<title>Dispersive coherence spectrotomography of a layered medium</title>

Abstract

In low-coherence reflectometry, the light backscattered from a scattering medium is expected to carry information about the spectral properties as well as range information about the reflective boundaries and backscattering sites. We show two alternative techniques to extract both the range and speciral properties of the sample by optically dispersed interferograms. The methods make the most of the brightness of white-light continuum, which is generated by focusing ultrashortlaser pulses into condensed matters. The output beam from an interferometer is dispersed by a spectroscopic optical element and the dispersed signal is detectedby a line detector. The salientfeature ofthe methods is that the spectral decomposition of the white-lightinterferograms enhances the dynamic range and signal-to-noise ratio. One method is a scanning type. By translating a sample, spectrallyresolved interferograms are detected. Appropriate grouping of the interferograms yields both range and spectral properties of the sample. The other method is based on the principle of spectral radar due to Häusler. The spectrally-resolved fringes are acquired without scanning. The signal-processing allows us to display both the scattering amplitude and spectral properties within the bandwidth of the filters. Experimental results will be presented.