2024/03/08 by Kazuki Hashimoto, D. B. Horoshko, Hashimoto, Kazuki +9
Biochemistry, Genetics and Molecular Biology · Neuroscience · Physics and Astronomy · #FOS: Physical sciences #Optics (physics.optics) #Photoreceptor and optogenetics research #Quantum Physics (quant-ph) #Spectroscopy Techniques in Biomedical and Chemical Research #Spectroscopy and Quantum Chemical Studies
paper · pdf · doi:10.48550/arxiv.2403.05423
openalex publication_date 2024/03/08 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
Fourier-transform infrared spectroscopy (FTIR) is an indispensable analytical method that allows label-free identification of substances via fundamental molecular vibrations. However, the sensitivity of FTIR is often limited by the low efficiency of mid-infrared (MIR) photodetectors. SU(1,1) interferometry has previously enabled FTIR with undetected MIR photons via spontaneous parametric down-conversion in the low-parametric-gain regime, where the number of photons per mode is much less than one and sensitive photodetectors are needed. In this work, we develop a high-parametric-gain SU(1,1) interferometer for MIR-range FTIR with undetected photons. Using our new method, we demonstrate three major advantages: a high photon number at the interferometer output, a considerably lower photon number at the sample, and improved interference contrast. In addition, we analyze different methods to broaden the spectral range of the interferometer by aperiodic poling and temperature gradient in the gain medium. Exploiting the broadband SU(1,1) interferometer, we measure and evaluate the MIR absorption spectra of polymers in the 3-μm region.