic laser beam L1 are absorbed by the damper 6 and converted into thermal energy. Only the third harmonic laser beam L2 passes through the emission window 7 from the prism 9 and is output from the wavelength converter 1.

Next, the configuration of the optical element support 8 will be described. FIG. 2 is a side view showing fixing of the prism 9 in the optical element support 8. Here, the metal holder 11 is two flat plates each having four screw holes (not shown), and the two flat plates are a pair of pressing portions that press the prism 9. The prism 9 is an optical element having two parallel surfaces that do not contribute to spectroscopy. One of the two parallel surfaces of the prism 9 is in contact with one flat surface of the two flat plates of the metal holder 11. The remaining one of the two parallel surfaces of the prism 9 overlaps the remaining one flat surface of the two flat plates of the metal holder 11 with the indium sheet 10 interposed therebetween. In other words, the metal holder 11 supports the prism 9 with the indium sheet 10 sandwiched between one of two parallel surfaces of the prism 9. The metal sheet is melted to fix the flat plate of the metal holder 11 and the prism 9. In addition to the prism 9, the metal holder 11, and the indium sheet 10, the optical element support 8 includes a screw 12 that is a pressing member and a spring 13 that is also a pressing member. The screw 12 passes through a spring 13 through the shaft and is inserted into a screw hole of one metal holder 11. The screw 12 is inserted into a screw hole of another metal holder 11 with the prism 9 and the indium sheet 10 interposed therebetween, and the spring 13 is loaded. It is screwed to take. The prism 9 and the indium sheet 10 are pressed so as not to be displaced from the metal holder 11 by the load of the spring 13. In the present embodiment, the pressing portion of the metal holder 11 in contact with the indium sheet 10 is a flat plate, but it may not be flat and may have a surface with unevenness that is equal to or less than the thickness of the indium sheet. In this case, since the friction between the indium sheet 10 and the metal holder 11 becomes larger than the flat surface, the prism 9 can be fixed to the metal holder 11 more stably.

In the above description, the indium sheet 10 is disposed on only one of the two parallel surfaces of the prism 9, but may be disposed on both surfaces. However, if the indium sheet 10 is disposed on only one of the two parallel surfaces, the number of parts, the number of manufacturing steps, or the cost can be reduced.

Next, a method for creating a wavelength conversion device will be described.
(1) First, all components used in the wavelength conversion device 1 are cleaned, and components other than the optical elements (prism, SHG crystal 4, THG crystal 5) are assembled in the housing 2.
(2) The case 2 assembled inside (1) is put in a thermostat, and the inside of the case 2 is evacuated from a valve (not shown in FIG. 1) attached to the case 2 and vacuum-baked. Open after baking. (Thus, the outgas from each component can be discharged once in advance. The optical element is excluded here because it may be contaminated by the outgas.)
(3) Next, outside the housing 2, the prism 9 and the indium sheet 10 are screwed with the fixing screws 12, so that they are mounted on the metal holder 11 and the optical element support 8 is assembled. (State of FIG. 2)
(4) The optical element support 8 assembled in (3) is heated in the assembled state. This heating melts indium, and the prism 9 is fixed to the metal holder. At this time, since the screw 12 passes the spring 13 through the shaft, the optical element and the metal holder are kept pressed by the load of the spring 13 even when the indium sheet 10 is melted and thinned.
(5) The optical element support 8 heated in (4) is fixed to the casing 2 baked in (2) with a screw.
(6) The optical path is adjusted with the cover of the housing 2 open. (Adjusting the angle of the wavelength conversion crystal and other lenses)
(7) Close the lid of the housing 2 and perform vacuum baking again.
(8) Finally, clean gas such as argon is put into the housing 2 to seal the housing 2.

Hereinafter, characteristics of various components, optical elements such as the wavelength conversion crystals 4 and 5 and the prism 9, and a metal sheet will be described. If the difference in thermal expansion coefficient between the prism 9 and the metal holder 11 is large, a stress is generated when the prism 9 is cooled after being heated in the above (4). For example, by setting the prism 9 to synthetic quartz (0.55 × 10 −6 / K) and the metal holder 11 to super invar (0.6 × 10 −6 / K), the coefficient of thermal expansion can be made close. it can.

