High-repetition-rate 2.4 W picosecond 213-nm deep ultraviolet light generation at 81 MHz

We report on the generation of a 213 nm deep ultraviolet (DUV) light with an average power of up to 2.4 W at 81 MHz. The 213 nm light is achieved through sum-frequency generation (SFG) of the 1064 nm and 266 nm light, based on a “1+4” scheme in a cesium lithium borate (CLBO) crystal. The conversion efficiency from 266 nm to 213 nm reaches as high as 68%, benefiting from the small walk-off of the CLBO crystal and the separated focusing design. By using a cylindrical lens as the beam shaping system, the beam quality factors are 1.24 and 1.34 in X and Y directions at the maximum output power. Furthermore, the monitored output power stability at 1 W over 9 h presents a calculated rootmean- square (RMS) power fluctuation of 2.67%. The beam pointing stabilities of the 213 nm beam are 15 μrad and 26 μrad in the X direction and Y direction, respectively. Such a DUV light system holds significant potential to make a substantial impact across applications, including semiconductor processing and materials research.