AlGaN-based UV-C distributed Bragg reflector with a λ-cavity designed for an external cavity structure electron-beam-pumped VCSEL

Abstract

The external cavity structure electron-beam-pumped (EB-pumped) vertical cavity surface emitting laser (VCSEL) has an important demand for the distributed Bragg reflector (DBR) with an emission window at the working wavelength called λ-cavity. Herein, AlGaN-based UV-C band DBRs with λ-cavities around 280 nm are designed and investigated in detail, which have almost no been reported so far. The DBRs based on alternate stacked Al0.47Ga0.53N/AlN bilayers are in-situ grown by low-pressure metal-organic chemical vapor deposition (LP-MOCVD). Through a comprehensive protocol of structure optimization by theoretical simulation, epitaxial growth and in-depth characterization and analysis, a high-performance UV-C band DBR with a λ-cavity around 280 nm is successfully fabricated. The DBR presents a reflectivity as high as 81.3% at the λ-cavity, a maximum reflectivity of 89.8% at 282 nm and a stopband with a full-width at half-maximum (FWHM) of 24.7 nm, laying a foundation for developing the external cavity structure EB-pumped AlGaN-based UV-C VCSELs emerging as a promising alternative to the electrically pumped AlGaN-based UV-C lasers.