SIMPLIFIED MODELING OF STEADY-STATE AND TRANSIENT BRILLOUIN GAIN IN MAGNETOACTIVE NON-CENTROSYMMETRIC SEMICONDUCTORS

2007 ◽  
Vol 21 (10) ◽  
pp. 603-614 ◽  
Author(s):  
M. SINGH ◽  
P. AGHAMKAR ◽  
P. K. SEN
Keyword(s):  
Magnetic Field ◽  
Steady State ◽  
Pulse Duration ◽  
Brillouin Scattering ◽  
Pump Intensity ◽  
Gain Coefficient ◽  
Analytical Investigation ◽  
Transient Regimes ◽  
Brillouin Gain ◽  
Simplified Modeling

With the aid of a hydrodynamic model of semiconductor-plasmas, a detailed analytical investigation is made to study both the steady-state and the transient Brillouin gain in magnetized non-centrosymmetric III-V semiconductors arising from the nonlinear interaction of an intense pump beam with the internally-generated acoustic wave, due to piezoelectric and electrostrictive properties of the crystal. Using the fact that the origin of coherent Brillouin scattering (CBS) lies in the third-order (Brillouin) susceptibility of the medium, we obtained an expression of the gain coefficient of backward Stokes mode in steady-state and transient regimes and studied the dependence of piezoelectricity, magnetic field and pump pulse duration on its growth rate. The threshold-pump intensity and optimum pulse duration for the onset of transient CBS are estimated. The piezoelectricity and externally-applied magnetic field substantially enhances the transient CBS gain coefficient in III-V semiconductors which can be of great use in the compression of scattered pulses.

INFLUENCE OF PIEZOELECTRICITY AND MAGNETIC FIELD ON STIMULATED BRILLOUIN SCATTERING IN III–V SEMICONDUCTORS

2006 ◽  
Vol 15 (04) ◽  
pp. 465-479 ◽  
Author(s):  
M. SINGH ◽  
P. AGHAMKAR ◽  
N. KISHORE ◽  
PRANAY K. SEN
Keyword(s):  
Magnetic Field ◽  
Brillouin Scattering ◽  
Phase Conjugation ◽  
Stimulated Brillouin Scattering ◽  
Gain Coefficient ◽  
Analytical Investigation ◽  
Magnetostatic Field ◽  
Brillouin Gain ◽  
Nonlinear Devices ◽  
Stimulated Brillouin

Using electromagnetic treatment, a detailed analytical investigation of stimulated Brillouin scattering (SBS) has been made for a semiconducting crystal in the presence of an external magnetostatic field. The effect of piezoelectricity (β) and magnetic field [Formula: see text] has been introduced through equation of motion of lattice vibration and Lorentz force, respectively. The analysis is applied to both cases viz. non-piezoelectric (β = 0) and piezoelectric (β ≠ 0) in the absence (B0 =0) and the presence (B0 ≠ 0) of external magnetostatic field. The numerical estimates are made for n-type InSb crystals, taken as representative III–V semiconductor, duly shined upon by pulsed 10.6 μm CO 2 laser. The inclination of applied magnetostatic field with respect to the direction of propagation of pump beam is found to augment the gain coefficient for the onset of stimulated Brillouin scattering. Moreover, the SBS gain coefficient increases with increasing scattering angle and results in a maximum value for the backscattered mode. The backward Brillouin gain is found to be nearly 104 times larger than forward gain when β ≠ 0 and B0 = 10T. The analysis also suggests the possibility of observing optical phase conjugation reflectivity as high as 106 in the weakly piezoelectric doped semiconductors with moderate magnetostatic field. The numerical estimation suggests that piezoelectric doped III–V semiconductors in the presence of magnetic field are candidate materials for fabrication of cubic nonlinear devices.

Characterisation of Liquid Brillouin Media at 532 nm

1997 ◽  
Vol 06 (01) ◽  
pp. 69-79 ◽  
Author(s):  
D. C. Jones
Keyword(s):  
Brillouin Scattering ◽  
Optical Breakdown ◽  
Gain Coefficient ◽  
High Gain ◽  
Four Wave Mixing ◽  
Wave Mixing ◽  
Phase Conjugate ◽  
Brillouin Gain ◽  
Stimulated Brillouin ◽  
532 Nm

