The Axicon-Scanned Fabry–Perot Spectrometer

The optical properties of a thin axicon or prism of revolution can be combined with a Fabry–Perot etalon to produce a simple, but useful, photoelectric spectrometer. The spectrum can be scanned without disturbing the etalon solely by displacing the axicon. The system is particularly useful for the case where a pressure or mechanical scan of the etalon is difficult, i.e., low resolution and high free-spectral range. The system is also applicable to spectroscopy in the vacuum ultraviolet. A device based on these principles has been constructed and used in an experiment. Test results are presented. The etalon–axicon combination is shown to lend itself readily to the construction of a high-resolution, high-luminosity multichannel photoelectric analyzer.