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Two Photon Absorption In Quantum Dotsquantum Dashes And Related Materials
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Book Synopsis Two-photon Absorption In Quantum Dots,quantum Dashes And Related Materials by :
Download or read book Two-photon Absorption In Quantum Dots,quantum Dashes And Related Materials written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We have proposed the use of USQDs for various deep-tissue biological imaging applications, notably wavelength-multiplexed multicolor imaging and intra-nuclear studies such as those involving cell apoptosis, and have studied the issue of maximizing two-photon absorption-induced fluorescence (TPAF) signals from CdSe/ZnS USQDs to be used for this application. In particular, using 2 nm USQDs, we have shown that the TPAF signal at 780 nm is ̃8 times that at 850 nm and 68 times that at 900 nm, two wavelengths that have been used in previous studies using CdSe/ZnS SQDs for deep-tissue imaging of biological studies via TPAF .
Book Synopsis Two-photon Absorption in Quantum Wells and Quantum Dots by : Weiliang Chen (M.S.)
Download or read book Two-photon Absorption in Quantum Wells and Quantum Dots written by Weiliang Chen (M.S.) and published by . This book was released on 2006 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Self-Assembled Quantum Dots by : Zhiming M Wang
Download or read book Self-Assembled Quantum Dots written by Zhiming M Wang and published by Springer Science & Business Media. This book was released on 2007-11-29 with total page 470 pages. Available in PDF, EPUB and Kindle. Book excerpt: This multidisciplinary book provides up-to-date coverage of carrier and spin dynamics and energy transfer and structural interaction among nanostructures. Coverage also includes current device applications such as quantum dot lasers and detectors, as well as future applications to quantum information processing. The book will serve as a reference for anyone working with or planning to work with quantum dots.
Book Synopsis Semiconductor Quantum Dots by : Ladislaus B nyai
Download or read book Semiconductor Quantum Dots written by Ladislaus B nyai and published by World Scientific. This book was released on 1993 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiconductor Quantum Dots presents an overview of the background and recent developments in the rapidly growing field of ultrasmall semiconductor microcrystallites, in which the carrier confinement is sufficiently strong to allow only quantized states of the electrons and holes. The main emphasis of this book is the theoretical analysis of the confinement induced modifications of the optical and electronic properties of quantum dots in comparison with extended materials. The book develops the theoretical background material for the analysis of carrier quantum-confinement effects, introduces the different confinement regimes for relative or center-of-mass motion quantization of the electron-hole-pairs, and gives an overview of the best approximation schemes for each regime. A detailed discussion of the carrier states in quantum dots is presented and surface polarization instabilities are analyzed, leading to the self-trapping of carriers near the surface of the dots. The influence of spin-orbit coupling on the quantum-confined carrier states is discussed. The linear and nonlinear optical properties of small and large quantum dots are studied in detail and the influence of the quantum-dot size distribution in many realistic samples is outlined. Phonons in quantum dots as well as the influence of external electric or magnetic fields are also discussed. Last but not least the recent developments dealing with regular systems of quantum dots are also reviewed. All things included, this is an important piece of work on semiconductor quantum dots not to be dismissed by serious researchers and physicists.
Book Synopsis Near Bandgap Two-photon Excited Luminescence of InAs Quantum Dots by : Xian Hu
Download or read book Near Bandgap Two-photon Excited Luminescence of InAs Quantum Dots written by Xian Hu and published by . This book was released on 2018 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiconductor quantum dots (QDs) confine carriers in three dimensions, resulting in atomic-like energy levels as well as size-dependent electrical and optical properties. Self-assembled III-V QD is one of the most studied semiconductor QDs thanks to their well-established fabrication techniques and versatile optical properties. This dissertation presents the photoluminescence (PL) study of the InAs/GaAs QDs with both above bandgap continuous-wave excitation (one-photon excitation) and below-bandgap pulse excitation (two-photon excitation). Samples of ensemble QDs, single QD (SQD), and QDs in a micro-cavity, all grown by molecular beam epitaxy, are used in this study. Morphology of these samples was examined using atomic force microscope and transmission electron microscope. Two-photon excitation uses energy near half of the QDs ground state transition, all the way up to half of the GaAs matrix bandgap. Power dependent QDs PL with both one-photon and two-photon excitation can be described by power laws, with power index of 1 for one-photon excitation and two for two-photon excitation. Photoluminescence excitation spectroscopy then provides evidence of direct two-photon absorption into the QDs when the two-photon excitation energy is resonant with the QDs state. For SQD without cavity, we observed PL of a SQD with excitation near its half bandgap. The QDs in a micro-cavity sample consists one layer of InAs QDs in a GaAs spacer sandwiched between two distributed Bragg reflectors made of alternating layers of GaAs and AlAs. We successfully observed PL from SQD emitted from the cavity mode with excitation slightly above half of the QD's transition. These observations help us to understand the nonlinear optical property of InAs QDs and can be potentially used in all-optical computation or reflective optical limiters.
