Design and Optimization of Angle-Dependent Grating Couplers for Wideband Near-Mid Infrared Transmission

This letter presents a novel multiwavelength, broadband trapezoidal bilayer grating structure designed for near to mid infrared (MIR) applications on two distinct platforms. At approximately 2
$\upmu \text{m}$
, our germanium on insulator grating structure demonstrated a 3-dB bandwidth of 50 and 168 nm for transverse electric (TE) and transverse magnetic (TM) modes, respectively, achieving coupling efficiencies of approximately 76% and 60%, along with additional coupling efficiency peaks. Conversely, our silicon nitride on insulator grating structure exhibited a 3-dB bandwidth of approximately 200 and 128 nm for TE and TM modes, respectively, achieving coupling efficiencies of approximately 42% and 52% at a wavelength of 1.7
$\upmu \text{m}$
.