Mid-infrared single-photon upconversion spectroscopy based on temporal-spectral quantum correlation

Abstract

Promoting the sensitivity of mid-infrared (MIR) spectroscopy to the single-photon level is a critical need for investigating photosensitive biological samples and chemical reactions. MIR spectroscopy based on frequency upconversion is a compelling pioneer allowing high-efficiency MIR spectral measurement with well-developed single-photon detectors, which overcomes the main limitations of high thermal noise of current MIR detectors. However, noise from other nonlinear processes caused by strong pump fields hinders the development of the upconversion-based MIR spectroscopy to reach the single-photon level. Here, a broadband MIR single-photon frequency upconversion spectroscopy is demonstrated based on the temporal-spectral quantum correlation of non-degenerate photon pairs, which is well preserved in the frequency upconversion process and is fully used in extracting the signals from tremendous noise caused by the strong pump. A correlation spectrum broader than 660 nm is achieved and applied for the demonstration of sample identification under a low incident photon flux of 0.09 average photons per pulse. The system is featured with non-destructive and robust operation, which makes single-photon-level MIR spectroscopy an appealing option in biochemical applications.

Mid-infrared single-photon upconversion spectroscopy enabled by nonlocal wavelength-to-time mapping

“…The time-stretched coincidence spectrum is averaged over a total measurement time of 30 min. In comparison to the previous demonstration (34), the suggested scheme is able to reduce overall exposure time notablely, in the case of illuminating samples with these low magnitudes of MIR photon flux. The time-tagged time-resolved mode of the TCSPC can record individual photon events with their arrival time in all the channels.…”

“…SPDC photon pairs are used to achieve nonlocal spectral measurement (32,33), effectively suppressing the noise uncorrelated to the upconverted MIR photons. On the basis of the notions of nondegenerate temporal-spectral correlation, broadband MIR upconversion spectroscopy with MIR probe intensities as low as 0.09 photons per pulse has been demonstrated previously (34). Nevertheless, spectrometers/monochromators or interferometers are required for all of the aforementioned MIR spectroscopy investigations.…”

Quantum entanglement and interference at 3 μm

“…Similar to its partner in NIR band, quantum light sources in the MIR region can also be generated by using spontaneously parametric processes (SPDCs) in a nonlinear crystal (26)(27)(28). Recently, there are some works about the generation and detection of MIR photon sources theoretically and experimentally (29)(30)(31), and the demonstration of quantum interference and entanglement (32). However, because of the limitations of optical devices and detector performance, research related to the generation of entanglement and photon interference in MIR band has progressed slowly in the past years.…”

“…Mancinelli et al ( 29 ) reported on the coincidence measurement of correlated MIR photons at room temperature by using the spectral translation technology to reduce the influence of ambient Planck radiation. Cai et al ( 31 ) reported on the generation of the nondegenerated correlated photon pairs using a short-pulse pump, and the signal photon between 3100 and 3800 nm was upconverted to NIR to detect. Both works above just showed that the strong time correlation between the upconverted photons can notably reduce the noise, but there is no any report on the demonstration of entanglement or nonclassical correlation between photons.…”

Single‐Photon Time‐Stretch Infrared Spectroscopy

“…[17] So far, there have been various approaches to implement the involved frequency transduction step. One common way is based on frequency upconversion of the MIR photons through a high-efficiency and low-noise parametric nonlinear conversion, which allows for demonstrating broadband MIR spectrometers at single-photon sensitivity [18][19][20][21] or kHz-above frame rates. [13,22,23] Another promising approach resorts to quantum interferometry of spectrally-entangled photons from spontaneous parametric down conversion (SPDC), [24,25] which features intrinsic single-photon-level sensitivity.…”