Growth of High-Quality CLBO Crystals for High-Power 266 nm DUV Laser

In this work, LiF was introduced as a flux additive to overcome the high viscosity challenge of the self-flux system, which successfully grew a large-scale cesium lithium borate (CLBO) single crystal with dimensions of 136 × 132 × 68 mm3 and a weight of 1275 g via the top-seeded solution growth (TSSG) method. The as-grown crystal showed an optical transmittance of over 90% in the spectral range of 230–1880 nm and an extremely low absorption coefficient of 2.8 ppm/cm at 1064 nm. Notably, under 120 W pumping at a high repetition rate of 2 MHz, the fabricated CLBO optical element achieved a record-high 266 nm output power of 26.1 W with an optical conversion efficiency of 21.75%. Moreover, the laser system maintained stable continuous operation at >23 W for over 120 h.