High-power, 420-nm, low-intensity-noise laser source for quantum computing applications

We demonstrate the generation of 20.2 W of continuous-wave, low-intensity noise, single-frequency light at 840 nm, obtained via sum-frequency mixing of two high-power infrared fiber laser systems in an MgO-doped periodically poled lithium niobate (ppLN) crystal. Subsequent cavity-enhanced frequency doubling to 420 nm yields an output power of 15.2 W. Respective conversion efficiencies of 48% and 79% are achieved for the sum-frequency and second-harmonic stages, with good beam quality (M² < 1.3), low intensity noise (<0.05% RMS [1 kHz-10 MHz]), and long-term continuous operation. Relative intensity noise and frequency noise of the generated signals are experimentally characterized.