Inline-delay Fourier transform imaging spectrometer for mid-IR ultrashort pulses

An inline-delay Fourier transform imaging spectrometer (iFTIS) is used to measure spatiospectral coupling in a mid-infrared (mid-IR) optical parametric amplifier (OPA). The method employs a compact inline delay line using a birefringent wedge pair and a microbolometer array as an imaging sensor, providing continuous spectral coverage from similar to 0.4 to 4.5 mu m in a single device. We find a spatial chirp that depends systematically on the OPA wavelength setting in the 3-4 mu m range and also identify spatiospectral couplings beyond spatial chirp, highlighting the importance of advanced metrological techniques for this spectral region. Furthermore, we investigate the effect of depletion on the 2 mu m pump beam and observe a complex spatiospectral reshaping. Our work opens the door to new applications of iFTIS to mid-IR laser science. (c) 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement