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Fourier transform spectrometers (FTSs) have been used for some time to determine the spectrum
of an electric field based on coherence measurements. Whereas a traditional FTS
sweeps the delay of one arm in a Michelson interferometer and records an interference pattern
over time, stationary FTSs form the interferogram in the spatial domain by introducing a
spatial deviation between two overlapping beams.
We demonstrated a simplified double-mirror stationary FTS that uses an all-reflective geometry, for use with spatially coherent fields such as those emitted by lasers and laser-like sources. The elimination of all spectrally-restrictive transmissive optics allows the spectrometer to be used over an extremely broad wavelength range, and we measured spectra from the mid-IR (10 um) to the near-UV (400 nm), a total span of some 4.6 octaves. An off-axis curved mirror is used to collect the highly astigmatic beam after the slit and focus it onto the detector.
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