Method for manufacturing a phase modulator for an optical phased array

Abstract

To provide a manufacturing method of a phase modulator for an optical phased array capable of preventing destruction of control circuits, etc. formed on the board without causing thermal damage to the board with a simple configuration.SOLUTION: A manufacturing method of a disclosed phase modulator for an optical phased array includes a precursor layer application step and a light irradiation step. The precursor layer application step applies a precursor layer 20 containing amorphous oxide directly or indirectly to the surface of a substrate 10. The infrared light irradiation step forms a crystallized nonlinear optical material layer 22 by irradiation with light 30 from the precursor layer 20 side while avoiding thermal damage to the substrate 10 and crystallizing the amorphous oxide in the precursor layer 20.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a phase modulator for an optical phased array, and more particularly to a method for manufacturing a phase modulator for an optical phased array that is capable of controlling the emission direction of a laser beam. [Background technology]

[0002] Light Detection and Ranging (LiDAR) sensors are used for remote sensing and ranging applications, such as detecting, tracking, and identifying objects, and performing real-time three-dimensional mapping in, for example, automotive driver assistance systems and / or autonomous driving systems.

[0003] A LiDAR sensor scans a space with a laser beam, irradiating the laser beam at an object in that space, and measures the distance to the object by measuring the time of flight (TOF) of the irradiated laser beam until it reflects off the object and returns to the LiDAR sensor.

[0004] LiDAR sensors include those that use mechanical rotating parts to scan a laser beam, and those that use solid-state beam scanners to scan a laser beam. For example, LiDAR sensors used in automotive driver assistance systems and / or autonomous driving systems must scan the laser beam at higher speeds than conventional LiDAR sensors. Furthermore, the sensors must be highly reliable, have a long lifespan, be small in size, and be lightweight. For such applications, LiDAR sensors that use solid-state beam scanners to scan a laser beam are useful.

[0005] An example of a solid-state beam scanner is an optical phased array (OPA), which includes a phase modulator that controls the emission direction of a laser beam.

[0006] For example, Patent Document 1 discloses an optical phased array including a phase modulator, and also discloses that the substrate of the phase modulator is made of any one of Si3N4, Si, SiON, LiNbO3, LiTaO3, and SiC. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2019 / 207638 Summary of the Invention [Problem to be solved by the invention]

[0008] A phase modulator includes a crystallized nonlinear optical material (hereinafter, sometimes referred to as a "crystallized nonlinear optical material"). In the phase modulator, a layer of the crystallized nonlinear optical material (hereinafter, sometimes referred to as a "crystallized nonlinear optical material layer") is applied to a substrate. The crystallized nonlinear optical material is obtained by crystallizing an amorphous oxide (including a complex oxide) as a precursor. The crystallization temperature is generally very high. The substrate is formed with various control circuits and other components required for the phase modulator. Therefore, applying a layer of the precursor (hereinafter, sometimes referred to as a "precursor layer") to the substrate and then crystallizing the precursor layer can cause thermal damage to the substrate, resulting in the destruction of the control circuits and other components formed on the substrate. In particular, when an LBO (Lithium Triborate or LiB3O5)-based material, which has a high crystallization temperature, is used, the thermal loss problem of the substrate is serious. To prevent this, conventional methods for manufacturing phase modulators involve preparing a crystallized nonlinear optical material layer in advance and then bonding it to the substrate. However, this bonding process requires many steps.

[0009] In view of these circumstances, the present inventors have discovered that there is a need for a simple method for manufacturing a phase modulator for an optical phased array that does not cause thermal damage to the substrate and that can avoid destruction of control circuits and the like formed on the substrate.

[0010] The present disclosure has been made to solve the above-mentioned problems. That is, an object of the present disclosure is to provide a simple method for manufacturing a phase modulator for an optical phased array that does not cause thermal damage to the substrate and that can avoid destruction of control circuits and the like formed on the substrate. [Means for solving the problem]

[0011] The present inventors have conducted extensive research to achieve the above object and have completed a method for manufacturing a phase modulator for an optical phased array according to the present disclosure. The method for manufacturing a phase modulator for an optical phased array according to the present disclosure includes the following aspects. <1> Applying a precursor layer containing an amorphous oxide directly or indirectly to a surface of a substrate; and irradiating the precursor layer with light from the precursor layer side to crystallize the amorphous oxide in the precursor layer while avoiding thermal damage to the substrate, thereby obtaining a crystallized nonlinear optical material layer; Including, A manufacturing method for a phase modulator for an optical phased array. <2> applying the precursor layer to the surface of the substrate via an underlayer; Including, The method for manufacturing a phase modulator for an optical phased array according to item <1>, wherein the light is infrared light, and the infrared light has a wavelength that does not cause thermal damage to the substrate and is capable of heating an underlayer in contact with the precursor with irradiation energy, thereby heating the precursor layer through the underlayer and crystallizing the amorphous oxide in the precursor layer. <3> The method for manufacturing a phase modulator for an optical phased array according to <2>, wherein a waveguide and an electrode are applied to a surface of the precursor layer or the crystallized nonlinear optical material layer opposite to the substrate. <4> applying the precursor layer to the surface of the substrate via a cladding layer and a waveguide; the light has a wavelength that does not crystallize the amorphous oxide in the precursor layer and heats the waveguide with the irradiation energy, thereby heating the precursor layer from the interface between the waveguide and the precursor layer and crystallizing the amorphous oxide in the precursor layer from the interface, while the cladding layer shields the irradiation energy of the light, thereby avoiding thermal damage to the substrate; A method for manufacturing a phase modulator for an optical phased array according to item <1>. <5> The method for manufacturing a phase modulator for an optical phased array according to <4>, wherein the cladding layer contains silicon dioxide. <6> The method for manufacturing a phase modulator for an optical phased array according to <4> or <5>, wherein the waveguide contains an amorphous silicon semiconductor, and the light has a wavelength that can heat the waveguide and avoid thermal damage to the substrate. <7> The method for manufacturing a phase modulator for an optical phased array according to any one of <4> to <6>, wherein an electrode is applied to a surface of the cladding layer opposite to the substrate. <8> The method for manufacturing a phase modulator for an optical phased array according to any one of <1> to <7>, wherein the amorphous oxide contains SrO, TiO2, and SiO2. <9> The method for manufacturing a phase modulator for an optical phased array according to any one of <1> to <8>, wherein the amorphous oxide contains BaO, TiO2, and GeO2. <10> The method for manufacturing a phase modulator for an optical phased array according to item <9>, wherein B2O3 is further mixed with a BaO-TiO2-GeO2-based amorphous oxide containing BaO, TiO2, and GeO2, and the mixing ratio is (BaO-TiO2-GeO2-based amorphous oxide):(B2O3)=1:x in molar ratio, where x is 1 to 10. [Effects of the Invention]

