Polarization-insensitive arrayed-waveguide grating wavelength multiplexer on silicon

A wavelength-division multiplexer with no polarization dependence is demonstrated. It is based on an arrayed-waveguide grating fabricated with silica-based optical waveguides on a silicon substrate. The polarization dependence that is due to the birefringence of the waveguide is eliminated by inserting a quartz lambda/2 plate in the middle of the arrayed waveguide. Moreover the grating is designed to operate in the 115th order for high wavelength resolution. The polarization insensitivity and the high resolution lead to the successful multiplexing of 13 wavelength channels with 1-nm spacing. A passband width of 0.3 nm and a cross-talk level of -30 dB are achieved.