All-solid-state, tunable, single-frequency source of yellow light for high-resolution spectroscopy.

We demonstrate a cw doubly resonant optical parametric oscillator that is frequency doubled in an external resonant cavity to the visible spectral range. We obtained single-frequency radiation in the range 565-590 nm with as much as 3.8 mW of power, which is continuously tunable over an 18-GHz range and step tunable over 160 GHz. The source is well suited for high-resolution spectroscopy in the visible region. As a demonstration, we performed persistent hyperfine spectral hole-burning spectroscopy of Eu(3+): Y(2)SiO(5) . Reliable operation of the source permitted studies of the hole's lifetime over several hours.