Optical Element, Optical Device, and Method for Manufacturing Optical Element

Abstract

To provide an optical element having a waveguide, with which a confinement effect can be improved and which is easily manufacturable, an optical device provided with the optical element, and a method for manufacturing the optical element.SOLUTION: An optical element 2A comprises: a substrate 4 having a first principal surface, and a second principal surface 4b which is reverse to the first principal surface and composed of a single crystal and a ceramic or glass; and a heat sink 6 joined to the second principal surface and having a smaller refractive index than the first substrate. A waveguide 8 is formed on the substrate. Each of a pair of side surfaces 8a, 8b intersecting an extending direction of the waveguide and a thickness direction of the substrate is a reformed surface having been reformed from the substrate. The reformed surface extends from the first principal surface to the second principal surface.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an optical element, an optical device, and a method for manufacturing an optical element.

Background Art

[0002] As conventional techniques in this technical field, there are Non-Patent Documents 1 to 5. In these documents, it is disclosed that by irradiating an optical material with an ultrashort pulse laser of femtoseconds, non-thermal processing and modification are performed on the irradiation region, and a waveguide is formed by utilizing the fact that the refractive index changes as the volume of the irradiation region expands.

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Non-Patent Document 4

Non-Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0004] For example, in the waveguide formation of Non-Patent Document 1, dot-drawing cylindrical laser processing was required for waveguide formation. Therefore, the waveguide formation was complicated, the confinement effect required for the waveguide was low, and the conventional waveguide laser oscillation characteristics and nonlinear wavelength conversion characteristics were poor. Further, since a femtosecond laser was used for processing, an optical element including a waveguide could not be easily manufactured.

[0005] Therefore, an object of the present invention is to provide an optical element having a waveguide, an optical device including the optical element, and a method for manufacturing the optical element, which can improve the confinement effect and can be easily manufactured.

Means for Solving the Problems

[0006] The optical element according to the present invention has a first main surface and a second main surface on the side opposite to the first main surface, and includes a substrate formed of a single crystal, ceramics, or glass, and a light confinement member provided on the second main surface. A waveguide is formed in the substrate, and each of a pair of side surfaces that intersect in the extending direction of the waveguide and the thickness direction of the substrate is a modified surface on which the substrate is modified, and the modified surface extends from the first main surface to the second main surface.

[0007] In the optical element, a waveguide is formed by a pair of side surfaces that are modified surfaces and a light confinement member. In this case, since the confinement of light on the second main surface side in the waveguide is performed by the light confinement member, the light confinement effect is improved. Further, since the confinement of light on the second main surface side in the waveguide is performed by the light confinement member, the optical element can be easily manufactured, for example, as compared with the case where the confinement on the second main surface side is performed on the modified surface.

[0008] The light confinement member may be a heat sink having a refractive index smaller than that of the substrate. In this configuration, even when heat is generated in the substrate when high-power laser light propagates through the waveguide, the heat sink can reduce the temperature rise of the substrate.

[0009] The above light confinement member has a reflective coating layer and a heat sink, and the reflective coating layer may be disposed between the second main surface and the heat sink. In this case, light is efficiently confined in the waveguide.

[0010] The above substrate may be formed of a solid laser base material. In this case, the optical element can be used as a laser element.

[0011] The above substrate may be formed of a nonlinear optical crystal. In this case, the optical element can be used as, for example, a wavelength conversion element.

[0012] The above substrate may have a quasi-phase matching structure.

[0013] The optical device according to the present invention includes the above optical element.

[0014] The method for manufacturing an optical element according to the present invention is a method for manufacturing an optical element having a waveguide, and has a first main surface and a second main surface on the opposite side of the first main surface, and is formed of a single crystal, ceramics or glass. A lamination step of laminating the substrate and the light confinement member so that the light confinement member is disposed on the second main surface of the substrate, and a pair of side surfaces intersecting the extending direction of the waveguide and the thickness direction of the substrate are formed on the substrate by modifying the substrate using pulsed laser light. And a modification step.

[0015] In the method for manufacturing the optical element, a pair of side surfaces formed by modifying the substrate by irradiation with pulsed laser light and a waveguide are formed by the light confinement member. In this case, since the confinement of light on the second main surface side in the waveguide is performed by the light confinement member, the light confinement effect is improved. Further, since the confinement of light on the second main surface side in the waveguide is realized by the light confinement member, the optical element can be manufactured more simply than, for example, when the confinement on the second main surface side is performed on the modified surface.

[0016] The pulse width of the pulsed laser light may be 0.2 ps to 10 ns. The pulse width of the pulsed laser light may be 1 ps to 1 ns. In this case, for example, compared with the case of using femtosecond laser light, the output device of the pulsed laser light can be simplified.

