Spatial Dependence of Inverse Raman Signals

The spatial dependence of inverse Raman signal intensities was investigated. Aqueous 0.5 M potassium nitrate in cells ranging from 1 to 50 mm was used as the test system. Three focusing lenses were used. The data do not fit the arctan dependence derived for Gaussian beams. The deviations are ascribed to the non-Gaussian profile of the pulsed dye laser beam.

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Spatial evolution of a q-Gaussian laser beam in relativistic plasma

Laser and Particle Beams ◽

10.1017/s0263034610000479 ◽

2010 ◽

Vol 28 (3) ◽

pp. 479-489 ◽

Cited By ~ 21

Author(s):

A. Sharma ◽

I. Kourakis

Keyword(s):

Laser Beam ◽

Beam Profile ◽

Relativistic Plasma ◽

Gaussian Laser Beam ◽

Transverse Beam ◽

Recent Experimental Study ◽

Gaussian Profile ◽

Spatial Beam ◽

Gaussian Distribution Function ◽

Non Gaussian

AbstractIn a recent experimental study, the beam intensity profile of the Vulcan petawatt laser beam was measured; it was found that only 20% of the energy was contained within the full width at half maximum of 6.9 μm and 50% within 16 μm, suggesting a long-tailed non-Gaussian transverse beam profile. A q-Gaussian distribution function was suggested therein to reproduce this behavior. The spatial beam profile dynamics of a q-Gaussian laser beam propagating in relativistic plasma is investigated in this article. A non-paraxial theory is employed, taking into account nonlinearity via the relativistic decrease of the plasma frequency. We have studied analytically and numerically the dynamics of a relativistically guided beam and its dependence on the q-parameter. Numerical simulation results are shown to trace the dependence of the focusing length on the q-Gaussian profile.

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Generation of Efficient Terahertz Radiation by Relativistic Self-Focusing of A Cosh-Gaussian Laser Beam in A Magnetized Plasma

10.21203/rs.3.rs-1195824/v1 ◽

2021 ◽

Author(s):

Gunjan Purohit ◽

Bineet Gaur ◽

Pradeep Kothiyal ◽

Amita Raizada

Keyword(s):

Laser Beam ◽

Numerical Study ◽

The Self ◽

Magnetized Plasma ◽

Thz Radiation ◽

Gaussian Laser Beam ◽

Plasma Parameters ◽

Gaussian Profile ◽

Self Focusing ◽

Incident Laser Intensity

Abstract This paper presents a scheme for the generation of terahertz (THz) radiation by self-focusing of a cosh-Gaussian laser beam in the magnetized and rippled density plasma, when relativistic nonlinearity is operative. The strong coupling between self-focused laser beam and pre-existing density ripple produces nonlinear current that originates THz radiation. THz radiation is produced by the interaction of the cosh-Gaussian laser beam with electron plasma wave under the appropriate phase matching conditions. Expressions for the beamwidth parameter of cosh-Gaussian laser beam and the electric vector of the THz radiation have been obtained using higher-order paraxial theory and solved numerically. The self-focusing of the cosh-Gaussian laser beam and its effect on the generated THz amplitude have been studied for specific laser and plasma parameters. Numerical study has been performed on various values of the decentered parameter, incident laser intensity, magnetic field, and relative density. The results have also been compared with the paraxial region as well as the Gaussian profile of laser beam. Numerical results suggest that the self-focusing of the cosh-Gaussian laser beam and the amplitude of THz radiation increase in the extended paraxial region compared to the paraxial region. It is also observed that the focusing of the cosh-Gaussian laser beam in the magnetized plasma and the amplitude of the THz radiation increases at higher values of the decentered parameter.

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Thermal-induced nonlinearities in rose, linseed, and chamomile oils using continuous wave visible laser beam

Canadian Journal of Physics ◽

10.1139/cjp-2017-0385 ◽

2018 ◽

Vol 96 (2) ◽

pp. 157-164 ◽

Cited By ~ 16

Author(s):

H.A. Sultan ◽

Qusay M.A. Hassan ◽

H. Bakr ◽

Ahmed S. Al-Asadi ◽

D.H. Hashim ◽

...

Keyword(s):

Laser Beam ◽

Continuous Wave ◽

Input Power ◽

Diffraction Ring ◽

Linear Absorption ◽

Gaussian Profile ◽

Diffraction Integral ◽

Visible Laser ◽

A Cell ◽

Kirchhoff Diffraction Integral

Self-diffraction rings or spatial self-phase modulation were observed in rose, linseed, and chamomile oils under 473 nm continuous wave laser irradiation. The measurements were performed by propagating the laser beam through a cell containing each sample. The number of rings as well as diameter of the outer-most ring in each pattern obtained increases monotonically with increasing input power. The diffraction ring patterns are theoretically simulated using Fresnel–Kirchhoff diffraction integral in the case of an optically thin medium. The experimental and simulation results show that when a laser beam with Gaussian profile is transmitted through an oil medium, a series of circular diffraction rings forms in the intensity distribution pattern in the far-field. The nonlinear refractive index, n2, was determined from the number of observed rings and by the Z-scan technique. The results obtained from self-diffraction rings experiment and Z-scan are compared and analyzed for the three different oils. A large value was obtained of the order of n2 = 1.32 × l0−6 cm2/W for chamomile oil using the diffraction ring pattern technique. This large nonlinearity is attributed to a thermal effect resulting from linear absorption. Moreover, the optical limiting characteristics of rose, linseed, and chamomile oils were investigated.

