Ajit Kumar Srivastava

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Under the illumination of intense off-resonant laser light, the electronic states of semiconductors are strongly modified, or dressed, by the oscillating electric field. We present a framework using linear combination of atomic orbital band theory to calculate the dressed band structure and optical absorption spectrum of covalent semiconductors in an(More)
We report the direct observation of spin-singlet dark excitons in individual single-walled carbon nanotubes through low-temperature micro-magneto-photoluminescence spectroscopy. A magnetic field (B) applied along the tube axis brightened the dark state, leading to the emergence of a new emission peak. The peak rapidly grew in intensity with increasing B at(More)
We report the observation of large (approximately 40%) laser-induced above-band-gap transparency in GaAs at room temperature. The induced transparency is present only during the pulse width of the driving midinfrared laser pulses and its spectral shape is consistent with a laser-induced blueshift of the band edge. Our simulations based on the dynamic(More)
Honey-bee bites which require urgent hospitalization is very rare. It is mainly seen as occupational hazards in farmers, tree dwellers and honey collectors. Common clinical presentation includes minor localized reactions in form of swelling and redness sometimes anaphylactic reaction. Infrequent major complications reported from different studies include(More)
A monolayer of a transition metal dichalcogenide such as WSe 2 is a two-dimensional direct-bandgap valley-semiconductor 1,2 having an eeective honeycomb lattice structure with broken inversion symmetry. The inequivalent valleys in the Brillouin zone could be selectively addressed using circularly polarized light fields 3–5 , suggesting the possibility for(More)
Single-walled carbon nanotubes (SWNTs) are fascinating materials to study one-dimensional photophysics. Their optical properties are strongly affected by strong Coulomb interactions and are determined by " excitons " which represent the quantum of polarization in non-metallic solids. In this thesis dissertation we have experimentally investigated both the(More)
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