[0017] The light confinement member is a heat sink having a refractive index smaller than that of the substrate, and in the lamination step, the heat sink may be joined to the second main surface at room temperature. In this case, even when the substrate generates heat when high-power laser light propagates through the waveguide, the heat sink can reduce the temperature rise of the substrate.

[0018] The light confinement member has a heat sink, and in the lamination step, after forming a reflective coating layer on the substrate or the heat sink, the substrate and the heat sink may be laminated so that the reflective coating layer is sandwiched between the heat sink and the substrate. In this case, light is efficiently confined in the waveguide.

[0019] The substrate may be formed of a solid laser base material. In this case, the optical element can be used as a laser element.

[0020] The substrate may be formed of a nonlinear optical crystal. In this case, the optical element can be used as, for example, a wavelength conversion element.

[0021] The substrate may have a quasi-phase matching structure.

Advantages of the Invention

[0022] According to the present invention, it is possible to provide an optical element having a waveguide, an optical device including the optical element, and a method for manufacturing the optical element, which can improve the confinement effect and can be easily manufactured.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0024] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or equivalent elements are denoted by the same reference numerals, and duplicate descriptions are omitted. The dimensional ratios in the drawings do not necessarily match those in the description.

[0025] (First Embodiment) As shown in FIG. 1, an optical element 2A according to an embodiment includes a substrate 4 and a heat sink (light confinement member) 6, and a waveguide 8 is formed on the substrate 4. In FIG. 1, for convenience of explanation, a pair of side surfaces 8a and 8b of the waveguide 8 are schematically shown by thick solid lines. The method of illustrating the side surfaces of the waveguide is the same in other figures.

[0026] The substrate 4 has a first main surface 4a and a second main surface 4b (a surface opposite to the first main surface 4a in the thickness direction of the substrate 4). An example of the thickness H of the substrate 4 is 5 μm to 1 mm. The planar shape of the substrate 4 (the shape seen from the thickness direction of the substrate 4) is not limited, but for example, it is rectangular or square. When the planar shape of the substrate 4 is rectangular, an example of the length L in the long side direction is 1 mm to 100 mm.

[0027] The substrate 4 is an optical member capable of transmitting light propagating through the waveguide 8. The substrate 4 is formed of single crystal, ceramics or glass. The substrate 4 may be formed from a solid laser base material (laser medium).

[0028] Examples of the above single crystals are garnet-based such as YAG, GGG, LuAG, YSAG, YGAG, YALO, sesquioxide-based such as Y2O3, Sr2O3, Lu2O3, vanadate-based such as YVO4, GdVO4, LuVO4, fluoride-based such as CaF2, YLF, apatite-based such as FAP, sFAP, and tungstate-based such as KYW, KGW. Examples of the above ceramics are polycrystals of the same materials as the above single crystals such as YAG ceramics, isotropic materials such as LuAG, YSAG, YGAG, Y2O3, Sr2O3, Lu2O3, and anisotropic FAP, etc. Such single crystals and ceramics function as solid laser base materials.

[0029] When the substrate 4 is formed from a solid laser base material, a light-emitting center may be added to the substrate 4. The light-emitting center includes rare earth elements (Nd, Yb, Tm, Ho, Er, Ce, Pr, etc.), transition metal elements (Cr, Ti, V, etc.).

[0030] The substrate 4 may be formed from a non-linear optical crystal. Examples of the material of the substrate 4 formed from a non-linear optical crystal include, for example, quartz (SiO2), ferroelectric material, semiconductor material, borate-based material, etc.

[0031] Examples of the above ferroelectric materials include, for example, LiNbO3 (including both cases where Mg is added and not added), LiTaO3 (including both cases where Mg is added and not added), KTiPO4 (including both cases where Rb is added and not added), RbTiPO4 (including both cases where Rb is added and not added), KTiOAsO4, RbTiOAsO4, etc. Examples of the semiconductor material include GaAs, GaP, GaN, ZnS, ZnSe, ZnTe, ZnGeP2, CdSiP2, etc. Examples of the borate-based material include LiB3O5, BaB2O4, Ca(BO3)3F, CsLiB6O 10 , Ca4LnO(BO3)3 (Ln = Gd, Y), etc.

[0032] The heat sink 6 is a member having a refractive index smaller than that of the substrate 4 and a thermal conductivity higher than that of the substrate 4. Examples of the material of the heat sink 6 include sapphire, diamond, etc. The heat sink 6 is joined to the second main surface 4b of the substrate 4. The heat sink 6 may be joined to the substrate 4 by room-temperature bonding.

