Aerodynamic laser-heated contactless furnace for neutron scattering experiments at elevated temperatures

NASA Astrophysics Data System (ADS)

Landron, Claude; Hennet, Louis; Coutures, Jean-Pierre; Jenkins, Tudor; Alétru, Chantal; Greaves, Neville; Soper, Alan; Derbyshire, Gareth

2000-04-01

Conventional radiative furnaces require sample containment that encourages contamination at elevated temperatures and generally need windows which restrict the entrance and exit solid angles required for diffraction and scattering measurements. We describe a contactless windowless furnace based on aerodynamic levitation and laser heating which has been designed for high temperature neutron scattering experiments. Data from initial experiments are reported for crystalline and amorphous oxides at temperatures up to 1900 °C, using the spallation neutron source ISIS together with our laser-heated aerodynamic levitator. Accurate reproduction of thermal expansion coefficients and radial distribution functions have been obtained, demonstrating the utility of aerodynamic levitation methods for neutron scattering methods.

Modeling experimental plasma diagnostics in the FLASH code: Thomson scattering

NASA Astrophysics Data System (ADS)

Weide, Klaus; Flocke, Norbert; Feister, Scott; Tzeferacos, Petros; Lamb, Donald

2017-10-01

Spectral analysis of the Thomson scattering of laser light sent into a plasma provides an experimental method to quantify plasma properties in laser-driven plasma experiments. We have implemented such a synthetic Thomson scattering diagnostic unit in the FLASH code, to emulate the probe-laser propagation, scattering and spectral detection. User-defined laser rays propagate into the FLASH simulation region and experience scattering (change in direction and frequency) based on plasma parameters. After scattering, the rays propagate out of the interaction region and are spectrally characterized. The diagnostic unit can be used either during a physics simulation or in post-processing of simulation results. FLASH is publicly available at flash.uchicago.edu. U.S. DOE NNSA, U.S. DOE NNSA ASC, U.S. DOE Office of Science and NSF.

Laser induced heat source distribution in bio-tissues

NASA Astrophysics Data System (ADS)

Li, Xiaoxia; Fan, Shifu; Zhao, Youquan

2006-09-01

During numerical simulation of laser and tissue thermal interaction, the light fluence rate distribution should be formularized and constituted to the source term in the heat transfer equation. Usually the solution of light irradiative transport equation is given in extreme conditions such as full absorption (Lambert-Beer Law), full scattering (Lubelka-Munk theory), most scattering (Diffusion Approximation) et al. But in specific conditions, these solutions will induce different errors. The usually used Monte Carlo simulation (MCS) is more universal and exact but has difficulty to deal with dynamic parameter and fast simulation. Its area partition pattern has limits when applying FEM (finite element method) to solve the bio-heat transfer partial differential coefficient equation. Laser heat source plots of above methods showed much difference with MCS. In order to solve this problem, through analyzing different optical actions such as reflection, scattering and absorption on the laser induced heat generation in bio-tissue, a new attempt was made out which combined the modified beam broaden model and the diffusion approximation model. First the scattering coefficient was replaced by reduced scattering coefficient in the beam broaden model, which is more reasonable when scattering was treated as anisotropic scattering. Secondly the attenuation coefficient was replaced by effective attenuation coefficient in scattering dominating turbid bio-tissue. The computation results of the modified method were compared with Monte Carlo simulation and showed the model provided reasonable predictions of heat source term distribution than past methods. Such a research is useful for explaining the physical characteristics of heat source in the heat transfer equation, establishing effective photo-thermal model, and providing theory contrast for related laser medicine experiments.

Laser-plasma interactions in magnetized environment

NASA Astrophysics Data System (ADS)

Shi, Yuan; Qin, Hong; Fisch, Nathaniel J.

2018-05-01

Propagation and scattering of lasers present new phenomena and applications when the plasma medium becomes strongly magnetized. With mega-Gauss magnetic fields, scattering of optical lasers already becomes manifestly anisotropic. Special angles exist where coherent laser scattering is either enhanced or suppressed, as we demonstrate using a cold-fluid model. Consequently, by aiming laser beams at special angles, one may be able to optimize laser-plasma coupling in magnetized implosion experiments. In addition, magnetized scattering can be exploited to improve the performance of plasma-based laser pulse amplifiers. Using the magnetic field as an extra control variable, it is possible to produce optical pulses of higher intensity, as well as compress UV and soft x-ray pulses beyond the reach of other methods. In even stronger giga-Gauss magnetic fields, laser-plasma interaction enters a relativistic-quantum regime. Using quantum electrodynamics, we compute a modified wave dispersion relation, which enables correct interpretation of Faraday rotation measurements of strong magnetic fields.

Laser Diagnostics for combustion temperature and species measurements

NASA Technical Reports Server (NTRS)

Eckbreth, Alan C.

1988-01-01

Laser optical diagnostic techniques for the measurement of combustion gaseous-phase temperatures and, or species concentrations are discussed. The techniques fall into two classes: incoherent (Rayleigh scattering, spontaneous Raman scattering, laser induced fluorescence spectroscopy) and coherent (coherent anti-Stokes Raman spectroscopy). The advantages, disadvantages and applicability of each method are outlined.

Indetermination of particle sizing by laser diffraction in the anomalous size ranges

NASA Astrophysics Data System (ADS)

Pan, Linchao; Ge, Baozhen; Zhang, Fugen

2017-09-01

The laser diffraction method is widely used to measure particle size distributions. It is generally accepted that the scattering angle becomes smaller and the angles to the location of the main peak of scattered energy distributions in laser diffraction instruments shift to smaller values with increasing particle size. This specific principle forms the foundation of the laser diffraction method. However, this principle is not entirely correct for non-absorbing particles in certain size ranges and these particle size ranges are called anomalous size ranges. Here, we derive the analytical formulae for the bounds of the anomalous size ranges and discuss the influence of the width of the size segments on the signature of the Mie scattering kernel. This anomalous signature of the Mie scattering kernel will result in an indetermination of the particle size distribution when measured by laser diffraction instruments in the anomalous size ranges. By using the singular-value decomposition method we interpret the mechanism of occurrence of this indetermination in detail and then validate its existence by using inversion simulations.

Method and apparatus for measuring micro structures, anisotropy and birefringence in polymers using laser scattered light

DOEpatents

Grek, Boris; Bartolick, Joseph; Kennedy, Alan D.

2000-01-01

A method and apparatus for measuring microstructures, anistropy and birefringence in polymers using laser scattered light includes a laser which provides a beam that can be conditioned and is directed at a fiber or film which causes the beam to scatter. Backscatter light is received and processed with detectors and beam splitters to obtain data. The data is directed to a computer where it is processed to obtain information about the fiber or film, such as the birefringence and diameter. This information provides a basis for modifications to the production process to enhance the process.

Laser and biological methods of biomonitoring of surrounding waters

NASA Astrophysics Data System (ADS)

Posudin, Yuri I.

1994-02-01

Three main methods are proposed for the biomonitoring of chemicals in water medium: laser spectrofluorometry, which is based on the excitation and recording of the spectra of fluorescence; laser scattering, which is connected with measurement of the Doppler shifts of the scattered light from the motile cells; videomicrography, which provides the analysis of parameters of photomovement of motile cells via microscope and video system. Such chemicals as surface-active substances, heavy metals and pesticides were determined in water medium due to these methods.

Through-transmission laser welding of glass fibre composite: Experimental light scattering identification

NASA Astrophysics Data System (ADS)

Cosson, Benoit; Asséko, André Chateau Akué; Dauphin, Myriam

2018-05-01

The purpose of this paper is to develop a cost-effective, efficient and quick to implement experimental optical method in order to predict the optical properties (extinction coefficient) of semi-transparent polymer composites. The extinction coefficient takes into account the effects due to the absorption and the scattering phenomena in a semi-transparent component during the laser processes, i.e. TTLW (through-transmission laser welding). The present method used a laser as light source and a reflex camera equipped with a macro lens as a measurement device and is based on the light transmission measurement through different thickness samples. The interaction between the incident laser beam and the semi-transparent composite is exanimated. The results are presented for the case of a semi-transparent composite reinforced with the unidirectional glass fiber (UD). A numerical method, ray tracing, is used to validate the experimental results. The ray tracing method is appropriate to characterize the light-scattering phenomenon in semi-transparent materials.

Device and method for noresonantly Raman shifting ultraviolet radiation

DOEpatents

Loree, Thomas R.; Barker, Dean L.

1979-01-01

A device and method for nonresonantly Raman shifting broad band uv excimer laser radiation, which enhances preselected Stokes signals by varying the pressure of the Raman scattering medium, the focal interaction length of the incident radiation within the Raman scattering medium and its power density level. Gaseous molecular H.sub.2, D.sub.2, CH.sub.4 (methane), HD and mixes thereof, and liquid N.sub.2 are used as the Raman scattering medium to frequency shift the outputs of high power KrF and ArF lasers. A cable fed discharge with an unstable resonant cavity configuration is utilized to produce the output laser power levels required for operation.

Robust authentication through stochastic femtosecond laser filament induced scattering surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Haisu; Tzortzakis, Stelios, E-mail: stzortz@iesl.forth.gr; Materials Science and Technology Department, University of Crete, 71003 Heraklion

2016-05-23

We demonstrate a reliable authentication method by femtosecond laser filament induced scattering surfaces. The stochastic nonlinear laser fabrication nature results in unique authentication robust properties. This work provides a simple and viable solution for practical applications in product authentication, while also opens the way for incorporating such elements in transparent media and coupling those in integrated optical circuits.

Experimental and Simulative Investigation of Laser Transmission Welding under Consideration of Scattering

NASA Astrophysics Data System (ADS)

Devrient, M.; Da, X.; Frick, T.; Schmidt, M.

Laser transmission welding is a well known joining technology for thermoplastics. Because of the needs of lightweight, cost effective and green production thermoplastics are usually filled with glass fibers. These lead to higher absorption and more scattering within the upper joining partner with a negative influence on the welding process. Here an experimental method for the characterization of the scattering behavior of semi crystalline thermoplastics filled with short glass fibers and a finite element model of the welding process capable to consider scattering as well as an analytical model are introduced. The experimental data is used for the numerical and analytical investigation of laser transmission welding under consideration of scattering. The scattering effects of several thermoplastics onto the calculated temperature fields as well as weld seam geometries are quantified.

Studies on remote sensing method of particle size and water density distribution in mists and clouds using laser radar techniques

NASA Technical Reports Server (NTRS)

Shimizu, H.; Kobayasi, T.; Inaba, H.

1979-01-01

A method of remote measurement of the particle size and density distribution of water droplets was developed. In this method, the size of droplets is measured from the Mie scattering parameter which is defined as the total-to-backscattering ratio of the laser beam. The water density distribution is obtained by a combination of the Mie scattering parameter and the extinction coefficient of the laser beam. This method was examined experimentally for the mist generated by an ultrasonic mist generator and applied to clouds containing rain and snow. Compared with the conventional sampling method, the present method has advantages of remote measurement capability and improvement in accuracy.

CH PLIF and PIV implementation using C-X (0,0) and intra-vibrational band filtered detection

NASA Astrophysics Data System (ADS)

Hammack, Stephen D.; Skiba, Aaron W.; Lee, Tonghun; Carter, Campbell D.

2018-02-01

This study demonstrates advancement in a low-pulse energy methylidyne (CH) planar laser-induced fluorescence (PLIF) method that facilitates its application alongside flows seeded for particle image velocimetry (PIV) or other particle scattering based methods, as well as in high scattering environments. The C-X (0,0) R-branch excitation and filtered detection are carefully selected such that the laser line frequency is heavily attenuated by an edge filter while allowing transmission of most of the (0,0) band fluorescence. There are strong OH A-X (0,0) lines in the vicinity, but they can be avoided or utilized through dye laser tuning. As a demonstration of efficacy, PIV is performed simultaneously with the PLIF imaging. Using the edge filter, particle scattering signal is reduced to sub-fluorescence levels, allowing for flame-front analysis. This achievement enables flame-front tracking at high repetition rates (due to the low-pulse energy required) in combination with a scattering method such as PIV or use in high scattering environments such as enclosed combustors or near burner surfaces.

Computation of tightly-focused laser beams in the FDTD method

PubMed Central

Çapoğlu, İlker R.; Taflove, Allen; Backman, Vadim

2013-01-01

We demonstrate how a tightly-focused coherent TEMmn laser beam can be computed in the finite-difference time-domain (FDTD) method. The electromagnetic field around the focus is decomposed into a plane-wave spectrum, and approximated by a finite number of plane waves injected into the FDTD grid using the total-field/scattered-field (TF/SF) method. We provide an error analysis, and guidelines for the discrete approximation. We analyze the scattering of the beam from layered spaces and individual scatterers. The described method should be useful for the simulation of confocal microscopy and optical data storage. An implementation of the method can be found in our free and open source FDTD software (“Angora”). PMID:23388899

Computation of tightly-focused laser beams in the FDTD method.

PubMed

Capoğlu, Ilker R; Taflove, Allen; Backman, Vadim

2013-01-14

We demonstrate how a tightly-focused coherent TEMmn laser beam can be computed in the finite-difference time-domain (FDTD) method. The electromagnetic field around the focus is decomposed into a plane-wave spectrum, and approximated by a finite number of plane waves injected into the FDTD grid using the total-field/scattered-field (TF/SF) method. We provide an error analysis, and guidelines for the discrete approximation. We analyze the scattering of the beam from layered spaces and individual scatterers. The described method should be useful for the simulation of confocal microscopy and optical data storage. An implementation of the method can be found in our free and open source FDTD software ("Angora").

High-speed laser anemometry based on spectrally resolved Rayleigh scattering

NASA Technical Reports Server (NTRS)

Seasholtz, Richard G.

1991-01-01

Laser anemometry in unseeded flows based on the measurement of the spectrum of Rayleigh scattered laser light is reviewed. The use of molecular scattering avoids the well known problems (particle lag, biasing effects, seed generation, seed injection) of seeded flows. The fundamental limits on velocity measurement accuracy are determined using maximum likelihood methods. Measurement of the Rayleigh spectrum with scanning Fabry-Perot interferometers is analyzed and accuracy limits are established for both single pass and multipass configurations. Multipass configurations have much higher selectivity and are needed for measurements where there is a large amount of excess noise caused by stray laser light. It is shown that Rayleigh scattering is particularly useful for supersonic and hypersonic flows. The results of the analysis are compared with measurements obtained with a Rayleigh scattering diagnostic developed for study of the exhaust plume of a small hydrogen-oxygen rocket, where the velocities are in the range of 1000 to 5000 m/sec.

Electron-beam conditioning by thomson scattering.

PubMed

Schroeder, C B; Esarey, E; Leemans, W P

2004-11-05

A method is proposed for conditioning electron beams via Thomson scattering. The conditioning provides a quadratic correlation between the electron energy deviation and the betatron amplitude of the electrons, which results in enhanced gain in free-electron lasers. Quantum effects imply conditioning must occur at high laser fluence and moderate electron energy. Conditioning of x-ray free-electron lasers should be achievable with present laser technology, leading to significant size and cost reductions of these large-scale facilities.

Interferometric apparatus and method for detection and characterization of particles using light scattered therefrom

DOEpatents

Johnston, Roger G.

1988-01-01

Interferometric apparatus and method for detection and characterization of particles using light scattered therefrom. Differential phase measurements on scattered light from particles are possible using the two-frequency Zeeman effect laser which emits two frequencies of radiation 250 kHz apart. Excellent discrimination and reproducibility for various pure pollen and bacterial samples in suspension have been observed with a single polarization element. Additionally, a 250 kHz beat frequency was recorded from an individual particle traversing the focused output from the laser in a flow cytometer.

Apparatus and method for detection and characterization of particles using light scattered therefrom

DOEpatents

Johnston, R.G.

1987-03-23

Apparatus and method for detection and characterization of particles using light scattered therefrom. Differential phase measurements on scattered light from particles are possible using the two-frequency Zeeman effect laser which emits two frequencies of radiation 250 kHz apart. Excellent discrimination and reproducibility for various pure pollen and bacterial samples in suspension have been observed with a single polarization element. Additionally, a 250 kHz beat frequency was recorded from an individual particle traversing the focused output from the laser in a flow cytometer. 13 figs.

High resolution resonance ionization imaging detector and method

DOEpatents

Winefordner, James D.; Matveev, Oleg I.; Smith, Benjamin W.

1999-01-01

A resonance ionization imaging device (RIID) and method for imaging objects using the RIID are provided, the RIID system including a RIID cell containing an ionizable vapor including monoisotopic atoms or molecules, the cell being positioned to intercept scattered radiation of a resonance wavelength .lambda..sub.1 from the object which is to be detected or imaged, a laser source disposed to illuminate the RIID cell with laser radiation having a wavelength .lambda..sub.2 or wavelengths .lambda..sub.2, .lambda..sub.3 selected to ionize atoms in the cell that are in an excited state by virtue of having absorbed the scattered resonance laser radiation, and a luminescent screen at the back surface of the RIID cell which presents an image of the number and position of charged particles present in the RIID cell as a result of the ionization of the excited state atoms. The method of the invention further includes the step of initially illuminating the object to be detected or imaged with a laser having a wavelength selected such that the object will scatter laser radiation having the resonance wavelength .lambda..sub.1.

Peak intensity measurement of relativistic lasers via nonlinear Thomson scattering.

PubMed

Har-Shemesh, Omri; Di Piazza, Antonino

2012-04-15

The measurement of peak laser intensities exceeding 10(20) W/cm(2) is in general a very challenging task. We suggest a simple method to accurately measure such high intensities up to about 10(23) W/cm(2), by colliding a beam of ultrarelativistic electrons with the laser pulse. The method exploits the high directionality of the radiation emitted by ultrarelativistic electrons via nonlinear Thomson scattering. Initial electron energies well within the reach of laser wake-field accelerators are required, allowing in principle for an all-optical setup. Accuracies of the order of 10% are theoretically envisaged. © 2012 Optical Society of America

Computing Radiative Transfer in a 3D Medium

NASA Technical Reports Server (NTRS)

Von Allmen, Paul; Lee, Seungwon

2012-01-01

A package of software computes the time-dependent propagation of a narrow laser beam in an arbitrary three- dimensional (3D) medium with absorption and scattering, using the transient-discrete-ordinates method and a direct integration method. Unlike prior software that utilizes a Monte Carlo method, this software enables simulation at very small signal-to-noise ratios. The ability to simulate propagation of a narrow laser beam in a 3D medium is an improvement over other discrete-ordinate software. Unlike other direct-integration software, this software is not limited to simulation of propagation of thermal radiation with broad angular spread in three dimensions or of a laser pulse with narrow angular spread in two dimensions. Uses for this software include (1) computing scattering of a pulsed laser beam on a material having given elastic scattering and absorption profiles, and (2) evaluating concepts for laser-based instruments for sensing oceanic turbulence and related measurements of oceanic mixed-layer depths. With suitable augmentation, this software could be used to compute radiative transfer in ultrasound imaging in biological tissues, radiative transfer in the upper Earth crust for oil exploration, and propagation of laser pulses in telecommunication applications.

Pseudo colour visualization of fused multispectral laser scattering images for optical diagnosis of rheumatoid arthritis

NASA Astrophysics Data System (ADS)

Zabarylo, U.; Minet, O.

2010-01-01

Investigations on the application of optical procedures for the diagnosis of rheumatism using scattered light images are only at the beginning both in terms of new image-processing methods and subsequent clinical application. For semi-automatic diagnosis using laser light, the multispectral scattered light images are registered and overlapped to pseudo-coloured images, which depict diagnostically essential contents by visually highlighting pathological changes.

Novel laser Doppler flowmeter for pulpal blood flow measurements

NASA Astrophysics Data System (ADS)

Zang, De Yu; Millerd, James E.; Wilder-Smith, Petra B. B.; Arrastia-Jitosho, Anna-Marie A.

1996-04-01

We have proposed and experimentally demonstrated a new configuration of laser Doppler flowmetry for dental pulpal blood flow measurements. To date, the vitality of a tooth can be determined only by subjective thermal or electric tests, which are of questionable reliability and may induced pain in patient. Non-invasive techniques for determining pulpal vascular reactions to injury, treatment, and medication are in great demand. The laser Doppler flowmetry technique is non-invasive; however, clinical studies have shown that when used to measure pulpal blood flow the conventional back-scattering Doppler method suffers from low signal-to-noise ratio (SNR) and unreliable flux readings rendering it impossible to calibrate. A simplified theoretical model indicates that by using a forward scattered geometry the detected signal has a much higher SNR and can be calibrated. The forward scattered signal is readily detectable due to the fact that teeth are relatively thin organs with moderate optical loss. A preliminary experiment comparing forward scattered detection with conventional back- scattered detection was carried out using an extracted human molar. The results validated the findings of the simple theoretical model and clearly showed the utility of the forward scattering geometry. The back-scattering method had readings that fluctuated by as much as 187% in response to small changes in sensor position relative to the tooth. The forward scattered method had consistent readings (within 10%) that were independent of the sensor position, a signal-to-noise ratio that was at least 5.6 times higher than the back-scattering method, and a linear response to flow rate.

In situ surface roughness measurement using a laser scattering method

NASA Astrophysics Data System (ADS)

Tay, C. J.; Wang, S. H.; Quan, C.; Shang, H. M.

2003-03-01

In this paper, the design and development of an optical probe for in situ measurement of surface roughness are discussed. Based on this light scattering principle, the probe which consists of a laser diode, measuring lens and a linear photodiode array, is designed to capture the scattered light from a test surface with a relatively large scattering angle ϕ (=28°). This capability increases the measuring range and enhances repeatability of the results. The coaxial arrangement that incorporates a dual-laser beam and a constant compressed air stream renders the proposed system insensitive to movement or vibration of the test surface as well as surface conditions. Tests were conducted on workpieces which were mounted on a turning machine that operates with different cutting speeds. Test specimens which underwent different machining processes and of different surface finish were also studied. The results obtained demonstrate the feasibility of surface roughness measurement using the proposed method.

High-resolution imaging and target designation through clouds or smoke

DOEpatents

Perry, Michael D.

2003-01-01

A method and system of combining gated intensifiers and advances in solid-state, short-pulse laser technology, compact systems capable of producing high resolution (i.e., approximately less than 20 centimeters) optical images through a scattering medium such as dense clouds, fog, smoke, etc. may be achieved from air or ground based platforms. Laser target designation through a scattering medium is also enabled by utilizing a short pulse illumination laser and a relatively minor change to the detectors on laser guided munitions.

Thomson scattering diagnostics of thermal plasmas: Laser heating of electrons and the existence of local thermodynamic equilibrium.

PubMed

Murphy, A B

2004-01-01

A number of assessments of electron temperatures in atmospheric-pressure arc plasmas using Thomson scattering of laser light have recently been published. However, in this method, the electron temperature is perturbed due to strong heating of the electrons by the incident laser beam. This heating was taken into account by measuring the electron temperature as a function of the laser pulse energy, and linearly extrapolating the results to zero pulse energy to obtain an unperturbed electron temperature. In the present paper, calculations show that the laser heating process has a highly nonlinear dependence on laser power, and that the usual linear extrapolation leads to an overestimate of the electron temperature, typically by 5000 K. The nonlinearity occurs due to the strong dependence on electron temperature of the absorption of laser energy and of the collisional and radiative cooling of the heated electrons. There are further problems in deriving accurate electron temperatures from laser scattering due to necessary averages that have to be made over the duration of the laser pulse and over the finite volume from which laser light is scattered. These problems are particularly acute in measurements in which the laser beam is defocused in order to minimize laser heating; this can lead to the derivation of electron temperatures that are significantly greater than those existing anywhere in the scattering volume. It was concluded from the earlier Thomson scattering measurements that there were significant deviations from equilibrium between the electron and heavy-particle temperatures at the center of arc plasmas of industrial interest. The present calculations indicate that such deviations are only of the order of 1000 K in 20 000 K, so that the usual approximation that arc plasmas are approximately in local thermodynamic equilibrium still applies.

Application of maximum likelihood methods to laser Thomson scattering measurements of low density plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Washeleski, Robert L.; Meyer, Edmond J. IV; King, Lyon B.

2013-10-15

Laser Thomson scattering (LTS) is an established plasma diagnostic technique that has seen recent application to low density plasmas. It is difficult to perform LTS measurements when the scattered signal is weak as a result of low electron number density, poor optical access to the plasma, or both. Photon counting methods are often implemented in order to perform measurements in these low signal conditions. However, photon counting measurements performed with photo-multiplier tubes are time consuming and multi-photon arrivals are incorrectly recorded. In order to overcome these shortcomings a new data analysis method based on maximum likelihood estimation was developed. Themore » key feature of this new data processing method is the inclusion of non-arrival events in determining the scattered Thomson signal. Maximum likelihood estimation and its application to Thomson scattering at low signal levels is presented and application of the new processing method to LTS measurements performed in the plume of a 2-kW Hall-effect thruster is discussed.« less

Application of maximum likelihood methods to laser Thomson scattering measurements of low density plasmas.

PubMed

Washeleski, Robert L; Meyer, Edmond J; King, Lyon B

2013-10-01

Laser Thomson scattering (LTS) is an established plasma diagnostic technique that has seen recent application to low density plasmas. It is difficult to perform LTS measurements when the scattered signal is weak as a result of low electron number density, poor optical access to the plasma, or both. Photon counting methods are often implemented in order to perform measurements in these low signal conditions. However, photon counting measurements performed with photo-multiplier tubes are time consuming and multi-photon arrivals are incorrectly recorded. In order to overcome these shortcomings a new data analysis method based on maximum likelihood estimation was developed. The key feature of this new data processing method is the inclusion of non-arrival events in determining the scattered Thomson signal. Maximum likelihood estimation and its application to Thomson scattering at low signal levels is presented and application of the new processing method to LTS measurements performed in the plume of a 2-kW Hall-effect thruster is discussed.

Dust-concentration measurement based on Mie scattering of a laser beam

PubMed Central

Yu, Xiaoyu; Shi, Yunbo; Wang, Tian; Sun, Xu

2017-01-01

To realize automatic measurement of the concentration of dust particles in the air, a theory for dust concentration measurement was developed, and a system was designed to implement the dust concentration measurement method based on laser scattering. In the study, the principle of dust concentration detection using laser scattering is studied, and the detection basis of Mie scattering theory is determined. Through simulation, the influence of the incident laser wavelength, dust particle diameter, and refractive index of dust particles on the scattered light intensity distribution are obtained for determining the scattered light intensity curves of single suspended dust particles under different characteristic parameters. A genetic algorithm was used to study the inverse particle size distribution, and the reliability of the measurement system design is proven theoretically. The dust concentration detection system, which includes a laser system, computer circuitry, air flow system, and control system, was then implemented according to the parameters obtained from the theoretical analysis. The performance of the designed system was evaluated. Experimental results show that the system performance was stable and reliable, resulting in high-precision automatic dust concentration measurement with strong anti-interference ability. PMID:28767662

Study of the effect of scattering from turbid water on the polarization of a laser beam

NASA Technical Reports Server (NTRS)

Henderson, R. G.; Hovanlou, A. H.

1978-01-01

A Monte Carlo simulation method was used to determine the effect of scattering from turbid water on the polarization of a backscattered beam of laser light. The relationship between the polarization and the type and amount of suspended particulates in the water was investigated.

A new method of quantitative cavitation assessment in the field of a lithotripter.

PubMed

Jöchle, K; Debus, J; Lorenz, W J; Huber, P

1996-01-01

Transient cavitation seems to be a very important effect regarding the interaction of pulsed high-energy ultrasound with biologic tissues. Using a newly developed laser optical system we are able to determine the life-span of transient cavities (relative error less than +/- 5%) in the focal region of a lithotripter (Lithostar, Siemens). The laser scattering method is based on the detection of scattered laser light reflected during a bubble's life. This method requires no sort of sensor material in the pathway of the sound field. Thus, the method avoids any interference with bubble dynamics during the measurement. The knowledge of the time of bubble decay allows conclusions to be reached on the destructive power of the cavities. By combining the results of life-span measurements with the maximum bubble radius using stroboscopic photographs we found that the measured time of bubble decay and the predicted time using Rayleigh's law only differs by about 13% even in the case of complex bubble fields. It can be shown that the laser scattering method is feasible to assess cavitation events quantitatively. Moreover, it will enable us to compare different medical ultrasound sources that have the capability to generate cavitation.

Real-time particulate mass measurement based on laser scattering

NASA Astrophysics Data System (ADS)

Rentz, Julia H.; Mansur, David; Vaillancourt, Robert; Schundler, Elizabeth; Evans, Thomas

2005-11-01

OPTRA has developed a new approach to the determination of particulate size distribution from a measured, composite, laser angular scatter pattern. Drawing from the field of infrared spectroscopy, OPTRA has employed a multicomponent analysis technique which uniquely recognizes patterns associated with each particle size "bin" over a broad range of sizes. The technique is particularly appropriate for overlapping patterns where large signals are potentially obscuring weak ones. OPTRA has also investigated a method for accurately training the algorithms without the use of representative particles for any given application. This streamlined calibration applies a one-time measured "instrument function" to theoretical Mie patterns to create the training data for the algorithms. OPTRA has demonstrated this algorithmic technique on a compact, rugged, laser scatter sensor head we developed for gas turbine engine emissions measurements. The sensor contains a miniature violet solid state laser and an array of silicon photodiodes, both of which are commercial off the shelf. The algorithmic technique can also be used with any commercially available laser scatter system.

Rapid computation of the amplitude and phase of tightly focused optical fields distorted by scattering particles

PubMed Central

Ranasinghesagara, Janaka C.; Hayakawa, Carole K.; Davis, Mitchell A.; Dunn, Andrew K.; Potma, Eric O.; Venugopalan, Vasan

2014-01-01

We develop an efficient method for accurately calculating the electric field of tightly focused laser beams in the presence of specific configurations of microscopic scatterers. This Huygens–Fresnel wave-based electric field superposition (HF-WEFS) method computes the amplitude and phase of the scattered electric field in excellent agreement with finite difference time-domain (FDTD) solutions of Maxwell’s equations. Our HF-WEFS implementation is 2–4 orders of magnitude faster than the FDTD method and enables systematic investigations of the effects of scatterer size and configuration on the focal field. We demonstrate the power of the new HF-WEFS approach by mapping several metrics of focal field distortion as a function of scatterer position. This analysis shows that the maximum focal field distortion occurs for single scatterers placed below the focal plane with an offset from the optical axis. The HF-WEFS method represents an important first step toward the development of a computational model of laser-scanning microscopy of thick cellular/tissue specimens. PMID:25121440

Stable method for estimation of laser ranging

NASA Astrophysics Data System (ADS)

Kurbasova, G. S.; Rykhlova, L. V.

A noise-immunity variant of the least squares method was developed for the preliminary analysis of laser-ranging data. The method takes into account the influence of many physical phenomena accompanying the generation of the laser-ranging signals, their passing through the optical channel, the distribution in the atmosphere, the scattering on the corner reflector, and their registration. The method was demonstrated on the example of Lageos observations made with the Intercosmos laser radar.

Blood cell counting and classification by nonflowing laser light scattering method

NASA Astrophysics Data System (ADS)

Yang, Ye; Zhang, Zhenxi; Yang, Xinhui; Jiang, Dazong; Yeo, Joon Hock

1999-11-01

A new non-flowing laser light scattering method for counting and classifying blood cells is presented. A linear charge- coupled device with 1024 elements is used to detect the scattered light intensity distribution of the blood cells. A pinhole plate is combined with the CCD to compete the focusing of the measurement system. An isotropic sphere is used to simulate the blood cell. Mie theory is used to describe the scattering of blood cells. In order to inverse the size distribution of blood cells from their scattered light intensity distribution, Powell method combined with precision punishment method is used as a dependent model method for measurement red blood cells and blood plates. Non-negative constraint least square method combined with Powell method and precision punishment method is used as an independent model for measuring white blood cells. The size distributions of white blood cells and red blood cells, and the mean diameter of red blood cells are measured by this method. White blood cells can be divided into three classes: lymphocytes, middle-sized cells and neutrocytes according to their sizes. And the number of blood cells in unit volume can also be measured by the linear dependence of blood cells concentration on scattered light intensity.

Modulated method for efficient, narrow-bandwidth, laser Compton X-ray and gamma-ray sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barty, Christopher P. J.

A method of x-ray and gamma-ray generation via laser Compton scattering uses the interaction of a specially-formatted, highly modulated, long duration, laser pulse with a high-frequency train of high-brightness electron bunches to both create narrow bandwidth x-ray and gamma-ray sources and significantly increase the laser to Compton photon conversion efficiency.

Method for efficient, narrow-bandwidth, laser compton x-ray and gamma-ray sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barty, Christopher P. J.

A method of x-ray and gamma-ray generation via laser Compton scattering uses the interaction of a specially-formatted, highly modulated, long duration, laser pulse with a high-frequency train of high-brightness electron bunches to both create narrow bandwidth x-ray and gamma-ray sources and significantly increase the laser to Compton photon conversion efficiency.

Electron scattering by molecules. II - Experimental methods and data

NASA Technical Reports Server (NTRS)

Trajmar, S.; Chutjian, A.; Register, D. F.

1983-01-01

Experimental techniques for measuring electron-molecule collision cross sections are briefly summarized. A survey of the available experimental cross section data is presented. The emphasis here is on elastic scattering, rotational, vibrational and electronic excitations, total electron scattering, and momentum transfer in the few eV to few hundred eV impact energy range. Reference is made to works concerned with high energy electron scattering, innershell and multi-electron excitations, conicidence methods and electron scattering in laser fields.

Nanoscale surface modification of glass using a 1064 nm pulsed laser

NASA Astrophysics Data System (ADS)

Theppakuttai, Senthil; Chen, Shaochen

2003-07-01

We report a method to produce nanopatterns on borosilicate glass by a Nd:yttrium-aluminum-garnet laser (10 ns, 1064 nm), using silica nanospheres. Nonlinear absorption of the enhanced optical field between the spheres and glass sample is believed to be the primary reason for the creation of nanofeatures on the glass substrate. By shining the laser beam from the backside of the glass sample, the scattering effects are minimized and only the direct field enhancement due to the spheres is utilized for surface patterning. To confirm this, calculations based on the Mie scattering theory were performed, and the resulting intensity as a function of scattering angles are presented. The nanofeatures thus obtained by this method are 350 nm in diameter and the distance between them is around 640 nm, which is same as the size of spheres used.

Laser scattering method applied to determine the concentration of alfa 1-antitrypsin

NASA Astrophysics Data System (ADS)

Riquelme, Bibiana D.; Foresto, Patricia; Valverde, Juana R.; Rasia, Rodolfo J.

2000-04-01

An optical method has been developed to find (alpha) 1- antitrypsin unknown concentrations in human serum samples. This method applies light scattering properties exhibited by initially formed enzyme-inhibitor complexes and uses the curves of aggregation kinetics. It is independent of molecular hydrodynamics. Theoretical approaches showed that scattering properties of transient complexes obey the Rayleigh-Debie conditions. Experiments were performed on the Trypsin/(alpha) 1-antitrypsin system. Measurements were performed in newborn, adult and pregnant sera containing (alpha) 1-antitrypsin in the Trypsin excess region. The solution was excite by a He-Ne laser beam. SO, the particles formed during the reaction are scattering centers for the interacting light. The intensity of the scattered light at 90 degrees from incident beam depends on the nature of those scattering centers. Th rate of increase in scattered intensity depends on the variation in size and shape of the scatterers, being independent of its original size. Peak values of the first derivative linearly correlate with the concentration of (alpha) 1-antitrypsin originally present in the sample. Results are displayed 5 minutes after the initiation of the experimental process. Such speed is of great importance in the immuno-biochemistry determinations.

Immunoassay control method based on light scattering

NASA Astrophysics Data System (ADS)

Bilyi, Olexander I.; Kiselyov, Eugene M.; Petrina, R. O.; Ferensovich, Yaroslav P.; Yaremyk, Roman Y.

1999-11-01

The physics principle of registration immune reaction by light scattering methods is concerned. The operation of laser nephelometry for measuring antigen-antibody reaction is described. The technique of obtaining diagnostic and immune reactions of interaction latex agglutination for diphtheria determination is described.

Laser focal profiler based on forward scattering of a nanoparticle

NASA Astrophysics Data System (ADS)

Ota, Taisuke

2018-03-01

A laser focal intensity profiling method based on the forward scattering from a nanoparticle is demonstrated for in situ measurements using a laser focusing system with six microscope objective lenses with different numerical apertures ranging from 0.15 to 1.4. The measured profiles showed Airy disc patterns although their rings showed some imperfections due to aberrations and misalignment of the test system. The dipole radiation model revealed that the artefact of this method was much smaller than the influence of the deterioration in the experimental system; a condition where no artefact appears was predicted based on proper selection of measurement angles.

Electron acceleration in combined intense laser fields and self-consistent quasistatic fields in plasma

NASA Astrophysics Data System (ADS)

Qiao, Bin; He, X. T.; Zhu, Shao-ping; Zheng, C. Y.

2005-08-01

The acceleration of plasma electron in intense laser-plasma interaction is investigated analytically and numerically, where the conjunct effect of laser fields and self-consistent spontaneous fields (including quasistatic electric field Esl, azimuthal quasistatic magnetic field Bsθ and the axial one Bsz) is completely considered for the first time. An analytical relativistic electron fluid model using test-particle method has been developed to give an explicit analysis about the effects of each quasistatic fields. The ponderomotive accelerating and scattering effects on electrons are partly offset by Esl, furthermore, Bsθ pinches and Bsz collimates electrons along the laser axis. The dependences of energy gain and scattering angle of electron on its initial radial position, plasma density, and laser intensity are, respectively, studied. The qualities of the relativistic electron beam (REB), such as energy spread, beam divergence, and emitting (scattering) angle, generated by both circularly polarized (CP) and linearly polarized (LP) lasers are studied. Results show CP laser is of clear advantage comparing to LP laser for it can generate a better REB in collimation and stabilization.

Analysis and testing of a new method for drop size measurement using laser scatter interferometry

NASA Technical Reports Server (NTRS)

Bachalo, W. D.; Houser, M. J.

1984-01-01

Research was conducted on a laser light scatter detection method for measuring the size and velocity of spherical particles. The method is based upon the measurement of the interference fringe pattern produced by spheres passing through the intersection of two laser beams. A theoretical analysis of the method was carried out using the geometrical optics theory. Experimental verification of the theory was obtained by using monodisperse droplet streams. Several optical configurations were tested to identify all of the parametric effects upon the size measurements. Both off-axis forward and backscatter light detection were utilized. Simulated spray environments and fuel spray nozzles were used in the evaluation of the method. The measurements of the monodisperse drops showed complete agreement with the theoretical predictions. The method was demonstrated to be independent of the beam intensity and extinction resulting from the surrounding drops. Signal processing concepts were considered and a method was selected for development.

Optical method and apparatus for detection of defects and microstructural changes in ceramics and ceramic coatings

DOEpatents

Ellingson, William A.; Todd, Judith A.; Sun, Jiangang

2001-01-01

Apparatus detects defects and microstructural changes in hard translucent materials such as ceramic bulk compositions and ceramic coatings such as after use under load conditions. The beam from a tunable laser is directed onto the sample under study and light reflected by the sample is directed to two detectors, with light scattered with a small scatter angle directed to a first detector and light scattered with a larger scatter angle directed to a second detector for monitoring the scattering surface. The sum and ratio of the two detector outputs respectively provide a gray-scale, or "sum" image, and an indication of the lateral spread of the subsurface scatter, or "ratio" image. This two detector system allows for very high speed crack detection for on-line, real-time inspection of damage in ceramic components. Statistical image processing using a digital image processing approach allows for the quantative discrimination of the presence and distribution of small flaws in a sample while improving detection reliability. The tunable laser allows for the penetration of the sample to detect defects from the sample's surface to the laser's maximum depth of penetration. A layered optical fiber directs the incoming laser beam to the sample and transmits each scattered signal to a respective one of the two detectors.

Detrimental Effect Elimination of Laser Frequency Instability in Brillouin Optical Time Domain Reflectometer by Using Self-Heterodyne Detection

PubMed Central

Li, Yongqian; Li, Xiaojuan; An, Qi; Zhang, Lixin

2017-01-01

A useful method for eliminating the detrimental effect of laser frequency instability on Brillouin signals by employing the self-heterodyne detection of Rayleigh and Brillouin scattering is presented. From the analysis of Brillouin scattering spectra from fibers with different lengths measured by heterodyne detection, the maximum usable pulse width immune to laser frequency instability is obtained to be about 4 µs in a self-heterodyne detection Brillouin optical time domain reflectometer (BOTDR) system using a broad-band laser with low frequency stability. Applying the self-heterodyne detection of Rayleigh and Brillouin scattering in BOTDR system, we successfully demonstrate that the detrimental effect of laser frequency instability on Brillouin signals can be eliminated effectively. Employing the broad-band laser modulated by a 130-ns wide pulse driven electro-optic modulator, the observed maximum errors in temperatures measured by the local heterodyne and self-heterodyne detection BOTDR systems are 7.9 °C and 1.2 °C, respectively. PMID:28335508

Method for identifying and probing phase transitions in materials

DOEpatents

Asay, Blaine W.; Henson, Bryan F.; Sander, Robert K.; Robinson, Jeanne M.; Son, Steven F.; Dickson, Peter M.

2002-01-01

The present invention includes a method for identifying and probing phase transitions in materials. A polymorphic material capable of existing in at least one non-centrosymmetric phase is interrogated with a beam of laser light at a chosen wavelength and frequency. A phase transition is induced in the material while it is interrogated. The intensity of light scattered by the material and having a wavelength equal to one half the wavelength of the interrogating laser light is detected. If the phase transition results in the production of a non-centrosymmetric phase, the intensity of this scattered light increases; if the phase transition results in the disappearance of a non-centrosymmetric phase, the intensity of this scattered light decreases.

Improvements of data quality of the LHD Thomson scattering diagnostics in high-temperature plasma experiments.

PubMed

Yamada, I; Narihara, K; Funaba, H; Hayashi, H; Kohmoto, T; Takahashi, H; Shimozuma, T; Kubo, S; Yoshimura, Y; Igami, H; Tamura, N

2010-10-01

In Large Helical Device (LHD) experiments, an electron temperature (T(e)) more than 15 keV has been observed by the yttrium-aluminum-garnet (YAG) laser Thomson scattering diagnostic. Since the LHD Thomson scattering system has been optimized for the temperature region, 50 eV≤T(e)≤10 keV, the data quality becomes worse in the higher T(e) region exceeding 10 keV. In order to accurately determine T(e) in the LHD high-T(e) experiments, we tried to increase the laser pulse energy by simultaneously firing three lasers. The technique enables us to decrease the uncertainties in the measured T(e). Another signal accumulation method was also tested. In addition, we estimated the influence of high-energy electrons on T(e) obtained by the LHD Thomson scattering system.

Study of Injection of Helium into Supersonic Air Flow Using Rayleigh Scattering

NASA Technical Reports Server (NTRS)

Seaholtz, Richard G.; Buggele, Alvin E.

1997-01-01

A study of the transverse injection of helium into a Mach 3 crossflow is presented. Filtered Rayleigh scattering is used to measure penetration and helium mole fraction in the mixing region. The method is based on planar molecular Rayleigh scattering using an injection-seeded, frequency-doubled ND:YAG pulsed laser and a cooled CCD camera. The scattered light is filtered with an iodine absorption cell to suppress stray laser light. Preliminary data are presented for helium mole fraction and penetration. Flow visualization images obtained with a shadowgraph and wall static pressure data in the vicinity of the injection are also presented.

Investigation of multiple scattering effects in aerosols

NASA Technical Reports Server (NTRS)

Deepak, A.

1980-01-01

The results are presented of investigations on the various aspects of multiple scattering effects on visible and infrared laser beams transversing dense fog oil aerosols contained in a chamber (4' x 4' x 9'). The report briefly describes: (1) the experimental details and measurements; (2) analytical representation of the aerosol size distribution data by two analytical models (the regularized power law distribution and the inverse modified gamma distribution); (3) retrieval of aerosol size distributions from multispectral optical depth measurements by two methods (the two and three parameter fast table search methods and the nonlinear least squares method); (4) modeling of the effects of aerosol microphysical (coagulation and evaporation) and dynamical processes (gravitational settling) on the temporal behavior of aerosol size distribution, and hence on the extinction of four laser beams with wavelengths 0.44, 0.6328, 1.15, and 3.39 micrometers; and (5) the exact and approximate formulations for four methods for computing the effects of multiple scattering on the transmittance of laser beams in dense aerosols, all of which are based on the solution of the radiative transfer equation under the small angle approximation.

Investigation of multiple scattering effects in aerosols

NASA Astrophysics Data System (ADS)

Deepak, A.

1980-05-01

The results are presented of investigations on the various aspects of multiple scattering effects on visible and infrared laser beams transversing dense fog oil aerosols contained in a chamber (4' x 4' x 9'). The report briefly describes: (1) the experimental details and measurements; (2) analytical representation of the aerosol size distribution data by two analytical models (the regularized power law distribution and the inverse modified gamma distribution); (3) retrieval of aerosol size distributions from multispectral optical depth measurements by two methods (the two and three parameter fast table search methods and the nonlinear least squares method); (4) modeling of the effects of aerosol microphysical (coagulation and evaporation) and dynamical processes (gravitational settling) on the temporal behavior of aerosol size distribution, and hence on the extinction of four laser beams with wavelengths 0.44, 0.6328, 1.15, and 3.39 micrometers; and (5) the exact and approximate formulations for four methods for computing the effects of multiple scattering on the transmittance of laser beams in dense aerosols, all of which are based on the solution of the radiative transfer equation under the small angle approximation.

Ultrasensitive detection of target analyte-induced aggregation of gold nanoparticles using laser-induced nanoparticle Rayleigh scattering.

PubMed

Lin, Jia-Hui; Tseng, Wei-Lung

2015-01-01

Detection of salt- and analyte-induced aggregation of gold nanoparticles (AuNPs) mostly relies on costly and bulky analytical instruments. To response this drawback, a portable, miniaturized, sensitive, and cost-effective detection technique is urgently required for rapid field detection and monitoring of target analyte via the use of AuNP-based sensor. This study combined a miniaturized spectrometer with a 532-nm laser to develop a laser-induced Rayleigh scattering technique, allowing the sensitive and selective detection of Rayleigh scattering from the aggregated AuNPs. Three AuNP-based sensing systems, including salt-, thiol- and metal ion-induced aggregation of the AuNPs, were performed to examine the sensitivity of laser-induced Rayleigh scattering technique. Salt-, thiol-, and metal ion-promoted NP aggregation were exemplified by the use of aptamer-adsorbed, fluorosurfactant-stabilized, and gallic acid-capped AuNPs for probing K(+), S-adenosylhomocysteine hydrolase-induced hydrolysis of S-adenosylhomocysteine, and Pb(2+), in sequence. Compared to the reported methods for monitoring the aggregated AuNPs, the proposed system provided distinct advantages of sensitivity. Laser-induced Rayleigh scattering technique was improved to be convenient, cheap, and portable by replacing a diode laser and a miniaturized spectrometer with a laser pointer and a smart-phone. Using this smart-phone-based detection platform, we can determine whether or not the Pb(2+) concentration exceed the maximum allowable level of Pb(2+) in drinking water. Copyright © 2014 Elsevier B.V. All rights reserved.

Local scattering property scales flow speed estimation in laser speckle contrast imaging

NASA Astrophysics Data System (ADS)

Miao, Peng; Chao, Zhen; Feng, Shihan; Yu, Hang; Ji, Yuanyuan; Li, Nan; Thakor, Nitish V.

2015-07-01

Laser speckle contrast imaging (LSCI) has been widely used in in vivo blood flow imaging. However, the effect of local scattering property (scattering coefficient µ s ) on blood flow speed estimation has not been well investigated. In this study, such an effect was quantified and involved in relation between speckle autocorrelation time τ c and flow speed v based on simulation flow experiments. For in vivo blood flow imaging, an improved estimation strategy was developed to eliminate the estimation bias due to the inhomogeneous distribution of the scattering property. Compared to traditional LSCI, a new estimation method significantly suppressed the imaging noise and improves the imaging contrast of vasculatures. Furthermore, the new method successfully captured the blood flow changes and vascular constriction patterns in rats’ cerebral cortex from normothermia to mild and moderate hypothermia.

Investigation of Doppler spectra of laser radiation scattered inside hand skin during occlusion test

NASA Astrophysics Data System (ADS)

Kozlov, I. O.; Zherebtsov, E. A.; Zherebtsova, A. I.; Dremin, V. V.; Dunaev, A. V.

2017-11-01

Laser Doppler flowmetry (LDF) is a method widely used in diagnosis of microcirculation diseases. It is well known that information about frequency distribution of Doppler spectrum of the laser radiation scattered by moving red blood cells (RBC) usually disappears after signal processing procedure. Photocurrent’s spectrum distribution contains valuable diagnostic information about velocity distribution of the RBC. In this research it is proposed to compute the indexes of microcirculation in the sub-ranges of the Doppler spectrum as well as investigate the frequency distribution of the computed indexes.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS Fibreoptic diffuse-light irradiators of biological tissues

NASA Astrophysics Data System (ADS)

Volkov, Vladimir V.; Loshchenov, V. B.; Konov, Vitalii I.; Kononenko, Vitalii V.

2010-10-01

We report techniques for the fabrication of laser radiation diffusers for interstitial photodynamic therapy. Using chemical etching of the distal end of silica fibre with a core diameter of 200 — 600 μm, we have obtained long (up to 40 mm) diffusers with good scattering uniformity. Laser ablation has been used to produce cylindrical diffusers with high emission contrast and a scattering uniformity no worse than ~10 % in their middle part. The maximum length of the diffusers produced by this method is 20 — 25 mm.

Compact quasi-monoenergetic photon sources from laser-plasma accelerators for nuclear detection and characterization

NASA Astrophysics Data System (ADS)

Geddes, Cameron G. R.; Rykovanov, Sergey; Matlis, Nicholas H.; Steinke, Sven; Vay, Jean-Luc; Esarey, Eric H.; Ludewigt, Bernhard; Nakamura, Kei; Quiter, Brian J.; Schroeder, Carl B.; Toth, Csaba; Leemans, Wim P.

2015-05-01

Near-monoenergetic photon sources at MeV energies offer improved sensitivity at greatly reduced dose for active interrogation, and new capabilities in treaty verification, nondestructive assay of spent nuclear fuel and emergency response. Thomson (also referred to as Compton) scattering sources are an established method to produce appropriate photon beams. Applications are however restricted by the size of the required high-energy electron linac, scattering (photon production) system, and shielding for disposal of the high energy electron beam. Laser-plasma accelerators (LPAs) produce GeV electron beams in centimeters, using the plasma wave driven by the radiation pressure of an intense laser. Recent LPA experiments are presented which have greatly improved beam quality and efficiency, rendering them appropriate for compact high-quality photon sources based on Thomson scattering. Designs for MeV photon sources utilizing the unique properties of LPAs are presented. It is shown that control of the scattering laser, including plasma guiding, can increase photon production efficiency. This reduces scattering laser size and/or electron beam current requirements to scale compatible with the LPA. Lastly, the plasma structure can decelerate the electron beam after photon production, reducing the size of shielding required for beam disposal. Together, these techniques provide a path to a compact photon source system.

Characterization of Diesel Soot Aggregates by Scattering and Extinction Methods

NASA Astrophysics Data System (ADS)

Kamimoto, Takeyuki

2006-07-01

Characteristics of diesel soot particles sampled from diesel exhaust of a common-rail turbo-charged diesel engine are quantified by scattering and extinction diagnostics using newly build two laser-based instruments. The radius of gyration representing the aggregates size is measured by the angular distribution of scattering intensity, while the soot mass concentration is measured by a two-wavelength extinction method. An approach to estimate the refractive index of diesel soot by an analysis of the extinction and scattering data using an aggregates scattering theory is proposed.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Spatial distribution of laser radiation scattered in a plasma formed by optical breakdown of a gas

NASA Astrophysics Data System (ADS)

Bufetov, Igor'A.; Bufetova, G. A.; Fyodorov, V. B.

1994-12-01

Spatial distributions of laser radiation scattered by a laser spark were determined at different laser radiation wavelengths (λ = 1060, 530, 353, and 265 nm) and gas pressures (air at 10-760 Torr). An interference structure of the cone of the scattered radiation behind the spark was detected for the first time. The structure was attributed to interference of the radiation scattered in two or more self-focusing centres in the laser-spark plasma in air. The dependences of the maximum scattering angle on the gas pressure and on the laser radiation wavelength were determined experimentally.

Investigation of thermodynamic equilibrium in laser-induced aluminum plasma using the H{sub α} line profiles and Thomson scattering spectra

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cvejić, M., E-mail: marko.cvejic@ipb.ac.rs, E-mail: krzysztof.dzierzega@uj.edu.pl; Faculty of Physics, Weizmann Institute of Science, Rehovot 7610001; Dzierżęga, K., E-mail: marko.cvejic@ipb.ac.rs, E-mail: krzysztof.dzierzega@uj.edu.pl

2015-07-13

We have studied isothermal equilibrium in the laser-induced plasma from aluminum pellets in argon at pressure of 200 mbar by using a method which combines the standard laser Thomson scattering and analysis of the H{sub α}, Stark-broadened, line profiles. Plasma was created using 4.5 ns, 4 mJ pulses from a Nd:YAG laser at 1064 nm. While electron density and temperature were determined from the electron feature of Thomson scattering spectra, the heavy particle temperature was obtained from the H{sub α} full profile applying computer simulation including ion-dynamical effects. We have found strong imbalance between these two temperatures during entire plasma evolution whichmore » indicates its non-isothermal character. At the same time, according to the McWhirter criterion, the electron density was high enough to establish plasma in local thermodynamic equilibrium.« less

Retrieval of target structure information from laser-induced photoelectrons by few-cycle bicircular laser fields

NASA Astrophysics Data System (ADS)

Hoang, Van-Hung; Le, Van-Hoang; Lin, C. D.; Le, Anh-Thu

2017-03-01

By analyzing theoretical results from a numerical solution of the time-dependent Schrödinger equation for atoms in few-cycle bicircular laser pulses, we show that high-energy photoelectron momentum spectra can be used to extract accurate elastic scattering differential cross sections of the target ion with free electrons. We find that the retrieval range for a scattering angle with bicircular pulses is wider than with linearly polarized pulses, although the retrieval method has to be modified to account for different returning directions of the electron in the continuum. This result can be used to extend the range of applicability of ultrafast imaging techniques such as laser-induced electron diffraction and for the accurate characterization of laser pulses.

Study on off-axis detection of pulsed laser in atmosphere

NASA Astrophysics Data System (ADS)

Liang, Weiwei

2018-02-01

Laser communication, designation, and ranging are point to point and have a high degree of specificity, current laser detection, such as laser warning receiver system, could detect the scattering laser from the off-axis distance by scattering track on natural aerosols, which is helpful to locate the laser source. However, the intensity of the scattering laser is extremely weak and affected by many factors, in order to evaluate the detection characteristic, a simplified model of off-axis detection for scattering laser in the lower atmosphere based on the Mie scattering theory is presented in this paper, the performances of the off-axis laser detection in different conditions such as off-axis distance, visibility, incidence angle, and delay time are investigated.

The distribution of the scattered laser light in laser-plate-target coupling

NASA Astrophysics Data System (ADS)

Xiao-bo, Nie; Tie-qiang, Chang; Dong-xian, Lai; Shen-ye, Liu; Zhi-jian, Zheng

1997-04-01

Theoretical and experimental studies of the angular distributions of scattered laser light in laser-Au-plate-target coupling are reported. A simple model that describes three-dimensional plasmas and scattered laser light is presented. The approximate shape of critical density surface has been given and the three-dimensional laser ray tracing is applied in the model. The theoretical results of the model are consistent with the experimental data for the scattered laser light in the polar angle range of 25° to 145° from the laser beam.

Optical extinction dependence on wavelength and size distribution of airborne dust

NASA Astrophysics Data System (ADS)

Pangle, Garrett E.; Hook, D. A.; Long, Brandon J. N.; Philbrick, C. R.; Hallen, Hans D.

2013-05-01

The optical scattering from laser beams propagating through atmospheric aerosols has been shown to be very useful in describing air pollution aerosol properties. This research explores and extends that capability to particulate matter. The optical properties of Arizona Road Dust (ARD) samples are measured in a chamber that simulates the particle dispersal of dust aerosols in the atmospheric environment. Visible, near infrared, and long wave infrared lasers are used. Optical scattering measurements show the expected dependence of laser wavelength and particle size on the extinction of laser beams. The extinction at long wavelengths demonstrates reduced scattering, but chemical absorption of dust species must be considered. The extinction and depolarization of laser wavelengths interacting with several size cuts of ARD are examined. The measurements include studies of different size distributions, and their evolution over time is recorded by an Aerodynamic Particle Sizer. We analyze the size-dependent extinction and depolarization of ARD. We present a method of predicting extinction for an arbitrary ARD size distribution. These studies provide new insights for understanding the optical propagation of laser beams through airborne particulate matter.

Comparison of stimulated and spontaneous laser-radar methods for the remote sensing of ocean physical properties

NASA Astrophysics Data System (ADS)

Leonard, Donald A.; Sweeney, Harold E.

