Optical waveguide structure and its control method

Abstract

The present invention provides an optical waveguide structure and a control method thereof that can suppress the reduction in directivity of an optical beam caused by the film thickness gradient of the optical waveguide or the warping of the tip. [Solution] The optical waveguide structure 1 comprises an optical phased array 4 consisting of a plurality of optical antennas 5, and a plurality of corrective antennas 6 arranged parallel to the optical antennas 5 and positioned on both sides of the optical phased array 4. The plurality of corrective antennas 6 are optically separated from the optical phased array 4. The optical waveguide structure 1 is controlled by a heater 7 to control the temperature distribution so that the difference in FFP between the corrective antennas 6 on both sides of the optical phased array 4 is below a predetermined level, thereby suppressing the reduction in directivity of the optical beam caused by the film thickness gradient and warping of the optical antennas 5. The control method includes measuring the optical characteristics of the corrective antennas 6, calculating the temperature distribution necessary to reduce the difference in said optical characteristics to below a predetermined level, and controlling to the calculated temperature distribution.

Description

[Technical Field]

[0001] This disclosure relates to an optical waveguide structure having an optical waveguide and capable of forming an optical beam in any direction, and to a method for controlling the same. [Background technology]

[0002] Conventionally, optical waveguide structures are known that have an optical waveguide and emit phase-controlled light from multiple optical antennas arranged in an array, and that can form an optical beam in any direction depending on the phase pattern (for example, Patent Document 1). This type of optical waveguide structure is also called an optical phased array.

[0003] The optical waveguide structure described in Patent Document 1 comprises an optical antenna consisting of a plurality of optical waveguides extending in one direction and a plurality of diffraction gratings adjacent to the optical waveguides and arranged along that direction. This optical waveguide structure separates the optical antenna between the optical waveguides and the diffraction gratings and arranges them along one direction, thereby increasing the length of the optical antenna, i.e., the antenna length, and forming an optical beam with a highly directional light intensity distribution (FFP). FFP is an abbreviation for Far-Field-Pattern. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-173992 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] As a result of diligent research by the inventors, it has been newly discovered that in this type of optical waveguide structure, if a film thickness gradient occurs in the optical antenna or if the chip on which the optical antenna is formed becomes warped, the phases of the light emitted from multiple diffraction gratings become misaligned, and the FFP (First Fine Frequency) decreases significantly.

[0006] In view of the above, this disclosure aims to provide an optical waveguide structure and a control method thereof that can suppress a decrease in FFP, i.e., a decrease in the directivity of the optical beam, caused by the film thickness gradient of the optical waveguide or the warping of the tip. [Means for solving the problem]

[0007] According to one aspect of this disclosure, the optical waveguide structure is An optical splitter (2) that splits the input optical signal and propagates it through multiple optical waveguides (21), Multiple phase adjusters (3) are connected to multiple optical waveguides and control the phase of light propagating through the optical waveguides, An optical phased array (4) consisting of multiple optical antennas (5) connected to a phase tuner, The system includes a plurality of correction antennas (6) arranged opposite each other with the optical phased array in between, and optically separated from the optical phased array.

[0008] This optical waveguide structure includes, in addition to the optical phased array, multiple corrective antennas that are optically separated from the optical phased array and positioned opposite it on either side of the optical phased array, so that light is also emitted from the multiple corrective antennas. This optical waveguide structure can estimate the film thickness gradient and warpage occurring in each of the multiple corrective antennas based on the optical characteristics of the light emitted from each corrective antenna. This optical waveguide structure is designed to suppress the reduction in directivity of the light beam emitted from the optical phased array sandwiched between the multiple corrective antennas by correcting the difference in optical characteristics of the multiple corrective antennas caused by the estimated film thickness gradient and warpage to below a predetermined level.

[0009] In another aspect of this disclosure, a method for controlling an optical waveguide structure comprises an optical phased array (4) composed of a plurality of optical antennas (5), a semiconductor substrate (10) having a plurality of correction antennas (6) arranged opposite the optical phased array and optically separated from the optical phased array, and heaters (7, 8) for heating the semiconductor substrate, Measuring the optical properties of light emitted from multiple correction antennas, Based on the measured optical characteristics, the temperature distribution between the multiple correction antennas and the correction antennas is calculated in order to reduce the difference in the optical characteristics of the multiple correction antennas to below a predetermined level. This includes heating the semiconductor substrate with a heater so that the calculated temperature distribution is achieved.

[0010] This optical waveguide structure control method comprises three steps: measuring the optical properties of light emitted from multiple correction antennas; calculating the temperature distribution required to reduce the difference between these optical properties to below a predetermined level based on the measured optical properties; and heating to realize the calculated temperature distribution. This makes it possible to correct the deviation in optical properties caused by film thickness gradient and warping occurring in the optical phased array sandwiched between multiple correction antennas, and to suppress the reduction in the directivity of the light beam emitted from the optical phased array.

