A simple in-situ optical film thickness monitor for infrared coatings

Texture evolution and infrared optical properties of praseodymium fluoride films

“…These include specific transparency, particular refractive index values, low extinction coefficient, good adhesion, low stress and survival from the harsh environment conditions. In the past several decades, thorium fluoride (ThF 4 ), as a favorite low-index material [1][2][3], has been successfully used in long-wave interference coating due to its excellent optical properties and good mechanical properties. Unfortunately, its radioactivity is hazardous to the worker's health and environment, which would not satisfy the new guidelines issued by many government agencies.…”

“…Due to the application into excimer laser, so far the investigation on rare earth fluorides used as coating materials has been mainly concentrated on the UV and DUV optical filters. Recent developments in IR transmitting materials have clearly emphasized the role of rare earth fluoride in long-wave interference filters, such as YF 3 [4,5], LaF 3 , CeF 3 , HfF 4 , NdF 3 [5], YbF 3 [6]. However, to our best knowledge, the research related to evaporated praseodymium fluoride (PrF 3 ) film has not been published.…”