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Sample records for laser beam distortion

  1. Propagation of coherently combined truncated laser beam arrays with beam distortions in non-Kolmogorov turbulence.

    PubMed

    Tao, Rumao; Si, Lei; Ma, Yanxing; Zhou, Pu; Liu, Zejin

    2012-08-10

    The propagation properties of coherently combined truncated laser beam arrays with beam distortions through non-Kolmogorov turbulence are studied in detail both analytically and numerically. The analytical expressions for the average intensity and the beam width of coherently combined truncated laser beam arrays with beam distortions propagating through turbulence are derived based on the combination of statistical optics methods and the extended Huygens-Fresnel principle. The effect of beam distortions, such as amplitude modulation and phase fluctuation, is studied by numerical examples. The numerical results reveal that phase fluctuations have significant influence on the spreading of coherently combined truncated laser beam arrays in non-Kolmogorov turbulence, and the effects of the phase fluctuations can be negligible as long as the phase fluctuations are controlled under a certain level, i.e., a>0.05 for the situation considered in the paper. Furthermore, large phase fluctuations can convert the beam distribution rapidly to a Gaussian form, vary the spreading, weaken the optimum truncation effects, and suppress the dependence of spreading on the parameters of the non-Kolmogorov turbulence.

  2. Distortion and residual stresses in laser beam weld shaft-hub joints

    NASA Astrophysics Data System (ADS)

    Buschenhenke, F.; Hofmann, M.; Seefeld, T.; Vollertsen, F.

    In laser beam welding, a serious challenge is to control the distortion during the process. Understanding the whole process chain in view of different distortion potentials applied in each processing step provides the ability to control the distortion of the welded components. Every manufacturing step induces residual stresses in the component which can be released by the heat of the welding process, while further residual stresses are introduced into the welded parts upon cooling. The laser beam sources of the new generation permit a high power welding process and high beam quality at the same time. These laser beams are capable of producing deep and narrow seams. Thus the thermal strains of the joined parts are expected to be minimized. Especially axial welded shaft-hub joints show an irregular distribution of bending deformation, which is caused by the self-influencing welding gap. This work deals with the investigation of different laser beam sources and their effect on the welding distortion in axial welded shafthub joints made of steel (20MnCr5). The aim of the work done was to achieve minimal distortion after the welding process. To characterize the influences on the distortion behaviour of the welded parts, residual stresses have been determined by neutron diffraction.

  3. Simulation of the wavefront distortion and beam quality for a high-power zigzag slab laser

    NASA Astrophysics Data System (ADS)

    Shin, Jae Sung; Cha, Yong-Ho; Cha, Byung Heon; Lee, Hyeon Cheor; Kim, Hyun Tae; Lee, Jung Hwan

    2016-12-01

    A simulation method of the beam quality for a high-power zigzag slab laser has been developed. This method can predict the wavefront distortion and beam quality for various optical arrangements and optimize the design effectively. A Nd:YAG zigzag slab laser amplifier was designed as an application. The optimized design shows a beam quality of 1.20 corresponding to the minimized wavefront distortion with a peak-to-valley of 0.568 μm and root mean square of 0.115 μm even under high-power operation with a total pump power of 14 kW. Although there are some effects other than the optical design error that incur wavefront distortions, this method can help to determine the first optical design of the zigzag slab laser without the need for many experimental studies.

  4. Signal distortion due to beam-pointing error in a chopper modulated laser system.

    PubMed

    Eklund, H

    1978-01-15

    The detector output has been studied for a long-distance system with a chopped cw laser as transmitter source. It is shown experimentally that the pulse distortion of the detected signal is dependent on the beam-pointing error. Parameters reflecting the pulse distortion are defined. The beam deviation in 1-D is found to be strongly related to these parameters. The result is in agreement with a theoretical model based upon the Fresnel diffraction theory. Possible applications in beam-tracking systems, communications systems, and atmospheric studies are discussed. PMID:20174398

  5. Severe Self-induced Beam Distortion in Laboratory Simulated Laser Propagation at 10.6 micro.

    PubMed

    Buser, R G; Rohde, R S

    1973-02-01

    Precision irradiance profiles have been determined for horizontally slewing high power laser beams through stationary absorbing gaseous media for the case of strong beam-medium interaction coupled with strong heating. Results are compared with the predictions of existing theoretical models concerning thermally induced lens effects in the presence of cross winds. Bending of the beam into the wind by beam slewing and intensification is found in reasonable agreement with the theory; for the observed overall beam spread, induced flow, turbulent tail, and concomitant beam breakup, no satisfactory theoretical treatment is available.

  6. Zigzag laser with reduced optical distortion

    DOEpatents

    Albrecht, Georg F.; Comaskey, Brian; Sutton, Steven B.

    1994-01-01

    The architecture of the present invention has been driven by the need to solve the beam quality problems inherent in Brewster's angle tipped slab lasers. The entrance and exit faces of a solid state slab laser are cut perpendicular with respect to the pump face, thus intrinsically eliminating distortion caused by the unpumped Brewster's angled faces. For a given zigzag angle, the residual distortions inherent in the remaining unpumped or lightly pumped ends may be reduced further by tailoring the pump intensity at these ends.

  7. Zigzag laser with reduced optical distortion

    DOEpatents

    Albrecht, G.F.; Comaskey, B.; Sutton, S.B.

    1994-04-19

    The architecture of the present invention has been driven by the need to solve the beam quality problems inherent in Brewster's angle tipped slab lasers. The entrance and exit faces of a solid state slab laser are cut perpendicular with respect to the pump face, thus intrinsically eliminating distortion caused by the unpumped Brewster's angled faces. For a given zigzag angle, the residual distortions inherent in the remaining unpumped or lightly pumped ends may be reduced further by tailoring the pump intensity at these ends. 11 figures.

  8. Simulations of far-field optical beam quality influenced by the thermal distortion of the secondary mirror for high-power laser system

    NASA Astrophysics Data System (ADS)

    Guo, Ruhai; Chen, Ning; Zhuang, Xinyu; Wang, Bing

    2015-02-01

    In order to research the influence on the beam quality due to thermal deformation of the secondary mirror in the high power laser system, the theoretical simulation study is performed. Firstly, three typical laser power 10kW, 50kW and 100kW with the wavelength 1.064μm are selected to analyze thermal deformation of mirror through the finite element analyze of thermodynamics instantaneous method. Then the wavefront aberration can be calculated by ray-tracing theory. Finally, focus spot radius,beam quality (BQ) of far-filed beam can be calculated and comparably analyzed by Fresnel diffraction integration. The simulation results show that with the increasing laser power, the optical aberration of beam director gets worse, the far-field optical beam quality decrease, which makes the laser focus spot broadening and the peak optical intensity of center decreasing dramatically. Comparing the clamping ring and the three-point clamping, the former is better than the latter because the former only induces the rotation symmetric deformation and the latter introduces additional astigmatism. The far-field optical beam quality can be improved partly by simply adjusting the distance between the main mirror and the secondary mirror. But the far-field power density is still the one tenth as that without the heat distortion of secondary mirror. These results can also provide the reference to the thermal aberration analyze for high power laser system and can be applied to the field of laser communication system and laser weapon etc.

  9. Laser beam monitoring system

    DOEpatents

    Weil, Bradley S.; Wetherington, Jr., Grady R.

    1985-01-01

    Laser beam monitoring systems include laser-transparent plates set at an angle to the laser beam passing therethrough and light sensor for detecting light reflected from an object on which the laser beam impinges.

  10. Optimized laser turrets for minimum phase distortion

    NASA Technical Reports Server (NTRS)

    Vanderplaats, G. N.; Fuhs, A. E.; Blaisdell, G. A.

    1980-01-01

    An analysis and computer program which optimizes laser turret geometry to obtain minimum phase distortion is described. Phase distortion due to compressible, inviscid flow over small perturbation laser turrets in subsonic or supersonic flow is calculated. The turret shape is determined by a two dimensional Fourier series; in a similar manner, the flow properties are given by a Fourier series. Phase distortion is calcualted for propagation at serveral combinations of elevation and azimuth angles. A sum is formed from the set of values, and this sum becomes the objective function for an optimization computer program. The shape of the turret is varied to provide minimum phase distortion.

  11. Analysis and validation of laser spot weld-induced distortion

    SciTech Connect

    Knorovsky, G.A.; Kanouff, M.P.; Maccallum, D.O.; Fuerschbach, P.W.

    1999-12-09

    Laser spot welding is an ideal process for joining small parts with tight tolerances on weld size, location, and distortion, particularly those with near-by heat sensitive features. It is also key to understanding the overlapping laser spot seam welding process. Rather than attempting to simulate the laser beam-to-part coupling (particularly if a keyhole occurs), it was measured by calorimetry. This data was then used to calculate the thermal and structural response of a laser spot welded SS304 disk using the finite element method. Five combinations of process parameter values were studied. Calculations were compared to experimental data for temperature and distortion profiles measured by thermocouples and surface profiling. Results are discussed in terms of experimental and modeling factors. The authors then suggest appropriate parameters for laser spot welding.

  12. Luminosity Loss due to Beam Distortion and the Beam-Beam Instability

    SciTech Connect

    Wu, Juhao; Raubenheimer, T.O.; Chao, A.W.; Seryi, A.; Sramek, C.K.; /Rice U.

    2005-06-30

    In a linear collider, sources of emittance dilution such as transverse wakefields or dispersive errors will couple the vertical phase space to the longitudinal position within the beam (the so-called ''banana effect''). When the Intersection Point (IP) disruption parameter is large, these beam distortions will be amplified by a single bunch kink instability which will lead to luminosity loss. We study this phenomena both analytically using linear theory and via numerical simulation. In particular, we examine the dependence of the luminosity loss on the wavelength of the beam distortions and the disruption parameter. This analysis may prove useful when optimizing the vertical disruption parameter for luminosity operation with given beam distortions.

  13. Laser-Beam Separator

    NASA Technical Reports Server (NTRS)

    Mcdermid, I. S.

    1984-01-01

    Train of prisms and optical stop separate fundamental beam of laser from second and higher order harmonics of beam produced in certain crystals and by stimulated Raman scattering in gases and liquids.

  14. Wind profile estimation from point to point laser distortion data

    NASA Technical Reports Server (NTRS)

    Leland, Robert

    1989-01-01

    The author's results on the problem of using laser distortion data to estimate the wind profile along the path of the beam are presented. A new model for the dynamics of the index of refraction in a non-constant wind is developed. The model agrees qualitatively with theoretical predictions for the index of refraction statistics in linear wind shear, and is approximated by the predictions of Taylor's hypothesis in constant wind. A framework for a potential in-flight experiment is presented, and the estimation problem is discussed in a maximum likelihood context.

  15. Laser beam alignment system

    DOEpatents

    Kasner, William H.; Racki, Daniel J.; Swenson, Clark E.

    1984-01-01

    A plurality of pivotal reflectors direct a high-power laser beam onto a workpiece, and a rotatable reflector is movable to a position wherein it intercepts the beam and deflects a major portion thereof away from its normal path, the remainder of the beam passing to the pivotal reflectors through an aperture in the rotating reflector. A plurality of targets are movable to positions intercepting the path of light traveling to the pivotal reflectors, and a preliminary adjustment of the latter is made by use of a low-power laser beam reflected from the rotating reflector, after which the same targets are used to make a final adjustment of the pivotal reflectors with the portion of the high-power laser beam passed through the rotating reflector.

  16. Diffraction of a Laser Beam.

    ERIC Educational Resources Information Center

    Jodoin, Ronald E.

    1979-01-01

    Investigates the effect of the nonuniform irradiance across a laser beam on diffraction of the beam, specifically the Fraunhofer diffraction of a laser beam with a Gaussian irradiance profile as it passes through a circular aperture. (GA)

  17. Jones calculus modeling and analysis of the thermal distortion in a Ti:sapphire laser amplifier.

    PubMed

    Cho, Seryeyohan; Jeong, Jihoon; Yu, Tae Jun

    2016-06-27

    The mathematical modeling of an anisotropic Ti:sapphire crystal with a significant thermal load is performed. The model is expressed by the differential Jones matrix. A thermally induced distortion in the chirped-pulse amplification process is shown by the solution of the differential Jones matrix. Using this model, the thermally distorted spatio-temporal laser beam shape is calculated for a high-power and high-repetition-rate Ti:sapphire amplifier. PMID:27410590

  18. Aerodynamic distortion propagation calculation in application of high-speed target detection by laser

    NASA Astrophysics Data System (ADS)

    Zheng, Yonghui; Sun, Huayan; Zhao, Yanzhong; Chen, Jianbiao

    2015-10-01

    Active laser detection technique has a broad application prospect in antimissile and air defense, however the aerodynamic flow field around the planes and missiles cause serious distortion effect on the detecting laser beams. There are many computational fluid dynamics(CFD) codes that can predict the air density distribution and also the density fluctuations of the flow field, it's necessary for physical optics to be used to predict the distortion properties after propagation through the complex process. Aiming at the physical process of laser propagation in "Cat-eye" lenses and aerodynamic flow field for twice, distortion propagation calculation method is researched in this paper. In the minds of dividing the whole process into two parts, and tread the aero-optical optical path difference as a phase distortion, the incidence and reflection process are calculated using Collins formula and angular spectrum diffraction theory respectively. In addition, turbulent performance of the aerodynamic flow field is estimated according to the electromagnetic propagation theory through a random medium, the rms optical path difference and Strehl ratio of the turbulent optical distortion are obtained. Finally, Computational fluid mechanics and aero-optical distortion properties of the detecting laser beams are calculated with the hemisphere-on-cylinder turret as an example, calculation results are showed and analysed.

  19. Single element laser beam shaper

    DOEpatents

    Zhang, Shukui; Michelle D. Shinn

    2005-09-13

    A single lens laser beam shaper for converting laser beams from any spatial profile to a flat-top or uniform spatial profile. The laser beam shaper includes a lens having two aspheric surfaces. The beam shaper significantly simplifies the overall structure in comparison with conventional 2-element systems and therefore provides great ease in alignment and reduction of cost.

  20. Nonlinear correction of atmospheric distortions in laser communication systems

    NASA Astrophysics Data System (ADS)

    Semenova, Irina V.; Dimakov, Sergei A.; Karavaev, Pavel M.

    2002-08-01

    A laser beam propagating through the atmosphere, undergoes attenuation through absorption and scattering on droplets of fog, clouds, different kinds of precipitation (rain, snow), smoke, dust; as well as it is subjected to a turbulence-induced scintillation. The resulting influence is a decrease of the information capacity of the system, rise of the bit-error rate and deterioration of the pointing accuracy at the receiver. Whereas the attenuation caused by scattering can be predicted by monitoring the weather conditions, the effects induced by turbulence have a random character and need to be overcome via some dynamic compensation procedure. This can be done using the phenomenon of wavefront reversal by means of dynamic holograms, which allows automatic compensation of disturbances. The unique advantages given by holographic technique make it rather promising to develop a relatively simple and reliable module for correction of atmospheric distortions in laser communication systems. One of the main problems though is to find an optimal medium for hologram recording that allows fast write-read-erase operation, high diffraction efficiency, high stability of characteristics and long lifetime.

  1. Optical beam distortions induced by a shock wave.

    PubMed

    Banakh, V A; Sukharev, A A; Falits, A V

    2015-03-10

    The mean intensity and the displacement from the initially given propagation direction of the optical beam passed through the shock wave have been calculated. It has been shown that the spatial inhomogeneity of the refractive index of air caused by the shock wave arising in supersonic flow flowing a conical body can cause the focusing of the beam and strong anisotropic distortions of the intensity distribution in its cross section. The angular displacement of the optical beam from the initially given propagation direction owing to the shock wave depends only on the height above the Earth's surface at which the shock wave is formed. As the height increases, the influence of the shock wave on the optical beam propagating through it decreases.

  2. The influence of gain nonlinearities on distortion in semiconductor lasers

    NASA Astrophysics Data System (ADS)

    Lysak, Vladimir V.; Schatz, Richard; Shulika, Aleksey V.; Sukhoivanov, Igor A.; Kjebon, O.

    2004-09-01

    The semiconductor laser is commonly used as a light source in fiber-optical telecommunication systems. In order to send as much information as possible in a short time, it is important that the laser has a large modulation bandwidth, i.e., the turn-on and turn-off time should be as short as possible. In analogue fiber optic systems for transmission of radio or television signals, it is also important that the light from the laser increases linearly with driving current even at high modulation frequencies. Otherwise, the transmitted signal will become distorted. The modulation bandwidth and the modulation distortion are dependent both on the laser structure and the gain characteristics of the active material. One of the most useful approaches for the time-domain description of the response of optoelectronic devices is the so-called "rate equation model," which has been widely used to describe laser performance. Commonly, laser models with simple gain expressions are used for simulation of laser dynamics. In these models the small-signal dynamic parameters like the differential gain and gain saturation parameter are extracted from modulation response measurements. However, we show that in order to correctly calculate distortion, an accurate model of the dependence of gain on carrier density, n, and photon density, s, is needed. Commonly used gain models, fitted to give exactly the same modulation response can give significantly different distortion behavior.

  3. Optical phase distortion due to compressible flow over laser turrets

    NASA Technical Reports Server (NTRS)

    Fuhs, A. E.; Fuhs, S. E.

    1980-01-01

    Analytical models for optical phase distortion due to compressible flow over a laser turret are developed. Phase distortion is calculated for both blunt and small perturbation turrets. For the blunt turret, the Janzen-Rayleigh technique is used to determine the flow field. Phase distortions of 2.2 wavelengths at 3.8 microns are calculated for the blunt turret. For small perturbation turrets, a versatile analytical model is developed for a turret on a fuselage with circular cross section. With a two dimensional Fourier series representation of the turret, any shape can be considered. Both subsonic and supersonic flows can be calculated. Phase distortions of 1.2 wavelengths at 3.8 microns are calculated for one turret at high subsonic Mach number. In addition to being of value for laser turrets, the methods are applicable to reconnaissance aircraft using photographic equipment and cruise missiles using celestial navigation.

  4. Shaping propagation invariant laser beams

    NASA Astrophysics Data System (ADS)

    Soskind, Michael; Soskind, Rose; Soskind, Yakov

    2015-11-01

    Propagation-invariant structured laser beams possess several unique properties and play an important role in various photonics applications. The majority of propagation invariant beams are produced in the form of laser modes emanating from stable laser cavities. Therefore, their spatial structure is limited by the intracavity mode formation. We show that several types of anamorphic optical systems (AOSs) can be effectively employed to shape laser beams into a variety of propagation invariant structured fields with different shapes and phase distributions. We present a propagation matrix approach for designing AOSs and defining mode-matching conditions required for preserving propagation invariance of the output shaped fields. The propagation matrix approach was selected, as it provides a more straightforward approach in designing AOSs for shaping propagation-invariant laser beams than the alternative technique based on the Gouy phase evolution, especially in the case of multielement AOSs. Several practical configurations of optical systems that are suitable for shaping input laser beams into a diverse variety of structured propagation invariant laser beams are also presented. The laser beam shaping approach was applied by modeling propagation characteristics of several input laser beam types, including Hermite-Gaussian, Laguerre-Gaussian, and Ince-Gaussian structured field distributions. The influence of the Ince-Gaussian beam semifocal separation parameter and the azimuthal orientation between the input laser beams and the AOSs onto the resulting shape of the propagation invariant laser beams is presented as well.

  5. Compensation of pulse-distortion in saturated laser amplifiers.

    PubMed

    Schimpf, Damian N; Ruchert, Clemens; Nodop, Dirk; Limpert, Jens; Tünnermann, Andreas; Salin, Francois

    2008-10-27

    We derive an expression describing pre-compensation of pulse-distortion due to saturation effects in short pulse laser-amplifiers. The analytical solution determines the optimum input pulse-shape required to obtain any arbitrary target pulse-shape at the output of the saturated laser-amplifier. The relation is experimentally verified using an all-fiber amplifier chain that is seeded by a directly modulated laser-diode. The method will prove useful in applications of high power, high energy laser-amplifier systems that need particular pulse-shapes to be efficient, e.g. micromachining and scientific laser-matter-interactions. PMID:18958044

  6. Laser beam guard clamps

    DOEpatents

    Dickson, Richard K.

    2010-09-07

    A quick insert and release laser beam guard panel clamping apparatus having a base plate mountable on an optical table, a first jaw affixed to the base plate, and a spring-loaded second jaw slidably carried by the base plate to exert a clamping force. The first and second jaws each having a face acutely angled relative to the other face to form a V-shaped, open channel mouth, which enables wedge-action jaw separation by and subsequent clamping of a laser beam guard panel inserted through the open channel mouth. Preferably, the clamping apparatus also includes a support structure having an open slot aperture which is positioned over and parallel with the open channel mouth.

  7. Beam uniformity of flat top lasers

    NASA Astrophysics Data System (ADS)

    Chang, Chao; Cramer, Larry; Danielson, Don; Norby, James

    2015-03-01

    Many beams that output from standard commercial lasers are multi-mode, with each mode having a different shape and width. They show an overall non-homogeneous energy distribution across the spot size. There may be satellite structures, halos and other deviations from beam uniformity. However, many scientific, industrial and medical applications require flat top spatial energy distribution, high uniformity in the plateau region, and complete absence of hot spots. Reliable standard methods for the evaluation of beam quality are of great importance. Standard methods are required for correct characterization of the laser for its intended application and for tight quality control in laser manufacturing. The International Organization for Standardization (ISO) has published standard procedures and definitions for this purpose. These procedures have not been widely adopted by commercial laser manufacturers. This is due to the fact that they are unreliable because an unrepresentative single-pixel value can seriously distort the result. We hereby propose a metric of beam uniformity, a way of beam profile visualization, procedures to automatically detect hot spots and beam structures, and application examples in our high energy laser production.

  8. Laser beam methane detector

    NASA Technical Reports Server (NTRS)

    Hinkley, E. D., Jr.

    1981-01-01

    Instrument uses infrared absorption to determine methane concentration in liquid natural gas vapor. Two sensors measure intensity of 3.39 mm laser beam after it passes through gas; absorption is proportional to concentration of methane. Instrument is used in modeling spread of LNG clouds and as leak detector on LNG carriers and installations. Unit includes wheels for mobility and is both vertically and horizontally operable.

  9. Laser beam pulse formatting method

    DOEpatents

    Daly, T.P.; Moses, E.I.; Patterson, R.W.; Sawicki, R.H.

    1994-08-09

    A method for formatting a laser beam pulse using one or more delay loops is disclosed. The delay loops have a partially reflective beam splitter and a plurality of highly reflective mirrors arranged such that the laser beam pulse enters into the delay loop through the beam splitter and circulates therein along a delay loop length defined by the mirrors. As the laser beam pulse circulates within the delay loop a portion thereof is emitted upon each completed circuit when the laser beam pulse strikes the beam splitter. The laser beam pulse is thereby formatted into a plurality of sub-pulses. The delay loops are used in combination to produce complex waveforms by combining the sub-pulses using additive waveform synthesis. 8 figs.

  10. Laser beam pulse formatting method

    DOEpatents

    Daly, Thomas P.; Moses, Edward I.; Patterson, Ralph W.; Sawicki, Richard H.

    1994-01-01

    A method for formatting a laser beam pulse (20) using one or more delay loops (10). The delay loops (10) have a partially reflective beam splitter (12) and a plurality of highly reflective mirrors (14) arranged such that the laser beam pulse (20) enters into the delay loop (10) through the beam splitter (12) and circulates therein along a delay loop length (24) defined by the mirrors (14). As the laser beam pulse (20) circulates within the delay loop (10) a portion thereof is emitted upon each completed circuit when the laser beam pulse (20) strikes the beam splitter (12). The laser beam pulse (20) is thereby formatted into a plurality of sub-pulses (50, 52, 54 and 56). The delay loops (10) are used in combination to produce complex waveforms by combining the sub-pulses (50, 52, 54 and 56) using additive waveform synthesis.

  11. Atomic laser-beam finder.

    PubMed

    Viering, Kirsten; Medellin, David; Mo, Jianyong; Raizen, Mark G

    2012-11-01

    We report on an experimental method to align a laser beam to a cloud of atoms trapped in a magneto-optical trap (MOT). We show how balanced lock-in detection leads to a very sensitive method to align the laser beam to the atoms in the plane perpendicular to the propagation direction. This provides a very reliable and fast way of aligning laser beams to atoms trapped in a MOT.

  12. Thermally induced distortion of a high-average-power laser system by an optical transport system

    NASA Astrophysics Data System (ADS)

    Chow, Robert; Ault, Linda E.; Taylor, John R.; Jedlovec, Don

    1999-11-01

    The atomic vapor laser isotope separation process uses high- average power lasers that have the commercial potential to enrich uranium for the electric power utilities. The transport of the laser beam through the laser system to the separation chambers requires high performance optical components, most of which have either fused silica or Zerodur as the substrate material. One of the requirements of the optical components is to preserve the wavefront quality of the laser beam that propagate over long distances. Full aperture tests with the high power process lasers and finite element analysis (FEA) have been performed on the transport optics. The wavefront distortions of the various sections of the transport path were measured with diagnostic Hartmann sensor packages. The FEA results were derived from an in-house thermal-structural- optical code which is linked to the commercially available CodeV program. In comparing the measured and predicted results, the bulk absorptance of fused silica was estimated to about 50 ppm/cm in the visible wavelength regime. Wavefront distortions will be reported on optics made from fused silica and Zerodur substrate materials.

  13. Laser-cooled continuous ion beams

    SciTech Connect

    Schiffer, J.P.; Hangst, J.S.; Nielsen, J.S.

    1995-08-01

    A collaboration with a group in Arhus, Denmark, using their storage ring ASTRID, brought about better understanding of ion beams cooled to very low temperatures. The longitudinal Schottky fluctuation noise signals from a cooled beam were studied. The fluctuation signals are distorted by the effects of space charge as was observed in earlier measurements at other facilities. However, the signal also exhibits previously unobserved coherent components. The ions` velocity distribution, measured by a laser fluorescence technique suggests that the coherence is due to suppression of Landau damping. The observed behavior has important implications for the eventual attainment of a crystalline ion beam in a storage ring. A significant issue is the transverse temperature of the beam -- where no direct diagnostics are available and where molecular dynamics simulations raise interesting questions about equilibrium.

  14. Laser beam alignment apparatus and method

    DOEpatents

    Gruhn, Charles R.; Hammond, Robert B.

    1981-01-01

    The disclosure relates to an apparatus and method for laser beam alignment. Thermoelectric properties of a disc in a laser beam path are used to provide an indication of beam alignment and/or automatic laser alignment.

  15. Laser beam alignment apparatus and method

    DOEpatents

    Gruhn, C.R.; Hammond, R.B.

    The disclosure related to an apparatus and method for laser beam alignment. Thermoelectric properties of a disc in a laser beam path are used to provide an indication of beam alignment and/or automatic laser alignment.

  16. Thermal-induced two dimensional beam distortion in planar waveguide amplifiers.

    PubMed

    Wang, Xiao-Jun; Ke, Wei-Wei; Su, Hua

    2013-07-29

    Mode characteristics in the solid-state planar waveguide (PWG) laser amplifiers are investigated theoretically, in consideration of the temperature gradient generated by cooling across the thickness and by pumping inhomogeneity along the width direction. When variation of the refractive index along the width direction is dominated by the lower spatial frequencies, the vector wave equation is solved analytically by means of the perturbation method. It is similar to the zigzag slab amplifier in which the phase aberration depending on the width coordinate plays the most important role to cause degradation of the beam quality. The crossing mode distortions owing to two dimension nature of the index variations are illustrated, and that mode profile is varied by the index variation along both the thickness and the width directions. Modes in the single-mode or the few-mode PWGs are shown to suffer weaker thermal-induced distortion across the thickness than those in the multi-mode PWGs.

  17. Phased laser array for generating a powerful laser beam

    DOEpatents

    Holzrichter, John F.; Ruggiero, Anthony J.

    2004-02-17

    A first injection laser signal and a first part of a reference laser beam are injected into a first laser element. At least one additional injection laser signal and at least one additional part of a reference laser beam are injected into at least one additional laser element. The first part of a reference laser beam and the at least one additional part of a reference laser beam are amplified and phase conjugated producing a first amplified output laser beam emanating from the first laser element and an additional amplified output laser beam emanating from the at least one additional laser element. The first amplified output laser beam and the additional amplified output laser beam are combined into a powerful laser beam.

  18. GAUSSIAN BEAM LASER RESONATOR PROGRAM

    NASA Technical Reports Server (NTRS)

    Cross, P. L.

    1994-01-01

    In designing a laser cavity, the laser engineer is frequently concerned with more than the stability of the resonator. Other considerations include the size of the beam at various optical surfaces within the resonator or the performance of intracavity line-narrowing or other optical elements. Laser resonators obey the laws of Gaussian beam propagation, not geometric optics. The Gaussian Beam Laser Resonator Program models laser resonators using Gaussian ray trace techniques. It can be used to determine the propagation of radiation through laser resonators. The algorithm used in the Gaussian Beam Resonator program has three major components. First, the ray transfer matrix for the laser resonator must be calculated. Next calculations of the initial beam parameters, specifically, the beam stability, the beam waist size and location for the resonator input element, and the wavefront curvature and beam radius at the input surface to the first resonator element are performed. Finally the propagation of the beam through the optical elements is computed. The optical elements can be modeled as parallel plates, lenses, mirrors, dummy surfaces, or Gradient Index (GRIN) lenses. A Gradient Index lens is a good approximation of a laser rod operating under a thermal load. The optical system may contain up to 50 elements. In addition to the internal beam elements the optical system may contain elements external to the resonator. The Gaussian Beam Resonator program was written in Microsoft FORTRAN (Version 4.01). It was developed for the IBM PS/2 80-071 microcomputer and has been implemented on an IBM PC compatible under MS DOS 3.21. The program was developed in 1988 and requires approximately 95K bytes to operate.

  19. Distortion-free femtosecond laser inscription in free-standing optical fiber.

    PubMed

    Chen, Yijing; Lai, Yicheng; Cheong, Marcus Weng Onn

    2016-07-20

    In this paper, we report the first experimental demonstration, to the best of our knowledge, of low-energy distortion-free femtosecond laser inscription in a free-standing fiber without the need for oil immersion. The methodology proposed features radial-plane beam shaping to eliminate the focal-point distortion induced by the cylindrical geometry of the fiber, thus achieving optimal focusing and spot-like inscription within the fiber. Based on the proposed methodology, a strong, first-order fiber Bragg grating is achieved for the first time, to the best of our knowledge, in a coated free-standing single-mode fiber by using the point-by-point inscription technique with only 50 nJ laser pulse energy. PMID:27463907

  20. Multi-beam laser altimeter

    NASA Technical Reports Server (NTRS)

    Bufton, Jack L.; Harding, David J.; Ramos-Izquierdo, Luis

    1993-01-01

    Laser altimetry provides a high-resolution, high-accuracy method for measurement of the elevation and horizontal variability of Earth-surface topography. The basis of the measurement is the timing of the round-trip propagation of short-duration pulses of laser radiation between a spacecraft and the Earth's surface. Vertical resolution of the altimetry measurement is determined primarily by laser pulsewidth, surface-induced spreading in time of the reflected pulse, and the timing precision of the altimeter electronics. With conventional gain-switched pulses from solid-state lasers and sub-nsec resolution electronics, sub-meter vertical range resolution is possible from orbital attitudes of several hundred kilometers. Horizontal resolution is a function of laser beam footprint size at the surface and the spacing between successive laser pulses. Laser divergence angle and altimeter platform height above the surface determine the laser footprint size at the surface, while laser pulse repetition-rate, laser transmitter beam configuration, and altimeter platform velocity determine the space between successive laser pulses. Multiple laser transitters in a singlaltimeter instrument provide across-track and along-track coverage that can be used to construct a range image of the Earth's surface. Other aspects of the multi-beam laser altimeter are discussed.

  1. Examination of the CLIC drive beam pipe design for thermal distortion caused by distributed beam line

    SciTech Connect

    C. Johnson; K. Kloeppel

    1997-01-01

    Beam transport programs are widely used to estimate the distribution of power deposited in accelerator structures by particle beams, either intentionally as for targets or beam dumps or accidentally owing the beam loss incidents. While this is usually adequate for considerations of radiation safety, it does not reveal the expected temperature rise and its effect on structural integrity. To find this, thermal diffusion must be taken into account, requiring another step in the analysis. The method that has been proposed is to use the output of a transport program, perhaps modified, as input for a finite element analysis program that can solve the thermal diffusion equation. At Cern, the design of the CLIC beam pipe has been treated in this fashion. The power distribution produced in the walls by a distributed beam loss was found according to the widely-used electron shower code EGS4. The distribution of power density was then used to form the input for the finite element analysis pro gram ANSYS, which was able to find the expected temperature rise and the resulting thermal distortion. As a result of these studies, the beam pipe design can be modified to include features that will counteract such distortion.

  2. Controllable laser ion beam generation

    NASA Astrophysics Data System (ADS)

    Kamiyama, D.; Takano, M.; Nagashima, T.; Barada, D.; Gu, Y. J.; Li, X. F.; Kong, Q.; Wang, P. X.; Kawata, S.

    2016-05-01

    In intense-laser plasma interaction, several issues still remain to be solved for a future laser particle acceleration. In this paper we focus on a bunching of ion beam, which is preaccelerated by a strong electric field generated in a laser plasma interaction. In this study, a nearcritical-density plasma target is illuminated by an intense short laser pulse. A moving strong inductive electric field is generated inside of the target. We have successfully obtained a bunched ion beam in our particle-in-cell simulations in this paper.

  3. Beam distortion of rotation double prisms with an arbitrary incident angle.

    PubMed

    Li, Anhu; Zuo, Qiyou; Sun, Wansong; Yi, Wanli

    2016-07-01

    The distortion of beam shape in rotation Risley prisms is discussed in this paper. Using the ray-tracing method based on vector refraction theorem, a rigorous theoretical model of beam distortion with an arbitrary incident angle is established to explore the influencing factors. For a specified double-prism pair, the emergent beam is squeezed in one direction while stretched in the mutual perpendicular direction, the distortion of which is determined by the relative rotation angle. Moreover, the distortion of beam shape is greatly influenced by the wedge angles and the refractive indices of the prisms, as well as different double-prism configurations, while uncorrelated to the prism thickness and the distance between two prisms. This paper demonstrates the regular change of the beam shape with multiparameter variations in rotation double prisms, which can be applied to the design of rotation double-prism systems. PMID:27409205

  4. Beam distortion of rotation double prisms with an arbitrary incident angle.

    PubMed

    Li, Anhu; Zuo, Qiyou; Sun, Wansong; Yi, Wanli

    2016-07-01

    The distortion of beam shape in rotation Risley prisms is discussed in this paper. Using the ray-tracing method based on vector refraction theorem, a rigorous theoretical model of beam distortion with an arbitrary incident angle is established to explore the influencing factors. For a specified double-prism pair, the emergent beam is squeezed in one direction while stretched in the mutual perpendicular direction, the distortion of which is determined by the relative rotation angle. Moreover, the distortion of beam shape is greatly influenced by the wedge angles and the refractive indices of the prisms, as well as different double-prism configurations, while uncorrelated to the prism thickness and the distance between two prisms. This paper demonstrates the regular change of the beam shape with multiparameter variations in rotation double prisms, which can be applied to the design of rotation double-prism systems.

  5. Laser processing with specially designed laser beam

    NASA Astrophysics Data System (ADS)

    Asratyan, A. A.; Bulychev, N. A.; Feofanov, I. N.; Kazaryan, M. A.; Krasovskii, V. I.; Lyabin, N. A.; Pogosyan, L. A.; Sachkov, V. I.; Zakharyan, R. A.

    2016-04-01

    The possibility of using laser systems to form beams with special spatial configurations has been studied. The laser systems applied had a self-conjugate cavity based on the elements of copper vapor lasers (LT-5Cu, LT-10Cu, LT-30Cu) with an average power of 5, 10, or 30 W. The active elements were pumped by current pulses of duration 80-100 ns. The duration of laser generation pulses was up to 25 ns. The generator unit included an unstable cavity, where one reflector was a special mirror with a reflecting coating. Various original optical schemes used were capable of exploring spatial configurations and energy characteristics of output laser beams in their interaction with micro- and nanoparticles fabricated from various materials. In these experiments, the beam dimensions of the obtained zones varied from 0.3 to 5 µm, which is comparable with the minimum permissible dimensions determined by the optical elements applied. This method is useful in transforming a large amount of information at the laser pulse repetition rate of 10-30 kHz. It was possible to realize the high-precision micromachining and microfabrication of microscale details by direct writing, cutting and drilling (with the cutting width and through-hole diameters ranging from 3 to 100 µm) and produce microscale, deep, intricate and narrow grooves on substrate surfaces of metals and nonmetal materials. This system is used for producing high-quality microscale details without moving the object under treatment. It can also be used for microcutting and microdrilling in a variety of metals such as molybdenum, copper and stainless steel, with a thickness of up to 300 µm, and in nonmetals such as silicon, sapphire and diamond with a thickness ranging from 10 µm to 1 mm with different thermal parameters and specially designed laser beam.

  6. Gaussian-Beam Laser-Resonator Program

    NASA Technical Reports Server (NTRS)

    Cross, Patricia L.; Bair, Clayton H.; Barnes, Norman

    1989-01-01

    Gaussian Beam Laser Resonator Program models laser resonators by use of Gaussian-beam-propagation techniques. Used to determine radii of beams as functions of position in laser resonators. Algorithm used in program has three major components. First, ray-transfer matrix for laser resonator must be calculated. Next, initial parameters of beam calculated. Finally, propagation of beam through optical elements computed. Written in Microsoft FORTRAN (Version 4.01).

  7. Helicopter engine exhaust rotor downwash effects on laser beams

    NASA Astrophysics Data System (ADS)

    Henriksson, Markus; Sjöqvist, Lars; Seiffer, Dirk

    2015-10-01

    The hot exhaust gases from engines on helicopters are pushed down by the rotor in a turbulent flow. When the optical path of a laser beam or optical sensor passes through this region severe aberrations of the optical field may result. These perturbations will lead to beam wander and beam distortions that can limit the performance of optical countermeasure systems. To quantify these effects the Italian Air Force Flight Test Centre hosted a trial for the "Airborne platform effects on lasers and warning sensors" (ALWS) EDA-project. Laser beams were propagated from the airport control tower to a target screen in a slant path with the helicopter hovering over this path. Collimated laser beams at 1.55-, 2- and 4.6-μm wavelength were imaged with high speed cameras. Large increases in beam wander and beam divergence were found, with beam wander up to 200 μrad root-mean-square and increases in beam divergence up to 1 mrad. To allow scaling to other laser beam parameters and geometries formulas for propagation in atmospheric turbulence were used even though the turbulence may not follow Kolmogorov statistics. By assuming that the plume is short compared to the total propagation distance the integrated structure parameter through the plume could be calculated. Values in the range 10-10 to 10-8 m1/3 were found when the laser beams passed through the exhaust gases below the helicopter tail. The integrated structure parameter values calculated from beam wander were consistently lower than those calculated from long term spot size, indicating that the method is not perfect but provides information about order of magnitudes. The measured results show that the engine exhaust for worst case beam directions will dominate over atmospheric turbulence even for kilometer path lengths from a helicopter at low altitude. How severe the effect is on system performance will depend on beam and target parameters.

  8. Single lens laser beam shaper

    DOEpatents

    Liu, Chuyu; Zhang, Shukui

    2011-10-04

    A single lens bullet-shaped laser beam shaper capable of redistributing an arbitrary beam profile into any desired output profile comprising a unitary lens comprising: a convex front input surface defining a focal point and a flat output portion at the focal point; and b) a cylindrical core portion having a flat input surface coincident with the flat output portion of the first input portion at the focal point and a convex rear output surface remote from the convex front input surface.

  9. Making Laser Beams Visible.

    ERIC Educational Resources Information Center

    Knotts, Michael

    1993-01-01

    Describes an inexpensive fog machine that is useful for photography and laser demonstrations. The apparatus uses liquid nitrogen to chill steam to make a fine mist safe for precision optics. The device can be made for around $50. (MVL)

  10. Independent assessment of laser power beaming options

    NASA Technical Reports Server (NTRS)

    Ponikvar, Donald R.

    1992-01-01

    Technical and architectural issues facing a laser power beaming system are discussed. Issues regarding the laser device, optics, beam control, propagation, and lunar site are examined. Environmental and health physics aspects are considered.

  11. Protective laser beam viewing device

    DOEpatents

    Neil, George R.; Jordan, Kevin Carl

    2012-12-18

    A protective laser beam viewing system or device including a camera selectively sensitive to laser light wavelengths and a viewing screen receiving images from the laser sensitive camera. According to a preferred embodiment of the invention, the camera is worn on the head of the user or incorporated into a goggle-type viewing display so that it is always aimed at the area of viewing interest to the user and the viewing screen is incorporated into a video display worn as goggles over the eyes of the user.

  12. Laser-Beam-Alignment Controller

    NASA Technical Reports Server (NTRS)

    Krasowski, M. J.; Dickens, D. E.

    1995-01-01

    In laser-beam-alignment controller, images from video camera compared to reference patterns by fuzzy-logic pattern comparator. Results processed by fuzzy-logic microcontroller, which sends control signals to motor driver adjusting lens and pinhole in spatial filter.

  13. Electron beam pumped semiconductor laser

    NASA Technical Reports Server (NTRS)

    Hug, William F. (Inventor); Reid, Ray D. (Inventor)

    2009-01-01

    Electron-beam-pumped semiconductor ultra-violet optical sources (ESUVOSs) are disclosed that use ballistic electron pumped wide bandgap semiconductor materials. The sources may produce incoherent radiation and take the form of electron-beam-pumped light emitting triodes (ELETs). The sources may produce coherent radiation and take the form of electron-beam-pumped laser triodes (ELTs). The ELTs may take the form of electron-beam-pumped vertical cavity surface emitting lasers (EVCSEL) or edge emitting electron-beam-pumped lasers (EEELs). The semiconductor medium may take the form of an aluminum gallium nitride alloy that has a mole fraction of aluminum selected to give a desired emission wavelength, diamond, or diamond-like carbon (DLC). The sources may be produced from discrete components that are assembled after their individual formation or they may be produced using batch MEMS-type or semiconductor-type processing techniques to build them up in a whole or partial monolithic manner, or combination thereof.

  14. Harmonic, Intermodulation and Cross-Modulation Distortion in Directly Modulated Quantum Cascade Lasers

    NASA Astrophysics Data System (ADS)

    Webb, J. F.; Yong, K. S. C.; Haldar, M. K.

    2016-05-01

    Using a simplified rate equation model, expressions for harmonic, intermodulation and cross-modulation distortion for a directly modulated quantum cascade laser can be derived. This paper shows how such derivations can be done and discusses some implications for quantum cascade lasers. It is important to understand such distortion, especially for applcations in communication systems.

  15. Centrifugal Distortion Causes Anderson Localization in Laser Kicked Molecules

    NASA Astrophysics Data System (ADS)

    Floss, Johannes; Averbukh, Ilya Sh.

    2014-05-01

    The periodically kicked 2D rotor is a textbook model in nonlinear dynamics. The classical kicked rotor can exhibit truly chaotic motion, whilst in the quantum regime this chaotic motion is suppressed by a mechanism similar to Anderson Localization. Up to now, these effects have been mainly observed in an atom optics analogue of a quantum rotor: cold atoms in a standing light wave. We demonstrate that common linear molecules (like N2, O2, CO2, ...), kicked by a train of short linearly polarized laser pulses, can exhibit a new mechanism for dynamical Anderson Localization due to their non-rigidity. When the pulses are separated by the rotational revival time trev = πℏ / B , the angular momentum J grows ballistically (Quantum Resonance). We show that, due to the centrifugal distortion of fast spinning molecules, above some critical value J =Jcr the Quantum Resonance is suppressed via the mechanism of Anderson Localization. This leads to a non-sinusoidal oscillation of the angular momentum distribution, which may be experimentally observed even at ambient conditions by using current techniques for laser molecular alignment.

  16. Laser beam steering device

    NASA Technical Reports Server (NTRS)

    Motamedi, M. E.; Andrews, A. P.; Gunning, W. J.

    1993-01-01

    Agile beam steering is a critical requirement for airborne and space based LIDAR and optical communication systems. Design and test results are presented for a compact beam steering device with low inertia which functions by dithering two complementary (positive and negative) binary optic microlens arrays relative to each other in directions orthogonal to the direction of light propagation. The miniaturized system has been demonstrated at scan frequencies as high as 300 Hz, generating a 13 x 13 spot array with a total field of view of 2.4 degrees. The design is readily extendable to a 9.5 degree field of view and a 52 x 52 scan pattern. The system is compact - less than 2 in. on a side. Further size reductions are anticipated.

  17. Electron-Beam Recombination Lasers

    NASA Astrophysics Data System (ADS)

    Rhoades, Robert Lewis

    1992-01-01

    The first known instance of electron-beam pumping of the 546.1 nm mercury laser is reported. This has been achieved using high-energy electrons to create intense ionization in a coaxial diode chamber containing a mixture of noble gases with a small amount of mercury vapor. Also reported are the results of a study of the 585.3 nm neon laser in He:Ne:Ar mixtures under similar experimental conditions. Both of these lasers are believed to be predominantly pumped by recombination. For the mercury laser, kinetic processes in the partially ionized plasma following the excitation pulse of high-energy electrons should favor the production of atomic mercury ions and molecular ions containing mercury. Subsequent recombination with electrons heavily favors the production of the 7^3S and 6^3 D states of Hg, of which 7^3S is the upper level of the reported laser. For the neon laser, the dominant recombining ion has been previously shown to be Ne_2^{+}. One of the dominant roles of helium in recombination lasers is inferred from the data for the neon laser at low helium concentrations. Helium appears to be necessary for the rapid relaxation of the electron energy which then increases the reaction rates for all known recombination processes thus increasing the pump rate into the upper state.

  18. Thermally induced mode distortion and its limit to power scaling of fiber lasers.

    PubMed

    Ke, Wei-Wei; Wang, Xiao-Jun; Bao, Xian-Feng; Shu, Xiao-Jian

    2013-06-17

    A general model is proposed to describe thermal-induced mode distortion in the step-index fiber (SIF) high power lasers. Two normalized parameters in the model are able to determine the mode characteristic in the heated SIFs completely. Shrinking of the mode fields and excitation of the high-order modes by the thermal-optic effect are investigated. A simplified power amplification model is used to describe the output power redistribution under various guiding modes. The results suggest that fiber with large mode area is more sensitive on the thermally induced mode distortion and hence is disadvantaged in keeping the beam quality in high power operation. The model is further applied to improve the power scaling analysis of Yb-doped fiber lasers. Here the thermal effect is considered to couple with the optical damage and the stimulated Raman scattering dynamically, whereas direct constraint from the thermal lens is relaxed. The resulting maximal output power is from 67kW to 97kW, depending on power fraction of the fundamental mode.

  19. LASER PROFILE MEASUREMENTS OF AN H BEAM.

    SciTech Connect

    CONNOLLY,R.; CAMERON,P.; CUPOLO,J.; GRAU,M.; KESSELMAN,M.; LIAW,C.J.; SIKORA,R.

    2001-06-18

    A non-intercepting beam profile monitor for He beams is being developed at Brookhaven National Lab. An H{sup {minus}} ion has a first ionization potential of 0.75eV. Electrons can be removed from an H{sup {minus}} beam by passing light from a near-infrared laser through it. Experiments have been performed on the BNL linac to measure the transverse profile of a 750keV beam by using a Nd:YAG laser to photoneutralize narrow slices of the beam. The laser beam is scanned across the ion beam neutralizing the portion of the beam struck by the laser. The electrons are removed from the ion beam and the beam current notch is measured.

  20. Scattering apodizer for laser beams

    DOEpatents

    Summers, M.A.; Hagen, W.F.; Boyd, R.D.

    1984-01-01

    A method is disclosed for apodizing a laser beam to smooth out the production of diffraction peaks due to optical discontinuities in the path of the laser beam, such method comprising introduction of a pattern of scattering elements for reducing the peak intensity in the region of such optical discontinuities, such pattern having smoothly tapering boundaries in which the distribution density of the scattering elements is tapered gradually to produce small gradients in the distribution density, such pattern of scattering elements being effective to reduce and smooth out the diffraction effects which would otherwise be produced. The apodizer pattern may be produced by selectively blasting a surface of a transparent member with fine abrasive particles to produce a multitude of minute pits. In one embodiment, a scattering apodizer pattern is employed to overcome diffraction patterns in a multiple element crystal array for harmonic conversion of a laser beam. The interstices and the supporting grid between the crystal elements are obscured by the gradually tapered apodizer pattern of scattering elements.

  1. Scattering apodizer for laser beams

    DOEpatents

    Summers, Mark A.; Hagen, Wilhelm F.; Boyd, Robert D.

    1985-01-01

    A method is disclosed for apodizing a laser beam to smooth out the production of diffraction peaks due to optical discontinuities in the path of the laser beam, such method comprising introduction of a pattern of scattering elements for reducing the peak intensity in the region of such optical discontinuities, such pattern having smoothly tapering boundaries in which the distribution density of the scattering elements is tapered gradually to produce small gradients in the distribution density, such pattern of scattering elements being effective to reduce and smooth out the diffraction effects which would otherwise be produced. The apodizer pattern may be produced by selectively blasting a surface of a transparent member with fine abrasive particles to produce a multitude of minute pits. In one embodiment, a scattering apodizer pattern is employed to overcome diffraction patterns in a multiple element crystal array for harmonic conversion of a laser beam. The interstices and the supporting grid between the crystal elements are obscured by the gradually tapered apodizer pattern of scattering elements.

  2. Cascaded injection resonator for coherent beam combining of laser arrays

    DOEpatents

    Kireev, Vassili [Sunnyvale, CA; Liu, Yun; Protopopescu, Vladimir [Knoxville, TN; Braiman, Yehuda [Oak Ridge, TN

    2008-10-21

    The invention provides a cascaded injection resonator for coherent beam combining of laser arrays. The resonator comprises a plurality of laser emitters arranged along at least one plane and a beam sampler for reflecting at least a portion of each laser beam that impinges on the beam sampler, the portion of each laser beam from one of the laser emitters being reflected back to another one of the laser emitters to cause a beam to be generated from the other one of the laser emitters to the beam reflector. The beam sampler also transmits a portion of each laser beam to produce a laser output beam such that a plurality of laser output beams of the same frequency are produced. An injection laser beam is directed to a first laser emitter to begin a process of generating and reflecting a laser beam from one laser emitter to another laser emitter in the plurality. A method of practicing the invention is also disclosed.

  3. Raman beam combining for laser brightness enhancement

    DOEpatents

    Dawson, Jay W.; Allen, Graham S.; Pax, Paul H.; Heebner, John E.; Sridharan, Arun K.; Rubenchik, Alexander M.; Barty, Chrisopher B. J.

    2015-10-27

    An optical source capable of enhanced scaling of pulse energy and brightness utilizes an ensemble of single-aperture fiber lasers as pump sources, with each such fiber laser operating at acceptable pulse energy levels. Beam combining involves stimulated Raman scattering using a Stokes' shifted seed beam, the latter of which is optimized in terms of its temporal and spectral properties. Beams from fiber lasers can thus be combined to attain pulses with peak energies in excess of the fiber laser self-focusing limit of 4 MW while retaining the advantages of a fiber laser system of high average power with good beam quality.

  4. Influence of thermal deformations of resonators on propagation properties of laser annular beams through turbulent atmosphere

    NASA Astrophysics Data System (ADS)

    Peng, Yufeng; Peng, Fang; Han, Junpeng

    2013-02-01

    Based on the laser field from a positive confocal unstable resonator, considering the influence of thermal distortion of the internal resonator mirror on the annular beam, the propagation characteristics of the annular beam through turbulent atmosphere are investigated by means of the fast Fourier transform algorithm (FFT). The intensity distributions of the output laser far-field are obtained to analyze the propagation characteristics of laser annular beam through the turbulent atmosphere, which is a function about different propagation distances. The results show that the peak intensity of the laser pattern becomes depressed and the spread of the far field diagram patterns is broadened under the increasing of the transmission distance and the thermal distortion of the laser resonator. β-parameter and strehl ratio are introduced to estimate the annular beam quality characteristics. It is found that the annular beam through strong turbulence influences much less obviously than the annular beam through weak turbulence on the quality characteristics with thermal distortion. In the same atmospheric conditions with a certain distance, the greater the mirror thermal distortion is, the worse the annular beam quality characteristics is.

  5. Separating Isotopes With Laser And Electron Beams

    NASA Technical Reports Server (NTRS)

    Trajmar, Sandor

    1989-01-01

    Need for second laser eliminated. In scheme for separation of isotopes, electrons of suitable kinetic energy ionize specific isotope excited by laser beam in magnetic field. Ionization by electron beams cheap and efficient in comparison to ionization by laser beams, and requires no special technical developments. Feasibility of new scheme demonstrated in selective ionization of Ba138, making possible separation of isotope from Ba isotopes of atomic weight 130, 132, 134, 135, 136, and 137.

  6. Method for splitting low power laser beams

    SciTech Connect

    Pierscionek, B.K. )

    1990-04-01

    A new method for producing parallel rays from a laser beam using a cylindrical lens and pinholes is presented. This method can produce a greater number of emergent rays than using a {ital beam} {ital splitter}.

  7. Diplexer for laser-beam heterodyne receiver

    NASA Technical Reports Server (NTRS)

    Koepf, G.

    1981-01-01

    Four prism interferometer superposes local oscillator beam on signal beam. Position of movable prism directs incident energy in both beams out one output port. Output port is spatially separated from input ports, and there is no limitation on size of frequency difference between laser beams.

  8. Experimental investigation on the beam quality improvement of the fiber laser by adaptive optics

    NASA Astrophysics Data System (ADS)

    Bian, Q.; Huang, L.; Wang, X. J.; Ma, X. K.; Yan, P.; Gong, M. L.

    2015-12-01

    This paper describes an adaptive optical system that is introduced to improve the beam quality of a fiber laser. Since a distorted wavefront would degrade the beam quality of a laser beam, a deformable mirror is employed to compensate for the wavefront aberration using closed-loop control in this system. The beam quality factor is measured and the far-field focus spot is detected as well. The experiment results show that the beam quality factor can be improved from 5-7 to 3-4 and the focus spot can be improved as well. The feasibility of the system is proved.

  9. 200 Hz repetition frequency joule-level high beam quality Nd:YAG nanosecond laser

    NASA Astrophysics Data System (ADS)

    Qiu, Jisi; Tang, Xiongxin; Fan, Zhongwei; Wang, Haocheng

    2016-06-01

    A joule-level Nd:YAG nanosecond laser of high repetition frequency and high beam quality is developed out. The laser is designed as a MOPA system mainly including single longitudinal mode seed, pre-amplifier unit an d power amplifier unit. In order to obtain the high-quality laser beam output, phase conjugation is adopted to compensate the laser beam distortion. Under the condition of 200 Hz high repetition frequency and 8.19 μJ single pulse energy injected by the single longitudinal mode seed, 1.53 J output energy is gained. The output laser beam is of 9 mm diameter, 7.41 ns pulse width, the far field beam spot 1.32 times the value of the diffraction limit, 1.2% energy stability (RMS) and less than 13 μrad far field beam spot angle shift.

  10. CO/sub 2/ laser beam weldability of Zircaloy 2

    SciTech Connect

    Ram, V.; Kohn, G.; Stern, A.

    1986-07-01

    BWR (boiling water reactor) fuel rods are manufactured by stacking pellets into a zirconium alloy, cladding tube-zircaloy 2(Zr2). A fuel rod is designed as a pressure vessel in order to prevent failure of the cladding and release of radioactive fission products. As a result, there are very strict requirements from the welding methods employed. The usual welding methods for Zr2 are based on the tungsten inert gas (GTAW) resistance welding (RW) and electron beam welding (EBW) processes. There is very little information about laser beam welding (LBW) of Zr2. The recent development of multikilowatt laser systems has led to dramatic improvements in their welding performance. In the present work, laser beam welding of Zr2 was investigated. A comparison with GTA welding was carried out. The use of a high-power laser beam to weld nuclear fuel containers made of zircaloy has many advantages: (1) The high-power density of the focused laser beam enables very high welding speeds in comparison with arc welding. As a result, a narrow heat-affected zone is produced and the distortion of the parts is reduced to a minimum. (2) The beam can be transmitted to different stations alternatively, even to ones located far from one another. It also transmits to hot cells, glove boxes or any inert gas pressure chamber through suitable windows. (3) The process can easily be automated to enhance mass production. It is very simple, does not require skilled welders, and does not need the use of different electrodes, collets, etc. (4) The laser beam does not contaminate the weld metal with tungsten or other elements.

  11. Space–time characterization of ultra-intense femtosecond laser beams

    NASA Astrophysics Data System (ADS)

    Pariente, G.; Gallet, V.; Borot, A.; Gobert, O.; Quéré, F.

