Investigations of whisper gallery mirrors for extreme ultraviolet (EUV) and soft X-rays

The authors have examined optical constants and predicted reflectivities of candidate surface coatings for whisper gallery mirrors (WGMs) in the extreme ultraviolet. The spectral regime near 100-150 Å has been identified in the literature as particularly promising due to the high WGM reflectivities of the noble metals in the vicinity of their Cooper minima in this regime. The authors confirm this basic result using newer EUV optical data, and they have sought candidate surface materials which would extend the range over which WGMs may be used to longer wavelengths. It is found that substantial WGM reflectivities are predicted for a variety of elements in the EUV, and that TE peak reflection is larger than TM peak reflection by on the order of 10%; however, most of the elements which do reflect well have surfaces which are vulnerable to oxygen contamination