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Evaluating the influence of laser wavelength and detection stage geometry on optical detection efficiency in a single-particle mass spectrometer
摘要： Single-particle mass spectrometry (SPMS) is a useful tool for the online study of aerosols with the ability to measure size-resolved chemical composition with a temporal resolution relevant to atmospheric processes. In SPMS, optical particle detection is used for the effective temporal alignment of an ablation laser pulse with the presence of a particle in the ion source, and it gives the option of aerodynamic sizing by measuring the offset of particle arrival times between two detection stages. The efficiency of the optical detection stage has a strong influence on the overall instrument performance. A custom detection laser system consisting of a high-powered fibre-coupled Nd:YAG solid-state laser with a collimated beam was implemented in the detection stage of a laser ablation aerosol particle time-of-flight (LAAP-TOF) single-particle mass spectrometer without major modifications to instrument geometry. The use of a collimated laser beam permitted the construction of a numerical model that predicts the effects of detection laser wavelength, output power, beam focussing characteristics, light collection angle, particle size, and refractive index on the effective detection radius (R) of the detection laser beam. We compare the model predictions with an ambient data set acquired during the Ice in Clouds Experiment – Dust (ICE-D) project. The new laser system resulted in an order-of-magnitude improvement in instrument sensitivity to spherical particles in the size range 500–800 nm compared to a focussed 405 nm laser diode system. The model demonstrates that the limit of detection in terms of particle size is determined by the scattering cross section (Csca) as predicted by Mie theory. In addition, if light is collected over a narrow collection angle, oscillations in the magnitude of Csca with respect to particle diameter result in a variation in R, resulting in large particle-size-dependent variation in detection efficiency across the particle transmission range. This detection bias is imposed on the aerodynamic size distributions measured by the instrument and accounts for some of the detection bias towards sea salt particles in the ambient data set.
关键词： LAAP-TOF,aerosol,single-particle mass spectrometry,Mie theory,laser wavelength,detection stage geometry,optical detection efficiency
更新于2025-09-23 15:19:57
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Calibration of free-space and fiber-coupled single-photon detectors
摘要： We measure the detection efficiency of single-photon detectors at wavelengths near 851 nm and 1533.6 nm. We investigate the spatial uniformity of one free-space-coupled single-photon avalanche diode and present a comparison between fusion-spliced and connectorized fiber-coupled single-photon detectors. We find that our expanded relative uncertainty for a single measurement of the detection efficiency is as low as 0.70 % for fiber-coupled measurements at 1533.6 nm and as high as 1.78 % for our free-space characterization at 851.7 nm. The detection-efficiency determination includes corrections for afterpulsing, dark count, and count-rate effects of the single-photon detector with the detection efficiency interpolated to operation at a specified detected count rate.
关键词： dark count,single-photon detectors,free-space-coupled,afterpulsing,detection efficiency,fiber-coupled
更新于2025-09-19 17:13:59
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Using quantum entangled photons to measure the absolute photon detection efficiency of a multi-pixel SiPM array
摘要： Spontaneous parametric down-conversion (SPDC) of a visible pump photon is the generation of two less energetic, quantum entangled photons (QEPs), often in the near infrared (NIR), using a non-linear crystal e.g. beta barium borate. Since the detection of one QEP predicates the existence of its entangled twin, QEPs have previously been used to measure the absolute photon detection efficiency (PDE), ??(??), of a detector under test by measuring time-coincident events with an additional trigger detector, allowing evaluation of ?????? ?? (??) without recourse to a calibrated reference detector. In this paper, the QEP absolute PDE measurement technique is outlined, and an extension of this technique is proposed to measure ??(??) for pixels on a multi-pixel array where each pixel provides an individual signal output. By treating all pixels in a multi-pixel array as indistinguishable, Monte Carlo simulations show that the symmetry of the measurement allows ??(??) to be determined for each pixel. A route towards experimental measurements using this technique with a 64-pixel SiPM array combined with a 64-channel waveform digitiser module is outlined.
关键词： Silicon photomultiplier,SiPM,Photon detection efficiency,Quantum entanglement
更新于2025-09-12 10:27:22
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Improving detection efficiency of superconducting nanowire single-photon detector using multilayer antireflection coating
摘要： Optical cavity with backside optical coupling is one of the prevalent optical structures for superconducting nanowire single photon detector. A single layer anti-re?ection coating (ARC) on the backside of the substrate is often adopted to enhance the transmittance to the substrate. We here apply a multilayer ARC to further increase the transmittance from 94.5% to 99.5%. An NbTiN SNSPD made on such a substrate with cavity structure presents a system detection ef?ciency of 90.1% at a dark count rate (DCR) of 100 Hz, which is the best value reported for backside optical coupled SNSPD at 1550 nm. It shows a timing jitter of ～40.7 ps and the recovery time constant of ～22.9 ns.
