Photoinduced optical second harmonic generation (SHG) and two-photon reflection (TPR) have been observed in In2O3-Sn films coated on silica (Na2O . CaO . 6SiO(2)) glass with different Si content. Theoretical molecular dynamic simulations have shown that [SnO4] tetrahedral interaction with [SiO4] clusters of the glass substrate, play a central role in the observed non-linear photoinduced changes. As a photoinducing light beam, a CO laser (lambda = 5.3 mu m) was used and a CO2 laser (lambda = 10.6 mu m) as a probing beam. Maximal non-linear optical response was observed for a time delay between CO-photoinducing and CO2 probing beams of about 45 ps. Experimental and theoretical investigations have shown that the output SHG signal essentially increases with increasing Si content in the glass substrate For the CO-laser photoinducing power values of 10(22) and 5 x 10(23) photons/cm(2), two TPR maxima are observed. An applied external electric field favors observation of the photoinduced SHG maximum at 50 V. Decreasing temperature leads to the appearance of two maxima in the SHG output signals (at 71 and 35 K). Hydrostatic pressure favors the appearance of at least three maxima at hydrostatic pressures of about 22, 57 and 73 Gpa.