INTERACTION OF INTENSE SHORT LASER PULSES WITH AIR AND DIELECTRIC MATERIALS

2007 ◽  
Vol 21 (03n04) ◽  
pp. 615-625 ◽  
Author(s):  
S. EISENMANN ◽  
Y. KATZIR ◽  
A. ZIGLER ◽  
G. FIBICH ◽  
E. LOUZON ◽  
...  
Keyword(s):  
Critical Power ◽  
Laser Pulses ◽  
Dielectric Materials ◽  
Laser Beams ◽  
Threshold Fluence ◽  
Short Pulses ◽  
Self Focusing ◽  
Chirped Pulses ◽  
Short Laser Pulses ◽  
Wide Gap

A study of the propagation of intense short laser pulses in air and the interaction of these pulses with distant targets is described. It is shown that the beam filamentation pattern can be controlled by introducing beam astigmatism. In addition, it is demonstrated that the collapse distance of intense femtosecond laser beams scales as P -1/2 for input powers that are moderately above the critical power for self focusing, and that at higher powers the collapse distance scales as P -1. Related to the interaction of intense short pulses with distant targets, it is measured that the threshold fluence for optical damage in wide gap materials is lower by up to 20% for negatively chirped pulses than for positively chirped, at pulse durations ranging from 60 fs to 1 ps.

scholarly journals Relativistic Propagation of Linearly/Circularly Polarized Laser Radiation in Plasmas

ISRN Optics ◽  
2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Sonu Sen ◽  
Meenu Asthana Varshney ◽  
Dinesh Varshney
Keyword(s):  
Dielectric Constant ◽  
Critical Power ◽  
Laser Pulses ◽  
Interaction Process ◽  
Laser Beams ◽  
Laser Beam Propagation ◽  
Circularly Polarized ◽  
Nonlinear Dielectric ◽  
Laser Plasma Interaction ◽  
Self Focusing

Paraxial theory of relativistic self-focusing of Gaussian laser beams in plasmas for arbitrary magnitude of intensity of the beam has been presented in this paper. The nonlinearity in the dielectric constant arises on account of relativistic variation of mass. An appropriate expression for the nonlinear dielectric constant has been used to study laser beam propagation for linearly/circularly polarized wave. The variation of beamwidth parameter with distance of propagation, self-trapping condition, and critical power has been evaluated. The saturating nature of nonlinearity yields two values of critical power of the beam ( and ) for self-focusing. When the beam diverges. When the beam first converges then diverges and so on. When the beam first diverges and then converges and so on. Numerical estimates are made for linearly/circularly polarized wave applicable for typical values of relativistic laser-plasma interaction process in underdense and overdense plasmas. Since the relativistic mechanism is instantaneous, this theory is applicable to understanding of self-focusing of laser pulses.

scholarly journals DEVELOPMENT OF ULTRA-SHORT HIGH INTENSITY LASERS FOR THE VISIBLE SPECTRA RANGE

2020 ◽  
Vol 17 (35) ◽  
pp. 739-752
Author(s):  
Hayder J. ABDULRAHMAN ◽  
Suzan B. MOHAMMED
Keyword(s):  
High Intensity ◽  
Laser Processing ◽  
Near Infrared ◽  
Laser Pulses ◽  
Dielectric Materials ◽  
Infrared Light ◽  
Near Infrared Light ◽  
Visible Spectra ◽  
Short Laser Pulses ◽  
Micro Tools

