DISPERSION OF THE 2ND-ORDER NONLINEAR SUSCEPTIBILITY IN ZNTE, ZNSE, AND ZNS

We have measured the absolute values of the second-harmonic generation (SHG) coefficient \d\ for the zinc-blende II-VI semiconductors ZnTe, ZnSe, and ZnS at room temperature. The investigated spectral region of the fundamental radiation lambda(F) ranges from 520 to 1321 nm using various pulsed laser sources. In the transparent region of the II-VI s emiconductors, the SHG coefficient exceeds the values of birefringent materials as ammonium dihydrogen phosphate (ADP) and potassium dihydro gen phosphate (KDP) by one or two orders of magnitudes. Above the E-0 band gap a strong dispersion of \d\ is observed, showing a maximum for a second-harmonic frequency close to the E-1 gap. The experimental re sults are compared to calculated values using a simple three-band mode l including spin-orbit splitting. Substantial agreement is found to th e experimentally observed dispersion of the second-order nonlinear sus ceptibility. [S0163-1829(98)06539-4].