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We report the slow-light enhanced spin-resolved in-plane emission from a single quantum dot (QD) in a photonic crystal waveguide (PCW). The slow light dispersions in PCWs are designed to match the emission wavelengths of single QDs. The resonance between two spin states emitted from a single QD and a slow light mode of a waveguide is investigated under a magnetic field with Faraday configuration. Two spin states of a single QD experience different degrees of enhancement as their emission wavelengths are shifted by combining diamagnetic and Zeeman effects with an optical excitation power control. A circular polarization degree up to 0.81 is achieved by changing the off-resonant excitation power. Strongly polarized photon emission enhanced by a slow light mode shows great potential to attain controllable spin-resolved photon sources for integrated optical quantum networks on chip., 7 pages,5 figures

In this study, time resolved (TR) Monte Carlo (MC) simulation program code was run to generate photon fluencies with increasing time steps. TR MC simulation was performed for ten time series from 4 ps to 52 ps. Generated photon fluencies were transferred to the image analysis programming platform. Imaging device geometry was created for test purpose in image reconstruction programming platform environment. Forward model weight matrix functions were calculated during each time period for 38 sources, and 38 detectors according to the back-reflected imaging geometry. A homogenous phantom, which simulated tissue, was chosen. Depending on the homogeneous tissue optical properties, such as tissue absorption coefficient μa, and tissue scattering coefficient μs, photons emitted from the laser source positions; migrated differently inside the imaging tissue. Photons migrate inside the tissue by some multiplication factor of ps depending on the tissue type for each 100-micrometer vertical distance. Superficial photons come photodetector point fast, depend on the source-detector neighborhood distances and tissue optical properties, respectively. Time resolved diffuse optic tomography (TRDOT) imaging systems are an emerging biomedical optic imaging modality due to progressive electronic technologies are helping to build the systems faster and cheap. As such, emerging microelectronic technology is giving important access to design and implement compact laser sources and photodetector units. Vertical cavity surface emitting light (VCSEL) as laser source and single photon avalanche diode (SPAD) arrays as photodetector units are becoming in common use as important hardware tools for designers and researchers in this field. TR diffuse photon analysis should be done routinely for better understanding of TRDOT devices. Hence, MC simulation driven TR photon fluence analysis was done for such a purpose in this study.

The excited state population of single solid-state emitters is subjected to energy fluctuations around the equilibrium driven by the bath and relaxation through the emission of phonons or photons. Simultaneous measurement of the associated spectral dynamics requires a technique with a high spectral and temporal resolution with an additionally high temporal dynamic range. We propose a pulsed excitation-laser analog of Photon-Correlation Fourier Spectroscopy (PCFS), which extracts the lineshape and spectral diffusion dynamics along the emission lifetime trajectory of the emitter, effectively discriminating spectral dynamics from relaxation and bath fluctuations. This lifetime-resolved PCFS correlates photon-pairs at the output arm of a Michelson interferometer in both their time-delay between laser-excitation and photon-detection and the time-delay between two photons. We propose the utility of the technique for systems with changing relative contributions to the emission from multiple states, for example, quantum emitters exhibiting phonon-mediated exchange between different fine-structure states., Comment: 15 pages, 5 figures total, including SI

The variation of photon fluence distributions [photon/cm2.s] for different input angle laser sources was shown by researchers experimentally [1]. According to this philosophy, different input angle source and detector photon entrance from tissue surface into imaging media have different photon fluence distributions for a specific tissue type. In this study, different input angle simulations were used for pulsed laser photons which uses time resolved (TR) Monte Carlo (MC) photon-tissue interaction simulation program to prove the philosophy in TR run mode. TR run mode MC simulation program trmc.c [2] was modified and used to generate TR photon counts inside the homogenous simulation environment. It has homogeneous tissue optical properties, absorption μa = 0.1 cm-1, scattering μs = 100 cm-1, and anisotropy g = 0.90 coefficients. Multi-input angle philosophy was first demonstrated by the researchers [1]. It was defined and experimentally proven. Photon fluencies which are forward model weight matrix coefficients differences were successfully shown for TR laser as a general procedure. In this study, differences were drawn for seven different input angle sources with pulsed laser photons. The proof-of-concept philosophy was shown successfully. The purpose of the use of pulsed laser is to show the righteousness of the philosophy in TR run mode, since the TR diffuse optical tomography (TRDOT) device would be made as a biomedical optic imaging (BOI) device. Cylindrical radial coordinate system which was defined in trmc.c [2] in earlier was used, the code was modified, and photon fluencies were generated based on the different input angle laser photons. Cylindrical coordinate system has 1 cm and 36-element radial r, and depth z grids. 100.000 photons were sent from pencil beam tissue surface point. Photons would be thought as group of ultra-narrow band pulsed laser photons. The main purpose of showing photon fluencies for different laser source input angles were succeeded and image reconstruction procedure was also applied. Ten time series were used which are [4, 8, 12, 16, 22, 26, 30, 38, 46, 52] picoseconds (ps). Different input angle photon fluence distribution figures were drawn. These are 0º, 15º, 30º, 45º, 60º, 75º, 90º. Photon fluence differences were also drawn and observed for different input angle laser sources. Forward model problem different input angle laser source and detector transfer functions were also drawn. Finally inlusion was embedded inside the homogenous simulation environment and images were reconstructed for both scenarios and localization error (LE), and concentration error (CE) was calculated for both scenarions and compared with each other.

The particle-like nature of light becomes evident in the photon statistics of fluorescence from single quantum systems as photon antibunching. In multichromophoric systems, exciton diffusion and subsequent annihilation occurs. These processes also yield photon antibunching but cannot be interpreted reliably. Here we develop picosecond time-resolved antibunching to identify and decode such processes. We use this method to measure the true number of chromophores on well-defined multichromophoric DNA-origami structures, and precisely determine the distance-dependent rates of annihilation between excitons. Further, this allows us to measure exciton diffusion in mesoscopic H- and J-type conjugated-polymer aggregates. We distinguish between one-dimensional intra-chain and three-dimensional inter-chain exciton diffusion at different times after excitation and determine the disorder-dependent diffusion lengths. Our method provides a powerful lens through which excitons can be studied at the single-particle level, enabling the rational design of improved excitonic probes such as ultra-bright fluorescent nanoparticles and materials for optoelectronic devices., Photon antibunching typically measures the time-averaged photophysics of multichromophoric nanoparticles. Here, the authors report on time-resolving photon antibunching, allowing the true number of chromophores and exciton diffusion to be measured in DNA origami and conjugated polymer aggregates.