1990-09-01

The physical properties of ocean water, in the top few ten meters, are of great interest in the scientific, engineering, and general oceanographic communities. Subsurface profiles of temperature, salinity, and sound speed measured by laser radar in real time on a synoptic basis over a wide area from an airborne platform would provide valuable information complementary to the data that is now readily available. The laser-radar technique specifically applicable to ocean sensing uses spectroscopic analysis of the inelastic backscattered optical signal. Two methods have received considerable attention for remote sensing and both have been demonstrated in field experiments. These are spontaneous Raman1 and spontaneous Brillouin2 scattering. A discussion of these two processes and a comparison of their properties that are useful for remote sensing was presented3 at SPIE Ocean Optics IX. This paper compares ocean remote sensing using stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS) processes with better known spontaneous methods. The results of laboratory measurements of temperature using SBS and some preliminary results of SRS are presented with extensions to performance estimates of potential field systems.

Rapid Antimicrobial Susceptibility Testing of Bacillus anthracis, Yersinia pestis, and Burkholderia pseudomallei by Use of Laser Light Scattering Technology.

PubMed

Bugrysheva, Julia V; Lascols, Christine; Sue, David; Weigel, Linda M

2016-06-01

Rapid methods to determine antimicrobial susceptibility would assist in the timely distribution of effective treatment or postexposure prophylaxis in the aftermath of the release of bacterial biothreat agents such as Bacillus anthracis, Yersinia pestis, or Burkholderia pseudomallei Conventional susceptibility tests require 16 to 48 h of incubation, depending on the bacterial species. We evaluated a method that is based on laser light scattering technology that measures cell density in real time. We determined that it has the ability to rapidly differentiate between growth (resistant) and no growth (susceptible) of several bacterial threat agents in the presence of clinically relevant antimicrobials. Results were available in <4 h for B. anthracis and <6 h for Y. pestis and B. pseudomallei One exception was B. pseudomallei in the presence of ceftazidime, which required >10 h of incubation. Use of laser scattering technology decreased the time required to determine antimicrobial susceptibility by 50% to 75% for B. anthracis, Y. pestis, and B. pseudomallei compared to conventional methods. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Nd:YAP laser pulse compression by three-stage transient stimulated Brillouin and Raman scattering

NASA Astrophysics Data System (ADS)

Kubeček, V.; Hamal, K.; Procházka, I.; Buzelis, R.; Girdauskas, V.; Dementiev, A.

1991-08-01

There is a continuous effort to generate stable, powerful picosecond laser pulses for application in spectroscopy, nonlinear optics and parametric light generation, as well. One of the possible methods is the compression of longer nanosecond laser pulses by stimulated Brillouin and stimulated Raman scattering. The advantages of such a technique, in comparison to the used mode locked picosecond lasers, are as follows: the absence of the active and/or passive mode lockers used to generate a train of picosecond pulses, and the absence of a fast electrooptical shutter used to select a single pulse from a train of pulses. The application of stimulated Brillouin and stimulated Raman scattering permits to generate picosecond pulses in the wavelength regions not covered by mode locked lasers. Of special interest is the wavelength region of 0·8 μm, which may be amplified by the attractive Titanium Sapphire lasers. In this paper we are summarizing our results in theoretical modelling and in real generation of picosecond pulses by means of cascaded stimulated Brillouin and Raman scattering. The models of scattering processes have been investigated. The stable generation of 5, 7, 3 picosecond pulses have been optimized for the wavelengths of 0·8, 0·64 and 0·54 μm, respectively. In all these cases, the pulses exhibited the far field pattern close to Gaussian, with the pulse energy ranging from 0·2 to 1 mJ.

Validity of Particle-Counting Method Using Laser-Light Scattering for Detecting Platelet Aggregation in Diabetic Patients

NASA Astrophysics Data System (ADS)

Nakadate, Hiromichi; Sekizuka, Eiichi; Minamitani, Haruyuki

We aimed to study the validity of a new analytical approach that reflected the phase from platelet activation to the formation of small platelet aggregates. We hoped that this new approach would enable us to use the particle-counting method with laser-light scattering to measure platelet aggregation in healthy controls and in diabetic patients without complications. We measured agonist-induced platelet aggregation for 10 min. Agonist was added to the platelet-rich plasma 1 min after measurement started. We compared the total scattered light intensity from small aggregates over a 10-min period (established analytical approach) and that over a 2-min period from 1 to 3 min after measurement started (new analytical approach). Consequently platelet aggregation in diabetics with HbA1c ≥ 6.5% was significantly greater than in healthy controls by both analytical approaches. However, platelet aggregation in diabetics with HbA1c < 6.5%, i.e. patients in the early stages of diabetes, was significantly greater than in healthy controls only by the new analytical approach, not by the established analytical approach. These results suggest that platelet aggregation as detected by the particle-counting method using laser-light scattering could be applied in clinical examinations by our new analytical approach.

Laser Doppler anemometer signal processing for blood flow velocity measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borozdova, M A; Fedosov, I V; Tuchin, V V

A new method for analysing the signal in a laser Doppler anemometer based on the differential scheme is proposed, which provides the flow velocity measurement in strongly scattering liquids, particularly, blood. A laser Doppler anemometer intended for measuring the absolute blood flow velocity in animal and human near-surface arterioles and venules is developed. The laser Doppler anemometer signal structure is experimentally studied for measuring the flow velocity in optically inhomogeneous media, such as blood and suspensions of scattering particles. The results of measuring the whole and diluted blood flow velocity in channels with a rectangular cross section are presented. (lasermore » applications and other topics in quantum electronics)« less

Signal evaluations using singular value decomposition for Thomson scattering diagnostics.

PubMed

Tojo, H; Yamada, I; Yasuhara, R; Yatsuka, E; Funaba, H; Hatae, T; Hayashi, H; Itami, K

2014-11-01

This paper provides a novel method for evaluating signal intensities in incoherent Thomson scattering diagnostics. A double-pass Thomson scattering system, where a laser passes through the plasma twice, generates two scattering pulses from the plasma. Evaluations of the signal intensities in the spectrometer are sometimes difficult due to noise and stray light. We apply the singular value decomposition method to Thomson scattering data with strong noise components. Results show that the average accuracy of the measured electron temperature (Te) is superior to that of temperature obtained using a low-pass filter (<20 MHz) or without any filters.

Signal evaluations using singular value decomposition for Thomson scattering diagnostics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tojo, H., E-mail: tojo.hiroshi@jaea.go.jp; Yatsuka, E.; Hatae, T.

2014-11-15

This paper provides a novel method for evaluating signal intensities in incoherent Thomson scattering diagnostics. A double-pass Thomson scattering system, where a laser passes through the plasma twice, generates two scattering pulses from the plasma. Evaluations of the signal intensities in the spectrometer are sometimes difficult due to noise and stray light. We apply the singular value decomposition method to Thomson scattering data with strong noise components. Results show that the average accuracy of the measured electron temperature (T{sub e}) is superior to that of temperature obtained using a low-pass filter (<20 MHz) or without any filters.

Laser control of natural disperse systems

NASA Astrophysics Data System (ADS)

Vlasova, Olga L.; Bezrukova, Alexandra G.

2003-10-01

Different water disperse systems were studied by integral (spectroturbidemetry) and differential light scattering method with a laser as a source of light. The investigation done concerns the state of kaolin dispersions at storage and under dilution as an example of mineral dispersion systems such as natural water. The role of some light scattering parameters for an optical analysis of water dispersions, like the dispersion of erythrocytes and bacterial cells -Escherichia coli is discussed. The results obtained can help to elaborate the methods for on-line optical control fo natural disperse systems (water, air) with mineral and biological particles.

Nonlinear absorption of short intense laser pulse in multispecies plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kargarian, A.; Hajisharifi, K.; Mehdian, H.

In the present paper, the detailed investigation concerning the effect of inclusion of heavy negative ions into the finite background plasma on the laser absorption has been carried out by employing particle-in-cell simulation method. For this purpose, in this configuration, the laser energy absorption relying on the nonlinear phenomena such as phase-mixing, wave-breaking, and scattering has been studied in the Raman-Brillouin regime. It is shown that the inclusion of heavy negative ions suppresses the scattering while increases the phase-mixing time. Moreover, it is illustrated that this inclusion can increase the laser absorption in finite plasma environment, after saturation. The obtainedmore » results are expected to be relevant to the experiments on the mass spectrometry with laser desorption techniques as well as on the laser-plasma interaction with application to particles acceleration.« less

Comparison of Retracking Algorithms Using Airborne Radar and Laser Altimeter Measurements of the Greenland Ice Sheet

NASA Technical Reports Server (NTRS)

Ferraro, Ellen J.; Swift, Calvin T.

1995-01-01

This paper compares four continental ice sheet radar altimeter retracking algorithms using airborne radar and laser altimeter data taken over the Greenland ice sheet in 1991. The refurbished Advanced Application Flight Experiment (AAFE) airborne radar altimeter has a large range window and stores the entire return waveform during flight. Once the return waveforms are retracked, or post-processed to obtain the most accurate altitude measurement possible, they are compared with the high-precision Airborne Oceanographic Lidar (AOL) altimeter measurements. The AAFE waveforms show evidence of varying degrees of both surface and volume scattering from different regions of the Greenland ice sheet. The AOL laser altimeter, however, obtains a return only from the surface of the ice sheet. Retracking altimeter waveforms with a surface scattering model results in a good correlation with the laser measurements in the wet and dry-snow zones, but in the percolation region of the ice sheet, the deviation between the two data sets is large due to the effects of subsurface and volume scattering. The Martin et al model results in a lower bias than the surface scattering model, but still shows an increase in the noise level in the percolation zone. Using an Offset Center of Gravity algorithm to retrack altimeter waveforms results in measurements that are only slightly affected by subsurface and volume scattering and, despite a higher bias, this algorithm works well in all regions of the ice sheet. A cubic spline provides retracked altitudes that agree with AOL measurements over all regions of Greenland. This method is not sensitive to changes in the scattering mechanisms of the ice sheet and it has the lowest noise level and bias of all the retracking methods presented.

A symmetrical laser Doppler velocity meter and its application to turbulence characterization

NASA Technical Reports Server (NTRS)

Mazumder, M. K.

1972-01-01

A symmetrical method of optical heterodyning of the Doppler shifted scattered laser radiation developed for velocity measurements with a minimal instrumental spectral broadening and a high signal-to-noise ratio. The method employs two laser beams incident on the moving scatterer and does not use any reference beam for heterodyning. The Doppler signal frequency is independent of the scattering angle and the signal possesses no receiving aperture broadening. Optical alignment is simple. Typical values of the instrumental spectral broadening were approximately 0.8 percent of the center frequency of the Doppler signal, and the signal-to-noise ratio was approximately 25 dB, obtained from an air flow system using submicron dioctylphthalate scattering aerosol. Experimental and theoretical studies were made on the characteristics of the Doppler signal and the effect of system parameters in turbulent flow measurement. The optimization process involved in the beam optics and in the use of a spatial filter is described. For localized flow measurement in any direction of the three-dimensional orthogonal coordinates, the system, using uncorrected optical components, had a sensing volume which can be described by a sensitive length of 600 microns and a diameter of 100 microns.

Bidirectional light-scattering image processing method for high-concentration jet sprays

NASA Astrophysics Data System (ADS)

Shimizu, I.; Emori, Y.; Yang, W.-J.; Shimoda, M.; Suzuki, T.

1985-01-01

In order to study the distributions of droplet size and volume density in high-concentration jet sprays, a new technique is developed, which combines the forward and backward light scattering method and an image processing method. A pulsed ruby laser is used as the light source. The Mie scattering theory is applied to the results obtained from image processing on the scattering photographs. The time history is obtained for the droplet size and volume density distributions, and the method is demonstrated by diesel fuel sprays under various injecting conditions. The validity of the technique is verified by a good agreement in the injected fuel volume distributions obtained by the present method and by injection rate measurements.

Nanometer-scale characterization of laser-driven compression, shocks, and phase transitions, by x-ray scattering using free electron lasers

DOE PAGES

Kluge, T.; Rödel, C.; Rödel, M.; ...

2017-10-23

In this paper, we study the feasibility of using small angle X-ray scattering (SAXS) as a new experimental diagnostic for intense laser-solid interactions. By using X-ray pulses from a hard X-ray free electron laser, we can simultaneously achieve nanometer and femtosecond resolution of laser-driven samples. This is an important new capability for the Helmholtz international beamline for extreme fields at the high energy density endstation currently built at the European X-ray free electron laser. We review the relevant SAXS theory and its application to transient processes in solid density plasmas and report on first experimental results that confirm the feasibilitymore » of the method. Finally, we present results of two test experiments where the first experiment employs ultra-short laser pulses for studying relativistic laser plasma interactions, and the second one focuses on shock compression studies with a nanosecond laser system.« less

Nanometer-scale characterization of laser-driven compression, shocks, and phase transitions, by x-ray scattering using free electron lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kluge, T.; Rödel, C.; Rödel, M.

In this paper, we study the feasibility of using small angle X-ray scattering (SAXS) as a new experimental diagnostic for intense laser-solid interactions. By using X-ray pulses from a hard X-ray free electron laser, we can simultaneously achieve nanometer and femtosecond resolution of laser-driven samples. This is an important new capability for the Helmholtz international beamline for extreme fields at the high energy density endstation currently built at the European X-ray free electron laser. We review the relevant SAXS theory and its application to transient processes in solid density plasmas and report on first experimental results that confirm the feasibilitymore » of the method. Finally, we present results of two test experiments where the first experiment employs ultra-short laser pulses for studying relativistic laser plasma interactions, and the second one focuses on shock compression studies with a nanosecond laser system.« less

Transient radiative transfer in a scattering slab considering polarization.

PubMed

Yi, Hongliang; Ben, Xun; Tan, Heping

2013-11-04

The characteristics of the transient and polarization must be considered for a complete and correct description of short-pulse laser transfer in a scattering medium. A Monte Carlo (MC) method combined with a time shift and superposition principle is developed to simulate transient vector (polarized) radiative transfer in a scattering medium. The transient vector radiative transfer matrix (TVRTM) is defined to describe the transient polarization behavior of short-pulse laser propagating in the scattering medium. According to the definition of reflectivity, a new criterion of reflection at Fresnel surface is presented. In order to improve the computational efficiency and accuracy, a time shift and superposition principle is applied to the MC model for transient vector radiative transfer. The results for transient scalar radiative transfer and steady-state vector radiative transfer are compared with those in published literatures, respectively, and an excellent agreement between them is observed, which validates the correctness of the present model. Finally, transient radiative transfer is simulated considering the polarization effect of short-pulse laser in a scattering medium, and the distributions of Stokes vector in angular and temporal space are presented.

Method for monitoring the crystallization of an organic material from a liquid

DOEpatents

Asay, Blaine W.; Henson, Bryan F.; Sander, Robert K.; Robinson, Jeanne M.; Son, Steven F.; Dickson, Peter M.

2004-10-05

Method for monitoring the crystallization of at least one organic material from a liquid. According to the method, a liquid having at least one organic material capable of existing in at least one non-centrosymmetric phase is prepared. The liquid is interrogated with a laser beam at a chosen wavelength. As at least a portion of the at least one organic material crystallizes from the liquid, the intensity of any light scattered by the crystallized material at a wavelength equal to one-half the chosen wavelength of the interrogating laser beam is monitored. If the intensity of this scattered light, increases, then the crystals that form include at least one non-cetrosymmetric phase.

Influence of surface light scattering in hydrophobic acrylic intraocular lenses on laser beam transmittance.

PubMed

Shiraya, Tomoyasu; Kato, Satoshi; Minami, Keiichiro; Miyata, Kazunori

2017-02-01

The aim of this study was to experimentally examine the changes in the transmittances of photocoagulation lasers when surface light scattering increases in AcrySof intraocular lenses (IOLs). SA60AT IOLs (Alcon) were acceleratingly aging for 0, 3, 5, and 10 years to simulate surface light scattering, and the surface light-scattering intensities of both IOL surfaces were measured using a Scheimpflug photographer. The powers of laser beams that passed from a laser photocoagulator through the aged IOLs were measured at 532, 577, and 647 nm. Changes in the laser power and transmittance with the years of aging and the intensities of surface light scattering were examined. Although the intensity of surface light scattering increased with the years of aging, the laser power did not change with the years of aging (P > 0.30, Kruskal-Wallis test). There were no significant changes in the laser transmittance with the years of aging or the laser wavelength (P > 0.30 and 0.57, respectively). The intensity of surface light scattering revealed no significant association with the laser transmittance at any wavelength (P > 0.37, liner regression). The increases in the surface light scattering of the AcrySof IOLs would not influence retinal photocoagulation treatments for up to 10 years after implantation.

Research on characteristics of forward scattering light based on Monte Carlo simulation

NASA Astrophysics Data System (ADS)

Ding, Kun; Jin, Wei-qi

2008-03-01

In ocean inspection, laser system has the advantages of high precision, high efficiency and being enacted on the temperature or salinity of seawater. It has been developed greatly in recent years. But it is not yet a mature inspection technique because of the complicacy of oceanic channel and water-scattering. There are many problems to be resolved. In this paper, the work principle and of general developing situation of ocean lidar techniques are introduced first. The author points out that the intense scattering and absorbing acting on light by water is the bottleneck to limit the development of ocean lidar. The Monet Carlo method is adopted finally to be a basal way of study in this paper after discussing several method of studying the light transmitting in seawater. Based on the theory of photon transmitted in the seawater and the particularity of underwater target detecting, we have studied the characters of laser scattering on underwater target surface and spatial and temporal characters of forward scattering. Starting from the particularity of underwater target detecting, a new model to describe the characters of laser scattering is presented. Based on this model, we developed the fast arithmetic, which enhanced the computation speed greatly and the precision was also assured. It made detecting real-time realizable. Basing on the Monte Carlo simulation and starting from the theory of photon transmitted in the seawater, we studied how the parameters of water quality and other systemic parameters affect the light forward scattering through seawater at spatial and temporal region and provided the theoretical sustentation of enhancing the SNR and operational distance.

A method of atmospheric density measurements during Shuttle entry using UV laser Rayleigh scattering

NASA Technical Reports Server (NTRS)

Mckenzie, Robert L.

1987-01-01

A detailed study is described of the performance capabilities and the hardware requirements for a method in which ambient density is measured along the Space Shuttle flight path using on-board optical instrumentation. The technique relies on Rayleigh scattering of light from a pulsed, ultraviolet, ArF excimer laser operating at a wavelength of 193 nm. The method is shown to be capable of providing direct measurements of ambient density with an uncertainty of less than 1 percent and with a spatial resolution of 1 km, over an altitude range from 50 to 90 km. In addition, extensions of this concept are discussed that allow measurements of the shock wave location and the density profile within the shock layer. Two approaches are identified that appear to be feasible, in which the same laser system is used for the extended measurements as that required for the ambient density measurements.

[Laser speckle suppression due to dynamic multiple scattering scheme introduced by oblique incidence].

PubMed

Xu, Mei-fang; Gao, Wen-hong; Shi, Yun-bo; Wang, Hao-quan; Du, Bin-bin

2014-06-01

Speckle suppression has been the research focus in laser display technology. In the present paper, the relation between multiple scattering and the size of speckle grains is established by analyzing the properties of speckle generated by the laser beam through SiO2 suspension. Combined with dynamic light scattering theory, laser speckle suppression due to dynamic multiple scattering scheme introduced by oblique incidence is proposed. A speckle suppression element consists of a static diffuser and a light pipe containing the water suspension of SiO2 microspheres with a diameter of 300 nm and a molar concentration of 3.0 x 10(-4) μm3, which is integrated with the laser display system. The laser beam with different incident angles into the SiO2 suspension affecting the contrast of the speckle images is analyzed by the experiments. The results demonstrate that the contrast of the speckle image can be reduced to 0.067 from 0.43 when the beam with the incident angle of approximately 8 degrees illuminates into the SiO2 suspension. The spatial average of speckle granules and the temporal average of speckle images were achieved by the proposed method, which improved the effect of speckle suppression. The proposed element for speckle suppression improved the reliability and reduced the cost of laser projection system, since no mechanical vibration is needed and it is convenient to integrate the element with the existing projection system.

Controlling the spectral shape of nonlinear Thomson scattering with proper laser chirping

DOE PAGES

Rykovanov, S. G.; Geddes, C. G. R.; Schroeder, C. B.; ...

2016-03-18

Effects of nonlinearity in Thomson scattering of a high intensity laser pulse from electrons are analyzed. Analytic expressions for laser pulse shaping in frequency (chirping) are obtained which control spectrum broadening for high laser pulse intensities. These analytic solutions allow prediction of the spectral form and required laser parameters to avoid broadening. Results of analytical and numerical calculations agree well. The control over the scattered radiation bandwidth allows narrow bandwidth sources to be produced using high scattering intensities, which in turn greatly improves scattering yield for future x- and gamma-ray sources.

High-repetition-rate interferometric Rayleigh scattering for flow-velocity measurements

NASA Astrophysics Data System (ADS)

Estevadeordal, Jordi; Jiang, Naibo; Cutler, Andrew D.; Felver, Josef J.; Slipchenko, Mikhail N.; Danehy, Paul M.; Gord, James R.; Roy, Sukesh

2018-03-01

High-repetition-rate interferometric-Rayleigh-scattering (IRS) velocimetry is demonstrated for non-intrusive, high-speed flow-velocity measurements. High temporal resolution is obtained with a quasi-continuous burst-mode laser that is capable of operating at 10-100 kHz, providing 10-ms bursts with pulse widths of 5-1000 ns and pulse energy > 100 mJ at 532 nm. Coupled with a high-speed camera system, the IRS method is based on imaging the flow field through an etalon with 8-GHz free spectral range and capturing the Doppler shift of the Rayleigh-scattered light from the flow at multiple points having constructive interference. The seed-laser linewidth permits a laser linewidth of < 150 MHz at 532 nm. The technique is demonstrated in a high-speed jet, and high-repetition-rate image sequences are shown.

Planar Laser Imaging of Scattering and Fluorescence of Zooplankton Feeding in Layers of Phytoplankton in situ

DTIC Science & Technology

2007-09-30

Planar Laser Imaging of Scattering and Fluorescence of Zooplankton Feeding in Layers of Phytoplankton in situ Peter J.S. Franks Scripps...herbivorous copepod feeding in the laboratory, and 2) to apply these methods in the field to observe the dynamics of copepod feeding in situ. In...particular we intend to test the “ feeding sorties” hypothesis vs. the “in situ feeding ” hypothesis regarding the location and timing of copepod feeding

Detectability limit and uncertainty considerations for laser induced fluorescence spectroscopy in flames

NASA Technical Reports Server (NTRS)

Daily, J. W.

1978-01-01

Laser induced fluorescence spectroscopy of flames is discussed, and derived uncertainty relations are used to calculate detectability limits due to statistical errors. Interferences due to Rayleigh scattering from molecules as well as Mie scattering and incandescence from particles have been examined for their effect on detectability limits. Fluorescence trapping is studied, and some methods for reducing the effect are considered. Fluorescence trapping places an upper limit on the number density of the fluorescing species that can be measured without signal loss.

Laser-Based Remote Sensing of Explosives by a Differential Absorption and Scattering Method

NASA Astrophysics Data System (ADS)

Ayrapetyan, V. S.

2018-01-01

A multifunctional IR parametric laser system is developed and tested for remote detection and identification of atmospheric gases, including explosive and chemically aggressive substances. Calculations and experimental studies of remote determination of the spectroscopic parameters of the best known explosive substances TNT, RDX, and PETN are carried out. The feasibility of high sensitivity detection ( 1 ppm) of these substances with the aid of a multifunctional IR parametric light source by differential absorption and scattering is demonstrated.

Laser plasma interaction at an early stage of laser ablation

NASA Astrophysics Data System (ADS)

Lu, Y. F.; Hong, M. H.; Low, T. S.

1999-03-01

Laser scattering and its interaction with plasma during KrF excimer laser ablation of silicon are investigated by ultrafast phototube detection. There are two peaks in an optical signal with the first peak attributed to laser scattering and the second one to plasma generation. For laser fluence above 5.8 J/cm2, the second peak rises earlier to overlap with the first one. The optical signal is fitted by a pulse distribution for the scattered laser light and a drifted Maxwell-Boltzmann distribution with a center-of-mass velocity for the plasma. Peak amplitude and its arrival time, full width at half maximum (FWHM), starting time, and termination time of the profiles are studied for different laser fluences and detection angles. Laser pulse is scattered from both the substrate and the plasma with the latter part as a dominant factor during the laser ablation. Peak amplitude of the scattered laser signal increases but its FWHM decreases with the laser fluence. Angular distribution of the peak amplitude can be fitted with cosn θ(n=4) while the detection angle has no obvious influence on the FWHM. In addition, FWHM and peak amplitude of plasma signal increase with the laser fluence. However, starting time and peak arrival time of plasma signal reduce with the laser fluence. The time interval between plasma starting and scattered laser pulse termination is proposed as a quantitative parameter to characterize laser plasma interaction. Threshold fluence for the interaction is estimated to be 3.5 J/cm2. For laser fluence above 12.6 J/cm2, the plasma and scattered laser pulse distributions tend to saturate.

Method of and apparatus for measuring temperature and pressure. [atmospheric sounding

NASA Technical Reports Server (NTRS)

Korb, C. L.; Kalshoven, J. E., Jr. (Inventor)

1985-01-01

Laser beams are transmitted through gas to a reflecting target, which may be either a solid surface or particulate matter in gas or the gas molecules. The return beams are measured to determine the amount of energy absorbed by the gas. For temperature measurements, the laser beam has a wavelength at which the gas exhibits a relatively temperature sensitive and pressure insensitive absorption characteristic for pressure measurements, the laser beam has a wavelength at which the gas has a relatively pressure sensitive and temperature insensitive absorption characteristic. To reduce the effects of scattering on the absorption measurements a reference laser beam with a weak absorption characteristic is transmitted colinearly with the data beam having a strong absorption characteristic. The two signals are processed as a ratio to eliminate back scattering. Embodiments of transmitters and receivers described include a sequential laser pulse transmitter and receiver, a simultaneous laser pulse transmitter and receiver.

Tunable lasers and their application in analytical chemistry

NASA Technical Reports Server (NTRS)

Steinfeld, J. I.

1975-01-01

The impact that laser techniques might have in chemical analysis is examined. Absorption, scattering, and heterodyne detection is considered. Particular emphasis is placed on the advantages of using frequency-tunable sources, and dye solution lasers are regarded as the outstanding example of this type of laser. Types of spectroscopy that can be carried out with lasers are discussed along with the ultimate sensitivity or minimum detectable concentration of molecules that can be achieved with each method. Analytical applications include laser microprobe analysis, remote sensing and instrumental methods such as laser-Raman spectroscopy, atomic absorption/fluorescence spectrometry, fluorescence assay techniques, optoacoustic spectroscopy, and polarization measurements. The application of lasers to spectroscopic methods of analysis would seem to be a rewarding field both for research in analytical chemistry and for investments in instrument manufacturing.

Laser-modified Coulomb scattering states of an electron in the parabolic quasi-Sturmian-Floquet approach

NASA Astrophysics Data System (ADS)

Zaytsev, A. S.; Zaytsev, S. A.; Ancarani, L. U.; Kouzakov, K. A.

2018-04-01

Electron scattering states in combined Coulomb and laser fields are investigated with a nonperturbative approach based on the Hermitian Floquet theory. Taking into account the Coulomb-specific asymptotic behavior of the electron wave functions at large distances, a Lippmann-Schwinger-Floquet equation is derived in the Kramers-Henneberger frame. Such a scattering-state equation is solved numerically employing a set of parabolic quasi-Sturmian functions which have the great advantage of possessing, by construction, adequately chosen incoming or outgoing Coulomb asymptotic behaviors. Our quasi-Sturmian-Floquet approach is tested with a calculation of triple differential cross sections for a laser-assisted (e ,2 e ) process on atomic hydrogen within a first-order Born treatment of the projectile-atom interaction. Convergence with respect to the number of Floquet-Fourier expansion terms is numerically demonstrated. The illustration shows that the developed method is very efficient for the computation of light-dressed states of an electron moving in a Coulomb potential in the presence of laser radiation.

Quantum imaging with incoherently scattered light from a free-electron laser

NASA Astrophysics Data System (ADS)

Schneider, Raimund; Mehringer, Thomas; Mercurio, Giuseppe; Wenthaus, Lukas; Classen, Anton; Brenner, Günter; Gorobtsov, Oleg; Benz, Adrian; Bhatti, Daniel; Bocklage, Lars; Fischer, Birgit; Lazarev, Sergey; Obukhov, Yuri; Schlage, Kai; Skopintsev, Petr; Wagner, Jochen; Waldmann, Felix; Willing, Svenja; Zaluzhnyy, Ivan; Wurth, Wilfried; Vartanyants, Ivan A.; Röhlsberger, Ralf; von Zanthier, Joachim

2018-02-01

The advent of accelerator-driven free-electron lasers (FEL) has opened new avenues for high-resolution structure determination via diffraction methods that go far beyond conventional X-ray crystallography methods. These techniques rely on coherent scattering processes that require the maintenance of first-order coherence of the radiation field throughout the imaging procedure. Here we show that higher-order degrees of coherence, displayed in the intensity correlations of incoherently scattered X-rays from an FEL, can be used to image two-dimensional objects with a spatial resolution close to or even below the Abbe limit. This constitutes a new approach towards structure determination based on incoherent processes, including fluorescence emission or wavefront distortions, generally considered detrimental for imaging applications. Our method is an extension of the landmark intensity correlation measurements of Hanbury Brown and Twiss to higher than second order, paving the way towards determination of structure and dynamics of matter in regimes where coherent imaging methods have intrinsic limitations.

Effects of polarization direction on laser-assisted free-free scattering

NASA Astrophysics Data System (ADS)

deHarak, B. A.; Kim, B. N.; Weaver, C. M.; Martin, N. L. S.; Siavashpouri, Mahsa; Nosarzewski, Benjamin

2016-06-01

This work will detail the effects of laser polarization direction (relative to the momentum transfer direction) on laser-assisted free-free scattering. Such processes play a role in the gas breakdown that occurs in electric discharges as well as providing a method for the laser heating of a plasma (Musa et al 2010 J. Phys. B: At. Mol. Opt. Phys. 43 175201, Mason 1993 Rep. Prog. Phys. 56 1275). Experimental results will be presented for electron-helium scattering in the presence of an Nd:YAG laser field (hν =1.17 eV) where the polarization direction was varied in a plane that is perpendicular to the scattering plane. To date, all of our experimental results are well described by the Kroll-Watson approximation (KWA) (Kroll and Watson 1973 Phys. Rev. A 8 804). The good agreement between our experiments and calculations using the KWA includes the case where the polarization is perpendicular to the momentum transfer direction, for which the KWA predicts vanishing cross section; other workers have found that the KWA tends to be inaccurate for cases where it predicts small cross sections (e.g. Musa et al 2010 J. Phys. B: At. Mol. Opt. Phys. 43 175201). We also present simulations of the effects that multiple scattering might have on experimental measurements. In particular, we examine conditions that are expected to be similar to those of the experiments reported by Wallbank and Holmes (Wallbank and Holmes 1993 Phys. Rev. A 48 R2515).

Investigations of the fabrication and the surface-enhanced Raman scattering detection applications for tapered fiber probes prepared with the laser-induced chemical deposition method.

PubMed

Fan, Qunfang; Cao, Jie; Liu, Ye; Yao, Bo; Mao, Qinghe

2013-09-01

The process of depositing nanoparticles onto tapered fiber probes with the laser-induced chemical deposition method (LICDM) and the surface-enhanced Raman scattering (SERS) detection performance of the prepared probes are experimentally investigated in this paper. Our results show that the nanoparticle-deposited tapered fiber probes prepared with the LICDM method depend strongly on the value of the cone angle. For small-angle tapered probes the nanoparticle-deposited areas are only focused at the taper tips, because the taper surfaces are mainly covered by a relatively low-intensity evanescent field. By lengthening the reaction time or increasing the induced power or solution concentration, it is still possible to deposit nanoparticles on small-angle tapers with the light-scattering effect. With 4-aminothiophenol as the testing molecule, it was found that for given preparation conditions, the cone angles for the tapered probes with the highest SERS spectral intensities for different excitation laser powers are almost the same. However, such an optimal cone angle is determined by the combined effects of both the localized surface plasmon resonance strength and the transmission loss generated by the nanoparticles deposited.

Automated Laser-Light Scattering measurements of Impurities, Bubbles, and Imperfections in Ice Cores

NASA Astrophysics Data System (ADS)

Stolz, M. R.; Ram, M.

2004-12-01

Laser- light scattering (LLS) on polar ice, or on polar ice meltwater, is an accepted method for measuring the concentration of water insoluble aerosol deposits (dust) in the ice. LLS on polar ice can also be used to measure water soluble aerosols, as well as imperfections (air bubbles and cavities) in the ice. LLS was originally proposed by Hammer (1977a, b) as a method for measuring the dust concentration in polar ice meltwater. Ram et al. (1995) later advanced the method and applied it to solid ice, measuring the dust concentration profile along the deep, bubble-free sections of the Greenland Ice Sheet Projetct 2 (GISP2) ice core (Ram et al., 1995, 2000) from central Greenland. In this paper, we will put previous empirical findings (Ram et al., 1995, 2000) on a theoretical footing, and extend the usability of LLS on ice into the realm of the non-transparent, bubbly polar ice. For LLS on clear, bubble-free polar ice, we studied numerically the scattering of light by soluble and insoluble (dust) aerosol particles embedded in the ice to complement previous experimental studies (Ram et al., 2000). For air bubbles in polar ice, we calculated the effects of multiple light scattering using Mie theory and Monte Carlo simulations, and found a method for determining the bubble number size and concentration using LLS on bubbly ice. We also demonstrated that LLS can be used on bubbly ice to measure annual layers rapidly in an objective manner. Hammer, C. U. (1977a), Dating of Greenland ice cores by microparticle concentration analyses., in International Symposium on Isotopes and Impurities in Snow and Ice, pp. 297-301, IAHS publ. no. 118. Hammer, C. U. (1977b), Dust studies on Greenland ice cores, in International Symposium on Isotopes and Impurities in Snow and Ice, pp. 365-370, IAHS publ. no. 118. Ram, M., M. Illing, P. Weber, G. Koenig, and M. Kaplan (1995), Polar ice stratigraphy from laser-light scattering: Scattering from ice, Geophys. Res. Lett., 22(24), 3525-3527. Ram, M., J. Donarummo, M. R. Stolz, and G. Koenig (2000), Calibration of laser-light scattering measurements of dust concentration for Wisconsinan GISP2 ice using instrumental neutron activation analysis of aluminum: Results and discussion, J. Geophys. Res., 105(D20), 24,731--24,738.

Investigation of change of tumor optical properties after laser-induced plasmon-resonant photothermal treatment of transplanted tumors in rats

NASA Astrophysics Data System (ADS)

Genin, Vadim D.; Genina, Elina A.; Bucharskaya, Alla B.; Tuchin, Valery V.; Khlebtsov, Nikolay G.; Terentyuk, Georgy S.; Bashkatov, Alexey N.

2018-04-01

The paper presents the investigation of change of tumor optical properties of the rat tumor doped by gold nanoparticles after laser-induced plasmon-resonant photothermal treatment. To obtain the model tumors the rats have been implanted by suspension of alveolar kidney cancer cells. An hour before the experiment the animals have been injected by the suspension of gold nanorods intratumorally. For irradiation a diode laser with wavelength 808 nm has been used. After the irradiation the tumor has been removed and sliced. Spectra of total and collimated transmission and diffuse reflectance of the samples of different layers of the tumors have been measured in the wavelength range 350-2500 nm. Absorption, scattering, reduced scattering coefficients and scattering anisotropy factor of tumor tissues have been calculated with inverse adding-doubling method. The results of the experiment have shown that after doping the tumor tissue by the plasmon resonant nanoparticles and NIR laser irradiating, there is the decreases of absorption as well as scattering properties of the tumor and surrounding tissues. However, despite the sufficiently high temperature on the surface (about 80°C), the changes in the center of the tumor are insignificant.

Investigation of superelastic electron scattering by laser-excited Ba - Experimental procedures and results

NASA Technical Reports Server (NTRS)

Register, D. F.; Trajmar, S.; Fineman, M. A.; Poe, R. T.; Csanak, G.; Jensen, S. W.

1983-01-01

Differential (in angle) electron scattering experiments on laser-excited Ba-138 1P were carried out at 30- and 100-eV impact energies. The laser light was linearly polarized and located in the scattering plane. The superelastic scattering signal was measured as a function of polarization direction of the laser light with respect to the scattering plane. It was found at low electron scattering angles that the superelastic scattering signal was asymmetric to reflection of the polarization vector with respect to the scattering plane. This is in contradiction with theoretical predictions. An attempt was made to pinpoint the reason for this observation, and a detailed investigation of the influence of experimental conditions on the superelastic scattering was undertaken. No explanation for the asymmetry has as yet been found.

Infrared laser transillumination CT imaging system using parallel fiber arrays and optical switches for finger joint imaging

NASA Astrophysics Data System (ADS)

Sasaki, Yoshiaki; Emori, Ryota; Inage, Hiroki; Goto, Masaki; Takahashi, Ryo; Yuasa, Tetsuya; Taniguchi, Hiroshi; Devaraj, Balasigamani; Akatsuka, Takao

2004-05-01

The heterodyne detection technique, on which the coherent detection imaging (CDI) method founds, can discriminate and select very weak, highly directional forward scattered, and coherence retaining photons that emerge from scattering media in spite of their complex and highly scattering nature. That property enables us to reconstruct tomographic images using the same reconstruction technique as that of X-Ray CT, i.e., the filtered backprojection method. Our group had so far developed a transillumination laser CT imaging method based on the CDI method in the visible and near-infrared regions and reconstruction from projections, and reported a variety of tomographic images both in vitro and in vivo of biological objects to demonstrate the effectiveness to biomedical use. Since the previous system was not optimized, it took several hours to obtain a single image. For a practical use, we developed a prototype CDI-based imaging system using parallel fiber array and optical switches to reduce the measurement time significantly. Here, we describe a prototype transillumination laser CT imaging system using fiber-optic based on optical heterodyne detection for early diagnosis of rheumatoid arthritis (RA), by demonstrating the tomographic imaging of acrylic phantom as well as the fundamental imaging properties. We expect that further refinements of the fiber-optic-based laser CT imaging system could lead to a novel and practical diagnostic tool for rheumatoid arthritis and other joint- and bone-related diseases in human finger.

Anisotropy enhanced X-ray scattering from solvated transition metal complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biasin, Elisa; van Driel, Tim B.; Levi, Gianluca

Time-resolved X-ray scattering patterns from photoexcited molecules in solution are in many cases anisotropic at the ultrafast time scales accessible at X-ray free-electron lasers (XFELs). This anisotropy arises from the interaction of a linearly polarized UV–Vis pump laser pulse with the sample, which induces anisotropic structural changes that can be captured by femtosecond X-ray pulses. In this work, a method for quantitative analysis of the anisotropic scattering signal arising from an ensemble of molecules is described, and it is demonstrated how its use can enhance the structural sensitivity of the time-resolved X-ray scattering experiment. This method is applied on time-resolvedmore » X-ray scattering patterns measured upon photoexcitation of a solvated di-platinum complex at an XFEL, and the key parameters involved are explored. Here it is shown that a combined analysis of the anisotropic and isotropic difference scattering signals in this experiment allows a more precise determination of the main photoinduced structural change in the solute,i.e.the change in Pt—Pt bond length, and yields more information on the excitation channels than the analysis of the isotropic scattering only. Finally, it is discussed how the anisotropic transient response of the solvent can enable the determination of key experimental parameters such as the instrument response function.« less

Anisotropy enhanced X-ray scattering from solvated transition metal complexes

DOE PAGES

Biasin, Elisa; van Driel, Tim B.; Levi, Gianluca; ...

2018-02-13

Time-resolved X-ray scattering patterns from photoexcited molecules in solution are in many cases anisotropic at the ultrafast time scales accessible at X-ray free-electron lasers (XFELs). This anisotropy arises from the interaction of a linearly polarized UV–Vis pump laser pulse with the sample, which induces anisotropic structural changes that can be captured by femtosecond X-ray pulses. In this work, a method for quantitative analysis of the anisotropic scattering signal arising from an ensemble of molecules is described, and it is demonstrated how its use can enhance the structural sensitivity of the time-resolved X-ray scattering experiment. This method is applied on time-resolvedmore » X-ray scattering patterns measured upon photoexcitation of a solvated di-platinum complex at an XFEL, and the key parameters involved are explored. Here it is shown that a combined analysis of the anisotropic and isotropic difference scattering signals in this experiment allows a more precise determination of the main photoinduced structural change in the solute,i.e.the change in Pt—Pt bond length, and yields more information on the excitation channels than the analysis of the isotropic scattering only. Finally, it is discussed how the anisotropic transient response of the solvent can enable the determination of key experimental parameters such as the instrument response function.« less

Light scattering in optical CT scanning of Presage dosimeters

NASA Astrophysics Data System (ADS)

Xu, Y.; Adamovics, J.; Cheeseborough, J. C.; Chao, K. S.; Wuu, C. S.

2010-11-01

The intensity of the scattered light from the Presage dosimeters was measured using a Thorlabs PM100D optical power meter (Thorlabs Inc, Newton, NJ) with an optical sensor of 1 mm diameter sensitive area. Five Presage dosimeters were made as cylinders of 15.2 cm, 10 cm, 4 cm diameters and irradiated with 6 MV photons using a Varian Clinac 2100EX. Each dosimeter was put into the scanning tank of an OCTOPUS" optical CT scanner (MGS Research Inc, Madison, CT) filled with a refractive index matching liquid. A laser diode was positioned at one side of the water tank to generate a stationary laser beam of 0.8 mm width. On the other side of the tank, an in-house manufactured positioning system was used to move the optical sensor in the direction perpendicular to the outgoing laser beam from the dosimeters at an increment of 1 mm. The amount of scattered photons was found to be more than 1% of the primary light signal within 2 mm from the laser beam but decreases sharply with increasing off-axis distance. The intensity of the scattered light increases with increasing light attenuations and/or absorptions in the dosimeters. The scattered light at the same off-axis distance was weaker for dosimeters of larger diameters and for larger detector-to-dosimeter distances. Methods for minimizing the effect of the light scattering in different types of optical CT scanners are discussed.

A phase screen model for simulating numerically the propagation of a laser beam in rain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lukin, I P; Rychkov, D S; Falits, A V

2009-09-30

The method based on the generalisation of the phase screen method for a continuous random medium is proposed for simulating numerically the propagation of laser radiation in a turbulent atmosphere with precipitation. In the phase screen model for a discrete component of a heterogeneous 'air-rain droplet' medium, the amplitude screen describing the scattering of an optical field by discrete particles of the medium is replaced by an equivalent phase screen with a spectrum of the correlation function of the effective dielectric constant fluctuations that is similar to the spectrum of a discrete scattering component - water droplets in air. Themore » 'turbulent' phase screen is constructed on the basis of the Kolmogorov model, while the 'rain' screen model utiises the exponential distribution of the number of rain drops with respect to their radii as a function of the rain intensity. Theresults of the numerical simulation are compared with the known theoretical estimates for a large-scale discrete scattering medium. (propagation of laser radiation in matter)« less

Comparison of the spatial landmark scatter of various 3D digitalization methods.

PubMed

Boldt, Florian; Weinzierl, Christian; Hertrich, Klaus; Hirschfelder, Ursula

2009-05-01

The aim of this study was to compare four different three-dimensional digitalization methods on the basis of the complex anatomical surface of a cleft lip and palate plaster cast, and to ascertain their accuracy when positioning 3D landmarks. A cleft lip and palate plaster cast was digitalized with the SCAN3D photo-optical scanner, the OPTIX 400S laser-optical scanner, the Somatom Sensation 64 computed tomography system and the MicroScribe MLX 3-axis articulated-arm digitizer. First, four examiners appraised by individual visual inspection the surface detail reproduction of the three non-tactile digitalization methods in comparison to the reference plaster cast. The four examiners then localized the landmarks five times at intervals of 2 weeks. This involved simply copying, or spatially tracing, the landmarks from a reference plaster cast to each model digitally reproduced by each digitalization method. Statistical analysis of the landmark distribution specific to each method was performed based on the 3D coordinates of the positioned landmarks. Visual evaluation of surface detail conformity assigned the photo-optical digitalization method an average score of 1.5, the highest subjectively-determined conformity (surpassing computer tomographic and laser-optical methods). The tactile scanning method revealed the lowest degree of 3D landmark scatter, 0.12 mm, and at 1.01 mm the lowest maximum 3D landmark scatter; this was followed by the computer tomographic, photo-optical and laser-optical methods (in that order). This study demonstrates that the landmarks' precision and reproducibility are determined by the complexity of the reference-model surface as well as the digital surface quality and individual ability of each evaluator to capture 3D spatial relationships. The differences in the 3D-landmark scatter values and lowest maximum 3D-landmark scatter between the best and the worst methods showed minor differences. The measurement results in this study reveal that it is not the method's precision but rather the complexity of the object analysis being planned that should determine which method is ultimately employed.

Laser light scattering from wood samples soaked in water or in benzyl benzoate

NASA Astrophysics Data System (ADS)

Simonaho, S.-P.; Tolonen, Y.; Rouvinen, J.; Silvennoinen, R.

Laser light scattering from Scots pine (Pinus Sylvesteris L.) wood samples soaked in two different liquids, which were tap water and benzyl benzoate, has been experimentally investigated. Differences in the characteristics of the scattering pattern as function of the soaking time as well as the moisture effect in the orientation of scattering pattern has been experimentally investigated. The wood samples soaked in the test liquids altered the laser light scattering in along and across the grain directions. No correlation between the content of the water in the wood sample and the orientation of laser light scattering pattern was observed.

Spatially-and Temporally-Resolved Multi-Parameter Interferometric Rayleigh Scattering System and Method

NASA Technical Reports Server (NTRS)

Bivolaru, Daniel (Inventor); Cutler, Andrew D. (Inventor); Danehy, Paul M. (Inventor)

2015-01-01

A system that simultaneously measures the translational temperature, bulk velocity, and density in gases by collecting, referencing, and analyzing nanosecond time-scale Rayleigh scattered light from molecules is described. A narrow-band pulsed laser source is used to probe two largely separated measurement locations, one of which is used for reference. The elastically scattered photons containing information from both measurement locations are collected at the same time and analyzed spectrally using a planar Fabry-Perot interferometer. A practical means of referencing the measurement of velocity using the laser frequency, and the density and temperature using the information from the reference measurement location maintained at constant properties is provided.

Observation of optically induced feshbach resonances in collisions of cold atoms

PubMed

Fatemi; Jones; Lett

2000-11-20

We have observed optically induced Feshbach resonances in a cold ( <1 mK) sodium vapor. The optical coupling of the ground and excited-state potentials changes the scattering properties of an ultracold gas in much the same way as recently observed magnetically induced Feshbach resonances, but allows for some experimental conveniences associated with using lasers. The scattering properties can be varied by changing either the intensity or the detuning of a laser tuned near a photoassociation transition to a molecular state in the dimer. In principle this method allows the scattering length of any atomic species to be altered. A simple model is used to fit the dispersive resonance line shapes.

Exhaust Plume Measurements of 15-Pound BATES (Ballistic Test and Evaluation System) Motors.

DTIC Science & Technology

1985-06-01

laser transmissometer measurements as a plume... System 7 3 AFRPL Laser Transmission/Scattering Measurement System During Motor Firing 8 4 Laser Scattering Detector Schematic 9 5 Laser Scattering... measurement goals. The instrumentation includes a multi -wavelength, single line-of-sight IR-E/A system , a UV emission spectrometer, an exhaust

Method and apparatus for fiber optic multiple scattering suppression

NASA Technical Reports Server (NTRS)

Ackerson, Bruce J. (Inventor)

2000-01-01

The instant invention provides a method and apparatus for use in laser induced dynamic light scattering which attenuates the multiple scattering component in favor of the single scattering component. The preferred apparatus utilizes two light detectors that are spatially and/or angularly separated and which simultaneously record the speckle pattern from a single sample. The recorded patterns from the two detectors are then cross correlated in time to produce one point on a composite single/multiple scattering function curve. By collecting and analyzing cross correlation measurements that have been taken at a plurality of different spatial/angular positions, the signal representative of single scattering may be differentiated from the signal representative of multiple scattering, and a near optimum detector separation angle for use in taking future measurements may be determined.

The rapid determination of fat and protein content in fresh raw milk using the laser light scattering technology

NASA Astrophysics Data System (ADS)

Xin, Qi; Zhi Ling, Hou; Jian Long, Tian; Zhu, Yu

2006-08-01

The aim was to develop a simple and rapid method for determination of fat and protein content in milk. Based on the laser light scattering theory, the ratio of the scattered light (at 90±0.05° scattering angles) intensity to the transmitted light intensity, which is called scattered-transmitted-ratio method, is adopted as the optical parameter representing the milk fat content and the protein content. In this way, the influence of the fluctuation of the power of the light source is eliminated and the accuracy of determination is improved accordingly. The system we use is real-time and can satisfy the challenging requirements of dairy farming. Results of this study indicate the feasibility of using this technology for fresh milk fat and protein analysis. The fat contents and protein contents of 50 milk samples determined by this method were consistent with the values obtained by the reference methods based on Rose-Gottlieb method and Kjeldahl determination of N method. In this paper, the operating principle of the instrument is introduced and the influence of the environmental conditions, such as the homogenization pressure and homogenization temperature, etc. on the result of the test is analyzed. Through data analysis, the concrete schemes for testing the fat using the curve fitting and testing the protein using the surface fitting technique are determined. Finally, the difference from the reference values of the test is discussed.

LASER BIOLOGY AND MEDICINE: Light scattering study of rheumatoid arthritis

NASA Astrophysics Data System (ADS)

Beuthan, J.; Netz, U.; Minet, O.; Klose, Annerose D.; Hielscher, A. H.; Scheel, A.; Henniger, J.; Müller, G.

2002-11-01

The distribution of light scattered by finger joints is studied in the near-IR region. It is shown that variations in the optical parameters of the tissue (scattering coefficient μs, absorption coefficient μa, and anisotropy factor g) depend on the presence of the rheumatoid arthritis (RA). At the first stage, the distribution of scattered light was measured in diaphanoscopic experiments. The convolution of a Gaussian error function with the scattering phase function proved to be a good approximation of the data obtained. Then, a new method was developed for the reconstruction of distribution of optical parameters in the finger cross section. Model tests of the quality of this reconstruction method show good results.

Hydrometeor Size Distribution Measurements by Imaging the Attenuation of a Laser Spot

NASA Technical Reports Server (NTRS)

Lane, John

2013-01-01

The optical extinction of a laser due to scattering of particles is a well-known phenomenon. In a laboratory environment, this physical principle is known as the Beer-Lambert law, and is often used to measure the concentration of scattering particles in a fluid or gas. This method has been experimentally shown to be a usable means to measure the dust density from a rocket plume interaction with the lunar surface. Using the same principles and experimental arrangement, this technique can be applied to hydrometeor size distributions, and for launch-pad operations, specifically as a passive hail detection and measurement system. Calibration of a hail monitoring system is a difficult process. In the past, it has required comparison to another means of measuring hydrometeor size and density. Using a technique recently developed for estimating the density of surface dust dispersed during a rocket landing, measuring the extinction of a laser passing through hail (or dust in the rocket case) yields an estimate of the second moment of the particle cloud, and hydrometeor size distribution in the terrestrial meteorological case. With the exception of disdrometers, instruments that measure rain and hail fall make indirect measurements of the drop-size distribution. Instruments that scatter microwaves off of hydrometeors, such as the WSR-88D (Weather Surveillance Radar 88 Doppler), vertical wind profilers, and microwave disdrometers, measure the sixth moment of the drop size distribution (DSD). By projecting a laser onto a target, changes in brightness of the laser spot against the target background during rain and hail yield a measurement of the DSD's second moment by way of the Beer-Lambert law. In order to detect the laser attenuation within the 8-bit resolution of most camera image arrays, a minimum path length is required. Depending on the intensity of the hail fall rate for moderate to heavy rainfall, a laser path length of 100 m is sufficient to measure variations in optical extinction using a digital camera. For hail fall only, the laser path may be shorter because of greater scattering due to the properties of hailstones versus raindrops. A photodetector may replace the camera in automated installations. Laser-based rain and hail measurement systems are available, but they are based on measuring the interruption of a thin laser beam, thus counting individual hydrometeors. These systems are true disdrometers since they also measure size and velocity. The method reported here is a simple method, requiring far less processing, but it is not a disdrometer.

Effect of part thickness, glass fiber and crystallinity on light scattering during laser transmission welding of thermoplastics

NASA Astrophysics Data System (ADS)

Xu, Xin Feng; Parkinson, Alexander; Bates, Philip J.; Zak, Gene

2015-12-01

It is important to understand how laser energy scatters within the transparent component in order to predict and optimize the laser transmission welding process. This paper examines the influence of part thickness, glass fiber and crystallinity levels on the distribution of laser light after transmission through amorphous polycarbonate (PC) and semi-crystalline polymers such as polyamide 6 (PA6), polypropylene (PP), and polyethylene (PE). An experimental technique based on laser-scanned lines of progressively increasing power was used to assess the transmitted energy distribution. This distribution was characterized using a two-parameter model that captures scattered and un-scattered components of the laser beam. The results clearly show how the scattering is increased by increasing the numbers of interactions between laser light and phase boundaries either by increasing the particle concentration (i.e., glass fiber level and crystallinity) or increasing part thickness.

Detuned surface plasmon resonance scattering of gold nanorods for continuous wave multilayered optical recording and readout.

PubMed

Taylor, Adam B; Kim, Jooho; Chon, James W M

2012-02-27

In a multilayered structure of absorptive optical recording media, continuous-wave laser operation is highly disadvantageous due to heavy beam extinction. For a gold nanorod based recording medium, the narrow surface plasmon resonance (SPR) profile of gold nanorods enables the variation of extinction through mulilayers by a simple detuning of the readout wavelength from the SPR peak. The level of signal extinction through the layers can then be greatly reduced, resulting more efficient readout at deeper layers. The scattering signal strength may be decreased at the detuned wavelength, but balancing these two factors results an optimal scattering peak wavelength that is specific to each layer. In this paper, we propose to use detuned SPR scattering from gold nanorods as a new mechanism for continuous-wave readout scheme on gold nanorod based multilayered optical storage. Using this detuned scattering method, readout using continuous-wave laser is demonstrated on a 16 layer optical recording medium doped with heavily distributed, randomly oriented gold nanorods. Compared to SPR on-resonant readout, this method reduced the required readout power more than one order of magnitude, with only 60 nm detuning from SPR peak. The proposed method will be highly beneficial to multilayered optical storage applications as well as applications using a continuous medium doped heavily with plasmonic nanoparticles.

Feedback mechanism for smart nozzles and nebulizers

DOEpatents

Montaser, Akbar [Potomac, MD; Jorabchi, Kaveh [Arlington, VA; Kahen, Kaveh [Kleinburg, CA

2009-01-27

Nozzles and nebulizers able to produce aerosol with optimum and reproducible quality based on feedback information obtained using laser imaging techniques. Two laser-based imaging techniques based on particle image velocimetry (PTV) and optical patternation map and contrast size and velocity distributions for indirect and direct pneumatic nebulizations in plasma spectrometry. Two pulses from thin laser sheet with known time difference illuminate droplets flow field. Charge coupled device (CCL)) captures scattering of laser light from droplets, providing two instantaneous particle images. Pointwise cross-correlation of corresponding images yields two-dimensional velocity map of aerosol velocity field. For droplet size distribution studies, solution is doped with fluorescent dye and both laser induced florescence (LIF) and Mie scattering images are captured simultaneously by two CCDs with the same field of view. Ratio of LIF/Mie images provides relative droplet size information, then scaled by point calibration method via phase Doppler particle analyzer.

Research remote laser methods for radionuclides monitoring

NASA Astrophysics Data System (ADS)

Kascheev, S. V.; Elizarov, Valentin V.; Grishkanich, Alexander S.; Bespalov, V. G.; Vasil'ev, Sergey K.; Zhevlakov, A. P.

2014-05-01

Laser sensing can serve as a highly effective method of searching and monitoring of radioactive contamination. The first method is essence consists in definition the Sr90 and Сs137 concentration by excitation and registration of fluorescence at wavelength of λ = 0.347÷7.0 μm at laser sounding. The second method experiments were carried out under the Raman-scattering circuit. Preliminary results of investigation show the real possibility to register of leakage of a radionuclide with concentration at level of 108÷109 сm-3 on a safe distance from the infected object.

Investigation of laser induced parametric interactions in optical waveguides and fibers

NASA Technical Reports Server (NTRS)

Yu, C.

1978-01-01

Experimental and theoretical aspects of the laser pump depletion characteristics in an optical fiber due to stimulated Raman scattering, and stimulated Brillouin scattering were studied. A review is presented of research in fiber transmission accompanied by stimulated scattering. Results of experimental work with tunable dye lasers and argon lasers are presented. The spectral profiles of the laser pump and its transmitted light through the fiber are given.

Ponderomotive phase plate for transmission electron microscopes

DOEpatents

Reed, Bryan W [Livermore, CA

2012-07-10

A ponderomotive phase plate system and method for controllably producing highly tunable phase contrast transfer functions in a transmission electron microscope (TEM) for high resolution and biological phase contrast imaging. The system and method includes a laser source and a beam transport system to produce a focused laser crossover as a phase plate, so that a ponderomotive potential of the focused laser crossover produces a scattering-angle-dependent phase shift in the electrons of the post-sample electron beam corresponding to a desired phase contrast transfer function.

