Simulation of Grating–WGM Hybrid Microcavity for Directional TM Polarization Lasing Emission

Whispering Gallery Mode (WGM) microcavities’ high-quality (Q)-factors enable WGM-X hybrid systems for multimode dynamics and light interconnects, yet their non-directional emission limits practicality. We propose a WGM–grating hybrid design that is predicted to enable stable, directional, polarization-resolved lasing. COMSOL simulations at λ = 620 nm show that phase matching requires Λ = 0.426 μm. Tuning Λ and duty cycle η controls grating–harmonic coupling, selectively enhancing the Ey field component. At η = 0.5, the simulation results suggest that the device is expected to achieve single-direction transverse magnetic (TM) polarized emission (TM mode contribution: 92%) with low loss (Q~105) and a divergence angle of approximately 3° (the angular difference at which the far-field emission intensity decreases to 1/e2 of its peak value). This model achieves strong coupling by tuning the refractive index of the photoresist and, by incorporating a four-harmonic resonant cavity coupling model, predicts a maximum Rabi splitting of 99.8 μeV. In this regime, the simulations predict that enhanced “Photonic Nanojet” effects create additional output channels, transforming single-direction into bidirectional emission with the total emission intensity increased to 1.5× its original value. This work advances understanding of directional, polarization-selective emission in high-Q WGM hybrid structures.