A number of transparent liquids have been evaluated for use in stimulated Brillouin scattering at 532 nm. Measurements were made of frequency shift, SBS threshold, reflectivity and optical breakdown properties. It was found that the alkanes, and in particular n-pentane, performed well and measurements were made of Brillouin gain coefficient and phonon lifetimes. It is suggested that these liquids are promising candidates for use in self-pumped phase conjugate mirrors, high gain Brillouin amplifiers and four-wave mixing mirrors.

scholarly journals Large evanescently-induced Brillouin scattering at the surrounding of a nanofibre

2021 ◽  
Author(s):  
Fan Yang ◽  
Flavien Gyger ◽  
Adrien Godet ◽  
Jacques Chretien ◽  
Li Zhang ◽  
...  
Keyword(s):  
Free Space ◽  
Brillouin Scattering ◽  
Single Mode ◽  
Gain Coefficient ◽  
Direct Access ◽  
Brillouin Spectroscopy ◽  
Acoustic Interaction ◽  
Photonic Waveguides ◽  
Brillouin Gain ◽  
First Time

Abstract Brillouin scattering has been widely exploited for advanced photonics functionalities such as microwave photonics, signal processing, sensing, lasing, and more recently in micro- and nano-photonic waveguides. So far, all the works have focused on the opto-acoustic interaction driven from the core region of micro- and nano-waveguides. Here we observe, for the first time, an efficient Brillouin scattering generated by an evanescent field nearby a sub-wavelength waveguide embedded in a pressurised gas cell, with a maximum gain coefficient of 18.90 ± 0.17 m^(-1)W^(-1). This gain is 11 times larger than the highest Brillouin gain obtained in a hollow-core fibre and 79 times larger than in a standard single-mode fibre. The realisation of strong free-space Brillouin scattering from a waveguide benefits from the flexibility of confined light while providing a direct access to the opto-acoustic interaction, as required in free-space optoacoustics such as Brillouin spectroscopy and microscopy. Therefore, our work creates an important bridge between Brillouin scattering in waveguides, Brillouin spectroscopy and microscopy, and opens new avenues in light-sound interactions, optomechanics, sensing, lasing and imaging.

Particle balance in a steady state plasma in a dipole magnetic field

2019 ◽  
Vol 1 (4) ◽  
pp. 045005 ◽  
Author(s):  
Anuj Ram Baitha ◽  
Ayesha Nanda ◽  
Sargam Hunjan ◽  
Sudeep Bhattacharjee
Keyword(s):  
Magnetic Field ◽  
Steady State ◽  
Dipole Magnetic Field ◽  
Particle Balance ◽  
State Plasma

scholarly journals Magnetoactive elastomers for magnetically tunable vibrating sensor systems

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Tatiana I. Becker ◽  
Yuriy L. Raikher ◽  
Oleg V. Stolbov ◽  
Valter Böhm ◽  
Klaus Zimmermann
Keyword(s):  
Magnetic Field ◽  
Steady State ◽  
Smart Materials ◽  
Excitation Frequency ◽  
Experimental Studies ◽  
Uniform Field ◽  
Sensor Systems ◽  
Ongoing Research ◽  
Amplification Ratio ◽  
Field Distortion

Abstract Magnetoactive elastomers (MAEs) are a special type of smart materials consisting of an elastic matrix with embedded microsized particles that are made of ferromagnetic materials with high or low coercivity. Due to their composition, such elastomers possess unique magnetic field-dependent material properties. The present paper compiles the results of investigations on MAEs towards an approach of their potential application as vibrating sensor elements with adaptable sensitivity. Starting with the model-based and experimental studies of the free vibrational behavior displayed by cantilevers made of MAEs, it is shown that the first bending eigenfrequency of the cantilevers depends strongly on the strength of an applied uniform magnetic field. The investigations of the forced vibration response of MAE beams subjected to in-plane kinematic excitation confirm the possibility of active magnetic control of the amplitude-frequency characteristics. With change of the uniform field strength, the MAE beam reveals different steady-state responses for the same excitation, and the resonance may occur at various ranges of the excitation frequency. Nonlinear dependencies of the amplification ratio on the excitation frequency are obtained for different magnitudes of the applied field. Furthermore, it is shown that the steady-state vibrations of MAE beams can be detected based on the magnetic field distortion. The field difference, which is measured simultaneously on the sides of a vibrating MAE beam, provides a signal with the same frequency as the excitation and an amplitude proportional to the amplitude of resulting vibrations. The presented prototype of the MAE-based vibrating unit with the field-controlled “configuration” can be implemented for realization of acceleration sensor systems with adaptable sensitivity. The ongoing research on MAEs is oriented to the use of other geometrical forms along with beams, e.g. two-dimensional structures such as membranes.