[0011] The reference numerals in parentheses attached to each component indicate an example of the correspondence between that component and the specific components described in the embodiments described later. [Brief explanation of the drawing]

[0012] [Figure 1] This is a block diagram showing the optical waveguide structure and control unit of the first embodiment. [Figure 2] This is a perspective view showing the schematic configuration of the optical waveguide structure of the first embodiment. [Figure 3] This is a perspective view showing the schematic configuration of the light emission areas of the optical antenna and the corrective antenna. [Figure 4]It shows the state as seen from the IV direction in FIG. 3, and is an explanatory diagram of the state where there is no film thickness gradient and warpage in the optical antenna. [Figure 5] It is a diagram corresponding to FIG. 4, and is an explanatory diagram of the state where a film thickness gradient occurs in the optical antenna. [Figure 6] It is a diagram showing the distribution of the light intensity of the emitted light with respect to the azimuth from the optical antenna in each of the states where there is no film thickness gradient and the state where there is a film thickness gradient in the optical antenna. [Figure 7] It is a diagram corresponding to FIG. 4, and is an explanatory diagram of the state where warpage occurs in the optical antenna. [Figure 8] It is a diagram showing the distribution of the light intensity of the emitted light with respect to the azimuth from the optical antenna in each of the states where there is no warpage and the state where there is warpage in the optical antenna. [Figure 9] It is an explanatory diagram of the estimation of the film thickness gradient and warpage of the correction antenna using the measured results of the FFP of the radiation light from the correction antenna. [Figure 10] It is an explanatory diagram of the effect of temperature control in the state where a film thickness gradient occurs in the optical antenna. [Figure 11] It is an explanatory diagram of the effect of temperature control in the state where warpage occurs in the optical antenna. [Figure 12] It is an explanatory diagram of the FFP of the radiation light from two correction antennas and the temperature distribution for correction. [Figure 13] It is an explanatory diagram of the temperature gradient in the optical waveguide structure of the first embodiment. [Figure 14] It is a diagram showing the FFP of the radiation light from the correction antenna before and after temperature distribution control, and the simulation results of the FFP of the correction antenna in the ideal state. [Figure 15] It is a perspective view showing the schematic configuration of the optical waveguide structure of the second embodiment. [Figure 16] It is a perspective view showing the schematic configuration of the optical waveguide structure of the third embodiment.

Embodiments for Carrying Out the Invention

[0013] The embodiments of this disclosure will be described below with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other will be denoted by the same reference numerals. Furthermore, if only a part of a component is described in an embodiment, the other parts of the component can be replaced with components described in a previous embodiment. The following embodiments can be partially combined with each other, even if not explicitly stated, as long as it does not impede the combination.

[0014] (First Embodiment) The optical waveguide structure 1 of the first embodiment will be described below.

[0015] [Basic configuration] As shown in Figure 1, for example, the optical waveguide structure 1 of this embodiment comprises an optical phased array 4, a correction antenna 6, and a heater 7. Incident light from a light source 100 is transmitted to the optical phased array 4, and a highly directional optical beam is emitted from the optical phased array 4. The light source 100 is, for example, a known infrared laser light source, but is not limited thereto.

[0016] The optical waveguide structure 1, as shown in Figure 2, for example, is formed on a semiconductor substrate 10 and includes an optical splitter 2, a plurality of phase adjusters 3, an optical phased array 4 composed of a plurality of optical antennas 5, and a plurality of correction antennas 6. In this embodiment, the heater 7 is bonded to the side of the semiconductor substrate 10 opposite to the side on which the optical phased array 4 is formed, using an adhesive (not shown).

[0017] The optical waveguide structure 1 is formed on a semiconductor substrate 10 by silicon photonics technology, for example, in parts other than the heater 7, and is configured as a single optical integrated chip. The semiconductor substrate 10 is, for example, a rectangular plate and is made of silicon, i.e., Si, but may be made of other known materials. The optical waveguide structure 1 is, for example, formed on the semiconductor substrate 10, with a lower cladding layer formed on the lower cladding layer, and a core layer with a pattern shape constituting each waveguide formed on the lower cladding layer, and an upper cladding layer that covers the core layer and the lower cladding layer laminated thereon. The lower cladding layer and the upper cladding layer are, for example, made of silicon oxide, i.e., SiO2, but may be made of other known materials. The core layer constitutes each optical waveguide that makes up the optical waveguide structure 1 and is, for example, made of Si, but may be made of other known materials.

[0018] For the sake of clarity, as shown in Figure 2, one of the two orthogonal directions in the plane formed by the semiconductor substrate 10 in a non-warped state, along the longitudinal direction of the multiple optical antennas 5, will be referred to as the "vertical direction D1," and the other direction will be referred to as the "horizontal direction D2." In addition, to make the structure of the optical waveguide structure 1 easier to understand, Figure 2 mainly shows the core layer portion that constitutes each waveguide, and also shows simplified versions of the optical antennas 5 and correction antennas 6.

[0019] The optical splitter 2 splits the incident light from the light source 100 into multiple beams and transmits them to multiple optical antennas 5 that constitute the optical phased array 4. The optical splitter 2 has a branching structure in which, for example, one end is an optical waveguide 21, and this optical waveguide 21 branches out to the other end into two optical waveguides, and these two optical waveguides further branch out to the other end into two optical waveguides each. The optical splitter 2 has separate phase adjusters 3 connected to each branch of the optical waveguide 21.

[0020] The multiple phase adjusters 3 adjust the phase of each waveguide light branched and transmitted from the optical splitter 2, and are used to control the emission angle and pattern of the light beam emitted from the optical phased array 4. The multiple phase adjusters 3 locally heat each waveguide using heaters (not shown) placed on each waveguide of the optical splitter 2, and change the refractive index of each waveguide by the thermo-optic effect, thereby creating a desired phase difference in each waveguide light. Each waveguide light transmitted through the multiple phase adjusters 3 is then transmitted to, for example, different optical antennas 5.

[0021] The optical phased array 4 has a plurality of optical antennas 5 that extend linearly along the vertical direction D1, and the plurality of optical antennas 5 are arranged apart from each other along the horizontal direction D2. In order to ensure the directivity of the light beam emitted to the outside, the optical phased array 4 has a length L of the plurality of optical antennas 5 along the vertical direction D1. OAA The width is set to be greater than or equal to a predetermined value (for example, several mm to several cm). For a similar purpose, the optical phased array 4 has a width along the horizontal direction D2 of multiple optical antennas 5, i.e., the antenna array width W. OAA The specified size is set to be greater than or equal to a certain value (for example, a few millimeters to a few centimeters).