[0012] According to the present disclosure, a substrate to which a precursor layer is directly or indirectly applied is irradiated with light from the precursor layer side to crystallize the amorphous oxide in the precursor layer, thereby providing a simple method for manufacturing a phase modulator for an optical phased array that is capable of avoiding destruction of control circuits and the like formed on the substrate without causing thermal damage to the substrate. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a cross-sectional view illustrating an example of heating an amorphous oxide in a precursor layer with irradiation energy of infrared light in the production method of the present disclosure. [Figure 2] FIG. 2 is a schematic diagram illustrating an example of a manufacturing method according to the present disclosure in which the waveguide is heated by infrared light irradiation energy, and the precursor layer is heated from the interface between the waveguide and the precursor layer. [Figure 3A] FIG. 3A is a graph showing an example of the relationship between wavelength and light absorption coefficient for light used in the manufacturing method of the present disclosure. [Figure 3B]FIG. 3B is a graph showing another example of the relationship between wavelength and light absorption coefficient for light used in the manufacturing method of the present disclosure. [Figure 4] FIG. 4 is a flowchart showing an example of the embodiment (first embodiment) shown in FIG. [Figure 5] FIG. 5 is a schematic diagram showing an outline of the device used to evaluate the SHG characteristics. [Figure 6] FIG. 6 is a graph showing the relationship between the rotation angle and the SHG intensity for the samples of Examples 3 and 4. [Figure 7] FIG. 7 is an explanatory diagram that schematically shows the structure of the crystallized nonlinear optical material, which is estimated from the graph of FIG. [Figure 8] FIG. 8 is a graph showing the relationship between the rotation angle and the SHG intensity for the samples of Examples 5 and 6. [Figure 9] FIG. 9 is an explanatory diagram that schematically shows the structure of the crystallized nonlinear optical material, which is estimated from the graph of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of a manufacturing method for a phase modulator for an optical phased array according to the present disclosure (hereinafter, sometimes referred to as the "manufacturing method according to the present disclosure") will be described in detail. Note that the embodiments described below do not limit the manufacturing method according to the present disclosure.

[0015] The reason why the manufacturing method of the present disclosure can crystallize an amorphous oxide in a precursor layer applied directly or indirectly to a substrate without causing thermal damage to the substrate and while avoiding destruction of control circuits and the like formed on the substrate will be explained using drawings. Note that, in this specification, "thermal damage" means that the substrate is damaged by heat to the extent that the resulting optical phased array becomes unusable.

[0016] Fig. 1 is a cross-sectional schematic diagram illustrating an example of an embodiment in which an amorphous oxide in a precursor layer is heated by infrared light irradiation energy in the manufacturing method of the present disclosure. Fig. 2 is a schematic diagram illustrating an example of an embodiment in which a waveguide is heated by infrared light irradiation energy, and the precursor layer is heated from the interface between the waveguide and the precursor layer in the manufacturing method of the present disclosure. Fig. 3A is a graph showing an example of the relationship between wavelength and optical absorption coefficient for light used in the manufacturing method of the present disclosure. Fig. 3B is a graph showing another example of the relationship between wavelength and optical absorption coefficient for light used in the manufacturing method of the present disclosure.

[0017] 1 and 2, a precursor layer 20 is applied directly or indirectly to the surface of a substrate 10. In both embodiments, light 30 is applied from the precursor layer 20 side (upper side in the drawing) rather than from the substrate 10 side (lower side in the drawing).

[0018] In the embodiment shown in FIG. 1 , the precursor layer 20 is indirectly applied to the surface of the substrate 10, so an underlayer 40 exists between the substrate 10 and the precursor layer 20. The underlayer 40 will be described in more detail later. When light 30 is irradiated from the precursor layer 20 side, the substrate 10 is also affected by the irradiation energy of light 30. In the embodiment shown in FIG. 1 , light 30 is typically infrared light. Because the crystallization temperature of the amorphous oxide in the precursor layer 20 is very high, a large amount of light irradiation energy is required to crystallize the amorphous oxide in the precursor layer 20. Therefore, light with a large irradiation energy is required. Not all of the light is absorbed by the thin precursor and passes through to the substrate. If the substrate absorbs this light, it will be heated and damaged. Therefore, to prevent thermal damage to the substrate 10 when light 30 is irradiated, light 30 has a wavelength indicated by arrow A in FIG. 3A or 3B . That is, the light 30 has a wavelength that is not absorbed by the substrate, and the irradiation energy of the light 30 has a wavelength that does not thermally damage the substrate 10 and can heat the underlayer 40 .

[0019] In the embodiment shown in Fig. 2, precursor layer 20 is applied to the surface of substrate 10 via cladding layer 50 and waveguide 60, and light 30 having a wavelength indicated by arrow B in Fig. 3A or 3B is irradiated from the precursor layer 20 side. Light 30 having the wavelength indicated by arrow B has irradiation energy that heats waveguide 60 without crystallizing the amorphous oxide in precursor layer 20. In this manner, precursor layer 20 is heated from the interface between waveguide 60 and precursor layer 20, and the amorphous oxide in precursor layer 20 is crystallized.

