Search query: Optical Gain and Stimulated Emission in Nanocrystal Quantum Dots

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abstract: The development of optical gain in chemically synthesized semiconductor nanoparticles (nanocrystal quantum dots) has been intensely studied as the first step toward nanocrystal quantum dot lasers. We examined the competing dynamical processes involved in optical amplification and lasing in nanocrystal quantum dots and found that, despite a highly efficient intrinsic nonradiative Auger recombination, large optical gain can be developed at the wavelength of the emitting transition for close packed solids of these dots. Narrowband stimulated emission with a pronounced gain threshold at wavelengths tunable with the size of the nanocrystal was observed, as expected from quantum confinement effects. These results unambiguously demonstrate the feasibility of nanocrystal quantum dot lasers.
author_names: Victor I Klimov

Alexander Mikhailovsky

S J Xu

Anton V Malko

Jennifer Ann Hollingsworth

Catherine A Leatherdale

Hans-Jurgen Eisler

Moungi G Bawendi
title: Optical gain and stimulated emission in nanocrystal quantum dots.
venue: Science
year: 2000

abstract: Semiconductor quantum dots are of interest as optical gain media for lasing applications. Here we report on efficient, broad bandwidth optical gain in the CdSe/ZnS/CdSe quantum dot/barrier/quantum shell nanocrystal. These nanocrystals are known to support spontaneous emission from both CdSe phases, offering promise for lasing applications via wave function engineering. The CdSe/ZnS/CdSe nanocrystals were found to have enhanced optical gain characteristics relative to CdSe quantum dots, as shown using femtosecond transient absorption spectroscopy. The enhancement of gain metrics such as bandwidth and efficiency arises from stimulated emission from quantum shell enabled excitations. These shell enabled excitations increase gain bandwidth via emission from new transitions and increase efficiencies via tailored biexciton interactions. This unique two color character in both spontaneous emission and optical gain is rationalized by slow exciton cooling from the core/shell states into the core localized quantum
author_names: Eva A Dias

Jonathan I Saari

Pooja Tyagi

Patanjali Kambhampati
title: Improving Optical Gain Performance in Semiconductor Quantum Dots via Coupled Quantum Shells
year: 2012

abstract: We study the effect of multiparticle interactions on optical gain and stimulated emission in close packed solids of chemically synthesized CdSe nanocrystals (nanocrystal quantum dots) An analysis of pump dependent nonlinear absorption signals indicates that the band edge optical gain is due to multiparticle states with a dominant contribution from doubly excited nanocrystals (quantum confined biexcitons) We observe that optical gain dynamics are due to the competition between ultrafast hole surface trapping and multiparticle Auger decay. We analyze the effect of intrinsic Auger recombination on optical gain lifetimes and gain pump intensity thresholds.
author_names: Alexander Mikhailovsky

Anton V Malko

Jennifer Ann Hollingsworth

Moungi G Bawendi

Victor I Klimov
title: Multiparticle interactions and stimulated emission in chemically synthesized quantum dots
year: 2002

abstract: Quantum dots(QD) can be fabricated by pulse laser irradiation on silicon samples in the oxygen and air atmospheres.Random stimulated emission at about 700nm can be observed on oxidized QD treated with annealing,which has optical gain and threshold behavior obviously.Simulated calculation of primary principle shows that the kind and the density of Si O bonds on QD surface play an important role in stimulated emission.We propose a physical model to explain the mechanism of stimulated emission.
author_names: Xu Li
title: Mechanism of Stimulated Emission on Nanocrystal Silicon by Irradiation of Laser
year: 2011