[0022] The optical antenna 5, as shown in Figure 3 for example, is composed of an optical waveguide 51 extending linearly along the vertical direction D1, and a plurality of diffraction gratings 52 arranged on both sides of the optical waveguide 51 along the horizontal direction D2 and periodically arranged at predetermined intervals along the vertical direction D1. As indicated by the arrows in Figure 3, the optical antenna 5 is configured such that input light L1 input to the optical waveguide 51 is propagated, and the input light L1 is emitted to the outside as radiated light L2 from the block-shaped plurality of diffraction gratings 52. The optical antenna 5 is optimized, for example, by optimizing the spacing between the optical waveguide 51 and the diffraction gratings 52 in the horizontal direction D2, the width of the optical waveguide 51 in the vertical direction D1, and the width of the diffraction gratings 52 in the vertical direction D1, so that the radiated light L2 from the diffraction gratings 52 is emitted uniformly. The optical waveguide 51 and the plurality of diffraction gratings 52 are composed of, for example, a core layer, arranged on the same layer on the semiconductor substrate 10, and made of the same material.

[0023] The correction antenna 6 is for correcting the fast-flow projection (FFP) of the optical beam of the optical phased array 4, which is caused by the film thickness gradient in the vertical direction D1 of the optical waveguide 51 of the optical phased array 4 and the warping of the semiconductor substrate 10. In this embodiment, one correction antenna 6 is positioned at each end of the optical phased array 4 along the horizontal direction D2. The first correction antenna 61, positioned to the left of the optical phased array 4, and the second correction antenna 62, positioned to the right, are arranged in parallel with the multiple optical antennas 5, with their extension directions aligned. The correction antennas 61 and 62 have similar configurations. The number of correction antennas 6 is less than the number of optical antennas 5 that make up the optical phased array 4.

[0024] Specifically, for example, the correction antenna 6, as shown in Figure 3, is composed of an optical waveguide 63 and a plurality of diffraction gratings 64, similar to the optical antenna 5. The optical waveguide 63 extends linearly along the vertical direction D1. The plurality of diffraction gratings 64 are, for example, in the shape of block-shaped rectangular plates and are arranged on both sides of the optical waveguide 63 along the horizontal direction D2, as well as periodically arranged at predetermined intervals along the vertical direction D1. For example, the correction antenna 6 is composed of an optical waveguide 63 and a plurality of diffraction gratings 64 in the region facing the optical antenna 5 in the horizontal direction D2, and composed of only the optical waveguide 63 in other regions.

[0025] For the sake of explanation, the regions of the correction antenna 6 where multiple diffraction gratings 64 are arranged, i.e., the regions that emit synchrotron radiation to the outside, will be referred to as "light emission regions." The light emission regions of the first correction antenna 61 and the second correction antenna 62 will be referred to as "light emission region 611" and "light emission region 621," respectively. In Figure 2, although it does not show a cross-section, hatching has been applied to the light emission regions 611 and 621 to make them easier to understand.

[0026] The light emission regions 611 and 621 are the regions of the correction antenna 6 from the diffraction grating 64 located at one end in the vertical direction D1 to the diffraction grating 64 located at the other end in the same direction. The length of the light emission regions 611 and 621 in the vertical direction D1 of the correction antenna 6, i.e., the antenna length, is approximately the same as that of the optical antenna 5. "Approximately the same" includes not only cases where they are completely identical, but also cases where there are slight differences due to unavoidable processing errors, etc., but they can be considered almost identical.

[0027] The correction antenna 6 has the same horizontal spacing D2 between the optical waveguide 63 and the diffraction grating 64, the same vertical width D1 of the optical waveguide 63, and the same vertical width D1 of the diffraction grating 64 as the optical antenna 5. The optical waveguide 63 and the multiple diffraction gratings 64 are, for example, composed of a core layer, arranged on the same layer on the semiconductor substrate 10, and made of the same material. The optical waveguide 63 is also arranged on the same layer as the optical waveguide 51 and made of the same material as the optical waveguide 51. The correction antenna 6 is formed simultaneously in the same process as the multiple optical antennas 5 so that the film thickness gradient in the vertical D1 of the optical waveguide 63 is the same as that of the optical waveguide 51. The correction of the FFP in the optical phased array 4 using the correction antenna 6 will be described later.

[0028] In this embodiment, the heater 7 is separate from the semiconductor substrate 10, and for example, a known microheater array in which minute-sized heating elements are arranged in an array is used. The heater 7 is, for example, bonded and fixed to the semiconductor substrate 10 on the side opposite to the side in which each optical waveguide is formed, using an adhesive (not shown). The heater 7 is, for example, approximately the same planar size as the semiconductor substrate 10, but is not limited to this, and only needs to be capable of heating a predetermined range including at least the optical phased array 4 and the multiple correction antennas 6. The heater 7 is driven and controlled by a temperature control unit 300, which will be described later, and is used to adjust the semiconductor substrate 10 to a predetermined temperature distribution.

[0029] The above describes the basic configuration of optical waveguide structure 1.

[0030] [Effects of film thickness gradient and warpage on FFP] Next, we will explain the effects of film thickness gradient and warpage in the optical phased array 4 on the FFP. For the sake of simplicity, the film thickness gradient in the vertical direction D1 of the optical antenna 5 and the correction antenna 6 will be simply referred to as "film thickness gradient," and the warpage of the semiconductor substrate 10 or the optical antenna 5 and the correction antenna 6 will be simply referred to as "warpage."