[0033] The waveguide 8 is formed on the substrate 4. In the form shown in FIG. 1, the waveguide 8 extends from the first end face 4c to the second end face 4d of the substrate 4. Each of the pair of side faces 8a, 8b of the waveguide 8 intersects with the extending direction (optical axis direction) of the waveguide 8 and the thickness direction of the substrate 4. In the form shown in FIG. 1, the pair of side faces 8a, 8b are perpendicular to the extending direction (optical axis direction) of the waveguide 8 and the thickness direction of the substrate 4. The pair of side faces 8a, 8b face each other. The pair of side faces 8a, 8b are modified surfaces where the substrate 4 is modified. The pair of side faces 8a, 8b can be formed by laser drawing. Specifically, the pair of side faces 8a, 8b are surfaces formed by modifying the substrate 4 such that the refractive index of the laser condensing region in the substrate 4 becomes smaller than that of the surroundings by condensing laser light on the substrate 4. The modified surface is also a surface with a modulated refractive index (refractive index modulation surface). As shown in FIG. 1, the length of each of the side faces 8a, 8b along the thickness direction of the substrate 4 is the same as the thickness H of the substrate 4. An example of the width W of the waveguide 8 (the length in the direction perpendicular to the optical axis direction of the waveguide 8 and the thickness direction of the substrate 4) is 5 μm to 1 mm.

[0034] The optical element 2A can be manufactured as follows.

[0035] First, the heat sink 6 is joined to the second main surface 4b of the substrate 4 to laminate the substrate 4 and the heat sink 6 (lamination step). The heat sink 6 may be joined to the substrate 4, for example, by surface activation room temperature bonding. Surface activation room temperature bonding (hereinafter, also simply referred to as "room temperature bonding") is a method of removing an oxide film or surface deposits on the bonding surface of materials to be bonded in a vacuum by ion beam irradiation or FAB (neutral atom beam) irradiation, and bonding flat bonding surfaces with exposed constituent atoms. Room temperature bonding is a direct bonding using intermolecular bonding.

[0036] Next, as shown in FIG. 2, while condensing the pulsed laser light PL with the condensing unit 10, the substrate 4 is irradiated with the pulsed laser light PL, and the substrate 4 at the irradiation position (condensing position) of the pulsed laser light PL is modified. According to the shape of the waveguide 8 to be formed, by three-dimensionally scanning the pulsed laser light PL, a modified surface to become a pair of side surfaces 8a and 8b of the waveguide 8 is formed (modification step).

[0037] The pulsed laser light PL may be pulsed laser light with a sub-nanosecond pulse width. The pulse width of the pulsed laser light PL may be 0.2 ps to 10 ns, preferably 1 ps to 1 ns. An example of a laser device that outputs the pulsed laser light PL is a microchip laser (MCL) that is small, low power consumption, and capable of outputting laser light with a sub-nanosecond pulse width (see, for example, Japanese Patent Application Laid-Open No. 2019-129252). An example of the wavelength when the substrate 4 is Nd:YAG and the pulsed laser light PL is the fundamental wave is 1064 nm to 1108 nm, and an example of the wavelength when the substrate 4 is Yb:YAG and the pulsed laser light PL is the fundamental wave is 1024 nm to 1108 nm. As the pulsed laser light PL, not only the fundamental wave but also harmonic waves such as the second harmonic wave, third harmonic wave, fourth harmonic wave, fifth harmonic wave, sixth harmonic wave, and seventh harmonic wave from a solid-state laser may be used. By using harmonic waves, it is possible to increase the photon energy without using a large and unstable ultrashort pulsed laser with a pulse width of 0.1 ps or less, so that it can interact strongly and efficiently with the substance, and finer processing is possible.

[0038] The power and irradiation time of the pulsed laser light PL etc. may be set so that the refractive index at the irradiation position (condensing position) of the pulsed laser light PL is smaller than the refractive index around the irradiation position (around the side surface to be formed). For example, the tip output of the pulsed laser light PL is in the range of 0.1 MW to 50 MW. The irradiation time of the pulsed laser light PL to the irradiation position is from 1 ps to 1 ns.

[0039] The scanning of the pulsed laser light PL may be performed by scanning the laser device itself, or the pulsed laser light PL output from the laser device may be scanned using a mirror or the like.

[0040] In the above example of the manufacturing method of the optical element 2A, after laminating the substrate 4 and the heat sink 6, the waveguide 8 is formed on the substrate 4. However, after forming the waveguide 8 on the substrate 4, the substrate 4 and the heat sink 6 may be laminated.

[0041] In the above optical element 2A, a pair of side surfaces 8a, 8b formed by modifying the substrate 4 by irradiation with the pulsed laser light PL, and the heat sink 6 forms the waveguide 8. Since the heat sink 6 has a refractive index smaller than that of the substrate 4, the heat sink 6 can confine the light on the second main surface 4b side in the waveguide 8. That is, the heat sink 6 functions as a light confinement member. Thus, since the confinement of the light on the second main surface 4b side in the waveguide 8 is realized by the heat sink 6, the light confinement effect in the waveguide 8 is improved. By forming a part of the waveguide 8 with the heat sink 6, the region to be modified by the pulsed laser light PL may be a region corresponding to the pair of side surfaces 8a, 8b. Therefore, for example, the optical element 2A can be manufactured more simply and in a shorter time than when forming all the surfaces for confining the waveguide 8 using the pulsed laser light PL.