Supplementary Document

Photochemistry is a largely unconsidered potential source of reactive species such as hydroxyl and peroxy radicals (OH and HO2, “HOx”) indoors. We present measured wavelength-resolved photon fluxes and distance dependences of indoor light sources including halogen, incandescent, and compact fluorescent lights (CFL) commonly used in residential buildings; fluorescent tubes common in industrial and commercial settings; and sunlight entering buildings through windows. We use these measurements to predict indoor HOx production rates from the photolysis of nitrous acid (HONO), hydrogen peroxide (H2O2), ozone (O3), formaldehyde (HCHO), and acetaldehyde (CH3CHO). Our results suggest that while most lamps can photolyze these molecules, only sunlight and fluorescent tubes will be important to room-averaged indoor HOx levels due to the strong distance dependence of the fluxes from compact bulbs. Under ambient conditions, we predict that sunlight and fluorescent lights will photolyze HONO to form OH at rates of 106–...

Dual-energy contrast-enhanced digital mammography (CEDM) has been used to decompose breast images and improve diagnostic accuracy for tumor detection. However, this technique causes an increase of radiation dose and an inaccuracy in material decomposition due to the limitations of conventional X-ray detectors. In this study, we simulated the dual-energy CEDM with an energy-resolved photon-counting detector (ERPCD) for reducing radiation dose and improving the quantitative accuracy of material decomposition images. The ERPCD-based dual-energy CEDM was compared to the conventional dual-energy CEDM in terms of radiation dose and quantitative accuracy. The correlation between radiation dose and image quality was also evaluated for optimizing the ERPCD-based dual-energy CEDM technique. The results showed that the material decomposition errors of the ERPCD-based dual-energy CEDM were 0.56–0.67 times lower than those of the conventional dual-energy CEDM. The imaging performance of the proposed technique was optimized at the radiation dose of 1.09 mGy, which is a half of the MGD for a single view mammogram. It can be concluded that the ERPCD-based dual-energy CEDM with an optimal exposure level is able to improve the quality of material decomposition images as well as reduce radiation dose.

Solvents lacking hydrogen atoms are very convenient models for elucidating the properties of singlet oxygen, since the lifetime of singlet oxygen in these solvents reaches tens milliseconds. Measuring intrinsic infrared (IR) phosphorescence of singlet oxygen at 1270 nm is the most reliable method of singlet oxygen detection. However, efficient application of the phosphorescence method to these models requires an equipment allowing reliable measurement of the phosphorescence kinetic parameters in the millisecond time range at low rates of singlet oxygen generation, which is a technically difficult problem. Here, we describe a highly sensitive LED (laser) spectrometer recently constructed in our laboratory for the steady-state and time-resolved measurements of the millisecond phosphorescence of singlet oxygen. In the steady-state mode, this spectrometer allows detection of singlet oxygen phosphorescence upon direct excitation of oxygen molecules in the region of dark-red absorption bands at 690 and 765 nm. For kinetic measurements, we used phenalenone as a photosensitizer, microsecond pulses of violet (405 nm) LED for excitation (irradiance intensity, ≤50 μW/cm2), a photomultiplier and a computer multichannel scaler for time-resolved photon counting. The decays of singlet oxygen in air-saturated CCl4, C6F6, and Freon 113 and quenching of singlet oxygen by phenalenone and dissolved molecules of triplet oxygen were measured. The relative values of the radiative rate constants of singlet oxygen in these media were determined. The results were compared with the absorption coefficients of oxygen measured by our group using the methods of laser photochemistry. Critical discussion of the obtained results and the data of other researchers is presented.

Frequency-resolved photon correlations have proven to be a useful resource to unveil nonlinearities hidden in standard observables such as the spectrum or the standard (color-blind) photon correlations. In this manuscript, we analyze the frequency-resolved correlations of the photons being emitted from an optomechanical system where light is nonlinearly coupled to the quantized motion of a mechanical mode of a resonator, but where the quantum nonlinear response is typically hard to evidence. We present and unravel a rich landscape of frequency-resolved correlations, and discuss how the time-delayed correlations can reveal information about the dynamics of the system. We also study the dependence of correlations on relevant parameters such as the single-photon coupling strength, the filtering linewidth, or the thermal noise in the environment. This enriched understanding of the system can trigger new experiments to probe nonlinear phenomena in optomechanics, and provide insights into dynamics of generic nonlinear systems., MKS thanks Michael J Steel for stimulating discussions, and acknowledges funding from Australian Research Council (Discovery Project No. DP160101691) and the Macquarie University Research Fellowship Scheme. AGT acknowledges support from CSIC Research Platform on Quantum Technologies PTI-001 and from Spanish Project No. PGC2018-094792-B-100 (MCIU/AEI/FEDER, EU). RE and JA acknowledge project PID2019-107432GB-I00 from the Spanish Ministry of Science and Innovation, Project No. H2020- FET Open 'THOR' Nr. 829067 from the European Commission, and Grant No. IT1164-19 from the Basque Government for consolidated groups of the Basque University.

This paper presents the development of an energy-resolved readout electronics for BGO and LYSO scintillator detectors for X-ray photon-counting imaging applications. The detector signal was modeled as an exponential decay waveform convoluted with the single photon response of SiPM detector. In order to achieve high counting rate, the detector signal was firstly processed by an active pole-zero compensation circuits. Then using the time-over-threshold (ToT) readout method, a time to digital converters (TDC) implemented in FPGA. Simulation and experimental results showed that the method can significantly shorten the pulse width. The spectrum measurement results showed that the signal from active Pole-Zero compensation circuit can almost retain the information of the original signal while the spectrum obtained by TOT method was badly distorted. The detailed analysis and test results will be presented in the paper.

