Near-Range Large Field-of-View Three-Dimensional Photon-Counting Imaging with a Single-Pixel Si-Avalanche Photodiode

Large field-of-view（FoV） three-dimensional（3 D） photon-counting imaging is demonstrated with a single-pixel single-photon detector based on a Geiger-mode Si-avalanche photodiode. By removing the collecting lens（CL）before the detector, the FoV is expanded to ±10°. Thanks to the high detection efficiency, the signal-to-noise ratio of the imaging system is as high as 7.8 dB even without the CL when the average output laser pulse energy is about 0.45 pJ/pulse for imaging the targets at a distance of 5 m. A 3 D image overlaid with the reflectivity data is obtained according to the photon-counting time-of-flight measurement and the return photon intensity.

Direct Measurement of Non-Classical Photon Statistics with a Multi-Pixel Photon Counter

Photon number resolving detectors with high accuracy bring broad applications in long-distance laser ranging, ultrafast spectroscopy, and quantum optics. In this paper, we observed the non-classical photon number distribution directly with a multi-pixel photon counter (MPPC) instead of a classic Hanbury-Brown and Twiss (HBT) system. The detector’s photon-number resolving ability was characterized by quantum detector tomography. To show the quantum feature of the detector, we further plotted the Wigner function, which was obtained corresponding to the positive operator value measure (POVM) elements. Finally, we declared the observation of non-classical photon statistics from a single color center in nanodiamond by using this detector.

High-Efficiency Broadband Near-Infrared Single-Photon Frequency Upconversion and Detection

We propose and demonstrate a high efficiency broadband near infrared single-photon upconversion and detection with a broadband pump laser based on sum frequency conversion in the PPLN crystal.By using a pump laser centered at 1040 nm with a spectral bandwidth of 10 nm,the signal single-photons centered at 1562 nm with a broadband bandwidth up to 7.2 nm are frequency-converted from the near infrared to the visible regime.A maximum conversion efficiency of 18.8%is achieved,while the background noise is measured to be only1.2×10^-3 counts/pulse.The corresponding spectral linewidth of the upconverted photons is 0.2 nm.This scheme of broadband infrared single-photon upconversion and detection provides potential solutions in infrared laser ranging,broadband infrared imaging and quantum key distribution.

Ultrafast optical modulation of the fluorescence from a single-photon emitter in silicon carbide

The quest for the room-temperature optical transistor based on nonlinearities in single atoms or molecules is attracting a lot of attention.In this work,a single-photon emitter in cubic silicon carbide is verified that can operate as an optical switch at room temperature under pulsed green laser illumination with a near-infrared pulsed laser as the control gate.We demonstrated an ultrafast and reversible optical modulation with a high photoluminescence intensity suppression ratio up to 97.9%and a response time as short as 287.9±5.7 ps.The current development provides insights for high-precision and ultrafast optical switches,with possibilities for integration with emerging electronic installations to realize more intelligent photoelectric integrated devices.

Mid-infrared single-photon 3D imaging

Active mid-infrared(MIR)imagers capable of retrieving three-dimensional(3D)structure and reflectivity information are highly attractive in a wide range of biomedical and industrial applications.However,infrared 3D imaging at lowlight levels is still challenging due to the deficiency of sensitive and fast MiR sensors.Here we propose and implement a MiR time-of-flight imaging system that operates at single-photon sensitivity and femtosecond timing resolution.Specifically,back-scattered infrared photons from a scene are optically gated by delay-controlled ultrashort pump pulses through nonlinear frequency upconversion.The upconverted images with time stamps are then recorded by a silicon camera to facilitate the 3D reconstruction with high lateral and depth resolutions.Moreover,an effective numerical denoiser based on spatiotemporal correlation allows us to reveal the object profle and reflectivity under photon-starving conditions with a detected flux below 0.05 photons/pixel/second.The presented MIR 3D imager features high detection sensitivity,precise timing resolution,and wide-field operation,which may open new possibilities in life and material sciences.

Frequency-multiplexing photon-counting multi-beam LiDAR

We report a frequency-multiplexing method for multi-beam photon-counting light detection and ranging(Li DAR),where only one single-pixel single-photon detector is employed to simultaneously detect the multibeam echoes.In this frequency-multiplexing multi-beam Li DAR,each beam is from an independent laser source with different repetition rates and independent phases.As a result,the photon counts from different beams could be discriminated from each other due to the strong correlation between the laser pulses and their respective echo photons.A 16-beam Li DAR system was demonstrated in three-dimensional laser imaging with 16 pulsed laser diodes at 850 nm and one single-photon detector based on a Si-avalanche photodiode.This frequencymultiplexing method can greatly reduce the number of single-photon detectors in multi-beam Li DAR systems,which may be useful for low-cost and eye-safe Li DAR applications.

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

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 than660 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. ? 2022 Chinese Laser Press.

Strong coupling with absorption and emission features of Ag@Au hollow nanoshells interacting with J-aggregated dye molecules

We investigate the strong coupling from 5,5’,6,6’-tetrachloro-1,1’-diethyl-3,3’-di(4-sulfobutyl)-benzimidazolocarbocyanine(TDBC)molecules near pure nano-triangular Ag prisms or Ag@Au hollow nanoshells.When TDBC molecules are deposited on pure Ag nanoprisms or Ag@Au hollow nanoshells with the plasmonic resonance peak,matching very closely with the absorption band of TDBC J-aggregates,obvious Rabi splitting can be observed due to the strong coupling regime.Meanwhile,the photoluminescence intensity decreased with the increasing of the temperature,verifying the decreasing plasmon-exciton coupling interaction in the higher temperature.Our experimental results are coincident with the simulation results calculated by finite-difference time-domain method.