Elimination of polarization sensitivity in silica-based wavelength division multiplexer using a polyimide half waveplate

This paper proposes a low-loss technique for eliminating polarization sensitivity in a silica-based planar lightwave circuit (PLC) which uses a polarization mode converter formed at the center of the circuit. This converter consists of a waveguide gap housing a polyimide half waveplate. The excess loss of the converter was drastically reduced to 0.26 dB with a /spl Delta/=0.75% waveguide by employing an 18 /spl mu/m-wide waveguide gap and a 14.5 /spl mu/m-thick polyimide half waveplate. A polarization mode conversion crosstalk of -37 dB was achieved at 1.55 /spl mu/m. Using this converter, we successfully eliminated the polarization sensitivity in some silica-based PLC-type wavelength division multiplexers. The converter is also insensitive to temperature and offers long term stability.