Book Synopsis Colloidal Quantum Dot Optoelectronics and Photovoltaics by : Gerasimos Konstantatos
Download or read book Colloidal Quantum Dot Optoelectronics and Photovoltaics written by Gerasimos Konstantatos and published by Cambridge University Press. This book was released on 2013-11-07 with total page 329 pages. Available in PDF, EPUB and Kindle. Book excerpt: Captures the most up-to-date research in the field, written in an accessible style by the world's leading experts.
Book Synopsis Correlation Between Diameter and Two Photon Absorption Cross Section of II-VI Semiconductor Quantum Dots by : 楊孟儒
Download or read book Correlation Between Diameter and Two Photon Absorption Cross Section of II-VI Semiconductor Quantum Dots written by 楊孟儒 and published by . This book was released on 2008 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Semiconductor Quantum Dots by : Y. Masumoto
Download or read book Semiconductor Quantum Dots written by Y. Masumoto and published by Springer Science & Business Media. This book was released on 2013-04-17 with total page 500 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiconductor quantum dots represent one of the fields of solid state physics that have experienced the greatest progress in the last decade. Recent years have witnessed the discovery of many striking new aspects of the optical response and electronic transport phenomena. This book surveys this progress in the physics, optical spectroscopy and application-oriented research of semiconductor quantum dots. It focuses especially on excitons, multi-excitons, their dynamical relaxation behaviour and their interactions with the surroundings of a semiconductor quantum dot. Recent developments in fabrication techniques are reviewed and potential applications discussed. This book will serve not only as an introductory textbook for graduate students but also as a concise guide for active researchers.
Book Synopsis Towards On-demand Generation of Entangled Photons with Quantum Dots by : Arash Ahmadi
Download or read book Towards On-demand Generation of Entangled Photons with Quantum Dots written by Arash Ahmadi and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The biexciton-exciton cascade in quantum dots (QDs) yields entangled photon pairs, and recent developments in engineering photonic structures around the dot for efficient light extraction and proper control of the fine-structure splitting, has led to significant breakthroughs in achieving an ideal entangled photon source -- exhibiting properties such as high extraction efficiency, low multi-photon emission and high entanglement fidelity. This thesis presents our development in enhancing the performance of entangled photon generation of QDs towards near-unity efficiency and fidelity. We study InAsP quantum dots in photonic nanowires for efficient light extraction and to reveal the effect of a quantum dot with high nuclear spin on the entanglement fidelity. Revealing the ultimate limit of entanglement in QDs is still a challenge, and it is generally believed that a sample made of atoms possessing high nuclear spins exhibits limited entanglement due to the dephasing caused by spin-spin interactions. Moreover, it is assumed that the fine-structure splitting of QDs degrades the entanglement fidelity, as it introduces a which-path information in the biexciton-exciton cascade. We have performed two-photon state tomography on InAsP QDs in InP nanowires, comprising of nuclear spin 9/2, and have realized that such a source is capable of generating entangled photon pairs with negligible dephasing during the emission lifetime, with a peak concurrence C = 77% and a count-weighted average concurrence 62%. This result was obtained by comparing the outcome of our measurements with a theoretical model that assumes no dephasing, however, takes into account the details of the detection system, i.e., dark-count rates and timing resolution, as well as, specific features of the QD, e.g., emission lifetime, fine-structure splitting, multi-photon emission probability, etc. Proper engineering of tapered nanowires allows for extraction of the emitted photons with high efficiency, which makes it possible to perform a complete two-photon state tomography and monitoring the evolution of the exciton state, as well as, the entanglement fidelity of the photon-pair, during the emission lifetime. This enabled us to reveal the effect of an imperfect detection system, as well as, multi-photon emission in recording low values for entanglement fidelity. Moreover, our calculations show that proper analysis of the time-energy uncertainty relation provides the necessary means to measure a high entanglement fidelity even in the presence of fine-structure splitting; since, a detection system with high timing resolution can overlook the which-path information, as the uncertainty in measuring the energy of the photons will be larger than the fine-structure splitting. Therefore, realizing near-unity entanglement fidelity using QDs is merely a technical challenge, i.e., resonant excitation of the QD, in order to suppress multi-photon emission, and use of a detection system with low timing jitter and dark-count rates. As a next step to achieve this goal, we have performed the resonant two-photon excitation scheme for the first time on a QD in a photonic nanowire, which resulted in an enhancement of the performance of our source. We managed to improve the single-photon purity of the source, g^(2)(0), by two orders of magnitude; moreover, analysis of the emission spectrum reveals that this scheme increases the pair-production efficiency to values above 93% for the biexciton-exciton cascade. Taking the efficiency of our experimental setup into consideration, the results indicate an approximately eight-fold enhancement of the pair-extraction efficiency as compared to the quasi-resonant excitation scheme (12.55% vs. 1.6%). Based on these results, two-photon state tomography on our source, under resonant two-photon excitation and performed by a detection system with high timing resolution and low dark-count rates, yields near-unity entanglement fidelity. By considering the enhancement in pair-extraction efficiency that we obtained, QDs in photonic nanowires can surpass the performance of spontaneous parametric down conversion sources in terms of entanglement fidelity and pair-extraction efficiency. Even though we have shown a finite fine-structure splitting does not degrade the entanglement fidelity in QDs, for various application in quantum information removing the fine-structure splitting is beneficial. Therefore, we have proposed a universal all-optical approach for removing the fine-structure splitting. In this scheme, the energy of the photons are shifted by using a pair of quarter-wave plates and fast-rotating half-wave plates after they have been emitted; and as a result, the energy difference between the two decay paths in the biexciton-exciton cascade is erased. This method is applicable to any QD source and can be easily implemented using the currently available technology; moreover, no further sample processing will be required in order to achieve zero fine-structure splitting.
