Self-induced transparency in InGaAs quantum-dot waveguides

2008

The linear electro-optic properties in waveguides containing self-organized InAs quantum dots were studied experimentally. Fabry-Perot measurements at 1515 nm on InAs/GaAs quantum dot structures yield a significantly enhanced linear electro-optic efficiency compared to bulk GaAs. ThP03

Applied Physics Letters, 2000

IEEE Photonics Technology Letters, 2000

The ultrafast dynamics of gain and refractive index in an electrically pumped InAs-InGaAs quantum-dot (QD) optical amplifier are measured at room temperature using differential transmission with femtosecond time resolution. Both absorption and gain regions are investigated. While the absorption bleaching recovery occurs on a picosecond time scale, the gain compression recovers with 100-fs time constant, making devices based on such dots promising for high-speed optical communications.

We have studied femtosecond pulse propagation in CdS quantum-dot-doped waveguides produced by the solgel and ion-exhange methods. The observed two-photon absorption and asymmetric spectral modulation of the transmitted pulses are explained by our theoretical model, which incorporates a near-resonant two-photon transition.

Applied Physics Letters, 2015

Broadband Purcell enhanced emission dynamics of quantum dots in linear photonic crystal waveguides J. Appl. Phys. 112, 093520 (2012); 10.1063/1.4764923 Spontaneous emission control of single quantum dots in bottom-up nanowire waveguides Appl. Phys. Lett. 100, 121106 (2012); 10.1063/1.3694935 Slow-light-enhanced single quantum dot emission in a unidirectional photonic crystal waveguide Appl. Phys. Lett. 96, 031109 (2010);

IEEE Journal of Quantum Electronics, 2004

We report systematic measurements of the linewidth enhancement factor (LEF) in an electrically pumped InGaAs quantum-dot (QD) amplifier in the temperature range from 50 K to room temperature. At injection currents below transparency, the value of the linewidth enhancement factor of the ground-state interband (excitonic) transition is between 0.4 and 1, and increases with increasing carrier density. Additionally, we investigate the spectral dependence of the LEF by tuning the wavelength of our optical probe from below resonance with the ground state of the QDs up to resonance with the first optically active excited-state transition. We find a decrease of the LEF with increasing photon energy at all investigated temperatures.

IEEE Photonics Technology Letters, 2005

Optics Express, 2008

Optical properties of multilayer InAs quantum dot waveguides, grown by molecular beam epitaxy, have been studied under applied electric field. Fabry-Perot measurements at 1515 nm on InAs/GaAs quantum dot structures yield a significantly enhanced linear electro-optic efficiency compared to bulk GaAs. Electro-absorption measurements at 1300 nm showed increased absorption with applied field accompanied with red shift of the spectra. Spectral shifts of up to 21% under 18 Volt bias was observed at 1320 nm.

Journal of Applied Physics, 2012

The authors investigate the spontaneous emission dynamics of selfassembled InGaAs quantum dots embedded in GaAs photonic crystal waveguides. For an ensemble of dots coupled to guided modes in the waveguide we report spatially, spectrally, and time-resolved photoluminescence measurements, detecting normal to the plane of the photonic crystal. For quantum dots emitting in resonance with the waveguide mode, a ∼ 21× enhancement of photoluminescence intensity is observed as compared to dots in the unprocessed region of the wafer. This enhancement can be traced back to the Purcell enhanced emission of quantum dots into leaky and guided modes of the waveguide with moderate Purcell factors up to ∼ 4×. Emission into guided modes is shown to be efficiently scattered out of the waveguide within a few microns, contributing to the out-of-plane emission and allowing the use of photonic crystal waveguides as broadband, efficiency-enhancing structures for surface-emitting diodes or single photon sources.

