Manufacturing method of Q-switch structure

Abstract

To provide a Q switch that contributes to downsizing of a laser device and can cope with high optical output.SOLUTION: A Q switch structure comprises a solid laser medium and a magnetic optical material, the solid laser medium and the magnetic optical material being joined and integrated. The solid laser medium's thickness is equal to or longer than 1 mm. The solid laser medium and the magnetic optical material are joined directly.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a Q-switch structure and a method for manufacturing a Q-switch structure. [Background technology]

[0002] In recent years, increasing the output power and miniaturizing the laser media that serve as the light source have become important issues in laser application equipment such as optical measurement and magneto-optical recording. From the perspective of miniaturization and high output, Q switches that use magneto-optical materials (also known as "MO materials") as their transmission mechanism have attracted attention.

[0003] Known laser devices equipped with a Q switch include a laser device in which a first resonant mirror, a solid-state laser material, a Q switch, and a second resonant mirror are arranged in that order. That is, a laser device is known in which a solid-state laser material and a Q switch are arranged between a pair of resonant mirrors consisting of a first resonant mirror and a second resonant mirror.

[0004] Non-Patent Document 1 discloses a small laser device in which a solid-state laser material and a Q-switch are placed between a pair of resonant mirrors. However, the Q-switch is a passive Q-switch that utilizes the saturable phenomenon, and the Q-switch cannot be actively controlled.

[0005] Non-patent document 2 discloses a technology for actively controlling a Q-switch by utilizing the electro-optic effect, but the thickness of the solid-state laser material is 0.5 mm, while the thickness of the Q-switch is 5 mm, making the Q-switch an obstacle to miniaturization of the laser device.

[0006] Non-Patent Document 3 discloses a technique for actively controlling a Q-switch by utilizing the acousto-optic effect, but the thickness of the Q-switch is as much as 32 mm, which is an obstacle to miniaturization of the laser device.

[0007] In conventional technology, actively controlling the Q-switch makes the Q-switch larger, which hinders the miniaturization of laser devices. Therefore, there was a need to achieve both miniaturization of the laser device and active Q-switching.

[0008] Patent Document 1 discloses a Q-switched solid-state laser device that, as a technology for activating a Q-switch within the constraint of not hindering the miniaturization of the laser device, has a solid-state laser material and a Q-switch arranged between a pair of resonant mirrors, and the Q-switch is composed of a combination of a film that exhibits a magneto-optical effect and a magnetic flux generator, and emits a pulsed laser when excitation light is incident on the solid-state laser material and a pulse is applied to the magnetic flux generator. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 2017-79283 [Non-patent literature]

[0010] [Non-Patent Document 1] T.Taira, M.Tsunekane, K.Kanehara, S.Morishima, N.Taguchi and A. Sugiura: “7. Promise of Giant Pulse Micro-Laser for Engine Ignition”, Journal of Plasma and Fusion Research, Vol. 89, No.4, pp.238-241(2013) [Non-patent document 2] T.Taira, and T.Kobayashi: “Q-Switching and Frequency Doubling of Solid-State Lasers by a Single Intracavity KTP Crystal”, IEEE Journal of Quantum Electronics of Vol. 30, No.3, pp.800-804(1994) [Non-patent document 3] Gooch & Housego Co.Ltd., Product number 1-QS041-1, 8C10G-4-GH21 Summary of the Invention [Problem to be solved by the invention]

[0011] As mentioned above, Patent Document 1 describes a Q switch using a magneto-optical (MO) mechanism. From the viewpoint of miniaturizing a laser device, it is desirable to minimize the space between the solid-state laser medium and the magneto-optical mechanism. In FIG. 13 of Patent Document 1, a configuration is proposed in which the solid-state laser medium and the magneto-optical film are integrated. However, no specific integration method is proposed.

[0012] The present invention has been made in view of the above problems, and has as its object to provide a Q switch that contributes to the miniaturization of laser devices and is capable of handling high optical output. [Means for solving the problem]

[0013] In order to solve the above problems, the present invention provides a Q-switch structure comprising a solid-state laser medium and a magneto-optical material, wherein the solid-state laser medium and the magneto-optical material are bonded together, the Q-switch structure being characterized in that the thickness of the solid-state laser medium is 1 mm or more, and the solid-state laser medium and the magneto-optical material are directly bonded together.

