AlGaN-based deep ultraviolet vertical-cavity surface-emitting lasers on a flexible substrate

Integrating vertical-cavity surface-emitting lasers (VCSELs) on flexible substrates offers significant opportunities for developing smart light sources and multifunctional photonic platforms. In this study, AlGaN-based deep ultraviolet VCSELs on a flexible substrate were demonstrated. The AlGaN quantum well heterojunction was separated from the sapphire substrate by selectively removing the thin n-GaN sacrificial layer using electrochemical etching and subsequently transferred onto a flexible substrate. Meanwhile, two dielectric distributed Bragg reflectors were deposited to construct the vertical resonant cavity. Single-mode lasing at 294.2 nm with a threshold power density of 7.4 MW/cm² and a linewidth of 0.39 nm was achieved at room temperature. Furthermore, multimode lasing attributed to non-uniformities within the distributed Bragg reflectors cavity was observed. This work opens up possibilities for advancing flexible VCSELs, as well as for the flexible photonic integration in the deep ultraviolet spectrum.