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Full-Text Articles in Physical Sciences and Mathematics
Induced Absorption Dynamics In Quantum Dot Based Waveguide Electroabsorbers, T. Piwonski, Jaroslaw Pulka, Guillaume Huyet, Et. Al.
Induced Absorption Dynamics In Quantum Dot Based Waveguide Electroabsorbers, T. Piwonski, Jaroslaw Pulka, Guillaume Huyet, Et. Al.
Physical Sciences Publications
Two-color pump-probe measurements are used to study the carrier dynamics of InAs/GaAs quantum dots in a waveguide structure under reverse bias conditions. For the case of initially populating the ground state (GS), we find relaxation dynamics that include both absorptive and bleaching components in the excited state (ES) wavelength range. We reproduce the main features of this induced absorption dynamics using a simple model with an additional term for induced absorption at the ES due to carriers injected at the GS. The induced absorption dynamics includes multiple recovery timescales which can be attributed to phonon-assisted processes of GS/ES interaction.
Veritas Search For Vhe Gamma-Ray Emission From Dwarf Spheroidal Galaxies, P. T. Reynolds, Et. Al.
Veritas Search For Vhe Gamma-Ray Emission From Dwarf Spheroidal Galaxies, P. T. Reynolds, Et. Al.
Physical Sciences Publications
Indirect dark matter searches with ground-based gamma-ray observatories provide an alternative for identifying the particle nature of dark matter that is complementary to that of direct search or accelerator production experiments. We present the results of observations of the dwarf spheroidal galaxies Draco, Ursa Minor, Boötes 1, and Willman 1 conducted by the Very Energetic Radiation Imaging Telescope Array System (VERITAS). These galaxies are nearby dark matter dominated objects located at a typical distance of several tens of kiloparsecs for which there are good measurements of the dark matter density profile from stellar velocity measurements. Since the conventional astrophysical background …
Refractive Index Dynamics Of Quantum Dot Based Waveguide Electroabsorbers, T. Piwonski, Jaroslaw Pulka, Guillaume Huyet, Et. Al.
Refractive Index Dynamics Of Quantum Dot Based Waveguide Electroabsorbers, T. Piwonski, Jaroslaw Pulka, Guillaume Huyet, Et. Al.
Physical Sciences Publications
The refractive index dynamics of InAs/GaAs quantum dot based waveguide absorbers is studied using heterodyne pump-probe measurements. Absorption reduction due to the pump can be accompanied by either positive or negative refractive index changes depending on the wavelength used. This change in sign of the phase amplitude coupling can be understood by considering the atomlike nature of the quantum dot transitions involved.
Veritas 2008-2009 Monitoring Of The Variable Gamma-Ray Source M 87, P. T. Reynolds, Et. Al.
Veritas 2008-2009 Monitoring Of The Variable Gamma-Ray Source M 87, P. T. Reynolds, Et. Al.
Physical Sciences Publications
M 87 is a nearby radio galaxy that is detected at energies ranging from radio to very high energy (VHE) gamma rays. Its proximity and its jet, misaligned from our line of sight, enable detailed morphological studies and extensive modeling at radio, optical, and X-ray energies. Flaring activity was observed at all energies, and multi-wavelength correlations would help clarify the origin of the VHE emission. In this paper, we describe a detailed temporal and spectral analysis of the VERITAS VHE gamma-ray observations of M 87 in 2008 and 2009. In the 2008 observing season, VERITAS detected an excess with a …