[0020] In the embodiment shown in FIG. 2 , without being bound by theory, it is believed that heating of the precursor layer 20 from the interface between the waveguide 60 and the precursor layer 20 is achieved by heat transfer from the heated waveguide 60 to the precursor layer 20. Furthermore, because the cladding layer 50 is generally an oxide, the light 30 having the wavelength indicated by arrow B in FIGS. 3A and 3B does not heat the cladding layer 50 with its irradiation energy. Furthermore, the cladding layer 50 has a thickness comparable to or thicker than the precursor layer 20. Therefore, even if light 30 is irradiated from the precursor layer 20 side, the cladding layer 50 blocks the irradiation energy of the light 30. As a result, the substrate 10 is not affected by the irradiation energy of the infrared light, or even if it is affected, the effect is within a practically negligible range, and thermal damage to the substrate 10 is avoided. In this specification, unless otherwise specified, "blocking the irradiation energy of the light" means preventing the transmission of the irradiation energy of the light.

[0021] Next, the constituent elements of the manufacturing method of the optical phased array according to the present disclosure, which has been completed based on the findings and the like described above, will be described.

[0022] <<Method for manufacturing optical phased array>> The manufacturing method of the phase modulator for an optical phased array disclosed herein (hereinafter, sometimes simply referred to as the "manufacturing method of the present disclosure") includes a precursor layer application step and an infrared light irradiation step. Each step will be described below.

[0023] <Precursor layer application process> A precursor layer containing an amorphous oxide is applied directly or indirectly to the surface of a substrate. This will be described separately for the embodiment shown in Fig. 1 (hereinafter sometimes referred to as "first embodiment") and the embodiment shown in Fig. 2 (hereinafter sometimes referred to as "second embodiment").

[0024] [First aspect] As shown in FIG. 1, a precursor layer 20 is applied to the surface of a substrate 10 indirectly through an underlayer 40 .

[0025] The substrate 10 contains Si (silicon semiconductor), Si3N4, SiON, LiNbO3, LiTaO3, SiC, and the like. It may also contain a combination of these. It may also contain unavoidable impurities. Unless otherwise specified, in this specification, unavoidable impurities refer to impurity elements whose inclusion cannot be avoided during the manufacture of raw materials and / or optical phased array phase modulators, or whose avoidance would result in a significant increase in manufacturing costs.

[0026] A control circuit and the like (not shown) are formed on the substrate 10. A known method can be used to form the control circuit and the like. Examples of methods for forming the control circuit and the like include printing and etching, and these may be combined.

[0027] The thickness of the substrate 10 may typically be 250 μm or more, 280 μm or more, 300 μm or more, or 400 μm or more, and may be 800 μm or less, 776 μm or less, 725 μm or less, 700 μm or less, 600 μm or less, or 500 μm or less.

[0028] The precursor layer 20 contains an amorphous oxide. The amorphous oxide crystallizes during the infrared light irradiation process described below. Examples of such amorphous oxides include SrO, TiO, SiO, BaO, and GeO, and combinations of these may also be used. In addition to the amorphous oxide, the precursor layer 20 may also contain unavoidable impurities.

[0029] When the above-mentioned amorphous oxides are combined, an amorphous oxide containing 30 mol% or more, 32 mol% or more, or 34 mol% or more and 40 mol% or less, 38 mol% or less, or 36 mol% or less of SrO, 15 mol% or more, 17 mol% or more, or 19 mol% or more and 25 mol% or less, 23 mol% or less, or 21 mol% or less of TiO2, and 40 mol% or more, 42 mol% or more, or 44 mol% or more and 50 mol% or less, 48 mol% or less, or 46 mol% or less of SiO2 is particularly preferred, and a typical example may be 35 mol%SrO-20 mol%TiO2-45 mol%SiO2. Also preferred is an amorphous oxide containing 35 mol% or more, 37 mol% or more, or 39 mol% or more and 45 mol% or less, 43 mol% or less, or 41 mol% or less BaO, 15 mol% or more, 17 mol% or more, or 19 mol% or more and 25 mol% or less, 23 mol% or less, or 21 mol% or less TiO2, and 35 mol% or more, 37 mol% or more, or 39 mol% or more and 45 mol% or less, 43 mol% or less, or 41 mol% or less GeO2, and typically may be 40 mol% BaO-20 mol% TiO2-40 mol% GeO2.

[0030] The method for applying the precursor layer 20 is not particularly limited as long as the amorphous oxide in the precursor layer 20 can be applied to the surface of the substrate 10 while remaining amorphous. Examples of methods for applying the precursor layer 20 include electron beam evaporation, sputtering, and pulsed laser ablation. These methods may also be combined.

[0031] The thickness of the precursor layer 20 may typically be 100 nm or more, 200 nm or more, 300 nm or more, 400 nm or more, or 450 nm or more, and may be 1000 nm or less, 990 nm or less, 900 nm or less, 800 nm or less, 700 nm or less, 600 nm or less, or 550 nm or less. In the infrared light irradiation step described below, the amorphous oxide in the precursor layer 20 is crystallized to obtain a crystallized nonlinear optical material layer 22, and the thickness of the crystallized nonlinear optical material layer 22 is substantially the same as the thickness of the precursor layer 20.

