Stimulated Brillouin scattering in magnetized diffusive semiconductor plasmas

Using the hydrodynamical model and following the coupled mode approach, detailed analytical investigation of stimulated Brillouin scattering is performed in an electrostrictive semiconductor. The total induced current density including diffusion current density and the effective Brillouin susceptibility are obtained under off-resonant laser irradiation. The analysis deals with the qualitative behaviour of the Brillouin gain and transmitted intensity with respect to excess doping concentration and magnetic field. Efforts are directed towards optimizing the doping level and magnetic field to achieve maximum Brillouin gain at pump intensities far below the optical damage threshold level. It is found that by immersing a moderately doped semiconductor in a sufficiently strong magnetic field in transverse direction, one can achieve resonant enhancement of Brillouin gain provided the generated acoustic mode lies in the dispersionless regime.     

Stimulated Brillouin scattering of an electromagnetic wave by an acoustic-like mode in multi-ion species plasmas

Using an hydrodynamical model, analytical investigation of the stimulated Brillouin scattering of an electromagnetic wave by an acoustic-like mode has been done in a multi-ion species plasma. The acoustic-like mode is a new mode which propagates in a multi-ion plasma only. The non-linear dispersion relation and the growth rate of the excited modes are derived. The non-linearity arises through the motion of ions which is introduced through ponderomotive force. It is found that the growth rate can be controlled by several parameters like charge number, mass, density and temperature of the ions.     

Stimulated Brillouin backscattering in magnetized plasmas

Stimulated Brillouin backscattering (SBBS) from a magnetized homogeneous plasma is investigated. Effect of a dc–magnetic field on SBBS growth rate is obtained and compared with that for non–magnetized plasmas. Numerical calculations show an increase in the instability growth rate for small magnetic fields, then a decrease in the growth rate as the magnetic field increases till a cut–off field is reached, beyond which SBBS is brought to stability. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Stimulated scattering of electromagnetic waves in a magnetised plasma

We present estimates of threshold powers, growth rates and amplification factors for stimulated scattering of electromagnetic waves off electrostatic modes in a magnetized plasma, The magnetic field strength is assumed to influence only the electrostatic modes and not the propagation of incident and scattered electromagnetic waves.     

Stimulated Brillouin scattering of Gaussian beams

The characteristic of stimulated Brillouin scattering of Gaussian beams is analysed. The result displays distinct threshold and saturation of the beam, precisely in agreement with the recent experimental data reported by Aoki and Tajima.     

Stimulated brillouin scattering of electromagnetic ion cyclotron waves in a plasma

Using the fluid model for the nonlinear response of ions, we have studied the nonlinear scattering of an electromagnetic ion cyclotron wave off the ion acoustic wave in a plasma. The low frequency nonlinearity arises through the parallel ponderomotive force on ions and the high frequency nonlinearity arises through the nonlinear current density of ions. For a typical nonisothermal plasma (T _e/T _i∼10) the threshold for this instability in a uniform plasma is ∼1mW/cm². At power densities ≳10² W/cm², the growth rate for backscatter turns out to be ∼10⁴s⁻¹.     

Stimulated brillouin scattering of electromagnetic waves in an-type InSb-filled rectangular waveguide

Summary This paper presents a theoretical investigation of the stimulated Brillouin scattering of a beam of electromagnetic radiation in a semiconductor-filled rectangular waveguide. The incident electromagnetic wave decays parametrically into a low-frequency electrostatic ion acoustic wave and a scattered electromagnetic sideband. For typical plasma parameters in an-InSb-filled rectangular waveguide and when the pump-induced drift velocity of electrons,v ₀, is comparable to the ion acoustic velocity,C _s , inn-InSb (i.e. |v ₀/C _s |≅1), the growth rate of the decay waves turns out to be ∼10³ rad s⁻¹ for a 3 cm microwave and ∼10⁷ rad s⁻¹ for a CO₂ laser radiation. The growth rate of the instability vanishes at the boundary of the waveguide.

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Riassunto Questo articolo presenta uno studio teorico dello scattering stimolato di Brillouin di un fascio di radiazione elettromagnetica, in una guida d’onda rettangolare riempita con un semiconduttore. L’onda elettromagnetica incidente decade parametricamente in un’onda elettrostatica a bassa frequenza di ioni e in una banda laterale elettromagnetica diffusa. Per parametri tipici del plasma in una guida d’onda rettangolare riempita conn-InSb e quando la velocità di deriva degli elettroni indotta dalla pompa,v ₀, è confrontabile con la velocità ionicaC _s inn-InSb (cioè |v ₀/C _s |≅1), la velocità di crescita delle onde di decadimento risulta di ∼10³ rad s⁻¹ per una microonda di 3 cm e ∼10⁷ rad s⁻¹ per una radiazione di laser a CO₂. La velocità di crescita dell’instabilità si annulla agli estremi delle guide d’onda.

