Carrier Dynamics of Quantum-Dot, Quantum-Dash, and Quantum-Well Semiconductor Optical Amplifiers Operating at 1.55 mu{ {m (original) (raw)
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… , 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.
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.
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.
Ultrafast gain dynamics in InP quantum-dot optical amplifiers
Applied Physics Letters, 2010
We measured the gain dynamics at the ground-state transition in an electrically pumped InP/ AlGaInP quantum-dot optical amplifier at room temperature by femtosecond differential transmission. The gain shows an ultrafast recovery within 200 fs, even faster than in state-of-the-art InAs/GaAs quantum-dot amplifiers. This finding, likely to be due to the less confined and more closely spaced hole levels in InP dots, is promising for optical signal processing at high bit rates. We furthermore measured the pump-induced refractive index changes and deduced a linewidth enhancement factor similar to the one in InAs/GaAs quantum dots.
IEEE/OSA Journal of Lightwave Technology, 2008
We report time-resolved measurements of the linewidth enhancement factors ( -factors) , CH , and TPA , associated with the adiabatic carrier recovery, carrier heating, and two-photon absorption dynamical processes, respectively, in semiconductor optical amplifiers (SOAs) with different degrees of dimensionality-one InAs/InGaAsP/InP quantum dot (0-D), one InAs/InAlGaAs/InP quantum dash (1-D), and a matching InGaAsP/InGaAsP/InP quantum well (2-D)-all operating near 1.55m wavelengths. We find the lowest values in the QD SOA, 2-10, compared to 8-16 in the QW, and values of CH and
InGaAs Quantum Dots Coupled to a Reservoir of Nonequilibrium Free Carriers
IEEE Journal of Quantum Electronics, 2009
We discuss the impact of a 2-D-charged carrier reservoir for high-speed optical amplification and modulated lasing in quantum dot (QD)-based devices by testing the amplification of short trains of high power, femtosecond optical pulses in an In-GaAs QD-in-a-well-based semiconductor optical amplifier (SOA). We adapt a laser-like rate equation model to describe heterodyne pump-and-probe experiments. After an optically induced perturbation, we identify the gain recovery process as a forced steadystate situation which can be consistently described within rateequation based laser theory. The model is systematically applied to analyze the experimental amplification and the overall SOA dynamics as a function of injected current. We conclude that, under conditions of high optical pump power close to the device saturation regime, the ultrafast SOA dynamics is governed by the overall injection current. The carrier relaxation pathway of a direct capture from the 2-D reservoir to the QD ground state is needed to explain the observed pulse train amplification. Index Terms-Quantum dot (QD), semiconductor optical amplifier (SOA).
IEEE Journal of Quantum Electronics, 2000
Ultrafast gain dynamics in an optical amplifier with an active layer of self-organized quantum dots (QDs) emitting near 1.3 m is characterized experimentally in a pump-probe experiment and modeled theoretically on the basis of QD Maxwell-Bloch equations. Experiment and theory are in good agreement and show ultrafast subpicoseconds gain recovery followed by a slower 5 ps recovery. This behavior is found to be mainly caused by longitudinal optical phonon scattering and strongly dependents on electronic structure and confinement energy of the dots. A low amplitude-phase coupling ( factor) is theoretically predicted and demonstrated in the experiments. The fundamental analysis reveals the underlying physical processes and indicates limitations to QD-based devices.