[0014] In such a Q switch structure, the solid-state laser medium and the magneto-optical material are bonded together, making it possible to create a compact Q switch structure. Furthermore, because the solid-state laser medium and the magneto-optical material are directly bonded together, there is no degradation in performance due to deterioration of the intervening material, as occurs when a material is interposed between them. In the present invention, the integrated combination of the solid-state laser medium and the magneto-optical material is referred to as a Q switch structure. The Q switch structure can function as a Q switch when combined with a magnetic flux generator.

[0015] Furthermore, in the Q switch structure of the present invention, it is preferable that the magneto-optical material is formed by crystal growth on a solid-state laser medium using the solid-state laser medium as a substrate, and is thereby bonded and integrated with the solid-state laser medium.

[0016] Such integration by crystal growth makes it possible to easily form a bonded structure between a solid-state laser medium and a magneto-optical material.

[0017] The magneto-optical material is preferably a bismuth-substituted rare earth iron garnet.

[0018] The solid-state laser medium is Y3Al5O4 doped with one element selected from the group consisting of Nd, Yb, and Cr. 12 , Gd3Ga5O 12 and (GdCa)3(GaMgZr)5O 12 It is preferable that the ceramic material is selected from one kind of ceramic material selected from the group consisting of:

[0019] These materials can be preferably used as the Q-switch structure of the present invention.

[0020] The present invention also provides a Q-switched solid-state laser device, characterized in that the above-mentioned Q-switch structure and a magnetic flux generator are disposed between a pair of resonant mirrors.

[0021] A Q-switched solid-state laser device equipped with such a Q-switch structure of the present invention is miniaturized because the solid-state laser medium and the magneto-optical material are directly bonded together, and because the solid-state laser medium and the magneto-optical material are directly bonded together, there is no degradation in performance due to deterioration of the materials interposed between them.

[0022] The present invention also provides a method for manufacturing a Q switch structure comprising a solid-state laser medium and a magneto-optical material, wherein the solid-state laser medium and the magneto-optical material are bonded together, the method comprising the steps of: preparing the solid-state laser medium having a thickness of 1 mm or more; and using the solid-state laser medium as a substrate, causing crystal growth of the magneto-optical material on the solid-state laser medium, thereby manufacturing a Q switch structure wherein the solid-state laser medium and the magneto-optical material are directly bonded together and integrated.

[0023] This manufacturing method of the Q-switch structure allows for easy integration of the solid-state laser medium and the magneto-optical material. Furthermore, since the solid-state laser medium and the magneto-optical material can be directly bonded, there is no degradation of performance due to deterioration of the material between the solid-state laser medium and the magneto-optical material in the manufactured Q-switch structure.

[0024] In this case, the crystal growth method is preferably liquid phase epitaxial growth.

[0025] In this way, by using the liquid phase epitaxial growth method, it is possible to more easily bond and integrate the solid laser medium and the magneto-optical material in the Q-switch structure.

[0026] The magneto-optical material is preferably a bismuth-substituted rare earth iron garnet.

[0027] The solid-state laser medium is preferably Y3Al5O4 doped with one element selected from the group consisting of Nd, Yb, and Cr. 12 , Gd3Ga5O 12 and (GdCa)3(GaMgZr)5O 12It is preferable that the ceramic material be one selected from the group consisting of:

[0028] These materials can be preferably used in the method for producing the Q-switch structure of the present invention.

[0029] The present invention also provides a method for manufacturing a Q-switched solid-state laser device, which comprises using a Q-switched structure manufactured by the above-mentioned method for manufacturing a Q-switched solid-state laser device and disposing the Q-switched structure and a magnetic flux generator between a pair of resonant mirrors.

