Effect of time relaxations on the carrier heating of InAs/GaAs quantum dot semiconductor optical amplifier (original) (raw)
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Spectral hole-burning and carrier-heating dynamics in InGaAs quantum-dot amplifiers
IEEE Journal of Selected Topics in Quantum Electronics, 2000
The ultrafast gain and index dynamics in a set of InAs-InGaAs-GaAs quantum-dot (QD) amplifiers are measured at room temperature with femtosecond resolution. The role of spectral hole-burning (SHB) and carrier heating (CH) in the recovery of gain compression is investigated in detail. An ultrafast recovery of the spectral hole within 100 fs is measured, comparable to bulk and quantum-well amplifiers, which is contradicting a carrier relaxation bottleneck in electrically pumped QD devices. The CH dynamics in the QD is quantitatively compared with results on an InGaAsP bulk amplifier. Reduced CH for both gain and refractive index dynamics of the QD devices is found, which is a promising prerequisite for high-speed applications. This reduction is attributed to reduced free-carrier absorption-induced heating caused by the small carrier density necessary to provide amplification in these low-dimensional systems.
Auger Capture Induced Carrier Heating in Quantum Dot Lasers and Amplifiers
Applied Physics Express, 2011
Carrier heating in quantum dot (QD) devices, which accompanies Auger capture of carriers from a carrier reservoir to discrete QD levels, is considered for the first time. Equations for carrier dynamics of QD structures are formulated and analyzed by taking into account the carrier heating. A numerical example shows that heating of carriers in a carrier reservoir of a QD structure can be much higher than that of bulk and quantum well devices. Auger capture carrier heating in QD devices can lead to a longer (more than a factor of 2 for the 90%-recovery time) relaxation time from a carrier reservoir to QDs.
Temperature-dependent modulation characteristics for 1.3 μm InAs/GaAs quantum dot lasers
Journal of Applied Physics, 2010
Temperature-dependent modulation characteristics of 1.3 m InAs/GaAs quantum dot ͑QD͒ lasers under small signals have been carefully studied at various bias currents. Based on experimental observations, it is found that the modulation bandwidth significantly increases when excited state ͑ES͒ lasing emerges at high temperature. This is attributed to additional photons emitted by ES lasing which contribute to the modulation response. A rate equation model including two discrete electron energy levels and the level of wetting layer has been used to investigate the temperature-dependent dynamic behavior of the QD lasers. Numerical investigations confirm that the significant jump for the small signal modulation response is indeed caused by ES photons. Furthermore, we identify how the electron occupation probabilities of the two discrete energy levels can influence the photon density of different states and finally the modulation rate. Both experiments and numerical analysis show that the modulation bandwidth of QD lasers at high temperature can be increased by injecting more carriers into the ES that has larger electron state degeneracy and faster carrier's relaxation time than the ground state.
2005
Self-assembled quantum dot (QD) Semiconductor Optical Amplifiers (SOAs) are believed to have faster carrier recovery times than conventional multiple quantum well, or bulk SOAs. It is therefore of interest to study the carrier dynamics of QD SOAs to assess their potential as ultrafast nonlinear devices for switching and signal processing. In this work we report experimental characterization of the ultrafast carrier dynamics of a novel InAs/InGaAsP selfassembled QD SOA with its peak gain in the important 1.55 m telecommunications wavelength range. The temporal dynamics are measured with a heterodyne pump-probe technique with 150 fs resolution. The measurements show carrier heating dynamics with lifetimes of 0.5-2.5 ps, and a 13.2 ps gain recovery, making the device a promising candidate for ultrafast switching applications. The results are compared to previous reports on QD amplifiers operating in the 1.3 m and 1.1 m spectral regions. This report represents the first study of the temporal dynamics of a QD SOA operating at 1.55 m.
2005
Self-assembled quantum dot (QD) Semiconductor Optical Amplifiers (SOAs) are believed to have faster carrier recovery times than conventional multiple quantum well, or bulk SOAs. It is therefore of interest to study the carrier dynamics of QD SOAs to assess their potential as ultrafast nonlinear devices for switching and signal processing. In this work we report experimental characterization of the ultrafast carrier dynamics of a novel InAs/InGaAsP selfassembled QD SOA with its peak gain in the important 1.55 m telecommunications wavelength range. The temporal dynamics are measured with a heterodyne pump-probe technique with 150 fs resolution. The measurements show carrier heating dynamics with lifetimes of 0.5-2.5 ps, and a 13.2 ps gain recovery, making the device a promising candidate for ultrafast switching applications. The results are compared to previous reports on QD amplifiers operating in the 1.3 m and 1.1 m spectral regions. This report represents the first study of the temporal dynamics of a QD SOA operating at 1.55 m.