[0042] When using pulsed laser light PL with a sub-nanosecond pulse width (for example, a pulse width of 0.2 ps to 10 ns), the laser device can be miniaturized compared to, for example, when using femtosecond pulsed laser light. For example, it is also possible to use the above-described microchip laser. In this case, since the laser device is easy to handle, it is easy to form the waveguide 8.

[0043] When the material of the substrate 4 is a single crystal or ceramics (particularly when it is a material used for a solid laser base material), it has high resistance to high-power laser light. Furthermore, since the heat sink 6 is used as part of the optical confinement, a high optical confinement effect can also be obtained. As a result, high-power laser light can propagate in the waveguide 8, and the optical element 2A can be used as an optical component (for example, a laser element) for high-power laser light used in laser processing or the like.

[0044] Also, single crystals or ceramics have a higher thermal conductivity and stimulated emission cross-sectional area than glass. Furthermore, in the optical element 2A, the confinement effect is improved as described above. Therefore, it is possible to realize a laser device that satisfies at least one of small size, high efficiency, and high power using the above-described optical element 2A formed from a single crystal or ceramics.

[0045] Since the optical element 2A is provided with the heat sink 6, even if heat is generated in the substrate 4 due to the propagation of high-power laser light as described above, the temperature rise of the substrate 4 can be reduced because the heat sink 6 is joined to the substrate 4.

[0046] When the joining of the substrate 4 and the heat sink 6 is a room-temperature joining, different materials are joined at room temperature. Therefore, compared to the case where, for example, an adhesive or the like is used for joining, it has high resistance to the power of the light propagating through the waveguide 8, can handle high-power light, and a waveguide 8 with a high confinement effect can be obtained.

[0047] When the substrate 4 is formed from a solid laser base material, the optical element 2A can be used as a laser element included in an optical oscillator, an optical amplifier, a laser device, or the like. When the substrate 4 is formed from a solid laser base material, it has high resistance to high-power laser light, and as described above, in the waveguide 8, the confinement effect can be improved. As a result, it is possible to realize an optical oscillator, an optical amplifier, or a laser device that satisfies at least one of small size, high efficiency, and high power.

[0048] When the optical element 2A is formed from a nonlinear optical crystal, the optical element 2A can be used, for example, as a wavelength conversion element. In a form in which the waveguide 8 is formed in the nonlinear optical crystal, it is possible to realize a nonlinear wavelength conversion element that satisfies at least one of small size and high power by the optical element 2A.

[0049] Next, various modified examples and application examples of the optical element 2A will be described as each embodiment.

[0050] (Second Embodiment) Like the optical element 2B shown in FIG. 3, the optical element 2B may have an intermediate layer 12 between the substrate 4 and the heat sink 6. The intermediate layer 12 can be formed, for example, from Al2O3, SiO2, or the like. The intermediate layer 12 may be a layer formed when joining the substrate 4 and the heat sink 6. In this case, the intermediate layer 12 is integrated with the substrate 4 or the heat sink 6. In the second embodiment, the intermediate layer 12 is a part of the optical confinement member.

[0051] For example, when the material of the substrate 4 is a solid laser base material and the substrate 4 and the heat sink 6 are joined at room temperature, the substrate 4 and the heat sink 6 are joined via the intermediate layer 12. In this case, the intermediate layer 12 functions as a buffer layer. The material of the intermediate layer 12 is as exemplified. The intermediate layer 12 may contain a constituent element of the substrate 4 and a constituent element of the heat sink 6. When the substrate 4 and the heat sink 6 are joined at room temperature, the intermediate layer 12 may contain Fe, Ar, or the like. The above room-temperature joining can be carried out, for example, as follows.

[0052] Place the substrate 4 and the heat sink 6 inside the chamber, and make the inside of the chamber a substantially vacuum environment. Form intermediate layers 12 on the second main surface 4b of the substrate 4 and on the surface of the heat sink 6 on the side of the substrate 4, respectively. The thicknesses of the intermediate layer 12 on the substrate 4 side and the intermediate layer 12 on the heat sink 6 side are, for example, about 10 nm. The intermediate layer 12 may be formed by sputtering, evaporation, or the like. The intermediate layer 12 for room temperature bonding contains an element that can be replaced with at least one constituent element of the substrate 4 and the heat sink 6.