Book Synopsis Electronic Structure and Photon Absorption in Semiconductor Quantum Dots by : Gregory von Winckel
Download or read book Electronic Structure and Photon Absorption in Semiconductor Quantum Dots written by Gregory von Winckel and published by . This book was released on 2006 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Quantum Dots for Quantum Information Technologies by : Peter Michler
Download or read book Quantum Dots for Quantum Information Technologies written by Peter Michler and published by Springer. This book was released on 2017-06-01 with total page 457 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book highlights the most recent developments in quantum dot spin physics and the generation of deterministic superior non-classical light states with quantum dots. In particular, it addresses single quantum dot spin manipulation, spin-photon entanglement and the generation of single-photon and entangled photon pair states with nearly ideal properties. The role of semiconductor microcavities, nanophotonic interfaces as well as quantum photonic integrated circuits is emphasized. The latest theoretical and experimental studies of phonon-dressed light matter interaction, single-dot lasing and resonance fluorescence in QD cavity systems are also provided. The book is written by the leading experts in the field.
Book Synopsis Optics of Quantum Dots and Wires by : Garnett W. Bryant
Download or read book Optics of Quantum Dots and Wires written by Garnett W. Bryant and published by Artech House Publishers. This book was released on 2005 with total page 574 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum technology is the key to next-generation optoelectronics and laser semiconductors, and this new cutting-edge book is an in-depth examination of how quantum dots and wires are fabricated and applied to optics. You find a solid tutorial on the optical properties of nanoscale dots and wires that explains the current state of this technology and why it is so promising. The book presents a detailed survey of techniques based on molecular beam epitaxial growth for fabricating semiconductor quantum dots and wires. You learn how to assess these growth strategies for insertion of dots and wires into devices.
Book Synopsis Experimental and Theoretical Study of the Optical Properties of Semiconductor Quantum Dots by : Gero Nootz
Download or read book Experimental and Theoretical Study of the Optical Properties of Semiconductor Quantum Dots written by Gero Nootz and published by . This book was released on 2010 with total page 113 pages. Available in PDF, EPUB and Kindle. Book excerpt: The aim of this dissertation is to gain a better understanding of the unique electronic structure of lead salt quantum dots (QDs) and its influences on the nonlinear optical (NLO) properties as well as the time dynamics of the photogenerated charge carriers. A variety of optical techniques such as Z-scan, two-photon excited fluorescence and time-resolved pump probe spectroscopy are used to measure these properties. The one-photon as well as the degenerate and nondegenerate two-photon absorption (2PA) spectra are measured and the electronic wave functions from a four-band envelope function formalism are used to model the results. We observe local maxima in the 2PA spectra for QD samples of many different sizes at energies where only 1PA is predicted by the model. This is similar to the previously measured transitions in the 1PA spectra which are not predicted by the model but accrue at the energies of the two-photon allowed transitions. Most importantly we observe 2PA peaks for all samples at the energy of the first one-photon allowed transition. This result can only be understood in terms of symmetry breaking and therefore is strong evidence that other transitions, not predicted by the model if the selection rules are left intact, also have the origin in the lifted spatial symmetry of the wave functions. On the other hand, the uniquely symmetric eigenenergies of these quantum-confined energy states in the conduction and valance bands explain the observed trend toward larger two-photon cross-sections as the quantum confinement is increased in smaller QDs. Moreover, this unique feature is shown to reduce the possible relaxation channels for photoexcited carriers, which is confirmed experimentally by the reduced carrier relaxation rate as compared to CdSe QDs which lack this symmetry. Carrier multiplication (CM), a process in which several electrons are excited by the absorption of a single photon is studied in PbS QDs. We show that for PbS QDs with radius smaller than 2.5 nm the parameters of CM get very close to the theoretical optimum. Next-generation solar cells operating under these ideal conditions could potentially have conversion efficiency of up to 42%. This compares favorably to the 30% efficiency limit of a single junction silicon solar cell.
