JP2018173523A - Wavelength conversion element and laser irradiation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To significantly improve the conversion efficiency of laser light while suppressing the number of bonded crystal plates in a wavelength conversion element using quartz. A wavelength conversion element 10-1 has pseudo-phase matching formed by bonding a plurality of crystal plates 11 with a metal diffusion layer 12. The wavelength conversion element 10-1 has a first prism 13 that repeatedly reflects the laser beam between the first main surface and the second main surface while transferring the laser light along the first direction, and a first prism 13. The laser beam, which is arranged at both ends in one direction and reaches the end in the first direction, is directed along the second direction, which is a direction orthogonal to the first direction in the first main surface and the second main surface. It is provided with a second prism 14 for shifting and folding back and reflecting the laser beam so that the traveling direction is opposite to that of the laser beam. The wavelength conversion element 10-1 alternately performs repeated reflection of the laser light by the first prism 13 and folded reflection of the laser light by the second prism 14, and forms a traveling path of the laser light in the three-dimensional space. .. [Selection diagram] Fig. 1

Description

  The present invention relates to a wavelength conversion element that converts the wavelength of incident light into a short wavelength and emits it, and a laser irradiation apparatus using the wavelength conversion element.

  In recent years, laser irradiation apparatuses are frequently used in fields such as manufacturing and medical treatment. In these fields, a laser with a short wavelength is necessary to perform finer processing, and an excimer laser has been put to practical use as a high output in the ultraviolet region. However, an excimer laser, which is a rare gas laser, requires complicated maintenance in terms of stability and safety. In addition, the excimer laser has a problem that the apparatus is large. For this reason, a laser irradiation apparatus which is excellent in stability and safety and can be miniaturized is desired.

  In order to obtain a laser irradiation apparatus that is excellent in stability and safety and can be miniaturized, it is preferable to use a solid laser oscillation element (for example, a YAG laser). However, in a wavelength region of 200 nm or less, the solid laser oscillation element itself is used. not exist. However, if a wavelength conversion element is used, it becomes possible to convert the wavelength of the laser beam (fundamental wave) emitted from the laser oscillation element and obtain a laser beam with a shorter wavelength. In general, there is known a laser irradiation apparatus that transmits a fundamental wave (1064 nm: infrared light) emitted from a YAG laser through a wavelength conversion element, converts the fundamental wave into a second harmonic (532 nm: green light), and outputs the second harmonic wave (532 nm: green light). ing.

A crystal having nonlinear optical characteristics (nonlinear crystal) is used for a wavelength conversion element used for converting the wavelength of laser light, and LT (LiTaO ₃ ), LN (LiNbO ₃ ) are generally used as nonlinear crystal materials. , LBO (LiB ₃ O ₅ ), KTP (KTiOPO ₄ ), CLBO (CsLiB ₆ O ₁₀ ) and the like.

However, wavelength conversion elements using these nonlinear crystal materials have the following problems.
-LT has a large amount of absorption during laser transmission with respect to a laser having a wavelength of 260 nm or less, and is severely damaged when irradiated with a laser.
-LN and LBO are severely damaged when irradiated with a laser, and are difficult to convert to a wavelength of 300 nm or less.
-KTP is difficult to convert to a wavelength of 300 nm or less.
-CLBO and LBO have deliquescent properties, so it is necessary to take measures against humidity.
Many other nonlinear crystal materials have problems such as weakness to damage to the laser, deliquescent properties, and limited wavelength range for conversion (a narrow wavelength transmission range).

On the other hand, Patent Documents 1 and 2 disclose wavelength conversion elements using quartz as a nonlinear crystal material. Compared to the wavelength conversion element described above,
・ High laser resistance (hard to damage),
・ There is no deliquescence,
-Wide transmission range of short wavelength,
・ High heat durability
・ Inexpensive, maintenance-free, easy to downsize,
Has many merits.

JP 2008-233143 A JP 2008-268245 A

  Quartz as a nonlinear crystal material has many merits described above, but also has a demerit that conversion efficiency is low (for example, conversion efficiency is about 1/100 compared with LT).

  Here, in order to produce a wavelength conversion element using quartz, quasi-phase matching formed with a domain-inverted structure is formed. Specifically, as shown in FIG. 12, the wavelength conversion element 100 has a structure in which a plurality of crystal plates (x plates) 110 are stacked (bonded) so that the polarization of crystals is periodically inverted. It is possible. When the wavelength conversion element 100 is irradiated with the fundamental wave L1 from the laser light source (laser oscillation element) 200, the second harmonic (wavelength is ½ of the fundamental wave) L2 is obtained in the transmitted light. The polarization inversion period Λ in the wavelength conversion element 100 is set according to the wavelength of the fundamental wave L1.

  In wavelength conversion elements using quasi-phase matching by quartz plates, the number of quartz plates stacked (number of bonded substrates) is increased, and the number of quartz plates through which laser light is transmitted increases, so that the conversion efficiency as a wavelength conversion device Can be increased. However, a wavelength conversion element using quartz requires a number of layers on the order of several thousand to obtain a practical conversion efficiency. Thus, in the configuration in which the number of bonded quartz plates is simply increased, there is a problem that the wavelength conversion element is enlarged.

  In Patent Document 2, a reflection film is provided on one main surface of a laminate of quartz plates, a transmission / reflection film (dichroic mirror) is provided on the other main surface, and laser light incident on the laminate is reflected as a reflection film. A configuration in which reflection (multiple reflection) is repeatedly performed between the transmission / reflection films is disclosed. With such a multiple reflection structure, the conversion efficiency can be improved while suppressing the number of crystal plates stacked in the stacked body.

  However, in the configuration of Patent Document 2, laser light is reflected along one direction (reflection direction) in the main surface of the crystal plate. For this reason, the main surface of the quartz plate used for the wavelength conversion element increases in size only in the reflection direction.

  In addition, the wavelength conversion element using quartz is produced by bonding together a quartz plate obtained by cutting a quartz wafer into a predetermined size, and the principal surface size of the quartz plate is naturally the size of the original quartz wafer. Limited by size. For this reason, it is difficult to significantly increase the number of repetitions of reflection along one direction (reflection direction) of the quartz plate, and improvement in conversion efficiency is also limited by the size of the quartz wafer.

  The present invention has been made in view of the above problems, and an object of the present invention is to greatly improve the conversion efficiency of laser light while suppressing the number of bonded quartz plates in a wavelength conversion element using crystal. .

  In order to solve the above-described problems, the present invention provides a wavelength conversion element having a quasi-phase matching in which a domain-inverted structure is formed by a crystal having nonlinear optical characteristics. The quartz crystal plate is bonded, and the laser beam is reflected while being shifted along the first direction in the first main surface and the second main surface of the wavelength conversion element, and the first First reflection means for repeatedly reflecting laser light between the main surface and the second main surface, and disposed at both ends in the first direction of the wavelength conversion element, reaching the end in the first direction And a second reflecting means for causing the laser beam to move while being reflected along a second direction which is a direction perpendicular to the first direction in the first main surface and the second main surface. Repetitively reflecting laser light by the first reflecting means; By causing the serial and reflection of the laser light by the second reflection means alternately, and characterized in that it is formed a traveling path of the laser beam in three-dimensional space.

  According to the above configuration, when laser light is incident on the wavelength conversion element, the laser light is repeatedly reflected by the first reflecting means and travels in the wavelength conversion element along the first direction. And the laser beam which reached | attained the edge part of a 1st direction is reflected so that it may transfer along a 2nd direction by a 2nd reflection means. By repeating the reflection, the traveling path of the laser light becomes a three-dimensional path formed in a space of (first direction × second direction × element thickness direction).

  Since the quartz plate used for the wavelength conversion element is manufactured with a plane size that is determined to some extent, the configuration in which reflection is repeatedly performed using only a two-dimensional path also increases the number of reflections of laser light (that is, increases in conversion efficiency). There is a limit. On the other hand, the number of reflections of laser light can be dramatically increased by using a repetitive reflection structure using a three-dimensional path, and the conversion efficiency of laser light can be greatly improved.

