Demonstration of long-term reliability of a 266-nm, continuous-wave, frequency-quadrupled solid-state laser using ?-BaB_2O_4

We report what we believe to be the first operation of more than 1000??h of a 266-nm (cw) frequency-quadrupled solid-state laser with a 100-mW output. We used ??BaB2O4 (BBO) crystal grown by the Czochralski method to double the green-light (532-nm) wavelength, using an external resonant cavity. The green light was generated with an intracavity frequency-doubled Nd:YVO4 laser pumped by a 4-W laser diode. When the incident 532-nm power on the external resonant doubler was 500??mW, we generated 100??mW of cw 266-nm radiation with the BBO crystal. The degradation rate seems to be proportional to the strength of the UV optical electric field. We also obtained a relative intensity noise of -130 dB/Hz at frequencies of 2 to 10??MHz for 266-nm laser light.