Optical Rectification

Optical rectification, which is the production of a steady polarization in certain crystals by the action of an intense optical electric field, was first observed in crystals of K${\mathrm{H}}_{2}$P${\mathrm{O}}_{4}$ upon transmission of ruby-laser radiation. The present paper describes measurements for several crystals, which have been accomplished with an improved version of the original technique. Values for the appropriate macroscopic coefficients are: (${{X}_{\mathrm{zxy}}}^{0}+{{X}_{\mathrm{zyx}}}^{0}$) (K${\mathrm{H}}_{2}$P${\mathrm{O}}_{4}$)=5\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ esu; (${{X}_{\mathrm{zxy}}}^{0}+{{X}_{\mathrm{zyx}}}^{0}$) (K${\mathrm{D}}_{2}$P${\mathrm{O}}_{4}$)=10.5\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ esu; ${{X}_{\mathrm{zxx}}}^{0}$ (CdS)=45\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ esu; ${{X}_{\mathrm{zzz}}}^{0}$ (CdS)=35\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ esu; ${{X}_{\mathrm{zxx}}}^{0}$ [Cd(${\mathrm{S}}_{0.75}$+${\mathrm{Se}}_{0.25}$)]=145\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ esu; and (${{X}_{\mathrm{zxy}}}^{0}+{{X}_{\mathrm{zyx}}}^{0}$) (ZnTe)=365\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ esu. These absolute values are considered reliable only to within a factor 3, owing largely to uncertainty in determining the ruby-laser beam intensity. The relative values, however, are considered to be reliable within 50%. These results are compared with theoretical predictions and found to be consistent with the currently accepted quantum-mechanical theory of nonlinear optical phenomena. In particular, the intimate connection between the linear electro-optic effect (Pockel's effect) and optical rectification now appears to be firmly established. The theory can also be used, with some severe approximations, to yield crude predictions of the relative values obtained in the present experiments.