Methods for Determining the Characteristics of Laser Beams and the Optical Transmission

2014 ◽  
Vol 656 ◽  
pp. 345-350
Author(s):  
Iulian Nicola ◽  
Tudor Prisecaru
Keyword(s):  
Laser Beam ◽  
Experimental Measurement ◽  
Optical Transmission ◽  
Optical Systems ◽  
Laser Beams ◽  
Laser Rangefinder ◽  
New Methods

The paper presents new methods and procedures to measure the characteristics of laser beams and their transmission through optical systems. The paper describes the work procedures and equipments used to measure the characteristics of laser beams and their transmission through optical systems. Using these working procedures, experimental measurement for the characteristics of the beam for a 1.54 µm laser rangefinder and the transmission of a 633 nm laser beam through laser protection glasses were made.

Adaptive Optical Systems in Russian Federal Nuclear Center - VNIIEF with Different Control Principles

2012 ◽  
Vol 82 ◽  
pp. 75-84 ◽  
Author(s):  
Sergey Garanin ◽  
Sergey Khokhlov ◽  
Aleksei Manachinsky ◽  
Fedor Starikov
Keyword(s):  
Laser Beam ◽  
Phase Correction ◽  
Gradient Algorithm ◽  
Optical Systems ◽  
Laser Beams ◽  
Control Units ◽  
Static Phase ◽  
Adaptive Mirror ◽  
Phase Aberrations ◽  
Special Control

We report the results of performance of closed-loop adaptive optical systems intended for phase correction of pulsed and cw laser beams. The conventional control of adaptive system is based on wavefront sensing (e.g., Hartmann-Shack) and following deformation of adaptive mirror surface. We demonstrate the results of such static phase correction in the cases of the vortex laser beam and the powerful laser beam of pulsed “Luch” facility. On other side, applying the sensor-less approach we perform the dynamic phase correction of tip-tilts and higher phase aberrations of laser beams using the stochastic parallel gradient algorithm embedded into the special control units with microcontroller that considerably broadens the system operation bandwidth.

Aberrational synthesis of optical systems intended for the conversion of laser beams

2011 ◽  
Vol 78 (9) ◽  
pp. 586 ◽  
Author(s):  
P. A. Nosov ◽  
V. Yu. Pavlov ◽  
I. I. Pakhomov ◽  
A. F. Shirankov
Keyword(s):  
Optical Systems ◽  
Laser Beams

scholarly journals A critical look at the prediction of the temperature field around a laser-induced melt pool on metallic substrates

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yi Shu ◽  
Daniel Galles ◽  
Ottman A. Tertuliano ◽  
Brandon A. McWilliams ◽  
Nancy Yang ◽  
...  
Keyword(s):  
Laser Beam ◽  
Constant Velocity ◽  
Three Dimensional ◽  
Laser Beams ◽  
Poor Control ◽  
Metallic Substrates ◽  
Melt Pool ◽  
Mechanical Models ◽  
Transport Effects ◽  
Thermal Histories

AbstractThe study of microstructure evolution in additive manufacturing of metals would be aided by knowing the thermal history. Since temperature measurements beneath the surface are difficult, estimates are obtained from computational thermo-mechanical models calibrated against traces left in the sample revealed after etching, such as the trace of the melt pool boundary. Here we examine the question of how reliable thermal histories computed from a model that reproduces the melt pool trace are. To this end, we perform experiments in which one of two different laser beams moves with constant velocity and power over a substrate of 17-4PH SS or Ti-6Al-4V, with low enough power to avoid generating a keyhole. We find that thermal histories appear to be reliably computed provided that (a) the power density distribution of the laser beam over the substrate is well characterized, and (b) convective heat transport effects are accounted for. Poor control of the laser beam leads to potentially multiple three-dimensional melt pool shapes compatible with the melt pool trace, and therefore to multiple potential thermal histories. Ignoring convective effects leads to results that are inconsistent with experiments, even for the mild melt pools here.

scholarly journals Investigation of serial coherent laser beam combination based on Brillouin amplification