Physical Review A, 2007

We study the detailed propagative characteristics of optical pulses in photonic band-gap ͑PBG͒ waveguides, coupled near resonantly to inhomogeneously broadened distributions of quantum dots. The line centers of the quantum-dot ͑QD͒ distributions are placed near a sharp discontinuity in the local electromagnetic density of states. Using finite-difference time-domain ͑FDTD͒ simulations of optical pulse dynamics and independent QD susceptibilities associated with resonance fluorescence, we demonstrate subpicosecond switching from pulse absorption to pulse amplification using steady-state optical holding and gate fields with power levels on the order of 1 milliwatt. In the case of collective response of QDs within the periodic dielectric microstructure, the gate power level is reduced to 200 microwatt for room temperature operation. In principle, this enables 200 Gbits per second optical information processing at wavelengths near 1.5 microns in various wavelength channels. The allowed pulse bandwidth in a given waveguide channel exceeds 0.5 THz allowing switching of subpicosecond laser pulses without pulse distortion. The switching contrast from absorption to gain is governed by the QD oscillator strength and dipole dephasing time scale. We consider dephasing time scales ranging from nanoseconds ͑low-temperature operation͒ to one picosecond ͑room-temperature operation͒. This all-optical transistor action is based on simple Markovian models of single-dot and collective-dot inversion and switching by coherent resonant pumping near the photon density of states discontinuity. The structured electromagnetic vacuum is provided by two-mode waveguide architectures in which one waveguide mode has a cutoff that occurs, with very large Purcell factor, near the QDs resonance, while the other waveguide mode exhibits nearly linear dispersion for fast optical propagation and modulation. Unlike optical switching based on Kerr nonlinearities in an optical cavity resonator, switching power levels and switching speeds for our QD device are not inversely proportional to cavity quality factors.

physica status solidi (a), 2002

Time-resolved four-wave mixing in strongly confined and electrically pumped InGaAs quantum dots is measured at different temperatures. Without electrical injection, the dephasing time of the dot ground state transition is lifetime-limited and of several hundred picoseconds at low temperature. Under electrical injection, the sum of the contributions from empty and populated dots with a relative phase shift of p is evidenced near transparency.

PHYSICAL REVIEW B, 2002

We present measurements and calculations of optical Rabi oscillations in the excitonic ground-state transition of an InGaAs quantum dot ensemble at low temperature. Rabi oscillations which are damped versus pulse area and change period when changing pulse duration are observed. Comparisons with calculations show that the observed damping is not intrinsic to a single dot. Dephasing processes and the biexciton resonance change the amplitude and the period of the oscillations, respectively, while the damping versus pulse area is due to a distribution of transition dipole moments in the ensemble.

We report Kerr nonlinearity due to intersubband transitions in a three-level InAs/GaAs domeshaped quantum dots (QDs) system. The impact of wetting layer and dot size on the electronic, linear and nonlinear optical properties is discussed. The results showed an overall shift of dispersion curves towards lower frequencies, pronounced reshaping of absorption and dispersion curves, and two orders of magnitude enhancement in Kerr nonlinearity due to the presence of a wetting layer.

2012

We report on the development of a new generation of high power ultrashort pulse quantum dot lasers with tapered gain section. Two device designs are proposed and fabricated, with different total lengths and absorber to gain section length ratios. These designs have been informed by numerical simulations of the dynamic mode locking regimes and their dependence on the structural parameters. One device design demonstrated a record high peak power of 17.7 W with 1.26 ps pulse width and a second design enabled the generation of a Fourier limited 672 fs pulse width with a peak power of 3.8 W. A maximum output average power of 288 mW with 28.7 pJ pulse energy was also attained. In addition, the integrated timing jitter of 2.6 ps and far field patterns are demonstrated.

International Journal of Optics and Applications, 2014

In recent years, effects that are concerned with quantum nature of light have attracted too attention. The more the devices become smaller, the quantum effects become more apparent. Single photon sources are the essential devices in many quantum information processes, such as quantum key distribution. One way for realization of single photon sources is to exploit quantum dots. Single quantum dot has the ability of single photon emission, which can be analyzed by quantum electrodynamics. Emission from quantum dots under special circumstances has non-classically effects. In present paper, first we extract a novel relation for computing optical absorption coefficient in k.p framework and three dimensional carrier confinements. Then with this relation, we analyze an electrically driven single photon source that its wavelength is more tunable in the fabrication process. This tunability is a consequence of exploiting a quantum dot surrounded by a quantum well. Eight-band k.p modeling is used for extracting of energy levels and spectral analyzing of quantum dot. In this work, we investigated theoretically, the emission from an InAs/InxGa1-xAs quantum dot. Using InxGa1-xAs alloy around the InAs provides us a freedom for tuning the source in a wide range of wavelengths. Eventually it is shown that for x=0.53, the peak gain occurs in 1.3µm wavelength which is used widely in fast fiber optic communication.