[0032] In the embodiment shown in FIG. 1 , the precursor layer 20 is applied indirectly to the surface of the substrate 10 via the underlayer 40. The underlayer 40 is expected to have the following effects: The conductivity of the underlayer 40 causes it to absorb infrared light transmitted through the precursor layer 20, heating the underlayer 40. Heat is transferred from the heated underlayer 40 to the precursor layer 20, heating the precursor layer 20 and crystallizing the amorphous oxide in the precursor layer 20, thereby obtaining the crystallized nonlinear optical material layer 22. Furthermore, heating the underlayer 40 causes interdiffusion of atoms between the substrate 10 and the crystallized nonlinear optical material layer 22 derived from the precursor layer 20, improving adhesion between the substrate 10 and the crystallized nonlinear optical material layer 22.

[0033] The underlayer 40 typically contains a conductive material and may contain inevitable impurities in addition to the conductive material. Examples of the underlayer 40 include Au, Al, Ag, and Ti, and combinations of these may also be used. These may be metals or alloys. Note that "metal" refers to unalloyed metals.

[0034] There are no particular limitations on the method for applying the underlayer 40, and examples include ion implantation, electron beam evaporation, sputtering, and pulsed laser ablation, or a combination of these.

[0035] The thickness of the underlayer 40 may typically be 3 nm or more, 5 nm or more, 10 nm or more, 20 nm or more, 30 nm or more, or 40 nm or more, or may be 100 nm or less, 90 nm or less, 80 nm or less, 70 nm or less, 60 nm or less, or 50 nm or less. After the infrared light irradiation step described below, the thickness of the underlayer 40 is substantially the same as that before the infrared light irradiation step.

[0036] [Second aspect] As shown in FIG. 2, a precursor layer 20 is applied to the surface of a substrate 10 via a cladding layer 50 and a waveguide 60 .

[0037] The substrate 10 contains Si, Si3N4, SiON, LiNbO3, LiTaO3, SiC, or the like, or may contain a combination of these, or may contain unavoidable impurities in addition to these.

[0038] A control circuit and the like (not shown) are formed on the substrate 10. A known method can be used to form the control circuit and the like. Examples of methods for forming the control circuit and the like include printing and etching, and these may be combined.

[0039] The thickness of the substrate 10 may typically be 250 μm or more, 280 μm or more, 300 μm or more, or 400 μm or more, and may be 800 μm or less, 776 μm or less, 725 μm or less, 700 μm or less, 600 μm or less, or 500 μm or less.

[0040] The precursor layer 20 contains amorphous oxides. The amorphous oxides are crystallized during the infrared light irradiation process described below. Examples of such amorphous oxides include SrO, TiO, SiO, BaO, and GeO, and combinations of these may also be used. In addition to such amorphous oxides, the precursor layer 20 may also contain unavoidable impurities.

[0041] When the above-mentioned amorphous oxides are combined, an amorphous oxide containing 30 mol% or more, 32 mol% or more, or 34 mol% or more and 40 mol% or less, 38 mol% or less, or 36 mol% or less of SrO, 15 mol% or more, 17 mol% or more, or 19 mol% or more and 25 mol% or less, 23 mol% or less, or 21 mol% or less of TiO2, and 40 mol% or more, 42 mol% or more, or 44 mol% or more and 50 mol% or less, 48 mol% or less, or 46 mol% or less of SiO2 is particularly preferred, and a typical example may be 35 mol%SrO-20 mol%TiO2-45 mol%SiO2. Also preferred is an amorphous oxide containing 35 mol% or more, 37 mol% or more, or 39 mol% or more and 45 mol% or less, 43 mol% or less, or 41 mol% or less BaO, 15 mol% or more, 17 mol% or more, or 19 mol% or more and 25 mol% or less, 23 mol% or less, or 21 mol% or less TiO2, and 35 mol% or more, 37 mol% or more, or 39 mol% or more and 45 mol% or less, 43 mol% or less, or 41 mol% or less GeO2, and typically may be 40 mol% BaO-20 mol% TiO2-40 mol% GeO2.

[0042] The method for applying the precursor layer 20 is not particularly limited as long as the amorphous oxide in the precursor layer 20 can be applied to the surface of the substrate 10 while remaining amorphous. Methods for applying the precursor layer include electron beam evaporation, sputtering, and pulsed laser ablation. These methods may also be combined.

[0043] The thickness of the precursor layer 20 may typically be 100 nm or more, 200 nm or more, 300 nm or more, 400 nm or more, or 450 nm or more, and may be 1000 nm or less, 990 nm or less, 900 nm or less, 800 nm or less, 700 nm or less, 600 nm or less, or 550 nm or less. In the infrared light irradiation step described below, the amorphous oxide in the precursor layer 20 is crystallized to obtain a crystallized nonlinear optical material layer 22, and the thickness of the crystallized nonlinear optical material layer 22 is substantially the same as the thickness of the precursor layer 20.

[0044] 2, the precursor layer 20 is applied indirectly to the surface of the substrate 10 via the cladding layer 50 and the waveguide 60. The substrate 10 is in contact with the cladding layer 50, and the precursor layer 20 is in contact with the waveguide 60. The reason for this will be explained in the "<Infrared Light Irradiation Step>" section below.

[0045] There are no particular restrictions on the cladding layer 50 as long as it has low conductivity and a refractive index smaller than that of the waveguide. For example, if the substrate 10 contains Si (silicon semiconductor, refractive index 3.82), the cladding layer 50 preferably contains SiO2 (silicon dioxide, refractive index 1.45). The cladding layer 50 may contain unavoidable impurities in addition to oxides.

[0046] There are no particular limitations on the method for applying the cladding layer 50, and examples include electron beam evaporation, sputtering, and pulsed laser ablation, or a combination of these.

[0047] The thickness of the cladding layer 50 may typically be 100 nm or more, 200 nm or more, 300 nm or more, 400 nm or more, 500 nm or more, 600 nm or more, 700 nm or more, 800 nm or more, 900 nm or more, 1000 nm or more, 1200 nm or more, 1400 nm or more, 1600 nm or more, 1800 nm or more, or 2000 nm or more, or 4000 nm or less, 3800 nm or less, 3600 nm or less, 3400 nm or less, 3200 nm or less, 3000 nm or less, 2800 nm or less, 2600 nm or less, 2400 nm or less, or 2200 nm or less. The thickness of the cladding layer 50 after the infrared light irradiation step described below is substantially the same as that before the infrared light irradiation step.

