Slanted VPHGs in astronomical instrumentation: tests and perspectives

Volume phase holographic gratings (VPHGs) are dispersing elements widely used in astronomical instrumentation thanks to some unique features (for example, the peak efficiency can reach 95%). The introduction of a slant angle to the fringes allow an increased versatility of these elements. The efficiencies of some samples produced by Kaiser Optical Systems Inc. are reported and discussed. Moreover, some cases of interest in the astronomical field are reported.