[0053] In a substantially vacuum environment, irradiate the surface of the substrate 4 on the intermediate layer 12 side and the surface of the heat sink 6 on the intermediate layer 12 side with an ion beam such as argon (Ar) or FAB (neutral atom beam). Thereby, oxygen or the like adsorbed on the surface is removed, and a fresh surface including dangling bonds is formed. The substantially vacuum environment is, for example, a vacuum or reduced pressure atmosphere with a background pressure of 1×10 -5 Pa or less.

[0054] As the ion beam or FAB (neutral atom beam), in addition to argon, noble gases or inert gases such as neon (Ne), krypton (Kr), xenon (Xe), and helium (He) can be employed. Since noble gases are less likely to cause chemical reactions, they do not significantly change the chemical properties of the irradiated surface. By using a particle beam source or a plasma generator to accelerate the particles of the ion beam toward the bonding surface, a predetermined kinetic energy can be imparted to the ion beam or FAB (neutral atom beam).

[0055] Next, oppose the intermediate layer 12 side of the substrate 4 and the intermediate layer 12 side of the heat sink 6. At room temperature, bring the fresh surfaces where the bonding hands of the substrate 4 and the heat sink 6 are exposed into contact with each other in a substantially vacuum environment. Thereby, a bonding force due to the interaction between atoms is generated, and the substrate 4 and the heat sink 6 are firmly bonded via the intermediate layer 12. The substantially vacuum environment is, for example, a vacuum or reduced pressure atmosphere with a background pressure of 1.5×10 -6 Pa or less. A predetermined pressure (1.5 to 2.0 MPa) may be applied to the contacted substrate 4 and heat sink 6.

[0056] The optical element 2B is the same as the optical element 2A of the first embodiment except that it has the intermediate layer 12. Therefore, the optical element 2B has the same operational effects as the optical element 2A.

[0057] (Third Embodiment) As in the optical element 2C shown in FIG. 4, a plurality of waveguides 8 may be formed on the substrate 4 included in the optical element 2C. The number and shape of each waveguide 8 may be determined according to the use of the optical element 2C. FIG. 4 shows a case where two waveguides 8 are formed. The two waveguides 8 shown in FIG. 4 are referred to as a waveguide 8A and a waveguide 8B. In the form shown in FIG. 4, the waveguide 8A and the waveguide 8B are close to each other such that light (for example, laser light) propagating through the waveguide 8A and the waveguide 8B is partially optically coupled.

[0058] The method for forming the plurality of waveguides 8 is the same as in the case of the first embodiment. That is, it can be formed by modifying, with the pulsed laser light PL, portions on the substrate 4 that are to become the side surfaces of the respective waveguides 8. In this case, since each waveguide 8 can be formed by scanning the pulsed laser light PL, it is easy to form a plurality of waveguides 8 on the substrate 4. The configuration of the optical element 2C is the same as that of the optical element 2A except that a plurality of waveguides 8 are formed on the substrate 4. Therefore, the optical element 2C has the same operational effects as the optical element 2A.

[0059] As shown in FIG. 4, in a form where the waveguide 8A and the waveguide 8B are close to each other such that light propagating through them is partially optically coupled, the optical element 2C functions as an optical coupling element that optically couples laser lights of different wavelengths propagating through the waveguide 8A and the waveguide 8B, respectively. The optical element 2C shown in FIG. 4 can also function as an optical branching element that branches a part of the laser light propagating through one waveguide 8 (for example, the waveguide 8A) to the other waveguide 8 (for example, the waveguide 8B).

[0060] (Fourth Embodiment) When the material of the substrate 4 is a solid laser base material, the optical element can be used in an optical oscillator, an optical amplifier, a laser device, etc. An example of an oscillator and a laser device using the optical element 2A will be described with reference to FIG. 5. The laser device is also an example of an optical device including an optical element.

[0061] As shown in FIG. 5, the laser device (optical device) 14 includes an optical oscillator 16 having an optical element 2A. The laser device 14 may include an excitation light source unit 18 that supplies excitation light L1 to the optical element 2A. In the fourth embodiment, the case where the laser device 14 includes the excitation light source unit 18 will be described. In the following description, the laser light output from the laser device 14 is referred to as laser light L2.

[0062] The optical oscillator 16 has an optical element 2A and a resonator 20. The optical element 2A is the optical element 2A described in the first embodiment. In the fourth embodiment, the material of the substrate 4 is a single crystal or ceramics that functions as a solid laser base material (laser medium), and a light-emitting center is added.

[0063] The resonator 20 has a first mirror (first reflection portion) 20A disposed on the excitation light source unit 18 side and a second mirror (second reflection portion) 20B disposed on the output side of the laser light L2. The first mirror 20A and the second mirror 20B only need to have transmittance and reflectance such that they function as a resonator for laser oscillation in the laser device 14.