    2016-08-01

    Femtosecond lasers can now deliver ultrahigh intensities at focus, making it possible to induce relativistic motion of charged particles with light and opening the way to new generations of compact particle accelerators and X-ray sources. With diameters of up to tens of centimetres, ultra-intense laser beams tend to suffer from spatiotemporal distortions, that is, a spatial dependence of their temporal properties that can dramatically reduce their peak intensities. At present, however, these intense electromagnetic fields are characterized and optimized in space and time separately. Here, we present the first complete spatiotemporal experimental reconstruction of the field E(t,r) for a 100 TW peak-power laser, and reveal the spatiotemporal distortions that can affect such beams. This new measurement capability opens the way to in-depth characterization and optimization of ultra-intense lasers and ultimately to the advanced control of relativistic motion of matter with femtosecond laser beams structured in space–time.

  12. Space-time characterization of ultra-intense femtosecond laser beams

    NASA Astrophysics Data System (ADS)

    Pariente, G.; Gallet, V.; Borot, A.; Gobert, O.; Quéré, F.

    2016-08-01

    Femtosecond lasers can now deliver ultrahigh intensities at focus, making it possible to induce relativistic motion of charged particles with light and opening the way to new generations of compact particle accelerators and X-ray sources. With diameters of up to tens of centimetres, ultra-intense laser beams tend to suffer from spatiotemporal distortions, that is, a spatial dependence of their temporal properties that can dramatically reduce their peak intensities. At present, however, these intense electromagnetic fields are characterized and optimized in space and time separately. Here, we present the first complete spatiotemporal experimental reconstruction of the field E(t,r) for a 100 TW peak-power laser, and reveal the spatiotemporal distortions that can affect such beams. This new measurement capability opens the way to in-depth characterization and optimization of ultra-intense lasers and ultimately to the advanced control of relativistic motion of matter with femtosecond laser beams structured in space-time.

  13. Enhanced laser beam coupling to a plasma

    DOEpatents

    Steiger, Arno D.; Woods, Cornelius H.

    1976-01-01

    Density perturbations are induced in a heated plasma by means of a pair of oppositely directed, polarized laser beams of the same frequency. The wavelength of the density perturbations is equal to one half the wavelength of the laser beams. A third laser beam is linearly polarized and directed at the perturbed plasma along a line that is perpendicular to the direction of the two opposed beams. The electric field of the third beam is oriented to lie in the plane containing the three beams. The frequency of the third beam is chosen to cause it to interact resonantly with the plasma density perturbations, thereby efficiently coupling the energy of the third beam to the plasma.

  14. Laser steering of particle beams: Refraction and reflection ofparticle beams

    SciTech Connect

    Esarey, Eric; Katsouleas, T.; Mori, W.B.; Dodd, E.; Lee, S.; Hemker, R.; Clayton, C.; Joshi, C.

    1999-11-01

    The co-propagation of an intense particle beam with an ionizing laser beam in a working gas/plasma is considered. When the axes of the laser and particle beam are not aligned, then asymmetric plasma lensing results in a net dipole field acting on the particle beam. The particle beam can be steered or bent (as well as focused) by steering the laser. An analogy is made between the bending of the particle beam by collective effects at a plasma boundary and the refraction or reflection of light at an interface. This mechanism of particle steering may be of interest in applications for which permanent magnets are inconvenient of a fast turn on is required. 3-D particle-in-cell simulations and relevance to a recent experiment are discussed.

  15. Propagation modeling results for narrow-beam undersea laser communications

    NASA Astrophysics Data System (ADS)

    Fletcher, Andrew S.; Hardy, Nicholas D.; Hamilton, Scott A.

    2016-03-01

    Communication links through ocean waters are challenging due to undersea propagation physics. Undersea optical communications at blue or green wavelengths can achieve high data rates (megabit- to gigabit-per-second class links) despite the challenging undersea medium. Absorption and scattering in ocean waters attenuate optical signals and distort the waveform through dense multipath. The exponential propagation loss and the temporal spread due to multipath limit the achievable link distance and data rate. In this paper, we describe the Monte Carlo modeling of the undersea scattering and absorption channel. We model photon signal attenuation levels, spatial photon distributions, time of arrival statistics, and angle of arrival statistics for a variety of lasercom scenarios through both clear and turbid water environments. Modeling results inform the design options for an undersea optical communication system, particularly illustrating the advantages of narrow-beam lasers compared to wide beam methods (e.g. LED sources). The modeled pupil plane and focal plane photon arrival distributions enable beam tracking techniques for robust pointing solutions, even in highly scattering harbor waters. Laser communication with collimated beams maximizes the photon transfer through the scattering medium and enables spatial and temporal filters to minimize waveform distortion and background interference.

  16. Microwave accelerator E-beam pumped laser

    DOEpatents

    Brau, Charles A.; Stein, William E.; Rockwood, Stephen D.

    1980-01-01

    A device and method for pumping gaseous lasers by means of a microwave accelerator. The microwave accelerator produces a relativistic electron beam which is applied along the longitudinal axis of the laser through an electron beam window. The incident points of the electron beam on the electron beam window are varied by deflection coils to enhance the cooling characteristics of the foil. A thyratron is used to reliably modulate the microwave accelerator to produce electron beam pulses which excite the laser medium to produce laser pulse repetition frequencies not previously obtainable. An aerodynamic window is also disclosed which eliminates foil heating problems, as well as a magnetic bottle for reducing laser cavity length and pressures while maintaining efficient energy deposition.

  17. Beam Stop For High-Power Lasers

    NASA Technical Reports Server (NTRS)

    Mcdermid, Iain S.; Williamson, William B.

    1990-01-01

    Graphite/aluminum plate absorbs most of light. Beam stop fits on standard optical mounting fixture. Graphite plate thick enough to absorb incident laser beam but thin enough to transfer heat quickly to heat sink. Device used for variety of blocking purposes. For example, blocks laser beam after it passes through experimental setup, or at each stage of setup so stages checked and tested in sequence. Negligible reflectance of device is valuable safety feature, protecting both users and equipment from reflections.

  18. Coherence delay augmented laser beam homogenizer

    DOEpatents

    Rasmussen, P.; Bernhardt, A.

    1993-06-29

    The geometrical restrictions on a laser beam homogenizer are relaxed by ug a coherence delay line to separate a coherent input beam into several components each having a path length difference equal to a multiple of the coherence length with respect to the other components. The components recombine incoherently at the output of the homogenizer, and the resultant beam has a more uniform spatial intensity suitable for microlithography and laser pantogography. Also disclosed is a variable aperture homogenizer, and a liquid filled homogenizer.

  19. Coherence delay augmented laser beam homogenizer

    DOEpatents

    Rasmussen, Paul; Bernhardt, Anthony

    1993-01-01

    The geometrical restrictions on a laser beam homogenizer are relaxed by ug a coherence delay line to separate a coherent input beam into several components each having a path length difference equal to a multiple of the coherence length with respect to the other components. The components recombine incoherently at the output of the homogenizer, and the resultant beam has a more uniform spatial intensity suitable for microlithography and laser pantogography. Also disclosed is a variable aperture homogenizer, and a liquid filled homogenizer.

  20. Robotics For High Power Laser Beam Manipulation

    NASA Astrophysics Data System (ADS)

    Watson, Henry E.

    1989-03-01

    The research and development programs in manufacturing science at The Pennsylvania State University have a major emphasis on laser materials processing technology development. A major thrust of this program is the development of an intelligent robotic system which can manipulate a laser beam in three dimension with the precision required for welding. The robot is called LARS for Laser Articulated Robotic System. A gantry based robot was selected as the foundation for LARS and the system is divided into five major subsystems: robot, electronic control, vision, workhead, beam transport, and software. An overview of the Laser Robotics program including laser materials processing research programs will be provided.

  1. Potential converter for laser-power beaming

    NASA Technical Reports Server (NTRS)

    Walker, Gilbert H.; Williams, Michael D.; Schuster, Gregory L.; Iles, Peter A.

    1991-01-01

    Future space missions, such as those associated with the Space Exploration Initiative (SEI), will require large amounts of power for operation of bases, rovers, and orbit transfer vehicles. One method for supplying this power is to beam power from a spaced based or Earth based laser power station to a receiver where laser photons can be converted to electricity. Previous research has described such laser power stations orbiting the Moon and beaming power to a receiver on the surface of the Moon by using arrays of diode lasers. Photovoltaic converters that can be efficiently used with these diode lasers are described.

  2. Method and apparatus for timing of laser beams in a multiple laser beam fusion system

    DOEpatents

    Eastman, Jay M.; Miller, Theodore L.

    1981-01-01

    The optical path lengths of a plurality of comparison laser beams directed to impinge upon a common target from different directions are compared to that of a master laser beam by using an optical heterodyne interferometric detection technique. The technique consists of frequency shifting the master laser beam and combining the master beam with a first one of the comparison laser beams to produce a time-varying heterodyne interference pattern which is detected by a photo-detector to produce an AC electrical signal indicative of the difference in the optical path lengths of the two beams which were combined. The optical path length of this first comparison laser beam is adjusted to compensate for the detected difference in the optical path lengths of the two beams. The optical path lengths of all of the comparison laser beams are made equal to the optical path length of the master laser beam by repeating the optical path length adjustment process for each of the comparison laser beams. In this manner, the comparison laser beams are synchronized or timed to arrive at the target within .+-.1.times.10.sup.-12 second of each other.

  3. [Signal analysis and spectrum distortion correction for tunable diode laser absorption spectroscopy system].

    PubMed

    Bao, Wei-Yi; Zhu, Yong; Chen, Jun; Chen, Jun-Qing; Liang, Bo

    2011-04-01

    In the present paper, the signal of a tunable diode laser absorption spectroscopy (TDLAS) trace gas sensing system, which has a wavelength modulation with a wide range of modulation amplitudes, is studied based on Fourier analysis method. Theory explanation of spectrum distortion induced by laser intensity amplitude modulation is given. In order to rectify the spectrum distortion, a method of synchronous amplitude modulation suppression by a variable optical attenuator is proposed. To validate the method, an experimental setup is designed. Absorption spectrum measurement experiments on CO2 gas were carried out. The results show that the residual laser intensity modulation amplitude of the experimental system is reduced to -0.1% of its original value and the spectrum distortion improvement is 92% with the synchronous amplitude modulation suppression. The modulation amplitude of laser intensity can be effectively reduced and the spectrum distortion can be well corrected by using the given correction method and system. By using a variable optical attenuator in the TDLAS (tunable diode laser absorption spectroscopy) system, the dynamic range requirements of photoelectric detector, digital to analog converter, filters and other aspects of the TDLAS system are reduced. This spectrum distortion correction method can be used for online trace gas analyzing in process industry.

  4. Adaptive optics for laser power beaming

    NASA Technical Reports Server (NTRS)

    Leland, Robert P.

    1992-01-01

    It has been proposed to use a high energy pulsed laser to beam power into space for satellites or a lunar base. The effects of atmospheric transmission are critical to such a system. Thermal blooming in the atmosphere can cause the beam to spread rapidly. Atmospheric turbulence can cause beam bending or beam spreading, resulting in the loss of transmitted energy that fails to hit the target receiver.

  5. Compact optical system for pulse-to-pulse laser beam quality measurement and applications in laser machining.

    PubMed

    Lambert, Robert W; Cortés-Martínez, Rodolpho; Waddle, Andrew J; Shephard, Jonathan D; Taghizadeh, Mohammad R; Greenaway, Alan H; Hand, Duncan P

    2004-09-10

    Fluctuations in beam quality (M2) have been observed on a pulse-to-pulse basis from an industrial Nd:YAG laser. This was achieved with a compact multiplane imaging method incorporating quadratically distorted diffraction gratings, which enabled simultaneous imaging of nine planes on a single CCD array. With this system, we measured across a range of beam qualities with an associated error (in M2 variation) of the order of 0.7%. Application of the system to fiber-optic beam delivery and laser drilling is demonstrated.

  6. Compact Optical System for Pulse-to-Pulse Laser Beam Quality Measurement and Applications in Laser Machining

    NASA Astrophysics Data System (ADS)

    Lambert, Robert W.; Cortés-Martínez, Rodolpho; Waddie, Andrew J.; Shephard, Jonathan D.; Taghizadeh, Mohammad R.; Greenaway, Alan H.; Hand, Duncan P.

    2004-09-01

    Fluctuations in beam quality (M^2) have been observed on a pulse-to-pulse basis from an industrial Nd:YAG laser. This was achieved with a compact multiplane imaging method incorporating quadratically distorted diffraction gratings, which enabled simultaneous imaging of nine planes on a single CCD array. With this system, we measured across a range of beam qualities with an associated error (in M^2 variation) of the order of 0.7%. Application of the system to fiber-optic beam delivery and laser drilling is demonstrated.

  7. Space Optical Communications Using Laser Beam Amplification

    NASA Technical Reports Server (NTRS)

    Agrawal, Govind

    2015-01-01

    The Space Optical Communications Using Laser Beam Amplification (SOCLBA) project will provide a capability to amplify a laser beam that is received in a modulating retro-reflector (MRR) located in a satellite in low Earth orbit. It will also improve the pointing procedure between Earth and spacecraft terminals. The technology uses laser arrays to strengthen the reflected laser beam from the spacecraft. The results of first year's work (2014) show amplification factors of 60 times the power of the signal beam. MMRs are mirrors that reflect light beams back to the source. In space optical communications, a high-powered laser interrogator beam is directed from the ground to a satellite. Within the satellite, the beam is redirected back to ground using the MMR. In the MMR, the beam passes through modulators, which encode a data signal onto the returning beam. MMRs can be used in small spacecraft for optical communications. The SOCLBA project is significant to NASA and small spacecraft due to its application to CubeSats for optical data transmission to ground stations, as well as possible application to spacecraft for optical data transmission.

  8. Processing of diamond by laser beam irradiation

    NASA Astrophysics Data System (ADS)

    Yoshikawa, Masanori; Hirata, Atsushi

    1998-10-01

    YAG and ArF excimer laser beams, of which wavelengths are 1.06 micrometers and 193 nm respectively, have been applied to processing of a variety of diamonds. Cutting and smoothing of natural, CVD and sintered diamonds have been performed. CVD diamond films were prepared by arc discharge plasma jet CVD and microwave plasma CVD, and sintered diamonds contain metallic or ceramic binder have been used. Fundamental removal processes of diamond with YAG and ArF excimer laser have been investigated using natural single crystal and CVD diamonds in various atmospheres changing laser irradiation conditions such as average power, energy density and pulse repetition rates. Cutting of natural and CVD diamonds with YAG laser proceeds at higher peal power that occurs at lower pulse repetition rates. Smooth surfaces are obtained by excimer laser irradiation at the incident angle of 80 percent. In the cases of the processing with YAG laser, the effect of local heating by laser beam irradiation mainly assists the diamond processing, and diamond appears to be removed after graphitization and oxidization following vaporization in the atmosphere contains oxygen. The temperature measurement was carried out at backside of irradiation surface, and increase of temperature when YAG laser beam was irradiated was larger than that when excimer laser was irradiated. On the contrary, the detection of C, C2, C+, O2 and CO from the emission at the irradiation area with ArF excimer laser beam suggest that processing partly proceeds by the separation of carbon atoms from the surface of diamond after braking bonds between carbon atoms caused by laser beam. Cutting of sintered diamond with metallic binder was difficult because metallic binder remains in the groove while ceramic binder was easily removed. Processing technique using laser beams has been applied to surface planing, chip preparation and edge formation of CVD diamond and curved surface formation on sintered diamond. Surface planing was

  9. Simulation based analysis of laser beam brazing

    NASA Astrophysics Data System (ADS)

    Dobler, Michael; Wiethop, Philipp; Schmid, Daniel; Schmidt, Michael

    2016-03-01

    Laser beam brazing is a well-established joining technology in car body manufacturing with main applications in the joining of divided tailgates and the joining of roof and side panels. A key advantage of laser brazed joints is the seam's visual quality which satisfies highest requirements. However, the laser beam brazing process is very complex and process dynamics are only partially understood. In order to gain deeper knowledge of the laser beam brazing process, to determine optimal process parameters and to test process variants, a transient three-dimensional simulation model of laser beam brazing is developed. This model takes into account energy input, heat transfer as well as fluid and wetting dynamics that lead to the formation of the brazing seam. A validation of the simulation model is performed by metallographic analysis and thermocouple measurements for different parameter sets of the brazing process. These results show that the multi-physical simulation model not only can be used to gain insight into the laser brazing process but also offers the possibility of process optimization in industrial applications. The model's capabilities in determining optimal process parameters are exemplarily shown for the laser power. Small deviations in the energy input can affect the brazing results significantly. Therefore, the simulation model is used to analyze the effect of the lateral laser beam position on the energy input and the resulting brazing seam.

  10. Electro-optic and acousto-optic laser beam scanners

    NASA Astrophysics Data System (ADS)

    Heberle, Johannes; Bechtold, Peter; Strauß, Johannes; Schmidt, Michael

    2016-03-01

    Electro-optical deflectors (EOD) and acousto-optical deflectors (AOD) are based on deflection of laser light within a solid state medium. As they do not contain any moving parts, they yield advantages compared to mechanical scanners which are conventionally used for laser beam deflection. Even for arbitrary scan paths high feed rates can be achieved. In this work the principles of operation and characteristic properties of EOD and AOD are presented. Additionally, a comparison to mirror based mechanical deflectors regarding deflection angles, speed and accuracy is made in terms of resolvable spots and the rate of resolvable spots. Especially, the latter one is up to one order of magnitude higher for EOD and AOD systems compared to conventional systems. Further characteristic properties such as response time, damage threshold, efficiency and beam distortions are discussed. Solid state laser beam deflectors are usually characterized by small deflection angles but high angular deflection velocities. As mechanical deflectors exhibit opposite properties an arrangement of a mechanical scanner combined with a solid state deflector provides a solution with the benefits of both systems. As ultrashort pulsed lasers with average power above 100 W and repetition rates in the MHz range have been available for several years this approach can be applied to fully exploit their capabilities. Thereby, pulse overlap can be reduced and by this means heat affected zones are prevented to provide proper processing results.

  11. High power laser beam delivery monitoring for laser safety

    NASA Astrophysics Data System (ADS)

    Corder, D. A.; Evans, D. R.; Tyrer, J. R.; Freeland, C. M.; Myler, J. K.

    1997-07-01

    The output of high power lasers used for material processing presents extreme radiation hazards. In normal operation this hazard is removed by the use of local shielding to prevent accidental exposure and system design to ensure efficient coupling of radiation into the workpiece. Faults in laser beam delivery or utilization can give rise to hazardous levels of laser radiation. A passive hazard control strategy requires that the laser system be enclosed such that the full laser power cannot burn through the housing under fault conditions. Usually this approach is too restrictive. Instead, active control strategies can be used in which a fault condition is detected and the laser cut off. This reduces the requirements for protective housing. In this work a distinction is drawn between reactive and proactive strategies. Reactive strategies rely on detecting the effects of an errant laser beam, whereas proactive strategies can anticipate as well as detect fault conditions. This can avoid the need for a hazardous situation to exist. A proactive strategy in which the laser beam is sampled at the final turning mirror is described in this work. Two control systems have been demonstrated; the first checks that beam power is within preset limits, the second monitors incoming beam power and position, and the radiation reflected back from the cutting head. In addition to their safety functions the accurate monitoring of power provides an additional benefit to the laser user.

  12. A critical review of laser beam welding

    NASA Astrophysics Data System (ADS)

    Martukanitz, Richard P.

    2005-03-01

    The use of lasers for welding has exhibited tremendous growth over the last decade for improving efficiency and reducing costs in a broad range of industries. Much of these successes are based on the development and availability of enabling technologies, which include improvements in process understanding, enhancements in laser sources and systems, and continued development and progression in process technology for laser beam welding of macro and micro components. The development of accurate numerical simulation techniques has provided an unprecedented opportunity to view the transient nature of laser processing. Advancements in laser source technology include the introduction of higher-power Nd:YAG lasers, utilizing diode pumped rods or disks, and fiber lasers, both providing the capability for fiber optic beam delivery. Although CO2 laser systems continue to dominate thick section welding, this influence will be challenged by emerging source technologies, namely high power fiber lasers. One of the most promising advances in laser process technology is laser-arc hybrid welding, which is seeing considerable interest worldwide and is currently being evaluated for various applications within heavy industry and manufacturing. The benefit of hybrid welding is the synergistic effect of improved processing rates and joint accommodation over either of the processes viewed separately. Other processing methods are also being developed to increase the utility of laser beam welding for industry, such as the use of dual beams and beam manipulation. The continued advancement in process knowledge is seen as a key element for facilitating the development of new processes and encouraging the acceptance of new source technology.

  13. Compensation of Hologram Distortion by Controlling Defocus Component in Reference Beam Wavefront for Angle Multiplexed Holograms

    NASA Astrophysics Data System (ADS)

    Muroi, T.; Kinoshita, N.; Ishii, N.; Kamijo, K.; Kawata, Y.; Kikuchi, H.

    2013-12-01

    Holographic memory has the potential to function as a recording system with a large capacity and high data-transfer-rate. Photopolymer materials are typically used as a write-once recording medium. When holograms are recorded on this medium, they can distort due to shrinkage or expansion of the materials, which degrades the reconstructed image and causes a higher bit error rate (bER) of the reproduced data. We propose optically compensating for hologram distortion by controlling aberration components in the reference beam wavefront while reproducing data, thereby improving the reproduced data quality. First, we investigated the relation between each aberration component of the reference beam and the signal to noise ratio (SNR) of the reproduced data using numerical simulation and found that horizontal tilt and the defocus component affect the SNR. Next, we experimentally evaluated the reproduced data by controlling the defocus component in the reference beam and found that the bER of the reproduced data could be decreased by controlling the defocus center with respect to the hologram position and phase modulation depth of the defocus component. Then, we investigated a practical control method of the defocus component using an evaluation value similar to the definition of the SNR for actual data reproduction from holograms. Using a defocus controlled wavefront enabled us to decrease the bER from 3.54 x 10^-3 with a plane wave to 3.14 x 10^-4. We also investigated how to reduce the bERs of reproduced data in angle multiplexed holograms. By using a defocus controlled wavefront to compensate for hologram distortion on the 40th data page in 80-page angle multiplexed holograms, the bERs of all pages could be decreased to less than 1x10^-3. We showed that controlling the defocus component is an effective way to compensate for hologram distortion and to decrease the bER of reproduced data in holographic memory.

  14. Laser beam riding artillery missiles guidance device is designed

    NASA Astrophysics Data System (ADS)

    Yan, Mingliang; Huo, Zhicheng; Chen, Wei

    2014-09-01

    Laser driving gun missile guidance type beam of laser information field formed by any link failure or reduced stability will directly lead to ballistic or miss out of control, and based on this, this paper designed the driving beam of laser guided missile guidance beam type forming device modulation and zoom mechanism, in order to make the missile can recognize its position in the laser beam, laser beam gun missile, by means of spatial encoding of the laser beam laser beam into information after forming device, a surface to achieve the purpose of precision guidance.

  15. Satellites Would Transmit Power By Laser Beams

    NASA Technical Reports Server (NTRS)

    Williams, M. D.; Walker, Gilbert H.; HUMES D. H.; Kwon, J. H.

    1995-01-01

    Arrays of diode lasers concentrate power into narrow beams. Baseline design of system formulated with regard to two particular missions that differ greatly in power requirements, thus showing scalability and attributes of basic system. Satellite system features large-scale array amplifier of high efficiency, injection-locked amplifiers, coherent combination of beams, and use of advanced lithographic technology to fabricate diode lasers in array. Extremely rapid development of applicable technologies make features realizable within decade.

  16. Effects of laser beam propagation and saturation on the spatial shape of sodium laser guide stars.

    PubMed

    Marc, Fabien; Guillet de Chatellus, Hugues; Pique, Jean-Paul

    2009-03-30

    The possibility to produce diffraction-limited images by large telescopes through Adaptive Optics is closely linked to the precision of measurement of the position of the guide star on the wavefront sensor. In the case of laser guide stars, many parameters can lead to a strong distortion on the shape of the LGS spot. Here we study the influence of both the saturation of the sodium layer excited by different types of lasers, the spatial quality of the laser mode at the ground and the influence of the atmospheric turbulence on the upward propagation of the laser beam. Both shape and intensity of the LGS spot are found to depend strongly on these three effects with important consequences on the precision on the wavefront analysis. PMID:19333251

  17. Effects of laser beam propagation and saturation on the spatial shape of sodium laser guide stars.

    PubMed

    Marc, Fabien; Guillet de Chatellus, Hugues; Pique, Jean-Paul

    2009-03-30

    The possibility to produce diffraction-limited images by large telescopes through Adaptive Optics is closely linked to the precision of measurement of the position of the guide star on the wavefront sensor. In the case of laser guide stars, many parameters can lead to a strong distortion on the shape of the LGS spot. Here we study the influence of both the saturation of the sodium layer excited by different types of lasers, the spatial quality of the laser mode at the ground and the influence of the atmospheric turbulence on the upward propagation of the laser beam. Both shape and intensity of the LGS spot are found to depend strongly on these three effects with important consequences on the precision on the wavefront analysis.

  18. High Average Power Laser Gain Medium With Low Optical Distortion Using A Transverse Flowing Liquid Host

    DOEpatents

    Comaskey, Brian J.; Ault, Earl R.; Kuklo, Thomas C.

    2005-07-05

    A high average power, low optical distortion laser gain media is based on a flowing liquid media. A diode laser pumping device with tailored irradiance excites the laser active atom, ion or molecule within the liquid media. A laser active component of the liquid media exhibits energy storage times longer than or comparable to the thermal optical response time of the liquid. A circulation system that provides a closed loop for mixing and circulating the lasing liquid into and out of the optical cavity includes a pump, a diffuser, and a heat exchanger. A liquid flow gain cell includes flow straighteners and flow channel compression.

  19. Rippled-beam free-electron laser

    SciTech Connect

    Carlsten, B.E.

    1997-10-01

    The authors describe a new microwave generation mechanism involving a scalloping annular electron beam. The beam interacts with the axial electric field of a TM{sub 0n} mode in a smooth circular waveguide through the axial free-electron laser interaction, in which the beam ripple period is synchronous with the phase slippage of the rf mode relative to the electron beam. Due to nonlinearities in the orbit equation, the interaction can be made autoresonant, where the phase and amplitude of the gain is independent of the beam energy.

  20. Nd:YAG laser beam diagnostics

    NASA Astrophysics Data System (ADS)

    Pope, L. E.; McDonald, T. G.

    1981-11-01

    A program to develop diagnostic techniques for pulsed Nd:YAG lasers for welding is described, and problems encountered when deviations from ideal optical collimation of a laser beam is defined, the diagnostic system is described, and the SNLA welding system is discussed.

  1. Vertical laser beam propagation through the troposphere

    NASA Technical Reports Server (NTRS)

    Minott, P. O.; Bufton, J. L.; Schaefer, W. H.; Grolemund, D. A.

    1974-01-01

    The characteristics of the earth's atmosphere and its effects upon laser beams was investigated in a series of balloon borne, optical propagation experiments. These experiments were designed to simulate the space to ground laser link. An experiment to determine the amplitude fluctuation, commonly called scintillation, caused by the atmosphere was described.

  2. Laser beam modeling in optical storage systems

    NASA Technical Reports Server (NTRS)

    Treptau, J. P.; Milster, T. D.; Flagello, D. G.

    1991-01-01

    A computer model has been developed that simulates light propagating through an optical data storage system. A model of a laser beam that originates at a laser diode, propagates through an optical system, interacts with a optical disk, reflects back from the optical disk into the system, and propagates to data and servo detectors is discussed.

  3. Controlling Second Harmonic Efficiency of Laser Beam Interactions

    NASA Technical Reports Server (NTRS)

    Barnes, Norman P. (Inventor); Walsh, Brian M. (Inventor); Reichle, Donald J. (Inventor)

    2011-01-01

    A method is provided for controlling second harmonic efficiency of laser beam interactions. A laser system generates two laser beams (e.g., a laser beam with two polarizations) for incidence on a nonlinear crystal having a preferred direction of propagation. Prior to incidence on the crystal, the beams are optically processed based on the crystal's beam separation characteristics to thereby control a position in the crystal along the preferred direction of propagation at which the beams interact.

  4. Varying the Divergence of Multiple Parallel Laser Beams

    NASA Technical Reports Server (NTRS)

    Kovalik, Joseph M.; Wright, Malcolm W.

    2008-01-01

    A provision for controlled variation of the divergence of a laser beam or of multiple parallel laser beams has been incorporated into the design of a conceptual free-space optical-communication station from which the transmitted laser beam(s) would be launched via a telescope. The original purpose to be served by this provision was to enable optimization, under various atmospheric optical conditions, of the divergence of a laser beam or beams transmitted from a ground station to a spacecraft.

  5. Laser beam welding of any metal.

    SciTech Connect

    Leong, K. H.

    1998-10-01

    The effect of a metal's thermophysical properties on its weldability are examined. The thermal conductivity, melting point, absorptivity and thermal diffusivity of the metal and the laser beam focused diameter and welding speed influence the minimum beam irradiance required for melting and welding. Beam diameter, surface tension and viscosity of the molten metal affect weld pool stability and weld quality. Lower surface tension and viscosity increases weld pool instability. With larger beam diameters causing wider welds, dropout also increases. Effects of focused beam diameter and joint fitup on weldability are also examined. Small beam diameters are sensitive to beam coupling problems in relation to fitup precision in addition to beam alignment to the seam. Welding parameters for mitigating weld pool instability and increasing weld quality are derived from the above considerations. Guidelines are presented for the tailoring of welding parameters to achieve good welds. Weldability problems can also be anticipated from the properties of a metal.

  6. Spiral laser beams in inhomogeneous media.

    PubMed

    Mahalov, Alex; Suazo, Erwin; Suslov, Sergei K

    2013-08-01

    Explicit solutions of the inhomogeneous paraxial wave equation in a linear and quadratic approximation are applied to wave fields with invariant features, such as oscillating laser beams in a parabolic waveguide and spiral light beams in varying media. A similar effect of superfocusing of particle beams in a thin monocrystal film, harmonic oscillations of cold trapped atoms, and motion in magnetic field are also mentioned. PMID:23903135

  7. Three-dimensional calculation of high-power, annularly distributed, laser-beam-induced thermal effects on reflectors and windows.

    PubMed

    Wang, Weiping; Tan, Fuli; Lü, Baida; Liu, Cangli

    2005-12-01

    Based on the three-dimensional transient heat conduction equation and the elastic stress-strain equation, the temperature rise, distortion, and equivalent stress distributions of a high-reflectivity silicon reflector and a white bijou window irradiated by a high-power sloped annularly distributed laser beam are simulated using a three-dimensional finite element model (FEM). The effects of laser intensity, output duration, beam obscure ratio, and laser intensity spatial gradient on the results are especially investigated. The effects of mirror and window thermal distortion on laser beam phase aberrations are also evaluated. This noncylindrosymmetric three-dimensional FEM can be used to evaluate high-power, high-energy, laser beam-induced thermal effects on optical components. PMID:16353817

  8. Generation of low-divergence laser beams

    DOEpatents

    Kronberg, James W.

    1993-01-01

    Apparatus for transforming a conventional beam of coherent light, having a Gaussian energy distribution and relatively high divergence, into a beam in which the energy distribution approximates a single, non-zero-order Bessel function and which therefore has much lower divergence. The apparatus comprises a zone plate having transmitting and reflecting zones defined by the pattern of light interference produced by the combination of a beam of coherent light with a Gaussian energy distribution and one having such a Bessel distribution. The interference pattern between the two beams is a concentric array of multiple annuli, and is preferably recorded as a hologram. The hologram is then used to form the transmitting and reflecting zones by photo-etching portions of a reflecting layer deposited on a plate made of a transmitting material. A Bessel beam, containing approximately 50% of the energy of the incident beam, is produced by passing a Gaussian beam through such a Bessel zone plate. The reflected beam, also containing approximately 50% of the incident beam energy and having a Bessel energy distribution, can be redirected in the same direction and parallel to the transmitted beam. Alternatively, a filter similar to the Bessel zone plate can be placed within the resonator cavity of a conventional laser system having a front mirror and a rear mirror, preferably axially aligned with the mirrors and just inside the front mirror to generate Bessel energy distribution light beams at the laser source.

  9. Generation of low-divergence laser beams

    DOEpatents

    Kronberg, J.W.

    1993-09-14

    Apparatus for transforming a conventional beam of coherent light, having a Gaussian energy distribution and relatively high divergence, into a beam in which the energy distribution approximates a single, non-zero-order Bessel function and which therefore has much lower divergence. The apparatus comprises a zone plate having transmitting and reflecting zones defined by the pattern of light interference produced by the combination of a beam of coherent light with a Gaussian energy distribution and one having such a Bessel distribution. The interference pattern between the two beams is a concentric array of multiple annuli, and is preferably recorded as a hologram. The hologram is then used to form the transmitting and reflecting zones by photo-etching portions of a reflecting layer deposited on a plate made of a transmitting material. A Bessel beam, containing approximately 50% of the energy of the incident beam, is produced by passing a Gaussian beam through such a Bessel zone plate. The reflected beam, also containing approximately 50% of the incident beam energy and having a Bessel energy distribution, can be redirected in the same direction and parallel to the transmitted beam. Alternatively, a filter similar to the Bessel zone plate can be placed within the resonator cavity of a conventional laser system having a front mirror and a rear mirror, preferably axially aligned with the mirrors and just inside the front mirror to generate Bessel energy distribution light beams at the laser source. 11 figures.

  10. Correction of amplitude distortions for truncated Bessel beam and SER estimation for 4ASK

    NASA Astrophysics Data System (ADS)

    Eyyuboğlu, Halil T.

    2016-08-01

    We apply amplitude corrections to a truncated Bessel beam that has propagated through turbulent atmosphere modelled by random phase screens. These corrections are realized via transmitting an unmodulated beam in parallel to the one carrying the 4 amplitude shift keying (ASK) modulated message signal. On the receiver side, the amplitude corrections are obtained by dividing the intensity of the unmodulated beam by its free space equivalence. The corrections are then used to restore the amplitude distortions of the beam carrying the 4ASK modulated message signal and in the determination of decision boundaries for the received 4ASK symbols. The success of the system is visually inspected by comparing the received intensity profiles before and after the application of corrections. Furthermore, simulation analysis of symbol error rate (SER) is made, where the proposed set-up is found to be quite insensitive to wavelength difference between the unmodulated and modulated beams. On the other hand, the difference in the structure constant values of these two beams seems to have profound effect on system performance.

  11. Apparatus and method for laser beam diagnosis

    DOEpatents

    Salmon, Jr., Joseph T.

    1991-01-01

    An apparatus and method is disclosed for accurate, real time monitoring of the wavefront curvature of a coherent laser beam. Knowing the curvature, it can be quickly determined whether the laser beam is collimated, or focusing (converging), or de-focusing (diverging). The apparatus includes a lateral interferometer for forming an interference pattern of the laser beam to be diagnosed. The interference pattern is imaged to a spatial light modulator (SLM), whose output is a coherent laser beam having an image of the interference pattern impressed on it. The SLM output is focused to obtain the far-field diffraction pattern. A video camera, such as CCD, monitors the far-field diffraction pattern, and provides an electrical output indicative of the shape of the far-field pattern. Specifically, the far-field pattern comprises a central lobe and side lobes, whose relative positions are indicative of the radius of curvature of the beam. The video camera's electrical output may be provided to a computer which analyzes the data to determine the wavefront curvature of the laser beam.

  12. Apparatus and method for laser beam diagnosis

    DOEpatents

    Salmon, J.T. Jr.

    1991-08-27

    An apparatus and method are disclosed for accurate, real time monitoring of the wavefront curvature of a coherent laser beam. Knowing the curvature, it can be quickly determined whether the laser beam is collimated, or focusing (converging), or de-focusing (diverging). The apparatus includes a lateral interferometer for forming an interference pattern of the laser beam to be diagnosed. The interference pattern is imaged to a spatial light modulator (SLM), whose output is a coherent laser beam having an image of the interference pattern impressed on it. The SLM output is focused to obtain the far-field diffraction pattern. A video camera, such as CCD, monitors the far-field diffraction pattern, and provides an electrical output indicative of the shape of the far-field pattern. Specifically, the far-field pattern comprises a central lobe and side lobes, whose relative positions are indicative of the radius of curvature of the beam. The video camera's electrical output may be provided to a computer which analyzes the data to determine the wavefront curvature of the laser beam. 11 figures.

  13. Transmission Of Power Via Combined Laser Beams

    NASA Technical Reports Server (NTRS)

    Kwon, Jin H.; Lee, Ja H.

    1992-01-01

    Laser Diode Array (LDA) appears to be most efficient means of transferring power from Earth to satellites and between satellites, in terms of mass and size, of various laser configurations. To form large-scale-array amplifier (LSAA), element LDA's must generate well-defined diffraction-limited beams. Coherent matching of phases among LDA's enables system to generate good beam pattern in far field over thousands of kilometers. By passing beam from master laser through number of LDA amplifiers simultaneously, one realizes coherence among amplified output beams. LSAA used for transmission of power with efficiency of approximately 80 percent into receiver of moderate size at 5,000 km. Also transmits data at high rates by line-of-sight rather than fiber optics.

  14. Collimation of laser-produced proton beam

    NASA Astrophysics Data System (ADS)

    Takano, M.; Nagashima, T.; Izumiyama, T.; Gu, Y. J.; Barada, D.; Kong, Q.; Wang, P. X.; Ma, Y. Y.; Wang, W. M.; Kawata, S.

    2016-03-01

    In intense laser plasma interaction for particle acceleration several issues remain to be solved. In this paper we focus on a collimation of ion beam, which is produced by a laser plasma interaction. In this study, the ion beam is collimated by a thin film target. When an intense short pulse laser illuminates a target, target electrons are accelerated, and create an electron cloud that generates a sheath electric field at the target surface. Such the ion acceleration mechanism is called the target normal sheath acceleration (TNSA). The TNSA field would be used for the ion beam collimation by the electric field. We have successfully obtained a collimated beam in our particle-in-cell simulations.

  15. Synchronous characterization of semiconductor microcavity laser beam.

    PubMed

    Wang, T; Lippi, G L

    2015-06-01

    We report on a high-resolution double-channel imaging method used to synchronously map the intensity- and optical-frequency-distribution of a laser beam in the plane orthogonal to the propagation direction. The synchronous measurement allows us to show that the laser frequency is an inhomogeneous distribution below threshold, but that it becomes homogeneous across the fundamental Gaussian mode above threshold. The beam's tails deviations from the Gaussian shape, however, are accompanied by sizeable fluctuations in the laser wavelength, possibly deriving from manufacturing details and from the influence of spontaneous emission in the very low intensity wings. In addition to the synchronous spatial characterization, a temporal analysis at any given point in the beam cross section is carried out. Using this method, the beam homogeneity and spatial shape, energy density, energy center, and the defects-related spectrum can also be extracted from these high-resolution pictures.

  16. Synchronous characterization of semiconductor microcavity laser beam.

    PubMed

    Wang, T; Lippi, G L

    2015-06-01

    We report on a high-resolution double-channel imaging method used to synchronously map the intensity- and optical-frequency-distribution of a laser beam in the plane orthogonal to the propagation direction. The synchronous measurement allows us to show that the laser frequency is an inhomogeneous distribution below threshold, but that it becomes homogeneous across the fundamental Gaussian mode above threshold. The beam's tails deviations from the Gaussian shape, however, are accompanied by sizeable fluctuations in the laser wavelength, possibly deriving from manufacturing details and from the influence of spontaneous emission in the very low intensity wings. In addition to the synchronous spatial characterization, a temporal analysis at any given point in the beam cross section is carried out. Using this method, the beam homogeneity and spatial shape, energy density, energy center, and the defects-related spectrum can also be extracted from these high-resolution pictures. PMID:26133832

  17. A Programmable Beam Shaping System for Tailoring the Profile of High Fluence Laser Beams

    SciTech Connect

    Heebner, J; Borden, M; Miller, P; Stolz, C; Suratwala, T; Wegner, P; Hermann, M; Henesian, M; Haynam, C; Hunter, S; Christensen, K; Wong, N; Seppala, L; Brunton, G; Tse, E; Awwal, A; Franks, M; Marley, E; Williams, K; Scanlan, M; Budge, T; Monticelli, M; Walmer, D; Dixit, S; Widmayer, C; Wolfe, J; Bude, J; McCarty, K; DiNicola, J

    2010-11-10

    Customized spatial light modulators have been designed and fabricated for use as precision beam shaping devices in fusion class laser systems. By inserting this device in a low-fluence relay plane upstream of the amplifier chain, 'blocker' obscurations can be programmed into the beam profile to shadow small isolated flaws on downstream optical components that might otherwise limit the system operating energy. In this two stage system, 1920 x 1080 bitmap images are first imprinted on incoherent, 470 nm address beams via pixilated liquid crystal on silicon (LCoS) modulators. To realize defined masking functions with smooth apodized shapes and no pixelization artifacts, address beam images are projected onto custom fabricated optically-addressable light valves. Each valve consists of a large, single pixel liquid cell in series with a photoconductive Bismuth silicon Oxide (BSO) crystal. The BSO crystal enables bright and dark regions of the address image to locally control the voltage supplied to the liquid crystal layer which in turn modulates the amplitude of the coherent beams at 1053 nm. Valves as large as 24 mm x 36 mm have been fabricated with low wavefront distortion (<0.5 waves) and antireflection coatings for high transmission (>90%) and etalon suppression to avoid spectral and temporal ripple. This device in combination with a flaw inspection system and optic registration strategy represents a new approach for extending the operational lifetime of high fluence laser optics.

  18. Optical distortions in end-pumped zigzag slab lasers.

    PubMed

    Tang, Bing; Zhou, Tangjian; Wang, Dan; Li, Mi

    2015-04-01

    Ray tracing is performed to investigate the optical distortions in the end-pumped, zigzag slab. Optical path differences caused by temperature, slab deformation, and stress birefringence are calculated under uniform pumping; the results show a steep edge in the width dimension and a thermal lens with an effective focal length as short as several meters in the thickness dimension. Dependence of depolarization on total internal reflection phase retardance as well as the slab's cut angle is studied by the Jones matrix technique; results show that although at the pumping power of 10 kW, the mean depolarization of the 2.5  mm×30  mm×150.2  mm Nd:YAG slab is generally below 3%, and it increases rapidly with pumping power. Besides, for the 0°- or 60°-cut slab, an optimal phase retardance range of 5° to 13° exists, in which the depolarization loss can be lower than 0.5%. Finally, experiments on temperature and depolarization measurements verify the numerical results. PMID:25967178

  19. Electron beam, laser beam and plasma arc welding studies

    NASA Technical Reports Server (NTRS)

    Banas, C. M.

    1974-01-01

    This program was undertaken as an initial step in establishing an evaluation framework which would permit a priori selection of advanced welding processes for specific applications. To this end, a direct comparison of laser beam, electron beam and arc welding of Ti-6Al-4V alloy was undertaken. Ti-6Al-4V was selected for use in view of its established welding characteristics and its importance in aerospace applications.

  20. Energy transfer between laser beams due to recording of optical axis gratings in liquid crystals

    NASA Astrophysics Data System (ADS)

    Nersisyan, Sarik R.; Tabiryan, Nelson V.; Stickley, C. Martin

    2006-10-01

    We have studied two-beam-coupling processes related to the generation of optical axis gratings in liquid crystals (LCs) due to the electromagnetic torque acting on the orientation of LCs in superimposed laser beams with spatially modulated polarization. Such gratings result in efficient coupling between the laser beams controlled by the frequency shift introduced between the beams at infrasound frequencies. Larger than 80% efficiency of energy transfer from a pump to a signal beam is reported at power density levels of the laser beams at 1-10 kW/cm2. The distinction between pump and signal beams is relative, since the sign of the frequency shift rather than the power ratio between the beams determines the direction of energy transfer. The experiments were performed for radiation at a 1.06 μm wavelength; high optical nonlinearity and low absorption make LCs suitable for use in visible and near-IR spectra, particularly in high-power laser systems. We have characterized the main fundamental features of the process of recording dynamic orientation gratings, plotting the gain spectra for several LCs and verifying the good quality of the amplified signal beam even for a strongly distorted pump. The obtained results set the groundwork for a variety of novel opportunities and applications that include combining high-power laser beams and wavelength division multiplexing at an ultranarrow interval of frequencies of the order of 1-100 Hz.

  1. Laser power beaming for satellite applications

    SciTech Connect

    Friedman, H.W.

    1993-09-22

    A serious consideration of laser power beaming for satellite applications appears to have grown out of a NASA mission analysis for transmitting power to lunar bases during the two week dark period. System analyses showed that laser power beaming to the moon in conjunction with efficient, large area solar cell collection panels, were an attractive alternative to other schemes such as battery storage and nuclear generators, largely because of the high space transportation costs. The primary difficulty with this scheme is the need for very high average power visible lasers. One system study indicated that lasers in excess of 10 MW at a wavelength of approximately 850 nm were required. Although such lasers systems have received much attention for military applications, their realization is still a long term goal.

  2. More on analyzing the reflection of a laser beam by a deformed highly reflective volume Bragg grating using iteration of the beam propagation method.

    PubMed

    Shu, Hong; Mokhov, Sergiy; Zeldovich, Boris Ya; Bass, Michael

    2009-01-01

    A further extension of the iteration method for beam propagation calculation is presented that can be applied for volume Bragg gratings (VBGs) with extremely large grating strength. A reformulation of the beam propagation formulation is presented for analyzing the reflection of a laser beam by a deformed VBG. These methods will be shown to be very accurate and efficient. A VBG with generic z-dependent distortion has been analyzed using these methods.

  3. Initial alignment method for free space optics laser beam

    NASA Astrophysics Data System (ADS)

    Shimada, Yuta; Tashiro, Yuki; Izumi, Kiyotaka; Yoshida, Koichi; Tsujimura, Takeshi

    2016-08-01

    The authors have newly proposed and constructed an active free space optics transmission system. It is equipped with a motor driven laser emitting mechanism and positioning photodiodes, and it transmits a collimated thin laser beam and accurately steers the laser beam direction. It is necessary to introduce the laser beam within sensible range of the receiver in advance of laser beam tracking control. This paper studies an estimation method of laser reaching point for initial laser beam alignment. Distributed photodiodes detect laser luminescence at respective position, and the optical axis of laser beam is analytically presumed based on the Gaussian beam optics. Computer simulation evaluates the accuracy of the proposed estimation methods, and results disclose that the methods help us to guide the laser beam to a distant receiver.

  4. Digital Controller For Laser-Beam-Steering Subsystem: Part 2

    NASA Technical Reports Server (NTRS)

    Ansari, Homayoon; Voisinet, Leeann

    1995-01-01

    A report presents additional information about laser-beam-steering apparatus described in "Digital Controller for Laser-Beam-Steering Subsystem" (NPO-19193) and "More About Beam-Steering Subsystem for Laser Communication" (NPO-19381). Reiterates basic principles of operation of beam-steering subsystem, with emphasis on modes of operation, basic design concepts, and initial experiments on partial prototype of apparatus.

  5. Laser beam shaping for biomedical microscopy techniques

    NASA Astrophysics Data System (ADS)

    Laskin, Alexander; Kaiser, Peter; Laskin, Vadim; Ostrun, Aleksei

    2016-04-01

    Uniform illumination of a working field is very important in optical systems of confocal microscopy and various implementations of fluorescence microscopy like TIR, SSIM, STORM, PALM to enhance performance of these laser-based research techniques. Widely used TEM00 laser sources are characterized by essentially non-uniform Gaussian intensity profile which leads usually to non-uniform intensity distribution in a microscope working field or in a field of microlenses array of a confocal microscope optical system, this non-uniform illumination results in instability of measuring procedure and reducing precision of quantitative measurements. Therefore transformation of typical Gaussian distribution of a TEM00 laser to flat-top (top hat) profile is an actual technical task, it is solved by applying beam shaping optics. Due to high demands to optical image quality the mentioned techniques have specific requirements to a uniform laser beam: flatness of phase front and extended depth of field, - from this point of view the microscopy techniques are similar to holography and interferometry. There are different refractive and diffractive beam shaping approaches used in laser industrial and scientific applications, but only few of them are capable to fulfil the optimum conditions for beam quality required in discussed microscopy techniques. We suggest applying refractive field mapping beam shapers πShaper, which operational principle presumes almost lossless transformation of Gaussian to flat-top beam with flatness of output wavefront, conserving of beam consistency, providing collimated low divergent output beam, high transmittance, extended depth of field, negligible wave aberration, and achromatic design provides capability to work with several lasers with different wavelengths simultaneously. The main function of a beam shaper is transformation of laser intensity profile, further beam transformation to provide optimum for a particular technique spot size and shape has to

  6. Optimization of beam configuration in laser fusion based on the laser beam pattern

    SciTech Connect

    Xu, Teng; Xu, Lixin; Wang, Anting; Gu, Chun; Wang, Shengbo; Liu, Jing; Wei, Ankun

    2013-12-15

    A simple method based on the laser beam pattern is proposed and numerically demonstrated to optimize a beam configuration for direct drive laser fusion. In this method, both the geometrical factor G{sub l} and the single beam factor B{sub l} are considered. By diminishing the product of B{sub l}·G{sub l}, the irradiation nonuniformity can be decreased to the order of 10{sup −5}. This optimization method can be applied on the design of irradiation systems for an arbitrary number of beams and any axially symmetric beam patterns.

  7. Method and apparatus for laser-controlled proton beam radiology

    DOEpatents

    Johnstone, C.J.

    1998-06-02

    A proton beam radiology system provides cancer treatment and proton radiography. The system includes an accelerator for producing an H{sup {minus}} beam and a laser source for generating a laser beam. A photodetachment module is located proximate the periphery of the accelerator. The photodetachment module combines the H{sup {minus}} beam and laser beam to produce a neutral beam therefrom within a subsection of the H{sup {minus}} beam. The photodetachment module emits the neutral beam along a trajectory defined by the laser beam. The photodetachment module includes a stripping foil which forms a proton beam from the neutral beam. The proton beam is delivered to a conveyance segment which transports the proton beam to a patient treatment station. The photodetachment module further includes a laser scanner which moves the laser beam along a path transverse to the cross-section of the H{sup {minus}} beam in order to form the neutral beam in subsections of the H{sup {minus}} beam. As the scanning laser moves across the H{sup {minus}} beam, it similarly varies the trajectory of the proton beam emitted from the photodetachment module and in turn varies the target location of the proton beam upon the patient. Intensity modulation of the proton beam can also be achieved by controlling the output of the laser. 9 figs.

  8. Method and apparatus for laser-controlled proton beam radiology

    DOEpatents

    Johnstone, Carol J.

    1998-01-01

    A proton beam radiology system provides cancer treatment and proton radiography. The system includes an accelerator for producing an H.sup.- beam and a laser source for generating a laser beam. A photodetachment module is located proximate the periphery of the accelerator. The photodetachment module combines the H.sup.- beam and laser beam to produce a neutral beam therefrom within a subsection of the H.sup.- beam. The photodetachment module emits the neutral beam along a trajectory defined by the laser beam. The photodetachment module includes a stripping foil which forms a proton beam from the neutral beam. The proton beam is delivered to a conveyance segment which transports the proton beam to a patient treatment station. The photodetachment module further includes a laser scanner which moves the laser beam along a path transverse to the cross-section of the H.sup.- beam in order to form the neutral beam in subsections of the H.sup.- beam. As the scanning laser moves across the H.sup.- beam, it similarly varies the trajectory of the proton beam emitted from the photodetachment module and in turn varies the target location of the proton beam upon the patient. Intensity modulation of the proton beam can also be achieved by controlling the output of the laser.

  9. Image distortion and its correction in linear galvanometric mirrors-based laser-scanning microscopy

    NASA Astrophysics Data System (ADS)

    Wang, Wenbo; Wu, Zhenguo; Zeng, Haishan

    2015-05-01

    To simplify imaging focusing and calibration tasks, a laser-scanning microscope needs to scan at a moderate frame rate. The inertia of a galvanometric scanner leads to time delays when following external commands, which subsequently introduces image distortions that deteriorate as scan frequency increases. Sinusoidal and triangular waveforms were examined as fast axis driving patterns. The interplay among driving pattern, frequency, sampling rate, phase shift, linear scanning range, and their effect on reconstructed images was discussed. Utilizing position feedback from the linear galvo scanners, the effect of response time could be automatically compensated in real time. Precompensated triangular driving waveform offered the least amount of image distortion.

  10. Image distortion and its correction in linear galvanometric mirrors-based laser-scanning microscopy.

    PubMed

    Wang, Wenbo; Wu, Zhenguo; Zeng, Haishan

    2015-05-01

    To simplify imaging focusing and calibration tasks, a laser-scanning microscope needs to scan ata moderate frame rate. The inertia of a galvanometric scanner leads to time delays when following external commands, which subsequently introduces image distortions that deteriorate as scan frequency increases. Sinusoidal and triangular waveforms were examined as fast axis driving patterns. The interplay among driving pattern, frequency, sampling rate, phase shift, linear scanning range, and their effect on reconstructed images was discussed. Utilizing position feedback from the linear galvo scanners, the effect of response time could be automatically compensated in real time. Precompensated triangular driving waveform offered the least amount of image distortion.

  11. Beam uniformity analysis of infrared laser illuminators

    NASA Astrophysics Data System (ADS)

    Allik, Toomas H.; Dixon, Roberta E.; Proffitt, R. Patrick; Fung, Susan; Ramboyong, Len; Soyka, Thomas J.

    2015-02-01

    Uniform near-infrared (NIR) and short-wave infrared (SWIR) illuminators are desired in low ambient light detection, recognition, and identification of military applications. Factors that contribute to laser illumination image degradation are high frequency, coherent laser speckle and low frequency nonuniformities created by the laser or external laser cavity optics. Laser speckle analysis and beam uniformity improvements have been independently studied by numerous authors, but analysis to separate these two effects from a single measurement technique has not been published. In this study, profiles of compact, diode laser NIR and SWIR illuminators were measured and evaluated. Digital 12-bit images were recorded with a flat-field calibrated InGaAs camera with measurements at F/1.4 and F/16. Separating beam uniformity components from laser speckle was approximated by filtering the original image. The goal of this paper is to identify and quantify the beam quality variation of illumination prototypes, draw awareness to its impact on range performance modeling, and develop measurement techniques and methodologies for military, industry, and vendors of active sources.

  12. Synchronous characterization of semiconductor microcavity laser beam

    SciTech Connect

    Wang, T. Lippi, G. L.

    2015-06-15

    We report on a high-resolution double-channel imaging method used to synchronously map the intensity- and optical-frequency-distribution of a laser beam in the plane orthogonal to the propagation direction. The synchronous measurement allows us to show that the laser frequency is an inhomogeneous distribution below threshold, but that it becomes homogeneous across the fundamental Gaussian mode above threshold. The beam’s tails deviations from the Gaussian shape, however, are accompanied by sizeable fluctuations in the laser wavelength, possibly deriving from manufacturing details and from the influence of spontaneous emission in the very low intensity wings. In addition to the synchronous spatial characterization, a temporal analysis at any given point in the beam cross section is carried out. Using this method, the beam homogeneity and spatial shape, energy density, energy center, and the defects-related spectrum can also be extracted from these high-resolution pictures.

  13. Phoenix's Laser Beam in Action on Mars

    NASA Technical Reports Server (NTRS)

    2008-01-01

    [figure removed for brevity, see original site] Click on image to view the animation

    The Surface Stereo Imager camera aboard NASA's Phoenix Mars Lander acquired a series of images of the laser beam in the Martian night sky. Bright spots in the beam are reflections from ice crystals in the low level ice-fog. The brighter area at the top of the beam is due to enhanced scattering of the laser light in a cloud. The Canadian-built lidar instrument emits pulses of laser light and records what is scattered back.

    The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  14. Rippled beam free electron laser amplifier

    DOEpatents

    Carlsten, Bruce E.

    1999-01-01

    A free electron laser amplifier provides a scalloping annular electron beam that interacts with the axial electric field of a TM.sub.0n mode. A waveguide defines an axial centerline and, a solenoid arranged about the waveguide produces an axial constant magnetic field within the waveguide. An electron beam source outputs a annular electron beam that interacts with the axial magnetic field to have an equilibrium radius and a ripple radius component having a variable radius with a ripple period along the axial centerline. An rf source outputs an axial electric field that propagates within the waveguide coaxial with the electron beam and has a radial mode that interacts at the electron beam at the equilibrium radius component of the electron beam.

  15. Pointing of laser-accelerated proton beams

    SciTech Connect

    Schreiber, J.; Ter-Avetisyan, S.; Risse, E.; Kalachnikov, M.P.; Nickles, P.V.; Sandner, W.; Schramm, U.; Habs, D.; Witte, J.; Schnuerer, M.

    2006-03-15

    Small fluctuations in the acceleration sheath change the pointing of a proton beam accelerated from the rear side of a laser irradiated thin aluminum foil. The proton acceleration was produced with 40 fs pulses of a Ti:sapphire laser at an intensity of approximately 10{sup 19} W/cm{sup 2}. This observation has been made with a high spatial resolution Thomson spectrometer. The proton beam pointing has appeared stable in the energy range between the high energy cutoff (3 MeV) and 50% of this value. Deviations of the beam position at lower energies changes in a range of 0-3 mrad. The recorded pictures show wiggled and continuous proton traces which imply a release of the proton beam from the acceleration zone with a velocity chirp.

