Surface-enhanced mid-infrared spectroscopy using a quantum cascade laser.

We report on the successful measurement of surface-enhanced infrared vibrational spectra from a few nanometer thick organic semiconductor layers on samples with resonant plasmonic nanoantennas arranged in arrays. For the first time, a setup with a tunable quantum cascade laser as the light source in mid-infrared range is used. The combination of the quantum cascade laser with a microbolometer array for infrared light allows to map an area 2.8 × 3.1 mm(2) with a spatial resolution of about 9 μm, a bandwidth from 1170 to 1300 cm(-1), and a spectral resolution of 2.5 cm(-1) within only five minutes versus 16 hours using a conventional FTIR micro-spectrometer. We present a quantitative comparison of the experimental results from the setup with the quantum cascade laser with those from the FTIR micro-spectrometer.