Coherent random lasing from liquid waveguide gain channels with biological scatters

NASA Astrophysics Data System (ADS)

Zhang, Hong; Feng, Guoying; Wang, Shutong; Yang, Chao; Yin, Jiajia; Zhou, Shouhuan

2014-12-01

A unidirectional coherent random laser based on liquid waveguide gain channels with biological scatters is demonstrated. The optical feedback of the random laser is provided by both light scattering and waveguide confinement. This waveguide-scattering-feedback scheme not only reduces the pump threshold but also makes the output of random laser directional. The threshold of our random laser is about 11 μJ. The emission spectra can be sensitively tuned by changing pump position due to the micro/nano-scale randomness of butterfly wings. It shows the potential applications of optofluidic random lasers for bio-chemical sensors on-chip.

Electron-molecule scattering in a strong laser field: Two-center interference effects

NASA Astrophysics Data System (ADS)

Dakić, J.; Habibović, D.; Čerkić, A.; Busuladžić, M.; Milošević, D. B.

2017-10-01

Laser-assisted scattering of electrons on diatomic molecules is considered using the S -matrix theory within the second Born approximation. The first term of the expansion in powers of the scattering potential corresponds to the direct or single laser-assisted scattering of electrons on molecular targets, while the second term of this expansion corresponds to the laser-assisted rescattering or double scattering. The rescattered electrons may have considerably higher energies in the final state than those that scattered only once. For multicenter polyatomic molecules scattering and rescattering may happen at any center and in any order. All these cases contribute to the scattering amplitude and the interference of different contributions leads to an increase or a decrease of the differential cross section in particular electron energy regions. For diatomic molecules there are two such contributions for single scattering and four contributions for double scattering. Analyzing the spectra of the scattered electrons, we find two interesting effects. For certain molecular orientations, the plateaus in the electron energy spectrum, characteristic of laser-assisted electron-atom scattering, are replaced by a sequence of gradually declining maxima, caused by the two-center interference effects. The second effect is the appearance of symmetric U -shaped structures in the angle-resolved energy spectra, which are described very well by the analytical formulas we provide.

Improved cross-calibration of Thomson scattering and electron cyclotron emission with ECH on DIII-D

DOE PAGES

Brookman, M. W.; Austin, M. E.; McLean, A. G.; ...

2016-08-08

Thomson scattering (TS) produces n e profiles from measurement of scattered laser beam intensity. In the case of Rayleigh scattering, it provides a first calibration of the relation n e / ITS, which depends on many factors (e.g. laser alignment and power, optics, and measurement systems). On DIII-D, the n e calibration is adjusted for each laser and optic path against an absolute n e measurement from a density-driven cutoff on the 48 channel 2nd harmonic X-mode electron cyclotron emission (ECE) system. This method has been used to calibrate Thompson densities from the edge to near the core (r/a >more » 0.15). Application of core electron cyclotron heating improves the quality of cutoff and depth of its penetration into the core. ECH also changes underlying MHD activity. Furthermore, on the removal of ECH power, cutoff penetrates in from the edge to the core and channels fall successively and smoothly into cutoff. This improves the quality of the TS n e calibration while minimizing wall loading.« less

Time differentiated nuclear resonance spectroscopy coupled with pulsed laser heating in diamond anvil cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kupenko, I., E-mail: kupenko@esrf.fr; Strohm, C.; ESRF-The European Synchrotron, CS 40220, 38043 Grenoble Cedex 9

2015-11-15

Developments in pulsed laser heating applied to nuclear resonance techniques are presented together with their applications to studies of geophysically relevant materials. Continuous laser heating in diamond anvil cells is a widely used method to generate extreme temperatures at static high pressure conditions in order to study the structure and properties of materials found in deep planetary interiors. The pulsed laser heating technique has advantages over continuous heating, including prevention of the spreading of heated sample and/or the pressure medium and, thus, a better stability of the heating process. Time differentiated data acquisition coupled with pulsed laser heating in diamondmore » anvil cells was successfully tested at the Nuclear Resonance beamline (ID18) of the European Synchrotron Radiation Facility. We show examples applying the method to investigation of an assemblage containing ε-Fe, FeO, and Fe{sub 3}C using synchrotron Mössbauer source spectroscopy, FeCO{sub 3} using nuclear inelastic scattering, and Fe{sub 2}O{sub 3} using nuclear forward scattering. These examples demonstrate the applicability of pulsed laser heating in diamond anvil cells to spectroscopic techniques with long data acquisition times, because it enables stable pulsed heating with data collection at specific time intervals that are synchronized with laser pulses.« less

Laser System for Photoelectron and X-Ray Production in the PLEIADES Compton Light Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gibson, D J; Barty, C J; Betts, S M

2005-04-21

The PLEIADES (Picosecond Laser-Electron Interaction for the Dynamic Evaluation of Structures) facility provides tunable short x-ray pulses with energies of 30-140 keV and pulse durations of 0.3-5 ps by scattering an intense, ultrashort laser pulse off a 35-75 MeV electron beam. Synchronization of the laser and electron beam is obtained by using a photoinjector gun, and using the same laser system to generate the electrons and the scattering laser. The Ti Ti:Sapphire, chirped pulse amplification based 500 mJ, 50 fs, 810 nm scattering laser and the similar 300 {micro}J, 5 ps, 266 nm photoinjector laser systems are detailed. Additionally, anmore » optical parametric chirped pulse amplification (OPCPA) system is studied as a replacement for part of the scattering laser front end. Such a change would significantly simplify the set-up the laser system by removing the need for active switching optics, as well as increase the pre-pulse contrast ratio which will be important when part of the scattering laser is used as a pump beam in pump-probe diffraction experiments using the ultrashort tunable x-rays generated as the probe.« less

Measuring the Contribution of Atmospheric Scatter to Laser Eye Dazzle

DTIC Science & Technology

2015-09-01

alignment of the detector was then fine tuned to ensure that the reflected beam traveled perfectly back through the aperture, thus indicating normal...spanning June and July 2014. A narrow acceptance angle detector was used to measure scattered laser radiation within the laser beam at different... scatter does not make a significant contribution to laser eye dazzle for short-range laser engagements in atmospheres of good to moderate air quality

New phase method of measuring particle size with laser Doppler radar

NASA Astrophysics Data System (ADS)

Zemlianskii, Vladimir M.

1996-06-01

A vast field of non-contact metrology, vibrometry, dynamics and microdynamics problems solved on the basis of laser Doppler method resulted in the development of great variety of laser Doppler radar (LDR). In coherent LDR few beams with various polarization are generally adopted, that are directed at the zone of measurement, through which the probing air stream moves. Studies of various coherent LDR demonstrated that polarization-phase effects of scattering can in some cases considerably effect on the signal-to-noise ratio of the Doppler signal. On the other side using phase effects can simultaneous measurement of size and velocity of spherical particles. New possibilities for improving the accuracy of measuring spherical particles' sizes come to light when application is made in coherent LDR of two waves- probing and one out of the types of symmetrical reception of scattered radiation, during which phase-conjugate signals are formed. The theoretical analysis on the basis of the scattering theory showed, that in symmetrical reception of scattered radiation with respect to the planes OXZ and OYZ output signal of the photoreceiver contains two high- frequency signal components, which in relation to parameters of the probing and size, can either be in phase or antiphase. Results of numerical modeling are presented: amplitude of high frequency signal, coefficient of phase and polarization matching of mixed waves, the depths of photocurrent modulation and also signal's phase in relation to the angle between the probing beams. Phase method of determining particle's sizes based on the use of two wavelengths probing and symmetrical reception of scattered radiation in which conditions for the formation of phase conjugated high-frequency signals are satisfied is presented.

Laser measure of sea salinity, temperature and turbidity in depth

NASA Technical Reports Server (NTRS)

Hirschberg, J. G.; Wouters, A. W.; Byrne, J. D.

1974-01-01

A method is described in which a pulsed laser is used to probe the sea. Backscattered light is analyzed in time, intensity and wavelength. Tyndall, Raman and Brillouin scattering are used to obtain the backscatter turbidity, sound velocity, salinity, and the temperature as a function of depth.

A method of atmospheric density measurements during space shuttle entry using ultraviolet-laser Rayleigh scattering

NASA Technical Reports Server (NTRS)

Mckenzie, Robert L.

1988-01-01

An analytical study and its experimental verification are described which show the performance capabilities and the hardware requirements of a method for measuring atmospheric density along the Space Shuttle flightpath during entry. Using onboard instrumentation, the technique relies on Rayleigh scattering of light from a pulsed ArF excimer laser operating at a wavelength of 193 nm. The method is shown to be capable of providing density measurements with an uncertainty of less than 1 percent and with a spatial resolution along the flightpath of 1 km, over an altitude range from 50 to 90 km. Experimental verification of the signal linearity and the expected signal-to-noise ratios is demonstrated in a simulation facility at conditions that duplicate the signal levels of the flight environment.

Thomson scattering laser-electron X-ray source for reduction of patient radiation dose in interventional coronary angiography

NASA Astrophysics Data System (ADS)

Artyukov, I. A.; Dyachkov, N. V.; Feshchenko, R. M.; Polunina, A. V.; Popov, N. L.; Shvedunov, V. I.; Vinogradov, A. V.

2017-05-01

It was medical applications that stimulated F. Carrol in the early 1990s to start the research of on relativistic Thomson scattering X-ray sources, as a part of the infrastructure of the future society. The possibility to use such a source in interventional cardiology is discussed in this paper. The replacement of X-ray tube by relativistic Thomson scattering Xray source is predicted to lower the patient radiation dose by a factor of 3 while image quality remains the same. The required general characteristics of accelerator and laser units are found. They can be reached by existing technology. A semiempirical method for simulation of medical and technical parameters of interventional coronary angiography systems is suggested.

NASA Laser Light Scattering Advanced Technology Development Workshop, 1988

NASA Technical Reports Server (NTRS)

Meyer, William V. (Editor)

1989-01-01

The major objective of the workshop was to explore the capabilities of existing and prospective laser light scattering hardware and to assess user requirements and needs for a laser light scattering instrument in a reduced gravity environment. The workshop addressed experimental needs and stressed hardware development.

Coherent random lasing controlled by Brownian motion of the active scatterer

NASA Astrophysics Data System (ADS)

Liang, Shuofeng; Yin, Leicheng; Zhang, ZhenZhen; Xia, Jiangying; Xie, Kang; Zou, Gang; Hu, Zhijia; Zhang, Qijin

2018-05-01

The stability of the scattering loop is fundamental for coherent random lasing in a dynamic scattering system. In this work, fluorescence of DPP (N, N-di [3-(isobutyl polyhedral oligomeric silsesquioxanes) propyl] perylene diimide) is scattered to produce RL and we realize the transition from incoherent RL to coherent RL by controlling the Brownian motion of the scatterers (dimer aggregates of DPP) and the stability of scattering loop. To produce coherent random lasers, the loop needs to maintain a stable state within the loop-stable time, which can be determined through controlled Brownian motion of scatterers in the scattering system. The result shows that the loop-stable time is within 5.83 × 10‑5 s to 1.61 × 10‑4 s based on the transition from coherent to incoherent random lasing. The time range could be tuned by finely controlling the viscosity of the solution. This work not only develops a method to predict the loop-stable time, but also develops the study between Brownian motion and random lasers, which opens the road to a variety of novel interdisciplinary investigations involving modern statistical mechanics and disordered photonics.

Applications of Laser Scattering Probes to Turbulent Diffusion Flames

DTIC Science & Technology

1983-11-01

APPLICATIONS OF LASER SCATTERING PROBES TO TURBULENT DIFFUSION FLAMES u ^ j FINAL REPORT Contract N00014-80-C-0882 Submitted to Office of...Include Security Classification) Applications of Laser Scattering Probes to Turbulent Diffusion Flames PROJECT NO. TASK NO. WORK UNIT NO. 12...for a co-flowing jet turbulent diffusion flame, and planar laser-induced fluorescence to provide two- dimensional instantaneous images of the flame

Diagnostics for the detection and evaluation of laser induced damage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheehan, L.; Kozlowski, M.; Rainer, F.

1995-12-31

The Laser Damage and Conditioning Group at LLNL is evaluating diagnostics which will help make damage testing more efficient and reduce the risk of damage during laser conditioning. The work to date has focused on photoacoustic and scattered light measurements on 1064-nm wavelength HfO{sub 2}/SiO{sub 2} multilayer mirror and polarizer coatings. Both the acoustic and scatter diagnostics have resolved 10 {mu}m diameter damage points in these coatings. Using a scanning stage, the scatter diagnostic can map both intrinsic and laser-induced scatter. Damage threshold measurements obtained using scatter diagnostics compare within experimental error with those measured using 100x Nomarski microscopy. Scattermore » signals measured during laser conditioning can be used to detect damage related to nodular defects.« less

Diagnostics for the detection and evaluation of laser induced damage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheehan, L.; Kozlowski, M.; Rainer, F.

1995-01-03

The Laser Damage and Conditioning Group at LLNL is evaluating diagnostics which will help make damage testing more efficient and reduce the risk of damage during laser conditioning. The work to date has focused on photoacoustic and scattered light measurements on 1064-nm wavelength HfO{sub 2}/SiO{sub 2} multilayer mirror and polarizer coatings. Both the acoustic and scatter diagnostics have resolved 10 {mu}m diameter damage points in these coatings. Using a scanning stage, the scatter diagnostic can map both intrinsic and laser-induced scatter. Damage threshold measurements obtained using scatter diagnostics compare within experimental error with those measured using 100x Nomarski microscopy. Scattermore » signals measured during laser conditioning can be used to detect damage related to nodular defects.« less

Spatially resolved Thomson scattering measurements of the transition from the collective to the non-collective regime in a laser-produced plasma

NASA Astrophysics Data System (ADS)

Schaeffer, D. B.; Constantin, C. G.; Bondarenko, A. S.; Everson, E. T.; Niemann, C.

2016-11-01

We present optical Thomson scattering results that image for the first time in a single measurement the spatial transition from collective to non-collective scattering. Data were taken in the Phoenix laser laboratory at the University of California, Los Angeles. The Raptor laser was used to ablate a carbon plasma, which was diagnosed with the frequency-doubled Phoenix laser serving as a Thomson scattering probe. Scattered light was collected from the laser plasma up to 10 cm from the target surface and up to 10 us after ablation, and imaged with high spatial and spectral resolutions. The results show a strong Thomson collective feature close to the target surface that smoothly transitions to a non-collective feature over several mm.

Spatially resolved Thomson scattering measurements of the transition from the collective to the non-collective regime in a laser-produced plasma.

PubMed

Schaeffer, D B; Constantin, C G; Bondarenko, A S; Everson, E T; Niemann, C

2016-11-01

We present optical Thomson scattering results that image for the first time in a single measurement the spatial transition from collective to non-collective scattering. Data were taken in the Phoenix laser laboratory at the University of California, Los Angeles. The Raptor laser was used to ablate a carbon plasma, which was diagnosed with the frequency-doubled Phoenix laser serving as a Thomson scattering probe. Scattered light was collected from the laser plasma up to 10 cm from the target surface and up to 10 us after ablation, and imaged with high spatial and spectral resolutions. The results show a strong Thomson collective feature close to the target surface that smoothly transitions to a non-collective feature over several mm.

Light scattering study of rheumatoid arthritis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beuthan, J; Netz, U; Minet, O

The distribution of light scattered by finger joints is studied in the near-IR region. It is shown that variations in the optical parameters of the tissue (scattering coefficient {mu}{sub s}, absorption coefficient {mu}{sub a}, and anisotropy factor g) depend on the presence of the rheumatoid arthritis (RA). At the first stage, the distribution of scattered light was measured in diaphanoscopic experiments. The convolution of a Gaussian error function with the scattering phase function proved to be a good approximation of the data obtained. Then, a new method was developed for the reconstruction of distribution of optical parameters in the fingermore » cross section. Model tests of the quality of this reconstruction method show good results. (laser biology and medicine)« less

Laser Light Scattering with Multiple Scattering Suppression Used to Measure Particle Sizes

NASA Technical Reports Server (NTRS)

Meyer, William V.; Tin, Padetha; Lock, James A.; Cannell, David S.; Smart, Anthony E.; Taylor, Thomas W.

1999-01-01

Laser light scattering is the technique of choice for noninvasively sizing particles in a fluid. The members of the Advanced Technology Development (ATD) project in laser light scattering at the NASA Lewis Research Center have invented, tested, and recently enhanced a simple and elegant way to extend the concentration range of this standard laboratory particle-sizing technique by several orders of magnitude. With this technique, particles from 3 nm to 3 mm can be measured in a solution. Recently, laser light scattering evolved to successfully size particles in both clear solutions and concentrated milky-white solutions. The enhanced technique uses the property of light that causes it to form tall interference patterns at right angles to the scattering plane (perpendicular to the laser beam) when it is scattered from a narrow laser beam. Such multiple-scattered light forms a broad fuzzy halo around the focused beam, which, in turn, forms short interference patterns. By placing two fiber optics on top of each other and perpendicular to the laser beam (see the drawing), and then cross-correlating the signals they produce, only the tall interference patterns formed by singly scattered light are detected. To restate this, unless the two fiber optics see the same interference pattern, the scattered light is not incorporated into the signal. With this technique, only singly scattered light is seen (multiple-scattered light is rejected) because only singly scattered light has an interference pattern tall enough to span both of the fiber-optic pickups. This technique is simple to use, easy to align, and works at any angle. Placing a vertical slit in front of the signal collection fibers enhanced this approach. The slit serves as an optical mask, and it significantly shortens the time needed to collect good data by selectively masking out much of the unwanted light before cross-correlation is applied.

Density matrix modeling of quantum cascade lasers without an artificially localized basis: A generalized scattering approach

NASA Astrophysics Data System (ADS)

Pan, Andrew; Burnett, Benjamin A.; Chui, Chi On; Williams, Benjamin S.

2017-08-01

We derive a density matrix (DM) theory for quantum cascade lasers (QCLs) that describes the influence of scattering on coherences through a generalized scattering superoperator. The theory enables quantitative modeling of QCLs, including localization and tunneling effects, using the well-defined energy eigenstates rather than the ad hoc localized basis states required by most previous DM models. Our microscopic approach to scattering also eliminates the need for phenomenological transition or dephasing rates. We discuss the physical interpretation and numerical implementation of the theory, presenting sets of both energy-resolved and thermally averaged equations, which can be used for detailed or compact device modeling. We illustrate the theory's applications by simulating a high performance resonant-phonon terahertz (THz) QCL design, which cannot be easily or accurately modeled using conventional DM methods. We show that the theory's inclusion of coherences is crucial for describing localization and tunneling effects consistent with experiment.

Visualization of the evaporation of a diesel spray using combined Mie and Rayleigh scattering techniques

NASA Astrophysics Data System (ADS)

Adam, Anne; Leick, Philippe; Bittlinger, Gerd; Schulz, Christof

2009-09-01

Evaporating Diesel sprays are studied by laser Rayleigh scattering measurements in an optically accessible high-pressure/high-temperature cell that reproduces the thermodynamic conditions which exist in the combustion chamber of a Diesel engine during injection. n-Decane is injected into the vessel using a state-of-the-art near-production three-hole nozzle. Global images of the distributions of the liquid and vapor phases of the injected fuel are obtained using a combined Schlieren and Mie scattering setup. More details about the evaporation are revealed when the spray is illuminated by a laser light sheet: laser light can be scattered by molecules in the gas phase (Rayleigh scattering) or comparably large fuel droplets (Mie scattering). The former is seen in regions where the fuel has completely evaporated, and the latter is dominant in regions with high droplet concentrations. Studying the polarization of the signal light allows the distinction of three different regions in the spray that are characterized by a moderate, low or negligible concentration of liquid fuel droplets. The characteristics of fuel evaporation are investigated for different observation times after the start of injection, chamber conditions and injection pressures. For the quantification of the fuel concentration measurements based on Rayleigh scattering, a calibration method that uses propane as a reference gas is presented and tested. At high ambient temperatures, the accuracy of the concentration measurements is limited by pyrolysis of the fuel molecules.

Technique to separate lidar signal and sunlight.

PubMed

Sun, Wenbo; Hu, Yongxiang; MacDonnell, David G; Weimer, Carl; Baize, Rosemary R

2016-06-13

Sunlight contamination dominates the backscatter noise in space-based lidar measurements during daytime. The background scattered sunlight is highly variable and dependent upon the surface and atmospheric albedo. The scattered sunlight contribution to noise increases over land and snow surfaces where surface albedos are high and thus overwhelm lidar backscatter from optically thin atmospheric constituents like aerosols and thin clouds. In this work, we developed a novel lidar remote sensing concept that potentially can eliminate sunlight induced noise. The new lidar concept requires: (1) a transmitted laser light that carries orbital angular momentum (OAM); and (2) a photon sieve (PS) diffractive filter that separates scattered sunlight from laser light backscattered from the atmosphere, ocean and solid surfaces. The method is based on numerical modeling of the focusing of Laguerre-Gaussian (LG) laser beam and plane-wave light by a PS. The model results show that after passing through a PS, laser light that carries the OAM is focused on a ring (called "focal ring" here) on the focal plane of the PS filter, very little energy arrives at the center of the focal plane. However, scattered sunlight, as a plane wave without the OAM, focuses at the center of the focal plane and thus can be effectively blocked or ducted out. We also find that the radius of the "focal ring" increases with the increase of azimuthal mode (L) of LG laser light, thus increasing L can more effectively separate the lidar signal away from the sunlight noise.

Light scattering from laser induced pit ensembles on high power laser optics

DOE PAGES

Feigenbaum, Eyal; Elhadj, Selim; Matthews, Manyalibo J.

2015-01-01

Far-field light scattering characteristics from randomly arranged shallow Gaussian-like shaped laser induced pits, found on optics exposed to high energy laser pulses, is studied. Closed-form expressions for the far-field intensity distribution and scattered power are derived for individual pits and validated using numerical calculations of both Fourier optics and FDTD solutions to Maxwell’s equations. It is found that the scattered power is proportional to the square of the pit width and approximately also to the square of the pit depth, with the proportionality factor scaling with pit depth. As a result, the power scattered from shallow pitted optics is expectedmore » to be substantially lower than assuming complete scattering from the total visible footprint of the pits.« less

Solid-State Division progress report for period ending March 31, 1983

DOE Office of Scientific and Technical Information (OSTI.GOV)

Green, P.H.; Watson, D.M.

1983-09-01

Progress and activities are reported on: theoretical solid-state physics (surfaces; electronic, vibrational, and magnetic properties; particle-solid interactions; laser annealing), surface and near-surface properties of solids (surface, plasma-material interactions, ion implantation and ion-beam mixing, pulsed-laser and thermal processing), defects in solids (radiation effects, fracture, impurities and defects, semiconductor physics and photovoltaic conversion), transport properties of solids (fast-ion conductors, superconductivity, mass and charge transport in materials), neutron scattering (small-angle scattering, lattice dynamics, magnetic properties, structure and instrumentation), and preparation and characterization of research materials (growth and preparative methods, nuclear waste forms, special materials). (DLC)

Measurements of Euglena motion parameters by laser light scattering.

PubMed Central

Ascoli, C; Barbi, M; Frediani, C; Murè, A

1978-01-01

Measurements of Euglena gracilis motion parameters have been performed by the spectral analysis of the scattered laser light. Samples were oriented by a radiofrequency field to obtain easily interpretable spectra. Cell rotation frequency and flagellar beating frequency distributions were obtained from the homodyne spectra, whereas the Doppler lines obtained at small observation angles by heterodyne detection yielded the swimming speed distributions. We discuss the broadening of the heterodyne spectra at large angles of observation. An application of this method to the study of the photo-kinetic effect is also described. Images FIGURE 3 PMID:104747

Intense laser pulse propagation in ionizing gases

NASA Astrophysics Data System (ADS)

Bian, Zhigang

2003-10-01

There have been considerable technological advances in the development of high intensity, short pulse lasers. However, high intensity laser pulses are subject to various laser-plasma instabilities. In this thesis, a theory is developed to study the scattering instability that occurs when a laser pulse propagates through and ionizes a gas. The instability is due to the intensity dependence of the ionization rate, which leads to a transversely structured free electron density. The instability is convective in the frame of laser pulse, but can have a relatively short growth length scaling as Lg˜k0/k2p where k0 is the laser wave number, k2p=w2p/c 2 and op is the plasma frequency. The most unstable perturbations correspond to a scattering angle for which the transverse wave number is around the plasma wave number, k p. The scattered light is frequency upshifted. The comparison between simple analytic theory and numerical simulation shows good agreement. Instabilities can drastically change the shape of the laser pulse and reduce the propagation distance of the laser pulse. Therefore, we change the propagation conditions and reduce the laser-plasma interaction possibilities in applications which require an interaction length well in excess of the Rayleigh length of the laser beam. One of the methods is to use a capillary to propagate the laser pulse. We studied the propagation of short pulses in a glass capillary. The propagation is simulated using the code WAKE, which has been modified to treat the case in which the simulation boundary is the wall of a capillary. Parameters that were examined include transmission efficiency of the waveguides as a function of gas pressure, laser intensity, and waveguide length, which is up to 40 Rayleigh lengths. The transmission efficiency decreases with waveguide length due to energy loss through the side-walls of the capillary. The loss increases with gas pressure due to ionization of the gas and scattering of the radiation. The intensity on the inner wall of the capillary is monitored to assure realistic simulations, consistent with optical breakdown of the waveguide material. Generally speaking the intensity on the wall increases with gas pressure due to the scattering of the lowest order capillary mode. Finally, the high order harmonic generation (HHG) in a capillary is investigated. The phase matching condition is studied to increase the conversion efficiency for high order harmonics generation. The phase matching occurs as a balance of the dispersion of the neutral gas, plasma and the waveguide.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Polulyakh, Valeriy; Poutivski, Iouri

Laser Doppler Vibrometer and Range Meter (3D-MRV) is designed for middle range distances [1–100 meters]. 3D-MRV combines more than one laser in one device for a simultaneous real time measuring the distance and movement of the targets. The first laser has a short pulse (t∼30psec) and low energy (E∼200nJ) for distance measurement and the second one is a CW (continuous wave) single frequency laser for the velocity measurement with output power (P∼30mW). Both lasers perform on the eye-safe wavelength 1.5 μm. 3D-MRV uses the same mono-static optical transmitting and receiving channel for both lasers including an output telescope and amore » scanning angular system. 3D-MRV has an optical polarization switch to combine linear polarized laser beams from two lasers into one optical channel. The laser beams from both lasers by turns illuminate the target and the scattered laser radiation is collected by the telescope on a photo detector. The electrical signal from photo detector is used for measuring the distance to the target and its movement. For distance measurement the time of flight method is employed. For targets movement the optical heterodyne method is employed. The received CW laser radiation is mixed on a photo detector with the frequency-shifted laser radiation that is taken from CW laser and passed through an acousto-optic cell. The electrical signal from a photo detector on the difference frequency and phase has information about movement of the scattered targets. 3D-MVR may be used for the real time picturing of vibration of the extensive targets like bridges or aircrafts.« less

Scattering properties of ultrafast laser-induced refractive index shaping lenticular structures in hydrogels

NASA Astrophysics Data System (ADS)

Wozniak, Kaitlin T.; Germer, Thomas A.; Butler, Sam C.; Brooks, Daniel R.; Huxlin, Krystel R.; Ellis, Jonathan D.

2018-02-01

We present measurements of light scatter induced by a new ultrafast laser technique being developed for laser refractive correction in transparent ophthalmic materials such as cornea, contact lenses, and/or intraocular lenses. In this new technique, called intra-tissue refractive index shaping (IRIS), a 405 nm femtosecond laser is focused and scanned below the corneal surface, inducing a spatially-varying refractive index change that corrects vision errors. In contrast with traditional laser correction techniques, such as laser in-situ keratomileusis (LASIK) or photorefractive keratectomy (PRK), IRIS does not operate via photoablation, but rather changes the refractive index of transparent materials such as cornea and hydrogels. A concern with any laser eye correction technique is additional scatter induced by the process, which can adversely affect vision, especially at night. The goal of this investigation is to identify sources of scatter induced by IRIS and to mitigate possible effects on visual performance in ophthalmic applications. Preliminary light scattering measurements on patterns written into hydrogel showed four sources of scatter, differentiated by distinct behaviors: (1) scattering from scanned lines; (2) scattering from stitching errors, resulting from adjacent scanning fields not being aligned to one another; (3) diffraction from Fresnel zone discontinuities; and (4) long-period variations in the scans that created distinct diffraction peaks, likely due to inconsistent line spacing in the writing instrument. By knowing the nature of these different scattering errors, it will now be possible to modify and optimize the design of IRIS structures to mitigate potential deficits in visual performance in human clinical trials.

Laser rods with undoped, flanged end-caps for end-pumped laser applications

DOEpatents

Meissner, Helmuth E.; Beach, Raymond J.; Bibeau, Camille; Sutton, Steven B.; Mitchell, Scott; Bass, Isaac; Honea, Eric

1999-01-01

A method and apparatus for achieving improved performance in a solid state laser is provided. A flanged, at least partially undoped end-cap is attached to at least one end of a laserable medium. Preferably flanged, undoped end-caps are attached to both ends of the laserable medium. Due to the low scatter requirements for the interface between the end-caps and the laser rod, a non-adhesive method of bonding is utilized such as optical contacting combined with a subsequent heat treatment of the optically contacted composite. The non-bonded end surfaces of the flanged end-caps are coated with laser cavity coatings appropriate for the lasing wavelength of the laser rod. A cooling jacket, sealably coupled to the flanged end-caps, surrounds the entire length of the laserable medium. Radiation from a pump source is focussed by a lens duct and passed through at least one flanged end-cap into the laser rod.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Characteristics of the scattering of neutral atoms by two counterpropagating pulsed optical fields

NASA Astrophysics Data System (ADS)

Grinchuk, V. A.; Grishina, I. A.; Kuzin, E. F.; Nagaeva, M. L.; Ryabenko, G. A.; Yakovlev, V. P.

1994-04-01

The scattering of neutral sodium atoms by a strong field of two counterpropagating (incident on and reflected from a mirror) short laser pulses was used in an experimental investigation of a stimulated radiation pressure. The reasons for the anomalous frequency structure in the scattering of atoms were identified. The oscillatory nature of the dependence of the scattering on the detuning from resonance was found to be significant in strong laser radiation fields. The oscillation period depended on the distance between the reflecting mirror and the atomic beam.

Widely tuneable scattering-type scanning near-field optical microscopy using pulsed quantum cascade lasers

NASA Astrophysics Data System (ADS)

Yoxall, Edward; Navarro-Cía, Miguel; Rahmani, Mohsen; Maier, Stefan A.; Phillips, Chris C.

2013-11-01

We demonstrate the use of a pulsed quantum cascade laser, wavelength tuneable between 6 and 10 μm, with a scattering-type scanning near-field optical microscope (s-SNOM). A simple method for calculating the signal-to-noise ratio (SNR) of the s-SNOM measurement is presented. For pulsed lasers, the SNR is shown to be highly dependent on the degree of synchronization between the laser pulse and the sampling circuitry; in measurements on a gold sample, the SNR is 26 with good synchronization and less than 1 without. Simulations and experimental s-SNOM images, with a resolution of 100 nm, corresponding to λ/80, and an acquisition time of less than 90 s, are presented as proof of concept. They show the change in the field profile of plasmon-resonant broadband antennas when they are excited with wavelengths of 7.9 and 9.5 μm.

Tapered fiber based Brillouin random fiber laser and its application for linewidth measurement.

PubMed

Gao, Song; Zhang, Liang; Xu, Yanping; Lu, Ping; Chen, Liang; Bao, Xiaoyi

2016-12-12

A one-end pumping Brillouin random fiber laser (BRFL) based on a 5-km tapered fiber (TF) is demonstrated. The enhanced Rayleigh scattering and the increased power density from tapering in the TF provide good directionality and a high degree of coherent feedback. Both the transmitting and TF enhanced Rayleigh scattered pump lights formed effective bi-direction pumping for the Brillouin gain in the standing cavity configuration in the distributed way as the gain and random feedback in the same fiber. The linewidth of the laser shows ~1.17 kHz while the relative intensity noise (RIN) has been verified to be suppressed comparing with that of the two-end pumping of the standard single mode fiber (SMF). Furthermore, utilizing the proposed laser, a high-resolution (~kHz) linewidth measurement method is demonstrated without long delay fiber (>100km) and extra frequency shifter thanks to the acoustic frequency shift from fiber itself.

Analysis of albumin Raman scattering in visible and near-infrared ranges

NASA Astrophysics Data System (ADS)

Lykina, Anastasia A.; Artemyev, Dmitry N.

2018-04-01

In this work the analysis of the shape and intensity of albumin Raman signals in visible and near-IR ranges was carried out. The experimental setup using lasers from the visible region first of all excites the fluorescence of the albumin solution, the main contribution to which is produced by sodium chloride, which is a component of the tested sample. At the same time, lasers from the near-infrared range excited the Raman signal of albumin most effectively. It was found that the highest ratio of Raman scattering to autofluorescence intensities in the detected signal was obtained using a laser with a wavelength of 1064 nm. To determine the albumin solution concentration by type of spectrum, a regression approach with the projection to latent structures method was applied. The lowest predicted error of albumin concentration of 2-3 g/l was obtained by using the near-infrared range lasers.

Characterization of single particle aerosols by elastic light scattering at multiple wavelengths

NASA Astrophysics Data System (ADS)

Lane, P. A.; Hart, M. B.; Jain, V.; Tucker, J. E.; Eversole, J. D.

2018-03-01

We describe a system to characterize individual aerosol particles using stable and repeatable measurement of elastic light scattering. The method employs a linear electrodynamic quadrupole (LEQ) particle trap. Charged particles, continuously injected by electrospray into this system, are confined to move vertically along the stability line in the center of the LEQ past a point where they are optically interrogated. Light scattered in the near forward direction was measured at three different wavelengths using time-division multiplexed collinear laser beams. We validated our method by comparing measured silica microsphere data for four selected diameters (0.7, 1.0, 1.5 and 2.0 μm) to a model of collected scattered light intensities based upon Lorenz-Mie scattering theory. Scattered light measurements at the different wavelengths are correlated, allowing us to distinguish and classify inhomogeneous particles.

New algorithm and system for measuring size distribution of blood cells

NASA Astrophysics Data System (ADS)

Yao, Cuiping; Li, Zheng; Zhang, Zhenxi

2004-06-01

In optical scattering particle sizing, a numerical transform is sought so that a particle size distribution can be determined from angular measurements of near forward scattering, which has been adopted in the measurement of blood cells. In this paper a new method of counting and classification of blood cell, laser light scattering method from stationary suspensions, is presented. The genetic algorithm combined with nonnegative least squared algorithm is employed to inverse the size distribution of blood cells. Numerical tests show that these techniques can be successfully applied to measuring size distribution of blood cell with high stability.

Effect of static scatterers in laser speckle contrast imaging: an experimental study on correlation and contrast.

PubMed

Vaz, Pedro G; Humeau-Heurtier, Anne; Figueiras, Edite; Correia, Carlos; Cardoso, João

2017-12-29

Laser speckle contrast imaging (LSCI) is a non-invasive microvascular blood flow assessment technique with good temporal and spatial resolution. Most LSCI systems, including commercial devices, can perform only qualitative blood flow evaluation, which is a major limitation of this technique. There are several factors that prevent the utilization of LSCI as a quantitative technique. Among these factors, we can highlight the effect of static scatterers. The goal of this work was to study the influence of differences in static and dynamic scatterer concentration on laser speckle correlation and contrast. In order to achieve this, a laser speckle prototype was developed and tested using an optical phantom with various concentrations of static and dynamic scatterers. It was found that the laser speckle correlation could be used to estimate the relative concentration of static/dynamic scatterers within a sample. Moreover, the speckle correlation proved to be independent of the dynamic scatterer velocity, which is a fundamental characteristic to be used in contrast correction.

Effect of static scatterers in laser speckle contrast imaging: an experimental study on correlation and contrast

NASA Astrophysics Data System (ADS)

Vaz, Pedro G.; Humeau-Heurtier, Anne; Figueiras, Edite; Correia, Carlos; Cardoso, João

2018-01-01

Laser speckle contrast imaging (LSCI) is a non-invasive microvascular blood flow assessment technique with good temporal and spatial resolution. Most LSCI systems, including commercial devices, can perform only qualitative blood flow evaluation, which is a major limitation of this technique. There are several factors that prevent the utilization of LSCI as a quantitative technique. Among these factors, we can highlight the effect of static scatterers. The goal of this work was to study the influence of differences in static and dynamic scatterer concentration on laser speckle correlation and contrast. In order to achieve this, a laser speckle prototype was developed and tested using an optical phantom with various concentrations of static and dynamic scatterers. It was found that the laser speckle correlation could be used to estimate the relative concentration of static/dynamic scatterers within a sample. Moreover, the speckle correlation proved to be independent of the dynamic scatterer velocity, which is a fundamental characteristic to be used in contrast correction.

Novel Raman Techniques for Imaging and Sensing

NASA Astrophysics Data System (ADS)

Edwards, Perry S.

Raman scattering spectroscopy is extensively demonstrated as a label-free, chemically selective sensing and imaging technique for a multitude of chemical and biological applications. The ability to detect "fingerprint" spectral signatures of individual molecules, without the need to introduce chemical labelers, makes Raman scattering a powerful sensing technique. However, spectroscopy based on spontaneous Raman scattering traditionally suffers from inherently weak signals due to small Raman scattering cross-sections. Thus, considerable efforts have been put forth to find pathways towards enhancing Raman signals to bolster sensitivity for detecting small concentrations of molecules or particles. The development of coherent Raman techniques that can offer orders of magnitude increase in signal have garnered significant interest in recent years for their application in imaging; such techniques include coherent anti-Stokes Raman scattering and stimulated Raman scattering. Additionally, methods to enhance the local field of either the pump or generated Raman signal, such as through surface enhanced Raman scattering, have been investigated for their orders of magnitude improvement in sensitivity and single molecule sensing capability. The work presented in this dissertation describes novel techniques for performing high speed and highly sensitive Raman imaging as well as sensing applications towards bioimaging and biosensing. Coherent anti-Stokes Raman scattering (CARS) is combined with holography to enable recording of high-speed (single laser shot), wide field CARS holograms which can be used to reconstruct the both the amplitude and the phase of the anti-Stokes field therefore allowing 3D imaging. This dissertation explores CARS holography as a viable label-free bio-imaging technique. A Raman scattering particle sensing system is also developed that utilizes wave guide properties of optical fibers and ring-resonators to perform enhanced particle sensing. Resonator-enhanced particle sensing is experimentally examined as a new method for enhancing Raman scattering from particles interacting with circulating optical fields within both a fiber ring-cavity and whispering gallery mode microtoroid microresonators. The achievements described in this dissertation include: (1) Demonstration of the bio-imaging capability of CARS holography by recording of CARS holograms of subcellular components in live cancer (HeLa) cells. (2) Label-free Raman microparticle sensing using a tapered optical fibers. A tapered fiber can guide light to particles adsorbed on the surface of the taper to generate scattered Raman signal which can be collected by a microRaman detection system. (3) Demonstration of the proof of concept of resonator-enhanced Raman spectroscopy in a fiber ring resonator consisting of a section of fiber taper. (4) A method for locking the pump laser to the resonate frequencies of a resonator. This is demonstrated using a fiber ring resonator and microtoroid microresonators. (5) Raman scattered signal from particles adhered to microtoroid microresonators is acquired using 5 seconds of signal integration time and with the pump laser locked to a cavity resonance. (6) Theoretical analysis is performed that indicates resonator-enhanced Raman scattering from microparticles adhered to microresonators can be achieved with the pump laser locked to the frequency of a high-Q cavity resonant mode.

Scattering-type scanning near-field optical microscopy with low-repetition-rate pulsed light source through phase-domain sampling

PubMed Central

Wang, Haomin; Wang, Le; Xu, Xiaoji G.

2016-01-01

Scattering-type scanning near-field optical microscopy (s-SNOM) allows spectroscopic imaging with spatial resolution below the diffraction limit. With suitable light sources, s-SNOM is instrumental in numerous discoveries at the nanoscale. So far, the light sources have been limited to continuous wave or high-repetition-rate pulsed lasers. Low-repetition-rate pulsed sources cannot be used, due to the limitation of the lock-in detection mechanism that is required for current s-SNOM techniques. Here, we report a near-field signal extraction method that enables low-repetition-rate pulsed light sources. The method correlates scattering signals from pulses with the mechanical phases of the oscillating s-SNOM probe to obtain near-field signal, by-passing the apparent restriction imposed by the Nyquist–Shannon sampling theorem on the repetition rate. The method shall enable s-SNOM with low-repetition-rate pulses with high-peak-powers, such as femtosecond laser amplifiers, to facilitate investigations of strong light–matter interactions and nonlinear processes at the nanoscale. PMID:27748360

Measurement of the main and critical parameters for optimal laser treatment of heart disease

NASA Astrophysics Data System (ADS)

Kabeya, FB; Abrahamse, H.; Karsten, AE

2017-10-01

Laser light is frequently used in the diagnosis and treatment of patients. As in traditional treatments such as medication, bypass surgery, and minimally invasive ways, laser treatment can also fail and present serious side effects. The true reason for laser treatment failure or the side effects thereof, remains unknown. From the literature review conducted, and experimental results generated we conclude that an optimal laser treatment for coronary artery disease (named heart disease) can be obtained if certain critical parameters are correctly measured and understood. These parameters include the laser power, the laser beam profile, the fluence rate, the treatment time, as well as the absorption and scattering coefficients of the target treatment tissue. Therefore, this paper proposes different, accurate methods for the measurement of these critical parameters to determine the optimal laser treatment of heart disease with a minimal risk of side effects. The results from the measurement of absorption and scattering properties can be used in a computer simulation package to predict the fluence rate. The computing technique is a program based on the random number (Monte Carlo) process and probability statistics to track the propagation of photons through a biological tissue.

Laser pulsing in linear Compton scattering

DOE PAGES

Krafft, G. A.; Johnson, E.; Deitrick, K.; ...

2016-12-16

Previous work on calculating energy spectra from Compton scattering events has either neglected considering the pulsed structure of the incident laser beam, or has calculated these effects in an approximate way subject to criticism. In this paper, this problem has been reconsidered within a linear plane wave model for the incident laser beam. By performing the proper Lorentz transformation of the Klein-Nishina scattering cross section, a spectrum calculation can be created which allows the electron beam energy spread and emittance effects on the spectrum to be accurately calculated, essentially by summing over the emission of each individual electron. Such anmore » approach has the obvious advantage that it is easily integrated with a particle distribution generated by particle tracking, allowing precise calculations of spectra for realistic particle distributions in collision. The method is used to predict the energy spectrum of radiation passing through an aperture for the proposed Old Dominion University inverse Compton source. In addition, as discussed in the body of the paper, many of the results allow easy scaling estimates to be made of the expected spectrum. A misconception in the literature on Compton scattering of circularly polarized beams is corrected and recorded.« less

Atmospheric Multiple Scattering Effects on GLAS Altimetry. Part 2; Analysis of Expected Errors in Antarctic Altitude Measurements

NASA Technical Reports Server (NTRS)

Mahesh, Ashwin; Spinhirne, James D.; Duda, David P.; Eloranta, Edwin W.; Starr, David O'C (Technical Monitor)

2001-01-01

The altimetry bias in GLAS (Geoscience Laser Altimeter System) or other laser altimeters resulting from atmospheric multiple scattering is studied in relationship to current knowledge of cloud properties over the Antarctic Plateau. Estimates of seasonal and interannual changes in the bias are presented. Results show the bias in altitude from multiple scattering in clouds would be a significant error source without correction. The selective use of low optical depth clouds or cloudfree observations, as well as improved analysis of the return pulse such as by the Gaussian method used here, are necessary to minimize the surface altitude errors. The magnitude of the bias is affected by variations in cloud height, cloud effective particle size and optical depth. Interannual variations in these properties as well as in cloud cover fraction could lead to significant year-to-year variations in the altitude bias. Although cloud-free observations reduce biases in surface elevation measurements from space, over Antarctica these may often include near-surface blowing snow, also a source of scattering-induced delay. With careful selection and analysis of data, laser altimetry specifications can be met.

Optical method and apparatus for detection of surface and near-subsurface defects in dense ceramics

DOEpatents

Ellingson, W.A.; Brada, M.P.

1995-06-20

A laser is used in a non-destructive manner to detect surface and near-subsurface defects in dense ceramics and particularly in ceramic bodies with complex shapes such as ceramic bearings, turbine blades, races, and the like. The laser`s wavelength is selected based upon the composition of the ceramic sample and the laser can be directed on the sample while the sample is static or in dynamic rotate or translate motion. Light is scattered off surface and subsurface defects using a preselected polarization. The change in polarization angle is used to select the depth and characteristics of surface/subsurface defects. The scattered light is detected by an optical train consisting of a charge coupled device (CCD), or vidicon, television camera which, in turn, is coupled to a video monitor and a computer for digitizing the image. An analyzing polarizer in the optical train allows scattered light at a given polarization angle to be observed for enhancing sensitivity to either surface or near-subsurface defects. Application of digital image processing allows subtraction of digitized images in near real-time providing enhanced sensitivity to subsurface defects. Storing known ``feature masks`` of identified defects in the computer and comparing the detected scatter pattern (Fourier images) with the stored feature masks allows for automatic classification of detected defects. 29 figs.

The role of plasma density scale length on the laser pulse propagation and scattering in relativistic regime

NASA Astrophysics Data System (ADS)

Pishdast, Masoud; Ghasemi, Seyed Abolfazl; Yazdanpanah, Jamal Aldin

2017-10-01

The role of plasma density scale length on two short and long laser pulse propagation and scattering in under dense plasma have been investigated in relativistic regime using 1 D PIC simulation. In our simulation, different density scale lengths and also two short and long pulse lengths with temporal pulse duration τL = 60 fs and τL = 300 fs , respectively have been used. It is found that laser pulse length and density scale length have considerable effects on the energetic electron generation. The analysis of total radiation spectrum reveals that, for short laser pulses and with reducing density scale length, more unstable electromagnetic modes grow and strong longitudinal electric field generates which leads to the generation of more energetic plasma particles. Meanwhile, the dominant scattering mechanism is Raman scattering and tends to Thomson scattering for longer laser pulse.

Laser Velocimeter for Studies of Microgravity Combustion Flowfields

NASA Technical Reports Server (NTRS)

Varghese, P. L.; Jagodzinski, J.

2001-01-01

We are currently developing a velocimeter based on modulated filtered Rayleigh scattering (MFRS), utilizing diode lasers to make measurements in an unseeded gas or flame. MFRS is a novel variation of filtered Rayleigh scattering, utilizing modulation absorption spectroscopy to detect a strong absorption of a weak Rayleigh scattered signal. A rubidium (Rb) vapor filter is used to provide the relatively strong absorption and semiconductor diode lasers generate the relatively weak Rayleigh scattered signal. Alkali metal vapors have a high optical depth at modest vapor pressures, and their narrow linewidth is ideally suited for high-resolution velocimetry; the compact, rugged construction of diode lasers makes them ideally suited for microgravity experimentation. Molecular Rayleigh scattering of laser light simplifies flow measurements as it obviates the complications of flow-seeding. The MFRS velocimeter should offer an attractive alternative to comparable systems, providing a relatively inexpensive means of measuring velocity in unseeded flows and flames.

Determination of optimal glycerol concentration for optical tissue clearing

NASA Astrophysics Data System (ADS)

Youn, Eungjun; Son, Taeyoon; Kim, Han-Sung; Jung, Byungjo

2012-02-01

The laser scattering in tissue is significant in diagnostic and therapeutic purposes of laser. Many studies have been conducted to minimize laser scattering in tissue and therefore, to maximize the clinical efficacy by enhancing photon density. Optical clearing agents (OCAs) have been employed for optical tissue clearing (OTC). This study was aimed to investigate the optimal concentration of an OCA, glycerol, in topical application,, so that it can be utilized for clinical diagnosis and therapy in dermatology. Glycerol was topically applied to avoid possible edema caused by dermal injection. The effect of OTC was quantitatively evaluated as a function of the concentration of glycerol with various methods. Optical methods such as optical coherence tomography (OCT) and an integrating sphere were used to assess the enhancement of light penetration depth and refractive index matching. In addition, a non-optical method, ultrasound scanner, was utilized to evaluate quantitatively collagen dissociation. The results revealed that 70 % glycerol was the optimal concentration of OTC for topical application. This study may provide a guideline regarding to the use of glycerol for optimal diagnostic and therapeutic effects in dermatology.

Nonintrusive Measurements for High-Speed, Supersonic, and Hypersonic Flows

NASA Astrophysics Data System (ADS)

Bonnet, J. P.; Grésillon, D.; Taran, J. P.

The need to develop new diagnostics for turbulent flows at supersonic and hypersonic regimes is discussed. New experimental results can be obtained in supersonic flows by using the collective light scattering method. Typical results obtained by this method in a supersonic mixing layer are illustrated. The collective light scattering method is a directional densitometer (with a new type of spectral analysis of density fluctuations), a nonparticle anemometer, a Mach-meter (or thermometer), and a directional remote microphone. Various other optical techniques that can be applied for point, line-of-sight, or imaging measurements are reviewed. For point measurements, light-scattering methods such as Raman, Rayleigh, or electron beam fluorescence are discussed, but only briefly, since they are of little use, especially when enthalpy is very high and flow naturally bright. Emphasis is placed instead on nonlinear laser spectroscopy such as coherent anti-Stokes Raman scattering, which has recently been successful in determining temperature and density in high-enthalpy shocks. A description of diode laser absorption spectroscopy follows. A high data-rate instrument now routinely gives the static temperature and the velocity of the stream in the hot shot facility F4 of ONERA, at stagnation enthalpies in excess of 15 MJ/kg. Finally, electron beam fluorescence imaging in the same facility has made it possible to perform measurements of velocity across the external boundary layer into the flow core using a high-energy-pulsed electron gun.

Primary particle diameter differentiation and bimodality identification by five analytical methods using gold nanoparticle size distributions synthesized by pulsed laser ablation in liquids

NASA Astrophysics Data System (ADS)

Letzel, Alexander; Gökce, Bilal; Menzel, Andreas; Plech, Anton; Barcikowski, Stephan

2018-03-01

For a known material, the size distribution of a nanoparticle colloid is a crucial parameter that defines its properties. However, measured size distributions are not easy to interpret as one has to consider weighting (e.g. by light absorption, scattering intensity, volume, surface, number) and the way size information was gained. The radius of a suspended nanoparticle can be given as e.g. sphere equivalent, hydrodynamic, Feret or radius of gyration. In this study, gold nanoparticles in water are synthesized by pulsed-laser ablation (LAL) and fragmentation (LFL) in liquids and characterized by various techniques (scanning transmission electron microscopy (STEM), small-angle X-ray scattering (SAXS), analytical disc centrifugation (ADC), dynamic light scattering (DLS) and UV-vis spectroscopy with Mie-Gans Theory) to study the comparability of different analytical techniques and determine the method that is preferable for a given task related to laser-generated nanoparticles. In particular, laser-generated colloids are known to be bimodal and/or polydisperse, but bimodality is sometimes not analytically resolved in literature. In addition, frequently reported small size shifts of the primary particle mode around 10 nm needs evaluation of its statistical significance related to the analytical method. Closely related to earlier studies on SAXS, different colloids in defined proportions are mixed and their size as a function of the nominal mixing ratio is analyzed. It is found that the derived particle size is independent of the nominal mixing ratio if the colloid size fractions do not overlap considerably. Conversely, the obtained size for colloids with overlapping size fractions strongly depends on the nominal mixing ratio since most methods cannot distinguish between such fractions. Overall, SAXS and ADC are very accurate methods for particle size analysis. Further, the ability of different methods to determine the nominal mixing ratio of sizes fractions is studied experimentally.

Improvement in Suppression of Pulsed Nd:YAG Laser Light With Iodine Absorption Cells for Filtered Rayleigh Scattering Measurements

NASA Technical Reports Server (NTRS)

Seasholtz, Richard G.; Buggele, Alvin E

1997-01-01

Filtered Rayleigh scattering using iodine absorption cells is an effective technique for obtaining density, temperature, and velocity measurements in high speed confined flows. By tuning a single frequency laser to a strong iodine absorption line, stray scattered laser light can be greatly suppressed. For example, the minimum transmission predicted by an iodine absorption model calculation is less than 10(exp -5) at the 18788.44/cm line using a 200 mm absorption cell containing iodine vapor at 0.46 T. Measurements obtained by other researches using a CW Nd:YAG laser agree with the model calculations. However, measurements made by us and by others using Q-switched, injection-seeded, frequency doubled Nd:YAG lasers only show minimum transmission of about 3 x 10(exp -3). This greatly reduces the applicability of the filtered Rayleigh scattering technique using these lasers in experiments having large amounts of stray scattered laser light. The purposes of the present study are to characterize the spectrum of the excess light transmitted by the iodine cell and to make changes to the laser to reduce the transmitted laser light. Transmission data as a function of laser frequency for the iodine absorption line at 18788.44/cm are presented. A planar mirror Fabry-Perot interferometer was used to characterize the frequency spectrum of the light passed through the cell. Measurements taken with the laser tuned to the center of the iodine absorption line show the light transmitted through the iodine cell to have a component with a bandwidth of about 40 GHz. This is probably caused by other modes in the laser that exist in spite of the single frequency injection beam. A second broadband component was also observed, possibly caused by the laser flash lamps or by fluorescence. An intracavity etalon was installed in the laser oscillator cavity to suppress the 40 GHz component. Measurements taken with the etalon tuned to the injection frequency showed a reduction in the transmitted laser light. This improvement allows the iodine cell to block significantly more of the stray laser light in filtered Rayleigh scattering experiments. Examples are given of filtered Rayleigh scattering measurements showing the effect of the etalon on measurements taken in a Mach 3 flow in the NASA Lewis 4 inch by 10 inch supersonic wind tunnel.

FIBER OPTICS. ACOUSTOOPTICS: Amplification of semiconductor laser radiation in the wavelength range 1.24-1.3 μm by stimulated Raman scattering in an optical fiber

NASA Astrophysics Data System (ADS)

Belotitskiĭ, V. I.; Kuzin, E. A.; Ovsyannikov, D. V.; Petrov, Mikhail P.

1990-07-01

An investigation was made of the influence of weak semiconductor laser radiation on the spectrum of stimulated Raman scattering in a single-mode optical waveguide pumped by a YAG:Nd3+ laser emitting at 1.06 μm. The scattered radiation power increased by a factor exceeding 10 at the semiconductor laser wavelength. A small-signal dynamic gain reached 47 dB. Simultaneous amplification was observed of several modes of multimode semiconductor laser radiation with an intermode spectral interval of 1.3 nm.

Direct wavefront sensing for high-resolution in vivo imaging in scattering tissue

PubMed Central

Wang, Kai; Sun, Wenzhi; Richie, Christopher T.; Harvey, Brandon K.; Betzig, Eric; Ji, Na

2015-01-01

Adaptive optics by direct imaging of the wavefront distortions of a laser-induced guide star has long been used in astronomy, and more recently in microscopy to compensate for aberrations in transparent specimens. Here we extend this approach to tissues that strongly scatter visible light by exploiting the reduced scattering of near-infrared guide stars. The method enables in vivo two-photon morphological and functional imaging down to 700 μm inside the mouse brain. PMID:26073070

Evolution of elastic x-ray scattering in laser-shocked warm dense lithium.

PubMed

Kugland, N L; Gregori, G; Bandyopadhyay, S; Brenner, C M; Brown, C R D; Constantin, C; Glenzer, S H; Khattak, F Y; Kritcher, A L; Niemann, C; Otten, A; Pasley, J; Pelka, A; Roth, M; Spindloe, C; Riley, D

2009-12-01

We have studied the dynamics of warm dense Li with near-elastic x-ray scattering. Li foils were heated and compressed using shock waves driven by 4-ns-long laser pulses. Separate 1-ns-long laser pulses were used to generate a bright source of 2.96 keV Cl Ly- alpha photons for x-ray scattering, and the spectrum of scattered photons was recorded at a scattering angle of 120 degrees using a highly oriented pyrolytic graphite crystal operated in the von Hamos geometry. A variable delay between the heater and backlighter laser beams measured the scattering time evolution. Comparison with radiation-hydrodynamics simulations shows that the plasma is highly coupled during the first several nanoseconds, then relaxes to a moderate coupling state at later times. Near-elastic scattering amplitudes have been successfully simulated using the screened one-component plasma model. Our main finding is that the near-elastic scattering amplitudes are quite sensitive to the mean ionization state Z[over ] and by extension to the choice of ionization model in the radiation-hydrodynamics simulations used to predict plasma properties within the shocked Li.

Laser light scattering instrument advanced technology development

NASA Technical Reports Server (NTRS)

Wallace, J. F.

1993-01-01

The objective of this advanced technology development (ATD) project has been to provide sturdy, miniaturized laser light scattering (LLS) instrumentation for use in microgravity experiments. To do this, we assessed user requirements, explored the capabilities of existing and prospective laser light scattering hardware, and both coordinated and participated in the hardware and software advances needed for a flight hardware instrument. We have successfully breadboarded and evaluated an engineering version of a single-angle glove-box instrument which uses solid state detectors and lasers, along with fiber optics, for beam delivery and detection. Additionally, we have provided the specifications and written verification procedures necessary for procuring a miniature multi-angle LLS instrument which will be used by the flight hardware project which resulted from this work and from this project's interaction with the laser light scattering community.

Design of a new Nd:YAG Thomson scattering system for MAST

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scannell, R.; Walsh, M. J.; Carolan, P. G.

