Efficient second-harmonic conversion of cw single-frequency Nd:YAG laser light by frequency locking to a monolithic...

Efficient second-harmonic conversion of the 1064-nm output of a diode-pumped cw single-frequency Nd:YAG laser to 532 nm was obtained by frequency locking the laser to a monolithic ring resonator constructed of magnesium-oxide-doped lithium niobate. The conversion efficiency from the fundamental to the second harmonic was 65%. Two hundred milliwatts of cw single-frequency 532-nm light were produced from 310 mW of power of 1064-nm light. This represents a conversion efficiency of 20% from the 1-W diode laser used to pump the Nd:YAG laser to single-frequency 532-nm output. No signs of degradation of the 532-nm power or photo-refractive damage in the crystal were observed for over 500 h of operation of the system at green output powers greater than 100 mW.