Analysis of optical spectra by Fourier methods

Results of a systematic investigation of reciprocal-space analysis, applied to optical spectroscopy, are reported. Filtering procedures for removing baseline and noise artifacts are more effective in reciprocal-than in real-space. Also, correlations among parameters are reduced and the functional dependence of real-space lineshapes need be known a priori only in very general terms. We apply reciprocal-space analysis to achieve accurate values of critical point energies for the E-1 and E-1 + Delta(1) transitions of GaAs from ellipsometric spectra and to locate critical point energies in low-temperature reflectance data of GaN. We show that data may easily be corrected for systematic artifacts such as the monochromator slit width, an optimum slit width can be defined, and the degree of improvement needed to achieve a particular level of performance can be predicted. (C) 1998 Elsevier Science S.A.