Photonics

Research

31 pages, 3241 KB

Open AccessArticle

A Two-Point Propagation Field of a Single Photon: A Way to X-Ray Picometer Displacement Detection and Nanometer Resolution 3D X-Ray Micro-Tomography

by Lihua Yu

Photonics 2026, 13(5), 495; https://doi.org/10.3390/photonics13050495 - 16 May 2026

Viewed by 258

Abstract

We introduce the two-point propagation field (TPPF)—a real-valued, phase-sensitive quantity defined as the functional derivative of the single-photon detection probability with respect to an infinitesimal opaque perturbation placed between the source and detection slits. The TPPF is analytically derived and shown to exhibit [...] Read more.

We introduce the two-point propagation field (TPPF)—a real-valued, phase-sensitive quantity defined as the functional derivative of the single-photon detection probability with respect to an infinitesimal opaque perturbation placed between the source and detection slits. The TPPF is analytically derived and shown to exhibit a stable, high-frequency sinusoidal structure with periods of 4~7 nm near the X-ray detection slit. This structure enables shot-noise-limited displacement detection with ∼200 pm precision for 6 keV X-rays using total photon counts on the order of 1 ×

10^{7}

and detector photon counting as low as 287. Beyond displacement detection, the TPPF physically performs a Fourier–Radon transformation of the projection data, providing a pathway to non-iterative frequency-domain tomography. Two conceptual strategies—a central blocker and off-axis multi-slit arrays—are estimated to lower the required incident photon budget by more than one order of magnitude each, yielding combined reductions of two to three orders of magnitude with near-term detector development. The TPPF concept, originally developed in a perturbative study of single-particle propagation, bridges quantum measurement questions with practical high-resolution X-ray physics. This work provides the foundational physics required for future discrete sampling and 3D numerical reconstruction algorithms. Full article

(This article belongs to the Special Issue Recent Progress in Single-Photon Generation and Detection)

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8 pages, 1003 KB

Open AccessArticle

A Complementary Approach for Characterizing Dark Count Rate in First-Photon-Gated Single-Photon Detectors

by Hanping Zhang, Xinyi Zhu, Yurong Wang, E Wu and Guang Wu

Photonics 2026, 13(5), 468; https://doi.org/10.3390/photonics13050468 - 9 May 2026

Viewed by 244

Abstract

In single-photon detection, dark count represents a critical limitation, particularly for high-sensitivity applications. Conventional estimators based on the binary per-gate observable become ill-conditioned when the dark count per-gate probability approaches unity, a situation common in first-photon-gated detectors with extended gate width. This work [...] Read more.

In single-photon detection, dark count represents a critical limitation, particularly for high-sensitivity applications. Conventional estimators based on the binary per-gate observable become ill-conditioned when the dark count per-gate probability approaches unity, a situation common in first-photon-gated detectors with extended gate width. This work proposes a complementary characterization method based on the statistical expectation of dark count arrival time. This approach captures the cumulative temporal behavior of dark count across multiple gating cycles, providing a more accurate estimation of the dark count rate. Both numerical simulations and experimental results demonstrate that our method yields significantly more stable and precise measurements compared to the conventional approach. Specifically, while the conventional method introduces errors up to ±4% at larger gate widths, the proposed timing-based method converges to a significantly lower residual error of approximately −0.17%. These findings offer a promising route to enhance the characterization and performance of first-photon-gated single-photon detectors in practical applications. Full article

(This article belongs to the Special Issue Recent Progress in Single-Photon Generation and Detection)

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13 pages, 1915 KB

Open AccessArticle

Weak Coherent and Heralded Single Photon Sources for Quantum Secured Imaging and Sensing

by Siddhant Vernekar and Jolly Xavier

Photonics 2026, 13(5), 457; https://doi.org/10.3390/photonics13050457 - 6 May 2026

Viewed by 679

Abstract

An ever-increasing demand for higher photon generation rates in quantum light sources often leads to the generation of multiple photon pairs, making quantum secure imaging, sensing, and communication vulnerable to photon number splitting (PNS) attacks. Here, we investigate the use of weak coherent [...] Read more.

