Computation analysis of Si waveguides on AlN substrate with GaN cladding

This study presents the computational design and analysis of a silicon (Si) core optical waveguide structure featuring a gallium nitride (GaN) cladding and an aluminum nitride (AlN) substrate, optimized for operation at the telecommunication wavelength of 1.55 µm. Using COMSOL Multiphysics simulations, key waveguide performance variables-including effective mode index, power confinement factor (PCF), and propagation loss have been thoroughly investigated. The optimized waveguide demonstrates strong optical confinement, achieving a high PCF of approximately 98% and low propagation losses of -0.925 dB/cm for TE and -0.94 dB/cm for TM mode, thus enabling efficient light guiding within the Si core. The effective mode index has the value of 3.31 for TE mode and 3.33 for the TM mode. Analysis of TE and TM mode profiles shows minimal mode leakage and high confinement, particularly under asymmetric and rotational configurations. Bending loss analysis further supports the waveguide's suitability for compact photonic circuits. The waveguide structure displays the reflecting loss of -22.76 dB as well as -16.07 dB for TE mode and transmission loss of -6.5 dB for TE and -13.38 dB for TM for the bending radius of 2 μm. These findings suggest that the proposed Si–GaN–AlN waveguide platform holds significant potential for next-generation integrated photonic devices requiring strong confinement, thermal stability, and low-loss transmission at 1.55 µm.