  16. Study on weld bead surface profile and angular distortion in 6 mm thick butt weld joints of SS304 using fiber laser

    NASA Astrophysics Data System (ADS)

    Bhargava, P.; Paul, C. P.; Mundra, G.; Premsingh, C. H.; Mishra, S. K.; Nagpure, D.; Kumar, Atul; Kukreja, L. M.

    2014-02-01

    We deployed a 2 kW continuous wave fiber laser integrated with the 5-axis workstation to understand the effect of various processing parameters (laser power, welding speed, beam spot size and chamfer at welded edges) on depth of penetration, angular distortion and welded bead surface profile during autogenous laser welding of 6 mm thick austenitic stainless steel type 304 plates. Full penetration with reduced weld bead surface undulation (<100 µm) and least angular distortion (<0.8°) was achieved for butt joints having chamfered edges of 0.8 mm. The microscopic studies revealed grossly defect-free fusion zone with a few porosities at isolated locations. The microstructure at the fusion zone was largely austenitic with few ferrites and the direction of growth was epitaxial towards the fusion line. The measured values of microhardness at base material and fusion zone were 208±4 HV0.1 and 235±10 HV0.1 respectively. The tensile testing of laser welded samples indicated the ultimate strength >605 MPa and these samples could be bent for an angle >170° without noticeable crack during bend test. The study opened the avenues for the deployment of fiber laser welding technology for applications demanding critical values of surface weld bead profile and distortion.

  17. Effects of mirror distortion by thermal deformation in an interferometry beam size monitor system at PLS-II

    NASA Astrophysics Data System (ADS)

    Hwang, Ji-Gwang; Kim, Eun-San; Kim, Changbum; Huang, Jung-Yun; Kim, Dotae

    2016-10-01

    Extraction mirrors installed at the most upstream position of interferometry beam size monitor are frequently used for measuring the beam size in storage rings. These mirrors receive the high power synchrotron radiation and are distorted owing to the heat distribution that depends on the position on the mirror surface. The distortion of the mirror changes the effective separation of the slit in the interferometry beam size monitor. Estimation of the effects of the front-end mirror distortion is important for measuring the beam size accurately. In this paper, we present the result of the numerical simulation of the temperature distribution and thermal expansion of the front-end mirror using ANSYS code, the theoretical basis of the effects of mirror distortion and compare with experimental results from Pohang Light Source II (PLS-II) at the Pohang Accelerator Laboratory (PAL). The equipment in the beam diagnosis line in PLS-II and experimental set-up for measuring the distortion of the front-end mirror using a multi-hole square array Hartmann screen are described.

  18. Beam shaping for laser initiated optical primers

    NASA Astrophysics Data System (ADS)

    Lizotte, Todd E.

    2008-08-01

    Remington was one of the first firearm manufacturing companies to file a patent for laser initiated firearms, in 1969. Nearly 40 years later, the development of laser initiated firearms has not become a mainstream technology in the civilian market. Requiring a battery is definitely a short coming, so it is easy to see how such a concept would be problematic. Having a firearm operate reliably and the delivery of laser energy in an efficient manner to ignite the shock-sensitive explosive primer mixtures is a tall task indeed. There has been considerable research on optical element based methods of transferring or compressing laser energy to ignite primer charges, including windows, laser chip primers and various lens shaped windows to focus the laser energy. The focusing of laser light needs to achieve igniting temperatures upwards of >400°C. Many of the patent filings covering this type of technology discuss simple approaches where a single point of light might be sufficient to perform this task. Alternatively a multi-point method might provide better performance, especially for mission critical applications, such as precision military firearms. This paper covers initial design and performance test of the laser beam shaping optics to create simultaneous multiple point ignition locations and a circumferential intense ring for igniting primer charge compounds. A simple initial test of the ring beam shaping technique was evaluated on a standard large caliber primer to determine its effectiveness on igniting the primer material. Several tests were conducted to gauge the feasibility of laser beam shaping, including optic fabrication and mounting on a cartridge, optic durability and functional ignition performance. Initial data will be presented, including testing of optically elements and empirical primer ignition / burn analysis.

  19. Correction of walk-off-induced wavefront distortion for continuous-wave laser

    NASA Astrophysics Data System (ADS)

    Zou, Hongxin; Chen, Guozhu; Wu, Yue; Shen, Yong; Liu, Qu

    2016-09-01

    We theoretically and experimentally investigate the wave front distortion in critically phase-matched continuous-wave (CW) second harmonic generation (SHG). Due to the walk-off effect in the nonlinear crystal, the generated second harmonic is extremely elliptical and quite non-Gaussian, which causes a very low matching and coupling efficiency in experiment. Cylindrical lenses and walk-off compensating crystals are adopted to correct distorted wave fronts, and obtain a good TEM00 mode efficiently. Theoretically, we simulate the correction effect of 266-nm laser generated with SHG. The experiment results accord well with the theoretical simulation and an above 80% TEM00 component is obtained for 266-nm continuous-wave laser with a 4.8°-walk-off angle in beta barium borate (BBO) crystal. Project supported by the National Natural Science Foundation of China (Grant No. 91436103) and Research Programme of National University of Defense Technology, China (Grant No. JC15-02-03).

  20. Unresonant interaction of laser beams with microdroplets

    NASA Astrophysics Data System (ADS)

    Pascu, M. L.; Popescu, G. V.; Ticos, C. M.; Andrei, I. R.

    2012-03-01

    The interaction of distilled water microdroplets (volumes of 3-4μl) with pulsed laser beams emitted at 532nm is described. At 532nm the distilled water absorption is very low and the interaction of a water bead with the laser radiation is dominated by unresonant phenomena. Following the collision of the laser beam with a microdroplet in suspended/ hanging/pendant position in air, deformations and mechanical vibrations of the droplets are produced. The conditions in which the droplets lose material as a consequence of the impact with laser beams are also explored. The effects produced on the droplet were studied pulse by pulse and depend on: droplet's content, beam wavelength, power and focusing conditions, irradiation geometry and adhesion of the bead to the capillary on which it is suspended. The laser pulses energies were varied in four steps: 0.25mJ, 0.4mJ, 0.7mJ and 1mJ. The pulse full time width was 5ns and the typical focus diameter on the droplet was 90μm; the beam had a relatively low divergence around the focus point. The microdroplets and the modification/evolution of their shapes are visualised by recordings performed at 10kframes/second. Following a microdroplet interaction with the laser beam one may also produce at a controlled moment in time nanodroplets propagating at high (probably supersonic) speeds and microdroplets propagating at slower speeds. One may also produce pendant droplets of smaller dimensions than the initial one as well as micro/nano gas bubbles in the pendant droplet's material/volume. In a second set of experiment was recorded at high speed the behaviour of the microdroplets of Rhodamine 6G in distilled water at resonant interaction with similar laser pulses, at the same power levels. The optical phenomena considering that the microdroplets contents are Newtonian liquids which dominate the beads behaviour at interaction with the laser beams, are discussed.

  1. Integration of a laser doppler vibrometer and adaptive optics system for acoustic-optical detection in the presence of random water wave distortions

    NASA Astrophysics Data System (ADS)

    Land, Phillip; Robinson, Dennis; Roeder, James; Cook, Dean; Majumdar, Arun K.

    2016-05-01

    A new technique has been developed for improving the Signal-to-Noise Ratio (SNR) of underwater acoustic signals measured above the water's surface. This technique uses a Laser Doppler Vibrometer (LDV) and an Adaptive Optics (AO) system (consisting of a fast steering mirror, deformable mirror, and Shack-Hartmann Wavefront Sensor) for mitigating the effect of surface water distortions encountered while remotely recording underwater acoustic signals. The LDV is used to perform non-contact vibration measurements of a surface via a two beam laser interferometer. We have demonstrated the feasibility of this technique to overcome water distortions artificially generated on the surface of the water in a laboratory tank. In this setup, the LDV beam penetrates the surface of the water and travels down to be reflected off a submerged acoustic transducer. The reflected or returned beam is then recorded by the LDV as a vibration wave measurement. The LDV extracts the acoustic wave information while the AO mitigates the water surface distortions, increasing the overall SNR. The AO system records the Strehl ratio, which is a measure of the quality of optical image formation. In a perfect optical system the Strehl ratio is unity, however realistic systems with imperfections have Strehl ratios below one. The operation of the AO control system in open-loop and closed-loop configurations demonstrates the utility of the AO-based LDV for many applications.

  2. Virtually distortion-free imaging system for large field, high resolution lithography using electrons, ions or other particle beams

    DOEpatents

    Hawryluk, Andrew M.; Ceglio, Natale M.

    1993-01-01

    Virtually distortion free large field high resolution imaging is performed using an imaging system which contains large field distortion or field curvature. A reticle is imaged in one direction through the optical system to form an encoded mask. The encoded mask is then imaged back through the imaging system onto a wafer positioned at the reticle position. Particle beams, including electrons, ions and neutral particles, may be used as well as electromagnetic radiation.

  3. Virtually distortion-free imaging system for large field, high resolution lithography using electrons, ions or other particle beams

    DOEpatents

    Hawryluk, A.M.; Ceglio, N.M.

    1993-01-12

    Virtually distortion free large field high resolution imaging is performed using an imaging system which contains large field distortion or field curvature. A reticle is imaged in one direction through the optical system to form an encoded mask. The encoded mask is then imaged back through the imaging system onto a wafer positioned at the reticle position. Particle beams, including electrons, ions and neutral particles, may be used as well as electromagnetic radiation.

  4. Virtually distortion-free imaging system for large field, high resolution lithography using electrons, ions or other particle beams

    SciTech Connect

    Hawryluk, A.M.; Ceglio, N.M.

    1991-04-10

    Virtually distortion free large field high resolution imaging is performed using an imaging system which contains large field distortion or field curvature. A reticle is imaged in one direction through the optical system to form an encoded mask. The encoded mask is then imaged back through the imaging system onto a wafer positioned at the reticle position. Particle beams, including electrons, ions and neutral particles, may be used as well as electromagnetic radiation.

  5. Laser beam propagation in atmospheric turbulence

    NASA Technical Reports Server (NTRS)

    Murty, S. S. R.

    1979-01-01

    The optical effects of atmospheric turbulence on the propagation of low power laser beams are reviewed in this paper. The optical effects are produced by the temperature fluctuations which result in fluctuations of the refractive index of air. The commonly-used models of index-of-refraction fluctuations are presented. Laser beams experience fluctuations of beam size, beam position, and intensity distribution within the beam due to refractive turbulence. Some of the observed effects are qualitatively explained by treating the turbulent atmosphere as a collection of moving gaseous lenses of various sizes. Analytical results and experimental verifications of the variance, covariance and probability distribution of intensity fluctuations in weak turbulence are presented. For stronger turbulence, a saturation of the optical scintillations is observed. The saturation of scintillations involves a progressive break-up of the beam into multiple patches; the beam loses some of its lateral coherence. Heterodyne systems operating in a turbulent atmosphere experience a loss of heterodyne signal due to the destruction of coherence.

  6. Laser synchrotron radiation and beam cooling

    SciTech Connect

    Esarey, E.; Sprangle, P.; Ting, A.

    1995-12-31

    The interaction of intense {approx_gt} 10{sup 18} W/cm{sup 2}, short pulse ({approx_lt} 1 ps) lasers with electron beams and plasmas can lead to the generation of harmonic radiation by several mechanisms. Laser synchrotron radiation may provide a practical method for generating tunable, near monochromatic, well collimated, short pulse x-rays in compact, relatively inexpensive source. The mechanism for the generation of laser synchrotron radiation is nonlinear Thomson scattering. Short wavelengths can be generated via Thomson scattering by two methods, (i) backscattering from relativistic electron beams, in which the radiation frequency is upshifted by the relativistic factor 4{gamma}{sup 2}, and (ii) harmonic scattering, in which a multitude of harmonics are generated with harmonic numbers extending out to the critical harmonic number nc{approx_equal}a{sub 0}{sup 3} {much_gt} 1, where a{sub 0} {approx_equal}10{sup -9}{lambda}I{sup 1/2}, {lambda} is the laser wavelength in {mu}m and I is the laser intensity in W/cm{sup 2}. Laser synchrotron sources are capable of generating short ({approx_lt} ps) x-ray pulses with high peak flux ({approx_gt} 10{sup 21} photons/s) and brightness ({approx_gt}{sup 19} photons/s-mm{sup 2}-mrad{sup 2} 0.1%BW. As the electron beam radiates via Thomson scattering, it can subsequently be cooled, i.e., the beam emittance and energy spread can be reduced. This cooling can occur on rapid ({approximately} ps) time scales. In addition, electron distributions with sufficiently small axial energy spreads can be used to generate coherent XUV radiation via a laser-pumped FEL mechanism.

  7. More About Beam-Steering Subsystem For Laser Communication

    NASA Technical Reports Server (NTRS)

    Page, Norman A.; Chen, Chien-Chu; Hemmati, Hamid; Lesh, James R.

    1995-01-01

    Two reports present additional information about developmental beam-steering subsystem of laser-communication system. Aspects of this subsystem described previously in "Beam-Steering Subsystem for Laser Communication" (NPO-19069) and "Digital Controller for Laser-Beam-Steering Subsystem" (NPO-19193). Reports reiterate basic principles of operation of beam-steering subsystem and of laser-communication system as whole. Also presents some of details of optical and mechanical design of prototype of subsystem, called Optical Communication Demonstrator.

  8. Systems analysis on laser beamed power

    NASA Technical Reports Server (NTRS)

    Zeiders, Glenn W., Jr.

    1993-01-01

    The NASA SELENE power beaming program is intended to supply cost-effective power to space assets via Earth-based lasers and active optics systems. Key elements of the program are analyzed, the overall effort is reviewed, and recommendations are presented.

  9. Coherent beam combiner for a high power laser

    DOEpatents

    Dane, C. Brent; Hackel, Lloyd A.

    2002-01-01

    A phase conjugate laser mirror employing Brillouin-enhanced four wave mixing allows multiple independent laser apertures to be phase locked producing an array of diffraction-limited beams with no piston phase errors. The beam combiner has application in laser and optical systems requiring high average power, high pulse energy, and low beam divergence. A broad range of applications exist in laser systems for industrial processing, especially in the field of metal surface treatment and laser shot peening.

  10. Safe Laser Beam Propagation for Interplanetary Links

    NASA Technical Reports Server (NTRS)

    Wilson, Keith E.

    2011-01-01

    Ground-to-space laser uplinks to Earth–orbiting satellites and deep space probes serve both as a beacon and an uplink command channel for deep space probes and Earth-orbiting satellites. An acquisition and tracking point design to support a high bandwidth downlink from a 20-cm optical terminal on an orbiting Mars spacecraft typically calls for 2.5 kW of 1030-nm uplink optical power in 40 micro-radians divergent beams.2 The NOHD (nominal ocular hazard distance) of the 1030nm uplink is in excess of 2E5 km, approximately half the distance to the moon. Recognizing the possible threat of high power laser uplinks to the flying public and to sensitive Earth-orbiting satellites, JPL developed a three-tiered system at its Optical Communications Telescope Laboratory (OCTL) to ensure safe laser beam propagation through navigational and near-Earth space.

  11. Phasing surface emitting diode laser outputs into a coherent laser beam

    DOEpatents

    Holzrichter, John F.

    2006-10-10

    A system for generating a powerful laser beam includes a first laser element and at least one additional laser element having a rear laser mirror, an output mirror that is 100% reflective at normal incidence and <5% reflective at an input beam angle, and laser material between the rear laser mirror and the output mirror. The system includes an injector, a reference laser beam source, an amplifier and phase conjugater, and a combiner.

  12. Laser-cooled bunched ion beam

    SciTech Connect

    Schiffer, J.P.; Hangst, J.S.; Nielsen, J.S.

    1995-08-01

    In collaboration with the Arhus group, the laser cooling of a beam bunched by an rf electrode was investigated at the ASTRID storage ring. A single laser is used for unidirectional cooling, since the longitudinal velocity of the beam will undergo {open_quotes}synchrotron oscillations{close_quotes} and the ions are trapped in velocity space. As the cooling proceeds the velocity spread of the beam, as well as the bunch length is measured. The bunch length decreases to the point where it is limited only by the Coulomb repulsion between ions. The measured length is slightly (20-30%) smaller than the calculated limit for a cold beam. This may be the accuracy of the measurement, or may indicate that the beam still has a large transverse temperature so that the longitudinal repulsion is less than would be expected from an absolutely cold beam. Simulations suggest that the coupling between transverse and longitudinal degrees of freedom is strong -- but this issue will have to be resolved by further measurements.

  13. Deformation of a laser beam in the fabrication of graphite microstructures inside a volume of diamond

    NASA Astrophysics Data System (ADS)

    Kononenko, T. V.; Zavedeev, E. V.

    2016-03-01

    We report a theoretical and experimental study of the energy profile deformation along the laser beam axis during the fabrication of graphite microstructures inside a diamond crystal. The numerical simulation shows that the use of a focusing lens with a numerical aperture NA < 0.1 at a focusing depth of up to 2 mm makes it possible to avoid a noticeable change in the energy profile of the beam due to the spherical aberration that occurs in the case of refraction of the focused laser beam at the air - diamond interface. The calculation results are confirmed by experimental data on the distribution of the laser intensity along the beam axis in front of its focal plane, derived from observations of graphitisation wave propagation in diamond. The effect of radiation self-focusing on laser-induced graphitisation of diamond is analysed. It is shown that if the wavefront distortion due to self-focusing can be neglected at a minimum pulse energy required for the optical breakdown of diamond, then an increase in the beam distortion with increasing pulse energy has no effect on the graphitisation process.

  14. Laser-driven ion acceleration with hollow laser beams

    SciTech Connect

    Brabetz, C. Kester, O.; Busold, S.; Bagnoud, V.; Cowan, T.; Deppert, O.; Jahn, D.; Roth, M.; Schumacher, D.

    2015-01-15

    The laser-driven acceleration of protons from thin foils irradiated by hollow high-intensity laser beams in the regime of target normal sheath acceleration (TNSA) is reported for the first time. The use of hollow beams aims at reducing the initial emission solid angle of the TNSA source, due to a flattening of the electron sheath at the target rear side. The experiments were conducted at the PHELIX laser facility at the GSI Helmholtzzentrum für Schwerionenforschung GmbH with laser intensities in the range from 10{sup 18} W cm{sup −2} to 10{sup 20} W cm{sup −2}. We observed an average reduction of the half opening angle by (3.07±0.42)° or (13.2±2.0)% when the targets have a thickness between 12 μm and 14 μm. In addition, the highest proton energies were achieved with the hollow laser beam in comparison to the typical Gaussian focal spot.

  15. Hybrid laser-beam-shaping system for rotatable dual beams with long depth of focus

    NASA Astrophysics Data System (ADS)

    Chou, Fu-Lung; Chen, Cheng-Huan; Lin, Yu-Chung; Lin, Mao-Chi

    2016-10-01

    A laser processing system consisting of two diffractive elements and one refractive element is proposed enabling a Gaussian laser beam to be transformed into two beams with a depth of focus of up to 150 µm and focal spot smaller than 5 µm. For specific laser processing, the two beams are rotatable when the beam-splitting diffractive element is rotated. The overall system is versatile for laser cutting and drilling.

  16. Hybrid laser-beam-shaping system for rotatable dual beams with long depth of focus

    NASA Astrophysics Data System (ADS)

    Chou, Fu-Lung; Chen, Cheng-Huan; Lin, Yu-Chung; Lin, Mao-Chi

    2016-08-01

    A laser processing system consisting of two diffractive elements and one refractive element is proposed enabling a Gaussian laser beam to be transformed into two beams with a depth of focus of up to 150 µm and focal spot smaller than 5 µm. For specific laser processing, the two beams are rotatable when the beam-splitting diffractive element is rotated. The overall system is versatile for laser cutting and drilling.

  17. Design process for NIF laser alignment and beam diagnostics

    SciTech Connect

    Grey, A., LLNL

    1998-06-09

    In a controller for an adaptive optic system designed to correct phase aberrations in a high power laser, the wavefront sensor is a discrete Hartmann-Shack design. It uses an army of lenslets (like a fly` s eye) to focus the laser into 77 spots on a CCD camera. Average local tilt of the wavefront across each lenslet changes the position of its focal spot. The system requires 0.1 pixel accuracy in determining the focal spot location. We determine a small area around each spot` s previous location. Within this area, we calculate the centroid of the light intensity in x and y. This calculation fails if the spot regions overlap. Especially during initial acquisition of a highly distorted beam, distinguishing overlapping spots is difficult. However, low resolution analysis of the overlapping spots allows the system to estimate their positions. With this estimate, it can use the deformable mirror to correct the beam enough so we can detect the spots using conventional image processing.

  18. Finite Element Modeling for the Structural Analysis of Al-Cu Laser Beam Welding

    NASA Astrophysics Data System (ADS)

    Hartel, Udo; Ilin, Alexander; Bantel, Christoph; Gibmeier, Jens; Michailov, Vesselin

    Laser beam welding of aluminum and copper (Al-Cu) materials is a cost efficient joining technology to produce e.g. connector elements for battery modules. Distortion low connections can be achieved, which have electrical favorable properties. Numerical simulation of the laser beam welding process of Al-Cu dissimilar materials can provide further insight into principal process mechanisms and mechanical response of the joint parts. In this paper a methodology is introduced to investigate the structural behavior of Al-Cu joints in overlap joint with respect to welding distortions and residual stresses. First the material model of the homogeneous base materials are validated. Next, a generic material model approach is used to simulate the structural behavior of heterogeneous Al-Cu connections.

  19. Radiative trapping in intense laser beams

    NASA Astrophysics Data System (ADS)

    Kirk, J. G.

    2016-08-01

    The dynamics of electrons in counter-propagating, circularly polarized laser beams are shown to exhibit attractors whose ability to trap particles depends on the ratio of the beam intensities and a single parameter describing radiation reaction. Analytical expressions are found for the underlying limit cycles and the parameter range in which they are stable. In high-intensity optical pulses, where radiation reaction strongly modifies the trajectories, the production of collimated gamma-rays and the initiation of non-linear cascades of electron-positron pairs can be optimized by a suitable choice of the intensity ratio.

  20. Radiative trapping in intense laser beams

    NASA Astrophysics Data System (ADS)

    Kirk, J. G.

    2016-08-01

    The dynamics of electrons in counter-propagating, circularly polarized laser beams are shown to exhibit attractors whose ability to trap particles depends on the ratio of the beam intensities and a single parameter describing radiation reaction. Analytical expressions are found for the underlying limit cycles and the parameter range in which they are stable. In high-intensity optical pulses, where radiation reaction strongly modifies the trajectories, the production of collimated gamma-rays and the initiation of non-linear cascades of electron–positron pairs can be optimized by a suitable choice of the intensity ratio.

  1. Beam-energy and laser beam-profile monitor at the BNL LINAC

    SciTech Connect

    Connolly, R.; Briscoe, B.; Degen, C.; DeSanto, L.; Meng, W.; Minty, M.; Nayak, S.; Raparia, D.; Russo, T.

    2010-05-02

    We are developing a non-interceptive beam profile and energy monitor for H{sup -} beams in the high energy beam transport (HEBT) line at the Brookhaven National Lab linac. Electrons that are removed from the beam ions either by laser photodetachment or stripping by background gas are deflected into a Faraday cup. The beam profile is measured by stepping a narrow laser beam across the ion beam and measuring the electron charge vs. transverse laser position. There is a grid in front of the collector that can be biased up to 125kV. The beam energy spectrum is determined by measuring the electron charge vs. grid voltage. Beam electrons have the same velocity as the beam and so have an energy of 1/1836 of the beam protons. A 200MeV H{sup -} beam yields 109keV electrons. Energy measurements can be made with either laser-stripped or gas-stripped electrons.

  2. Freeform beam shaping for high-power multimode lasers

    NASA Astrophysics Data System (ADS)

    Laskin, Alexander; Laskin, Vadim

    2014-03-01

    Widening of using high power multimode lasers in industrial laser material processing is accompanied by special requirements to irradiance profiles in such technologies like metal or plastics welding, cladding, hardening, brazing, annealing, laser pumping and amplification in MOPA lasers. Typical irradiance distribution of high power multimode lasers: free space solid state, fiber-coupled solid state and diodes lasers, fiber lasers, is similar to Gaussian. Laser technologies can be essentially improved when irradiance distribution on a workpiece is uniform (flattop) or inverse-Gauss; when building high-power pulsed lasers it is possible to enhance efficiency of pumping and amplification by applying super-Gauss irradiance distribution with controlled convexity. Therefore, "freeform" beam shaping of multimode laser beams is an important task. A proved solution is refractive field mapping beam shaper like Shaper capable to control resulting irradiance profile - with the same unit it is possible to get various beam profiles and choose optimum one for a particular application. Operational principle of these devices implies transformation of laser irradiance distribution by conserving beam consistency, high transmittance, providing collimated low divergent output beam. Using additional optics makes it possible to create resulting laser spots of necessary size and round, elliptical or linear shape. Operation out of focal plane and, hence, in field of lower wavefront curvature, allows extending depth of field. The refractive beam shapers are implemented as telescopes and collimating systems, which can be connected directly to fiber-coupled lasers or fiber lasers, thus combining functions of beam collimation and irradiance transformation.

  3. Laser beam propagation through an atmospheric transitional and turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Katz, Richard A.; Manzur, Tariq

    2015-05-01

    This study investigates laser beam propagation through an atmospheric boundary layer near the ocean surface. Objectives of this research are to ascertain feasibility limits for achieving maximum energy efficiency at extended ranges in the face of atmospheric and other distortions as the laser beam penetrates through transitional (anisotropic) and turbulent (isotropic) boundary layer regimes. Various aspects of turbulence modeling of laser beam propagation near the ocean surface are discussed including: Kolmogorov's model of atmospheric turbulence, parameterized structure functions (e.g., velocity and temperature gradients, gradients in refractive index) and other important factors affecting near surface propagation such as humidity, aerosols, and wave slap. Various preliminary modeled propagation results are shown, and a new methodology is proposed for improving existing model estimates with new time domain measurement procedures.

  4. Beam control and laser characterization for NIF

    SciTech Connect

    Boege, S. J., LLNL

    1998-06-10

    The demanding energy, power, pulse shape, focusability, pointing, and availability requirements placed on the 192 National Ignition Facility (NIF) beams lead to the need for an automatic operation capability that is well beyond that of previous inertial confinement fusion (ICF) lasers. Alignment, diagnostic, and wavefront correction subsystems are integrated in an approach that, by permitting maximal sharing of instrumentation between subsystems, meets performance requirements at a reasonable cost.

  5. Laser beamed power: Satellite demonstration applications

    NASA Technical Reports Server (NTRS)

    Landis, Geoffrey A.; Westerlund, Larry H.

    1992-01-01

    It is possible to use a ground-based laser to beam light to the solar arrays of orbiting satellites, to a level sufficient to provide all or some of the operating power required. Near-term applications of this technology for providing supplemental power to existing satellites are discussed. Two missions with significant commercial pay-off are supplementing solar power for radiation-degraded arrays and providing satellite power during eclipse for satellites with failed batteries.

  6. Self-induced thermal distortion effects on target image quality.

    PubMed

    Gebhardt, F G

    1972-06-01

    Experimental results are reported that show the effects of the self-induced thermal lens due to a high power laser beam on imaging or tracking systems viewing along the same propagation path. The thermal distortion effects of a wind are simulated with a low power ( less, similar 3-W) CO(2) laser beam propagating through a cell of liquid CS(2) moving across the beam. The resulting image distortion includes a warping effect analogous to the deflection of the CO(2) beam, together with a pronounced demagnification of the central portion of the object. An active optical tracker is simulated with a He-Ne laser beam propagating collinearly with the CO(2) beam. The He-Ne beam pattern returned from a specular target is distorted and sharply confined to the outline of the crescent shaped CO(2) beam. Simple ray optics models are used to provide qualitative explanations for the experimental results.

  7. Laser beam collimation using Talbot interferometry

    NASA Technical Reports Server (NTRS)

    Ganesan, A. R.; Venkateswarlu, Putcha

    1993-01-01

    A modified method of checking laser beam collimation using a single grating and a right-angled prism is presented. The self-images (Talbot images) of a grating illuminated by a collimated beam are formed at some distance from the grating. The use of a right-angled prism makes it possible to carry out the folding of the self-image with respect to the original grating and to ensure that the grating lines in the self-image and the actual grating are inclined at equal angles with respect to horizontal direction. It is concluded that the proposed collimation test method has an in-built reference and does not require precise orientation of the grating as in the two-grating method. Large beams can be tested with a small-size assembly.

  8. Active annular-beam laser autocollimator system.

    PubMed

    Yoder, P R; Schlesinger, E R; Chickvary, J L

    1975-08-01

    An autocollimator using an axicon and a beam expander telescope to generate a 12.5-cm. o.d. annular beam of helium-neon laser light with high (25:1) diameter-to-width ratio has been developed. It is used with a two-axis, electromagnetically actuated mirror assembly to acquire automatically and maintain dynamically autocollimation from a nearby but separately mounted annular mirror. The servo system controls beam alignment even though angular vibratory motions of the annular mirror make it appear to tilt relative to the autocollimator as much as 7 mrad at frequencies below 300 Hz. This paper describes the optical system and the alignment sensing and control system.

  9. Beam Emittance Measurement with Laser Wire Scanners in the ILC Beam Delivery System

    SciTech Connect

    Agapov, I.; Blair, G.A.; Woodley, M.; /SLAC

    2008-02-01

    Accurate measurement of the beam phase-space is essential for the next generation of electron accelerators. A scheme for beam optics optimization and beam matrix reconstruction algorithms for the diagnostics section of the beam delivery system of the International Linear Collider based on laser-wire beam profile monitors are discussed. Possible modes of operation of the laser-wire system together with their corresponding performance are presented. Based on these results, prospects for reconstructing the ILC beam emittance from representative laser-wire beam size measurements are evaluated.

  10. Laser-Beam-Absorption Chemical-Species Monitor

    NASA Technical Reports Server (NTRS)

    Gersh, Michael; Goldstein, Neil; Lee, Jamine; Bien, Fritz; Richtsmeier, Steven

    1996-01-01

    Apparatus measures concentration of chemical species in fluid medium (e.g., gaseous industrial process stream). Directs laser beam through medium, and measures intensity of beam after passage through medium. Relative amount of beam power absorbed in medium indicative of concentration of chemical species; laser wavelength chosen to be one at which species of interest absorbs.

  11. T-3 electron-beam-excited laser system

    SciTech Connect

    Klein, R A

    1981-02-01

    A laser system specifically designed to study the kinetics of electron-beam driven systems is described. Details of the system are given along with measurements of the electron-beam uniformity and deposition in the laser medium. Some HF laser results obtained with this system are also given.

  12. A laser beam quality definition based on induced temperature rise.

    PubMed

    Miller, Harold C

    2012-12-17

    Laser beam quality metrics like M(2) can be used to describe the spot sizes and propagation behavior of a wide variety of non-ideal laser beams. However, for beams that have been diffracted by limiting apertures in the near-field, or those with unusual near-field profiles, the conventional metrics can lead to an inconsistent or incomplete description of far-field performance. This paper motivates an alternative laser beam quality definition that can be used with any beam. The approach uses a consideration of the intrinsic ability of a laser beam profile to heat a material. Comparisons are made with conventional beam quality metrics. An analysis on an asymmetric Gaussian beam is used to establish a connection with the invariant beam propagation ratio. PMID:23263122

  13. A laser beam quality definition based on induced temperature rise.

    PubMed

    Miller, Harold C

    2012-12-17

    Laser beam quality metrics like M(2) can be used to describe the spot sizes and propagation behavior of a wide variety of non-ideal laser beams. However, for beams that have been diffracted by limiting apertures in the near-field, or those with unusual near-field profiles, the conventional metrics can lead to an inconsistent or incomplete description of far-field performance. This paper motivates an alternative laser beam quality definition that can be used with any beam. The approach uses a consideration of the intrinsic ability of a laser beam profile to heat a material. Comparisons are made with conventional beam quality metrics. An analysis on an asymmetric Gaussian beam is used to establish a connection with the invariant beam propagation ratio.

  14. Collaborative Research: Instability and transport of laser beam in plasma

    SciTech Connect

    Rose, Harvey Arnold; Lushnikov, Pavel

    2014-11-18

    Our goal was to determine the onset of laser light scattering due to plasma wave instabilities. Such scatter is usually regarded as deleterious since laser beam strength is thereby diminished. While this kind of laser-plasma-instability (LPI) has long been understood for the case of coherent laser light, the theory of LPI onset for a laser beam with degraded coherence is recent. Such a laser beam fills plasma with a mottled intensity distribution, which has large fluctuations. The key question is: do the exceptionally large fluctuations control LPI onset or is it controlled by the relatively quiescent background laser intensity? We have answered this question. This is significant because LPI onset power in the former case is typically small compared to that of the latter. In addition, if large laser intensity fluctuations control LPI onset, then nonlinear effects become significant for less powerful laser beams than otherwise estimated.

  15. Quantum well, beam deflecting surface emitting lasers

    NASA Technical Reports Server (NTRS)

    Kim, Jae H. (Inventor)

    1992-01-01

    This invention relates to surface emitting semiconductor lasers (SELs), with integrated 45 deg. beam deflectors. A SEL is formed on a wafer including vertical mirrors and 45 deg. beam deflectors formed in grooves by tilted ion beam etching. A SEL is a lattice matched, or unstrained, AlGaAs/GaAs GRINSCH SQW SEL. An alternate embodiment is shown, in which a SEL is lattice mismatched, strained or pseudomorphic, or InGaAs/AlGaAs GRINSCH SQW SEL which emits radiation at a wavelength to which its substrate is transparent. Both SELs exhibit high output power, low threshold current density, and relatively high efficiency, and each are processing compatible with conventional large scale integration technology. Such SELs may be fabricated in large numbers from single wafers. The novel features of this invention include the use of tilted ion beam etching to form a pair of grooves each including vertical mirrors and 45 deg. beam deflectors. The embodiment provides substantial circuit design flexibility because radiation may be coupled both up and/or down through the substrate.

  16. Quantum well, beam deflecting surface emitting lasers

    NASA Astrophysics Data System (ADS)

    Kim, Jae H.

    1992-10-01

    This invention relates to surface emitting semiconductor lasers (SELs), with integrated 45 deg. beam deflectors. A SEL is formed on a wafer including vertical mirrors and 45 deg. beam deflectors formed in grooves by tilted ion beam etching. A SEL is a lattice matched, or unstrained, AlGaAs/GaAs GRINSCH SQW SEL. An alternate embodiment is shown, in which a SEL is lattice mismatched, strained or pseudomorphic, or InGaAs/AlGaAs GRINSCH SQW SEL which emits radiation at a wavelength to which its substrate is transparent. Both SELs exhibit high output power, low threshold current density, and relatively high efficiency, and each are processing compatible with conventional large scale integration technology. Such SELs may be fabricated in large numbers from single wafers. The novel features of this invention include the use of tilted ion beam etching to form a pair of grooves each including vertical mirrors and 45 deg. beam deflectors. The embodiment provides substantial circuit design flexibility because radiation may be coupled both up and/or down through the substrate.

  17. Quantum well, beam deflecting surface emitting lasers

    NASA Astrophysics Data System (ADS)

    Kim, Jae H.

    1991-06-01

    This invention relates to surface emitting semiconductor lasers (SELs), with integrated 45 deg. beam deflectors. A SEL is formed on a wafer including vertical mirrors and 45 deg. beam deflectors formed in grooves by tilted ion beam etching. A SEL is a lattice matched, or unstrained, AlGaAs/GaAs GRINSCH SQW SEL. An alternate embodiment is shown, in which a SEL is lattice mismatched, strained or pseudomorphic, or InGaAs/AlGaAs GRINSCH SQW SEL which emits radiation at a wavelength to which its substrate is transparent. Both SELs exhibit high output power, low threshold current density, and relatively high efficiency, and each are processing compatible with conventional large scale integration technology. Such SELs may be fabricated in large numbers from single wafers. The novel features of this invention include the use of tilted ion beam etching to form a pair of grooves each including vertical mirrors and 45 deg. beam deflectors. The embodiment provides substantial circuit design flexibility because radiation may be coupled both up and/or down through the substrate.

  18. Efficient laser production of energetic neutral beams

    NASA Astrophysics Data System (ADS)

    Mollica, F.; Antonelli, L.; Flacco, A.; Braenzel, J.; Vauzour, B.; Folpini, G.; Birindelli, G.; Schnuerer, M.; Batani, D.; Malka, V.

    2016-03-01

    Laser-driven ion acceleration by intense, ultra-short, laser pulse has received increasing attention in recent years, and the availability of much compact and versatile ions sources motivates the study of laser-driven sources of energetic neutral atoms. We demonstrate the production of a neutral and directional beam of hydrogen and carbon atoms up to 200 keV per nucleon, with a peak flow of 2.7× {{10}13} atom s-1. Laser accelerated ions are neutralized in a pulsed, supersonic argon jet with tunable density between 1.5× {{10}17} cm-3and 6× {{10}18} cm-3. The neutralization efficiency has been measured by a time-of-flight detector for different argon densities. An optimum is found, for which complete neutralization occurs. The neutralization rate can be explained only at high areal densities (>1× {{10}17} cm-2) by single electron charge transfer processes. These results suggest a new perspective for the study of neutral production by laser and open discussion of neutralization at a lower density.

  19. Laser beam riding guided system principle and design research

    NASA Astrophysics Data System (ADS)

    Qu, Zhou; Jin, Yi; Xu, Zhou; Xing, Hao

    2016-01-01

    With the development of science and technology, precision-strike weapons has been considered to be important for winning victory in military field. Laser guidance is a major method to execute precision-strike in modern warfare. At present, the problems of primary stage of Laser guidance has been solved with endeavors of countries. Several technical aspects of laser-beam riding guided system have been mature, such as atmosphere penetration of laser beam, clutter inhibition on ground, laser irradiator, encoding and decoding of laser beam. Further, laser beam quality, equal output power and atmospheric transmission properties are qualified for warfare situation. Riding guidance instrument is a crucial element of Laser-beam riding guided system, and is also a vital element of airborne, vehicle-mounted and individual weapon. The optical system mainly consist of sighting module and laser-beam guided module. Photoelectric detector is the most important sensing device of seeker, and also the key to acquire the coordinate information of target space. Currently, in consideration of the 1.06 u m of wavelength applied in all the semi-active laser guided weapons systems, lithium drifting silicon photodiode which is sensitive to 1.06 u m of wavelength is used in photoelectric detector. Compared to Solid and gas laser, diode laser has many merits such as small volume, simple construction, light weight, long life, low lost and easy modulation. This article introduced the composition and operating principle of Laser-beam riding guided system based on 980 nm diode laser, and made a analysis of key technology; for instance, laser irradiator, modulating disk of component, laser zooming system. Through the use of laser diode, Laser-beam riding guided system is likely to have smaller shape and very light.

  20. Laser-induced Bessel beams can realize fast all-optical switching in gold nanosol prepared by pulsed laser ablation

    SciTech Connect

    Joseph, Santhi Ani; Hari, Misha; Nampoori, V. P. N.; Sharma, Gaurav; Mathew, S.; Radhakrishnan, P.

    2010-03-15

    We demonstrate the possibility of realizing, all-optical switching in gold nanosol. Two overlapping laser beams are used for this purpose, due to which a low-power beam passing collinear to a high-power beam will undergo cross phase modulation and thereby distort the spatial profile. This is taken to advantage for performing logic operations. We have also measured the threshold pump power to obtain a NOT gate and the minimum response time of the device. Contrary to the general notion that the response time of thermal effects used in this application is of the order of milliseconds, we prove that short pump pulses can result in fast switching. Different combinations of beam splitters and combiners will lead to the formation of other logic functions too.

  1. Correction of walk-off-induced wavefront distortion for continuous-wave laser

    NASA Astrophysics Data System (ADS)

    Zou, Hongxin; Chen, Guozhu; Wu, Yue; Shen, Yong; Liu, Qu

    2016-09-01

    We theoretically and experimentally investigate the wave front distortion in critically phase-matched continuous-wave (CW) second harmonic generation (SHG). Due to the walk-off effect in the nonlinear crystal, the generated second harmonic is extremely elliptical and quite non-Gaussian, which causes a very low matching and coupling efficiency in experiment. Cylindrical lenses and walk-off compensating crystals are adopted to correct distorted wave fronts, and obtain a good TEM00 mode efficiently. Theoretically, we simulate the correction effect of 266-nm laser generated with SHG. The experiment results accord well with the theoretical simulation and an above 80% TEM00 component is obtained for 266-nm continuous-wave laser with a 4.8°-walk-off angle in beta barium borate (BBO) crystal. Project supported by the National Natural Science Foundation of China (Grant No. 91436103) and Research Programme of National University of Defense Technology, China (Grant No. JC15-02-03).

  2. Application of reactor-pumped lasers to power beaming

    SciTech Connect

    Repetti, T.E.

    1991-10-01

    Power beaming is the concept of centralized power generation and distribution to remote users via energy beams such as microwaves or laser beams. The power beaming community is presently performing technical evaluations of available lasers as part of the design process for developing terrestrial and space-based power beaming systems. This report describes the suitability of employing a nuclear reactor-pumped laser in a power beaming system. Although there are several technical issues to be resolved, the power beaming community currently believes that the AlGaAs solid-state laser is the primary candidate for power beaming because that laser meets the many design criteria for such a system and integrates well with the GaAs photodiode receiver array. After reviewing the history and physics of reactor-pumped lasers, the advantages of these lasers for power beaming are discussed, along with several technical issues which are currently facing reactor-pumped laser research. The overriding conclusion is that reactor-pumped laser technology is not presently developed to the point of being technially or economically competitive with more mature solid-state technologies for application to power beaming. 58 refs.

  3. Ultraviolet laser beam monitor using radiation responsive crystals

    DOEpatents

    McCann, Michael P.; Chen, Chung H.

    1988-01-01

    An apparatus and method for monitoring an ultraviolet laser beam includes disposing in the path of an ultraviolet laser beam a substantially transparent crystal that will produce a color pattern in response to ultraviolet radiation. The crystal is exposed to the ultraviolet laser beam and a color pattern is produced within the crystal corresponding to the laser beam intensity distribution therein. The crystal is then exposed to visible light, and the color pattern is observed by means of the visible light to determine the characteristics of the laser beam that passed through crystal. In this manner, a perpendicular cross sectional intensity profile and a longitudinal intensity profile of the ultraviolet laser beam may be determined. The observation of the color pattern may be made with forward or back scattered light and may be made with the naked eye or with optical systems such as microscopes and television cameras.

  4. High-power multi-beam diode laser transmitter for a flash imaging lidar

    NASA Astrophysics Data System (ADS)

    Holmlund, Christer; Aitta, Petteri; Kivi, Sini; Mitikka, Risto; Tyni, Lauri; Heikkinen, Veli

    2013-10-01

    VTT Technical Research Centre of Finland is developing the transmitter for the "Flash Optical Sensor for TErrain Relative NAVigation" (FOSTERNAV) multi-beam flash imaging lidar. FOSTERNAV is a concept demonstrator for new guidance, navigation and control (GNC) technologies to fulfil the requirements for landing and docking of spacecraft as well as for navigation of rovers. This paper presents the design, realisation and testing of the multi-beam continuous-wave (CW) laser transmitter to be used in a 256x256 pixel flash imaging lidar. Depending on the target distance, the lidar has three operation modes using either several beams with low divergence or one single beam with a large divergence. This paper describes the transmitter part of the flash imaging lidar with focus on the electronics and especially the laser diode drivers. The transmitter contains eight fibre coupled commercial diode laser modules with a total peak optical power of 32 W at 808 nm. The main requirement for the laser diode drivers was linear modulation up to a frequency of 20 MHz allowing, for example, low distortion chirps or pseudorandom binary sequences. The laser modules contain the laser diode, a monitoring photodiode, a thermo-electric cooler, and a thermistor. The modules, designed for non-modulated and low-frequency operation, set challenging demands on the design of the drivers. Measurement results are presented on frequency response, and eye diagrams for pseudo-random binary sequences.

  5. Repositioning and steering laser beam power via coherent combination of multiple Airy beams.

    PubMed

    Zhang, Ze; Ye, Zhuoyi; Song, Daohong; Zhang, Peng; Chen, Zhigang

    2013-12-10

    We study numerically and experimentally laser coherent combination (LCC) with multiple one- or two-dimensional Airy beams. It is shown that the method of LCC using Airy beams leads to a higher combining efficiency and a better feature of propagation than that using conventional Gaussian beams. Based on such coherent Airy beams combination, we propose a laser steering approach that could achieve large-angle beam steering (over 0.6°) without the need of using any mechanical steering component.

  6. Laser systems configured to output a spectrally-consolidated laser beam and related methods

    DOEpatents

    Koplow, Jeffrey P.

    2012-01-10

    A laser apparatus includes a plurality of pumps each of which is configured to emit a corresponding pump laser beam having a unique peak wavelength. The laser apparatus includes a spectral beam combiner configured to combine the corresponding pump laser beams into a substantially spatially-coherent pump laser beam having a pump spectrum that includes the unique peak wavelengths, and first and second selectively reflective elements spaced from each other to define a lasing cavity including a lasing medium therein. The lasing medium generates a plurality of gain spectra responsive to absorbing the pump laser beam. Each gain spectrum corresponds to a respective one of the unique peak wavelengths of the substantially spatially-coherent pump laser beam and partially overlaps with all other ones of the gain spectra. The reflective elements are configured to promote emission of a laser beam from the lasing medium with a peak wavelength common to each gain spectrum.

  7. Power limitations and pulse distortions in an Yb : KGW chirped-pulse amplification laser system

    SciTech Connect

    Kim, G H; Yang, J; Kulik, A V; Sall, E G; Chizhov, S A; Kang, U; Yashin, V E

    2013-08-31

    We have studied self-action effects (self-focusing and self-phase modulation) and stimulated Raman scattering in an Yb : KGW chirped-pulse amplification laser system. The results demonstrate that self-focusing in combination with thermal lensing may significantly limit the chirped pulse energy in this system (down to 200 μJ) even at a relatively long pulse duration (50 ps). Nonlinear lenses in the laser crystals in combination with thermal lenses bring the regenerative amplifier cavity in the laser system to the instability zone and limit the average output power at pulse repetition rates under 50 kHz. Self-phase modulation, a manifestation of self-action, may significantly distort a recompressed femtosecond pulse at energies near the self-focusing threshold. Stimulated Raman scattering in such a laser has a weaker effect on output parameters than do self-focusing and thermal lensing, and Raman spectra are only observed in the case of pulse energy instability. (nonlinear optical phenomena)

  8. Continuous adaptive beam pointing and tracking for laser power transmission.

    PubMed

    Schäfer, Christian A

    2010-06-21

    The adaptive beam pointing concept has been revisited for the purpose of controlled transmission of laser energy from an optical transmitter to a target. After illumination, a bidirectional link is established by a retro-reflector on the target and an amplifier-phase conjugate mirror (A-PCM) on the transmitter. By setting the retro-reflector's aperture smaller than the diffraction limited spot size but big enough to provide sufficient amount of optical feedback, a stable link can be maintained and light that hits the retro-reflector's surrounded area can simultaneously be reconverted into usable electric energy. The phase conjugate feedback ensures that amplifier's distortions are compensated and the target tracked accurately.After deriving basic arithmetic expressions for the proposed system, a section is devoted for the motivation of free-space laser power transmission which is supposed to find varied applicability in space. As an example, power transmission from a satellite to the earth is described where recently proposed solar power generating structures on high-altitudes receive the power above the clouds to provide constant energy supply.In the experimental part, an A-PCM setup with reflectivity of about R(A-PCM) = 100 was realized using a semiconductor optical amplifier and a photorefractive self-pumped PCM. Simulation results show that a reflectivity of R(A-PCM)>1000 could be obtained by improving the self-pumped PCM's efficiency. That would lead to a transmission efficiency of eta>90%.

  9. Further remarks on electron beam pumping of laser materials.

    PubMed

    Klein, C A

    1966-12-01

    This article demonstrates that recently completed studies on the energy dissipation of kilovolt electron beams in solids provide readily applicable methods for assessing the situation in electron beam pumped lasers. PMID:20057662

  10. Beam shaping in high-power laser systems with using refractive beam shapers

    NASA Astrophysics Data System (ADS)

    Laskin, Alexander; Laskin, Vadim

    2012-06-01

    Beam Shaping of the spatial (transverse) profile of laser beams is highly desirable by building optical systems of high-power lasers as well in various applications with these lasers. Pumping of the crystals of Ti:Sapphire lasers by the laser radiation with uniform (flattop) intensity profile improves performance of these ultrashort pulse high-power lasers in terms of achievable efficiency, peak-power and stability, output beam profile. Specifications of the solid-state lasers built according to MOPA configuration can be also improved when radiation of the master oscillator is homogenized and then is amplified by the power amplifier. Features of building these high power lasers require that a beam shaping solution should be capable to work with single mode and multimode beams, provide flattop and super-Gauss intensity distributions, the consistency and divergence of a beam after the intensity re-distribution should be conserved and low absorption provided. These specific conditions are perfectly fulfilled by the refractive field mapping beam shapers due to their unique features: almost lossless intensity profile transformation, low output divergence, high transmittance and flatness of output beam profile, extended depth of field, adaptability to real intensity profiles of TEM00 and multimode laser sources. Combining of the refractive field mapping beam shapers with other optical components, like beam-expanders, relay imaging lenses, anamorphic optics makes it possible to generate the laser spots of necessary shape, size and intensity distribution. There are plenty of applications of high-power lasers where beam shaping bring benefits: irradiating photocathode of Free Electron Lasers (FEL), material ablation, micromachining, annealing in display making techniques, cladding, heat treating and others. This paper will describe some design basics of refractive beam shapers of the field mapping type, with emphasis on the features important for building and applications

  11. Conceptual development of the Laser Beam Manifold (LBM)

    NASA Technical Reports Server (NTRS)

    Campbell, W.; Owen, R. B.

    1979-01-01

    The laser beam manifold, a device for transforming a single, narrow, collimated beam of light into several beams of desired intensity ratios is described. The device consists of a single optical substrate with a metallic coating on both optical surfaces. By changing the entry point, the number of outgoing beams can be varied.

  12. Beam-path conditioning for high-power laser systems

    SciTech Connect

    Stephens, T.; Johnson, D.; Languirand, M.

    1990-01-01

    Heating of mirrors and windows by high-power radiation from a laser transmitter produces turbulent density gradients in the gas near the optical surfaces. If the gradients are left uncontrolled, the resulting phase errors reduce the intensity on the target and degrade the signal returned to a receiver. Beam path conditioning maximizes the efficiency of the optical system by alleviating thermal turbulence within the beam path. Keywords: High power radiation, Beam path, Optical surface, Laser beams, Reprints. (JHD)

  13. Energy transfer between laser beams crossing in ignition hohlraums

    SciTech Connect

    Michel, P; Divol, L; Williams, E A; Thomas, C A; Callahan, D A; Weber, S; Haan, S W; Salmonson, J D; Dixit, S; Hinkel, D E; Edwards, M J; MacGowan, B J; Lindl, J D; Glenzer, S H; Suter, L J

    2008-10-03

    The full scale modeling of power transfer between laser beams crossing in plasmas is presented. A new model was developed, allowing calculation of the propagation and coupling of pairs of laser beams with their associated plasma wave in three dimensions. The full laser beam smoothing techniques used in ignition experiments are modeled, and their effects on crossed-beam energy transfer is investigated. A shift in wavelength between the beams can move the instability off resonance and reduce the transfer, hence preserving the symmetry of the capsule implosion.

  14. Influence of beam radii on a common-path compensation method for laser beam drifts in laser collimation systems

    NASA Astrophysics Data System (ADS)

    Zhao, Yuqiong; Feng, Qibo; Zhang, Bin; Cui, Cunxing

    2016-08-01

    The laser beam drift is a main factor that influences laser collimation measurement accuracies. In such measurements, the common-path compensation method is an efficient way to eliminate errors which are normally produced by the laser beam drift. Based on our current common-path compensation system, compensations for the laser beam drift were studied by different laser beam radii and detectors. The measurements have shown that the compensation effect for 3 mm beam radius is better than the ones of 1.5 mm and 4.0 mm beam radii. Based on this, the ratio between the 3 mm beam radius and the total area of the quadrant detector, which is 36%, has indicated the best compensation effect.

  15. Staging Laser Plasma Accelerators for Increased Beam Energy

    SciTech Connect

    Panasenko, D.; Shu, A. J.; Schroeder, C. B.; Gonsalves, A. J.; Nakamura, K.; Matlis, N. H.; Cormier-Michel, E.; Plateau, G.; Lin, C.; Toth, C.; Geddes, C. G. R.; Esarey, E.; Leemans, W. P.

    2009-01-22

    Staging laser plasma accelerators is an efficient way of mitigating laser pump depletion in laser driven accelerators and necessary for reaching high energies with compact laser systems. The concept of staging includes coupling of additional laser energy and transporting the electron beam from one accelerating module to another. Due to laser damage threshold constraints, in-coupling laser energy with conventional optics requires distances between the accelerating modules of the order of 10 m, resulting in decreased average accelerating gradient and complicated e-beam transport. In this paper we use basic scaling laws to show that the total length of future laser plasma accelerators will be determined by staging technology. We also propose using a liquid jet plasma mirror for in-coupling the laser beam and show that it has the potential to reduce distance between stages to the cm-scale.

  16. Staging laser plasma accelerators for increased beam energy

    SciTech Connect

    Panasenko, Dmitriy; Shu, Anthony; Schroeder, Carl; Gonsalves, Anthony; Nakamura, Kei; Matlis, Nicholas; Cormier-Michel, Estelle; Plateau, Guillaume; Lin, Chen; Toth, Csaba; Geddes, Cameron; Esarey, Eric; Leemans, Wim

    2008-09-29

    Staging laser plasma accelerators is an efficient way of mitigating laser pump depletion in laser driven accelerators and necessary for reaching high energies with compact laser systems. The concept of staging includes coupling of additional laser energy and transporting the electron beam from one accelerating module to another. Due to laser damage threshold constraints, in-coupling laser energy with conventional optics requires distances between the accelerating modules of the order of 10m, resulting in decreased average accelerating gradient and complicated e-beam transport. In this paper we use basic scaling laws to show that the total length of future laser plasma accelerators will be determined by staging technology. We also propose using a liquid jet plasma mirror for in-coupling the laser beam and show that it has the potential to reduce distance between stages to the cm-scale.

  17. Beam optimization of a TEA-CO2 laser

    NASA Astrophysics Data System (ADS)

    Gross, Tobias; Ristau, Detlev; Wallas, Gordon; Dumitru, Gabriel; Sporea, Dan G.; Timus, Clementina A.

    1998-07-01

    The paper describes the methods used to adapt an industrial TEA- CO2 laser to the requirements of the ISO standard 11 254-2 for a laser induced damage threshold experimental facility. The goals were to improve the pulse energy stability and the laser beam spatial profile and the methods were: (1) finding the best discharge voltage; (2) adapting the laser cavity, (3) using suitable apertures. There is also presented the experimental set- up for beam characterization, which included a laser beam profiler (a line of 60 pyroelectric detectors), an energy-meter to monitor the pulse energies and KCl optical components for beam splitting and beam guiding. Every beam distribution was regarded as a linear combination of normalized Gauss-Hermite functions and the fitting algorithm allows the calculation of the coefficients of this combination.

  18. Inviscid Flow Field Effects: Experimental results. [optical distortions over airborne laser turrets

    NASA Technical Reports Server (NTRS)

    Otten, L. J., III; Gilbert, K. G.

    1980-01-01

    The aero-optical distortions due to invisid flow effects over airborne laser turrets is investigated. Optical path differences across laser turret apertures are estimated from two data sources. The first is a theoretical study of main flow effects for a spherical turret assembly for a Mach number (M) of 0.6. The second source is an actual wind tunnel density field measurement on a 0.3 scale laser turret/fairing assembly, with M = 0.75. A range of azimuthal angles from 0 to 90 deg was considered, while the elevation angle was always 0 deg (i.e., in the plane of the flow). The calculated optical path differences for these two markedly different geometries are of the same order. Scaling of results to sea level conditions and an aperture diameter of 50 cm indicated up to 0.0007 cm of phase variation across the aperture for certain forward look angles and a focal length of F = -11.1 km. These values are second order for a 10.6 micron system.

  19. Dye laser amplifier including an improved window configuration for its dye beam

    DOEpatents

    O'Neil, R.W.; Davin, J.M.

    1992-12-01

    A dye laser amplifier in which a continuously replenished supply of dye is excited with a first light beam in order to amplify the intensity of a second different light beam passing therethrough is disclosed herein. This amplifier includes a cell though which a continuous stream of the dye is caused to pass, and means for directing the first beam into the cell while the second beam is directed into and through the same cell. There is also disclosed herein a specific improvement to this amplifier which resides in the use of a pair of particularly configured windows through which the second beam passes along fixed paths as the second beam enters and exits the dye cell. Each of these windows has a relatively thick main section which is substantially larger in dimensions transverse to its beam path than the cross section of the second beam itself, whereby to add structural integrity to the overall window. At the same time, the latter includes a second section which is disposed entirely within the confines of the main section and through which the second beam is intended to pass in its entirety. This second section is made substantially thinner than the main section in order to reduce optical distortion as the second beam passes therethrough. 4 figs.