An ever-increasing demand for higher photon generation rates in quantum light sources often leads to the generation of multiple photon pairs, making quantum secure imaging, sensing, and communication vulnerable to photon number splitting (PNS) attacks. Here, we investigate the use of weak coherent sources (WCS) and heralded single-photon sources (HSPS) in conjunction with quantum key distribution protocols to mitigate these risks. Our initial observation shows that the BB84 protocol using HSPS has an advantage in secured information transfer over the WCS. We then extend our comparative study between WCS and HSPS to high dimensional protocols and conduct a rigorous analysis to estimate a benchmark for quantum advantage in secure bit rate thresholds for secure information transfer. When combined with high-dimensional states (hybrid encoding), the two-state non-orthogonal encoding protocol offers an increased resistance to PNS and unambiguous state discrimination attacks. These findings suggest that integrating high dimensional encoding would strengthen the security and performance of quantum secure imaging, sensing, and communication systems for practical and resilient implementations at shorter distances. Full article

(This article belongs to the Special Issue Recent Progress in Single-Photon Generation and Detection)

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10 pages, 3854 KB

Open AccessArticle

Study on Diamond NV Centers Excited by Green Light Emission from Upconversion Luminescence

by Yangyang Guo, Fuwen Shi and Bo Li

Photonics 2025, 12(12), 1163; https://doi.org/10.3390/photonics12121163 - 26 Nov 2025

Cited by 1 | Viewed by 1095

Abstract

The NV center in diamonds has been widely employed in quantum sensing, quantum computing, and bioimaging due to its controllable ground-state spin, detectable magnetic resonance, excellent photostability, favorable biocompatibility, and chemical inertness. However, conventional excitation using 532 nm green light still exhibits certain [...] Read more.

The NV center in diamonds has been widely employed in quantum sensing, quantum computing, and bioimaging due to its controllable ground-state spin, detectable magnetic resonance, excellent photostability, favorable biocompatibility, and chemical inertness. However, conventional excitation using 532 nm green light still exhibits certain limitations in practical applications. To address this, we propose a novel NV center excitation method based on the upconversion of near-infrared light to green emission. Through the synthesis of molybdenum-doped NaYF₄: 20% Yb³⁺, 1.5% Er³⁺ upconversion materials, efficient excitation of NV centers has been achieved. Both UC-LED luminescence spectroscopy and ODMR measurements confirm that the green light generated via the upconversion process exhibits sufficient intensity to effectively excite NV centers. Meanwhile, the characteristic sharp emission peaks of rare-earth upconversion materials eliminate the need for optical filters, facilitating device miniaturization, and a miniaturized UC-LED sensor has been developed. Full article

(This article belongs to the Special Issue Recent Progress in Single-Photon Generation and Detection)

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12 pages, 1545 KB

Open AccessArticle

Temperature-Dependent Fluorescent Properties of Single-Photon Emitters in 3C-SiC

by Mengting He, Yurong Wang, Junjie Lin, Yujing Cao, Botao Wu and E Wu

Photonics 2025, 12(9), 920; https://doi.org/10.3390/photonics12090920 - 15 Sep 2025

Cited by 1 | Viewed by 1160

Abstract

Silicon carbide (SiC) is a representative wideband-gap semiconductor with remarkable properties, such as high breakdown field strength, high thermal conductivity, and high carrier saturation mobility. Meanwhile, single-photon emitters (SPEs) in SiC have attracted considerable attention owing to their excellent fluorescence performances and promising [...] Read more.

Silicon carbide (SiC) is a representative wideband-gap semiconductor with remarkable properties, such as high breakdown field strength, high thermal conductivity, and high carrier saturation mobility. Meanwhile, single-photon emitters (SPEs) in SiC have attracted considerable attention owing to their excellent fluorescence performances and promising applications in the quantum realm. Here, we conducted a systematic experimental investigation into the temperature-dependent characteristics of the SPEs in cubic silicon carbide (3C-SiC) crystal. Over a temperature span from 293 K to 373 K, the variations in fluorescence intensity, fluorescence lifetime, fluorescence spectra, polarization characteristics, and second-order autocorrelation function g²(τ) were examined. The fluorescence properties of defects showed extraordinary stabilization even when the temperature was raised to 373 K. Based on the above characteristics and combined with the excellent properties of SiC materials, this study provides strong evidence that SPEs in 3C-SiC can serve as information carriers capable of operating stably under high-temperature conditions. Full article

(This article belongs to the Special Issue Recent Progress in Single-Photon Generation and Detection)

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10 pages, 6301 KB

Open AccessArticle

Study on Diamond NV Centers Excited by Green Light Emission from OLEDs

by Yangyang Guo, Xin Li, Fuwen Shi, Wenjun Wang and Bo Li

Photonics 2025, 12(9), 833; https://doi.org/10.3390/photonics12090833 - 22 Aug 2025

Viewed by 3296

Abstract

This study demonstrates the feasibility of exciting NV centers using ITO-anode OLED devices, followed by the fabrication of GO/PEDOT:PSS hybrid anodes via spin-coating. Through interfacial modification, the OLED devices exhibit significantly enhanced luminescence intensity, leading to improved NV center excitation efficiency. Experimental results [...] Read more.