[0048] The waveguide 60 is not particularly limited as long as it functions as a waveguide of a phase modulator for an optical phased array, and typically contains a semiconductor. The waveguide 60 may contain unavoidable impurities in addition to the semiconductor. Typical semiconductors include a-Si (amorphous silicon), a-Si:H (hydrogenated amorphous silicon), p + -Si (p-type silicon), n --Si (n-type silicon), poly-Si (polycrystalline silicon), and c-Si (crystalline silicon).

[0049] There is no particular limitation on the method for applying the waveguide 60, and examples thereof include electron beam evaporation, sputtering, and pulsed laser ablation, or a combination of these.

[0050] The thickness of the waveguide 60 may typically be 10 nm or more, 20 nm or more, 30 nm or more, 40 nm or more, or 45 nm or more, and may be 200 nm or less, 180 nm or less, 160 nm or less, 140 nm or less, 120 nm or less, 100 nm or less, 90 nm or less, 80 nm or less, 70 nm or less, 60 nm or less, 55 nm or less, or 50 nm or less.

[0051] <Infrared light irradiation process> Light 30 is irradiated from the precursor layer 20 side to crystallize the amorphous oxide in the precursor layer 20 while avoiding thermal damage to the substrate 10, thereby obtaining a crystallized nonlinear optical material layer 22. This will be described separately in a first embodiment and a second embodiment.

[0052] [First aspect] 1, light 30 is irradiated from the precursor layer 20 side to crystallize the amorphous oxide in the precursor layer 20 while avoiding thermal damage to the substrate 10, thereby obtaining a crystallized nonlinear optical material layer 22. In the embodiment shown in FIG. 1, an underlayer 40 is present, but as described above, the underlayer 40 may not be present.

[0053] In the first embodiment, light 30 having a wavelength indicated by arrow A in Fig. 3A or 3B is irradiated. Specifically, light 30 having an irradiation energy that does not thermally damage substrate 10 and that heats and crystallizes the amorphous oxide in precursor layer 20 is irradiated.

[0054] Here, "a wavelength at which the irradiation energy of light 30 does not cause thermal damage to substrate 10" means a wavelength at which substrate 10 does not absorb light 30, or at which, even if substrate 10 absorbs light 30, the heating of substrate 10 due to the absorption does not cause thermal damage to substrate 10. Furthermore, "a wavelength at which the irradiation energy of light 30 heats and crystallizes the amorphous oxide in precursor layer 20" means a wavelength at which, when precursor layer 20 absorbs light 30 and heats the amorphous oxide in precursor layer 20, the degree of absorption of light 30 crystallizes the amorphous oxide.

[0055] The wavelength of such light 30 (the wavelength indicated by arrow A in FIG. 3A or 3B) may typically be 3000 nm or more, 3500 nm or more, 4000 nm or more, or 5000 nm or more. As long as the wavelength satisfies the above-mentioned wavelength, the wavelength is not particularly limited as long as it is infrared light (including far-infrared light), and may be 12000 nm or less, 10000 nm or less, 9000 nm or less, 8000 nm or less, 7000 nm or less, or 6000 nm or less.

[0056] 1, when light 30 having the above-mentioned wavelength is irradiated from the precursor layer 20 side, thermal damage is not caused to the substrate 10. At the same time, the precursor layer 20 is heated from the side irradiated with light 30 (the upper side in FIG. 1) by the irradiation energy of light 30, and the amorphous oxide in the precursor layer 20 is crystallized from the side irradiated with light 30 (the upper side in FIG. 1), thereby obtaining a crystallized nonlinear optical material layer 22.

[0057] The type of light 30 is not particularly limited as long as it satisfies the above-mentioned wavelength, but typically, the light 30 is infrared light, particularly infrared laser light or continuous infrared laser. The irradiation intensity and irradiation time of the light 30 may be appropriately determined taking into consideration the thickness of the precursor layer 20, etc. The irradiation intensity of the light 30 is, for example, 100 W / cm 2 More than 200W / cm 2 More than 300W / cm 2 or more than 350W / cm 2 may be greater than or equal to 100,000 W / cm 2 Below, 50000W / cm 2Below, 10000W / cm 2 Below, 5000W / cm 2 Below, 4000W / cm 2 Below, 3000W / cm 2 Below, 2000W / cm 2 Below, 1000W / cm 2 Below, 500W / cm 2 or less, or 400W / cm 2 The irradiation time of the light 30 may be, for example, 1 μsec or more, 10 μsec or more, 100 μsec or more, 1000 μsec or more, 10,000 μsec or more, 100,000 μsec or more, or 1 second or more, and may be 10 seconds or less, 8 seconds or less, 6 seconds or less, 4 seconds or less, or 2 seconds or less.

[0058] [Second aspect] As shown in FIG. 2, light 30 is irradiated from the precursor layer 20 side to crystallize the amorphous oxide in the precursor layer 20 while avoiding thermal damage to the substrate 10, thereby obtaining a crystallized nonlinear optical material layer 22.

[0059] In the second embodiment, light 30 having a wavelength indicated by arrow B in Fig. 3A or 3B is irradiated. Specifically, light 30 is irradiated with energy having a wavelength that does not directly heat the amorphous oxide in precursor layer 20 but directly heats waveguide 60.