[0031] When there is no film thickness gradient or warping in the optical antenna 5, the phases of the synchrotron radiation emitted from the multiple diffraction gratings 52 to the outside are aligned, as shown in Figure 4, for example. The same applies to the correction antenna 6.

[0032] In Figures 4, 5, and 7, although they do not show cross-sections, hatching is applied to the diffraction grating 52 to distinguish it from the optical waveguide 51. Each synchrotron radiation beam from multiple diffraction gratings 52 is indicated by a thick arrow, and the phase of each beam is conveniently shown by a dashed line. Furthermore, in Figures 4, 5, and 7, to make it easier to see whether there is a phase difference between the synchrotron radiation beams from the diffraction grating 52, the height of the dashed lines is aligned when the phases are aligned, and shifted when the phases are misaligned. Similarly, in Figures 10 and 11, hatching is applied to the diffraction grating 64, each synchrotron radiation beam is indicated by a thick arrow, the phase of each beam is shown by a dashed line, and the position of the phase is represented by the height.

[0033] Through diligent research by the inventors, it has been newly discovered that if the optical antenna 5 experiences film thickness gradient, warping, or both, the FFP changes, and the directivity of the optical beam from the optical phased array 4 decreases.

[0034] For example, as shown in Figure 5, suppose that in the optical waveguide 51 of the optical antenna 5, while no warping occurs, a film thickness gradient Ts occurs in which the film thickness gradually decreases from one end to the other in the vertical direction D1. Here, the film thickness gradient Ts refers to, for example, the amount of variation (nm / mm) in the film thickness (nm) of the optical waveguide 51 per unit length (mm) along the vertical direction D1. In this case, since the film thickness of adjacent optical waveguides 51 will differ for the multiple diffraction gratings 52 arranged periodically, the phase of the synchrotron radiation will be shifted. For example, as shown in Figure 6, when there is no film thickness gradient, the FFP of the light emitted from the optical phased array 4 forms a light beam with high light intensity in a predetermined direction, whereas when the above-mentioned film thickness gradient occurs, a light beam with high light intensity is not formed.

[0035] Furthermore, as shown in Figure 7, for example, if there is no film thickness gradient in the optical antenna 5, but a warp occurs along the vertical direction D1, the emission positions of the synchrotron radiation from the multiple diffraction gratings 52 will shift, causing a phase shift in each of the synchrotron radiation beams. For example, as shown in Figure 8, when there is no warp, the FFP of the light emitted from the optical phased array 4 forms a light beam with high light intensity in a predetermined direction, whereas when the above-mentioned warp occurs, a light beam with high light intensity is not formed.

[0036] In the optical waveguide structure 1, if the optical waveguide 51 experiences a film thickness gradient, warping, or both, the FFP of the optical phased array 4 will change unintended, resulting in a decrease in the directivity of the optical beam. However, the optical waveguide structure 1 is equipped with multiple correction antennas 6 positioned on either side of the optical phased array 4, and the decrease in the directivity of the optical beam can be suppressed by controlling the temperature distribution using heaters 7 based on the analysis results of the FFP of the radiant light from the correction antennas 6.

[0037] [Control and effects of temperature distribution] As shown in Figure 1, for example, the optical waveguide structure 1 has an optical measurement unit 200 that measures the light emitted from the correction antenna 6, and a temperature control unit 300 that controls the temperature distribution, thereby suppressing a decrease in the directivity of the optical beam.

[0038] The optical measurement unit 200 measures the light emitted from multiple correction antennas 6 positioned on both sides of the optical phased array 4, and is, for example, an infrared camera. The data of the emitted light measured by the optical measurement unit 200 is output to, for example, the temperature control unit 300 and used for analyzing the optical characteristics of the multiple correction antennas 6.

[0039] The temperature control unit 300 controls the temperature distribution of the semiconductor substrate 10 in order to suppress the phase shift of the synchrotron radiation L2 caused by the film thickness gradient in the vertical direction D1 of the optical phased array 4 and the warping of the semiconductor substrate 10. The temperature control unit 300 is configured to include, for example, a microcomputer having a processor such as a CPU, a recording medium such as ROM or RAM, and I / O. CPU, ROM, RAM, and I / O are abbreviations for Central Processing Unit, Read Only Memory, Random Access Memory, and Input / Output, respectively. The temperature control unit 300 is configured to include, for example, an optical analysis unit 310, a temperature distribution calculation unit 320, and a temperature adjustment unit 330, as shown in Figure 1.

[0040] The optical analysis unit 310 analyzes the optical characteristics of each of the multiple correction antennas 6 based on the measurement data of the light emitted from the correction antennas 6 measured by the optical measurement unit 200. The optical analysis unit 310 analyzes the FFP of each of the correction antennas 61 and 62 using known optical analysis techniques.

[0041] For example, the optical analysis unit 310 has multiple FFP data calculated by the following equation (1) pre-stored on a recording medium (not shown), and compares this FFP data with the measured FFP of the correction antennas 61 and 62 to estimate the film thickness gradient and warpage.

