scholarly journals The role of electric field polarization of the incident laser beam in the short pulse damage mechanism of pulse compression gratings

2011 ◽  
Vol 99 (6) ◽  
pp. 061101 ◽  
Author(s):  
Steve Hocquet ◽  
Jerome Neauport ◽  
Nicolas Bonod
Keyword(s):  
Electric Field ◽  
Laser Beam ◽  
Pulse Compression ◽  
Short Pulse ◽  
Damage Mechanism ◽  
Incident Laser Beam ◽  
Incident Laser ◽  
Field Polarization ◽  
Electric Field Polarization

scholarly journals Remote sensing of a NTC radio source from a Cluster tilted spacecraft pair

2013 ◽  
Vol 31 (11) ◽  
pp. 2097-2121 ◽  
Author(s):  
P. M. E. Décréau ◽  
S. Kougblénou ◽  
G. Lointier ◽  
J.-L. Rauch ◽  
J.-G. Trotignon ◽  
...  
Keyword(s):  
Electric Field ◽  
Circular Polarization ◽  
Source Region ◽  
Plane Waves ◽  
Geomagnetic Latitude ◽  
Magnetic Activity ◽  
Spectral Signature ◽  
Time Interval ◽  
Field Polarization ◽  
Electric Field Polarization

Abstract. The Cluster mission operated a "tilt campaign" during the month of May 2008. Two of the four identical Cluster spacecraft were placed at a close distance (~50 km) from each other and the spin axis of one of the spacecraft pair was tilted by an angle of ~46°. This gave the opportunity, for the first time in space, to measure global characteristics of AC electric field, at the sensitivity available with long boom (88 m) antennas, simultaneously from the specific configuration of the tilted pair of satellites and from the available base of three satellites placed at a large characteristic separation (~1 RE). This paper describes how global characteristics of radio waves, in this case the configuration of the electric field polarization ellipse in 3-D-space, are identified from in situ measurements of spin modulation features by the tilted pair, validating a novel experimental concept. In the event selected for analysis, non-thermal continuum (NTC) waves in the 15–25 kHz frequency range are observed from the Cluster constellation placed above the polar cap. The observed intensity variations with spin angle are those of plane waves, with an electric field polarization close to circular, at an ellipticity ratio e = 0.87. We derive the source position in 3-D by two different methods. The first one uses ray path orientation (measured by the tilted pair) combined with spectral signature of magnetic field magnitude at source. The second one is obtained via triangulation from the three spacecraft baseline, using estimation of directivity angles under assumption of circular polarization. The two results are not compatible, placing sources widely apart. We present a general study of the level of systematic errors due to the assumption of circular polarization, linked to the second approach, and show how this approach can lead to poor triangulation and wrong source positioning. The estimation derived from the first method places the NTC source region in the dawn sector, at a large L value (L ~ 10) and a medium geomagnetic latitude (35° S). We discuss these untypical results within the frame of the geophysical conditions prevailing that day, i.e. a particularly quiet long time interval, followed by a short increase of magnetic activity.

INVESTIGATION OF PECULIARITIES OF LIGHT SCATTERING BY NANOSTRUCTURAL CHANGES IN THE CRYSTAL LATTICE OF FERROELECTRIC BARIUM SODIUM NIOBATE CRYSTAL

2004 ◽  
Vol 03 (06) ◽  
pp. 815-818 ◽  
Author(s):  
S. V. IVANOVA
Keyword(s):  
Light Scattering ◽  
Laser Beam ◽  
Beam Width ◽  
Far Field ◽  
Sodium Niobate ◽  
Incident Laser Beam ◽  
Incident Laser ◽  
Elastic Light Scattering ◽  
Temperature Range ◽  
Thermal Changes

Thermal changes of light scattering images in the far-field were observed under steady illumination by an incident laser beam of finite beam width on barium sodium niobate crystals in the temperature range of 20–500°C. Different patterns of light scattering in far-field were observed — from striped to round-like form with dependence on temperature, conditions of grown, direction of beam and polarization. The round-like form was observed on cooling from 450°C to 240°C. Striped forms of light scattering were observed below 200°C. Correlation of the behavior of elastic light scattering was observed in this temperature range.

A high-speed-modulated retro-reflector for lasers using an acousto-optic modulator

2003 ◽  
Vol 81 (4) ◽  
pp. 625-638 ◽  
Author(s):  
G Spirou ◽  
I Yavin ◽  
M Weel ◽  
A Vorozcovs ◽  
A Kumarakrishnan ◽  
...  
Keyword(s):  
Laser Beam ◽  
Acoustic Waves ◽  
High Speed ◽  
Incident Beam ◽  
Bragg Diffraction ◽  
Heterodyne Detection ◽  
Incident Laser Beam ◽  
Signal To Noise ◽  
Incident Laser ◽  
Acousto Optic Modulator

We have used an acousto-optic modulator (AOM) to impose a frequency-modulated signal on an incident laser beam. The incident laser beam is focussed into the AOM where it undergoes Bragg diffraction and is then retro-reflected. The diffracted beam is also retro-reflected so that it is diffracted again by the AOM and overlaps the incident beam. The overlapped beams are frequency shifted with respect to each other. These features allow us to detect the frequency-modulated signal with high signal-to-noise ratio using heterodyne detection. Since the optical setup is simple and can be made very compact, this device may be ideal for certain forms of high-speed, free-space optical communication. We demonstrate a 1 MHz data transmission rate in the Bragg regime. We measured the acceptance angle of the device and find that it is limited only by the divergence of the focussed laser beam and the divergence of the acoustic waves in the AOM crystal. We have also studied the range of acoustic frequencies and drive power of the AOM, for which the retro-reflected beam can be detected with adequate signal to noise. PACS Nos.: 42.60.–V, 42.62.Cf, 42.62.Fi, 42.79.Sz, 42.79.Hp

scholarly journals Electric, magnetic Wakefields, and electron acceleration in quantum plasma

2012 ◽  
Vol 30 (2) ◽  
pp. 267-273 ◽  
Author(s):  
P. Kumar ◽  
C. Tewari
Keyword(s):  
Laser Pulse ◽  
Laser Beam ◽  
Quantum Effects ◽  
Electron Acceleration ◽  
Quantum Plasma ◽  
Incident Laser Beam ◽  
Incident Laser ◽  
High Energies ◽  
Test Electron ◽  
Radial Forces

AbstractA detailed study of Wakefield excitation in very dense quantum plasma is presented. Electric and magnetic Wakefields have been obtained for a particular profile of the laser pulse, using perturbative technique involving orders of the incident laser beam. The Wakefields can trap electrons and accelerate them to extremely high energies. It is observed that the quantum effects significantly change the classical nature of the Wakefield. The axial and radial forces acting on a test electron due to the Wakefields have been evaluated.

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