[0030] In this manufacturing method for a Q-switched solid-state laser device, the solid-state laser medium and the magneto-optical material in the Q-switch structure are directly bonded, so that a miniaturized Q-switched solid-state laser device can be manufactured, and because the solid-state laser medium and the magneto-optical material are directly bonded, there is no degradation in performance due to deterioration of the material between them. [Effects of the Invention]

[0031] The Q-switch structure of the present invention can be made compact because the solid-state laser medium and magneto-optical material are bonded together. Furthermore, because the solid-state laser medium and magneto-optical material are directly bonded together, there is no degradation in performance due to deterioration of the intervening material. This allows for higher optical output. Furthermore, because the solid-state laser medium and magneto-optical material are bonded together, the distance between the two components is zero, contributing to the miniaturization of laser devices. Furthermore, it prevents vibrations associated with the activation of the magnetic switch (generated by changes in magnetic flux), optical resonance between the magneto-optical material and the solid-state laser medium, output instability due to changes in the magnetic domain pattern caused by distortion due to differences in the fixation of the magneto-optical material, variations in switching speed, and an increase in the resonator length due to the generation of space between the two, resulting in a decrease in switching speed. Furthermore, the method for manufacturing a Q-switch structure of the present invention allows for easy production of such a Q-switch structure. [Brief explanation of the drawings]

[0032] [Figure 1] FIG. 1 is a schematic diagram showing an example of the structure of a Q-switch structure of the present invention. [Figure 2] 1 is a cross-sectional view schematically showing an example of the structure of the Q switch structure of the present invention. [Figure 3] 1 is a cross-sectional view schematically showing an example of a Q-switched solid-state laser device equipped with a Q-switch structure of the present invention. [Figure 4] FIG. 1 is a flow chart showing an example of a method for producing a Q switch structure of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0033] The present invention will be described in detail below with reference to the drawings, but the present invention is not limited thereto. An example of the structure of the Q-switch structure of the present invention will be described with reference to Figures 1 and 2. Figure 1 shows a schematic diagram of the structure of the Q-switch structure, and Figure 2 shows its cross-sectional view.

[0034] The Q-switch structure 10 of the present invention comprises a solid-state laser medium 11 and a magneto-optical material 12, which are bonded together. The present invention is further characterized in that the thickness of the solid-state laser medium 11 is 1 mm or more, and the solid-state laser medium 11 and the magneto-optical material 12 are directly bonded together.

[0035] More specifically, the magneto-optical material 12 is formed by crystal growth on the solid-state laser medium 11 using the solid-state laser medium 11 as a substrate, and is preferably bonded and integrated with the solid-state laser medium 11 by such crystal growth.

[0036] Such a Q switch structure 10 functions as a Q switch by combining a magneto-optical material 12 and a magnetic flux generator. FIG. 3 shows an example of the structure of a Q-switched solid-state laser device. In a Q-switched solid-state laser device 20, the above-mentioned Q switch structure 10 and a magnetic flux generator 23 are arranged between a pair of resonant mirrors (a first resonant mirror 21 and a second resonant mirror 22). FIG. 3 shows an example in which all of these structures are bonded together. However, in the present invention, it is sufficient that the solid-state laser medium 11 and the magneto-optical material 12 constituting the Q switch structure 10 are bonded together, and other structural materials can be arranged as appropriate. For example, the magnetic flux generator can be a combination of a permanent magnet and an excitation coil, and the excitation coil can be arranged around the permanent magnet.

[0037] In the Q-switch structure 10 of the present invention, any material that can be used as a solid-state laser medium can be used as the material for the solid-state laser medium 11. Among them, in consideration of crystal growth when the solid-state laser medium 11 is used as a substrate, the material is preferably Y3Al5O4 doped with one element selected from the group consisting of Nd, Yb, and Cr. 12 , Gd3Ga5O 12 and (GdCa)3(GaMgZr)5O 12 It is preferable that the material be one type of ceramic selected from the group consisting of: Furthermore, in the Q switch structure 10 of the present invention, the material for the magneto-optical material 12 can be any material that can be used as a magneto-optical material. Among them, in consideration of the above-mentioned crystal growth, it is preferable that the magneto-optical material 12 be bismuth-substituted rare earth iron garnet.

