학술논문
실리카 광도파로에 고분자 상부클래드를 적용한 온도 무의존 배열형 도파로 격자 연구 / A study on temperature-independent arrayed waveguide grating using a polymer upper cladding applied to silica optical waveguides
Document Type
Dissertation/ Thesis
Author
Source
Subject
Language
Korean
Abstract
배열형 도파로 격자 (Arrayed waveguide grating : AWG)는 데이터 전송 용량을 증가시키기 위한 대용량 고밀도 파장분할 다중화기 (Dense wavelength division multiplexer : DWDM) 시스템의 핵심 소자이며 고밀도 통신망의 제어관리와 분배 등에 사용된다. 고분자 광도파로 소재는 편광무의존성 (polarization independent)를 가지며 WDM 광소자 및 열광학 소자에 사용할 수 있다.실리카를 이용한 광도파로 소자는 0.01 dB/cm 이하의 낮은 광도파로 손실과 높은 안정성을 가지고 있으나 고가 제조 장비가 필요하며, 고분자에 비해 1/10 정도의 낮은 열광학 효과를 가지며 높은 소비전력이 필요하다. 고분자 광도파로 소재는 실리카를 이용한 광도파로 소재보다 제작이 쉬우며, 열 및 환경 안정성, 광통신 파장영역에서 낮은 광 손실, 미세한 굴절률 조절, 낮은 복굴절률, 다양한 기판에 대한 접착성 등 많은 장점을 가지고 있다. 본 연구에서는 광통신용 실리카 평면 도파로 기반의 광학 소자를 제작하고 실리카 광도파로에 고분자 상부클래드를 적용하여 온도무의존 0.75 %Δ, 100 GHz 16채녈 배열형 도파로 격자를 연구하였다. 상부클래드용 고분자 소재 연구와 더불어 포토리소그래피, RIE (Reactive Ion Etching), ICP (Inductively Coupled Plasma), 화염 가수 분해 증착 (Flame Hydrolysis Deposition : FHD)와 같은 반도체 공정 기술을 사용하였다. 배열형 도파로 격자는 배열된 도파로의 회절 현상에 의해 작동하며 광도파로 해석은 유효굴절률 법을 적용하였고 프로메테우스 프로그램을 사용하여 전산 시물레이션하고 설계하였다. 상부클래드로 사용된 고분자는 높은 열적 안정성과 저 손실, 낮은 음의 열광학 계수를 가지는 불소 치환계 단량체와 가교 결합을 형성하는 에폭사이드 작용기를 갖는 3종의 단량체를 일정 비율로 혼합하여 합성하였다. 공중합체의 Tg를 조절하기 위해 메타크릴계 pentafluorostyrene을 사용하였으며 fluoroethyl methacrylate는 낮은 음의 열광학계수를 가지는 공중합체를 제조하기 위하여 사용하였다. 실리카 코어 박막에 용액으로 스핀 코팅 후 공중합체의 가교결합을 형성하기 위하여 glycidyl methacrylate를 사용하였다. 합성된 공중합체의 열광학 계수 (dn/dT)는 –1.11×10-4/K, 실리카 유리는 1×10-5/K 이었다. 고분자로 상부클래딩하여 제작된 100 GHz 16채널 배열형 도파로 격자의 비근접 채널 누화 31.67 dB, 평균 삽입손실 5.33 dB, 손실 균일도 0.86 dB, PDL 0.162 dB를 보였다. 온도변화에 따른 파장 이동은 20~90 ℃에서 약 0.15 nm ( 0.002 nm/℃)의 차이를 보였다.
