Search query: carrier dynamics pulse

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abstract: We present an analysis of carrier dynamics of the single photon detection process, i.e. from Geiger mode pulse generation to its quenching, in a single photon avalanche diode (SPAD) The device is modeled by a parallel circuit of a SPAD and a capacitance representing both space charge accumulation inside the SPAD and parasitic components. The carrier dynamics inside the SPAD is described by time dependent bipolar coupled continuity equations (BCE) Numerical solutions of BCE show that the entire process completes within a few hundreds of picoseconds. More importantly, we find that the total amount of charges stored on the series capacitance gives rise to a voltage swing of the internal bias of SPAD twice of the excess bias voltage with respect to the breakdown voltage. This, in turn, gives a design methodology to control precisely generated charges and enables one to use SPADs as conventional photodiodes (PDs) in a four transistor pixel of a complementary metal oxide semiconductor (CMOS) image sensor (CIS) with short exposure time and without carrier overflow. Such operation is demonstrated by experiments with a 6 um size 400 x 400 pixels SPAD based CIS designed with this methodology.
author_names: Akito Inoue

Toru Okino

Shinzo Koyama

Yutaka Hirose
title: Modeling and Analysis of Capacitive Relaxation Quenching in a Single Photon Avalanche Diode (SPAD) Applied to a CMOS Image Sensor
venue: Sensors
year: 2020

abstract: Exploring the nonlinear photonics of emerging promising two dimensional (2D) materials like MXenes will boost the development of broad band optoelectronic and photonic applications. In this paper, the broad band nonlinear optical response and the excited carrier dynamics of an emerging MXenes, Nb2C, are systematically investigated for the wavelength range of visible to near infrared band. The obtained nonlinear optical response shows a wavelength and excitation intensity dependence. The imaginary part of the third order nonlinear optical susceptibility Imkh(3) and figure of merit (FOM) were found to be 1.4x10 10 esu and 7.5x10 12 esu cm, respectively. The interesting nonlinear absorption response inversion properties (e.g. a shift from saturable absorption to two photon absorption) of Nb2C nanosheets in the near infrared promise possible important applications in nonlinear photonics, such as optical switch. We also demonstrate that the wavelength dependent relaxation times consist of two different relaxation components, i.e. time constants, where one is hundreds of femtoseconds and the other several picoseconds. Our results indicate promising potential in near infrared nanophotonic applications of 2D Nb2C and offer a promising candidate for 2D material based nanophotonic devices and beyond.
author_names: Yiduo Wang

Yingwei Wang

Kun Qi

Tianyu Xue
title: Niobium Carbide Mxenes with Broadband Nonlinear Optic Response and Ultrafast Carrier Dynamics.
venue: ACS nano
year: 2020

abstract: Time and angle resolved photoemission spectroscopy (tr ARPES) constitutes a powerful tool to inspect the dynamics and thermalization of hot carriers. The identification of the processes that drive the dynamics, however, is challenging even for the simplest systems owing to the coexistence of several relaxation mechanisms. Here, we devise a Green's function formalism for predicting the tr ARPES spectral function and establish the origin of carrier thermalization entirely from first principles. The predictive power of this approach is demonstrated by an excellent agreement with experiments for graphene over time scales ranging from a few tens of femtoseconds up to several picoseconds. Our work provides compelling evidence of a non equilibrium dynamics dominated by the establishment of a hot phonon regime.
author_names: Fabio Caruso

Dino Novko

Claudia Draxl
title: Photoemission signatures of nonequilibrium carrier dynamics from first principles
year: 2020

abstract: Abstract Pump fluence and probe wavelength dependent ultrafast carrier dynamics and optical nonlinear absorption in black phosphorus nanosheets are investigated by transient absorption spectroscopy and open aperture Z scan techniques. The decay time becomes longer with larger wavelengths under pump wavelengths of both 400 nm and 800 nm excitation. For 800 nm excitation, pump fluence dependent lifetime shows complex behaviors, which might be due to the competition between the linear absorption and two photon absorption. For 400 nm excitation, an additional decaying channel is observed at a larger pump fluence, which is explained by an effective subband structure. In open aperture Z scan measurements, strong saturation absorption is observed in the visible region over a broad band from 450 nm to 700 nm. The saturation intensity shows an increasing trend with increase in the wavelength. Also, the saturation intensities under different pulse widths and solvents are discussed in detail. Our results show that black phosphorus nanosheets have great potential in future ultrathin optoelectronic devices.
author_names: Wenzhi Wu

Yongjian Zhou

Jianglong Wang

Yabin Shao

Degui Kong

Yachen Gao

Yaguo Wang
title: The pump fluence and wavelength dependent ultrafast carrier dynamics and optical nonlinear absorption in black phosphorus nanosheets
year: 2020

abstract: This chapter presents a review of the current results on the carrier dynamics in activated and self activated scintillators, which are obtained by using time resolved photoluminescence spectroscopy and differential optical absorption techniques with time resolution in picosecond and subpicosecond domains. The optical techniques ensuring a high time resolution are introduced. The formation of the luminescence response to a short pulse excitation is in a special focus. The importance of carrier trapping, peculiarities of the trapping in mixed garnet and orthosilicate type scintillators, and the influence of codoping on excitation transfer are discussed in more detail.
author_names: Mikhail Korzhik