This study demonstrates the feasibility of exciting NV centers using ITO-anode OLED devices, followed by the fabrication of GO/PEDOT:PSS hybrid anodes via spin-coating. Through interfacial modification, the OLED devices exhibit significantly enhanced luminescence intensity, leading to improved NV center excitation efficiency. Experimental results show that the optimized GO/PEDOT:PSS (40%) hybrid anode device achieves a lower turn-on voltage, with the NV center fluorescence peak intensity reaching 3.7 times that of the ITO-anode device, confirming the enhanced excitation effect through interfacial engineering of the light source. By integrating NV centers with OLED technology, this work establishes a new approach for efficient excitation. This integration approach provides a new pathway for applications such as quantum sensing. Full article

(This article belongs to the Special Issue Recent Progress in Single-Photon Generation and Detection)

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8 pages, 1476 KB

Open AccessCommunication

Characterization of a Wide-Band Single-Photon Detector Based on Transition-Edge Sensor

by Jingkai Xia, Shuo Zhang and Bingjun Wu

Photonics 2025, 12(6), 609; https://doi.org/10.3390/photonics12060609 - 13 Jun 2025

Cited by 1 | Viewed by 1353

Abstract

A superconducting transition-edge sensor (TES) as a microcalorimeter detects incoming photons by measuring heat converted from photon energy. With high resolving power and low noise levels, a TES is sensitive to single photons and able to count photons within a wide spectral band [...] Read more.

A superconducting transition-edge sensor (TES) as a microcalorimeter detects incoming photons by measuring heat converted from photon energy. With high resolving power and low noise levels, a TES is sensitive to single photons and able to count photons within a wide spectral band from X-ray to near-infrared. We have developed a TES detector aiming at soft X-ray spectroscopy applications. In this work, the performance of this detector is characterized. It is shown that the energy resolution of this detector is about 1.8 eV for 1.5 keV photons. The good resolution is also kept in visible range, enabling photon-number resolving for 405 nm photons. Full article

(This article belongs to the Special Issue Recent Progress in Single-Photon Generation and Detection)

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12 pages, 34228 KB

Open AccessArticle

Time-Resolved Calibration of Photon Detection Efficiency and Afterpulse Probability in 100 MHz Gated InGaAs/InP Single-Photon Avalanche Diodes

by Zeyun Wang, Yiping Zhang, Hanqin Gu, Chao Han, Liang Yin and Yan Liang

Photonics 2025, 12(6), 534; https://doi.org/10.3390/photonics12060534 - 24 May 2025

Cited by 1 | Viewed by 2260

Abstract

InGaAs/InP single-photon avalanche diodes (SPADs) are widely used in applications such as quantum information, deep-space communication, and LiDAR. However, the existence of afterpulsing effects leads to inaccuracies in the calibration of their performance, particularly in terms of photon detection efficiency (PDE). In this [...] Read more.

InGaAs/InP single-photon avalanche diodes (SPADs) are widely used in applications such as quantum information, deep-space communication, and LiDAR. However, the existence of afterpulsing effects leads to inaccuracies in the calibration of their performance, particularly in terms of photon detection efficiency (PDE). In this paper, we employ the capacitance-balancing method to achieve a 100 MHz gated InGaAs/InP SPAD and propose a time-correlated calibration method to measure its performance. The distribution of the afterpulse counts over time is predicted, enabling a valid distinction between photogenerated counts and error counts. A PDE higher than ~30% is reached with an afterpulse probability of ~15%, while the repetition frequency of the incident laser (f_laser) changes from 1 MHz to 50 MHz. A comparison of the existing methodologies for calculating PDE reveals that PDE increases with f_laser. This increase is particularly pronounced when the PDE is high. However, under the time-correlated calibration scheme employed, the PDE remains almost constant, thereby validating the reliability of the results. Full article

(This article belongs to the Special Issue Recent Progress in Single-Photon Generation and Detection)

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28 pages, 5568 KB

Open AccessArticle

Research on Low-Altitude Aircraft Point Cloud Generation Method Using Single Photon Counting Lidar

by Zhigang Su, Shaorui Liang, Jingtang Hao and Bing Han

Photonics 2025, 12(3), 205; https://doi.org/10.3390/photonics12030205 - 27 Feb 2025

Viewed by 1106

Abstract

To address the deficiency of aircraft point cloud training data for low-altitude environment perception systems, a method termed APCG (aircraft point cloud generation) is proposed. APCG can generate aircraft point cloud data in the single photon counting Lidar (SPC-Lidar) system based on information [...] Read more.

