Electro‐optic and piezo‐optic tuning of second‐order nonlinear processes in crystals

摘要

The power‐handling capability of crystals utilized for second harmonic generation (SHG) and other nonlinear frequency conversions has until recently been limited to a few watts of average output power, chiefly because of two conditions, namely, thermal instability and thermal gradients. Now, techniques have been invented that correct these conditions with a resulting order of magnitude increase in the average output power produced by SHG. This paper presents the theory for two techniques that solve the problem of thermal instability, namely, electro‐optical tuning (EOT) and piezo‐optical tuning (POT). Beam shaping, which prevents thermal gradients, will be treated in a separate paper. In this paper, the general physical theory is discussed both for EOT and POT. The equation for the phase‐match condition is given. Interactive effects of temperature change ΔT, the applied electric field (E), and the stress field σ on a fixed‐position crystal are treated. The general equations for EOT and POT are developed. Examples of the effect on SHG in cesium dideuterium arsenate (CD*A) are given. Using these techniques, with beam shaping to be described in a separate paper, 35 W of average output power at 0.53 μ has already been demonstrated.