  Further, in the wavelength conversion element, the first reflecting means is a plurality of first prisms arranged on a laser beam incident surface side and an emission surface side, respectively, and the plurality of first prisms have a predetermined incident angle. The laser light is repeatedly reflected between the first principal surface side prism and the second principal surface side prism of the wavelength conversion element, and the wavelength An optical path of laser light traveling from the first main surface side to the second main surface side in the conversion element, and an optical path of laser light traveling from the second main surface side to the first main surface side. The laser beam can be reflected so as to be parallel, and the second reflecting means is a plurality of second prisms respectively disposed on the incident surface side and the emission surface side of the laser light, The plurality of second prisms from the first direction A laser beam that travels from the first main surface side to the second main surface side in the wavelength conversion element, and the first main surface side from the second main surface side. The laser beam is reflected so that the optical path of the laser beam traveling to is parallel and can be shifted while being reflected along the second direction that is orthogonal to the first direction. Can do.

  According to the above configuration, by using the prism as the first reflecting means, it is possible to make the outgoing laser beam and the returning laser beam parallel to each other, and while suppressing an increase in the area of the wavelength conversion element, the reflection is performed. It is possible to increase the number of repetitions of (to improve the conversion efficiency of laser light).

  Further, in the wavelength conversion element, when the laser beams are incident on the plurality of first prisms at an incident angle that is a Brewster angle with respect to the incident surface from a predetermined position on the incident surface of the wavelength converting element, The plurality of quartz plates are configured such that the laser light can be repeatedly reflected between the first principal surface side prism and the second principal surface side prism of the wavelength conversion element. Is attached so that the approximate straight line with respect to the center of gravity of all the quartz plates to be bonded is parallel to the optical path of the refracted light when the laser light is incident on the light incident surface of the wavelength conversion element at the Brewster angle. It can be set as the structure united.

  According to the above configuration, by repeatedly reflecting the laser beam incident at the Brewster angle, the number of repetitions of the reflection is increased while suppressing an increase in the area of the wavelength conversion element (the conversion efficiency of the laser beam is increased). Improvement). By matching the incident angle with the Brewster angle, reflection of the laser beam can be suppressed, and a decrease in conversion efficiency can also be suppressed. Further, even when the number of quartz plates to be bonded increases and the thickness of the wavelength conversion element increases, the laser light can be transmitted from the incident surface of the wavelength conversion element without increasing the area of each quartz plate more than necessary. It can be transmitted to the exit surface.

  In the wavelength conversion element, the plurality of first prisms may receive the laser beam when a laser beam is incident from a predetermined position on the incident surface of the wavelength conversion element at an incident angle perpendicular to the incident surface. The light can be repeatedly reflected between the prism on the first main surface side and the prism on the second main surface side of the wavelength conversion element.

  According to the above configuration, the number of repetitions of reflection is increased while the increase in the area of the wavelength conversion element is suppressed by repeatedly reflecting the vertically incident laser beam (improving the laser beam conversion efficiency). ) Is possible.

  Further, the wavelength conversion element has a package for sandwiching and fixing the plurality of bonded crystal plates and the first prism and the second prism from both sides, and the first prism and the second prism. The prism may be positioned with respect to the quartz plate by the package.

  According to the above configuration, the prism can be positioned without being fixed (adhered) to the crystal plate by fixing the prism with the package. Therefore, when the prism design can be changed or the prism can be downsized, the prism can be easily replaced.

  In the wavelength conversion element, the first reflecting means is formed on the first main surface side of the laser light in the wavelength conversion element, and includes a reference laser light having a predetermined wavelength, and a first laser light of the reference laser light. A reflection film that reflects both of the converted laser light that is a second harmonic and a second main surface side of the laser light in the wavelength conversion element, reflects the reference laser light, and transmits the converted laser light The second reflecting means may be a prism.

  According to the above configuration, the reflecting film and the reflecting / transmitting film used for the first reflecting means can be easily formed, and particularly high-precision alignment with the laser is not required. For this reason, the structure of a wavelength conversion element can be simplified and manufacturing cost can also be suppressed.

  Further, the wavelength conversion element has a package for sandwiching and fixing the plurality of bonded crystal plates and the prism from both sides, and the prism is positioned with respect to the crystal plate by the package. Can be configured.

  According to the above configuration, the prism can be positioned without being fixed (adhered) to the crystal plate by fixing the prism with the package. Therefore, when the prism design can be changed or the prism can be downsized, the prism can be easily replaced.

The laser irradiation apparatus of the present invention has a laser light source and a wavelength conversion element, transmits a reference laser beam emitted from the laser light source to the wavelength conversion element, and converts the converted laser light by the transmission. The wavelength conversion element is a laser irradiation apparatus that irradiates to the outside,
It is the wavelength conversion element described above.

  In the wavelength conversion element and the laser irradiation apparatus of the present invention, the traveling path of the laser light incident on the wavelength conversion element is formed in a three-dimensional space formed in a space of (first direction × second direction × element thickness direction). By using the path, it is possible to dramatically increase the number of reflections of the laser beam and to greatly improve the conversion efficiency of the laser beam.

It is a top view of the wavelength conversion element which concerns on Embodiment 1, (a) is a figure which shows arrangement | positioning of the reflection means in the 1st main surface of a wavelength conversion element, (b) is the 2nd of a wavelength conversion element. It is a figure which permeate | transmits and shows the arrangement | positioning of the reflection means in a main surface from the 1st main surface side. 2 is a cross-sectional view of the wavelength conversion element of FIG. 1 viewed from the Y2 direction side, where (a) is a cross-sectional view taken along the line AA in FIG. 1, (b) is a cross-sectional view taken along the line BB in FIG. It is CC sectional drawing of. 2 is a cross-sectional view of the wavelength conversion element of FIG. 1 as viewed from the X2 direction side, where (a) is a DD cross-sectional view of FIG. 1 and (b) is a EE cross-sectional view of FIG. It is a top view which shows an example of the arrangement pattern of the metal diffusion layer in the wavelength conversion element shown in FIG. It is a top view of the wavelength conversion element which concerns on Embodiment 2, (a) is a figure which shows arrangement | positioning of the reflection means in the 1st main surface of a wavelength conversion element, (b) is the 2nd of a wavelength conversion element. It is a figure which permeate | transmits and shows the arrangement | positioning of the reflection means in a main surface from the 1st main surface side. 6 is a cross-sectional view of the wavelength conversion element of FIG. 5 as viewed from the Y2 direction side, where (a) is a cross-sectional view taken along line AA in FIG. 5, (b) is a cross-sectional view taken along line BB in FIG. It is CC sectional drawing of. It is a top view of the wavelength conversion element which concerns on Embodiment 3, (a) is a figure which shows arrangement | positioning of the reflection means in the 1st main surface of a wavelength conversion element, (b) is the 2nd of a wavelength conversion element. It is a figure which permeate | transmits and shows the arrangement | positioning of the reflection means in a main surface from the 1st main surface side. 6 is a cross-sectional view of the wavelength conversion element of FIG. 5 as viewed from the Y2 direction side, where (a) is a cross-sectional view taken along line AA in FIG. 5, (b) is a cross-sectional view taken along line BB in FIG. It is CC sectional drawing of. 6 is a cross-sectional view illustrating a schematic configuration of a wavelength conversion element according to Embodiment 4. FIG. It is a figure which shows schematic structure of the laser irradiation apparatus using the wavelength conversion element of FIG. It is a figure which shows schematic structure of the laser irradiation apparatus using the wavelength conversion element of FIG. It is a figure which shows the basic composition of the wavelength conversion element using quartz as a nonlinear crystal.