  20. Dye laser amplifier including an improved window configuration for its dye beam

    DOEpatents

    O'Neil, Richard W.; Davin, James M.

    1992-01-01

    A dye laser amplifier in which a continuously replenished supply of dye is excited with a first light beam in order to amplify the intensity of a second different light beam passing therethrough is disclosed herein. This amplifier includes a cell though which a continuous stream of the dye is caused to pass, and means for directing the first beam into the cell while the second beam is directed into and through the same cell. There is also disclosed herein a specific improvement to this amplifier which resides in the use of a pair of particularly configured windows through which the second beam passes along fixed paths as the second beam enters and exits the dye cell. Each of these windows has a relatively thick main section which is substantially larger in dimensions transverse to its beam path than the cross section of the second beam itself, whereby to add structural integrity to the overall window. At the same time, the latter includes a second section which is disposed entirely within the confines of the main section and through which the second beam is intended to pass in its entirety. This second section is made substantially thinner than the main section in order to reduce optical distortion as the second beam passes therethrough.

  1. Effect of Travel Speed and Beam Focus on Porosity in Alloy 690 Laser Welds

    NASA Astrophysics Data System (ADS)

    Tucker, Julie D.; Nolan, Terrance K.; Martin, Anthony J.; Young, George A.

    2012-12-01

    Advances in laser welding technology, including fiber optic delivery and high power density, are increasing the applicability of this joining technique. The inherent benefits of laser welding include small heat-affected zones, minimal distortion, and limited susceptibility to cracking. These advantages are of special interest to next-generation nuclear power systems where welding solute-rich alloys is expected to increase. Alloy 690 (A690) is an advanced corrosion-resistant structural material used in many replacement components and in construction of new commercial power plants. However, the application of A690 is hindered by its difficult weldability using conventional arc welding, and laser welding is a promising alternate. This work studies the effects of travel speed and beam focus on porosity formation in partial penetration, autogenous A690 laser welds. Porosity has been characterized by light optical microscopy and x-ray computed tomography to quantify its percent volume in the welds. This work describes the tradeoff between weld penetration and defect density as a function of beam defocus and travel speed. Additionally, the role of shield gas in porosity formation is discussed to provide a mitigation strategy for A690 laser welding. A process map is provided that shows the optimal combinations of travel speed and beam defocus to minimize porosity and maximize weld penetration at a laser power of 4 kW.

  2. Characterizing the beam properties of terahertz quantum-cascade lasers

    NASA Astrophysics Data System (ADS)

    Richter, H.; Rothbart, N.; Hübers, H.-W.

    2014-08-01

    Terahertz quantum-cascade lasers (QCLs) are very promising radiation sources for many scientific and commercial applications. Shaping and characterizing the beam profile of a QCL is crucial for any of these applications. Usually the beam profile should be as close as possible to a fundamental Gaussian TEM00 mode. In order to completely characterize the laser beam the power and the wavefront have to be measured. We describe methods for characterizing the beam properties of QCLs. Several QCLs with single-plasmon waveguide and emission frequencies between 2 and 5 THz are investigated. The beam profiles of these lasers are shaped into almost fundamental Gaussian modes using dedicated lenses. The beam propagation factor M2 is as low as 1.2. The wavefront is measured along the axis of propagation with a THz Hartmann sensor. Its curvature behaves as expected for a Gaussian beam. The applied methods can be transferred to any other THz beam.

  3. Beam dynamics simulations in laser electron storage rings and optical stochastic cooling

    NASA Astrophysics Data System (ADS)

    Duru, Alper

    Laser-electron storage rings are potential compact X-ray sources. Longitudinal dynamics in laser-electron storage rings is studied including the effects of both laser interaction and synchrotron radiation. It is shown that the steady state energy spread can reach as high as a few percent. The main reason is the wide spread in the energy loss by electrons to laser photons. Optical stochastic cooling has been studied numerically. The effects of the finite bandwidth of the amplifier are mixing and signal distortion. Both are included in the simulations and the results are compared to theoretical results. It is shown that the beam can be cooled both in transverse and longitudinal phase phase spaces simultaneously.

  4. Beam splitting target reflector based compensation for angular drift of laser beam in laser autocollimation of measuring small angle deviations

    NASA Astrophysics Data System (ADS)

    Zhu, Fan; Tan, Jiubin; Cui, Jiwen

    2013-06-01

    Beam splitting target reflector based compensation for the angular drift of laser beam in laser autocollimation is proposed in this article to improve the measurement accuracy and stability of small angle deviations. A beam splitting target reflector is used to replace the plane mirror in laser autocollimation to generate a reference beam when returning the measurement beam. The reference beam and measurement beam have the same angular drift, but have different sensitivities to the rotation angle of the reflector due to the unique characteristics of the reflector. Thus, the angular drift of laser beam in laser autocollimation can be compensated in real time by using the drift of reference beam. Experimental results indicate that an output stability of 0.085 arc sec in 2 h can be achieved after compensation. And a measurement accuracy of ±0.032 arc sec can be obtained over the range of ±1190 arc sec with an effective resolution of 0.006 arc sec. It is confirmed that the compensation method for the angular drift of laser beam is necessary for improving the measurement accuracy and stability in laser autocollimation.

  5. Beam splitting target reflector based compensation for angular drift of laser beam in laser autocollimation of measuring small angle deviations

    SciTech Connect

    Zhu Fan; Tan Jiubin; Cui Jiwen

    2013-06-15

    Beam splitting target reflector based compensation for the angular drift of laser beam in laser autocollimation is proposed in this article to improve the measurement accuracy and stability of small angle deviations. A beam splitting target reflector is used to replace the plane mirror in laser autocollimation to generate a reference beam when returning the measurement beam. The reference beam and measurement beam have the same angular drift, but have different sensitivities to the rotation angle of the reflector due to the unique characteristics of the reflector. Thus, the angular drift of laser beam in laser autocollimation can be compensated in real time by using the drift of reference beam. Experimental results indicate that an output stability of 0.085 arc sec in 2 h can be achieved after compensation. And a measurement accuracy of {+-}0.032 arc sec can be obtained over the range of {+-}1190 arc sec with an effective resolution of 0.006 arc sec. It is confirmed that the compensation method for the angular drift of laser beam is necessary for improving the measurement accuracy and stability in laser autocollimation.

  6. Characterisation of electron beams from laser-driven particle accelerators

    SciTech Connect

    Brunetti, E.; Manahan, G. G.; Shanks, R. P.; Islam, M. R.; Ersfeld, B.; Anania, M. P.; Cipiccia, S.; Issac, R. C.; Vieux, G.; Welsh, G. H.; Wiggins, S. M.; Jaroszynski, D. A.

    2012-12-21

    The development, understanding and application of laser-driven particle accelerators require accurate measurements of the beam properties, in particular emittance, energy spread and bunch length. Here we report measurements and simulations showing that laser wakefield accelerators can produce beams of quality comparable to conventional linear accelerators.

  7. Laser cooling of electron beams for linear colliders

    SciTech Connect

    Telnov, V.

    1996-10-01

    A novel method of electron beam cooling is considered which can be used for linear colliders. The electron beam is cooled during collision with focused powerful laser pulse. With reasonable laser parameters (laser flash energy about 10 J) one can decrease transverse beam emittances by a factor about 10 per one stage. The ultimate transverse emittances are much below that given by other methods. Depolarization of a beam during the cooling is about 5--15% for one stage. This method is especially useful for photon colliders and open new possibilities for e{sup +}e{sup {minus}} colliders and x-ray FEL based on high energy linacs.

  8. Suppression of beam steering in an injection-locked laser diode array

    SciTech Connect

    Brewer, L.R. )

    1991-12-09

    Experimental measurements were made to demonstrate that the degree of beam steering in an injection-locked laser diode array is related to the divergence of the master laser beam. For a collimated master laser beam the beam steering was suppressed. The injection-locked laser diode array beam steers with the master laser wavelength because only a portion of the divergent master laser beam satisfies the round trip mode condition.

  9. Do twisted laser beams evoke nuclear hyperpolarization?

    PubMed

    Schmidt, A B; Andrews, D L; Rohrbach, A; Gohn-Kreuz, C; Shatokhin, V N; Kiselev, V G; Hennig, J; von Elverfeldt, D; Hövener, J-B

    2016-07-01

    The hyperpolarization of nuclear spins promises great advances in chemical analysis and medical diagnosis by substantially increasing the sensitivity of nuclear magnetic resonance (NMR). Current methods to produce a hyperpolarized sample, however, are arduous, time-consuming or costly and require elaborate equipment. Recently, a much simpler approach was introduced that holds the potential, if harnessed appropriately, to revolutionize the production of hyperpolarized spins. It was reported that high levels of hyperpolarization in nuclear spins can be created by irradiation with a laser beam carrying orbital angular momentum (twisted light). Aside from these initial reports however, no further experimental verification has been presented. In addition, this effect has so far evaded a critical theoretical examination. In this contribution, we present the first independent attempt to reproduce the effect. We exposed a sample of immersion oil or a fluorocarbon liquid that was placed within a low-field NMR spectrometer to Laguerre-Gaussian and Bessel laser beams at a wavelength of 514.5nm and various topological charges. We acquired (1)H and (19)F NMR free induction decay data, either during or alternating with the irradiation that was parallel to B0. We observed an irregular increase in NMR signal in experiments where the sample was exposed to beams with higher values of the topological charge. However, at no time did the effect reach statistical significance of 95%. Given the measured sensitivity of our setup, we estimate that a possible effect did not exceed a hyperpolarization (at 5mT) of 0.14-6%, depending on the assumed hyperpolarized volume. It should be noted though, that there were some differences between our setup and the previous implementation of the experiment, which may have inhibited the full incidence of this effect. To approach a theoretical description of this effect, we considered the interaction of an electron with a plane wave, which is known to be

  10. Do twisted laser beams evoke nuclear hyperpolarization?

    PubMed

    Schmidt, A B; Andrews, D L; Rohrbach, A; Gohn-Kreuz, C; Shatokhin, V N; Kiselev, V G; Hennig, J; von Elverfeldt, D; Hövener, J-B

    2016-07-01

    The hyperpolarization of nuclear spins promises great advances in chemical analysis and medical diagnosis by substantially increasing the sensitivity of nuclear magnetic resonance (NMR). Current methods to produce a hyperpolarized sample, however, are arduous, time-consuming or costly and require elaborate equipment. Recently, a much simpler approach was introduced that holds the potential, if harnessed appropriately, to revolutionize the production of hyperpolarized spins. It was reported that high levels of hyperpolarization in nuclear spins can be created by irradiation with a laser beam carrying orbital angular momentum (twisted light). Aside from these initial reports however, no further experimental verification has been presented. In addition, this effect has so far evaded a critical theoretical examination. In this contribution, we present the first independent attempt to reproduce the effect. We exposed a sample of immersion oil or a fluorocarbon liquid that was placed within a low-field NMR spectrometer to Laguerre-Gaussian and Bessel laser beams at a wavelength of 514.5nm and various topological charges. We acquired (1)H and (19)F NMR free induction decay data, either during or alternating with the irradiation that was parallel to B0. We observed an irregular increase in NMR signal in experiments where the sample was exposed to beams with higher values of the topological charge. However, at no time did the effect reach statistical significance of 95%. Given the measured sensitivity of our setup, we estimate that a possible effect did not exceed a hyperpolarization (at 5mT) of 0.14-6%, depending on the assumed hyperpolarized volume. It should be noted though, that there were some differences between our setup and the previous implementation of the experiment, which may have inhibited the full incidence of this effect. To approach a theoretical description of this effect, we considered the interaction of an electron with a plane wave, which is known to be

  11. Do twisted laser beams evoke nuclear hyperpolarization?

    NASA Astrophysics Data System (ADS)

    Schmidt, A. B.; Andrews, D. L.; Rohrbach, A.; Gohn-Kreuz, C.; Shatokhin, V. N.; Kiselev, V. G.; Hennig, J.; von Elverfeldt, D.; Hövener, J.-B.

    2016-07-01

    The hyperpolarization of nuclear spins promises great advances in chemical analysis and medical diagnosis by substantially increasing the sensitivity of nuclear magnetic resonance (NMR). Current methods to produce a hyperpolarized sample, however, are arduous, time-consuming or costly and require elaborate equipment. Recently, a much simpler approach was introduced that holds the potential, if harnessed appropriately, to revolutionize the production of hyperpolarized spins. It was reported that high levels of hyperpolarization in nuclear spins can be created by irradiation with a laser beam carrying orbital angular momentum (twisted light). Aside from these initial reports however, no further experimental verification has been presented. In addition, this effect has so far evaded a critical theoretical examination. In this contribution, we present the first independent attempt to reproduce the effect. We exposed a sample of immersion oil or a fluorocarbon liquid that was placed within a low-field NMR spectrometer to Laguerre-Gaussian and Bessel laser beams at a wavelength of 514.5 nm and various topological charges. We acquired 1H and 19F NMR free induction decay data, either during or alternating with the irradiation that was parallel to B0. We observed an irregular increase in NMR signal in experiments where the sample was exposed to beams with higher values of the topological charge. However, at no time did the effect reach statistical significance of 95%. Given the measured sensitivity of our setup, we estimate that a possible effect did not exceed a hyperpolarization (at 5 mT) of 0.14-6%, depending on the assumed hyperpolarized volume. It should be noted though, that there were some differences between our setup and the previous implementation of the experiment, which may have inhibited the full incidence of this effect. To approach a theoretical description of this effect, we considered the interaction of an electron with a plane wave, which is known to be

  12. Mitigating the relativistic laser beam filamentation via an elliptical beam profile.

    PubMed

    Huang, T W; Zhou, C T; Robinson, A P L; Qiao, B; Zhang, H; Wu, S Z; Zhuo, H B; Norreys, P A; He, X T

    2015-11-01

    It is shown that the filamentation instability of relativistically intense laser pulses in plasmas can be mitigated in the case where the laser beam has an elliptically distributed beam profile. A high-power elliptical Gaussian laser beam would break up into a regular filamentation pattern-in contrast to the randomly distributed filaments of a circularly distributed laser beam-and much more laser power would be concentrated in the central region. A highly elliptically distributed laser beam experiences anisotropic self-focusing and diffraction processes in the plasma channel ensuring that the unstable diffractive rings of the circular case cannot be produced. The azimuthal modulational instability is thereby suppressed. These findings are verified by three-dimensional particle-in-cell simulations.

  13. Beam intensity reshaping by pump modification in a laser amplifier.

    PubMed

    Litvin, Igor A; Collet, Oliver J P; King, Gary; Strauss, Hencharl

    2015-11-16

    We propose a new technique for laser beam shaping into a desirable beam profile by using a laser amplifier with a pump beam that has a modified intensity profile. We developed the analytical formula, which describes the transformation of the seed beam into the desired beam profile in a four level amplifiers small signal regime. We propose a numerically method to obtain the required pump intensity profile in the case where high pump power saturated the laser crystal or for three level materials. The theory was experimentally verified by one dimensionally shaping a Gaussian shaped seed into a Flat-Top beam in a Ho:YLF amplifier pumped by a Tm:YLF laser with a HG(01) intensity profile. PMID:26698497

  14. The Effect of Laser Scan Strategy on Distortion and Residual Stresses of Arches Made With Selective Laser Melting

    NASA Technical Reports Server (NTRS)

    Bagg, Stacey D.; Sochalski-Kolbus, Lindsay M.; Bunn, Jeffrey R.

    2016-01-01

    The NASA Marshall Space Flight Center (MSFC) is developing Additive Manufacturing (AM) - both in-space AM for on-demand parts, tools, or structures, and on-earth AM for rapid, reduced-cost, small volume production of complex space-flight hardware. Selective Laser Melting (SLM) is an on-earth AM technology that MSFC is using to build Alloy 718 rocket engine components. An understanding of the SLM-718 material properties is required to design, build, and qualify these components for space flight. Residual stresses and are of particular interest for this AM process, since SLM is a series of approximately 100 micron-wide welds, where highly non-linear heating and cooling, severe thermal gradients and repeated thermal cycling can result in high residual stresses within the component. These stresses may cause degraded material properties, and warp or distort the geometry of the SLM component. The distortions can render the component out-of-tolerance when inspected, and even interrupt or halt the build process if the warped material prevents the SLM machine from operating properly. The component must be scrapped and re-designed, which is time consuming and costly. If residual stresses are better understood, and can be predicted, these effects can be mitigated early in the component's design. the compressive residual stresses in the z-direction were highest in the chess sample, followed by island then continuous. This may be due to the binding nature of the segments

  15. PLASMA WAKE EXCITATION BY LASERS OR PARTICLE BEAMS

    SciTech Connect

    Schroeder, Carl B.; Esarey, Eric; Benedetti, Carlo; Toth, Csaba; Geddes, Cameron; Leemans, Wim

    2011-04-01

    Plasma accelerators may be driven by the ponderomotive force of an intense laser or the space-charge force of a charged particle beam. Plasma wake excitation driven by lasers or particle beams is examined, and the implications of the different physical excitation mechanisms for accelerator design are discussed. Plasma-based accelerators have attracted considerable attention owing to the ultrahigh field gradients sustainable in a plasma wave, enabling compact accelerators. These relativistic plasma waves are excited by displacing electrons in a neutral plasma. Two basic mechanisms for excitation of plasma waves are actively being researched: (i) excitation by the nonlinear ponderomotive force (radiation pressure) of an intense laser or (ii) excitation by the space-charge force of a dense charged particle beam. There has been significant recent experimental success using lasers and particle beam drivers for plasma acceleration. In particular, for laser-plasma accelerators (LPAs), the demonstration at LBNL in 2006 of high-quality, 1 GeV electron beams produced in approximately 3 cm plasma using a 40 TW laser. In 2007, for beam-driven plasma accelerators, or plasma-wakefield accelerators (PWFAs), the energy doubling over a meter to 42 GeV of a fraction of beam electrons on the tail of an electron beam by the plasma wave excited by the head was demonstrated at SLAC. These experimental successes have resulted in further interest in the development of plasma-based acceleration as a basis for a linear collider, and preliminary collider designs using laser drivers and beam drivers are being developed. The different physical mechanisms of plasma wave excitation, as well as the typical characteristics of the drivers, have implications for accelerator design. In the following, we identify the similarities and differences between wave excitation by lasers and particle beams. The field structure of the plasma wave driven by lasers or particle beams is discussed, as well as the

  16. Photovoltaic receivers for laser beamed power in space

    NASA Technical Reports Server (NTRS)

    Landis, Geoffrey A.

    1991-01-01

    There has recently been a resurgence of interest in the use of beamed power to support space exploration activities. One of the most promising beamed power concepts uses a laser beam to transmit power to a remote photovoltaic array. Large lasers can be located on cloud-free sites at one or more ground locations and illuminate solar arrays to a level sufficient to provide operating power. Issues involved in providing photovoltaic receivers for such applications are discussed.

  17. Post-acceleration of laser-induced ion beams

    NASA Astrophysics Data System (ADS)

    Nassisi, V.; Delle Side, D.

    2015-04-01

    A complete review of the essential and recent developments in the field of post-acceleration of laser-induced ion beams is presented. After a brief introduction to the physics of low-intensity nanosecond laser-matter interaction, the details of ions extraction and acceleration are critically analyzed and the key parameters to obtain good-quality ion beams are illustrated. A description of the most common ion beam diagnosis system is given, together with the associated analytical techniques.

  18. Apparatus Translates Crossed-Laser-Beam Probe Volume

    NASA Technical Reports Server (NTRS)

    Herring, Gregory C.; South, Bruce W.; Exton, Reginald J.

    1994-01-01

    Optomechanical apparatus translates probe volume of crossed-beam laser velocimeter or similar instrument while maintaining optical alignment of beams. Measures velocity, pressure, and temperature of flowing gas at several locations. Repeated tedious realignments no longer necessary. Designed to accommodate stimulated-Raman-gain spectrometer for noninvasive measurement of local conditions in flowing gas in supersonic wind tunnel. Applicable to other techniques like coherent anti-Stokes Raman spectroscopy involving use of laser beams crossed at small angles (10 degrees or less).

  19. Laser frequency bandwidth narrowing by photorefractive two-beam coupling.

    PubMed

    Chomsky, D; Sternklar, S; Zigler, A; Jackel, S

    1992-04-01

    We present a theoretical analysis and experimental demonstration of a new method for spectral narrowing of laser radiation. The bandwidth narrowing is experienced by a laser beam subjected to a photorefractive two-beam coupling process. Contrary to the conventional method of frequency filtering by a Fabry-Perot étalon, this technique has no intrinsic finesse limitation on its resolution. A factor of 2 in frequency bandwidth narrowing is achieved with an argon-ion laser.

  20. Method for changing the cross section of a laser beam

    DOEpatents

    Sweatt, William C.; Seppala, Lynn

    1995-01-01

    A technique is disclosed herein in which a circular optical beam, for example a copper vapor laser (CVL) beam, is converted to a beam having a profile other than circular, e.g. square or triangular. This is accomplished by utilizing a single optical mirror having a reflecting surface designed in accordance with a specifically derived formula in order to make the necessary transformation, without any substantial light loss and without changing substantially the intensity profile of the circular beam which has a substantially uniform intensity profile. In this way, the output beam can be readily directed into the dye cell of a dye laser.

  1. Method for changing the cross section of a laser beam

    DOEpatents

    Sweatt, W.C.; Seppala, L.

    1995-12-05

    A technique is disclosed herein in which a circular optical beam, for example a copper vapor laser (CVL) beam, is converted to a beam having a profile other than circular, e.g. square or triangular. This is accomplished by utilizing a single optical mirror having a reflecting surface designed in accordance with a specifically derived formula in order to make the necessary transformation, without any substantial light loss and without changing substantially the intensity profile of the circular beam which has a substantially uniform intensity profile. In this way, the output beam can be readily directed into the dye cell of a dye laser. 4 figs.

  2. Isotope separation using tuned laser and electron beam

    NASA Technical Reports Server (NTRS)

    Trajmar, Sandor (Inventor)

    1987-01-01

    The apparatus comprises means for producing an atomic beam containing the isotope of interest and other isotopes. Means are provided for producing a magnetic field traversing the path of the atomic beam of an intensity sufficient to broaden the energy domain of the various individual magnetic sublevels of the isotope of interest and having the atomic beam passing therethrough. A laser beam is produced of a frequency and polarization selected to maximize the activation of only individual magnetic sublevels of the isotope of interest with the portion of its broadened energy domain most removed from other isotopes with the stream. The laser beam is directed so as to strike the atomic beam within the magnetic field and traverse the path of the atomic beam whereby only the isotope of interest is activated by the laser beam. The apparatus further includes means for producing a collimated and high intensity beam of electrons of narrow energy distribution within the magnetic field which is aimed so as to strike the atomic beam while the atomic beam is simultaneously struck by the laser beam and at an energy level selected to ionize the activated isotope of interest but not ground state species included therewith. Deflection means are disposed in the usual manner to collect the ions.

  3. Controlled Electron Acceleration in a Plane Laser Beam

    NASA Astrophysics Data System (ADS)

    Tataronis, J. A.; Petržílka, V.; Krlín, L.

    2002-11-01

    Through numerical modeling of the relativistic test particle motion of an ensemble of electrons in a plane laser beam, we show in the present contribution that a significant electron acceleration arises if an additional perpendicularly propagagating transverse laser beam with a randomized phase is present. We also demonstrate that the acceleration rate can be controlled by the power flux intensity of the additional laser beam. The power flux intensity of the additional beam can be typically much lower than the power flux intensity of the main laser beam. In the main laser beam, the electrons perform also a forward oscillating motion because of the effects of the magnetic field intensity of the beam. The acceleration results from the accumulation of the forward electron motion due to phase changes provided by the additional laser beam. For parameters of the PALS^1 device (Prague Asterix Laser System), the attainable electron energy is about 40 MeV in 10^4 wave periods. [2pt] Acknowledgments: This work has been supported by Czech grant GACR 202/00/1217 and USDOE Grant DE-FG02-97ER54398. [2pt] ^1K.Jungwirth et al., Phys. Plasmas 8 (2001) 2495.

  4. Near-term feasibility demonstration of laser power beaming

    SciTech Connect

    Friedman, H.W.

    1994-01-01

    A mission to recharge batteries of satellites in geostationary orbits (geosats) may be a commercially viable application which could be achieved with laser systems somewhat larger than present state-of-the-art. The lifetime of batteries on geosats is limited by repetitive discharge cycles which occur when the satellites are eclipsed by the earth during the spring and fall equinoxes. By coupling high power lasers with modern, large aperture telescopes and laser guide star adaptive optics systems, present day communications satellites could be targeted. It is important that a near term demonstration of laser power beaming be accomplished using lasers in the kilowatt range so that issues associated with high average power be addressed. The Laser Guide Star Facility at LLNL has all the necessary subsystems needed for such a near term demonstration, including high power lasers for both the power beam and guide star, beam directors and satellite tracking system.

  5. Propagation of a laser beam in a plasma

    NASA Technical Reports Server (NTRS)

    Chapman, J. M.; Kevorkian, J.; Steinhauer, L. C.; Vagners, J.

    1975-01-01

    This paper shows that for a nonabsorbing medium with a prescribed index of refraction, the effects of beam stability, line focusing, and beam distortion can be predicted from simple ray optics. When the paraxial approximation is used, diffraction effects are examined for Gaussian, Lorentzian, and square beams. Most importantly, it is shown that for a Gaussian beam, diffraction effects can be included simply by adding imaginary solutions to the paraxial ray equations. Also presented are several procedures to extend the paraxial approximation so that the solution will have a domain of validity of greater extent.

  6. Simulation of wavefront reconstruction in beam reshaping system for rectangular laser beam

    NASA Astrophysics Data System (ADS)

    Zhou, Qiong; Liu, Wenguang; Jiang, Zongfu

    2014-05-01

    A new method to calculating the wavefront of slap laser is studied in this paper. The method is based on the ray trace theory of geometrical optics. By using the Zemax simulation software and Matlab calculation software, the wavefront of rectangular beam in beam reshaping system is reconstructed. Firstly, with the x- and y-slope measurement of reshaping beam the direction cosine of wavefront can be calculated. Then, the inverse beam path of beam reshaping system is built by using Zemax simulation software and the direction cosine of rectangular beam can be given, too. Finally, Southwell zonal model is used to reconstruct the wavefront of rectangular beam in computer simulation. Once the wavefront is received, the aberration of laser can be eliminated by using the proper configuration of beam reshaping system. It is shown that this method to reconstruct the wavefront of rectangular beam can evidently reduce the negative influence of additional aberration induced by beam reshaping system.

  7. Chirped microlens arrays for diode laser circularization and beam expansion

    NASA Astrophysics Data System (ADS)

    Schreiber, Peter; Dannberg, Peter; Hoefer, Bernd; Beckert, Erik

    2005-08-01

    Single-mode diode lasers are well-established light sources for a huge number of applications but suffer from astigmatism, beam ellipticity and large manufacturing tolerances of beam parameters. To compensate for these shortcomings, various approaches like anamorphic prism pairs and cylindrical telescopes for circularization as well as variable beam expanders based on zoomed telescopes for precise adjustment of output beam parameters have been employed in the past. The presented new approach for both beam circularization and expansion is based on the use of microlens arrays with chirped focal length: Selection of lenslets of crossed cylindrical microlens arrays as part of an anamorphic telescope enables circularization, astigmatism correction and divergence tolerance compensation of diode lasers simultaneously. Another promising application of chirped spherical lens array telescopes is stepwise variable beam expansion for circular laser beams of fiber or solid-state lasers. In this article we describe design and manufacturing of beam shaping systems with chirped microlens arrays fabricated by polymer-on-glass replication of reflow lenses. A miniaturized diode laser module with beam circularization and astigmatism correction assembled on a structured ceramics motherboard and a modulated RGB laser-source for photofinishing applications equipped with both cylindrical and spherical chirped lens arrays demonstrate the feasibility of the proposed system design approach.

  8. Electron beam switched discharge for rapidly pulsed lasers

    DOEpatents

    Pleasance, Lyn D.; Murray, John R.; Goldhar, Julius; Bradley, Laird P.

    1981-01-01

    Method and apparatus for electrical excitation of a laser gas by application of a pulsed voltage across the gas, followed by passage of a pulsed, high energy electron beam through the gas to initiate a discharge suitable for laser excitation. This method improves upon current power conditioning techniques and is especially useful for driving rare gas halide lasers at high repetition rates.

  9. The study of laser beam riding guided system based on 980nm diode laser

    NASA Astrophysics Data System (ADS)

    Qu, Zhou; Xu, Haifeng; Sui, Xin; Yang, Kun

    2015-10-01

    With the development of science and technology, precision-strike weapons has been considered to be important for winning victory in military field. Laser guidance is a major method to execute precision-strike in modern warfare. At present, the problems of primary stage of Laser guidance has been solved with endeavors of countries. Several technical aspects of laser-beam riding guided system have been mature, such as atmosphere penetration of laser beam, clutter inhibition on ground, laser irradiator, encoding and decoding of laser beam. Further, laser beam quality, equal output power and atmospheric transmission properties are qualified for warfare situation. Riding guidance instrument is a crucial element of Laser-beam riding guided system, and is also a vital element of airborne, vehicle-mounted and individual weapon. The optical system mainly consist of sighting module and laser-beam guided module. Photoelectric detector is the most important sensing device of seeker, and also the key to acquire the coordinate information of target space. Currently, in consideration of the 1.06 u m of wavelength applied in all the semi-active laser guided weapons systems, lithium drifting silicon photodiode which is sensitive to 1.06 u m of wavelength is used in photoelectric detector. Compared to Solid and gas laser, diode laser has many merits such as small volume, simple construction, light weight, long life, low lost and easy modulation. This article introduced the composition and operating principle of Laser-beam riding guided system based on 980 nm diode laser, and made a analysis of key technology; for instance, laser irradiator, modulating disk of component, laser zooming system. Through the use of laser diode, Laser-beam riding guided system is likely to have smaller shape and very light.

  10. Intensity influence on Gaussian beam laser based measurements using quadrant photodiodes.

    PubMed

    Panduputra, Yohannes; Ng, Tuck Wah; Neild, Adrian; Robinson, Michael

    2010-07-01

    In many measurement applications using quadrant photodiodes, the signal is normally obtained from integrated devices incorporating current-to-voltage amplifiers that provide the necessary difference outputs with amplification. Quadrant photodiodes permit two-axis laser beam size and beam deflection determination. We show here that photodiode saturation, nonlinear characteristics of amplifying circuits, and voltage clipping features meant to prevent the output of a circuit from exceeding a predetermined voltage level to distort applied waveforms, play a significant role in measurement at low and high intensity levels, respectively. These two factors conspire to underestimate laser beam size measurement. A best-fit computation of the size versus power trend was found to permit satisfactory estimation of the beam size as well as the optimal laser power to be used. The intensity of light was also found to strongly affect the sensitivity of beam deflection measurements, in which a correction based on best-fit computation was deficient. In this case, calibration steps would be needed when light levels changed. PMID:20648132

  11. Improvement of the beam quality of a gasdynamically cooled CO laser with an unstable resonator by use of a cylindrical mirror.

    PubMed

    Schellhorn, M; Büllow, H V

    1995-06-15

    The beam quality of a gasdynamically cooled CO laser with an unstable resonator (M = 1.7) has been improved by use of an extracavity cylindrical mirror. This mirror corrects the phase distortion resulting from the supersonic f low. A 4.5-kW laser beam with a total divergence of 1.4 mrad is obtained with an efficiency of 9% and a Strehl ratio of 0.4. A strong degradation of the beam quality has been observed outside the resonator owing to water-vapor absorption. The use of dry air in the beam-guiding system signif icantly reduces this effect of thermal blooming. PMID:19862021

  12. Wide-aperture laser beam measurement using transmission diffuser: errors modeling

    NASA Astrophysics Data System (ADS)

    Matsak, Ivan S.

    2015-06-01

    Instrumental errors of measurement wide-aperture laser beam diameter were modeled to build measurement setup and justify its metrological characteristics. Modeled setup is based on CCD camera and transmission diffuser. This method is appropriate for precision measurement of large laser beam width from 10 mm up to 1000 mm. It is impossible to measure such beams with other methods based on slit, pinhole, knife edge or direct CCD camera measurement. The method is suitable for continuous and pulsed laser irradiation. However, transmission diffuser method has poor metrological justification required in field of wide aperture beam forming system verification. Considering the fact of non-availability of a standard of wide-aperture flat top beam modelling is preferred way to provide basic reference points for development measurement system. Modelling was conducted in MathCAD. Super-Lorentz distribution with shape parameter 6-12 was used as a model of the beam. Using theoretical evaluations there was found that the key parameters influencing on error are: relative beam size, spatial non-uniformity of the diffuser, lens distortion, physical vignetting, CCD spatial resolution and, effective camera ADC resolution. Errors were modeled for 90% of power beam diameter criteria. 12-order Super-Lorentz distribution was primary model, because it precisely meets experimental distribution at the output of test beam forming system, although other orders were also used. The analytic expressions were obtained analyzing the modelling results for each influencing data. Attainability of <1% error based on choice of parameters of expression was shown. The choice was based on parameters of commercially available components of the setup. The method can provide up to 0.1% error in case of using calibration procedures and multiple measurements.

  13. Evaluation and Correction of the Non-linear Distortion of CEBAF Beam Position Monitors

    SciTech Connect

    M. Spata, T.L. Allison, K.E. Cole, J. Musson, J. Yan

    2011-09-01

    The beam position monitors at CEBAF have four antenna style pickups that are used to measure the location of the beam. There is a strong nonlinear response when the beam is far from the electrical center of the device. In order to conduct beam experiments at large orbit excitation we need to correct for this nonlinearity. The correction algorithm is presented and compared to measurements from our stretched wire BPM test stand.

  14. CO2 laser beam propagation with ZnSe optics

    NASA Astrophysics Data System (ADS)

    Leong, K. H.; Liu, Yi; Holdridge, D. J.

    Beam propagation characteristics of ZnSe optics used in kiloWatt power CO2 laser aided material processing applications are determined using the Prometec Laser Beam Analyzer. The laser used was a Rofin Sinar RS6000 CO2 laser with mode aperturing. Beam power varied from 500W to 6300W and beam modes used were TEM(sub 00), TEM(sub 01), TEM(sub 10), and TEM(sub 20). Both transmissive and reflective optics were examined. The ZnSe lenses tested included meniscus, diffractive, and cylindrical lenses of 5 in. focal length and a 10 in. focal length integrating lens. Reflective optics included an integrator and a 5 in. focal length parabolic mirror for welding. Parameters obtained included beam propagation profiles, intensity profiles, depth of focus, spot size, and back focal length. A subset of the data obtained is presented here. Details of the work will appear in a full length paper.

  15. Precision atomic beam density characterization by diode laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Oxley, Paul; Wihbey, Joseph

    2016-09-01

    We provide experimental and theoretical details of a simple technique to determine absolute line-of-sight integrated atomic beam densities based on resonant laser absorption. In our experiments, a thermal lithium beam is chopped on and off while the frequency of a laser crossing the beam at right angles is scanned slowly across the resonance transition. A lock-in amplifier detects the laser absorption signal at the chop frequency from which the atomic density is determined. The accuracy of our experimental method is confirmed using the related technique of wavelength modulation spectroscopy. For beams which absorb of order 1% of the incident laser light, our measurements allow the beam density to be determined to an accuracy better than 5% and with a precision of 3% on a time scale of order 1 s. Fractional absorptions of order 10-5 are detectable on a one-minute time scale when we employ a double laser beam technique which limits laser intensity noise. For a lithium beam with a thickness of 9 mm, we have measured atomic densities as low as 5 × 104 atoms cm-3. The simplicity of our technique and the details we provide should allow our method to be easily implemented in most atomic or molecular beam apparatuses.

  16. Beam Cooling and Laser Spectroscopy (BECOLA) Project at NSCL

    NASA Astrophysics Data System (ADS)

    Minamisono, K.; Barquest, B. R.; Bollen, G.; Mantica, P. F.; Morrissey, D. J.; Ringle, R.; Schwarz, S.

    2009-10-01

    A new beam line for beam cooling and laser spectroscopy (BECOLA) has been designed and is being installed at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University. The BECOLA beam line will be capable of accepting ions of energy up to 60 keV. A linear Radio Frequency Quadrupole (RFQ) ion trap [1] will be used to cool and bunch the beam upstream of the BECOLA beam line. This beam line will have two dedicated experimental legs, one for collinear-laser spectroscopy with the bunched beam and another for polarization by optical pumping of low energy atoms/ions for β-NMR experiments. Initial studies at NSCL will include the measurement of μ, Q and of light- and medium-mass refractory isotopes, using both the laser spectroscopy and the β-NMR technique. A frequency doubled light of Ti:Sapphire ring laser pumped by diode-pumped solid state laser will be used for spectroscopy and optical pumping for polarization. The present status of BECOLA beam line as well as the laser system will be presented. [4pt] [1] G. Bollen et al., Nucl. Instr. and Meth. A 532, 203 (2004).

  17. Effect of ultrarelativistic laser beam filamentation on third harmonic spectrum

    SciTech Connect

    Gupta, Ruchika; Rafat, M.; Sharma, Prerana; Chauhan, Prashant K.; Sharma, R. P.

    2009-04-15

    This paper investigates the generation of plasma wave and third harmonic generation in a hot collision less plasma by an intense laser beam. On the account of the V-vectorxB-vector force, a plasma wave at 2{omega}{sub 0} (here {omega}{sub 0} is the pump laser frequency) is generated. The solution of the pump laser beam has been obtained within the nonparaxial ray approximation. Filamentary structures of the laser beam are observed due to relativistic nonlinearity. By expanding the eikonal and the other relevant quantities up to the fourth power of r it is observed that the focusing of the laser beams become fast in the nonparaxial region. Interaction of the plasma wave with the incident laser beam generates the third harmonics. The mechanism of the plasma wave, third harmonic generation, and the parameters, which govern the third harmonic yield and hence the spectrum of third harmonics, have been studied in detail. Correlation of the third harmonic spectrum with the filamentation has been pointed out. Therefore, the broadening of the third harmonic spectra can be used as a diagnostic tool to study the presence of the filamentation of laser beams in laser plasma experiments.

  18. Compact two-beam push-pull free electron laser

    DOEpatents

    Hutton, Andrew

    2009-03-03

    An ultra-compact free electron laser comprising a pair of opposed superconducting cavities that produce identical electron beams moving in opposite directions such that each set of superconducting cavities accelerates one electron beam and decelerates the other electron beam. Such an arrangement, allows the energy used to accelerate one beam to be recovered and used again to accelerate the second beam, thus, each electron beam is decelerated by a different structure than that which accelerated it so that energy exchange rather than recovery is achieved resulting in a more compact and highly efficient apparatus.

  19. The output beam quality of a Q-switched Nd:glass slab laser

    NASA Technical Reports Server (NTRS)

    Reed, Murray K.; Byer, Robert L.

    1990-01-01

    The authors have constructed and tested a flashlamp pumped, Q-switched, Nd:glass zigzag slab laser. The thermally induced optical distortion through the slab is minimized by uniform pumping and cooling and the use of corrective pump shields at the slab ends. The laser spatial output for Q-switched resonators has been measured and modeled. It is shown that a larger aperture planar oscillator has an output divergence many times above the diffraction limit. Operation as a one-dimensional unstable resonator in the wide direction of the slab allows the efficient extraction of energy in a high-quality beam. Near-diffraction-limited laser output of 5 J at 4 Hz is achieved with a resonator that includes an intracavity telescope to correct for residual defocusing in the thin direction of the slab.

  20. Genomic Physics. Multiple Laser Beam Treatment of Alzheimer's Disease

    NASA Astrophysics Data System (ADS)

    Stefan, V. Alexander

    2014-03-01

    The synapses affected by Alzheimer's disease can be rejuvenated by the multiple ultrashort wavelength laser beams.[2] The guiding lasers scan the whole area to detect the amyloid plaques based on the laser scattering technique. The scanning lasers pinpoint the areas with plaques and eliminate them. Laser interaction is highly efficient, because of the focusing capabilities and possibility for the identification of the damaging proteins by matching the protein oscillation eigen-frequency with laser frequency.[3] Supported by Nikola Tesla Labs, La Jolla, California, USA.

  1. Photothermal single particle microscopy using a single laser beam

    SciTech Connect

    Selmke, Markus; Heber, André; Braun, Marco; Cichos, Frank

    2014-07-07

    We introduce a single-laser-beam photothermal microscopy scheme for the detection of single absorbing nano-objects. Here, a modulated incident laser beam with a constant intensity offset serves as pump and probe beam at the same time. Using the out-of-phase scattering response of the retarded thermorefractive wave field, the method provides a selective contrast for absorbers over a possible background of scatterers. The use of a single wavelength and a single beam, considerably simplifies the setup and integration of photothermal detection in existing microscopy schemes.

  2. Acceleration of electrons by a tightly focused intense laser beam.

    PubMed

    Li, Jian-Xing; Zang, Wei-Ping; Li, Ya-Dong; Tian, Jian-Guo

    2009-07-01

    The recent proposal to use Weinger transformation field (WTF) [Opt. Express 17, 4959-4969 (2009)] for describing tightly focused laser beams is investigated here in detail. In order to validate the accuracy of WTF, we derive the numerical field (NF) from the plane wave spectrum method. WTF is compared with NF and Lax series field (LSF). Results show that LSF is accurate close to the beam axis and divergent far from the beam axis, and WTF is always accurate. Moreover, electron dynamics in a tightly focused intense laser beam are simulated by LSF, WTF and NF, respectively. The results obtained by WTF are shown to be accurate.

  3. Acceleration of electrons by a tightly focused intense laser beam.

    PubMed

    Li, Jian-Xing; Zang, Wei-Ping; Li, Ya-Dong; Tian, Jian-Guo

    2009-07-01

    The recent proposal to use Weinger transformation field (WTF) [Opt. Express 17, 4959-4969 (2009)] for describing tightly focused laser beams is investigated here in detail. In order to validate the accuracy of WTF, we derive the numerical field (NF) from the plane wave spectrum method. WTF is compared with NF and Lax series field (LSF). Results show that LSF is accurate close to the beam axis and divergent far from the beam axis, and WTF is always accurate. Moreover, electron dynamics in a tightly focused intense laser beam are simulated by LSF, WTF and NF, respectively. The results obtained by WTF are shown to be accurate. PMID:19582099

  4. Beam profile shaping for laser radars that use detector arrays.

    PubMed

    Veldkamp, W B; Kastner, C J

    1982-01-15

    The beam shaper we developed shapes the transmit beam of a CO(2) laser radar that uses a linear detector array. It consists of a diffraction grating and an anamorphic prism beam compressor and produces a stretched profile that efficiently and uniformly illuminates the far-field footprint of the detector array. The diffraction grating phase modulates the near field or the laser beam to generate a far-field flattop intensity profile, whereas the compressor produces the necessary profile eccentricity. We have achieved conversion efficiencies in the 70-90% range.

  5. Possibilities and limitations of rod-beam theories. [nonlinear distortion tensor and nonlinear stress tensors

    NASA Technical Reports Server (NTRS)

    Peterson, D.

    1979-01-01

    Rod-beam theories are founded on hypotheses such as Bernouilli's suggesting flat cross-sections under deformation. These assumptions, which make rod-beam theories possible, also limit the accuracy of their analysis. It is shown that from a certain order upward terms of geometrically nonlinear deformations contradict the rod-beam hypotheses. Consistent application of differential geometry calculus also reveals differences from existing rod theories of higher order. These differences are explained by simple examples.

  6. Laser ion source for high brightness heavy ion beam

    NASA Astrophysics Data System (ADS)

    Okamura, M.

    2016-09-01

    A laser ion source is known as a high current high charge state heavy ion source. However we place great emphasis on the capability to realize a high brightness ion source. A laser ion source has a pinpoint small volume where materials are ionized and can achieve quite uniform low temperature ion beam. Those features may enable us to realize very small emittance beams. In 2014, a low charge state high brightness laser ion source was successfully commissioned in Brookhaven National Laboratory. Now most of all the solid based heavy ions are being provided from the laser ion source for regular operation.

  7. Reference beam laser Doppler velocimeter incorporating fiber optic components

    SciTech Connect

    James, S.W.; Lockey, R.A.; Egan, D.; Tatam, R.P.

    1995-12-31

    A compact reference beam laser Doppler velocimeter, constructed using a semiconductor laser diode, optical fiber components and semiconductor detectors, is reported. The device has been designed to overcome many of the problems commonly associated with reference beam configurations. The anemometer may be operated with the laser diode operating in cw and pulsed modes, demonstrating its applicability to wavelength and time division multiplexing schemes for 3D laser Doppler velocimetry. The probe is used to measure the velocity of a spinning disk in the range {minus}20 m/s to +20 m/s.

  8. Laser beam combiner for Thomson scattering core LIDAR.

    PubMed

    Balboa, I; Huang, B; Naylor, G; Walsh, M; Sirinelli, A; Parsons, P; Fessey, J; Townsend, M; Beurskens, M; Conway, N; Flanagan, J; Kempenaars, M; Kirk, A

    2010-10-01

    The light detection and ranging Thomson scattering (TS) diagnostic is advantageous since it only requires a single view port into the tokamak. This technique requires a short pulse laser at high energy, usually showing a limited repetition rate. Having multiple lasers will increase the repetition rate. This paper presents a scanning mirror as a laser beam combiner. Measurements of the position accuracy and jitter show that the pointing stability of the laser beam is within ±25 μrad for over tens of seconds. A control feedback loop is implemented to demonstrate the long term stability. Such a system could be applied for ITER and JET. PMID:21033888

  9. Parametric study of transport beam lines for electron beams accelerated by laser-plasma interaction

    NASA Astrophysics Data System (ADS)

    Scisciò, M.; Lancia, L.; Migliorati, M.; Mostacci, A.; Palumbo, L.; Papaphilippou, Y.; Antici, P.

    2016-03-01

    In the last decade, laser-plasma acceleration of high-energy electrons has attracted strong attention in different fields. Electrons with maximum energies in the GeV range can be laser-accelerated within a few cm using multi-hundreds terawatt (TW) lasers, yielding to very high beam currents at the source (electron bunches with up to tens-hundreds of pC in a few fs). While initially the challenge was to increase the maximum achievable electron energy, today strong effort is put in the control and usability of these laser-generated beams that still lack of some features in order to be used for applications where currently conventional, radio-frequency (RF) based, electron beam lines represent the most common and efficient solution. Several improvements have been suggested for this purpose, some of them acting directly on the plasma source, some using beam shaping tools located downstream. Concerning the latter, several studies have suggested the use of conventional accelerator magnetic devices (such as quadrupoles and solenoids) as an easy implementable solution when the laser-plasma accelerated beam requires optimization. In this paper, we report on a parametric study related to the transport of electron beams accelerated by laser-plasma interaction, using conventional accelerator elements and tools. We focus on both, high energy electron beams in the GeV range, as produced on petawatt (PW) class laser systems, and on lower energy electron beams in the hundreds of MeV range, as nowadays routinely obtained on commercially available multi-hundred TW laser systems. For both scenarios, our study allows understanding what are the crucial parameters that enable laser-plasma accelerators to compete with conventional ones and allow for a beam transport. We show that suitable working points require a tradeoff-combination between low beam divergence and narrow energy spread.

  10. Diffractive beam shaping for enhanced laser polymer welding

    NASA Astrophysics Data System (ADS)

    Rauschenberger, J.; Vogler, D.; Raab, C.; Gubler, U.

    2015-03-01

    Laser welding of polymers increasingly finds application in a large number of industries such as medical technology, automotive, consumer electronics, textiles or packaging. More and more, it replaces other welding technologies for polymers, e. g. hot-plate, vibration or ultrasonic welding. At the same rate, demands on the quality of the weld, the flexibility of the production system and on processing speed have increased. Traditionally, diode lasers were employed for plastic welding with flat-top beam profiles. With the advent of fiber lasers with excellent beam quality, the possibility to modify and optimize the beam profile by beam-shaping elements has opened. Diffractive optical elements (DOE) can play a crucial role in optimizing the laser intensity profile towards the optimal M-shape beam for enhanced weld seam quality. We present results on significantly improved weld seam width constancy and enlarged process windows compared to Gaussian or flat-top beam profiles. Configurations in which the laser beam diameter and shape can be adapted and optimized without changing or aligning the laser, fiber-optic cable or optical head are shown.

  11. Activation of cells using femtosecond laser beam (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Batabyal, Subrata; Satpathy, Sarmishtha; Kim, Young-tae; Mohanty, Samarendra K.

    2016-03-01

    Study of communication in cellular systems requires precise activation of targeted cell(s) in the network. In contrast to chemical, electrical, thermal, mechanical stimulation, optical stimulation is non-invasive and is better suited for stimulation of targeted cells. As compared to visible lasers, the near infrared (NIR) microsecond/nanosecond pulsed laser beams are being used as preferred stimulation tool as they provide higher penetration depth in tissues. Femotosecond (FS) laser beams in NIR are also being used for direct and indirect (i.e. via two-photon optogenetics) stimulation of cells. Here, we present a comparative evaluation of efficacy of NIR FS laser beam for direct (no optogenetic sensitization) and 2ph optogenetic stimulation of cells. Further, for the first time, we demonstrate the use of blue (~450 nm, obtained by second harmonic generation) FS laser beam for stimulation of cells with and without Channelrhodopisn-2 (ChR2) expression. Comparative analysis of photocurrent generated by blue FS laser beam and continuous wave blue light for optogenetics stimulation of ChR2 transfected HEK cells will be presented. The use of ultrafast laser micro-beam for focal, non-contact, and repeated stimulation of single cells in a cellular circuitry allowed us to study the communication between different cell types.

  12. Intense ion beams accelerated by ultra-intense laser pulses

    NASA Astrophysics Data System (ADS)

    Roth, Markus; Cowan, T. E.; Gauthier, J. C.; Vehn, J. Meyer-Ter; Allen, M.; Audebert, P.; Blazevic, A.; Fuchs, J.; Geissel, M.; Hegelich, M.; Karsch, S.; Pukhov, A.; Schlegel, T.

    2002-04-01

    The discovery of intense ion beams off solid targets irradiated by ultra-intense laser pulses has become the subject of extensive international interest. These highly collimated, energetic beams of protons and heavy ions are strongly depending on the laser parameters as well as on the properties of the irradiated targets. Therefore we have studied the influence of the target conditions on laser-accelerated ion beams generated by multi-terawatt lasers. The experiments were performed using the 100 TW laser facility at Laboratoire pour l'Utilisation des Laser Intense (LULI). The targets were irradiated by pulses up to 5×1019 W/cm2 (~300 fs,λ=1.05 μm) at normal incidence. A strong dependence on the surface conditions, conductivity, shape and purity was observed. The plasma density on the front and rear surface was determined by laser interferometry. We characterized the ion beam by means of magnetic spectrometers, radiochromic film, nuclear activation and Thompson parabolas. The strong dependence of the ion beam acceleration on the conditions on the target back surface was confirmed in agreement with predictions based on the target normal sheath acceleration (TNSA) mechanism. Finally shaping of the ion beam has been demonstrated by the appropriate tailoring of the target. .

  13. DPSS Laser Beam Quality Optimization Through Pump Current Tuning

    SciTech Connect

    Omohundro, Rob; Callen, Alice; Sukuta, Sydney; /San Jose City Coll.

    2012-03-30

    The goal of this study is to demonstrate how a DPSS laser beam's quality parameters can be simultaneously optimized through pump current tuning. Two DPSS lasers of the same make and model were used where the laser diode pump current was first varied to ascertain the lowest RMS noise region. The lowest noise was found to be 0.13% in this region and the best M{sup 2} value of 1.0 and highest laser output power were simultaneously attained at the same current point. The laser manufacturer reported a M{sup 2} value of 1.3 and RMS noise value of .14% for these lasers. This study therefore demonstrates that pump current tuning a DPSS laser can simultaneously optimize RMS Noise, Power and M{sup 2} values. Future studies will strive to broaden the scope of the beam quality parameters impacted by current tuning.

  14. Influence of laser array performance on spectrally combined beam

    NASA Astrophysics Data System (ADS)

    Wu, Zhen; Yang, Lei; Zhong, Zheqiang; Zhang, Bin

    2016-10-01

    Incoherent spectral beam combining (SBC) of multiple laser beams is accomplished along the emitters' arraying direction. Considering that the output beams from a laser array (LA) usually have deflection angles, positional displacements and divergence angles even after being collimated, a propagation model of SBC systems based on multilayer dielectric gratings has been built up. On the basis, properties of the spectrally combined beam affected by parameters of the LA have been discussed in detail. Simulation results show that with the increase in the deflection angle, both the power and the beam quality of the combined beam degrade dramatically. The positional displacement has little impact on the intensity distribution and the beam quality of combined beam but change the wavelength composition of the combined beam. The divergence angle strongly affects the intensity distribution and the beam quality of the combined beam. Additionally, the effect of the deflection angle on the output beam quality is more obvious and may shift the beam spot when comparing with that of the divergence angle.

  15. Multiple scattering of laser beams in dense hydrosols

    NASA Technical Reports Server (NTRS)

    Zardecki, A.; Gerstl, S. A. W.; Unruh, W. P.; Stokes, G. H.; Stupin, D. M.; Elliott, N. E.; Weinman, J. A.

    1986-01-01

    The multiple scattering of laser beams is usually described within the framework of small-angle scattering theory. The validity of this approximation as well as improvements due to the incorporation of diffusion theory in the calculations were studied.

  16. Multiple scattering of laser beams in dense hydrosols

    NASA Astrophysics Data System (ADS)

    Zardecki, A.; Gerstl, S. A. W.; Unruh, W. P.; Stokes, G. H.; Stupin, D. M.; Elliott, N. E.; Weinman, J. A.

    1986-08-01

    The multiple scattering of laser beams is usually described within the framework of small-angle scattering theory. The validity of this approximation as well as improvements due to the incorporation of diffusion theory in the calculations were studied.

  17. Investigation of laser-beam weldability of aluminum alloys

    NASA Astrophysics Data System (ADS)

    Zuo, Tiechuan; Xiao, Y. H.; Sepold, Gerd

    1993-05-01

    The conditions for laser beam welding of aluminum alloys and measures for increasing the weld penetration depth are discussed. The mechanisms of creating pores and cracks are thoroughly analyzed and several countermeasures are proposed.

  18. Laser Doppler instrument measures fluid velocity without reference beam

    NASA Technical Reports Server (NTRS)

    Bourquin, K. R.; Shigemoto, F. H.

    1971-01-01

    Fluid velocity is measured by focusing laser beam on moving fluid and measuring Doppler shift in frequency which results when radiation is scattered by particles either originally present or deliberately injected into moving fluid.

  19. Effects of laser fluence on silicon modification by four-beam laser interference

    SciTech Connect

    Zhao, Le; Li, Dayou; Wang, Zuobin Yue, Yong; Zhang, Jinjin; Yu, Miao; Li, Siwei

    2015-12-21

    This paper discusses the effects of laser fluence on silicon modification by four-beam laser interference. In this work, four-beam laser interference was used to pattern single crystal silicon wafers for the fabrication of surface structures, and the number of laser pulses was applied to the process in air. By controlling the parameters of laser irradiation, different shapes of silicon structures were fabricated. The results were obtained with the single laser fluence of 354 mJ/cm{sup 2}, 495 mJ/cm{sup 2}, and 637 mJ/cm{sup 2}, the pulse repetition rate of 10 Hz, the laser exposure pulses of 30, 100, and 300, the laser wavelength of 1064 nm, and the pulse duration of 7–9 ns. The effects of the heat transfer and the radiation of laser interference plasma on silicon wafer surfaces were investigated. The equations of heat flow and radiation effects of laser plasma of interfering patterns in a four-beam laser interference distribution were proposed to describe their impacts on silicon wafer surfaces. The experimental results have shown that the laser fluence has to be properly selected for the fabrication of well-defined surface structures in a four-beam laser interference process. Laser interference patterns can directly fabricate different shape structures for their corresponding applications.

  20. A comparison of the physics of Gas Tungsten Arc Welding (GTAW), Electron Beam Welding (EBW), and Laser Beam Welding (LBW)

    NASA Technical Reports Server (NTRS)

    Nunes, A. C., Jr.

    1985-01-01

    The physics governing the applicability and limitations of gas tungsten arc (GTA), electron beam (EB), and laser beam (LB) welding are compared. An appendix on the selection of laser welding systems is included.

  1. Integrated Electro-optical Laser-Beam Scanners

    NASA Technical Reports Server (NTRS)

    Boord, Warren T.

    1990-01-01

    Scanners using solid-state devices compact, consume little power, and have no moving parts. Integrated electro-optical laser scanner, in conjunction with external lens, points outgoing beam of light in any number of different directions, depending on number of upper electrodes. Offers beam-deflection angles larger than those of acousto-optic scanners. Proposed for such diverse applications as nonimpact laser printing, color imaging, ranging, barcode reading, and robotic vision.

  2. Single electron beam rf feedback free electron laser

    DOEpatents

    Brau, C.A.; Stein, W.E.; Rockwood, S.D.

