Highly efficient doubling of a high-repetition-rate diode-pumped laser with bulk periodically poled KTP.

An internal doubling efficiency of 64% at 2 MW/cm2 was obtained in a single-pass configuration with an uncoated, 1-cm-long, bulk periodically poled KTP crystal placed outside the resonator of a pulsed, diode-pumped Nd:YAG laser. An average of 4.8  W of green light was obtained from a 7.5-W pump beam inside the crystal. Doubling efficiency exceeded 50% at levels of 0.75 MW/cm2. The measured thermal tolerance of the doubling process (FWHM) was 3.3 C° cm, and the measured temperature tuning coefficient was 0.053 nm/C°.