Applied Surface Science, Vol.257, No.3, 954-959, 2010
Pulsed laser deposition of fluoride glass thin films
The development of integrated waveguide lasers for different applications such as marking, illumination or medical technology has become highly desirable. Diode pumped planar waveguide lasers emitting in the green visible spectral range, e. g. thin films from praseodymium doped fluorozirconate glass matrix (called ZBLAN, owing to the main components ZrF4, BaF2, LaF3, AlF3 and NaF) as the active material pumped by a blue laser diode, have aroused great interest. In this work we have investigated the deposition of Pr:ZBLAN thin films using pulsed laser radiation of lambda = 193 and lambda = 248 nm. The deposition has been carried out on MgF2 single crystal substrates in a vacuum chamber by varying both processing gas pressure and energy fluence. The existence of an absorption line at 210 nm in Pr: ZBLAN leads to absorption and radiative relaxation of the absorbed laser energy of lambda = 193 nm preventing the evaporation of target material. The deposited thin films consist of solidified and molten droplets and irregular particulates only. Furthermore, X-ray radiation has been applied to fluoride glass targets to enhance the absorption in the UV spectral region and to investigate the deposition of X-ray treated targets applying laser radiation of lambda = 248 nm. It has been shown that induced F-centres near the target surface are not thermally stable and can be easily ablated. Therefore, lambda = 248 nm is not suitable for evaporation of Pr: ZBLAN. (C) 2010 Elsevier B.V. All rights reserved.
Keywords:Pulsed laser deposition;Thin films;Praseodymium;Fluoride glass;Induced absorption;X-ray irradiation