abstract: Nanocrystal quantum dots have favourable light emitting properties. They show photoluminescence with high quantum yields, and their emission colours depend on the nanocrystal size owing to the quantum confinement effect and are therefore tunable. However, nanocrystals are difficult to use in optical amplification and lasing. Because of an almost exact balance between absorption and stimulated emission in nanoparticles excited with single electron hole pairs (excitons) optical gain can only occur in nanocrystals that contain at least two excitons. A complication associated with this multiexcitonic nature of light amplification is fast optical gain decay induced by non radiative Auger recombination, a process in which one exciton recombines by transferring its energy to another. Here we demonstrate a practical approach for obtaining optical gain in the single exciton regime that eliminates the problem of Auger decay. Specifically, we develop core/shell hetero nanocrystals engineered in such a way as to spatially separate electrons and holes between the core and the shell (type II heterostructures) The resulting imbalance between negative and positive charges produces a strong local electric field, which induces a giant ~100 meV or greater) transient Stark shift of the absorption spectrum with respect to the luminescence line of singly excited nanocrystals. This effect breaks the exact balance between absorption and stimulated emission, and allows us to demonstrate optical amplification due to single excitons.
author_names: Victor I Klimov

Sergei Ivanov

Jagjit Nanda

Marc Achermann

Ilya Bezel

John A McGuire

Andrei Piryatinski
title: Single exciton optical gain in semiconductor nanocrystals
venue: Nature
year: 2007

abstract: Colloidal perovskite quantum dots are candidate materials for solution processable lasers, although stimulated emission in a semiconductor usually occurs in the multiexciton regime. Due to the quantum confinement effect of semiconductor quantum dots, the non radiative recombination transition dominates the relaxation of multiexcitons. Hence, the implementation of low threshold stimulated emission of perovskite quantum dots in the single exciton regime is meaningful. Herein, we show that this problem can be partially solved by employing a locally enhanced electric field. By applying the metal surface plasmon resonance energy transfer effect, we demonstrate a considerable reduction of the optical gain threshold due to the newly generated coupling level induced by the local surface plasmon, and obtain optical gain in the single exciton regime at room temperature in colloidal perovskite quantum dots. At the same time, we achieve a more than fourfold reduction in the amplified spontaneous emission threshold. This may provide a new concept for the further design of low threshold stimulated emission colloidal nanocrystal lasers and even for improving their energy conversion efficiency.
author_names: Litao Zhao

Yi-Hsien Chen

Xiantong Yu

Xiao Xing

Jinquan Chen

Jun Song

Junle Qu
title: Low threshold stimulated emission in perovskite quantum dots: single exciton optical gain induced by surface plasmon polaritons at room temperature
year: 2020

abstract: Colloidal semiconductor nanocrystals (NCs) represent a promising class of nanomaterials for lasing applications. Currently, one of the key challenges facing the development of high performance NC optical gain media lies in enhancing the lifetime of biexciton populations. This usually requires the employment of charge delocalizing particle architectures, such as core/shell NCs, nanorods, and nanoplatelets. Here, we report on a two dimensional nanoshell quantum dot (QD) morphology that enables a strong delocalization of photoinduced charges, leading to enhanced biexciton lifetimes and low lasing thresholds. A unique combination of a large exciton volume and a smoothed potential gradient across interfaces of the reported CdSbulk/CdSe/CdSshell (core/shell/shell) nanoshell QDs results in strong suppression of Auger processes, which was manifested in this work though the observation of stable amplified stimulated emission (ASE) at low pump fluences. An extensive charge delocalization in nanoshell QDs was confirmed by transient absorption measurements, showing that the presence of a bulk size core in CdSbulk/CdSe/CdSshell QDs reduces exciton exciton interactions. Overall, present findings demonstrate unique advantages of the nanoshell QD architecture as a promising optical gain medium in solid state lighting and lasing applications.
author_names: Dmitry A Porotnikov

