共查询到20条相似文献,搜索用时 25 毫秒
1.
Four-wave parametric processes in multicascade SRS conversion of neodymium laser radiation into an eye-safe region are studied
in relation to the phase mismatch of parametric coupling, which is determined by the refractive index dispersion of the SRS
medium. The numerical simulation showed that the generation of multicascade SRS at a particular wavelength in the IR region
can be even more efficient than the single-cascade conversion if the parametric coupling between the first Stokes and anti-Stokes
components is weak and higher Stokes components are strongly parametrically coupled with each other. This situation is observed
in the eye-safe IR region, where the refractive index dispersion of solid-state SRS media is minimal, which allows one to
optimize the SRS conversion by choosing an SRS medium and its length. 相似文献
2.
A theory for the formation of Mach cones in a magnetized dusty plasma with strongly correlated charged dust grains has been presented. We use the electron and ion susceptibilities for weakly correlated magnetized electrons and ions as well as the strongly correlated unmagnetized dust grain susceptibilities which are obtained by means of the quasilocalized charge approximation and a generalized hydrodynamic model. The plasma dielectric response of the present system reveals the parametric regimes for which Mach cones in a strongly coupled laboratory dusty magnetoplasma can be formed. We suggest conducting experiments in radiofrequency dusty plasma discharges with superconducting magnets for verifying the theoretical prediction of Mach cones that is made herein. 相似文献
3.
4.
A new type of coupled nonlinear optical interactions that can be implemented in crystals with an aperiodic modulation of the nonlinear susceptibility is studied. The quasi-phase matching condition is satisfied simultaneously for several conventional three-frequency processes involved in the interaction due to the aperiodic variation of the nonlinearity in space. A simple method for designing aperiodically poled nonlinear optical crystals is proposed and analyzed. The method is based on the superposition of nonlinearity modulations produced by several periodic functions simultaneously so that each of these functions individually corresponds to its own quasi-phase-matched nonlinear process. The dynamics of energy exchange during interaction of five waves with different frequencies that involves three coupled three-frequency parametric interaction processes is investigated thoroughly. The ratio between the effective nonlinear wave coupling coefficients and the amplitudes of pump waves is determined for the case in which the initial stage of the interaction is characterized by the parametric instability. It is demonstrated that the secondary simplification of the coupled differential equations with spatially modulated nonlinear coefficients, which leads to the system of equations with constant nonlinear coefficients, correctly describes the dynamics of interaction of the waves at distances of the order of 50 characteristic nonlinear lengths. 相似文献
5.
Parametric instabilities induced by the nonlinear interaction between high frequency quantum Langmuir waves and low frequency quantum ion-acoustic waves in quantum plasmas with the electron exchange-correlation effects are presented.By using the quantum hydrodynamic equations with the electron exchange-correlation correction,we obtain an effective quantum Zaharov model,which is then used to derive the modified dispersion relations and the growth rates of the decay and four-wave instabilities.The influences of the electron exchange-correlation effects and the quantum effects on the existence of quantum Langmuir waves and the parametric instabilities are discussed in detail.It is shown that the electron exchange-correlation effects and quantum effects are strongly coupled.The quantum Langmuir wave can propagate in quantum plasmas only when the electron exchange-correlation effects and the quantum effects satisfy a certain condition.The electron exchange-correlation effects tend to enhance the parametric instabilities,while quantum effects suppress the instabilities. 相似文献
6.
由于子系统的时空耦合作用及参数的摄动性,实现参数摄动的耦合时空混沌的跟踪控制非常困难。然而模型未知的耦合时空混沌的每个子系统可由一系列模糊逻辑模型逼近,每个模糊逻辑模型代表子系统在特定运行点的局部线性化模型,同时考虑子系统状态的不可测性,采用模糊观测器来估计子系统的状态。基于模糊模型及状态观测器,计及混沌参数的摄动性,提出一种模糊跟踪控制方案,实现了参数摄动的耦合时空混沌的鲁棒跟踪控制,并将模糊跟踪控制表征为线性矩阵不等式问题,用线性矩阵不等式的凸优化方法求解控制器参数,确保系统的全局渐近稳定性。仿真验证了方案的有效性。 相似文献
7.
