G. Ya. Slepyan

Theory of multiwall carbon nanotubes as waveguides and antennas in the infrared and the visible regimes

The propagation of azimuthally symmetric guided waves in multiwalled carbon nanotubes (MWCNTs) was analyzed theoretically in the mid-infrared and the visible regimes. The MWCNTs were modeled as ensembles of concentric, cylindrical, conducting shells. Slightly attenuated guided waves and antenna resonances due to the edge effect exist for not-too-thick MWCNTs in the far- and mid-infrared regimes. Interband transitions hinder the propagation of guided waves and have a deleterious effect on the performance of a finite-length MWCNT as an antenna. Propagation of surface-plasmon waves along an MWCNT with a gold core was also analyzed. In the near-infrared and the visible regimes, the shells behave effectively as lossy dielectrics suppressing surface-plasmon-wave propagation along the gold core.

Propagation, Scattering and Dissipation of Electromagnetic Waves

* Chapter 1: Introduction * Chapter 2: Surface-impedance technique for the study of dissipation processes in bodies with finite conductivity * Chapter 3: Normal modes in waveguides with losses * Chapter 4: Normal oscillations in resonators with losses * Chapter 5: Electromagnetic-wave diffraction by finitely conducting comb-shaped structures * Chapter 6: Dissipation in comb-shaped structures in inhomogeneous and anisotropic media * Chapter 7: Eigenmodes in corrugated waveguides and resonators with finitely conducting walls * Appendix 1: Shooting method and its modifications * Appendix 2: Expressions for current-density distributions in a microstrip line with a strip of finite thickness * Appendix 3: General formulae for the coefficients alpha(i)nm, ss(i)nm, gamma(i)nm, delta(i)nm

Thermal radiation from carbon nanotubes in the terahertz range.

The thermal radiation from an isolated finite-length carbon nanotube (CNT) is theoretically investigated both in near- and far-field zones. The formation of the discrete spectrum in metallic CNTs in the terahertz range is demonstrated due to the reflection of strongly slowed-down surface-plasmon modes from CNT ends. The effect does not appear in semiconductor CNTs. The concept of a CNT as a thermal nanoantenna is proposed.

Spontaneous decay of excited atomic states near a carbon nanotube.

The spontaneous decay process of an excited atom placed inside or outside a carbon nanotube is analyzed. Calculations have been performed for various achiral nanotubes. The effect of the nanotube surface is shown to increase the atomic spontaneous decay rate by up to 6 orders of magnitude compared with that of the same atom in vacuum. This increase is associated with nonradiative decay via surface excitations in the nanotube.

Strong electron-photon coupling in a one-dimensional quantum dot chain: Rabi waves and Rabi wave packets

We predict and theoretically investigate the new coherent effect of nonlinear quantum optics -- spatial propagation of Rabi oscillations (Rabi waves) in one-dimensional quantum dot (QD) chain. QD-chain is modeled by the set of two-level quantum systems with tunnel coupling between neighboring QDs. The space propagation of Rabi waves in the form of traveling waves and wave packets is considered. It is shown, that traveling Rabi waves are quantum states of QD-chain dressed by radiation. The dispersion characteristics of traveling Rabi waves are investigated and their dependence on average number of photons in wave is demonstrated. The propagation of Rabi wave packets is accompanied by the transfer of the inversion and quantum correlations along the QD-chain and by the transformation of quantum light statistics. The conditions of experimental observability are analyzed. The effect can find practical use in quantum computing and quantum informatics.

Matter Coupling to Strong Electromagnetic Fields in Two-Level Quantum Systems with Broken Inversion Symmetry

We demonstrate theoretically the parametric oscillator behavior of a two-level quantum system with broken inversion symmetry exposed to a strong electromagnetic field. A multitude of resonance frequencies and additional harmonics in the scattered light spectrum as well as an altered Rabi frequency are predicted to be inherent to such systems. In particular, dipole radiation at the Rabi frequency appears to be possible. Since the Rabi frequency is controlled by the strength of the coupling electromagnetic field, the effect can serve for the frequency-tuned parametric amplification and generation of electromagnetic waves. Manifestation of the effect is discussed for III-nitride quantum dots with strong built-in electric field breaking the inversion symmetry. Terahertz emission from arrays of such quantum dots is shown to be experimentally observable.

TWT-gyrotrons: Non-linear theory, optimization and analysis

The present paper describes a relativistic non-linear theory of waveguide gyrotrons with the irregular electrodynamic system and inhomogeneous magnetostatic field, taking into account space-charge quasi-static and dynamic forces effect and an electron velocity angle spread. Efficiency- and amplification band optimized gyrotron variants of various designs with a circular waveguide operating H01 mode and an H11 mode are presented. Optimum waveguide systems and magnetostatic field distribution profiles are determined. The main effects due to the space-charge forces, electron velocity angle spread and dynamic deformation of the amplification band have been investigated. A comparison is drawn between gyrotron amplifiers operating with the H01 mode and H11 mode. The technique of synthetizing a gyro-TWT output device by frequency dependence of the operating-mode reflection coefficient has been reported.

Gaussian pulse propagation in a linear, lossy chiral medium

Pulse propagation in a linear, lossy chiral medium with single-resonance dispersion is considered. A relevant time-domain Green function is derived, after assuming that the medium is weakly dispersive. As an example, the propagation of Beltrami–Gaussian pulses in the slow-amplitude approximation is analyzed and graphically explained.

HIGH-ORDER OPTICAL HARMONIC GENERATION ON CARBON NANOTUBES: QUANTUM-MECHANICAL APPROACH

The high harmonic generation by a single-wall carbon nanotube (CNT) due to the interaction with femtosecond laser pulses is investigated. The analysis utilizes the quantum kinetic equations for π-electrons with both intra-band and inter-band transitions. Nonperturbative approach using numerical solution of the quantum kinetic equations in the time domain has been developed and the density of the axial electric current in CNT has been calculated. The amplitude of this current and the conversion efficiency in dependence on the number of the high-order harmonics, the CNT type, the frequency and the intensity of the driving field have been investigated.

Microscopic theory of quantum dot interactions with quantum light: Local field effect

A theory of both linear and nonlinear electromagnetic responses of a single quantum dot (QD) exposed to quantum light, accounting for depolarization induced local field has been developed. Based on the microscopic Hamiltonian accounting for the electron-hole exchange interaction, an effective two-body Hamiltonian has been derived and expressed in terms of the incident electric field, with a separate term describing the QD depolarization. The quantum equations of motion have been formulated and solved using the Hamiltonian for various types of the QD optical excitation, such as Fock qubit, coherent fields, vacuum state of electromagnetic field, and light with arbitrary photonic state distribution. For a QD exposed to coherent light, we predict the appearance of two oscillatory regimes in the Rabi effect separated by the bifurcation. In the first regime, the standard collapse-revival phenomenon does not reveal itself and the QD population inversion is found to be negative, while in the second one, the collapse-revival picture is found to be strongly distorted as compared to that predicted by the standard Jaynes-Cummings model. For the case of QD interaction with an arbitrary quantum light state in the linear regime, it has been shown that the local field induces a fine structure of the absorbtion spectrum. Instead of a single line with frequency corresponding to the exciton transition frequency, a duplet appears, with one component shifted by the amount of the local field coupling parameter. It has been demonstrated that the strong light--matter coupling regime arises in the weak-field limit. A physical interpretation of the predicted effects has been proposed.