Low-loss passive optical waveguides based on photosensitive poly(pentafluorostyrene-co-glycidyl methacrylate)

Abstract

Low-loss optical waveguides have been fabricated from fluorinated copolymers designed to incorporate photochemical amplification based on acid catalysis. Core and cladding layers were made, for single-mode (SM) channel waveguides, from the poly(pentafluorostyrene-co-glycidyl methacrylate) copolymer series and, for multimode (MM) ridge waveguides, from poly(tert-butyl methacrylate-co-glycidyl methacrylate) as the cladding and poly(pentafluorostyrene-co-glycidyl methacrylate) as core layer. The reactivity ratios for PFS and GMA monomers have been measured to be r(PFS) = 0.38±0.01 and r(GMA) = 0.89±0.01 in free radical polymerization. Variation of the copolymer composition allowed precise control over the refractive index measured at 589, 633, 1320, and 1550 nm. These amorphous copolymers were photo-cross-linked by contact printing and developed by wet etching to produce high quality ridge waveguides with very smooth top surfaces. Low loss single-mode (SM) waveguides exhibit averaged losses over eight channel waveguides as low as 0.39 dB/cm at 1320 nm and 0.42 dB/cm at 1550 nm. Thermal properties have been examined and optical losses were measured after two different annealings at 200 and 250 °C for 1 h.