    1981-02-11

    A free electron laser system and electron beam system for a free electron laser which uses rf feedback to enhance efficiency are described. Rf energy is extracted from a single electron beam by decelerating cavities and energy is returned to accelerating cavities using rf returns, such as rf waveguides, rf feedthroughs, resonant feedthroughs, etc. This rf energy is added to rf klystron energy to reduce the required input energy and thereby enhance energy efficiency of the system.

  3. Dual-Beam Atom Laser Driven by Spinor Dynamics

    NASA Technical Reports Server (NTRS)

    Thompson, Robert; Lundblad, Nathan; Maleki, Lute; Aveline, David

    2007-01-01

    An atom laser now undergoing development simultaneously generates two pulsed beams of correlated Rb-87 atoms. (An atom laser is a source of atoms in beams characterized by coherent matter waves, analogous to a conventional laser, which is a source of coherent light waves.) The pumping mechanism of this atom laser is based on spinor dynamics in a Bose-Einstein condensate. By virtue of the angular-momentum conserving collisions that generate the two beams, the number of atoms in one beam is correlated with the number of atoms in the other beam. Such correlations are intimately linked to entanglement and squeezing in atomic ensembles, and atom lasers like this one could be used in exploring related aspects of Bose-Einstein condensates, and as components of future sensors relying on atom interferometry. In this atom-laser apparatus, a Bose-Einstein condensate of about 2 x 10(exp 6) Rb-87 atoms at a temperature of about 120 micro-K is first formed through all-optical means in a relatively weak singlebeam running-wave dipole trap that has been formed by focusing of a CO2-laser beam. By a technique that is established in the art, the trap is loaded from an ultrahigh-vacuum magnetooptical trap that is, itself, loaded via a cold atomic beam from an upstream two-dimensional magneto-optical trap that resides in a rubidium-vapor cell that is differentially pumped from an adjoining vacuum chamber, wherein are performed scientific observations of the beams ultimately generated by the atom laser.

  4. Laser forming of a bowl shaped surface with a stationary laser beam

    NASA Astrophysics Data System (ADS)

    Chakraborty, Shitanshu Shekhar; More, Harshit; Nath, Ashish Kumar

    2016-02-01

    Despite a lot of research done in the field of laser forming, generation of a symmetric bowl shaped surface by this process is still a challenge mainly because only a portion of the sheet is momentarily deformed in this process, unlike conventional sheet metal forming like deep drawing where the entire blank undergoes forming simultaneously reducing asymmetry to a minimum. The motion of laser beam also makes the process asymmetric. To counter these limitations this work proposes a new approach for laser forming of a bowl shaped surface by irradiating the centre of a flat circular blank with a stationary laser beam. With high power lasers, power density sufficient for laser forming, can be availed at reasonably large spot sizes. This advantage is exploited in this technique. Effects of duration of laser irradiation and beam spot diameter on the amount of bending and asymmetry in the formed surface were investigated. Laser power was kept constant while varying irradiation time. While varying laser spot diameter laser power was chosen so as to keep the surface temperature nearly constant at just below melting. Experimental conditions promoted almost uniform heating through sheet thickness. The amount of bending increased with irradiation time and spot diameter. It was interesting to observe that blanks bent towards the laser beam for smaller laser beam diameters and the reverse happened for larger spot diameters (~10 times of the sheet thickness). Effect of spot diameter variation has been explained with the help of coupled thermal-structural finite element simulations.

  5. Polarization/Spatial Combining of Laser-Diode Pump Beams

    NASA Technical Reports Server (NTRS)

    Gelsinger, Paul; Liu, Duncan

    2008-01-01

    A breadboard version of an optical beam combiner is depicted which make it possible to use the outputs of any or all of four multimode laser diodes to pump a non-planar ring oscillator (NPRO) laser. The output of each laser diode has a single-mode profile in the meridional plane containing an axis denoted the 'fast' axis and a narrower multimode profile in the orthogonal meridional plane, which contains an axis denoted the 'slow' axis and a narrower multimode profile in the orthogonal meridional plane, which contains an axis denoted the 'slow' axis. One of the purposes served by the beam-combining optics is to reduce the fast-axis numerical aperture (NA) of the laser-diode output to match the NA of the optical fiber. Along the slow axis, the unmodified laser-diode NA is already well matched to the fiber optic NA, so no further slow-axis beam shaping is needed. In this beam combiner, the laser-diode outputs are collimated by aspherical lenses, then half-wave plates and polarizing beam splitters are used to combine the four collimated beams into two beams. Spatial combination of the two beams and coupling into the optical fiber is effected by use of anamorphic prisms, mirrors, and a focusing lens. The anamorphic prisms are critical elements in the NA-matching scheme, in that they reduce the fast-axis beam width to 1/6 of its original values. Inasmuch as no slow-axis beam shaping is needed, the collimating and focusing lenses are matched for 1:1 iumaging. Because these lenses are well corrected for infinite conjugates the combiner offers diffraction-limited performance along both the fast and slow axes.

  6. Laser-based profile and energy monitor for H beams

    SciTech Connect

    Connolly,R.; Alessi, J.; Bellavia, S.; Dawson, C.; Degen, C.; Meng, W.; Raparia, D.; Russo, T.; Tsoupas, N.

    2008-09-29

    A beam profile and energy monitor for H{sup -} beams based on laser photoneutralization was built at Brookhaven National Laboratory (BNL)* for use on the High Intensity Neutrino Source (HMS) at Fermilab. An H{sup -} ion has a first ionization potential of 0.75eV and can be neutralized by light from a Nd:YAG laser ({lambda}=1064nm). To measure beam profiles, a narrow laser beam is stepped across the ion beam, removing electrons from the portion of the H{sup -} beam intercepted by the laser. These electrons are channeled into a Faraday cup by a curved axial magnetic field. To measure the energy distribution of the electrons, the laser position is fixed and the voltage on a screen in front of the Faraday cup is raised in small steps. We present a model which reproduces the measured energy spectrum from calculated beam energy and space-charge fields. Measurements are reported from experiments in the BNL linac MEBT at 750keV.

  7. A study of laser-beam welding conducted at the Centre for Laser Technologies of Metals

    NASA Astrophysics Data System (ADS)

    Antoszewski, Bogdan; Gradoń, Ryszard; Trela, Paweł; Cendrowicz, Edward

    2013-01-01

    The study reported here is part of a larger research project on laser-beam welding conducted at the Centre for Laser Technologies of Metals. The primary objectives were to compare laser-beam welding with a conventional process when used for longitudinal seams in street lamp posts, to select the process parameters for girth welds in cylindrical high-strength steel machine elements, and to assess whether laser-beam welding can be used for magnesium alloys. The paper includes recommendations for the selection of welding parameters.

  8. Laser-driven particle and photon beams and some applications

    NASA Astrophysics Data System (ADS)

    Ledingham, K. W. D.; Galster, W.

    2010-04-01

    Outstanding progress has been made in high-power laser technology in the last 10 years with laser powers reaching petawatt (PW) values. At present, there are 15 PW lasers built or being built around the world and plans are afoot for new, even higher power, lasers reaching values of exawatt (EW) or even zetawatt (ZW) powers. Petawatt lasers generate electric fields of 1012 V m-1 with a large fraction of the total pulse energy being converted to relativistic electrons with energies reaching in excess of 1 GeV. In turn these electrons result in the generation of beams of protons, heavy ions, neutrons and high-energy photons. These laser-driven particle beams have encouraged many to think of carrying out experiments normally associated with conventional nuclear accelerators and reactors. To this end a number of introductory articles have been written under a trial name 'Laser Nuclear Physics' (Ledingham and Norreys 1999 Contemp. Phys. 40 367, Ledingham et al 2002 Europhys. News. 33 120, Ledingham et al 2003 Science 300 1107, Takabe et al 2001 J. Plasma Fusion Res. 77 1094). However, even greater strides have been made in the last 3 or 4 years in laser technology and it is timely to reassess the potential of laser-driven particle and photon beams. It must be acknowledged right from the outset that to date laser-driven particle beams have yet to compete favourably with conventional nuclear accelerator-generated beams in any way and so this is not a paper comparing laser and conventional accelerators. However, occasionally throughout the paper as a reality check, it will be mentioned what conventional nuclear accelerators can do.

  9. Monoenergetic collimated nano-Coulomb electron beams driven by crossed laser beams

    SciTech Connect

    Wang Jingwei; Murakami, M.; Weng, S. M.; Ruhl, H.; Luan Shixia; Yu Wei

    2013-07-08

    Monoenergetic collimated electron acceleration by two crossed laser beams is investigated through an analytical model and particle-in-cell simulations. Electron bunches with a total charge of order nano-Coulombs are accelerated by the axial electric field formed by the crossed laser beams to nearly 760 MeV with an energy spread of 2.7%. The transverse components of both electric and magnetic fields vanish along the axis, making the electron beam highly collimated. This acceleration scheme appears promising in producing high quality electron beams.

  10. Optimization of beam transformation system for laser-diode bars.

    PubMed

    Yu, Junhong; Guo, Linhui; Wu, Hualing; Wang, Zhao; Gao, Songxin; Wu, Deyong

    2016-08-22

    An optimized beam transformation system (BTS) is proposed to improve the beam quality of laser-diode bars. Through this optimized design, the deterioration of beam quality after the BTS can be significantly reduced. Both the simulation and experimental results demonstrate that the optimized system enables the beam quality of a mini-bar (9 emitters) approximately equal to 5.0 mm × 3.6 mrad in the fast-axis and slow-axis. After beam shaping by the optimized BTS, the laser-diode beam can be coupled into a 100 μm core, 0.15 numerical aperture (NA) fiber with an output power of over 100 W and an electric-optical efficiency of 46.8%.

  11. Optimization of beam transformation system for laser-diode bars.

    PubMed

    Yu, Junhong; Guo, Linhui; Wu, Hualing; Wang, Zhao; Gao, Songxin; Wu, Deyong

    2016-08-22

    An optimized beam transformation system (BTS) is proposed to improve the beam quality of laser-diode bars. Through this optimized design, the deterioration of beam quality after the BTS can be significantly reduced. Both the simulation and experimental results demonstrate that the optimized system enables the beam quality of a mini-bar (9 emitters) approximately equal to 5.0 mm × 3.6 mrad in the fast-axis and slow-axis. After beam shaping by the optimized BTS, the laser-diode beam can be coupled into a 100 μm core, 0.15 numerical aperture (NA) fiber with an output power of over 100 W and an electric-optical efficiency of 46.8%. PMID:27557249

  12. Program Models A Laser Beam Focused In An Aerosol Spray

    NASA Technical Reports Server (NTRS)

    Barton, J. P.

    1996-01-01

    Monte Carlo analysis performed on packets of light. Program for Analysis of Laser Beam Focused Within Aerosol Spray (FLSPRY) developed for theoretical analysis of propagation of laser pulse optically focused within aerosol spray. Applied for example, to analyze laser ignition arrangement in which focused laser pulse used to ignite liquid aerosol fuel spray. Scattering and absorption of laser light by individual aerosol droplets evaluated by use of electromagnetic Lorenz-Mie theory. Written in FORTRAN 77 for both UNIX-based computers and DEC VAX-series computers. VAX version of program (LEW-16051). UNIX version (LEW-16065).

  13. A picosecond beam-timing system for the OMEGA laser

    DOE PAGESBeta

    Donaldson, W. R.; Katz, J.; Huff, R.; Hill, E. M.; Kelly, J. H.; Kwaitkowski, J.; Brannon, R. B.; Boni, R.

    2016-05-27

    Here, a timing system is demonstrated for the OMEGA Laser System that guarantees all 60 beams will arrive on target simultaneously with a root mean square variability of 4 ps. The system relies on placing a scattering sphere at the target position to couple the UV light from each beam into a single photodetector.

  14. Dual beam translator for use in Laser Doppler anemometry

    DOEpatents

    Brudnoy, David M.

    1987-01-01

    A method and apparatus for selectively translating the path of at least one pair of light beams in a Laser Doppler anemometry device whereby the light paths are translated in a direction parallel to the original beam paths so as to enable attainment of spacial coincidence of the two intersection volumes and permit accurate measurements of Reynolds shear stress.

  15. Dual beam translator for use in Laser Doppler anemometry

    DOEpatents

    Brudnoy, D.M.

    1984-04-12

    A method and apparatus for selectively translating the path of at least one pair of light beams in a Laser Doppler anemometry device whereby the light paths are translated in a direction parallel to the original beam paths so as to enable attainment of spacial coincidence of the two intersection volumes and permit accurate measurements of Reynolds shear stress.

  16. Digital Controller For Laser-Beam-Steering Subsystem

    NASA Technical Reports Server (NTRS)

    Ansari, Homayoon

    1995-01-01

    Report presents additional information about proposed apparatus described in "Beam-Steering Subsystem for Laser Communication" (NPO-19069). Discusses design of digital beam-steering control subsystem and, in particular, that part of design pertaining to digital compensation for frequency response of steering mirror.

  17. Laser beam scintillation beyond the turbulent atmosphere A numerical computation

    NASA Technical Reports Server (NTRS)

    Bufton, J. L.; Taylor, L. S.

    1976-01-01

    The extended Huygens-Fresnel formulation for propagation through turbulence is used to examine scintillation of a finite laser beam. The method is demonstrated analytically for propagation beyond a weak Gaussian phase screen. A numerical integration technique is used to extend the results to a more realistic turbulence model. Results are compared with existing Gaussian beam propagation theory.

  18. Acoustical problems in high energy pulsed E-beams lasers

    NASA Technical Reports Server (NTRS)

    Horton, T. E.; Wylie, K. F.

    1976-01-01

    During the pulsing of high energy, CO2, electron beam lasers, a significant fraction of input energy ultimately appears as acoustical disturbances. The magnitudes of these disturbances were quantified by computer analysis. Acoustical and shock impedance data are presented on materials (Rayleigh type) which show promise in controlling acoustical disturbance in E-beam systems.

  19. Vectorial rotating vortex Hankel laser beams

    NASA Astrophysics Data System (ADS)

    Kotlyar, Victor V.; Kovalev, Alexey A.; Soifer, Victor A.

    2016-09-01

    We propose a generalization of spherical waves in the form of linearly polarized beams with embedded optical vortices. The source of these beams is an infinitely narrow light ring with an infinitely small radius. These vectorial beams are obtained based on scalar Hankel beams discovered by the authors recently. We have derived explicit relations for complex amplitudes of all six components of vectorial vortex Hankel beams. A closed analytical expression for the axial projection of the orbital angular momentum density in far field has been obtained. We also showed that the intensity distribution of the electric vector rotates by 90 degrees upon the beam propagation in near field.

  20. Multiple quasi-monoenergetic electron beams from laser-wakefield acceleration with spatially structured laser pulse

    SciTech Connect

    Ma, Y.; Li, M. H.; Li, Y. F.; Wang, J. G.; Tao, M. Z.; Han, Y. J.; Zhao, J. R.; Huang, K.; Yan, W. C.; Ma, J. L.; Li, Y. T.; Chen, L. M.; Li, D. Z.; Chen, Z. Y.; Sheng, Z. M.; Zhang, J.

    2015-08-15

    By adjusting the focus geometry of a spatially structured laser pulse, single, double, and treble quasi-monoenergetic electron beams were generated, respectively, in laser-wakefield acceleration. Single electron beam was produced as focusing the laser pulse to a single spot. While focusing the laser pulse to two spots that are approximately equal in energy and size and intense enough to form their own filaments, two electron beams were produced. Moreover, with a proper distance between those two focal spots, three electron beams emerged with a certain probability owing to the superposition of the diffractions of those two spots. The energy spectra of the multiple electron beams are quasi-monoenergetic, which are different from that of the large energy spread beams produced due to the longitudinal multiple-injection in the single bubble.

  1. Modeling beam propagation and frequency conversion for the beamlet laser

    SciTech Connect

    Auerbach, J.M.

    1996-06-01

    The development of the Beamlet laser has involved extensive and detailed modeling of laser performance and beam propagation to: (1) predict the performance limits of the laser, (2) select system configurations with higher performance, (3) analyze experiments and provide guidance for subsequent laser shots, and (4) design optical components and establish component manufacturing specifications. In contrast to modeling efforts of previous laser systems such as Nova, those for Beamlet include as much measured optical characterization data as possible. This article concentrates on modeling of beam propagation in the Beamlet laser system, including the frequency converter, and compares modeling predictions with experimental results for several Beamlet shots. It briefly describes the workstation-based propagation and frequency conversion codes used to accomplish modeling of the Beamlet.

  2. Radially polarized cylindrical vector beams from a monolithic microchip laser

    NASA Astrophysics Data System (ADS)

    Naidoo, Darryl; Fromager, Michael; Ait-Ameur, Kamel; Forbes, Andrew

    2015-11-01

    Monolithic microchip lasers consist of a thin slice of laser crystal where the cavity mirrors are deposited directly onto the end faces. While this property makes such lasers very compact and robust, it prohibits the use of intracavity laser beam shaping techniques to produce complex light fields. We overcome this limitation and demonstrate the selection of complex light fields in the form of vector-vortex beams directly from a monolithic microchip laser. We employ pump reshaping and a thermal gradient across the crystal surface to control both the intensity and polarization profile of the output mode. In particular, we show laser oscillation on a superposition of Laguerre-Gaussian modes of zero radial and nonzero azimuthal index in both the scalar and vector regimes. Such complex light fields created directly from the source could find applications in fiber injection, materials processing and in simulating quantum processes.

  3. Laser beam complex amplitude measurement by phase diversity.

    PubMed

    Védrenne, Nicolas; Mugnier, Laurent M; Michau, Vincent; Velluet, Marie-Thérèse; Bierent, Rudolph

    2014-02-24

    The control of the optical quality of a laser beam requires a complex amplitude measurement able to deal with strong modulus variations and potentially highly perturbed wavefronts. The method proposed here consists in an extension of phase diversity to complex amplitude measurements that is effective for highly perturbed beams. Named camelot for Complex Amplitude MEasurement by a Likelihood Optimization Tool, it relies on the acquisition and processing of few images of the beam section taken along the optical path. The complex amplitude of the beam is retrieved from the images by the minimization of a Maximum a Posteriori error metric between the images and a model of the beam propagation. The analytical formalism of the method and its experimental validation are presented. The modulus of the beam is compared to a measurement of the beam profile, the phase of the beam is compared to a conventional phase diversity estimate. The precision of the experimental measurements is investigated by numerical simulations.

  4. EFFECT OF ORBIT DISTORTIONS LAND BETATRON TUNE ON THE RHIC POLARIZED BEAM.

    SciTech Connect

    LUCCIO,A.U.; PILAT,F.; PTITSYN,V.

    2001-06-18

    Polarized protons have been stored and accelerated in RHIC from G{sub {gamma}} = 46.5 to 60 during Run2000 with only one Siberian snake installed. We simulated with the spin tracking code Spink the behavior of polarized protons, in particular the effect of closed orbit distortions and betatron tune variation on the spin dynamics. According to simulation results, closed orbit and tune effects will be translated into requirements for the tune and orbit correction systems for the RHIC polarized proton Run2001, when both Siberian snakes will be available.

  5. Helium-tight Laser Beam Welding of Aluminum with Brillant Laser Beam Radiation

    NASA Astrophysics Data System (ADS)

    Heinen, Paul; Wu, Hao; Olowinsky, Alexander; Gillner, Arnold

    The substitution of steel as base metal for casings and packaging applications has increased during the last years. Especially aluminum with advantages in weight and machining effort has become a versatile solution for applications in fine mechanics (e.g. sensor housings) and automotive applications. Joining of aluminum components is more critical due to possible crack formation in the joining seam and uneven seam geometry. With the high intensity of brillant laser beam sources the specific challenges of aluminum welding can be overcome. Due to its hydrogen affinity and high degree of reflection for laser radiation at a wavelength of 1 μm (95%) aluminum needs to be welded with proper shielding gas support and high beam quality in order to avoid seam defects. Cracks and pores can lead to non-sufficient tightness for sensor applications and early failure. Housing components have been joined to form a functioning unit in order to seal electrical or measuring components, which are helium-tight for these applications.

  6. Electron beam-switched discharge for rapidly pulsed lasers

    DOEpatents

    Pleasance, L.D.; Murray, J.R.; Goldhar, J.; Bradley, L.P.

    1979-12-11

    A method and apparatus are designed for electrical excitation of a laser gas by application of a pulsed voltage across the gas, followed by passage of a pulsed, high energy electron beam through the gas to initiate a discharge suitable for laser excitation. This method improves upon current power conditioning techniques and is especially useful for driving rare gas halide lasers at high repetition rates.

  7. Earth-to-geosynchronous satellite laser beam transmission.

    PubMed

    Aruga, T; Araki, K; Hayashi, R; Iwabuchi, T; Takahashi, M; Nakamura, S

    1985-01-01

    Some experimental results for detection of a ground-based laser beacon by a geosynchronous satellite are reported. A 50-cm diam telescope and silicon intensifier tube camera were used for optical observation of the satellite. The transmitted argon laser beam was detected by the visible channel of a radiometer on board the Japanese Geostationary Meteorological Satellite. Two activities, (1) orbit prediction correction using optical observation and (2) detection of the earth laser beacon by the radiometer, are described.

  8. Resonant Ionization Laser Ion Source for Radioactive Ion Beams

    SciTech Connect

    Liu, Yuan; Beene, James R; Havener, Charles C; Vane, C Randy; Gottwald, T.; Wendt, K.; Mattolat, C.; Lassen, J.

    2009-01-01

    A resonant ionization laser ion source based on all-solid-state, tunable Ti:Sapphire lasers is being developed for the production of pure radioactive ion beams. It consists of a hot-cavity ion source and three pulsed Ti:Sapphire lasers operating at a 10 kHz pulse repetition rate. Spectroscopic studies are being conducted to develop ionization schemes that lead to ionizing an excited atom through an auto-ionization or a Rydberg state for numerous elements of interest. Three-photon resonant ionization of 12 elements has been recently demonstrated. The overall efficiency of the laser ion source measured for some of these elements ranges from 1 to 40%. The results indicate that Ti:Sapphire lasers could be well suited for laser ion source applications. The time structures of the ions produced by the pulsed lasers are investigated. The information may help to improve the laser ion source performance.

  9. Adaptive laser beam forming for laser shock micro-forming for 3D MEMS devices fabrication

    NASA Astrophysics Data System (ADS)

    Zou, Ran; Wang, Shuliang; Wang, Mohan; Li, Shuo; Huang, Sheng; Lin, Yankun; Chen, Kevin P.

    2016-07-01

    Laser shock micro-forming is a non-thermal laser forming method that use laser-induced shockwave to modify surface properties and to adjust shapes and geometry of work pieces. In this paper, we present an adaptive optical technique to engineer spatial profiles of the laser beam to exert precision control on the laser shock forming process for free-standing MEMS structures. Using a spatial light modulator, on-target laser energy profiles are engineered to control shape, size, and deformation magnitude, which has led to significant improvement of the laser shock processing outcome at micrometer scales. The results presented in this paper show that the adaptive-optics laser beam forming is an effective method to improve both quality and throughput of the laser forming process at micrometer scales.

  10. beam timing diagnostic for the OMEGA laser facility

    NASA Astrophysics Data System (ADS)

    Katz, J.; Donaldson, W. R.; Huff, R.; Hill, E. M.; Kelly, J. H.; Kwiatkowski, J.; Brannon, R. B.

    2015-08-01

    The Omega Laser Facility at the University of Rochester's Laboratory for Laser Energetics is a 60-beam system used for inertial confinement fusion experiments. Uniform drive of the target surface requires precise beam timing to achieve accurate power balance. A new diagnostic has been implemented for measuring the relative beam-to-beam arrival time of each of the 60 beamlines. A 900-μm spherical diffuser placed at the target chamber center serves as a quasi-isotropic scattering source that allows a fixed optical detector to view light from any individual beamline. During a beam-timing run, the OMEGA laser is configured to generate frequency-tripled, 351-nm ultraviolet (UV) pulses with energies of ~50 pJ at a repetition rate of 5 Hz. Light from the scattering target is optically relayed to a fast photomultiplier tube and recorded on a digital oscilloscope. A portion of the original infrared (IR) seed pulse is fiber optically delivered to the beam-timing oscilloscope and recorded using a photodiode. By recording the scattered UV pulse and the IR seed on the same oscilloscope trace, a jitter-free measurement of the beam's arrival time can be made. Discrepancies in beam timing are corrected by adjusting the total optical path length of the beamlines. Typical variation in the measured arrival times of all 60 OMEGA beams after adjustment is <5 ps root mean square

  11. New method of beam bunching in free-ion lasers

    SciTech Connect

    Bessonov, E.G.

    1995-12-31

    An effective ion beam bunching method is suggested. This method is based on a selective interaction of line spectrum laser light (e.g. axial mode structure light) with non-fully stripped ion beam cooled in a storage rings, arranging the ion beam in layers in radial direction of an energy-longitudinal coordinate plane and following rotation of the beam at the right angle after switching on the RF cavity or undulator grouper/buncher. Laser cooling of the ion beam can be used at this position after switching off the resonator to decrease the energy spread caused by accelerating field of the resonator. A relativistic multilayer ion mirror will be produced this way. Both monochromatic laser beams and intermediate monochromaticity and bandwidth light sources of spontaneous incoherent radiation can be used for production of hard and high power electromagnetic radiation by reflection from this mirror. The reflectivity of the mirror is rather high because of the cross-section of the backward Rayleigh scattering of photon light by non-fully stripped relativistic ions ({approximately}{lambda}{sup 2}) is much greater ({approximately} 10{divided_by}15 orders) then Thompson one ({approximately} r{sub e}{sup 2}). This position is valid even in the case of non-monochromatic laser light ({Delta}{omega}/{omega} {approximately} 10{sup -4}). Ion cooling both in longitudinal plane and three-dimensional radiation ion cooling had been proposed based on this observation. The using of these cooling techniques will permit to store high current and low emittance relativistic ion beams in storage rings. The bunched ion beam can be used in ordinary Free-Ion Lasers as well. After bunching the ion beam can be extracted from the storage ring in this case. Storage rings with zero momentum compaction function will permit to keep bunching of the ion beam for a long time.

  12. Measurement system with high accuracy for laser beam quality.

    PubMed

    Ke, Yi; Zeng, Ciling; Xie, Peiyuan; Jiang, Qingshan; Liang, Ke; Yang, Zhenyu; Zhao, Ming

    2015-05-20

    Presently, most of the laser beam quality measurement system collimates the optical path manually with low efficiency and low repeatability. To solve these problems, this paper proposed a new collimated method to improve the reliability and accuracy of the measurement results. The system accuracy controlled the position of the mirror to change laser beam propagation direction, which can realize the beam perpendicularly incident to the photosurface of camera. The experiment results show that the proposed system has good repeatability and the measuring deviation of M2 factor is less than 0.6%.

  13. Intense ion beams accelerated by relativistic laser plasmas

    NASA Astrophysics Data System (ADS)

    Roth, Markus; Cowan, Thomas E.; Gauthier, Jean-Claude J.; Allen, Matthew; Audebert, Patrick; Blazevic, Abel; Fuchs, Julien; Geissel, Matthias; Hegelich, Manuel; Karsch, S.; Meyer-ter-Vehn, Jurgen; Pukhov, Alexander; Schlegel, Theodor

    2001-12-01

    We have studied the influence of the target properties on laser-accelerated proton and ion beams generated by the LULI multi-terawatt laser. A strong dependence of the ion emission on the surface conditions, conductivity, shape and material of the thin foil targets were observed. We have performed a full characterization of the ion beam using magnetic spectrometers, Thompson parabolas, radiochromic film and nuclear activation techniques. The strong dependence of the ion beam acceleration on the conditions on the target back surface was found in agreement with theoretical predictions based on the target normal sheath acceleration (TNSA) mechanism. Proton kinetic energies up to 25 MeV have been observed.

  14. Measurement system with high accuracy for laser beam quality.

    PubMed

    Ke, Yi; Zeng, Ciling; Xie, Peiyuan; Jiang, Qingshan; Liang, Ke; Yang, Zhenyu; Zhao, Ming

    2015-05-20

    Presently, most of the laser beam quality measurement system collimates the optical path manually with low efficiency and low repeatability. To solve these problems, this paper proposed a new collimated method to improve the reliability and accuracy of the measurement results. The system accuracy controlled the position of the mirror to change laser beam propagation direction, which can realize the beam perpendicularly incident to the photosurface of camera. The experiment results show that the proposed system has good repeatability and the measuring deviation of M2 factor is less than 0.6%. PMID:26192526

  15. Saturation of fluorescence in flames with a Gaussian laser beam

    NASA Technical Reports Server (NTRS)

    Daily, J. W.

    1978-01-01

    The method of saturated fluorescence for measuring species concentrations in flames is usually performed with laser beams that do not provide a constant intensity distribution across the focal volume. Because of the intensity distribution across the beam, the fluorescence signal does not depend on laser power or intensity in the same manner as for uniform illumination. This leads to anomolous apparent saturation intensities. In the following, the effect is considered for atomic fluorescence. Relations for the fluorescence signal under two common excitation geometries are derived and uncertainty relations used to consider the benefits of high laser intensity.

  16. Scaling of solid state lasers for satellite power beaming applications

    SciTech Connect

    Friedman, H.W.; Albrecht, G.F.; Beach, R.J.

    1994-01-01

    The power requirements for a satellite power beaming laser system depend upon the diameter of the beam director, the performance of the adaptive optics system, and the mission requirements. For an 8 meter beam director and overall Strehl ratio of 50%, a 30 kW laser at 850 nm can deliver an equivalent solar flux to a satellite at geostationary orbit. Advances in Diode Pumped Solid State Lasers (DPSSL) have brought these small, efficient and reliable devices to high average power and they should be considered for satellite power beaming applications. Two solid state systems are described: a diode pumped Alexandrite and diode pumped Thulium doped YAG. Both can deliver high average power at 850 nm in a single aperture.

  17. Scaling of solid state lasers for satellite power beaming applications

    SciTech Connect

    Friedman, H.; Albrecht, G.; Beach, R.

    1994-12-31

    The power requirements for a satellite power beaming laser system depend upon the diameter of the beam director, the performance of the adaptive optics system, and the mission requirements. For an 8 meter beam director and overall Strehl ratio of 50%, a 30 kW laser at 850 nm can deliver an equivalent solar flux to a satellite at geostationary orbit. Advances in Diode Pumped Solid State Lasers (DPSSL) have brought these small, efficient and reliable devices to high average power and they should be considered for satellite power beaming applications. Two solid state systems are described: a diode pumped Alexandrite and diode pumped Thulium doped YAG. Both can deliver high average power at 850 nm in a single aperture.

  18. THE LASER EMITTANCE SCANNER FOR 1 GEV H- BEAM

    SciTech Connect

    Jeon, Dong-O; Pogge, James R; Menshov, Alexander A; Nesterenko, Igor N; Aleksandrov, Alexander V; Webster, Anthony W; Grice, Warren P

    2009-01-01

    A transverse phase space laser emittance scanner is proposed [1] and under development for the 1-GeV H- SNS linac, using a laser beam as a slit. For a 1-GeV H- beam, it is difficult to build a slit because the stopping distance is more than 50 cm in copper. We propose a Laser Emittance Scanner (LES) to use a laser beam as an effective slit by stripping off the outer electron of the H- (making it neutral) upstream of a bend magnet and measuring the stripped component downstream of the bend magnet. The design and modeling of the system will be discussed. We are expecting to make a preliminary measurement in 2009.

  19. Emittance of positron beams produced in intense laser plasma interaction

    SciTech Connect

    Chen Hui; Hazi, A.; Link, A.; Anderson, S.; Gronberg, J.; Izumi, N.; Tommasini, R.; Wilks, S.; Sheppard, J. C.; Meyerhofer, D. D.; Baldis, H. A.; Marley, E.; Park, J.; Williams, G. J.; Fedosejev, R.; Kerr, S.

    2013-01-15

    The first measurement of the emittance of intense laser-produced positron beams has been made. The emittance values were derived through measurements of positron beam divergence and source size for different peak positron energies under various laser conditions. For one of these laser conditions, we used a one dimensional pepper-pot technique to refine the emittance value. The laser-produced positrons have a geometric emittance between 100 and 500 mm{center_dot}mrad, comparable to the positron sources used at existing accelerators. With 10{sup 10}-10{sup 12} positrons per bunch, this low emittance beam, which is quasi-monoenergetic in the energy range of 5-20 MeV, may be useful as an alternative positron source for future accelerators.

  20. Multimode laser beam analyzer instrument using electrically programmable optics

    NASA Astrophysics Data System (ADS)

    Marraccini, Philip J.; Riza, Nabeel A.

    2011-12-01

    Presented is a novel design of a multimode laser beam analyzer using a digital micromirror device (DMD) and an electronically controlled variable focus lens (ECVFL) that serve as the digital and analog agile optics, respectively. The proposed analyzer is a broadband laser characterization instrument that uses the agile optics to smartly direct light to the required point photodetectors to enable beam measurements of minimum beam waist size, minimum waist location, divergence, and the beam propagation parameter M2. Experimental results successfully demonstrate these measurements for a 500 mW multimode test laser beam with a wavelength of 532 nm. The minimum beam waist, divergence, and M2 experimental results for the test laser are found to be 257.61 μm, 2.103 mrad, 1.600 and 326.67 μm, 2.682 mrad, 2.587 for the vertical and horizontal directions, respectively. These measurements are compared to a traditional scan method and the results of the beam waist are found to be within error tolerance of the demonstrated instrument.

  1. Multimode laser beam analyzer instrument using electrically programmable optics.

    PubMed

    Marraccini, Philip J; Riza, Nabeel A

    2011-12-01

    Presented is a novel design of a multimode laser beam analyzer using a digital micromirror device (DMD) and an electronically controlled variable focus lens (ECVFL) that serve as the digital and analog agile optics, respectively. The proposed analyzer is a broadband laser characterization instrument that uses the agile optics to smartly direct light to the required point photodetectors to enable beam measurements of minimum beam waist size, minimum waist location, divergence, and the beam propagation parameter M(2). Experimental results successfully demonstrate these measurements for a 500 mW multimode test laser beam with a wavelength of 532 nm. The minimum beam waist, divergence, and M(2) experimental results for the test laser are found to be 257.61 μm, 2.103 mrad, 1.600 and 326.67 μm, 2.682 mrad, 2.587 for the vertical and horizontal directions, respectively. These measurements are compared to a traditional scan method and the results of the beam waist are found to be within error tolerance of the demonstrated instrument.

  2. Evolution of branch points for a laser beam propagating through an uplink turbulent atmosphere.

    PubMed

    Ge, Xiao-Lu; Liu, Xuan; Guo, Cheng-Shan

    2014-03-24

    Evolution of branch points in the distorted optical field is studied when a laser beam propagates through turbulent atmosphere along an uplink path. Two categories of propagation events are mainly explored for the same propagation height: fixed wavelength with change of the turbulence strength and fixed turbulence strength with change of the wavelength. It is shown that, when the beam propagates to a certain height, the density of the branch-points reaches its maximum and such a height changes with the turbulence strength but nearly remains constant with different wavelengths. The relationship between the density of branch-points and the Rytov number is also given. A fitted formula describing the relationship between the density of branch-points and propagation height with different turbulence strength and wavelength is found out. Interestingly, this formula is very similar to the formula used for describing the Blackbody radiation in physics. The results obtained may be helpful for atmospheric optics, astronomy and optical communication.

  3. Beam conditioner for free electron lasers and synchrotrons

    DOEpatents

    Liu, H.; Neil, G.R.

    1998-09-08

    A focused optical has been used to introduce an optical pulse, or electromagnetic wave, collinear with the electron beam in a free electron laser or synchrotron thereby adding an axial field component that accelerates the electrons on the radial outside of the distribution of electrons in the electron beam. This invention consists of using the axial electrical component of a TEM{sub 10} mode Gaussian beam in vacuum to condition the electron beam and speed up the outer electrons in the beam. The conditioning beam should possess about the same diameter as the electron beam. The beam waist of the conditioning wave must be located around the entrance of the undulator longitudinally to have a net energy exchange between the electrons in the outer part of the distribution and the conditioning wave owing to the natural divergence of a Gaussian beam. By accelerating the outer electrons, the outer and core electrons are caused to stay in phase. This increases the fraction of the electron beam energy that is converted to light thereby improving the efficiency of conversion of energy to light and therefore boosting the power output of the free electron laser and synchrotron. 4 figs.

  4. Beam conditioner for free electron lasers and synchrotrons

    DOEpatents

    Liu, Hongxiu; Neil, George R.

    1998-01-01

    A focused optical is been used to introduce an optical pulse, or electromagnetic wave, colinearly with the electron beam in a free electron laser or synchrotron thereby adding an axial field component that accelerates the electrons on the radial outside of the distribution of electrons in the electron beam. This invention consists of using the axial electrical component of a TEM.sub.10 mode Gaussian beam in vacuum to condition the electron beam and speed up the outer electrons in the beam. The conditioning beam should possess about the same diameter as the electron beam. The beam waist of the conditioning wave must be located around the entrance of the undulator longitudinally to have a net energy exchange between the electrons in the outer part of the distribution and the conditioning wave owing to the natural divergence of a Gaussian beam. By accelerating the outer electrons, the outer and core electrons are caused to stay in phase. This increases the fraction of the electron beam energy that is converted to light thereby improving the efficiency of conversion of energy to light and therefore boosting the power output of the free electron laser and synchrotron.

  5. High Power Laser Beam Welding of Thick-walled Ferromagnetic Steels with Electromagnetic Weld Pool Support

    NASA Astrophysics Data System (ADS)

    Fritzsche, André; Avilov, Vjaceslav; Gumenyuk, Andrey; Hilgenberg, Kai; Rethmeier, Michael

    The development of modern high power laser systems allows single pass welding of thick-walled components with minimal distortion. Besides the high demands on the joint preparation, the hydrostatic pressure in the melt pool increases with higher plate thicknesses. Reaching or exceeding the Laplace pressure, drop-out or melt sagging are caused. A contactless electromagnetic weld support system was used for laser beam welding of thick ferromagnetic steel plates compensating these effects. An oscillating magnetic field induces eddy currents in the weld pool which generate Lorentz forces counteracting the gravity forces. Hysteresis effects of ferromagnetic steels are considered as well as the loss of magnetization in zones exceeding the Curie temperature. These phenomena reduce the effective Lorentz forces within the weld pool. The successful compensation of the hydrostatic pressure was demonstrated on up to 20 mm thick plates of duplex and mild steel by a variation of the electromagnetic power level and the oscillation frequency.

  6. UV laser ionization and electron beam diagnostics for plasma lenses

    SciTech Connect

    Govil, R.; Volfbeyn, P.; Leemans, W.

    1995-04-01

    A comprehensive study of focusing of relativistic electron beams with overdense and underdense plasma lenses requires careful control of plasma density and scale lengths. Plasma lens experiments are planned at the Beam Test Facility of the LBL Center for Beam Physics, using the 50 MeV electron beam delivered by the linac injector from the Advanced Light Source. Here we present results from an interferometric study of plasmas produced in tri-propylamine vapor with a frequency quadrupled Nd:YAG laser at 266 nm. To study temporal dynamics of plasma lenses we have developed an electron beam diagnostic using optical transition radiation to time resolve beam size and divergence. Electron beam ionization of the plasma has also been investigated.

  7. Optical parametric amplifier pumped by two mutually incoherent laser beams

    NASA Astrophysics Data System (ADS)

    Tamošauskas, G.; Dubietis, A.; Valiulis, G.; Piskarskas, A.

    2008-05-01

    We report on the experimental proof-of-principle demonstration of the ultrashort pulse single-pass beta-barium borate, BBO optical parametric amplifier pumped by two mutually incoherent laser sources. We show that the amplified signal at 1054 nm gains energy from both pump pulses with wavelengths of 680 and 527 nm, respectively, with overall energy conversion of 36%, and exhibits low wavefront distortions and improved energy stability in the gain saturation regime.

  8. Aerosol beam-focus laser-induced plasma spectrometer device

    DOEpatents

    Cheng, Meng-Dawn

    2002-01-01

    An apparatus for detecting elements in an aerosol includes an aerosol beam focuser for concentrating aerosol into an aerosol beam; a laser for directing a laser beam into the aerosol beam to form a plasma; a detection device that detects a wavelength of a light emission caused by the formation of the plasma. The detection device can be a spectrometer having at least one grating and a gated intensified charge-coupled device. The apparatus may also include a processor that correlates the wavelength of the light emission caused by the formation of the plasma with an identity of an element that corresponds to the wavelength. Furthermore, the apparatus can also include an aerosol generator for forming an aerosol beam from bulk materials. A method for detecting elements in an aerosol is also disclosed.

  9. Research on method for laser beam shape parameters detection

    NASA Astrophysics Data System (ADS)

    Su, Jun-hong; Bai, Zhao-feng

    2014-09-01

    The laser beam quality measurement has become a hot topic in the field of laser engineering nowadays. Based on the method of Hartmann-Shack, the four-wave lateral shearing interferometer is presented in this paper to achieve the laser beam shape parameters. The principle of shearing technology is described in detail. Parameters of semiconductor laser at 532nm and ZYGO interferometer laser are tested based on the method of four-wave lateral shearing interference and their test results are compared with the nominal parameters. As the results, the test results are basically consistent with the nominal value, which fully shows the feasibility of the four-wave lateral shearing interference method.

  10. Optodynamics: dynamic aspects of laser beam-surface interaction

    NASA Astrophysics Data System (ADS)

    Možina, J.; Diaci, J.

    2012-05-01

    This paper presents a synthesis of the results of our original research in the area of laser-material interaction and pulsed laser material processing with a special emphasis on the dynamic aspects of laser beam-surface interaction, which include the links between the laser material removal and the resulting material motion. In view of laser material processing, a laser beam is not only considered as a tool but also as a generator of information about the material transformation. The information is retained and conveyed by different kinds of optically induced mechanical waves. Several generation/detection schemes have been developed to extract this information, especially in the field of non-destructive material evaluation. Blast and acoustic waves, which propagate in the air surrounding the work-piece, have been studied using microphone detection as well as various setups of the laser beam deflection probe. Stress waves propagating through the work-piece have been studied using piezoelectric transducers and laser interferometers.

  11. Free Electron Lasers with Slowly Varying Beam and Undulator Parameters

    SciTech Connect

    Huang, Z; Stupakov, G.; /SLAC

    2005-05-25

    The performance of a free electron lasers (FEL) is affected when the electron beam energy varies alone the undulator as would be caused by vacuum pipe wakefields and/or when the undulator strength parameter is tapered in the small signal regime until FEL saturation. In this paper, we present a self-consistent theory of FELs with slowly-varying beam and undulator parameters. A general method is developed to apply the WKB approximation to the beam-radiation system by employing the adjoint eigenvector that is orthogonal to the eigenfunctions of the coupled Maxwell-Vlasov equations. This method may be useful for other slowly varying processes in beam dynamics.

  12. Near spherical illumination of ion-beam and laser targets

    SciTech Connect

    Mark, J.W.K.

    1985-12-12

    A procedure is developed for reducing energy-deposition asymmetry in spherical targets driven directly by ion or laser beams. This work is part of a strategy for achieving illumination symmetry in such targets, which is proposed as an alternative to those in the literature. This strategy allows an axially symmetric placement of beamlets, which would be convenient for some driven or reactor scenarios. It also allows the use of beam currents or energy fluxes and beam transverse profiles to help reduce deposition asymmetry with fewer beamlets. In the ideal limit of thin deposition layers and controlled beam profiles, at most six beamlets are needed for target symmetry.

  13. Terahertz plasmonic laser radiating in an ultra-narrow beam

    DOE PAGESBeta

    Wu, Chongzhao; Khanal, Sudeep; Reno, John L.; Kumar, Sushil

    2016-07-07

    Plasmonic lasers (spasers) generate coherent surface plasmon polaritons (SPPs) and could be realized at subwavelength dimensions in metallic cavities for applications in nanoscale optics. Plasmonic cavities are also utilized for terahertz quantum-cascade lasers (QCLs), which are the brightest available solid-state sources of terahertz radiation. A long standing challenge for spasers that are utilized as nanoscale sources of radiation, is their poor coupling to the far-field radiation. Unlike conventional lasers that could produce directional beams, spasers have highly divergent radiation patterns due to their subwavelength apertures. Here, we theoretically and experimentally demonstrate a new technique for implementing distributed feedback (DFB) thatmore » is distinct from any other previously utilized DFB schemes for semiconductor lasers. The so-termed antenna-feedback scheme leads to single-mode operation in plasmonic lasers, couples the resonant SPP mode to a highly directional far-field radiation pattern, and integrates hybrid SPPs in surrounding medium into the operation of the DFB lasers. Experimentally, the antenna-feedback method, which does not require the phase matching to a well-defined effective index, is implemented for terahertz QCLs, and single-mode terahertz QCLs with a beam divergence as small as 4°×4° are demonstrated, which is the narrowest beam reported for any terahertz QCL to date. Moreover, in contrast to a negligible radiative field in conventional photonic band-edge lasers, in which the periodicity follows the integer multiple of half-wavelengths inside the active medium, antenna-feedback breaks this integer limit for the first time and enhances the radiative field of the lasing mode. Terahertz lasers with narrow-beam emission will find applications for integrated as well as standoff terahertz spectroscopy and sensing. Furthermore, the antenna-feedback scheme is generally applicable to any plasmonic laser with a Fabry–Perot cavity

  14. Dense Monoenergetic Proton Beams from Chirped Laser-Plasma Interaction

    NASA Astrophysics Data System (ADS)

    Galow, Benjamin J.; Salamin, Yousef I.; Liseykina, Tatyana V.; Harman, Zoltán; Keitel, Christoph H.

    2011-10-01

    Interaction of a frequency-chirped laser pulse with single protons and a hydrogen gas target is studied analytically and by means of particle-in-cell simulations, respectively. The feasibility of generating ultraintense (107 particles per bunch) and phase-space collimated beams of protons (energy spread of about 1%) is demonstrated. Phase synchronization of the protons and the laser field, guaranteed by the appropriate chirping of the laser pulse, allows the particles to gain sufficient kinetic energy (around 250 MeV) required for such applications as hadron cancer therapy, from state-of-the-art laser systems of intensities of the order of 1021W/cm2.

  15. Design and fabrication of hollow-core photonic crystal fibers for high power fast laser beam transportation and pulse compression

    NASA Astrophysics Data System (ADS)

    Wang, Y. Y.; Peng, Xiang; Alharbi, M.; Dutin, C. F.; Bradley, T. D.; Mielke, Michael; Booth, Timothy; Benabid, F.

    2012-03-01

    We report on recent design and fabrication of Kagome type hollow-core photonic crystal fiber (HC-PCF) for the purpose of high power fast laser beam transportation. The fabricated seven-cell three-ring hypocycloid-shaped large core fiber exhibits an up-to-date lowest attenuation (among all Kagome fibers) of 40dB/km over a broadband transmission centered at 1500nm. We show that the large core size, low attenuation, broadband transmission, single modedness, low dispersion and relatively low banding loss makes it an ideal host for high power laser beam transportation. By filling the fiber with helium gas, a 74μJ, 850fs and 40kHz repetition rate ultra-short pulse at 1550nm has been faithfully delivered with little propagation pulse distortion. Compression of a 105μJ laser pulse from 850fs to 300fs has been achieved by operating the fiber in ambient air.

  16. Full-Duplex Digital Communication on a Single Laser Beam

    NASA Technical Reports Server (NTRS)

    Hazzard, D. A.; MacCannell, J. A.; Lee, G.; Selves, E. R.; Moore, D.; Payne, J. A.; Garrett, C. D.; Dahlstrom, N.; Shay, T. M.

    2006-01-01

    A proposed free-space optical communication system would operate in a full-duplex mode, using a single constant-power laser beam for transmission and reception of binary signals at both ends of the free-space optical path. The system was conceived for two-way data communication between a ground station and a spacecraft in a low orbit around the Earth. It has been estimated that in this application, a data rate of 10 kb/s could be achieved at a ground-station-to-spacecraft distance of 320 km, using a laser power of only 100 mW. The basic system concept is also applicable to terrestrial free-space optical communications. The system (see figure) would include a diode laser at one end of the link (originally, the ground station) and a liquid-crystal- based retroreflecting modulator at the other end of the link (originally, the spacecraft). At the laser end, the beam to be transmitted would be made to pass through a quarter-wave plate, which would convert its linear polarization to right circular polarization. For transmission of data from the laser end to the retroreflector end, the laser beam would be modulated with subcarrier phase-shift keying (SC-PSK). The transmitted beam would then pass through an aperture- sharing element (ASE) - basically, a mirror with a hole in it, used to separate the paths of the transmitted and received light beams. The transmitted beam would continue outward through a telescope (which, in the original application, would be equipped with a spacecraft-tracking system) that would launch the transmitted beam along the free-space optical path to the retroreflector end.

  17. Laser beacon adaptive optics for power beaming applications

    SciTech Connect

    Fugate, R.Q.

    1994-12-31

    This paper discusses the laser beam control system requirements for power beaming applications. Power beaming applications include electric and thermal engine propulsion for orbit transfer, station changing, and recharging batteries. Beam control includes satellite acquisition, high accuracy tracking, higher order atmospheric compensation using adaptive optics, and precision point-ahead. Beam control may also include local laser beam clean-up with a low order adaptive optics system. This paper also presents results of tracking and higher-order correction experiments on astronomical objects. The results were obtained with a laser beacon adaptive optics system at Phillips Laboratory`s Starfire Optical Range near Albuquerque, NM. At a wavelength of 0.85 {mu}m, the author has achieved Strehl ratios of {approximately}0.50 using laser beacons and {approximately}0.65 using natural stars for exposures longer than one minute on objects of {approximately}8{sup th} magnitude. The resulting point spread function has a full width half maximum (FWHM) of 0.13 arcsec.

  18. Radially and azimuthally polarized laser beams by thin-disk laser.

    PubMed

    Aghbolaghi, Reza; Charehjolo, Habib Sahebghoran

    2016-05-01

    The generation of radially and azimuthally polarized beams is theoretically investigated in thin-disk laser configurations by writing Jones matrices for optical elements. Higher modes are omitted by aperture and the mode-selection operation is done by discontinuous phase elements. Two modes, TEM01x and TEM01y, are combined to generate the radially and azimuthally polarized laser beam. The polarization of the output beams is studied by the extended Jones matrices. In addition, the output power of the thin-disk laser is numerically estimated by solving the rate equations in ytterbium-doped materials. PMID:27140363

  19. Physics of elliptical reflectors at large reflection and divergence angles II: Analysis of optical beam distortions in integrated ultra-large-angle elliptical curved reflectors

    NASA Astrophysics Data System (ADS)

    Hou, Z.; Li, X.; Huang, Y.; Ho, S. T.; Member, IEEE

    2013-01-01

    In this work, we study the behavior of elliptical reflectors in nanophotonic integrated circuits in the context of two-dimensional multimode Gaussian beam. We show that the transformation of the beam profile at the input/output waveguide mouths, and the transformation of the beam profile at the reflector can be described in terms of 2D Hermite-Gaussian (HG) beam modes under first order approximation (FOA), referred to as HG-FOA. Due to the wavelength-scale waveguides in nanophotonic integrated circuits, the beams incident on the elliptical reflector have large diffraction angle which will result in asymmetric amplitude distortion upon non-normal reflection even for ideal elliptical reflecting surfaces. The amplitude distortion can be illustrated in the oscillation of the peaks of the reflected beam profiles around the propagation axis of the reflected beam. The amplitude distortion can also be shown by the deterioration in the coupling efficiency from the input waveguide to the output waveguide due to the excitation of higher order HG modes during the reflection. These two observations can both be explained by the HG-FOA method and are verified with Finite-Difference Time-Domain (FDTD) method. Moreover, we show that the coupling loss from the input waveguide to the output waveguide due to the higher order modes excited can be eliminated via insertion of a second reflector. Two specific arrangement of the second reflector are discussed and verified by the FDTD simulation.

  20. Nanoparticles based laser-induced surface structures formation on mesoporous silicon by picosecond laser beam interaction

    NASA Astrophysics Data System (ADS)

    Talbi, A.; Petit, A.; Melhem, A.; Stolz, A.; Boulmer-Leborgne, C.; Gautier, G.; Defforge, T.; Semmar, N.

    2016-06-01

    In this study, laser induced periodic surface structures were formed on mesoporous silicon by irradiation of Nd:YAG picosecond pulsed laser beam at 266 nm wavelength at 1 Hz repetition rate and with 42 ps pulse duration. The effects of laser processing parameters as laser beam fluence and laser pulse number on the formation of ripples were investigated. Scanning electron microscopy and atomic force microscopy were used to image the surface morphologies and the cross section of samples after laser irradiation. At relatively low fluence ∼20 mJ/cm2, ripples with period close to the laser beam wavelength (266 nm) and with an always controlled orientation (perpendicular to the polarization of ps laser beam) appeared after a large laser pulse number of 12,000. It has been found that an initial random distribution of SiOx nanoparticles is periodically structured with an increase of the laser pulse number. Finally, it is experimentally demonstrated that we formed a 100 nm liquid phase under the protusion zones including the pores in the picosecond regime.

  1. Beam Extraction from Laser Driven Multi-Charged Ion Source

    SciTech Connect

    Anderson, O A; Logan, B G

    2001-03-19

    A newly proposed type of multicharged ion source offers the possibility of an economically advantageous high-charge-state fusion driver. Multiphoton absorption in an intense uniform laser focus can give multiple charge states of high purity, simplifying or eliminating the need for charge-state separation downstream. Very large currents (hundreds of amperes) can be extracted from this type of source. Several arrangements are possible. For example, the laser plasma could be tailored for storage in a magnetic bucket, with beam extracted from the bucket. A different approach, described in this report, is direct beam extraction from the expanding laser plasma. They discuss extraction and focusing for the particular case of a 4.1-MV beam of Xe{sup 16+} ions. The maximum duration of the beam pulse is limited by the total charge in the plasma, while the practical pulse length is determined by the range of plasma radii over which good beam optics can be achieved. The extraction electrode contains a solenoid for beam focusing. The design studies were carried out first with an envelope code and then with a self-consistent particle code. Results from the initial model showed that hundreds of amperes could be extracted, but that most of this current missed the solenoid entrance or was intercepted by the wall and that only a few amperes were able to pass through. They conclude with an improved design which increases the surviving beam to more than 70 amperes.

  2. Wedged Fibers Suppress Feedback of Laser Beam

    NASA Technical Reports Server (NTRS)

    Ladany, I.

    1986-01-01

    When injected laser is coupled into optical fiber, emission instabilities arise because of optical feedback losses from fiber into laser. Coupling efficiencies as high as 80 percent, however, obtained by shaping end of multimode fiber into obtuse-angled wedge. Because slanted sides eliminate back reflection, such wedged fiber achieves high coupling efficiency.

  3. Numerical study of neutron beam divergence in a beam-fusion scenario employing laser driven ions

    NASA Astrophysics Data System (ADS)

    Alejo, A.; Green, A.; Ahmed, H.; Robinson, A. P. L.; Cerchez, M.; Clarke, R.; Doria, D.; Dorkings, S.; Fernandez, J.; McKenna, P.; Mirfayzi, S. R.; Naughton, K.; Neely, D.; Norreys, P.; Peth, C.; Powell, H.; Ruiz, J. A.; Swain, J.; Willi, O.; Borghesi, M.; Kar, S.

    2016-09-01

    The most established route to create a laser-based neutron source is by employing laser accelerated, low atomic-number ions in fusion reactions. In addition to the high reaction cross-sections at moderate energies of the projectile ions, the anisotropy in neutron emission is another important feature of beam-fusion reactions. Using a simple numerical model based on neutron generation in a pitcher-catcher scenario, anisotropy in neutron emission was studied for the deuterium-deuterium fusion reaction. Simulation results are consistent with the narrow-divergence (∼ 70 ° full width at half maximum) neutron beam recently served in an experiment employing multi-MeV deuteron beams of narrow divergence (up to 30° FWHM, depending on the ion energy) accelerated by a sub-petawatt laser pulse from thin deuterated plastic foils via the Target Normal Sheath Acceleration mechanism. By varying the input ion beam parameters, simulations show that a further improvement in the neutron beam directionality (i.e. reduction in the beam divergence) can be obtained by increasing the projectile ion beam temperature and cut-off energy, as expected from interactions employing higher power lasers at upcoming facilities.

  4. Laser initiation and beam quality evolution in a confocal unstable resonator, short-pulse-duration laser.

    PubMed

    Ewanizky, T F

    1997-11-20

    The subjects of laser initiation and beam quality evolution in short-pulse-duration systems that employ confocal unstable resonators motivated this work. Experimentation and analysis of the performance of a laser-pumped, organic dye laser are presented. Combined results indicate that a saturation flux arises through a coalescence of stabilized, diverging-mode components of the initially emitted fluorescence. The ABCD law method was used to devise calculational techniques that clearly demonstrate the particular mechanisms responsible for rapid mode stabilization, subsequent beam quality development, and laser initiation. PMID:18264413

  5. Radiobiological study by using laser-driven proton beams

    SciTech Connect

    Yogo, A.; Nishikino, M.; Mori, M.; Ogura, K.; Sagisaka, A.; Orimo, S.; Nishiuchi, M.; Pirozhkov, A. S.; Ikegami, M.; Tampo, M.; Sakaki, H.; Suzuki, M.; Daito, I.; Kiriyama, H.; Okada, H.; Kanazawa, S.; Kondo, S.; Shimomura, T.; Nakai, Y.; Kawachi, T.

