Polarization-Division Interferometry: Time-Resolved Infrared Vibrational Dichroism Spectroscopy

Abstract

We report the first direct measurements of time-resolved Fourier transform infrared vibrational dichroism (TR/FT-IR/VD). The central component for these measurements is a polarization-division interferometer (PDI). This interferometer uses an in-house-designed beamsplitter constructed in-house from a BaF 2 polarizer and a matching substrate. In conjunction with a linear polarizer in front of the source and two rooftop mirrors, one in each arm of the interferometer, the PDI divides the input beam into two orthogonal linear polarization components, recombines them for interference at the beamsplitter, and directs the output beam at 90° to the direction of input beam. The signals measured as a function of the moving mirror position in the PDI represent the linear/circular dichroism interferograms, whose cosine/sine Fourier transforms yield linear/circular dichroism spectra. Time-resolved dichroism interferograms were measured with the use of this PDI with the asynchronous external perturbation method. Microsecond time-resolved linear dichroism spectra of a nematic liquid crystal, under the influence of bipolar electric field oscillating at 2 kHz, were measured and presented as the first examples.