In this work we demonstrate an approach of double arrival time monitors (ATM), which is employed to increase synchronization level between external femtosecond laser systems and 4th generation light sources. With comparison to the single arrival time monitor technique, which was routinely used for time resolved experiments at accelerator based light sources, here we demonstrate more than twice increase in the temporal resolution and elimination of temporal drifts. The proposed technique opens a way for sub femtosecond synchronization within large-scale facilities and laser systems.

We developed a prototype photon-counting mammography unit with a cadmium zinc telluride detector, which provides a new type of image with physical analysis parameters. Using the X-ray attenuation information obtained from this device, we examined the ability of this technique in discriminating substances and estimating their compositions. To estimate the substance compositions, we used resected breast tissues immediately after a surgical operation for invasive carcinoma of no special type, and used phantoms to reproduce mammary glands and adipose tissue. In our system, the spectrum penetrating the substance was measured with three energy bins in each pixel. The products of linear-attenuation coefficient and thicknesses for each bin were calculated. Using these three values, the scatterplots displaying all the values calculated from each pixel inside the region of interest (ROI) on the image were created. The scatterplot displaying only gravity values calculated for each ROI on the image was created for evaluating the separation of plot points to discriminate between different substance compositions. The gravity points placed on the malignant tumor tissue were plotted separately from those on the normal tissue. Furthermore, a fusion image was created by overlapping an X-ray image and values of this scatterplot points represented on a 10-step color scale. The fusion image was highlighting the differences in substance compositions using color tone, such as malignant tumor or mammary gland tissue, by adjusting the color scale level.

Spectrally resolved photon echo spectroscopy in the off-resonance condition is reported for the first time to study the coherence and population dynamics of CdSe quantum dots. In this case, the information related to the system dynamics can be inferred indirectly. This is especially useful when such dynamical information might be hidden under the absorption maxima of the sample. We observe that a substantial intensity of the photon echo signal was obtained in two different CdSe quantum dot samples (CdSe 610 and CdSe 640), which have absorption maxima at 620 nm and 590 nm, respectively. Due to the difference in sizes of these two quantum dots, a small change is observed in the molecular dynamics of these two quantum-dot samples. Specifically, the spectral diffusion of CdSe 640 occurs within the first 50 fs, whereas that for CdSe 610 occurs at about 100 fs timescale. The integrated plots of the photon echo signal, as a function of population time, result in two decay constants. The faster among the two decay components is pulse width limited and is in between 30 and 40 fs at different fixed coherence times for both samples. The slower decay component for the CdSe 610 sample is found to be in the range of 75–85 fs, while that for CdSe 640, it is between 82 and 92 fs at different fixed coherence times. SYNOPSIS Excitonic dynamics of CdSe quantum-dots is presented using time-dependent spectrally-resolved photon-echo spectroscopy at 810 nm, which is ~160 nm red-shifted from their absorption maxima. Information related to system dynamics is inferred indirectly from such ‘far-from-resonance’ photon-echo experiments, which would be especially useful when the information is hidden within the sample’s absorption maxima.

Energy-resolved photon counting detectors (ERPCD) are currently being developed for medical application. It is hoped that these detectors can be used for deriving precise material information. When used for that purpose, many researchers are concerned with the necessity to consider the response of ERPCD for analysis of measured spectra. To solve this issue, we plan to apply a correction for incomplete energy signals using the application of software. For establishing a correction procedure, we should know the response of ERPCD in terms of interactions between detector materials (Cd, Zn and Te), charge sharing effect, and energy resolution. First, to derive the ideal response of the ERPCD "R1", Monte-Carlo simulation was carried out. In the simulated R1, characteristic X-ray peaks of Cd and Te were clearly observed; these peaks are produced in multi-pixel-type detectors. Second, taking into consideration the charge sharing effect and energy resolution, response function "R2" was determined; constant-component-type charge sharing function and energy dependent Gaussian function were assumed based on published articles. Then comparing the experimental spectra (50 and 80 kV) measured with our test-model detector, parameters for R2 were determined. As a result, we can reproduce X-ray spectra measured with a multi-pixel-type ERPCD; typical parameters for R2 are peak efficiency 25% and energy resolution 8% at 80 keV. Next, using the X-ray spectra folded with R1×R2, ratios of full-energy peaks in the spectra were analyzed. X-ray attenuation of aluminum having a thickness of 1 cm was calculated for dental radiography application. In our application for material identification, attenuation coefficient μt should be determined from the measured spectra. When a tube voltage of 80 kV was applied, obtained μt for 50-80 keV is in good agreement with the theoretical values. Based on the present research, the results of response function experiments will be applied to our material identification method which was developed using ideal X-ray spectra.

A new energy-resolved photon-counting mammography (ERPCM) device with a cadmium telluride (CdTe) series detector (JOB Corporation, Japan) is currently being developed. The CdTe series detector can detect higher-energy photons with high sensitivity, enabling the use of high-energy X-rays for imaging. Our previous research, in which we compared ERPCM using high-energy X-rays (tube voltage 50 kV) with general mammography using low-energy X-rays (tube voltage about 30 kV), reported that ERPCM had a higher CNR (contrast-to-noise ratio) than general mammography. The purpose of this study was to examine the magnitude of the CNR using a simulation and ERPCM; especially we would like to examine the CNR when the tube voltage of higher than 50 kV was adopted. In the comparison of the CNRs, It was necessary to pay attention to equalizing the average glandular dose (AGD). Using the simulation and ERPCM, we compared the CNR between images taken at 50 kV and 75 kV under a constant AGD. The simulation phantom was composed of 50% mammary gland and 50% adipose tissue, and contained tumor regions. The thickness of the simulation phantom was varied. We put an acrylic plate (1 mm thickness) on an RMI-156 phantom. Furthermore, we placed the thicker acrylic plate (10, 20, 30, 40 mm) on the 156 phantom and 1 mm-thick acrylic plate to simulate thicker breast. Based on the results from the simulation, in the phantom thickness of 80 mm, the CNR of image taken by 75kV got extremely closer to that taken by 50kV. The advantage of the image taken at 75 kV for the thicker breast was also confirmed in ERPCM.

