Quasi-linear Dispersion Spherical Fabry-Perot Interferograms for Giant Pulse Laser Spectroscopy

Abstract

SPHERICAL interferometer fringes have previously been considered unsuitable for the production of a spectrum extending over several orders of the spectral range, chiefly because when the spherical mirrors are separated by exactly their radius of curvature^1,2, the order of interference of the fringe pattern decreases as the fourth power of the radius. (With a plane Fabry–Perot instrument, the order of interference varies with the square of the radius.) In practice, however, spherical interferometers have been used successfully to measure the time resolved spectra of ruby laser relaxation oscillations³ and, more recently, for the direct spectral detection of off-axis modes in giant pulse ruby lasers⁴ and an intensity dependent frequency shift⁵. In circumstances like these the spherical instrument has the advantage of the high intensity of the illumination of the detector and the fact that the plates are always well adjusted.