Benjamin T Diroll

Dulanjan Harankahage

Laura Obloy

Mingrui Yang

James Cassidy

Cole Ellison

Emily Miller

Spencer Rogers

Alexander N Tarnovsky

Richard D Schaller

Mikhail Zamkov
title: Low threshold laser medium utilizing semiconductor nanoshell quantum dots.
venue: Nanoscale
year: 2020

abstract: ABSTRACT Time resolved luminescence measurements on silicon nanocrystal waveguides have revealeda fast recombination dynamics, related to population inversion which leads to net optical gain.The waveguide samples were obtained by thermal annealing of plasma enhanced chemicalvapour deposited thin layers of silicon rich oxide Variable stripe length measurements performedon the fast emission signal have shown an exponential growth of the amplified spontaneousemission, with net gain values of about 10 cm 1 Both the fast component intensity and itstemporal width revealed threshold behaviour as a function of the incident pump intensity. Amodelling of the decay dynamics is suggested within an effective four level rate equationtreatment including the delicate interplay among stimulated emission and Auger recombinations. INTRODUCTION One goal for silicon microphotonics consists in the demonstration of a laser device based onsilicon [1,2] Following the initial observations of optical gain in highly packed siliconnanocrystals (Si nc) prepared by ion implantation [3] other works have recently demonstrated thepossibility of stimulated emission in Si nc [4 6] Nanosecond gain dynamics [4] and evidences forspeckle patterns [5] in the spatially coherent emission have been recently reported.As in other quantum dot based systems [7,8] a severe competition with efficient non radiativeprocesses, mainly Auger type, is present in Si nc, which causes very fast dynamics in the opticalgain. Although a clear understanding of the microscopic gain mechanism is still under debate, ithas been realised that interface radiative states associated with oxygen atoms can play a crucialrole in determining the emission properties of the Si nc systems [9,10] Here we report on lightamplification dynamic studies in Si nc and we propose a simple phenomenological model toexplain our experimental results.
author_names: Luca Dal Negro

Massimo Cazzanelli

Zeno Gaburro

Paolo Bettotti

Lorenzo Pavesi

Domenico Pacifici

G Franzo

Francesco Priolo

Fabio Iacona
title: Optical gain and stimulated emission in silicon nanocrystals
year: 2002

abstract: Amplification of surface plasmon polaritons in planar metal dielectric structure through stimulated emission is investigated using leakage radiation microscopy configuration. The gain medium is a thin polymethylmethacrylate layer doped with lead sulphide nanocrystals emitting at near infrared wavelengths. We demonstrate an optical gain of ~200 cm( 1) for the mode under consideration, which corresponds to ~32% compensation of SPP loss.
author_names: Ilya P Radko

Michael Grondahl Nielsen

Ole Albrektsen

Sergei I Bozhevolnyi
title: Stimulated emission of surface plasmon polaritons by lead sulphide quantum dots at near infra red wavelengths.
venue: Optics express
year: 2010

abstract: With regards to developing miniaturized coherent light sources, the temperature insensitivity in gain spectrum and threshold is highly desirable. Quantum dots (QDs) are predicted to possess a temperature insensitive threshold by virtue of the separated electronic states; however, it is never observed in colloidal QDs due to the poor thermal stability. Besides, for the classical II VI QDs, the gain profile generally redshifts with increasing temperature, plaguing the device chromaticity. Herein, this paper addresses the above two issues simultaneously by embedding ligands free CsPbBr3 nanocrystals in a wider band gap Cs4 PbBr6 matrix by solution phase synthesis. The unique electronic structures of CsPbBr3 nanocrystals enable temperature insensitive gain spectrum while the lack of ligands and protection from Cs4 PbBr6 matrix ensure the thermal stability and high temperature operation. Specifically, a color drift free stimulated emission irrespective of temperature change (20 150 degC) upon two photon pumping is presented and the characteristic temperature is determined to be as high as 260 K. The superior gain properties of the CsPbBr3 /Cs4 PbBr6 perovskite nanocomposites are directly validated by a vertical cavity surface emitting laser operating at temperature as high as 100 degC. The results shed light on manipulating optical gain from the advantageous CsPbBr3 nanocrystals and represent a significant step toward the temperature insensitive frequency upconverted lasers.
author_names: Yue Wang

Dejian Yu

Zeng-Rong Wang

Xiaomin Li

Xiaoxuan Chen

Venkatram Nalla

Haibo Zeng

Handong Sun
title: Solution Grown CsPbBr3 /Cs4 PbBr6 Perovskite Nanocomposites: Toward Temperature Insensitive Optical Gain.
venue: Small
year: 2017