[0038] [Manufacturing method of Q-switch structure] Next, a manufacturing method of the Q switch structure of the present invention will be described. The manufacturing method of the Q switch structure of the present invention is a method for manufacturing Q switch structure 10, which includes solid-state laser medium 11 and magneto-optical material 12 and is shown in Figures 1 and 2, and in which solid-state laser medium 11 and magneto-optical material 12 are bonded together. This invention includes the steps of preparing solid-state laser medium 11 having a thickness of 1 mm or more and using solid-state laser medium 11 as a substrate to grow crystals of magneto-optical material 12 on solid-state laser medium 11, thereby manufacturing Q switch structure 10 in which solid-state laser medium 11 and magneto-optical material 12 are directly bonded together and integrated.

[0039] The method for manufacturing the Q-switch structure of the present invention will be described in more detail with reference to FIG. 4. First, as shown in S1 of FIG. 4, a solid-state laser medium 11 having a thickness of 1 mm or more is prepared (step S1). The solid-state laser medium 11 prepared here is used as a substrate for crystal growth, so it must have a thickness of 1 mm or more. Materials that can be used as solid-state laser media can be used as the material for the solid-state laser medium 11. Among these, Y3Al5O4 doped with one element selected from the group consisting of Nd, Yb, and Cr is preferred. 12 , Gd3Ga5O 12 and (GdCa)3(GaMgZr)5O 12 It is preferable that the ceramic material be one selected from the group consisting of: Yttrium aluminum garnet (YAG), gadolinium gallium garnet (GGG), and CaMgZr-substituted gadolinium gallium garnet (SGGG), which are not only excellent as solid-state laser media, but are also particularly preferable when the magneto-optical material 12, which will be described later, is a bismuth-substituted rare earth iron garnet.

[0040] Next, as shown in S2 of Fig. 4, the magneto-optical material 12 is grown as a crystal on the solid-state laser medium 11, which serves as a substrate (step S2). At this time, it is preferable to grow the magneto-optical material 12 as a crystal by liquid phase epitaxial growth (LPE). As the liquid phase epitaxial growth method, a conventional method can be used. For example, the material for the magneto-optical material 12 is heated and melted in a platinum crucible, and the melt surface of the magneto-optical material 12 is applied to one side of the solid-state laser medium 11, which serves as a substrate.

[0041] Any material that can generally be used as a magneto-optical material can be used as the material for the magneto-optical material 12. Among these, it is preferable that the magneto-optical material 12 be bismuth-substituted rare earth iron garnet. Bismuth-substituted rare earth iron garnet is an excellent material for the magneto-optical material 12 that constitutes a Q switch. Furthermore, when the above-mentioned yttrium aluminum garnet (YAG), gadolinium gallium garnet (GGG), or CaMgZr-substituted gadolinium gallium garnet (SGGG) is used as the material for the solid-state laser medium 11, which also serves as a crystal growth substrate, if the magneto-optical material 12 is bismuth-substituted rare earth iron garnet, crystal growth is facilitated because they are all the same garnet.

[0042] Using the Q switch structure manufactured by the above-described manufacturing method for a Q switch structure, a Q switch solid-state laser device can be manufactured by placing the Q switch structure and a magnetic flux generator between a pair of resonant mirrors. [Example]

[0043] EXAMPLES The present invention will be explained in more detail below by showing examples and comparative examples, but the present invention is not limited to these.

[0044] [Example 1-1] The Q-switch structure 10 shown in FIGS. 1 and 2 was manufactured as follows.

[0045] First, a solid-state laser medium 11 (Nd:SGGG) was prepared by doping CaMgZr-substituted gadolinium gallium garnet (SGGG) with Nd (step S1 in Figure 4). This solid-state laser medium 11 was used as a substrate material with a thickness of 1.5 mm and a diameter of 1 inch (25.4 mm). This solid-state laser medium 11 was used as a crystal growth substrate.

[0046] Next, Tb4O7, Eu2O3, Fe2O3, Ga2O3, and Bi2O3 were placed in a platinum crucible and melted by heating at 1050°C. The melt was then cooled to 850°C. Next, a solid-state laser medium 11, which serves as the crystal growth substrate, was attached to the surface of the melt in the platinum crucible, and a crystal was grown to a thickness of 250 μm by the LPE method (step S2 in FIG. 4). This resulted in crystal growth of a magneto-optical material 12 (bismuth-substituted rare earth iron garnet) on the solid-state laser medium 11, and a Q-switch structure 10 was produced in which the solid-state laser medium 11 and the magneto-optical material 12 were directly bonded and integrated.