[Embodiment 1]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a plan view of the wavelength conversion element 10-1 according to the first embodiment, and FIG. 1A is a diagram illustrating the arrangement of reflecting means on the first main surface of the wavelength conversion element 10-1. (B) is a figure which permeate | transmits and shows arrangement | positioning of the reflection means in the 2nd main surface of the wavelength conversion element 10-1 from the 1st main surface side. 2 is a cross-sectional view of the wavelength conversion element 10-1 of FIG. 1 as viewed from the Y2 direction side, where (a) is a cross-sectional view taken along line AA in FIG. 1, and (b) is a cross-sectional view taken along line BB in FIG. (C) is CC sectional drawing of FIG. 3 is a cross-sectional view of the wavelength conversion element 10-1 of FIG. 1 as viewed from the X2 direction side, where (a) is a cross-sectional view taken along the line DD in FIG. 1, and (b) is a cross-sectional view taken along the line EE of FIG. It is. In the description here, the X direction (X1 and X2 directions) and the Y direction (Y1 and Y2 directions) are two directions orthogonal to each other within the main surface of the wavelength conversion element 10-1.

  As shown in FIG. 1, the wavelength conversion element 10-1 has a structure in which a plurality of crystal plates 11 are bonded together with a metal diffusion layer 12. That is, the quartz plate 11 is bonded by diffusion bonding. Further, in the wavelength conversion element 10-1, the crystal plate 11 is bonded so as to form a pseudo phase matching as shown in FIG. 2 and 3 are drawn with the number of the quartz plates 11 greatly reduced for simplification of the drawings, but in actuality, the quartz plates 11 are bonded to each other with several hundreds. A specific bonding structure of the crystal plate 11 by the metal diffusion layer 12 will be described later.

  The wavelength conversion element 10-1 has a multiple reflection structure. Therefore, both the first main surface (upper surface in FIGS. 2 and 3) and the second main surface (lower surface in FIGS. 2 and 3) A plurality of first prisms 13 serving as one reflecting means and a plurality of second prisms 14 serving as second reflecting means are arranged. In the present embodiment, quartz glass or the like can be used as the material of the prisms (first and second prisms 13 and 14), and the size in the width direction of the prism is preferably 1 mm or more. Moreover, the size of the main surface of the wavelength conversion element 10-1 is, for example, 25 mm × 30 mm.

  The plurality of first prisms 13 have the same shape and the same size, and are arranged in the same direction and the same pitch in the region near the center of both main surfaces. Specifically, each first prism 13 is a triangular prism whose cross section perpendicular to the Y direction is a right-angled isosceles triangle, and its longitudinal direction is the Y direction.

  As shown in FIG. 2, each first prism 13 is arranged such that one side surface 13 a of the three side surfaces of the triangular prism is in contact with the surface of the uppermost and lowermost quartz plates 11. The angle formed by the remaining two side surfaces 13b and 13c is set to 90 °. Further, in each of the first main surface and the second main surface, when the arrangement pitch of the first prisms 13 is P1, the first prism 13 disposed on the first main surface and the second main surface The first prisms 13 arranged at a distance of P1 / 2 in the arrangement direction (X direction) are arranged.

  The plurality of second prisms 14 have the same shape and the same size, and are arranged at the same direction and the same pitch on both main surfaces. Specifically, each second prism 14 is a triangular prism having a cross section perpendicular to the X direction that is a right-angled isosceles triangle. The second prism 14 is arranged only in the end region on the X1 direction side of the arrangement region of the first prism 13 on the first main surface, and in the arrangement region of the first prism 13 on the second main surface. They are arranged only in the end region on the X2 direction side.

  As shown in FIG. 3, each of the second prisms 14 is arranged such that one side surface 14 a of the three side surfaces of the triangular prism is in contact with the surface of the uppermost and lowermost quartz plates 11. The angle formed by the remaining two side surfaces 14b and 14c is set to 90 °. Further, in each of the first main surface and the second main surface, when the arrangement pitch of the second prisms 14 is P2, the second prism 14 arranged on the first main surface and the second main surface The second prism 14 arranged at the position is shifted by P2 / 2 in the arrangement direction (Y direction). The length in the longitudinal direction (Y direction) of the first prism 13 is longer than the length in the arrangement direction (Y direction) of the arrangement region of the second prism 14.

  The first prism 13 and the second prism 14 can be fixed to a predetermined position with respect to the crystal plate 11 by, for example, adhesion using an adhesive.

  In the wavelength conversion element 10-1, laser light (fundamental wave L1: FIG. 2) from a predetermined incident position on the first main surface at a predetermined incident angle (0 ° in the example of FIGS. 1 to 3, ie, vertical incident). When (a) and FIG. 3 (a)) are incident, it is designed to obtain a desired wavelength conversion effect. Specifically, on the first main surface, the intersection of the AA cross section and the DD cross section shown in FIG. 1 is the incident position of the fundamental wave L1. Note that the first prism 13 and the second prism 14 are not provided at this incident position. Instead, an antireflection film 15 is preferably provided at this incident position. Although not shown, it is preferable that an antireflection film is provided in the laser light transmission region even between the quartz plates 11 to be bonded.

  The laser beam perpendicularly incident on the wavelength conversion element 10-1 from the incident position is transmitted through the second main surface of the wavelength conversion element 10-1, and is first disposed on the second main surface side first. 1 (the first prism 13 at the right end in FIGS. 1B and 2A). The laser light that has entered the first prism 13 is reflected back by the two side surfaces 13b and 13c, and is again vertically incident on the wavelength conversion element 10-1 from the second main surface. At this time, the incident angle of the laser beam with respect to the side surfaces 13 b and 13 c is 45 °, and the laser beam is totally reflected by the first prism 13. Before and after the reflection by the first prism 13, the optical path of the laser light (hereinafter referred to as the forward laser beam) traveling from the first main surface side to the second main surface side and the first main surface side from the first main surface side The optical path of laser light (hereinafter referred to as “return laser light”) traveling toward the main surface is parallel. The laser beam reflected and reflected by the first prism 13 disposed on the second principal surface side is transmitted through the first principal surface of the wavelength conversion element 10-1 and is disposed on the first principal surface side. It enters one of the prisms 13 and is similarly reflected back.

  The laser beam reflected back by the first prism 13 is shifted in optical path by P1 / 2 along the arrangement direction (X direction) of the first prism 13 every time it is turned back. Therefore, as shown in FIG. 2A, the laser light incident on the wavelength conversion element 10-1 is disposed on the first prism 13 disposed on the first principal surface side and on the second principal surface side. The light travels in the X2 direction while repeating reflection with the first prism 13. In FIG. 2, the optical path of laser light traveling in the element is indicated by a broken line arrow.

  The laser beam shown in FIG. 2A (the laser beam traveling in the AA cross section in FIG. 1) is the last first prism 13 on the X2 direction side (FIGS. 1A and 2A). One of the second prisms 14 (see FIG. 3) disposed on the second principal surface side after passing through the second principal surface of the wavelength conversion element 10-1 after being reflected by the leftmost first prism 13 in FIG. It enters the second prism 14) at the lower end in 1 (b) and at the right end in FIG. 3 (b).

  The laser light incident on the second prism 14 is reflected back by the two side surfaces 14b and 14c, and is again vertically incident on the wavelength conversion element 10-1 from the second main surface (see FIG. 3B). At this time, the incident angle of the laser beam with respect to the side surfaces 14 b and 14 c is 45 °, and the laser beam is totally reflected by the second prism 14. Also, before and after the reflection by the second prism 14, the optical path of the laser light (outward laser light) traveling from the first main surface side to the second main surface side and the first main surface from the second main surface side The optical path of the laser beam (outward laser beam) traveling to the side becomes parallel. The laser light reflected back by the second prism 14 is deviated in the P2 / 2 optical path along the arrangement direction (Y direction) of the second prism 14 due to the return.