Crystals
Carrier transfer in vertically-coupled InAs/GaAs quantum dot (QD) pairs is investigated. Photoluminescence (PL) and PL excitation spectra measured at low temperature indicate that the PL peak intensity ratio between the emission from the two sets of QDs-i.e., the relative population of carriers between the two layers of QDs-changes with increasing excitation intensity. Temperature-dependent PL reveals unexpected non-monotonic variations in the peak wavelength and linewidth of the seed layer of QDs with temperature. The PL intensity ratio exhibits a "W" behavior with respect to the temperature due to the interplay between temperature and excitation intensity on the inter-layer carrier transfer.
IEEE Journal of Quantum Electronics, 2007
We assess the influence of the degree of quantum confinement on the carrier recovery times in semiconductor optical amplifiers (SOAs) through an experimental comparative study of three amplifiers, one InAs-InGaAsP-InP quantum dot (0-D), one InAs-InAlGaAs-InP quantum dash (1-D), and one InGaAsP-In-GaAsP-InP quantum well (2-D), all of which operate near 1.55-m wavelengths. The short-lived (around 1 ps) and long-lived (up to 2 ns) amplitude and phase dynamics of the three devices are characterized via heterodyne pump-probe measurements. The quantum-dot device is found to have the shortest long-lived gain recovery ( 80 ps) as well as gain and phase changes indicative of a smaller linewidth enhancement factor, making it the most promising for high-bit-rate applications. The quantum-dot amplifier is also found to have reduced ultrafast transients, due to a lower carrier density in the dots. The quantum-dot gain saturation characteristics and temporal dynamics also provide insight into the nature of the dot energy-level occupancy and the interactions of the dot states with the wetting layer.
… , IEEE Journal of, 2007
We assess the influence of the degree of quantum confinement on the carrier recovery times in semiconductor optical amplifiers (SOAs) through an experimental comparative study of three amplifiers, one InAs-InGaAsP-InP quantum dot (0-D), one InAs-InAlGaAs-InP quantum dash (1-D), and one InGaAsP-In-GaAsP-InP quantum well (2-D), all of which operate near 1.55-m wavelengths. The short-lived (around 1 ps) and long-lived (up to 2 ns) amplitude and phase dynamics of the three devices are characterized via heterodyne pump-probe measurements. The quantum-dot device is found to have the shortest long-lived gain recovery ( 80 ps) as well as gain and phase changes indicative of a smaller linewidth enhancement factor, making it the most promising for high-bit-rate applications. The quantum-dot amplifier is also found to have reduced ultrafast transients, due to a lower carrier density in the dots. The quantum-dot gain saturation characteristics and temporal dynamics also provide insight into the nature of the dot energy-level occupancy and the interactions of the dot states with the wetting layer.
Numerical characterization of InP-based quantum dot semiconductor optical amplifier
Applied Optics, 2016
This paper is devoted to the development of a steady-state behavior of a quantum dot-semiconductor optical amplifier (QD-SOA). The investigated performance characteristics cover a wide range that includes material gain coefficient, spatial distribution of the occupation probabilities, fiber to fiber gain, gain spectrum as a function of the bias current, relaxation time, and capture time. A set of traveling-wave equations is used to model the signal and spontaneous photons along the device active region. The obtained results indicate a high gain that reaches 34 dB for an InAs/InGaAsP/InP-based QD-SOA, with a corresponding device length of 4 mm. The obtained signal-to-noise ratio is larger than 75 dB for all input powers without using an output filter.
Femtosecond gain and index dynamics in an InAs/InGaAsP quantum dot amplifier operating at 1.55 µm
Opt. …, 2006
We report on the characterization of the ultrafast gain and refractive index dynamics of an InAs/InGaAsP self-assembled quantum dot semiconductor optical amplifier (SOA) operating at 1.55 μ m through heterodyne pump-probe measurements with 150 fs resolution. The measurements show a 15 ps gain recovery time at a wavelength of 1560 nm, promising for ultrafast switching at >40 GHz in the important telecommunications wavelength bands. Ultrafast dynamics with 0.2-1.5 ps lifetimes were also found consistent with carrier heating and spectral hole burning. Comparing with previous reports on quantum dot SOAs at 1.1-1.3 μ m wavelengths, we conclude that the carrier heating is caused by a combination of free-carrier absorption and stimulated transition processes.