[0042]

number

[0043] When there is no film thickness gradient and no warping, as shown in FIG. 4 for example, the phases ψ n of the emitted light from the plurality of diffraction gratings 64 are constant. However, when there is a film thickness gradient as shown in FIG. 5, the phase ψ n changes according to the gradient. ψ n can be said to be the term that reflects the effect of the film thickness gradient. Also, when there is no warping, for the plurality of diffraction gratings 64, r n becomes (x n , 0) and the y-component of the emission position is constant. However, when there is warping, r n becomes (x n , y n ) and the y-component fluctuates according to the warping. r nThis can be said to be a term that reflects the effect of warping. Then, assuming multiple combinations of film thickness gradient and warp radius that can occur (for example, 100 combinations), ψ in equation (1) is calculated according to the film thickness gradient and warp radius. n and r n By changing these parameters, multiple FFP data sets corresponding to each pattern of film thickness gradient and warpage are created. The optical analysis unit 310 compares the multiple FFP data sets created in advance as described above with the FFP data obtained by actual measurement, as shown in Figure 9, for example, and estimates the combination of film thickness gradient and warpage radius that best matches the measured FFP. Patterns A, B, and C in Figure 9 are representative examples of multiple FFP data sets with different combinations of film thickness gradient and warpage that were created in advance. The measured results in Figure 9 are an example of FFP data obtained by measuring and analyzing the light emitted from the correction antenna 6. The optical analysis unit 310 then outputs the estimated film thickness gradient and warpage data of the estimated correction antennas 61 and 62 to the temperature distribution calculation unit 320.

[0044] The temperature distribution calculation unit 320 calculates the temperature distribution necessary to align the FFP of each of the multiple correction antennas 6, for example, based on the estimated film thickness gradient and warpage of each of the multiple correction antennas 6 obtained from the optical analysis unit 310. If, for example, as shown in Figure 10, only a film thickness gradient occurs in the correction antenna 6, the temperature distribution calculation unit 320 calculates the refractive index distribution of the optical waveguide 63 necessary to align the phase of the radiated light from the multiple diffraction gratings 64 arranged along the vertical direction D1. Since the refractive index of the optical waveguide 63 is temperature-dependent, the temperature distribution calculation unit 320 calculates the temperature distribution of the optical waveguide 63 necessary to align the phase of each radiated light, as shown in Figure 10, based on the calculated refractive index distribution. In the example in Figure 10, the phase of the radiated light emitted from the diffraction gratings 64 adjacent to the areas where the film thickness of the optical waveguide 63 is thin is delayed, so a temperature distribution is created in the optical waveguide 63 such that the temperature is relatively higher towards the areas where the film thickness is thin. This makes it possible to correct the phase shift of the synchrotron radiation from multiple diffraction gratings 64 caused by the film thickness gradient of the optical waveguide 63.

[0045] Furthermore, the temperature distribution calculation unit 320 calculates the temperature distribution of the optical waveguide 63 necessary to align the phases of each radiant light from the diffraction gratings 64 arranged along the vertical direction D1, even if only warping occurs in the correction antenna 6, as shown in Figure 11, for example. In the example in Figure 11, the phase of the radiant light emitted from the diffraction gratings 64 located closer to the tip of the warping of the optical waveguide 63 is delayed, so a temperature distribution is created in the optical waveguide 63 such that the temperature is relatively higher towards the tip. This makes it possible to correct the phase shift of the radiant light from multiple diffraction gratings 64 caused by the warping of the optical waveguide 63. Figures 10 and 11 show the case where either a film thickness gradient or warping occurs in the correction antenna 6 for clarity, but the temperature distribution calculation unit 320 performs the same calculation process even if both a film thickness gradient and warping occur in the correction antenna 6.

[0046] Specifically, for example, suppose the optical analysis unit 310 obtains the FFP of the first correction antenna 61 shown on the left side of Figure 12 and the FFP of the second correction antenna 62 shown on the right side of Figure 12. In this case, the temperature distribution calculation unit 320 calculates the temperature distribution ΔT1 necessary to correct the shape of the FFP of the first correction antenna 61 and the temperature distribution ΔT2 necessary to correct the shape of the FFP of the second correction antenna 62. The temperature distribution ΔT1 is the temperature distribution between points P1 and P2, where P1 and P2 are the ends of the light emission region 611 in the vertical direction D1, as shown in Figure 13. The temperature distribution ΔT2 is the temperature distribution between points P3 and P4, where P3 and P4 are the ends of the light emission region 621 in the vertical direction D1, as shown in Figure 13. When temperature control is performed on the correction antennas 61 and 62 so that the temperature distributions ΔT1 and ΔT2 become aligned, the shapes of the FFPs of the correction antennas 61 and 62 become aligned, but the positions of these FFPs are not yet aligned.

[0047] Therefore, the temperature distribution calculation unit 320 calculates the temperature distribution ΔT3 necessary to align the positions of the FFPs of the correction antennas 61 and 62. The temperature distribution ΔT3 is the temperature distribution in the area connecting the light emission region 611 and the light emission region 621 along the horizontal direction D2, as shown in Figure 13. When temperature control is performed so that the temperature distribution ΔT3 is achieved between the light emission regions 611 and 621, the positions of the FFPs of the correction antennas 61 and 62 are aligned.

[0048] Here, the results of the inventors' simulation are shown in Figure 14. The dashed line in Figure 14, "before correction," represents the FFP when the first correction antenna 61 has a curvature of 10 m and a film thickness gradient of 0.1 nm / mm along the vertical direction D1. The solid line in Figure 14, "ideal state," represents the FFP when the first correction antenna 61 has no film thickness gradient and no curvature, i.e., when there is no phase shift in the synchrotron radiation from the diffraction grating 64. At this time, the temperature distribution ΔT1 required to make the first correction antenna 61 before correction have the same shape as the FFP in the ideal state was calculated, and ΔT1 was found to be 11.5°C. When the FFP was simulated after correcting the temperature distribution of the light emission region 611 to ΔT1, the FFP of the first correction antenna 61 became the "after correction" state shown by the dashed line in Figure 14, which is almost the same as the ideal state. These results suggest that by controlling the temperature distribution of the optical waveguide 63 of the corrective antenna 6, which has film thickness gradient and warping, it is possible to achieve an FFP close to an ideal state without film thickness gradient and warping. Furthermore, by correcting each of the multiple corrective antennas 6 by controlling the temperature distribution as described above, the multiple corrective antennas 6 can be brought closer to an ideal state. And by controlling the temperature distribution of the multiple corrective antennas 6, the optical phased array 4 sandwiched between them also approaches an ideal state, improving the reduction in optical beam directivity caused by film thickness gradient and warping.

