112 research outputs found
Terahertz Radiation Detection by Field Effect Transistor in Magnetic Field
We report on terahertz radiation detection with InGaAs/InAlAs Field Effect
Transistors in quantizing magnetic field. The photovoltaic detection signal is
investigated at 4.2 K as a function of the gate voltage and magnetic field.
Oscillations analogous to the Shubnikov-de Haas oscillations, as well as their
strong enhancement at the cyclotron resonance, are observed. The results are
quantitatively described by a recent theory, showing that the detection is due
to rectification of the terahertz radiation by plasma waves related
nonlinearities in the gated part of the channel.Comment: 4 pages, 3 figure
Solitons in coupled atomic-molecular Bose-Einstein condensates in a trap
We consider coupled atomic-molecular Bose-Einstein condensate system in a
quasi-one-dimensional trap. In the vicinity of a Feshbach resonance the system
can reveal soliton-like behavior. We analyze bright soliton solutions for the
system in the trap and in the presence of the interactions between particles.
We show that with increasing number of particles in the system two bright
soliton solutions start resembling dark soliton profiles known in an atomic
Bose-Einstein condensate with repulsive interactions between atoms. We analyze
also methods for experimental preparation and detection of the soliton states.Comment: 7 pages, 7 figures, published versio
Proceedings of the XXXVI International School of Semiconducting Compounds
The new approach to the understanding of intrashallow donor transition in the reduced dimensionality systems is presented. The magnetospectroscopy experiments done on the CdTe/CdMgTe quantum well based samples, uniformly n-doped, show indications that the surprising lack of spectral sensitivity on applied photon energy can be understood as a result of sample response coming from its different regions. This "non spectroscopic" behaviour (in a sense of the Zeeman splitting) is a consequence of the properties of systems with reduced dimensionality where variety of centre locations in the structure results in continuous density of states available for absorption
Optical limiting efficiency of an electroactive bis-iminopyridine ligand and its zinc complex
An electroactive based bis-iminopyridine ligand has been synthesized by a condensation reaction between (4-(6,7-dimethyldithio-tetrathiafulvalene)-aniline) with 2,6-diformylpyridine. The complexation of this ligand with ZnCl2 afforded a tetrahedral neutral Zinc metal complex. Nonlinear optical measurements of these structures have given good results in picosecond regime. The nonlinear absorption of the ligand was significantly enhanced upon complexation with ZnCl2. This prompted us to conduct the experiment of optical limiting at wavelength 532nm. The nonlinear absorption properties of these structures were studied and compared to the reference material C60
Dependence of the Third Order Nonlinear Optical Susceptibility on Concentration and Peripheral Substituent of Metallophthalocyanines
Third order nonlinear optical properties of metallophthalocyanines (MPcs) were investigated using degenerate four wave mixing (DFWM) method. We also studied how the replacement of peripheral substituent around the MPcs cores correlates with nonlinear optical properties. Therefore third order nonlinear optical susceptibilities (χ<3>) of MPcs with liquid crystal (MPcs-LC) were investigated. We found that the χ<3> values of MPcs-LC increase in comparison with the corresponding values of MPcs. We supposed that this is caused by the increase of the charge transfer effects and change of the dipole moments of the molecule with the increase of molecules dimension
Optical limiting efficiency of an electroactive bis-iminopyridine ligand and its zinc complex
An electroactive based bis-iminopyridine ligand has been synthesized by a condensation reaction between (4-(6,7-dimethyldithio-tetrathiafulvalene)-aniline) with 2,6-diformylpyridine. The complexation of this ligand with ZnCl2 afforded a tetrahedral neutral Zinc metal complex. Nonlinear optical measurements of these structures have given good results in picosecond regime. The nonlinear absorption of the ligand was significantly enhanced upon complexation with ZnCl2. This prompted us to conduct the experiment of optical limiting at wavelength 532nm. The nonlinear absorption properties of these structures were studied and compared to the reference material C60
Standard and Embedded Solitons in Nematic Optical Fibers
A model for a non-Kerr cylindrical nematic fiber is presented. We use the
multiple scales method to show the possibility of constructing different kinds
of wavepackets of transverse magnetic (TM) modes propagating through the fiber.
This procedure allows us to generate different hierarchies of nonlinear partial
differential equations (PDEs) which describe the propagation of optical pulses
along the fiber. We go beyond the usual weakly nonlinear limit of a Kerr medium
and derive an extended Nonlinear Schrodinger equation (eNLS) with a third order
derivative nonlinearity, governing the dynamics for the amplitude of the
wavepacket. In this derivation the dispersion, self-focussing and diffraction
in the nematic are taken into account. Although the resulting nonlinear
may be reduced to the modified Korteweg de Vries equation (mKdV), it also has
additional complex solutions which include two-parameter families of bright and
dark complex solitons. We show analytically that under certain conditions, the
bright solitons are actually double embedded solitons. We explain why these
solitons do not radiate at all, even though their wavenumbers are contained in
the linear spectrum of the system. Finally, we close the paper by making
comments on the advantages as well as the limitations of our approach, and on
further generalizations of the model and method presented.Comment: "Physical Review E, in press
Field Effect Transistors for Terahertz Detection: Physics and First Imaging Applications
Resonant frequencies of the two-dimensional plasma in FETs increase with the
reduction of the channel dimensions and can reach the THz range for sub-micron
gate lengths. Nonlinear properties of the electron plasma in the transistor
channel can be used for the detection and mixing of THz frequencies. At
cryogenic temperatures resonant and gate voltage tunable detection related to
plasma waves resonances, is observed. At room temperature, when plasma
oscillations are overdamped, the FET can operate as an efficient broadband THz
detector. We present the main theoretical and experimental results on THz
detection by FETs in the context of their possible application for THz imaging.Comment: 22 pages, 12 figures, review pape
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