  Since the P2 / 2 optical path of the laser beam shown in FIG. 2A is shifted due to reflection by the second prism 14, this time, the laser beam shown in FIG. 2B (within the BB cross section in FIG. 1). The laser beam travels through the device as a laser beam. That is, the light travels in the X1 direction while repeating reflection between the first prism 13 arranged on the first main surface side and the first prism 13 arranged on the second main surface side again. When the laser light traveling in the X1 direction reaches the end on the X1 direction side, it is reflected again by the second prism 14 disposed on the first main surface side (see FIG. 3A).

  The laser light incident on the wavelength conversion element 10-1 travels in the element while being repeatedly reflected by the first prism 13 and the second prism 14, and finally has a wavelength as shown in FIG. The light is emitted out of the second main surface of the conversion element 10-1. The emitted laser light includes the second harmonic L2 obtained by converting the wavelength of the fundamental wave L1 and the fundamental wave L1 that remains without being converted to the end. However, the transmission / reflection plate (for example, a dichroic mirror) The second harmonic L2 can be separated from the fundamental wave L1 by use, and only the second harmonic L2 can be used as a wavelength converted wave.

  In the example of FIGS. 1 to 3, the first prism 13 that finally reflects and reflects the laser light is provided on the first main surface side, and the emitted laser light is the second main light of the wavelength conversion element 10-1. It is emitted from the surface. However, the present invention is not limited to this, and the first prism 13 that reflects and reflects the laser light last is provided on the second main surface side, and the emitted laser light is emitted from the first main surface. It may be a configuration. In this case, the second prism 14 provided on the X2 direction side is provided not on the second main surface side but on the first main surface side.

  As described above, the wavelength conversion element 10-1 that performs the multiple reflection structure using the first prism 13 and the second prism 14 can transmit the laser light to each crystal plate 11 a plurality of times. The conversion efficiency of the wavelength conversion element can be increased while suppressing the number of 11 layers.

  When laser light is incident on the wavelength conversion element 10-1, the laser light is repeatedly reflected by the first prism 13 and travels in the element along the X direction (first direction). Then, the laser beam that has reached the end in the X direction is reflected along the opposite direction in the X direction while being shifted along the Y direction (second direction) by the second prism 14. By repeating the reflection, the traveling path of the laser beam becomes a three-dimensional path formed in a space of (X direction × Y direction × element thickness direction).

  Since the crystal plate 11 used for the wavelength conversion element 10-1 is manufactured with a plane size determined to some extent (for example, 25 mm × 30 mm), the number of times of reflection of the laser light is increased in a configuration in which reflection is repeatedly performed using only a two-dimensional path. (In other words, there is a limit to the increase in conversion efficiency). On the other hand, the number of reflections of laser light can be dramatically increased by using a repetitive reflection structure using a three-dimensional path, and the conversion efficiency of laser light can be greatly improved.

  Further, in the wavelength conversion element 10-1, the first prism 13 and the second prism 14 are used as the laser beam reflecting means, so that the laser beam traveling from the first main surface to the second main surface (outbound laser beam). Then, the reflection can be performed so that the laser beam (return laser beam) traveling from the second main surface to the first main surface is parallel. Thereby, even if the number of bonded crystal plates 11 is increased, the number of reflections does not decrease, and a larger number of repeated reflections can be performed within a smaller area, while suppressing an increase in the area of the wavelength conversion element, It is possible to increase the number of repetitions of reflection (improve laser beam conversion efficiency).

  The wavelength conversion element 10-1 has a larger effective area than a wavelength conversion element that does not use a multiple reflection structure, in order to secure a transmission region for laser light that travels in the element while being multiple reflected. Is required. In other words, it is necessary to use the crystal plate 11 formed in a large area in order to increase the number of repetitions of reflection.

  Quartz is relatively easy to make in a large area compared to other nonlinear crystals (LT, LN, etc.) used in conventional wavelength conversion elements. When quartz is used for the nonlinear crystal, it is easy to create a wavelength conversion element 10-1 using a multiple reflection structure, which can be said to be an advantage of using quartz for the wavelength conversion element.

  Next, a specific bonding structure of the crystal plate 11 by the metal diffusion layer 12 will be described with reference to FIG. FIG. 4 shows an example of an arrangement pattern of the metal diffusion layers 12 in the wavelength conversion element 10-1. However, in the wavelength conversion element 10-1, the bonding of the crystal plate 11 by the metal diffusion layer 12 is not an essential configuration, and the crystal plates 11 may be directly bonded to each other.

  As shown in FIG. 4, the metal diffusion layer 12 is not formed over the entire main surface (bonding surface) of the crystal plate 11 but is formed in a part of the region. That is, a region (opening region) where the metal diffusion layer 12 does not exist is provided on the main surface of the quartz plate 11. The metal diffusion layer 12 is preferably formed mainly on the outer peripheral portion of the main surface of the crystal plate 11, and most of the inner region of the crystal plate 11 is an open region where the metal diffusion layer 12 does not exist.

  In a wavelength conversion element using a crystal plate, when the crystal plate is bonded to the entire main surface of the crystal plate using an adhesive layer or a metal diffusion layer, the laser beam that passes through the wavelength conversion element is not limited to the crystal plate. It is also necessary to pass through the adhesive layer and the metal diffusion layer. Then, the transmittance of the laser light decreases due to absorption when the laser light passes through the adhesive layer or the metal diffusion layer, reflection at the interface between the adhesive layer or the metal diffusion layer and the crystal plate, or the like. In the method using an adhesive, there are problems that it is difficult to control the gap between the quartz plates, and the transmittance is greatly lowered depending on the wavelength of the laser beam. This decrease in laser light is particularly noticeable when a UV curable adhesive is used.

  On the other hand, in the wavelength conversion element 10-1 according to the first embodiment, the crystal plate 11 is bonded by the metal diffusion layer 12 and the main surface of the crystal plate 11 does not have the metal diffusion layer 12 ( An opening region) is provided. For this reason, in the wavelength conversion element 10-1, by using an opening region where the metal diffusion layer 12 does not exist as a laser transmission region, absorption or reflection by the metal diffusion layer 12 is eliminated, and the wavelength conversion element 10-1 Laser light can be transmitted efficiently.

  The metal diffusion layer 12 is mainly formed on the outer peripheral portion of the main surface of the crystal plate 11, and most of the inner region of the crystal plate 11 is an opening region where the metal diffusion layer 12 does not exist. This makes it easy to use the internal region of the wavelength conversion element 10-1 as a laser transmission region. In addition, the bonding at the outer peripheral portion of the quartz plate 11 has an effect that it is easy to secure the mechanical strength of the wavelength conversion element 10-1.

  In the wavelength conversion element 10-1, the quartz plate 11 is bonded by diffusion bonding using the metal diffusion layer 12, and the following advantages are obtained as compared with the case where bonding is performed using an adhesive. That is, in bonding using an adhesive, even if the adhesive is applied to a partial area of the quartz plate to form an opening area where no adhesive is present, the adhesive is applied to the application area by the pressure during bonding. It expands to the above and it becomes difficult to obtain the opening area as designed. In diffusion bonding, the metal diffusion layer does not expand undesirably, and it is easy to obtain an opening region as designed.

  Diffusion bonding using the metal diffusion layer 12 is performed, for example, in the following steps.

  First, a base film and a bonding film are formed on the bonded surfaces of the two crystal plates 11 to be bonded. The base film is formed by physical vapor deposition of a base metal (Ti, Ni, etc.) on the flat smooth surface (mirror finish) of the crystal plate 11. The bonding film is formed by laminating a metal capable of diffusion bonding such as Au and Pt on the base film by physical vapor deposition.