[0047] The crystal surface of this magneto-optical material 12 and the surface of the solid laser medium 11 serving as the substrate were optically polished and adjusted so that the Faraday rotation angle would be 45 degrees when irradiated with infrared light having a wavelength of 1064 nm.

[0048] To evaluate the optical characteristics of this Q-switch structure 10 (a sample in which the solid-state laser medium 11 and the magneto-optical material 12 are integrated), an air-resistant anti-reflection coating was applied to both the surface (polished surface) of the magneto-optical material 12 and the solid-state laser medium 11, and the optical characteristics were evaluated. As a result, an insertion loss of 1.1 dB and an extinction ratio of 29 dB were obtained. The extinction ratio of less than 30 dB is due to the influence of interface reflection caused by the difference in refractive index between the solid-state laser medium 11 and the magneto-optical material 12, and is within the acceptable range for this combination of materials.

[0049] [Example 1-2] A Q-switch structure 10 was manufactured in the same manner as in Example 1-1, but the thickness was adjusted by polishing to a Faraday rotation angle of 22.5°. When the optical characteristics were evaluated in the same manner as in Example 1-1, an insertion loss of 0.65 dB and an extinction ratio of 29 dB were obtained, and although the rotation angle was small, the insertion loss in the magneto-optical material 12 portion could be reduced.

[0050] [Examples 1-3] In a Q-switch structure 10 manufactured in the same manner as in Example 1-1, a layer of a first resonant mirror 21 was formed on the surface of the solid-state laser medium 11, and a layer of a second resonant mirror 22 was formed on the surface of the magneto-optical material 12, thereby enabling the manufacture of a Q-switch solid-state laser device 20.

[0051] [Example 2-1] The Q-switch structure 10 shown in FIGS. 1 and 2 was manufactured as follows.

[0052] First, a solid-state laser medium 11 (Nd:GGG) was prepared by doping gadolinium gallium garnet (GGG) with Nd (step S1 in Figure 4). This solid-state laser medium 11 was used as a substrate material with a thickness of 1.5 mm and a diameter of 1 inch (25.4 mm). This solid-state laser medium 11 was used as a substrate for crystal growth.

[0053] Next, Tb4O7, Yb2O3, Fe2O3, Al2O3, and Bi2O3 were placed in a platinum crucible and melted by heating at 1100°C. The melt was then cooled to 850°C. Next, a solid-state laser medium 11, which serves as the crystal growth substrate, was attached to the surface of the melt in the platinum crucible, and a crystal was grown to a thickness of 300 μm by the LPE method (step S2 in FIG. 4). This resulted in crystal growth of a magneto-optical material 12 (bismuth-substituted rare earth iron garnet) on the solid-state laser medium 11, and a Q-switch structure 10 was manufactured in which the solid-state laser medium 11 and the magneto-optical material 12 were directly bonded and integrated.

[0054] The crystal surface of this magneto-optical material 12 and the surface of the solid laser medium 11 serving as the substrate were optically polished and adjusted so that the Faraday rotation angle would be 22.5 degrees when irradiated with infrared light having a wavelength of 1064 nm.

[0055] To evaluate the optical properties of this Q-switch structure 10 (a sample in which the solid-state laser medium 11 and the magneto-optical material 12 are integrated), an air-resistant anti-reflection coating was applied to both the surface (polished surface) of the magneto-optical material 12 and the solid-state laser medium 11, and the optical properties were evaluated. As a result, an insertion loss of 0.7 dB and an extinction ratio of 30 dB were obtained. The low extinction ratio of 30 dB is due to the effect of interface reflection caused by the difference in refractive index between the solid-state laser medium 11 and the magneto-optical material 12, and is within the acceptable range for this combination of materials.

