Watt-level all-solid-state single-frequency 248 nm DUV source

An all-solid-state single-frequency 248 nm deep-ultraviolet (DUV) source with watt-level (~1.2 W) average power was realized by sum-frequency generation (SFG) between 355 nm and 827 nm lasers, which is nearly one order-of-magnitude higher than our previous result [Opt. Lett.50, 1881 (2025)10.1364/OL.553247]. For this advancement, pulsed pumping was employed to increase the pulse energy of the 1064-nm fundamental driver. Meanwhile, simulation-guided optimization on the length of the LBO crystal was performed to maximize the conversion efficiency of the 827-nm optical parametric oscillator (OPO). Benefiting from both, the conversion efficiency from 1064 nm to 248 nm source was improved from 1.41% to 3.93% at 4 kHz. The beam quality factors M² in the x and y directions were measured to be 1.61 and 1.10, respectively, and the linewidth was estimated to be ~270 MHz. To the best of our knowledge, this is the first watt-level output reported for all-solid-state single-frequency 248 nm source.