  Thus, when the two crystal plates 11 on which the base film and the bonding film are formed are overlapped, the bonding films are diffusion-bonded to each other, and the two crystal plates 11 are bonded to each other. In this case, the base film and the bonding film become the metal diffusion layer 12. The thickness of the bonding film is preferably in the range of 40 nm to 1 μm, and more preferably in the range of 40 nm to 500 nm in order to bring the quartz plates 11 into close contact with each other. The thickness of the metal diffusion layer 12 is preferably in the range of 80 nm to 2 μm, and more preferably in the range of 80 nm to 1000 nm. By setting the thickness of the metal diffusion layer 12 to 80 nm or more, even if the crystal plate 11 is warped due to the flexibility of the metal, the warp can be absorbed and the number of stacked layers can be increased. Further, even if there is a foreign matter or the like on the joining surface, it becomes possible to join flexibly. Further, by setting the thickness of the metal diffusion layer 12 to 1000 nm or less, it is possible to reduce the warp of the crystal plate 11 due to the film stress of the metal film, and to increase the number of laminated layers.

  Further, the metal diffusion layer 12 shown in FIG. 4 is not formed so as to surround the entire outer periphery of the crystal plate 11, and a ventilation portion for allowing the internal region (gap space) of the bonded crystal plate 11 to vent to the outside. 12a is provided. This is to provide a structure that does not form a sealed space between the quartz plates 11 by providing the ventilation portion 12a, and to prevent moisture from being enclosed in the sealed space. If there is a sealed space in which moisture is enclosed between the quartz plates 11, there is a risk of condensation depending on the temperature. When this condensation hits the laser beam, undesired refraction occurs, resulting in energy loss in the transmission laser. . In addition, by providing an opening (ventilation portion 12a) on the outer peripheral portion of the bonding surface, it is possible to relieve stress on the bonding surface and prevent deformation of the element when the number of stacked layers is increased. It becomes.

  Further, as a method for preventing condensation in the gap space of the crystal plate 11, there is also a method in which the gap space of the bonded crystal plate 11 is a sealed space filled with an inert gas such as vacuum or nitrogen. In this way, moisture is not sealed in the sealed space, and condensation can be prevented.

[Embodiment 2]
As in the wavelength conversion element 10-1 shown in the first embodiment, in a structure in which a plurality of crystal plates 11 are bonded together by the metal diffusion layer 12 and an opening region where the metal diffusion layer 12 does not exist is provided, this opening region The gap space is formed between the quartz plates 11 to be bonded. If the refractive index of the medium in the gap space (medium in the gap) and the crystal plate 11 are different, reflection occurs at the interface between the medium in the gap and the crystal plate 11, and this reflection may cause energy loss in the transmission laser. There is.

  As an effective means for preventing the reflection, it is conceivable that the incident angle of the laser light incident on the wavelength conversion element (incident angle with respect to the main surface of the quartz plate 11) is the Brewster angle. As described above, by causing the laser beam to be incident on the wavelength conversion element at the Brewster angle, energy loss due to reflection can be significantly suppressed.

  5 and 6 are a plan view and a cross-sectional view of the wavelength conversion element 10-2 corresponding to the case where the incident angle of the laser light is set to the Brewster angle. FIG. 5 is a plan view of the wavelength conversion element 10-2 according to the second embodiment, and FIG. 5A is a diagram illustrating the arrangement of the reflecting means on the first main surface of the wavelength conversion element 10-2. (B) is a figure which permeate | transmits and shows the arrangement | positioning of the reflection means in the 2nd main surface of the wavelength conversion element 10-2 from the 1st main surface side. 6 is a cross-sectional view of the wavelength conversion element 10-2 in FIG. 5 as viewed from the Y2 direction side, where (a) is a cross-sectional view taken along line AA in FIG. 5 and (b) is a cross-sectional view taken along line BB in FIG. (C) is CC sectional drawing of FIG. In the description here, the X direction (X1 and X2 directions) and the Y direction (Y1 and Y2 directions) are two directions orthogonal to each other within the main surface of the wavelength conversion element 10-2.

  The wavelength conversion element 10-2 has a multiple reflection structure. Therefore, both the first main surface (upper surface in FIG. 6) and the second main surface (lower surface in FIG. 6) are provided with the first reflecting means. A plurality of first prisms 16 and a plurality of second prisms 17 as second reflecting means are arranged.

  The plurality of first prisms 16 have the same shape and the same size, and are arranged in the same direction and the same pitch in the region near the center of both main surfaces. Specifically, each first prism 16 is a quadrangular prism having a quadrangular cross section perpendicular to the Y direction, and its longitudinal direction is the Y direction.

  As shown in FIG. 6, each first prism 16 is arranged such that one side surface 16 a of the four side surfaces of the quadrangular prism is in contact with the surface of the uppermost and lowermost quartz plates 11. The angle formed by the two side surfaces 16b and 16c used as the laser light reflecting surface is set to 90 °.

  The plurality of second prisms 17 have the same shape and the same size, and are arranged at the same direction and the same pitch on both main surfaces. The second prism 17 is arranged only in the end region on the X1 direction side of the arrangement region of the first prism 16 on the first main surface, and in the arrangement region of the first prism 16 on the second main surface. They are arranged only in the end region on the X2 direction side.

  As shown in FIG. 6, each second prism 17 is arranged such that one side surface 17 a is in contact with the surface of the uppermost and lowermost quartz plates 11. The angle formed by the two side surfaces 17b and 17c used as the laser light reflecting surface is set to 90 °.

  The first prism 16 and the second prism 17 can be fixed at predetermined positions to the crystal plate 11 by, for example, bonding using an adhesive.

  In the wavelength conversion element 10-2 shown in FIGS. 5 and 6, the laser light (fundamental wave L1) whose incident angle α (see FIG. 6A) is a Brewster angle from a predetermined incident position on the first main surface. It is designed to obtain a desired wavelength conversion effect when it is incident. Specifically, on the first main surface, the incident position of the fundamental wave L1 is provided on the right end side of the AA cross section shown in FIG. Note that the first prism 16 and the second prism 17 are not provided at this incident position. Further, by setting the incident angle α to the Brewster angle, an antireflection film is not required at the incident position, and an antireflection film between the quartz plates 11 is not required.

  The laser light incident on the wavelength conversion element 10-2 at the Brewster angle from the incident position passes through the second main surface of the wavelength conversion element 10-2 and is arranged on the second main surface side. The light enters one of the prisms 16 (the first prism 16 at the right end in FIG. 6). The laser light incident on the first prism 16 is reflected back at the two side surfaces 16b and 16c, and is incident on the wavelength conversion element 10-2 again at the Brewster angle from the second main surface. At this time, the incident angle of the laser beam with respect to the side surfaces 16 b and 16 c is 45 °, and the laser beam is totally reflected by the first prism 16. Further, before and after reflection by the first prism 16, the optical path of the laser light (outward laser light) traveling from the first main surface side to the second main surface side and the first main surface from the second main surface side The optical path of the laser beam (return laser beam) traveling to the side becomes parallel. The laser light reflected and reflected by the first prism 16 disposed on the second principal surface side is transmitted through the first principal surface of the wavelength conversion element 10-2 and is disposed on the first principal surface side. The light enters one of the prisms 16 and is similarly reflected back.

  The laser beam reflected and reflected by the first prism 16 is shifted in optical path by a predetermined pitch along the arrangement direction (X direction) of the first prism 16 every time it is folded. Specifically, when the arrangement pitch of the first prisms 16 on each of the first main surface and the second main surface is P1, the optical path of the laser beam reflected back is shifted by P1 / 2. Therefore, as shown in FIG. 6A, the laser light incident on the wavelength conversion element 10-2 is arranged on the first principal surface side and the second principal surface side arranged on the first principal surface side. The light travels in the X2 direction while repeating reflection with the first prism 16. In FIG. 6, the optical path of laser light traveling in the element is indicated by a broken line arrow.

