JP-7856926-B2 - Optical circuit and method for manufacturing an optical circuit

Inventors

• 藤原 裕士
• 片寄 里美

Assignees

• ＮＴＴ株式会社

Dates

Publication Date

20260512

Application Date

20221028

Claims (7)

1. A method for manufacturing an optical circuit, The steps include creating grooves on a wafer that will form the end faces of optical circuits with waveguides, The steps include creating a self-forming waveguide on the extension of the waveguide within the groove, The steps include forming a light-shielding film around the self-formed waveguide and on the wafer, The steps include removing the self-forming waveguide and forming an opening on the end face of the optical circuit that includes the cross-section of the waveguide core, The steps include forming a gas barrier film on the wafer, A manufacturing method comprising the steps of cutting the groove to produce a chip-shaped optical circuit.
2. A method for manufacturing an optical circuit, The steps include creating grooves on a wafer that will form the end faces of optical circuits with waveguides, The steps include forming a gas barrier film on the wafer, The steps include creating a self-forming waveguide on the extension of the waveguide within the groove, The steps include forming a light-shielding film around the self-formed waveguide and on the wafer, The steps include removing the self-forming waveguide and forming an opening on the end face of the optical circuit that includes the cross-section of the waveguide core, The steps include cutting the groove to produce a chip-shaped optical circuit and A manufacturing method that includes the following features .
3. The optical circuit is The waveguide is composed of a cladding layer on the wafer and a core formed within the cladding layer, The light-shielding film covers the end face of the chip including the cross-section of the core, and has an opening that leaves open the region including the cross-section, The gas barrier film covers the upper surface and all end faces of the chip. A manufacturing method according to claim 1 or 2, comprising :
4. The optical circuit is The system comprises two or more input waveguides into which visible light of different wavelengths is input, a multiplexer for the visible light of different wavelengths, and an output waveguide for the combined light. The manufacturing method according to claim 1 or 2, wherein each end of the input waveguide and the output waveguide has the opening .
5. The manufacturing method according to claim 1 or 2, wherein the diameter of the opening is 10 μm or less .
6. The manufacturing method according to claim 1 or 2 , wherein the core is composed of zirconium ( ZrO₂ ) doped SiO₂ or undoped SiO₂ .
7. The manufacturing method according to claim 3 , wherein the cladding layer is composed of boron-doped SiO2 or fluorine-doped SiO2 .

Description

The present invention relates to an optical circuit, and more specifically to an end structure for an optical circuit and a method for manufacturing the same. The technology of applying silica-based planar lightwave circuits (PLCs), which have primarily been developed in the field of optical communications, to visible light is attracting attention. PLCs form optical waveguides on a planar substrate such as a Si wafer by patterning using photolithography and reactive ion etching. The optical waveguide is formed by first creating a core and then filling the surrounding area with a cladding that has a lower refractive index than the core. PLCs are characterized by the high transmittance of their optical waveguides, and by combining several basic optical circuits such as directional couplers and Mach-Zehnder interferometers, low-loss optical functional circuits can be realized. PLCs also exhibit high transparency in the visible light band and have low propagation loss, making it possible to mass-produce low-loss, high-performance optical circuits. Examples of PLC applications in the visible light field include circuit elements that combine the three primary colors of visible light (R, G, B) for use in small projectors for eyewear-type displays and head-up displays. Furthermore, the use of silica-based PLCs is also progressing in optical circuits for ultra-compact analyzers for bio- and life science applications (Non-Patent Literature 1). When constructing optical circuits for optical instruments that use visible light, as described above, using silica-based PLCs, it is necessary to suppress the degradation of glass materials caused by visible light. In conventional silica-based PLCs, germania ( GeO₂ ) was commonly used as a dopant to increase the refractive index of the core constituting the waveguide. However, it is known that the refractive index of a germania-doped core fluctuates, especially when light with wavelengths close to blue (400-490 nm) is input (Non-Patent Literature 2). In recent years, in response to the increasing demand for silica-based PLCs for visible light, several waveguide structures with higher visible light resistance have been proposed. For example, those with zirconia ( ZrO₂ ) doped in the core (Patent Literature 1) and those using undoped SiO₂ as the core, i.e., undoped core PLCs, have attracted attention. Japanese Patent Publication No. 2017-187719Japanese Patent Publication No. 2020-204642 J. Sakamoto, S. Katayose, K. Watanabe, M. Itoh and T. Hashimoto, Proc. SPIE 10126, Advances in Display Technologies VII, 101260M, 2017N. Takato, T. Kominato, A. Sugita, K. Jinguji, H. Toba and M. Kawachi, in IEEE Journal on Selected Areas in Communications, vol. 8, p. 1120, 1990 The perspective view and cross-sectional view of the area near the tip of the optical circuit of Embodiment 1 are shown.This figure illustrates the procedure for fabricating the end face structure of the optical circuit disclosed herein.This diagram illustrates the position and function of chips and grooves in a wafer state.This figure shows the configuration of an optical circuit chip using a silica-based PLC according to Embodiment 2.This figure shows an optical circuit chip made of a silica-based PLC, which is a modified example of Embodiment 2. The optical circuit disclosed herein has an opening in the light-shielding film at the end face of the waveguide of the optical circuit, leaving an area including the core cross-section open. Furthermore, it is provided with a gas barrier film covering the top surface and end face of the chip of the optical circuit. The gas barrier film covering both the top surface and the end face of the chip prevents the shape of the emitted light from degrading over time due to moisture absorption. The light-shielding film can remove stray light from inside the chip. A novel structure for the chip end face in an optical circuit including a PLC is presented. The present invention also has aspects of a method for manufacturing an optical circuit. Hereinafter, embodiments of the optical circuit of the present invention will be described in detail with reference to the drawings. [Embodiment 1] Figure 1 shows a perspective view and a cross-sectional view of the chip end of the optical circuit of Embodiment 1. Figure 1(a) is a perspective view of the end face of the optical circuit chip 50, where the core cross-section of the input or output end of the waveguide is visible on the chip end face. To show the structure near the core cross-section, the front and back surfaces perpendicular to the chip end face including the core cross-section are shown in a cutaway view. Figure 1(b) is a cross-sectional view taken by a plane that includes the Ib-Ib line and cuts through the waveguide core 3 longitudinally. Both are schematic diagrams, and the size of the core 3 is depicted as significantly larger than it actually is, differing from the actual size relationships of each part. Also, note that the actua