We have studied plasma-induced smoothing due to stimulated Brillouin scattering (SBS) under the aspect of the extremal statistics of smoothed laser beams. As pointed out in the work by Rose and ...DuBois (1994 Phys. Rev. Lett. 72 2883), scattered light can be subject to uncontrolled (or even 'explosive') behaviour, associated with a critical gain value for SBS. In this work we show how this critical behaviour can be predicted on the basis of the order statistics of laser speckle fields, and we analyse the transition to uncontrolled behaviour of the laser beam due to the dominance of high intensity speckles.
GINGER and GINGERINO Virgilio, A. D. V. Di; Belfi, J.; Bosi, F. ...
Journal of physics. Conference series,
01/2020, Letnik:
1342, Številka:
1
Journal Article
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GINGER (Gyroscopes IN General Relativity) is a proposal aiming at measuring the Lense-Thirring effect with an Earth based experiment, using an array of ringlasers, which are the most sensitive ...inertial sensors to measure the rotation rate of the Earth. The long term stability of the apparatus plays a crucial role for this experiment, and an underground location is advantageous from this point of view. GINGERINO is a single axis ring laser located inside the Gran Sasso laboratory. Gingerino has demonstrated that the very high thermal stability of the underground laboratory allows a continuous operation, sensitivity well below fractions of nrad/s, and with a duty cycle above 90% even in free running operation, without stabilisation of the scale factor of the ring laser.
We study the crossed beam energy transfer (CBET) between laser fields generated by optical smoothing methods. The energy transfer, as well as the angular distribution of the outgoing light fields are ...investigated for two incident smoothed laser beams in a plasma with a flow gradient, allowing for resonant transfer close to the sonic point. Simulations with the code HARMONY based on time-dependent paraxial light propagation are compared to simulations using a new approach based on paraxial complex geometrical optics (PCGO). Both approaches show good agreement for the average energy transfer past a short transient period, which is a promising result for the use of the PCGO method as a module within a hydrodynamics code to efficiently compute CBET in mm-scale plasma configurations. Statistical aspects related to role of laser speckles in CBET are considered via an ensemble of different phase plate realizations.
We test a turbulent plasma emission model previously proposed to interpret micropulses in individual pulses received from a certain number of pulsars. In this model, we assumed that pulsar radio ...emissions can be related to the development of a strong Langmuir turbulence in a pulsar emission region. As shown, the elements of such a turbulence in this region are stable Langmuir solitons which have electrostatic and electromagnetic components at the same time. Consequently, they radiate electromagnetic waves likely to reach an observer. On this basis, we assumed that such a strong Langmuir turbulence would give rise to a lattice of stable Langmuir structures, regularly spaced, all with the same amplitude, width, position and velocity along the open magnetic field lines of the pulsar magnetosphere. Properties of such radiating Langmuir structures were associated with micropulses observed in radio pulses. Actually, such Langmuir structures in strongly turbulent pulsar plasmas should have random amplitudes, positions and velocities. Considering these as elementary structures in strongly turbulent pulsar plasmas, we propose a statistical theory for such plasmas. We start with the elementary soliton-like solutions of a non-linear Schrödinger equation, describing the strong turbulence in terms of a set of random solitons. The initial amplitudes, positions and velocities of these solitons are themselves random variables whose distributions act as free parameters for our statistical description. Assuming an ensemble of initial conditions, we are able to determine the mean number of solitons, the dynamical form factor, the resulting energy spectrum, the associated intensity and the intensity distribution. The energy spectrum qualitatively agrees with some of the observed pulsar spectra. The variation with time of the intensity distribution shows a realistic behaviour in a large part of the domain of the intensities.
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