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Резюме Эта статья представляет теоретическое исследование стимулированного бриллюэновского рассеяния пучка электромагнитного излучения в полупроводнике, заполняющем прямоугольный волновод. Падающая электромагнитная волна распадается параметрически на низкочастотную электростатическую ионную акустическую волну и рассеянную электромагнитную побочную полосу. Для типичных плазменных параметров вn-InSb, заполняющем прямоугольный волновод, и когда насос индуцирует дрейфовую скорость электронов,v ₀, сравнимую с ионной акустической скоростью,C _s , вn-InSb (т.е. |v ₀/C _s |≅1), интенсивность образования распадных волн составляет ∼10³ рал c⁻¹ для 3 см микроволнового излучения и ∼10⁷ рад c⁻¹ для излучения CO₂ лазера. Интенсивность образования неустойчивости обращается нуль на границе волновода.

     

光纤放大器中的受激布里渊散射阈值

从受激布里渊散射(SBS)耦合波理论出发,根据双包层光纤放大器中的受激布里渊散射阈值模型,理论仿真了信号带宽、纤芯直径、放大器增益对SBS阈值的影响,并从实验上研究了单频百纳秒脉冲信号在掺镱双包层光纤放大器中的受激布里渊散射现象。实验中输入脉冲信号重复频率1 Hz,脉宽200 ns,对不同的输入脉冲信号放大,前向放大脉冲在脉冲能量660 nJ、峰值功率3.3 W时出现畸变,产生后向SBS窄脉冲,达到了SBS阈值,实验计算的SBS阈值与理论分析结果基本一致。     

光纤放大器中的受激布里渊散射阈值

 从受激布里渊散射(SBS)耦合波理论出发,根据双包层光纤放大器中的受激布里渊散射阈值模型,理论仿真了信号带宽、纤芯直径、放大器增益对SBS阈值的影响,并从实验上研究了单频百纳秒脉冲信号在掺镱双包层光纤放大器中的受激布里渊散射现象。实验中输入脉冲信号重复频率1 Hz,脉宽200 ns,对不同的输入脉冲信号放大,前向放大脉冲在脉冲能量660 nJ、峰值功率3.3 W时出现畸变,产生后向SBS窄脉冲,达到了SBS阈值,实验计算的SBS阈值与理论分析结果基本一致。     

Stimulated Brillouin scattering slow-light-based fiber-optic temperature sensor

We propose and experimentally demonstrate a method for temperature sensing using stimulated Brillouin scattering (SBS)-based slow light. The approach relies on temperature dependence of the Brillouin frequency shift in a fiber, hence the time delay of an input probe pulse. By measuring the delay, temperature sensing can be realized. We achieve temperature measurement in a 100 m single-mode fiber (SMF) using a cw pump. The main temperature-sensing range is ～18°C from the room temperature, limited by the SBS gain bandwidth. To apply the technique for measurement of a shorter fiber segment, a pulsed pump is used to introduce SBS slow light. Temperature sensing is achieved in a 2 m SMF with a main sensing range of around ～25°C. The scheme is easily implemented, exhibits a relatively high temperature sensitivity with a resolution better than 1.0°C, and is potentially applicable for distributed sensing.     

Stimulated Brillouin scattering of an electromagnetic wave in weakly magnetized plasma with variably charged dust particles

We have investigated analytically the stimulated Brillouin scattering (SBS) of an electromagnetic wave in non-dissipative weakly magnetized plasma in the presence of dust particles with variable charge.     

Large-amplitude electromagnetic waves in relativistic plasmas

The propagation of linearly polarized large-amplitude electromagnetic waves in relativistic plasmas is studied in the framework of the Akhiezer-Polovin-model. Different forms of the basic equations are reviewed and important solutions are presented for small and critical plasma densities. The well-known periodic solutions are generalized to quasiperiodic solutions taking account of additional electrostatic oscillations.     

Stimulated Brillouin scattering in a plasma with ion-acoustic turbulence

A theory of stimulated Brillouin scattering (STBS) in a plasma with ion-acoustic turbulence is developed using concepts of parametric instability under conditions when equations of two-temperature hydrodynamics can be used to describe ion-acoustic perturbations of the electron density. The temporal growth rate of the absolute instability and the spatial gain of the scattered wave are determined. The dependence of the threshold density of the radiation flux on the angle between the scattering wave vector and the direction of anisotropy of the turbulent noise is described. A new effect of STBS forbiddenness caused by anomalous turbulent heating of the ions is predicted for a plasma with a high level of turbulent noise.     

Self-reflection of intense electromagnetic waves in plasmas

A uniform electromagnetic wave of high power density, propagating in a collisional plasma gives rise to a modification in temperature-dependent collision frequency and in turn induces a gradient in the complex refractive index of the medium. A WKB solution of the problem predicts a backward propagating wave on account of the self-induced inhomogeneity. The amplitude of the backward (i.e. reflected) wave increases with increasing power density of the wave. This is a volume nonlinear effect and is appreciable for usually employed power densities.     

High frequency Brillouin scattering in metals and gaseous plasmas

Spontaneous and stimulated Brillouin scattering are studied in metals and gaseous plasmas, for an incident laser frequencyω ₁ greater than the corresponding plasma frequencyω _plin the medium. The calculation of threshold powers for the stimulated scattering in aluminium metal and non-degenerate Al-plasmas shows that their values become quite small asω ₁ approachesω _plFor the case of backward wave scattering we also estimate the critical power above which a temporal instability sets in such media. It is argued that this instability may be one of the factors for anomalously large absorption of high power laser beams in laser-induced plasmas.