660 nm GaInP-Enhanced Red VCSEL With Low Threshold and High-Purity Single-Mode Output

Red vertical-cavity surface-emitting lasers (VCSELs) are widely used in sensing, imaging, and short-reach optical interconnects. However, conventional GaAs-based red VCSELs often suffer from strong optical absorption in the heavily doped p-GaAs contact layer, which limits output power and deteriorates single-mode stability. In this work, a 660 nm oxide-confined VCSEL is developed using a transparent GaInP current spreading layer above the p-type distributed Bragg reflector. This design effectively reduces optical loss while maintaining efficient lateral current injections. The fabricated device achieves a threshold current of 0.3 mA and a continuous-wave output power of 0.51 mW. High beam quality is demonstrated by a side-mode suppression ratio exceeding 30 dB, a Gaussian far-field divergence of 11.5° - 14.0° (1/e<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>), and a polarization degree of 99.6% with an orthogonal polarization suppression ratio of 26.8 dB. This transparent-contact architecture improves modal purity and polarization stability in red VCSELs, providing a scalable pathway toward high-performance, single-mode visible light sources.