2025/03/17 by Gattinger, Paul, Schell, Andreas W., Ramelow, Sven +2
#FOS: Physical sciences #Optics (physics.optics)
paper · doi:10.48550/arxiv.2503.13233
Sensing with undetected photons has enabled new, unconventional approaches to Fourier transform infrared (FTIR) spectroscopy. Leveraging properties of non-degenerated entangled photon pairs, mid-IR information can be accessed in the near-IR spectral domain to perform mid-IR spectroscopy with silicon-based detection schemes. Here, we address practical aspects of vibrational spectroscopy with undetected photons using a quantum-FTIR (QFTIR) implementation. The system operates in the spectral range from around 3000~cm-1 to 2380~cm-1 (detection at around 12500~cm-1) and possesses only 68~pW of mid-IR probing power for spectroscopic measurements with a power-dependence of the signal-to-noise ratio of 1.5⋅ 105~mW-1/2. We evaluate the system's short- and long-term stability and experimentally compare it to a commercial FTIR instrument using Allan-Werle plots to benchmark our QFTIR implementation's overall performance and stability. In addition, comparative qualitative spectroscopic measurements of polymer thin films are performed using the QFTIR spectrometer and a commercial FTIR with identical resolution and integration times. Our results show under which conditions QFTIR can practically be competitive or potentially outperform conventional FTIR technology.