scholarly journals Combined laser and magnetic field treatment of YFeO3—containing films grown by spray-pyrolysis

2004 ◽  
Vol 2 (1) ◽  
pp. 188-195
Author(s):  
N. Mihailov ◽  
O. Vankov ◽  
N. Petrova ◽  
D. Kovacheva
Keyword(s):  
Magnetic Field ◽  
Spray Pyrolysis ◽  
Pulse Duration ◽  
Fused Silica ◽  
Crystallite Sizes ◽  
Citric Complexes ◽  
Magnetic Field Treatment ◽  
Glycol Solution ◽  
The Magnetic Field ◽  
Post Deposition

AbstractThin films (50–1200 nm) of YFeO3 were deposited on fused silica substrates by spray-pyrolysis using ethylene glycol solution of Y-Fe(III) citric complexes. The films were post deposition annealed at 750°C in static air for 2 h. Films obtained in this way were afterwards irradiated by a burst mode operated Nd-YAG laser (pulse energy 650 mJ, pulse duration 700 μs, energy density 110 mJ/cm2). The laser’s onset was synchronized with that of a magnetic field pulse of nearly square shape (magnetic induction 0.5 T, pulse duration 900 μs). The samples were placed normally to the direction of the magnetic field. The treatment does not affect the phase composition of the film but significantly increases the crystallite sizes of the phases presenting in the sample. The saturation magnetization of the films decreases as a result of the laser and magnetic field treatment and the coercive force increases by 50%.

Steady-State Unbalance Response of Continuous Rotors on Anisotropic Supports

1993 ◽  
Author(s):  
Graziano Curti ◽  
Francesco A. Raffa ◽  
Furio Vatta
Keyword(s):  
Steady State ◽  
Stiffness Matrix ◽  
Dynamic Stiffness ◽  
Analytical Investigation ◽  
Dynamic Stiffness Matrix ◽  
Rotor Systems ◽  
Beam Elements ◽  
Unbalance Response ◽  
Constant Coefficients ◽  
Linearized Model

Abstract An analytical investigation of the steady-state unbalance response of axisymmetric rotor systems with anisotropic, flexible and damped bearings is presented. According to the exact approach of the dynamic stiffness method, the rotor is modelled by means of continuous beam elements. In this work, the expression of the 8 × 8 dynamic stiffness matrix of a rotating Timoshenko beam is derived and it is shown that it is related, by means of a simple law, to the previously published 4 × 4 dynamic stiffness matrix, which holds for the isotropic bearings case. The effects of concentrated disks and bearings are included into the formulation; in particular, each bearing is described by eight constant coefficients, according to the well-known linearized model of the bearing forces. The unbalance response of a typical rotor system taken from the literature is analyzed. A comparison is presented with the finite element results reported by other authors.

scholarly journals Mapping of steady-state electric fields and convective drifts in geomagnetic fields – Part 1: Elementary models

2016 ◽  
Vol 34 (1) ◽  
pp. 55-65 ◽  
Author(s):  
A. D. M. Walker ◽  
G. J. Sofko
Keyword(s):  
Magnetic Field ◽  
Steady State ◽  
Electric Field ◽  
Electric Fields ◽  
Magnetic Field Line ◽  
Geomagnetic Field ◽  
Geomagnetic Field Models ◽  
Spatial Derivatives ◽  
Field Lines ◽  
The Magnetic Field

Abstract. When studying magnetospheric convection, it is often necessary to map the steady-state electric field, measured at some point on a magnetic field line, to a magnetically conjugate point in the other hemisphere, or the equatorial plane, or at the position of a satellite. Such mapping is relatively easy in a dipole field although the appropriate formulae are not easily accessible. They are derived and reviewed here with some examples. It is not possible to derive such formulae in more realistic geomagnetic field models. A new method is described in this paper for accurate mapping of electric fields along field lines, which can be used for any field model in which the magnetic field and its spatial derivatives can be computed. From the spatial derivatives of the magnetic field three first order differential equations are derived for the components of the normalized element of separation of two closely spaced field lines. These can be integrated along with the magnetic field tracing equations and Faraday's law used to obtain the electric field as a function of distance measured along the magnetic field line. The method is tested in a simple model consisting of a dipole field plus a magnetotail model. The method is shown to be accurate, convenient, and suitable for use with more realistic geomagnetic field models.

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