    2009-07-25

    Particle acceleration driven by high-intensity laser systems is widely attracting interest as a potential alternative to conventional ion acceleration, including ion accelerator applications to tumor therapy. Recent works have shown that a high intensity laser pulse can produce single proton bunches of a high current and a short pulse duration. This unique feature of laser-ion acceleration can lead to progress in the development of novel ion sources. However, there has been no experimental study of the biological effects of laser-driven ion beams. We describe in this report the first demonstrated irradiation effect of laser-accelerated protons on human lung cancer cells. In-vitro A549 cells are irradiated with a proton dose of 20 Gy, resulting in a distinct formation of gamma-H2AX foci as an indicator of DNA double-strand breaks. This is a pioneering result that points to future investigations of the radiobiological effects of laser-driven ion beams. The laser-driven ion beam is apotential excitation source for time-resolved determination of hydroxyl (OH) radical yield, which will explore relationship between the fundamental chemical reactions of radiation effects and consequent biological processes.

  6. Radiobiological study by using laser-driven proton beams

    NASA Astrophysics Data System (ADS)

    Yogo, A.; Sato, K.; Nishikino, M.; Mori, M.; Teshima, T.; Numasaki, H.; Murakami, M.; Demizu, Y.; Akagi, S.; Nagayama, S.; Ogura, K.; Sagisaka, A.; Orimo, S.; Nishiuchi, M.; Pirozhkov, A. S.; Ikegami, M.; Tampo, M.; Sakaki, H.; Suzuki, M.; Daito, I.; Oishi, Y.; Sugiyama, H.; Kiriyama, H.; Okada, H.; Kanazawa, S.; Kondo, S.; Shimomura, T.; Nakai, Y.; Tanoue, M.; Sugiyama, H.; Sasao, H.; Wakai, D.; Kawachi, T.; Nishimura, H.; Bolton, P. R.; Daido, H.

    2009-07-01

    Particle acceleration driven by high-intensity laser systems is widely attracting interest as a potential alternative to conventional ion acceleration, including ion accelerator applications to tumor therapy. Recent works have shown that a high intensity laser pulse can produce single proton bunches of a high current and a short pulse duration. This unique feature of laser-ion acceleration can lead to progress in the development of novel ion sources. However, there has been no experimental study of the biological effects of laser-driven ion beams. We describe in this report the first demonstrated irradiation effect of laser-accelerated protons on human lung cancer cells. In-vitro A549 cells are irradiated with a proton dose of 20 Gy, resulting in a distinct formation of γ-H2AX foci as an indicator of DNA double-strand breaks. This is a pioneering result that points to future investigations of the radiobiological effects of laser-driven ion beams. The laser-driven ion beam is apotential excitation source for time-resolved determination of hydroxyl (OH) radical yield, which will explore relationship between the fundamental chemical reactions of radiation effects and consequent biological processes.

  7. Longitudinal discharge laser baffles

    DOEpatents

    Warner, B.E.; Ault, E.R.

    1994-06-07

    The IR baffles placed between the window and the electrode of a longitudinal discharge laser improve laser performance by intercepting off-axis IR radiation from the laser and in doing so reduce window heating and subsequent optical distortion of the laser beam. 1 fig.

  8. Longitudinal discharge laser baffles

    DOEpatents

    Warner, Bruce E.; Ault, Earl R.

    1994-01-01

    The IR baffles placed between the window and the electrode of a longitudinal discharge laser improve laser performance by intercepting off-axis IR radiation from the laser and in doing so reduce window heating and subsequent optical distortion of the laser beam.

  9. Deflection of a Reflected Intense Vortex Laser Beam.

    PubMed

    Zhang, Lingang; Shen, Baifei; Zhang, Xiaomei; Huang, Shan; Shi, Yin; Liu, Chen; Wang, Wenpeng; Xu, Jiancai; Pei, Zhikun; Xu, Zhizhan

    2016-09-01

    An interesting deflection effect deviating the optical reflection law is revealed in the relativistic regime of intense vortex laser plasma interaction. When an intense vortex laser obliquely impinges onto an overdense plasma target, the reflected beam deflects out of the plane of incidence with an experimentally observable deflection angle. The mechanism is demonstrated by full three-dimensional particle-in-cell simulation as well as analytical modeling using the Maxwell stress tensor. The deflection results from the rotational symmetry breaking of the foil driven by the unsymmetrical shear stress of the vortex beam. The l-dependent shear stress, where l is the topological charge, as an intrinsic characteristic to the vortex beam, plays an important role as the ponderomotive force in relativistic vortex laser matter interaction. PMID:27661689

  10. Turbulence-induced persistence in laser beam wandering.

    PubMed

    Zunino, Luciano; Gulich, Damián; Funes, Gustavo; Pérez, Darío G

    2015-07-01

    We have experimentally confirmed the presence of long-memory correlations in the wandering of a thin Gaussian laser beam over a screen after propagating through a turbulent medium. A laboratory-controlled experiment was conducted in which coordinate fluctuations of the laser beam were recorded at a sufficiently high sampling rate for a wide range of turbulent conditions. Horizontal and vertical displacements of the laser beam centroid were subsequently analyzed by implementing detrended fluctuation analysis. This is a very well-known and widely used methodology to unveil memory effects from time series. Results obtained from this experimental analysis allow us to confirm that both coordinates behave as highly persistent signals for strong turbulent intensities. This finding is relevant for a better comprehension and modeling of the turbulence effects in free-space optical communication systems and other applications related to propagation of optical signals in the atmosphere.

  11. Turbulence-induced persistence in laser beam wandering.

    PubMed

    Zunino, Luciano; Gulich, Damián; Funes, Gustavo; Pérez, Darío G

    2015-07-01

    We have experimentally confirmed the presence of long-memory correlations in the wandering of a thin Gaussian laser beam over a screen after propagating through a turbulent medium. A laboratory-controlled experiment was conducted in which coordinate fluctuations of the laser beam were recorded at a sufficiently high sampling rate for a wide range of turbulent conditions. Horizontal and vertical displacements of the laser beam centroid were subsequently analyzed by implementing detrended fluctuation analysis. This is a very well-known and widely used methodology to unveil memory effects from time series. Results obtained from this experimental analysis allow us to confirm that both coordinates behave as highly persistent signals for strong turbulent intensities. This finding is relevant for a better comprehension and modeling of the turbulence effects in free-space optical communication systems and other applications related to propagation of optical signals in the atmosphere. PMID:26125388

  12. Designing Light Beam Transmittance Measuring Tool Using a Laser Pointer

    NASA Astrophysics Data System (ADS)

    Nuroso, H.; Kurniawan, W.; Marwoto, P.

    2016-08-01

    A simple instrument used for measuring light beam transmittance percentage made of window film has been developed. The instrument uses a laser pointer of 405 nm and 650 nm ±10% as a light source. Its accuracy approaches 80%. Transmittance data was found by comparing the light beam before and after passing the window film. The light intensity measuring unit was deleted by splitting the light source into two beams through a beam splitter. The light beam was changed into resistance by a NORP12 LDR sensor designed at a circuit of voltage divider rule of Khirchoff's laws. This conversion system will produce light beam intensity received by the sensor to become an equal voltage. This voltage will, then, be presented on the computer screen in the form of a real time graph via a 2.0 USB data transfer.

  13. Laser beam temporal and spatial tailoring for laser shock processing

    DOEpatents

    Hackel, Lloyd; Dane, C. Brent

    2001-01-01

    Techniques are provided for formatting laser pulse spatial shape and for effectively and efficiently delivering the laser energy to a work surface in the laser shock process. An appropriately formatted pulse helps to eliminate breakdown and generate uniform shocks. The invention uses a high power laser technology capable of meeting the laser requirements for a high throughput process, that is, a laser which can treat many square centimeters of surface area per second. The shock process has a broad range of applications, especially in the aerospace industry, where treating parts to reduce or eliminate corrosion failure is very important. The invention may be used for treating metal components to improve strength and corrosion resistance. The invention has a broad range of applications for parts that are currently shot peened and/or require peening by means other than shot peening. Major applications for the invention are in the automotive and aerospace industries for components such as turbine blades, compressor components, gears, etc.

  14. System for obtaining smooth laser beams where intensity variations are reduced by spectral dispersion of the laser light (SSD)

    DOEpatents

    Skupsky, Stanley; Kessler, Terrance J.; Short, Robert W.; Craxton, Stephen; Letzring, Samuel A.; Soures, John

    1991-01-01

    In an SSD (smoothing by spectral dispersion) system which reduces the time-averaged spatial variations in intensity of the laser light to provide uniform illumination of a laser fusion target, an electro-optic phase modulator through which a laser beam passes produces a broadband output beam by imposing a frequency modulated bandwidth on the laser beam. A grating provides spatial and angular spectral dispersion of the beam. Due to the phase modulation, the frequencies ("colors") cycle across the beam. The dispersed beam may be amplified and frequency converted (e.g., tripled) in a plurality of beam lines. A distributed phase plate (DPP) in each line is irradiated by the spectrally dispersed beam and the beam is focused on the target where a smooth (uniform intensity) pattern is produced. The color cycling enhances smoothing and the use of a frequency modulated laser pulse prevents the formation of high intensity spikes which could damage the laser medium in the power amplifiers.

  15. LASER APPLICATIONS: H- BEAM PHOTO-DETACHMENT AND PUSH BUTTON DIAGNOSTICS

    SciTech Connect

    Liu, Yun

    2012-01-01

    The laser based nonintrusive H- beam diagnostics and laser assisted H- beam stripping technologies have been developed at the Spallation Neutron Source (SNS). This paper reviews the present status of the SNS laser based diagnostics and the recent R&D progress on the fiber transmission of laser pulses and power enhancement optical cavity which will be used in diagnostics and laser stripping.

  16. Mid-IR laser source using hollow waveguide beam combining

    NASA Astrophysics Data System (ADS)

    Elder, Ian F.; Thorne, Daniel H.; Lamb, Robert A.; Jenkins, R. M.

    2016-03-01

    Hollow waveguide technology is a route to efficient beam combining of multiple laser sources in a compact footprint. It is a technology appropriate for combining free-space or fibre-coupled beams generated by semiconductor, fibre or solidstate laser sources. This paper will present results of a breadboard mid-IR system comprising four laser sources combined using a hollow waveguide optical circuit. In this approach the individual dichroic beam combiner components are held in precision alignment slots in the hollow waveguide circuit and the different input wavelengths are guided between the components to a common output port. The hollow waveguide circuit is formed in the surface of a Macor (machinable glass-ceramic) substrate using precision CNC machining techniques. The hollow waveguides have fundamentally different propagation characteristics to solid core waveguides leading to transmission characteristics close to those of the atmosphere while still providing useful light guidance properties. The transmission efficiency and power handling of the hollow waveguide circuit can be designed to be very high across a broad waveband range. Three of the sources are quantum cascade lasers (QCLs), a semiconductor laser technology providing direct generation of midwave IR output. The combined beams provide 4.2 W of near diffraction-limited output co-boresighted to better than 20 µrad. High coupling efficiency into the waveguides is demonstrated, with negligible waveguide transmission losses. The overall transmission of the hollow waveguide beam combining optical circuit, weighted by the laser power at each wavelength, is 93%. This loss is dominated by the performance of the dichroic optics used to combine the beams.

  17. UNDULATOR-BASED LASER WAKEFIELD ACCELERATOR ELECTRON BEAM DIAGNOSTIC

    SciTech Connect

    Bakeman, M.S.; Fawley, W.M.; Leemans, W. P.; Nakamura, K.; Robinson, K.E.; Schroeder, C.B.; Toth, C.

    2009-05-04

    to couple the THUNDER undulator to the LOASIS Lawrence Berkeley National Laboratory (LBNL) laser wakefield accelerator (LWFA). Currently the LWFA has achieved quasi-monoenergetic electron beams with energies up to 1 GeV. These ultra-short, high-peak-current, electron beams are ideal for driving a compact XUV free electron laser (FEL). Understanding the electron beam properties such as the energy spread and emittance is critical for achieving high quality light sources with high brightness. By using an insertion device such as an undulator and observing changes in the spontaneous emission spectrum, the electron beam energy spread and emittance can be measured with high precision. The initial experiments will use spontaneous emission from 1.5 m of undulator. Later experiments will use up to 5 m of undulator with a goal of a high gain, XUV FEL.

  18. Spacecraft Power Beaming Using High-Energy Lasers, Experimental Validation

    NASA Astrophysics Data System (ADS)

    Michael, Sherif

    2008-04-01

    The lifetime of many spacecrafts are often limited by degradation of their electrical power subsystem, e.g. radiation-damaged solar arrays or failed batteries. Being able to beam power from terrestrial sites using high energy lasers, could alleviate this limitation, extending the lifetime of billions of dollars of satellite assets, as well as providing additional energy for electric propulsion that can be used for stationkeeping and orbital changes. In addition, extensive research at the Naval Postgraduate School (NPS) has shown the potential for annealing damaged solar cells using lasers. This paper describes that research and a proposed experiment to demonstrate the relevant concepts of high energy laser power beaming to an NPS-built and operated satellite. Preliminary results of ground experiment of laser illuminations of some of the solar panels of one of the spacecrafts are also presented.

  19. Influence of the pump-to-laser beam overlap on the performance of optically pumped cesium vapor laser.

    PubMed

    Cohen, Tom; Lebiush, Eyal; Auslender, Ilya; Barmashenko, Boris D; Rosenwaks, Salman

    2016-06-27

    Experimental and theoretical study of the influence of the pump-to-laser beam overlap, a crucial parameter for optimization of optically pumped alkali atom lasers, is reported for Ti:Sapphire pumped Cs laser. Maximum laser power > 370 mW with an optical-to-optical efficiency of 43% and slope efficiency ~55% was obtained. The dependence of the lasing power on the pump power was found for different pump beam radii at constant laser beam radius. Non monotonic dependence of the laser power (optimized over the temperature of the Cs cell) on the pump beam radius was observed with a maximum achieved at the ratio ~0.7 between the pump and laser beam radii. The optimal temperature decreased with increasing pump beam radius. A simple optical model of the laser, where Gaussian spatial shapes of the pump and laser intensities in any cross section of the beams were assumed, was compared to the experiments. Good agreement was obtained between the measured and calculated dependence of the laser power on the pump power at different pump beam radii and also of the laser power, threshold pump power and optimal temperature on the pump beam radius. The model does not use empirical parameters such as mode overlap efficiency and can be applied to different Ti:Sapphire and diode pumped alkali lasers with arbitrary spatial distributions of the pump and laser beam widths. PMID:27410591

  20. Characteristic of laser diode beam propagation through a collimating lens.

    PubMed

    Xu, Qiang; Han, Yiping; Cui, Zhiwei

    2010-01-20

    A mathematical model of a laser diode beam propagating through a collimating lens is presented. Wave propagation beyond the paraxial approximation is studied. The phase delay of the laser diode wave in passing through the lens is analyzed in detail. The propagation optical field after the lens is obtained from the diffraction integral by the stationary phase method. The model is employed to predict the light intensity at various beam cross sections, and the computed intensity distributions are in a good agreement with the corresponding measurements.

  1. Electron Acceleration by a Tightly Focused Laser Beam

    NASA Astrophysics Data System (ADS)

    Salamin, Yousef I.; Keitel, Christoph H.

    2002-03-01

    State-of-the-art petawatt laser beams may be focused down to few-micron spot sizes and can produce violent electron acceleration as a result of the extremely intense and asymmetric fields. Classical fifth-order calculations in the diffraction angle show that electrons, injected sideways into the tightly focused laser beam, get captured and gain energy in the GeV regime. We point out the most favorable points of injection away from the focus, along with an efficient means of extracting the energetic electron with a static magnetic field.

  2. Harmonic generation by circularly polarized laser beams propagating in plasma

    SciTech Connect

    Agrawal, Ekta; Hemlata,; Jha, Pallavi

    2015-04-15

    An analytical theory is developed for studying the phenomenon of generation of harmonics by the propagation of an obliquely incident, circularly polarized laser beam in homogeneous, underdense plasma. The amplitudes of second and third harmonic radiation as well as detuning distance have been obtained and their variation with the angle of incidence is analyzed. The amplitude of harmonic radiation increases with the angle of incidence while the detuning distance decreases, for a given plasma electron density. It is observed that the generated second and third harmonic radiation is linearly and elliptically polarized, respectively. The harmonic radiation vanishes at normal incidence of the circularly polarized laser beam.

  3. Laser beam centering and pointing system

    DOEpatents

    Rushford, Michael Charles

    2015-01-13

    An optical instrument aligns an optical beam without the need for physical intervention of the instrument within the apparatus or platforms from which the trajectory of the beam to be ascertained. The alignment apparatus and method enable the desired function to be realized without the placement of physical apertures or sensors directly in the path of the beam through the system whose spatial position and slope is to be sought. An image plane provides the observer with a pair of well-defined images that are indicative of the beam centering and pointing alignment parameters. The optical alignment can be realized without the need for referencing to an external or fixed set of coordinates or fiducials. The instrument can therefore service situations where adverse environments would otherwise prohibit the use of such instruments, including regions of high radiation, high temperature, vacuum and/or cryogenic atmospheres.

  4. Development of a fast position-sensitive laser beam detector

    SciTech Connect

    Chavez, Isaac; Huang Rongxin; Henderson, Kevin; Florin, Ernst-Ludwig; Raizen, Mark G.

    2008-10-15

    We report the development of a fast position-sensitive laser beam detector. The detector uses a fiber-optic bundle that spatially splits the incident beam, followed by a fast balanced photodetector. The detector is applied to the study of Brownian motion of particles on fast time scales with 1 A spatial resolution. Future applications include the study of molecule motors, protein folding, as well as cellular processes.

  5. Beam Delivery System For UV Laser Ablation Of The Cornea

    NASA Astrophysics Data System (ADS)

    Yoder, P. R.; Telfair, W. B.; Warner, J. W.; Martin, C. A.; Bennett, P. S.

    1988-06-01

    We describe an electro-optical apparatus capable of delivering a homogenized, intensity-contoured 193 nm wavelength laser beam to the anterior surface of the cornea. Beam fluence is adequate to produce controlled ablation over areas as large as 7 mm diameter. Preliminary experimental results demonstrating recontouring of the corneal surface as a means of correcting myopia are presented. Means to be used for reducing hyperopia and astigmatism also are described.

  6. Optimized x/y scanning head for laser beam positioning

    NASA Astrophysics Data System (ADS)

    Muth, Michael

    1996-08-01

    As a fast two-axis deflection unit for laser beam positioning, an X/Y scanning head based on two galvanometric scanners with vertical crossed axes is a central component of different applications in industry, medicine and communications. Some of these are laser markers, stereolithography devices, scanning laser vibrometers, laser trimmers, laser cutting machines, infrared scanners, lead bonders, Q-switches, laser ophthalmoscope, robotic vision systems, range finders, image digitizers, and laser graphic projectors for entertainment. Velocity and accuracy of the X/Y scanning heads are very important for the performance of the devices in which they are used. Therefore the dynamic properties of the X/Y scanning head must be optimized. One important criterion is the mass moment of inertia of the second scanning mirror. It can be reduced by inclining the axis of the first galvanometric scanner. To solve these problems both computer tools for the optical and mechanical optimization, and measuring devices to minimize the wobble and jitter of galvanometric scanners were developed. The development of scanning heads for different apertures (laser beam diameters), scan angles and F-(Theta) -objectives was done for SCANLAB GmbH (Puchheim/Munchen, Germany), one of the three leading manufacturers for galvanometric scanners.

  7. Concrete "Waffle" Provides Laser Beam Accuracy

    ERIC Educational Resources Information Center

    Building Design and Construction, 1978

    1978-01-01

    A massive concrete "waffle," riding on a bed of specially treated gravel and sand inside another building, provides the structural rigidity needed by the University of Rochester's Laboratory for Laser Energetics. (Author)

  8. Nonparaxial optical vortices and Kummer laser beams

    NASA Astrophysics Data System (ADS)

    Kovalev, Alexey A.; Kotlyar, Victor V.; Nalimov, Anton G.

    2013-09-01

    Two approaches to describe nonparaxial optical vortices were considered. One approach is to use a revised Kirchhoff integral, which does not neglect the relief of an optical element. Using this integral and the finite-difference time-domain method it is shown that an optical vortex generated by a refractive spiral plate with a relief step has an asymmetric profile. The annular diffraction pattern in the vortex beam cross-section is found to be disturbed not only for the near-field diffraction but also for the middle-field diffraction, at a distance of several Fresnel lengths. Another approach is to solve the Helmholtz equation without any approximations. An analytical solution to describe propagation of a light beam in the positive direction of the optical axis was found. The complex amplitude of such a beam is found to be in direct proportion to the product of two linearly independent solutions of Kummer's differential equation. Relationships for a particular case of such beams-namely, the Hankel-Bessel (HB) beams-are deduced. The autofocusing of the HB beams is studied.

  9. Measurements of asymmetry due to diagnostic holes, laser timing and beam imbalance in Hohlraums irradiated with NOVA laser beams

    NASA Astrophysics Data System (ADS)

    Magelssen, G. R.; Delamater, N. D.; Culbertson, C.; Lindman, E. L.; Macfarlane, J. J.

    1998-11-01

    Using the NOVA laser facility at Lawerence Livermore National Laboratory, asymmetries due to diagnostic holes, and laser timing and beam imbalance were studied in gas-filled hohlraums irradiated with laser beams with Kineform phase plates. The measurements were made the reemission ball technique(N. D. Delamater et al., Phys. Rev. E, 53, 1, 1996) (G. R. Magelssen et al., Phys. Rev. E, 57, 4663, 1998.) by viewing the ball along the hohlraum axis. Using a 3-D radiation transport viewfactor code developed by MacFarlane (J. J. MacFarlane, Un. Of Wisconsin report UWFDM-1061 (1998)), and the measured power profile for each beam, direct comparisons between the experimental data and calculations have been made and will be presented.

  10. Beam-shaping technique for improving the beam quality of a high-power laser-diode stack.

    PubMed

    Gao, Xin; Ohashi, Hiroyuki; Okamoto, Hiroshi; Takasaka, Masaomi; Shinoda, Kazunori

    2006-06-01

    We report a beam-shaping technique that reconfigures the beams to improve the beam quality and enhance the power density for a ten-array high-power laser-diode stack by using two optical rectangular cubes and two stripe-mirror plates. The reshaped beam has threefold improvement in beam quality, and its power density is effectively enhanced. On the basis of this technique, we focus the beam of the high-power laser-diode stack to effectively end pump a high-power fiber laser.

  11. A laser-wire beam-energy and beam-profile monitor at the BNL linac

    SciTech Connect

    Connolly, R.; Degen, C.; DeSanto, L.; Meng, W.; Michnoff, R.; Minty, M.; Nayak, S.

    2011-03-28

    In 2009 a beam-energy monitor was installed in the high energy beam transport (HEBT) line at the Brookhaven National Lab linac. This device measures the energies of electrons stripped from the 40mA H{sup -} beam by background gas. Electrons are stripped by the 2.0x10{sup -7}torr residual gas at a rate of {approx}1.5x10{sup -8}/cm. Since beam electrons have the same velocities as beam protons, the beam proton energy is deduced by multiplying the electron energy by m{sub p}/m{sub e}=1836. A 183.6MeV H{sup -} beam produces 100keV electrons. In 2010 we installed an optics plates containing a laser and scanning optics to add beam-profile measurement capability via photodetachment. Our 100mJ/pulse, Q-switched laser neutralizes 70% of the beam during its 10ns pulse. This paper describes the upgrades to the detector and gives profile and energy measurements.

  12. Instability versus equilibrium propagation of a laser beam in plasma.

    PubMed

    Lushnikov, Pavel M; Rose, Harvey A

    2004-06-25

    We obtain, for the first time, an analytic theory of the forward stimulated Brillouin scattering instability of a spatially and temporally incoherent laser beam that controls the transition between statistical equilibrium and nonequilibrium (unstable) self-focusing regimes of beam propagation. The stability boundary may be used as a comprehensive guide for inertial confinement fusion designs. Well into the stable regime, an analytic expression for the angular diffusion coefficient is obtained, which provides an essential correction to a geometric optic approximation for beam propagation.

  13. High-Quality Ion Beam Generation in Laser Plasma Interaction

    NASA Astrophysics Data System (ADS)

    Nagashima, Toshihiro; Takano, Masahiro; Izumiyzma, Takeshi; Barada, Daisuke; Kawata, Shigeo; Gu, Yan Jun; Kong, Qing; Xiao Wang, Ping; Ma, Yan Yun; Wang, Wei Min

    We focus on a control of generation of high-quality ion beam. In this study, near-critical density plasmas are employed and are illuminated by high intensity short laser pulses; we have successfully generated high-energy ions by multiple-stages acceleration. We performed particle-in-cell simulations in this paper. Near-critical density plasmas are employed at the proton source and also in the post acceleration. A beam bunching method is also proposed to control the ion beam length.

  14. Delivering pump light to a laser gain element while maintaining access to the laser beam

    DOEpatents

    Beach, Raymond J.; Honea, Eric C.; Payne, Stephen A.

    2001-01-01

    A lens duct is used for pump delivery and the laser beam is accessed through an additional component called the intermediate beam extractor which can be implemented as part of the gain element, part of the lens duct or a separate component entirely.

  15. Digital replacement of the distorted dentition acquired by cone beam computed tomography (CBCT): a pilot study.

    PubMed

    Nairn, N J; Ayoub, A F; Barbenel, J; Moos, K; Naudi, K; Ju, X; Khambay, B S

    2013-11-01

    During cone beam computed tomography (CBCT) scanning, intra-oral metallic objects may produce streak artefacts, which impair the occlusal surface of the teeth. This study aimed to determine the accuracy of replacement of the CBCT dentition with a more accurate dentition and to determine the clinical feasibility of the method. Impressions of the teeth of six cadaveric skulls with unrestored dentitions were taken and acrylic base plates constructed incorporating radiopaque registration markers. Each appliance was fitted to the skull and a CBCT performed. Impressions were taken of the dentition with the devices in situ and dental models were produced. These were CBCT-scanned and the images of the skulls and models imported into computer-aided design/computer-aided manufacturing (CAD/CAM) software and aligned on the registration markers. The occlusal surfaces of each dentition were then replaced with the occlusal image of the corresponding model. The absolute mean distance between the registration markers in the skulls and the dental models was 0.09±0.02mm, and for the dentition was 0.24±0.09mm. When the method was applied to patients, the distance between markers was 0.12±0.04mm for the maxilla and 0.16±0.02mm for the mandible. It is possible to replace the inaccurate dentition on a CBCT scan using this method and to create a composite skull which is clinically acceptable.

  16. Accuracy of laser beam center and width calculations.

    PubMed

    Mana, G; Massa, E; Rovera, A

    2001-03-20

    The application of lasers in high-precision measurements and the demand for accuracy make the plane-wave model of laser beams unsatisfactory. Measurements of the variance of the transverse components of the photon impulse are essential for wavelength determination. Accuracy evaluation of the relevant calculations is thus an integral part of the assessment of the wavelength of stabilized-laser radiation. We present a propagation-of-error analysis on variance calculations when digitized intensity profiles are obtained by means of silicon video cameras. Image clipping criteria are obtained that maximize the accuracy of the computed result.

  17. Characteristics of the electron beam pumped iodine monofluoride laser

    SciTech Connect

    Champagne, L.F.; Ehrlich, J.E.

    1983-02-01

    Electron beam pumping of Ar/CF/sub 3/I/NF/sub 3/ mixtures yields optical pulse lengths about 0.5 ..mu..s from iodine monofluoride. Laser efficiency in this system is about0.04 percent. Laser performance is limited by the formation of molecular iodine. The formation of molecular iodine in the excited state (I/sub 2/) reduces the number of iodine atoms available to form IF. In the ground state, molecular iodine (I/sub 2/) absorbs the IF laser emission at 485 and 491 nm.

  18. Characteristics of the electron beam pumped iodine monofluoride laser

    NASA Astrophysics Data System (ADS)

    Champagne, L. F.; Ehrlich, J. E.

    1983-02-01

    Electron beam pumping of Ar/CF3I/NF3 mixtures yields optical pulse lengths approximately 0.5 microsec from iodine monofluoride. Laser efficiency in this system is approximately 0.04 percent. Laser performance is limited by the formation of molecular iodine. The formation of molecular iodine in the excited state reduces the number of iodine atoms available to form excited-state IF. In the ground state, molecular iodine absorbs the excited-state IF laser emission at 485 and 491 nm.

  19. Modeling of dynamic effects of a low power laser beam

    NASA Technical Reports Server (NTRS)

    Lawrence, George N.; Scholl, Marija S.; Khatib, AL

    1988-01-01

    Methods of modeling some of the dynamic effects involved in laser beam propagation through the atmosphere are addressed with emphasis on the development of simple but accurate models which are readily implemented in a physical optics code. A space relay system with a ground based laser facility is considered as an example. The modeling of such characteristic phenomena as laser output distribution, flat and curved mirrors, diffraction propagation, atmospheric effects (aberration and wind shear), adaptive mirrors, jitter, and time integration of power on target, is discussed.

  20. Indium phosphide solar cells for laser power beaming applications

    NASA Technical Reports Server (NTRS)

    Jain, Raj K.; Landis, Geoffrey A.

    1992-01-01

    Lasers can be used to transmit power to photovoltaic cells. Solar cell efficiencies are enhanced significantly under monochromatic light, and therefore a laser beam of proper wavelength could be a very effective source of illumination for a solar array operating at very high efficiencies. This work reviews the modeling studies made on indium phosphide solar cells for such an application. These cells are known to be very radiation resistant and have a potential for high efficiency. Effects of cell series resistance, laser intensity, and temperature on cell performance have been discussed.

  1. Intense Laser Ionization and Acceleration of Electrons in Highly-Charged Ions Using Vortex Laser Beams

    NASA Astrophysics Data System (ADS)

    Pi, Liang-Wen; Vikartofsky, Andrew; Starace, Anthony F.

    2016-05-01

    Recent advances in laser technology have led to the development of high-power petawatt lasers, making possible laser intensities of the order of 1022 W /cm2 . An electron in a highly-charged ion can be ionized in a laser field at its peak intensity and swiftly accelerated to GeV energies. Our prior investigation of laser acceleration of electrons using linearly-polarized Gaussian beams (with zero orbital angular momentum) has revealed that the final-state energies and ejection angles of the electrons depend on the initial target ion positions relative to the laser focus. We report here recent simulations of laser ionization and acceleration of electrons using linearly-polarized vortex laser beams (i.e., Laguerre-Gaussian beams), which carry orbital angular momentum and can spin microscopic objects. These simulations show that the inherent spiral phase structure of the vortex beams leads to improved final-state energy and ejection angle distributions of the electrons. This work is supported in part by DOE, Office of Science, Division of Chemical Sciences, Geosciences, and Biosciences, under Grant No. DE-FG02-96ER14646.

  2. Laser-Bioplasma Interaction: The Blood Type Transmutation Induced by Multiple Ultrashort Wavelength Laser Beams

    NASA Astrophysics Data System (ADS)

    Stefan, V. Alexander

    2015-11-01

    The interaction of ultrashort wavelength multi laser beams with the flowing blood thin films leads to the transmutation of the blood types A, B, and AB into O type. This is a novel mechanism of importance for the transfusion medicine. Laser radiation is in resonance with the eigen-frequency modes of the antigen proteins and forces the proteins to parametrically oscillate until they get kicked out from the surface. The stripping away of antigens is done by the scanning-multiple-lasers of a high repetition rate in the blue-purple frequency domain. The guiding-lasers are in the red-green frequency domain. The laser force, (parametric interaction with the antigen eigen-oscillation), upon the antigen protein molecule must exceed its weight. The scanning laser beam is partially reflected as long as the antigen(s) is not eliminated. The process of the protein detachment can last a few minutes. Supported by Nikola Tesla Labs., Stefan University.

  3. HUBBLE DISCOVERS POWERFUL LASER BEAMED FROM CHAOTIC STAR

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This is an artist's concept of a gas cloud (left) that acts as a natural ultraviolet laser, near the huge, unstable star Eta Carinae (right) -- one of most massive and energetic stars in our Milky Way Galaxy. The super-laser was identified by a team led by Kris Davidson of the University of Minnesota, and including nine other collaborators in the U.S. and Sweden during spectroscpic observations made with the Goddard High Resolution spectrograph aboard NASA's Hubble Space Telescope. Since it's unlikely that a single beam from the cloud would happen to be precisely aimed in earth's driection, the astronomers conclude that numerous beams must be radiating from the cloud in all directions - beams from a dance hall mirror-ball. The interstellar laser may result from Eta Carinae's violently chaotic eruptions, illustrated here as a reddish (due to light scattering by dust) outflow from the bright star. A laser, (an acronym for Light Amplification by Stimulated Emission of Radiation) creates an intense coherent beam of light when atoms or molecules in a gas, liquid or solid medium, force an incoming mix of wavelengths (or colors) of light to work in phase, or, at the same wavelength. Though a natural infrared laser was identified in space in 1995, lasers are very rare in space and nothing like the UV laser has ever been seen before. Eta Carinae is several million times brighter than the Sun, and one hundred times as massive. The superstar, located 8,000 light-years away in the souther constellation Carina, underwent a colossal outburst 150 years ago. Illustration courtesy James Gitlin/STScI

  4. Experimental study of laser beam propagation in turbulent atmosphere

    NASA Astrophysics Data System (ADS)

    Yang, Chun-Ping; He, Wu-Guang; Wu, Jian

    2009-05-01

    Intensity of atmospheric turbulence may overly affect bit error rate for a ground-based laser wireless communication system, so it is necessary to measure of atmospheric turbulence intensity and fluctuation of image centroid while laser beam propagates in turbulent atmosphere. In this paper, an experiment system is set up based on theory of light transmission in turbulent atmosphere. In the system, a laser named Nd : YAG is used horizontally to emit a laser beam with wavelength 1.06 μm on a platform at the height of 1.5 m. Three infrared CCD cameras are set at 200 m, 300 m(or 600 m) and 1000 m far from laser, which are applied to receive laser facula images from Lambertian boards, respectively. A lot of laser facula images are collected within some serial days under different periods of time every day, and hundreds of image frames are gathered at a time by making use of this experiment device. Fluctuation of image centroid is computed with these image frames, and the structure constant of atmospheric refractive index (C 2n) is also derived. Finally, a comparison is made between aforementioned C2n and those derived by meteorology factors.

  5. Laser-beam interactions with materials

    SciTech Connect

    Allmen, M.V.

    1987-01-01

    Lasers are becoming popular tools and research instruments in materials research, metallurgy, semiconductor technology and engineering. This text treats, from a physicist's point of view, the processes that lasers can induce in materials. A broad view of the field and its perspectives is given: physical topics covered range from optics to shock waves, and applications range from semiconductor annealing to fusion-plasma production. Intuitive analytical models are used whenever possible, in order to foster creative thinking and facilitate access to newcomers and nonspecialists.

  6. Two-photon flow cytometer with laser scanning Bessel beams

    NASA Astrophysics Data System (ADS)

    Wang, Yongdong; Ding, Yu; Ray, Supriyo; Paez, Aurelio; Xiao, Chuan; Li, Chunqiang

    2016-03-01

    Flow cytometry is an important technique in biomedical discovery for cell counting, cell sorting and biomarker detection. In vivo flow cytometers, based on one-photon or two-photon excited fluorescence, have been developed for more than a decade. One drawback of laser beam scanning two-photon flow cytometer is that the two-photon excitation volume is fairly small due to the short Rayleigh range of a focused Gaussian beam. Hence, the sampling volume is much smaller than one-photon flow cytometry, which makes it challenging to count or detect rare circulating cells in vivo. Bessel beams have narrow intensity profiles with an effective spot size (FWHM) as small as several wavelengths, making them comparable to Gaussian beams. More significantly, the theoretical depth of field (propagation distance without diffraction) can be infinite, making it an ideal solution as a light source for scanning beam flow cytometry. The trade-off of using Bessel beams rather than a Gaussian beam is the fact that Bessel beams have small concentric side rings that contribute to background noise. Two-photon excitation can reduce this noise, as the excitation efficiency is proportional to intensity squared. Therefore, we developed a two-photon flow cytometer using scanned Bessel beams to form a light sheet that intersects the micro fluidic channel.

  7. Electro-optic harmonic conversion to switch a laser beam out of a cavity

    DOEpatents

    Haas, R.A.; Henesian, M.A.

    1984-10-19

    The present invention relates to switching laser beams out of laser cavities, and more particularly, it relates to the use of generating harmonics of the laser beam to accomplish the switching. When laser light is generatd in a laser cavity the problem arises of how to switch the laser light out of the cavity in order to make use of the resulting laser beam in a well known multitude of ways. These uses include range finding, communication, remote sensing, medical surgery, laser fusion applications and many more. The switch-out problem becomes more difficult as the size of the laser aperture grows such as in laser fusion applications. The final amplifier stages of the Nova and Novette lasers at Lawrence Livermore National Laboratory are 46 centimeters with the laser beam expanded to 74 centimeters thereafter. Larger aperture lasers are planned.

  8. Optical Device for Converting a Laser Beam into Two Co-aligned but Oppositely Directed Beams

    NASA Technical Reports Server (NTRS)

    Jennings, Donald

    2013-01-01

    Optical systems consisting of a series of optical elements require alignment from the input end to the output end. The optical elements can be mirrors, lenses, sources, detectors, or other devices. Complex optical systems are often difficult to align from end-to-end because the alignment beam must be inserted at one end in order for the beam to traverse the entire optical path to the other end. The ends of the optical train may not be easily accessible to the alignment beam. Typically, when a series of optical elements is to be aligned, an alignment laser beam is inserted into the optical path with a pick-off mirror at one end of the series of elements. But it may be impossible to insert the beam at an end-point. It can be difficult to locate the pick-off mirror at the desired position because there is not enough space, there is no mounting surface, or the location is occupied by a source, detector, or other component. Alternatively, the laser beam might be inserted at an intermediate location (not at an end-point) and sent, first in one direction and then the other, to the opposite ends of the optical system for alignment. However, in this case, alignment must be performed in two directions and extra effort is required to co-align the two beams to make them parallel and coincident, i.e., to follow the same path as an end-to-end beam. An optical device has been developed that accepts a laser beam as input and produces two co-aligned, but counter-propagating beams. In contrast to a conventional alignment laser placed at one end of the optical path, this invention can be placed at a convenient position within the optical train and aligned to send its two beams simultaneously along precisely opposite paths that, taken together, trace out exactly the same path as the conventional alignment laser. This invention allows the user the freedom to choose locations within the optical train for placement of the alignment beam. It is also self-aligned by design and requires

  9. Earth Model with Laser Beam Simulating Seismic Ray Paths.

    ERIC Educational Resources Information Center

    Ryan, John Arthur; Handzus, Thomas Jay, Jr.

    1988-01-01

    Described is a simple device, that uses a laser beam to simulate P waves. It allows students to follow ray paths, reflections and refractions within the earth. Included is a set of exercises that lead students through the steps by which the presence of the outer and inner cores can be recognized. (Author/CW)

  10. Laser Brazing with Beam Scanning: Experimental and Simulative Analysis

    NASA Astrophysics Data System (ADS)

    Heitmanek, M.; Dobler, M.; Graudenz, M.; Perret, W.; Göbel, G.; Schmidt, M.; Beyer, E.

    Laser beam brazing with copper based filler wire is a widely established technology for joining zinc-coated steel plates in the body-shop. Successful applications are the divided tailgate or the zero-gap joint, which represents the joint between the side panel and the roof-top of the body-in-white. These joints are in direct view to the customer, and therefore have to fulfil highest optical quality requirements. For this reason a stable and efficient laser brazing process is essential. In this paper the current results on quality improvement due to one dimensional laser beam deflections in feed direction are presented. Additionally to the experimental results a transient three-dimensional simulation model for the laser beam brazing process is taken into account. With this model the influence of scanning parameters on filler wire temperature and melt pool characteristics is analyzed. The theoretical predictions are in good accordance with the experimental results. They show that the beam scanning approach is a very promising method to increase process stability and seam quality.

  11. Image Processing In Laser-Beam-Steering Subsystem

    NASA Technical Reports Server (NTRS)

    Lesh, James R.; Ansari, Homayoon; Chen, Chien-Chung; Russell, Donald W.

    1996-01-01

    Conceptual design of image-processing circuitry developed for proposed tracking apparatus described in "Beam-Steering Subsystem For Laser Communication" (NPO-19069). In proposed system, desired frame rate achieved by "windowed" readout scheme in which only pixels containing and surrounding two spots read out and others skipped without being read. Image data processed rapidly and efficiently to achieve high frequency response.

  12. A Laser Lock System using Multiple Overlapping Beams

    NASA Astrophysics Data System (ADS)

    Harper, Stuart; Francis, Ben; Erickson, Christopher; Durfee, Dallin

    2010-10-01

    We describe a system wherein the lock of trapping, ionizing, and ion resonance lasers for a Sr experiment are bootstrapped together in a single neutral atom vapor cell. This is done by overlapping beams to optically pump the atoms into the necessary states.

  13. High efficiency solar cells for laser power beaming applications

    NASA Technical Reports Server (NTRS)

    Jain, Raj K.; Landis, G. A.

    1995-01-01

    Understanding solar cell response to pulsed laser outputs is important for the evaluation of power beaming applications. The time response of high efficiency GaAs and silicon solar cells to a 25 nS monochromatic pulse input is described. The PC-1D computer code is used to analyze the cell current during and after the pulse for various conditions.

  14. Laser induced focusing for over-dense plasma beams

    SciTech Connect

    Schmidt, Peter; Boine-Frankenheim, Oliver; Mulser, Peter

    2015-09-15

    The capability of ion acceleration with high power, pulsed lasers has become an active field of research in the past years. In this context, the radiation pressure acceleration (RPA) mechanism has been the topic of numerous theoretical and experimental publications. Within that mechanism, a high power, pulsed laser beam hits a thin film target. In contrast to the target normal sheath acceleration, the entire film target is accelerated as a bulk by the radiation pressure of the laser. Simulations predict heavy ion beams with kinetic energy up to GeV, as well as solid body densities. However, there are several effects which limit the efficiency of the RPA: On the one hand, the Rayleigh-Taylor-instability limits the predicted density. On the other hand, conventional accelerator elements, such as magnetic focusing devices are too bulky to be installed right after the target. Therefore, we present a new beam transport method, suitable for RPA-like/over-dense plasma beams: laser induced focusing.

  15. An online, energy-resolving beam profile detector for laser-driven proton beams.

    PubMed

    Metzkes, J; Zeil, K; Kraft, S D; Karsch, L; Sobiella, M; Rehwald, M; Obst, L; Schlenvoigt, H-P; Schramm, U

    2016-08-01

    In this paper, a scintillator-based online beam profile detector for the characterization of laser-driven proton beams is presented. Using a pixelated matrix with varying absorber thicknesses, the proton beam is spatially resolved in two dimensions and simultaneously energy-resolved. A thin plastic scintillator placed behind the absorber and read out by a CCD camera is used as the active detector material. The spatial detector resolution reaches down to ∼4 mm and the detector can resolve proton beam profiles for up to 9 proton threshold energies. With these detector design parameters, the spatial characteristics of the proton distribution and its cut-off energy can be analyzed online and on-shot under vacuum conditions. The paper discusses the detector design, its characterization and calibration at a conventional proton source, as well as the first detector application at a laser-driven proton source. PMID:27587116

  16. An online, energy-resolving beam profile detector for laser-driven proton beams

    NASA Astrophysics Data System (ADS)

    Metzkes, J.; Zeil, K.; Kraft, S. D.; Karsch, L.; Sobiella, M.; Rehwald, M.; Obst, L.; Schlenvoigt, H.-P.; Schramm, U.

    2016-08-01

    In this paper, a scintillator-based online beam profile detector for the characterization of laser-driven proton beams is presented. Using a pixelated matrix with varying absorber thicknesses, the proton beam is spatially resolved in two dimensions and simultaneously energy-resolved. A thin plastic scintillator placed behind the absorber and read out by a CCD camera is used as the active detector material. The spatial detector resolution reaches down to ˜4 mm and the detector can resolve proton beam profiles for up to 9 proton threshold energies. With these detector design parameters, the spatial characteristics of the proton distribution and its cut-off energy can be analyzed online and on-shot under vacuum conditions. The paper discusses the detector design, its characterization and calibration at a conventional proton source, as well as the first detector application at a laser-driven proton source.

  17. Developing beam phasing on the Nova laser

    SciTech Connect

    Ehrlich, R.B.; Amendt, P.A.; Dixit, S.N.; Hammel, B.A.; Kalantar, D.H.; Pennington, D.M.; Weiland, T.L.

    1997-03-10

    We are presently adding the capability to irradiate indirectly-driven Nova targets with two rings of illumination inside each end of the hohlraum for studies of time-dependent second Legendre (P2) and time- integrated fourth Legendre (P4) flux asymmetry control. The rings will be formed with specially designed kinoform phase plates (KPPs), which will direct each half of each beam into two separate rings that are nearly uniform azimuthally. The timing and temporal pulse shape of the outer rings will be controlled independently from those of the inner rings, allowing for phasing of the pulse shapes to control time dependent asymmetry. Modifications to the incident beam diagnostics (IBDS) will enable us to verify that acceptable levels of power balance among the contributing segments of each ring have been achieved on each shot. Current techniques for precision beam pointing and timing are expected to be sufficiently accurate for these experiments. We present a design for an affordable retrofit to achieve beam phasing on Nova, results of a simplified demonstration, and calculations highlighting the anticipated benefits.

  18. Numerical analysis of the beam quality and spectrum of wavelength-beam-combined laser diode arrays

    NASA Astrophysics Data System (ADS)

    Tang, Xuan; Wang, Xiao-Jun; Ke, Wei-Wei

    2015-02-01

    In this paper, a numerical model is presented to simulation the performance of the wavelength-beam-combined laser diode arrays (LDA) system. The eigen mode expansion method is used to describe the two-dimensional optical amplification and the strength of field feedback of external cavity. To describe the mode competition in laser diodes, the gain saturation effect is considered. The two-dimension distributions of the carrier concentration, recombination rates, and optical gain are calculated for solving the laser dynamic equation. The Fresnel integration, grating equation and mode overlap integration are used to obtain the feedback coefficient of extent cavity diffraction. Quantum noise is considered to evaluate the spectral linewidth of semiconductor laser. Based on the numerical model, the impact of the mutual optical feedback on the beam quality and spectrum of the LDA is present and analysis.

  19. Influence of periodic compressible vortices on laser beam intensity

    NASA Astrophysics Data System (ADS)

    Weston, C. P.

    1982-12-01

    This study explored the effect of narrow-band, vortex-induced density fluctuations on the beam quality of a laser propagated through the fluctuating flow. The research was a dual investigation. First, the ability to create and characterize 'tailored', fluctuating flows was explored. Second, the degradation of the laser beam due to these various flows was assessed. The flows of periodic vortices were created by cylindrical rods placed at the exit plane of a 1 cm by 10 cm rectangular free jet issuing air at M = .6. Reynolds number based on rod diameter varied from 4,600 to 110,000. Mean and fluctuating mass flux, total pressure and static pressure time histories of the flows were measured in order to derive fluid eddy passage frequency, eddy length and periodic density fluctuation data. Schlieren photographs were obtained for further assessment of the flow fields. A nominal 1 mW laser beam was propagated at two wavelengths transversely through the periodic portion of each flow. The far field beam cross-section was analyzed to determine beam intensity degradation. A Strehl ratio for each flow field was deduced from pseudo-quantitative data.

  20. Gamma-ray generation using laser-accelerated electron beam

    NASA Astrophysics Data System (ADS)

    Park, Seong Hee; Lee, Ho-Hyung; Lee, Kitae; Cha, Yong-Ho; Lee, Ji-Young; Kim, Kyung-Nam; Jeong, Young Uk

    2011-06-01

    A compact gamma-ray source using laser-accelerated electron beam is being under development at KAERI for nuclear applications, such as, radiography, nuclear activation, photonuclear reaction, and so on. One of two different schemes, Bremsstrahlung radiation and Compton backscattering, may be selected depending on the required specification of photons and/or the energy of electron beams. Compton backscattered gamma-ray source is tunable and quasimonochromatic and requires electron beams with its energy of higher than 100 MeV to produced MeV photons. Bremsstrahlung radiation can generate high energy photons with 20 - 30 MeV electron beams, but its spectrum is continuous. As we know, laser accelerators are good for compact size due to localized shielding at the expense of low average flux, while linear RF accelerators are good for high average flux. We present the design issues for a compact gamma-ray source at KAERI, via either Bremsstrahlung radiation or Compton backscattering, using laser accelerated electron beams for the potential nuclear applications.

  1. Ion beam control in laser plasma interaction

    NASA Astrophysics Data System (ADS)

    Kawata, S.; Izumiyama, T.; Sato, D.; Nagashima, T.; Takano, M.; Barada, D.; Gu, Y. J.; Ma, Y. Y.; Kong, Q.; Wang, P. X.; Wang, W. M.

    2016-03-01

    By a two-stage successive acceleration in laser ion acceleration, our 2.5-dimensional particle-in-cell simulations demonstrate a remarkable increase in ion energy by a few hundreds of MeV; the maximum proton energy reaches about 250MeV. The ions are accelerated by the inductive continuous post-acceleration in a laser plasma interaction together with the target normal sheath acceleration and the breakout afterburner mechanism. An intense short-pulse laser generates a strong current by high-energy electrons accelerated, when an intense short- pulse laser illuminates a plasma target. The strong electric current creates a strong magnetic field along the high-energy electron current in the plasma. During the increase phase in the magnetic field strength, the moving longitudinal inductive electric field is induced by the Faraday law, and accelerates the forward-moving ions continously. The multi-stage acceleration provides a unique controllability in the ion energy and its quality.

  2. Improving laser beam coherence - A concept

    NASA Technical Reports Server (NTRS)

    Heflinger, L. O.

    1971-01-01

    Laser frequencies may be reduced to single frequency or selected frequencies. For single frequency performance, spacing of frequencies falls in natural line width. For two or more frequencies, thicker spacing is used. Configuration adapts to operation with Kerr or Pockel cell for Q switching.

  3. Pixel diamond detectors for excimer laser beam diagnostics

    NASA Astrophysics Data System (ADS)

    Girolami, M.; Allegrini, P.; Conte, G.; Salvatori, S.

    2011-05-01

    Laser beam profiling technology in the UV spectrum of light is evolving with the increase of excimer lasers and lamps applications, that span from lithography for VLSI circuits to eye surgery. The development of a beam-profiler, able to capture the excimer laser single pulse and process the acquired pixel current signals in the time period between each pulse, is mandatory for such applications. 1D and 2D array detectors have been realized on polycrystalline CVD diamond specimens. The fast diamond photoresponse, in the ns time regime, suggests the suitability of such devices for fine tuning feedback of high-power pulsed-laser cavities, whereas solar-blindness guarantees high performance in UV beam diagnostics, also under high intensity background illumination. Offering unique properties in terms of thermal conductivity and visible-light transparency, diamond represents one of the most suitable candidate for the detection of high-power UV laser emission. The relatively high resistivity of diamond in the dark has allowed the fabrication of photoconductive vertical pixel-detectors. A semitransparent light-receiving back-side contact has been used for detector biasing. Each pixel signal has been conditioned by a multi-channel read-out electronics made up of a high-sensitive integrator and a Σ-Δ A/D converter. The 500 μs conversion time has allowed a data acquisition rate up to 2 kSPS (Sample Per Second).

  4. Laser beaming demonstrations to high-orbit satellites

    SciTech Connect

    Lipinski, R.J.; Meister, D.C.; Tucker, S.

    1993-12-31

    Laser power beaming to satellites and orbital transfer vehicles requires the accurate pointing of a low-divergence laser beam to its target, whether the target is in the sunlight or the earth`s shadow. The Air Force Phillips Laboratory (AFPL) has demonstrated reduction in the image size of stars by a factor of 10 or more by using laser beacons and adaptive optics for atmospheric compensation. This same technology is applicable to reducing the divergence of laser beams propagated from earth to space. A team of Phillips Laboratory, COMSAT Laboratories, and Sandia National Laboratories plans to demonstrate the state of the art in this area with laser-beaming demonstrations to high-orbit satellites. The demonstrations will utilize the 1.5-m diameter telescope with adaptive optics at the AFPL Starfire Optical Range (SOR) and a ruby laser provided by the Air Force and Sandia (1--50 kill and 6 ms at 694.3 nm). The first targets will be corner-cube retro-reflectors left on the moon by the Apollo 11, 14, and 15 landings. We will attempt to use adaptive optics for atmospheric compensation to demonstrate accurate and reliable beam projection with a series of shots over a span of time and shot angle. We will utilize the return signal from the retro-reflectors to help determine the beam diameter on the moon and the variations in pointing accuracy caused by atmospheric tilt. This will be especially challenging because the retro-reflectors will need to be in the lunar shadow to allow detection over background light. If the results from this experiment are encouraging, we will at a later date direct the beam at a COMSAT satellite in geosynchronous orbit as it goes into the shadow of the earth. We will utilize an onboard monitor to measure the current generated in the solar panels on the satellite while the beam is present. A threshold irradiance of about 4 W/m{sup 2} on orbit is needed for this demonstration.

  5. Laser beaming demonstrations at the Starfire Optical Range

    SciTech Connect

    Lipinski, R.J.; Meister, D.C.; Tucker, S.; Leatherman, P.; Fugate, R.Q.; Maes, C.; Lange, W.J.; Cowan, W.

    1995-03-01

    The ability to acquire, track, and accurately direct a laser beam to a satellite is crucial for power-beaming and laser-communications. To assess the state of the art in this area, a team consisting of Air Force Phillips Laboratory, Sandia National Laboratories, and COMSAT Corporation personnel performed some laser beaming demonstrations to various satellites. A ruby laser and a frequency-doubled YAG laser were used with the Phillips Lab Starfire Optical Range (SOR) beam director for this activity. The ruby laser projected 20 J in 6 ms out the telescope with a beam divergence that increased from 1.4 to 4 times the diffraction limit during that time. The doubled YAG projected 0.09 J in 10 ns at 20 Hz. The SOR team demonstrated the ability to move rapidly to a satellite, center it in the telescope, then lock onto it with the tracker, and establish illumination. Several low-earth-orbit satellites with corner-cube retro-reflectors were illuminated at ranges from 1000 to 6000 km with a beam divergence estimated to be about 20 {mu}radians. The return signal from the ruby laser was collected in a 15-cm telescope, detected by a photomultiplier tube, and recorded at 400 kHz. Rapid variations in intensity (as short at 15 {mu}s) were noted, which may be due to speckles caused by phase interference from light reflected from different retro-reflectors on the satellite. The return light from the YAG was collected by a 35-cm telescope and detected by an intensified CCD camera. The satellite brightened by about a factor of 30 in the sunlight when the laser was turned on, and dimmed back to normal when the 50-{mu}radian point-ahead was turned off. The satellite was illuminated at 1 Hz as it entered the earth`s shadow and followed for about 10 seconds in the shadow. In another demonstration, four neighboring GEO satellites were located and centered in succession with a 3.5-m telescope at a rate of about 16 seconds per satellite.

  6. Laser-driven beam lines for delivering intensity modulated radiation therapy with particle beams

    SciTech Connect

    Hofmann, K. M.; Schell, S.; Wilkens, J. J.

    2013-07-26

    Laser-accelerated particles can provide a promising opportunity for radiation therapy of cancer. Potential advantages arise from combining a compact, cost-efficient treatment unit with the physical advantages in dose delivery of charged particle beams. We consider different dose delivery schemes and the required devices to design a possible treatment unit. The secondary radiation produced in several beam line elements remains a challenge to be addressed.

  7. Design and testing of a refractive laser beam homogenizer

    NASA Astrophysics Data System (ADS)

    Fernelius, N. C.; Bradley, K. R.; Hoekstra, B. L.

    1984-09-01

    A survey is made of various techniques to create a homogeneous or flat top laser beam profile. A refractive homogenizer was designed for use with a ND:YAG laser with output at its fundamental (1.06 micrometer) and frequency doubled (532 nm) modes. The system consists of a 2X beam expander and two faceted cylindrical lenses with differing focal lengths. Each cylindrical lens focusses its input into a strip the width of a facet. By orienting their axes at a 90 degree angle and focussing them on the same plane, the beam is concentrated into a square focus. Formulae for calculating the facet angles are derived and a FORTRAN computer square focus. Formulae for calculating the facet angles are derived and a FORTRAN computer program was written to calculate them with a precision greater than one is able to fabricate them.

  8. LASER-BASED PROFILE MONITOR FOR ELECTRON BEAMS

    SciTech Connect

    Ross, Marc C

    2003-05-27

    High performance TeV energy electron / positron colliders (LC) are the first machines to require online, non-invasive beam size monitors for micron and sub-micron for beam phase space optimization. Typical beam densities in the LC are well beyond the threshold density for single pulse melting and vaporization of any material, making conventional wire scanners ineffective. Using a finely focused, diffraction limited high power laser, it is possible to devise a sampling profile monitor that, in operation, resembles a wire scanner. Very high resolution laser-based profile monitors have been developed and tested, first at FFTB (SLAC) and later at SLC and ATF. The monitor has broad applicability and we review here the technology, application and status of ongoing research programs.

  9. Simultaneous ion beam profile scan using a single laser source

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Long, C.; Huang, C.; Dickson, R.; Aleksandrov, A.

    2013-01-01

    We report on the world’s first experiment of a simultaneous profile scan of the hydrogen ion (H-) beam using a laser wire system. The system was developed and brought to operational level of application at the superconducting linac of the Spallation Neutron Source accelerator complex. The laser wire profile scanner is based on a photodetachment process and therefore can be conducted on a 1-MW neutron production H- beam in a nonintrusive manner. The new simultaneous profile scanning system allows one to simultaneously measure profiles of the H- beam at nine different locations of the linac with high speed and accuracy, and therefore provides a unique tool for accelerator tuning and physics study. This paper describes the design, optical system and software platform developments, and measurement results of the simultaneous profile scanning system.

  10. Laser beam apparatus and method for analyzing solar cells

    DOEpatents

    Staebler, David L.

    1980-01-01

    A laser beam apparatus and method for analyzing, inter alia, the current versus voltage curve at the point of illumination on a solar cell and the open circuit voltage of a solar cell. The apparatus incorporates a lock-in amplifier, and a laser beam light chopper which permits the measurement of the AC current of the solar cell at an applied DC voltage at the position on the solar cell where the cell is illuminated and a feedback scheme which permits the direct scanning measurements of the open circuit voltage. The accuracy of the measurement is a function of the intensity and wavelength of the laser light with respect to the intensity and wavelength distribution of sunlight and the percentage the dark current is at the open circuit voltage to the short circuit current of the solar cell.

  11. Observation of laser multiple filamentation process and multiple electron beams acceleration in a laser wakefield accelerator

    SciTech Connect

    Li, Wentao; Liu, Jiansheng; Wang, Wentao; Chen, Qiang; Zhang, Hui; Tian, Ye; Zhang, Zhijun; Qi, Rong; Wang, Cheng; Leng, Yuxin; Li, Ruxin; Xu, Zhizhan

    2013-11-15

    The multiple filaments formation process in the laser wakefield accelerator (LWFA) was observed by imaging the transmitted laser beam after propagating in the plasma of different density. During propagation, the laser first self-focused into a single filament. After that, it began to defocus with energy spreading in the transverse direction. Two filaments then formed from it and began to propagate independently, moving away from each other. We have also demonstrated that the laser multiple filamentation would lead to the multiple electron beams acceleration in the LWFA via ionization-induced injection scheme. Besides, its influences on the accelerated electron beams were also analyzed both in the single-stage LWFA and cascaded LWFA.

  12. Energy gain and spectral tailoring of ion beams using ultra-high intensity laser beams

    NASA Astrophysics Data System (ADS)

    Prasad, Rajendra; Swantusch, Marco; Cerchez, Mirela; Spickermann, Sven; Auorand, Bastian; Wowra, Thomas; Boeker, Juergen; Willi, Oswald

    2015-11-01

    The field of laser driven ion acceleration over the past decade has produced a huge amount of research. Nowadays, several multi-beam facilities with high rep rate system, e.g. ELI, are being developed across the world for different kinds of experiments. The study of interaction dynamics of multiple beams possessing ultra-high intensity and ultra-short pulse duration is of vital importance. Here, we present the first experimental results on ion acceleration using two ultra-high intensity beams. Thanks to the unique capability of Arcturus laser at HHU Düsseldorf, two almost identical, independent beams in laser parameters such as intensity (>1020 W/cm2), pulse duration (30 fs) and contrast (>1010), could be accessed. Both beams are focused onto a 5 μm thin Ti target. While ensuring spatial overlap of the two beams, at relative temporal delay of ~ 50 ps (optimum delay), the proton and carbon ion energies were enhanced by factor of 1.5. Moreover, strong modulation in C4+ions near the high energy cut-off is observed later than the optimum delay for the proton enhancement. This offers controlled tailoring of the spectral content of heavy ions.

  13. ELIMED, future hadrontherapy applications of laser-accelerated beams

    NASA Astrophysics Data System (ADS)

    Cirrone, Giuseppe A. P.; Carpinelli, Massimo; Cuttone, Giacomo; Gammino, Santo; Bijan Jia, S.; Korn, Georg; Maggiore, Mario; Manti, Lorenzo; Margarone, Daniele; Prokupek, Jan; Renis, Marcella; Romano, Francesco; Schillaci, Francesco; Tomasello, Barbara; Torrisi, Lorenzo; Tramontana, Antonella; Velyhan, Andriy

    2013-12-01

    Laser-ion acceleration has recently gained a great interest as an alternative to conventional and more expensive acceleration techniques. These ion beams have desirable qualities such as small source size, high luminosity and small emittance to be used in different fields as Nuclear Physics, Medical Physics, etc. This is very promising specially for the future perspective of a new concept of hadrontherapy based on laser-based devices could be developed, replacing traditional accelerating machines. Before delivering laser-driven beams for treatments they have to be handled, cleaned from unwanted particles and characterized in order to have the clinical requirements. In fact ion energy spectra have exponential trend, almost 100% energy spread and a wide angular divergence which is the biggest issue in the beam transport and, hence, in a wider use of this technology. In order to demonstrate the clinical applicability of laser-driven beams new collaboration between ELI-Beamlines project researchers from Prague (Cz) and a INFN-LNS group from Catania (I) has been already launched and scientists from different countries have already express their will in joining the project. This cooperation has been named ELIMED (MEDical application at ELIBeamlines) and will take place inside the ELI-Beamlines infrastructure located in Prague. This work describes the schedule of the ELIMED project and the design of the energy selector which will be realized at INFN-LNS. The device is an important part of the whole transport beam line which will be realised in order to make the ion beams suitable for medical applications.

  14. Beam shaping to provide round and square-shaped beams in optical systems of high-power lasers

    NASA Astrophysics Data System (ADS)

    Laskin, Alexander; Laskin, Vadim

    2016-05-01

    Optical systems of modern high-power lasers require control of irradiance distribution: round or square-shaped flat-top or super-Gaussian irradiance profiles are optimum for amplification in MOPA lasers and for thermal load management while pumping of crystals of solid-state ultra-short pulse lasers to control heat and minimize its impact on the laser power and beam quality while maximizing overall laser efficiency, variable profiles are also important in irradiating of photocathode of Free Electron lasers (FEL). It is suggested to solve the task of irradiance re-distribution using field mapping refractive beam shapers like piShaper. The operational principle of these devices presumes transformation of laser beam intensity from Gaussian to flat-top one with high flatness of output wavefront, saving of beam consistency, providing collimated output beam of low divergence, high transmittance, extended depth of field, negligible residual wave aberration, and achromatic design provides capability to work with ultra-short pulse lasers having broad spectrum. Using the same piShaper device it is possible to realize beams with flat-top, inverse Gauss or super Gauss irradiance distribution by simple variation of input beam diameter, and the beam shape can be round or square with soft edges. This paper will describe some design basics of refractive beam shapers of the field mapping type and optical layouts of their applying in optical systems of high-power lasers. Examples of real implementations and experimental results will be presented as well.

  15. Laser beam shaping profiles and propagation.

    PubMed

    Shealy, David L; Hoffnagle, John A

    2006-07-20

    We consider four families of functions--the super-Gaussian, flattened Gaussian, Fermi-Dirac, and super-Lorentzian--that have been used to describe flattened irradiance profiles. We determine the shape and width parameters of the different distributions, when each flattened profile has the same radius and slope of the irradiance at its half-height point, and then we evaluate the implicit functional relationship between the shape and width parameters for matched profiles, which provides a quantitative way to compare profiles described by different families of functions. We conclude from an analysis of each profile with matched parameters using Kirchhoff-Fresnel diffraction theory and M2 analysis that the diffraction patterns as they propagate differ by small amounts, which may not be distinguished experimentally. Thus, beam shaping optics is designed to produce either of these four flattened output irradiance distributions with matched parameters will yield similar irradiance distributions as the beam propagates.

  16. Parametric distortion of the optical absorption edge of a magnetic semiconductor by a strong laser field

    SciTech Connect

    Nunes, O.A.C.

    1985-09-15

    The influence of a strong laser field on the optical absorption edge of a direct-gap magnetic semiconductor is considered. It is shown that as the strong laser intensity increases the absorption coefficient is modified so as to give rise to an absorption tail below the free-field forbidden gap. An application is made for the case of the EuO.

  17. Photovoltaic cells for laser power beaming

    NASA Technical Reports Server (NTRS)

    Landis, Geoffrey A.; Jain, Raj K.

    1992-01-01

    To better understand cell response to pulsed illumination at high intensity, the PC-1DC finite-element computer model was used to analyze the response of solar cells to pulsed laser illumination. Over 50% efficiency was calculated for both InP and GaAs cells under steady-state illumination near the optimum wavelength. The time-dependent response of a high-efficiency GaAs concentrator cell to a laser pulse was modelled, and the effect of laser intensity, wavelength, and bias point was studied. Designing a cell to accommodate pulsed input can be done either by accepting the pulsed output and designing a cell to minimize adverse effects due to series resistance and inductance, or to design a cell with a long enough minority carrier lifetime, so that the output of the cell will not follow the pulse shape. Two such design possibilities are a monolithic, low-inductance voltage-adding GaAs cell, or a high-efficiency, light-trapping silicon cell. The advantages of each design will be discussed.

  18. Laser beam control and diagnostic systems for the copper-pumped dye laser system at Lawrence Livermore National Laboratory

    SciTech Connect

    Bliss, E.S.; Peterson, R.L.; Salmon, J.T.; Thomas, R.A.

    1992-11-01

    The laser system described in the previous paper is used for experiments in which success requires tight tolerances on beam position, direction, and wavefront. Indeed, the optimum performance of the laser itself depends on careful delivery of copper laser light to the dye amplifiers, precise propagation of dye laser beams through restricted amplifier apertures, and accurate monitoring of laser power at key locations. This paper describes the alignment systems, wavefront correction systems, and laser diagnostics systems which ensure that the control requirements of both the laser and associated experiments are met. Because laser isotope separation processes utilize more than one wavelength, these systems monitor and control multiple wavelengths simultaneously.

  19. Transient self-action of periodically modulated laser beams

    NASA Astrophysics Data System (ADS)

    Derbov, Vladimir L.; Serov, V. V.; Plastun, I. L.; Shilov, S. V.

    2003-09-01

    We study the self-action of an amplitude-modulated beam in a two-level saturable absorbing medium. We also consider the radial quadratic dependence of the linear refraction index to apply the results to doped waveguides. As the modulation period approaches the relaxation times, the medium response is no more instantaneous, so that one should solve the full set of Maxwell-Bloch equations. We propose a second-order scheme with the Gauss-Laguerre transformation of the transverse field pattern. A simplified approach based on the synchronous interaction approximation is used for thin layers. We analyze the transient behavior of the medium response and its manifestation in the modulation of the beam diffracting after a thin saturable absorber. Nonlinear distortions of the modulation signal passed through a doped waveguide appeared to be unexpectedly small compared with those of the local polarization and population difference.

  20. Vectorial detection of sub-microscale capillary curvature by laser beam profile

    NASA Astrophysics Data System (ADS)

    Verma, Gopal; Singh, Kamal P.

    2015-10-01

    We demonstrate a simple and non-invasive optical technique to detect direction and magnitude of long-range, sub-microscale capillary curvature of fluid interfaces in various situations. By analyzing magnitude and direction of the distorted spatial profile of the laser beam, following its weak Fresnel's reflection from the air-water interface, ultra-low curvature of 0.1 μm-1 caused by dipped slides, glass tubes, and microscopic twisted silk fibers was measured up to six capillary lengths away from the object. The flexibility of this technique allows us to measure curvature of remotely placed fluid-fluid interfaces and interaction between capillary curves of multiple objects. The high sensitivity of our technique is demonstrated in measuring magnetic susceptibility of water and the full spatial profile of deformation under weak magnetic field. This technique might find applications in precision measurements in optofluidics and interface physics.

  1. Advances In Laser Beam Profiling Using A Pyroelectric Staring Array

    NASA Astrophysics Data System (ADS)

    Harper, Brian M.

    1988-10-01

    Laser beam profiling measurement is a difficult task to perform. Various techniques have evolved over the past twenty years. These have ranged from intercepting the beam with a simple piece of paper and viewing it by eye to x,y scanning of the beam with a simple detector. The drawbacks of these approaches range from inaccuracy to slow capture of data. A need exists for a fast real time detector that can operate in a staring array mode. It must use a wide spectral range to cover lasers operating out of the visual waveband, particularly the middle and far infrared. High definition staring arrays operating at these w.ivelengths are only at the research phase, except one. The pyroelectric vidicon has been commercially available since the 1970's. Not often thought of as a staring array it is however, a very good one. A 16mm slice of D.T.G.S. gives a circular array of approx. 200 by 200 pixels. Spectral response is flat from ipm to 20μm when combined with a ZnSe faceplate. Signal readout is by scanning with an electron beam. These devices are used in low cost thermal imagers operating in the 8-14μm window. We have optimised the tube and camera operation to perform laser beam profiling. These changes take into account the much higher power available from a laser and have concentrated on extending dynamic range. This has lead to a peak signal to peak noise ratio of 30:1. Care has been paid to the optical path to minimise unwanted moire fringes. Maximum power for signal overload and damage threshold have been verified together with ensuring a linear transfer function in the normal operating range. Both C.W. and pulsed lasers can be accommodated. A mechanical shutter allows capture of single pulses from lasers of less than 500Hz rep rate. The research allows TV images of laser profiles. However, other means is display and analysis have been investigated. Firstly a pseudo 3D display utilising an oscilloscope providing real time, low cost performance. Secondly computer

  2. Refractive beam shapers for material processing with high power single mode and multimode lasers

    NASA Astrophysics Data System (ADS)

    Laskin, Alexander; Laskin, Vadim

    2013-02-01

    The high power multimode fiber-coupled laser sources, like solid state lasers or laser diodes as well as single mode and multimode fiber lasers, are now widely used in various industrial laser material processing technologies like metal or plastics welding, cladding, hardening, brazing, annealing. Performance of these technologies can be essentially improved by varying the irradiance profile of a laser beam with using beam shaping optics, for example, the field mapping refractive beam shapers like piShaper. Operational principle of these devices presumes transformation of laser beam irradiance distribution from Gaussian to flattop, super-Gauss, or inverse-Gauss profile with high flatness of output wave front, conserving of beam consistency, providing collimated output beam of low divergence, high transmittance, extended depth of field. Important feature of piShaper is in capability to operate with TEM00 and multimode lasers, the beam shapers can be implemented not only as telescopic optics but also as collimating systems, which can be connected directly to fiber-coupled lasers or fiber lasers, thus combining functions of beam collimation and irradiance transformation. This paper will describe some features of beam shaping of high-power laser sources, including multimode fiber coupled lasers, and ways of adaptation of beam shaping optical systems design to meet requirements of modern laser technologies. Examples of real implementations will be presented as well.

  3. Beam Conditioning for Free Electron Lasers:Consequences and Methods

    SciTech Connect

    Wolski, A.; Penn, G.; Sessler, A.; Wurtele, J.; /LBL, Berkeley /UC, Berkeley, Astron. Dept.

    2010-12-14

    The consequences of beam conditioning in four example cases [VISA, a soft x-ray free-electron laser (FEL), LCLS, and a 'Greenfield' FEL] are examined. It is shown that in emittance limited cases, proper conditioning reduces sensitivity to the transverse emittance and, furthermore, allows for stronger focusing in the undulator. Simulations show higher saturation power, with gain lengths reduced by a factor of 2 or more. The beam dynamics in a general conditioning system are studied, with 'matching conditions' derived for achieving conditioning without growth in the effective emittance. Various conditioning lattices are considered, and expressions derived for the amount of conditioning provided in each case when the matching conditions are satisfied. These results show that there is no fundamental obstacle to producing beam conditioning, and that the problem can be reduced to one of proper lattice design. Nevertheless, beam conditioning will not be easy to implement in practice.

  4. Proceedings of the laser beam propagation in the atmosphere

    SciTech Connect

    Leader, J.C.

    1983-01-01

    Among the topics discussed are the atmospheric attenuation of laser radiation, the determination of atmospheric properties from lidar measurements, laser transmission measurement limitations due to correlated atmospheric effects, high spatial resolution studies of propagation, multiple scattering of laser beam propagation in clouds, the probability density of the irradiance in atmospheric turbulence, source statistics effects on irradiance scintillations in turbulence, and numerical solutions of the fourth-moment equation. Also discussed are the characteristics and effects of speckle propagation through turbulence, the application of random medium propagation theory to communication and radar system analyses, multiple scattering corrections to the Beer-Lambert Law, millimeter wave propagation through a clear atmosphere, endoatmospheric laser arrays for thermal blooming environments, the wavelength dependence of adaptive optics compensation, time-dependent thermal blooming in axial pipe flow, and turbulence-induced adaptive optics performance degradation.

  5. The random walk of a drilling laser beam

    NASA Technical Reports Server (NTRS)

    Anthony, T. R.

    1980-01-01

    The disregistry of holes drilled with a pulse laser beam in 330-micron-thick single-crystal silicon-on-sapphire wafers is examined. The exit positions of the holes were displaced from the hole entrance positions on the opposing face of the wafer, and this random displacement increased with the number of laser pulses required. A model in which the bottom of the drill hole experiences small random displacements during each laser pulse is used to describe the experimental observations. It is shown that the average random displacement caused by each pulse is only a few percent of the hole diameter and can be reduced by using as few laser pulses as necessary while avoiding the cracking and spalling of the wafer that occur with a hole drilled with a single pulse.

  6. Beaconless stochastic parallel gradient descent laser beam control: numerical experiments.

    PubMed

    Piatrou, Piotr; Roggemann, Michael

    2007-09-20

    We apply a target-in-the-loop strategy to the case of adaptive optics beam control in the presence of strong atmospheric turbulence for air-to-ground directed energy laser applications. Using numerical simulations we show that in the absence of a cooperative beacon to probe the atmosphere it is possible to extract information suitable for effective beam control from images of the speckled and strongly turbulence degraded intensity distribution of the laser energy at the target. We use a closed-loop, single-deformable-mirror adaptive optics system driven by a target-in-the-loop stochastic parallel gradient descent optimization algorithm minimizing a mean-radius performance metric defined on the image of the laser beam intensity distribution formed at the receiver. We show that a relatively low order 25-channel zonal adaptive optical beam control system controlled in this way is capable of achieving a high degree of turbulence compensation with respect to energy concentration if the tilt can be corrected separately.

  7. Diode laser power module for beamed power transmission

    NASA Technical Reports Server (NTRS)

    Choi, S. H.; Williams, M. D.; Lee, J. H.; Conway, E. J.

    1991-01-01

    Recent progress with powerful, efficient, and coherent monolithic diode master-oscillator/power-amplifier (M-MOPA) systems is promising for the development of a space-based diode laser power station. A conceptual design of a 50-kW diode laser power module was made for space-based power stations capable of beaming coherent power to the moon, Martian rovers, or other satellites. The laser diode power module consists of a solar photovoltaic array or nuclear power source, diode laser arrays (LDAs), a phase controller, beam-steering optics, a thermal management unit, and a radiator. Thermal load management and other relevant aspects of the system (such as power requirements and system mass) are considered. The 50-kW power module described includes the highest available efficiency of LD M-MOPA system to date. However, the overall efficiency of three amplifier stages, including the coupling efficiency, turns out to be 55.5 percent. Though a chain of PA stages generates a high-power coherent beam, there is a penalty due to the coupling loss between stages. The specific power of the 50-kW module using solar power is 6.58 W/kg.

  8. Undulator radiation driven by laser-wakefield accelerator electron beams

    NASA Astrophysics Data System (ADS)

    Wiggins, S. M.; Anania, M. P.; Welsh, G. H.; Brunetti, E.; Cipiccia, S.; Grant, P. A.; Reboredo, D.; Manahan, G.; Grant, D. W.; Jaroszynski, D. A.

    2015-05-01

    The Advanced Laser-Plasma High-Energy Accelerators towards X-rays (ALPHA-X) programme is developing laserplasma accelerators for the production of ultra-short electron bunches with subsequent generation of coherent, bright, short-wavelength radiation pulses. The new Scottish Centre for the Application of Plasma-based Accelerators (SCAPA) will develop a wide range of applications utilising such light sources. Electron bunches can be propagated through a magnetic undulator with the aim of generating fully coherent free-electron laser (FEL) radiation in the ultra-violet and Xrays spectral ranges. Demonstration experiments producing spontaneous undulator radiation have been conducted at visible and extreme ultra-violet wavelengths but it is an on-going challenge to generate and maintain electron bunches of sufficient quality in order to stimulate FEL behaviour. In the ALPHA-X beam line experiments, a Ti:sapphire femtosecond laser system with peak power 20 TW has been used to generate electron bunches of energy 80-150 MeV in a 2 mm gas jet laser-plasma wakefield accelerator and these bunches have been transported through a 100 period planar undulator. High peak brilliance, narrow band spontaneous radiation pulses in the vacuum ultra-violet wavelength range have been generated. Analysis is provided with respect to the magnetic quadrupole beam transport system and subsequent effect on beam emittance and duration. Requirements for coherent spontaneous emission and FEL operation are presented.

  9. Ion Beam Analysis applied to laser-generated plasmas

    NASA Astrophysics Data System (ADS)

    Cutroneo, M.; Macková, A.; Havranek, V.; Malinsky, P.; Torrisi, L.; Kormunda, M.; Barchuk, M.; Ullschmied, J.; Dudzak, R.

    2016-04-01

    This paper presents the research activity on Ion Beam Analysis methods performed at Tandetron Laboratory (LT) of the Institute of Nuclear Physics AS CR, Rez, Czech Republic. Recently, many groups are paying attention to implantation by laser generated plasma. This process allows to insert a controllable amount of energetic ions into the surface layers of different materials modifying the physical and chemical properties of the surface material. Different substrates are implanted by accelerated ions from plasma through terawatt iodine laser, at nominal intensity of 1015 W/cm2, at the PALS Research Infrastructure AS CR, in the Czech Republic. This regime of the laser matter interaction generates, multi-MeV proton beams, and multi-charged ions that are tightly confined in time (hundreds ps) and space (source radius of a few microns). These ion beams have a much lower transverse temperature, a much shorter duration and a much higher current than those obtainable from conventional accelerators. The implementation of protons and ions acceleration driven by ultra-short high intensity lasers is exhibited by adopting suitable irradiation conditions as well as tailored targets. An overview of implanted targets and their morphological and structural characterizations is presented and discussed.

  10. Evolution of a Gaussian laser beam in warm collisional magnetoplasma

    NASA Astrophysics Data System (ADS)

    Jafari, M. J.; Jafari Milani, M. R.; Niknam, A. R.

    2016-07-01

    In this paper, the spatial evolution of an intense circularly polarized Gaussian laser beam propagated through a warm plasma is investigated, taking into account the ponderomotive force, Ohmic heating, external magnetic field, and collisional effects. Using the momentum transfer and energy equations, both modified electron temperature and electron density in plasma are obtained. By introducing the complex dielectric permittivity of warm magnetized plasma and using the complex eikonal function, coupled differential equations for beam width parameter are established and solved numerically. The effects of polarization state of laser and magnetic field on the laser spot size evolution are studied. It is observed that in case of the right-handed polarization, an increase in the value of external magnetic field causes an increase in the strength of the self-focusing, especially in the higher values, and consequently, the self-focusing occurs in shorter distance of propagation. Moreover, the results demonstrate the existence of laser intensity and electron temperature ranges where self-focusing can occur, while the beam diverges outside of these regions; meanwhile, in these intervals, there exists a turning point for each of intensity and temperature in which the self-focusing process has its strongest strength. Finally, it is found that the self-focusing effect can be enhanced by increasing the plasma frequency (plasma density).

  11. Beam profile measurement and evaluation of far field high energy laser

    NASA Astrophysics Data System (ADS)

    Yang, Pengling; Feng, Guobin; Wang, Zhenbao; Wang, Ping; Wu, Yong; Zhang, Jianmin; Cheng, Shaowu; Feng, Gang; Wang, Fei; Shao, Bibo

    2015-05-01

    The far field beam profile is of significant importance to the analysis of the atmospheric propagation effect and evaluation of the beam control capability, tracking and aiming precision of laser system. In the paper, technology of laser beam measurement such as mid-infrared laser detection at wide temperature range, power density attenuation, photoelectric and calorimetric compound method for laser measurement, synchronous detecting of multi-channel pulsed signal are introduced. A series of instrumented target with detector array are developed for laser beam power density distribution measurement at far field. The power in the bucket, strehl ratio, centroid and jitter of beam can be calculated from the measured results.

  12. Method and apparatus for monitoring the power of a laser beam

    DOEpatents

    Paris, R.D.; Hackel, R.P.

    1996-02-06

    A method for monitoring the power of a laser beam in real time is disclosed. At least one optical fiber is placed through the laser beam, where a portion of light from the laser beam is coupled into the optical fiber. The optical fiber may be maintained in a stationary position or moved periodically over a cross section of the laser beam to couple light from each area traversed. Light reaching both fiber ends is monitored according to frequency and processed to determine the power of the laser beam. 6 figs.

  13. Method and apparatus for monitoring the power of a laser beam

    DOEpatents

    Paris, Robert D.; Hackel, Richard P.

    1996-01-01

    A method for monitoring the power of a laser beam in real time is disclosed. At least one optical fiber is placed through the laser beam, where a portion of light from the laser beam is coupled into the optical fiber. The optical fiber may be maintained in a stationary position or moved periodically over a cross section of the laser beam to couple light from each area traversed. Light reaching both fiber ends is monitored according to frequency and processed to determine the power of the laser beam.

  14. A first approach to the detection and equalization of distorted latent fingerprints and microtraces on non-planar surfaces with confocal laser microscopy

    NASA Astrophysics Data System (ADS)

    Kirst, Stefan; Clausing, Eric; Dittmann, Jana; Vielhauer, Claus

    2012-10-01

    Fingerprints and microtraces play an important role as evidence within the field of criminalistics. Their conservative acquisition processes, are established, but are altering and impurifying the traces often. In case of microtraces even the integrity of the trace complex is affected. Using contactless methods, the acquisition process becomes non-invasiv and repeatable, but might be distorting on the other hand, when non-planar substrates are in use. Detecting and dealing with distortion in contactless aquired scans of non-planar surfaces is a novel field of research. Nowadays highly distorted fingerprints can only be used, if the substrate can be manually distorted by destroying or deforming it. In this paper we suggest methods for detection and equalization of distortion for use in combination of types of traces. Therefore we define different types of distortion in fingerprints and microtraces. A standardization of types is necessary to develop different solution for equalization. For usage within the field of forensics, each method is evaluated via proper error rates and adaptively used to acquire fingerprints and microtraces. Using our techniques, we are able to detect distortion and equalize fingerprints to support the investigators work. In case of microtraces the presented methods can even be used to equalize mircotraces themselves for better determination of their scale and topology. For all scans the confocal 3D laser microscope "Keyence VK-X110" is used to gather color-, intensity- and topography information in 22 different measurement conditions within 6 different samples consisting of a total of 880 scans. Despite our achievements in the field of distortion detection and equalization there are still challenges, like the non-isometric projection, that need to be focused on. Also, the presented equalization methods may not completely remove any kind of distortion, such as added by deformation. Therefore we suggest and discuss future work for improving the

  15. EUV Scintillator for Localization and Detection of Laser Beam

    NASA Astrophysics Data System (ADS)

    Monserud, Nils; Urabanski, Lukasz; Malm, Eric; Brown, Christopher; Marconi, Mario

    2011-10-01

    We set out to find a means of detecting and locating an EUV laser beam at the wavelength of 46.9 nm in real time. This will facilitate the alignment of our experiments in nano-patterning, nano-fabrication, and holography, consequently allowing multiple experiments to be aligned simultaneously. Methods of detection are either CCD cameras or prints made with Poly(methyl methacrylate) (PMMA) on a coated wafer, neither of which are efficient to operate. We describe the implementation of an alternative imaging method which combines a phosphor scintillator and a web-cam. Using a phosphor scintillator screen provided by Applied Scintillations Technologies Limited the detection and localization of the EUV laser beam at 46.9 nm was seen consistently through reflection providing a distinct image of the beam in the initial tests. We were able to capture an image of the beam using the webcam through the use of a user interface developed in labview which allowed a snap shot to be taken at the exact moment the beam past through the screen.

  16. A new beam source for free electron lasers

    SciTech Connect

    Wang, M.C.; Wang, Z.J.; Zhu, J.B.

    1995-12-31

    A high power, high current density and high voltage electron beam was generated with the pseudospark discharge (PS), this is a new beam source for free electron lasers. The design and construction of the pseudospark discharge was described, the device has low cost and is easy to fabricate. The experiments are presented, the configuration parameters of the modified pulse line accelerator (PLA) are as follows. The PS hollow cavity has a 3 cm diameter and 4.1 cm long. The discharge chamber consists of planar cathode with hollow cavity, sets of intermediate electrodes and insulators with a common channel, and a planar anode. The electrodes are made of brass and the insulators are made of Plexiglas. The diameter of the channel is 3.2 mm. The anode-cathode gap distance is varied in 10-100 mm. The electron beams have voltage of 200 KeV, current of 2 KA and beam diameter of 1mm. The beam penetrated a 0.3 mm hole on a copper foil of 0.05 mm thick at the distance of 5 cm from the anode and penetrated a 0.6 mm hole on an acid-sensitive film at the distance of 15 cm. A compact free electron laser with a table size is discussed.

  17. Measuring effective area of spots from pulsed laser beams

    NASA Astrophysics Data System (ADS)

    Stratan, Aurel; Zorila, Alexandru; Rusen, Laurentiu; Nemes, George

    2014-12-01

    The effective area of a laser spot is an important quantity used to characterize the laser-induced damage threshold of optical materials according to ISO 21254-1:2011 standard. A method for measuring the effective area/diameter of spots from pulsed laser beams using charge-coupled device camera-based beam profilers is presented. Factors affecting the measurement's accuracy, as the background noise and the size of the summation area, were evaluated using MATLAB. To minimize the noise contribution, we use an iterative method similar to the one used to measure the second-moment-based spot sizes. We find that the two analyzed components of the background noise, its zero-mean noise and its offset, have an opposite effect on the measurements of the effective area/diameter as compared with the second-moment-based measurements. We prove that there is an upper limit of the relative error of such iterative measurements of effective area, the iteration limit parameter, and that it is a measurable quantity. We measure the effective area/diameter of laser spots with different sizes from a Nd:YAG laser at 1064 nm, 6 ns pulse duration, 10 Hz repetition frequency, and estimate the standard uncertainty of the measurements. Further, we generalize the effective area/diameter concept to include elongated (elliptical/rectangular) spots.

  18. Vortex array laser beam generation from a Dove prism-embedded unbalanced Mach-Zehnder interferometer.

    PubMed

    Chu, Shu-Chun; Yang, Chao-Shun; Otsuka, Kenju

    2008-11-24

    This paper proposes a new scheme for generating vortex laser beams from a laser. The proposed system consists of a Dove prism embedded in an unbalanced Mach-Zehnder interferometer configuration. This configuration allows controlled construction of p x p vortex array beams from Ince-Gaussian modes, IG(e) (p,p) modes. An incident IG(e)(p,p) laser beam of variety order p can easily be generated from an end-pumped solid-state laser system with an off-axis pumping mechanism. This study simulates this type of vortex array laser beam generation, analytically derives the vortex positions of the resulting vortex array laser beams, and discusses beam propagation effects. The resulting vortex array laser beam can be applied to optical tweezers and atom traps in the form of two-dimensional arrays, or used to study the transfer of angular momentum to micro particles or atoms (Bose-Einstein condensate).

  19. Spatter Formation in Laser Welding with Beam Oscillation

    NASA Astrophysics Data System (ADS)

    Schweier, M.; Heins, J. F.; Haubold, M. W.; Zaeh, M. F.

    The investigation presented in this paper aims on a quantitative analysis of spatter formation in laser beam welding with superposed beam oscillation. After a discussion of design space limitations, which result from the scanner dynamics and theoretical considerations on the welding process itself, an optimal experimental design is created. By the use of high speed camera imaging, spatters were captured during statistically designed welding experiments and correlations between the number of spatters and the welding parameters have been derived. To evaluate the spatter characteristics in the high speed videos, a state space approach was applied, which is based on automated image data processing.

  20. Laser beam self-focusing in the atmosphere

    SciTech Connect

    Rubenchik, A M; Fedoruk, M P; Turitsyn, S K

    2008-09-09

    We propose to exploit a self-focusing effect in the atmosphere to assist delivering powerful laser beams from orbit to the ground. We demonstrate through numerical modeling that if the self-focusing length is comparable with the atmosphere height the self-focusing can reduce the spot size on the ground well below the diffraction limited one without beam quality degradation. The use of light self-focusing in the atmosphere can greatly relax the requirements for the orbital optics and ground receivers.

  1. Asymmetrical prism for beam shaping of laser diode stacks.

    PubMed

    Zeng, Xiaodong; Cao, Changqing; An, Yuying

    2005-09-10

    A beam-shaping scheme for a laser diode stack to obtain a flattop output intensity profile is proposed. The shaping element consists of an asymmetrical glass prism. The large divergence-angle compression in the direction perpendicular to the junction plane and the small divergence-angle expansion in the parallel direction are performed simultaneously by a single shaping element. The transformation characteristics are presented, and the optimization performance is investigated based on the ray-tracing method. Analysis shows that a flattop intensity profile can be obtained. This beam-shaping system can be fabricated easily and has a large alignment tolerance.

  2. Electron capture acceleration channel in a slit laser beam

    SciTech Connect

    Wang, P. X.; Scheid, W.; Ho, Y. K.

    2007-03-12

    Using numerical simulations, the authors find that the electrons can be captured and accelerated to high energies (GeV) in a slit laser beam with an intensity of I{lambda}{sup 2}{approx}10{sup 20} W/cm{sup 2} {mu}m{sup 2}, where {lambda} is the laser wavelength in units of {mu}m. The range of the optimum incident energy is very wide, even up to GeV. These results are of interest for experiments because the relatively low intensity can be achieved with present chirped pulse amplification technique and a wide range of incident energies means that a multistage acceleration is possible.

  3. The Final Focus Test Beam laser referene system

    SciTech Connect

    Bressler, V.E.; Ruland, R.E.

    1993-05-01

    The original design for the SLAC linac included an alignment reference system with 270 diffraction gratings situated along the 3000 meter linac. These gratings have provided SLAC with a global reference line repeatable to within 200 micro meters. For the Final Focus Test Beam, this laser system has been extended and 13 new diffraction gratings have been installed. Improvements targets and the availability of new instruments allows us to evaluate the performance of the laser reference system at the 510 micro meter level. An explanation of the system and the results of our evaluation are presented.

  4. Cold-atom dynamics in crossed-laser-beam waveguides

    SciTech Connect

    Torrontegui, E.; Muga, J. G.; Echanobe, J.; Ruschhaupt, A.; Guery-Odelin, D.

    2010-10-15

    We study the dynamics of neutral cold atoms in an L-shaped crossed-beam optical waveguide formed by two perpendicular red-detuned lasers of different intensities and a blue-detuned laser at the corner. The motion in one sense is optimized, and the motion in the other sense may be suppressed even if it is energetically allowed. Quantum and classical simulations are performed and give similar results. Complemented with a vibrational cooling process we find a range of parameters for which this setting works as a one-way device or 'atom diode'.

  5. Optomechanical design of the grating laser beam combiner (GLBC) laser diode header

    NASA Technical Reports Server (NTRS)

    Rall, Jonathan A. R.; Spadin, Paul L.

    1989-01-01

    A laser diode header has been fabricated for a grating laser beam combiner (GLBC). The laser diode header provides the thermal control, the drive electronics, and the optical system necessary for proper operation of the beam combiner. The diode header is required to provide diffraction limited optical performance while providing correction for worst case defocus aberration, 0.6 mrad excess divergence, and worst case decenter aberration, 1.0 mrad pointing error. The design of the header considered the mechanical design and the optical design together resulting in a small, self-contained header with 0.7 mrad range for focus correction and +/- 2.5 mrad of beam steering. The complete diode header is currently undergoing optical and mechanical performance testing.

  6. Rippled beam free-electron laser amplifier using the axial free-electron laser interaction

    SciTech Connect

    Carlsten, B.E.

    1997-05-01

    A new microwave generation mechanism involving a scalloping annular electron beam is discussed. The beam interacts with the axial electric field of a TM{sub 0n} mode in a smooth circular waveguide through the axial free-electron laser interaction, in which the beam ripple period is synchronous with the phase slippage of the rf mode relative to the electron beam. In this paper, we analyze the ripple motion of the electron beam and derive the dispersion relation describing the exponential growth of the rf mode. We calculate the gain for a nominal design and as a function of beam current and ripple amplitude, and show that power gain on the order of 30 dB/m of interaction is achievable. We additionally demonstrate that, under the right conditions, the interaction is autoresonant. {copyright} {ital 1997 American Institute of Physics.}

  7. Non-intrusive beam power monitor for high power pulsed or continuous wave lasers

    DOEpatents

    Hawsey, Robert A.; Scudiere, Matthew B.

    1993-01-01

    A system and method for monitoring the output of a laser is provided in which the output of a photodiode disposed in the cavity of the laser is used to provide a correlated indication of the laser power. The photodiode is disposed out of the laser beam to view the extraneous light generated in the laser cavity whose intensity has been found to be a direct correlation of the laser beam output power level. Further, the system provides means for monitoring the phase of the laser output beam relative to a modulated control signal through the photodiode monitor.

  8. Electro-optic harmonic conversion to switch a laser beam out of a cavity

    DOEpatents

    Haas, Roger A.; Henesian, Mark A.

    1987-01-01

    The invention is a switch to permit a laser beam to escape a laser cavity through the use of an externally applied electric field across a harmonic conversion crystal. Amplification takes place in the laser cavity, and then the laser beam is switched out by the laser light being harmonically converted with dichroic or polarization sensitive elements present to alter the optical path of the harmonically converted laser light. Modulation of the laser beam can also be accomplished by varying the external electric field.

  9. Effects of Sealing Run Welding with Defocused Laser Beam on the Quality of T-joint Fillet Weld

    NASA Astrophysics Data System (ADS)

    Unt, Anna; Poutiainen, Ilkka; Salminen, Antti

    Fillet weld is the predominant weld type used for connecting different elements e.g. in shipbuilding, offshore and bridge structures. One of prevalent research questions is the structural integrity of the welded joint. Post weld improvement techniques are being actively researched, as high stress areas like an incomplete penetration on the root side or fluctuations in penetration depth cannot be avoided. Development of laser and laser-arc hybrid welding processes have greatly contributed to increase of production capacity and reduction of heat-induced distortions by producing single pass full penetration welds in thin- and medium thickness structural steel parts. Present study addresses the issue of how to improve the quality of the fillet welds by welding the sealing run on the root side with defocused laser beam. Welds having incomplete or excessive penetration were produced with several beam angles and laser beam spot sizes on surface. As a conclusion, significant decrease or even complete elimination of the seam irregularities, which act as the failure starting points during service, is achieved.

  10. Power transmission by laser beam from lunar-synchronous satellite

    NASA Technical Reports Server (NTRS)

    Williams, M. D.; Deyoung, R. J.; Schuster, G. L.; Choi, S. H.; Dagle, J. E.; Coomes, E. P.; Antoniak, Z. I.; Bamberger, J. A.; Bates, J. M.; Chiu, M. A.

    1993-01-01

    The possibility of beaming power from synchronous lunar orbits (the L1 and L2 Lagrange points) to a manned long-range lunar rover is addressed. The rover and two versions of a satellite system (one powered by a nuclear reactor, the other by photovoltaics) are described in terms of their masses, geometries, power needs, missions, and technological capabilities. Laser beam power is generated by a laser diode array in the satellite and converted to 30 kW of electrical power at the rover. Present technological capabilities, with some extrapolation to near future capabilities, are used in the descriptions. The advantages of the two satellite/rover systems over other such systems and over rovers with onboard power are discussed along with the possibility of enabling other missions.

  11. High-quality electron beam from laser wake-field acceleration in laser produced plasma plumes

    SciTech Connect

    Sanyasi Rao, Bobbili; Moorti, Anand; Rathore, Ranjana; Ali Chakera, Juzer; Anant Naik, Prasad; Dass Gupta, Parshotam

    2013-06-10

    Generation of highly collimated ({theta}{sub div}{approx}10 mrad), quasi-monoenergetic electron beam with peak energy 12 MeV and charge {approx}50 pC has been experimentally demonstrated from self-guided laser wake-field acceleration (LWFA) in a plasma plume produced by laser ablation of solid nylon (C{sub 12}H{sub 22}N{sub 2}O{sub 2}){sub n} target. A 7 TW, 45 fs Ti:sapphire laser system was used for LWFA, and the plasma plume forming pulse was derived from the Nd:YAG pump laser of the same system. The results show that a reproducible, high quality electron beam could be produced from this scheme which is simple, low cost and has the capability for high repetition rate operation.

  12. The entire beam wavefront control of high power laser facility

    NASA Astrophysics Data System (ADS)

    Dai, Wanjun; Wang, Deen; Hu, Dongxia; Zhang, Xin; Zhou, Wei; Yuan, Qiang; Deng, Xuewei; Wang, Yuancheng; Deng, Wu; Yang, Ying; Zhu, Qihua; Jing, Feng

    2015-02-01

    Experiment of entire beam wavefront compensation was carried out in a beamline of a high power laser facility, and two adaptive optics systems with different intentions were applied in the chosen beamline. After correction, the far-filed irradiance distribution is concentrated evidently and the entrance rate of 3ω focal spot to a 500-μm hole is improved to be about 95% under number kilojoules energy.

  13. Investigation on the Influence of Different Laser Beam Intensity Distributions on Keyhole Geometry During Laser Welding

    NASA Astrophysics Data System (ADS)

    Volpp, J.

    An analytical quasi-static model of the keyhole during laser deep penetration welding is introduced. This model is used to calculate the keyhole geometry depending on spatial laser beam intensity. Keyhole shapes can be found solving the energy and pressure equations. All necessary physical effects like Fresnel and plasma absorption, heat conduction and vaporization are implemented in the model. For evaluation a Gaussian and a top hat beam profile were used. Experimental measurements of the keyhole shape using copper inlays in aluminum base material show good agreement with the results of the modeling.

  14. Laser beam active brazing of metal ceramic joints

    NASA Astrophysics Data System (ADS)

    Haferkamp, Heinz; Bach, Friedrich W.; von Alvensleben, Ferdinand; Kreutzburg, K.

    1996-04-01

    The use of engineering ceramics is becoming more and more important. Reasons for this are the specific properties of these materials, such as high strength, corrosion resistance and wear resistance. To apply the advantages of ceramics, joining techniques of metal ceramic parts are required. In this paper, joining of metal ceramic joints by laser beam brazing is presented. This joining technique is characterized by local heat input, and the minimal thermal stress of the brazed components. During the investigations, an Nd:YAG laser and a vacuum chamber were applied. The advantages of Nd:YAG lasers are the simple mechanical construction, and laser beam guidance via quartz glass fibers, which leads to high handling flexibility. In addition, most of the materials show a high absorption rate for this kind of radiation. As materials, ceramic Al2O3 with a purity of 99.4% and metals such as X5CrNi189 and Fe54Ni29Co17 were used. As a filler material, commercially available silver and silver- copper brazes with chemically active elements like titanium were employed. During this study, the brazing wetting behavior and the formation of diffusion layers in dependence on processing parameters were investigated. The results have shown that high brazing qualities can be achieved by means of the laser beam brazing process. Crack-free joining of metal ceramic parts is currently only possible by the use of metals such as Fe54Ni29Co17 because of its low thermal expansion coefficient, which reduces thermal stresses within the joining zone.

  15. Applications of power beaming from space-based nuclear power stations. [Laser beaming to airplanes; microwave beaming to ground

    SciTech Connect

    Powell, J.R.; Botts, T.E.; Hertzberg, A.

    1981-01-01

    Power beaming from space-based reactor systems is examined using an advanced compact, lightweight Rotating Bed Reactor (RBR). Closed Brayton power conversion efficiencies in the range of 30 to 40% can be achieved with turbines, with reactor exit temperatures on the order of 2000/sup 0/K and a liquid drop radiator to reject heat at temperatures of approx. 500/sup 0/K. Higher RBR coolant temperatures (up to approx. 3000/sup 0/K) are possible, but gains in power conversion efficiency are minimal, due to lower expander efficiency (e.g., a MHD generator). Two power beaming applications are examined - laser beaming to airplanes and microwave beaming to fixed ground receivers. Use of the RBR greatly reduces system weight and cost, as compared to solar power sources. Payback times are a few years at present prices for power and airplane fuel.

  16. Dissociation phenomena in electron-beam sustained carbon dioxide lasers

    NASA Technical Reports Server (NTRS)

    Harris, Michael R.; Willetts, David V.

    1990-01-01

    A number of applications are emerging requiring efficient, long pulse, long-life sealed CO2 lasers. Examples include the proposed NASA and ESA wind lidars. Electron-beam sustained discharge devices are strong contenders. Unlike self-sustained discharges, e-beam sustenance readily provides efficient performance from large volume discharges and offers pulse lengths well in excess of the microsecond or so generally associated with self-sustained devices. In the case of the e-beam sustained laser, since the plasma is externally maintained and operated at electric field strengths less than that associated with the glow to arc transition, the discharges can be run even in the presence of strongly attacking species such as O2. Build up of large levels of attacking contaminants is nevertheless undesirable as their presence reduces the current drawn by the plasma and thus the pumping rate to the upper laser level. The impedance rise leads to a mismatch of the pulse forming network with a consequent loss of control over energy deposition, operating E/N, and gain. Clearly CO2 dissociation rates, the influence of dissociation products on the discharge and gain, and tolerance of the discharge to these products need to be determined. This information can then be used to assess co-oxidation catalyst requirements for sealed operation.

  17. Femtosecond laser processing with a holographic line-shaped beam.

    PubMed

    Hasegawa, Satoshi; Shiono, Koji; Hayasaki, Yoshio

    2015-09-01

    Line-shaped femtosecond pulses are well-suited to large-area machining with high throughput in laser cutting, peeling, and grooving of materials. First, we demonstrated the single-shot fabrication of a line structure in a glass surface using a line-shaped pulse generated by a holographic cylindrical lens displayed on a liquid-crystal spatial light modulator. We found the line structure was uniform and smooth near the ends because of the ability to precisely control the intensity distribution and to achieve single-shot fabrication. Second, we demonstrated a line-shaped beam deformed three-dimensionally for showing the potential of holographic line-shaped beam processing. Third, we demonstrated laser peeling of an indium tin oxide film. We found that little debris around the fabricated area was observed, because the debris was removed by the beam itself. Last, we demonstrated laser grooving of stainless steel. We found the swelling of the surface included upwardly growing nanogratings, although many line-shaped pulse irradiations were given. The swelling was caused by the depositions of the debris on the top of the nanogratings.

  18. Low-damage surface smoothing of laser crystallized polycrystalline silicon using gas cluster ion beam

    NASA Astrophysics Data System (ADS)

    Tokioka, H.; Yamarin, H.; Fujino, T.; Inoue, M.; Seki, T.; Matsuo, J.

    2007-04-01

    Surface smoothing of laser crystallized polycrystalline silicon (poly-Si) films using gas cluster ion beam (GCIB) technology has been studied. It is found that both SF6-GCIB and O2-GCIB decrease the height of hillocks and reduce the surface roughness of the irradiated films. The mean surface roughness value of poly-Si films was reduced from 10.8 nm to 2.8 nm by SF6-GCIB irradiation at 80°. Ultraviolet reflectance measurement reveals that GCIB irradiation causes damage near-surface of the poly-Si films. Formation of the damage, however, can be suppressed by using GCIB irradiation at high incident angle. Effect of GCIB irradiation in a metal-insulator-semiconductor (MIS) capacitor has also been investigated. The capacitance-voltage curves of MIS capacitor with SF6-GCIB irradiation are distorted. On the contrary, the distortion is reduced by O2-GCIB irradiation at 80, which suggests that electrical-activated damage of the films can be decreased by using O2-GCIB irradiation.

  19. Mid-Infrared Laser Beam Diagnostic Wavefront Analyzer

    NASA Astrophysics Data System (ADS)

    Goranson, Rex; Blea, Joe; Chipps, Art; Denton, Grant; Houchard, Jeff

    1988-08-01

    The Rockwell Wavefront Analyzer (RWA) is an integrated beam diagnostic tool developed for the US Army, STEWS, WSMR, for the MIRACL device. It accepts a 2.5 cm square nominally collimated DF laser beam input of approximately 5 W power level. The electrical signals are reduced and analyzed by an on-line computer processor. The ultimate outputs are plots including total beam power and angular jitter in the x and y axes, an irradiance map of the beam on a 32 X 32 square grid, and a wavefront map of the beam on the same grid. Wavefront aberration poly-nomial coefficient listings are also generated. The wavefront is obtained from measurements of its local slope in two axes by means of a classical Hartmann test done by scanning the pupil with holes in a rotating drum. Earlier versions of this instrument we called SHAPE, for Scanning Hartmann Analyzer Plate Experiment. This design would be SHAPE IV. A single indium antimonide photopot detector measures the transverse ray aberrations, which are then subjected to elaborate processing to extract the polynomial wavefront coefficients. Another photopot is the jitter sensor. Each photopot measures power to normalize the X and Y signals; these "Z" signals also provide the beam power and local irradiance signals.

  20. Compensation for the distortion in satellite laser range predictions due to varying pulse travel times

    NASA Technical Reports Server (NTRS)

    Paunonen, Matti

    1993-01-01

    A method for compensating for the effect of the varying travel time of a transmitted laser pulse to a satellite is described. The 'observed minus predicted' range differences then appear to be linear, which makes data screening or use in range gating more effective.

  1. The study of the structural stability of the spiral laser beams propagation through inhomogeneous phase medium

    NASA Astrophysics Data System (ADS)

    Zinchik, Alexander A.; Muzychenko, Yana B.

    2015-06-01

    This paper discusses theoretical and experimental results of the investigation of light beams that retain their intensity structure during propagation and focusing. Spiral laser beams are a family of laser beams that preserve the structural stability up to scale and rotation with the propagation. Properties of spiral beams are of practical interest for laser technology, medicine and biotechnology. Researchers use a spiral beams for movement and manipulation of microparticles. Functionality laser manipulators can be significantly enhanced by using spiral beams whose intensity remains invariable. It is well known, that these beams has non-zero orbital angular momentum. Spiral beams have a complicated phase distribution in cross section. In this paper we investigate the structural stability of the laser beams having a spiral phase structure by passing them through an inhomogeneous phase medium. Laser beam is passed through a medium is characterized by a random distribution of phase in the range 0..2π. The modeling was performed using VirtualLab 5.0 (manufacturer LightTrans GmbH). Compared the intensity distribution of the spiral and ordinary laser beam after the passage of the inhomogeneous medium. It is shown that the spiral beams exhibit a significantly better structural stability during the passage phase heterogeneous environments than conventional laser beams. The results obtained in the simulation are tested experimentally. Experimental results show good agreement with the theoretical results.

  2. Development of laser beam injection system for the Edge Thomson Scattering (ETS) in ITER

    NASA Astrophysics Data System (ADS)

    Yatsuka, E.; Hatae, T.; Suitoh, S.; Ohara, M.; Hagita, K.; Inoue, K.; Bassan, M.; Walsh, M.; Itami, K.

    2016-01-01

    This paper focuses on the design and development of the laser injection system for the ITER Edge Thomson Scattering system (ETS). The ITER ETS achieves a temporal resolution of 100 Hz by firing two 50 Hz laser beams alternatively. The use of dual lasers enables us to perform the Thomson scattering measurements at a temporal resolution of 50 Hz in case that one of the laser systems stops functioning. A new type of beam combiner was developed to obtain a single beam that is collinear and fixed linearly polarized from two laser beams using a motor-driven rotating half-wave plate. The rotating half-wave plate method does not induce misalignment even if the rotating mechanism malfunctions. The combined beam is relayed from the diagnostic hall to the plasma using mirror optics and is absorbed at the beam dump integrated on the inner blanket. The beam alignment system was designed to direct the laser beam onto the center of the beam dump head. The beam position at the beam dump is monitored by four alignment laser beams which propagate parallel to the diagnostic Nd:YAG laser beam and imaging systems installed outside the diagnostic port.

  3. Editorial: Focus on Laser- and Beam-Driven Plasma Accelerators

    NASA Astrophysics Data System (ADS)

    Joshi, Chan; Malka, Victor

    2010-04-01

    The ability of short but intense laser pulses to generate high-energy electrons and ions from gaseous and solid targets has been well known since the early days of the laser fusion program. However, during the past decade there has been an explosion of experimental and theoretical activity in this area of laser-matter interaction, driven by the prospect of realizing table-top plasma accelerators for research, medical and industrial uses, and also relatively small and inexpensive plasma accelerators for high-energy physics at the frontier of particle physics. In this focus issue on laser- and beam-driven plasma accelerators, the latest advances in this field are described. Focus on Laser- and Beam-Driven Plasma Accelerators Contents Slow wave plasma structures for direct electron acceleration B D Layer, J P Palastro, A G York, T M Antonsen and H M Milchberg Cold injection for electron wakefield acceleration X Davoine, A Beck, A Lifschitz, V Malka and E Lefebvre Enhanced proton flux in the MeV range by defocused laser irradiation J S Green, D C Carroll, C Brenner, B Dromey, P S Foster, S Kar, Y T Li, K Markey, P McKenna, D Neely, A P L Robinson, M J V Streeter, M Tolley, C-G Wahlström, M H Xu and M Zepf Dose-dependent biological damage of tumour cells by laser-accelerated proton beams S D Kraft, C Richter, K Zeil, M Baumann, E Beyreuther, S Bock, M Bussmann, T E Cowan, Y Dammene, W Enghardt, U Helbig, L Karsch, T Kluge, L Laschinsky, E Lessmann, J Metzkes, D Naumburger, R Sauerbrey, M. Scḧrer, M Sobiella, J Woithe, U Schramm and J Pawelke The optimum plasma density for plasma wakefield excitation in the blowout regime W Lu, W An, M Zhou, C Joshi, C Huang and W B Mori Plasma wakefield acceleration experiments at FACET M J Hogan, T O Raubenheimer, A Seryi, P Muggli, T Katsouleas, C Huang, W Lu, W An, K A Marsh, W B Mori, C E Clayton and C Joshi Electron trapping and acceleration on a downward density ramp: a two-stage approach R M G M Trines, R Bingham, Z Najmudin

  4. Laser Beam MicroMachining (LBMM) - A review

    NASA Astrophysics Data System (ADS)

    Mishra, Sanjay; Yadava, Vinod

    2015-10-01

    The use of short and ultrashort laser pulses for micromachining application is an emerging technology. Laser Beam MicroMachining (LBMM) has revolutionized many industries by providing innovative solutions in numerous industrial micro-engineering applications. High-intensity short or ultrashort laser pulses are powerful thermal energy source for creating micro-features in wide range of materials. These lasers can precisely ablate various types of materials with little or no collateral damage. An overview of LBMM is given so that we can obtain a current view of capabilities and tradeoffs associated with LBMM of sub-micron size. The fundamental understanding of ultrafast laser ablation process has been elucidated and the various research activities performed with nanosecond, picosecond and femtosecond, lasers have been discussed to understand the physical mechanisms and the critical experimental parameters involved in the LBMM. The critical analysis of various theoretical and experimental models used to describe the performance analysis of LBMM has been elaborated so that we can identify the relevant principles underlying the process.

  5. High-power beam combining: a step to a future laser weapon system

    NASA Astrophysics Data System (ADS)

    Protz, Rudolf; Zoz, Jürgen; Geidek, Franz; Dietrich, Stephan; Fall, Michael

    2012-11-01

    Due to the enormous progress in the field of high-power fiber lasers during the last years commercial industrial fiber lasers are now available, which deliver a near-diffraction limited beam with power levels up to10kW. For the realization of a future laser weapon system, which can be used for Counter-RAM or similar air defence applications, a laser source with a beam power at the level of 100kW or more is required. At MBDA Germany the concept for a high-energy laser weapon system is investigated, which is based on such existing industrial laser sources as mentioned before. A number of individual high-power fiber laser beams are combined together, using one common beam director telescope. By this "geometric" beam coupling scheme, sufficient laser beam power for an operational laser weapon system can be achieved. The individual beams from the different lasers are steered by servo-loops, using fast tip-tilt mirrors. This principle enables the concentration of the total laser beam power at the common focal point on a distant target, also allowing fine tracking of target movements and first order compensation of turbulence effects on laser beam propagation. The proposed beam combination concept was demonstrated using several experimental set-ups. Different experiments were performed, to investigate laser beam target interaction and target fine tracking also at large distances. Content and results of these investigations are reported. An example for the lay-out of an Air Defence High Energy Laser Weapon (ADHELW ) is given. It can be concluded, that geometric high-power beam combining is an important step for the realization of a laser weapon system in the near future.

