RAMAN SPECTRAL ESTIMATION VIA FAST ORTHOGONAL SEARCH

A Fourier transform (PT) spectrometer measures the autocorrelation (in terferogram) of radiation emitted from a source and estimates the opti cal power spectral density through application of the discrete Fourier transform (DFT) to the recorded interferogram. Although a widely used method, FT spectrometry suffers because its frequency resolution is l imited to the sampling rate divided by the number of time-series data points. A large number of points are therefore required to resolve an optical spectrum properly. In this paper, it is shown that a noise-res istant technique known as fast orthogonal search (FOS) can be used to achieve accurate optical spectrum estimation. Further, it is shown tha t frequency accuracy comparable to the DFT applied to the full interfe rogram can be obtained with FOS even if the original interferogram is contaminated with noise and then reduced by a factor of up to 10 by ir regularly spaced sampling. The FOS application presented here is for t he estimation of Raman spectra from interferograms acquired with an FT Raman spectrometer.