关键词： superconducting nanowire single-photon detector,multilayer antire?ection coating,detection efficiency
更新于2025-09-10 09:29:36
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Optical Transition-Edge Sensors: Dependence of System Detection Efficiency on Wavelength
摘要： Optical transition-edge sensors (TESs) that can resolve the energy of a single photon have been proven useful in quantum information and biology. TESs can provide spectra ranging from near-infrared to visible regions and have the potential to reveal new phenomena in biology. In this paper, we have investigated the responses of TESs to photons at near-infrared and visible wavelengths, from 450 to 1000 nm in 10-nm increments using a supercontinuum laser and a tunable bandpass filter, which converted the multichromatic light source into monochromatic light. The system detection efficiency of an optical TES optimized for photon detection at 950 nm was nearly 100% at some wavelengths and was more than 10% for the overall bandwidth. We found that the detector responses strongly depended on the wavelengths. A spectrum of the filtered light at shorter wavelengths was more likely to show a second peak with energy lower than that of the primary peak.
关键词： system detection efficiency,Single-photon detection,superconducting detector,transition-edge sensor (TES),supercontinuum (SC) laser
更新于2025-09-09 09:28:46
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[IEEE 2018 34th International Conference on Lightning Protection (ICLP) - Rzeszow (2018.9.2-2018.9.7)] 2018 34th International Conference on Lightning Protection (ICLP) - Optical Lightning Measurement System and First Results
摘要： This paper introduces a newly developed optical lightning measurement system (OLMS). The OLMS is based on a video system using a camera with a 360° panorama view and a frame rate of 60 frames per second. The OLMS locates the lightning from the direction of the illuminated lightning channel and the travel time of the thunder sound. The analysis comprises 34 flashes containing 144 strokes, which occurred during the time period from 30th of July 2017 to 24th of August 2017. The results are compared to data obtained by the European lightning location network EUCLID. The comparison revealed a flash detection efficiency of 100 % and a stroke detection efficiency of 93.1 % for EUCLID. With EUCLID, the fraction of 92.5 % was classified correctly as cloud-to-ground lightning and the minor fraction of 7.5 % was miss-classified as cloud-to-cloud lightning. On average (arithmetic mean), the negative flashes contained 4.3 return strokes with 1.7 different striking points. For multi-stroke flashes with return strokes using the same lightning channel, EUCLID located the individual striking points with a median deviation of 57.3 m. The average striking distance was about 10 km. Due to the far distance the thunder sound could often not be separated from the thunder sound of other lightning. Therefore, the OLMS located the lightning with a relatively high deviation compared to the data of EUCLID. The arithmetic (geometric) mean value of the deviation was 1330 m (670 m).
关键词： optical measurement,detection efficiency,Lightning location system (LLS),multiple lightning flash,location accuracy,selectivity CG/CC
更新于2025-09-09 09:28:46
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Microchannel Plate Efficiency to Detect Low Velocity Dust Impacts
摘要： Recent space experiments suggest that electron and ion energy analyzers using microchannel plates (MCPs) as detectors are also registering direct hits by nanodust particles. To allow the analysis and interpretation of these putative dust events, the detection e?ciency of MCPs has to be characterized. We report on a series of experiments to investigate the detection e?ciency of MCP detectors to direct impacts for both positively and negatively charged micron and submicron sized iron particles. A double-stack MCP detector in a chevron con?guration was mounted as a target in a dust accelerator. A range of particle velocities and masses were used for a comprehensive examination. The MCP detected and produced de?nite signals associated with con?rmed particle impacts of the MCP for both positively and negatively charged dust particles. The detection e?ciency was found to be (6 ± 1)% for positively charged dust and (9 ± 3)% for negatively charged dust particles with a characteristic mass of 6.0 × 1011 μ (10?15 kg) and speed of 100 m/s. The examined particle velocity range accurately replicates Rosseta’s interaction with dust grains emanating from comet 67P/ Churyumov-Gerasimenko’s nucleus. Additionally, the MCP detection e?ciency for low velocity particles shows a possible underestimate of higher speed nanograin signals from Cassini’s electron plasma spectrometer during its ?yby through Enceladus’ active south pole.
关键词： Microchannel plate,Cassini,detection efficiency,dust impacts,Rosetta
更新于2025-09-09 09:28:46