In this study, we propose a new image display method to obtain high contrast-to-noise ratio (CNR) using energy resolved photon-counting mammography (ERPCM) with a cadmium telluride (CdTe) series detector manufactured by JOB CORPOLATION. The CdTe series detector can detect high-energy photons with high sensitivity, enabling users to image with high-energy X-rays. Using this detector, it is possible to reduce the dose given to a patient while increasing the CNR. First, the spectrum was divided into three bins and their corresponding linear attenuation coefficients were calculated from input and output photon numbers. Further, absorption vector length (AVL) and average absorption length (AAL) were calculated from the linear attenuation coefficients and from thicknesses of objects after beam-hardening correction. We further compared the CNR between ERPCM and general mammography images under the constant average glandular dose (AGD). We imaged an acrylic plate (1 mm thick) on RMI-156 phantom, determined regions of interest (ROIs) on an acrylic plate and background, and calculated the CNR. Our ERPCM generated two types of images: an AVL image and an AAL image. AMULET Innovality manufactured by FUJIFILM generated an integrated image. MicroDose SI manufactured by Philips generated a count image and removed electrical noise by the photon-counting technique. The four images, in order of decreasing CNR, were the AAL image, AVL image, MicroDose image, and AMULET image. The proposed method using ERPCM generated an image with higher CNR than images using general mammography under the constant AGD.

Recently, the concept of an ''$N$-photon spectrum'' -- a spectrally resolved $N$-photon correlation function -- has been introduced as an innovative quantum optics characterization tool that uniquely reveals information about pathways underlying the generation of light in a given source. Here, the authors investigate experimentally the three-photon spectrum of resonance fluorescence from a single semiconductor quantum dot. The observations agree with previous theoretical work, revealing significantly more pronounced photon antibunching at the Mollow triplet sidebands and more strongly correlated emission through virtual states compared to the two-photon counterpart.

Atomic excitation to excited states in strong laser field is the key to high-order harmonic generation below ionization threshold, yet remains unclear mainly due to the lack of proper detection methods. We propose a frequency-resolved photon-electron spectroscopy technique to reconstruct population of excited states with the second delayed laser pulse. The technique utilizes Fourier transformation to separate ionization from different excited states to different positions on the spectrum. With the advantage of separation, we provide a scheme to reconstruct populations on different excited states after the first pulse. The scheme is validated by high-precision population reconstruction of helium and hydrogen atoms., Comment: 6 pages,3 figures

We propose an alternative formulation of the sensor method presented in [Phys. Rev. Lett 109, 183601 (2012)] for the calculation of frequency-filtered and time-resolved photon correlations. Our approach is based on an algebraic expansion of the joint steady state of quantum emitter and sensors with respect to the emitter-sensor coupling parameter \epsilon. This allows us to express photon correlations in terms of the open quantum dynamics of the emitting system only and ensures that computation of correlations are independent on the choice of a small value of \epsilon. Moreover, using time-dependent perturbation theory, we are able to express the frequency- and time- resolved second-order photon correlation as the addition of three components, each of which gives insight into the physical processes dominating the correlation at different time scales. We consider a bio-inspired vibronic dimer model to illustrate the agreement between the original formulation and our approach., Comment: 12 pages, 5 figures

Photochemistry is a largely unconsidered potential source of reactive species such as hydroxyl and peroxy radicals (OH and HO

The coherent optical response from 140 nm and 65 nm thick ZnO epitaxial layers is studied using four-wave-mixing spectroscopy with picosecond temporal resolution. Resonant excitation of neutral donor-bound excitons results in two-pulse and three-pulse photon echoes. For the donor-bound A exciton (${\mathrm{D}}^{0}{\mathrm{X}}_{\text{A}}$) at temperature of 1.8 K we evaluate optical coherence times ${T}_{2}=33--50$ ps corresponding to homogeneous line widths of $13--19\phantom{\rule{0.222222em}{0ex}}\ensuremath{\mu}\mathrm{eV}$, about two orders of magnitude smaller as compared with the inhomogeneous broadening of the optical transitions. The coherent dynamics is determined mainly by the population decay with time ${T}_{1}=30--40$ ps, while pure dephasing is negligible. Temperature increase leads to a significant shortening of ${T}_{2}$ due to interaction with acoustic phonons. In contrast, the loss of coherence of the donor-bound B exciton (${\mathrm{D}}^{0}{\mathrm{X}}_{\text{B}}$) is significantly faster (${T}_{2}=3.6\phantom{\rule{0.16em}{0ex}}\mathrm{ps}$) and governed by pure dephasing processes.

We consider the photon-assisted tunneling (PAT) and the Landau-Zener-Stueckelberg (LZS) interference for double quantum dots induced electrostatically along a semiconducting carbon nanotube. An atomistic tight-binding approach and the time-dependent configuration interaction method are employed for description of the systems of a few confined electrons and holes. We reproduce the patterns of the LZS interference recently observed for the quantum double dots describing transport across hole-localized states. Moreover, we indicate that for charge configurations for which the ground-state is Pauli blocked PAT can be used for resolution of the transitions that involve spin-flip or intervalley transitions without the spin-valley conserving background signal.

New horizons in x-ray imaging have been opened up with the emergence of energy-resolved photon counting detectors (PCDs). These include the ability to differentiate material components and estimate their equivalent thickness or relative ratio by processing a single shot acquisition image. However, such techniques require highly accurate images, especially for materials close in terms of attenuation. The presence of scattered radiation leads to a loss of contrast and, more importantly, a bias in radiographic material imaging and artefacts in cone-beam CT. The aim of the present study was to evaluate the performance gain in material imaging when a Partial Attenuation Spectral Scatter Separation Approach (PASSSA) is used. This evaluation was based on numerical simulations using Sindbad-SFFD. The comparison of water and bone thickness images acquired from scatter free, scatter corrupted and PASSSA-corrected images showed that the application of the considered correction method improved thickness estimation accuracy. The average relative thickness estimation error per pixel was reduced by around a factor of 4.7 for both water and bone images when comparing scatter corrupted and PASSSA-corrected cases.

