Low Divergence Angle Extended-Cavity Single-Mode VCSEL Based on Dielectric DBR Mirror

We present a vertical cavity surface emitting laser (VCSEL) employing the extended-cavity structure and dielectric film reflector, with a 4.5 µm oxide aperture diameter. The laser operates in fundamental transverse mode with side-mode suppression ratio (SMSR) exceeding 30 dB at 1090 nm. The divergence angle is limited to only 4°, attributed to increased diffraction loss for high-order transverse modes and a larger mode field size facilitated by the extended-cavity. The top reflector comprises sputtered dielectric distributed Bragg reflector, while current spreading and partial reflectivity are facilitated by 3 pairs of p-doped DBRs. The device demonstrates a low thermal resistance of 1.3 K/mW and exhibits robust temperature stability. The combination of stable single-mode performance, minimal divergence angle, and low thermal resistance establish this VCSEL design as a promising candidate for high-performance single-mode VCSELs suitable for applications in atomic sensing and high-precision metrology.