TE-Pass Polarizer Based on Epsilon-Near-Zero Material Embedded in a Slot Waveguide

A horizontal silicon slot waveguide TE-pass polarizer with thin indium-tin oxide (ITO) layer embedded in the slot region is proposed and investigated. Since the dispersion relation of the material can be tuned by properly adjusting the carrier concentration, ITO is able to act as epsilon-near-zero (ENZ) material with high absorption near 1.55-μm wavelength. With thin ENZ material embedded in the slot waveguide, huge polarization-dependent loss between fundamental TE mode and TM mode can be induced. Therefore, the slot waveguide functions as a TE-pass polarizer with good performance. Our simulation shows that in a 3-μm-long polarizer with 10-nm-thick ITO layer embedded in the slot region, insertion loss of 42 dB for TM mode, and 0.38 dB for TE mode can be achieved simultaneously. The polarizer possesses the advantages of low insertion loss, high extinction ratio, ultra-compact, broadband, and large fabrication tolerance.