title: Nonlinear infrared spectroscopy free from spectral selection.
abstract: Infrared (IR) spectroscopy is an indispensable tool for many practical applications including material analysis and sensing. Existing IR spectroscopy techniques face challenges related to the inferior performance and the high cost of IR-grade components. Here, we develop a new method, which allows studying properties of materials in the IR range using only visible light optics and detectors. It is based on the nonlinear interference of entangled photons, generated via Spontaneous Parametric Down Conversion (SPDC). In our interferometer, the phase of the signal photon in the visible range depends on the phase of an entangled IR photon. When the IR photon is traveling through the media, its properties can be found from observations of the visible photon. We directly acquire the SPDC signal with a visible range CCD camera and use a numerical algorithm to infer the absorption coefficient and the refraction index of the sample in the IR range. Our method does not require the use of a spectrometer and a slit, thus it allows achieving higher signal-to-noise ratio than the earlier developed method.
authors.affiliation: Data Storage Institute, Agency for Science Technology and Research (A*STAR), 138634 Singapore.|School of Electrical and Electronic Engineering, Nanyang Technological University, 639798, Singapore.
authors.forename: Anna
authors.initials: A
authors.lastname: Paterova
authors.affiliation: Data Storage Institute, Agency for Science Technology and Research (A*STAR), 138634 Singapore.|Department of Physics, National University of Singapore, 117542, Singapore.
authors.forename: Shaun
authors.initials: S
authors.lastname: Lung
authors.affiliation: Data Storage Institute, Agency for Science Technology and Research (A*STAR), 138634 Singapore.
authors.forename: Dmitry A
authors.initials: DA
authors.lastname: Kalashnikov
authors.affiliation: Data Storage Institute, Agency for Science Technology and Research (A*STAR), 138634 Singapore.
authors.forename: Leonid A
authors.initials: LA
authors.lastname: Krivitsky