Increase Of Plasma Frequency Research Articles

The impact of lutetium doping on the structure and physical characteristics of aluminum arsenide quantum dots

This report mentioned the synthesis of self-assembly Al1-xLuxAs quantum dot nanocrystals using the L-Glutamine-assisted wet chemical route. The effect of Lu-doping on the structural phase, lattice strain, and deformation lattice energy was studied. The morphology and elemental compositions were emphasized using transmission electron microscopy, selected area of electron diffraction, and energy dispersive X-ray spectroscopy. The effect of Lu-doping on the oxidation state and vibrational modes was studied using X-ray photoelectron spectroscopy and Raman scattering spectroscopy. The influence of Lu-dopant on the optical bandgap and Urbach tail energy of AlAs nanocrystals was investigated. The tendency of Lu doping to create localized levels inside the band gap of AlAs gives rise to an increase in plasma frequency and a decrease in the high-frequency dielectric constant. The Lu-dopant improved the conductivity and the charge carrier mobility of AlAs nanocrystals. The luminescence measurements revealed the ability of Lu-dopant to suppress the crystal defects of the AlAs nanocrystals. The Lu doping improved the quantum yield (84 %) and the luminescent emission spectra of the AlAs QDs by 7-fold. The prepared self-assembly Al1-xLuxAs quantum dots revealed great encouragement for developing Al1-xLuxAs quantum dot diode lasers and optical broadbands.

Structural phase transition and manifestation of eddy currents in IR reflection spectra of PbSnTe semiconductor films

Infrared reflection spectra of thin (∼60 nm) Pb1−x SnxTe (x = 0.25, 0.53, 0.59) films grown by molecular beam epitaxy on GaAs/CdTe hybrid substrates have been measured at frequencies from 20 to 5500 cm−1 and temperatures from 5 to 300 K. The spectra have been used to determine temperature-dependent transverse phonon and plasmon frequencies in the films, which has made it possible to identify a structural phase transition at TC ≈ 50 K. The plasma frequency of the films has been shown to increase with decreasing band gap on cooling from 300 to 77 K. The increase in plasma frequency is mainly attributable to the increase in carrier concentration and a transition of the carriers from vortex states on the film surface to the valence band.

Self-focusing of a laser beam in the rippled density magnetoplasma

In the present paper, we have investigated the self-focusing of intense laser beam in rippled density magnetoplasma. The differential equation for the beam width parameter is obtained by following WKB and paraxial approximations and solved it numerically. The behaviour of beam width parameter with dimensionless distance of propagation is extensively investigated for different values of laser and plasma parameters and is strongly influenced by the magnetic field. The results are discussed and presented graphically. It is seen that the density ripple of suitable wave number increases the self-focusing property of laser beam in magnetoplasma. Meanwhile, an increase in the values of magnetic field increases the strength of the self-focusing, especially in shorter distance of propagation. Furthermore, increase in plasma frequency (plasma density) causes more reduction in the spot size of laser beam and consequently increases the rate of self-focusing of laser beam in magnetoplasma.

Properties of surface modes in one dimensional plasma photonic crystals

Properties of surface modes supported at the interface of air and a semi-infinite one dimensional plasma photonic crystal are analyzed. The surface mode equation is obtained by using transfer matrix method and applying continuity conditions of electric fields and its derivatives at the interface. It is observed that with increase in the width of cap layer, frequencies of surface modes are shifted towards lower frequency side, whereas increase in tangential component of wave-vector increases the mode frequency and total energy carried by the surface modes. With increase in plasma frequency, surface modes are found to shift towards higher frequency side. The group velocity along interface is found to control by cap layer thickness.

TO CONTROL THE PROPAGATION CHARACTERISTIC OF ONE-DIMENSIONAL PLASMA PHOTONIC CRYSTAL USING EXPONENTIALLY GRADED DIELECTRIC MATERIAL

The efiect of exponentially graded material on the modal dispersion characteristics, group velocity and efiective group index as well as phase index of refraction of a binary One-Dimensional Plasma Photonic Crystals (1D-PPCs) has been studied. The dispersion relation is derived by solving Maxwell's equations and using the transfer matrix method. The anomalous dispersion characteristics are observed for difierent values of selection parameters. The introduction of graded dielectric layers in 1D-PPCs provides additional parameters for controlling the propagation characteristics of 1D-PPCs. Also, the band gap is shown to become larger with the increase of plasma frequency and plasma width. Hence the structure having plasma and exponentially graded dielectric layer in unit cell is more useful for controlling and tuning of the plasma functioning devices than the structure having plasma and homogeneous dielectric layer in one unit cell.

Modal propagation characteristics of EM waves in ternary one-dimensional plasma photonic crystals

We have theoretically studied the modal dispersion characteristics, group velocity, and effective group as well as phase index of refraction of ternary one-dimensional (1D) plasma photonic band gap (PBG) structure having periodic multilayers of three different materials in one unit cell. The dispersion characteristics related for such structure is derived by solving Maxwell wave equation based on principle of Kronig–Penny model. From the computed results we observe that the dispersion characteristics of such structure also show the frequency gap and cutoffs as found in (binary) one-dimensional plasma photonic crystal. The frequency gap is shown to become larger with the increase of plasma frequency as well as plasma width. It is seen that such structure provide additional degree of freedom to control dispersion characteristic, group velocity and effective index of refraction compared to conventional one-dimensional plasma photonic crystal.

Magnetoreflection of Ion-Implanted Bismuth

ABSTRACTBi single crystals have been implanted with isoelectronic ions (As, Sb and Bi) and the electronic structur of these implanted materials has been studied using the magnetoreflection technique. Since the ion penetration depth and optical skin depths are of roughly the same magnitude, this technique provides a sensitive test for implantation-induced changes in the electronic structure. Explicitly, the magnetoreflection spectra show changes in lineshape, resonant frequency and in some cases the introduction of Landau level transitions forbidden in unimplanted bismuth. In particular, implantation-induced changes in the resonance lineshapes indicate an increase in plasma frequency as either the fluence of the implants or the ion size is increased. Further analysis of the data shows that the Lax model, which accounts for the magnetoreflection spectra of unimplanted bismuth, is equally applicable to bismuth implanted with isoelectronic ions. Our results yield measurable changes in the L-point band gap and smaller relative changes in the band parameter combination Eg/m* . The mechanism responsible for these changes in the electronic structure of bismuth is suggested.