Optimization of silicon-photonic crystal (PhC) waveguide for a compact and high extinction ratio TM-pass polarization filter

A silicon photonic crystal waveguide based design of a highly-compact transverse-magnetic pass polarization filter has been proposed in this paper. The device utilizes both the index guiding and bandgap property simultaneously to realize its operation as a polarizer. Optimizations of different device-parameters, such as the radius of the holes, width, thickness, and length of the waveguide, have been performed for attaining its paramount performance. A small waveguide length, in the order of 5 μm, has shown a high extinction ratio, i.e., 45 dB, at the wavelength of 1550 nm. A uniform bandwidth of ≈120 nm is observed, beyond the extinction ratio of 40 dB, along with a remarkably low insertion loss, i.e., ≈0.6 dB. Investigations are also performed to evaluate performances of the polarizer under possible fabrication disorders, which depicts a sustained performance up to at least a random fabrication disorder of 30 nm. These merits make the polarizer suitable for applications in densely integrable photonic integrated circuits.