Compact 2 x 2 polarization-diversity Si-wire switch

A polarization-independent 2 x 2 switch based on silicon-wire waveguides has been realized with a compact size of 600 x 500 mu m(2). Polarization-independent operation was achieved with a polarization-diversity technique which implements polarization splitters, TE-TM intersections, and Mach-Zehnder switches. The extinction ratios of the 2 x 2 switch for TE, TM, and a mixed polarization at a wavelength of 1550 nm were measured to be larger than 30 dB, 25 dB, and 30 dB, respectively. The measured switching powers for the TE and TM polarizations were 25 and 55 mW, respectively. The measured polarization-dependent loss was lower than 1 dB. The differential group delay (DGD) between the TE and TM modes was also evaluated using the Mueller matrix method, which was in good agreement with the values estimated from the path lengths for each mode. A path-length-compensated switch was fabricated, whose DGDs for all paths were indeed as small as similar to 2 ps, mainly from the access waveguides. The switch could provide an important route to develop ultra-compact polarization-independent integrated circuits based on silicon-wire waveguides. (C) 2014 Optical Society of America