Quantum and semiclassical Cooper–pair tunneling in finite systems

We derive analytic solutions for the tunneling dynamics of two weakly coupled finite BCS–condensates. Pairing interaction between the finite–size condensates is taken into account. Using particle–number dependent chemical potentials the time–dependent transfer of Cooper pairs is obtained from a phenomenological calculation. The results of this theory are compared to a microscopic calculation within the quasispin formulation in its semiclassical limit. In both cases the tunneling current can be mapped onto the motion of a simple pendulum: The results are analogous to the Josephson current between two superconductors and can be used as a starting point to include quantum fluctuations and Josephson radiation.

Coherent anti-Stokes Raman spectroscopy: Understanding the essentials

This paper is a brief overview to coherent anti- Stokes Raman spectroscopic technique and introduces the strengths and barriers to its use all based on the interpretation of simple theoretical formulae. The use of the Gaussian ultrashort pulses is highlighted as a practical elucidatory reconstruction tool of coherent Raman spectra. The paper presents the integral formulae for coherent anti-Stokes and Stokes Raman scattering, and discusses the closed-form solutions, its complex error function, and the delay time formula for enhancement of the inferred pure coherent Raman spectra. As an example, the timeresolved coherent Stokes Raman scattering experimental observations are quantitatively elucidated.Understanding the essentials of coherent Raman spectroscopy, therefore, promotes the importance of a number of experiments including the ones utilizing a broadband excitation with a narrowband delayed probing for successful background suppression.

Suppression of coherent scattering by coherent population trapping on molecular vibrational levels

Raman scattering has been studied in molecular media. The role of rotational levels has been investigated. It is shown that the molecular vibrational coherence strongly depends on the effect of coherent population trapping for rotational levels. The obtained results are important for application of Raman spectroscopy to molecular detection for engineering, chemical, and biological applications.

Second-harmonic generation in a sphere

We consider nonlinear muti-wave mixing in a sphere. We compare the efficiency of wave mixing in a sphere with the efficiency in a bulk or in the slab where, as well-known, the phase-matching plays an important role. We have found the optimal conditions for nonlinear generation in a sphere. The obtained results can be applied to coherent Raman microscopy and allow us to maximize the signal for arbitrary shpae of nanoparticles.

Engineering semiconductor hybrids for sensing

The effect of screening of the coulomb interaction between two layers of two-dimensional electrons, such as in graphene, by a highly doped semiconducting substrate is investigated. We employ the random-phase approximation to calculate the dispersion equation of this hybrid structure in order to determine the plasmon excitation spectrum. When an electric current is passed through a layer, the low-frequency plasmons in the layer may bifurcate into separate streams due to the current-driving effect. At a critical wave vector, determined by the separation between layers and their distance from the surface, their phase velocities may be in opposite directions and a surface plasmon instability leads to the emission of radiation. Applications to detectors and other electromagnetic devices exploiting nano-plasmonics are discussed.

Modes and Noise Propagation in Phase Space

We show that phase space methods developed for quantum mechanics, such as the Wigner distribution, can be effectively used to study the evolution of nonstationary noise in dispersive media. We formulate the issue in terms of modes and show how modes evolve and how they are effected by sources.We show that each mode satisfies a Schrödinger type equation where the “Hamiltonian” may not be Hermitian. The Hamiltonian operator corresponds to dispersion relationwhere thewavenumber is replaced by the wavenumber operator. A complex dispersion relation corresponds to a non Hermitian operator and indicates that we have attenuation. A number of examples are given.

Magneto-Optical Trap for Preparation and Study of Rydberg Matter

Our goal is the preparation and study of ultracold plasma and Rydberg matter. We assembled an experimental setup for laser cooling of lithium atoms in a magneto-optical trap (MOT). Trapping of

Parametric generation of high frequency coherent light in negative index materials and materials with strong anomalous dispersion

We demonstrate the possibility of generation of coherent radiation with tunable frequencies higher than the frequency of the driving field v

Amplifier Noise Based Optical Steganography with Coherent Detection

We summarize the principle and experimental setup of optical steganography based on amplified spontaneous emission (ASE) noise. Using ASE noise as the signal carrier, optical steganography effectively hides a stealth channel in both the time domain and the frequency domain. Coherent detection is used at the receiver of the stealth channel. Because ASE noise has short coherence length and random phase, it only interferes with itself within a very short range. Coherent detection requires the stealth transmitter and stealth receiver to precisely match the optical delay,which generates a large key space for the stealth channel. Several methods to further improve optical steganography, signal to noise ratio, compatibility with the public channel, and applications of the stealth channel are also summarized in this review paper.

Effect of Fano Resonance in photovoltaic

We have shown that the Fano interference in the decay channels of a three-level system can lead to considerably different absorption and emission profiles. We found that a coherence can be built up in the ground state doublet, with strength depending on a coupling parameter that arises from the Fano interference. The coherence can in principle lead to breaking of the detail balance between the absorption and emission processes in atomic systems.