Three terminal laser structure for high-speed modulation using dynamic carrier heating

A three-terminal laser structure is proposed as a means to achieve laser modulation using dynamic carrier heating. The injection of hot electrons, with energy tuned by variable joule heating over a high electric field region, is used to govern the carrier temperature in the active layer of a laser, while a separate heterojunction controls the injection rate. Simulations show the possibility of generating good-shaped picosecond optical pulses by modulating the voltage that controls the heating electric field

Hyperspherical calculations of low-energy rearrangement processes in dtμ

The results of accurate hyperspherical calculations of the reaction dμ(ni)+t→tμ(nf)+d between states of the ni=nf=1 and ni=nf=2 manifolds for zero total angular momentum of the collision system are reported. A parametrization of the threshold behavior of the ground-to-ground?state muon transfer cross section in the spirit of the effective range theory is discussed

Quantum-mechanical and semiclassical study of the collinear three-body Coulomb problem: Inelastic collisions below the three-body disintegration threshold

A quantum-mechanical (QM) and semiclassical (SC) study of inelastic collisions in collinear three-body Coulomb systems below the three-body disintegration threshold is presented. The QM results are obtained by solving the stationary Schr?dinger equation in hyperspherical coordinates using the slow/smooth variable discretization method. After appropriate rescaling of the hyperspherical coordinates, an asymptotic parameter 0?h?1 that depends only on the masses of particles and has the meaning of an effective Planck’s constant for the motion in hyperradius emerges. The SC results are obtained in the leading order approximation of the asymptotic expansion in h . The main attention is paid to investigating how the SC and QM results converge as h→0 . It is shown that the overall agreement for a wide spectrum of systems and processes is surprisingly good even for h?1 . However, because of interference effects the convergence is not monotonic, and the SC results may be grossly in error in the situations where a destructive interference occurs. The analysis of hidden crossings clarifies mechanisms of the nonadiabatic transitions. It is shown that if the oppositely charged particle is located between the two others, the nonadiabatic transitions occur near the top of the potential barrier via the well-known T series of hidden crossings. If it is located on one end of the system, then there is no potential barrier for real values of the angular variable, but there still exists an extremum in the complex plane; the mechanism of nonadiabatic transitions in this case is called the complex T series of hidden crossings

Interference effects in the decay of resonance states in three-body Coulomb systems

The lowest 1Se resonance state in a family of symmetric three-body Coulomb systems is systematically studied as a function of the mass-ratio M for the constituting particles. The Siegert pseudostate method for calculating resonances is described and accurate results obtained by this method for the resonance position E(M) and width Γ(M) in the interval 0<~M<~30 are reported. The principal finding of these calculations is that the function Γ(M) oscillates, almost vanishing for certain values of M, which indicates the existence of an interference mechanism in the resonance decay dynamics. To clarify this mechanism, a simplified model obtained from the three-body Coulomb problem in the limit M→∞ is analyzed. This analysis extends the range of M up to M=300 and confirms that Γ(M) continues to oscillate with an increasing period and decreasing envelope as M grows. Simultaneously it points to semiclassical theory as an appropriate framework for explaining the oscillations. On the basis of Demkov’s construction, the oscillations are interpreted as a result of interference between two paths of the resonance decay on the Riemann surface of adiabatic potential energy, i.e., as a manifestation of the Stueckelberg phase. It is shown that the implications of this interpretation for the period and envelope of the oscillations of Γ(M) agree excellently with the calculated results

Effect of nuclear motion on tunneling ionization rates of molecules

ISSN:1094-1622ISSN:0556-2791ISSN:1050-294

Resonant-state expansion of the Green's function of open quantum systems

Our series of recent work on the transmission coefficient of open quantum systems in one dimension will be reviewed. The transmission coefficient is equivalent to the conductance of a quantum dot connected to leads of quantum wires. We will show that the transmission coefficient is given by a sum over all discrete eigenstates without a background integral. An apparent "background" is in fact not a background but generated by tails of various resonance peaks. By using the expression, we will show that the Fano asymmetry of a resonance peak is caused by the interference between various discrete eigenstates. In particular, an unstable resonance can strongly skew the peak of a nearby resonance.Comment: 7 pages, 7 figures. Submitted to International Journal of Theoretical Physics as an article in the Proceedings for PHHQP 2010 (http://www.math.zju.edu.cn/wjd/