2008-10-15

A new infrared Thomson scattering system has been designed for the MAST tokamak. The system will measure at 120 spatial points with {approx_equal}10 mm resolution across the plasma. Eight 30 Hz 1.6 J Nd:YAG lasers will be combined to produce a sampling rate of 240 Hz. The lasers will follow separate parallel beam paths to the MAST vessel. Scattered light will be collected at approximately f/6 over scattering angles ranging from 80 deg. to 120 deg. The laser energy and lens size, relative to an existing 1.2 J f/12 system, greatly increases the number of scattered photons collected per unitmore » length of laser beam. This is the third generation of this polychromator to be built and a number of modifications have been made to facilitate mass production and to improve performance. Detected scattered signals will be digitized at a rate of 1 GS/s by 8 bit analog to digital converters (ADCs.) Data may be read out from the ADCs between laser pulses to allow for real-time analysis.« less

Filtered Rayleigh Scattering Measurements in a Buoyant Flow Field

DTIC Science & Technology

2008-03-01

ENY/08-M22 Abstract Filtered Rayleigh Scattering (FRS) is a non-intrusive, laser -based flow characterization technique that consists of a narrow...linewidth laser , a molecular absorption filter, and a high resolution camera behind the filter to record images. Gases of different species have...different molecular scattering cross-sections that become apparent as they pass through the interrogating laser light source, and this difference is

Diagnostic apparatus and method for use in the alignment of one or more laser means onto a fiber optics interface

DOEpatents

Johnson, Steve A.; Shannon, Robert R.

1987-01-01

Diagnostic apparatus for use in determining the proper alignment of a plurality of laser beams onto a fiber optics interface is disclosed. The apparatus includes a lens assembly which serves two functions, first to focus a plurality of laser beams onto the fiber optics interface, and secondly to reflect and image the interface using scattered light to a monitor means. The monitor means permits indirect observation of the alignment or focusing of the laser beams onto the fiber optics interface.

Diagnostic apparatus and method for use in the alignment of one or more laser means onto a fiber optics interface

DOEpatents

Johnson, S.A.; Shannon, R.R.

1985-01-18

Diagnostic apparatus for use in determining the proper alignment of a plurality of laser beams onto a fiber optics interface is disclosed. The apparatus includes a lens assembly which serves two functions, first to focus a plurality of laser beams onto the fiber optics interface, and secondly to reflect and image the interface using scattered light to a monitor means. The monitor means permits indirect observation of the alignment or focusing of the laser beams onto the fiber optics interface.

Laser application to measure vertical sea temperature and turbidity, design phase

NASA Technical Reports Server (NTRS)

Hirschberg, J. G.; Wouters, A. W.; Simon, K. M.; Byrne, J. D.; Deverdun, C. E.

1976-01-01

An experiment to test a new method was designed, using backscattered radiation from a laser beam to measure oceanographic parameters in a fraction of a second. Tyndall, Rayleigh, Brillouin, and Raman scattering all are utilized to evaluate the parameters. A beam from a continuous argon ion laser is used together with an interferometer and interference filters to gather the information. The results are checked by direct measurements. Future shipboard and airborne experiments are described.

Laser one-dimensional range profile and the laser two-dimensional range profile of cylinders

NASA Astrophysics Data System (ADS)

Gong, Yanjun; Wang, Mingjun; Gong, Lei

2015-10-01

Laser one-dimensional range profile, that is scattering power from pulse laser scattering of target, is a radar imaging technology. The laser two-dimensional range profile is two-dimensional scattering imaging of pulse laser of target. Laser one-dimensional range profile and laser two-dimensional range profile are called laser range profile(LRP). The laser range profile can reflect the characteristics of the target shape and surface material. These techniques were motivated by applications of laser radar to target discrimination in ballistic missile defense. The radar equation of pulse laser is given in this paper. This paper demonstrates the analytical model of laser range profile of cylinder based on the radar equation of the pulse laser. Simulations results of laser one-dimensional range profiles of some cylinders are given. Laser range profiles of cylinder, whose surface material with diffuse lambertian reflectance, is given in this paper. Laser range profiles of different pulse width of cylinder are given in this paper. The influences of geometric parameters, pulse width, attitude on the range profiles are analyzed.

Interaction of 1.05 μm and 0.53 μm lasers with gold disks

NASA Astrophysics Data System (ADS)

Shenye, Liu; Yaonan, Ding; Zhijian, Zheng; Daoyuan, Tang

1996-05-01

Gold disks were irradiated with 1.05 μm and 0.53 μm lasers at pulse duration of ˜0.8 ns, intensity ranging from 5×1013 W/cm2 to 4×1015 W/cm2 on the SHEN GUANG I laser facility in China. The experimental results of laser absorption, scattering light, x-ray emission and plasma blow-off are presented in this paper. When the laser irradiated the gold disk obliquely, the angular distribution of scattered lights produced by 0.53 μm lasers disagree with that predicted by the Brillouin scattering theory. The angular distribution is different from that reported previously by the others.

Improved cross-calibration of Thomson scattering and electron cyclotron emission with ECH on DIII-D.

PubMed

Brookman, M W; Austin, M E; McLean, A G; Carlstrom, T N; Hyatt, A W; Lohr, J

2016-11-01

Thomson scattering produces n e profiles from measurement of scattered laser beam intensity. Rayleigh scattering provides a first calibration of the relation n e ∝ I TS , which depends on many factors (e.g., laser alignment and power, optics, and measurement systems). On DIII-D, the n e calibration is adjusted against an absolute n e from the density-driven cutoff of the 48 channel 2nd harmonic X-mode electron cyclotron emission system. This method has been used to calibrate Thomson n e from the edge to near the core (r/a > 0.15). Application of core electron cyclotron heating improves the quality of cutoff and depth of its penetration into the core, and also changes underlying MHD activity, minimizing crashes which confound calibration. Less fueling is needed as "ECH pump-out" generates a plasma ready to take up gas. On removal of gyrotron power, cutoff penetrates into the core as channels fall successively and smoothly into cutoff.

New method for investigation of cells and other biological objects in analytical cytology

NASA Astrophysics Data System (ADS)

Bilyi, Olexander I.; Getman, Vasyl B.; Kostyukevych, Sergey A.

2001-05-01

New method and instrument intended for checking the content of biology particles in dimension band 0.1-10.0 mkm in water flow is described in this report. The instrument measures the intensity of light scattered by the particles suspended in liquid flow when they are crossing the laser beam. The results of studying light scattered by platelet and bacterium's such a Pseudomonas aeruginosa, Escherichia coli, Micrococcus lutteus in such a liquid mediums as physiological solution and glucose solution are described.

Characterization of Subsurface Defects in Ceramic Rods by Laser Scattering and Fractography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, J. M.; Sun, J. G.; Andrews, M. J.

2006-03-06

Silicon nitride ceramics are leading materials being evaluated for valve train components in diesel engine applications. The surface and subsurface defects and damage induced by surface machining can significantly affect component strength and lifetime. In this study, a nondestructive evaluation (NDE) technique based upon laser scattering has been utilized to analyze eight transversely ground silicon nitride cylindrical rods before fracture tests. The fracture origins (machining cracks or material-inherent flaws) identified by fractography after fracture testing were correlated with laser scattering images. The results indicate that laser scattering is able to identify possible fracture origin in the silicon nitride subsurface withoutmore » the need for destructive fracture tests.« less

LASER APPLICATIONS AND OTHER ASPECTS OF QUANTUM ELECTRONICS Measurement of angular parameters of divergent optical radiation by light diffraction on sound

NASA Astrophysics Data System (ADS)

Kotov, V. M.; Averin, S. V.; Shkerdin, G. N.

2010-12-01

A method is proposed to measure the scattering angle of optical radiation, the method employing two Bragg diffraction processes in which divergent optical radiation propagates close to the optical axis of a uniaxial crystal, while the acoustic wave — orthogonally to this axis. The method does not require additional angular tuning of the acousto-optic cell. We suggest using a mask to measure the light divergence that is larger than the angle of Bragg scattering. The method can be used to measure the size of the polished glass plate inhomogeneities.

Laser rods with undoped, flanged end-caps for end-pumped laser applications

DOEpatents

Meissner, H.E.; Beach, R.J.; Bibeau, C.; Sutton, S.B.; Mitchell, S.; Bass, I.; Honea, E.

1999-08-10

A method and apparatus for achieving improved performance in a solid state laser is provided. A flanged, at least partially undoped end-cap is attached to at least one end of a laserable medium. Preferably flanged, undoped end-caps are attached to both ends of the laserable medium. Due to the low scatter requirements for the interface between the end-caps and the laser rod, a non-adhesive method of bonding is utilized such as optical contacting combined with a subsequent heat treatment of the optically contacted composite. The non-bonded end surfaces of the flanged end-caps are coated with laser cavity coatings appropriate for the lasing wavelength of the laser rod. A cooling jacket, sealably coupled to the flanged end-caps, surrounds the entire length of the laserable medium. Radiation from a pump source is focused by a lens duct and passed through at least one flanged end-cap into the laser rod. 14 figs.

Characterization of micron-size hydrogen clusters using Mie scattering.

PubMed

Jinno, S; Tanaka, H; Matsui, R; Kanasaki, M; Sakaki, H; Kando, M; Kondo, K; Sugiyama, A; Uesaka, M; Kishimoto, Y; Fukuda, Y

2017-08-07

Hydrogen clusters with diameters of a few micrometer range, composed of 10 8-10 hydrogen molecules, have been produced for the first time in an expansion of supercooled, high-pressure hydrogen gas into a vacuum through a conical nozzle connected to a cryogenic pulsed solenoid valve. The size distribution of the clusters has been evaluated by measuring the angular distribution of laser light scattered from the clusters. The data were analyzed based on the Mie scattering theory combined with the Tikhonov regularization method including the instrumental functions, the validity of which was assessed by performing a calibration study using a reference target consisting of standard micro-particles with two different sizes. The size distribution of the clusters was found discrete peaked at 0.33 ± 0.03, 0.65 ± 0.05, 0.81 ± 0.06, 1.40 ± 0.06 and 2.00 ± 0.13 µm in diameter. The highly reproducible and impurity-free nature of the micron-size hydrogen clusters can be a promising target for laser-driven multi-MeV proton sources with the currently available high power lasers.

Development of an optical microscopy system for automated bubble cloud analysis.

PubMed

Wesley, Daniel J; Brittle, Stuart A; Toolan, Daniel T W

2016-08-01

Recently, the number of uses of bubbles has begun to increase dramatically, with medicine, biofuel production, and wastewater treatment just some of the industries taking advantage of bubble properties, such as high mass transfer. As a result, more and more focus is being placed on the understanding and control of bubble formation processes and there are currently numerous techniques utilized to facilitate this understanding. Acoustic bubble sizing (ABS) and laser scattering techniques are able to provide information regarding bubble size and size distribution with minimal data processing, a major advantage over current optical-based direct imaging approaches. This paper demonstrates how direct bubble-imaging methods can be improved upon to yield high levels of automation and thus data comparable to ABS and laser scattering. We also discuss the added benefits of the direct imaging approaches and how it is possible to obtain considerable additional information above and beyond that which ABS and laser scattering can supply. This work could easily be exploited by both industrial-scale operations and small-scale laboratory studies, as this straightforward and cost-effective approach is highly transferrable and intuitive to use.

Isotopic imaging via nuclear resonance fluorescence with laser-based Thomson radiation

DOEpatents

Barty, Christopher P. J. [Hayward, CA; Hartemann, Frederic V [San Ramon, CA; McNabb, Dennis P [Alameda, CA; Pruet, Jason A [Brentwood, CA

2009-07-21

The present invention utilizes novel laser-based, high-brightness, high-spatial-resolution, pencil-beam sources of spectrally pure hard x-ray and gamma-ray radiation to induce resonant scattering in specific nuclei, i.e., nuclear resonance fluorescence. By monitoring such fluorescence as a function of beam position, it is possible to image in either two dimensions or three dimensions, the position and concentration of individual isotopes in a specific material configuration. Such methods of the present invention material identification, spatial resolution of material location and ability to locate and identify materials shielded by other materials, such as, for example, behind a lead wall. The foundation of the present invention is the generation of quasimonochromatic high-energy x-ray (100's of keV) and gamma-ray (greater than about 1 MeV) radiation via the collision of intense laser pulses from relativistic electrons. Such a process as utilized herein, i.e., Thomson scattering or inverse-Compton scattering, produces beams having diameters from about 1 micron to about 100 microns of high-energy photons with a bandwidth of .DELTA.E/E of approximately 10E.sup.-3.

Aerodynamic measurement techniques. [laser based diagnostic techniques

NASA Technical Reports Server (NTRS)

Hunter, W. W., Jr.

1976-01-01

Laser characteristics of intensity, monochromatic, spatial coherence, and temporal coherence were developed to advance laser based diagnostic techniques for aerodynamic related research. Two broad categories of visualization and optical measurements were considered, and three techniques received significant attention. These are holography, laser velocimetry, and Raman scattering. Examples of the quantitative laser velocimeter and Raman scattering measurements of velocity, temperature, and density indicated the potential of these nonintrusive techniques.

Nonlinear Thomson scattering of a relativistically strong tightly focused ultrashort laser pulse

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vais, O. E.; Bochkarev, S. G., E-mail: bochkar@sci.lebedev.ru; Bychenkov, V. Yu.

The problem of nonlinear Thomson scattering of a relativistically strong linearly polarized ultrashort laser pulse tightly focused into a spot with a diameter of D{sub F} ≳ λ (where λ is the laser wavelength) is solved. The energy, spectral, and angular distributions of radiation generated due to Thomson scattering from test electrons located in the focal region are found. The characteristics of scattered radiation are studied as functions of the tightness of laser focusing and the initial position of test particles relative to the center of the focal region for a given laser pulse energy. It is demonstrated that themore » ultratight focusing is not optimal for obtaining the brightest and hardest source of secondary electromagnetic radiation. The hardest and shortest radiation pulse is generated when the beam waist diameter is ≃10λ.« less

Calculation of optical properties of dental composites as a basis for determining color impression and penetration depth of laser light

NASA Astrophysics Data System (ADS)

Weniger, Kirsten K.; Muller, Gerhard J.

2005-03-01

In order to achieve esthetic dental restorations, there should be no visible difference between restorative material and treated teeth. This requires a match of the optical properties of both restorative material and natural teeth. These optical properties are determined by absorption and scattering of light emerging not only on the surface but also inside the material. Investigating different dental composites in several shades, a method has been developed to calculate the optical parameters absorption coefficient μa, scattering coefficient μs, anisotropy factor g and reduced scattering coefficient μs'. The method includes sample preparation and measurements of transmittance and reflectance in an integrating sphere spectrometer, followed by inverse Monte Carlo simulations. Determination of optical properties is more precise and comprehensive than with the previously used Kubelka Munk theory because scattering can be looked at separated into pure scattering with the scattering coefficient μs and its direction with the anisotropy factor g. Moreover the use of the inverse Monte Carlo simulation not only minimizes systematic errors and considers the scattering phase function, but also takes into account the measuring geometry. The compilation of a data pool of optical parameters now enables the application of further calculation models as a basis for optimization of the composition of new materials. For example, a prediction of the general color impression for multiple layers can be carried out as well as the calculation of the wavelength dependent penetration depths of light with regard to photo polymerization. Further applications are possible in the area of laser ablation.

Study of Fabry-Perot Etalon Stability and Tuning for Spectroscopic Rayleigh Scattering

NASA Technical Reports Server (NTRS)

Clem, Michelle M.; Mielke-Fagan, Amy F.; Elam, Kristie A.

2010-01-01

The Fabry-Perot interferometer is a commonly employed instrument for resolving the spectrum of molecular Rayleigh scattered light for the purpose of evaluating flow properties such as gas velocity and temperature. Rayleigh scattered light from a focused laser beam can be directly imaged through a solid Fabry-Perot etalon onto a CCD detector to provide the spectral content of the scattered light. The spatial resolution of the measurements is governed by the locations of interference fringes. The location of the fringes can be changed by altering the etalon?s physical characteristics, such as thickness and index of refraction. For a fused silica solid etalon the physical properties can be adjusted by changing the etalon temperature; hence changing the order of the interference pattern and the physical fringe locations. Controlling the temperature of the etalon can provide for a slow time-response spatial scanning method for this type of etalon system. A custom designed liquid crystal Fabry-Perot (LCFP) can provide for a fast time-response method of scanning the etalon system. Voltage applied to the liquid crystal interface sets the etalon?s properties allowing Rayleigh measurements to be acquired at varying spatial locations across the image of the laser beam over a very short time period. A standard fused silica etalon and a tunable LCFP etalon are characterized to select the system that is best suited for Rayleigh scattering measurements in subsonic and supersonic flow regimes. A frequency-stabilized laser is used to investigate the apparent frequency stability and temperature sensitivity of the etalon systems. Frequency stability and temperature sensitivity data of the fused silica and LCFP etalon systems are presented in this paper, along with measurements of the LCFP etalon?s tuning capabilities. Rayleigh scattering velocity measurements with both etalon systems are presented, in an effort to determine which etalon is better suited to provide optical flow measurements of velocity, temperature, and density.

Estimation of viscoelastic surface wave parameters using a low cost optical deflection method

NASA Astrophysics Data System (ADS)

Brum, J.; Balay, G.; Arzúa, A.; Núñez, I.; Negreira, C.

2010-01-01

In this work an optical deflection method was used to study surface vibrations created by a low frequency source placed on the sample's surface. The optical method consists in placing a laser beam perpendicularly the sample's surface (gelatine based phantom). A beam-splitter is placed between the laser and the sample to project the reflected beam into a screen. As the surface moves due to the action of the low frequency source the laser beam on the screen also moves. Recording this movement with a digital camera allow us to reconstruct de surface motion using the light reflection law. If the scattering of the surface is very strong (such the one in biological tissue) a lens is placed between the surface and the beam-splitter to collect the scattered light. As validation method the surface movement was measured using a 10 MHz ultrasonic transducer placed normal to the surface in pulse-eco mode. The optical measurements were in complete agreement with the acoustical measurements. The optical measurement has the following advantages over the acoustic: 2-dimensional motion could be recorded and it is low cost. Since the acquisition was synchronized and the source-laser beam distance is known, measuring the time of flight an estimation of the surface wave velocity is obtained in order to measure the elasticity of the sample. The authors conclude that a reliable optical, low cost method for obtaining surface wave parameters of biological tissue was developed and successfully validate.

Optical method and apparatus for detection of surface and near-subsurface defects in dense ceramics

DOEpatents

Ellingson, William A.; Brada, Mark P.

1995-01-01

A laser is used in a non-destructive manner to detect surface and near-subsurface defects in dense ceramics and particularly in ceramic bodies with complex shapes such as ceramic bearings, turbine blades, races, and the like. The laser's wavelength is selected based upon the composition of the ceramic sample and the laser can be directed on the sample while the sample is static or in dynamic rotate or translate motion. Light is scattered off surface and subsurface defects using a preselected polarization. The change in polarization angle is used to select the depth and characteristics of surface/subsurface defects. The scattered light is detected by an optical train consisting of a charge coupled device (CCD), or vidicon, television camera which, in turn, is coupled to a video monitor and a computer for digitizing the image. An analyzing polarizer in the optical train allows scattered light at a given polarization angle to be observed for enhancing sensitivity to either surface or near-subsurface defects. Application of digital image processing allows subtraction of digitized images in near real-time providing enhanced sensitivity to subsurface defects. Storing known "feature masks" of identified defects in the computer and comparing the detected scatter pattern (Fourier images) with the stored feature masks allows for automatic classification of detected defects.

Laser velocimetry with fluorescent dye-doped polystyrene microspheres.

PubMed

Lowe, K Todd; Maisto, Pietro; Byun, Gwibo; Simpson, Roger L; Verkamp, Max; Danehy, Paul M; Tiemsin, Pacita I; Wohl, Christopher J

2013-04-15

Simultaneous Mie scattering and laser-induced fluorescence (LIF) signals are obtained from individual polystyrene latex microspheres dispersed in an air flow. Microspheres less than 1 μm mean diameter were doped with two organic fluorescent dyes, Rhodamine B (RhB) and dichlorofluorescein (DCF), intended either to provide improved particle-based flow velocimetry in the vicinity of surfaces or to provide scalar flow information (e.g., marking one of two fluid streams). Both dyes exhibit measureable fluorescence signals that are on the order of 10(-3) to 10(-4) times weaker than the simultaneously measured Mie signals. It is determined that at the conditions measured, 95.5% of RhB LIF signals and 32.2% of DCF signals provide valid laser-Doppler velocimetry measurements compared with the Mie scattering validation rate with 6.5 W of 532 nm excitation, while RhB excited with 1.0 W incident laser power still exhibits 95.4% valid velocimetry signals from the LIF channel. The results suggest that the method is applicable to wind tunnel measurements near walls where laser flare can be a limiting factor and monodisperse particles are essential.

Laser intensity scaling through stimulated scattering in optical fibers

NASA Astrophysics Data System (ADS)

Russell, Timothy H.

The influence of stimulated scattering on laser intensity in fiber optic waveguides is examined. Stimulated Brillouin scattering (SBS) in long, multimode optical waveguides is found to generate a Stokes beam that propagates in the fiber LP01 mode. This characteristic of the Stokes beam was first applied to beam cleanup, where an aberrated pump generated a Gaussian-like Stokes beam. Additionally, the same process is found to combine multiple laser beams into a single spatially coherent source. The mean square difference between the two beams was used to measure the degree of spatial overlap, demonstrating spatial coherence between the Stokes beams even when the pump beams are not spatially correlated. This result is obtained regardless of whether the pump beams are at the same or different frequencies; producing two temporally coherent or incoherent Stokes beams respectively. Limitations in beam cleanup and combining are also examined to identify ways to overcome them. Output couplers are designed that could be used to spatially filter the Stokes beam from the pump, thus increasing the number of beams that could be combined. The combined power restriction induced by second order Stokes threshold is examined experimentally and theoretically and is not found to be a significant limitation. Finally, stimulated Raman scattering (SRS) beam cleanup is examined to overcome the stringent spectral requirements on the pump beams required by SBS. The last portion of the dissertation theoretically examines suppression of stimulated Raman scattering in fibers to eliminate the restriction this imposes on the power of a fiber laser or amplifier. The suppression was modeled using both a holmium dopant and adding a long period grating to the fiber. Both methods were shown to have a significant effect on the SRS threshold.

High-power laser radiation in atmospheric aerosols: Nonlinear optics of aerodispersed media

NASA Astrophysics Data System (ADS)

Zuev, V. E.; Zemlianov, A. A.; Kopytin, Iu. D.; Kuzikovskii, A. V.

The bulk of this book contains the results of investigations carried out at the Institute of Atmospheric Optics, Siberian Branch, USSR Academy of Science with the participation of the authors. The microphysical and optical characteristics of atmospheric aerosols are considered, taking into account light scattering by a single aerosol particle, light scattering by a system of particles, the scattering phase matrix, light scattering by clouds and fogs, light scattering by hazes, and scattering phase functions of polydispersed aerosols. Other topics studies are related to low-energy (subexplosive) effects of radiation on individual particles, the formation of clear zones in clouds and fogs due to the vaporization of droplets under regular regimes, self-action of a wave beam in a water aerosol under conditions of regular droplet vaporization, laser beam propagation through an explosively evaporating water-droplet aerosol, the propagation of high-power laser radiation through hazes, the ionization and optical breakdown in aerosol media, and laser monitoring of a turbid atmosphere using nonlinear effects.

Investigation of vesicle-capsular plague antigen complex formation by elastic laser radiation scattering

NASA Astrophysics Data System (ADS)

Guseva, N. P.; Maximova, Irina S.; Romanov, Sergey V.; Shubochkin, L. P.; Tatarintsev, Sergey N.

1991-05-01

Recently a great deal of attention has been given to the investigation artificial lipid liposomes, due to their application as "containers" for directed transport of biologically active compounds into particular cells, organs and tissues for prophylaxis and therapy of infectious diseases. The use of traditional methods of liposome investigation, such as sedimentation, electrophoresis and chromatography is impeded by low liposome resistivity to different deformations. In conjunction with this, optical methods of laser light scattering are promising as they allow nondisturbing, precise and quick investigations. This paper describes the investigation of vesicle systems prepared from egg lecithin of Serva Corporation and their complexes with the capsular antigen of the plague microbe. The capsular antigen Fl was obtained from EV plague microbe grown at 37° C on Huttinger agar. Fl was isolated by gel-filtration on ASA-22 followed by freeze drying of the preparation. Angular dependences of polarized radiation scattering were measured for several liposome suspension samples in a saline solution before and after the interaction with the plague microbe capsular antigen. The aim of the investigation was to analyze the nature of mutual antigen arrangement in a liposome and to develop methods for measuring its inclusion percentage.

Holographic method for site-resolved detection of a 2D array of ultracold atoms

NASA Astrophysics Data System (ADS)

Hoffmann, Daniel Kai; Deissler, Benjamin; Limmer, Wolfgang; Hecker Denschlag, Johannes

2016-08-01

We propose a novel approach to site-resolved detection of a 2D gas of ultracold atoms in an optical lattice. A near-resonant laser beam is coherently scattered by the atomic array, and after passing a lens its interference pattern is holographically recorded by superimposing it with a reference laser beam on a CCD chip. Fourier transformation of the recorded intensity pattern reconstructs the atomic distribution in the lattice with single-site resolution. The holographic detection method requires only about two hundred scattered photons per atom in order to achieve a high reconstruction fidelity of 99.9 %. Therefore, additional cooling during detection might not be necessary even for light atomic elements such as lithium. Furthermore, first investigations suggest that small aberrations of the lens can be post-corrected in imaging processing.

Density Determination of Metallic Melts from Diffuse X-Ray Scattering

NASA Astrophysics Data System (ADS)

Brauser, N.; Davis, A.; Greenberg, E.; Prakapenka, V. B.; Campbell, A.

2017-12-01

Liquids comprise several important structural components of the deep Earth, for example, the present outer core and a hypothesized magma ocean early in Earth history. However, the physical properties of the constituent materials of these structures at high pressures and temperatures are less well constrained than their crystalline counterparts. Determination of the physical properties of these liquids can inform geophysical models of the composition and structure of the Earth, but methods for studying the physical properties of liquids at high pressure and temperatures are underdeveloped. One proposed method for direct determination of density of a melt requires analysis of the diffuse scattered X-ray signal of the liquid. Among the challenges to applying this technique to high-pressure melts within a laser heated diamond anvil cell are the low signal-to-noise ratio and overlapping diffraction peaks from the crystalline components of the sample assembly interfering with the diffuse scattering from the liquid. Recent advances in instrumentation at synchrotron X-ray sources have made this method more accessible for determination of density of melted material. In this work we present the technique and report the densities of three high-pressure melts of the FCC metals iron, nickel, and gold derived from diffuse scattered X-ray spectra collected from in situ laser-heated diamond anvil cell synchrotron experiments. The results are compared to densities derived from shock wave experiments.

Study of magnetofluidic laser scattering under rotating magnetic field

NASA Astrophysics Data System (ADS)

Pai, Chintamani; Shalini, M.; Varma, Vijaykumar B.; Radha, S.; Nagarajan, R.; Ramanujan, Raju V.

2018-04-01

Magnetic field driven self-assembly of magnetic nanoparticles provides wireless programmable approach for tunable magnetofluidic laser scattering. In this work, we study magnetofluidic laser scattering from a commercial aqueous magnetic fluid (EMG 707) under an external rotating magnetic field. A set-up is developed to generate rotating magnetic field for the purpose. Self-assembled magnetic nanoparticle structures in the form of chains and bundles are formed along the magnetic field. This creates a linear streak formation in the forward laser scattering. Rotating magnetic field produces rotating linear streak. We report our initial results of rotating linear streaks at 3 rpm, 6 rpm and 10 rpm and our analysis of the patterns. The studies are useful for developing magnetic fluid based optical devices.

Instantaneous flow measurements in a supersonic wind tunnel using spectrally resolved Rayleigh scattering

NASA Technical Reports Server (NTRS)

Seasholtz, Richard G.; Buggele, Alvin E.; Reeder, Mark F.

1995-01-01

Results of a feasibility study to apply laser Rayleigh scattering to non-intrusively measure flow properties in a small supersonic wind tunnel are presented. The technique uses an injection seeded, frequency doubled Nd:YAG laser tuned to an absorption band of iodine. The molecular Rayleigh scattered light is filtered with an iodine cell to block light at the laser frequency. The Doppler-shifted Rayleigh scattered light that passes through the iodine cell is analyzed with a planar mirror Fabry-Perot interferometer used in a static imaging mode. An intensified CCD camera is used to record the images. The images are analyzed at several subregions, where the flow velocity is determined. Each image is obtained with a single laser pulse, giving instantaneous measurements.

Spectrum bandwidth narrowing of Thomson scattering X-rays with energy chirped electron beams from laser wakefield acceleration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Tong; Chen, Min, E-mail: minchen@sjtu.edu.cn; Li, Fei-Yu

2014-01-06

We study incoherent Thomson scattering between an ultrashort laser pulse and an electron beam accelerated from a laser wakefield. The energy chirp effects of the accelerated electron beam on the final radiation spectrum bandwidth are investigated. It is found that the scattered X-ray radiation has the minimum spectrum width and highest intensity as electrons are accelerated up to around the dephasing point. Furthermore, it is proposed that the electron acceleration process inside the wakefield can be studied by use of 90° Thomson scattering. The dephasing position and beam energy chirp can be deduced from the intensity and bandwidth of themore » scattered radiation.« less

Scattering (stochastic) recoupling of a coupled ten-stripe AlGaAs-GaAs-InGaAs quantum-well heterostructure laser

NASA Astrophysics Data System (ADS)

Kellogg, D. A.; Holonyak, N.

2001-04-01

Data are presented on coupled ten-stripe AlGaAs-GaAs-InGaAs quantum well heterostructure (QWH) lasers recoupled stochastically at the cleaved end mirrors. Recoupling of neighboring elements of a ten-stripe laser is accomplished by the scattering (random feedback) afforded by applying ˜10-μm-diam Al powder or 0.3 μm α-Al2O3 polishing compound in microscopy immersion oil or in epoxy at the cleaved ends (mirrors). Data on QWH samples with the end mirrors coated with the scatterer (Al or Al2O3 powder in "liquid") exhibit spectral and far-field broadening, as well as increased laser threshold because of the reduced cavity Q. Single mode operation is possible with the conventional evanescent wave coupling of the ten-stripe QWH and is destroyed, even the laser operation itself, with the scattering recoupling (dephasing) at the end mirrors, which is reversible (removable). The narrow ten-stripe QWH laser with strong end-mirror scattering, a long amplifier with random feedback, indicates that a photopumped III-V or II-VI powder (a random "wall" cavity) has little or no merit.

Potential Elevation Biases for Laser Altimeters from Subsurface Scattered Photons: Laboratory and Model Exploration of Green Light Scattering in Snow

NASA Astrophysics Data System (ADS)

Greeley, A.; Neumann, T.; Markus, T.; Kurtz, N. T.; Cook, W. B.

2015-12-01

Existing visible light laser altimeters such as MABEL (Multiple Altimeter Beam Experimental Lidar) - a single photon counting simulator for ATLAS (Advanced Topographic Laser Altimeter System) on NASA's upcoming ICESat-2 mission - and ATM (Airborne Topographic Mapper) on NASA's Operation IceBridge mission provide scientists a view of Earth's ice sheets, glaciers, and sea ice with unprecedented detail. Precise calibration of these instruments is needed to understand rapidly changing parameters like sea ice freeboard and to measure optical properties of surfaces like snow covered ice sheets using subsurface scattered photons. Photons travelling into snow, ice, or water before scattering back to the altimeter receiving system (subsurface photons) travel farther and longer than photons scattering off the surface only, causing a bias in the measured elevation. We seek to identify subsurface photons in a laboratory setting using a flight-tested laser altimeter (MABEL) and to quantify their effect on surface elevation estimates for laser altimeter systems. We also compare these estimates with previous laboratory measurements of green laser light transmission through snow, as well as Monte Carlo simulations of backscattered photons from snow.

Ultraviolet Raman scattering from persistent chemical warfare agents

NASA Astrophysics Data System (ADS)

Kullander, Fredrik; Wästerby, Pär.; Landström, Lars

2016-05-01

Laser induced Raman scattering at excitation wavelengths in the middle ultraviolet was examined using a pulsed tunable laser based spectrometer system. Droplets of chemical warfare agents, with a volume of 2 μl, were placed on a silicon surface and irradiated with sequences of laser pulses. The Raman scattering from V-series nerve agents, Tabun (GA) and Mustard gas (HD) was studied with the aim of finding the optimum parameters and the requirements for a detection system. A particular emphasis was put on V-agents that have been previously shown to yield relatively weak Raman scattering in this excitation band.

Nonlinear Raman forward scattering of a short laser pulse in a collisional transversely magnetized plasma

NASA Astrophysics Data System (ADS)

Paknezhad, Alireza

2013-01-01

Nonlinear Raman forward scattering (NRFS) of an intense short laser pulse with a duration shorter than the plasma period through a homogenous collisional transversely magnetized plasma is investigated theoretically when ponderomotive, relativistic and collioninal nonlinearities are taken into account. The plasma is embedded in a uniform magnetic field perpendicular to both, the direction of propagation and electric vector of the radiation field. Nonlinear wave equation is set up and Fourier transformation method is used to solve the coupled equations describing NRFS instability. Finally, the growth rate of this instability is obtained. Thermal effects of plasma electrons and effect of the electron-ion collisions are examined. It is found that the growth rate of Raman forward scattering first decreases on increasing electron thermal velocity, minimizes at an optimum value, and then increases. Our results also show that the growth rate increases by increasing the electron-ion collisions.

The time resolved SBS and SRS research in heavy water and its application in CARS

NASA Astrophysics Data System (ADS)

Liu, Jinbo; Gai, Baodong; Yuan, Hong; Sun, Jianfeng; Zhou, Xin; Liu, Di; Xia, Xusheng; Wang, Pengyuan; Hu, Shu; Chen, Ying; Guo, Jingwei; Jin, Yuqi; Sang, Fengting

2018-05-01

We present the time-resolved character of stimulated Brillouin scattering (SBS) and backward stimulated Raman scattering (BSRS) in heavy water and its application in Coherent Anti-Stokes Raman Scattering (CARS) technique. A nanosecond laser from a frequency-doubled Nd: YAG laser is introduced into a heavy water cell, to generate SBS and BSRS beams. The SBS and BSRS beams are collinear, and their time resolved characters are studied by a streak camera, experiment show that they are ideal source for an alignment-free CARS system, and the time resolved property of SBS and BSRS beams could affect the CARS efficiency significantly. By inserting a Dye cuvette to the collinear beams, the time-overlapping of SBS and BSRS could be improved, and finally the CARS efficiency is increased, even though the SBS energy is decreased. Possible methods to improve the efficiency of this CARS system are discussed too.

Robust sensor for turbidity measurement from light scattering and absorbing liquids.

PubMed

Kontturi, Ville; Turunen, Petri; Uozumi, Jun; Peiponen, Kai-Erik

2009-12-01

Internationally standardized turbidity measurements for probing solid particles in liquid are problematic in the case of simultaneous light scattering and absorption. A method and a sensor to determine the turbidity in the presence of light absorption are presented. The developed sensor makes use of the total internal reflection of a laser beam at the liquid-prism interface, and the turbidity is assessed using the concept of laser speckle pattern. Using average filtering in speckle data analyzing the observed dynamic speckle pattern, which is due to light scattering from particles and the static speckle due to stray light of the sensor, can be separated from each other. Good correlation between the standard deviation of dynamic speckle and turbidity value for nonabsorbing and for absorbing liquids was observed. The sensor is suggested, for instance, for the measurement of ill-behaved as well as small-volume turbid liquids in both medicine and process industry.

The spectroscopy of singlets and triplets excites electronic states, spatial and electronic structure of hydrocarbons and quantum classifications in chemmotology

NASA Astrophysics Data System (ADS)

Obukhov, A. E.

2017-01-01

In this work we demonstrate the physical foundations of the spectroscopy of the grounds states: E- and X-ray, (RR) Raman scattering the NMR 1H and 13C and IR-, EPR- absorption and the singlets and triplets electronic excited states in the multinuclear hydrocarbons in chemmotology. The parameters of UV-absorption, RR-Raman scattering of light, the fluorescence and the phosphorescence and day-lasers at the pumping laser and lamp, OLEDs and OTETs- are measurements. The spectral-energy properties are briefly studied. The quantum-chemical LCAO-MO SCF expanded-CI PPP/S and INDO/S methods in the electronic and spatial structure hidrocarbons are considered.

First refraction contrast imaging via Laser-Compton Scattering X-ray at KEK

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sakaue, Kazuyuki; Aoki, Tatsuro; Washio, Masakazu

2012-07-31

Laser-Compton Scattering (LCS) is one of the most feasible techniques for high quality, high brightness, and compact X-ray source. High energy electron beam produced by accelerators scatters off the laser photon at a small spot. As a laser target, we have been developing a pulsedlaser storage cavity for increasing an X-ray flux. The X-ray flux was still inadequate that was 2.1 Multiplication-Sign 10{sup 5}/sec, however, we performed first refraction contrast imaging in order to evaluate the quality of LCS X-ray. Edge enhanced contrast imaging was achieved by changing the distance from sample to detector. The edge enhancement indicates that themore » LCS X-ray has small source size, i.e. high brightness. We believe that the result has demonstrated good feasibility of linac-based high brightness X-ray sources via laser-electron Compton scatterings.« less

Plasma Jet Interaction with Thomson Scattering Probe Laser

NASA Astrophysics Data System (ADS)

Byvank, Tom; Banasek, Jacob; Potter, William; Kusse, Bruce

2016-10-01

Thomson scattering systems can diagnose plasma temperatures and velocities. When probing a plasma jet with the Thomson scattering laser, we observe a laser-plasma interaction that inputs energy into the plasma jet. The absorbed energy causes a bubble of low density ( 5*1017 cm-2) in the jet (unperturbed 1018 cm-2). A pulsed power machine (1 MA peak current, 100 ns rise time) with a radial foil (15 μm thick Al) configuration generates the plasma jet. We compare the effects of using 10 J and 1 J laser energies, for which the 10 J laser is a larger perturbation. We discuss how the interaction affects the Thomson scattering temperature and velocity measurements. Work supported by National Nuclear Security Administration (NNSA) Stewardship Sciences Academic Programs under Department of Energy (DOE) Cooperative Agreement DE-NA0001836 and National Science Foundation (NSF) Grant PHY-1102471.

A study of optical scattering methods in laboratory plasma diagnosis

NASA Technical Reports Server (NTRS)

Phipps, C. R., Jr.

1972-01-01

Electron velocity distributions are deduced along axes parallel and perpendicular to the magnetic field in a pulsed, linear Penning discharge in hydrogen by means of a laser Thomson scattering experiment. Results obtained are numerical averages of many individual measurements made at specific space-time points in the plasma evolution. Because of the high resolution in k-space and the relatively low maximum electron density 2 x 10 to the 13th power/cu cm, special techniques were required to obtain measurable scattering signals. These techniques are discussed and experimental results are presented.

Research on energy transmission calculation problem on laser detecting submarine

NASA Astrophysics Data System (ADS)

Fu, Qiang; Li, Yingchao; Zhang, Lizhong; Wang, Chao; An, Yan

2014-12-01

The laser detection and identification is based on the method of using laser as the source of signal to scan the surface of ocean. If the laser detection equipment finds out the target, it will immediately reflect the returning signal, and then through receiving and disposing the returning signal by the receiving system, to realize the function of detection and identification. Two mediums channels should be though in the process of laser detection transmission, which are the atmosphere and the seawater. The energy loss in the process of water transport, mainly considering the surface reflection and scattering attenuation and internal attenuation factors such as seawater. The energy consumption though atmospheric transmission, mainly considering the absorption of atmospheric and the attenuation causing by scattering, the energy consumption though seawater transmission, mainly considering the element such as surface reflection, the attenuation of scattering and internal attenuation of seawater. On the basis of the analysis and research, through the mode of establishment of atmospheric scattering, the model of sea surface reflection and the model of internal attenuation of seawater, determine the power dissipation of emitting lasers system, calculates the signal strength that reaches the receiver. Under certain conditions, the total attenuation of -98.92 dB by calculation, and put forward the related experiment scheme by the use of Atmospheric analog channel, seawater analog channel. In the experiment of the theory, we use the simulation pool of the atmosphere and the sea to replace the real environment where the laser detection system works in this kind of situation. To start with, we need to put the target in the simulating seawater pool of 10 meters large and then control the depth of the target in the sea level. We, putting the laser detection system in position where it is 2 kilometers far from one side, secondly use the equipment to aim at the target in some distance. Lastly, by launching and detecting the signal of returning wave, identify the effect of the image produced by the system.

Methods for SBS Threshold Reduction

DTIC Science & Technology

1994-01-30

We have investigated methods for reducing the threshold for stimulated Brillouin scattering (SBS) using a frequency-narrowed Cr,Tm,Ho:YAG laser...operating at 2.12 micrometers. The SBS medium was carbon disulfide. Single-focus SBS and threshold reduction by using two foci, a loop, and a ring have

Neodymium glass laser with a phase conjugate mirror producing 220 J pulses at 0.02 Hz repetition rate.

PubMed

Kuzmin, A A; Khazanov, E A; Kulagin, O V; Shaykin, A A

2014-08-25

For pumping multipetawatt Ti:sapphire laser facilities we developed a compact repetitively pulsed laser based on neodymium phosphate glass with pulse energy of 220 J, pulse repetition rate of 0.02 Hz, beam diameter of 43 mm, aperture fill factor of 0.8, and FWHM pulse duration of 30 ns. The phase distortions of laser radiation were compensated by optical phase conjugation via stimulated Brillouin scattering. The depolarization was reduced to 0.4% using linear compensation methods. The beam quality was 2.5 x diffraction limit (150 µrad).

Scattering of Femtosecond Laser Pulses on the Negative Hydrogen Ion

NASA Astrophysics Data System (ADS)

Astapenko, V. A.; Moroz, N. N.

2018-05-01

Elastic scattering of ultrashort laser pulses (USLPs) on the negative hydrogen ion is considered. Results of calculations of the USLP scattering probability are presented and analyzed for pulses of two types: the corrected Gaussian pulse and wavelet pulse without carrier frequency depending on the problem parameters.

Laser Studies of Gas Phase Radical Reactions.

DTIC Science & Technology

1989-01-01

synchronised chopper ( Rofin 7500) to block the laser beam on alternate shots to allow background subtraction. Signal due to scattered laser light was...synchronised chopper ( Rofin 7500) to block the laser beam on alternate shots to allow background subtraction. Signal due to scattered laser light was...Cassufication) (U) Laser Studies of Gas Phase Radical Reactions 𔃼 ,ERSRP4AL UTHOR($) I3a. TYPE Of REPORT 13b. TIME COVERtD 14 D T8?’F JPORT (Year, Maonlth, Da

A diode laser-based velocimeter providing point measurements in unseeded flows using modulated filtered Rayleigh scattering (MFRS)

NASA Astrophysics Data System (ADS)

Jagodzinski, Jeremy James

2007-12-01

The development to date of a diode-laser based velocimeter providing point-velocity-measurements in unseeded flows using molecular Rayleigh scattering is discussed. The velocimeter is based on modulated filtered Rayleigh scattering (MFRS), a novel variation of filtered Rayleigh scattering (FRS), utilizing modulated absorption spectroscopy techniques to detect a strong absorption of a relatively weak Rayleigh scattered signal. A rubidium (Rb) vapor filter is used to provide the relatively strong absorption; alkali metal vapors have a high optical depth at modest vapor pressures, and their narrow linewidth is ideally suited for high-resolution velocimetry. Semiconductor diode lasers are used to generate the relatively weak Rayleigh scattered signal; due to their compact, rugged construction diode lasers are ideally suited for the environmental extremes encountered in many experiments. The MFRS technique utilizes the frequency-tuning capability of diode lasers to implement a homodyne detection scheme using lock-in amplifiers. The optical frequency of the diode-based laser system used to interrogate the flow is rapidly modulated about a reference frequency in the D2-line of Rb. The frequency modulation is imposed on the Rayleigh scattered light that is collected from the probe volume in the flow under investigation. The collected frequency modulating Rayleigh scattered light is transmitted through a Rb vapor filter before being detected. The detected modulated absorption signal is fed to two lock-in amplifers synchronized with the modulation frequency of the source laser. High levels of background rejection are attained since the lock-ins are both frequency and phase selective. The two lock-in amplifiers extract different Fourier components of the detected modulated absorption signal, which are ratioed to provide an intensity normalized frequency dependent signal from a single detector. A Doppler frequency shift in the collected Rayleigh scattered light due to a change in the velocity of the flow under investigation results in a change in the detected modulated absorption signal. This change in the detected signal provides a quantifiable measure of the Doppler frequency shift, and hence the velocity in the probe volume, provided that the laser source exhibits acceptable levels of frequency stability (determined by the magnitude of the velocities being measured). An extended cavity diode laser (ECDL) in the Littrow configuration provides frequency tunable, relatively narrow-linewidth lasing for the MFRS velocimeter. Frequency stabilization of the ECDL is provided by a proportional-integral-differential (PID) controller based on an error signal in the reference arm of the experiment. The optical power of the Littrow laser source is amplified by an antireflection coated (AR coated) broad stripe diode laser. The single-mode, frequency-modulatable, frequency-stable O(50 mW) of optical power provided by this extended cavity diode laser master oscillator power amplifier (ECDL-MOPA) system provided sufficient scattering signal from a condensing jet of CO2 to implement the MFRS technique in the frequency-locked mode of operation.

Propagation of laser beams in scattering media.

PubMed

Zuev, V E; Kabanov, M V; Savelev, B A

1969-01-01

Experimental investigations have been undertaken of some aspects of the propagation of helium-neon gas laser radiation at lambda = 0.63 micro for different scattering media (artificial water fogs, wood smokes, model media). It has been shown that the attenuation coefficients practically coincide when coherent and incoherent radiation is scattered. The applicability limits of Bouguer-Beer's law for describing the attenuation of radiation in scattering media are investigated and the intensity of multiple forward-scattered light for different geometrical parameters of the source and radiation receiver are measured. The applicability of single scattering theory formulas for describing forward-scattered light intensity are discussed.

Post-PRK corneal scatter measurements with a scanning confocal slit photon counter

NASA Astrophysics Data System (ADS)

Taboada, John; Gaines, David; Perez, Mary A.; Waller, Steve G.; Ivan, Douglas J.; Baldwin, J. Bruce; LoRusso, Frank; Tutt, Ronald C.; Perez, Jose; Tredici, Thomas; Johnson, Dan A.

2000-06-01

Increased corneal light scatter or 'haze' has been associated with excimer laser photorefractive surgery of the cornea. The increased scatter can affect visual performance; however, topical steroid treatment post surgery substantially reduces the post PRK scatter. For the treatment and monitoring of the scattering characteristics of the cornea, various methods have been developed to objectively measure the magnitude of the scatter. These methods generally can measure scatter associated with clinically observable levels of haze. For patients with moderate to low PRK corrections receiving steroid treatment, measurement becomes fairly difficult as the haze clinical rating is non observable. The goal of this development was to realize an objective, non-invasive physical measurement that could produce a significant reading for any level including the background present in a normal cornea. As back-scatter is the only readily accessible observable, the instrument is based on this measurement. To achieve this end required the use of a confocal method to bias out the background light that would normally confound conventional methods. A number of subjects with nominal refractive errors in an Air Force study have undergone PRK surgery. A measurable increase in corneal scatter has been observed in these subjects whereas clinical ratings of the haze were noted as level zero. Other favorable aspects of this back-scatter based instrument include an optical capability to perform what is equivalent to an optical A-scan of the anterior chamber. Lens scatter can also be measured.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Rui; Su, Rongxin, E-mail: surx@tju.edu.cn; Tianjin Key Laboratory of Membrane Science and Desalination Technology, Tianjin University, Tianjin 300072

Highlights: {yields} We compare the structures of insulin upon heating with or without laser irradiation. {yields} Laser irradiation inhibits insulin fibrillation and may be of insert for mechanistic disease studies. {yields} Online laser measurements should be carefully used in the study of amyloid proteins. -- Abstract: Protein aggregation and amyloid fibrillation can lead to several serious diseases and protein drugs ineffectiveness; thus, the detection and inhibition of these processes have been of great interest. In the present study, the inhibition of insulin amyloid fibrillation by laser irradiation was investigated using dynamic light scattering (DLS), transmission electron microscopy (TEM), far-UV circularmore » dichroism (far-UV CD), and thioflavin T (ThT) fluorescence. During heat-induced aggregation, the size distribution of two insulin solutions obtained by online and offline dynamic light scattering were different. The laser-on insulin in the presence of 0.1 M NaCl exhibited fewer fibrils than the laser-off insulin, whereas no insulin fibril under laser irradiation was observed in the absence of 0.1 M NaCl for 45 h incubation. Moreover, our CD results showed that the laser-irradiated insulin solution maintained mainly an {alpha}-helical conformation, but the laser-off insulin solution formed bulk fibrils followed by a significant increase in {beta}-sheet content for 106 h incubation. These findings provide an inhibition method for insulin amyloid fibrillation using the laser irradiation and demonstrate that the online long-time laser measurements should be carefully used in the study of amyloid proteins because they may change the original results.« less

System and method for linearly amplifying optical analog signals by backward Raman scattering

DOEpatents

Lin, Cheng-Heui

1988-01-01

A system for linearly amplifying an optical analog signal by backward stimulated Raman scattering comprises a laser source for generating a pump pulse; and an optic fiber having two opposed apertures, a first aperture for receiving the pump pulse and a second aperture for receiving the optical analog signal, wherein the optical analog signal is linearly amplified to an amplified optical analog signal.

System and method for linearly amplifying optical analog signals by backward Raman scattering

DOEpatents

Lin, Cheng-Heui

1988-07-05

A system for linearly amplifying an optical analog signal by backward stimulated Raman scattering comprises a laser source for generating a pump pulse; and an optic fiber having two opposed apertures, a first aperture for receiving the pump pulse and a second aperture for receiving the optical analog signal, wherein the optical analog signal is linearly amplified to an amplified optical analog signal.

Optical properties of human colon tissues in the 350 – 2500 nm spectral range

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bashkatov, A N; Genina, E A; Kochubey, V I

2014-08-31

We present the optical characteristics of the mucosa and submucosa of human colon tissue. The experiments are performed in vitro using a LAMBDA 950 spectrophotometer in the 350 – 2500 nm spectral range. The absorption and scattering coefficients and the scattering anisotropy factor are calculated based on the measured diffuse reflectance and total and collimated transmittance spectra using the inverse Monte Carlo method. (laser biophotonics)

Diffraction Pattern Analysis as an Optical Inspection Technique

DTIC Science & Technology

1991-08-01

BACKGROUND Diameters of fiber samples have commonly been measured manually with an optical microscope. Marcuse and Presby developed an automatic...by analyzing the back-scattered light when a beam of laser light impinged upon the fiber [2]. Presby and Marcuse extended this back-scattering tech...be im- proved further in order to become a feasible method for detecting a small number of blocked openings in CRT screens. 20 REFERENCES 1. Marcuse

Using acoustic levitation in synchrotron based laser pump hard x-ray probe experiments

NASA Astrophysics Data System (ADS)

Hu, Bin; Lerch, Jason; Suthar, Kamlesh; Dichiara, Anthony

Acoustic levitation provides a platform to trap and hold a small amount of material by using standing pressure waves without a container. The technique has a potential to be used for laser pump x-ray probe experiments; x-ray scattering and laser distortion from the container can be avoided, sample consumption can be minimized, and unwanted chemistry that may occur at the container interface can be avoided. The method has been used at synchrotron sources for studying protein and pharmaceutical solutions using x-ray diffraction (XRD) and small angle x-ray scattering (SAXS). However, pump-probe experiments require homogeneously excited samples, smaller than the absorption depth of the material that must be held stably at the intersection of both the laser and x-ray beams. We discuss 1) the role of oscillations in acoustic levitation and the optimal acoustic trapping conditions for x-ray/laser experiments, 2) opportunities to automate acoustic levitation for fast sample loading and manipulation, and 3) our experimental results using SAXS to monitor laser induced thermal expansion in gold nanoparticles solution. We also performed Finite Element Analysis to optimize the trapping performance and stability of droplets ranging from 0.4 mm to 2 mm. Our early x-ray/laser demonstrated the potential of the technique for time-resolved X-ray science.

Bandwidth Dependence of Laser Plasma Instabilities Driven by the Nike KrF Laser

NASA Astrophysics Data System (ADS)

Weaver, J. L.; Oh, J.; Seely, J.; Kehne, D.; Brown, C. M.; Obenschain, S.; Serlin, V.; Schmitt, A. J.; Phillips, L.; Lehmberg, R. H.; McLean, E.; Manka, C.; Feldman, U.

2011-10-01

The Nike krypton-fluoride (KrF) laser at the Naval Research Laboratory operates in the deep UV (248 nm) and employs beam smoothing by induced spatial incoherence (ISI). In the first ISI studies at longer wavelengths (1054 nm and 527 nm) [Obenschain, PRL 62, 768(1989);Mostovych, PRL, 59, 1193(1987); Peyser, Phys. Fluids B 3, 1479(1991)], stimulated Raman scattering, stimulated Brillouin scattering, and the two plasmon decay instability were reduced when wide bandwidth ISI (δν / ν ~ 0.03-0.19%) pulses irradiated targets at moderate to high intensities (1014-1015W/cm2) . Recent Nike work showed that the threshold for quarter critical instabilities increased with the expected wavelength scaling, without accounting for the large bandwidth (δν ~ 1-3 THz). New experiments will compare laser plasma instabilities (LPI) driven by narrower bandwidth pulses to those observed with the standard operation. The bandwidth of KrF lasers can be reduced by adding narrow filters (etalons or gratings) in the initial stages of the laser. This talk will discuss the method used to narrow the output spectrum of Nike, the laser performance for this new operating mode, and target observations of LPI in planar CH targets. Work supported by DoE/NNSA.

Low-loss spinel windows for high-energy lasers

NASA Astrophysics Data System (ADS)

Kim, Woohong; Baker, Colin; Villalobos, Guillermo; Bayya, Shyam; Hunt, Michael; Sadowski, Bryan; Aggarwal, Ishwar; Sanghera, Jasbinder

2014-05-01

Ideal exit aperture windows for high-energy laser (HEL) should possess low absorption and scattering losses and be environmentally rugged and strong in order to protect the laser gain medium without compromising the light propagating through the window. Spinel is an ideal candidate for this application due to its high mechanical strength, high thermal conductivity, and excellent optical transmission between 0.2~5 μm. However, spinel ceramics fabricated with commercial powders often show inhomogeneity and suffer from absorption and scattering caused by various types of intrinsic and extrinsic impurities present in the powders. Here, we report on a convenient and economical powder purification method to significantly lower the absorption loss of transparent spinel ceramics using commercial powders. Acid washing was successfully used to reduce absorption loss in spinel ceramic fabricated using commercial powder from >20,000 ppm/cm down to 75 ppm/cm.

Stimulated Brillouin scattering mirror system, high power laser and laser peening method and system using same

DOEpatents

Dane, C Brent [Livermore, CA; Hackel, Lloyd [Livermore, CA; Harris, Fritz B [Rocklin, CA

2007-04-24

A laser system, such as a master oscillator/power amplifier system, comprises a gain medium and a stimulated Brillouin scattering SBS mirror system. The SBS mirror system includes an in situ filtered SBS medium that comprises a compound having a small negative non-linear index of refraction, such as a perfluoro compound. An SBS relay telescope having a telescope focal point includes a baffle at the telescope focal point which blocks off angle beams. A beam splitter is placed between the SBS mirror system and the SBS relay telescope, directing a fraction of the beam to an alternate beam path for an alignment fiducial. The SBS mirror system has a collimated SBS cell and a focused SBS cell. An adjustable attenuator is placed between the collimated SBS cell and the focused SBS cell, by which pulse width of the reflected beam can be adjusted.

Nitrogen dioxide and kerosene-flame soot calibration of photoacoustic instruments for measurement of light absorption by aerosols

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arnott, W. Patrick; Moosmu''ller, Hans; Walker, John W.

2000-12-01

A nitrogen dioxide calibration method is developed to evaluate the theoretical calibration for a photoacoustic instrument used to measure light absorption by atmospheric aerosols at a laser wavelength of 532.0 nm. This method uses high concentrations of nitrogen dioxide so that both a simple extinction and the photoacoustically obtained absorption measurement may be performed simultaneously. Since Rayleigh scattering is much less than absorption for the gas, the agreement between the extinction and absorption coefficients can be used to evaluate the theoretical calibration, so that the laser gas spectra are not needed. Photoacoustic theory is developed to account for strong absorptionmore » of the laser beam power in passage through the resonator. Findings are that the photoacoustic absorption based on heat-balance theory for the instrument compares well with absorption inferred from the extinction measurement, and that both are well within values represented by published spectra of nitrogen dioxide. Photodissociation of nitrogen dioxide limits the calibration method to wavelengths longer than 398 nm. Extinction and absorption at 532 and 1047 nm were measured for kerosene-flame soot to evaluate the calibration method, and the single scattering albedo was found to be 0.31 and 0.20 at these wavelengths, respectively.« less

One-dimensional transient radiative transfer by lattice Boltzmann method.

