MULTIPLE-BEAM INTERFEROMETRIC DETERMINATION OF THE COHERENCE LENGTH OF SPECTRAL SOURCES

A theoretical treatment for multiple-beam fringe visibility taking int o consideration the profile of the spectral source is derived for (a) a Gaussian profile; and (b) a Lorentzian profile. A comparative study between the visibility of the two profiles is presented. Expressions f or the intensity distribution for Doppler and Voigt cases are given. T he fringe visibility dependence on the half-width of the spectral prof ile of the light illuminating the interferometer for the two cases, na mely Lorentzian and Gaussian, is presented. This leads to the view tha t the coherence length for a Voigt profile is less than it is in the a bsence of Doppler or pressure broadening. Multiple-beam Fabry-Perot fr iNG D[ J {[ J [ D{K ABB[ KJDI of the visibility of the recorded interf erence fringes with path difference. 58 angstrom. The method for deter mination is based on the variation of the visibility of the recorded i nterference fringes with path difference.