[0060] Here, "a wavelength at which the irradiating energy of light 30 does not crystallize the amorphous oxide in the precursor layer 20" refers to a wavelength at which the amorphous oxide in the precursor layer 20 does not absorb light 30, or at which the amorphous oxide in the precursor layer 20 absorbs light 30 but the heating of the amorphous oxide in the precursor layer 20 due to the absorption does not crystallize the amorphous oxide in the precursor layer 20. Furthermore, "a wavelength at which the irradiating energy of light 30 heats the waveguide 60" refers to a wavelength at which the waveguide 60 absorbs light 30 and heats the waveguide 60 to the extent described below. That is, the wavelength is such that heating the waveguide 60 heats the precursor layer 20 from the interface between the waveguide 60 and the precursor layer 20, crystallizing the amorphous oxide in the precursor layer 20 from the interface, while the cladding layer 50 shields the irradiating energy of light 30, thereby avoiding thermal damage to the substrate 10. Ideally, the cladding layer 50 completely blocks the irradiation energy of the light 30, but complete blocking is not necessary; the blocking should be to the extent that the substrate 10 is not thermally damaged.

[0061] Such light 30 (wavelength indicated by arrow B in FIG. 3A or FIG. 3B ) may typically be 400 nm or more, 450 nm or more, 500 nm or more, or 550 nm or more, and may be 3000 nm or less, 2500 nm or less, 2000 nm or less, 1500 nm or less, 1000 nm or less, 900 nm or less, 800 nm or less, 700 nm or less, or 600 nm or less. As shown by arrow B in FIG. 3A and FIG. 3B , when the waveguide 60 contains a-Si:H or a-Si, light 30 having a wavelength capable of directly heating the waveguide 60 and avoiding thermal damage to the substrate 10 can be selected. Note that “direct heating” refers to heating due to absorption of the irradiation energy of light 30. Furthermore, “thermal damage” refers to thermal damage to the substrate to the extent that the resulting optical phased array becomes unusable. And, "amorphous silicon semiconductor" means at least one of a-Si:H and a-Si.

[0062] The type of light 30 is not particularly limited as long as it satisfies the above wavelength, but typically the type of light 30 is visible light or ultraviolet light. The irradiation intensity and irradiation time of the light 30 may be appropriately determined taking into consideration the thickness of the precursor layer 20, etc. The irradiation intensity of the light 30 is, for example, 100 W / cm 2 More than 200W / cm 2 More than 300W / cm 2 or more than 350W / cm 2 may be greater than or equal to 100,000 W / cm 2 Below, 50000W / cm 2 Below, 10000W / cm 2 Below, 5000W / cm 2 Below, 4000W / cm 2 Below, 3000W / cm 2 Below, 2000W / cm 2 Below, 1000W / cm 2 Below, 500W / cm 2 or less, or 400W / cm 2 The irradiation time of the light 30 may be, for example, 1 μsec or more, 10 μsec or more, 100 μsec or more, 1000 μsec or more, 10,000 μsec or more, 100,000 μsec or more, or 1 second or more, and may be 10 seconds or less, 8 seconds or less, 6 seconds or less, 4 seconds or less, or 2 seconds or less.

[0063] <Other processes> In addition to the precursor layer application step and light irradiation step described above, the following steps may be included, which will be described separately for a first embodiment and a second embodiment.

[0064] [First aspect] 1, after the amorphous oxide in the precursor layer 20 is crystallized, the waveguide 60 and the electrode 70 may be applied to the surface of the crystallized nonlinear optical material layer 22 opposite the substrate 10, but this is not limiting. For example, the waveguide 60 and the electrode 70 may be applied to the surface of the precursor layer 20 opposite the substrate 10 before the amorphous oxide in the precursor layer 20 is crystallized.

[0065] There is no particular limitation on the method for applying the waveguide 60 and the electrode 70. Examples of methods for applying the waveguide 60 and the electrode 70 include electron beam evaporation, sputtering, and pulsed laser ablation. These methods may also be combined.

[0066] The waveguide 60 is not particularly limited as long as it functions as a waveguide of a phase modulator for an optical phased array, and typically contains a semiconductor. The waveguide 60 may contain inevitable impurities in addition to the semiconductor. Typical semiconductors include a-Si (amorphous silicon), a-Si:H (hydrogenated amorphous silicon), p + -Si (p-type silicon), n - -Si (n-type silicon), poly-Si (polycrystalline silicon), and c-Si (crystalline silicon).

[0067] The thickness of the waveguide 60 may typically be 10 nm or more, 20 nm or more, 30 nm or more, 40 nm or more, or 45 nm or more, and may be 200 nm or less, 180 nm or less, 160 nm or less, 140 nm or less, 120 nm or less, 100 nm or less, 90 nm or less, 80 nm or less, 70 nm or less, 60 nm or less, 55 nm or less, or 50 nm or less.

[0068] The electrode 70 is not particularly limited as long as it functions as a waveguide for the optical phased array phase modulator, and contains a conductive material. In addition to the conductive material, it may contain unavoidable impurities. A typical example of the electrode 70 is Al. Al may be metallic Al or an alloy with other elements. Note that "metallic Al" means unalloyed Al.

[0069] The thickness of the electrode 70 may typically be 10 nm or more, 30 nm or more, 50 nm or more, 70 nm or more, 90 nm or more, 100 nm or more, 200 nm or more, 300 nm or more, or 400 nm or more, and may be 1000 nm or less, 900 nm or less, 800 nm or less, 700 nm or less, 600 nm or less, or 500 nm or less.

[0070] 1, optionally, after the amorphous oxide in the precursor layer 20 is crystallized, a clad layer 50 may be applied to the surface of the crystallized nonlinear optical material layer 22 opposite the substrate 10, but this is not limiting. For example, before the amorphous oxide in the precursor layer 20 is crystallized, the clad layer 50 may be applied to the surface of the precursor layer 20 opposite the substrate 10. The clad layer 50 can suppress discharge and efficiently modulate the phase.

[0071] There is no particular limitation on the method for applying the cladding layer 50. Examples of methods for applying the cladding layer 50 include electron beam evaporation, sputtering, and pulsed laser ablation, and these methods may also be combined.

