WorldCat Identities

Pandey, Lakshmi N.

Overview
Works: 12 works in 12 publications in 1 language and 12 library holdings
Publication Timeline
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Most widely held works by Lakshmi N Pandey
Effect of Light-Induced Drift in Confined Semiconductors Heterostructures( Book )

1 edition published in 1992 in English and held by 1 WorldCat member library worldwide

The effect of light-induced drift (LID) in gases, predicted by Gel'mukhanov and Shalagin and observed later, is manifested in mechanical drift of the absorbing atoms (molecules) in response to optical excitation. The effect of LID takes place if the atom interaction with light is velocity-dependent (due to the Doppler effect), the spectrum of the exciting radiation is asymmetric with respect to the the absorption line, and the absorbing molecules experience collisions with a buffer gas, with the collision rate dependent upon their internal state. The idea of LID is the following. Suppose for the sake of definiteness that the collision frequency of the absorbing molecules with the buffer is greater in the excited state and that the exciting light is red-shifted with respect to the absorption contour. Then due to the Doppler shift, the radiation interacts mainly with the counter-moving molecules, which undergo transitions into an excited state, in which their friction upon the buffer component is increased. Due to this increase, the counter-flying molecules are slowed down, while the molecules moving in the direction of light are not affected. The net effect is a drift of the absorbing component in the direction of light. The drift alternates its direction with the change of signs of either the detaining or the difference in the collision frequencies
Intersubband Transitions in Quantum-Well Heterostructures with Delta-Doped Barriers( )

1 edition published in 1992 in English and held by 0 WorldCat member libraries worldwide

A single quantum well doped by a negative delta-function potential (Delta-potential) in the barrier regions is analyzed in terms of the optical transitions in between subbands. The first two states of the quantum well do not change at all as a function of the strength of the delta-potential up to a certain value, whereas the third one gets lowered almost exponentially. An important point is that the delta-potential brings a state from the continuum to the bound region. There is a range of the strength of the delta-potential during which the transition energy from the first to second state decreases rapidly, and at a certain strength the first an second states disappear, and the third and fourth, which have been brought from the continuum, take their places. The oscillator strengths of the allowed transitions have a kind of oscillatory behavior in that range
Escape Time from a Biased Asymmetric Double Quantum Well( )

1 edition published in 1990 in English and held by 0 WorldCat member libraries worldwide

The escape time from the quasibound states of an asymmetrical structure consisting of a narrow well and a wide well separated by a relatively thick barrier under bias has been calculated. As expected, a monotonic decrease in the escape time from the ground state of the wide well as a function of applied voltage has been found. However, the variation of the escape times from the ground state of the narrow well and the first-excited state of the wide well versus applied voltage form a minimum at a common point. This is the signature of resonant tunneling when these two states almost coincide. (jhd)
Reply to Comment on 'Light-Induced Drift of Quantum-Confined Electrons in Semiconductor Heterostructures' by A.A. Grinberg and S. Luryi( )

1 edition published in 1991 in English and held by 0 WorldCat member libraries worldwide

Width Anomaly in Resonant Tunneling Structures( )

1 edition published in 1991 in English and held by 0 WorldCat member libraries worldwide

Anomalous behavior is found in the variation of width and position of the resonance as a function of the effective mass Hamiltonian parameter
Theoretical Studies of Electron Transport in Quantum-Well Structures( )

1 edition published in 1990 in English and held by 0 WorldCat member libraries worldwide

The study of resonant tunneling structures (RTS) has become increasingly important because of possible device applications and also because of the basic physics they involve. Within the static picture we have calculated the dwell time, i.e., the average time an electron spends inside an RTS. The actual time involved in the tunneling process can be described by the solution of the time-dependent effective mass Schrodinger equation (TDEMSE), and a code based on the fast Fourier transform method is developed to solve the TDEMSE for a potential profile such as RTS. The physical properties of an RTS investigated are the build-up time, which is the time taken by an electron to accumulate probability inside the well, and the escape time. (JHD)
Photoinduced Electron Transfer Counter to the Bias Field in Coupled Quantum Wells( )