[0064] The first mirror 20A transmits the excitation light L1 and reflects the laser light L2. The second mirror 20B reflects the laser light L2. For example, the reflectivity of the second mirror 20B with respect to the laser light L2 is about 80% - 95% in the case of CW and about 40% - 90% in the case of Q-switch. The first mirror 20A is, for example, a dielectric multilayer film formed on the first end face 4c of the substrate 4. The first mirror 20A is a dielectric multilayer film that functions as an AR coat with respect to the excitation light L1 and as an HR coat with respect to the laser light L2. The second mirror 20B is a dielectric multilayer film that functions as a PR coat (partial reflection coat) with respect to the laser light L2, for example.

[0065] The first mirror 20A and the second mirror 20B may be arranged away from the first end face 4c and the second end face 4d. Since the first mirror 20A and the second mirror 20B are dielectric multilayer films formed on the first end face 4c and the second end face 4d, a small-sized laser device 14 can be obtained.

[0066] The excitation light source unit 18 includes a light source unit 18A that outputs the excitation light L1 and a condensing optical system 18B that condenses the excitation light L1 so as to be incident on the waveguide 8. In FIG. 5, the condensing optical system 18B is schematically shown as a lens. An example of the light source unit 18A is a semiconductor laser element.

[0067] In the laser device 14 having the above configuration, the laser light L2 can be generated by outputting the excitation light L1 from the excitation light source unit 18.

[0068] The single crystal or ceramics that function as the solid laser base material has a higher thermal conductivity and stimulated emission cross-sectional area than glass. Further, in the optical element 2A, the confinement effect can be improved as described above. Therefore, it is possible to realize a laser device that satisfies at least one of small size, high efficiency, and high output by using the optical element 2A formed of a single crystal or ceramics.

[0069] The laser device 14 may further include a saturable absorber such as a Q-switch element. An example of the material of the saturable absorber is YAG added with Cr. The saturable absorber is disposed, for example, between the second end face 4d and the second mirror 20B. The saturable absorber may be bonded (for example, room temperature bonding) to the substrate 4. By providing the laser device 14 with the saturable absorber, the laser device 14 can output pulsed laser light. In this case, the laser device 14 can be used as a laser processing device.

[0070] For example, when using, as the optical element 2A, an optical element 2C having two waveguides 8 that are partially close to each other as shown in FIG. 4 instead of the optical element 2A, for example, excitation light may be incident on the waveguide 8, and the solid laser base material in the waveguide 8 may be excited by the excitation light leaking to the waveguide 8 side.

[0071] (Fifth Embodiment) Referring to FIG. 6, the optical element 2D according to the fifth embodiment will be described. The optical element 2D includes a substrate 4A and a heat sink 6, and a waveguide 8 is formed on the substrate 4A. Hereinafter, for convenience of explanation, in the fifth embodiment, as shown in FIG. 6, the X direction, the Y direction, and the Z direction may be used. The Z direction is the thickness direction of the substrate 4A. The X direction and the Y direction are directions orthogonal to the Z direction. In FIG. 6, the Y direction is the extending direction of the waveguide 8, and the X direction is a direction orthogonal to the Y direction. When the planar shape (shape viewed from the thickness direction) of the substrate 4A is rectangular, the Y direction is the longitudinal direction of the substrate 4A, and the X direction is the short side direction.

[0072] The material of the substrate 4A is a nonlinear optical crystal, and the substrate 4A has a quasi-phase matching (QPM) structure 22. Examples of the material of the substrate 4A include quartz and ferroelectric materials (for example, lithium niobate (LiNbO3)).

[0073] The pseudo-phase matching structure 22 has a plurality of polarity inversion regions 22a and a plurality of non-polarity inversion regions 22b. In FIG. 6, for convenience of explanation, the interface between the polarity inversion region 22a and the non-polarity inversion region 22b is shown by a solid line. The plurality of polarity inversion regions 22a and the plurality of non-polarity inversion regions 22b are arranged along one direction (in FIG. 6, the extending direction of the waveguide 8 or the longitudinal direction of the substrate 4A) such that the polarity inversion regions 22a and the non-polarity inversion regions 22b alternate with each other. The polarity axis of the polarity inversion region 22a and the polarity axis of the non-polarity inversion region 22b are, for example, in a state of being inverted by 180° with respect to each other. Each polarity inversion region 22a is provided from one side surface to the other side surface in the X direction and from the first main surface 4a to the second main surface 4b in the Z direction. The polarity inversion regions 22a and the non-polarity inversion regions 22b are arranged alternately in the Y direction. Also, the dimension along the X direction in each polarity inversion region 22a corresponds to the dimension of the substrate 4A along the X direction, and the depth along the Z direction in each polarity inversion region 22a corresponds to the thickness of the substrate 4A. Therefore, the light propagating in the waveguide 8 passes through all of the plurality of polarity inversion regions 22a.

