Carrier‐carrier and carrier‐phonon scattering in the low‐density and low‐temperature regime for resonantly pumped semiconductor quantum dots

Seebeck, J.; Lorke, Michael; Gärtner, P.; Jahnke, F.

doi:10.1002/pssc.200880330

Cited by 4 publications

(3 citation statements)

References 9 publications

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“…However, it has been shown that the Markov approximation, leading to the emergence of the energy conserving δ-function in the scattering rates, can underestimate its actual value [SEE05,SEE09,STE12]. This is due to a broadening of the transition probabilities in energy space by non-Markovian dynamics, which makes scattering possible also for energy differences not matching the LO phonon energy exactly.…”

Section: Theory Of Quantum-dot Optical Devicesmentioning

confidence: 99%

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: Theory Of Quantum-dot Optical Devicesmentioning

confidence: 99%

Nonlinear and Nonequilibrium Dynamics of Quantum-Dot Optoelectronic Devices

Lingnau

2015

Springer Theses

View full text Add to dashboard Cite

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“…However, it has been shown that the Markov approximation, leading to the emergence of the energy conserving δ-function in the scattering rates, can underestimate its actual value [42][43][44]. This is due to a broadening of the transition probabilities in energy space by non-Markovian dynamics, which makes scattering possible also for energy differences not matching the LO phonon energy exactly.…”

Section: Carrier-phonon Scatteringmentioning

confidence: 95%

“…Assuming that τ cav is small compared to all other processes determining the electric field dynamics, the above equation can be transformed to a quasi-continuous change in time: 43) where the losses have been combined to a total loss rate κ. Inserting these additional losses into Eq. (2.41), we arrive at the dynamic equation governing the time evolution of the electric field inside the cavity:…”

Section: Optical Lossesmentioning

confidence: 99%

Theory of Quantum-Dot Optical Devices

Lingnau

2015

Nonlinear and Nonequilibrium Dynamics of Quantum-Dot Optoelectronic Devices

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Modern semiconductor optical devices can consist of a complex arrangement of several different semiconductor crystal layers. By further processing, the semiconductor structure is then shaped into the desired device geometry. Additional steps, such as planarization and contacting, are then required to yield the final usable device. Naturally, a complete microscopic description of the resulting object in all its degrees of freedom is not tractable. Therefore, a restriction to only few degrees of freedom is required, while still maintaining all necessary aspects determining the system behavior.In the theoretical description of quantum-dot semiconductor optical devices, this means a restriction to the active region, i.e., the parts where the light-matter interaction occurs, and the immediate surrounding matter. Since the optical interactions between the electric field and charge carriers (electrons and holes) are being considered, dynamic equations for these quantities must be derived.There exist theoretical models for quantum-dot lasers on varying levels of sophistication. Microscopic models that take into account the exact band structure and many-body interactions [1][2][3][4] can describe the complex energy structure of quantum dots very realistically, but these approaches are too complicated to be applied in dynamic problems. On the other hand, simple rate-equation models exist [5][6][7] that can be easily implemented and require little computation power, and often allow for analytical treatment. These models, however, are prone to oversimplification, possibly neglecting important aspects that would lead to different results. In between these two types of approaches there exist multi-rate equation models [8][9][10][11], that take into account the delicate energy structure of quantum-dot active media. These models offer a balance between complexity and practicability. In this spirit, we will develop a quantum-dot laser model that takes into account the most important effects needed to realistically describe the laser behavior, while still being simple enough for thorough dynamic studies.

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