Effective nonlinear coefficients of organic powders measured by second-harmonic generation in total reflection: numerical and experimental analysis

A second-harmonic wave generated by an evanescent wave (SHEW) is used to me asure the effective nonlinear coefficient of organic materials in powder fo rm. The SHEW signal is less sensitive than the powder method to the phase-m atching conditions of the material. For this reason, the SHEW technique can be used to survey a wide variety of samples. The effective nonlinear coeff icient and the refractive indices of the sample are obtained as fitting par ameters. The influence of experimental conditions on the fitting process is discussed. The results obtained from our powders are compared with the non linear coefficients of the same materials in bulk crystal form. Good agreem ent is found between experimental results and literature values. (C) 1999 O ptical Society of America. [S0740-3224(99)00301-X]. OCIS codes: 190.4710, 1 90.2620, 160.4330, 160.4760, 160.4890.