Existence of a phonon bottleneck for excitons in quantum dots

Heitz, R.; Born, H.; Guffarth, F.; Stier, O.; Schliwa, A.; Hoffmann, A.; Bimberg, D.

doi:10.1103/physrevb.64.241305

Cited by 155 publications

(109 citation statements)

References 26 publications

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“…The bandwidth can be seen to increase with the effective scattering rate in the overdamped and synchronized dynamic regimes. This is in line with the common assumption of a carrier "bottleneck" between the reservoir and the quantum-dot states limiting the modulation response [HEI01,TON09]. However, when comparing the modulation bandwidth of the quantum-dot laser within the synchronized regime with the analytically predicted bandwidth using Eq.…”

Section: Modulation Response Of Quantum-dot Lasersmentioning

confidence: 61%

Nonlinear and Nonequilibrium Dynamics of Quantum-Dot Optoelectronic Devices

Lingnau

2015

Springer Theses

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In this thesis the dynamics and performance of optoelectronic devices based on semiconductor quantum-dots are investigated.In the first part, the dynamics of quantum-dot lasers under external perturbations is discussed. Using a microscopically based balance equation model that incorporates detailed charge-carrier scattering dynamics and the possibility to describe nonequilibrium between intra-band electronic states, the relaxation oscillations of the quantum-dot laser are investigated. Three qualitatively different dynamic regimes are identified in dependence of the scattering rates -the "constantreservoir" regime for slow scattering, the "overdamped" regime, and the "synchronized" regime for high scattering -characterized by a varying degree of nonequilibrium between the quantum-dot and reservoir states.Important differences to conventional lasers are found in the modulation response and the dynamics in optical injection and feedback setups. Common theoretical models and approaches used to describe these applications are shown to yield inaccurate predictions, especially in the "constant-reservoir" and "overdamped" dynamic regimes. An important consequence is that the amplitude-phase coupling in quantum-dot lasers, commonly described by the α-factor, differs from conventional descriptions due to the desynchronization of gain and refractive index. While the α-factor describes bifurcations of fixed points accurately, it fails in describing dynamic solutions and overestimates the extent of complex dynamics. The observed low sensitivity to optical perturbations in quantum-dot lasers can therefore be attributed partly to the charge-carrier nonequilibrium. Three quantum-dot laser models on different levels of sophistication are presented that can accurately describe the quantum-dot nonequilibrium dynamics.In the second part of the thesis, the performance of quantum-dot semiconductor optical amplifiers is investigated, and two types of applications unique to quantum-dots as active medium are discussed. The ground and excited states of the quantum-dots allow an ultra-broad-band amplification of optical data streams. Amplified signals on the ground-state frequencies are shown to generally exhibit higher quality than on the excited state, due to a lower sensitivity of the groundstate to carrier-density variations. Nevertheless the quantum-dot amplifier is found to allow effective amplification on both frequency ranges. Furthermore, a parameter range is identified that allows for a simultaneous amplification of data signals on the ground and excited state in a counter-propagating setup.The long microscopically polarization dephasing times in quantum-dots are found to enable quantum-coherent interactions on a macroscopic scale at room-temperature. By comparison with experiments, the occurrence of Rabi-oscillations by amplification of ultra-short pulses is demonstrated. Quantum-dot based devices could therefore be used for future applications based on quantum-coherent effects.

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Section: Modulation Response Of Quantum-dot Lasersmentioning

confidence: 61%

Nonlinear and Nonequilibrium Dynamics of Quantum-Dot Optoelectronic Devices

Lingnau

2015

Springer Theses

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“…Thus, the used population decay rates are similar to those measured in Ref. 4, while the dephasing rate ␥ 21 is similar to Ref. 8 at T = 7 K. We tentatively set ␥ 31 and ␥ 32 equal to ␥ 21 .…”

