We report on deposition of zinc oxide thin films on glass substrate at room temperature in ambient oxygen pressure ranging from 10 mTorr to 1 Torr by pulsed laser deposition. As grown polycrystalline thin films were optically pumped to investigate the dependence of laser action and photoluminescence (PL) on stoichiometry and microstructure of the films. The intensity of the laser emission increases with thickness of the film and depends on the size of nano-crystallites. Films deposited at pressures lower than 300 mTorr showed better morphology, stoichiometry and adhesion quality. X-ray diffraction, atomic force microscopy. Rutherford back scattering and PL techniques were used to characterize as grown films.