Quantum Fourier-Transform Infrared Spectroscopy for Complex Transmittance Measurements

Abstract

Harnessing the quantum interference of the pair generation processes, infrared quantum spectroscopy, based on nonlinear interferometers with visible-infrared photon-pair sources, enables the extraction of the infrared optical properties of a sample through visible photon detection without the need for an infrared optical source or detector. We develop a theoretical framework for quantum Fourier-transform infrared (QFTIR) spectroscopy. The proposed Fourier analysis method, which fully utilizes the phase information in the interferogram, allows us to determine the complex transmittance and optical constants for a sample in a simple setup without the use of any dispersive optics for spectral selection. In the experimental demonstrations, the transmittance spectrum of a bandpass filter and the refractive index of silica glass are measured in the near-infrared region using QFTIR operated in a low gain regime; these results agree well with the independently measured spectrum using a conventional spectrometer and an value estimated from references. These demonstrations prove the validity and great potential of QFTIR spectroscopy.

Delayed-choice quantum erasure with nonlocal temporal double-slit interference

“…Now let us consider an alternative quantum eraser experiment that focuses on the distinguishability of temporal modes. In analogy to the link between position and momentum domains as a direct result of uncertainty principle, we exploit the Fourier transform that connects the temporal and spectral domains to explore the nonlocal temporal double-slit interference [43][44][45][46]. Thus the interference pattern can be observed by scanning the spectral correlation rather than the complicated temporal measurement.…”

“…As a direct result of the inherent stability of HOM interferometry, our scheme does not have any requirement for active interferometric stabilization [37][38][39][40][41][42]. To harness the temporal distinguishability by concise spectral modulation, we observe the interference pattern in spectral domain as the biphoton temporal and spectral wavefunctions can be connected by using a Fourier transform [43][44][45][46]. Thus, when the distinct temporal modes are measured deterministically, the photons do not show interference.…”

Quantum interferometric metrology with entangled photons

“…It is obvious that the second-order temporal correlation and the difference-frequency spectrum intensity can be connected by performing a Fourier transform. As a direct result, this approach has a variety of potential applications, such as quantum interferometric spectroscopy [29,30,128] and spectraldomain quantum coherence tomography [97, 129].…”

“…Therefore, quantum light provides a powerful tool to extract the spectroscopic information of target materials by using a singlephoton monochromator [27] or tunable frequency-correlated photons [26], which may be particularly relevant for photonsensitive biological and chemical samples [25]. In order to tackle the experimental issues, quantum Fourier spectroscopy is presented as an alternative route [14,28,29]. In analogy to classical Fourier transform between time and frequency domains, the spectral and temporal degrees of freedom of biphoton wavefunction can also be connected by a Fourier transform [30].…”

Quantum optical induced-coherence tomography by a hybrid interferometer

“…Therefore, changes in the probe photon path by a target are measurable with interferometry for the signal photons, and the probe photons need not be measured eventually because their existence is guaranteed through energy conservation. This induced-coherence phenomenon, observed since 1991 [8,9], has led to the demonstration of optical measurement techniques with ever-increasing complexity, such as optical on-off imaging [5], spectroscopy [10,11], optical coherence tomography (OCT) [12][13][14][15], microscopy [16,17], Fourier-transform infrared (IR) spectroscopy [18,19] and holography [20].…”