  The laser light shown in FIG. 6A (laser light traveling in the AA cross section in FIG. 5) is the last first prism 16 on the X2 direction side (FIG. 5A, FIG. 6A). One of the second prisms 17 (see FIG. 3) disposed on the second principal surface side after passing through the second principal surface of the wavelength conversion element 10-2. It enters the second prism 17) at the lower end in 1 (b) and the right end in FIG. 3 (b).

  The laser light incident on the second prism 17 is reflected back at the two side surfaces 17b and 17c, and is incident on the wavelength conversion element 10-2 from the second main surface again at the Brewster angle (see FIG. 6B). ). At this time, the incident angle of the laser beam with respect to the side surfaces 17 b and 17 c is 45 °, and the laser beam is totally reflected by the second prism 17. Further, even before and after reflection by the second prism 17, the optical path of the laser light (outward laser light) traveling from the first main surface side to the second main surface side, and the first main surface from the second main surface side The optical path of the laser beam (outward laser beam) traveling to the side becomes parallel. The laser beam reflected and reflected by the second prism 17 is shifted in optical path by a predetermined pitch along the arrangement direction (Y direction) of the second prism 17 by folding. Specifically, when the arrangement pitch of the second prisms 17 on each of the first main surface and the second main surface is P2, the optical path of the laser light reflected back is shifted by P2 / 2.

  Since the P2 / 2 optical path of the laser light shown in FIG. 6A is shifted by reflection by the second prism 17, this time, the laser light shown in FIG. 6B (within the BB cross section in FIG. 5). The laser beam travels through the device as a laser beam. That is, the light travels in the X1 direction while repeating reflection between the first prism 16 arranged on the first main surface side and the first prism 16 arranged on the second main surface side again. When the laser beam traveling in the X1 direction reaches the end on the X1 direction side, it is reflected again by the second prism 17 disposed on the first main surface side.

  The laser light incident on the wavelength conversion element 10-2 travels inside the element while being repeatedly reflected by the first prism 16 and the second prism 17, and finally has a wavelength as shown in FIG. The light is emitted from the second main surface of the conversion element 10-2 to the outside of the element. The emitted laser light includes the second harmonic L2 obtained by converting the wavelength of the fundamental wave L1 and the fundamental wave L1 that remains without being converted to the end. However, the transmission / reflection plate (for example, a dichroic mirror) The second harmonic L2 can be separated from the fundamental wave L1 by use, and only the second harmonic L2 can be used as a wavelength converted wave.

  As described above, the wavelength conversion element 10-2 that performs the multiple reflection structure using the first prism 16 and the second prism 17 can transmit the laser light to each crystal plate 11 a plurality of times. The conversion efficiency of the wavelength conversion element can be increased while suppressing the number of 11 layers. Also in the wavelength conversion element 10-2, by using the first prism 16 having a quadrangular prism shape, a laser beam (hereinafter referred to as an outward laser beam) from the first main surface to the second main surface, It is possible to perform reflection so that a laser beam (hereinafter referred to as a return laser beam) directed from the main surface to the first main surface becomes parallel. As a result, a larger number of repetitive reflections can be performed within a smaller area, and the number of repetitive reflections can be increased (laser light conversion efficiency can be improved) while suppressing an increase in the area of the wavelength conversion element. Become.

  When the laser light is incident on the main surface of the crystal plate 11 obliquely instead of perpendicularly like the wavelength conversion element 10-2, as shown in FIG. 6, the crystal plate 11 is matched with the incident angle of the laser. It is good also as the bonding which shifted diagonally. The term “laminatedly bonded” means that all the crystal plates 11 have the same shape and the same dimensions, and an approximate straight line with respect to the center of gravity of all the crystal plates 11 to be bonded is formed on the main surface of the crystal plate 11. It means a bonded structure that is inclined obliquely. The approximate straight line is preferably set so as to be parallel to the optical path of the refracted light traveling in the quartz plate 11 when the incident angle α of the incident laser light is the Brewster angle.

  As described above, by bonding the quartz plates 11 obliquely in accordance with the incident angle of the laser, the area of each quartz plate 11 can be reduced, and the wavelength conversion element 10-2 can be reduced in size and weight. Contributes to In this embodiment, the use of the quartz plate 11 having the same shape and the same area facilitates processing and increases the material efficiency, which is also effective for reducing the cost.

[Embodiment 3]
The wavelength conversion elements 10-1 and 10-2 shown in the first and second embodiments exemplify a configuration using the first prisms 13 and 16 as the first reflecting means, but the present invention is not limited to this. Instead of this, it is also possible to use a reflection film (including a transmission / reflection film) as the first reflection means.

  7 and 8 are a plan view and a cross-sectional view of the wavelength conversion element 10-3 using a reflective film as the first reflecting means. FIG. 7 is a plan view of the wavelength conversion element 10-3 according to the third embodiment. FIG. 7A is a diagram illustrating the arrangement of the reflecting means on the first main surface of the wavelength conversion element 10-3. (B) is a figure which permeate | transmits and shows the arrangement | positioning of the reflection means in the 2nd main surface of the wavelength conversion element 10-3 from the 1st main surface side. 8 is a cross-sectional view of the wavelength conversion element 10-3 in FIG. 7 as viewed from the Y2 direction side, where (a) is a cross-sectional view taken along line AA in FIG. 7, and (b) is a cross-sectional view taken along line BB in FIG. (C) is CC sectional drawing of FIG. In the description here, the X direction (X1 and X2 directions) and the Y direction (Y1 and Y2 directions) are two directions orthogonal to each other within the main surface of the wavelength conversion element 10-3.

  The wavelength conversion element 10-3 has a multiple reflection structure. Therefore, on the first main surface (upper surface in FIG. 8), the reflection film 18 which is a part of the first reflection means and the second reflection means. A plurality of second prisms 17 are arranged. On the second main surface (lower surface in FIG. 8), a transmission / reflection film 19 that is a part of the first reflecting means and a plurality of second prisms 17 that are the second reflecting means are arranged.

  The reflection film 18 is formed over a wide range in the central region of the first main surface, and is converted in wavelength in the process in which the fundamental wave (reference laser light) L1 and the second harmonic wave (fundamental wave pass through the wavelength conversion element). The generated reflected wave (converted laser beam) L2 is reflected. The transmission / reflection film 19 is formed over a wide range in the central region of the second main surface, and has a characteristic of reflecting the fundamental wave L1 and transmitting the second harmonic L2.

  The reflective film 18 preferably has a high reflectance (for example, a reflectance of 99% or more) with respect to both the fundamental wave L1 and the second harmonic L2. The material of the reflective film 18 is not particularly limited, and a metal reflective film or the like can be used. However, it is preferable to use a dielectric multilayer film in order to realize the high reflectance as described above.

  The transmission / reflection film 19 has a high reflectance (for example, a reflectance of 99% or more) with respect to the fundamental wave L1, and a high transmittance (for example, a transmittance of 99% or more) with respect to the second harmonic L2. ). In order to realize the optical characteristics as described above, it is preferable to use a dielectric multilayer film for the transmission / reflection film 19.

  The plurality of second prisms 17 can have the same configuration as the wavelength conversion element 10-2 in the second embodiment. The second prism 17 is arranged on the first main surface only in the end region on the X1 direction side of the formation region of the reflection film 18, and on the second main surface, the formation region of the transmission / reflection film 19 is arranged. They are arranged only in the end region on the X2 direction side.

  In the wavelength conversion element 10-3 shown in FIGS. 7 and 8, laser light (fundamental wave L1) having an incident angle α (see FIG. 8A) from a predetermined incident position on the first main surface is a Brewster angle. It is designed to obtain a desired wavelength conversion effect when it is incident. Specifically, on the first main surface, the incident position of the fundamental wave L1 is provided on the right end side of the AA cross section shown in FIG. Note that the reflecting film 18 and the second prism 17 are not provided at this incident position. Further, by making the incident angle α a Brewster angle, an antireflection film is not required at the incident position.