To address the deficiency of aircraft point cloud training data for low-altitude environment perception systems, a method termed APCG (aircraft point cloud generation) is proposed. APCG can generate aircraft point cloud data in the single photon counting Lidar (SPC-Lidar) system based on information such as aircraft type, position, and attitude. The core of APCG is the aircraft depth image generator, which is obtained through adversarial training of an improved conditional generative adversarial network (cGAN). The training data of the improved cGAN are composed of aircraft depth images formed by spatial sampling and transformation of fine point clouds of 76 types of aircraft and 4 types of drone. The experimental results demonstrate that APCG is capable of efficiently generating diverse aircraft point clouds that reflect the acquisition characteristics of the SPC-Lidar system. The generated point clouds exhibit high similarity to the standard point clouds. Furthermore, APCG shows robust adaptability and stability in response to the variation in aircraft slant range. Full article

(This article belongs to the Special Issue Recent Progress in Single-Photon Generation and Detection)

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10 pages, 2038 KB

Open AccessArticle

Room-Temperature Fiber-Coupled Single-Photon Source from CdTeSeS Core Quantum Dots

by Surasak Chiangga

Photonics 2025, 12(1), 52; https://doi.org/10.3390/photonics12010052 - 9 Jan 2025

Viewed by 2561

Abstract

Single-photon sources with photon antibunching characteristics are essential for quantum information technologies. This paper investigates the potential of quaternary-alloy CdTeSeS colloidal core quantum dots (cQDs) as compact, room-temperature, and fiber-integrated single-photon sources. Single-photon emission from CdTeSeS cQDs was verified by measuring the second-order [...] Read more.

Single-photon sources with photon antibunching characteristics are essential for quantum information technologies. This paper investigates the potential of quaternary-alloy CdTeSeS colloidal core quantum dots (cQDs) as compact, room-temperature, and fiber-integrated single-photon sources. Single-photon emission from CdTeSeS cQDs was verified by measuring the second-order correlation function,

g^{(2)} (τ)

, using a Hanbury-Brown and Twiss setup. A novel method to determine zero-time delay through afterpulsing analysis is presented. The results demonstrate strong photon antibunching with

g^{(2)} (0) = 0.13

, confirming that the photoemission from the CdTeSeS cQDs function as a single-photon source. This work highlights the potential of CdTeSeS cQDs as reliable and efficient single-photon sources for practical use in fiber-based quantum information technologies. Full article

(This article belongs to the Special Issue Recent Progress in Single-Photon Generation and Detection)

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10 pages, 761 KB

Open AccessArticle

Two-Way Single-Photon Laser Time Transfer for High-Speed Moving Platforms

by Xinyi Zhu, Yurong Wang, Zhaohui Li, Xue Li and Guang Wu

Photonics 2024, 11(11), 1028; https://doi.org/10.3390/photonics11111028 - 31 Oct 2024

Cited by 2 | Viewed by 2281

Abstract

The two-way laser time transfer technology, based on single-photon detection, is among the techniques requiring the least weight and power consumption for ultra-long-distance clock synchronization. It holds promise as the most viable technology for high-accuracy inter-satellite clock synchronization, particularly for small satellites that [...] Read more.

The two-way laser time transfer technology, based on single-photon detection, is among the techniques requiring the least weight and power consumption for ultra-long-distance clock synchronization. It holds promise as the most viable technology for high-accuracy inter-satellite clock synchronization, particularly for small satellites that are highly sensitive to weight and power consumption. In this study, we analyze laser time transfer in fast-moving platforms and find that not only does the relative motion speed between platforms significantly impact the clock offset measurement, but also the components of each platform’s relative motion velocity are critical. We introduce a lightweight scenario for laser time transfer, capable of achieving high-precision and high-accuracy interstellar clock offset measurements within a 5000 km range using high repetition rate microchip lasers and single-pixel single-photon detectors. With a speed accuracy of ±0.06 m/s, the precision of clock offset measurement surpasses 3 ps at full width at half maximum (FWHM), making it suitable for high-speed and high-precision clock synchronization between near-Earth satellites. Full article

(This article belongs to the Special Issue Recent Progress in Single-Photon Generation and Detection)

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