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JP-2026074597-A - Optical devices

JP2026074597AJP 2026074597 AJP2026074597 AJP 2026074597AJP-2026074597-A

Abstract

[Problem] To provide an optical device that can suppress the propagation loss of light even when the distance of the optical waveguide is increased or the radius of curvature of the curved portion in the path is reduced. [Solution] The optical device comprises a substrate, a waveguide layer having a slab portion provided in contact with the substrate and a ridge portion protruding from the slab portion, a buffer layer provided so as to cover the waveguide layer and containing SiO2 as its main component with a refractive index adjusted to 1.2 or more and less than 1.4, and a protective layer provided so as to cover the buffer layer and suppressing changes in the refractive index of the buffer layer. [Selection Diagram] Figure 3

Inventors

  • 田家 裕
  • 王 進武
  • 箕野 哲哉
  • 小菅 拓

Assignees

  • ＴＤＫ株式会社

Dates

Publication Date
20260507
Application Date
20241021

Claims (10)

  1. circuit board and A waveguide layer having a slab portion provided in contact with the substrate and a ridge portion provided protruding from the slab portion, A buffer layer is provided so as to cover the waveguide layer and contains SiO2 as its main component, which is adjusted to have a refractive index of 1.2 or more and less than 1.4. An optical device comprising a protective layer provided so as to cover the buffer layer and suppressing changes in the refractive index of the buffer layer.
  2. The optical device according to claim 1, wherein the protective layer is made of a light-transmitting material having a refractive index greater than that of the buffer layer.
  3. The optical device according to claim 1, wherein the protective layer has a thickness of 500 nm or more.
  4. The optical device according to claim 3, wherein the buffer layer has a thickness of 10 nm or more and less than 300 nm.
  5. The optical device according to claim 1, wherein the waveguide layer comprises lithium niobate as a main component.
  6. The optical device according to claim 1, wherein the angle formed by the side wall of the ridge portion with respect to the reference plane of the substrate is 70° or more and 90° or less.
  7. The optical device according to claim 1, wherein the thickness of the slab portion gradually decreases as it moves away from the point where it intersects with the side wall of the ridge portion.
  8. The optical device according to claim 1, wherein the SiO2 in the buffer layer comprises Si-H groups.
  9. The optical device according to claim 1, wherein the protective layer comprises any of the following materials: M-Si-O system (where M is at least one of Al, Zr, Hf, La, Ba, Bi, Ti, Ca, Mo, In), SiN, SiON, or SiO2 having a refractive index of 1.5 or higher.
  10. The optical device according to claim 1, wherein the buffer layer and the protective layer are provided in regions corresponding to the curved path formed by the ridge portion.

Description

This invention relates to an optical device. Optical devices with optical waveguides on a substrate include optical modulation devices that convert electrical signals into optical signals, and coupler devices that mix and emit incident RGB laser light. Due to the need to fit long paths onto small chips, the optical waveguides in such optical devices often have partially curved paths (see, for example, Patent Document 1). Special Publication No. 2023-522151 This figure shows the overall configuration of an optical modulation device, which is one type of optical device.This diagram shows the configuration of an optical modulation element used in an optical modulation device.This is a cross-sectional view of the laminate along line III-III.This diagram schematically shows the configuration of a plasma CVD apparatus for forming a buffer layer.This is a cross-sectional view of a laminate having a waveguide layer according to a modified example. The embodiments of the present invention will be described with reference to the attached drawings. In each drawing, components with the same reference numerals have the same or similar configuration. Furthermore, in cases where multiple structures with the same or similar configuration exist in each drawing, reference numerals may be assigned to some components while omitting those to avoid complexity. Note that the invention claimed is not limited to the following embodiments. Also, not all configurations described in the embodiments are necessarily essential for solving the problem. Figure 1 shows the overall configuration of an optical modulation device 100, which is one embodiment of an optical device. The optical modulation device 100 is mainly composed of a package 101 in which an optical modulation element 102 and a relay substrate 103 are hermetically sealed. The optical modulation element 102 is, for example, a DP-QPSK modulator. The optical modulation device 100 also has a plurality of signal pins 105 for inputting high-frequency electrical signals used to modulate the optical modulation element 102, and a feedthrough section 104 for introducing these signal pins 105 into the package 101. Furthermore, the optical modulation device 100 has an input optical fiber 111 for inputting light into the package 101, and an output optical fiber 118 for guiding the light modulated by the optical modulation element 102 to the outside of the package 101, on the same side of the package 101. The input optical fiber 111 and the output optical fiber 118 are fixed to the package 101, respectively, via support members 112 and 116. The light input from the input optical fiber 111 is collimated by a lens 113 located within the support 112, and then input to the optical modulation element 102 via lens 114. Alternatively, the end face of the input optical fiber 111 may be directly connected to the input section of the optical waveguide described later, without using a lens. The optical modulation device 100 also includes an optical unit 115 that polarization-combines the two modulated lights output from the optical modulation element 102. The polarization-combined light output from the optical unit 115 is focused by a lens 117 located within the support 116 and led to the output optical fiber 118. The relay board 103 relays the high-frequency electrical signal input from the signal pin 105 to the optical modulation element 102 via a conductor pattern (not shown). This conductor pattern is connected to one end of the signal electrode of the optical modulation element 102, for example, by wire bonding. The optical modulation device 100 also includes a plurality of terminators 109 having a predetermined impedance within the package 101. Figure 2 shows the configuration of the optical modulation element 102 used in the optical modulation device 100. The optical modulation element 102 has an optical waveguide 210 formed as part of the laminate 200, and performs DP-QPSK modulation at, for example, 200 gigabits per second (200G). The laminated structure of the laminate 200 will be described in detail later, but the optical waveguide 210 is mainly a ridge portion protruding from the waveguide layer contained in the laminate 200, and is formed as a path for guiding light on the plane of the laminate 200. In this embodiment, the laminated board 200 is formed in a rectangular shape. As shown in the figure, the direction of the long side is defined as the X-axis direction, the direction of the short side as the Y-axis direction, and the direction of the thickness as the Z-axis direction. The orientation of the laminated board 200 is indicated by the same coordinate axes in subsequent drawings. The optical waveguide 210 has an input section 210a on one of the short sides of the laminate 200 that receives input light from the input optical fiber 111. It then extends in the X-axis direction, passes through a semicircular curved section 210b that changes direction by 180°, and reaches a branching se