Photon Sensitivity Research Articles

Highly Sensitive Photonic Crystal Fiber Sensor for Detection of Hemoglobin and Sucrose Concentration

Highly Sensitive Photonic Crystal Fiber Sensor for Detection of Hemoglobin and Sucrose Concentration

Modeling the effect of superconductor properties on sensitivity and responsivity of superconducting nanowire single photon detector

Superconducting nanowire single photon detector (SNSPD) is a leading candidate for applications requiring the fundamental limit of light detection at high detection rates. While SNSPD technology employing nanowires from conventional low temperature superconducting detectors is mature with several commercial solutions, other material options with higher transition temperature approaching liquid nitrogen with faster signal responses are actively being explored. In this context, we develop a comprehensive model that predicts the final potential response from an SNSPD incorporating several physical and material aspects. A phase diagram of photon detection is developed that describes the latching phases and the photon sensitivity as a function of biasing current and temperature for both low temperature and high temperature superconductors. On the one hand, while low temperature superconductors are observed to be more sensitive than high temperature superconductors (HTSs) under any given biasing condition, a biasing window for a single photon detection with HTS nanowires is identified. On the other hand, HTS nanowires demonstrate three orders of magnitude faster response times than the low temperature superconductor nanowire at the same biasing condition, making it uniquely suited for several practical applications.

Gated InAs quantum dots embedded in surface acoustic wave cavities for low-noise optomechanics

Self-assembled InAs quantum dots (QDs) are promising optomechanical elements due to their excellent photonic properties and sensitivity to local strain fields. Microwave-frequency modulation of photons scattered from these efficient quantum emitters has been recently demonstrated using surface acoustic wave (SAW) cavities. However, for optimal performance, a gate structure is required to deterministically control the charge state and reduce the charge noise of the QDs. Here, we integrate gated QDs and SAW cavities using molecular beam epitaxy and nanofabrication. We demonstrate that with careful design of the substrate layer structure, integration of the two systems can be accomplished while retaining the optimal performance of each subsystem. These results mark a critical step toward efficient and low-noise optomechanical systems that truly leverage the excellent properties of semiconductor QDs.

Design of a new scintillator-based fast ion loss detector on the HL-2A tokamak

A new scintillator-based fast ion loss detector (FILD) has been devised for the HL-2A tokamak, with the objective of discerning the temporal evolution of energy and pitch angle among lost fast ions. A code named FILD Simulation (FSC) has been developed to assist in the design of the detector head and the interpretation of experimental data. By optimising the geometric design, the resolutions of energy and pitch angle are optimised to 5 keV and 3°, respectively. A branched imaging fiber bundle is used to relay the fluorescence image on the scintillator to two distinct instruments. One of these is a high-speed camera, while the other is a silicon photomultiplier tube (SiPM) array with a sampling rate of up to 1 MSamples/s. This configuration enables the attainment of superior temporal and spatial resolution, as well as high photon sensitivity.

Avalanche Terahertz Photon Detection in a Rydberg Tweezer Array.

We propose a protocol for the amplified detection of low-intensity terahertz radiation using Rydberg tweezer arrays. The protocol offers single photon sensitivity together with a low dark count rate. It is split into two phases: during a sensing phase, it harnesses strong terahertz-range transitions between highly excited Rydberg states to capture individual terahertz photons. During an amplification phase it exploits the Rydberg facilitation mechanism which converts a single terahertz photon into a substantial signal of Rydberg excitations. We discuss a concrete realization based on realistic atomic interaction parameters, develop a comprehensive theoretical model that incorporates the motion of trapped atoms and study the many-body dynamics using tensor network methods.

Development of a phoswich imaging detector to simultaneously acquire neutron and gamma photon images