《中国物理 B》2019,(4)
We demonstrate a direct, fluorescence-free measurement of the oscillation frequency of cold atoms in an optical dipole trap based on a high-finesse optical cavity strongly coupled to atoms. The parametric heating spectra of the trapped atoms are obtained by recording the transmitted photons from the cavity with the trap depth is modulated by different frequency.Moreover, in our method the oscillation can be observed directly in the time scale. Being compared to the conventional fluorescence-dependent method, our approach avoids uncertainties associated with the illuminating light and auxiliary imaging optics. This method has the potential application of determining the motion of atoms with stored quantum bits or degenerate gases without destroying them. 相似文献
8.
Colored conical emission was observed experimentally in a thick beta-barium borate crystal as a result of spatiotemporal modulational instability. In the presence of both dispersion and diffraction, colored conical emission showed specific features that were characteristic of the nonlinear dynamics of the strongly coupled fundamental and harmonic fields. Experimental observation directly demonstrated that beam angular spectra were substantially modified as a result of exponential growth of perturbations by means of parametric wave mixing. Seeded amplification of colored conical emission was demonstrated to support ultrabroadband up-conversion. 相似文献
9.
We have observed a novel type of parametric oscillation in sodium atomic vapor where four off-axis signal waves simultaneously build up under resonant and counterpropagating pump beams with elliptical beam profiles. The four waves, two of them Stokes shifted and the other two anti-Stokes shifted, have similar output powers of up to 10 mW with a conversion efficiency of 30% and are parametrically coupled by electromagnetically induced diffraction. 相似文献
10.
We study the quantum properties of four coupled parametric down-conversion processes which can be realized in an aperiodical
nonlinear photonic crystal. In the interaction under consideration, each mode is created by two parametric processes. The
photon statistics of particular modes and correlation functions for photon numbers and their fluctuations are studied in detail.
It is shown that photon number correlations are nonclassical at small interaction lengths. We calculate the covariance matrix
for continuous quantum variables of the generated modes and make use of the criterion of separability based on the partial
scaling transform to reveal the entanglement between the variables. It is established that cluster entangled states are created
in these coupled parametric processes. 相似文献
11.
J. Zhu C. Q. Ru A. Mioduchowski 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(4):411-421
This paper studies parametric resonance of coupled
micromechanical oscillators under periodically varying nonlinear coupling
forces. Different from most of previous related works in which the
periodically varying coupling forces between adjacent oscillators are
linearized, our work focuses on new physical phenomena caused by the
periodically varying nonlinear coupling. Harmonic balance method (HBM)
combined with Newton iteration method is employed to find steady-state
periodic solutions. Similar to linearly coupled oscillators studied
previously, the present model predicts superharmonic parametric resonance
and the lower-order subharmonic parametric resonance. On the other hand, the
present analysis shows that periodically varying nonlinear coupling
considered in the present model does lead to the appearance of high-order
subharmonic parametric resonance when the external excitation frequency is a
multiple or nearly a multiple (≥3) of one of the natural
frequencies of the oscillator system. This remarkable new phenomenon does
not appear in the linearly coupled micromechanical oscillators studied
previously, and makes the range of exciting resonance frequencies expanded
to infinity. In addition, the effect of a linear damping on parametric
resonance is studied in detail, and the conditions for the occurrence of the
high-order subharmonics with a linear damping are discussed. 相似文献
12.
We investigate continuous variable entanglement produced in two distant coupled cavities, in which two four-level atoms are driven by classical fields respectively. Under the large detuning condition, an effective Hamiltonian containing the square of the creation (annihilation) operator of the cavity field is derived. Due to the nonlinearity, entanglement formally created by the beam splitter type interaction is transformed into the nondegenerate parametric down conversion type. Employing the operator algebraic method, we study the time evolution of the entanglement condition, and show that the system provides us an advantage in achieving a larger photon number with better entanglement. We also discuss the dissipation of the cavities affecting the entanglement. 相似文献
13.
We describe renormalizable supersymmetric four-dimensional theories which lead to gaugino mediation and various generalizations thereof. Even though these models are strongly coupled, we can demonstrate the parametric suppression of soft scalar masses via Seiberg duality. We show that our models have a parameter which continuously interpolates between suppressed soft scalar masses and their conventional gauge mediated contribution. The main physical effect which we utilize is the general relation between massive deformations in one frame and the Higgs mechanism in the dual frame. Some compelling and relatively unexplored phenomenological scenarios arise naturally in this framework. We offer preliminary comments on various aspects of the phenomenology and outline several of the outstanding open problems. 相似文献
14.
