Improvement of conversion efficiency of DUV light generation at 221-nm using CLBO crystal

We are developing a 100-W level DUV light source using a solid-state seed laser and an ArF amplifier. Seed pulse at 193nm is generated by the sum frequency mixing of the pulse at 221nm and the pulse at 1553nm using CLBO crystals. To realize a compact and robust seed laser, we improved the conversion efficiency of DUV light generation. In case of the 221nm pulse generation, the conversion efficiency was increased from 22% to nearly 50% by optimizing the conversion process which enables the reduction of amplifier unit of fundamental light source to obtain the 1W seed pulse at 193nm.