In addition, when the wavelength conversion crystals 4 and 5 are deliquescent crystals, water remaining on the components in the casing is evaporated, so that the baking temperature in the above steps (2) and (7) ensures water. A temperature higher than the temperature at which it can be evaporated (100 ° C. under normal atmospheric pressure) is essential. For this reason, each component, the optical element, and the metal sheet need to have a heat resistant temperature and a melting point higher than 100 ° C., and further need not be deformed under vacuum. As described above, the metal sheet needs to have a melting point higher than 100 ° C. However, in mass production, it must be melted at a temperature that is easy to heat ((4)). It is desirable that there is. (In this embodiment, indium is used and melting point is 156 ° C.)

It should be noted that all components, optical elements, and metal sheets used in the wavelength converter need to be made of a material that does not generate outgas with respect to ultraviolet light. For example, in the present embodiment, the housing 2 and the holder 11 are made of metal, the clothing of the wiring is PTFE, and the metal sheet is indium. Indium is a pure metal, and the generation of outgas is equivalent to that of other metal parts during the heating of (4). As long as the above characteristics are satisfied, each component, optical element, and metal sheet are not limited to the examples given here. In this embodiment, the optical element supported by the metal holder 11 in the optical element support 8 is the prism 9, but may be used to support other optical elements such as a wavelength conversion element.

By melting the metal sheet and fixing the optical element to the metal holder in this manner, the optical element is not displaced when an external force exceeding the frictional force of the surface pressed by transportation or the like is applied. In particular, even when the supporting optical element has a shape having only two parallel surfaces such as the prism 9, it can be fixed only from one direction of the two parallel surfaces. Also, by fixing the optical element to the metal holder with a molten metal sheet, the pressure for pressing the optical element against the holder 11 can be reduced, so that stress is applied to the optical element as in the case of screwing and distortion occurs. In addition, the mode of the transmitted laser beam is not distorted. Further, as in the case where the optical element is fixed with an adhesive, the optical element can be reliably fixed without generating outgas. In other words, the optical element does not shift, the optical path of the laser beam does not shift, the optical element is not stressed, the laser beam mode is not distorted, and no outgas is generated, thereby preventing damage to the optical element and extending the life of the optical element be able to.

Further, in the present embodiment, a case has been described in which two wavelength conversion elements 4 and 5 are arranged to generate and output a third harmonic wave. However, one or more wavelength conversion elements are arranged and an N harmonic wave is emitted. (N is an integer of 2 or more) may be generated. In this case, the incident / exiting of the prism is a Brewster angle with respect to the N-th harmonic, and the prism is made of a material having a low N-wave absorption factor.

8 Optical element support
9 Prism
10 Indium sheet
11 Metal holder

Claims (6)

An optical element having two parallel surfaces;
A holder having a pair of pressing portions;
At least one of the two parallel surfaces of the optical element, and a molten metal sheet interposed between the holder pressing portions,
An optical element support including a pressing member that applies pressure to the holder in a direction between which the optical element and the metal sheet are sandwiched. The optical element support according to claim 1, wherein the optical element is a part having no reflection prevention or reflection coating. 3. The optical device according to claim 1, wherein the metal sheet has a melting point higher than that of water, and is a substance that does not emit outgas and does not deform under vacuum and in a temperature environment equal to or lower than the melting point. Element support. The optical element support according to claim 3, wherein the metal sheet is made of indium. The optical element support according to any one of claims 1 to 4, wherein the optical element is a prism;
A wavelength conversion crystal that converts the wavelength of the laser light;
A housing in which the optical element support and the wavelength conversion crystal are arranged inside, and the inside is in an airtight state;
The wavelength conversion device, wherein the wavelength conversion crystal converts the wavelength of the laser light, and the optical element separates a part of the laser output light from the laser output light output from the wavelength conversion crystal. Assembling so as to sandwich the optical element and the metal sheet with a holder through a metal sheet on at least one of two parallel surfaces of the optical element;
The manufacturing method of the optical element support body including the process which heats the said assembled optical element, the said metal sheet, and the said holder above the melting | fusing point of the said metal sheet, and fixes the said optical element to the said holder.

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