Pump Field Frequency Research Articles

Transient hole burning in exciton-phonon systems

The imaginary part of the nonlinear optical susceptibility experienced by a test field is calculated for a coupled exciton-phonon system in the transient regime when a strong pump field is directed on the system. Hole burning is found in the absorption spectrum when the pump field frequency is either on resonance with the exciton frequency or one phonon frequency lower than the exciton frequency. The results strongly indicate the saturation of excitons in the system excited either directly or phonon-assisted by the pump field. Other characteristic features of the bleaching in the absorption spectrum are found and their physical implications discussed.

Parametric instabilities of finite amplitude Alfvén waves

We consider the stability of a finite amplitude circularly polarized Alfvén-ion-cyclotron magnetic field. Various forms of the dispersion relation are derived. A new instability is found. Its threshold is comparatively low when the helical magnetic pump field frequency is close to the ion cyclotron frequency

Side bands in collective resonance fluorescence

The fluorescence spectrum of a system of strongly driven atoms, contained in a region that is small compared with the wavelength, is calculated using a screened interaction model. Coulomb dipole–dipole interaction is neglected, but a Markov approximation is not made. The side bands at ω′ = ω ± Ω and ω ± 2Ω are investigated in detail (ω′(ω) is the emitted photon (pump field) frequency; Ω is the Rabi frequency). The intensity and line width of the side bands at ω ± 2Ω is reduced owing to S breaking in our model. Non-Markovian corrections split the side band at ω ± Ω.

Russian Text Ignored

AbstractA nonlinear theory of the interaction of an external pump field with ion‐acoustic and h.f. surface waves in a plasma layer with inhomogeneous boundary regions is presented for the case, when the pump field frequency is less than the electron plasma frequency. The evolution of the parametrically excited turbulence and its stationary state are both analytically treated and numerically demonstrated. Dependent on the pump field strength, two mechanisms are to be distinguished: (i) nonlinear generation of damped ion‐acoustic harmonics, (ii) cascade excitation of secondary eigenmodes by growing surface oscillations. At only slight overthreshold values, mechanism (i) is responsible for the occurence of the steady state, whereas, for higher pump field strength, the wave amplitudes as well as their saturated levels are mainly determined by mechanism (ii).

Parametric instabilities below the electron plasma frequency due to relativistic corrections

We present a model which describes the interaction of a cold homogeneous plasma with a strong linearly polarized external electromagnetic wave, taking into account relativistic terms. Instabilities appear for transverse and longitudinal waves when the pump-field frequency is at the same time below the electron plasma frequency and above but very near the cutoff frequency obtained by Kaw and Dawson with a nonlinear relativistic theory.