Ultra-short laser pulses are particularly suitable for processing micro tools made of ultra-hard and dielectric materials. Ultra-short laser pulses provide a contact-free and precise fabrication of heat-sensitive materials such as visible spectra range. Visible spectra range has unique properties, which makes it an essential material in the tool, jewelry, and semiconductor industries. The processing of visible spectra range by ultra-short laser pulses is complex, as visible and near-infrared light is generally not absorbed. However, the intensity of ultra-short laser pulses is extremely high, so that the absorption scales nonlinearly with the intensity and, thus, visible or near-infrared light can be absorbed. The complexity also results from many partially interdependent process variables, such as the repetition rate, pulse overlap, track overlap, and scan speed. Excellent knowledge of the process is, therefore, essential for the production of micro tools. To make the laser processing accessible to a broader user field, the operator can be supported by a computer-aided design (CAD). The aim of this research was to the modeling of an ultra-short high-intensity laser for the visible spectra range in different environments of the angle of incidence, scanning speed, pulse, and track overlap. The experimental process included ultra-short pulsed laser processing of visible spectra range and surface analysis concerning modifications and ablation of the ultra-short laser. Ablation volumes were analyzed for single pulses, multi-pulses, and pockets. Pump-probe experiments reveal transient optical properties such as transmission or reflectivity. It was concluded that ultraviolet laser pulses are best suited to induce damage or modifications to visible spectra range surfaces. Additionally, shorter wavelengths have further advantages such as potentially longer Rayleigh lengths and smaller spot sizes.

Steady-state self-focusing of rippled laser beams in plasmas: arbitrary nonlinearity

1992 ◽  
Vol 48 (1) ◽  
pp. 107-118 ◽  
Author(s):  
M. S. Sodha ◽  
S. Konar ◽  
K. P. Maheshwari
Keyword(s):  
Dielectric Constant ◽  
Thermal Conduction ◽  
Critical Power ◽  
Laser Beams ◽  
Main Beam ◽  
Effective Dielectric Constant ◽  
Beam Power ◽  
Nonlinear Part ◽  
Self Focusing ◽  
Paraxial Ray

This paper presents an analysis of the self-focusing of a rippled Gaussian laser beam in a plasma when the nonlinear part of the effective dielectric constant is arbitrarily large. Considering the nonlinearity to arise from ponderomotive, collisional or thermal-conduction phenomena and following the approach of Akhmanov, Sukhorukov and Khokhlov (which is based on the WKB and paraxial-ray approximation) the phenomenon of self-focusing of rippled laser beams is studied for arbitrary magnitude of nonlinearity. For ponderomotive and collisional nonlinearities, the present theory leads to two values of the critical power for self-focusing of the beam, Pcrl and Pcr2, which depend on the amplitudes and phase difference of the main beam and the ripple. When the beam power P lies between the two critical values (i.e. Pcr1 < P < Pcr2), the medium behaves as an oscillatory waveguide; the beam first converges and then diverges, again converges, and so on. For P < Pcr2, the beam first diverges, then converges, then diverges, and so on. When thermal conduction is the dominant mechanism of nonlinearity of the dielectric constant, only one value of the threshold critical power Pcr for self-focusing of the beam exists. When the beam power P < Pcr, the medium behaves as an oscillatory waveguide.

Relativistic cross-focusing of two coaxial Gaussian laser beams in a plasma

1998 ◽  
Vol 60 (4) ◽  
pp. 811-818 ◽  
Author(s):  
RAJ KUMAR ◽  
H. D. PANDEY ◽  
R. P. SHARMA ◽  
M. KUMAR
Keyword(s):  
Laser Beam ◽  
Relativistic Effect ◽  
Laser Pulses ◽  
The Self ◽  
Laser Beams ◽  
Particle Accelerators ◽  
Wave Excitation ◽  
Homogeneous Plasma ◽  
Self Focusing ◽  
Ponderomotive Nonlinearity

The paper presents a paraxial theory of the relativistic cross-focusing of two coaxial Gaussian laser beams of different frequencies in a homogeneous plasma. We discuss the self-focusing of a weaker laser beam in the plasma due to the optical inhomogeneities introduced by another stronger copropagating laser beam. In the presence of the second stronger beam (Pcr21<P2<Pcr22), the plasma behaves as an oscillatory waveguide for the first, weaker, beam (P1<Pcr11) as it propagates in the plasma. When both the beams are strong (Pcr11,21<P1,2<Pcr12,22), the nonlinearities introduced by the relativistic effect are additive in nature, such that one beam can undergo oscillatory self-focusing and the other simultaneously defocusing, and vice versa. A comparison reveals that cross-focusing due to relativistic nonlinearity is possible for a wider range of powers of the laser pulses than is cross-focusing due to ponderomotive nonlinearity. Relativistic cross-focusing is important in plasma beat-wave excitation and collective laser particle accelerators.

