INFLUENCE OF LN(2) SUBSTRATE COOLING ON OPTICAL-PROPERTIES OF LASER-PULSE-DEPOSITED OXIDE-FILMS

In this paper we will present the results of investigations of the inf luence of substrate cooling by liquid nitrogen during film deposition on the optical properties of oxide films prepared by means of laser pu lse deposition. A CO2-TEA laser at 10.6 mu m wavelength (pulse duratio n 200 ns, repetition rate 40 Hz, laser fluence 4 X 10(7) W/cm(2) monom ode) and an excimer laser at 248 nm wavelength (pulse duration 20 ns, repetition rate 200 Hz, laser fluence 5 X 10; W/cm(2)) were used for t he evaporation and, respectively, the ablation of sintered oxide targe ts. Moreover, the growing films were bombarded by oxygen ions of varyi ng energy and current density. As will be shown, the variation of refr active index with ion bombardment changed only imperceptibly due to su bstrate cooling, i.e. films deposited at relatively low ion energy and current density possess a high bulk-like refractive index and films d eposited at relatively high ion energy and current density possess a r ather low refractive index. We could observe, however, that, in compar ison with uncooled substrates, cooling of the substrates by liquid nit rogen results in a marked decrease in absorption together with a marke d increase of the laser damage thresholds of the films at 1.06 mu m wa velength. For example, the laser damage threshold of hafnia films incr eased by a factor of 1.5.