LASER-ASSISTED DEPOSITION OF OPTICAL COATINGS

The demand for bulk-like films in the field of optical coatings stimul ates the development of novel deposition techniques. Laser beams can s erve as a controlled source of heat in order to modify both the deposi tion process and the microstructure of thin films. HfO2 and Y2O3 are e vaporated by focused irradiation with the beam of a continuous-wave CO 2 laser under ultrahigh vacuum conditions. Compared with conventional deposition methods the laser is an extremely clean evaporation source. Also the electron beam deposition process is modified by laser irradi ation of the substrate during deposition. The refractive index, surfac e morphology, film structure, absorption and laser damage threshold ar e studied on HfO2 and Y2O3 films. A comparison of films produced by la ser-assisted techniques with similar films deposited by conventional e lectron beam evaporation demonstrates that the porosity and absorption are reduced and the values of refractive index and laser damage thres hold are increased for coatings prepared by laser-assisted techniques.