Section: Reducing the Impact Of Inhomogeneous Broadening On Quantum Dmentioning

confidence: 60%

“…However, QDs with such long intraband relaxation time can in fact be fabricated, as demonstrated in Ref. 4. For comparison, we also calculate the slowdown factor of the V-scheme with a short intraband relaxation time 1 / ⌫ 32 = 10 ps and with a population decay limited dephasing time.…”

Section: Reducing the Impact Of Inhomogeneous Broadening On Quantum Dmentioning

confidence: 99%

“…At cryogenic temperatures, IHB is several orders of magnitude wider than the transition linewidth. 4 The broadening causes the probe and coupling laser fields to experience different detunings depending on the individual QD size and, as a result, the overall EIT features are smeared out. EIT was previously demonstrated in quantum well structures by exploiting excitonic effects 5 and, in Ref.…”

Section: Reducing the Impact Of Inhomogeneous Broadening On Quantum Dmentioning

confidence: 99%

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Reducing the impact of inhomogeneous broadening on quantum dot based electromagnetically induced transparency

Lunnemann

Mørk

2009

Applied Physics Letters

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Slow light based on electromagnetically induced transparency in an inhomogeneously broadened quantum dot medium is investigated theoretically. Three schemes, Ξ, V, and Λ, are compared and it is shown that the V-scheme gives a group velocity that is more than three orders of magnitude smaller compared to the Ξ- and Λ-schemes. The physical mechanisms that make the V-scheme less vulnerable to inhomogeneous broadening are analyzed and discussed.

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“…The interaction with the quasicontinuum of lattice degrees of freedom (phonons) constitutes an inherent feature of these nanometer-size systems and cannot be neglected in any realistic modeling of QD properties, especially when the coherence of confined carriers is of importance. The understanding of the decisive role played by the QD coupling to lattice modes has increased recently due to both experimental and theoretical study (spectrum reconstruction [1-4], relaxation [5][6][7][8][9][10], phonon replicas and phonon-assisted transitions [11][12][13][14][15][16], phonon-induced pure dephasing upon ultrafast excitation [17][18][19][20][21][22]). The phonon-induced decoherence seems to be crucial for any quantum information processing application and for any nanotechnological device relying on quantum coherence of confined carriers [23,24].…”

Section: Introductionmentioning

confidence: 99%

Fast Control of Quantum States in Quantum Dots: Limits due to Decoherence

Jacak

Machnikowski

Krasnyj

Quantum Dots: Fundamentals, Applications, and Frontiers

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We study the kinetics of confined carrier-phonon system in a quantum dot under fast optical driving and discuss the resulting limitations to fast coherent control over the quantum state in such systems. IntroductionUnlike natural atoms, semiconductor quantum dots (QDs) always form part of a macroscopic crystal. The interaction with the quasicontinuum of lattice degrees of freedom (phonons) constitutes an inherent feature of these nanometer-size systems and cannot be neglected in any realistic modeling of QD properties, especially when the coherence of confined carriers is of importance. The understanding of the decisive role played by the QD coupling to lattice modes has increased recently due to both experimental and theoretical study (spectrum reconstruction [1-4], relaxation [5][6][7][8][9][10], phonon replicas and phonon-assisted transitions [11][12][13][14][15][16], phonon-induced pure dephasing upon ultrafast excitation [17][18][19][20][21][22]). The phonon-induced decoherence seems to be crucial for any quantum information processing application and for any nanotechnological device relying on quantum coherence of confined carriers [23,24].There are three major mechanisms of carrier-phonon interaction [25]: (1) Coulomb interaction with the lattice polarization induced by the relative shift of the positive and negative sub-lattices of the polar compound, * On leave from Odessa University, Ukraine

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Existence of a phonon bottleneck for excitons in quantum dots

Cited by 155 publications

References 26 publications

Nonlinear and Nonequilibrium Dynamics of Quantum-Dot Optoelectronic Devices

Nonlinear and Nonequilibrium Dynamics of Quantum-Dot Optoelectronic Devices

Reducing the impact of inhomogeneous broadening on quantum dot based electromagnetically induced transparency

Fast Control of Quantum States in Quantum Dots: Limits due to Decoherence

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