2025/01/06 by Laureano Moreno‐Pozas, Moreno-Pozas, Laureano, Miguel Barona-Ruiz +13 · 2 citations
Engineering · Materials Science · #Applied Physics (physics.app-ph) #FOS: Physical sciences #Optics (physics.optics) #Phase-change materials and chalcogenides #Photonic and Optical Devices #Semiconductor Lasers and Optical Devices
paper · pdf · doi:10.48550/arxiv.2501.03206
openalex publication_date 2025/01/06 · openalex created_date 2025/01/08 · openalex updated_date 2026/07/28
Spot-size converters 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 um-wide waveguide to a 285 um-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.