  Laser light incident at a Brewster angle on the wavelength conversion element 10-3 from the incident position travels in the element in the X2 direction while being repeatedly reflected between the reflection film 18 and the transmission / reflection film 19. In FIG. 8, the optical path of laser light traveling in the element is indicated by a broken line arrow.

  The laser light shown in FIG. 8A (laser light traveling in the AA cross section in FIG. 7) is subjected to the second reflection of the wavelength conversion element 10-3 after receiving the final reflection by the reflective film 18. While being reflected by one of the second prisms 17 (the lower end in FIG. 7B, the lower second prism 17 in FIG. 8A) that is transmitted through the main surface and disposed on the second main surface side, Y Move in the direction. The laser beam reflected in this way then travels through the device as laser light shown in FIG. 8B (laser light traveling in the BB cross section in FIG. 7). That is, the light travels in the X1 direction while repeating reflection between the reflection film 18 and the transmission / reflection film 19 again. When the laser beam traveling in the element in the X1 direction reaches the end portion on the X1 direction side, it is reflected back by the second prism 17 disposed on the first main surface side.

  When the fundamental wave L1 passes through the quartz plate 11, the fundamental wave L1 is wavelength-converted to generate the second harmonic L2. In the wavelength conversion element 10-3, the generated second harmonic L2 is transmitted through the transmission / reflection film 19 and is parallel to each other (in each of a plurality of laser beams (FIGS. 8A to 8C), Laser light). The second harmonic L2 emitted in this way can be used as an amplified wavelength converted wave by condensing it with, for example, a condenser lens.

  In the wavelength conversion element 10-3 according to the third embodiment, the laser light that is reflected back by the second prism 17 has an optical path length that shifts the laser light along the Y direction and has a wavelength of the fundamental wave L1. Must be an integer multiple. This is a condition for aligning the phases of the second harmonic L2 emitted from the transmission / reflection film 19 as a plurality of laser beams. If the phase of the second harmonic L2 emitted from the transmission / reflection film 19 is not aligned, the second harmonic L2 cannot be used as an amplified wavelength-converted wave even if it is collected by the condenser lens. .

  Further, the fundamental wave L1 that is not converted to the end after being incident on the wavelength conversion element 10-3 is finally the last second prism 17 (the upper end in FIG. 7B, FIG. 8C). ) And then is emitted from the first main surface of the wavelength conversion element 10-3. For this reason, the reflective film 18 is not formed in the emission part of the fundamental wave L1, and this part is opened.

  As described above, the wavelength conversion element 10-3 that performs the multiple reflection structure using the reflection film 18, the transmission / reflection film 19, and the second prism 17 can transmit the laser light to each crystal plate 11 a plurality of times. Therefore, the conversion efficiency of the wavelength conversion element can be increased while suppressing the number of stacked crystal plates 11. In addition, the reflective film 18 and the transmissive / reflective film 19 used for the first reflecting means are easier to form than the first prisms 13 and 16 in the first and second embodiments, and particularly for the laser. High-precision alignment is not required. For this reason, the structure of the wavelength conversion element 10-3 can be simplified and manufacturing cost can also be suppressed.

[Embodiment 4]
In the wavelength conversion elements 10-1 to 10-3 according to the first to third embodiments, the first prisms 13 and 16 and the second prisms 14 and 17 are bonded to the crystal plate 11 by using, for example, an adhesive. , Can be fixed in place. However, in such a prism fixing method by adhesion, when the prism design can be changed or the prism can be downsized, it is impossible to replace only the prism, and the entire element needs to be replaced.

  In the fourth embodiment, a configuration of a wavelength conversion element that allows replacement of only a prism will be described. FIG. 9 is a cross-sectional view of the wavelength conversion element 10-4 according to the fourth embodiment.

  The wavelength conversion element 10-4 is a laminate in which the first prism 13 and the second prism 14 are not bonded and fixed to the crystal plate 11, and the crystal plate 11 is bonded with a metal diffusion layer 12 as shown in FIG. In this configuration, the body (hereinafter referred to as a quartz plate laminate), the first prism 13 and the second prism 14 are sandwiched by the package 20 and the relative positional relationship thereof is maintained.

  The package 20 includes a first package member 201 disposed on the first main surface side and a second package member 202 disposed on the second main surface side. The first package member 201 and the second package member 202 have flange portions 20a at both ends thereof. By fastening the flange portions 20a with bolts 21, the crystal plate laminate, the first prism 13 and the second package member 20 are connected. The prism 14 is sandwiched and held between them. In addition, a laser incident window (not shown) and a laser emission window (not shown) are formed in the package 20 corresponding to the incident position and the emitting position of the laser beam in the wavelength conversion element 10-4. Yes.

  Note that the package 20 shown in FIG. 9 has a shape that holds the first prism 13 and the second prism 14 in the first embodiment. However, if the shape of the package 20 is changed, prisms having different shapes are used. It is also possible to hold the crystal plate laminated body in an aligned state. For example, the first prism 16 and the second prism 17 in the second embodiment and the second prism 17 in the third embodiment may be held.

  Thus, if the package 20 is used, the prism can be positioned without being fixed (adhered) to the quartz plate laminate. Therefore, when the prism design can be changed or the prism can be downsized, the prism can be easily replaced.

[Embodiment 5]
In the fifth embodiment, a laser irradiation apparatus to which the present invention is applied will be described with reference to FIGS.

  FIG. 10 is a diagram showing a schematic configuration of a laser irradiation apparatus 50-1 using the wavelength conversion element 10-2 shown in the second embodiment. The laser irradiation apparatus 50-1 irradiates the wavelength conversion element 10-2 with the fundamental wave (reference laser light) L1 from the laser light source (laser oscillation element) 51, and the second harmonic (wavelength is 1/2 of the fundamental wave). : Conversion laser beam) L2.

  In the laser irradiation apparatus 50-1 shown in FIG. 10, the laser beam (fundamental wave L1) incident on the wavelength conversion element 10-2 is relative to the incident surface (first main surface) of the wavelength conversion element 10-2. It is necessary to enter at a predetermined incident angle (Brewster angle) from a predetermined incident position. For this reason, in the laser irradiation apparatus 50-1, the laser light source 51 is appropriately positioned so that the laser light can be accurately incident on the wavelength conversion element 10-2. Note that the laser irradiation apparatus 50-1 may have fine adjustment means for positioning the laser light source 51 with high accuracy.

  In the laser irradiation apparatus 50-1, the laser beam emitted from the wavelength conversion element 10-2 includes a fundamental wave L1 and a second harmonic L2. For this reason, the laser irradiation apparatus 50-1 is provided with a transmission / reflection plate (for example, a dichroic mirror) 52 in the subsequent stage of the wavelength conversion element 10-2 to separate the fundamental wave L1 and the second harmonic L2 and separate them. Only the second harmonic L2 is used as output laser light. In addition, although the transmission / reflection plate 52 in FIG. 10 illustrates the one that transmits the second harmonic L2 and reflects the fundamental wave L1, conversely, the second harmonic L2 is reflected, It may transmit the fundamental wave L1.

  Further, in the laser irradiation apparatus 50-1, the second harmonic L2 emitted after being repeatedly reflected by the wavelength conversion element 10-2 may not be completely overlapped and may be emitted with some expansion. is there. For this reason, in the laser irradiation apparatus 50-1, the condensing lens 53 may be provided in the back | latter stage of the wavelength conversion element 10-2. Thereby, the 2nd harmonic L2 radiate | emitted from the wavelength conversion element 10-2 is condensed by the condensing lens 53, and can be utilized as an amplified wavelength conversion wave. 10 illustrates the case where the condensing lens 53 is disposed at the rear stage of the transmission / reflection plate 52, the condensing lens 53 may be disposed at the front stage of the transmission / reflection plate 52.

  In the laser irradiation apparatus 50-1 shown in FIG. 10, the wavelength conversion element 10-2 may be replaced with the wavelength conversion element 10-1 shown in the first embodiment.