PubMed

Zhang, Yong; Yi, Hongliang; Tan, Heping

2013-10-21

The lattice Boltzmann method (LBM) is extended to solve transient radiative transfer in one-dimensional slab containing scattering media subjected to a collimated short laser irradiation. By using a fully implicit backward differencing scheme to discretize the transient term in the radiative transfer equation, a new type of lattice structure is devised. The accuracy and computational efficiency of this algorithm are examined firstly. Afterwards, effects of the medium properties such as the extinction coefficient, the scattering albedo and the anisotropy factor, and the shapes of laser pulse on time-resolved signals of transmittance and reflectance are investigated. Results of the present method are found to compare very well with the data from the literature. For an oblique incidence, the LBM results in this paper are compared with those by Monte Carlo method generated by ourselves. In addition, transient radiative transfer in a two-Layer inhomogeneous media subjected to a short square pulse irradiation is investigated. At last, the LBM is further extended to study the transient radiative transfer in homogeneous medium with a refractive index discontinuity irradiated by the short pulse laser. Several trends on the time-resolved signals different from those for refractive index of 1 (i.e. refractive-index-matched boundary) are observed and analysed.

Design of fiber optic probes for laser light scattering

NASA Technical Reports Server (NTRS)

Dhadwal, Harbans S.; Chu, Benjamin

1989-01-01

A quantitative analysis is presented of the role of optical fibers in laser light scattering. Design of a general fiber optic/microlens probe by means of ray tracing is described. Several different geometries employing an optical fiber of the type used in lightwave communications and a graded index microlens are considered. Experimental results using a nonimaging fiber optic detector probe show that due to geometrical limitations of single mode fibers, a probe using a multimode optical fiber has better performance, for both static and dynamic measurements of the scattered light intensity, compared with a probe using a single mode fiber. Fiber optic detector probes are shown to be more efficient at data collection when compared with conventional approaches to measurements of the scattered laser light. Integration of fiber optic detector probes into a fiber optic spectrometer offers considerable miniaturization of conventional light scattering spectrometers, which can be made arbitrarily small. In addition static and dynamic measurements of scattered light can be made within the scattering cell and consequently very close to the scattering center.

X-ray Thomson scattering measurements from hohlraum-driven spheres on the OMEGA laser [X-ray Thomson scattering measurements from hohlraum targets on the OMEGA laser

DOE PAGES

Saunders, A. M.; Jenei, A.; Doppner, T.; ...

2016-08-30

X-ray Thomson scattering (XRTS) is a powerful diagnostic for probing warm and hot dense matter. We present the design and results of the first XRTS experiments with hohlraum-driven CH 2 targets on the OMEGA laser. X-rays seen directly from the XRTS x-ray source overshadow the elastic scattering signal from the target capsule, but can be controlled in future experiments. From the inelastic scattering signal, an average plasma temperature is inferred that is in reasonable agreement with the temperatures predicted by simulations. Here, knowledge gained in this experiment show a promising future for further XRTS measurements on indirectly driven OMEGA targets.

X-ray Thomson scattering measurements from hohlraum-driven spheres on the OMEGA laser [X-ray Thomson scattering measurements from hohlraum targets on the OMEGA laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saunders, A. M.; Jenei, A.; Doppner, T.

X-ray Thomson scattering (XRTS) is a powerful diagnostic for probing warm and hot dense matter. We present the design and results of the first XRTS experiments with hohlraum-driven CH 2 targets on the OMEGA laser. X-rays seen directly from the XRTS x-ray source overshadow the elastic scattering signal from the target capsule, but can be controlled in future experiments. From the inelastic scattering signal, an average plasma temperature is inferred that is in reasonable agreement with the temperatures predicted by simulations. Here, knowledge gained in this experiment show a promising future for further XRTS measurements on indirectly driven OMEGA targets.

Development of polarization-controlled multi-pass Thomson scattering system in the GAMMA 10 tandem mirror

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoshikawa, M.; Morimoto, M.; Shima, Y.

2012-10-15

In the GAMMA 10 tandem mirror, the typical electron density is comparable to that of the peripheral plasma of torus-type fusion devices. Therefore, an effective method to increase Thomson scattering (TS) signals is required in order to improve signal quality. In GAMMA 10, the yttrium-aluminum-garnet (YAG)-TS system comprises a laser, incident optics, light collection optics, signal detection electronics, and a data recording system. We have been developing a multi-pass TS method for a polarization-based system based on the GAMMA 10 YAG TS. To evaluate the effectiveness of the polarization-based configuration, the multi-pass system was installed in the GAMMA 10 YAG-TSmore » system, which is capable of double-pass scattering. We carried out a Rayleigh scattering experiment and applied this double-pass scattering system to the GAMMA 10 plasma. The integrated scattering signal was made about twice as large by the double-pass system.« less

Fourier-Transform Raman Spectroscopy Of Biological Assemblies

NASA Astrophysics Data System (ADS)

Levin, Ira W.; Lewis, E. Neil

1989-12-01

Although the successful coupling of Raman scattered near-infrared radiation to a Michelson interferometer has recently created an outburst of intense interest in Fourier-transform (FT) Raman spectrometry," extended applications of the technique to macromolecular assemblies of biochemical and biophysical relevance have not progressed as rapidly as studies directed primarily at more conventional chemical characterizations. Since biological materials sampled with visible laser excitation sources typically emit a dominant fluorescence signal originating either from the intrinsic fluorescence of the molecular scatterer or from unrelenting contaminants, the use of near-infrared Nd:YAG laser excitation offers a convenient approach for avoiding this frequently overwhelming effect. In addition, the FT-Raman instrumentation provides a means of eliminating the deleterious resonance and decomposition effects often observed with the more accessible green and blue laser emissions. However, in choosing the incident near-infrared wavelength at, for example, 1064nm, the Raman scattered intensity decreases by factors of eighteen to forty from the Raman emissions induced by the shorter, visible excitations. Depending upon the experiment, this disadvantage is offset by the throughput and multiplex advantages afforded by the interferometric design. Thus, for most chemical systems, near-infrared FT-Raman spectroscopy, clearly provides a means for obtaining vibrational Raman spectra from samples intractable to the use of visible laser sources. In particular, for neat liquids, dilute solutions or polycrystalline materials, the ability to achieve high quality, reproducible spectra is, with moderate experience and perhaps relatively high laser powers, as straightforward as the conventional methods used to obtain Raman spectra with visible excitation and dispersive monochromators. In using near-infrared FT techniques to determine the Raman spectra of biological samples, one encounters new sets of experimental problems that may entail an initial, relatively steep learning curve. These difficulties originate particularly from the fragility of the weakly scattering aggregate paired with the dilute nature of the biochemical or cellular dispersion. Often, the Raman scattered intensity from these samples can be increased by carefully peileting the biological suspension using ultracentrifugation techniques. Since the overtone region of water, the usual medium for biological samples, absorbs radiation from both the Rayleigh signal at the exciting wavelength of the Nd:YAG laser and the longer wavelength Raman scattering from the sample, reproducible temperature measurements and temperature control become significant concerns. In these cases one appeals to internal temperature calibrations, use of deuterium oxide (D20) as a solvent (since absorptions of the laser exciting wavelength and Raman scattered photons are minimized), manipulation of incident laser spot size and the use of fiber optic bundles to carry the exciting and scattered radiation. In the present discussion we briefly cite some of the experimental approaches we have developed and experiences we have encountered in adapting near-infrared FT-Raman spectroscopy to the more challenging biophysical and biochemical systems amenable to vibrational analysis. We emphasize here the determination of the spectra of membrane assemblies and membrane related materials; in particular, we elucidate the interaction of several polyene antibiotics, including amphotericin A, amphotericin B and nystatin, with a model membrane system composed of dipalmitoylphosphatidylcholine bilayers.

Stimulated Electronic X-Ray Raman Scattering

NASA Astrophysics Data System (ADS)

Weninger, Clemens; Purvis, Michael; Ryan, Duncan; London, Richard A.; Bozek, John D.; Bostedt, Christoph; Graf, Alexander; Brown, Gregory; Rocca, Jorge J.; Rohringer, Nina

2013-12-01

We demonstrate strong stimulated inelastic x-ray scattering by resonantly exciting a dense gas target of neon with femtosecond, high-intensity x-ray pulses from an x-ray free-electron laser (XFEL). A small number of lower energy XFEL seed photons drive an avalanche of stimulated resonant inelastic x-ray scattering processes that amplify the Raman scattering signal by several orders of magnitude until it reaches saturation. Despite the large overall spectral width, the internal spiky structure of the XFEL spectrum determines the energy resolution of the scattering process in a statistical sense. This is demonstrated by observing a stochastic line shift of the inelastically scattered x-ray radiation. In conjunction with statistical methods, XFELs can be used for stimulated resonant inelastic x-ray scattering, with spectral resolution smaller than the natural width of the core-excited, intermediate state.

Laser photocoagulation - eye

MedlinePlus

Laser coagulation; Laser eye surgery; Photocoagulation; Laser photocoagulation - diabetic eye disease; Laser photocoagulation - diabetic retinopathy; Focal photocoagulation; Scatter (or pan retinal) photocoagulation; Proliferative ...

Diffraction based method to reconstruct the spectrum of the Thomson scattering x-ray source

NASA Astrophysics Data System (ADS)

Chi, Zhijun; Yan, Lixin; Zhang, Zhen; Zhou, Zheng; Zheng, Lianmin; Wang, Dong; Tian, Qili; Wang, Wei; Nie, Zan; Zhang, Jie; Du, Yingchao; Hua, Jianfei; Shi, Jiaru; Pai, Chihao; Lu, Wei; Huang, Wenhui; Chen, Huaibi; Tang, Chuanxiang

2017-04-01

As Thomson scattering x-ray sources based on the collision of intense laser and relativistic electrons have drawn much attention in various scientific fields, there is an increasing demand for the effective methods to reconstruct the spectrum information of the ultra-short and high-intensity x-ray pulses. In this paper, a precise spectrum measurement method for the Thomson scattering x-ray sources was proposed with the diffraction of a Highly Oriented Pyrolytic Graphite (HOPG) crystal and was demonstrated at the Tsinghua Thomson scattering X-ray source. The x-ray pulse is diffracted by a 15 mm (L) ×15 mm (H)× 1 mm (D) HOPG crystal with 1° mosaic spread. By analyzing the diffraction pattern, both x-ray peak energies and energy spectral bandwidths at different polar angles can be reconstructed, which agree well with the theoretical value and simulation. The higher integral reflectivity of the HOPG crystal makes this method possible for single-shot measurement.

Diffraction based method to reconstruct the spectrum of the Thomson scattering x-ray source.

PubMed

Chi, Zhijun; Yan, Lixin; Zhang, Zhen; Zhou, Zheng; Zheng, Lianmin; Wang, Dong; Tian, Qili; Wang, Wei; Nie, Zan; Zhang, Jie; Du, Yingchao; Hua, Jianfei; Shi, Jiaru; Pai, Chihao; Lu, Wei; Huang, Wenhui; Chen, Huaibi; Tang, Chuanxiang

2017-04-01

As Thomson scattering x-ray sources based on the collision of intense laser and relativistic electrons have drawn much attention in various scientific fields, there is an increasing demand for the effective methods to reconstruct the spectrum information of the ultra-short and high-intensity x-ray pulses. In this paper, a precise spectrum measurement method for the Thomson scattering x-ray sources was proposed with the diffraction of a Highly Oriented Pyrolytic Graphite (HOPG) crystal and was demonstrated at the Tsinghua Thomson scattering X-ray source. The x-ray pulse is diffracted by a 15 mm (L) ×15 mm (H)× 1 mm (D) HOPG crystal with 1° mosaic spread. By analyzing the diffraction pattern, both x-ray peak energies and energy spectral bandwidths at different polar angles can be reconstructed, which agree well with the theoretical value and simulation. The higher integral reflectivity of the HOPG crystal makes this method possible for single-shot measurement.

Interaction of doughnut-shaped laser pulses with glasses

DOE PAGES

Zhukov, Vladimir P.; Rubenchik, Alexander M.; Fedoruk, Mikhail P.; ...

2017-01-26

Non-Gaussian laser beams can open new opportunities for microfabrication, including ultrashort laser direct writing. By using a model based on Maxwell’s equations, we investigate the dynamics of doughnut-shaped laser beams focused inside fused silica glass, in comparison with Gaussian pulses of the same energy. The laser propagation dynamics reveals intriguing features of beam splitting and sudden collapse toward the beam axis, overcoming the intensity clamping effect. The resulting structure of light absorption represents a very hot, hollow nanocylinder, which can lead to an implosion process that brings matter to extreme thermodynamic states. Furthermore, by monitoring the simulations of the lasermore » beam scattering we see a considerable difference in both the blueshift and the angular distribution of scattered light for different laser energies, suggesting that investigations of the spectra of scattered radiation can be used as a diagnostic of laser-produced electron plasmas in transparent materials.« less

Single laser pulse compression via strongly coupled stimulated Brillouin scattering in plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peng, H.; Wu, Z. H.; Zhang, Z. M.

2016-07-15

Laser amplification in plasma, including stimulated Raman scattering amplification and strongly coupled stimulated Brillouin scattering (sc-SBS) amplification, is very promising to generate ultrahigh-power and ultrashort laser pulses. But both are quite complex in experiments: at least three different laser pulses must be prepared; temporal delay and spatial overlap of these three pulses are difficult. We propose a single pulse compression scheme based on sc-SBS in plasma. Only one moderately long laser is applied, the front part of which ionizes the gas to produced plasma, and gets reflected by a plasma mirror at the end of the gas channel. The reflectedmore » front quickly depletes the remaining part of the laser by sc-SBS in the self-similar regime. The output laser is much stronger and shorter. This scheme is at first considered theoretically, then validated by using 1D PIC simulations.« less

Laser Scattering from the Dense Plasma Focus.

DTIC Science & Technology

plasma focus (DPF) illuminated by a pulse of laser light. Scattering was observable from 10 nanoseconds prior to arrival of the collapse on axis and for an additional 50 nanoseconds. The frequency spectrum is markedly asymmetric about the laser frequency, a feature which is inconsistent with spectral expectations based on thermal particle distributions even if particle drifts or waves excitations are included. A model is postulated which attributes the asymmetry to lateral displacement of scattering region from the axis of the focus. Analysis based on this model yields

Blood group typing based on recording the elastic scattering of laser radiation using the method of digital imaging

NASA Astrophysics Data System (ADS)

Dolmashkin, A. A.; Dubrovskii, V. A.; Zabenkov, I. V.

2012-05-01

The possibility is demonstrated to determine the human blood group by recording the scattering of laser radiation with the help of the digital imaging method. It is experimentally shown that the action of a standing ultrasound wave leads to acceleration of the agglutination reaction of red blood cells, to formation of larger immune complexes of red blood cells, and, as a consequence, to acceleration of their sedimentation. In the absence of agglutination of red blood cells the ultrasound does not enhance the relevant processes. This difference in the results of ultrasound action on the mixture of blood and serum allows a method of blood typing to be offered. Theoretical modelling of the technique of the practical blood typing, carried out on the basis of the elastic light scattering theory, agrees well with the experimental results, which made it possible to plan further improvement of the proposed method. The studies of specific features of sedimentation of red blood cells and their immune complexes were aimed at the optimisation of the sample preparation, i.e., at the search for such experimental conditions that provide the maximal resolution of the method and the device for registering the reaction of red blood cells agglutination. The results of the study may be used in designing the instrumentation for blood group assessment in humans.

The interaction of intense subpicosecond laser pulses with underdense plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coverdale, Christine Ann

1995-05-11

Laser-plasma interactions have been of interest for many years not only from a basic physics standpoint, but also for their relevance to numerous applications. Advances in laser technology in recent years have resulted in compact laser systems capable of generating (psec), 10 16 W/cm 2 laser pulses. These lasers have provided a new regime in which to study laser-plasma interactions, a regime characterized by L plasma ≥ 2L Rayleigh > cτ. The goal of this dissertation is to experimentally characterize the interaction of a short pulse, high intensity laser with an underdense plasma (n o ≤ 0.05n cr). Specifically, themore » parametric instability known as stimulated Raman scatter (SRS) is investigated to determine its behavior when driven by a short, intense laser pulse. Both the forward Raman scatter instability and backscattered Raman instability are studied. The coupled partial differential equations which describe the growth of SRS are reviewed and solved for typical experimental laser and plasma parameters. This solution shows the growth of the waves (electron plasma and scattered light) generated via stimulated Raman scatter. The dispersion relation is also derived and solved for experimentally accessible parameters. The solution of the dispersion relation is used to predict where (in k-space) and at what frequency (in ω-space) the instability will grow. Both the nonrelativistic and relativistic regimes of the instability are considered.« less

Rapid Antimicrobial Susceptibility Testing Using Forward Laser Light Scatter Technology

PubMed Central

Clinton, Lani K.; Hewitt, Carolyn; Koyamatsu, Terri; Sun, Yilun; Jamison, Ginger; Perkins, Rosalie; Tang, Li; Pounds, Stanley; Bankowski, Matthew J.

2016-01-01

The delayed reporting of antimicrobial susceptibility testing remains a limiting factor in clinical decision-making in the treatment of bacterial infection. This study evaluates the use of forward laser light scatter (FLLS) to measure bacterial growth for the early determination of antimicrobial susceptibility. Three isolates each (two clinical isolates and one reference strain) of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa were tested in triplicate using two commercial antimicrobial testing systems, the Vitek2 and the MicroScan MIC panel, to challenge the BacterioScan FLLS. The BacterioScan FLLS showed a high degree of categorical concordance with the commercial methods. Pairwise comparison with each commercial system serving as a reference standard showed 88.9% agreement with MicroScan (two minor errors) and 72.2% agreement with Vitek (five minor errors). FLLS using the BacterioScan system shows promise as a novel method for the rapid and accurate determination of antimicrobial susceptibility. PMID:27558176

Molecular characterization of multivalent bioconjugates by size-exclusion chromatography with multiangle laser light scattering.

PubMed

Pollock, Jacob F; Ashton, Randolph S; Rode, Nikhil A; Schaffer, David V; Healy, Kevin E

2012-09-19

The degree of substitution and valency of bioconjugate reaction products are often poorly judged or require multiple time- and product-consuming chemical characterization methods. These aspects become critical when analyzing and optimizing the potency of costly polyvalent bioactive conjugates. In this study, size-exclusion chromatography with multiangle laser light scattering was paired with refractive index detection and ultraviolet spectroscopy (SEC-MALS-RI-UV) to characterize the reaction efficiency, degree of substitution, and valency of the products of conjugation of either peptides or proteins to a biopolymer scaffold, i.e., hyaluronic acid (HyA). Molecular characterization was more complete compared to estimates from a protein quantification assay, and exploitation of this method led to more accurate deduction of the molecular structures of polymer bioconjugates. Information obtained using this technique can improve macromolecular engineering design principles and help to better understand multivalent macromolecular interactions in biological systems.

Molecular characterization of multivalent bioconjugates by size-exclusion chromatography (SEC) with multi-angle laser light scattering (MALS)

PubMed Central

Pollock, Jacob F.; Ashton, Randolph S.; Rode, Nikhil A.; Schaffer, David V.; Healy, Kevin E.

2013-01-01

The degree of substitution and valency of bioconjugate reaction products are often poorly judged or require multiple time- and product- consuming chemical characterization methods. These aspects become critical when analyzing and optimizing the potency of costly polyvalent bioactive conjugates. In this study, size-exclusion chromatography with multi-angle laser light scattering was paired with refractive index detection and ultraviolet spectroscopy (SEC-MALS-RI-UV) to characterize the reaction efficiency, degree of substitution, and valency of the products of conjugation of either peptides or proteins to a biopolymer scaffold, i.e., hyaluronic acid (HyA). Molecular characterization was more complete compared to estimates from a protein quantification assay, and exploitation of this method led to more accurate deduction of the molecular structures of polymer bioconjugates. Information obtained using this technique can improve macromolecular engineering design principles and better understand multivalent macromolecular interactions in biological systems. PMID:22794081

Improved cross-calibration of Thomson scattering and electron cyclotron emission with ECH on DIII-D

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brookman, M. W., E-mail: brookmanmw@fusion.gat.com; Austin, M. E.; McLean, A. G.

2016-11-15

Thomson scattering produces n{sub e} profiles from measurement of scattered laser beam intensity. Rayleigh scattering provides a first calibration of the relation n{sub e} ∝ I{sub TS}, which depends on many factors (e.g., laser alignment and power, optics, and measurement systems). On DIII-D, the n{sub e} calibration is adjusted against an absolute n{sub e} from the density-driven cutoff of the 48 channel 2nd harmonic X-mode electron cyclotron emission system. This method has been used to calibrate Thomson n{sub e} from the edge to near the core (r/a > 0.15). Application of core electron cyclotron heating improves the quality of cutoffmore » and depth of its penetration into the core, and also changes underlying MHD activity, minimizing crashes which confound calibration. Less fueling is needed as “ECH pump-out” generates a plasma ready to take up gas. On removal of gyrotron power, cutoff penetrates into the core as channels fall successively and smoothly into cutoff.« less

Determination of scattering properties and damage thresholds in tissue using ultrafast laser ablation

NASA Astrophysics Data System (ADS)

Martin, Chris; Ben-Yakar, Adela

2016-11-01

Ultrafast laser surgery of tissue requires precise knowledge of the tissue's optical properties to control the extent of subsurface ablation. Here, we present a method to determine the scattering lengths, ℓs, and fluence thresholds, Fth, in multilayered and turbid tissue by finding the input energies required to initiate ablation at various depths in each tissue layer. We validated the method using tissue-mimicking phantoms and applied it to porcine vocal folds, which consist of an epithelial (ep) layer and a superficial lamina propia (SLP) layer. Across five vocal fold samples, we found ℓ=51.0±3.9 μm, F=1.78±0.08 J/cm2, ℓ=26.5±1.6 μm, and F=1.14±0.12 J/cm2. Our method can enable personalized determination of tissue optical properties in a clinical setting, leading to less patient-to-patient variability and more favorable outcomes in operations, such as femto-LASIK surgery.

Ultraviolet Molecular Rayleigh Scattering Used to Measure Velocity in High-Speed Flow

NASA Technical Reports Server (NTRS)

Seasholtz, Richard G.

1997-01-01

Molecular Rayleigh scattering offers a means to measure gas flow parameters including density, temperature, and velocity. No seeding of the flow is necessary. The Rayleigh scattered power is proportional to the gas density, the spectral width is related to the gas temperature, and the shift in the frequency of the spectral peak is proportional to one component of the fluid velocity. Velocity measurements based on Rayleigh scattering are more suitable for high-speed flow, where the bulk fluid velocity is on the order of, or larger than, the molecular thermal velocities. Use of ultraviolet wavelengths for Rayleigh scattering diagnostics is attractive for two reasons. First, the Rayleigh scattering cross section is proportional to the inverse 4th power of the wavelength. And second, the reflectivity of metallic surfaces is generally less than it is at longer wavelengths. This is of particular interest in confined flow situations, such as in small wind tunnels and aircraft engine components, where the stray laser light scattered from the windows and internal surfaces in the test facility limits the application of Rayleigh scattering diagnostics. In this work at the NASA Lewis Research Center, molecular Rayleigh scattering of the 266-nm fourth harmonic of a pulsed, injection seeded Nd:YAG (neodymium:yttriumaluminum- garnet) laser was used to measure velocity in a supersonic free air jet with a 9.3- mm exit diameter. The frequency of the Rayleigh scattered light was analyzed with a planar mirror Fabry-Perot interferometer used in a static imaging mode, with the images recorded on a cooled, high-quantum-efficiency charge-coupled discharge (CCD) camera. In addition, some unshifted light from the same laser pulse was imaged through the interferometer to generate a reference. Data were obtained with single laser pulses at velocities up to Mach 1.3. The measured velocities were in good agreement with velocities calculated from isentropic flow relations. Our conclusion from this study was that ultraviolet Rayleigh scattering is preferable in confined flow situations because of the increase in the ratio of Rayleigh scattering signal to stray laser light. On the other hand, in open flows, such as free jets and larger wind tunnels where stray laser light can be controlled, visible Rayleigh scattering is preferable.

Laser scattering induced holograms in lithium niobate. [observation of diffraction cones

NASA Technical Reports Server (NTRS)

Magnusson, R.; Gaylord, T. K.

1974-01-01

A 3.0-mm thick poled single crystal of lithium niobate doped with 0.1 mole% iron was exposed to a single beam and then to two intersecting beams of an argon ion laser operating at 515-nm wavelength. Laser scattering induced holograms were thus written and analyzed. The presence of diffraction cones was observed and is shown to result from the internally recorded interference pattern resulting from the interference of the original incident laser beam with light scattered from material inhomogeneities. This phenomenon is analyzed using Ewald sphere construction techniques which reveal the geometrical relationships existing for the diffraction cones.

X-ray radiation from nonlinear Thomson scattering of an intense femtosecond laser on relativistic electrons in a helium plasma.

PubMed

Ta Phuoc, K; Rousse, A; Pittman, M; Rousseau, J P; Malka, V; Fritzler, S; Umstadter, D; Hulin, D

2003-11-07

We have generated x-ray radiation from the nonlinear Thomson scattering of a 30 fs/1.5 J laser beam on plasma electrons. A collimated x-ray radiation with a broad continuous spectrum peaked at 0.15 keV with a significant tail up to 2 keV has been observed. These characteristics are found to depend strongly on the laser strength parameter a(0). This radiative process is dominant for a(0) greater than unity at which point the relativistic scattering of the laser light originates from MeV energy electrons inside the plasma.

rotational Raman spectroscopy methods for probing energy thermalisation processes during spin-exchange optical pumping

NASA Astrophysics Data System (ADS)

Newton, Hayley; Walkup, Laura L.; Whiting, Nicholas; West, Linda; Carriere, James; Havermeyer, Frank; Ho, Lawrence; Morris, Peter; Goodson, Boyd M.; Barlow, Michael J.

2014-05-01

Spin-exchange optical pumping (SEOP) has been widely used to produce enhancements in nuclear spin polarisation for hyperpolarised noble gases. However, some key fundamental physical processes underlying SEOP remain poorly understood, particularly in regards to how pump laser energy absorbed during SEOP is thermalised, distributed and dissipated. This study uses in situ ultra-low frequency Raman spectroscopy to probe rotational temperatures of nitrogen buffer gas during optical pumping under conditions of high resonant laser flux and binary Xe/N2 gas mixtures. We compare two methods of collecting the Raman scattering signal from the SEOP cell: a conventional orthogonal arrangement combining intrinsic spatial filtering with the utilisation of the internal baffles of the Raman spectrometer, eliminating probe laser light and Rayleigh scattering, versus a new in-line modular design that uses ultra-narrowband notch filters to remove such unwanted contributions. We report a ~23-fold improvement in detection sensitivity using the in-line module, which leads to faster data acquisition and more accurate real-time monitoring of energy transport processes during optical pumping. The utility of this approach is demonstrated via measurements of the local internal gas temperature (which can greatly exceed the externally measured temperature) as a function of incident laser power and position within the cell.

Microscale Concentration Measurements Using Laser Light Scattering Methods

NASA Technical Reports Server (NTRS)

Niederhaus, Charles; Miller, Fletcher

2004-01-01

The development of lab-on-a-chip devices for microscale biochemical assays has led to the need for microscale concentration measurements of specific analyses. While fluorescence methods are the current choice, this method requires developing fluorophore-tagged conjugates for each analyte of interest. In addition, fluorescent imaging is also a volume-based method, and can be limiting as smaller detection regions are required.

Laser radar studies: A study of the feasibility of remote measurement of atmospheric density and turbidity by means of rotational Raman scattering of laser light

NASA Technical Reports Server (NTRS)

Reiss, N.; Schotland, R. M.

1973-01-01

A remote sensing technique is described which utilizes elastic scattering and rotational Raman scattering of laser light in the atmosphere to obtain soundings of turbidity, transmissivity and density. A scheme is devised whereby, through selective weighting of the rotational Raman lines, the effect of atmospheric temperature structure may be eliminated. The close spectral proximity of the elastic and Raman-scattered signals, combined with the fact that the Raman scattering is quite weak, produces special requirements for the spectroscopic and light-gathering components of a rotational Raman laser radar system. These requirements are investigated. A computation of typical signal-to-noise ratios is made. It is shown that daytime signal-to-noise ratios greater than 10 db are to be expected for observation heights of 5 km and below. For nighttime work, 10 db signal-to-noise ratios are achievable to altitudes as high as 15 km.

Catadioptric optics for laser Doppler velocimeter applications

NASA Technical Reports Server (NTRS)

Dunagan, Stephen E.

1989-01-01

This paper examines the adaptation of low-cost Schmidt-Cassegrain astronomical telescopes to perform the laser-beam-focusing and scattered-light collection tasks associated with dual-beam laser Doppler velocimetry. A generic telescope design is analyzed using ray-tracing methods and Gaussian beam-propagation theory. A straightforward modification procedure to convert from infinite to near unity conjugate-ratio operation with very low residual aberration is identified and tested with a 200-mm-aperture telescope modified for f/10 operation. Performance data for this modified telescope configuration are near the diffraction limit and agree well with predictions.

FIBER AND INTEGRATED OPTICS, LASER APPLICATIONS, AND OTHER PROBLEMS IN QUANTUM ELECTRONICS: Raman scattering spectra recorded in the course of the water-ice phase transition and laser diagnostics of heterophase water systems

NASA Astrophysics Data System (ADS)

Glushkov, S. M.; Panchishin, I. M.; Fadeev, V. V.

1989-04-01

The method of laser Raman spectroscopy was used to study heterophase water systems. The apparatus included an argon laser, an optical multichannel analyzer, and a microcomputer. The temperature dependences of the profiles of the valence (stretching) band in the Raman spectrum of liquid water between + 50 °C and - 7 °C and of polycrystalline ice Ih (from 0 to - 62 °C) were determined, as well as the spectral polarization characteristics of the Raman valence band. A method was developed for the determination of the partial concentrations of the H2O molecules in liquid and solid phases present as a mixture. An analysis was made of the errors of the method and the sources of these errors. Applications of the method to multiparameter problems in more complex water systems (for example, solutions of potassium iodide in water) were considered. Other potential practical applications of the method were discussed.

High flux, narrow bandwidth compton light sources via extended laser-electron interactions

DOEpatents

Barty, V P

2015-01-13

New configurations of lasers and electron beams efficiently and robustly produce high flux beams of bright, tunable, polarized quasi-monoenergetic x-rays and gamma-rays via laser-Compton scattering. Specifically, the use of long-duration, pulsed lasers and closely-spaced, low-charge and low emittance bunches of electron beams increase the spectral flux of the Compton-scattered x-rays and gamma rays, increase efficiency of the laser-electron interaction and significantly reduce the overall complexity of Compton based light sources.

Optical radiation hazards of laser welding processes. Part II: CO2 laser.

PubMed

Rockwell, R J; Moss, C E

1989-08-01

There has been an extensive growth within the last five years in the use of high-powered lasers in various metalworking processes. The two types of lasers used most frequently for laser welding/cutting processes are the Neodymium-yttrium-aluminum-garnet (Nd:YAG) and the carbon dioxide (CO2) systems. When such lasers are operated in an open beam configuration, they are designated as a Class IV laser system. Class IV lasers are high-powered lasers that may present an eye and skin hazard under most common exposure conditions, either directly or when the beam has been diffusely scattered. Significant control measures are required for unenclosed (open beam), Class IV laser systems since workers may be exposed to scattered or reflected beams during the operation, maintenance, and service of these lasers. In addition to ocular and/or skin exposure hazards, such lasers also may present a multitude of nonlaser beam occupational concerns. Radiant energy measurements are reported for both the scattered laser radiation and the plasma-related plume radiations released during typical high-powered CO2 laser-target interactions. In addition, the application of the nominal hazard zone (NHZ) and other control measures also are discussed with special emphasis on Class IV industrial CO2 laser systems.

The application of laser pointers for demonstration experiments in nanotechnology lessons at secondary school level

NASA Astrophysics Data System (ADS)

Markin, Alexey V.; Markina, Natalia E.; Eilks, Ingo

2017-03-01

The article contains description of several demonstration experiments connected with application of light scattering (LS) for investigation of optical properties of nanoparticles solutions. The demonstrations are based on the usage of laser pointers with different wavelengths (405, 532, and 650 nm) for observing of light scattering and absorbance by various nanoparticles (silver, gold, sulfur, and cadmium selenide). These experiments were used during short course for secondary school students ("Introduction to Nanotechnology") and applied as hands-on activities in order to introduce students to methods of investigation of nanostructures. The demonstrations (included to the course) were tested during summer-camp school (in 2015 and 2016) and in club in chemistry (2016) for secondary school students (15-17 years old).

Flow Visualization of Density in a Cryogenic Wind Tunnel Using Planar Rayleigh and Raman Scattering

NASA Technical Reports Server (NTRS)

Herring, Gregory C.; Shirinzadeh, Behrooz

2002-01-01

Using a pulsed Nd:YAG laser (532 nm) and a gated, intensified charge-coupled device, planar Rayleigh and Raman scattering techniques have been used to visualize the unseeded Mach 0.2 flow density in a 0.3-meter transonic cryogenic wind tunnel. Detection limits are determined for density measurements by using both unseeded Rayleigh and Raman (N2 vibrational) methods. Seeding with CO2 improved the Rayleigh flow visualization at temperatures below 150 K. The seeded Rayleigh version was used to demonstrate the observation of transient flow features in a separated boundary layer region, which was excited with an oscillatory jet. Finally, a significant degradation of the laser light sheet, in this cryogenic facility, is discussed.

Laser absorption spectroscopy of oxygen confined in highly porous hollow sphere xerogel.

PubMed

Yang, Lin; Somesfalean, Gabriel; He, Sailing

2014-02-10

An Al2O3 xerogel with a distinctive microstructure is studied for the application of laser absorption spectroscopy of oxygen. The xerogel has an exceptionally high porosity (up to 88%) and a large pore size (up to 3.6 µm). Using the method of gas-in-scattering media absorption spectroscopy (GASMAS), a long optical path length (about 3.5m) and high enhancement factor (over 300 times) are achieved as the result of extremely strong multiple-scattering when the light is transmitted through the air-filled, hollow-sphere alumina xerogel. We investigate how the micro-physical feature influences the optical property. As part of the optical sensing system, the material's gas exchange dynamics are also experimentally studied.

A random Q-switched fiber laser

PubMed Central

Tang, Yulong; Xu, Jianqiu

2015-01-01

Extensive studies have been performed on random lasers in which multiple-scattering feedback is used to generate coherent emission. Q-switching and mode-locking are well-known routes for achieving high peak power output in conventional lasers. However, in random lasers, the ubiquitous random cavities that are formed by multiple scattering inhibit energy storage, making Q-switching impossible. In this paper, widespread Rayleigh scattering arising from the intrinsic micro-scale refractive-index irregularities of fiber cores is used to form random cavities along the fiber. The Q-factor of the cavity is rapidly increased by stimulated Brillouin scattering just after the spontaneous emission is enhanced by random cavity resonances, resulting in random Q-switched pulses with high brightness and high peak power. This report is the first observation of high-brightness random Q-switched laser emission and is expected to stimulate new areas of scientific research and applications, including encryption, remote three-dimensional random imaging and the simulation of stellar lasing. PMID:25797520

Modern methods and systems for precise control of the quality of agricultural and food production

NASA Astrophysics Data System (ADS)

Bednarjevsky, Sergey S.; Veryasov, Yuri V.; Akinina, Evgeniya V.; Smirnov, Gennady I.

1999-01-01

The results on the modeling of non-linear dynamics of strong continuous and impulse radiation in the laser nephelometry of polydisperse biological systems, important from the viewpoint of applications in biotechnologies, are presented. The processes of nonlinear self-action of the laser radiation by the multiple scattering in the disperse biological agro-media are considered. The simplified algorithms of the calculation of the parameters of the biological media under investigation are indicated and the estimates of the errors of the laser-nephelometric measurements are given. The universal high-informative optical analyzers and the standard etalon specimens of agro- objects make the technological foundation of the considered methods and systems.

Effect of void shape in Czochralski-Si wafers on the intensity of laser-scattering

NASA Astrophysics Data System (ADS)

Takahashi, J.; Kawakami, K.; Nakai, K.

2001-06-01

The shape effect of anisotropic-shaped microvoid defects in Czochralski-grown silicon wafers on the intensity of laser scattering has been investigated. The size and shape of the defects were examined by means of transmission electron microscopy. Octahedral voids in conventional (nitrogen-undoped) wafers showed an almost isotropic scattering property under the incident condition of a p-polarization beam. On the other hand, parallelepiped-plate-shaped voids in nitrogen-doped wafers showed an anisotropic scattering property on both p- and s-polarized components of scattered light, depending strongly on the incident laser direction. The measured results were explained not by scattering calculation using Born approximation but by calculation based on Rayleigh scattering. It was found that the s component is explained by an inclination of a dipole moment induced on a defect from the scattering plane. Furthermore, using numerical electromagnetic analysis it was shown that the asymmetric behavior of the s component on the parallelepiped-plate voids is ascribed to the parallelepiped shape effect. These results suggest that correction of the scattering intensity is necessary to evaluate the size and volume of anisotropic-shaped defects from the scattered intensity.

Effects of aggregate morphology and size on laser-induced incandescence and scattering from black carbon (mature soot)

DOE PAGES

Bambha, Ray P.; Michelsen, Hope A.

2015-07-03

We have used a Single-Particle Soot Photometer (SP2) to measure time-resolved laser-induced incandescence (LII) and laser scatter from combustion-generated mature soot with a fractal dimension of 1.88 extracted from a burner. We have also made measurements on restructured mature-soot particles with a fractal dimension of 2.3–2.4. We reproduced the LII and laser-scatter temporal profiles with an energy- and mass-balance model, which accounted for heating of particles passed through a CW-laser beam over laser–particle interaction times of ~10 μs. Furthermore, the results demonstrate a strong influence of aggregate size and morphology on LII and scattering signals. Conductive cooling competes with absorptivemore » heating on these time scales; the effects are reduced with increasing aggregate size and fractal dimension. These effects can lead to a significant delay in the onset of the LII signal and may explain an apparent low bias in the SP2 measurements for small particle sizes, particularly for fresh, mature soot. The results also reveal significant perturbations to the measured scattering signal from LII interference and suggest rapid expansion of the aggregates during sublimation.« less

Multiparameter thermo-mechanical OCT-based characterization of laser-induced cornea reshaping

NASA Astrophysics Data System (ADS)

Zaitsev, Vladimir Yu.; Matveyev, Alexandr L.; Matveev, Lev A.; Gelikonov, Grigory V.; Vitkin, Alex; Omelchenko, Alexander I.; Baum, Olga I.; Shabanov, Dmitry V.; Sovetsky, Alexander A.; Sobol, Emil N.

2017-02-01

Phase-sensitive optical coherence tomography (OCT) is used for visualizing dynamic and cumulative strains and corneashape changes during laser-produced tissue heating. Such non-destructive (non-ablative) cornea reshaping can be used as a basis of emerging technologies of laser vision correction. In experiments with cartilaginous samples, polyacrilamide phantoms and excised rabbit eyes we demonstrate ability of the developed OCT system to simultaneously characterize transient and cumulated strain distributions, surface displacements, scattering tissue properties and possibility of temperature estimation via thermal-expansion measurements. The proposed approach can be implemented in perspective real-time OCT systems for ensuring safety of new methods of laser reshaping of cornea.

The improved z-scan technique: potentialities of the additional right-angle scattering channel and the input polarization control

NASA Astrophysics Data System (ADS)

Volchkov, S. S.; Yuvchenko, S. A.; Zimnyakov, D. A.

2018-04-01

The theoretical possibility of retrieving the additional information on the dielectric properties of the nanoparticles material by single scattering in suspensions was studied. We have demonstrated a method of recreating the dielectric function of the material in the fundamental absorption band using the closed aperture z-scanning with the simultaneous Rayleigh scattering intensity measurements and the polarization control of an input laser beam. A possibility to recreate the form factor of the non-spherical particles or anisotropic nonlinear sensitivity for the sphere-like particles was also observed.

Measurement and analysis of aircraft and vehicle LRCS in outfield test

NASA Astrophysics Data System (ADS)

Cao, Chang-Qing; Zeng, Xiao-dong; Fan, Zhao-jin; Feng, Zhe-jun; Lai, Zhi

2015-04-01

The measurement of aircraft and vehicle Laser Radar Cross Section (LRCS) is of crucial importance for the detection system evaluation and the characteristic research of the laser scattering. A brief introduction of the measuring theory of the laser scattering from the full-scale aircraft and vehicle targets is presented in this paper. By analyzing the measuring condition in outfield test, the laser systems and test steps are designed for full-scale aircraft and vehicle LRCS and verified by the experiment in laboratory. The processing data error 7% below is obtained of the laser radar cross section by using Gaussian compensation and elimination of sky background for original test data. The study of measurement and analysis proves that the proposed method is effective and correct to get laser radar cross section data in outfield test. The objectives of this study were: (1) to develop structural concepts for different LRCS fuselage configurations constructed of conventional materials; (2) to compare these findings with those of aircrafts or vehicles; (3) to assess the application of advanced materials for each configuration; (4) to conduct an analytical investigation of the aerodynamic loads, vertical drag and mission performance of different LRCS configurations; and (5) to compare these findings with those of the aircrafts or vehicles.

Bioaerosol detection and classification using dual excitation wavelength laser-induced fluorescence

NASA Astrophysics Data System (ADS)

Jonsson, Per; Wästerby, Pär.; Gradmark, Per-Åke; Hedborg, Julia; Larsson, Anders; Landström, Lars

2015-05-01

We present results obtained by a detection system designed to measure laser-induced fluorescence from individual aerosol particles using dual excitation wavelengths. The aerosol is sampled from ambient air and via a 1 mm diameter nozzle, surrounded by a sheath air flow, confined into a particle beam. A continuous wave blue laser at 404 nm is focused on the aerosol beam and two photomultiplier tubes monitor the presence of individual particles by simultaneous measuring the scattered light and any induced fluorescence. When a particle is present in the detection volume, a laser pulse is triggered from an ultraviolet laser at 263 nm and the corresponding fluorescence spectrum is acquired with a spectrometer based on a diffraction grating and a 32 channel photomultiplier tube array with single-photon sensitivity. The spectrometer measures the fluorescence spectra in the wavelength region from 250 to 800 nm. In the present report, data were measured on different monodisperse reference aerosols, simulants of biological warfare agents, and different interference aerosol particles, e.g. pollen. In the analysis of the experimental data, i.e., the time-resolved scattered and fluorescence signals from 404 nm c.w. light excitation and the fluorescence spectra obtained by a pulsed 263 nm laser source, we use multivariate data analysis methods to classify each individual aerosol particle.

Measurement of xenon plasma properties in an ion thruster using laser Thomson scattering technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yamamoto, N.; Tomita, K.; Sugita, K.

2012-07-15

This paper reports on the development of a method for measuring xenon plasma properties using the laser Thomson scattering technique, for application to ion engine system design. The thresholds of photo-ionization of xenon plasma were investigated and the number density of metastable atoms, which are photo-ionized by a probe laser, was measured using laser absorption spectroscopy, for several conditions. The measured threshold energy of the probe laser using a plano-convex lens with a focal length of 200 mm was 150 mJ for a xenon mass flow rate of 20 {mu}g/s and incident microwave power of 6 W; the probe lasermore » energy was therefore set as 80 mJ. Electron number density was found to be (6.2 {+-} 0.4) Multiplication-Sign 10{sup 17} m{sup -3} and electron temperature was found to be 2.2 {+-} 0.4 eV at a xenon mass flow rate of 20 {mu}g/s and incident microwave power of 6 W. The threshold of the probe laser intensity against photo-ionization in a miniature xenon ion thruster is almost constant for various mass flow rates, since the ratio of population of the metastable atoms to the electron number density is little changed.« less

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: On the possibility of studying the temporal evolution of a surface relief directly during exposure to high-power radiation

NASA Astrophysics Data System (ADS)

Abramov, D. V.; Arakelyan, S. M.; Galkin, A. F.; Klimovskii, Ivan I.; Kucherik, A. O.; Prokoshev, V. G.

2006-06-01

The video image of the graphite surface exposed to focused laser radiation is obtained with the help of a laser monitor. A bright ring moving over the heated surface was observed. A method for reconstructing the surface relief from the video image is proposed and realised. The method is based on the measurement of the angular distribution of the light intensity scattered by the graphite sample surface. The surface relief of the graphite sample changing in time is reconstructed. The relative change in the relief height during laser excitation is measured. The statistical characteristics of the reconstructed graphite surface shape and their variation during laser irradiation are studied. It is found that a circular convexity appears within the bright ring. The formation mechanism of this convexity requires further investigations.

Effect of collisions on amplification of laser beams by Brillouin scattering in plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Humphrey, K. A.; Speirs, D. C.; Trines, R. M. G. M.

2013-10-15

We report on particle in cell simulations of energy transfer between a laser pump beam and a counter-propagating seed beam using the Brillouin scattering process in uniform plasma including collisions. The results presented show that the ion acoustic waves excited through naturally occurring Brillouin scattering of the pump field are preferentially damped without affecting the driven Brillouin scattering process resulting from the beating of the pump and seed fields together. We find that collisions, including the effects of Landau damping, allow for a more efficient transfer of energy between the laser beams, and a significant reduction in the amount ofmore » seed pre-pulse produced.« less

Microcavity Enhanced Raman Scattering

NASA Astrophysics Data System (ADS)

Petrak, Benjamin J.

Raman scattering can accurately identify molecules by their intrinsic vibrational frequencies, but its notoriously weak scattering efficiency for gases presents a major obstacle to its practical application in gas sensing and analysis. This work explores the use of high finesse (≈50 000) Fabry-Perot microcavities as a means to enhance Raman scattering from gases. A recently demonstrated laser ablation method, which carves out a micromirror template on fused silica--either on a fiber tip or bulk substrates-- was implemented, characterized, and optimized to fabricate concave micromirror templates ˜10 mum diameter and radius of curvature. The fabricated templates were coated with a high-reflectivity dielectric coating by ion-beam sputtering and were assembled into microcavities ˜10 mum long and with a mode volume ˜100 mum 3. A novel gas sensing technique that we refer to as Purcell enhanced Raman scattering (PERS) was demonstrated using the assembled microcavities. PERS works by enhancing the pump laser's intensity through resonant recirculation at one longitudinal mode, while simultaneously, at a second mode at the Stokes frequency, the Purcell effect increases the rate of spontaneous Raman scattering by a change to the intra-cavity photon density of states. PERS was shown to enhance the rate of spontaneous Raman scattering by a factor of 107 compared to the same volume of sample gas in free space scattered into the same solid angle subtended by the cavity. PERS was also shown capable of resolving several Raman bands from different isotopes of CO2 gas for application to isotopic analysis. Finally, the use of the microcavity to enhance coherent anti-Stokes Raman scattering (CARS) from CO2 gas was demonstrated.

Surface intervalley scattering on GaAs(110): Direct observation with picosecond laser photoemission

NASA Astrophysics Data System (ADS)

Haight, R.; Silberman, J. A.

1989-02-01

Angle-resolved laser photoemission investigations of the laser excited GaAs(110) surface have revealed a previously unobserved valley of the C3 unoccupied surface band whose minimum is at X¯ in the surface Brillouin zone. Electron population in this valley increases only as a result of scattering from the directly photoexcited valley at Γ¯. With high momentum resolution, we have isolated the dynamic electron population changes at both Γ¯ and X¯ and deduced the scattering time between the two valleys.

Simple scattering analysis and simulation of optical components created by additive manufacturing

NASA Astrophysics Data System (ADS)

Rank, M.; Horsak, A.; Heinrich, A.

2017-10-01

Additive manufacturing of optical elements is known but still new to the field of optical fabrication. In 3D printers, the parts are deposited layer-by-layer approximating the shape defined in optics design enabling new shapes, which cannot be manufactured using conventional methods. However, the layered structure also causes surface roughness and subsurface scattering, which decrease the quality of optical elements. Illuminating a flat sample with a laser beam, different light distributions are generated on a screen depending on the printing orientation of the sample. Whereas the laser beam is mainly diffused by the samples, a line shaped light distribution can be achieved for a special case in which the laser light goes parallel to the layer structure. These optical effects of 3D printed parts are analyzed using a goniometric setup and fed back into the optics simulation with the goal to improve the design considering the characteristics of the real sample. For a detailed look on the effect, the total scattering is split up into surface contributions and subsurface scattering using index matching techniques to isolate the effects from each other. For an index matched sample with negligible surface effects the line shaped distribution turns into a diffraction pattern which corresponds to the layer thickness of the printer. Finally, an optic simulation with the scattering data is set up for a simple curved sample. The light distribution measured with a robot-based goniophotometer differs from the simulation, because the curvature is approximated by the layer structure. This makes additional analysis necessary.

Optimizing laser crater enhanced Raman scattering spectroscopy

NASA Astrophysics Data System (ADS)

Lednev, V. N.; Sdvizhenskii, P. A.; Grishin, M. Ya.; Fedorov, A. N.; Khokhlova, O. V.; Oshurko, V. B.; Pershin, S. M.

2018-05-01

The laser crater enhanced Raman scattering (LCERS) spectroscopy technique has been systematically studied for chosen sampling strategy and influence of powder material properties on spectra intensity enhancement. The same nanosecond pulsed solid state Nd:YAG laser (532 nm, 10 ns, 0.1-1.5 mJ/pulse) was used for laser crater production and Raman scattering experiments for L-aspartic acid powder. Increased sampling area inside crater cavity is the key factor for Raman signal improvement for the LCERS technique, thus Raman signal enhancement was studied as a function of numerous experimental parameters including lens-to-sample distance, wavelength (532 and 1064 nm) and laser pulse energy utilized for crater production. Combining laser pulses of 1064 and 532 nm wavelengths for crater ablation was shown to be an effective way for additional LCERS signal improvement. Powder material properties (particle size distribution, powder compactness) were demonstrated to affect LCERS measurements with better results achieved for smaller particles and lower compactness.

Confocal detection of Rayleigh scattering for residual stress measurement in chemically tempered glass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hödemann, S., E-mail: siim.hodemann@ut.ee; Möls, P.; Kiisk, V.

2015-12-28

A new optical method is presented for evaluation of the stress profile in chemically tempered (chemically strengthened) glass based on confocal detection of scattered laser beam. Theoretically, a lateral resolution of 0.2 μm and a depth resolution of 0.6 μm could be achieved by using a confocal microscope with high-NA immersion objective. The stress profile in the 250 μm thick surface layer of chemically tempered lithium aluminosilicate glass was measured with a high spatial resolution to illustrate the capability of the method. The confocal method is validated using transmission photoelastic and Na{sup +} ion concentration profile measurement. Compositional influence on the stress-optic coefficientmore » is calculated and discussed. Our method opens up new possibilities for three-dimensional scattered light tomography of mechanical imaging in birefringent materials.« less

Z-pinch Plasma Temperature and Implosion Velocity from Laboratory Plasma Jets using Thomson Scattering

NASA Astrophysics Data System (ADS)

Banasek, Jacob; Byvank, Tom; Kusse, Bruce; Hammer, David

2016-10-01

We discuss the use of collective Thomson scattering to determine the implosion velocity and other properties of laboratory plasma jets. The plasma jet is created using a 1 MA pulsed power machine with a 15 μm Al radial foil load. The Thomson scattering laser has a maximum energy of 10 J at 526.5 nm with a pulse duration of 3 ns. Using a time gated ICCD camera and spectrometer system we are able to record the scattered spectrum from 9 or 18 regions along the laser path with sub-mm spatial resolution. Collecting scattered radiation from the same area at two different angles simultaneously enables determination of both the radial and azimuthal velocities. The scattered spectrum for non-magnetized jets indicates a radial implosion velocity of 27 km/s into the jets. A determination of ion and electron temperatures from the scattered spectrum is in progress. Comparing results using a laser energy of 10 J and 1 J shows noticeable effects on plasma jet properties when using 10 J. Therefore the lower laser energy must be used to determine the plasma properties. This research is supported by the NNSA Stewardship Sciences Academic Programs under DOE Cooperative Agreement DE-NA0001836.

Spatial Frequency Domain Imaging of Port Wine Stain Biochemical Composition in Response to Laser Therapy: A Pilot Study

PubMed Central

Mazhar, Amaan; Sharif, Seyed A.; Cuccia, J. David; Nelson, J. Stuart; Kelly, Kristen M.; Durkin, Anthony J.

2012-01-01

Background and Objective Objective methods to assess port wine stain (PWS) response to laser treatment have been the subject of various research efforts for several years. Herein, we present a pilot study using a newly developed, light emitting diode (LED) based spatial frequency domain imaging (SFDI) device to record quantitatively biochemical compositional changes in PWS after laser therapy. Study Design/Patients and Methods A SFDI system was used to image before, and after, five PWS treatment sessions [n = 4 subjects (one subject was imaged before and after two consecutive laser treatments)]. SFDI derived wide-field optical properties (absorption and scattering) and tissue chromophore concentrations including oxy-hemoglobin (ctO2Hb), deoxy-hemoglobin (ctHHb), total hemoglobin (ctTHb), and tissue oxygen saturation (stO2) are presented for skin imaged prior to and immediately after laser treatment. The SFDI derived images were analyzed by comparing the above measurements in PWS to those of normal skin and tracking changes immediately after laser exposure. Results Elevated oxy-hemoglobin (>20%) and tissue oxygen saturation (>5%) were measured in all PWS lesions and compared to values for normal skin prior to treatment. Laser treatment resulted in an increase in deoxy-hemoglobin (>100%), decrease in tissue oxygen saturation (>10%), and reduced scattering (>15%) in all PWS lesions. One subject was followed before and after two consecutive laser treatments and the overall improvement in PWS lesion blanching was quantitatively assessed by measuring a 45% decrease in dermal blood volume. Conclusion SFDI is a rapid non-contact wide-field optical technique that shows potential as an imaging device that can be used to quantify biochemical compositional changes in PWS after laser therapy. Future work will investigate the potential of SFDI to provide intra-operative guidance for laser therapy of PWS lesions on an individual patient basis. PMID:22911574

R-on-1 automatic mapping: A new tool for laser damage testing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hue, J.; Garrec, P.; Dijon, J.

1996-12-31

Laser damage threshold measurement is statistical in nature. For a commercial qualification or for a user, the threshold determined by the weakest point is a satisfactory characterization. When a new coating is designed, threshold mapping is very useful. It enables the technology to be improved and followed more accurately. Different statistical parameters such as the minimum, maximum, average, and standard deviation of the damage threshold as well as spatial parameters such as the threshold uniformity of the coating can be determined. Therefore, in order to achieve a mapping, all the tested sites should give data. This is the major interestmore » of the R-on-1 test in spite of the fact that the laser damage threshold obtained by this method may be different from the 1-on-1 test (smaller or greater). Moreover, on the damage laser test facility, the beam size is smaller (diameters of a few hundred micrometers) than the characteristic sizes of the components in use (diameters of several centimeters up to one meter). Hence, a laser damage threshold mapping appears very interesting, especially for applications linked to large optical components like the Megajoule project or the National Ignition Facility (N.I.F). On the test bench used, damage detection with a Nomarski microscope and scattered light measurement are almost equivalent. Therefore, it becomes possible to automatically detect on line the first defects induced by YAG irradiation. Scattered light mappings and laser damage threshold mappings can therefore be achieved using a X-Y automatic stage (where the test sample is located). The major difficulties due to the automatic capabilities are shown. These characterizations are illustrated at 355 nm. The numerous experiments performed show different kinds of scattering curves, which are discussed in relation with the damage mechanisms.« less

Measurement of optical scattered power from laser-induced shallow pits on silica

DOE PAGES

Feigenbaum, Eyal; Nielsen, Norman; Matthews, Manyalibo J.

2015-10-01

We describe a model for far-field scattered power and irradiance by a silica glass slab with a shallow-pitted exit surface and is experimentally validated. The comparison to the model is performed using a precisely micromachined ensemble of ~11 μm wide laser ablated shallow pits producing 1% of the incident beam scatter in a 10 mrad angle. This series of samples with damage initiations and laser-induced shallow pits resulting from 351 nm, 5 ns pulsed laser cleaning of metal microparticles at different fluences between 2 J/cm 2 and 11 J/cm 2 are characterized as well and found in good agreement withmore » model predictions.« less

Airborne Polarized Lidar Detection of Scattering Layers in the Ocean

NASA Astrophysics Data System (ADS)

Vasilkov, Alexander P.; Goldin, Yury A.; Gureev, Boris A.; Hoge, Frank E.; Swift, Robert N.; Wright, C. Wayne

2001-08-01

A polarized lidar technique based on measurements of waveforms of the two orthogonal-polarized components of the backscattered light pulse is proposed to retrieve vertical profiles of the seawater scattering coefficient. The physical rationale for the polarized technique is that depolarization of backscattered light originating from a linearly polarized laser beam is caused largely by multiple small-angle scattering from particulate matter in seawater. The magnitude of the small-angle scattering is determined by the scattering coefficient. Therefore information on the vertical distribution of the scattering coefficient can be derived potentially from measurements of the timedepth dependence of depolarization in the backscattered laser pulse. The polarized technique was verified by field measurements conducted in the Middle Atlantic Bight of the western North Atlantic Ocean that were supported by in situ measurements of the beam attenuation coefficient. The airborne polarized lidar measured the timedepth dependence of the backscattered laser pulse in two orthogonal-polarized components. Vertical profiles of the scattering coefficient retrieved from the timedepth depolarization of the backscattered laser pulse were compared with measured profiles of the beam attenuation coefficient. The comparison showed that retrieved profiles of the scattering coefficient clearly reproduce the main features of the measured profiles of the beam attenuation coefficient. Underwater scattering layers were detected at depths of 2025 m in turbid coastal waters. The improvement in dynamic range afforded by the polarized lidar technique offers a strong potential benefit for airborne lidar bathymetric applications.