A neutron detector requires selectively detecting neutrons not detecting gamma photons. However, since gamma photons are commonly emitted from a neutron source, the separation of neutrons and gamma photons is sometimes difficult. To solve this problem, we developed a phoswich imaging detector that can simultaneously but independently acquire images of neutrons and gamma photons. The developed neutron imaging system consists of a lithium-containing silver doped zinc sulfide (Li–ZnS(Ag)) plate stacked on a cerium doped yttrium aluminum perovskite (YAP(Ce)) plate to form a phoswich detector, which is optically coupled to a position sensitive photomultiplier tube (PSPMT). Neutrons are detected by the Li–ZnS(Ag) plate while gamma photons are detected by the YAP(Ce) plate. The scintillation light from the Li–ZnS(Ag) and YAP(Ce) plates is detected by the PSPMT, and the position of interaction is calculated. Pulse shape discrimination is used to separate the images of neutrons and gamma photons. The spatial resolution of the imaging detector for neutrons is ∼2.6 mm FWHM, and the sensitivity for 252Cf neutrons at 2 cm from the source enclosed in 2-cm-thick polystyrene plates is 5.2 cps/MBq. The spatial resolution of the imaging detector for gamma photons is also ∼2.6 mm FWHM, and the sensitivity for 60Co gamma photons at 2 cm from the source within 2-cm-thick polystyrene plates is 375 cps/MBq. The contamination by gamma photons in the neutron window was negligible. The developed phoswich imaging detector can simultaneously and independently acquire the images of neutrons and gamma photons, and thus it will impact the relevant research and applications of neutron detectors and imaging.

Effective self-power photodetector based on photogalvanic effect: A case study for Janus MoSSe-CrSSe lateral heterojunction

The photogalvanic effect (PGE) can produce a photocurrent independent of a p–n junction or bias voltage, but the resulting photocurrent is usually very small. An appropriate lateral heterojunction can effectively enhance PGE. Here, we studied the PGE of a monolayer (ML) Janus MoSSe-CrSSe lateral heterojunction through ab initio quantum transport simulation. Compared with that of a homogeneous material, PGE is enhanced due to the reduced symmetry of the lateral heterojunction, and the maximum increase ratio in the photocurrent is more than two orders of magnitude greater than that of the homogeneous ML MoSSe and CrSSe photodetectors. A peak maximum photocurrent of 13.85 a[Formula: see text]/photon and high polarization sensitivity with a maximum extinction ratio of 308 are obtained for the ML MoSSe-CrSSe lateral heterojunction. These favorable properties indicate that the MoSSe-CrSSe lateral heterojunction is a promising candidate for photodetectors.

64 picosecond time resolved time-correlated single photon counting imaging.

High-speed imaging of dynamic scenes is a challenging and important task in many applications. However, conventional imaging methods based on charge coupled devices or complementary metal oxide semiconductors have limitations in temporal resolution and photon sensitivity. To address this problem, we propose a novel high-speed imaging scheme that combines single-pixel imaging with single photon detection and time-correlated single photon counting. Our scheme can achieve high-speed imaging with 64ps resolution by repeating the motion scenes and using binary outputs from single photon detectors. We demonstrate our scheme by reconstructing the switching process of a digital micro-mirror device and a liquid crystal spatial light modulator. Our scheme can be further improved to 1ps resolution by using a more accurate time-correlated single photon counting system. Moreover, our scheme can adapt to different speed scenes by adjusting the temporal resolution and reducing the sampling time. Our high temporal resolution imaging scheme further expands the application areas of single-pixel imaging and provides solutions for scenes requiring single photon detection and higher temporal resolution, such as reproducible chemical reaction processes imaging, cellular or sub-cellular bio imaging, single-molecule imaging of rotary motors, high-speed equipment inspection, and other periodic high-speed scenes imaging.

High Sensitivity Photon Pressure Sensitive Skin of Piercing Robot Based on Balloon-Shaped Fiber Optic Sensor

High Sensitivity Photon Pressure Sensitive Skin of Piercing Robot Based on Balloon-Shaped Fiber Optic Sensor

Sensitive Thermography via Sensing Visible Photons Detected from the Manipulation of the Trap State in MAPbX3.

Sensitive thermometry or thermography by responding to blackbody radiation is urgently desired in the intelligent information life, including scientific research, medical diagnosis, remote sensing, defense, etc. Even though thermography techniques based on infrared sensing have undergone unprecedented development, the poor compatibility with common optical components and the high diffraction limit impose an impediment to their integration into the established photonic integrated circuit or the realization of high-spatial-resolution and high-thermal-resolution imaging. In this work, we present a sensitive temperature-dependent visible photon detection in Bi-doped MAPbX3 (X = Cl, Br, and I) and employ it for uncooled thermography. Systematic measurements reveal that the Bi dopant introduces trap states in MAPbX3, thermal energy facilitates the carriers jumping from trap states to the conduction band, while the vacancies of trap states ensure the sequential absorption of visible photons with energy less than the band gap. Subsequently, the change of response toward the visible photon is applied to construct the thermograph, and it possesses a specific sensitivity of 2.11% K-1 along temperature variation. As a result, our thermograph presents a temperature resolution of 0.21 nA K-1, a high responsivity of 2.06 mA W-1, and a high detectivity of 2.08 × 109 Jones at room temperature. Furthermore, remote thermal imaging is successfully achieved with our thermograph.