  6. Spectroscopic Analysis of High Intensity Laser Beam Jets Interaction Experiments on the Leopard Laser at UNR

    NASA Astrophysics Data System (ADS)

    Petkov, E. E.; Weller, M. E.; Kantsyrev, V. L.; Safronova, A. S.; Moschella, J. J.; Shrestha, I.; Shlyapsteva, V. V.; Stafford, A.; Keim, S. F.; University of Nevada Reno Team

    2013-10-01

    Results of Ar gas-puff experiments performed on the high power Leopard laser at UNR are presented. Flux density of laser radiation in focal spot was up to 2 × 1016 W/cm2 (pulse duration was 0.8 ns and laser wavelength was 1.057 μm). Specifically, spectroscopic analysis of K-shell Ar spectra are investigated and compared as functions of the orientation of the laser beam to linear gas jet. The laser beam axis was positioned either along the jet plane or orthogonal to it at a distance of 1 mm from the nozzle output. The diagnostics used included a time-integrated x-ray spectrometer along with a set of filtered Si diodes with various cutoff energies. In order to identify lines, a non-local thermodynamic equilibrium (non-LTE) kinetic model was utilized and was also used to determine plasma parameters such as electron temperature and density. The importance of the spectroscopic study of high intensity laser beam-jets interaction experiments is discussed. This work was supported by the Defense Threat Reduction Agency, Basic Research Award # HDTRA1-13-1-0033, to University of Nevada, Reno, and in part by the DOE/NNSA Cooperative agreements DE-NA0001984 and DE-FC52-06NA27616.

  7. Production of pulsed atomic oxygen beams via laser vaporization methods

    NASA Technical Reports Server (NTRS)

    Brinza, David E.; Coulter, Daniel R.; Liang, Ranty H.; Gupta, Amitava

    1986-01-01

    The generation of energetic pulsed atomic oxygen beams by laser-driven evaporation of cryogenically frozen ozone/oxygen films and thin indium-tin oxide (ITO) films is reported. Mass spectroscopy is used in the mass and energy characterization of beams from the ozone/oxygen films, and a peak flux of 3 x 10 to the 20th/sq m per sec at 10 eV is found. Analysis of the time-of-flight data suggests that several processes contribute to the formation of the oxygen beam. Results show the absence of metastable states such as the 2p(3)3s(1)(5S) level of atomic oxygen blown-off from the ITO films. The present process has application to the study of the oxygen degradation problem of LEO materials.

  8. Long-Distance Axial Trapping with Focused Annular Laser Beams

    PubMed Central

    Yan, Shaohui; Yao, Baoli; Dan, Dan; Qi, Yujiao; Qian, Jia; Yang, Yanlong; Gao, Peng; Ye, Tong

    2013-01-01

    Focusing an annular laser beam can improve the axial trapping efficiency due to the reduction of the scattering force, which enables the use of a lower numerical aperture (NA) objective lens with a long working distance to trap particles in deeper aqueous medium. In this paper, we present an axicon-to-axicon scheme for producing parallel annular beams with the advantages of higher efficiency compared with the obstructed beam approach. The validity of the scheme is verified by the observation of a stable trapping of silica microspheres with relatively low NA microscope objective lenses (NA = 0.6 and 0.45), and the axial trapping depth of 5 mm is demonstrated in experiment. PMID:23505449

  9. GaAs solar cells for laser power beaming

    NASA Technical Reports Server (NTRS)

    Olsen, Larry C.; Dunham, Glen; Huber, Daniel A.; Addis, F. William; Anheier, Norman; Coomes, E. P.

    1991-01-01

    Efforts to develop GaAs solar cells for coupling to laser beams in the wavelength range of 800 to 840 nm are described. This work was motivated primarily by interests in space-tp-space power beaming applications. In particular, the Battelle Pacific Northwest Laboratories is conducting studies of the utilization of power beaming for several future space missions. Modeling calculations of GaAs cell performance were carried out using PC-1D to determine an appropriate design for a p/n cell structure. Epitaxial wafers were grown by MOCVD and cells fabricated at WSU Tri-Cities. Under simulated conditions, an efficiency of 53 percent was achieved for a cell coupled to 806 nm light at 400 mW/sq cm.

  10. Dual-beam laser thermal processing of silicon photovoltaic materials

    NASA Astrophysics Data System (ADS)

    Simonds, Brian J.; Teal, Anthony; Zhang, Tian; Hadler, Josh; Zhou, Zibo; Varlamov, Sergey; Perez-Würfl, Ivan

    2016-03-01

    We have developed an all-laser processing technique by means of two industrially-relevant continuous-wave fiber lasers operating at 1070 nm. This approach is capable of both substrate heating with a large defocused beam and material processing with a second scanned beam, and is suitable for a variety of photovoltaic applications. We have demonstrated this technique for rapid crystallization of thin film (~10 μm) silicon on glass, which is a low cost alternative to wafer-based solar cells. We have also applied this technique to wafer silicon to control dopant diffusion at the surface region where the focused line beam rapidly melts the substrate that then regrows epitaxially. Finite element simulations have been used to model the melt depth as a function of preheat temperature and line beam power. This process is carried out in tens of seconds for an area approximately 10 cm2 using only about 1 kW of total optical power and is readily scalable. In this paper, we will discuss our results with both c-Si wafers and thin-film silicon.

  11. Mono-Energetic Beams from Laser Plasma Interactions

    SciTech Connect

    Geddes, C.G.R.; Esarey, E.; Leemans, W.P.; Schroeder, C.B.; Toth,Cs.; van Tilborg, J.; Cary, John R.; Bruhwiler, David L.; Nieter, Chet

    2005-05-09

    A laser driven wakefield accelerator has been tuned to produce high energy electron bunches with low emittance and energy spread by extending the interaction length using a plasma channel. Wakefield accelerators support gradients thousands of times those achievable in RF accelerators, but short acceleration distance, limited by diffraction, has resulted in low energy beams with 100 percent electron energy spread. In the present experiments on the L'OASIS laser, the relativistically intense drive pulse was guided over 10 diffraction ranges by a plasma channel. At a drive pulse power of 9 TW, electrons were trapped from the plasma and beams of percent energy spread containing > 200 pC charge above 80 MeV and with normalized emittance estimated at< 2pi-mm-mrad were produced. Data and simulations (VORPAL code) show the high quality bunch was formed when beam loading turned off injection after initial trapping, and when the particles were extracted as they dephased from the wake. Up to 4TW was guided without trapping, potentially providing a platform for controlled injection. The plasma channel technique forms the basis of a new class of accelerators, with high gradients and high beam quality.

  12. Research on beam splitting prism in laser heterodyne interferometer

    NASA Astrophysics Data System (ADS)

    Fu, Xiu-hua; Xiong, Shi-fu; Kou, Yang; Pan, Yong-gang; Chen, Heng; Li, Zeng-yu; Zhang, Chuan-xin

    2014-08-01

    With the rapid development of optical testing technology, laser heterodyne interferometer has been used more and more widely. As the testing precision requirements continue to increase, the technical prism is an important component of heterodyne interference. The research utilizing thin film technology to improve optical performance of interferometer has been a new focus. In the article, based on the use requirements of interferometer beam splitting prism, select Ta2O5 and SiO2 as high and low refractive index materials respectively, deposit on substrate K9. With the help of TFCalc design software and Needle method, adopting electron gun evaporation and ion assisted deposition, the beam splitting prism is prepared successfully and the ratio of transmittance and reflectance for this beam splitting prism in 500~850 nm band, incident angle 45 degree is 8:2. After repeated tests, solved the difference problem of film deposition process parameters ,controlled thickness monitoring precision effectively and finally prepared the ideal beam splitting prism which is high adhesion and stable optics properties. The film the laser induced damage threshold and it meet the requirements of heterodyne interferometer for use.

  13. Divergence of laser-driven relativistic electron beams

    NASA Astrophysics Data System (ADS)

    Debayle, A.; Honrubia, J. J.; D'Humières, E.; Tikhonchuk, V. T.

    2010-09-01

    Electron acceleration by ultrahigh intensity lasers is studied by means of two-dimensional planar particle-in-cell simulations. It is shown that the full divergence of the fast electron beam is defined by two complementary physical effects: the regular radial beam deviation depending on the electron radial position and the angular dispersion. If the scale length of the preplasma surrounding the solid target is sufficiently low, the radial deviation is determined by the transverse component of the laser ponderomotive force. The random angular dispersion is due to the small scale magnetic fields excited near the critical density due to the collisionless Weibel instability. When a preplasma is present, the radial beam deviation increases due to the electron acceleration in larger volumes and can become comparable to the local angular dispersion. This effect has been neglected so far in most of the fast electron transport calculations, overestimating significantly the beam collimation by resistive magnetic fields. Simulations with a two-dimensional cylindrically-symmetric hybrid code accounting for the electron radial velocity demonstrate a substantially reduced strength and a shorter penetration of the azimuthal magnetic field in solid targets.

  14. Laser and focused ion beam combined machining for micro dies.

    PubMed

    Yoshida, Y; Okazaki, W; Uchida, T

    2012-02-01

    We have developed a laser and focused ion beam (FIB) compound process for press mold dies of a micro lens array (MLA) and a micro needle array (MNA) in a glassy carbon (GC). The press mold die of the MLA was roughly fabricated by UV-YAG laser. After this process, we finished this surface by scanning FIB. As a result, higher accuracy and good roughness of surface profile can be realized. An optical glass is used to confirm the shape of lens. Moreover, we fabricated 6 × 6 through-holes in the GC by the spiral drilling in addition to the focus position movement of the UV laser for press mold die of the MNA. After the FIB process, we were able to make the needle die of surface and hole wall roughness less than 0.9 μm. A silicon rubber is used to confirm the shape of the holes.

  15. Diode laser satellite systems for beamed power transmission

    NASA Technical Reports Server (NTRS)

    Williams, M. D.; Kwon, J. H.; Walker, G. H.; Humes, D. H.

    1990-01-01

    A power system composed of an orbiting laser satellite and a surface-based receiver/converter is described. Power is transmitted from the satellite to the receiver/converter by laser beam. The satellite components are: (1) solar collector; (2) blackbody; (3) photovoltaic cells; (4) heat radiators; (5) laser system; and (6) transmission optics. The receiver/converter components are: receiver dish; lenticular lens; photocells; and heat radiator. Although the system can be adapted to missions at many locations in the solar system, only two are examined here: powering a lunar habitat; and powering a lunar rover. Power system components are described and their masses, dimensions, operating powers, and temperatures, are estimated using known or feasible component capabilities. The critical technologies involved are discussed and other potential missions are mentioned.

  16. Laser beam propagation through turbulence and adaptive optics for beam delivery improvement

    NASA Astrophysics Data System (ADS)

    Nicolas, Stephane

    2015-10-01

    We report results from numerical simulations of laser beam propagation through atmospheric turbulence. In particular, we study the statistical variations of the fractional beam energy hitting inside an optical aperture placed at several kilometer distance. The simulations are performed for different turbulence conditions and engagement ranges, with and without the use of turbulence mitigation. Turbulence mitigation is simulated with phase conjugation. The energy fluctuations are deduced from time sequence realizations. It is shown that turbulence mitigation leads to an increase of the mean energy inside the aperture and decrease of the fluctuations even in strong turbulence conditions and long distance engagement. As an example, the results are applied to a high energy laser countermeasure system, where we determine the probability that a single laser pulse, or one of the pulses in a sequence, will provide a lethal energy inside the target aperture. Again, turbulence mitigation contributes to increase the performance of the system at long-distance and for strong turbulence conditions in terms of kill probability. We also discuss a specific case where turbulence contributes to increase the pulse energy within the target aperture. The present analysis can be used to evaluate the performance of a variety of systems, such as directed countermeasures, laser communication, and laser weapons.

  17. Ponderomotive self-focusing of Gaussian laser beam in warm collisional plasma

    SciTech Connect

    Jafari Milani, M. R.; Niknam, A. R.; Farahbod, A. H.

    2014-06-15

    The propagation characteristics of a Gaussian laser beam through warm collisional plasma are investigated by considering the ponderomotive force nonlinearity and the complex eikonal function. By introducing the dielectric permittivity of warm unmagnetized plasma and using the WKB and paraxial ray approximations, the coupled differential equations defining the variations of laser beam parameters are obtained and solved numerically. Effects of laser and plasma parameters such as the collision frequency, the initial laser intensity and its spot size on the beam width parameter and the axis laser intensity distribution are analyzed. It is shown that, self-focusing of the laser beam takes place faster by increasing the collision frequency and initial laser spot size and then after some distance propagation the laser beam abruptly loses its initial diameter and vastly diverges. Furthermore, the modified electron density distribution is obtained and the collision frequency effect on this distribution is studied.

  18. Real-time determination of laser beam quality by modal decomposition.

    PubMed

    Schmidt, Oliver A; Schulze, Christian; Flamm, Daniel; Brüning, Robert; Kaiser, Thomas; Schröter, Siegmund; Duparré, Michael

    2011-03-28

    We present a real-time method to determine the beam propagation ratio M2 of laser beams. The all-optical measurement of modal amplitudes yields M2 parameters conform to the ISO standard method. The experimental technique is simple and fast, which allows to investigate laser beams under conditions inaccessible to other methods.

  19. A survey of beam-combining technologies for laser space power transmission

    NASA Technical Reports Server (NTRS)

    Kwon, J. H.; Williams, M. D.; Lee, J. H.

    1988-01-01

    The combination of laser beams holds much promise for obtaining powerful beams. Methods are surveyed for beam combination (coherent and incoherent) and two of them are identified as the most effective means for achieving high power transmission in space. The two methods as applied to laser diode arrays are analyzed, and potentially productive work areas for the advancement of technology are delineated.

  20. Experimental setup for investigation of narrow IR laser beam propagation along horizontal 1300m urban path

    NASA Astrophysics Data System (ADS)

    Kapranov, Vitaliy; Tugaenko, Vjatcheslav; Marakasov, Dmitrii; Kudryavtsev, Andrei

    2015-11-01

    In this paper, we describe an experimental setup for laser beam propagation along a horizontal urban path that can be useful for applications such as wireless power transfer or free-space laser communications. This setup can be used for experiments in different atmosphere conditions. Part of obtained results from experiments for 1064 nm laser beam is presented.

  1. Excitation of Accelerating Plasma Waves by Counter-propagating Laser Beams

    SciTech Connect

    Gennady Shvets; Nathaniel J. Fisch; and Alexander Pukhov

    2001-08-30

    Generation of accelerating plasma waves using two counter-propagating laser beams is considered. Colliding-beam accelerator requires two laser pulses: the long pump and the short timing beam. We emphasize the similarities and differences between the conventional laser wakefield accelerator and the colliding-beam accelerator (CBA). The highly nonlinear nature of the wake excitation is explained using both nonlinear optics and plasma physics concepts. Two regimes of CBA are considered: (i) the short-pulse regime, where the timing beam is shorter than the plasma period, and (ii) the parametric excitation regime, where the timing beam is longer than the plasma period. Possible future experiments are also outlined.

  2. Energy Spread Reduction of Electron Beams Produced via Laser Wake

    SciTech Connect

    Pollock, Bradley Bolt

    2012-01-01

    Laser wakefield acceleration of electrons holds great promise for producing ultra-compact stages of GeV scale, high quality electron beams for applications such as x-ray free electron lasers and high energy colliders. Ultra-high intensity laser pulses can be self-guided by relativistic plasma waves over tens of vacuum diffraction lengths, to give >1 GeV energy in cm-scale low density plasma using ionization-induced injection to inject charge into the wake at low densities. This thesis describes a series of experiments which investigates the physics of LWFA in the self-guided blowout regime. Beginning with high density gas jet experiments the scaling of the LWFA-produced electron beam energy with plasma electron density is found to be in excellent agreement with both phenomenological theory and with 3-D PIC simulations. It is also determined that self-trapping of background electrons into the wake exhibits a threshold as a function of the electron density, and at the densities required to produce electron beams with energies exceeding 1 GeV a different mechanism is required to trap charge into low density wakes. By introducing small concentrations of high-Z gas to the nominal He background the ionization-induced injection mechanism is enabled. Electron trapping is observed at densities as low as 1.3 x 1018 cm-3 in a gas cell target, and 1.45 GeV electrons are demonstrated for the first time from LWFA. This is currently the highest electron energy ever produced from LWFA. The ionization-induced trapping mechanism is also shown to generate quasi-continuous electron beam energies, which is undesirable for accelerator applications. By limiting the region over which ionization-induced trapping occurs, the energy spread of the electron beams can be controlled. The development of a novel two-stage gas cell target provides the capability to tailor the gas composition in the longitudinal direction, and confine the trapping process to occur only in a

  3. Selective Laser Sintering of Filled Polymer Systems: Bulk Properties and Laser Beam Material Interaction

    NASA Astrophysics Data System (ADS)

    Wudy, Katrin; Lanzl, Lydia; Drummer, Dietmar

    Additive manufacturing techniques, such as selective laser melting of plastics, generate components directly from a CAD data set without using a specific mold. The range of materials commercially available for selective laser sintering merely includes some semi crystalline polymers mainly polyamides, which leads to an absence of realizable component properties. The presented investigations are concerned with the manufacturing and analysis of components made from filled polymer systems by means of selective laser sintering. The test specimens were generated at varied filler concentration, filler types and manufacturing parameter like laser power or scan speed. In addition to the characterization of the mixed powders, resulting melt depth were analyzed in order to investigate the beam material interaction. The basic understanding of the influence of different fillers, filler concentration and manufacturing parameters on resulting component properties will lead to new realizable component properties and thus fields of application of selective laser sintering.

  4. Laser beam shape and curvature radius of the laser wavefront passing through ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Mousavi, S. H.; Haratizadeh, H.

    2012-03-01

    In the present work, we focus on synthesis and optical properties of ZnO nanostructures prepared by the chemical vapour deposition method. The nonlinear optical properties of ZnO nanostructures in ethanol solution were studied by the Z-scan technique using CW He-Ne laser at 632.8 nm. The results show a negative nonlinearity and a large nonlinear refractive index. The magnitude and the sign of nonlinear refractive index, n2, were measured using the single beam Z-scan technique. The effect of morphology on nonlinear optical properties of ZnO nanowires is investigated. The laser beam shape and variation of the curvature radius of the wavefront have been simulated when the Gaussian laser beam passes through ZnO nanowires in ethanol. The effect of concentration is investigated in the nonlinearity. We have reported the curvature radius of the wavefront to the nonlinearity for ZnO nanowires as nonlinear sample. Also we found good agreement between the results of theoretical laser beam shape passing through ZnO nanostructure and the experimental data.

  5. Intense laser beams; Proceedings of the Meeting, Los Angeles, CA, Jan. 23, 24, 1992

    NASA Technical Reports Server (NTRS)

    Wade, Richard C. (Editor); Ulrich, Peter B. (Editor)

    1992-01-01

    Various papers on intense laser beams are presented. Individual topics addressed include: novel methods of copper vapor laser excitation, UCLA IR FEL, lasing characteristics of a large-bore copper vapor laser (CVL), copper density measurement of a large-bore CVL, high-power XeCl excimer laser, solid state direct-drive circuit for pumping gas lasers, united energy model for FELs, intensity and frequency instabilities in double-mode CO2 lasers, comparison of output power stabilities of CO and CO2 lasers, increasing efficiency of sealed-off CO lasers, thermal effects in singlet delta oxygen generation, optical extraction from the chemical oxygen-iodine laser medium, generation and laser diagnostic analysis of bismuth fluoride. Also discussed are: high-Q resonator design for an HF overtone chemical lasers, improved coatings for HF overtone lasers, scaled atmospheric blooming experiment, simulation on producing conjugate field using deformable mirrors, paraxial theory of amplitude correction, potential capabilities of adaptive optical systems in the atmosphere, power beaming research at NASA, system evaluations of laser power beaming options, performance projections for laser beam power to space, independent assessment of laser power beaming options, removal of atmospheric CFCs by lasers, efficiency of vaporization cutting by CVL.

  6. Guiding of Laser Beams in Plasmas by Radiation Cascade Compression

    NASA Astrophysics Data System (ADS)

    Kalmykov, Serguei; Shvets, Gennady

    2006-11-01

    The near-resonant heatwave excitation of an electron plasma wave (EPW) can be employed for generating trains of few-fs electromagnetic pulses in rarefied plasmas. The EPW produces a co-moving index grating that induces a laser phase modulation at the beat frequency. Consequently, the cascade of sidebands red- and blue-shifted from the fundamental by integer multiples of the beat frequency is generated in the laser spectrum. When the beat frequency is lower than the electron plasma frequency, the phase chirp enables laser beatnote compression by the group velocity dispersion [S. Kalmykov and G. Shvets, Phys. Rev. E 73, 046403 (2006)]. In the 3D cylindrical geometry, the frequency-downshifted EPW not only modulates the laser frequency, but also causes the pulse to self-focus [P. Gibbon, Phys. Fluids B 2, 2196 (1990)]. After self-focusing, the multi-frequency laser beam inevitably diverges. Remarkably, the longitudinal beatnote compression can compensate the intensity drop due to diffraction. A train of high-intensity radiation spikes with continually evolving longitudinal profile can be self-guided over several Rayleigh lengths in homogeneous plasmas. High amplitude of the EPW is maintained over the entire propagation length. Numerical experiments on the electron acceleration in the cascade-driven (cascade-guided) EPW [using the code WAKE by P. Mora and T. M. Antonsen Jr., Phys. Plasmas 4, 217 (1997)] show that achieving GeV electron energy is possible under realistic experimental parameters.

  7. Guiding of Laser Beams in Plasmas by Radiation Cascade Compression

    SciTech Connect

    Kalmykov, Serguei; Shvets, Gennady

    2006-11-27

    The near-resonant heatwave excitation of an electron plasma wave (EPW) can be employed for generating trains of few-fs electromagnetic pulses in rarefied plasmas. The EPW produces a co-moving index grating that induces a laser phase modulation at the beat frequency. Consequently, the cascade of sidebands red- and blue-shifted from the fundamental by integer multiples of the beat frequency is generated in the laser spectrum. When the beat frequency is lower than the electron plasma frequency, the phase chirp enables laser beatnote compression by the group velocity dispersion [S. Kalmykov and G. Shvets, Phys. Rev. E 73, 046403 (2006)]. In the 3D cylindrical geometry, the frequency-downshifted EPW not only modulates the laser frequency, but also causes the pulse to self-focus [P. Gibbon, Phys. Fluids B 2, 2196 (1990)]. After self-focusing, the multi-frequency laser beam inevitably diverges. Remarkably, the longitudinal beatnote compression can compensate the intensity drop due to diffraction. A train of high-intensity radiation spikes with continually evolving longitudinal profile can be self-guided over several Rayleigh lengths in homogeneous plasmas. High amplitude of the EPW is maintained over the entire propagation length. Numerical experiments on the electron acceleration in the cascade-driven (cascade-guided) EPW [using the code WAKE by P. Mora and T. M. Antonsen Jr., Phys. Plasmas 4, 217 (1997)] show that achieving GeV electron energy is possible under realistic experimental parameters.

  8. Guiding of laser beams in plasmas by electromagnetic cascade compression

    NASA Astrophysics Data System (ADS)

    Kalmykov, S.; Shvets, G.

    2006-10-01

    The near-resonant beatwave excitation of an electron plasma wave (EPW) can be employed for generating trains of few- femtosecond electromagnetic pulses in rarefied plasmas. The EPW produces a co-moving index grating that induces a laser phase modulation at the difference frequency. As a result, the cascade of sidebands red- and blue-shifted by integer multiples of the beat frequency is generated in the laser spectrum. When the beat frequency is lower than the electron plasma frequency, the phase chirp enables laser beatnote compression by the group velocity dispersion. In the 3D cylindrical geometry, the frequency-downshifted EPW not only modulates the laser phase, but also causes the pulse to self-focus [P. Gibbon, Phys. Fluids B 2, 2196 (1990)]. After self-focusing, the laser beam inevitably diverges. Remarkably, the longitudinal beatnote compression can compensate the intensity drop due to diffraction. Thus, a train of high intensity radiation spikes with continually evolving longitudinal profile can be self- guided over several Rayleigh lengths in homogeneous plasma. High amplitude of the EPW is maintained over the entire propagation length. Numerical experiments on the electron acceleration in the cascade-driven (cascade-guided) EPW show that achieving GeV energy is possible under realistic experimental conditions.

  9. Fiber laser beam combining and power scaling progress: Air Force Research Laboratory Laser Division

    NASA Astrophysics Data System (ADS)

    Wagner, T. J.

    2012-02-01

    Numerous achievements have been made recently by researchers in the areas of fiber laser beam combining and power scaling. Industry has demonstrated multi-kW power from a single fiber amplifier, and a US national laboratory has coherently combined eight fiber amplifiers totaling 4 kW. This paper will survey the recent literature and then focus on fiber laser results from the Laser Division, Directed Energy Directorate of the Air Force Research Laboratory (AFRL). Progress has been made in the power scaling of narrow-linewidth fiber amplifiers, and we are transitioning lessons learned from PCF power scaling into monolithic architectures. SBS suppression has been achieved using a variety of techniques to lower the Brillioun gain, including acoustically tailored fiber, laser gain competition resulting from multitone seeding and inducing a longitudinal thermal gradient. We recently demonstrated a 32-channel coherent beam combination result using AFRL's phaselocking technique and are focused on exploring the limitations of this technique including linewidth broadening, kW-induced phase nonlinearities and auto-tuning methods for large channel counts. Additionally, we have recently refurbished our High Energy Laser Joint Technology Office-sponsored 16-amplifier fiber testbed to meet strict PER, spatial drift, power stability and beam quality requirements.

  10. Saturation of multi-laser beams laser-plasma instabilities from stochastic ion heating

    SciTech Connect

    Michel, P.; Williams, E. A.; Divol, L.; Berger, R. L.; Glenzer, S. H.; Callahan, D. A.; Rozmus, W.

    2013-05-15

    Cross-beam energy transfer (CBET) has been used as a tool on the National Ignition Facility (NIF) since the first energetics experiments in 2009 to control the energy deposition in ignition hohlraums and tune the implosion symmetry. As large amounts of power are transferred between laser beams at the entrance holes of NIF hohlraums, the presence of many overlapping beat waves can lead to stochastic ion heating in the regions where laser beams overlap [P. Michel et al., Phys. Rev. Lett. 109, 195004 (2012)]. This increases the ion acoustic velocity and modifies the ion acoustic waves’ dispersion relation, thus reducing the plasma response to the beat waves and the efficiency of CBET. This pushes the plasma oscillations driven by CBET in a regime where the phase velocities are much smaller than both the electron and ion thermal velocities. CBET gains are derived for this new regime and generalized to the case of multi ion species plasmas.

  11. Performance predictions of a focused ion beam from a laser cooled and compressed atomic beam

    SciTech Connect

    Haaf, G. ten; Wouters, S. H. W.; Vredenbregt, E. J. D.; Mutsaers, P. H. A.; Geer, S. B. van der

    2014-12-28

    Focused ion beams are indispensable tools in the semiconductor industry because of their ability to image and modify structures at the nanometer length scale. Here, we report on performance predictions of a new type of focused ion beam based on photo-ionization of a laser cooled and compressed atomic beam. Particle tracing simulations are performed to investigate the effects of disorder-induced heating after ionization in a large electric field. They lead to a constraint on this electric field strength which is used as input for an analytical model which predicts the minimum attainable spot size as a function of, amongst others, the flux density of the atomic beam, the temperature of this beam, and the total current. At low currents (I < 10 pA), the spot size will be limited by a combination of spherical aberration and brightness, while at higher currents, this is a combination of chromatic aberration and brightness. It is expected that a nanometer size spot is possible at a current of 1 pA. The analytical model was verified with particle tracing simulations of a complete focused ion beam setup. A genetic algorithm was used to find the optimum acceleration electric field as a function of the current. At low currents, the result agrees well with the analytical model, while at higher currents, the spot sizes found are even lower due to effects that are not taken into account in the analytical model.

  12. Characterization and control of tunable quantum cascade laser beam parameters for stand-off spectroscopy

    NASA Astrophysics Data System (ADS)

    Furstenberg, Robert; Kendziora, Christopher A.; Papantonakis, Michael R.; Nguyen, Viet; McGill, R. Andrew

    2016-05-01

    Infrared active stand-off detection techniques often employ high power tunable quantum cascade lasers (QCLs) for target illumination. Due to the distances involved, any fluctuation of the laser beam direction and/or beam profile is amplified at the sample position. If not accounted for, this leads to diminished performance (both sensitivity and selectivity) of the detection technique as a direct result of uncertainties in laser irradiance at each imaged pixel of the sample. This is especially true for detection approaches which illuminate a relatively small footprint at the target since the laser beam profile spatial fluctuations are often comparable to the (focused) laser spot size. Also, there is often a necessary trade-off between high output QCL power and beam quality. Therefore, precise characterization of the laser beam profile and direction as a function of laser properties (tuning wavelength, current and operating mode: pulsed or CW) is imperative. We present detailed measurements of beam profiles, beam wander and power fluctuations and their reproducibility as function of laser wavelength and stand-off distance for a commercially available tunable quantum cascade laser. We present strategies for improving beam quality by compensating for fluctuations using a motorized mirror and a pair of motorized lenses. We also investigate QCL mode hops and how they affect laser beam properties at the sample. Detailed mode-hop stability maps were measured.

  13. Automated analysis for detecting beams in laser wakefield simulations

    SciTech Connect

    Ushizima, Daniela M.; Rubel, Oliver; Prabhat, Mr.; Weber, Gunther H.; Bethel, E. Wes; Aragon, Cecilia R.; Geddes, Cameron G.R.; Cormier-Michel, Estelle; Hamann, Bernd; Messmer, Peter; Hagen, Hans

    2008-07-03

    Laser wakefield particle accelerators have shown the potential to generate electric fields thousands of times higher than those of conventional accelerators. The resulting extremely short particle acceleration distance could yield a potential new compact source of energetic electrons and radiation, with wide applications from medicine to physics. Physicists investigate laser-plasma internal dynamics by running particle-in-cell simulations; however, this generates a large dataset that requires time-consuming, manual inspection by experts in order to detect key features such as beam formation. This paper describes a framework to automate the data analysis and classification of simulation data. First, we propose a new method to identify locations with high density of particles in the space-time domain, based on maximum extremum point detection on the particle distribution. We analyze high density electron regions using a lifetime diagram by organizing and pruning the maximum extrema as nodes in a minimum spanning tree. Second, we partition the multivariate data using fuzzy clustering to detect time steps in a experiment that may contain a high quality electron beam. Finally, we combine results from fuzzy clustering and bunch lifetime analysis to estimate spatially confined beams. We demonstrate our algorithms successfully on four different simulation datasets.

  14. Compact prisms for polarisation splitting of fibre laser beams

    SciTech Connect

    Davydov, B L; Yagodkin, D I

    2005-11-30

    Simple compact monoprisms for spatial splitting of polarised laser beams with relatively small diameters (no more than 1 mm) are considered. Prisms can be made of optically inactive CaCO{sub 3}, {alpha}-BaB{sub 2}O{sub 4} ({alpha}-BBO), LiIO{sub 3}, LiNbO{sub 3}, YVO{sub 4}, and TiO{sub 2} crystals known in polarisation optics. The exact solution of the Snell equation for the extraordinary wave reflected from a surface arbitrarily tilted to its wave vector is obtained. The analysis of variants of the solution allows the fabrication of prisms with any deviation angles of the extraordinary wave by preserving the propagation direction of the ordinary wave. Three variants of prisms are considered: with minimised dimensions, with the Brewster output of the extraordinary beam, and with the deviation of the extraordinary wave by 90{sup 0}. Calcite prisms with the deviation angles for the extraordinary beam {approx}19{sup 0} and 90{sup 0} are tested experimentally. (control of laser radiation parameters)

  15. Detection of transient reflections during laser beam welding of copper

    NASA Astrophysics Data System (ADS)

    Ganser, Andreas; Liebl, Stefan; Schmitz, Patrick; Zaeh, Michael F.

    2016-03-01

    The advantages of laser beam welding, such as its high flexibility, its high local energy input, and its fast processing speed, led to a substantial increase of industrial applications using this technology. However, only a portion of the laser energy is absorbed during welding due to reflections. These reflections can damage the system components and lead to a reduced process efficiency. Especially when welding copper materials with infrared laser beam sources, the reflections play a significant role, since the reflection coefficient of copper is very high at infrared wavelengths. Therefore, a formation of a keyhole is necessary for a stable and efficient welding process. A theoretical model for the calculation of the reflections on an arbitrary position above the process zone, as well as a radiation analyzer based on a modular set-up are presented. This device enables a time- and space-resolved measurement of the reflected radiation. Using the experimental results, characteristic positions on the hemisphere could be identified to calibrate the theoretical model. The calibrated model allows to analyze the reflected radiation during the welding process to determine the energy which is absorbed by the work piece.

  16. Laser-driven relativistic electron beam interaction with solid dielectric

    NASA Astrophysics Data System (ADS)

    Sarkisov, G. S.; Ivanov, V. V.; Leblanc, P.; Sentoku, Y.; Yates, K.; Wiewior, P.; Chalyy, O.; Astanovitskiy, A.; Bychenkov, V. Yu.; Jobe, D.; Spielman, R. B.

    2012-07-01

    The multi-frames shadowgraphy, interferometry and polarimetry diagnostics with sub-ps time resolution were used for an investigation of ionization wave dynamics inside a glass target induced by laser-driven relativistic electron beam. Experiments were done using the 50 TW Leopard laser at the UNR. For a laser flux of ˜2×1018W/cm2 a hemispherical ionization wave propagates at c/3. The maximum of the electron density inside the glass target is ˜2×1019cm-3. Magnetic and electric fields are less than ˜15 kG and ˜1 MV/cm, respectively. The electron temperature has a maximum of ˜0.5 eV. 2D interference phase shift shows the "fountain effect" of electron beam. The very low ionization inside glass target ˜0.1% suggests a fast recombination at the sub-ps time scale. 2D PIC-simulations demonstrate radial spreading of fast electrons by self-consistent electrostatic fields.

  17. Laser-driven relativistic electron beam interaction with solid dielectric

    SciTech Connect

    Sarkisov, G. S.; Ivanov, V. V.; Leblanc, P.; Sentoku, Y.; Yates, K.; Wiewior, P.; Chalyy, O.; Astanovitskiy, A.; Bychenkov, V. Yu.; Jobe, D.; Spielman, R. B.

    2012-07-30

    The multi-frames shadowgraphy, interferometry and polarimetry diagnostics with sub-ps time resolution were used for an investigation of ionization wave dynamics inside a glass target induced by laser-driven relativistic electron beam. Experiments were done using the 50 TW Leopard laser at the UNR. For a laser flux of {approx}2 Multiplication-Sign 10{sup 18}W/cm{sup 2} a hemispherical ionization wave propagates at c/3. The maximum of the electron density inside the glass target is {approx}2 Multiplication-Sign 10{sup 19}cm{sup -3}. Magnetic and electric fields are less than {approx}15 kG and {approx}1 MV/cm, respectively. The electron temperature has a maximum of {approx}0.5 eV. 2D interference phase shift shows the 'fountain effect' of electron beam. The very low ionization inside glass target {approx}0.1% suggests a fast recombination at the sub-ps time scale. 2D PIC-simulations demonstrate radial spreading of fast electrons by self-consistent electrostatic fields.

  18. The Collinear Fast Beam laser Spectroscopy (CFBS) experiment at TRIUMF

    NASA Astrophysics Data System (ADS)

    Voss, A.; Procter, T. J.; Shelbaya, O.; Amaudruz, P.; Buchinger, F.; Crawford, J. E.; Daviel, S.; Mané, E.; Pearson, M. R.; Tamimi, W. Al

    2016-03-01

    Laser spectroscopy experiments at radioactive ion beam facilities around the world investigate properties of exotic nuclei for scientific endeavours such as, but not limited to, the investigation of nuclear structure. Advancements in experimental sensitivity and performance are continuously needed in order to extend the reach of nuclei that can be measured. The collinear fast beam laser spectroscopy (CFBS) setup at TRIUMF, coupled to an out-of-plane radio-frequency quadrupole Paul trap, enables measurements of some of the most fundamental nuclear properties for long-lived ground and isomeric states. The first comprehensive overview of the CFBS experiment is provided along with descriptions of key developments that extend the reach of laser spectroscopy experiments. A novel data acquisition technique structured around three-dimensional spectra is presented, where the integration of a custom multi-channel-scalar provides photon counts correlated with arrival time and acceleration voltage for post-experiment analysis. In addition, new rapid light manipulation techniques are discussed that suppress undesirable hyperfine pumping effects and regain losses in experimental efficiency.

  19. Dual-beam laser traps in biology and medicine: when one beam is not enough

    NASA Astrophysics Data System (ADS)

    Whyte, Graeme; Lautenschläger, Franziska; Kreysing, Moritz; Boyde, Lars; Ekpenyong, Andrew; Delabre, Ulysse; Chalut, Kevin; Franze, Kristian; Guck, Jochen

    2010-08-01

    Optical traps are nowadays quite ubiquitous in biophysical and biological studies. The term is often used synonymously with optical tweezers, one particular incarnation of optical traps. However, there is another kind of optical trap consisting of two non-focused, counter-propagating laser beams. This dual-beam trap predates optical tweezers by almost two decades and currently experiences a renaissance. The advantages of dual-beam traps include lower intensities on the trapped object, decoupling from imaging optics, and the possibility to trap cells and cell clusters up to 100 microns in diameter. When used for deforming cells this trap is referred to as an optical stretcher. I will review several applications of such traps in biology and medicine for the detection of cancer cells, sorting stem cells, testing light guiding properties of retinal cells and the controlled rotation of cells for single cell tomography.

  20. Hollow circular-truncated cone resonator and its hollow variable biconical laser beam

    NASA Astrophysics Data System (ADS)

    Liu, Jinglun; Chen, Mei; Wang, Qionghua; Sun, Nianchun

    2014-05-01

    To obtain a hollow variable biconical laser beam (HVBLB), a CO2 laser having a hollow circular-truncated cone resonator (HCTCR) is presented. This HCTCR comprises a rotationally symmetric total-reflecting concave mirror at the bottom, a rotationally symmetric part-reflecting convex mirror at the top, and a hollow circular-truncated cone discharge tube at the middle. The cross section of this generated biconical laser beam changes from annulus to circular to annulus and the size of this cross section from big to small to large as the propagation distance increases. So, a kind of laser beam with variable center intensity from zero to peak value to zero is obtained and is known as HVBLB. Due to the inclusion of part of the hollow laser beam (HLB) and solid laser beam, this HVBLB requires no additional beam-shaping element and has broad applications such as optical trapping and commercial manufacturing.

  1. Random wandering of laser beams with orbital angular momentum during propagation through atmospheric turbulence.

    PubMed

    Aksenov, Valerii P; Kolosov, Valeriy V; Pogutsa, Cheslav E

    2014-06-10

    The propagation of laser beams having orbital angular momenta (OAM) in the turbulent atmosphere is studied numerically. The variance of random wandering of these beams is investigated with the use of the Monte Carlo technique. It is found that, among various types of vortex laser beams, such as the Laguerre-Gaussian (LG) beam, modified Bessel-Gaussian beam, and hypergeometric Gaussian beam, having identical initial effective radii and OAM, the LG beam occupying the largest effective volume in space is the most stable one.

  2. Numerical analysis of the effects of non-conventional laser beam geometries during laser melting of metallic materials

    NASA Astrophysics Data System (ADS)

    Safdar, Shakeel; Li, Lin; Sheikh, M. A.

    2007-01-01

    Laser melting is an important industrial activity encountered in a variety of laser manufacturing processes, e.g. selective laser melting, welding, brazing, soldering, glazing, surface alloying, cladding etc. The majority of these processes are carried out by using either circular or rectangular beams. At present, the melt pool characteristics such as melt pool geometry, thermal gradients and cooling rate are controlled by the variation of laser power, spot size or scanning speed. However, the variations in these parameters are often limited by other processing conditions. Although different laser beam modes and intensity distributions have been studied to improve the process, no other laser beam geometries have been investigated. The effect of laser beam geometry on the laser melting process has received very little attention. This paper presents an investigation of the effects of different beam geometries including circular, rectangular and diamond shapes on laser melting of metallic materials. The finite volume method has been used to simulate the transient effects of a moving beam for laser melting of mild steel (EN-43A) taking into account Marangoni and buoyancy convection. The temperature distribution, melt pool geometry, fluid flow velocities and heating/cooling rates have been calculated. Some of the results have been compared with the experimental data.

  3. Wind Tunnel Testing of a One-Dimensional Laser Beam Scanning and Laser Sheet Approach to Shock Sensing

    NASA Technical Reports Server (NTRS)

    Tokars, Roger; Adamovsky, Grigory; Anderson, Robert; Hirt, Stefanie; Huang, John; Floyd, Bertram

    2012-01-01

    A 15- by 15-cm supersonic wind tunnel application of a one-dimensional laser beam scanning approach to shock sensing is presented. The measurement system design allowed easy switching between a focused beam and a laser sheet mode for comparison purposes. The scanning results were compared to images from the tunnel Schlieren imaging system. The tests revealed detectable changes in the laser beam in the presence of shocks. The results lend support to the use of the one-dimensional scanning beam approach for detecting and locating shocks in a flow, but some issues must be addressed in regards to noise and other limitations of the system.

  4. Laser beam scanning by rotary mirrors. I. Modeling mirror-scanning devices.

    PubMed

    Li, Y; Katz, J

    1995-10-01

    Avector approach to tracing the path of a laser beam through an optical system containing movable plane mirrors is described, which permits a unified treatment of a number of basic mirror-scanning devices. We show that the scan field produced by the mirror-scanning system is a curved surface with a straight line as its generating element. The cross section of the scan field can be a circle, an ellipse, or a curve in the shape of an egg. Based on this understanding, some advanced topics are addressed, e.g., the relationship between the scan field and the scan pattern, the dependence of the scan pattern on the location and orientation of the observation surface, optical distortions in a scan pattern, spot-size enlargement caused by non-normal incidence of the scan beam on the observation plane, and so on. Design equations and curves are derived for the mirror-scanning devices that most frequently exist in linear and circular scan technology. Part II contains an analysis of the galvanometer-based optical scanner paddle scanner and the regular polygon. In Part III, X-Y scanning systems are studied. PMID:21060488

  5. Adaptive slit beam shaping for direct laser written waveguides.

    PubMed

    Salter, P S; Jesacher, A; Spring, J B; Metcalf, B J; Thomas-Peter, N; Simmonds, R D; Langford, N K; Walmsley, I A; Booth, M J

    2012-02-15

    We demonstrate an improved method for fabricating optical waveguides in bulk materials by means of femtosecond laser writing. We use an LC spatial light modulator (SLM) to shape the beam focus by generating adaptive slit illumination in the pupil of the objective lens. A diffraction grating is applied in a strip across the SLM to simulate a slit, with the first diffracted order mapped onto the pupil plane of the objective lens while the zeroth order is blocked. This technique enables real-time control of the beam-shaping parameters during writing, facilitating the fabrication of more complicated structures than is possible using nonadaptive methods. Waveguides are demonstrated in fused silica with a coupling loss to single-mode fibers in the range of 0.2 to 0.5 dB and propagation loss <0.4 dB/cm.

  6. Beam-diagnostics techniques for multiterawatt CO2 lasers

    NASA Astrophysics Data System (ADS)

    Bigio, I. J.; Jackson, S. V.; Laird, A.; Seagrave, J.

    1980-03-01

    The mechanical, optical and electrical designs of beam-diagnostics system for the eight-beam 10-kJ, Helios CO2 laser fusion facility at Los Alamos are described. The measurement of the prepulse, main pulse and postpulse regions of the temporal distribution of energy is discussed; signals are recorded by individually timed, linear gated, charge-integrating digitizers. For prepulse energy, photoconductive detectors with low-noise properties and fast rise time (about 0.5 nsec) are considered, while a simple photon-drag detector can be used for mainpulse vs. postpulse energy measurements. In addition, a combined pyroelectric detector and 5-GHz oscilloscope is suitable for measuring temporal pulse shape.

  7. Beam wandering of femtosecond laser filament in air.

    PubMed

    Yang, Jing; Zeng, Tao; Lin, Lie; Liu, Weiwei

    2015-10-01

    The spatial wandering of a femtosecond laser filament caused by the filament heating effect in air has been studied. An empirical formula has also been derived from the classical Karman turbulence model, which determines quantitatively the displacement of the beam center as a function of the propagation distance and the effective turbulence structure constant. After fitting the experimental data with this formula, the effective turbulence structure constant has been estimated for a single filament generated in laboratory environment. With this result, one may be able to estimate quantitatively the displacement of a filament over long distance propagation and interpret the practical performance of the experiments assisted by femtosecond laser filamentation, such as remote air lasing, pulse compression, high order harmonic generation (HHG), etc.

  8. Analysis of laser beam weldability of Inconel 738 superalloy

    SciTech Connect

    Egbewande, A.T.; Buckson, R.A.; Ojo, O.A.

    2010-05-15

    The susceptibility of pre-weld heat treated laser beam welded IN 738 superalloy to heat affected zone (HAZ) cracking was studied. A pre-weld heat treatment that produced the minimal grain boundary liquation resulted in a higher level of cracking compared to those with more intergranular liquation. This deviation from the general expectation of influence of intergranular liquation extent on HAZ microfissuring is attributable to the reduction in the ability of the base alloy to accommodate welding tensile stress that accompanied a pre-weld heat treatment condition designed to minimize intergranular liquation. Furthermore, in contrast to what has been generally reported in other nickel-based superalloys, a decrease in laser welding speed resulted in increased HAZ cracking in the IN 738, which can be attributed to exacerbated process instability at lower welding speeds.

  9. Beam wandering of femtosecond laser filament in air.

    PubMed

    Yang, Jing; Zeng, Tao; Lin, Lie; Liu, Weiwei

    2015-10-01

    The spatial wandering of a femtosecond laser filament caused by the filament heating effect in air has been studied. An empirical formula has also been derived from the classical Karman turbulence model, which determines quantitatively the displacement of the beam center as a function of the propagation distance and the effective turbulence structure constant. After fitting the experimental data with this formula, the effective turbulence structure constant has been estimated for a single filament generated in laboratory environment. With this result, one may be able to estimate quantitatively the displacement of a filament over long distance propagation and interpret the practical performance of the experiments assisted by femtosecond laser filamentation, such as remote air lasing, pulse compression, high order harmonic generation (HHG), etc. PMID:26480079

  10. Electrostatic-accelerator free-electron lasers for power beaming

    SciTech Connect

    Pinhasi, Y.; Yakover, I.M.; Gover, A.

    1995-12-31

    Novel concepts of electrostatic-accelerator free-electron lasers (EA-FELs) for energy transfer through the atmosphere are presented. The high average power attained from an EA-FEL makes it an efficient source of mm-wave for power beaming from a ground stations. General aspects of operating the FEL as a high power oscillator (like acceleration voltage, e-beam. current, gain and efficiency) are studied and design considerations are described. The study takes into account requirements of power beaming application such as characteristic dips in the atmospheric absorption spectrum, sizes of transmitting and receiving antennas and meteorological conditions. We present a conceptual design of a moderate voltage (.5-3 MeV) high current (1-10 Amp) EA-FEL operating at mm-wavelength bands, where the atmospheric attenuation allows efficient power beaming to space. The FEL parameters were calculated, employing analytical and numerical models. The performance parameters of the FEL (power, energy conversion efficiency average power) will be discussed in connection to the proposed application.

  11. Production of pulsed atomic oxygen beams via laser vaporization methods

    NASA Technical Reports Server (NTRS)

    Brinza, David E.; Coulter, Daniel R.; Liang, Ranty H.; Gupta, Amitava

    1987-01-01

    Energetic pulsed atomic oxygen beams were generated by laser-driven evaporation of cryogenically frozen ozone/oxygen films and thin films of indium-tin oxide (ITO). Mass and energy characterization of beams from the ozone/oxygen films were carried out by mass spectrometry. The peak flux, found to occur at 10 eV, is estimated from this data to be 3 x 10(20) m(-2) s(-1). Analysis of the time-of-flight data indicates a number of processes contribute to the formation of the atomic oxygen beam. The absence of metastable states such as the 2p(3) 3s(1) (5S) level of atomic oxygen blown off from ITO films is supported by the failure to observe emission at 777.3 nm from the 2p(3) 3p(1) (5P sub J) levels. Reactive scattering experiments with polymer film targets for atomic oxygen bombardment are planned using a universal crossed molecular beam apparatus.

  12. Evolution of decentred laser beams propagating through atmospheric turbulence

    NASA Astrophysics Data System (ADS)

    Li, Xiaoqing; Ji, Xiaoling; Zhu, Wenyue

    2012-07-01

    The changes of the average intensity, the centre of beam gravity and the position of intensity maximum of decentred laser beams propagating through atmospheric turbulence are examined in detail. It is shown that the decentred intensity distribution is amended gradually with increasing the propagation distance and the strength of turbulence, and it becomes an off-axis Gaussian-like beam when the propagation distance and the strength of turbulence become large enough. The centre of beam gravity is independent of both the propagation distance and the strength of turbulence. On the other hand, there are two intensity maxima, and their positions are symmetrical around the propagation z-axis when the propagation distance z is small. With increasing z, there is only one intensity maximum. As z further increases, position of the intensity maximum is further shifted towards the z-axis. When z is large enough, the position of the intensity maximum is unchanged. The unchanged position of the intensity maximum moves further away from the z-axis with an increase in the refraction index structure constant, the decentred parameter and the waist width.

  13. Optical guiding and beam bending in free-electron lasers

    SciTech Connect

    Scharlemann, E.T.

    1987-01-01

    The electron beam in a free-electron laser (FEL) can act as an optical fiber, guiding or bending the optical beam. The refractive and gain effects of the bunched electron beam can compensate for diffraction, making possible wigglers that are many Rayleigh ranges (i.e., characteristic diffraction lengths) long. The origin of optical guiding can be understood by examining gain and refractive guiding in a fiber with a complex index of refraction, providing a mathematical description applicable also to the FEL, with some extensions. In the exponential gain regime of the FEL, the electron equations of motion must be included, but a self-consistent description of exponential gain with diffraction fully included becomes possible. The origin of the effective index of refraction of an FEL is illustrated with a simple example of bunched, radiating dipoles. Some of the properties of the index of refraction are described. The limited experimental evidence for optical beam bending is summarized. The evidence does not yet provide conclusive proof of the existence of optical guiding, but supports the idea. Finally, the importance of refractive guiding for the performance of a high-gain tapered-wiggler FEL amplifier is illustrated with numerical simulations.

  14. Parametric study of beam refraction problems across laser anemometer windows

    NASA Technical Reports Server (NTRS)

    Owen, A. K.

    1986-01-01

    The experimenter is often required to view flows through a window with a different index of refraction than either the medium being observed or the medium that the laser anemometer is immersed in. The refraction that occurs at the window surfaces may lead to undesirable changes in probe volume position or beam crossing angle and can lead to partial or complete beam uncrossing. This report describes the results of a parametric study of this problem using a ray tracing technique to predict these changes. The windows studied were a flat plate and a simple cyclinder. For the flat-plate study: (1) surface thickness, (2) beam crossing angle, (3) bisecting line - surface normal angle, and (4) incoming beam plane surface orientation were varied. For the cylindrical window additional parameters were also varied: (1) probe volume immersion, (2) probe volume off-radial position, and (3) probe volume position out of the R-theta plane of the lens. A number of empirical correlations were deduced to aid the interested reader in determining the movement, uncrossing, and change in crossing angle for a particular situation.

  15. Introduction of a CAM feature model for laser beam welding

    NASA Astrophysics Data System (ADS)

    Kittel, Jochen; Dahmen, Michael J.; Fuerst, B.; Kaierle, Stefan; Kreutz, Ernst-Wolfgang; Poprawe, Reinhart

    1997-09-01

    An approach to improve the quality of offline programming for laser beam welding is described. A CAD-dataset is combined with technological information using a feature model. A feature consists of the basic geometry, process parameters, a set of strategies in which way it can be processed, and rules to select the optimum strategy depending on the boundary conditions. The resulting welding task is represented by a list of features from which an NC-dataset is generated, containing all process information. The aim of the development is to design a feature based technology module which is integrated into a flexible, fault tolerant and process near planning tool.

  16. One-dimensional parabolic-beam photonic crystal laser.

    PubMed

    Ahn, Byeong-Hyeon; Kang, Ju-Hyung; Kim, Myung-Ki; Song, Jung-Hwan; Min, Bumki; Kim, Ki-Soo; Lee, Yong-Hee

    2010-03-15

    We report one-dimensional (1-D) parabolic-beam photonic crystal (PhC) lasers in which the width of the PhC slab waveguide is parabolically tapered. A few high-Q resonant modes are confirmed in the vicinity of the tapered region where Gaussian-shaped photonic well is formed. These resonant modes originate from the dielectric PhC guided mode and overlap with the gain medium efficiently. It is also shown that the far-field radiation profile is closely associated with the symmetry of the structural perturbation.

  17. Edge-emitting diode lasers with narrow circular beam output

    NASA Astrophysics Data System (ADS)

    Wang, Lijie; Tong, Cunzhu; Zeng, Yugang; Ning, Yongqiang; Wang, Lijun

    2015-05-01

    We report near circular beam output from 808 nm edge-emitting diode lasers based on Bragg reflection waveguide design. Increasing quantum well number combined with reducing defect layer index and thickness was used to achieve high power output and extremely low vertical far field divergence. The TQW-BRLs achieve the lowest vertical divergence of 4.91° (full width at half maximum) and 9.8° (95% power). The maximum power of 4.6 W was achieved in the mounted DQW-BRL device under continuous-wave operation, being limited by thermal rollover.

  18. High power laser beam machining of structural ceramics

    NASA Astrophysics Data System (ADS)

    Firestone, R. F.; Vesely, E. J., Jr.

    Machining fully dense, structural ceramics to final dimensions using diamond abrasives is a slow and expensive process that weakens the ceramic. The objective of this research program was to investigate the feasibility of laser beam machining (LBM) to final dimensions without incurring loss of strength. The ceramics studied were all candidates for heat engine applications: reaction sintered silicon nitride; hot pressed silicon carbide; and sintered, partially magnesia-stabilized zirconia (PSZ). These fully dense ceramics are very hard; silicon carbide is close to diamond in hardness. In addition, a refractory grade, clay-bonded porous silicon carbide was machined during preliminary investigations.

  19. Ion-beam assisted laser fabrication of sensing plasmonic nanostructures

    PubMed Central

    Kuchmizhak, Aleksandr; Gurbatov, Stanislav; Vitrik, Oleg; Kulchin, Yuri; Milichko, Valentin; Makarov, Sergey; Kudryashov, Sergey

    2016-01-01

    Simple high-performance, two-stage hybrid technique was developed for fabrication of different plasmonic nanostructures, including nanorods, nanorings, as well as more complex structures on glass substrates. In this technique, a thin noble-metal film on a dielectric substrate is irradiated by a single tightly focused nanosecond laser pulse and then the modified region is slowly polished by an accelerated argon ion (Ar+) beam. As a result, each nanosecond laser pulse locally modifies the initial metal film through initiation of fast melting and subsequent hydrodynamic processes, while the following Ar+-ion polishing removes the rest of the film, revealing the hidden topography features and fabricating separate plasmonic structures on the glass substrate. We demonstrate that the shape and lateral size of the resulting functional plasmonic nanostructures depend on the laser pulse energy and metal film thickness, while subsequent Ar+-ion polishing enables to vary height of the resulting nanostructures. Plasmonic properties of the fabricated nanostructures were characterized by dark-field micro-spectroscopy, Raman and photoluminescence measurements performed on single nanofeatures, as well as by supporting numerical calculations of the related electromagnetic near-fields and Purcell factors. The developed simple two-stage technique represents a new step towards direct large-scale laser-induced fabrication of highly ordered arrays of complex plasmonic nanostructures. PMID:26776569

  20. Investigation of the accuracy of M2 measurement of CO2 laser beams

    NASA Astrophysics Data System (ADS)

    Ward, Brooke A.; Assa, Shlomo; Davis, Brian W.; Edwards, Christopher B.; Muys, Peter F.

    1995-04-01

    The propagation parameters of CO2 laser beams have been investigated using second moment and knife-edge width measurement techniques. The characteristics of two laser types have been measured: a low power stabilized single frequency instrument and a prototype 3 kW laser. The propagation parameters have been estimated by using two commercial beam analyzing instruments: a rotating drum knife-edge device and a 2D array scanner. The propagation of errors through the analysis procedures has been investigated. The experiments were designed to assess the viability of the draft ISO standard for the measurement of beam width and propagation characteristics of real laser beams. Uncertainties in the estimated beam parameters, resulting from the propagation of errors, are taken into account when assessing the relative merits of the width measurement procedures. It was found that, for the high quality laser beam investigated, there were some small but systematic variations in estimating the width of waists of subject laser beams. In the case of the lower quality, high power laser beam, both the knife-edge and second moment techniques produced estimates of the input beam waist properties that were within the experimental uncertainty limits but again some inconsistency was displayed. It is suggested that the source of the inconsistency is diffraction by hard-edge apertures in the beam path. Nevertheless, the ISO standard procedures are judged to be suitable for the measurement of important beam parameters with an accuracy that is sufficient for the majority of industrial applications.