Ultra-compact ITO-based plasmonic electro-absorption modulator and polarizer with enhanced performance

Plasmonic electro-absorption modulators offer a promising route toward compact and high-speed photonic integrated circuits, although their performance is often constrained by weak optical interaction with the active ITO accumulation region and the inherent trade-off between extinction ratio (ER) and insertion loss (IL). To address these limitations, this work presents a dual-functional ITO-based electro-absorption modulator and TE-pass polarizer employing a compact diagonal Si/ITO/HfO 2 /Si stack on a silica substrate. The device is optimized and analyzed using the finite-element method in COMSOL Multiphysics. The diagonal ITO layer intersects the maximum TM electric-field region, enhancing light-matter interaction and OFF-state absorption, while a reduced ON-state carrier concentration minimizes IL. The proposed modulator achieves an ER of 21.12 dB/µm, an IL of 0.0182 dB/µm, and a figure of merit (FOM) of 1159, corresponding to a 3-dB length of 142 nm and a footprint of 0.0497 µm 2 . It also provides a switching frequency of 424.4 GHz and an optical bandwidth of 230 nm covering the standard telecommunication wavelength of 1550 nm. By combining TM-mode modulation and TE-pass polarization in a single ultra-compact component, the design can reduce the footprint and complexity of CMOS-compatible photonic integrated circuits for high-speed optical communication and integrated polarization control.