Self-focusing and channel-coupling effects on short laser pulses propagating in a plasma channel

2004 ◽  
Vol 11 (6) ◽  
pp. 3259-3263 ◽  
Author(s):  
Pallavi Jha ◽  
Navina Wadhwani ◽  
Ajay. K. Upadhyaya ◽  
Gaurav Raj
Keyword(s):  
Plasma Channel ◽  
Laser Pulses ◽  
Coupling Effects ◽  
Channel Coupling ◽  
Self Focusing ◽  
Short Laser Pulses

Self-focusing and the initial stages of plasma generation by short laser pulses

1978 ◽  
Vol 29 (2) ◽  
pp. 357-357
Author(s):  
J. E. Balmer ◽  
T. P. Donaldson ◽  
J. A. Zimmermann
Keyword(s):  
Laser Pulses ◽  
Plasma Generation ◽  
Self Focusing ◽  
Short Laser Pulses

scholarly journals X-ray spectroscopy observation of fast ions generation in plasma produced by short low-contrast laser pulse irradiation of solid targets

2007 ◽  
Vol 25 (2) ◽  
pp. 267-275 ◽  
Author(s):  
A.YA. Faenov ◽  
A.I. Magunov ◽  
T.A. Pikuz ◽  
I. YU. Skobelev ◽  
S.V. Gasilov ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Laser Intensity ◽  
Laser Pulses ◽  
Intense Laser ◽  
Low Contrast ◽  
X Ray ◽  
Fast Ions ◽  
Self Focusing ◽  
Short Laser Pulses ◽  
Charged Ions

X-ray spectra of plasma produced by the interaction of Ti:Sa laser pulses (duration from 60 fs to 1 ps, and energy from 15 mJ to 128 mJ) with foil and solid Teflon and AL targets are investigated. It is shown experimentally and theoretically that the use of low contrast (10−2 – 10−4) short laser pulses, essentially promotes the conditions for generation of fast multi-charged ions. This effect is caused by self-focusing of the main laser pulse in a preplasma produced by intense laser prepulses. Modeling of the observed spectral line shape gives evidence of a considerable (about 3%) amount of multi-charged He-like F ions with energy E ∼ 1 MeV at rather low values of laser intensity IL ≈ 6 × 1016 W cm−2.

scholarly journals Nonlinear relativistic self-focusing of laser radiation in plasmas: Arbitrary intensity

1994 ◽  
Vol 12 (4) ◽  
pp. 623-632 ◽  
Author(s):  
M. Asthana ◽  
K.P. Maheshwari ◽  
M.S. Sodha
Keyword(s):  
Dielectric Constant ◽  
Critical Power ◽  
Laser Pulses ◽  
Density Fluctuations ◽  
Effective Dielectric Constant ◽  
Gaussian Laser Beam ◽  
Nonlinear Part ◽  
Self Focusing ◽  
Paraxial Ray ◽  
Arbitrary Intensity

A paraxial theory of relativistic self-focusing of a Gaussian laser beam in plasmas, when the nonlinear part of the effective dielectric constant is arbitrarily large, is presented. The plasma is taken to be homogeneous without any density fluctuations being necessary. The approach of Akhmanov et al. based on the WKB and paraxial ray approximations has been followed. It is seen that the saturating nature of nonlinearity leads to two values of critical power of the beam (Pcrl and Pcr2) for self-focusing. When the power of the beam P lies between the two critical values (i.e., Pcr1 < P < Pcr2), the medium behaves as an oscillatory waveguide; the beam first converges and then diverges, converges again, and so on. For P > Pcr2 the beam first diverges, then converges, then diverges, and so on. Because the relativistic mechanism is instantaneous, the theory is applicable to the understanding of selffocusing of laser pulses also.

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