Highly Sensitive Photonic Crystal Fiber Biosensor Based on Surface Plasmon Resonance for Six Distinct Types of Cancer Detection

Highly Sensitive Photonic Crystal Fiber Biosensor Based on Surface Plasmon Resonance for Six Distinct Types of Cancer Detection

Most DNA repair defects do not modify the relationship between relative biological effectiveness and linear energy transfer in CRISPR-edited cells.

Cancer is a highly heterogeneous disease, driven by frequent genetic alterations which have significant effects on radiosensitivity. However, radiotherapy for a given cancer type is typically given with a standard dose determined from population-level trials. As a result, a proportion of patients are under- or over-dosed, reducing the clinical benefit of radiotherapy. Biological optimization would not only allow individual dose prescription but also a more efficient allocation of limited resources, such as proton and carbon ion therapy. Proton and ion radiotherapy offer an advantage over photons due to their elevated Relative Biological Effectiveness (RBE) resulting from their elevated Linear Energy Transfer (LET). Despite significant interest in optimizing LET by tailoring radiotherapy plans, RBE's genetic dependence remains unclear. The aim of this study is to better define the RBE/LET relationship in a panel of cell lines with different defects in DSB repair pathways, but otherwise identical biological features and genetic background to isolate these effects. Normal human cells (RPE1), genetically modified to introduce defects in DNA double-strand break (DSB) repair genes, ATM, BRCA1, DCLRE1C, LIG4, PRKDC and TP53, were used to map the RBE-LET relationship. Cell survival was measured with clonogenic assays after exposure to photons, protons (LET 1 and 12keV/µm) and alpha particles (129keV/µm). Gene knockout sensitizer enhancement ratio (SER) values were calculated as the ratio of the mean inactivation dose (MID) of wild-type cells to repair-deficient cells, and RBE values were calculated as the ratio of the MID of X-ray and particle irradiated cells. 53BP1 foci were used to quantify radiation-induced DSBs and their repair following irradiation. Deletion of NHEJ genes had the greatest impact on photon sensitivity (ATM-/- SER=2.0 and Lig4-/- SER=1.8), with genes associated with HR having smaller effects (BRCA1-/- SER=1.2). Wild-type cells showed RBEs of 1.1, 1.3, 5.0 for low- and high-LET protons and alpha particles respectively. SERs for different genes were independent of LET, apart from NHEJ knockouts which proved to be markedly hypersensitive across all tested LETs. Due to this hypersensitivity, the impact of high LET was reduced in cell models lacking the NHEJ repair pathway. HR-defective cells had moderately increased sensitivity across all tested LETs, but, notably, the contribution of HR pathway to survival appeared independent of LET. Analysis of 53BP1 foci shows that NHEJ-defective cells had the least DSB repair capacity after low LET exposure, and no visible repair after high LET exposure. HR-defective cells also had slower repair kinetics, but the impact of HR defects is not as severe as NHEJ defects. DSB repair defects, particularly in NHEJ, conferred significant radiosensitivity across all LETs. This sensitization appeared independent of LET, suggesting that the contribution of different DNA repair pathways to survival does not depend on radiation quality.

Attosecond-Level Delay Sensing via Temporal Quantum Erasing.

Traditional Hong-Ou-Mandel (HOM) interferometry, insensitive to photons phase mismatch, proved to be a rugged single-photon interferometric technique. By introducing a post-beam splitter polarization-dependent delay, it is possible to recover phase-sensitive fringes, obtaining a temporal quantum eraser that maintains the ruggedness of the original HOM with enhanced sensitivity. This setup shows promising applications in biological sensing and optical metrology, where high sensitivity requirements are coupled with the necessity to keep light intensity as low as possible to avoid power-induced degradation. In this paper, we developed a highly sensitive single photon birefringence-induced delay sensor operating in the telecom range (1550 nm). By using a temporal quantum eraser based on common path Hongr-Ou-Mandel Interferometry, we were able to achieve a sensitivity of 4 as for an integration time of 2·104 s.

