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High-power wavelength converters with feedback.

We have shown theoretically and experimentally that very high conversion efficiencies can be obtained in high-peak-power wavelength converters utilizing small amounts of feedback, at fluences similar to the no-feedback case. Maximum efficiencies are obtained with radially varying reflectivity profiles. We have demonstrated the concept, using second-harmonic generation in a deuterated potassium dihydrogen phosphate crystal in which 70% energy conversion was obtained, in agreement with simulation results. Energy conversion efficiencies of 56% were also obtained in a beta-barium borate optical parametric oscillator.