[0072] The cladding layer 50 is not particularly limited as long as it functions as a cladding layer of the optical phased array phase modulator, and typically contains an oxide. The cladding layer 50 may contain unavoidable impurities in addition to the oxide. A typical example of the oxide is SiO2 (silicon dioxide).

[0073] The thickness of the cladding layer 50 may typically be 100 nm or more, 300 nm or more, 500 nm or more, 700 nm or more, 900 nm or more, 1100 nm or more, 1300 nm or more, 1500 nm or more, 1700 nm or more, or 1900 nm or more, and may be 4000 nm or less, 3500 nm or less, 3000 nm or less, 2500 nm or less, 2300 nm or less, 2100 nm or less, or 2000 nm or less.

[0074] An example of the first embodiment described above is shown in a flowchart in FIG. 4, but as mentioned above, the present invention is not limited to this.

[0075] [Second aspect] 2, an electrode 70 may be applied to the surface of the cladding layer 50 opposite the substrate 10 before or during irradiation with light 30, but is not limited to this. For example, the precursor layer 20 may be applied to the substrate 10 via the cladding layer 50 and the waveguide 60, and then irradiated with light 30 to crystallize the amorphous oxide in the precursor layer 20, after which the electrode 70 may be applied to the surface of the cladding layer 50 opposite the substrate 10.

[0076] There is no particular limitation on the method for applying the electrode 70. Examples of methods for applying the electrode 70 include electron beam evaporation, sputtering, and pulsed laser ablation. These methods may also be combined.

[0077] The electrode 70 is not particularly limited as long as it functions as an electrode of the optical phased array phase modulator, and contains a conductive material. In addition to the conductive material, it may contain unavoidable impurities. A typical example of the electrode 70 is Al. Al may be metallic Al or an alloy with other elements. Note that "metallic Al" means unalloyed Al.

[0078] The thickness of the electrode 70 may typically be 10 nm or more, 30 nm or more, 50 nm or more, 70 nm or more, 90 nm or more, 100 nm or more, 200 nm or more, 300 nm or more, or 400 nm or more, and may be 1000 nm or less, 900 nm or less, 800 nm or less, 700 nm or less, 600 nm or less, or 500 nm or less.

[0079] Transform In addition to what has been described above, various modifications can be made to the manufacturing method of the present disclosure within the scope of the claims.

[0080] For example, when an amorphous oxide containing 35 mol% or more, 37 mol% or more, or 39 mol% or more and 45 mol% or less, 43 mol% or less, or 41 mol% or less of BaO, 15 mol% or more, 17 mol% or more, or 19 mol% or more and 25 mol% or less, 23 mol% or less, or 21 mol% or less of TiO, and 35 mol% or more, 37 mol% or more, or 39 mol% or more and 45 mol% or less, 43 mol% or less, or 41 mol% or less of GeO (hereinafter sometimes referred to as a "BaO-TiO-GeO-based amorphous oxide") is selected as the amorphous oxide in the precursor layer 20, even when B2O3 is mixed, BaO-TiO-GeO-B2O3 can be used to obtain an optical phase modulator that does not cause thermal damage to the substrate and avoids destruction of control circuits and the like formed on the substrate. The BaO-TiO2-GeO2 amorphous oxide is typically, but not limited to, 40 mol % BaO-20 mol % TiO2-40 mol % GeO2.

[0081] When B2O3 is mixed with a BaO-TiO2-GeO2-based amorphous oxide, the molar ratio of the mixture (BaO-TiO2-GeO2-based amorphous oxide):(B2O3)=1:x may be 1 or more, 2 or more, 3 or more, 4 or more, or 5 or more, and may be 10.0 or less, 9.5 or less, 9.0 or less, 8.5 or less, 8.0 or less, or 7.5 or less. When B2O3 is mixed, uniaxial crystal growth becomes prominent during crystallization. As a result, nonlinear optical properties are further improved, and more efficient phase modulation is possible. [Example]

[0082] The production method of the present disclosure will be explained in more detail below with reference to examples. Note that the production method of the present disclosure is not limited to the conditions used in the following examples.

[0083] <Sample Preparation> The samples of Examples 1 to 7 were prepared as follows.

[0084] Example 1 A sample of a phase modulator for an optical phased array was prepared in the manner shown in Figures 1 and 4. The substrate 10 was a Si substrate with a thickness of 725 μm. The precursor layer 20 was 35 mol % SrO-20 mol % TiO2-45 mol % SiO2 with a thickness of 500 nm. The underlayer 40 was metallic Au with a thickness of 5 nm. The waveguide 60 was a-Si (amorphous silicon) with a thickness of 50 nm. The electrode 70 was metallic Al with a thickness of 100 nm. The cladding layer 80 was silicon dioxide (SiO2) with a thickness of 2000 nm. The irradiated light 30 was a continuous infrared laser with a wavelength of 5000 nm and an irradiation intensity of 400 W / cm. 2 and the exposure time was 1 ms.

[0085] Example 2 A sample of Example 2 was prepared in the same manner as Example 1, except that the precursor layer 20 was 40 mol % BaO-20 mol % TiO2-40 mol % GeO2 with a thickness of 500 nm.

[0086] Example 3 The precursor layer 20 was prepared by mixing 40 mol% BaO-20 mol% TiO2-40 mol% GeO2 with B2O3, and the mixture ratio (molar ratio) was expressed as (40 mol% BaO-20 mol% TiO2-40 mol% GeO2):B2O3=1:x, where x=5. The sample of Example 3 was prepared in the same manner as Example 2, except that

[0087] Example 4 A sample of Example 4 was prepared in the same manner as in Example 2, except that when B2O3 was mixed, x was 10 for (40 mol % BaO-20 mol % TiO2-40 mol % GeO2):B2O3=1:x.

