High Contrast Grating Optimization for a Tunable 1060 nm MEMS-VCSEL

This paper focuses on the design and optimization of high contrast gratings (HCGs) used in tunable microelectromechanical system - vertical-cavity surface emitting lasers (MEMS-VCSELs). The optimization consists of mitigating reflectivity dips, that can present when incidence angle effects are not considered, to obtain a broad reflectivity bandwidth. Two new designs are proposed, low-duty-cycle and focusing HCG. These designs are verified using FDTD 3D simulations and then fabricated. From the characterization, the best result was obtained with a low-duty-cycle design, that achieved a maximum tuning range of 67.8nm and an average tuning range 62.2nm and 50.2nm respectively. Furthermore, the new designs and a better far-field profile compared to the standard design, indicating improved light extraction efficiency. These findings demonstrate the promise of optimized HCGs, although further fabrication refinement is crucial to consistently achieve and maximize their performance for swept-source optical coherence tomography (SS-OCT) applications.