1 edition published in 1992 in English and held by 0 WorldCat member libraries worldwide

Optical excitation of electrons in an asymmetric double quantum well is theoretically examined. The well is biased to align the excited levels and permit resonant electron tunneling. Emphasis is made on the photoinduced transfer of electrons counter to the bias electric field force. A density- matrix approach is developed to describe optical excitations in the presence of an arbitrary dephasing. The excitation profiles obtained for cases of different dephasing reveal the full range of tunneling coupling between the wells from completely coherent to incoherent (stepwise)
Theoretical Study of Phase-Shifted Quantum Beats in Time-Resolved Luminescence Spectra from a Biased Asymmetric Double Quantum Well( )

1 edition published in 1992 in English and held by 0 WorldCat member libraries worldwide

Analytical expressions have been developed for time-dependent luminescence intensities for a practically feasible asymmetric double quantum well under bias and numerically demonstrated to elucidate the characteristic of phase-shifted quantum beats. It is clear analytically as well as numerically that the magnitude of the tunneling interaction can be quantitatively estimated by the beat modulation depth
Light-Induced Electron Transfer Counter to an Electric Field Force in an Asymmetric Double Quantum Well( )

1 edition published in 1992 in English and held by 0 WorldCat member libraries worldwide

Electron transfer counter to an electric-field force is predicted for an asymmetrical double quantum well subjected to a dc bias in response to optical (far ir) excitation of an intersubband electronic transition. This transfer exhibits a resonance enhancement when the bias electric field aligns the excited levels in the wide and narrow wells. The transfer effect is driven by the quantum-mechanical delocalization caused by the coherent resonant tunneling which prevails over the electric force. The effect brings about photoinduced increase of the potential difference at the double well and a transient electric current opposite to the direction favored by the bias
Position Expectation Value and Oscillator Strength of a Biased Asymmetric Quantum Well( )

1 edition published in 1990 in English and held by 0 WorldCat member libraries worldwide

The change in the position expectation values of an electron in the first three quasibound states of the structure as a function of the external (biased) voltage is calculated. At the resonance voltage, the most probable position to find an electron in the second and third quasibound states lies in the barrier separating the two wells, and these two states interchange their identities, meaning that the ground state of the narrow well becomes the first- excited state of the wide well and vice versa. Keywords: Quantum well, Biased asymmetric, Oscillator strength, Position expectation, Resonance, State parties
Light-Induced Drift of Quantum-Confined Electrons in Semiconductor Heterostructures( )

1 edition published in 1990 in English and held by 0 WorldCat member libraries worldwide

The effect of light-induced drift of quantum-confined electrons in semiconductor heterostructures is predicted. The effect manifests itself as the electric current in the heterostructure plane in response to optical excitation with the frequency close, but not exactly equal, to a transition frequency between levels in the heterostructure. The current reverses its direction with a change in the detuning sign, and vanishes if the radiation polarization is normal to the heterostructure plane. (js)
Kinetics of Intersubband Optical Excitation and Photoinduced Electron Transfer in an Asymmetric Double Quantum Well( )

1 edition published in 1992 in English and held by 0 WorldCat member libraries worldwide

Optical excitation of electrons in an asymmetric double quantum well is theoretically examined. The well is biased to align the excited levels and permit resonant electron tunneling. Emphasis is made on the photoinduced transfer of electrons counter to the bias electric field force. Systems with a weak polarization relaxation (dephasing), are studied using the conventional technique of the Schrodinger equation. A density matrix approach is developed to describe optical excitations in the presence of an arbitrary dephasing. Quantum beats, which follow a short-pulse excitation of the double well, are shown to crucially depend on the dephasing. The excitation profiles obtained for cases of different dephasing reveal the full range of tunneling coupling between the wells from completely coherent to incoherent (stepwise)
 
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English (12)