[0049] As described above, the temperature distribution calculation unit 320 calculates the temperature distribution for correcting each of the correction antennas 6 to an ideal state based on the FFP of the synchrotron radiation from the correction antennas 6 on both sides of the optical phased array 4. The temperature distribution calculation results from the temperature distribution calculation unit 320 are output to, for example, the temperature adjustment unit 330 and used for temperature control using the heater 7.

[0050] The temperature control unit 330 controls the heater 7 based on the temperature distribution calculation result by the temperature distribution calculation unit 320. The temperature control unit 330 outputs a control signal to the heater 7 and controls the temperature so that the temperature distributions in the light emission regions 611, 621 and the areas between them become ΔT1, ΔT2, and ΔT3, respectively. As a result, the temperature distributions in the light emission regions 611, 621 and the areas between them are set to the desired distribution, and the decrease in the directivity of the light beam of the optical phased array 4 caused by film thickness gradient and warping is suppressed.

[0051] According to this embodiment, the optical waveguide structure 1 has an optical phased array 4 and a plurality of corrective antennas 6 that are optically separated from the optical phased array 4, positioned opposite each other with the optical phased array 4 in between, and emit light. The optical waveguide structure 1 has a structure that allows estimation of the film thickness gradient and warping that occurs in the plurality of corrective antennas 6 based on the FFP of the light emitted from the plurality of corrective antennas 6. The optical waveguide structure 1 has a structure that can suppress the reduction in the directivity of the light beam emitted from the optical phased array 4 by correcting the difference in the optical characteristics of the plurality of corrective antennas to below a predetermined level.

[0052] The control method for the optical waveguide structure 1 of this embodiment includes the following three steps. The first step is to measure the optical properties of the light emitted from the multiple correction antennas 6. The second step is to calculate the temperature distribution between the multiple correction antennas 6 and the correction antennas 6 necessary to reduce the difference in the optical properties of the multiple correction antennas 6 to below a predetermined level, based on the optical properties measured in the first step. The third step is to heat the semiconductor substrate 10 with a heater 7 so that the temperature distribution calculated in the second step is achieved. This control method aligns the optical properties of the multiple correction antennas 6, improves the optical properties of the optical phased array 4 sandwiched between them, and makes it possible to suppress the decrease in directivity of the light beam caused by film thickness gradient and warping.

[0053] Furthermore, the optical waveguide structure 1 has the following features.

[0054] (1) The optical waveguide structure 1 has multiple optical antennas 5 and multiple correction antennas 6 arranged in the same layer and made of the same material. As a result, if film thickness gradient and warping occur in the multiple correction antennas 6, similar film thickness gradient and warping will occur in the optical phased array 4 sandwiched between them. By correcting the optical properties of the multiple correction antennas 6 to match, the optical properties of the optical phased array 4 are similarly improved, and the reduction in directivity of the optical beam can be suppressed more effectively.

[0055] (2) The optical waveguide structure 1 is arranged such that the extension directions of the multiple correction antennas 6 are aligned with the extension directions of the multiple optical antennas 5.

[0056] (3) The optical waveguide structure 1 has fewer correction antennas 6 than optical antennas 5.

[0057] (4) The optical waveguide structure 1 further includes a heater 7 that heats the optical phased array 4 to create a predetermined temperature distribution. The heater 7 is separate from the semiconductor substrate 10 on which the optical phased array 4 is formed, and is attached to the semiconductor substrate 10. As a result, the optical waveguide structure 1 has a structure in which the temperature distribution of the multiple correction antennas 6 is controlled by the heater 7, thereby aligning the optical characteristics of the multiple correction antennas 6 and, consequently, suppressing a decrease in the directivity of the optical beam of the optical phased array 4.

[0058] (Second Embodiment) The optical waveguide structure 1 of the second embodiment will be described below.

[0059] The optical waveguide structure 1 of this embodiment differs from the first embodiment in that the configuration of the multiple correction antennas 6 has been changed, as shown in Figure 15, for example. This embodiment will mainly describe this difference.

[0060] In this embodiment, four correction antennas 6 are arranged, two on the left side and two on the right side of the optical phased array 4 in the horizontal direction D2. For the sake of explanation, as shown in Figure 15, the multiple correction antennas 6 will be referred to as "first antenna 6A," "second antenna 6B," "third antenna 6C," and "fourth antenna 6D," respectively, from left to right in the horizontal direction D2. Antennas 6A, 6B, 6C, and 6D are arranged parallel to each other along the horizontal direction D2, with their extension direction aligned with the optical antenna 5. The second antenna 6B is positioned closer to the optical phased array 4 than the first antenna 6A. The third antenna 6C is positioned closer to the optical phased array 4 than the fourth antenna 6D.

[0061] The second antenna 6B and the third antenna 6C have, for example, light emission regions 6B1 and 6C1 in the horizontal direction D2 that face the optical antenna 5 and do not face the first antenna 6A or the fourth antenna 6D. The second antenna 6B and the third antenna 6C consist only of optical waveguides 63 in areas other than the light emission regions 6B1 and 6C1.

[0062] The first antenna 6A and the fourth antenna 6D, for example, have light emission regions 6A1 and 6D1 in the horizontal direction D2, facing the optical antenna 5, while the other regions consist only of optical waveguides 63. The light emission regions 6A1 and 6B1 are, for example, assumed to have the same antenna length, but are not limited to this. The same applies to the light emission regions 6C1 and 6D1. Note that, as with Figure 2, Figure 15 does not show a cross-section, but hatching has been applied to the light emission regions 6A1, 6B1, 6C1, and 6D1 for clarity.

