Fig. 5: MIR spectroscopy of polymers.
a, b MIR (intensity) transmittance spectra of a polystyrene film and a plastic wrap, respectively, measured with the ppKTP crystal using the temperature tuning scheme. The red points are measured with the SU(1,1) interferometer and the dotted gray lines, with a standard FTIR spectrometer with a spectral resolution of 16 cm−1. The solid and dotted arrows show the aromatic CH stretching and CH2 asymmetric stretching modes, respectively. c FTIR spectra obtained with the apKTP crystal. The red line represents the spectrum with a polystyrene film, and the orange line represents the one without the sample. d MIR (intensity) transmittance spectra of a polystyrene film. The solid-red and dotted-gray lines show the transmittance spectra measured with our system (with the apKTP crystal) and a standard FTIR spectrometer with a spectral resolution of 5 cm−1, respectively.
