Parabolic dielectric reflector for extreme on-chip spot-size conversion with broad bandwidth

作     者：Moreno-pozas, Laureano Barona-ruiz, Miguel Halir, Robert De-oliva-rubio, Jose Rivas-fernandez, Jorge Molina-fernandez, Inigo Wanguemert-Perez, J. gonzalo Ortega-monux, Alejandro 

作者机构：Univ Malaga Telecommun Res Inst TELMA Photon & RF Res Lab Louis Pasteur 35 Malaga 29010 Spain 

出 版 物：《OPTICS LETTERS》 (Opt. Lett.)

年 卷 期：2025年第50卷第4期

页      面：1073-1076页

核心收录：

学科分类：070207[理学-光学] 07[理学] 08[工学] 0803[工学-光学工程] 0702[理学-物理学] 

基　　金：Ministerio de Ciencia  Innovacion y Universidades [TED2021-130400B-I00  PDC2023-145833-I00] 

主　　题：Chemical vapor deposition Deflectors Grating coupler Polarization control Reflectors Waveguides 

摘      要：Spot-size converters (SSCs) are key for efficient coupling of light between waveguides of different sizes. While adiabatic tapers are well suited for small size differences, they become impractically long for expansion factors around x100, which are often required when coupling integrated waveguides and free-space beams. Evanescent couplers and Bragg deflectors can be used in this scenario, but their operation is inherently limited in bandwidth. Here, we propose a solution based on a parabolic dielectric interface that couples light from a 0.5 mu m wide waveguide to a 285 mu m wide waveguide, i.e., an expansion factor of x570. We experimentally demonstrate an unprecedented bandwidth of more than 380 nm with insertion losses below 0.35 dB. We furthermore provide analytical expressions for the design of such parabolic spot-size converters for arbitrary expansion factors. (c) 2025 Optica Publishing Group. All rights, including for text and data mining are reserved.