[0063] The light-emitting regions 6A1 and 6B1 are located at different positions in the direction of antenna extension, i.e., the vertical direction D1. The light-emitting regions 6A1 and 6D1 are located at the same position in the direction of antenna extension. The light-emitting regions 6B1 and 6C1 are located at the same position in the direction of antenna extension. In other words, the first antenna 6A and the fourth antenna 6D form a pair, and the second antenna 6B and the third antenna 6C form a pair.

[0064] In this embodiment, the temperature control unit 300 controls the temperature of the heater 7 so that the difference between the FFP of the first antenna 6A and the FFP of the fourth antenna 6D, and the difference between the FFP of the second antenna 6B and the FFP of the third antenna 6C, are below a predetermined value. This further improves the accuracy of correcting the FFP deviation caused by the film thickness gradient and warping of the correction antennas 6 arranged on the left and right sides of the optical phased array 4, thereby ensuring the directivity of the optical beam in the optical phased array 4. In particular, when the film thickness gradient or warping of the optical waveguides 51 and 63 in the vertical direction D1 is not uniform, the effect of suppressing the phase shift of light in the optical phased array 4 by temperature distribution control is improved compared to the first embodiment.

[0065] In the above explanation, a representative example was described in which two corrective antennas 6 are arranged on each side of the optical phased array 4 in the horizontal direction D2, so to speak, with two pairs of corrective antennas 6. However, the system is not limited to this. For example, there may be three or more pairs of corrective antennas 6, and the number and the length of the light emission area of ​​each antenna can be changed as appropriate. Also, the arrangement of the first antenna 6A and the second antenna 6B, and the arrangement of the third antenna 6C and the fourth antenna 6D may be reversed, and the arrangement of the corrective antennas 6 can also be changed as appropriate.

[0066] According to this embodiment, in addition to the same effects as in the first embodiment described above, the optical waveguide structure 1 is provided with an even greater effect in suppressing the reduction in the directivity of the optical beam of the optical phased array 4 caused by film thickness gradient and warping.

[0067] (Third embodiment) The optical waveguide structure 1 of the third embodiment will be described below.

[0068] The optical waveguide structure 1 of this embodiment differs from the first embodiment in that, as shown in Figure 16, for example, a heater 8 is formed on the semiconductor substrate 10 instead of a separate heater 7. This embodiment will mainly explain this difference.

[0069] The heater 8 is, for example, a microheater made of titanium nitride, i.e., TiN, and is formed directly on the semiconductor substrate 10 by sputtering or the like. The amount of current supplied to the heater 8 is controlled by, for example, a temperature control unit 330 and is used to control the temperature distribution of the optical phased array 4. For example, one heater 8 is placed on each side of the optical phased array 4 in the horizontal direction D2. For example, the heater 8 is positioned so that its extension direction is aligned with that of the optical antenna 5, and its length is approximately the same as that of the optical antenna 5.

[0070] This embodiment also provides an optical waveguide structure 1 that achieves the effects of the first embodiment described above. Furthermore, in this embodiment, the heater 8 is formed directly on the semiconductor substrate 10, and is not affected by uneven adhesion as in the method of bonding a separate heater 7, thus suppressing the decrease in temperature distribution control caused by uneven adhesion.

[0071] (Other embodiments) This disclosure is described in accordance with the embodiments, but it is understood that this disclosure is not limited to such embodiments or structures. This disclosure also includes various modifications and variations within the equivalence range. In addition, various combinations and forms, as well as other combinations and forms including one, more, or less of those elements, fall within the scope and concept of this disclosure.

[0072] (1) The optical waveguide structure 1 of each of the above embodiments can be freely combined to the extent possible. For example, the optical waveguide structure 1 of the second embodiment may have a heater 8 instead of a heater 7. Also, in the optical waveguide structure 1 of each of the above embodiments, the optical antenna 5 and the correction antenna 6 were arranged on the same plane as the optical waveguide and the diffraction grating, and were separated, but this is not limited to this, and other known optical antenna configurations may be used. In other words, the optical waveguide structure 1 may have a configuration in which, in addition to the optical phased array 4, a plurality of correction antennas 6 are arranged on both sides of the optical phased array 4, and the configuration of the light emission regions of the optical antenna 5 and the correction antennas 6 can be changed as appropriate.

[0073] (2) The control unit (e.g., temperature control unit 300) and its method described herein may be implemented by a dedicated computer provided by configuring a processor and memory programmed to perform one or more functions embodied by a computer program. Alternatively, the control unit and its method described herein may be implemented by a dedicated computer provided by configuring a processor by one or more dedicated hardware logic circuits. Alternatively, the control unit and its method described herein may be implemented by one or more dedicated computers configured by a combination of a processor and memory programmed to perform one or more functions and a processor configured by one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions to be executed by the computer on a computer-readable non-transitional tangible recording medium.

[0074] (3) It goes without saying that, in each of the above embodiments, the elements constituting the embodiment are not necessarily essential unless explicitly stated to be particularly essential or unless they are clearly considered essential in principle. Furthermore, in each of the above embodiments, when numerical values ​​such as the number, numerical values, quantities, or ranges of the components of the embodiment are mentioned, the embodiment is not limited to those specific numbers unless explicitly stated to be particularly essential or unless it is clearly limited to a specific number in principle. Furthermore, in each of the above embodiments, when the shape, positional relationship, etc. of the components are mentioned, the embodiment is not limited to those shapes, positional relationships, etc. unless explicitly stated or unless it is clearly limited to a specific shape, positional relationship, etc. in principle.

