We introduce a new variant of spectral interferometry, using spectrally dispersed ultrafast laser pulses and quadrature detection to measure optical thickness variations related to surface structure. We can resolve surface features with depths of 3 mm to 25 nm, using a lateral resolution of similar to 100 mum. Quadrature detection gives a larger dynamic range and solves the sign ambiguity problem. This method has potential applications in device manufacture, optical communications, and error compensation in pulse shaping. (C) 2001 Optical Society of America. [References: 9]
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