[0074] The plurality of polarity inversion regions 22a are separated from each other via the non-polarity inversion regions 22b. That is, a non-polarity inversion region 22b is located between adjacent polarity inversion regions 22a. The plurality of polarity inversion regions 22a are arranged at predetermined positions derived from the refractive index dispersion of the crystal within the substrate 4A. In the fifth embodiment, the plurality of polarity inversion regions 22a are arranged periodically in the Y direction. The positions (or periods) of the plurality of polarity inversion regions 22a may be determined according to the wavelength and refractive index of the light.

[0075] When the material of the substrate 4 is quartz, each polarization inversion region 22a can be formed by heating the substrate 4 and applying stress thereto. In this case, the non-polarization inversion region 22b is a region where no stress application or the like is performed. When the material of the substrate 4A is a ferroelectric material, for example, each polarization inversion region 22a can be formed by applying an electric field. In this case, the non-polarization inversion region 22b is a region where no electric field is applied. For example, when room temperature bonding is employed as the bonding method between the substrate 4 and the heat sink 6, the substrate 4 which is quartz having a QPM structure and the heat sink 6 can be bonded in advance.

[0076] A waveguide 8 is formed in the substrate 4A. The method for forming the waveguide 8 is the same as in the case of the optical element 2A.

[0077] The optical element 2D is the same as the optical element 2A except that the substrate 4A is provided instead of the substrate 4. Therefore, the optical element 2D has the same operational effects as the optical element 2A.

[0078] The waveguide 8 formed in the substrate 4A having the quasi-phase matching structure 22 functions as a quasi-phase matching waveguide, and the optical element 2D functions as a QPM element. Therefore, the optical element 2D is used for optical harmonic generation, sum frequency generation, difference frequency generation, parametric optical amplification, parametric optical oscillation, ultra-high speed optical-optical switching, etc. In particular, due to the confinement effect of the waveguide 8, its wavelength conversion efficiency is improved. The optical element 2D can be used as a non-linear optical element required for high-performance optical parametric processes required for miniaturized high-power non-linear wavelength conversion, particularly for quantum optics (such as quantum communication and quantum computing). For example, the optical element 2D can be used instead of QPM elements used in a coherent optical engine, a quantum computer, a quantum sensor, a wavelength conversion device, a laser processing device, etc. Therefore, examples of optical devices provided with the optical element 2D include a coherent optical engine, a quantum computer, a quantum sensor, a wavelength conversion device, a laser processing device, etc.

[0079] When the material of the substrate 4A is quartz, since the optical element 2D as a QPM element has high light resistance and can transmit light up to short wavelengths, it is used in various high-output short-wavelength generation devices, laser processing devices, quantum computing devices that require high endurance, and devices that require multi-photon processes.

[0080] (Sixth Embodiment) As in the optical element 2E shown in FIG. 7, the optical element 2E may have a structure in which a light confinement member 5 having a reflection coating layer 24 and a heat sink 6 and a substrate 4 are laminated. The reflection coating layer 24 is optimally a dielectric multilayer film, for example, but a material having a refractive index lower than that of the substrate 4 and a thickness of about the wavelength to about one-tenth of the wavelength is sufficient. The reflection coating layer 24 may be any layer that can reflect the light to be propagated in the waveguide 8. The optical element 2E can be manufactured, for example, by forming the reflection coating layer 24 on the heat sink 6 or the substrate 4 and then laminating the substrate 4 and the heat sink 6 so as to sandwich the reflection coating layer 24 between the heat sink 6 and the substrate 4.

[0081] In the optical element 2E, the light propagating in the waveguide 8 is reflected by the reflection coating layer 24. Therefore, leakage of light from the heat sink 6 side can be further suppressed, and light can be efficiently propagated in the waveguide 8. In this way, the reflection coating layer 24 contributes to light confinement on the heat sink 6 side. Therefore, even when the refractive index difference between the heat sink 6 and the substrate 4 is small, the waveguide 8 can be formed. Since the reflection coating layer 24 contributes to light confinement on the heat sink 6 side, the refractive index of the heat sink 6 included in the optical element 2E can be made larger than that of the substrate 4. Therefore, the degree of freedom in selecting the materials of the substrate 4 and the heat sink 6 is improved. When the substrate 4 is a nonlinear material, the refractive index difference between the substrate 4 and the heat sink 6 tends to be small. Therefore, for example, when the substrate 4 is quartz, KTiPO4, KTiOAsO4, RbTiOAsO4, LiB3O5, BaB2O4, Ca(BO3)3F, CsLiB6O 10 In such cases, the configuration of the optical element 2E is more effective.