2007 ◽  
Vol 25 (1) ◽  
pp. 79-83 ◽  
Author(s):  
SHUANGYI WANG ◽  
ZHIWEI LÜ ◽  
DIANYANG LIN ◽  
LEI DING ◽  
DONGBIN JIANG
Keyword(s):  
Laser Beam ◽  
High Power ◽  
Simple Structure ◽  
Low Cost ◽  
Coupling Efficiency ◽  
Laser Beams ◽  
Beam Combination ◽  
Multiple Beams ◽  
Combination Scheme ◽  
Stokes Beam

Based on transferring energy from multiple pump beams into one Stokes beam using Brillouin amplification, a serial coherent laser beam combination scheme is presented, which has many advantages, such as, simple structure, low cost, ease of adjustment, higher load capability, scalable easily, etc. Furthermore, it has been demonstrated that the combination of several beams using this method is theoretically possible. But in practice, the amplification of high power Stokes beam is a key problem to solve. In this paper, the amplification of Stokes beam whose power is higher than the pump beam is first studied and proved experimentally. Coupling the two laser beams by this method is proved experimentally, and the coupling efficiency reaches more than 80%. Then the feasibility of multiple beams combination based on Brillouin amplification is analyzed and tested theoretically.

Relativistic self-focusing of a rippled laser beam in a plasma

1999 ◽  
Vol 62 (4) ◽  
pp. 389-396 ◽  
Author(s):  
M. V. ASTHANA ◽  
A. GIULIETTI ◽  
DINESH VARSHNEY ◽  
M. S. SODHA
Keyword(s):  
Refractive Index ◽  
Laser Beam ◽  
The Self ◽  
Laser Beams ◽  
Radial Dependence ◽  
Main Beam ◽  
Gaussian Laser Beam ◽  
Self Focusing ◽  
Saturation Effects ◽  
Paraxial Ray

This paper presents an analysis of the relativistic self-focusing of a rippled Gaussian laser beam in a plasma. Considering the nonlinearity as arising owing to relativistic variation of mass, and following the WKB and paraxial-ray approximations, the phenomenon of self-focusing of rippled laser beams is studied for arbitrary magnitude of nonlinearity. Pandey et al. [Phys. Fluids82, 1221 (1990)] have shown that a small ripple on the axis of the main beam grows very rapidly with distance of propagation as compared with the self-focusing of the main beam. Based on this analogy, we have analysed relativistic self-focusing of rippled beams in plasmas. The relativistic intensities with saturation effects of nonlinearity allow the nonlinear refractive index in the paraxial regime to have a slower radial dependence, and thus the ripple extracts relatively less energy from its neighbourhood.

scholarly journals Self-compression of two co-propagating laser pulse having relativistic nonlinearity in plasma

2017 ◽  
Vol 35 (4) ◽  
pp. 722-729
Author(s):  
S. Kumar ◽  
P. K. Gupta ◽  
R. K. Singh ◽  
R. Uma ◽  
R. P. Sharma
Keyword(s):  
Laser Beam ◽  
Pulse Width ◽  
Pulse Compression ◽  
Group Velocity Dispersion ◽  
Refractive Index Profile ◽  
Intense Laser ◽  
Laser Beams ◽  
Critical Parameters ◽  
Beam Power ◽  
Laser Beam Intensity

AbstractThe study proposes a semi-analytical model for the pulse compression of two co-propagating intense laser beams having Gaussian intensity profile in the temporal domain. The high power laser beams create the relativistic nonlinearity during propagation in plasma, which leads to the modification of the refractive index profile. The co-propagating laser beams get self- compressed by virtue of group velocity dispersion and induced nonlinearity. The induced nonlinearity in the plasma broadens the frequency spectrum of the pulse via self-phase modulation, turn to shorter the pulse duration and enhancement of laser beam intensity. The nonlinear Schrodinger equations were set up for co-propagating laser beams in plasmas and have been solved in Matlab by considering paraxial approximation. The propagation characteristics of both laser beams inside plasma are divided into three regions through the critical divider curve, which has been plotted between pulse width τ01 and laser beam power P01. Based on the preferred value of critical parameters, these regions are oscillatory compression, oscillatory broadening, and steady broadening. In findings, it is observed that the compression of the laser beam depends on the combined intensity of both beams, plasma density, and initial pulse width.

