Laser treatment of optical Nb2O5‐ and HfO2‐films |
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Authors: | D Huber Mag F Prein Dipl Phys / Dipl‐Ing HK Pulker Prof Dr |
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Affiliation: | Thin Film Technology Group, Institute of Ion Physics and Applied Physics University of Innsbruck, Technikerstr. 25, A‐6020 Innsbruck – Austria |
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Abstract: | Optical thin films have to fulfil high quality requirements, which can be achieved for example by reactive low voltage ion plating (RLVIP). But especially for applications in precision optics, additional treatments are necessary to reduce residual optical absorption and compressive stress arising in the coatings, and to enhance the stability of the coatings – specifically for laser applications. In practice, post deposition heat treatment and backside coatings are mostly used to overcome these problems. In order to provide alternative methods to handle the disadvantages of the RLVIP‐process, the idea was to replace the mentioned steps by a laser treatment. This means that a laser beam is directed onto the sample after deposition or even during the coating process. In this study, the influence of a high power CO2‐laser beam on thin Nb2O5‐ and HfO2‐films was investigated. The effects on the refractive index and the film thickness are presented for different energy densities of a TEA‐CO2‐laser beam (10.59μm). For Nb2O5‐films a thickness increase up to 12.2nm (6.4 %) and a refractive index decrease of 0.074 (3.1 %) were found. In case of HfO2 the values were 2.3nm (1.2 %) in thickness and 0.007 (0.3 %) in refractive index. From the observed changes also distinct impacts on the film stress can be expected. One intention of this research was also to call attention to an alternative technique for enhancement of thin film properties. |
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