Using an energy-resolving photon counting detector, the amount of k-edge material in the x-ray path can be estimated using a process known as material decomposition. However, non-ideal effects within the detector make it difficult to accurately perform this decomposition. This work evaluated the k-edge material decomposition accuracy of two empirical estimators. A neural network estimator and a linearized maximum likelihood estimator with error look-up tables (A-table method) were evaluated through simulations and experiments. Each estimator was trained on system-specific calibration data rather than specific modeling of non-ideal detector effects or the x-ray source spectrum. Projections through a step-wedge calibration phantom consisting of different path lengths through PMMA, aluminum, and a k-edge material was used to train the estimators. The estimators were tested by decomposing data acquired through different path lengths of the basis materials. The estimators had similar performance in the chest phantom simulations with gadolinium. They estimated four of the five densities of gadolinium with less than 2mg/mL bias. The neural networks estimates demonstrated lower bias but higher variance than the A-table estimates in the iodine contrast agent simulations. The neural networks had an experimental variance lower than the CRLB indicating it is a biased estimator. In the experimental study, the k-edge material contribution was estimated with less than 14% bias for the neural network estimator and less than 41% bias for the A-table method.

Niedrigdimensionale Nanostrukturen gelten als aussichtsreiche Kandidaten f��r die Realisierung von ultrakleinen Photodetektoren f��r zuk��nftige optische on-Chip Verbindungsleitungen. Aufgrund der CMOS-Kompatibilit��t und der herausragenden elektrischen und optischen Eigenschaften k��nnte insbesondere Germanium ein vielversprechendes Material f��r diese Strukturen sein. Die Verwendung von Ge Nanodr��hten f��r hochsensitive Photoleiter ist bisher jedoch weitgehend unerforscht. Diese Arbeit widmet sich der systematischen Untersuchung der elektrooptischen Eigenschaften von Ge Nanodr��hten. Dazu wurden monolithische Al-Ge-Al Heterostrukturen mit abrupten Grenzfl��chen und high-k Passivierung hergestellt. Der verwendete Fertigungsprozess erlaubte dabei die Erzeugung von ultrakurzen Ge-Segmenten ohne Limitierung durch die Aufl��sung eines Lithografiesystems. Nach der Integration der Nanodr��hte in Back-Gate gesteuerte Feldeffekttransistoren konnte ein p-Typ Verhalten festgestellt werden, das auf Oberfl��chendefekte zur��ckzuf��hren ist. Bei Anlegen eines externen elektrischen Feldes konnten zeitabh��ngige ��nderungen der Leitf��higkeit von ��ber 3 Gr����enordnungen beobachtet werden. Um dieses Ph��nomen zu erkl��ren wurde ein Modell entwickelt, in dem die langsame Umverteilung von Ladungen an der Oberfl��che, externen elektrischen Feldern entgegenwirkt. Das Zusammenspiel von elektrostatischem Gating und Trap-Besetzung kann einen Transportzustand bewirken, in dem Elektronenleitung f��r einige Minuten dominierend ist, was durch die Beobachtung eines negativen differentiellen Widerstandes belegt werden konnte. Tieftemperaturmessungen best��tigten die vorhergesagten kinetischen Barrieren und zahlreiche optische Untersuchungen zeigten ein dynamisches Verhalten wie es von Oberfl��chenst��rstellen in GeOx zu erwarten ist. Optische Messungen wurden an einem speziell entwickeltem Aufbau mit spektral durchstimmbaren Laser und Lock-In Verst��rker durchgef��hrt. Dabei konnte eine in Ge Nanodr��hten bisher unerreichte optische Verst��rkungen von ��ber 10 7 gezeigt werden. Dies wurde, in ��bereinstimmung mit Literaturberichten, auf das effektive Trapping von lichtgenerierten Ladungstr��gern an der Oberfl��che zur��ckgef��hrt. Es konnte au��erdem nachgewiesen werden, dass diese hohe Sensitivit��t f��r das gesamte sichtbare Spektrum und f��r Modulationsfrequenzen bis zu 10 kHz aufrecht erhalten bleibt. Durch systematische Reduzierung der Kanall��ngen konnten Photodetektoren mit Strukturgr����en unterhalb der Beugungsgrenze des einfallenden Lichtes hergestellt werden., Low dimensional nanostructures such as semiconductor nanowires (NW) have recently attracted increasing attention for their potential use as photodetectors in future optical on-chip interconnectors. In particular, germanium (Ge) may be a promising material, due to its CMOS compatibility and exceptional electrical and optical properties. However, the application of Ge NWs as highly sensitive photoconductive elements has been largely overlooked up till now. This work is dedicated to the systematic study of the electro-optical properties of vapor-liquid-solid (VLS) grown Ge NWs. Therefore, monolithic Al-Ge-Al NW heterostructures featuring abrupt interfaces and reliable high-k passivation were established during the course of this thesis. The employed fabrication techniques thereby allowed for the formation of ultrasmall Ge segments without being limited by the alignment of a lithography tool. For such NW systems integrated in back gated field effect transistors, transfer characteristics revealed p-type behavior, which is attributed to trapping effects at the surface. Further, by controlling the charge carrier density through electrostatic gating, a time-dependent change in conductivity over more than 3 orders of magnitude could be observed, with relaxation times in the range of several minutes. To explain this phenomenon, a model was developed in which the slow redistribution of surface charges compensates external electrical fields on the longterm. It was shown that the interplay of electrostatic gating and trap population can cause the charge transport to be electron dominated for several minutes, which was substantiated by the observation of negative differential resistance (NDR) in this regime. Further, low temperature measurements confirmed the proposed kinetic trapping barriers and numerous optical experiments demonstrated dynamic behavior as expected from trapping time constants of surface states in GeOx. Optical experiments were carried out by using a specifically designed measurement setup featuring a spectrally tunable laser source and a lock-in amplifier. Investigations revealed photoconductive gains exceeding 10 7, which is, to the best of my knowledge, the highest ever reported in Ge NWs. In agreement with literature, this was attributed to the photo-enhanced trapping of charge carriers at the surface. Moreover, this high sensitivity remains effective for the whole visible spectral range and for modulation frequencies up to 10 kHz. By systematically reducing channel lengths, ultrasmall photodetectors could be established with feature sizes far below the diffraction limit of incident light.

In the following section, the requirements for the creation and the growth of a normal conducting domain due to single-photon-, or more general energy-absorption, that lead to a temporally measurable signal, are explained in more mathematical and physical depth than in the introductory chapter 1.2.

