Abstract
We report spectral and intensity-dependent measurements of the two-photon photoconductivity in ZnS crystals using two different frequency radiations. Photocurrents produced by each beam separately were determined and subtracted. We found that the two-photon photoconductivity usually varies linearly with the intensity of one source when that of the other source is held constant. The spectral measurement shows a rise of the two-photon photoconductivity at the crystal energy gap (3.82 eV), and an interesting forbidden one-photon but allowed two-photon transition at 4.57 eV.