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Study of self-focusing of Non Gaussian laser beam in a plasma with density variation using moment theory approach

10.1063/1.5032748 ◽

2018 ◽

Cited By ~ 2

Author(s):

Nidhi Pathak ◽

Sukhdeep Kaur ◽

Sukhmander Singh

Keyword(s):

Laser Beam ◽

Density Variation ◽

Theory Approach ◽

Gaussian Laser Beam ◽

Moment Theory ◽

Self Focusing ◽

Non Gaussian

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Generalized Thermoelastic Functionally Graded on a Thin Slim Strip Non-Gaussian Laser Beam

Symmetry ◽

10.3390/sym12071094 ◽

2020 ◽

Vol 12 (7) ◽

pp. 1094 ◽

Cited By ~ 4

Author(s):

Sayed M. Abo-Dahab ◽

Ahmed E. Abouelregal ◽

Marin Marin

Keyword(s):

Laser Beam ◽

Pulse Length ◽

Generalized Thermoelasticity ◽

Functionally Graded ◽

Strong Impact ◽

Problem Solution ◽

Gaussian Laser Beam ◽

Laser Parameters ◽

Non Gaussian ◽

The Impact

The present study utilizes the generalized thermoelasticity theory, with one thermal relaxation time (TR), to examine the thermoelastic problem of a functionally graded thin slim strip (TSS). The authors heated the plane surface bounding using a non-Gaussian laser beam with a pulse length of 2 ps. The material characteristics varied continually based on exponential functions. Moreover, the equations governing the generalized thermoelasticity for a functionally graded material (FGM) are recognized. The problem’s ideal solution was primarily obtained in the Laplace transform (LT) space. The LTs were converted numerically because of the considerable importance of the response in the transient state. For a hypothetical substance, the numerical procedures calculating the displacement, stress, temperature and strain were given. The analogous problem solution to an isotropic homogeneous material was provided by defining the parameter of non-homogeneity adequately. The obtained results were displayed using graphs to illustrate the extent to which non-homogeneity affected displacement, stress, temperature and strain. A comparison was been made between the present study and those previously obtained by others, when the new parameters vanish to show the impact of the non-homogeneity, TSS and laser parameters on the phenomenon. The results obtained indicate a significant strong impact of FGM, TSS and laser parameters.

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A CAD coupled laser beam test system for digital circuit failure analysis

Microelectronics Reliability ◽

10.1016/0026-2714(92)90251-f ◽

1992 ◽

Vol 32 (1-2) ◽

pp. 300-301

Keyword(s):

Laser Beam ◽

Failure Analysis ◽

Digital Circuit ◽

Test System ◽

Beam Test

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Advanced LIGO: non-Gaussian beams

Classical and Quantum Gravity ◽

10.1088/0264-9381/21/5/074 ◽

2004 ◽

Vol 21 (5) ◽

pp. S867-S873 ◽

Cited By ~ 14

Author(s):

Erika D'Ambrosio ◽

Richard O'Shaugnessy ◽

Kip Thorne ◽

Phil Willems ◽

Sergey Strigin ◽

...

Keyword(s):

Gaussian Beams ◽

Non Gaussian

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Raman Signal Enhancement in Deep Spectroscopy of Turbid Media

Applied Spectroscopy ◽

10.1366/000370207781540178 ◽

2007 ◽

Vol 61 (8) ◽

pp. 845-854 ◽

Cited By ~ 49

Author(s):

P. Matousek

Keyword(s):

Raman Spectroscopy ◽

Laser Radiation ◽

Laser Beam ◽

Near Infrared ◽

Optical Element ◽

Disease Diagnosis ◽

Pharmaceutical Products ◽

Turbid Media ◽

Raman Signal

A new, passive method for enhancing spontaneous Raman signals for the spectroscopic investigation of turbid media is presented. The main areas to benefit are transmission Raman and spatially offset Raman spectroscopy approaches for deep probing of turbid media. The enhancement, which is typically several fold, is achieved using a multilayer dielectric optical element, such as a bandpass filter, placed within the laser beam over the sample. This element prevents loss of the photons that re-emerge from the medium at the critical point where the laser beam enters the sample, the point where major photon loss occurs. This leads to a substantial increase of the coupling of laser radiation into the sample and consequently an enhanced laser photon–medium interaction process. The method utilizes the angular dependence of dielectric optical elements on impacting photon direction with its transmission spectral profile shifting to the blue with increase in the deviation of photons away from normal incidence. This feature enables it to act as a unidirectional mirror passing a semi-collimated laser beam through unhindered from one side, and at the other side, reflecting photons emerging from the sample at random directions back into it with no restrictions to the detected Raman signal. With substantial restrictions to the spectral range, the concept can also be applied to conventional backscattering Raman spectroscopy. The use of additional reflective elements around the sample to enhance the Raman signal further is also discussed. The increased signal strength yields higher signal quality, a feature important in many applications. Potential uses include sensitive noninvasive disease diagnosis in vivo, security screening, and quality control of pharmaceutical products. The concept is also applicable in an analogous manner to other types of analytical methods such as fluorescence or near-infrared (NIR) absorption spectroscopy of turbid media or it can be used to enhance the effectiveness of the coupling of laser radiation into tissue in applications such as photodynamic therapy for cancer treatment.

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