[0075] (Perspective of this disclosure) The above disclosure can be understood from the following perspectives, for example. [First point of view] An optical splitter (2) that splits the input optical signal and propagates it through multiple optical waveguides (21), Multiple phase adjusters (3) are connected to each of the multiple optical waveguides and control the phase of the light propagating through the optical waveguides, An optical phased array (4) consisting of a plurality of optical antennas (5) connected to the phase adjuster, An optical waveguide structure comprising a plurality of correction antennas (6) arranged opposite to the aforementioned optical phased array and optically separated from the aforementioned optical phased array. [Second perspective] The optical waveguide structure according to the first aspect, wherein the plurality of optical antennas and the plurality of corrective antennas are arranged in the same layer and are made of the same material. [Third perspective] An optical waveguide structure according to the first or second aspect, wherein the plurality of correction antennas are arranged such that their extension directions are aligned with the extension directions of the plurality of optical antennas. [Fourth perspective] The optical waveguide structure according to any one of the first to third aspects, wherein the number of correction antennas is fewer than the number of optical antennas. [Fifth perspective] Multiple correction antennas are arranged on both sides of the optical phased array. The optical waveguide structure according to any one of the first to fourth views, wherein the light-emitting regions (6A1, 6B1, 6C1, 6D1) of the corrective antenna that emit light to the outside are located in a position in the extension direction of the corrective antenna that is different from the light-emitting regions of other adjacent corrective antennas. [Sixth perspective] The optical waveguide structure according to any one of the first to fifth aspects, further comprising heaters (7, 8) for heating the optical phased array and generating a predetermined temperature distribution. [Seventh perspective] The optical waveguide structure according to the sixth aspect, wherein the heater is separate from the semiconductor substrate (10) on which the optical phased array is formed, and is attached to the semiconductor substrate. [Perspective 8] The heater is formed on the semiconductor substrate (10) on which the optical phased array is formed, in the optical waveguide structure according to the sixth aspect. [Perspective 9] The optical waveguide structure according to the eighth aspect, wherein the heater is arranged opposite to the optical phased array. [Perspective 10] A method for controlling an optical waveguide structure comprising: an optical phased array (4) composed of multiple optical antennas (5); a semiconductor substrate (10) having multiple correction antennas (6) arranged opposite the optical phased array and optically separated from the optical phased array; and heaters (7, 8) for heating the semiconductor substrate, wherein Measuring the optical properties of light emitted from multiple correction antennas, Based on the measured optical characteristics, the temperature distribution between the multiple correction antennas and the correction antennas is calculated in order to reduce the difference in the optical characteristics of the multiple correction antennas to a predetermined level or less. A method for controlling an optical waveguide structure, comprising heating the semiconductor substrate with the heater so that the calculated temperature distribution is achieved. [Explanation of symbols]

[0076] 2...Optical splitter, 21...Optical waveguide, 3...Phase adjuster, 4...Optical phased array, 5...Optical antenna, 6...Correction antenna, 6A1, 6B1, 6C1, 6D1...Optical emission area, 7, 8...Heater, 10...Semiconductor substrate

Claims

1. An optical splitter (2) that splits the input optical signal and propagates it through multiple optical waveguides (21), Multiple phase adjusters (3) are connected to each of the multiple optical waveguides and control the phase of light propagating through the optical waveguides, An optical phased array (4) consisting of a plurality of optical antennas (5) connected to the phase adjuster, An optical waveguide structure comprising a plurality of correction antennas (6) arranged opposite to the aforementioned optical phased array and optically separated from the aforementioned optical phased array.

2. The optical waveguide structure according to claim 1, wherein the plurality of optical antennas and the plurality of correction antennas are arranged in the same layer and are made of the same material.

3. The optical waveguide structure according to claim 1, wherein the plurality of correction antennas are arranged so that their extension directions are aligned with the extension directions of the plurality of optical antennas.

4. The optical waveguide structure according to claim 1, wherein the number of correction antennas is fewer than the number of optical antennas.

5. Multiple correction antennas are arranged on both sides of the optical phased array. The optical waveguide structure according to claim 1, wherein the light-emitting regions (6A1, 6B1, 6C1, 6D1) of the corrective antenna that emit light to the outside are located in a position in the extension direction of the corrective antenna that is different from the light-emitting regions of other adjacent corrective antennas.

6. The optical waveguide structure according to any one of claims 1 to 5, further comprising heaters (7, 8) for heating the optical phased array and generating a predetermined temperature distribution.

7. The optical waveguide structure according to claim 6, wherein the heater is separate from the semiconductor substrate (10) on which the optical phased array is formed, and is attached to the semiconductor substrate.

8. The optical waveguide structure according to claim 6, wherein the heater is formed on the semiconductor substrate (10) on which the optical phased array is formed.

9. The optical waveguide structure according to claim 8, wherein the heater is arranged opposite to the optical phased array.

10. A control method for an optical waveguide structure comprising: an optical phased array (4) composed of multiple optical antennas (5); a semiconductor substrate (10) having multiple correction antennas (6) arranged opposite the optical phased array and optically separated from the optical phased array; and heaters (7, 8) for heating the semiconductor substrate, wherein Measuring the optical properties of light emitted from multiple correction antennas, Based on the measured optical characteristics, the temperature distribution between the multiple correction antennas and the correction antennas is calculated in order to reduce the difference in the optical characteristics of the multiple correction antennas to a predetermined level or less. A method for controlling an optical waveguide structure, comprising heating the semiconductor substrate with the heater so that the calculated temperature distribution is achieved.

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