Scaling EUV and X-ray Thomson sources to optical free-electron laser operation with traveling-wave Thomson scattering (Conference Presentation)

NASA Astrophysics Data System (ADS)

Steiniger, Klaus; Albach, Daniel; Debus, Alexander; Loeser, Markus; Pausch, Richard; Roeser, Fabian; Schramm, Ulrich; Siebold, Matthias; Bussmann, Michael

2017-05-01

Traveling-Wave Thomson-Scattering (TWTS) allows for the realization of optical free-electron lasers (OFELs) from the interaction of short, high-power laser pulses with brilliant relativistic electron bunches. The laser field provides the optical undulator which is traversed by the electrons. In order to achieve coherent amplification of radiation through electron microbunching the interaction between electrons and laser must be maintained over hundreds to thousands of undulator periods. Traveling-Wave Thomson-Scattering is the only scattering geometry so far allowing for the realization of optical undulators of this length which is at the same time scalable from extreme ultraviolet to X-ray photon energies. TWTS is also applicable for the realization of incoherent high peak brightness hard X-ray to gamma-ray sources which can provide orders of magnitude higher photon output than classic head-on Thomson sources. In contrast to head-on Thomson sources TWTS employs a side-scattering geometry where laser and electron propagation direction of motion enclose an angle. Tilting the laser pulse front with respect to the wave front by half of this interaction angle optimizes electron and laser pulse overlap. In the side-scattering geometry the tilt of the pulse-front compensates the spatial offset between electrons and laser pulse-front which would be present otherwise for an electron bunch far from the interaction point where it overlaps with the laser pulse center. Thus the laser pulse-front tilt ensures continuous overlap between laser pulse and electrons while these traverse the laser pulse cross-sectional area. This allows to control the interaction distance in TWTS by the laser pulse width rather than laser pulse duration as is the case for head-on Thomson scattering. Utilizing petawatt class laser pulses with millimeter to centimeter scale width allows for the realization of compact optical undulators with thousands of periods. When laser pulses for TWTS are prepared, care has to be taken of laser dispersion. Especially for scenarios featuring interaction angles of several ten to over one hundred degree the angular dispersion originating from laser pulse-front tilt can significantly prolong the pulse duration during the interaction which leads to a decrease in optical undulator amplitude and eventually terminates the interaction long before the target interaction distance is reached. In the talk it is shown how a pair of two gratings can be used to first generate the pulse-front tilt and second control and compensate dispersion during the interaction by utilizing the plane of optimum compression. Furthermore an experimental setup strategy is presented allowing for an interaction outside the laser pulse focus. This is a necessity for TWTS OFELs requiring focusing to reach optical undulator strengths on the order of unity since the centimeter scale laser pulse width at the interaction point result in turn in Rayleigh lengths on the order of one hundred meter and thus in laser focusing distances of several hundred meter. The talk shows how an out-of-focus interaction geometry utilizing strong focusing of the incident laser pulse needs to be designed in order to regain compactness by reducing the focusing distance by one to two orders of magnitude.

Time of flight imaging through scattering environments (Conference Presentation)

NASA Astrophysics Data System (ADS)

Le, Toan H.; Breitbach, Eric C.; Jackson, Jonathan A.; Velten, Andreas

2017-02-01

Light scattering is a primary obstacle to imaging in many environments. On small scales in biomedical microscopy and diffuse tomography scenarios scattering is caused by tissue. On larger scales scattering from dust and fog provide challenges to vision systems for self driving cars and naval remote imaging systems. We are developing scale models for scattering environments and investigation methods for improved imaging particularly using time of flight transient information. With the emergence of Single Photon Avalanche Diode detectors and fast semiconductor lasers, illumination and capture on picosecond timescales are becoming possible in inexpensive, compact, and robust devices. This opens up opportunities for new computational imaging techniques that make use of photon time of flight. Time of flight or range information is used in remote imaging scenarios in gated viewing and in biomedical imaging in time resolved diffuse tomography. In addition spatial filtering is popular in biomedical scenarios with structured illumination and confocal microscopy. We are presenting a combination analytical, computational, and experimental models that allow us develop and test imaging methods across scattering scenarios and scales. This framework will be used for proof of concept experiments to evaluate new computational imaging methods.

Visualization of the 3-dimensional flow around a model with the aid of a laser knife

NASA Technical Reports Server (NTRS)

Borovoy, V. Y.; Ivanov, V. V.; Orlov, A. A.; Kharchenko, V. N.

1984-01-01

A method for visualizing the three-dimensional flow around models of various shapes in a wind tunnel at a Mach number of 5 is described. A laser provides a planar light flux such that any plane through the model can be selectively illuminated. The shape of shock waves and separation regions is then determined by the intensity of light scattered by soot particles in the flow.

Design of practical alignment device in KSTAR Thomson diagnostic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, J. H., E-mail: jhlee@nfri.re.kr; University of Science and Technology; Lee, S. H.

2016-11-15

The precise alignment of the laser path and collection optics in Thomson scattering measurements is essential for accurately determining electron temperature and density in tokamak experiments. For the last five years, during the development stage, the KSTAR tokamak’s Thomson diagnostic system has had alignment fibers installed in its optical collection modules, but these lacked a proper alignment detection system. In order to address these difficulties, an alignment verifying detection device between lasers and an object field of collection optics is developed. The alignment detection device utilizes two types of filters: a narrow laser band wavelength for laser, and a broadmore » wavelength filter for Thomson scattering signal. Four such alignment detection devices have been successfully developed for the KSTAR Thomson scattering system in this year, and these will be tested in KSTAR experiments in 2016. In this paper, we present the newly developed alignment detection device for KSTAR’s Thomson scattering diagnostics.« less

Design of practical alignment device in KSTAR Thomson diagnostic.

PubMed

Lee, J H; Lee, S H; Yamada, I

2016-11-01

The precise alignment of the laser path and collection optics in Thomson scattering measurements is essential for accurately determining electron temperature and density in tokamak experiments. For the last five years, during the development stage, the KSTAR tokamak's Thomson diagnostic system has had alignment fibers installed in its optical collection modules, but these lacked a proper alignment detection system. In order to address these difficulties, an alignment verifying detection device between lasers and an object field of collection optics is developed. The alignment detection device utilizes two types of filters: a narrow laser band wavelength for laser, and a broad wavelength filter for Thomson scattering signal. Four such alignment detection devices have been successfully developed for the KSTAR Thomson scattering system in this year, and these will be tested in KSTAR experiments in 2016. In this paper, we present the newly developed alignment detection device for KSTAR's Thomson scattering diagnostics.

Laser-induced free-free transitions in elastic electron scattering from CO2

NASA Astrophysics Data System (ADS)

Musa, Mohamed; MacDonald, Amy; Tidswell, Lisa; Holmes, Jim; St. Francis Xavier Laser Scattering Lab Team

2011-03-01

This report presents measurements of laser-induced free-free transitions of electrons scattered from CO2 molecules in the ground electronic state at incident electron energies of 3.8 and 5.8 eV under pulsed CO2 laser field. The differential cross section of free-free transitions involving absorption and emission of up to two photons were measured at various scattering angles with the polarization of the laser either parallel with or perpendicular to the the momentum change vector of the scattered electrons. The results of the parallel geometry are found to be in qualitative agreement with the predictions of the Kroll-Watson approximation within the experimental uncertainty whereas those of the perpendicular geometry show marked discrepancy with the Kroll-Watson predictions. This work was supported by the Natural Sciences and Engineering Research Council of Canada and the St. Francis Xavier University Council for Research.

Polar nephelometer for atmospheric particulate studies

NASA Technical Reports Server (NTRS)

Hansen, M. Z.; Evans, W. H.

1980-01-01

A polar nephelometer for use in studying atmospheric aerosols was developed. The nephelometer detects molecular scatter from air and measures scattering from very clean air using pure molecular scattering for calibration. A compact system using a folded light path with an air cooled argon laser for the light source was designed. A small, sensitive detector unit permits easy angular rotation for changing the scattering angle. A narrow detector field of view of + or - 1/4 degree of scattering along with a single wavelength of incident light is used to minimize uncertainties in the scattering theory. The system is automated for data acquisition of the scattering matrix elements over an angular range from 2 degrees to 178 degrees of scattering. Both laser output and detector sensitivity are monitored to normalize the measured light scattering.

Subsurface Scattered Photons: Friend or Foe? Improving visible light laser altimeter elevation estimates, and measuring surface properties using subsurface scattered photons

NASA Astrophysics Data System (ADS)

Greeley, A.; Kurtz, N. T.; Neumann, T.; Cook, W. B.; Markus, T.

2016-12-01

Photon counting laser altimeters such as MABEL (Multiple Altimeter Beam Experimental Lidar) - a single photon counting simulator for ATLAS (Advanced Topographical Laser Altimeter System) - use individual photons with visible wavelengths to measure their range to target surfaces. ATLAS, the sole instrument on NASA's upcoming ICESat-2 mission, will provide scientists a view of Earth's ice sheets, glaciers, and sea ice with unprecedented detail. Precise calibration of these instruments is needed to understand rapidly changing parameters such as sea ice freeboard, and to measure optical properties of surfaces like snow covered ice sheets using subsurface scattered photons. Photons that travel through snow, ice, or water before scattering back to an altimeter receiving system travel farther than photons taking the shortest path between the observatory and the target of interest. These delayed photons produce a negative elevation bias relative to photons scattered directly off these surfaces. We use laboratory measurements of snow surfaces using a flight-tested laser altimeter (MABEL), and Monte Carlo simulations of backscattered photons from snow to estimate elevation biases from subsurface scattered photons. We also use these techniques to demonstrate the ability to retrieve snow surface properties like snow grain size.

Laser Technology in Aerodynamic Measurements.

DTIC Science & Technology

holography; Laser beam probing for aerodynamic flow field analysis; The laser in high speed photography; Laser metrology; Application of duel scatter laser doppler velocimeters for wind tunnel measurements.

Nearly-octave wavelength tuning of a continuous wave fiber laser

PubMed Central

Zhang, Lei; Jiang, Huawei; Yang, Xuezong; Pan, Weiwei; Cui, Shuzhen; Feng, Yan

2017-01-01

The wavelength tunability of conventional fiber lasers are limited by the bandwidth of gain spectrum and the tunability of feedback mechanism. Here a fiber laser which is continuously tunable from 1 to 1.9 μm is reported. It is a random distributed feedback Raman fiber laser, pumped by a tunable Yb doped fiber laser. The ultra-wide wavelength tunability is enabled by the unique property of random distributed feedback Raman fiber laser that both stimulated Raman scattering gain and Rayleigh scattering feedback are available at any wavelength. The dispersion property of the gain fiber is used to control the spectral purity of the laser output. PMID:28198414

Rugged TDLAS system for High Energy Laser atmospheric propagation characterization

NASA Astrophysics Data System (ADS)

Perram, Glen; Rice, Christopher

2008-10-01

An active remote sensing instrument for the characterization of atmospheric absorption, scattering, and scintillation at several key high energy laser wavelengths is in development. The instrument is based on narrow band tunable diode lasers fiber coupled to a 12'' Ritchey-Chretien transmit telescope and a second receive telescope with visible or near infrared imager. For example, tunable diode lasers have been used to obtain absorption spectra in the laboratory for the Cs D2 lines near 852 nm and the oxygen X-b lines near 760 nm, key to the Diode Pumped Alkali Laser (DPAL) concept. Absorbencies of less than 0.5% are observable. Applications will be assessed including effects to HEL atmospheric propagation from molecular and aerosol absorption and scattering, Cn2 estimation from atmospheric turbulence, hazardous chemical emission detection, and laser communication interception from side scattering. The system will soon be deployed to a military laser test range to characterize path lengths of greater than 1 km.

Electron-hydrogen collisions in a laser field. (Reannouncement with new availability information)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, P.H.; Flannery, M.R.

1991-12-31

The Floquet treatment has already been successfully employed (Chu, Potvliege and Shakeshaft) in calculations of laser-induced multiphoton ionizations, where it provides dressed states for an atom in a laser field. The (perturbative) dressing of target states can have important consequences in laser-assisted scattering was illustrated by Byron and Joachain. These dressed states are useful, not only for laser-induced phenomena, but also as a collisional basis set for laser-assisted collisions. In this role they are in fact very appealing, since the Floquet treatment naturally lends itself to a time-independent analysis, and hence are compatible with present field-free scattering theories. Despite themore » apparent applicability of this approach, work along these lines has only just recently appeared (Sharma and Mohan, Smith and Flannery, Burke et al). Byron and Joachain have illustrated that perturbative dressing of the target states can have important consequences in laser-assisted scattering. Floquet dressing however provides a more complete description (Smith and Flannery).« less

Laser Speckle Imaging of Blood Flow Beneath Static Scattering Media

NASA Astrophysics Data System (ADS)

Regan, Caitlin Anderson

Laser speckle imaging (LSI) is a wide-field optical imaging technique that provides information about the movement of scattering particles in biological samples. LSI is used to create maps of relative blood flow and perfusion in samples such as the skin, brain, teeth, gingiva, and other biological tissues. The presence of static, or non-moving, optical scatterers affects the ability of LSI to provide true quantitative and spatially resolved measurements of blood flow. With in vitro experiments using tissue-simulating phantoms, we determined that temporal analysis of raw speckle image sequences improved the quantitative accuracy of LSI to measure flow beneath a static scattering layer. We then applied the temporal algorithm to assess the potential of LSI to monitor oral health. We designed and tested two generations of miniature LSI devices to measure flow in the pulpal chamber of teeth and in the gingiva. Our preliminary clinical pilot data indicated that speckle contrast may correlate with gingival health. To improve visualization of subsurface blood vessels, we developed a technique called photothermal LSI. We applied a short pulse of laser energy to selectively perturb the motion of red blood cells, increasing the signal from vasculature relative to the surroundings. To study the spectral and depth dependence of laser speckle contrast, we developed a Monte Carlo model of light and momentum transport to simulate speckle contrast. With an increase in the thickness of the overlying static-scattering layer, we observed a quadratic decrease in the quantity of dynamically scattered light collected by the detector. We next applied the model to study multi-exposure speckle imaging (MESI), a method that purportedly improves quantitative accuracy of subsurface blood flow measurements. We unexpectedly determined that MESI faced similar depth limitations as conventional LSI, findings that were supported by in vitro experimental data. Finally, we used the model to study the effects of epidermal melanin absorption on LSI, and demonstrated that speckle contrast is less sensitive to varying melanin content than reflectance. We then proposed a two-wavelength measurement protocol that may enable melanin-independent LSI measurements of blood flow in patients with varying skin types. In conclusion, through in vitro and in silico experiments, we were able to further the understanding of the depth dependent origins of laser speckle contrast as well as the inherent limitations of this technology.

Laser Rayleigh and Raman Diagnostics for Small Hydrogen/oxygen Rockets

NASA Technical Reports Server (NTRS)

Degroot, Wilhelmus A.; Zupanc, Frank J.

1993-01-01

Localized velocity, temperature, and species concentration measurements in rocket flow fields are needed to evaluate predictive computational fluid dynamics (CFD) codes and identify causes of poor rocket performance. Velocity, temperature, and total number density information have been successfully extracted from spectrally resolved Rayleigh scattering in the plume of small hydrogen/oxygen rockets. Light from a narrow band laser is scattered from the moving molecules with a Doppler shifted frequency. Two components of the velocity can be extracted by observing the scattered light from two directions. Thermal broadening of the scattered light provides a measure of the temperature, while the integrated scattering intensity is proportional to the number density. Spontaneous Raman scattering has been used to measure temperature and species concentration in similar plumes. Light from a dye laser is scattered by molecules in the rocket plume. Raman spectra scattered from major species are resolved by observing the inelastically scattered light with linear array mounted to a spectrometer. Temperature and oxygen concentrations have been extracted by fitting a model function to the measured Raman spectrum. Results of measurements on small rockets mounted inside a high altitude chamber using both diagnostic techniques are reported.

Software design of control system of CCD side-scatter lidar

NASA Astrophysics Data System (ADS)

Kuang, Zhiqiang; Liu, Dong; Deng, Qian; Zhang, Zhanye; Wang, Zhenzhu; Yu, Siqi; Tao, Zongming; Xie, Chenbo; Wang, Yingjian

2018-03-01

Because of the existence of blind zone and transition zone, the application of backscattering lidar in near-ground is limited. The side-scatter lidar equipped with the Charge Coupled Devices (CCD) can separate the transmitting and receiving devices to avoid the impact of the geometric factors which is exited in the backscattering lidar and, detect the more precise near-ground aerosol signals continuously. Theories of CCD side-scatter lidar and the design of control system are introduced. The visible control of laser and CCD and automatic data processing method of the side-scatter lidar are developed by using the software of Visual C #. The results which are compared with the calibration of the atmospheric aerosol lidar data show that signals from the CCD side- scatter lidar are convincible.

Diode injection - seeded, 940 nanometer (nm), titanium - sapphire laser for H2O DIAL (differential absorption lidar), measurements

NASA Technical Reports Server (NTRS)

Miller, George E.

1992-01-01

Differential absorption of laser radiation by various molecular species represents both a selective and a sensitive method of measuring specific atmospheric constituents. DIAL measurements can be carried out via two different means. Both involve using two laser pulses with slightly different wavelengths (lambda), (one lambda at a strong absorption line of the molecule of interest, the other detuned into the wing of the line), and comparing the attenuation of the pulses. One approach relies on scattering of the radiation from some conveniently located topographical target. In the other technique elastic scattering from atmospheric aerosols and particulates is used to return the radiation to the lidar receiver system. This case is referred to as the differential absorption and scattering technique, and is the technique we are interested in to measure water vapor at 940 nm. The 940 nm wavelength is extremely desirable to atmospheric scientist interested in accurate DIAL measurements of H2O in the upper and lower troposphere. Simulated measurements using approximately 940 nm and 815 nm lasers at a range of altitudes and experimental conditions are shown. By offering access to larger absorption cross-sections, injected seeded, 940 nm DIAL laser transmitters would allow for more accurate water profile measurements at altitudes from 6 to 16 km than is currently possible with 730 nm and 815 nm DIAL laser transmitters. We have demonstrated the operation of an injected seeded titanium-sapphire (TS) laser operating at approximately 940 nm with an energy of more than 90 mJ per pulse. The TS laser is pumped by a commercial, 600 mJ, 532 nm, 10 Hz Nd:YAG laser. The slope efficiency of the laser using a flat 50 percent R output coupler and a 10 m end-mirror is shown. The laser was injected seeded with a CW, AlGaAs, semiconductor diode laser which had an output of 83 mW. The CW diode seed beam was introduced into the TS laser cavity through a HR end-mirror. When the diode beam is aligned to the TS resonator, it controls the TS laser output wavelength and its spectral line width with the required resolution for DIAL applications. This work supports the need for the development of 940 nm, titanium-sapphire DIAL transmitters.

Optical spectral singularities as threshold resonances

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mostafazadeh, Ali

2011-04-15

Spectral singularities are among generic mathematical features of complex scattering potentials. Physically they correspond to scattering states that behave like zero-width resonances. For a simple optical system, we show that a spectral singularity appears whenever the gain coefficient coincides with its threshold value and other parameters of the system are selected properly. We explore a concrete realization of spectral singularities for a typical semiconductor gain medium and propose a method of constructing a tunable laser that operates at threshold gain.

Particle Size Determination in Small Solid Propellant Rocket Motors Using the Diffractively Scattered Light Method.

DTIC Science & Technology

1982-10-01

calibrated by using spherical glass beads and aluminum oxide powder . Measurements were successfully made at both locations. Because DO 1473 EoITioN OF I NOVy...determined using measurements of diffrac- tively scattered laser power spectra. The apparatus was calibrated by using spherical glass beads and aluminum oxide... powder . Measurements were successfully made at both loca- tions. Because of the presence of char agglomerates in the exhaust, continued effort is

Damage Effects Identified By Scatter Evaluation Of Supersmooth Surfaces

NASA Astrophysics Data System (ADS)

Stowell, W. K.; Orazio, Fred D.

1983-12-01

The surface quality of optics used in an extremely sensitive laser instrument, such as a Ring Laser Gyro (RLG), is critical. This has led to the development of a Variable Angle Scatterometer at the Air Force Wright Aeronautical Laboratories at Wright-Patterson Air Force Base, which can detect low level light scatter from the high quality optics used in RLG's, without first overcoating with metals. With this instrument we have been able to identify damage effects that occur during the typical processing and handling of optics which cause wide variation in subsequent measurements depending on when, in the process, one takes data. These measurements indicate that techniques such as a Total Integrated Scatter (TIS) may be inadequate for standards on extremely low scatter optics because of the lack of sensitivity of the method on such surfaces. The general term for optical surfaces better than the lowest level of the scratch-dig standards has become "supersmooth", and is seen in technical literature as well as in advertising. A performance number, such as Bidirectional Radiation Distribution Function (BRDF), which can be measured from the uncoated optical surface by equipment such as the Variable Angle Scatterometer (VAS) is proposed as a method of generating better optical surface specifications. Data show that surfaces of average BRDF values near 10 parts per billion per steriadian (0.010 PPM/Sr) for 0-(301 = 0.5, are now possible and measurable.

Damage Effects Identified By Scatter Evaluation Of Supersmooth Surfaces

NASA Astrophysics Data System (ADS)

Stowell, W. K.

1984-10-01

The surface quality of optics used in an extremely sensitive laser instrument, such as a Ring Laser Gyro (RLG), is critical. This has led to the development of a Variable Angle Scatterometer at the Air Force Wright Aeronautical Laboratories at Wright-Patterson Air Force Base, which can detect low level light scatter from the high quality optics used in RLG's, without first overcoating with metals. With this instrument we have been able to identify damage effects that occur during the typical processing and handling of optics which cause wide variation in subsequent measurements depending on when, in the process, one takes data. These measurements indicate that techniques such as a Total Integrated Scatter (TIS) may be inadequate for standards on extremely low scatter optics because of the lack of sensitivity of the method on such surfaces. The general term for optical surfaces better than the lowest level of the scratch-dig standards has become "supersmooth", and is seen in technical literature as well as in advertising. A performance number, such as Bidirectional Radiation Distribution Function (BRDF), which can be measured from the uncoated optical surface by equipment such as the Variable Angle Scatterometer (VAS) is proposed as a method of generating better optical surface specifications. Data show that surfaces of average BRDF values near 10 parts per billion per steriadian (0.010 PPM/Sr) for 0-(301 = 0.5, are now possible and measurable.

Single shot, double differential spectral measurements of inverse Compton scattering in the nonlinear regime

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sakai, Y.; Gadjev, I.; Hoang, P.

Inverse Compton scattering (ICS) is a unique mechanism for producing fast pulses$-$picosecond and below$-$of bright photons, ranging from x to γ rays. These nominally narrow spectral bandwidth electromagnetic radiation pulses are efficiently produced in the interaction between intense, well-focused electron and laser beams. The spectral characteristics of such sources are affected by many experimental parameters, with intense laser effects often dominant. A laser field capable of inducing relativistic oscillatory motion may give rise to harmonic generation and, importantly for the present work, nonlinear redshifting, both of which dilute the spectral brightness of the radiation. As the applications enabled by thismore » source often depend sensitively on its spectra, it is critical to resolve the details of the wavelength and angular distribution obtained from ICS collisions. With this motivation, we present an experimental study that greatly improves on previous spectral measurement methods based on x-ray K -edge filters, by implementing a multilayer bent-crystal x-ray spectrometer. In tandem with a collimating slit, this method reveals a projection of the double differential angular-wavelength spectrum of the ICS radiation in a single shot. The measurements enabled by this diagnostic illustrate the combined off-axis and nonlinear-field-induced redshifting in the ICS emission process. The spectra obtained illustrate in detail the strength of the normalized laser vector potential, and provide a nondestructive measure of the temporal and spatial electron-laser beam overlap.« less

Single shot, double differential spectral measurements of inverse Compton scattering in the nonlinear regime

DOE PAGES

Sakai, Y.; Gadjev, I.; Hoang, P.; ...

2017-06-05

Inverse Compton scattering (ICS) is a unique mechanism for producing fast pulses$-$picosecond and below$-$of bright photons, ranging from x to γ rays. These nominally narrow spectral bandwidth electromagnetic radiation pulses are efficiently produced in the interaction between intense, well-focused electron and laser beams. The spectral characteristics of such sources are affected by many experimental parameters, with intense laser effects often dominant. A laser field capable of inducing relativistic oscillatory motion may give rise to harmonic generation and, importantly for the present work, nonlinear redshifting, both of which dilute the spectral brightness of the radiation. As the applications enabled by thismore » source often depend sensitively on its spectra, it is critical to resolve the details of the wavelength and angular distribution obtained from ICS collisions. With this motivation, we present an experimental study that greatly improves on previous spectral measurement methods based on x-ray K -edge filters, by implementing a multilayer bent-crystal x-ray spectrometer. In tandem with a collimating slit, this method reveals a projection of the double differential angular-wavelength spectrum of the ICS radiation in a single shot. The measurements enabled by this diagnostic illustrate the combined off-axis and nonlinear-field-induced redshifting in the ICS emission process. The spectra obtained illustrate in detail the strength of the normalized laser vector potential, and provide a nondestructive measure of the temporal and spatial electron-laser beam overlap.« less

Observations of strong ion-ion correlations in dense plasmas

DOE PAGES

Ma, T.; Fletcher, L.; Pak, A.; ...

2014-04-24

Using simultaneous spectrally, angularly, and temporally resolved x-ray scattering, we measure the pronounced ion-ion correlation peak in a strongly coupled plasma. Laser-driven shock-compressed aluminum at ~3× solid density is probed with high-energy photons at 17.9 keV created by molybdenum He-α emission in a laser-driven plasma source. The measured elastic scattering feature shows a well-pronounced correlation peak at a wave vector of k=4Å –1. The magnitude of this correlation peak cannot be described by standard plasma theories employing a linear screened Coulomb potential. Advanced models, including a strong short-range repulsion due to the inner structure of the aluminum ions are howevermore » in good agreement with the scattering data. These studies have demonstrated a new highly accurate diagnostic technique to directly measure the state of compression and the ion-ion correlations. Furthermore, we have since applied this new method in single-shot wave-number resolved S(k) measurements to characterize the physical properties of dense plasmas.« less

Using a laser source to measure the refractive index of glass beads and Debye theory analysis.

PubMed

Li, Shui-Yan; Qin, Shuang; Li, Da-Hai; Wang, Qiong-Hua

2015-11-20

Using a monochromatic laser beam to illuminate a homogeneous glass bead, some rainbows will appear around it. This paper concentrates on the study of the scattering intensity distribution and the method of measuring the refractive index for glass beads based on the Debye theory. It is found that the first rainbow due to the scattering superposition of backward light of the low-refractive-index glass beads can be explained approximately with the diffraction, the external reflection plus the one internal reflection, while the second rainbow of high-refractive-index glass beads is due to the contribution from the diffraction, the external reflection, the direct transmission, and the two internal reflections. The scattering intensity distribution is affected by the refractive index, the radius of the glass bead, and the incident beam width. The effects of the refractive index and the glass bead size on the first and second minimum deviation angle position are analyzed in this paper. The results of the measurements agree very well with the specifications.

Silver nanowires as infrared-active materials for surface-enhanced Raman scattering.

PubMed

Becucci, Maurizio; Bracciali, Monica; Ghini, Giacomo; Lofrumento, Cristiana; Pietraperzia, Giangaetano; Ricci, Marilena; Tognaccini, Lorenzo; Trigari, Silvana; Gellini, Cristina; Feis, Alessandro

2018-05-17

Surface-enhanced Raman scattering (SERS) is increasing in significance as a bioanalytical tool. Novel nanostructured metal substrates are required to improve performances and versatility of SERS spectroscopy. In particular, as biological tissues are relatively transparent in the infrared wavelength range, SERS-active materials suitable for infrared laser excitation are needed. Nanowires appear interesting in this respect as they show a very broad localized surface plasmon resonance band, ranging from near UV to near infrared wavelengths. The SERS activity of silver nanowires has been tested at three wavelengths and a fair enhancement at 1064 and 514 nm has been observed, whereas a very weak enhancement was present when exciting close to the nanowire extinction maximum. These experimentally measured optical properties have been contrasted with finite element method simulations. Furthermore, laser-induced optoacoustic spectroscopy measurements have shown that the extinction at 1064 nm is completely due to scattering. This result has an important implication that no heating occurs when silver nanowires are utilized as SERS-active substrates, thereby preventing possible thermal damage.

Optoelectronic methods in potential application in monitoring of environmental conditions

NASA Astrophysics Data System (ADS)

Mularczyk-Oliwa, Monika; Bombalska, Aneta; Kwaśny, Mirosław; Kopczyński, Krzysztof; Włodarski, Maksymilian; Kaliszewski, Miron; Kostecki, Jerzy

2016-12-01

Allergic rhinitis, also known as hay fever is a type of inflammation which occurs when the immune system overreacts to allergens in the air. It became the most common disease among people. It became important to monitor air content for the presence of a particular type of allergen. For the purposes of environmental monitoring there is a need to widen the group of traditional methods of identification of pollen for faster and more accurate research systems. The aim of the work was the characterization and classification of certain types of plant pollens by using laser optical methods, which were supported by the chemmometrics. Several species of pollen were examined, for which a database of spectral characteristics was created, using LIF, Raman scattering and FTIR methods. Spectral database contains characteristics of both common allergens and pollen of minor importance. Based on registered spectra, statistical analysis was made, which allows the classification of the tested pollen species. For the study of the emission spectra Nd:YAG laser was used with the fourth harmonic generation (266 nm) and GaN diode laser (375 nm). For Raman scattering spectra spectrometer Nicolet IS-50 with a excitation wavelength of 1064 nm was used. The FTIR spectra, recorded in the mid infrared1 range (4000-650 cm-1) were collected with use of transmission mode (KBr pellet), ATR and DRIFT.

Laser Light Scattering, from an Advanced Technology Development Program to Experiments in a Reduced Gravity Environment

NASA Technical Reports Server (NTRS)

Meyer, William V.; Tscharnuter, Walther W.; Macgregor, Andrew D.; Dautet, Henri; Deschamps, Pierre; Boucher, Francois; Zuh, Jixiang; Tin, Padetha; Rogers, Richard B.; Ansari, Rafat R.

1994-01-01

Recent advancements in laser light scattering hardware are described. These include intelligent single card correlators; active quench/active reset avalanche photodiodes; laser diodes; and fiber optics which were used by or developed for a NASA advanced technology development program. A space shuttle experiment which will employ aspects of these hardware developments is previewed.

Ponderomotive perturbations of low density low-temperature plasma under laser Thomson scattering diagnostics

NASA Astrophysics Data System (ADS)

Shneider, Mikhail N.

2017-10-01

The ponderomotive perturbation in the interaction region of laser radiation with a low density and low-temperature plasma is considered. Estimates of the perturbation magnitude are determined from the plasma parameters, geometry, intensity, and wavelength of laser radiation. It is shown that ponderomotive perturbations can lead to large errors in the electron density when measured using Thomson scattering.

Lateral scattered light used to study laser light propagation in turbid media phantoms

NASA Astrophysics Data System (ADS)

Valdes, Claudia; Solarte, Efrain

2010-02-01

Laser light propagation in soft tissues is important because of the growing biomedical applications of lasers and the need to optically characterize the biological media. Following previous developments of the group, we have developed low cost models, Phantoms, of soft tissue. The process was developed in a clean room to avoid the medium contamination. Each model was characterized by measuring the refractive index, and spectral reflectance and transmittance. To study the laser light propagation, each model was illuminated with a clean beam of laser light, using sources such as He-Ne (632nm) and DPSSL (473 nm). Laterally scattered light was imaged and these images were digitally processed. We analyzed the intensity distribution of the scattered radiation in order to obtain details of the beam evolution in the medium. Line profiles taken from the intensity distribution surface allow measuring the beam spread, and to find expressions for the longitudinal (along the beam incident direction) and transversal (across the beam incident direction) intensities distributions. From these behaviors, the radiation penetration depth and the total coefficient of extinction have been determined. The multiple scattering effects were remarkable, especially for the low wavelength laser beam.

Nonlinear X-Ray and Auger Spectroscopy at X-Ray Free-Electron Laser Sources

NASA Astrophysics Data System (ADS)

Rohringer, Nina

2015-05-01

X-ray free-electron lasers (XFELs) open the pathway to transfer non-linear spectroscopic techniques to the x-ray domain. A promising all x-ray pump probe technique is based on coherent stimulated electronic x-ray Raman scattering, which was recently demonstrated in atomic neon. By tuning the XFEL pulse to core-excited resonances, a few seed photons in the spectral tail of the XFEL pulse drive an avalanche of resonant inelastic x-ray scattering events, resulting in exponential amplification of the scattering signal by of 6-7 orders of magnitude. Analysis of the line profile of the emitted radiation permits to demonstrate the cross over from amplified spontaneous emission to coherent stimulated resonance scattering. In combination with statistical covariance mapping, a high-resolution spectrum of the resonant inelastic scattering process can be obtained, opening the path to coherent stimulated x-ray Raman spectroscopy. An extension of these ideas to molecules and a realistic feasibility study of stimulated electronic x-ray Raman scattering in CO will be presented. Challenges to realizing stimulated electronic x-ray Raman scattering at present-day XFEL sources will be discussed, corroborated by results of a recent experiment at the LCLS XFEL. Due to the small gain cross section in molecular targets, other nonlinear spectroscopic techniques such as nonlinear Auger spectroscopy could become a powerful alternative. Theory predictions of a novel pump probe technique based on resonant nonlinear Auger spectroscopic will be discussed and the method will be compared to stimulated x-ray Raman spectroscopy.

Upgraded divertor Thomson scattering system on DIII-D

NASA Astrophysics Data System (ADS)

Glass, F.; Carlstrom, T. N.; Du, D.; McLean, A. G.; Taussig, D. A.; Boivin, R. L.

2016-11-01

A design to extend the unique divertor Thomson scattering system on DIII-D to allow measurements of electron temperature and density in high triangularity plasmas is presented. Access to this region is selectable on a shot-by-shot basis by redirecting the laser beam of the existing divertor Thomson system inboard — beneath the lower floor using a moveable, high-damage threshold, in-vacuum mirror — and then redirecting again vertically. The currently measured divertor region remains available with this mirror retracted. Scattered light is collected from viewchords near the divertor floor using in-vacuum, high temperature optical elements and relayed through the port window, before being coupled into optical fiber bundles. At higher elevations from the floor, measurements are made by dynamically re-focusing the existing divertor system collection optics. Nd:YAG laser timing, analysis of the scattered light spectrum via polychromators, data acquisition, and calibration are all handled by existing systems or methods of the current multi-pulse Thomson scattering system. Existing filtered polychromators with 7 spectral channels are employed to provide maximum measurement breadth (Te in the range of 0.5 eV-2 keV, ne in the range of 5 × 1018-1 × 1021 m3) for both low Te in detachment and high Te measurement up beyond the separatrix.

Upgraded divertor Thomson scattering system on DIII-D.

PubMed

Glass, F; Carlstrom, T N; Du, D; McLean, A G; Taussig, D A; Boivin, R L

2016-11-01

A design to extend the unique divertor Thomson scattering system on DIII-D to allow measurements of electron temperature and density in high triangularity plasmas is presented. Access to this region is selectable on a shot-by-shot basis by redirecting the laser beam of the existing divertor Thomson system inboard - beneath the lower floor using a moveable, high-damage threshold, in-vacuum mirror - and then redirecting again vertically. The currently measured divertor region remains available with this mirror retracted. Scattered light is collected from viewchords near the divertor floor using in-vacuum, high temperature optical elements and relayed through the port window, before being coupled into optical fiber bundles. At higher elevations from the floor, measurements are made by dynamically re-focusing the existing divertor system collection optics. Nd:YAG laser timing, analysis of the scattered light spectrum via polychromators, data acquisition, and calibration are all handled by existing systems or methods of the current multi-pulse Thomson scattering system. Existing filtered polychromators with 7 spectral channels are employed to provide maximum measurement breadth (T e in the range of 0.5 eV-2 keV, n e in the range of 5 × 10 18 -1 × 10 21 m 3 ) for both low T e in detachment and high T e measurement up beyond the separatrix.

Optical measurement methods in thermogasdynamics

NASA Technical Reports Server (NTRS)

Stursberg, K.; Erhardt, K.; Krahr, W.; Becker, M.

1978-01-01

A review is presented of a number of optical methods of flow measurements. Consideration is given to such spectroscopic methods as emission and absorption techniques, electron beam-stimulated fluorescence, and light scattering - Rayleigh, Raman and Mie - methods. The following visualization methods are also discussed: shadow photography, schlieren photography, interferometry, holographic interferometry, laser anemometry, particle holography, and electron-excitation imaging. A large bibliography is presented and the work is copiously illustrated with figures and photographs.

Laser plasma source for soft x-ray imaging in CIOM

NASA Astrophysics Data System (ADS)

Shao, Zhongxing; Wang, Zhanshan; Xu, Fengming; Lu, Junxia; Chen, Xingdan

1997-10-01

We previously reported 18 nm Schwartzchild microscope by using a laser plasma source. Now we are planning to improve our Nd:YAG laser system and the multilayers mirror of Mo/B4C instead of Mo/Si, for producing shorter wavelength radiation and developing a new soft x-ray imaging setup. To compress the pulse width of the laser, the SBS (Stimulated Brillouin Scattering) cells is available. To short the wavelength to the 4th harmonics of the laser with high as 0.4 J energy per pulse, the hindrance is the low, less than 20%, nonlinear conversion efficiency. In this paper we are going to briefly introduce the new method to overcome the hindrance and the configuration of the SBS cell.

Second order nonlinear QED processes in ultra-strong laser fields

NASA Astrophysics Data System (ADS)

Mackenroth, Felix

2017-10-01

In the interaction of ultra-intense laser fields with matter the ever increasing peak laser intensities render nonlinear QED effects ever more important. For long, ultra-intense laser pulses scattering large systems, like a macroscopic plasma, the interaction time can be longer than the scattering time, leading to multiple scatterings. These are usually approximated as incoherent cascades of single-vertex processes. Under certain conditions, however, this common cascade approximation may be insufficient, as it disregards several effects such as coherent processes, quantum interferences or pulse shape effects. Quantifying deviations of the full amplitude of multiple scatterings from the commonly employed cascade approximations is a formidable, yet unaccomplished task. In this talk we are going to discuss how to compute second order nonlinear QED amplitudes and relate them to the conventional cascade approximation. We present examples for typical second order processes and benchmark the full result against common approximations. We demonstrate that the approximation of multiple nonlinear QED scatterings as a cascade of single interactions has certain limitations and discuss these limits in light of upcoming experimental tests.

Two-dimensional simulations of stimulated Brillouin scattering in laser produced plasmas

NASA Astrophysics Data System (ADS)

Amin, M. R.; Capjack, C. E.; Frycz, P.; Rozmus, W.; Tikhonchuk, V. T.

1993-07-01

A system of electromagnetic and ion acoustic wave equations coupled via the ponderomotive force are solved numerically in a two-dimensional planar geometry. The competition between forward, side, and backward Brillouin scattering of the finite size laser beam is studied for the first time without the standard paraxial optics approximation. Simulations reveal a strong dependence of the scattered light characteristics on the geometry of the interaction region, the shape of the pump beam, and the ion acoustic wave damping. The main effects include side and forward scattering enhancement and a stimulation of collimated backward scattered radiation.

Consistency analysis on laser signal in laser guided weapon simulation

NASA Astrophysics Data System (ADS)

Yin, Ruiguang; Zhang, Wenpan; Guo, Hao; Gan, Lin

2015-10-01

The hardware-in-the-loop simulation is widely used in laser semi-active guidance weapon experiments, the authenticity of the laser guidance signal is the key problem of reliability. In order to evaluate the consistency of the laser guidance signal, this paper analyzes the angle of sight, laser energy density, laser spot size, atmospheric back scattering, sun radiation and SNR by comparing the different working state between actual condition and hardware-in-the-loop simulation. Based on measured data, mathematical simulation and optical simulation result, laser guidance signal effects on laser seeker are determined. By using Monte Carlo method, the laser guided weapon trajectory and impact point distribution are obtained, the influence of the systematic error are analyzed. In conclusion it is pointed out that the difference between simulation system and actual system has little influence in normal guidance, has great effect on laser jamming. The research is helpful to design and evaluation of laser guided weapon simulation.

Physical properties of organic particulate UV-absorbers used in sunscreens. I. Determination of particle size with fiber-optic quasi-elastic light scattering (FOQELS), disc centrifugation, and laser diffractometry.

PubMed

Herzog, Bernd; Katzenstein, Armin; Quass, Katja; Stehlin, Albert; Luther, Helmut

2004-03-01

In this study microparticles consisting of a benzotriazole derivative, which are used as absorbers for UV radiation in cosmetic sunscreens, were investigated. The particles were micronized in presence of a dispersing agent by means of a ball milling process. According to the energy input different particle sizes were produced in the range of 0.16 to 4 microm. The particle sizes obtained after different stages of the micronization process were measured using fiber-optic quasi-elastic light scattering (FOQELS), disc centrifugation, and laser diffractometry. All methods showed satisfactory agreement over the whole range of sizes. With the FOQELS technique the particle size distribution could be resolved to sizes well below 0.1 microm.

UV Raman scattering measurements in a Mach 2 H2-air flame for assessment of CFD models

NASA Technical Reports Server (NTRS)

Cheng, T. S.; Wehrmeyer, J. A.; Pitz, R. W.; Jarrett, O., Jr.; Northam, G. B.

1991-01-01

An UV narrowband tunable excimer laser is used for spontaneous Raman scattering measurements in hydrogen diffusion flames. The UV Raman system is characterized by a repetition rate of about 100 Hz, a temporal resolution of about 20 ns, and a spatial resolution of about 0.4 mm. It is concluded that a single KrF excimer laser based on spontaneous Raman scattering in conjunction with laser-induced predissociative fluorescence is capable of measuring instantaneously and simultaneously major species (H2, O2, N2, H2O), minor species (OH), and temperature.

On radiation forces acting on a transparent nanoparticle in the field of a focused laser beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Afanas'ev, A A; Rubinov, A N; Gaida, L S

2015-10-31

Radiation forces acting on a transparent spherical nanoparticle in the field of a focused Gaussian laser beam are studied theoretically in the Rayleigh scattering regime. Expressions are derived for the scattering force and Cartesian components of the gradient force. The resultant force acting on a nanoparticle located in the centre of a laser beam is found. The parameters of the focused beam and optical properties of the nanoparticle for which the longitudinal component of the gradient force exceeds the scattering force are determined. Characteristics of the transverse gradient force are discussed. (nanophotonics)

Single-crystal Brillouin spectroscopy with CO{sub 2} laser heating and variable q

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Jin S.; Bass, Jay D.; Zhu, Gaohua

2015-06-15

We describe a Brillouin spectroscopy system integrated with CO{sub 2} laser-heating and Raman spectroscopic capabilities. Temperature is determined by measurements of the grey-body thermal radiation emitted by the hot sample, with the system response calibrated relative to a standard tungsten ribbon lamp. High-pressure laser-heating Brillouin scattering measurements of acoustic velocities on liquid water and ice compressed in a diamond-anvil cell were performed at temperatures up to 2500 ± 150 K at high pressure. Single-crystal laser-heating Brillouin measurements were made on the (111) plane of San Carlos olivine at ∼13 GPa, 1300 ± 200 K. The pressure as measured by rubymore » fluorescence is shown to be within ±0.5 GPa of the pressure on the olivine sample during laser heating when KCl and KBr are used as pressure-transmitting media. In addition, the system is designed for continuously variable scattering angles from forward scattering (near 0° scattering angle) up to near back scattering (∼141°). This novel setup allows us to probe a wide range of wave vectors q for investigation of phonon dispersion on, for example, crystals with large unit cells (on the scale of hundreds of nm)« less

UV Resonant Raman Spectrometer with Multi-Line Laser Excitation

NASA Technical Reports Server (NTRS)

Lambert, James L.; Kohel, James M.; Kirby, James P.; Morookian, John Michael; Pelletier, Michael J.

2013-01-01

A Raman spectrometer employs two or more UV (ultraviolet) laser wavel engths to generate UV resonant Raman (UVRR) spectra in organic sampl es. Resonant Raman scattering results when the laser excitation is n ear an electronic transition of a molecule, and the enhancement of R aman signals can be several orders of magnitude. In addition, the Ra man cross-section is inversely proportional to the fourth power of t he wavelength, so the UV Raman emission is increased by another fact or of 16, or greater, over visible Raman emissions. The Raman-scatter ed light is collected using a high-resolution broadband spectrograph . Further suppression of the Rayleigh-scattered laser light is provi ded by custom UV notch filters.

Investigation of magneto-optical properties of ferrofluids by laser light scattering techniques

NASA Astrophysics Data System (ADS)

Nepomnyashchaya, E. K.; Prokofiev, A. V.; Velichko, E. N.; Pleshakov, I. V.; Kuzmin, Yu I.

2017-06-01

Investigation of magnetooptical characteristics of ferrofluids is an important task aimed at the development of novel optoelectronic systems. This article reports on the results obtained in the experimental studies of the factors that affect the intensity and spatial distribution of the laser radiation scattered by magnetic particles and their agglomerates in a magnetic field. Laser correlation spectroscopy and direct measurements of laser radiation scattering for studies of the interactions and magnetooptical properties of magnetic particles in solutions were employed. The objects were samples of nanodispersed magnetite (Fe3O4) suspended in kerosene and in water. Our studies revealed some new behavior of magnetic particles in external magnetic and light fields, which make ferrofluids promising candidates for optical devices.

Design of a submillimeter laser Thomson scattering system for measurement of ion temperature in SUMMA

NASA Technical Reports Server (NTRS)

Praddaude, H. C.; Woskoboinikow, P.

1978-01-01

A thorough discussion of submillimeter laser Thomson scattering for the measurement of ion temperature in plasmas is presented. This technique is very promising and work is being actively pursued on the high power lasers and receivers necessary for its implementation. In this report we perform an overall system analysis of the Thomson scattering technique aimed to: (1) identify problem areas; (2) establish specifications for the main components of the apparatus; (3) study signal processing alternatives and identify the optimum signal handling procedure. Because of its importance for the successful implementation of this technique, we also review the work presently being carried out on the optically pumped submillimeter CH3F and D2O lasers.

Sub-diffraction Laser Synthesis of Silicon Nanowires

PubMed Central

Mitchell, James I.; Zhou, Nan; Nam, Woongsik; Traverso, Luis M.; Xu, Xianfan

2014-01-01

We demonstrate synthesis of silicon nanowires of tens of nanometers via laser induced chemical vapor deposition. These nanowires with diameters as small as 60 nm are produced by the interference between incident laser radiation and surface scattered radiation within a diffraction limited spot, which causes spatially confined, periodic heating needed for high resolution chemical vapor deposition. By controlling the intensity and polarization direction of the incident radiation, multiple parallel nanowires can be simultaneously synthesized. The nanowires are produced on a dielectric substrate with controlled diameter, length, orientation, and the possibility of in-situ doping, and therefore are ready for device fabrication. Our method offers rapid one-step fabrication of nano-materials and devices unobtainable with previous CVD methods. PMID:24469704

Laser modified processes: bremsstrahlung and inelastic photon atom scattering

NASA Astrophysics Data System (ADS)

Budriga, Olimpia; Dondera, Mihai; Florescu, Viorica

2007-08-01

We consider the influence of a low-frequency monochromatic external electromagnetic field (the laser) on two basic atomic processes: electron Coulomb bremsstrahlung and inelastic photon scattering on an electron bound in the ground state of a hydrogenic atom. We briefly describe the approximations adopted and illustrate in figures how the laser parameters modify the shape of the differential cross-sections and extend the energy domain for emitted electrons, due to simultaneous absorption or emission of a large number (hundreds) of laser photons.

Ex-CARS: exotic configuration for coherent anti-Stokes Raman scattering microspectroscopy utilizing two laser sources

PubMed Central

Yakovlev, Vladislav V.; Petrov, Georgi I.; Noojin, Gary D.; Harbert, Corey; Denton, Michael; Thomas, Robert

2011-01-01

We propose and experimentally demonstrate a new coherent anti-Stokes Raman scattering setting, which relies on a coherent excitation of Raman vibration using a broadband ultrashort laser pulse and signal read-out using a conventional continuous wave laser radiation. Such an exotic arrangement does not require any synchronization of two laser sources and can be used for direct comparison of amplitudes of nonlinear and spontaneous Raman signals. Ex-CARS in time- (top panel) and frequency- (bottom panel) domain. PMID:20635427

Particle-in-cell modeling of laser Thomson scattering in low-density plasmas at elevated laser intensities

NASA Astrophysics Data System (ADS)

Powis, Andrew T.; Shneider, Mikhail N.

2018-05-01

Incoherent Thomson scattering is a non-intrusive technique commonly used for measuring local plasma density. Within low-density, low-temperature plasmas and for sufficient laser intensity, the laser may perturb the local electron density via the ponderomotive force, causing the diagnostic to become intrusive and leading to erroneous results. A theoretical model for this effect is validated numerically via kinetic simulations of a quasi-neutral plasma using the particle-in-cell technique.

Feasibility of a Novel Optoacoustic Device to Precisely Localize Endotracheal Tube Positioning in a Cadaver Model

DTIC Science & Technology

2016-11-02

million per year to U.S. hospitals [1,2]. Current methods of assessing ETT position include chest radiography, end- tidal carbon dioxide (EtCO2...lasers to generate sound waves to determine the position of “labeled” ETTs within millimeters of accuracy. Laser optoacoustic imaging combines the merits...of optical tomography (high optical contrast) and ultrasound imaging (minimal scattering of acoustic waves ) to yield high contrast, sensitivity, and

Locally-enhanced light scattering by a monocrystalline silicon wafer

NASA Astrophysics Data System (ADS)

Ma, Li; Zhang, Pan; Li, Zhen-Hua; Liu, Chun-Xiang; Li, Xing; Zhan, Zi-Jun; Ren, Xiao-Rong; He, Chang-Wei; Chen, Chao; Cheng, Chuan-Fu

2018-03-01

We study the optical properties of light scattering by a monocrystalline silicon wafer, by using transparent material to replicate its surface structure and illuminating a fabricated sample with a laser source. The experimental results show that the scattering field contains four spots of concentrated intensity with high local energy, and these spots are distributed at the four vertices of a square with lines of intensity linking adjacent spots. After discussing simulations of and theory about the formation of this light scattering, we conclude that the scattering field is formed by the effects of both geometrical optics and physical optics. Moreover, we calculate the central angle of the spots in the light field, and the result indicates that the locally-enhanced intensity spots have a definite scattering angle. These results may possibly provide a method for improving energy efficiency within mono-Si based solar cells.

Advanced Laser-Based Techniques for Gas-Phase Diagnostics in Combustion and Aerospace Engineering.

PubMed

Ehn, Andreas; Zhu, Jiajian; Li, Xuesong; Kiefer, Johannes

2017-03-01

Gaining information of species, temperature, and velocity distributions in turbulent combustion and high-speed reactive flows is challenging, particularly for conducting measurements without influencing the experimental object itself. The use of optical and spectroscopic techniques, and in particular laser-based diagnostics, has shown outstanding abilities for performing non-intrusive in situ diagnostics. The development of instrumentation, such as robust lasers with high pulse energy, ultra-short pulse duration, and high repetition rate along with digitized cameras exhibiting high sensitivity, large dynamic range, and frame rates on the order of MHz, has opened up for temporally and spatially resolved volumetric measurements of extreme dynamics and complexities. The aim of this article is to present selected important laser-based techniques for gas-phase diagnostics focusing on their applications in combustion and aerospace engineering. Applicable laser-based techniques for investigations of turbulent flows and combustion such as planar laser-induced fluorescence, Raman and Rayleigh scattering, coherent anti-Stokes Raman scattering, laser-induced grating scattering, particle image velocimetry, laser Doppler anemometry, and tomographic imaging are reviewed and described with some background physics. In addition, demands on instrumentation are further discussed to give insight in the possibilities that are offered by laser flow diagnostics.

A microfluidic laser scattering sensor for label-free detection of waterborne pathogens

NASA Astrophysics Data System (ADS)

Wei, Huang; Yang, Limei; Li, Feng

2016-10-01

A microfluidic-based multi-angle laser scattering (MALS) sensor capable of acquiring scattering pattern of single particle is demonstrated. The size and relative refractive index (RI) of polystyrene (PS) microspheres were deduced with accuracies of 60 nm and 0.001 by analyzing the scattering patterns. We measured scattering patterns of waterborne parasites i.e., cryptosporidium parvum (c.parvum) and giardia lamblia (g.lamblia), and some other representative species in 1 L water within 1 hour, and the waterborne parasites were identified with accuracy better than 96% by classification of distinctive scattering patterns with a support-vector-machine (SVM) algorithm. The system provides a promising tool for label-free and rapid detection of waterborne parasites.

Characterization of highly scattering media by measurement of diffusely backscattered polarized light

DOEpatents

Hielscher, Andreas H.; Mourant, Judith R.; Bigio, Irving J.

2000-01-01

An apparatus and method for recording spatially dependent intensity patterns of polarized light that is diffusely backscattered from highly scattering media are described. These intensity patterns can be used to differentiate different turbid media, such as polystyrene-sphere and biological-cell suspensions. Polarized light from a He-Ne laser (.lambda.=543 nm) is focused onto the surface of the scattering medium, and a surface area of approximately 4.times.4 cm centered on the light input point is imaged through polarization analysis optics onto a CCD camera. A variety of intensity patterns may be observed by varying the polarization state of the incident laser light and changing the analyzer configuration to detect different polarization components of the backscattered light. Experimental results for polystyrene-sphere and Intralipid suspensions demonstrate that the radial and azimuthal variations of the observed pattern depend on the concentration, size, and anisotropy factor, g, of the particles constituting the scattering medium. Measurements performed on biological cell suspensions show that intensity patterns can be used to differentiate between suspensions of cancerous and non-cancerous cells. Introduction of the Mueller-matrix for diffusely backscattered light, permits the selection of a subset of measurements which comprehensively describes the optical properties of backscattering media.

Dust grain characterization — Direct measurement of light scattering

NASA Astrophysics Data System (ADS)

BartoÅ, P.; Pavlů, J.

2018-01-01

Dust grains play a key role in dusty plasma since they interact with the plasma we can use them to study plasma itself. The grains are illuminated by visible light (e.g., a laser sheet) and the situation is captured with camera. Despite of simplicity, light scattering on similar-to-wavelength sized grains is complex phenomenon. Interaction of the electromagnetic wave with material has to be computed with respect to Maxwell equations — analytic solution is nowadays available only for several selected shapes like sphere, coated sphere, or infinite cylinder. Moreover, material constants needed for computations are usually unknown. For computation result verification and material constant determination, we designed and developed a device directly measur­ing light scattering profiles. Single dust grains are trapped in the ultrasonic field (so called "acoustic levitation") and illuminated by the laser beam. Scattered light is then measured by a photodiode mounted on rotating platform. Synchronous detection is employed for a noise reduction. This setup brings several benefits against conventional methods: (1) it works in the free air, (2) the measured grain is captured for a long time, and (3) the grain could be of arbitrary shape.

A Dual-Line Detection Rayleigh Scattering Diagnostic Technique for the Combustion of Hydrocarbon Fuels and Filtered UV Rayleigh Scattering for Gas Velocity Measurements

NASA Technical Reports Server (NTRS)

Otugen, M. Volkan

1997-01-01

Non-intrusive techniques for the dynamic measurement of gas flow properties such as density, temperature and velocity, are needed in the research leading to the development of new generation high-speed aircraft. Accurate velocity, temperature and density data obtained in ground testing and in-flight measurements can help understand the flow physics leading to transition and turbulence in supersonic, high-altitude flight. Such non-intrusive measurement techniques can also be used to study combustion processes of hydrocarbon fuels in aircraft engines. Reliable, time and space resolved temperature measurements in various combustor configurations can lead to a better understanding of high temperature chemical reaction dynamics thus leading to improved modeling and better prediction of such flows. In view of this, a research program was initiated at Polytechnic University's Aerodynamics Laboratory with support from NASA Lewis Research Center through grants NAG3-1301 and NAG3-1690. The overall objective of this program has been to develop laser-based, non-contact, space- and time-resolved temperature and velocity measurement techniques. In the initial phase of the program a ND:YAG laser-based dual-line Rayleigh scattering technique was developed and tested for the accurate measurement of gas temperature in the presence of background laser glare. Effort was next directed towards the development of a filtered, spectrally-resolved Rayleigh/Mie scattering technique with the objective of developing an interferometric method for time-frozen velocity measurements in high-speed flows utilizing the uv line of an ND:YAG laser and an appropriate molecular absorption filter. This effort included both a search for an appropriate filter material for the 266 nm laser line and the development and testing of several image processing techniques for the fast processing of Fabry-Perot images for velocity and temperature information. Finally, work was also carried out for the development of a new laser-based strain-rate and vorticity technique for the time-resolved measurement of vorticity and strain-rates in turbulent flows.

A simple method for computing the relativistic Compton scattering kernel for radiative transfer

NASA Technical Reports Server (NTRS)

Prasad, M. K.; Kershaw, D. S.; Beason, J. D.

