High-performance transverse magnetic mode-pass polarizer based on silicon nitride–silicon subwavelength grating waveguide for mid-infrared wavelengths

Abstract

A high-performance transverse-magnetic (TM) mode-pass polarizer for mid-infrared wavelengths based on a silicon nitride–silicon subwavelength grating (SWG) waveguide is proposed. The designed device supports the Bloch mode for the TM mode only, whereas the transverse-electric mode is reflected by the SWG. Simulations show that with a device length of 7 µm, this polarizer is capable of achieving an ultrahigh polarization extinction ratio (PER) of ∼50 dB and an insertion loss of ∼0.3 dB at a wavelength of 2 µm. The device bandwidth is increased to 60 nm for PER > 30 dB. The polarizer also shows good tolerance to fabrication uncertainties.