scholarly journals Self-Focusing of Hermite-Cosh-Gaussian Laser Beams in Plasma under Density Transition

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
Manzoor Ahmad Wani ◽  
Niti Kant
Keyword(s):  
Laser Beam ◽  
Plasma Density ◽  
Focal Spot ◽  
Beam Width ◽  
Spot Size ◽  
Laser Beams ◽  
Equation Approach ◽  
Focal Spot Size ◽  
Self Focusing ◽  
Small Spot

Self-focusing of Hermite-Cosh-Gaussian (HChG) laser beam in plasma under density transition has been discussed here. The field distribution in the medium is expressed in terms of beam-width parameters and decentered parameter. The differential equations for the beam-width parameters are established by a parabolic wave equation approach under paraxial approximation. To overcome the defocusing, localized upward plasma density ramp is considered, so that the laser beam is focused on a small spot size. Plasma density ramp plays an important role in reducing the defocusing effect and maintaining the focal spot size up to several Rayleigh lengths. To discuss the nature of self-focusing, the behaviour of beam-width parameters with dimensionless distance of propagation for various values of decentered parameters is examined by numerical estimates. The results are presented graphically and the effect of plasma density ramp and decentered parameter on self-focusing of the beams has been discussed.

Holographic Pattern Etching of Silicon—Carbide by Excimer Laser

1989 ◽  
Vol 158 ◽  
Author(s):  
M. Murahara ◽  
M. Yonekawa ◽  
K. Shirakawa
Keyword(s):  
Laser Beam ◽  
Present Method ◽  
Etching Rate ◽  
The Other ◽  
Laser Beams ◽  
Excimer Lasers ◽  
Holographic Method ◽  
Etching Depth ◽  
Krf Laser ◽  
193 Nm

ABSTRACTThe diffraction grating on SiC mirror was performed by a laser holographic method. In the present method, KrF laser and CIF3 was used for etchant gas. The ClF3 gas has an absorption band in the range between 200 and 400 nm. Therefore, CIF3 gas is effectively decomposed by the XeF, KrF and ArF excimer lasers' radiation. It is found that absorption of Si—C is about 50% in the range of between200 and 400 nm, and that the bonding energy of Si—C is lower than the photon energy of KrF laser beam. The above results indicate the direct decomposition of Si—Cbond. On the other hand, the threshold fluence energy for etching was 800 mJ/cm2 in 249 nm and in 193 nm as high as 7 J/cm2. In these results, the KrF laser is more effective than ArF laser. Then we applied KrF laser to crystalline SiC in an atmosphere of C1F3 gas. The divided two polarized KrF laser beams were interfered on the substrate. And the beams were used to photodissociated CIF3 gas in the proximity of substrate. Fluence of KrF laser beam was 1 J/cm2. The incidential angle of KrF laser beams was 20º and the grating gaps were 7170 Å, etching depth 1000 Å, and etching rate was 5 Å/pulse.

Raman Apparatus Using Laser Excitation and Polarization Measurements. Rotational Spectrum of Fluorine

1969 ◽  
Vol 23 (1) ◽  
pp. 8-12 ◽  
Author(s):  
Howard H. Claassen ◽  
Henry Selig ◽  
Jacob Shamir
Keyword(s):  
Laser Beam ◽  
Raman Spectra ◽  
Laser Excitation ◽  
Scattered Light ◽  
Rotational Constant ◽  
Emission Lines ◽  
Optical Systems ◽  
Rotational Spectrum ◽  
Polarization Measurements

Various schemes are compared for measuring depolarization factors in Raman spectra with laser excitation. Optical systems are discussed for producing a laser beam free of unwanted emission lines and for focusing scattered light on the slit and on the detector. The rotational spectrum of gaseous F2 has been used to determine a rotational constant of Bo=0.8841 ±0.0006 cm−1, corresponding to r0=1.4168±0.0005 Å.

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