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.
Highlights
Infrared (IR) spectroscopy is an indispensable tool for many practical applications including material analysis and sensing
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)
When the IR photon is traveling through the media, its properties can be found from observations of the visible photon
Summary
Infrared (IR) spectroscopy is an indispensable tool for many practical applications including material analysis and sensing. 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). FTIR spectroscopy still faces technical challenges, including low efficiency and high dark noise of IR photodetectors (which often require cryogenic cooling), absorption of the signal by water vapor and the requirement of using specialized IR-grade optics[8]. A number of techniques using entangled states of light have been suggested and demonstrated They offered certain beneficial features and extended the functionality of traditional approaches[9,10,11,12]. The technique is tested with an IR absorption line of the carbon dioxide gas at 4.3 microns, which is widely used for environmental sensing and biomedical applications
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