rrayed waveguide grating (AWG) is a key element of a large-capacity dense wavelength division multiplexer (DWDM) system to increase data transmission capacity and is used for control management and distribution of high-density communication networks. Polymeric optical waveguide materials can be used for polarization independent, WDM-related optical devices, optical interconnector, passive devices such as optical splitters and optical couplers, thermal optical switches that control optical signals by heat, and variable attenuators.The optical waveguide device using silica has low optical waveguide loss and high stability under 0.01 dB/cm, but requires a high temperature manufacturing process of 1,000 ℃ or higher and expensive manufacturing equipment, and has a thermo-optical effect that is about 1/10 lower than that of the polymer, so high power consumption is required to drive the device. Polymer optical waveguide materials can be manufactured more easily than optical waveguide using silica, and have many advantages such as thermal and environmental stability, low light loss in optical communication wavelength, fine refractive index controllability, low birefringence, and adhesion to various substrates. In this study, an optical device based on a silica planar waveguide for optical communication was fabricated and a temperature-independent 0.75 Δ%, 100 GHz 16-channel arrayed waveguide grating was studied by applying a polymer upper cladding to the silica optical waveguide. In addition to research on polymer materials for upper cladding, semiconductor process techniques such as photolithography, reactive ion etching (RIE), inductively coupled plasma (ICP) etching, and flame hydrolysis deposition (FHD) were used. The arrayed waveguide grating operates by the diffraction phenomenon of the arrayed waveguide, and the optical waveguide analysis was simulated and designed using the effective refractive index method and the Beam Propagation Method (BPM) optical tool.The polymer used as the upper cladding was synthesized by mixing a fluorine-substituted monomer having high thermal stability, low loss, and low negative thermo-optical coefficient and three monomers having an epoxide functional group forming a cross-linking bond at a constant ratio. Methacrylic pentafluorostyrene was used to control Tg of the copolymer, and trifluoroethyl methacrylate was used to prepare a copolymer having a low negative thermo-optical coefficient. After spin-coating with a solution on a silica core thin film, glycidyl methacrylate was used to form a cross-linking bond of the copolymer. The thermo-optical coefficient (dn/dT) of the synthesized copolymer was –1.11×10-4/K and that of silica glass was 1×10-5/K. A 100 GHz 16-channel arrayed waveguide manufactured by upper cladding with a polymer showed 31.67 dB of non-adjacent channel crosstalk, 5.33 dB of average insertion loss, 0.86 dB of loss uniformity, and 0.162 dB of PDL. The wavelength shift according to the temperature change showed a difference of about 0.15 nm (0.002 nm/°C) at 20~90 °C.
rrayed waveguide grating (AWG) is a key element of a large-capacity dense wavelength division multiplexer (DWDM) system to increase data transmission capacity and is used for control management and distribution of high-density communication networks. Polymeric optical waveguide materials can be used for polarization independent, WDM-related optical devices, optical interconnector, passive devices such as optical splitters and optical couplers, thermal optical switches that control optical signals by heat, and variable attenuators.The optical waveguide device using silica has low optical waveguide loss and high stability under 0.01 dB/cm, but requires a high temperature manufacturing process of 1,000 ℃ or higher and expensive manufacturing equipment, and has a thermo-optical effect that is about 1/10 lower than that of the polymer, so high power consumption is required to drive the device. Polymer optical waveguide materials can be manufactured more easily than optical waveguide using silica, and have many advantages such as thermal and environmental stability, low light loss in optical communication wavelength, fine refractive index controllability, low birefringence, and adhesion to various substrates. In this study, an optical device based on a silica planar waveguide for optical communication was fabricated and a temperature-independent 0.75 Δ%, 100 GHz 16-channel arrayed waveguide grating was studied by applying a polymer upper cladding to the silica optical waveguide. In addition to research on polymer materials for upper cladding, semiconductor process techniques such as photolithography, reactive ion etching (RIE), inductively coupled plasma (ICP) etching, and flame hydrolysis deposition (FHD) were used. The arrayed waveguide grating operates by the diffraction phenomenon of the arrayed waveguide, and the optical waveguide analysis was simulated and designed using the effective refractive index method and the Beam Propagation Method (BPM) optical tool.The polymer used as the upper cladding was synthesized by mixing a fluorine-substituted monomer having high thermal stability, low loss, and low negative thermo-optical coefficient and three monomers having an epoxide functional group forming a cross-linking bond at a constant ratio. Methacrylic pentafluorostyrene was used to control Tg of the copolymer, and trifluoroethyl methacrylate was used to prepare a copolymer having a low negative thermo-optical coefficient. After spin-coating with a solution on a silica core thin film, glycidyl methacrylate was used to form a cross-linking bond of the copolymer. The thermo-optical coefficient (dn/dT) of the synthesized copolymer was –1.11×10-4/K and that of silica glass was 1×10-5/K. A 100 GHz 16-channel arrayed waveguide manufactured by upper cladding with a polymer showed 31.67 dB of non-adjacent channel crosstalk, 5.33 dB of average insertion loss, 0.86 dB of loss uniformity, and 0.162 dB of PDL. The wavelength shift according to the temperature change showed a difference of about 0.15 nm (0.002 nm/°C) at 20~90 °C.