Compact all-fiber quantum-inspired LiDAR with over 100 dB noise rejection and single photon sensitivity

Entanglement and correlation of quantum light can enhance LiDAR sensitivity in the presence of strong background noise. However, the power of such quantum sources is fundamentally limited to a stream of single photons and cannot compete with the detection range of high-power classical LiDAR transmitters. To circumvent this, we develop and demonstrate a quantum-inspired LiDAR prototype based on coherent measurement of classical time-frequency correlation. This system uses a high-power classical source and maintains the high noise rejection advantage of quantum LiDARs. In particular, we show that it can achieve over 100dB rejection (with 100ms integration time) of indistinguishable (with statistically identical properties in every degree of freedom) in-band noise while still being sensitive to single photon signals. In addition to the LiDAR demonstration, we also discuss the potential of the proposed LiDAR receiver for quantum information applications. In particular, we propose the chaotic quantum frequency conversion technique for coherent manipulation of high dimensional quantum states of light. It is shown that this technique can provide improved performance in terms of selectivity and efficiency as compared to pulse-based quantum frequency conversion.

Cr2S3-Cr2O3/Poly-2-aminobenzene-1-thiol as a Highly Photocatalytic Material for Green Hydrogen Generation from Sewage Water.

This study highlights the utilization of the Cr2S3-Cr2O3/P2ABT nanocomposite photoelectrode for efficient and highly sensitive photon absorption, enabling the generation of green hydrogen through the production of hot electrons upon illumination. The nanocomposite is synthesized via a one-pot reaction using K2Cr2O7 and 2-aminobenzene-1-thiol monomer, and the presence of Cr2S3-Cr2O3 is confirmed by XRD and XPS analysis within the composite. The optical properties of the Cr2S3-Cr2O3/poly-2-aminobenzene-1-thiol composite exhibit wide spectral coverage from UV to IR, with a bandgap of 1.6 eV. The diverse morphological behavior observed in the composite correlates with its optical properties, with the cleft spherical particles of the pure polymer transforming into rod-like structures embedded within the polymer matrix. The generated hydrogen gas demonstrates an impressive efficiency of 40.5 mole/10.cm2.h through electrochemical testing. The current density (Jph) values are evaluated under different light frequencies using optical filters ranging from 730 to 340 nm, resulting in Jph values of 0.012 and 0.014 mA.cm-2, respectively. These findings present a promising avenue as green hydrogen for industrial applications, leveraging the potential of the Cr2S3-Cr2O3/P2ABT nanocomposite photoelectrode.

Large-Area Niobium Titanium Nitride Superconducting Microstrip Single-Photon Detector Fabricated Using a Photolithography Process

In this paper, we present a large-area niobium titanium nitride (NbTiN) superconducting microstrip single-photon detector (SMSPD) fabricated using a photolithography process. We fabricated a 1-μm-wide NbTiN-SMSPD covering 420 × 420 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> active area with a filling factor of 20% using an i-line stepper. The detector is cooled down to approximately 2.2 K, and its performance is evaluated at the wavelengths from visible to near-infrared. The detector operates stably without a shunt resistor and shows single-photon sensitivity for photons with a wavelength of 1550 nm. The bias current dependence of the detection count rate is measured at the wavelengths from 406 to 1550 nm. The saturation of the detection count rate with increasing the bias current was successfully observed at wavelengths below 850 nm, suggesting an internal detection efficiency approaching 100%. Furthermore, we evaluated the timing jitter performance using the femtosecond pulse laser with a wavelength of 1550 nm. Consequently, we achieved a system timing jitter of 85 ps for a light spot diameter of 100 µm.

CT technology: photon-counting detector computed tomography

Photon-counting detector computed tomography (PCD-CT) is aCT technology that overcomes many limitations of conventional detectors. Direct conversion of photons hitting the detector into electrical signals combined with more sensitive and accurate photon detection simultaneously allows spectral evaluation and also potential reduction in radiation exposure to the patient. The combination of energy thresholds and elimination of detector septa allows for areduction of electronic noise, an increase of spatial resolution, and an improvement of dose efficiency. Recent research has confirmed significantly reduced image noise, reduced radiation dose, increased spatial resolution, improved iodine signal, and areduction in artifacts. Spectral imaging potentiates these effects and also allows retrospective calculation of virtual monoenergetic images, virtual noncontrast images or iodine maps. Thus, the photon-counting technique offers the possibility of using various contrast agents, with the prospect of single-scan multiphase imaging or visualization of specific metabolic processes. Therefore, further research and complementary approval processes are necessary for clinical application. Likewise, further research is needed to develop and validate optimal settings and reconstructions for awide variety of situations, as well as to test new application possibilities. The only photon-counting detector CT device available on the market to date received clinical approval in 2021. It remains to be seen which other applications will become possible through improvements in hardware and software. This technology has already demonstrated an impressive superiority compared with the current standard of CT imaging, especially regarding high-resolution imaging of detailed structures and examinations with high radiation exposure.

