Over 20 W alexandrite laser with beam quality M² < 1.05

Alexandrite lasers exhibit exceptional power-scaling potential at room temperature, yet this capability remains underexplored. We have demonstrated a continuous-wave (CW) alexandrite laser achieving a record output power of 20.4 W in single transverse-mode operation, surpassing all prior reports for laser diode pumped systems. The demonstrated fundamental-mode laser exhibits a high optical-to-optical efficiency of 34%, near-diffraction-limited beam quality M² < 1.05, and exceptional stability (RMS < 0.2% over 2 hours), stemming from elaborate dynamically stable resonator optimization and excellent heat dissipation. This advance provides compelling evidence for the superior room-temperature power-scaling capability of alexandrite with excellent efficiency and exceptional beam quality.