[0082] As described above, the present invention is not limited to the various exemplary embodiments illustrated, but includes the scope indicated by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0083] The optical element according to the present disclosure can be used instead of a conventional waveguide (including an optical fiber). Therefore, examples of the optical device including the optical element according to the present disclosure include, in addition to the examples shown in the above various embodiments, a laser measurement device, a laser inspection device, a laser diagnostic device, a laser medical device, an optical communication device, an optical information processing device, a device using laser light and applicable to the bio field, and the like.

[0084] Although the case where the light confinement member has a heat sink has been exemplified, the light confinement member does not necessarily have to have a heat sink as long as it can confine light in the waveguide. Therefore, for example, the reflection coating layer itself described in the sixth embodiment may be the light confinement member.

[0085] The various embodiments, modifications, etc. described above may be appropriately combined without departing from the spirit of the invention.

Explanation of Reference Numerals

[0086] 2A, 2B, 2C, 2D... optical element, 4, 4A... substrate, 4a... first main surface, 4b... second main surface, 5... light confinement member, 6... heat sink (light confinement member), 8... waveguide, 8a, 8b... side surfaces (a pair of side surfaces), 14... laser device (optical device), 22... quasi-phase matching structure, 24... reflection coating layer (light confinement member), PL... pulsed laser light.

Claims

1. A substrate having a first major surface and a second major surface opposite to the first major surface, the substrate being formed of a single crystal, ceramics or glass, An optical confinement member provided on the second major surface, comprising, A waveguide is formed in the substrate, Each of a pair of side surfaces intersecting in the extending direction of the waveguide and the thickness direction of the substrate is a modified surface where the substrate is modified, The modified surface extends from the first major surface to the second major surface, The refractive indices on both sides of each of the pair of side surfaces are the same, The substrate is formed of a solid laser base material, An optical element.

2. A substrate having a first major surface and a second major surface opposite to the first major surface, the substrate being formed of a single crystal, ceramics or glass, An optical confinement member provided on the second major surface, comprising, A waveguide is formed in the substrate, Each of a pair of side surfaces intersecting in the extending direction of the waveguide and the thickness direction of the substrate is a modified surface where the substrate is modified, The modified surface extends from the first major surface to the second major surface, The substrate is formed of a solid laser base material, An optical element.

3. The surface of the optical confinement member that is in contact with the second major surface is a flat surface, The optical element according to claim 1 or 2.

4. The characteristics of the surface of the optical confinement member that is in contact with the second major surface are uniform, The optical element according to any one of claims 1 to 3.

5. The optical confinement member is a heat sink having a refractive index smaller than that of the substrate, The optical element according to any one of claims 1 to 4.

6. The light confinement member has a reflective coating layer and a heat sink, The reflective coating layer is disposed between the second main surface and the heat sink. The optical element according to any one of claims 1 to 5.

7. The light confinement member has an intermediate layer in contact with the second main surface and a heat sink located opposite to the second main surface with respect to the intermediate layer, The intermediate layer is provided over the entire surface of the heat sink on the second main surface side. The optical element according to any one of claims 1 to 6.

8. An optical device including the optical element according to any one of claims 1 to 7.

9. A method for manufacturing an optical element having a waveguide, A lamination step of laminating the substrate and the light confinement member such that the light confinement member is disposed on the second main surface of a substrate having a first main surface and a second main surface opposite to the first main surface and formed of single crystal, ceramics or glass, A modification step of forming a pair of side surfaces intersecting the extending direction of the waveguide and the thickness direction of the substrate by modifying the substrate using pulsed laser light such that the refractive indices on both sides of each of the pair of side surfaces are the same, comprising The substrate is formed of a solid laser base material. A method for manufacturing an optical element.

10. A method for manufacturing an optical element having a waveguide, A lamination step of laminating the substrate and the light confinement member such that the light confinement member is disposed on the second main surface of a substrate having a first main surface and a second main surface opposite to the first main surface and formed of single crystal, ceramics or glass, A modification step of forming, on the substrate, a pair of side surfaces that intersect the extending direction of the waveguide and the thickness direction of the substrate by modifying the substrate using pulsed laser light; comprising; The substrate is formed of a solid laser base material. A method for manufacturing an optical element.

11. The pulse width of the pulsed laser light is from 0.2 ps to 10 ns. The method for manufacturing an optical element according to claim 9 or 10.

12. The pulse width of the pulsed laser light is from 1 ps to 1 ns. The method for manufacturing an optical element according to claim 9 or 10.

13. The light confinement member is a heat sink having a refractive index smaller than that of the substrate, In the lamination step, the heat sink is joined to the second main surface at room temperature. The method for manufacturing an optical element according to any one of claims 9 to 12.

14. The light confinement member has a heat sink, In the lamination step, after forming a reflective coating layer on the substrate or the heat sink, the substrate and the heat sink are laminated so that the reflective coating layer is sandwiched between the heat sink and the substrate. The method for manufacturing an optical element according to any one of claims 9 to 12.

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