K. Allakhverdiev et al., LOW-TEMPERATURE 2ND-HARMONIC GENERATION IN GALLIUM SELENIDE UNDER RESONANT EXCITATION OF THE DIRECT FREE-EXCITONS, Solid state communications, 93(2), 1995, pp. 147-150
Second harmonic generation in epsilon-GaSe was measured at 10K when th
e energy of the excited laser radiation passed through the absorption
band of the ground state of the direct free excitons. The resonant beh
avior was observed and qualitatively explained using the three-band mo
del, taking into account also the input to nonlinear response from hig
her lying energy level in the conduction band.