Download or read book Quantum Dots written by Peter A. Ling and published by Nova Publishers. This book was released on 2005 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since first developed in the early sixties, silicon chip technology has made vast leaps forward. From a rudimentary circuit with a mere handful of transistors, the chip has evolved into a technological wonder, packing millions of bits of information on a surface no larger that a human thumbnail. And most experts predict that in the near future, we will see chips with over a billion bits. Quantum dots are small devices that contain a tiny droplet of free electrons. They are fabricated in semiconductor materials and have typical dimensions ranging from nanometres to a few microns. The size and shape of these structures and therefore the number of electrons they contain can be precisely controlled; a quantum dot can have anything from a single electron to a collection of several thousands. The physics of quantum dots shows many parallels with the behaviour of naturally occurring quantum systems in atomic and nuclear physics. As in an atom, the energy levels in a quantum dot become quantised due to the confinement of electrons. Unlike atoms however, quantum dots can be easily connected to electrodes and are therefore excellent tools for studying atomic-like properties. This new book brings together leading research from throughout the world in this field of the future which has become the field of today.
Book Synopsis Spins in Optically Active Quantum Dots by : Oliver Gywat
Download or read book Spins in Optically Active Quantum Dots written by Oliver Gywat and published by John Wiley & Sons. This book was released on 2010-02-01 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: Filling a gap in the literature, this up-to-date introduction to the field provides an overview of current experimental techniques, basic theoretical concepts, and sample fabrication methods. Following an introduction, this monograph deals with optically active quantum dots and their integration into electro-optical devices, before looking at the theory of quantum confined states and quantum dots interacting with the radiation field. Final chapters cover spin-spin interaction in quantum dots as well as spin and charge states, showing how to use single spins for break-through quantum computation. A conclusion and outlook round off the volume. The result is a primer providing the essential basic knowledge necessary for young researchers entering the field, as well as semiconductor and theoretical physicists, PhD students in physics and material sciences, electrical engineers and materials scientists.
Book Synopsis Quantum Dot Photodetectors by : Xin Tong
Download or read book Quantum Dot Photodetectors written by Xin Tong and published by Springer Nature. This book was released on 2021-09-17 with total page 319 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a comprehensive overview of state-of-the-art quantum dot photodetectors, including device fabrication technologies, optical engineering/manipulation strategies, and emerging photodetectors with building blocks of novel quantum dots (e.g. perovskite) as well as their hybrid structured (e.g. 0D/2D) materials. Semiconductor quantum dots have attracted much attention due to their unique quantum confinement effect, which allows for the facile tuning of optical properties that are promising for next-generation optoelectronic applications. Among these remarkable properties are large absorption coefficient, high photosensitivity, and tunable optical spectrum from ultraviolet/visible to infrared region, all of which are very attractive and favorable for photodetection applications. The book covers both fundamental and frontier research in order to stimulate readers' interests in developing novel ideas for semiconductor photodetectors at the center of future developments in materials science, nanofabrication technology and device commercialization. The book provides a knowledge sharing platform and can be used as a reference for researchers working in the fields of photonics, materials science, and nanodevices.
Download or read book Quantum Dots written by N. Thejo Kalyani and published by Woodhead Publishing. This book was released on 2023-01-18 with total page 612 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum dots: Emerging materials for versatile applications is an introduction to the fundamentals and important advances of research of this important category of semiconductor nanostructured materials. After a brief review of relevant nanotechnology concepts and the unique properties of nanomaterials, the book describes the fundamentals of quantum dots with definitions of the primary classifications of quantum dots. There is an emphasis on practical considerations of the commercial translation of quantum dots such as their toxicity, stability, and disposal. Moreover, the book focuses on a review of the advances in research in emerging quantum dot materials along with the latest innovations in materials design and fabrication methods. Quantum Dots is suitable for materials scientists and engineers in academia or industry R&D who are looking for an introduction to this research topic or a key reference on the latest advances and applications. - Introduces the primary classifications, properties, synthesis, characterization and fabrication strategies of quantum dots - Reviews the latest applications of quantum dots for LEDs, displays, energy storage devices, photovoltaic cells, medicine, and more - Discusses the practical barriers to commercial translation of quantum dots, including toxicity, stability, and their safe disposal