We propose a new time discriminating method based on a single-flux quantum (SFQ) circuit to realize a high time-resolved single-photon detection scheme that uses a superconducting nanowire single-photon detector (SSPD). The timing discriminator consists of an SFQ comparator and an interface circuit for converting the output signals of an SSPD into SFQ pulses. Prior to connecting with the SSPD, we evaluated the timing jitters of the SFQ timing discriminator itself by applying external electrical pulses. The timing jitters of the SFQ timing discriminator were found to be dominated by the timing jitters in the interface circuit. However, it was estimated to be below 10 ps even with an input pulse amplitude of 20 μA, which is close to the typical output amplitude of the SSPD.

Nowadays, CdZnTe (CZT) is one of the key materials for the development of room temperature X-ray and gamma ray detectors and great efforts have been made on both the device and the crystal growth technologies. In this work, we present the results of spectroscopic investigations on new boron oxide encapsulated vertical Bridgman (B-VB) grown CZT detectors, recently developed at IMEM-CNR Parma, Italy. Several detectors, with the same electrode layout (gold electroless contacts) and different thicknesses (1 and 2.5 mm), were realized: the cathode is a planar electrode covering the detector surface (4.1×4.1 mm2), while the anode is a central electrode (2×2 mm2) surrounded by a guard-ring electrode. The detectors are characterized by electron mobility-lifetime product (µeτe) values ranging between 0.6 and 1·10−3 cm2/V and by low leakage currents at room temperature and at high bias voltages (38 nA/cm2 at 10000 V/cm). The spectroscopic response of the detectors to monochromatic X-ray and gamma ray sources (109Cd, 241Am and 57Co), at different temperatures and fluxes (up to 1 Mcps), was measured taking into account the mitigation of the effects of incomplete charge collection, pile-up and high flux radiation induced polarization phenomena. A custom-designed digital readout electronics, developed at DiFC of University of Palermo (Italy), able to perform a fine pulse shape and height analysis even at high fluxes, was used. At low rates (200 cps) and at room temperature (T=25 °C), the detectors exhibit an energy resolution FWHM around 4% at 59.5 keV, for comparison an energy resolution of 3% was measured with Al/CdTe/Pt detectors by using the same electronics (A250F/NF charge sensitive preamplifier, Amptek, USA; nominal ENC of 100 electrons RMS). At high rates (750 kcps), energy resolution values of 7% and 9% were measured, with throughputs of 2% and 60% respectively. No radiation polarization phenomena were observed at room temperature up to 1 Mcps (241Am source, 60 keV), while a detector collapse characterizes the samples at T Comparison with two traveling heater method (THM) grown CZT detectors (REDLEN, Canada), fabricated with the same electrode layout, is also presented. These activities are in the framework of an Italian research project on the development of energy-resolved photon counting (ERPC) systems for high flux energy-resolved X-ray imaging.

Cadmium-zinc-telluride (CZT) arrays with photon-counting and energy-resolving capabilities are widely proposed for next-generation X-ray imaging systems. This work presents the performance of a 2â...mm-thick CZT pixel detector, with pixel pitches of 500 and 250â...μm, dc coupled to a fast and low-noise ASIC (PIXIE ASIC), characterized only by the preamplifier stage. A custom 16-channel digital readout electronics was used, able to digitize and process continuously the signals from each output ASIC channel. The digital system performs on-line fast pulse shape and height analysis, with a low dead-time and reasonable energy resolution at both low and high fluxes. The spectroscopic response of the system to photon energies below (109Cd source) and above (241Am source) the K-shell absorption energy of the CZT material was investigated, with particular attention to the mitigation of charge sharing and pile-up. The detector allows high bias voltage operation (>5000â...Vâ...cm-1) and good energy resolution at moderate cooling (3.5% and 5% FWHM at 59.5â...keV for the 500 and 250â...μm arrays, respectively) by using fast pulse shaping with a low dead-time (300â...ns). Charge-sharing investigations were performed using a fine time coincidence analysis (TCA), with very short coincidence time windows up to 10â...ns. For the 500â...μm pitch array (250â...μm pitch array), sharing percentages of 36% (52%) and 60% (82%) at 22.1 and 59.5â...keV, respectively, were measured. The potential of the pulse shape analysis technique for charge-sharing detection for corner/border pixels and at high rate conditions (250â...kcpsâ...pixel-1), where the TCA fails, is also shown. Measurements demonstrated that significant amounts of charge are lost for interactions occurring in the volume of the inter-pixel gap. This charge loss must be accounted for in the correction of shared events. These activities are within the framework of an international collaboration on the development of energy-resolved photon-counting systems for high-flux energy-resolved X-ray imaging (1-140â...keV).This work presents the performance of a 2â...mm-thick CZT pixel detector, with pixel pitches of 500 and 250â...μm coupled to a custom 16-channel digital readout electronics, performing on-line fast pulse shape and height analysis. Charge-sharing investigations were performed, at both low and high fluxes, using fine time coincidence analysis and pulse shape analysis.

We report measurements of isospin asymmetry $\Delta_{0-}$ and difference of direct $CP$ asymmetries $\Delta A_{CP}$ between charged and neutral $B \to X_s \gamma$ decays. This analysis is based on the data sample containing $772 \times 10^6 B\bar{B}$ pairs that was collected with the Belle detector at the KEKB energy-asymmetric $e^+ e^-$ collider. Using a sum-of-exclusive technique with invariant $X_s$ mass up to 2.8~GeV/$c^2$, we obtain $\Delta_{0-} = \bigl[-0.48 \pm 1.49 {\rm (stat.)} \pm 0.97 {\rm (syst.)} \pm 1.15 {(f_{+-}/f_{00})}\bigr]$\% and $\Delta A_{CP} = \bigl[+3.69 \pm 2.65 {\rm (stat.)} \pm 0.76{\rm (syst.)}\bigr]$\%, where the last uncertainty for $\Delta_{0-}$ is due to the uncertainty on the production ratio of $B^+B^-$ to $B^0\bar{B}^0$ in $\Upsilon(4S)$ decays. The measured value of $\Delta_{0-}$ is consistent with zero, allowing us to constrain the resolved photon contribution in the $B \to X_s \gamma$, and improve the branching fraction prediction. The result for $\Delta A_{CP}$ is consistent with the prediction of the SM. We also measure the direct $CP$ asymmetries for charged and neutral $B \to X_s \gamma$ decays. All the measurements are the most precise to date., Comment: 20 pages, 10 figures, submitted to PRD