  FIG. 11 is a diagram showing a schematic configuration of a laser irradiation apparatus 50-2 using the wavelength conversion element 10-3 shown in the third embodiment. The laser irradiation apparatus 50-2 is configured to irradiate the wavelength conversion element 10-2 with the fundamental wave L1 from the laser light source (laser oscillation element) 51 to obtain the second harmonic (wavelength is ½ of the fundamental wave) L2. It is. In the laser irradiation apparatus 50-2, the incident angle of the laser light (fundamental wave L1) incident on the wavelength conversion element 103 is preferably a Brewster angle. In this case, energy loss due to reflection can be significantly suppressed.

  In the laser irradiation apparatus 50-2, the second harmonic L2 emitted from the wavelength conversion element 10-3 is emitted as a plurality of laser beams. At this time, the second harmonics L2 (for example, the emitted lights in FIGS. 8A and 8C) emitted from the odd-numbered optical paths in the wavelength conversion element 10-3 are parallel to each other, and the even-numbered optical paths The second harmonics L2 emitted from (for example, the emitted light in FIG. 8B) are also parallel to each other. However, the second harmonic L2 emitted from the odd-numbered optical paths and the second harmonic L2 emitted from the even-numbered optical paths are emitted in opposite directions in the X direction. For this reason, the laser irradiation apparatus 50-2 is provided with the reflecting plate 54, and all the second harmonics L2 are reflected by reflecting the second harmonics L2 emitted from the even-numbered optical paths by the reflecting plate 54. They are parallel. Note that the reflection plate 54 may be configured to reflect all the second harmonics L2 in parallel by reflecting the second harmonics L2 emitted from the odd-numbered optical paths.

  Further, in the laser irradiation apparatus 50-2, a condenser lens 55 is disposed at the subsequent stage of the wavelength conversion element 10-3 and the reflection plate 54. The condensing lens 55 condenses all the second harmonics L2 that are parallel to each other. That is, the second harmonic L2 emitted from the wavelength conversion element 10-3 can be used as a wavelength-converted wave that is collected by the condenser lens 55 and amplified.

  Moreover, in the laser irradiation apparatus 50-2 shown in FIG. 10, the condensing lens 55 may be parallel-movable along the optical axis direction, and the structure which can adjust a focus position may be sufficient.

  In the laser irradiation apparatuses 50-1 and 50-2, the laser light source 51 is preferably a solid laser oscillation element, and for example, a YAG laser is preferably used. The wavelength of the fundamental wave L1 emitted from the YAG laser is 1064 nm, and the wavelength of the second harmonic L2 is 532 nm. 10 and 11 illustrate the case where the number of wavelength conversion elements used is one, the present invention is not limited to this, and a plurality of wavelength conversions are performed along the optical path of the laser light. The structure which arrange | positions an element may be sufficient.

  For example, in the laser irradiation apparatus 50-1 shown in FIG. 10, if a plurality of wavelength conversion elements 10-2 are arranged along the optical path of the laser light, the fundamental wave L1 having a wavelength of 1064 nm is sequentially converted to 532 nm, 266 nm,. Finally, a short wavelength laser beam in the ultraviolet region can be obtained. This also applies to the laser irradiation apparatus 50-2 shown in FIG.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

10-1 to 10-3 Wavelength conversion element 11 Crystal plate 12 Metal diffusion layer 12A, 12B Metal pattern 13, 16 First prism 14, 17 Second prism 15 Antireflection film 18 Reflection film 19 Transmission / reflection film 20 Package 201 First 1 package member 202 2nd package members 50-1, 50-2 Laser irradiation device 51 Laser light source 52 Transmission / reflection plate 53 Condensing lens 54 Reflecting plate 55 Condensing lens L1 Fundamental wave (reference laser light)
L2 Second harmonic (conversion laser light)

Claims (8)

A wavelength conversion element having a quasi-phase matching in which a domain-inverted structure is formed by a crystal having nonlinear optical characteristics,
Quartz is used for the crystal and has a structure in which a plurality of quartz plates are bonded together.
The laser beam is transferred while being reflected along the first direction in the first main surface and the second main surface of the wavelength conversion element, and between the first main surface and the second main surface. First reflecting means for repeatedly reflecting laser light;
Laser light that is disposed at both ends in the first direction of the wavelength conversion element and reaches the end in the first direction is changed to the first direction in the first main surface and the second main surface. Second reflecting means for shifting while reflecting along a second direction which is a direction orthogonal to each other,
The traveling path of the laser beam can be formed in a three-dimensional space by alternately performing the repeated reflection of the laser beam by the first reflecting unit and the reflection of the laser beam by the second reflecting unit. And a wavelength conversion element. The wavelength conversion element according to claim 1,
The first reflecting means is a plurality of first prisms respectively disposed on the incident surface side and the emitting surface side of the laser light,
The plurality of first prisms convert the laser light into the first principal surface side prism and the second principal surface side prism when the laser light is incident at a predetermined incident angle. Between the first main surface side and the second main surface side in the wavelength conversion element, and the first main surface side from the first main surface side. The laser beam can be reflected so that the optical path of the laser beam traveling to the main surface side of the
The second reflecting means is a plurality of second prisms respectively disposed on the incident surface side and the emitting surface side of the laser beam,
The plurality of second prisms include an optical path of laser light that travels laser light incident from the first direction from the first main surface side to the second main surface side in the wavelength conversion element; The laser beam is reflected so that the optical path of the laser beam traveling from the main surface side of the second light to the first main surface side is parallel, and along the second direction which is a direction orthogonal to the first direction. A wavelength conversion element characterized in that it can be shifted while being reflected. The wavelength conversion element according to claim 2,
The plurality of first prisms convert the laser light into the wavelength conversion element when the laser light is incident at a Brewster angle with respect to the incident surface from a predetermined position on the incident surface of the wavelength conversion element. Of the first principal surface side prism and the second principal surface side prism can be repeatedly reflected,
In the plurality of quartz plates, an approximate straight line with respect to the center of gravity of all the quartz plates to be bonded is parallel to the optical path of the refracted light when the laser beam is incident on the light incident surface of the wavelength conversion element at a Brewster angle. The wavelength conversion element characterized by being bonded so that it may become. The wavelength conversion element according to claim 2,
The plurality of first prisms, when a laser beam is incident from a predetermined position on the incident surface of the wavelength conversion element at an incident angle perpendicular to the incident surface, causes the laser beam to be emitted from the wavelength conversion element. A wavelength conversion element characterized in that it can be repeatedly reflected between a prism on the first main surface side and a prism on the second main surface side. The wavelength conversion element according to any one of claims 2 to 4,
A plurality of bonded quartz plates and the first prism and the second prism are sandwiched from both sides and fixed;
The wavelength conversion element, wherein the first prism and the second prism are positioned with respect to the crystal plate by the package. The wavelength conversion element according to claim 1,
The first reflecting means includes
A reflective film that is formed on the first principal surface side of the laser light in the wavelength conversion element and reflects both the reference laser light having a predetermined wavelength and the converted laser light that is the second harmonic of the reference laser light When,
A reflection / transmission film that is formed on the second principal surface side of the laser light in the wavelength conversion element, reflects the reference laser light, and transmits the converted laser light;
The wavelength conversion element, wherein the second reflecting means is a prism. The wavelength conversion element according to claim 6,
Having a package for sandwiching and fixing the plurality of bonded quartz plates and the prism from both sides;
The wavelength conversion element, wherein the prism is positioned with respect to the crystal plate by the package. The laser irradiation apparatus includes a laser light source and a wavelength conversion element, transmits a reference laser light emitted from the laser light source to the wavelength conversion element, and irradiates the converted laser light wavelength-converted by the transmission to the outside. And
The laser irradiation apparatus according to claim 1, wherein the wavelength conversion element is the wavelength conversion element according to claim 1.

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