Fig. 1
A stationary Fourier transform spectrometer measures the spatial interference pattern of a signal in a single dimension (a) and obtains the spectrum by Fourier transformation. While increasing the interference angle will squeeze more fringes into the detector column and increase the interferogram window, the sampling rate along the delay axis is simultaneously reduced by the fixed pixel width, and a full-bandwidth Nyquist rate limits the recovered spectral resolution for un-aliased spectra. Spectral dispersion in a CDFT spectrometer (b) creates an array of narrowband interferograms in the detector columns that partition the signal spectrum. Measurement and Fourier transformation of each channel (column) interference pattern, unwrapping around the carrier frequency, and summation recovers the total spectrum signal. Since the bandwidth in each channel is reduced by the partition factor, the interference window can be increased proportionally over the one-dimensional counterpart. Schematic diagram of a CDFT spectrometer (c). Spatial interference is generated by Sagnac interferometric arm; interference angle is determined by tuning mirror tilt. Periscope assembly rotates the interference plane by 90° to allow for dispersion in the propagation plane. Dispersive arm spreads the signal interference pattern into sub-band spectral channels to form the CDFT interferogram and is recorded by a 2D imager (Detector)