Multi-wavelength SPAD photoplethysmography for cardio-respiratory monitoring

There is a growing interest in photoplethysmography (PPG) for the continuous monitoring of cardio-respiratory signals by portable instrumentation aimed at the early diagnosis of cardiovascular diseases. In this context, it is conceivable that PPG sensors working at different wavelengths simultaneously can optimize the identification of apneas and the quantification of the associated heart-rate changes or other parameters that depend on the PPG shape (e.g., systematic vascular resistance and pressure), when evaluating the severity of breathing disorders during sleep and in general for health monitoring. Therefore, the objective of this work is to present a novel pulse oximeter that provides synchronous data logging related to three light wavelengths (green, red, and infrared) in transmission mode to optimize both heart rate measurements and a reliable and continuous assessment of oxygen saturation. The transmission mode is considered more robust over motion artifacts than reflection mode, but current pulse oximeters cannot employ green light in transmission mode due to the high absorbance of body tissues at this wavelength. For this reason, our device is based on a Single-Photon Avalanche Diode (SPAD) with very short deadtime (less than 1 ns) to have, at the same time, the single photon sensitivity and high-count rate that allows acquiring all the wavelengths of interest on the same site and in transmission mode. Previous studies have shown that SPAD cameras can be used for measuring the heart rate through remote PPG, but oxygen saturation and heart-rate measures through contact SPAD-based PPG sensors have never been addressed so far. The results of the preliminary validation on six healthy volunteers reflect the expected physiological phenomena, providing rms errors in the Inter Beat Interval estimation smaller than 70 ms (with green light) and a maximum error in the oxygen saturation smaller than 1% during the apneas. Our prototype demonstrates the reliability of SPAD-based devices for continuous long-term monitoring of cardio-respiratory variables as an alternative to photodiodes especially when minimal area and optical power are required.

ArduSiPM technology: Compact and light All-in-one detectors for space application

ArduSiPM technology integrates System on Chip (SoC) innovation and Silicon photomultiplier (SiPM) detector improvements into a new generation of all-in-one scintillation detectors, developed by INFN Rome since 2014. To minimize reliance on pre-built Commercial off-the-shelf (COTS) components, we utilize the peripherals and CPU of the SoC for edge computing tasks and various functions, such as Counters, Analog-to-Digital Converters (ADCs), Digital-to-Analog Converters (DACs), Pulse-Width modulation (PWM), and digital input/output interfaces. Our compact electronic system eliminates the need for external data acquisition systems and ASICs, while also enabling the CPU to perform edge computing functions. The detector, capable of measuring the rate, arrival time (with a resolution of 7 ns correlated to the SoC main clock), and number of photons arriving on the SiPM, is ideal for radiation monitoring and highly sensitive photon detection. The INFN MICRO experiment explores circuits and engineering solutions for developing detectors for diverse fields such as Transient Luminous Events, analytical chemistry, and nano/picosatellites. Our ultimate goal is to integrate the detector into the onboard computer of a satellite, akin to navigation instruments and attitude control systems, with future improvements in SoC technology easily leveraged thanks to our approach’s independence from the specific SoC.

PHOTOLUMINESCENCE PROPERTIES OF Nd3+, Yb3+ CODOPED Ga2O3 NANOPARTICLES

The availability of sensitive photon detectors and inexpensive lasers allowed us to explore more efficient fluorescent probes that will work in the second near-infrared optical window. In this study, the optical properties of Nd3+ and Yb3+ co-doped Ga2O3 nanoparticles were studied. In order to indicate the correlation between particle size, crystallinity, and optical property of present samples XRD, TEM, and Photoluminescence analyses were performed. Various excitation wavelengths and dopant concentrations were used to understand the energy transfer mechanism in Nd3+ and Yb3+ co-doped Ga2O3 nanoparticles. As the excitation wavelength increased from 325 nm to 477 and 515 nm, Yb3+ emission peak intensity decreased while Nd3+ emission peak intensity increased. This inverse relationship between the emission intensities of Yb3+ and Nd3+ ion showed the presence of energy transfer between them. The resulting emission peaks were broad and weak, indicating the presence of a non-radiative decay channel due to the crystal defects.