Lateral mode selection of a novel laser structure with surface tapered distributed Bragg reflectors

Abstract

This study proposes a theoretical model and optical simulation framework to achieve single lateral mode operation in broad-area mesa lasers by integrating surface narrow distributed Bragg grating (DBR) reflectors. By introducing an effective grating confinement factor (Γ_g,eff) to refine the coupling coefficient formula for buried heterostructure gratings, we systematically analyze the impact of grating parameters—etching depth (d_g), width (W_g), and filling factor (γ)—on the coupling coefficients (κ) and reflectivity of TE₀₀ and TE₀₁ modes. Key relationships between modal discrimination (MD) and grating parameters, as well as cavity length (L), are established. We propose a novel surface tapered DBR structure with varying W_g, which enhances MD notably compared to uniform gratings, while maintaining high TE₀₀ reflectivity. This work provides a design paradigm for high-power, single-lateral-mode lasers, bridging the gap between broad-area mesa scalability and spectral purity requirements in applications such as atomic clocks and precision navigation systems.