Gintautas Tamulaitis

Andrey N Vasil'ev
title: Free Carrier Dynamics in Scintillation Materials
year: 2020

abstract: We present experimental results on measurement of free carrier dynamics in p type silicon crystal in high electric fields of THz pulses in the MV/cm range. Carrier recombination dynamics in p type silicon is analyzed through time resolved pump probe experiments in which THz pulse is used as a pump, and a femtosecond optical pulse is used as a probe.
author_names: O V Chefonov

Andrey V Ovchinnikov

Mikhail B Agranat
title: Free carrier dynamics in p doped silicon induced by an intense terahertz field
venue: Other Conferences
year: 2020

abstract: The influence of doping on the ultrafast carrier dynamics in InSb has been studied by time resolved terahertz spectroscopy with photogenerated carrier densities from 1.5x1018 to 9.5x1019cm 3 at 800 nm. The photoinduced absorption and carrier recovery process show doping type dependence. The carrier recovery time of intrinsic InSb is greater than that of p doped InSb but less than that of n doped InSb at low carrier densities. At high carrier densities, compared with intrinsic InSb, the doped InSb is more prone to transient Auger recombination, which indicates that the appearance of the fast decay process depends on the carrier densities. The photoinduced absorption of terahertz probe pulse of n doped InSb is significantly less than that of p doped and intrinsic InSb; however, that of p doped InSb is close to that of intrinsic InSb, which demonstrates that the high concentration of electrons can accelerate the efficiency of transient Auger recombination. Our analysis provides assistance to the design, manufacture, and improvement of photovoltaic detectors.
author_names: Gaofang Li

Xiaobo Nie

Wei Zhou

Wenjie Zhang

Hao Yang Cui

Nenghong Xia

Zhiming Huang

Jun-hao Chu

Guohong Ma
title: Influence of doping for InSb on ultrafast carrier dynamics measured by time resolved terahertz spectroscopy.
venue: Applied optics
year: 2020

abstract: A theoretical study on the coupled electron nuclear dynamics of HD+ molecular ions under ultrashort, intense laser pulses is performed by employing a well established quasi classical model. The influence of the laser carrier envelope phase on various channel (H D+ D H+ and H+ D+ probabilities is investigated at different laser field intensities. The carrier envelope phase is found to govern the dissociation (H D+ and D H+ and Coulomb explosion (H+ D+ channel probabilities. The kinetic energy release distributions of the fragments are also found to be sensitive to the carrier envelope phase of the laser pulse. Our results are in agreement with the previously reported quantum dynamics studies and experiments.
author_names: Gaurav Pandey

Diptesh Dey

Ashwani Kumar Tiwari
title: Controlling the Ultrafast Dynamics of HD+ by the Carrier Envelope Phases of an Ultrashort Laser Pulse: A Quasi Classical Dynamics Study.
venue: The journal of physical chemistry. A
year: 2020

abstract: The electronic response of surface deposited nanoparticles to a few cycle near infrared pump pulse is traced by attosecond XUV transient absorption spectroscopy.
author_names: Florian Lackner

Julia Anthea Gessner

Florian Siegrist

Alexander Schiffmann

Roman Messner

Maximilian Lasserus

Martin Schnedlitz

Benjamin W Toulson

Daniel Knez

Ferdinand Hofer

Oliver Gessner

Wolfgang E Ernst

Martin Schultze
title: Attosecond Spectroscopy of Ultrafast Carrier Dynamics in Nanoparticles
year: 2020

abstract: A type II InAs/AlAs\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin} 69pt} \begin{document}$_{0.16}\end{document}0.16Sb\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin} 69pt} \begin{document}$_{0.84}\end{document}0.84 multiple quantum well sample is investigated for the photoexcited carrier dynamics as a function of excitation photon energy and lattice temperature. Time resolved measurements are performed using a near infrared pump pulse, with photon energies near to and above the band gap, probed with a terahertz probe pulse. The transient terahertz absorption is characterized by a multi rise, multi decay function that captures long lived decay times and a metastable state for an excess photon energy of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin} 69pt} \begin{document}>100$\end{document}>100 meV. For sufficient excess photon energy, excitation of the metastable state is followed by a transition to the long lived states. Excitation dependence of the long lived states map onto a nearly direct band gap \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin} 69pt} \begin{document}$E{_g}\end{document}Eg) density of states with an Urbach tail below \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin} 69pt} \begin{document}$E{_g}\end{document}Eg. As temperature increases, the long lived decay times increase \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin} 69pt} \begin{document}<E{_g}\end{document}<Eg, due to the increased phonon interaction of the unintentional defect states, and by phonon stabilization of the hot carriers \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin} 69pt} \begin{document}>E{_g}\end{document}>Eg. Additionally, Auger (and/or trap assisted Auger) scattering above the onset of the plateau may also contribute to longer hot carrier lifetimes. Meanwhile, the initial decay component shows strong dependence on excitation energy and temperature, reflecting the complicated initial transfer of energy between valence band and defect states, indicating methods to further prolong hot carriers for technological applications.
author_names: Herath P Piyathilaka

Rishmali Sooriyagoda

Hamidreza Esmaielpour

Vincent R Whiteside

Tetsuya D Mishima

Michael B Santos

Ian R Sellers

A D Bristow
title: Hot carrier dynamics in InAs/AlAsSb multiple quantum wells
venue: Scientific reports
year: 2021