The possibility of induced backscattering parametric decay instability resonant suppression by harmonic pump-frequency modulation is demonstrated experimentally. It is shown that the pump anomalous reflection is strongly reduced at the modulation frequency equal to the difference of the decay instability eigenfrequencies. The parametric instability feedback control method is proposed based on this effect. 相似文献
15.
We describe a widely tunable synchronously pumped coherent source based on the process of narrowband parametric amplification in a dispersion-shifted fiber. Using an experimental fiber with a zero-dispersion wavelength of 1590 nm and pump wavelengths of 1530 to 1570 nm yields oscillations at 1970 to 2140 nm-the longest reported wavelength for a fiber parametric oscillator. The long-wavelength oscillations are accompanied by simultaneous short-wavelength oscillations at 1200 to 1290 nm. The parametric gain is coupled to stimulated Raman scattering. For parametric oscillations close to the Raman gain peak, the two gain processes must be discriminated from each other. We devised two configurations that achieve this discrimination: one is based on the exploitation of the difference in group delay between the wavelengths where Raman and parametric gain peak, and the other uses intracavity polarization tuning. 相似文献
16.
We explicitly compute nonperturbative effects in a supersymmetric double-well matrix model corresponding to two-dimensional type IIA superstring theory on a nontrivial Ramond–Ramond background. We analytically determine the full one-instanton contribution to the free energy and one-point function, including all perturbative fluctuations around the one-instanton background. The leading order two-instanton contribution is determined as well. We see that supersymmetry is spontaneously broken by instantons, and that the breaking persists after taking a double scaling limit which realizes the type IIA theory from the matrix model. The result implies that spontaneous supersymmetry breaking occurs by nonperturbative dynamics in the target space of the IIA theory. Furthermore, we numerically determine the full nonperturbative effects by recursive evaluation of orthogonal polynomials. The free energy of the matrix model appears well-defined and finite even in the strongly coupled limit of the corresponding type IIA theory. The result might suggest a weakly coupled theory appearing as an S-dual to the two-dimensional type IIA superstring theory. 相似文献
17.
采用傅里叶变换的方法将脉冲光分解成不同的频率成分,建立了非单色光抽运的光参量放大耦合方程组的数值求解模型.研究了非单色抽运光对光参量啁啾脉冲放大的小信号增益、大信号增益以及增益带宽的影响.非单色抽运光降低参量放大的增益水平,但同时可提高增益带宽,且抽运光谱宽越宽,对增益带宽的提高作用越大.还进一步从相位失配和参量带宽的角度分析了非单色抽运光使参量放大的增益降低、带宽增大的原因.
关键词:
光参量啁啾脉冲放大
非单色光
增益带宽
飞秒激光 相似文献
18.
G. Patera N. Treps C. Fabre G. J. de Valcárcel 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,56(1):123-140
Quantum models for synchronously pumped type I optical parametric
oscillators (SPOPO) are presented. The study of the dynamics of SPOPOs,
which typically involves millions of coupled signal longitudinal modes, is
significantly simplified when one considers the “supermodes", which are
independent linear superpositions of all the signal modes diagonalizing the
parametric interaction. In terms of these supermodes the SPOPO dynamics
becomes that of about a hundred of independent, single mode degenerate OPOs,
each of them being a squeezer. One derives a general expression for the
squeezing spectrum measured in a balanced homodyne detection experiment,
valid for any temporal shape of the local oscillator. Realistic cases are
then studied using both analytical and numerical methods: the oscillation
threshold is derived, and the spectral and temporal shapes of the squeezed
supermodes are characterized. 相似文献
19.
The aim of this paper is to study the squeezing and statistical properties of the light produced by a degenerate three-level laser whose cavity contains a degenerate parametric amplifier. In this quantum optical system the top and bottom levels of the three-level atoms injected into the laser cavity are coupled by the pump mode emerging from the parametric amplifier. For a linear gain coefficient of 100 and for a cavity damping constant of 0.8, the maximum intracavity squeezing is found at steady state and at threshold to be 93%. 相似文献
20.
Quantum properties of parametric amplification and frequency conversion of an optical image in coupled parametric interactions
are analyzed for the case of a remote object. The coupled-wave interaction consists of a traditional process of parametric
amplification in the high-frequency pump field accompanied by the frequency mixing of generated and pump waves. The photon
number density and signal-to-noise ratio at the interacting frequencies are studied in the image plane at the output of the
nonlinear frequency converter in the fixed pump field approximation. The degree of entanglement of optical images at frequencies
above and below the pump frequency is investigated. 相似文献