1986-01-01

Correct computation of the Compton scattering kernel (CSK), defined to be the Klein-Nishina differential cross section averaged over a relativistic Maxwellian electron distribution, is reported. The CSK is analytically reduced to a single integral, which can then be rapidly evaluated using a power series expansion, asymptotic series, and rational approximation for sigma(s). The CSK calculation has application to production codes that aim at understanding certain astrophysical, laser fusion, and nuclear weapons effects phenomena.

Laser scattering by transcranial rat brain illumination

NASA Astrophysics Data System (ADS)

Sousa, Marcelo V. P.; Prates, Renato; Kato, Ilka T.; Sabino, Caetano P.; Suzuki, Luis C.; Ribeiro, Martha S.; Yoshimura, Elisabeth M.

2012-06-01

Due to the great number of applications of Low-Level-Laser-Therapy (LLLT) in Central Nervous System (CNS), the study of light penetration through skull and distribution in the brain becomes extremely important. The aim is to analyze the possibility of precise illumination of deep regions of the rat brain, measure the penetration and distribution of red (λ = 660 nm) and Near Infra-Red (NIR) (λ = 808 nm) diode laser light and compare optical properties of brain structures. The head of the animal (Rattus Novergicus) was epilated and divided by a sagittal cut, 2.3 mm away from mid plane. This section of rat's head was illuminated with red and NIR lasers in points above three anatomical structures: hippocampus, cerebellum and frontal cortex. A high resolution camera, perpendicularly positioned, was used to obtain images of the brain structures. Profiles of scattered intensities in the laser direction were obtained from the images. There is a peak in the scattered light profile corresponding to the skin layer. The bone layer gives rise to a valley in the profile indicating low scattering coefficient, or frontal scattering. Another peak in the region related to the brain is an indication of high scattering coefficient (μs) for this tissue. This work corroborates the use of transcranial LLLT in studies with rats which are subjected to models of CNS diseases. The outcomes of this study point to the possibility of transcranial LLLT in humans for a large number of diseases.

Measuring the light scattering and orientation of a spheroidal particle using in-line holography.

PubMed

Seo, Kyung Won; Byeon, Hyeok Jun; Lee, Sang Joon

2014-07-01

The light scattering properties of a horizontally and vertically oriented spheroidal particle under laser illumination are experimentally investigated using digital in-line holography. The reconstructed wave field shows the bright singular points as a result of the condensed beam formed by a transparent spheroidal particle acting as a lens. The in-plane (θ) and out-of-plane (ϕ) rotating angles of an arbitrarily oriented spheroidal particle are measured by using these scattering properties. As a feasibility test, the 3D orientation of a transparent spheroidal particle suspended in a microscale pipe flow is successfully reconstructed by adapting the proposed method.

Model-based review of Doppler global velocimetry techniques with laser frequency modulation

NASA Astrophysics Data System (ADS)

Fischer, Andreas

2017-06-01

Optical measurements of flow velocity fields are of crucial importance to understand the behavior of complex flow. One flow field measurement technique is Doppler global velocimetry (DGV). A large variety of different DGV approaches exist, e.g., applying different kinds of laser frequency modulation. In order to investigate the measurement capabilities especially of the newer DGV approaches with laser frequency modulation, a model-based review of all DGV measurement principles is performed. The DGV principles can be categorized by the respective number of required time steps. The systematic review of all DGV principle reveals drawbacks and benefits of the different measurement approaches with respect to the temporal resolution, the spatial resolution and the measurement range. Furthermore, the Cramér-Rao bound for photon shot is calculated and discussed, which represents a fundamental limit of the achievable measurement uncertainty. As a result, all DGV techniques provide similar minimal uncertainty limits. With Nphotons as the number of scattered photons, the minimal standard deviation of the flow velocity reads about 106 m / s /√{Nphotons } , which was calculated for a perpendicular arrangement of the illumination and observation direction and a laser wavelength of 895 nm. As a further result, the signal processing efficiencies are determined with a Monte-Carlo simulation. Except for the newest correlation-based DGV method, the signal processing algorithms are already optimal or near the optimum. Finally, the different DGV approaches are compared regarding errors due to temporal variations of the scattered light intensity and the flow velocity. The influence of a linear variation of the scattered light intensity can be reduced by maximizing the number of time steps, because this means to acquire more information for the correction of this systematic effect. However, more time steps can result in a flow velocity measurement with a lower temporal resolution, when operating at the maximal frame rate of the camera. DGV without laser frequency modulation then provides the highest temporal resolutions and is not sensitive with respect to temporal variations but with respect to spatial variations of the scattered light intensity. In contrast to this, all DGV variants suffer from velocity variations during the measurement. In summary, the experimental conditions and the measurement task finally decide about the ideal choice from the reviewed DGV methods.

Calculation method for laser radar cross sections of rotationally symmetric targets.

PubMed

Cao, Yunhua; Du, Yongzhi; Bai, Lu; Wu, Zhensen; Li, Haiying; Li, Yanhui

2017-07-01

The laser radar cross section (LRCS) is a key parameter in the study of target scattering characteristics. In this paper, a practical method for calculating LRCSs of rotationally symmetric targets is presented. Monostatic LRCSs for four kinds of rotationally symmetric targets (cone, rotating ellipsoid, super ellipsoid, and blunt cone) are calculated, and the results verify the feasibility of the method. Compared with the results for the triangular patch method, the correctness of the method is verified, and several advantages of the method are highlighted. For instance, the method does not require geometric modeling and patch discretization. The method uses a generatrix model and double integral, and its calculation is concise and accurate. This work provides a theory analysis for the rapid calculation of LRCS for common basic targets.

Pulsed laser ablation of complex oxides: The role of congruent ablation and preferential scattering for the film stoichiometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wicklein, S.; Koehl, A.; Dittmann, R.

2012-09-24

By combining structural and chemical thin film analysis with detailed plume diagnostics and modeling of the laser plume dynamics, we are able to elucidate the different physical mechanisms determining the stoichiometry of the complex oxides model material SrTiO{sub 3} during pulsed laser deposition. Deviations between thin film and target stoichiometry are basically a result of two effects, namely, incongruent ablation and preferential scattering of lighter ablated species during their motion towards the substrate in the O{sub 2} background gas. On the one hand, a progressive preferential ablation of the Ti species with increasing laser fluence leads to a regime ofmore » Ti-rich thin film growth at larger fluences. On the other hand, in the low laser fluence regime, a more effective scattering of the lighter Ti plume species results in Sr rich films.« less

Intense γ ray generated by refocusing laser pulse on wakefield accelerated electrons

NASA Astrophysics Data System (ADS)

Feng, Jie; Wang, Jinguang; Li, Yifei; Zhu, Changqing; Li, Minghua; He, Yuhang; Li, Dazhang; Wang, Weimin; Chen, Liming

2017-09-01

Ultrafast x/γ ray emission from the combination of laser wake-field acceleration and plasma mirror has been investigated as a promising Thomson scattering source. However, the photon energy and yield of radiation are limited to the intensity of reflected laser pulses. We use the 2D particle in cell simulation to demonstrate that a 75TW driven laser pulse can be refocused on the accelerated electron bunches through a hemispherical plasma mirror with a small f number of 0.25. The energetic electrons with the maximum energy about 350 MeV collide with the reflected laser pulse of a0 = 3.82 at the focal spot, producing high order multi-photon Thomson scattering, and resulting in the scattering spectrum which extends up to 21.2 MeV. Such a high energy γ ray source could be applied to photonuclear reaction and materials science.

Characteristics of 1.9 μm laser emission from hydrogen-filled hollow-core fiber by stimulated Raman scattering

NASA Astrophysics Data System (ADS)

Gu, Bo; Chen, Yubin; Wang, Zefeng

2016-11-01

We report here the detailed characteristics of 1.9 μm laser emission from hydrogen-filled hollow-core fiber by stimulated Raman scattering. A 6.5 m hydrogen-filled Ice-cream negative curvature hollow-core fiber is pumped with a high peak power, narrow linewidth, liner polarized subnanosecond pulsed 1064 nm microchip laser, generating pulsed 1908.5 nm vibrational Stokes wave. The linewidth of the pump laser and the vibrational Stokes wave is about 1 GHz and 2 GHz respectively. And the maximum Raman conversion quantum efficiency is about 48%. We also studied the pulse shapes of the pump laser and the vibrational Stokes wave. The polarization dependence of the vibrational and the rotational stimulated Raman scattering is also investigated. In addition, the beam profile of vibrational Stokes wave shows good quality, which may be taken advantage of in many applications.

LASER RADIATION CHARACTERISTICS (BRIEF COMMUNICATIONS): Conversion of KrCl and XeCl laser radiation to the visible spectral range by stimulated Raman scattering in lead vapor

NASA Astrophysics Data System (ADS)

Evtushenko, Gennadii S.; Mel'chenko, S. V.; Panchenko, Aleksei N.; Tarasenko, Viktor F.

1990-04-01

Conversion of KrCl and XeCl laser radiation by stimulated Raman scattering was achieved in lead vapor. The KrCl laser radiation was converted into three lines in the visible region at λ = 406, 590, and 723 nm by transitions from both the ground and first excited levels of the lead atom. The conversion efficiency of XeCl laser radiation of low spatial coherence was found to be limited by the activation of a competing nonlinear process.

Quantum state-resolved energy transfer dynamics at gas-liquid interfaces: IR laser studies of CO2 scattering from perfluorinated liquids.

PubMed

Perkins, Bradford G; Häber, Thomas; Nesbitt, David J

2005-09-01

An apparatus for detailed study of quantum state-resolved inelastic energy transfer dynamics at the gas-liquid interface is described. The approach relies on supersonic jet-cooled molecular beams impinging on a continuously renewable liquid surface in a vacuum and exploits sub-Doppler high-resolution laser absorption methods to probe rotational, vibrational, and translational distributions in the scattered flux. First results are presented for skimmed beams of jet-cooled CO(2) (T(beam) approximately 15 K) colliding at normal incidence with a liquid perfluoropolyether (PFPE) surface at E(inc) = 10.6(8) kcal/mol. The experiment uses a tunable Pb-salt diode laser for direct absorption on the CO(2) nu(3) asymmetric stretch. Measured rotational distributions in both 00(0)0 and 01(1)0 vibrational manifolds indicate CO(2) inelastically scatters from the liquid surface into a clearly non-Boltzmann distribution, revealing nonequilibrium dynamics with average rotational energies in excess of the liquid (T(s) = 300 K). Furthermore, high-resolution analysis of the absorption profiles reveals that Doppler widths correspond to temperatures significantly warmer than T(s) and increase systematically with the J rotational state. These rotational and translational distributions are consistent with two distinct gas-liquid collision pathways: (i) a T approximately 300 K component due to trapping-desorption (TD) and (ii) a much hotter distribution (T approximately 750 K) due to "prompt" impulsive scattering (IS) from the gas-liquid interface. By way of contrast, vibrational populations in the CO(2) bending mode are inefficiently excited by scattering from the liquid, presumably reflecting much slower T-V collisional energy transfer rates.

Atmospheric influences on infrared-laser signals used for occultation measurements between Low Earth Orbit satellites

NASA Astrophysics Data System (ADS)

Schweitzer, S.; Kirchengast, G.; Proschek, V.

2011-10-01

LEO-LEO infrared-laser occultation (LIO) is a new occultation technique between Low Earth Orbit (LEO) satellites, which applies signals in the short wave infrared spectral range (SWIR) within 2 μm to 2.5 μm. It is part of the LEO-LEO microwave and infrared-laser occultation (LMIO) method that enables to retrieve thermodynamic profiles (pressure, temperature, humidity) and altitude levels from microwave signals and profiles of greenhouse gases and further variables such as line-of-sight wind speed from simultaneously measured LIO signals. Due to the novelty of the LMIO method, detailed knowledge of atmospheric influences on LIO signals and of their suitability for accurate trace species retrieval did not yet exist. Here we discuss these influences, assessing effects from refraction, trace species absorption, aerosol extinction and Rayleigh scattering in detail, and addressing clouds, turbulence, wind, scattered solar radiation and terrestrial thermal radiation as well. We show that the influence of refractive defocusing, foreign species absorption, aerosols and turbulence is observable, but can be rendered small to negligible by use of the differential transmission principle with a close frequency spacing of LIO absorption and reference signals within 0.5%. The influences of Rayleigh scattering and terrestrial thermal radiation are found negligible. Cloud-scattered solar radiation can be observable under bright-day conditions, but this influence can be made negligible by a close time spacing (within 5 ms) of interleaved laser-pulse and background signals. Cloud extinction loss generally blocks SWIR signals, except very thin or sub-visible cirrus clouds, which can be addressed by retrieving a cloud layering profile and exploiting it in the trace species retrieval. Wind can have a small influence on the trace species absorption, which can be made negligible by using a simultaneously retrieved or a moderately accurate background wind speed profile. We conclude that the set of SWIR channels proposed for implementing the LMIO method (Kirchengast and Schweitzer, 2011) provides adequate sensitivity to accurately retrieve eight trace species of key importance to climate and atmospheric chemistry (H2O, CO2, 13CO2, C18OO, CH4, N2O, O3, CO) in the upper troposphere/lower stratosphere region outside clouds under all atmospheric conditions. Two further species (HDO, H218O) can be retrieved in the upper troposphere.

Rapid Antimicrobial Susceptibility Testing Using Forward Laser Light Scatter Technology.

PubMed

Hayden, Randall T; Clinton, Lani K; Hewitt, Carolyn; Koyamatsu, Terri; Sun, Yilun; Jamison, Ginger; Perkins, Rosalie; Tang, Li; Pounds, Stanley; Bankowski, Matthew J

2016-11-01

The delayed reporting of antimicrobial susceptibility testing remains a limiting factor in clinical decision-making in the treatment of bacterial infection. This study evaluates the use of forward laser light scatter (FLLS) to measure bacterial growth for the early determination of antimicrobial susceptibility. Three isolates each (two clinical isolates and one reference strain) of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa were tested in triplicate using two commercial antimicrobial testing systems, the Vitek2 and the MicroScan MIC panel, to challenge the BacterioScan FLLS. The BacterioScan FLLS showed a high degree of categorical concordance with the commercial methods. Pairwise comparison with each commercial system serving as a reference standard showed 88.9% agreement with MicroScan (two minor errors) and 72.2% agreement with Vitek (five minor errors). FLLS using the BacterioScan system shows promise as a novel method for the rapid and accurate determination of antimicrobial susceptibility. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Two-wavelength LIDAR Thomson scattering for ITER core plasma

NASA Astrophysics Data System (ADS)

Nielsen, P.; Gowers, C.; Salzmann, H.

2017-07-01

Our proposal for a LIDAR Thomson scattering system to measure Te and ne profiles in the ITER core plasma, is based on experience with the LIDAR system on JET, which is still operational after 30 years. The design uses currently available technology and complies with the measurement requirements given by ITER. In addition, it offers the following advantages over the conventional imaging approach currently being adopted by ITER: 1) No gas fill of the vessel required for absolute calibration. 2) Easier alignment. 3) Measurements over almost the complete plasma diameter. 4) Two mirrors only as front optics. For a given laser wavelength the dynamic range of the Te measurements is mainly limited by the collection optics' transmission roll-off in the blue and the range of spectral sensitivity of the required fast photomultipliers. With the originally proposed Ti:Sapphire laser, measurements of the envisaged maximum temperature of 40 keV are marginally possible. Here we present encouraging simulation results on the use of other laser systems and on the use of two lasers with different wavelength. Alternating two wavelengths was proposed already in 1997 as a method for calibrating the transmission of the collection system. In the present analysis, the two laser pulses are injected simultaneously. We find that the use of Nd:YAG lasers operated at fundamental and second harmonic, respectively, yields excellent results and preserves the spectral recalibration feature.

Optical Extinction Measurements of Laser Side-Scatter During Tropical Storm Colin

NASA Technical Reports Server (NTRS)

Lane, John E.; Kasparis, Takis; Metzger, Philip; Michaelides, Silas

2017-01-01

A side-scatter imaging (SSI) technique using a 447 nm, 500 mW laser and a Nikon D80 camera was tested at Kennedy Space Center, Florida during the passing of a rain band associated with Tropical Storm Colin. The June 6, 2016, 22:00 GMT rain event was intense but short-lived owing to the strong west-to-east advection of the rain band. An effort to validate the optical extinction measurement was conducted by setting up a line of three tipping rain gauges along an 80 m east-west path and below the laser beam. Differences between tipping bucket measurements were correlated to the extinction coefficient profile along the lasers path, as determined by the SSI measurement. In order to compare the tipping bucket to the optical extinction data, a Marshall-Palmer DSD model was assumed. Since this was a daytime event, the laser beam was difficult to detect in the camera images, pointing out an important limitation of SSI measurements: the practical limit of DSD density that can be effectively detected and analyzed under daylight conditions using this laser and camera, corresponds to a fairly moderate rainfall rate on the order of 20 mmh (night measurements achieve a much improved sensitivity). The SSI analysis model under test produced promising results, but in order to use the SSI method for routine meteorological studies, improvements to the math model will be required.

Bibliography of Soviet Laser Developments, Number 44 November - December 1979.

DTIC Science & Technology

1980-08-13

Laser Materials, Ultrashort Pulse Generation, X-ray Lasers , Gamma Lasers , Laser Theory, Laser Biological Effects, Laser Communications, Laser Beam... lasers ; components; nonlinear optics; spectroscopy of laser materials; ultrashort pulse generation; theoretical aspects of advanced lasers ; and...and V.P. Feshchenko (51). Stimulated Raman scattering in absorbing media during pumping by ultrashort laser

LASER APPLICATIONS IN MEDICINE: Effect of glucose concentration in a model light-scattering suspension on propagation of ultrashort laser pulses

NASA Astrophysics Data System (ADS)

Popov, A. P.; Priezzhev, A. V.; Myllylä, Risto

2005-11-01

The propagation of laser pulses in the 2% aqueous solution of intralipid — a suspension of lipid particles with optical properties close to those of the human skin, is numerically simulated at different glucose concentrations. The temporal profiles of 820-nm laser pulses diffusely backscattered from a flat, 2-mm thick solution layer are simulated. The laser pulse profiles are detected by fibreoptic detectors of diameter 0.3 mm with the numerical apertures 0.19, 0.29, and 0.39. It is shown that this method can be used to detect changes in the glucose level in the physiological concentration range (100-500 mg dL-1) by monitoring variations in the peak intensity and area of the laser pulse temporal profile (pulse energy).

Scientific applications of frequency-stabilized laser technology in space

NASA Technical Reports Server (NTRS)

Schumaker, Bonny L.

1990-01-01

A synoptic investigation of the uses of frequency-stabilized lasers for scientific applications in space is presented. It begins by summarizing properties of lasers, characterizing their frequency stability, and describing limitations and techniques to achieve certain levels of frequency stability. Limits to precision set by laser frequency stability for various kinds of measurements are investigated and compared with other sources of error. These other sources include photon-counting statistics, scattered laser light, fluctuations in laser power, and intensity distribution across the beam, propagation effects, mechanical and thermal noise, and radiation pressure. Methods are explored to improve the sensitivity of laser-based interferometric and range-rate measurements. Several specific types of science experiments that rely on highly precise measurements made with lasers are analyzed, and anticipated errors and overall performance are discussed. Qualitative descriptions are given of a number of other possible science applications involving frequency-stabilized lasers and related laser technology in space. These applications will warrant more careful analysis as technology develops.

Third-harmonic generation and scattering in combustion flames using a femtosecond laser filament.

PubMed

Zang, Hong-Wei; Li, He-Long; Su, Yue; Fu, Yao; Hou, Meng-Yao; Baltuška, Andrius; Yamanouchi, Kaoru; Xu, Huailiang

2018-02-01

Coherent radiation in the ultraviolent (UV) range has high potential applicability to the diagnosis of the formation processes of soot in combustion because of the high scattering efficiency in the UV wavelength region, even though the UV light is lost largely by the absorption within the combustion flames. We show that the third harmonic (TH) of a Ti:sapphire 800 nm femtosecond laser is generated in a laser-induced filament in a combustion flame and that the conversion efficiency of the TH varies sensitively by the ellipticity of the driver laser pulse but does not vary so much by the choice of alkanol species introduced as fuel for the combustion flames. We also find that the TH recorded from the side direction of the filament is the Rayleigh scattering of the TH by soot nanoparticles within the flame and that the intensity of the TH varies depending on the fuel species as well as on the position of the laser filament within the flame. Our results show that a remote and in situ measurement of distributions of soot nanoparticles in a combustion flame can be achieved by Rayleigh scattering spectroscopy of the TH generated by a femtosecond-laser-induced filament in the combustion flame.

Observation of the Second Harmonic in Thomson Scattering from Relativistic Electrons

NASA Astrophysics Data System (ADS)

Babzien, Marcus; Ben-Zvi, Ilan; Kusche, Karl; Pavlishin, Igor V.; Pogorelsky, Igor V.; Siddons, David P.; Yakimenko, Vitaly; Cline, David; Zhou, Feng; Hirose, Tachishige; Kamiya, Yoshio; Kumita, Tetsuro; Omori, Tsunehiko; Urakawa, Junji; Yokoya, Kaoru

2006-02-01

A free relativistic electron in an electromagnetic field is a pure case of a light-matter interaction. In the laboratory environment, this interaction can be realized by colliding laser pulses with electron beams produced from particle accelerators. The process of single photon absorption and reemission by the electron, so-called linear Thomson scattering, results in radiation that is Doppler shifted into the x-ray and γ-ray regions. At elevated laser intensity, nonlinear effects should come into play when the transverse motion of the electrons induced by the laser beam is relativistic. In the present experiment, we achieved this condition and characterized the second harmonic of Thomson x-ray scattering using the counterpropagation of a 60 MeV electron beam and a subterawatt CO2 laser beam.

Observation of the second harmonic in Thomson scattering from relativistic electrons.

PubMed

Babzien, Marcus; Ben-Zvi, Ilan; Kusche, Karl; Pavlishin, Igor V; Pogorelsky, Igor V; Siddons, David P; Yakimenko, Vitaly; Cline, David; Zhou, Feng; Hirose, Tachishige; Kamiya, Yoshio; Kumita, Tetsuro; Omori, Tsunehiko; Urakawa, Junji; Yokoya, Kaoru

2006-02-10

A free relativistic electron in an electromagnetic field is a pure case of a light-matter interaction. In the laboratory environment, this interaction can be realized by colliding laser pulses with electron beams produced from particle accelerators. The process of single photon absorption and reemission by the electron, so-called linear Thomson scattering, results in radiation that is Doppler shifted into the x-ray and gamma-ray regions. At elevated laser intensity, nonlinear effects should come into play when the transverse motion of the electrons induced by the laser beam is relativistic. In the present experiment, we achieved this condition and characterized the second harmonic of Thomson x-ray scattering using the counterpropagation of a 60 MeV electron beam and a subterawatt CO2 laser beam.

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.

Surface intervalley scattering on GaAs(110) studied with picosecond laser photoemission

NASA Astrophysics Data System (ADS)

Haight, R.; Silberman, J. A.

1990-01-01

Laser-based photoemission sources provide the unique opportunity to study dynamic electronic processes at surfaces and interfaces. Using angle-resolved, laser photoemission with < 1 ps time resolution, we have directly observed a new surface band at the X¯ point in the GaAs(110) surface Brillouin zone. The appearance of electron population in this valley occurs only as a result of scattering from the directly photoexcited valley at overlineГ. The momentum resolution of our experiment has permitted us to isolate the dynamic electron population changes at both overlineГ and X¯ and to deduce the scattering time between the two valleys.

Laser-induced stimulated Raman scattering in the forward direction of a droplet - Comparison of Mie theory with geometrical optics

NASA Technical Reports Server (NTRS)

Srivastava, Vandana; Jarzembski, Maurice A.

1991-01-01

This paper uses Mie theory to treat electromagnetic scattering and to evaluate field enhancement in the forward direction of a small droplet irradiated by a high-energy beam and compares the results of calculations with the field-enhancement evaluation obtained via geometrical optics treatment. Results of this comparison suggest that the field enhancement located at the critical ring region encircling the axis in the forward direction of the droplet can support laser-induced Raman scattering. The results are supported by experimental observations of the interaction of a 120-micron-diam water droplet with a high-energy Nd:YAG laser beam.

Contribution of High-Order Rainbows to the Scattering of a Gaussian Laser Beam by a Spherical Particle

NASA Technical Reports Server (NTRS)

Lock, James A.

1993-01-01

I review the theory of the scattering of a Gaussian laser beam by a dielectric spherical particle and give the details for constructing a computer program to implement the theory. Computational results indicate that if the width of the laser beam is much less than the diameter of the particle and if the axis of the beam is incident near the edge of the particle, the fifth-, sixth-, and ninth-order rainbows should be evident in the far-field scattered intensity. I performed an experiment that yielded tentative evidence for the presence of the sixth- order rainbow.

Modeling of Optoelectronic Devices

NASA Technical Reports Server (NTRS)

Li, Jian-Zhong; Woo, Alex C. (Technical Monitor)

2000-01-01

Ultrafast modulation of semiconductor quantum well (QW) laser is of technological importance for information technology. Improvement by order(s) of magnitude in data transfer rate is possible as terahertz (THz) radiation is available for heating the laser at picosecond time scale. Optical gain modulation in the QW is achieved via temperature modulation of electron-hole plasma (EHP). Applications include free-space THz communication, optical switching, and pulse generation. The EHP in the semiconductor QW is described with a two-band model. Semiconductor Bloch equations with many-body effects are used to derive a hydrodynamical model for the active QW region. Because of ultrafast carrier-carrier scatterings in the order of 50 fs, EHP follows quasiequilibrium Fermi-Dirac distributions and THz field interacts incoherently with it. Carrier-longitudinal optical (LO) phonon scatterings and coherent laser-EHP interaction are treated microscopically in our physical model. A set of hydrodynamical equations for plasma density, temperature, and laser envelop amplitude are derived and Runge-Kutta method is adopted for numerical simulation. A typical 8 nm GaAs/Al(0.3)Ga(0.7) As single QW at 300 K is used. Additional information is contained in the original extended abstract.

In-situ high-resolution visualization of laser-induced periodic nanostructures driven by optical feedback.

PubMed

Aguilar, Alberto; Mauclair, Cyril; Faure, Nicolas; Colombier, Jean-Philippe; Stoian, Razvan

2017-11-28

Optical feedback is often evoked in laser-induced periodic nanostructures. Visualizing the coupling between surfaces and light requires highly-resolved imaging methods. We propose in-situ structured-illumination-microscopy to observe ultrafast-laser-induced nanostructures during fabrication on metallic glass surfaces. This resolves the pulse-to-pulse development of periodic structures on a single irradiation site and indicates the optical feedback on surface topographies. Firstly, the quasi-constancy of the ripples pattern and the reinforcement of the surface relief with the same spatial positioning indicates a phase-locking mechanism that stabilizes and amplifies the ordered corrugation. Secondly, on sites with uncorrelated initial corrugation, we observe ripple patterns spatially in-phase. These feedback aspects rely on the electromagnetic interplay between the laser pulse and the surface relief, stabilizing the pattern in period and position. They are critically dependent on the space-time coherence of the exciting pulse. This suggests a modulation of energy according to the topography of the surface with a pattern phase imposed by the driving pulse. A scattering and interference model for ripple formation on surfaces supports the experimental observations. This relies on self-phase-stabilized far-field interaction between surface scattered wavelets and the incoming pulse front.

Methods for estimating the optical constants of atmospheric hazes based on complex optical measurements

NASA Technical Reports Server (NTRS)

Zuev, V. E.; Kostin, B. S.; Naats, I. E.

1986-01-01

The methods of multifrequency laser sounding (MLS) are the most effective remote methods for investigating the atmospheric aerosols, since it is possible to obtain complete information on aerosol microstructure and the effective methods for estimating the aerosol optical constants can be developed. The MLS data interpretation consists in the solution of the set of equations containing those of laser sounding and equations for polydispersed optical characteristics. As a rule, the laser sounding equation is written in the approximation of single scattering and the equations for optical characteristics are written assuming that the atmospheric aerosol is formed by spherical and homogeneous particles. To remove the indeterminacy of equations, the method of optical sounding of atmospheric aerosol, consisting in a joint use of a mutifrequency lidar and a spectral photometer in common geometrical scheme of the optical experiment was suggested. The method is used for investigating aerosols in the cases when absorption by particles is small and indicates the minimum necessary for interpretation of a series of measurements.

Simulating propagation of coherent light in random media using the Fredholm type integral equation

NASA Astrophysics Data System (ADS)

Kraszewski, Maciej; Pluciński, Jerzy

2017-06-01

Studying propagation of light in random scattering materials is important for both basic and applied research. Such studies often require usage of numerical method for simulating behavior of light beams in random media. However, if such simulations require consideration of coherence properties of light, they may become a complex numerical problems. There are well established methods for simulating multiple scattering of light (e.g. Radiative Transfer Theory and Monte Carlo methods) but they do not treat coherence properties of light directly. Some variations of these methods allows to predict behavior of coherent light but only for an averaged realization of the scattering medium. This limits their application in studying many physical phenomena connected to a specific distribution of scattering particles (e.g. laser speckle). In general, numerical simulation of coherent light propagation in a specific realization of random medium is a time- and memory-consuming problem. The goal of the presented research was to develop new efficient method for solving this problem. The method, presented in our earlier works, is based on solving the Fredholm type integral equation, which describes multiple light scattering process. This equation can be discretized and solved numerically using various algorithms e.g. by direct solving the corresponding linear equations system, as well as by using iterative or Monte Carlo solvers. Here we present recent development of this method including its comparison with well-known analytical results and a finite-difference type simulations. We also present extension of the method for problems of multiple scattering of a polarized light on large spherical particles that joins presented mathematical formalism with Mie theory.

Measurement of ablation threshold of oxide-film-coated aluminium nanoparticles irradiated by femtosecond laser pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chefonov, O V; Ovchinnikov, A V; Il'ina, I V

We report the results of experiments on estimation of femtosecond laser threshold intensity at which nanoparticles are removed from the substrate surface. The studies are performed with nanoparticles obtained by femtosecond laser ablation of pure aluminium in distilled water. The attenuation (or extinction, i.e. absorption and scattering) spectra of nanoparticles are measured at room temperature in the UV and optical wavelength ranges. The size of nanoparticles is determined using atomic force microscopy. A new method of scanning photoluminescence is proposed to evaluate the threshold of nanoparticle removal from the surface of a glass substrate exposed to IR femtosecond laser pulsesmore » with intensities 10{sup 11} – 10{sup 13} W cm{sup -2}. (interaction of laser radiation with matter)« less

Fabrication of low-loss ridge waveguides in z-cut lithium niobate by combination of ion implantation and UV picosecond laser micromachining

NASA Astrophysics Data System (ADS)

Stolze, M.; Herrmann, T.; L'huillier, J. A.

2016-03-01

Ridge waveguides in ferroelectric materials like LiNbO3 attended great interest for highly efficient integrated optical devices, for instance, electro-optic modulators, frequency converters and ring resonators. The main challenges are the realization of high index barrier towards the substrate and the processing of smooth ridges for minimized scattering losses. For fabricating ridges a variety of techniques, like chemical and wet etching as well as optical grade dicing, have been investigated in detail. Among them, laser micromachining offers a versatile and flexible processing technology, but up to now only a limited side wall roughness has been achieved by this technique. Here we report on laser micromachining of smooth ridges for low-loss optical waveguides in LiNbO3. The ridges with a top width of 7 µm were fabricated in z-cut LiNbO3 by a combination of UV picosecond micromachining and thermal annealing. The laser processing parameters show a strong influence on the achievable sidewall roughness of the ridges and were systematically investigated and optimized. Finally, the surface quality is further improved by an optimized thermal post-processing. The roughness of the ridges were analysed with confocal microscopy and the scattering losses were measured at an optical characterization wavelength of 632.8 nm by using the end-fire coupling method. In these investigations the index barrier was formed by multi-energy low dose oxygen ion implantation technology in a depth of 2.7 μm. With optimized laser processing parameters and thermal post-processing a scattering loss as low as 0.1 dB/cm has been demonstrated.

Characterizations of Nanofluid Heat Transfer Enhancements

DTIC Science & Technology

2013-09-06

nanoparticles used were measured using a dynamic light scattering method through Delsa Nano C (Beckman Coulter Inc, Brea, CA) with 658 nm laser and...Alfa Aesar, Ward Hill, MA, 12733), size was verified at 54.2 ± 2.0 nm with a polydispersity index of 0.25 ± 0.02 using DLS with a 658 nm laser and a... polypropylene centrifuge tube (Thermo Fisher Scientific Inc., Pittsburgh, PA, 12-565-286B) creating a total volume of 16.7 mL of mixture that excluded any

Laser Doppler spectrometer method of particle sizing. [for air pollution

NASA Technical Reports Server (NTRS)

Weber, F. N.

1976-01-01

A spectrometer for the detection of airborne particulate pollution in the submicron size range is described. In this device, airborne particles are accelerated through a supersonic nozzle, with different sizes achieving different velocities in the gas flow. Information about the velocities of the accelerated particles is obtained with a laser-heterodyne optical system through the Doppler shift of light scattered from the particles. Detection is accomplished by means of a photomultiplier. Nozzle design and signal processing techniques are also discussed.

Nonlinear Brightness Optimization in Compton Scattering

DOE PAGES

Hartemann, Fred V.; Wu, Sheldon S. Q.

2013-07-26

In Compton scattering light sources, a laser pulse is scattered by a relativistic electron beam to generate tunable x and gamma rays. Because of the inhomogeneous nature of the incident radiation, the relativistic Lorentz boost of the electrons is modulated by the ponderomotive force during the interaction, leading to intrinsic spectral broadening and brightness limitations. We discuss these effects, along with an optimization strategy to properly balance the laser bandwidth, diffraction, and nonlinear ponderomotive force.

Coherent anti-Stokes Raman scattering and spontaneous Raman scattering diagnostics of nonequilibrium plasmas and flows

NASA Astrophysics Data System (ADS)

Lempert, Walter R.; Adamovich, Igor V.

2014-10-01

The paper provides an overview of the use of coherent anti-Stokes Raman scattering (CARS) and spontaneous Raman scattering for diagnostics of low-temperature nonequilibrium plasmas and nonequilibrium high-enthalpy flows. A brief review of the theoretical background of CARS, four-wave mixing and Raman scattering, as well as a discussion of experimental techniques and data reduction, are included. The experimental results reviewed include measurements of vibrational level populations, rotational/translational temperature, electric fields in a quasi-steady-state and transient molecular plasmas and afterglow, in nonequilibrium expansion flows, and behind strong shock waves. Insight into the kinetics of vibrational energy transfer, energy thermalization mechanisms and dynamics of the pulse discharge development, provided by these experiments, is discussed. Availability of short pulse duration, high peak power lasers, as well as broadband dye lasers, makes possible the use of these diagnostics at relatively low pressures, potentially with a sub-nanosecond time resolution, as well as obtaining single laser shot, high signal-to-noise spectra at higher pressures. Possibilities for the development of single-shot 2D CARS imaging and spectroscopy, using picosecond and femtosecond lasers, as well as novel phase matching and detection techniques, are discussed.

Melanin-targeted nonlinear microscopy for label-free molecular diagnosis and staining (Conference Presentation)

NASA Astrophysics Data System (ADS)

Warren, Warren S.

2017-02-01

Visible absorption in tissue is dominated by a very small number of chromophores (hemoglobins and melanins) with broad optical spectra; for melanins in particular, the optical absorption spectrum is typically featureless. In addition, scattering limits penetration depth. As a result, the most common microscopy application by far is with excised tissue, which can be stained. However, nonlinear optical methods have the additional advantages of greater penetration depth and reduced sensitivity to scattering. Traditional nonlinear microscopy relies on mechanisms which produce light of a different color than the irradiating lasers, such as second harmonic generation or two photon induced fluorescence, and this contrast is sparse in biological issue without expressing or injecting different chromophores. Recently, stable laser sources and pulse shaping/pulse train modulation methods have made it possible to detect a much wider range of nonlinear molecular signatures, even at modest laser powers (much less than a laser pointer). Here we show the utility of a variety of such signatures (pump-probe, pulse-shaped stimulated Raman, cross-phase modulation) to quantitatively image the biochemical composition of transparent or pigmented tissue in a variety of applications, ranging from thin, unstained tissue sections to live knockout mice. The rich biochemical information provided by this method can be used as an indicator of melanocyte activity, which in turn (for example) reflects the status of melanocytic lesions. Comparisons with model systems (synthetic melanin nanoparticles, sepia melanin) and analysis of melanin degradation pathways in vivo have led to a quantitative understanding of the molecular basis of these changes.

Two-tint pump-probe measurements using a femtosecond laser oscillator and sharp-edged optical filters.

PubMed

Kang, Kwangu; Koh, Yee Kan; Chiritescu, Catalin; Zheng, Xuan; Cahill, David G

2008-11-01

We describe a simple approach for rejecting unwanted scattered light in two types of time-resolved pump-probe measurements, time-domain thermoreflectance (TDTR) and time-resolved incoherent anti-Stokes Raman scattering (TRIARS). Sharp edged optical filters are used to create spectrally distinct pump and probe beams from the broad spectral output of a femtosecond Ti:sapphire laser oscillator. For TDTR, the diffusely scattered pump light is then blocked by a third optical filter. For TRIARS, depolarized scattering created by the pump is shifted in frequency by approximately 250 cm(-1) relative to the polarized scattering created by the probe; therefore, spectral features created by the pump and probe scattering can be easily distinguished.

Study of ocean red tide multi-parameter monitoring technology based on double-wavelength airborne lidar system

NASA Astrophysics Data System (ADS)

Lin, Hong; Wang, Xinming; Liang, Kun

2010-10-01

For monitoring and forecasting of the ocean red tide in real time, a marine environment monitoring technology based on the double-wavelength airborne lidar system is proposed. An airborne lidar is father more efficient than the traditional measure technology by the boat. At the same time, this technology can detect multi-parameter about the ocean red tide by using the double-wavelength lidar.It not only can use the infrared laser to detect the scattering signal under the water and gain the information about the red tise's density and size, but also can use the blue-green laser to detect the Brillouin scattering signal and deduce the temperature and salinity of the seawater.The red tide's density detecting model is firstly established by introducing the concept about the red tide scattering coefficient based on the Mie scattering theory. From the Brillouin scattering theory, the relationship about the blue-green laser's Brillouin scattering frequency shift value and power value with the seawater temperature and salinity is found. Then, the detecting mode1 of the saewater temperature and salinity can be established. The value of the red tide infrared scattering signal is evaluated by the simulation, and therefore the red tide particles' density can be known. At the same time, the blue-green laser's Brillouin scattering frequency shift value and power value are evaluated by simulating, and the temperature and salinity of the seawater can be known. Baed on the multi-parameters, the ocean red tide's growth can be monitored and forecasted.

Monitoring the process of tissue healing of rat skin in vivo after laser irradiation based on optical coherence tomography

NASA Astrophysics Data System (ADS)

He, Youwu; Wu, Shulian; Li, Zhifang; Cai, Shoudong; Li, Hui

2010-11-01

It is imperative to evaluate the tissue wound healing response after laser irradiation so as to develop effective devices for this clinical indication, and evaluate the thermal damage degree to take appropriate treatment. In our research, we prepare 6 white rat (approximately 2 months old, weight :28+/-2g). Each rat was injected intraperitoneally a single dose of 2% pentobarbital sodium. After the rat was anesthetized, the two side of the rats' back were denuded and antisepsised a standardized. An Er:YAG laser (2940nm, 2.5J/cm2, single spot, 4 times) was irradiated on rat skin in vivo, and the skin which before irradiated and the process of renovating scathe that irradiated after Er:YAG laser were observed by an Optical coherence tomography (OCT). The tissue recovery is about a twelve -day period. The results indicate that the scattering coefficient of post- tissue has changed distinctly. The and flexibility fiber is the chief component of rat dermis and the collagen is the main scattering material. The normal tissue has a large scattering coefficient, after laser irradiated, the collagen became concreting and putrescence and caused the structure change. It became more uniform density distribution, which results in a reduced scattering coefficient. In a word, OCT can noninvasively monitor changes in collagen structure and the recover process in thermal damage through monitor the tissue scattering coefficient.

Collective effects in the Thomson back-scattering between a laser pulse and a relativistic electron beam

NASA Astrophysics Data System (ADS)

Bacci, A.; Maroli, C.; Petrillo, V.; Serafini, L.

2006-08-01

Collective effects in the radiation emission via Thomson back-scattering of an intense optical laser pulse by high brightness electron beams are analyzed. The micro-bunching of the electron beam on the scale of the wavelength of the emitted radiation and the consequent free-electron-laser instability may significantly enhance the number of photons emitted. Scaling-laws of the radiation properties, both in the collective and incoherent spontaneous regimes versus laser and electron beam parameters are discussed in the framework of the one-dimensional model.

LASERS IN MEDICINE: Determination of the optical characteristics of turbid media by the laser optoacoustic method

NASA Astrophysics Data System (ADS)

Karabutov, Aleksander A.; Pelivanov, Ivan M.; Podymova, N. B.; Skipetrov, S. E.

1999-12-01

A method, based on the optoacoustic effect for determination of the spatial distribution of the light intensity in turbid media and of the optical characteristics of such media was proposed (and implemented experimentally). A temporal profile of the pressure of a thermo-optically excited acoustic pulse was found to be governed by the absorption coefficient and by the spatial distribution of the light intensity in the investigated medium. The absorption coefficient and the reduced light-scattering coefficient of model turbid water-like media were measured by the optoacoustic method. The results of a direct determination of the spatial light-intensity distribution agreed with a theoretical calculation made in the diffusion approximation.

Corneal imaging by second and third harmonic generation microscopy

NASA Astrophysics Data System (ADS)

Brocas, Arnaud; Jay, Louis; Mottay, Eric; Brunette, Isabelle; Ozaki, Tsuneyuki

2008-02-01

Advanced imaging methods are essential tools for improved outcome of refractive surgery. Second harmonic generation (SHG) and third harmonic generation (THG) microscopy are noninvasive high-resolution imaging methods, which can discriminate the different layers of the cornea, thus having strong impact on the outcome of laser surgery. In this work, we use an Ytterbium femtosecond laser as the laser source, the longer wavelength of which reduces scattering, and allows simultaneous SHG and THG imaging. We present SHG and THG images and profiles of pig corneas that clearly show the anterior surface of the cornea, the entry in the stroma and its end, and the posterior surface of the cornea. These observations allow localizing the epithelium, the stroma and the endothelium. Other experiments give information about the structure and cytology of the corneal layers.

Laser-Induced-Fluorescence Photogrammetry and Videogrammetry

NASA Technical Reports Server (NTRS)

Danehy, Paul; Jones, Tom; Connell, John; Belvin, Keith; Watson, Kent

2004-01-01

An improved method of dot-projection photogrammetry and an extension of the method to encompass dot-projection videogrammetry overcome some deficiencies of dot-projection photogrammetry as previously practiced. The improved method makes it possible to perform dot-projection photogrammetry or videogrammetry on targets that have previously not been amenable to dot-projection photogrammetry because they do not scatter enough light. Such targets include ones that are transparent, specularly reflective, or dark. In standard dot-projection photogrammetry, multiple beams of white light are projected onto the surface of an object of interest (denoted the target) to form a known pattern of bright dots. The illuminated surface is imaged in one or more cameras oriented at a nonzero angle or angles with respect to a central axis of the illuminating beams. The locations of the dots in the image(s) contain stereoscopic information on the locations of the dots, and, hence, on the location, shape, and orientation of the illuminated surface of the target. The images are digitized and processed to extract this information. Hardware and software to implement standard dot-projection photogrammetry are commercially available. Success in dot-projection photogrammetry depends on achieving sufficient signal-to-noise ratios: that is, it depends on scattering of enough light by the target so that the dots as imaged in the camera(s) stand out clearly against the ambient-illumination component of the image of the target. In one technique used previously to increase the signal-to-noise ratio, the target is illuminated by intense, pulsed laser light and the light entering the camera(s) is band-pass filtered at the laser wavelength. Unfortunately, speckle caused by the coherence of the laser light engenders apparent movement in the projected dots, thereby giving rise to errors in the measurement of the centroids of the dots and corresponding errors in the computed shape and location of the surface of the target. The improved method is denoted laser-induced-fluorescence photogrammetry.

Development of a YAG laser system for the edge Thomson scattering system in ITER.

PubMed

Hatae, T; Yatsuka, E; Hayashi, T; Yoshida, H; Ono, T; Kusama, Y

2012-10-01

A prototype YAG laser system for the edge Thomson scattering system in ITER has been newly developed. Performance of the laser amplifier was improved by using flow tubes made of samarium-doped glass; the small signal gain reached 20 at its maximum. As a result, an output energy of 7.66 J at 100 Hz was successfully achieved, and the performance exceeded the target performance (5 J, 100 Hz).

Stimulated Brillouin Scattering Phase Conjugation in Fiber Optic Waveguides

DTIC Science & Technology

2008-07-01

61] The discrepancy is reduced since the effective length of the interaction may be limited by the coherence length of the signal laser as in Eq...these cases, the coherence length of the pulsed laser typically limits the effective length of the Brillouin scattering interaction. Long... coherence length lasers with long fiber SBS media have been used to reduce threshold energy, but as indicated at the end of Chapter 2, this has produced

Considerations on the Retrieval of Plume Particle Properties from the AFRPL Transmissometer and Polarization-Scattering Experiments.

DTIC Science & Technology

1984-08-01

transmissometer experiment. In these measure - ments, simple transmission measurements of laser radiation through a diameter of the plume are made. With...Air Force Rocket Propulsion Laboratory4{AFRPL). In one experiment, simple laser transmission measurements are made over a full diameter line of sight...consist of measure - ments of the polarization of laser radiation which has been scattered by plume particulates. The analysis is presented in Section

Upgraded divertor Thomson scattering system on DIII-D

DOE Office of Scientific and Technical Information (OSTI.GOV)

Glass, F., E-mail: glassf@fusion.gat.com; Carlstrom, T. N.; Du, D.

2016-11-15

A design to extend the unique divertor Thomson scattering system on DIII-D to allow measurements of electron temperature and density in high triangularity plasmas is presented. Access to this region is selectable on a shot-by-shot basis by redirecting the laser beam of the existing divertor Thomson system inboard — beneath the lower floor using a moveable, high-damage threshold, in-vacuum mirror — and then redirecting again vertically. The currently measured divertor region remains available with this mirror retracted. Scattered light is collected from viewchords near the divertor floor using in-vacuum, high temperature optical elements and relayed through the port window, beforemore » being coupled into optical fiber bundles. At higher elevations from the floor, measurements are made by dynamically re-focusing the existing divertor system collection optics. Nd:YAG laser timing, analysis of the scattered light spectrum via polychromators, data acquisition, and calibration are all handled by existing systems or methods of the current multi-pulse Thomson scattering system. Existing filtered polychromators with 7 spectral channels are employed to provide maximum measurement breadth (T{sub e} in the range of 0.5 eV–2 keV, n{sub e} in the range of 5 × 10{sup 18}–1 × 10{sup 21} m{sup 3}) for both low T{sub e} in detachment and high T{sub e} measurement up beyond the separatrix.« less

Laser applications and system considerations in ocular imaging

PubMed Central

Elsner, Ann E.; Muller, Matthew S.

2009-01-01

We review laser applications for primarily in vivo ocular imaging techniques, describing their constraints based on biological tissue properties, safety, and the performance of the imaging system. We discuss the need for cost effective sources with practical wavelength tuning capabilities for spectral studies. Techniques to probe the pathological changes of layers beneath the highly scattering retina and diagnose the onset of various eye diseases are described. The recent development of several optical coherence tomography based systems for functional ocular imaging is reviewed, as well as linear and nonlinear ocular imaging techniques performed with ultrafast lasers, emphasizing recent source developments and methods to enhance imaging contrast. PMID:21052482

Molecular-beam epitaxy of 7-8 μm range quantum-cascade laser heterostructures

NASA Astrophysics Data System (ADS)

Babichev, A. V.; Denisov, D. V.; Filimonov, A. V.; Nevedomsky, V. N.; Kurochkin, A. S.; Gladyshev, A. G.; Karachinsky, L. Ya; Sokolovskii, G. S.; Novikov, I. I.; Bousseksou, A.; Egorov, A. Yu

2017-11-01

The method of molecular beam epitaxy demonstrates the possibility to create high quality heterostructures of quantum cascade lasers in a spectral range of 7-8 μm containing 50 quantum cascades in an active region. Design based on the principle of two-phonon resonant scattering is used. X-ray diffraction and transmission electron microscopy experiments confirm high structural properties of the created heterostructures, e.g. the identity of the composition and thickness of epitaxial layers in all 50 cascades. Edge-emitting lasers based on the grown heterostructure demonstrate lasing with threshold current density of 2.8 kA/cm2 at a temperature of 78 K.

III-V semiconductor Quantum Well systems: Physics of Gallium Arsenide two-dimensional hole systems and engineering of mid-infrared Quantum Cascade lasers

NASA Astrophysics Data System (ADS)

Chiu, YenTing

This dissertation examines two types of III-V semiconductor quantum well systems: two-dimensional holes in GaAs, and mid-infrared Quantum Cascade lasers. GaAs holes have a much reduced hyperfine interaction with the nuclei due to the p-like orbital, resulting in a longer hole spin coherence time comparing to the electron spin coherence time. Therefore, holes' spins are promising candidates for quantum computing qubits, but the effective mass and the Lande g-factor, whose product determines the spin-susceptibility of holes, are not well known. In this thesis, we measure the effective hole mass through analyzing the temperature dependence of Shubnikov-de Haas oscillations in a relatively strong interacting two-dimensional hole systems confined to a 20 nm-wide, (311)A GaAs quantum well. The holes in this system occupy two nearly-degenerate spin subbands whose effective mass we measure to be ˜ 0.2 me. We then apply a sufficiently strong parallel magnetic field to fully depopulate one of the spin subbands, and the spin susceptibility of the two-dimensional hole system is deduced from the depopulation field. We also confine holes in closely spaced bilayer GaAs quantum wells to study the interlayer tunneling spectrum as a function of interlayer bias and in-plane magnetic field, in hope of probing the hole's Fermi contour. Quantum Cascade lasers are one of the major mid-infrared light sources well suited for applications in health and environmental sensing. One of the important factors that affect Quantum Cascade laser performance is the quality of the interfaces between the epitaxial layers. What has long been neglected is that interface roughness causes intersubband scattering, and thus affecting the relation between the lifetimes of the upper and lower laser states, which determines if population inversion is possible. We first utilize strategically added interface roughness in the laser design to engineer the intersubband scattering lifetimes. We further experimentally prove the importance of interface roughness on intersubband scattering by measuring the electron transit time of different quantum cascade lasers and comparing them to the calculated upper laser level lifetimes with and without taking into account interface roughness induced intersubband scattering. A significantly better correlation is found between the experimental results and the calculation when the interface roughness scattering is included. Lastly, we study the effect of growth asymmetry on scattering mechanisms in mid-infrared Quantum Cascade lasers. Due to the dopant migration of around 10 nm along the growth direction of InGaAs/InAlAs Quantum Cascade laser structures, ionized impurity scattering is found to have a non-negligible influence on the lifetime of the upper laser level when the laser is biased in the polarity that electrons flow along the growth direction, in sharp contrast to the situation for the opposite polarity.

Observation of motion of colloidal particles undergoing flowing Brownian motion using self-mixing laser velocimetry with a thin-slice solid-state laser.

PubMed

Sudo, S; Ohtomo, T; Otsuka, K

2015-08-01

We achieved a highly sensitive method for observing the motion of colloidal particles in a flowing suspension using a self-mixing laser Doppler velocimeter (LDV) comprising a laser-diode-pumped thin-slice solid-state laser and a simple photodiode. We describe the measurement method and the optical system of the self-mixing LDV for real-time measurements of the motion of colloidal particles. For a condensed solution, when the light scattered from the particles is reinjected into the solid-state laser, the laser output is modulated in intensity by the reinjected laser light. Thus, we can capture the motion of colloidal particles from the spectrum of the modulated laser output. For a diluted solution, when the relaxation oscillation frequency coincides with the Doppler shift frequency, f_d, which is related to the average velocity of the particles, the spectrum reflecting the motion of the colloidal particles is enhanced by the resonant excitation of relaxation oscillations. Then, the spectral peak reflecting the motion of colloidal particles appears at 2×f_d. The spectrum reflecting the motion of colloidal particles in a flowing diluted solution can be measured with high sensitivity, owing to the enhancement of the spectrum by the thin-slice solid-state laser.

Free–free experiments: the search for dressed atom effects

NASA Astrophysics Data System (ADS)

Martin, N. L. S.; Weaver, C. M.; Kim, B. N.; deHarak, B. A.

2018-07-01

Experiments on free–free electron scattering, specifically the absorption or emission of 1.17 eV photons from a Nd:YAG laser field by an unbound electron when it is scattered by an atom or molecule, are reviewed. For large scattering angles such experiments are well described by a simple analytical theory that is independent of the properties of the target. At small scattering angles this theory breaks down for targets with a high dipole polarizability α, and an additional term needs to be incorporated in the scattering amplitude. This term is proportional to the dipole polarizability, and hence introduces the properties of the target into the free–free cross section—i.e., the laser field ‘dresses’ the atom. A progress report is given of free–free experiments designed to look for such ‘dressed atom’ effects during the electron-impact excitation of argon in the presence of a laser field; the lowest excited states of argon have α ≈ 300 atomic units.

Study of resonance light scattering for remote optical probing

NASA Technical Reports Server (NTRS)

Penney, C. M.; Morey, W. W.; St. Peters, R. L.; Silverstein, S. D.; Lapp, M.; White, D. R.

1973-01-01

Enhanced scattering and fluorescence processes in the visible and UV were investigated which will enable improved remote measurements of gas properties. The theoretical relationship between scattering and fluorescence from an isolated molecule in the approach to resonance is examined through analysis of the time dependence of re-emitted light following excitation of pulsed incident light. Quantitative estimates are developed for the relative and absolute intensities of fluorescence and resonance scattering. New results are obtained for depolarization of scattering excited by light at wavelengths within a dissociative continuum. The experimental work was performed in two separate facilities. One of these utilizes argon and krypton lasers, single moded by a tilted etalon, and a 3/4 meter double monochromator. This facility was used to determine properties of the re-emission from NO2, I2 and O3 excited by visible light. The second facility involves a narrow-line dye laser, and a 3/4 meter single monochromator. The dye laser produces pulsed light with 5 nsec pulse duration and 0.005 nm spectral width.

Extraction of inhomogeneous broadening and nonradiative losses in InAs quantum-dot lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chow, Weng W.; Liu, Alan Y.; Gossard, Arthur C.

2015-10-28

We present a method to quantify inhomogeneous broadening and nonradiative losses in quantum dot lasers by comparing the gain and spontaneous emission results of a microscopic laser theory with measurements made on 1.3 μm InAs quantum-dot lasers. Calculated spontaneous-emission spectra are first matched to those measured experimentally to determine the inhomogeneous broadening in the experimental samples. This is possible because treatment of carrier scattering at the level of quantum kinetic equations provides the homogeneously broadened spectra without use of free parameters, such as the dephasing rate. Thus we then extract the nonradiative recombination current associated with the quantum-dot active regionmore » from a comparison of measured and calculated gain versus current relations.« less

Extraction of inhomogeneous broadening and nonradiative losses in InAs quantum-dot lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chow, Weng W., E-mail: wwchow@sandia.gov; Liu, Alan Y.; Gossard, Arthur C.

2015-10-26

We present a method to quantify inhomogeneous broadening and nonradiative losses in quantum dot lasers by comparing the gain and spontaneous emission results of a microscopic laser theory with measurements made on 1.3 μm InAs quantum-dot lasers. Calculated spontaneous-emission spectra are first matched to those measured experimentally to determine the inhomogeneous broadening in the experimental samples. This is possible because treatment of carrier scattering at the level of quantum kinetic equations provides the homogeneously broadened spectra without use of free parameters, such as the dephasing rate. We then extract the nonradiative recombination current associated with the quantum-dot active region from amore » comparison of measured and calculated gain versus current relations.« less

LASER METHODS IN MEDICINE: Light absorption in blood during low-intensity laser irradiation of skin

NASA Astrophysics Data System (ADS)

Barun, V. V.; Ivanov, A. P.

2010-06-01

An analytical procedure is proposed for describing optical fields in biological tissues inhomogeneous in the depth direction, such as human skin, with allowance for multiple scattering. The procedure is used to investigate the depth distribution of the optical power density in homogeneous and multilayer dermis when the skin is exposed to a laser beam. We calculate the absorbed laser power spectra for oxy- and deoxyhaemoglobin at different depths in relation to the absorption selectivity of these haemoglobin derivatives and the spectral dependence of the optical power density and demonstrate that the spectra vary considerably with depth. A simple exponential approximation is proposed for the depth distribution of the power density in the epidermis and dermis.

Diagnostic principles of four-wave mixing for plasmas

NASA Astrophysics Data System (ADS)

Meng, Yuedong; Li, Jiangang; Luo, Jiarong

1994-11-01

A new method is used to diagnose plasma density space-profiles that involves phase conjugate reflection of four-wave mixing. Theoretical calculations for plasma parameters in the HT-6M tokamak show that two pump-wave beams (HCN laser), with a power of 1 W together with a signal beam (D2O or CH3F laser) of 0.1 W, can create a reflection of 0.1 to 0.43 mW with a phase conjugate to the signal where the cross section of all external beams is 1 cm2. This means that the reflective ratio of four-wave mixing is two orders larger than the ratio of laser superheating scatter. The lower power laser, therefore, can be used to diagnose plasmas.