Photon counting detectors with energy resolving capabilities are desired for high flux X-ray imaging. In this work, we present the performance of a pixelated Schottky Al/p-CdTe/Pt detector (4×4) coupled to a custom-designed digital readout electronics for high flux measurements. The detector (4×4×2 mm 3 ) has an anode layout based on an array of 16 pixels with a geometric pitch of 1 mm (pixel size of 0.6 mm). The 4-channel readout electronics is able to continuously digitize and process the signals from each pixel, performing multi-parameter analysis (event arrival time, pulse shape, pulse height, pulse time width, etc.) even at high fluxes and at different throughput and energy resolution conditions. The spectroscopic response of the system to monochromatic X-ray sources, at both low and high rates, is presented with particular attention to the mitigation of some typical spectral distortions (pile-up, baseline shifts and charge sharing). At a photon counting rate of 520 kcps/pixel, the system exhibits an energy resolution (FWHM at 59.5 keV) of 4.6%, 7.1% and 9% at throughputs of 0.9%, 16% and 82%, respectively. Measurements of Ag-target X-ray spectra also show the ability of the system to perform accurate estimation of the input counting rate up to 1.1 Mcps/pixel. The aim of this work is to point out, beside the appealing properties of CdTe detectors, the benefits of the digital approach in the development of high-performance energy resolved photon counting (ERPC) systems for high flux X-ray imaging.

Recently, CdZnTe (CZT) detectors have been widely proposed and developed for room-temperature X-ray spectroscopy even at high fluxes, and great efforts have been made on both the device and the crystal growth technologies. In this work, the performance of new travelling-heater-method (THM)-grown CZT detectors, recently developed at IMEM-CNR Parma, Italy, is presented. Thick planar detectors (3 mm thick) with gold electroless contacts were realised, with a planar cathode covering the detector surface (4.1 mm × 4.1 mm) and a central anode (2 mm × 2 mm) surrounded by a guard-ring electrode. The detectors, characterized by low leakage currents at room temperature (4.7 nA cm−2 at 1000 V cm−1), allow good room-temperature operation even at high bias voltages (>7000 V cm−1). At low rates (200 counts s−1), the detectors exhibit an energy resolution around 4% FWHM at 59.5 keV (241Am source) up to 2200 V, by using commercial front-end electronics (A250F/NF charge-sensitive preamplifier, Amptek, USA; nominal equivalent noise charge of 100 electrons RMS). At high rates (1 Mcounts s−1), the detectors, coupled to a custom-designed digital pulse processing electronics developed at DiFC of University of Palermo (Italy), show low spectroscopic degradations: energy resolution values of 8% and 9.7% FWHM at 59.5 keV (241Am source) were measured, with throughputs of 0.4% and 60% at 1 Mcounts s−1, respectively. An energy resolution of 7.7% FWHM at 122.1 keV (57Co source) with a throughput of 50% was obtained at 550 kcounts s−1 (energy resolution of 3.2% at low rate). These activities are in the framework of an Italian research project on the development of energy-resolved photon-counting systems for high-flux energy-resolved X-ray imaging.

Collinear laser spectroscopy is performed on the nickel isotopes Ni58-68,70, using a time-resolved photon counting system. From the measured isotope shifts, nuclear charge radii Rc are extracted and compared to theoretical results. Three ab initio approaches all employ, among others, the chiral interaction NNLOsat, which allows an assessment of their accuracy. We find agreement with experiment in differential radii δ⟨rc2⟩ for all employed ab initio methods and interactions, while the absolute radii are consistent with data only for NNLOsat. Within nuclear density functional theory, the Skyrme functional SV-min matches experiment more closely than the Fayans functional Fy(Δr,HFB). Collinear laser spectroscopy is performed on the nickel isotopes $^{58-68,70}$Ni, using a time-resolved photon counting system. From the measured isotope shifts, nuclear charge radii $R_c$ are extracted and compared to theoretical results. Three ab initio approaches all employ, among others, the chiral interaction NNLO$_{\rm sat}$, which allows an assessment of their accuracy. We find agreement with experiment in differential radii $\delta \left\langle r_\mathrm{c}^2 \right\rangle$ for all employed ab initio methods and interactions, while the absolute radii are consistent with data only for NNLO$_{\rm sat}$. Within nuclear density functional theory, the Skyrme functional SV-min matches experiment more closely than the Fayans functional Fy($\Delta r$,HFB).

The rare decay $$ \overline{B} $$ B ¯ → Xsγ is an important probe of physics beyond the standard model. The largest uncertainty on the total rate and the CP asymmetry arises from resolved photon contributions. These appear first at order 1/mb and are related to operators other than Q7γ in the effective weak Hamiltonian. One of the three leading contributions, $$ {Q}_1^q-{Q}_{7\gamma } $$ Q 1 q − Q 7 γ , is described by a non-local function whose moments are related to HQET parameters. We use recent progress in our knowledge of these parameters to reevaluate the resolved photon contribution to $$ \overline{B} $$ B ¯ → Xsγ total rate and CP asymmetry.

International audience; Spectral computerized tomography (Spectral CT) is an imaging technique which uses the spectral information of the attenuated X-ray beam. Energy-resolved photon-counting detector is a promising technique for improved spectral CT imaging and allows to obtain material selective images. While energy-resolved photon-counting detectors can have good spectral resolution (with many energy bins), the size of these detectors is often limited. For their part Multi-Source Inverse Geometry CT (MS-IGCT) architectures allow the use of a smaller detector than conventional Cone Beam CT architecture (CBCT). In a previous work, we have proposed a one-step reconstruction algorithm validated with spectral data from classical Cone Beam CT architecture. In this work we propose to adapt this one-step method on spectral data from MS-IGCT architecture. From noisy simulated data, we compare the proposed one-step method with two two-step decomposition methods.