[0056] [Example 2-2] In a Q-switch structure 10 manufactured in the same manner as in Example 2-1, a layer of a first resonant mirror 21 was formed on the surface of the solid-state laser medium 11, and a layer of a second resonant mirror 22 was formed on the surface of the magneto-optical material 12, thereby enabling the manufacture of a Q-switch solid-state laser device 20.

[0057] [Example 3-1] The Q-switch structure 10 shown in FIGS. 1 and 2 was manufactured as follows.

[0058] First, a solid-state laser medium 11 (Nd:GGG) was prepared by doping gadolinium gallium garnet (GGG) with Nd (step S1 in Figure 4). This solid-state laser medium 11 was used as a substrate material with a thickness of 1.5 mm and a diameter of 1 inch (25.4 mm). This solid-state laser medium 11 was used as a substrate for crystal growth.

[0059] Next, Pr2O3, Lu2O3, Fe2O3, Ga2O3, and Bi2O3 were placed in a platinum crucible and melted by heating at 1100°C. The melt was then cooled to 850°C. Next, a solid-state laser medium 11, which serves as the crystal growth substrate, was attached to the surface of the melt in the platinum crucible, and a crystal was grown to a thickness of 120 μm by the LPE method (step S2 in FIG. 4). This resulted in crystal growth of a magneto-optical material 12 (bismuth-substituted rare earth iron garnet) on the solid-state laser medium 11, and a Q-switch structure 10 was produced in which the solid-state laser medium 11 and the magneto-optical material 12 were directly bonded and integrated.

[0060] The crystal surface of this magneto-optical material 12 and the surface of the solid laser medium 11 serving as the substrate were optically polished, and adjusted so that the Faraday rotation angle would be 7.5 degrees when irradiated with infrared light having a wavelength of 1064 nm.

[0061] In order to evaluate the optical characteristics of this Q-switch structure 10 (a sample in which the solid-state laser medium 11 and the magneto-optical material 12 are integrated), an air-resistant anti-reflection coating was applied to both the surfaces (polished surfaces) of the magneto-optical material 12 and the solid-state laser medium 11, and the optical characteristics were evaluated. As a result, an insertion loss of 0.6 dB and an extinction ratio of 30 dB were obtained. [Example 3-2] In a Q-switch structure 10 manufactured in the same manner as in Example 3-1, a layer of a first resonant mirror 21 was formed on the surface of the solid-state laser medium 11, and a layer of a second resonant mirror 22 was formed on the surface of the magneto-optical material 12, thereby enabling the manufacture of a Q-switch solid-state laser device 20.

[0062] In the compositions of Examples 3-1 and 3-2, the magneto-optical material 12 exhibits in-plane magnetic anisotropy and has a steep magnetic hysteresis, which enables low magnetic flux driving when a Q switch is fabricated.

[0063] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention. [Explanation of symbols]

[0064] 10... Q switch structure, 11... solid-state laser medium, 12... magneto-optical material, 20...Q-switched solid-state laser device, 21...first resonant mirror; 22...second resonant mirror; 23...magnetic flux generator.

Claims

1. a solid-state laser medium; Magneto-optical materials A method for manufacturing a Q-switch structure in which the solid-state laser medium and the magneto-optical material are bonded together, comprising: Y doped with one selected from the group consisting of Nd, Yb and Cr ３ Al ５ O １２ , Gd ３ Ga ５ O １２ and (GdCa) ３ (GaMgZr) ５ O １２ preparing the solid-state laser medium, which is selected from one type of ceramic selected from the group consisting of: a step of growing a crystal of the magneto-optical material, which is a bismuth-substituted rare earth iron garnet, on the solid-state laser medium as a substrate; a manufacturing method of a Q switch structure, characterized in that the Q switch structure is manufactured by directly bonding the solid-state laser medium and the magneto-optical material to each other and integrating them.

2. 2. The method for manufacturing a Q-switch structure according to claim 1, wherein the crystal growth method is a liquid phase epitaxial growth method.

3. 3. A method for manufacturing a Q-switched solid-state laser device, comprising: using a Q-switched structure manufactured by the method for manufacturing a Q-switched structure according to claim 1 or 2; and disposing the Q-switched structure and a magnetic flux generator between a pair of resonant mirrors to manufacture a Q-switched solid-state laser device.

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