[0088] Example 5 A sample of Example 5 was prepared in the same manner as in Example 2, except that when B2O3 was mixed, x was 1 for 40 mol % BaO-20 mol % TiO2-40 mol % GeO2):B2O3=1:x.

[0089] Example 6 A sample of Example 6 was prepared in the same manner as in Example 2, except that when B2O3 was mixed, x was 3 for 40 mol % BaO-20 mol % TiO2-40 mol % GeO2):B2O3=1:x.

[0090] Example 7 A sample of a phase modulator for an optical phased array was prepared in the manner shown in Figure 2. The substrate 10 was a Si substrate with a thickness of 725 μm. The precursor layer 20 was 35 mol% SrO-20 mol% TiO2-45 mol% SiO2 with a thickness of 500 nm. The cladding layer 50 was silicon dioxide (SiO2) with a thickness of 2000 nm. The waveguide 60 was a-Si (amorphous silicon) with a thickness of 50 nm. The electrode 70 was metallic Al with a thickness of 100 nm. The irradiated light 30 was a continuous visible laser with a wavelength of 500 nm and an irradiation intensity of 400 W / cm. 2 and the irradiation time was 1 millisecond. The Si of the substrate 10 had a refractive index of 3.82. The silicon dioxide (SiO2) of the cladding layer 50 had a refractive index of 1.45. For the electrode 70, the amorphous oxide in the precursor layer 20 was crystallized by irradiation with light 30 to obtain a crystallized nonlinear optical material layer 22, and then the electrode 70 was applied.

[0091] Evaluation and Results It was confirmed that the substrate 10 of each of the samples of Examples 1 to 7 was not thermally damaged and could function as a phase modulator for an optical phased array.

[0092] The samples of Examples 3 to 6 were evaluated for SHG (Second Harmonic Generation) characteristics using the apparatus shown in Fig. 5. Fig. 6 is a graph showing the relationship between rotation angle and SHG intensity for the samples of Examples 3 and 4. Fig. 7 is an explanatory diagram showing a schematic representation of the structure of the crystallized nonlinear optical material estimated from the graph of Fig. 6. Fig. 8 is a graph showing the relationship between rotation angle and SHG intensity for the samples of Examples 5 and 6. Fig. 9 is an explanatory diagram showing a schematic representation of the structure of the crystallized nonlinear optical material estimated from the graph of Fig. 8.

[0093] 8 and 9, it can be confirmed that the crystal growth direction of the samples of Example 5 and Example 6 is not uniaxial. However, as described above, it has been confirmed that they operate without problems in practice as phase modulators for optical phased arrays. In contrast, it can be seen from FIGS. 6 and 7 that the crystal growth is uniaxial in the samples of Example 3 and Example 4. This confirms that the samples of Example 3 and Example 4 are phase modulators for optical phased arrays with very excellent nonlinear optical properties.

[0094] From the above results, the effectiveness of the manufacturing method of the present disclosure was confirmed. [Explanation of symbols]

[0095] 10 Substrate 20 precursor layer 22 Crystallized nonlinear optical material layer 30 light 40 Base layer 50 cladding layers 60 Waveguide 70 electrodes

Claims

1. applying a precursor layer containing an amorphous oxide to a surface of a substrate via an underlayer; irradiating the precursor layer with light from the precursor layer side to crystallize the amorphous oxide in the precursor layer while avoiding thermal damage to the substrate, thereby obtaining a crystallized nonlinear optical material layer; Including, the light is infrared light, and the infrared light has a wavelength that does not thermally damage the substrate with irradiation energy and is capable of heating an underlayer in contact with the precursor layer, thereby heating the precursor layer through the underlayer and crystallizing the amorphous oxide in the precursor layer.

2. The method for manufacturing a phase modulator for an optical phased array according to claim 1 , further comprising applying a waveguide and an electrode to a surface of the precursor layer or the crystallized nonlinear optical material layer opposite to the substrate.

3. Applying a precursor layer containing an amorphous oxide to a surface of a substrate via a cladding layer and a waveguide; and irradiating the precursor layer with light from the precursor layer side to crystallize the amorphous oxide in the precursor layer while avoiding thermal damage to the substrate, thereby obtaining a crystallized nonlinear optical material layer; Including, the light has a wavelength that does not crystallize the amorphous oxide in the precursor layer with the irradiation energy and heats the waveguide, thereby heating the precursor layer from the interface between the waveguide and the precursor layer and crystallizing the amorphous oxide in the precursor layer from the interface, while the cladding layer shields the irradiation energy of the light, thereby avoiding thermal damage to the substrate.

4. The method for manufacturing a phase modulator for an optical phased array according to claim 3 , wherein the cladding layer contains silicon dioxide.

5. 5. The method for manufacturing a phase modulator for an optical phased array according to claim 3, wherein the waveguide contains an amorphous silicon semiconductor, and the light has a wavelength capable of heating the waveguide and avoiding thermal damage to the substrate.

6. The method for manufacturing a phase modulator for an optical phased array according to any one of claims 3 to 5, wherein an electrode is applied to a surface of the cladding layer opposite to the substrate.

7. The amorphous oxide is SrO, TiO ２ , and SiO ２ The method for manufacturing the phase modulator for an optical phased array according to any one of claims 1 to 6, comprising:

8. The amorphous oxide is BaO, TiO ２ , and GeO ２ The method for manufacturing the phase modulator for an optical phased array according to any one of claims 1 to 7, comprising:

9. BaO, TiO ２ , and GeO ２ BaO—TiO ２ -GeO ２ The amorphous oxide further contains B ２ O ３ The mixing ratio is, in molar ratio, (BaO-TiO ２ -GeO ２ Amorphous oxides based on: (B ２ O ３ 9. The method for manufacturing a phase modulator for an optical phased array according to claim 8, wherein, when x=1:x, x is 1 to 10.

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