Photon number resolving (PNR) is an important capacity for detectors working in quantum and classical applications. Although a conventional superconducting nanowire single-photon detector (SNSPD) is not a PNR detector, by arranging nanowires in a series array and multiplexing photons over space, such series PNR-SNSPD can gain quasi-PNR capacity. However, the accuracy and maximum resolved photon number are both limited by the signal-to-noise (SNR) ratio of the output pulses. Here, we introduce a matched filter, which is an optimal filter in terms of SNR for SNSPD pulses. Experimentally, compared to conventional readout using a room-temperature amplifier, the normalized spacing between pulse amplitudes from adjacent photon number detections increased by a maximum factor of 2.1 after the matched filter. Combining with a cryogenic amplifier to increase SNR further, such spacing increased by a maximum factor of 5.3. In contrast to a low pass filter, the matched filter gave better SNRs while maintaining good timing jitters. Minimum timing jitter of 55 ps was obtained experimentally. Our results suggest that the matched filter is a useful tool for improving the performance of the series PNR-SNSPD and the maximum resolved photon number can be expected to reach 65 or even large.

The rare decay $\bar B\to X_s\gamma$ is an important probe of physics beyond the standard model. The largest uncertainty on the total rate and the CP asymmetry arises from resolved photon contributions. These appear first at order $1/m_b$ and are related to operators other than $Q_{7\gamma}$ in the effective weak Hamiltonian. One of the three leading contributions, $Q^q_1-Q_{7\gamma}$, is described by a non-local function whose moments are related to HQET parameters. We use recent progress in our knowledge of these parameters to reevaluate the resolved photon contribution to $\bar B\to X_s\gamma$ total rate and CP asymmetry., Comment: Text and references added. Journal version

The rare decay $\bar B\to X_s��$ is an important probe of physics beyond the standard model. The largest uncertainty on the total rate and the CP asymmetry arises from resolved photon contributions. These appear first at order $1/m_b$ and are related to operators other than $Q_{7��}$ in the effective weak Hamiltonian. One of the three leading contributions, $Q^q_1-Q_{7��}$, is described by a non-local function whose moments are related to HQET parameters. We use recent progress in our knowledge of these parameters to reevaluate the resolved photon contribution to $\bar B\to X_s��$ total rate and CP asymmetry., Text and references added. Journal version

A gas monitor detector was implemented and characterized at the Soft X-ray Research instrument (SXR) to measure the average, absolute and pulse-resolved photon flux of the LCLS beam in the energy range between 280 and 2000 eV., A gas monitor detector was implemented and characterized at the Soft X-ray Research (SXR) instrument to measure the average, absolute and pulse-resolved photon flux of the LCLS beam in the energy range between 280 and 2000 eV. The detector is placed after the monochromator and addresses the need to provide reliable absolute pulse energy as well as pulse-resolved measurements for the various experiments at this instrument. This detector provides a reliable non-invasive measurement for determining flux levels on the samples in the downstream experimental chamber and for optimizing signal levels of secondary detectors and for the essential need of data normalization. The design, integration into the instrument and operation are described, and examples of its performance are given.

The photon counting detector with energy discrimination capabilities provides the spectral information and energy of each photon with single exposure. The energy-resolved photon counting detector makes it possible to improve the visualization of contrast agent by selecting the appropriate energy window. In this study, we simulated the photon counting spectral mammography system using a Monte Carlo method and compared three contrast enhancement methods (K-edge imaging, projection-based energy weighting imaging, and dual energy subtraction imaging). For the quantitative comparison, we used the homogeneous cylindrical breast phantom as a reference and the heterogeneous XCAT breast phantom. To evaluate the K-edge imaging methods, we obtained images by increasing the energy window width based on K-edge absorption energy of iodine. The iodine which has the K-edge discontinuity in the attenuation coefficient curve can be separated from the background. The projection-based energy weighting factor was defined as the difference in the transmissions between the contrast agent and the background. Each weighting factor as a function of photon energy was calculated and applied to the each energy bin. For the dual energy subtraction imaging, we acquired two images with below and above the iodine K-edge energy using single exposure. To suppress the breast tissue in high energy images, the weighting factor was applied as the ratio of the linear attenuation coefficients of the breast tissue at high and low energies. Our results demonstrated the CNR improvement of the K-edge imaging was the highest among the three methods. These imaging techniques based on the energy-resolved photon counting detector improved image quality with the spectral information.

Neural radiance fields (NeRFs) have become a ubiquitous tool for modeling scene appearance and geometry from multiview imagery. Recent work has also begun to explore how to use additional supervision from lidar or depth sensor measurements in the NeRF framework. However, previous lidar-supervised NeRFs focus on rendering conventional camera imagery and use lidar-derived point cloud data as auxiliary supervision; thus, they fail to incorporate the underlying image formation model of the lidar. Here, we propose a novel method for rendering transient NeRFs that take as input the raw, time-resolved photon count histograms measured by a single-photon lidar system, and we seek to render such histograms from novel views. Different from conventional NeRFs, the approach relies on a time-resolved version of the volume rendering equation to render the lidar measurements and capture transient light transport phenomena at picosecond timescales. We evaluate our method on a first-of-its-kind dataset of simulated and captured transient multiview scans from a prototype single-photon lidar. Overall, our work brings NeRFs to a new dimension of imaging at transient timescales, newly enabling rendering of transient imagery from novel views. Additionally, we show that our approach recovers improved geometry and conventional appearance compared to point cloud-based supervision when training on few input viewpoints. Transient NeRFs may be especially useful for applications which seek to simulate raw lidar measurements for downstream tasks in autonomous driving, robotics, and remote sensing.

A future Electron-Ion Collider (EIC) will deliver luminosities of $10^{33} - 10^{34}$ cm$^{-2}$s$^{-1}$ for collisions of polarized electrons and protons and heavy ions over a wide range of center-of-mass energies (40 $\mathrm{GeV}$ to 145 $\mathrm{GeV}$). One of its promising physics programs is to study the partonic structure of quasi-real photons. Measuring di-jet in photoproduction events, one can effectively access the underlying parton dynamics of the photons through the selection of the resolved photon processes. In this paper, we discuss the feasibility of tagging resolved photon processes and measuring the di-jet cross section as a function of jet transverse momentum in ranges of $x_{\gamma}^{rec}$ at an EIC. These studies show that parton distributions in the photon can be extracted at an EIC.