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

Area of Science:

• Quantum optics
• Spectroscopy
• Photonics

Background:

• Ultrasensitive spectroscopy is crucial for mid-infrared (MIR) technology.
• Existing MIR detectors face challenges in achieving robust single-photon level spectroscopy.
• Limitations hinder sensitive analysis of materials and quantum systems in the MIR range.

Purpose of the Study:

• To propose and demonstrate a novel MIR single-photon frequency upconversion spectroscopy.
• To overcome the limitations of conventional MIR detectors for single-photon spectroscopy.
• To enable ultrasensitive spectral analysis in the MIR region.

Main Methods:

• Frequency upconversion of broadband MIR photons to the near-infrared band while preserving quantum correlations.
• Nonlocal mapping of MIR spectral information to the time domain using fiber group delay.
• Demonstration of transmission spectra of polymers with single-photon sensitivity using single-pixel detectors.

Main Results:

• Successful projection of MIR spectral information (2.76–3.94 µm bandwidth) to arrival times of correlated photon pairs.
• Achieved single-photon sensitivity under high illumination conditions (6.4 × 10^6 photons/second).
• Demonstrated transmission spectra of polymers, showcasing the method's capability.

Conclusions:

• The developed approach circumvents scanning and frequency selection instability, offering robustness.
• The technique is compatible with evolving environments and scalable for various wavelengths.
• High sensitivity and robustness enable potential applications in biochemical sample characterization and quantum system measurements.