High efficiency frequency tripling schemes for high-power Nd: Glass lasers

A comparison is made of three schemes ("angle-detuned," "polarization-mismatch," and "polarization-bypass") permitting high efficiency frequency tripling of 1 μm laser radiation. The overall characteristics of each are examined in terms of sensitivity to input intensity, polarization angles, and mismatch angles. The "polarization-mismatch" scheme is favored for tripling current high-power 1 μm Nd:glass laser radiation with KDP crystals, while for future systems the "polarization-bypass" scheme may be optimum. All schemes permit the tripling of some shaped pulses without substantial degradation in efficiency. The theory of tripling in KDP is reviewed.