Using scattering theory to compute invariant manifolds and numerical results for the laser-driven Hénon-Heiles system.

PubMed

Blazevski, Daniel; Franklin, Jennifer

2012-12-01

Scattering theory is a convenient way to describe systems that are subject to time-dependent perturbations which are localized in time. Using scattering theory, one can compute time-dependent invariant objects for the perturbed system knowing the invariant objects of the unperturbed system. In this paper, we use scattering theory to give numerical computations of invariant manifolds appearing in laser-driven reactions. In this setting, invariant manifolds separate regions of phase space that lead to different outcomes of the reaction and can be used to compute reaction rates.

First results from the Thomson scattering diagnostic on Proto-MPEX

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biewer, Theodore M; Meitner, Steven J; Rapp, Juergen

2016-01-01

A Thomson scattering diagnostic has been successfully implemented on the prototype Material Plasma Exposure eXperiment (Proto-MPEX) at Oak Ridge National Laboratory. The diagnostic collects the light scattered by plasma electrons and spectroscopically resolves the Doppler shift imparted to the light by the velocity of the electrons. The spread in velocities is proportional to the electron temperature, while the total number of photons is proportional to the electron density. Thomson scattering is a technique used on many devices to measure the electron temperature (Te) and electron density (ne) of the plasma. A challenging aspect of the technique is to discriminate themore » small number of Thomson scattered photons against the large peak of background photons from the high-power laser used to probe the plasma. A variety of methods are used to mitigate the background photons in Proto-MPEX, including Brewster angled windows, viewing dumps, and light baffles. With these methods, first results were measured from Argon plasmas in Proto-MPEX, indicating Te ~ 2 eV and ne ~ 1x1019 m-3. The configuration of the Proto-MPEX Thomson scattering diagnostic will be described and plans for improvement will be given.« less

Evaluation of blood microcirculation parameters by combined use of laser Doppler flowmetry and videocapillaroscopy methods

NASA Astrophysics Data System (ADS)

Volkov, M. V.; Kostrova, D. A.; Margaryants, N. B.; Gurov, I. P.; Erofeev, N. P.; Dremin, V. V.; Zharkikh, E. V.; Zherebtsov, E. A.; Kozlov, I. O.; Dunaev, A. V.

2017-03-01

Laser Doppler flowmetry (LDF) is widely used for diagnosing blood microcirculation diseases. It is well known that the Doppler shift of laser radiation scattered by moving red blood cells (RBC) can be assessed through analyzing photocurrent produced by a photodetector. LDF signal contains information about regulating blood flow rhythms: myogenic, cardiac, nervous and endothelial. The method of videocapillaroscopy (VCS) allows local capillary blood flow velocity evaluation and, using video data processing algorithms, is able to assess RBC velocity changes into capillary. We present the results of simultaneous investigations of changes in tissue perfusion of the distal phalanx of human finger by the LDF as well as changes in capillary blood flow velocity in the nail bed evaluated by the VCS method during arterial occlusion test. The experimental results confirmed the correspondence between blood perfusion and blood flow velocity.

Total Internal Reflection Microscopy (TIRM) as a nondestructive surface damage assessment tool

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liao, Z.M.; Cohen, S.J.; Taylor, J.R.

1994-10-01

An easy to use, nondestructive, method for evaluating subsurface damage in polished substrates has been established at LLNL. Subsurface damage has been related to laser damage in coated optical components used in high power, high repetition rate laser systems. Total Internal Reflection Microscopy (TIRM) has been shown to be a viable nondestructive technique in analyzing subsurface damage in optical components. A successful TIRM system has been established for evaluating subsurface damage on fused silica components. Laser light scattering from subsurface damage sites is collected through a Nomarski microscope. These images are then captured by a CCD camera for analysis onmore » a computer. A variety of optics, including components with intentional subsurface damage due to grinding and polishing, have been analyzed and their TIRM images compared to an existing destructive etching method. Methods for quantitative measurement of subsurface damage are also discussed.« less

Further Evaluation of Spray Characterization of Sprayers Typically Used in Vector Control

DTIC Science & Technology

2012-01-01

E1260. Standard test method for determining liquid drop size characteristics in a spray using optical nonimaging light-scattering instru- ments...The time that the spray cloud was directed through the optical path of the laser varied between sprayers depending on the width of the spray plume

Spray Characterization of Ultra-Low-Volume Sprayers Typically Used in Vector Control

DTIC Science & Technology

2009-01-01

Standard test method for determining liquid drop size characteristics in a spray using optical nonimaging light-scattering instruments. An- nual book of...cloud was directed through the optical path of the laser varied between sprayers, depending on the width of the spray 1 Mention of a trademark

Hyperbolic umbilic caustics from oblate water drops with tilted illumination: Observations

NASA Astrophysics Data System (ADS)

Jobe, Oli; Thiessen, David B.; Marston, Philip L.

2017-11-01

Various groups have reported observations of hyperbolic umbilic diffraction catastrophe patterns in the far-field scattering by oblate acoustically levitated drops with symmetric illumination. In observations of that type the drop's symmetry axis is vertical and the illuminating light beam (typically an expanded laser beam) travels horizontally. In the research summarized here, scattering patterns in the primary rainbow region and drop measurements were recorded with vertically tilted laser beam illumination having a grazing angle as large as 4 degrees. The findings from these observations may be summarized as follows: (a) It remains possible to adjust the drop aspect ratio (diameter/height) = D/H so as to produce a V-shaped hyperbolic umbilic focal section (HUFS) in the far-field scattering. (b) The shift in the required D/H was typically an increase of less than 1% and was quadratic in the tilt. (c) The apex of the V-shaped HUFS was shifted vertically by an amount proportional to the tilt with a coefficient close to unity. The levitated drops had negligible up-down asymmetry. Our method of investigation should be useful for other generalized rainbows with tilted illumination.

Sensitivity of Depth-Integrated Satellite Lidar to Subaqueous Scattering

NASA Technical Reports Server (NTRS)

Barton, Jonathan S.; Jasinski, Michael F.

2011-01-01

A method is presented for estimating subaqueous integrated backscatter from the CALIOP lidar. The algorithm takes into account specular reflection of laser light, laser scattering by wind-generated foam as well as sun glint and solar scattering from the foam Analyses show that the estimated subaqueous integrated backscatter is most sensitive to the estimate of transmittance used in the atmospheric correction, and is very insensitive to the estimate of wind speed used. As a case study, CALIOP data over Tampa Bay were compared to MODIS 645 nm remote sensing reflectance, which previously has been shown to be nearly linearly related to turbidity. The results indicate good correlation on nearly all CALIOP clear-free dates during the period 2006 through 2007, particularly those with relatively high atmospheric transmittance. When data are composited over the entire period the correlation is reduced but still statistically significant, an indication of variability in the biogeochemical composition in the water. Overall, the favorable results show promise for the application of satellite lidar integrated backscatter in providing information about subsurface backscatter properties, which can be extracted using appropriate models

Scattered UV irradiation during VISX excimer laser keratorefractive surgery.

PubMed

Hope, R J; Weber, E D; Bower, K S; Pasternak, J P; Sliney, D H

2008-04-01

To evaluate the potential occupational health hazards associated with scattered ultraviolet (UV) radiation during photorefractive keratectomy (PRK) using the VISX Star S3 excimer laser. The Laser Vision Center, National Naval Medical Center, Bethesda, Maryland, USA. Intraoperative radiometric measurements were made with the Ophir Power/Energy Meter (LaserStar Model PD-10 with silicon detector) during PRK treatments as well as during required calibration procedures at a distance of 20.3 cm from the left cornea. These measurements were evaluated using a worst-case scenario for exposure, and then compared with the American Conference of Governmental Industrial Hygeinists (ACGIH) Threshold Value Limits (TVL) to perform a risk/hazard analysis. During the PRK procedures, the highest measured value was 248.4 nJ/pulse. During the calibration procedures, the highest measured UV scattered radiation level was 149.6 nJ/pulse. The maximum treatment time was 52 seconds. Using a worst-case scenario in which all treatments used the maximum power and time, the total energy per eye treated was 0.132 mJ/cm2 and the total UV radiation at close range (80 cm from the treated eye) was 0.0085 mJ/cm2. With a workload of 20 patients, the total occupational exposure at 80 cm to actinic UV radiation in an 8-hour period would be 0.425 mJ/cm2. The scattered actinic UV laser radiation from the VISX Star S3 excimer laser did not exceed occupational exposure limits during a busy 8-hour workday, provided that operating room personnel were at least 80 cm from the treated eye. While the use of protective eyewear is always prudent, this study demonstrates that the trace amounts of scattered laser emissions produced by this laser do not pose a serious health risk even without the use of protective eyewear.

Femtosecond laser-ablated Fresnel zone plate fiber probe and sensing applications

NASA Astrophysics Data System (ADS)

Tan, Xiaoling; Geng, Youfu; Chen, Yan; Li, Shiguo; Wang, Xinzhong

2018-02-01

We investigate the Fresnel zone plate (FZP) inscribed on multimode fiber endface using femtosecond laser ablation and its application in sensing. The mode transmission through fiber tips with FZP is investigated both by the beam propagation method theoretically and by measuring the beam images with a charge-coupled device camera experimentally, which show a good agreement. Such devices are tested for surface-enhanced Raman scattering (SERS) using the aqueous solution of rhodamine 6G under a Raman spectroscopy. The experimental results demonstrate that the SERS signal is enhanced benefiting from focal ability of FZP, which is a promising method for the particular biochemical spectra sensing applications.

Propagation of terahertz pulses in random media.

PubMed

Pearce, Jeremy; Jian, Zhongping; Mittleman, Daniel M

2004-02-15

We describe measurements of single-cycle terahertz pulse propagation in a random medium. The unique capabilities of terahertz time-domain spectroscopy permit the characterization of a multiply scattered field with unprecedented spatial and temporal resolution. With these results, we can develop a framework for understanding the statistics of broadband laser speckle. Also, the ability to extract information on the phase of the field opens up new possibilities for characterizing multiply scattered waves. We illustrate this with a simple example, which involves computing a time-windowed temporal correlation between fields measured at different spatial locations. This enables the identification of individual scattering events, and could lead to a new method for imaging in random media.

FIBER LASER CONSTRUCTION AND THEORY INCLUDING FIBER BRAGG GRATINGS Photonic Crystal Fibers (PCFs) and applications of gas filled PCFs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sutton, Jacob O.

The principles used in fiber lasers have been around for a while but it is only within the past few years that fiber lasers have become commercially available and used in high power laser applications. This paper will focus on the basic design principles of fiber lasers, including fiber Bragg gratings, principles of operation, and forms of non-linear effects. It will describe the type and associated doping of the fiber used and difficult designs used to guide energy from the pump to the active medium. Topics covered include fiber laser design, fiber Bragg gratings, materials used, differences in quantum energymore » loss, thermo-optical effects, stimulated Raman scattering, Brillouin scattering, photonic crystal fibers and applications of gas filled Photonic Crystal Fibers (PCFs). Thanks to fiber lasers, the energy required to produce high power lasers has greatly dropped and as such we can now produce kW power using a standard 120V 15A circuit. High power laser applications are always requiring more power. The fiber laser can now deliver the greater power that these applications demand. Future applications requiring more power than can be combined using standard materials or configurations will need to be developed to overcome the high energy density and high non-linear optical scattering effects present during high power operations.« less

Interaction physics for the stimulated Brillouin scattering of a laser in laser driven fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yadav, Pinki; Gupta, D.N.; Avinash, K., E-mail: dngupta@physics.du.ac.in

2014-07-01

Energy exchange between pump wave and ion-acoustic wave during the stimulated Brillouin Scattering process in relativistic laser-plasma interactions is studied, including the effect of damping coefficient of electron-ion collision by obeying the energy and momentum conservations. The variations of plasma density and damping coefficient of electron-ion collision change the amplitudes of the interacting wave. The relativistic mass effect modifies the dispersion relations of the interacting waves and consequently, the energy exchange during the stimulated Brillouin Scattering is affected. The collisional damping of electron-ion collision in the plasma is shown to have an important effect on the evolution of the interactingmore » waves. (author)« less

Self-mixing detection of backscattered radiation in a single-mode erbium fibre laser for Doppler spectroscopy and velocity measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dmitriev, A K; Konovalov, A N; Ul'yanov, V A

2014-04-28

We report an experimental study of the self-mixing effect in a single-mode multifrequency erbium fibre laser when radiation backscattered from an external moving object arrives at its cavity. To eliminate resulting chaotic pulsations in the laser, we have proposed a technique for suppressing backscattered radiation through the use of multimode fibre for radiation delivery. The multifrequency operation of the laser has been shown to lead to strong fluctuations of the amplitude of the Doppler signal and a nonmonotonic variation of the amplitude with distance to the scattering object. In spite of these features, the self-mixing signal was detected with amore » high signal-to-noise ratio (above 10{sup 2}) when the radiation was scattered by a rotating disc, and the Doppler frequency shift, evaluated as the centroid of its spectrum, had high stability (0.15%) and linearity relative to the rotation rate. We conclude that the self-mixing effect in this type of fibre laser can be used for measuring the velocity of scattering objects and in Doppler spectroscopy for monitoring the laser evaporation of materials and biological tissues. (control of laser radiation parameters)« less

Absorption and scattering of laser radiation by the diffusion flame of aviation kerosene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gvozdev, S V; Glova, A F; Dubrovskii, V Yu

2012-04-30

The absorption coefficient of the radiation of a repetitively pulsed Nd : YAG laser with an average output power up to 6 W and of a cw ytterbium optical fibre laser with an output power up to 3 kW was measured in the diffusion flame of aviation kerosene burning on a free surface in the atmospheric air. The absorption coefficient as a function of flame length, radiation power, and radiation intensity, which was varied in the {approx}10{sup 3} - 5 Multiplication-Sign 10{sup 4} W cm{sup -2} range, was obtained for two distances (1 and 2 cm) between the laser beammore » axis and the surface. The coefficient of radiation absorption by kerosene flame was compared with that in ethanol and kerosene - ethanol mixture flames. The radiation power scattered by a small segment of the kerosene flame irradiated by Nd : YAG laser radiation was measured as a function of longitudinal and azimuthal coordinates. An estimate was made of the total scattered radiation power.« less

Plasma turbulence imaging using high-power laser Thomson scattering

NASA Astrophysics Data System (ADS)

Zweben, S. J.; Caird, J.; Davis, W.; Johnson, D. W.; Le Blanc, B. P.

2001-01-01

The two-dimensional (2D) structure of plasma density turbulence in a magnetically confined plasma can potentially be measured using a Thomson scattering system made from components of the Nova laser of Lawrence Livermore National Laboratory. For a plasma such as the National Spherical Torus Experiment at the Princeton Plasma Physics Laboratory, the laser would form an ≈10-cm-wide plane sheet beam passing vertically through the chamber across the magnetic field. The scattered light would be imaged by a charge coupled device camera viewing along the direction of the magnetic field. The laser energy required to make 2D images of density turbulence is in the range 1-3 kJ, which can potentially be obtained from a set of frequency-doubled Nd:glass amplifiers with diameters in the range of 208-315 mm. A laser pulse width of ⩽100 ns would be short enough to capture the highest frequency components of the expected density fluctuations.

Absorption and scattering of laser radiation by the diffusion flame of aviation kerosene

NASA Astrophysics Data System (ADS)

Gvozdev, S. V.; Glova, A. F.; Dubrovskii, V. Yu; Durmanov, S. T.; Krasyukov, A. G.; Lysikov, A. Yu; Smirnov, G. V.; Solomakhin, V. B.

2012-04-01

The absorption coefficient of the radiation of a repetitively pulsed Nd : YAG laser with an average output power up to 6 W and of a cw ytterbium optical fibre laser with an output power up to 3 kW was measured in the diffusion flame of aviation kerosene burning on a free surface in the atmospheric air. The absorption coefficient as a function of flame length, radiation power, and radiation intensity, which was varied in the ~103 — 5×104 W cm-2 range, was obtained for two distances (1 and 2 cm) between the laser beam axis and the surface. The coefficient of radiation absorption by kerosene flame was compared with that in ethanol and kerosene — ethanol mixture flames. The radiation power scattered by a small segment of the kerosene flame irradiated by Nd : YAG laser radiation was measured as a function of longitudinal and azimuthal coordinates. An estimate was made of the total scattered radiation power.

Catadioptric Optics for laser Doppler velocimeter applications

NASA Technical Reports Server (NTRS)

Dunagan, Stephen E.

1989-01-01

In the design of a laser velocimeter system, attention must be given to the performance of the optical elements in their two principal tasks: focusing laser radiation into the probe volume, and collecting the scattered light. For large aperture applications, custom lens design and fabrication costs, long optical path requirements, and chromatic aberration (for two color operation) can be problematic. The adaptation of low cost Schmidt-Cassegrain astronomical telescopes to perform these laser beam manipulation and scattered light collection tasks is examined. A generic telescope design is analyzed using ray tracing and Gaussian beam propagation theory, and a simple modification procedure for converting from infinite to near unity conjugate ratio operation with image quality near the diffraction limit was identified. Modification requirements and performance are predicted for a range of geometries. Finally, a 200-mm-aperture telescope was modified for f/10 operation; performance data for this modified optic for both laser beam focusing and scattered light collection tasks agree well with predictions.

LASER BIOLOGY AND MEDICINE: Visualisation of details of a complicated inner structure of model objects by the method of diffusion optical tomography

NASA Astrophysics Data System (ADS)

Tret'yakov, Evgeniy V.; Shuvalov, Vladimir V.; Shutov, I. V.

2002-11-01

An approximate algorithm is tested for solving the problem of diffusion optical tomography in experiments on the visualisation of details of the inner structure of strongly scattering model objects containing scattering and semitransparent inclusions, as well as absorbing inclusions located inside other optical inhomogeneities. The stability of the algorithm to errors is demonstrated, which allows its use for a rapid (2 — 3 min) image reconstruction of the details of objects with a complicated inner structure.

Particle Image Velocimetry Applications Using Fluorescent Dye-Doped Particles

NASA Technical Reports Server (NTRS)

Petrosky, Brian J.; Maisto, Pietro; Lowe, K. Todd; Andre, Matthieu A.; Bardet, Philippe M.; Tiemsin, Patsy I.; Wohl, Christopher J.; Danehy, Paul M.

2015-01-01

Polystyrene latex sphere particles are widely used to seed flows for velocimetry techniques such as Particle Image Velocimetry (PIV) and Laser Doppler Velocimetry (LDV). These particles may be doped with fluorescent dyes such that signals spectrally shifted from the incident laser wavelength may be detected via Laser Induced Fluorescence (LIF). An attractive application of the LIF signal is achieving velocimetry in the presence of strong interference from laser scatter, opening up new research possibilities very near solid surfaces or at liquid/gas interfaces. Additionally, LIF signals can be used to tag different fluid streams to study mixing. While fluorescence-based PIV has been performed by many researchers for particles dispersed in water flows, the current work is among the first in applying the technique to micron-scale particles dispersed in a gas. A key requirement for such an application is addressing potential health hazards from fluorescent dyes; successful doping of Kiton Red 620 (KR620) has enabled the use of this relatively safe dye for fluorescence PIV for the first time. In this paper, basic applications proving the concept of PIV using the LIF signal from KR620-doped particles are exhibited for a free jet and a twophase flow apparatus. Results indicate that while the fluorescence PIV techniques are roughly 2 orders of magnitude weaker than Mie scattering, they provide a viable method for obtaining data in flow regions previously inaccessible via standard PIV. These techniques have the potential to also complement Mie scattering signals, for example in multi-stream and/or multi-phase experiments.

Current use and future perspectives of diagnostic and therapeutic lasers in Oral Medicine.

PubMed

Maia, A M A; Barkokebas, A; Pires, A P; Barros, L F; Carvalho, A A T; Leão, J C

2008-10-01

Several diagnostic and therapeutic methods are based on the optical properties of lasers. In therapeutic applications, laser light is absorbed in a specific manner, whereas light is scattered, reflected, or transmitted from different structures. Improvements in laser technology allow new procedures and broaden the scope of applications for both diagnosis and therapy. The focus of laser application in Oral Medicine diagnosis should be early detection of oral squamous cell carcinoma. Novel modalities for the detection of oral malignancy are urgently needed, while others must be continuously improved. Optical coherence tomography and laser-induced fluorescence spectroscopy are currently being studied. In addition to diagnosis of non-malignant lesions, laser therapy has been used based upon the biological reactions and molecular wound healing mechanisms as an alternative for the treatment of a variety of oral soft tissue lesions. The aim of the present article is to review current knowledge and future perspectives of lasers in Oral Medicine.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bambha, Ray P.; Michelsen, Hope A.

We have used a Single-Particle Soot Photometer (SP2) to measure time-resolved laser-induced incandescence (LII) and laser scatter from combustion-generated mature soot with a fractal dimension of 1.88 extracted from a burner. We have also made measurements on restructured mature-soot particles with a fractal dimension of 2.3–2.4. We reproduced the LII and laser-scatter temporal profiles with an energy- and mass-balance model, which accounted for heating of particles passed through a CW-laser beam over laser–particle interaction times of ~10 μs. Furthermore, the results demonstrate a strong influence of aggregate size and morphology on LII and scattering signals. Conductive cooling competes with absorptivemore » heating on these time scales; the effects are reduced with increasing aggregate size and fractal dimension. These effects can lead to a significant delay in the onset of the LII signal and may explain an apparent low bias in the SP2 measurements for small particle sizes, particularly for fresh, mature soot. The results also reveal significant perturbations to the measured scattering signal from LII interference and suggest rapid expansion of the aggregates during sublimation.« less

Heat treatment of transparent Yb:YAG and YAG ceramics and its influence on laser performance

NASA Astrophysics Data System (ADS)

Fujioka, Kana; Mochida, Tetsuo; Fujimoto, Yasushi; Tokita, Shigeki; Kawanaka, Junji; Maruyama, Momoko; Sugiyama, Akira; Miyanaga, Noriaki

2018-05-01

Composite transparent ceramic materials are promising for improving the performance of high-average-power lasers. A combination of room-temperature bonding via surface treatment by a fast atom beam and diffusion bonding via heating, which effectively controls the ion diffusion distance near the interface, makes the laser materials suitable for a variety of oscillator/amplifier. During the heat treatment of yttrium aluminum garnet (YAG) ceramics, the Si ions in the solid solution of the sintering aid incorporated within the grains were seen to segregate at the grain boundary, resulting in an increase of scattering sites. The number density and size of the scattering sites strongly depended on the post-heating temperature rather than the heating time. Specifically, heating at 1300 °C did not affect the transmittance of the YAG ceramic, whereas both the size and number of scattering sites substantially increased with a heat treatment at 1400 °C. The laser oscillation experiment using cryogenically-cooled Yb:YAG ceramics exhibited heating temperature dependence of the slope efficiency owing to the increasing scattering loss.

Measurement of high-dynamic range x-ray Thomson scattering spectra for the characterization of nano-plasmas at LCLS

DOE PAGES

MacDonald, M. J.; Gorkhover, T.; Bachmann, B.; ...

2016-08-08

Atomic clusters can serve as ideal model systems for exploring ultrafast (~100 fs) laser-driven ionization dynamics of dense matter on the nanometer scale. Resonant absorption of optical laser pulses enables heating to temperatures on the order of 1 keV at near solid density conditions. To date, direct probing of transient states of such nano plasmas was limited to coherent x-ray imaging. Here we present the first measurement of spectrally-resolved incoherent x-ray scattering from clusters, enabling measurements of transient temperature, densities and ionization. Single shot x-ray Thomson scatterings signals were recorded at 120 Hz using a crystal spectrometer in combination withmore » a single-photon counting and energy-dispersive pnCCD. A precise pump laser collimation scheme enabled recording near background-free scattering spectra from Ar clusters with an unprecedented dynamic range of more than 3 orders of magnitude. As a result, such measurements are important for understanding collective effects in laser-matter interactions on femtosecond timescales, opening new routes for the development of schemes for their ultrafast control.« less

Measurement of high-dynamic range x-ray Thomson scattering spectra for the characterization of nano-plasmas at LCLS

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacDonald, M. J., E-mail: macdonm@umich.edu; SLAC National Accelerator Laboratory, Menlo Park, California 94025; Gorkhover, T.

2016-11-15

Atomic clusters can serve as ideal model systems for exploring ultrafast (∼100 fs) laser-driven ionization dynamics of dense matter on the nanometer scale. Resonant absorption of optical laser pulses enables heating to temperatures on the order of 1 keV at near solid density conditions. To date, direct probing of transient states of such nano-plasmas was limited to coherent x-ray imaging. Here we present the first measurement of spectrally resolved incoherent x-ray scattering from clusters, enabling measurements of transient temperature, densities, and ionization. Single shot x-ray Thomson scattering signals were recorded at 120 Hz using a crystal spectrometer in combination withmore » a single-photon counting and energy-dispersive pnCCD. A precise pump laser collimation scheme enabled recording near background-free scattering spectra from Ar clusters with an unprecedented dynamic range of more than 3 orders of magnitude. Such measurements are important for understanding collective effects in laser-matter interactions on femtosecond time scales, opening new routes for the development of schemes for their ultrafast control.« less

Development of fiber lasers and devices for coherent Raman scattering microscopy

NASA Astrophysics Data System (ADS)

Lamb, Erin Stranford

As ultrafast laser technology has found expanding application in machining, spectroscopy, microscopy, surgery, and numerous other areas, the desire for inexpensive and robust laser sources has grown. Until recently, nonlinear effects in fiber systems due to the tight confinement of the light in the core have limited their performance. However, with advances in managing nonlinearity through pulse propagation physics and the use of large core fibers, the performance of fiber lasers can compete with that of their solid-state counterparts. As specific applications, such as coherent Raman scattering microscopy, emerge that stand to benefit from fiber technology, new performance challenges in areas such as laser noise are anticipated. This thesis studies nonlinear pulse propagation in fiber lasers and fiber parametric devices. Applications of dissipative solitons and self-similar pulse propagation to low-repetition rate oscillators that have the potential to simplify short-pulse amplification schemes will be examined. The rest of this thesis focuses on topics relevant to fiber laser development for coherent Raman scattering microscopy sources. Coherent pulse division and recombination inside the laser cavity will be introduced as an energy-scaling mechanism and demonstrated for a fiber soliton laser. The relative intensity noise properties of mode-locked fiber lasers, with a particular emphasis on normal dispersion lasers, will be explored in simulation and experiment. A fiber optical parametric oscillator will be studied in detail for low noise frequency conversion of picosecond pulses, and its utility for coherent Raman imaging will be demonstrated. Spectral compression of femtosecond pulses is used to generate picosecond pulses to pump this device, and this technique provides a route to future noise reduction in the system. Furthermore, this device forms a multimodal source capable of providing the picosecond pulses for coherent Raman scattering microscopy and the high energy femtosecond pulses for other multiphoton imaging techniques. Finally, ideas for future extensions of this work will be discussed.

On the saturation of stimulated Raman scattering in laser amplification

NASA Astrophysics Data System (ADS)

Dodd, E. S.; Ren, J.; Kwan, T. J. T.; Schmitt, M. J.

2012-10-01

The use of stimulated Raman scattering (SRS) in plasmas has been proposed as an alternative to the CPA technique for laser pulse amplification and compression [1]. Initial experiments demonstrated the amplification and compression of laser pulses in plasma to an unfocused intensity of ˜10^16 W/cm^2 [2], however the amplification was saturated at this level and was accompanied by deleterious spatial and temporal incoherence. The reasons for this incoherence have not been well understood. A physical picture has been developed with results from PIC simulations using the LSP code where spontaneous SRS in the pump modifies the plasma conditions, and which in turn significantly weakens the coupling strength for seed amplification. This led to the development of a novel experimental method to significantly increase the amplified power in the short-pulses via SRS.[4pt] [1] G. Shvets, N. J. Fisch, A. Pukhov, and J. Meyer-ter-Vehn, Phys. Rev. Lett. 81 4879 (1998).[0pt] [2] J. Ren, W.-F. Cheng, S.-L Li, and S. Suckewer, Nat. Phys. 3 732 (2007). LA-UR-12-22734

Apparatus and method for high-speed characterization of surfaces

NASA Technical Reports Server (NTRS)

Simmons, Stephen M. (Inventor); Hooker, Jeffery A. (Inventor)

1997-01-01

This invention permits rapid determination of a three-dimensional contour of an object. The apparatus directs a laser beam onto a point on an object, and the scattered light is received by a position sensitive detector (PSD). The location at which scattered light is received can be related to the displacement of the point on the object, using basic trigonometry. The laser beam is deflected non-mechanically, by passing it through a crystal whose index of refraction is varied in a controlled manner. By proper control of the index of refraction, one can scan the beam across a desired area of the object, without using any moving parts, and can therefore obtain complete information about the contour of the object. The device operates without making any conventional images, and is therefore much faster than comparable devices of the prior art. Also, the laser and beam deflector can be housed in a small optical head which enables the device to reach normally inaccessible areas. The device can compare the test object with a reference object, or it can compare two objects for differences.

5D-Tracking of a nanorod in a focused laser beam--a theoretical concept.

PubMed

Griesshammer, Markus; Rohrbach, Alexander

2014-03-10

Back-focal plane (BFP) interferometry is a very fast and precise method to track the 3D position of a sphere within a focused laser beam using a simple quadrant photo diode (QPD). Here we present a concept of how to track and recover the 5D state of a cylindrical nanorod (3D position and 2 tilt angles) in a laser focus by analyzing the interference of unscattered light and light scattered at the cylinder. The analytical theoretical approach is based on Rayleigh-Gans scattering together with a local field approximation for an infinitely thin cylinder. The approximated BFP intensities compare well with those from a more rigorous numerical approach. It turns out that a displacement of the cylinder results in a modulation of the BFP intensity pattern, whereas a tilt of the cylinder results in a shift of this pattern. We therefore propose the concept of a local QPD in the BFP of a detection lens, where the QPD center is shifted by the angular coordinates of the cylinder tilt.

longitudinal space charge assisted echo seeding of a free electron laser

NASA Astrophysics Data System (ADS)

Hacker, Kirsten

2015-05-01

Seed lasers are employed to improve the temporal coherence of free-electron laser light. However, when seed pulses are short relative to the particle bunch, the noisy, temporally incoherent radiation from the un-seeded electrons can overwhelm the coherent, seeded radiation. In this paper a new seeding mechanism to improve the contrast between coherent and incoherent free electron laser radiation is employed together with a novel, simplified echo-seeding method. The concept relies on a combination of longitudinal space charge wakes and an echo-seeding technique to make a short, coherent pulse of FEL light together with noise background suppression. Several different simulation codes are used to illustrate the concept with conditions at the soft x-ray Free-electron LASer in Hamburg, FLASH. The impacts of coherent synchrotron radiation, intra beam scattering, and high peak current operation are investigated.

Laser beam combining and cleanup by stimulated Brillouin scattering in a multimode optical fiber.

PubMed

Rodgers, B C; Russell, T H; Roh, W B

1999-08-15

A new technique for combining low-power laser beams has been demonstrated by use of semiconductor diode lasers. The technique, which is appropriate for any single-longitudinal-mode laser, is based on stimulated Brillouin scattering (SBS) in long multimode optical fibers. It produces a clean Gaussian-like beam that corresponds to the fundamental fiber mode, irrespective of the profile of the pump. Coherent as well as incoherent combining was demonstrated, and conversion slope efficiencies as high as 67% and 83% were shown to be achievable for the single-pass and ring-cavity SBS geometries, respectively.

Electron scattering by laser-excited barium atoms

NASA Technical Reports Server (NTRS)

Register, D. F.; Trajmar, S.; Jensen, S. W.; Poe, R. T.

1978-01-01

Inelastic and superelastic scattering of 30- and 100-eV electrons by laser-excited 6s 6p 1P and subsequent cascade-populated 6s 6p 3P, 6s 5d 1D, and 6s 5d 3D Ba atoms have been observed. Absolute differential cross sections for the singlet and relative scattering intensities for the triplet species have been determined in the 5 to 20 deg angular region. Under the present conditions excitations dominate over deexcitations.

Intracavity brillouin scattering from passive Q-spoiling cells.

PubMed

Wick, R V; Guenther, A H

1968-01-01

Stimulated Brillouin scattering from the methanol solvent used in conjunction with cryptocyanine bleachable dye in a ruby laser cavity has been observed at low megawatt output powers. The frequency shifts of the Brillouin scattered radiation produced within the laser cavity are slightly less than frequency shifts produced in an external methanol cell. The Brillouin radiation was eliminated even at output power levels in excess of 250 MW when a 3-mm length cell was used in place of the 25.4-mm commercial cell.

In vitro double-integrating-sphere optical properties of tissues between 630 and 1064 nm

NASA Astrophysics Data System (ADS)

Beek, J. F.; Blokland, P.; Posthumus, P.; Aalders, M.; Pickering, J. W.; Sterenborg, H. J. C. M.; van Gemert, M. J. C.

1997-11-01

The optical properties (absorption and scattering coefficients and the scattering anisotropy factor) were measured in vitro for cartilage, liver, lung, muscle, myocardium, skin, and tumour (colon adenocarcinoma CC 531) at 630, 632.8, 790, 850 and 1064 nm. Rabbits, rats, piglets, goats, and dogs were used to obtain the tissues. A double-integrating-sphere setup with an intervening sample was used to determine the reflectance, and the diffuse and collimated transmittances of the sample. The inverse adding - doubling algorithm was used to determine the optical properties from the measurements. The overall results were comparable to those available in the literature, although only limited data are available at 790 - 850 nm. The results were reproducible for a specific sample at a specific wavelength. However, when comparing the results of different samples of the same tissue or different lasers with approximately the same wavelength (e.g. argon dye laser at 630 nm and HeNe laser at 632.8 nm) variations are large. We believe these variations in optical properties should be explained by biological variations of the tissues. In conclusion, we report on an extensive set of in vitro absorption and scattering properties of tissues measured with the same equipment and software, and by the same group. Although the accuracy of the method requires further improvement, it is highly likely that the other existing data in the literature have a similar level of accuracy.

Observation of Langmuir Cascade in Single Hot Spot Laser-Plasma Experiments

NASA Astrophysics Data System (ADS)

Johnson, R. P.; Montgomery, D. S.; Fernandez, J. C.; Focia, R. J.

2001-10-01

We present results from the sixth in a series of experiments designed to investigate the interaction of a single laser hot spot, or speckle, with a preformed, quasi-homogeneous plasma. The experiments were conducted at the Los Alamos National Laboratory (LANL) using the TRIDENT laser. Thomson scattering was used to probe plasma waves driven by stimulated Raman scattering (SRS) and structure was observed in the scattered spectra consistent with multiple steps of the Langmuir decay instability (LDI).(R. J. Focia et al., PSFC Report PSFC/JA-01-17, M.I.T.) The experimental setup is described. The Thomson scattered spectra, resolved in both wavelength versus time and wavelength versus wave vector (effectively ω vs. k), are well-correlated with measurements of the backscattered SRS light and calculations based on linear theory. Parameter regimes are identified in which the LDI cascade exists.

Setting up a Rayleigh Scattering Based Flow Measuring System in a Large Nozzle Testing Facility

NASA Technical Reports Server (NTRS)

Panda, Jayanta; Gomez, Carlos R.

2002-01-01

A molecular Rayleigh scattering based air density measurement system has been built in a large nozzle testing facility at NASA Glenn Research Center. The technique depends on the light scattering by gas molecules present in air; no artificial seeding is required. Light from a single mode, continuous wave laser was transmitted to the nozzle facility by optical fiber, and light scattered by gas molecules, at various points along the laser beam, is collected and measured by photon-counting electronics. By placing the laser beam and collection optics on synchronized traversing units, the point measurement technique is made effective for surveying density variation over a cross-section of the nozzle plume. Various difficulties associated with dust particles, stray light, high noise level and vibration are discussed. Finally, a limited amount of data from an underexpanded jet are presented and compared with expected variations to validate the technique.

A high-power spatial filter for Thomson scattering stray light reduction

NASA Astrophysics Data System (ADS)

Levesque, J. P.; Litzner, K. D.; Mauel, M. E.; Maurer, D. A.; Navratil, G. A.; Pedersen, T. S.

2011-03-01

The Thomson scattering diagnostic on the High Beta Tokamak-Extended Pulse (HBT-EP) is routinely used to measure electron temperature and density during plasma discharges. Avalanche photodiodes in a five-channel interference filter polychromator measure scattered light from a 6 ns, 800 mJ, 1064 nm Nd:YAG laser pulse. A low cost, high-power spatial filter was designed, tested, and added to the laser beamline in order to reduce stray laser light to levels which are acceptable for accurate Rayleigh calibration. A detailed analysis of the spatial filter design and performance is given. The spatial filter can be easily implemented in an existing Thomson scattering system without the need to disturb the vacuum chamber or significantly change the beamline. Although apertures in the spatial filter suffer substantial damage from the focused beam, with proper design they can last long enough to permit absolute calibration.

Inelastic Light Scattering Processes

NASA Technical Reports Server (NTRS)

Fouche, Daniel G.; Chang, Richard K.

1973-01-01

Five different inelastic light scattering processes will be denoted by, ordinary Raman scattering (ORS), resonance Raman scattering (RRS), off-resonance fluorescence (ORF), resonance fluorescence (RF), and broad fluorescence (BF). A distinction between fluorescence (including ORF and RF) and Raman scattering (including ORS and RRS) will be made in terms of the number of intermediate molecular states which contribute significantly to the scattered amplitude, and not in terms of excited state lifetimes or virtual versus real processes. The theory of these processes will be reviewed, including the effects of pressure, laser wavelength, and laser spectral distribution on the scattered intensity. The application of these processes to the remote sensing of atmospheric pollutants will be discussed briefly. It will be pointed out that the poor sensitivity of the ORS technique cannot be increased by going toward resonance without also compromising the advantages it has over the RF technique. Experimental results on inelastic light scattering from I(sub 2) vapor will be presented. As a single longitudinal mode 5145 A argon-ion laser line was tuned away from an I(sub 2) absorption line, the scattering was observed to change from RF to ORF. The basis, of the distinction is the different pressure dependence of the scattered intensity. Nearly three orders of magnitude enhancement of the scattered intensity was measured in going from ORF to RF. Forty-seven overtones were observed and their relative intensities measured. The ORF cross section of I(sub 2) compared to the ORS cross section of N2 was found to be 3 x 10(exp 6), with I(sub 2) at its room temperature vapor pressure.

Diffraction-controlled backscattering threshold and application to Raman gap

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rose, Harvey A.; Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87544; Mounaix, Philippe

2011-04-15

In most classic analytical models of linear stimulated scatter, light diffraction is omitted, a priori. However, modern laser optic typically includes a variant of the random phase plate [Y. Kato et al., Phys. Rev. Lett. 53, 1057 (1984)], resulting in diffraction limited laser intensity fluctuations - or localized speckles - which may result in explosive reflectivity growth as the average laser intensity approaches a critical value [H. A. Rose and D. F. DuBois, Phys. Rev. Lett. 72, 2883 (1994)]. Among the differences between stimulated Raman scatter (SRS) and stimulated Brillouin scatter is that the SRS scattered light diffracts more stronglymore » than the laser light with increase of electron density. This weakens the tendency of the SRS light to closely follow the most amplified paths, diminishing gain. Let G{sub 0} be the one-dimensional power gain exponent of the stimulated scatter. In this paper we show that differential diffraction gives rise to an increase of G{sub 0} at the SRS physical threshold with increase of electron density up to a drastic disruption of SRS as electron density approaches one fourth of its critical value from below. For three wave interaction lengths not small compared to a speckle length, this is a physically robust Raman gap mechanism.« less

10 GHz dual loop opto-electronic oscillator without RF-amplifiers

NASA Astrophysics Data System (ADS)

Zhou, Weimin; Okusaga, Olukayode; Nelson, Craig; Howe, David; Carter, Gary

2008-02-01

We report the first demonstration of a 10 GHz dual-fiber-loop Opto-Electronic Oscillator (OEO) without RF-amplifiers. Using a recently developed highly efficient RF-Photonic link with RF-to-RF gain facilitated by a high power laser, highly efficient optical modulator and high power phototectectors, we have built an amplifier-less OEO that eliminates the phase noise produced by the electronic amplifier. The dual-loop approach can provide additional gain and reduce unwanted multi-mode spurs. However, we have observed RF phase noise produced by the high power laser include relative intensity noise (RIN) and noise related to the laser's electronic control system. In addition, stimulated Brillouin scattering limits the fiber loop's length to ~2km at the 40mW laser power needed to provide the RF gain which limits the system's quality factor, Q. We have investigated several different methods for solving these problems. One promising technique is the use of a multi-longitudinal-mode laser to carry the RF signal, maintaining the total optical power but reducing the optical power of each mode to eliminate the Brillouin scattering in a longer fiber thereby reducing the phase noise of the RF signal produced by the OEO. This work shows that improvement in photonic components increases the potential for more RF system applications such as an OEO's with higher performance and new capabilities.

Advanced Compton scattering light source R&D at LLNL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Albert, F; Anderson, S G; Anderson, G

2010-02-16

We report the design and current status of a monoenergetic laser-based Compton scattering 0.5-2.5 MeV {gamma}-ray source. Previous nuclear resonance fluorescence results and future linac and laser developments for the source are presented. At MeV photon energies relevant for nuclear processes, Compton scattering light sources are attractive because of their relative compactness and improved brightness above 100 keV, compared to typical 4th generation synchrotrons. Recent progress in accelerator physics and laser technology have enabled the development of a new class of tunable Mono-Energetic Gamma-Ray (MEGa-Ray) light sources based on Compton scattering between a high-brightness, relativistic electron beam and a highmore » intensity laser pulse produced via chirped-pulse amplification (CPA). A new precision, tunable gamma-ray source driven by a compact, high-gradient X-band linac is currently under development and construction at LLNL. High-brightness, relativistic electron bunches produced by an X-band linac designed in collaboration with SLAC will interact with a Joule-class, 10 ps, diode-pumped CPA laser pulse to generate tunable {gamma}-rays in the 0.5-2.5 MeV photon energy range via Compton scattering. Based on the success of the previous Thomson-Radiated Extreme X-rays (T-REX) Compton scattering source at LLNL, the source will be used to excite nuclear resonance fluorescence lines in various isotopes; applications include homeland security, stockpile science and surveillance, nuclear fuel assay, and waste imaging and assay. After a brief presentation of successful nuclear resonance fluorescence (NRF) experiments done with T-REX, the new source design, key parameters, and current status are presented.« less

Brillouin scattering-induced rogue waves in self-pulsing fiber lasers

PubMed Central

Hanzard, Pierre-Henry; Talbi, Mohamed; Mallek, Djouher; Kellou, Abdelhamid; Leblond, Hervé; Sanchez, François; Godin, Thomas; Hideur, Ammar

2017-01-01

We report the experimental observation of extreme instabilities in a self-pulsing fiber laser under the influence of stimulated Brillouin scattering (SBS). Specifically, we observe temporally localized structures with high intensities that can be referred to as rogue events through their statistical behaviour with highly-skewed intensity distributions. The emergence of these SBS-induced rogue waves is attributed to the interplay between laser operation and resonant Stokes orders. As this behaviour is not accounted for by existing models, we also present numerical simulations showing that such instabilities can be observed in chaotic laser operation. This study opens up new possibilities towards harnessing extreme events in highly-dissipative systems through adapted laser cavity configurations. PMID:28374840

Brillouin scattering-induced rogue waves in self-pulsing fiber lasers.

PubMed

Hanzard, Pierre-Henry; Talbi, Mohamed; Mallek, Djouher; Kellou, Abdelhamid; Leblond, Hervé; Sanchez, François; Godin, Thomas; Hideur, Ammar

2017-04-04

We report the experimental observation of extreme instabilities in a self-pulsing fiber laser under the influence of stimulated Brillouin scattering (SBS). Specifically, we observe temporally localized structures with high intensities that can be referred to as rogue events through their statistical behaviour with highly-skewed intensity distributions. The emergence of these SBS-induced rogue waves is attributed to the interplay between laser operation and resonant Stokes orders. As this behaviour is not accounted for by existing models, we also present numerical simulations showing that such instabilities can be observed in chaotic laser operation. This study opens up new possibilities towards harnessing extreme events in highly-dissipative systems through adapted laser cavity configurations.

Laser Doppler velocimetry using a modified computer mouse

NASA Astrophysics Data System (ADS)

Zaron, Edward D.

2016-10-01

A computer mouse has been modified for use as a low-cost laser Doppler interferometer and used to measure the two-component fluid velocity of a flowing soap film. The mouse sensor contains two vertical cavity surface emitting lasers, photodiodes, and signal processing hardware integrated into a single package, approximately 1 cm2 in size, and interfaces to a host computer via a standard USB port. Using the principle of self-mixing interferometry, whereby laser light re-enters the laser cavity after being scattered from a moving target, the Doppler shift and velocity of scatterers dispersed in the flow are measured. Observations of the boundary layer in a turbulent soap film channel flow demonstrate the capabilities of the sensor.

Method for estimating optimal spectral and energy parameters of laser irradiation in photodynamic therapy of biological tissue

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lisenko, S A; Kugeiko, M M

We have solved the problem of layer-by-layer laser-light dosimetry in biological tissues and of selecting an individual therapeutic dose in laser therapy. A method is proposed for real-time monitoring of the radiation density in tissue layers in vivo, concentrations of its endogenous (natural) and exogenous (specially administered) chromophores, as well as in-depth distributions of the spectrum of light action on these chromophores. As the background information use is made of the spectrum of diffuse light reflected from a patient's tissue, measured by a fibre-optic spectrophotometer. The measured spectrum is quantitatively analysed by the method of approximating functions for fluxes ofmore » light multiply scattered in tissue and by a semi-analytical method for calculating the in-depth distribution of the light flux in a multi-layered medium. We have shown the possibility of employing the developed method for monitoring photosensitizer and oxyhaemoglobin concentrations in tissue, light power absorbed by chromophores in tissue layers at different depths and laser-induced changes in the tissue morphology (vascular volume content and ratios of various forms of haemoglobin) during photodynamic therapy. (biophotonics)« less

Thomson scattering diagnostic for the measurement of ion species fraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ross, J S; Park, H S; Amendt, A

2012-05-01

Simultaneous Thomson scattering measurements of collective electron-plasma and ion-acoustic fluctuations have been utilized to determine ion species fraction from laser produced CH plasmas. The CH{sub 2} foil is heated with 10 laser beams, 500 J per beam, at the Omega Laser facility. Thomson scattering measurements are made 4 mm from the foil surface using a 30 J 2{omega} probe laser with a 1 ns pulse length. Using a series of target shots the plasma evolution is measured from 2.5 ns to 9 ns after the rise of the heater beams. Measuring the electron density and temperature from the electron-plasma fluctuationsmore » constrains the fit of the two-ion species theoretical form factor for the ion feature such that the ion temperature, plasma flow velocity and ion species fraction are determined. The ion species fraction is determined to an accuracy of {+-}0.06 in species fraction.« less

Nanoscale femtosecond imaging of transient hot solid density plasmas with elemental and charge state sensitivity using resonant coherent diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kluge, T., E-mail: t.kluge@hzdr.de; Bussmann, M.; Huang, L. G., E-mail: lingen.huang@hzdr.de

Here, we propose to exploit the low energy bandwidth, small wavelength, and penetration power of ultrashort pulses from XFELs for resonant Small Angle Scattering (SAXS) on plasma structures in laser excited plasmas. Small angle scattering allows to detect nanoscale density fluctuations in forward scattering direction. Typically, the SAXS signal from laser excited plasmas is expected to be dominated by the free electron distribution. We propose that the ionic scattering signal becomes visible when the X-ray energy is in resonance with an electron transition between two bound states (resonant coherent X-ray diffraction). In this case, the scattering cross-section dramatically increases somore » that the signal of X-ray scattering from ions silhouettes against the free electron scattering background which allows to measure the opacity and derived quantities with high spatial and temporal resolution, being fundamentally limited only by the X-ray wavelength and timing. Deriving quantities such as ion spatial distribution, charge state distribution, and plasma temperature with such high spatial and temporal resolution will make a vast number of processes in shortpulse laser-solid interaction accessible for direct experimental observation, e.g., hole-boring and shock propagation, filamentation and instability dynamics, electron transport, heating, and ultrafast ionization dynamics.« less

X-ray lasers for structural and dynamic biology

NASA Astrophysics Data System (ADS)

Spence, J. C. H.; Weierstall, U.; Chapman, H. N.

2012-10-01

Research opportunities and techniques are reviewed for the application of hard x-ray pulsed free-electron lasers (XFEL) to structural biology. These include the imaging of protein nanocrystals, single particles such as viruses, pump-probe experiments for time-resolved nanocrystallography, and snapshot wide-angle x-ray scattering (WAXS) from molecules in solution. The use of femtosecond exposure times, rather than freezing of samples, as a means of minimizing radiation damage is shown to open up new opportunities for the molecular imaging of biochemical reactions at room temperature in solution. This is possible using a ‘diffract-and-destroy’ mode in which the incident pulse terminates before radiation damage begins. Methods for delivering hundreds of hydrated bioparticles per second (in random orientations) to a pulsed x-ray beam are described. New data analysis approaches are outlined for the correlated fluctuations in fast WAXS, for protein nanocrystals just a few molecules on a side, and for the continuous x-ray scattering from a single virus. Methods for determining the orientation of a molecule from its diffraction pattern are reviewed. Methods for the preparation of protein nanocrystals are also reviewed. New opportunities for solving the phase problem for XFEL data are outlined. A summary of the latest results is given, which now extend to atomic resolution for nanocrystals. Possibilities for time-resolved chemistry using fast WAXS (solution scattering) from mixtures is reviewed, toward the general goal of making molecular movies of biochemical processes.

Potential accuracy of methods of laser Doppler anemometry in the single-particle scattering mode

NASA Astrophysics Data System (ADS)

Sobolev, V. S.; Kashcheeva, G. A.

2017-05-01

Potential accuracy of methods of laser Doppler anemometry is determined for the singleparticle scattering mode where the only disturbing factor is shot noise generated by the optical signal itself. The problem is solved by means of computer simulations with the maximum likelihood method. The initial parameters of simulations are chosen to be the number of real or virtual interference fringes in the measurement volume of the anemometer, the signal discretization frequency, and some typical values of the signal/shot noise ratio. The parameters to be estimated are the Doppler frequency as the basic parameter carrying information about the process velocity, the signal amplitude containing information about the size and concentration of scattering particles, and the instant when the particles arrive at the center of the measurement volume of the anemometer, which is needed for reconstruction of the examined flow velocity as a function of time. The estimates obtained in this study show that shot noise produces a minor effect (0.004-0.04%) on the frequency determination accuracy in the entire range of chosen values of the initial parameters. For the signal amplitude and the instant when the particles arrive at the center of the measurement volume of the anemometer, the errors induced by shot noise are in the interval of 0.2-3.5%; if the number of interference fringes is sufficiently large (more than 20), the errors do not exceed 0.2% regardless of the shot noise level.

Improvements, upgrades, and plans for Thomson scattering on DIII-D

NASA Astrophysics Data System (ADS)

Carlstrom, T. N.; Du, D.; Glass, F.; Liu, C.; Watkins, M.; McLean, A. G.

2016-10-01

The Thomson scattering diagnostic on DIII-D consists of 3 beam lines that probe vertically, horizontally, and in the divertor region of the tokamak, with 54 spatial locations, edge spatial resolution down to 5 mm, and 10 Nd:YAG lasers. In its 25-year history, the collection lens optics and interference filters degraded and have been replaced, restoring previous performance. In addition, improved calibrations and detector temperature control (+/- 0.1 C) have reduced systematic errors. Cross calibration with the CO2 interferometer and ECE cut-off have improved the density calibration. Improvements to the beam line and lasers have increased the laser energy delivered to the scattering volume in the plasma. Future plans include moving the divertor system to measure regions of high triangularity using in-vessel mirrors to redirect the laser beam; adding a wide angle lens to the horizontal system to view the entire plasma radius near the plasma mid plane; and reversing the direction of the laser beam on the horizontal system to reduce the scattering angle and compressing the spectrum in wavelength space so that higher central Te measurements (<5 KeV) can be made with improved accuracy. Work supported by the US DOE under DE-FC02-04ER54698 and by LLNL under DE-AC52-07NA27344.

Fast photomultiplier tube gating system for underwater laser detector

NASA Astrophysics Data System (ADS)

Lei, Xuanhua; Yang, Kecheng; Rao, Jionghui; Zhang, Xiaohui; Xia, Min; Zheng, Yi; Li, Wei

2007-01-01

Laser will attenuate during its propagation in water and also be backward scattered by water when it is used to detect bubbles in the ocean. Meanwhile backward scattering intensity of the bubbles is feeble, its dynamic range reaches to the order of 6, which saturates PMT and its post-treatment circuit. Timely gating system is used to solve the problem. The system contains pulsed laser and gating PMT receiver. The wavelength of the laser is 532nm, with pulse width of several nanometers. Its operational delay is matched with the time period between laser traveling forward and back after scattered by the target. By doing this, the light scattered by other object is eliminated, dynamic range of the signal reduces, and consequently SNR increases. In order to avoid Signal Induced Noise(SIN), we choose PMT R1333 having no HA coating. TTL logical level, which is used as gating signal, controls the first dynode voltage of PMT to implement gating. Gating speed is about 100ns, of which the width is tunable. By carefully designing the electronic system, SNR is eliminated to a level as low as possible, and the output signal of PMT is fast integrated in order to reduce the influences of signal induced by opening the gate.

Femtosecond ultrasonic spectroscopy using a piezoelectric nanolayer: Hypersound attenuation in vitreous silica films

NASA Astrophysics Data System (ADS)

Wen, Yu-Chieh; Guol, Shi-Hao; Chen, Hung-Pin; Sheu, Jinn-Kong; Sun, Chi-Kuang

2011-08-01

We report ultra-broadband ultrasonic spectroscopy with an impedance-matched piezoelectric nanolayer, which enables optical generation and detection of a 730-fs acoustic pulse (the width of ten lattice constants). The bandwidth improvement facilitates THz laser ultrasonics to bridge the spectral gap between inelastic light and x-ray scatterings (0.1-1 THz) in the studies of lattice dynamics. As a demonstration, this method is applied to measure sound attenuation α in a vitreous SiO2 thin film. Our results extend the existing low-frequency data obtained by ultrasonic-based and light scattering methods and also show a α∝ f2 behavior for frequencies f up to 650 GHz.

Sentinel lymph node detection by an optical method using scattered photons

PubMed Central

Tellier, Franklin; Ravelo, Rasata; Simon, Hervé; Chabrier, Renée; Steibel, Jérôme; Poulet, Patrick

2010-01-01

We present a new near infrared optical probe for the sentinel lymph node detection, based on the recording of scattered photons. A two wavelengths setup was developed to improve the detection threshold of an injected dye: the Patent Blue V dye. The method used consists in modulating each laser diode at a given frequency. A Fast Fourier Transform of the recorded signal separates both components. The signal amplitudes are used to compute relative Patent Blue V concentration. Results on the probe using phantoms model and small animal experimentation exhibit a sensitivity threshold of 3.2 µmol/L, which is thirty fold better than the eye visible threshold. PMID:21258517

Differential Multiphoton Laser Scanning Microscopy

PubMed Central

Field, Jeffrey J.; Sheetz, Kraig E.; Chandler, Eric V.; Hoover, Erich E.; Young, Michael D.; Ding, Shi-you; Sylvester, Anne W.; Kleinfeld, David; Squier, Jeff A.

2016-01-01

Multifocal multiphoton microscopy (MMM) in the biological and medical sciences has become an important tool for obtaining high resolution images at video rates. While current implementations of MMM achieve very high frame rates, they are limited in their applicability to essentially those biological samples that exhibit little or no scattering. In this paper, we report on a method for MMM in which imaging detection is not necessary (single element point detection is implemented), and is therefore fully compatible for use in imaging through scattering media. Further, we demonstrate that this method leads to a new type of MMM wherein it is possible to simultaneously obtain multiple images and view differences in excitation parameters in a single shot. PMID:27390511

Coherent anti-Stokes Raman scattering spectroscope/microscope based on a widely tunable laser source

NASA Astrophysics Data System (ADS)

Dementjev, A.; Gulbinas, V.; Serbenta, A.; Kaucikas, M.; Niaura, G.

2010-03-01

We present a coherent anti-Stokes Raman scattering (CARS) microscope based on a robust and simple laser source. A picosecond laser operating in a cavity dumping regime at the 1 MHz repetition rate was used to pump a traveling wave optical parametric generator, which serves as a two-color excitation light source for the CARS microscope. We demonstrate the ability of the presented CARS microscope to measure CARS spectra and images by using several detection schemes.

Non-invasive detection of laser-induced retinal injury through the vitreous using dynamic light scattering (Conference Presentation)

NASA Astrophysics Data System (ADS)

Ansari, Rafat R.; Naiman, Melissa; Bouhenni, Rachida; Dunmire, Jeffery; Liu, Ying; Rafiq, Qundeel; Edward, Deepak; Gothard, David

2016-03-01

Laser radiation entering the eye has the potential of damaging the retina. As an inflammatory response, the proteins can rush to the lesion site created by laser exposure. We explore the hypothesis if these proteins can be detected non-invasively. In this preliminary study, we developed a new brief-case size dynamic light scattering instrument to detect these proteins in-vivo in the rabbit vitreous. The results were validated with bio-chemical analysis.

The application of laser-Raman light scattering to the determination of sulfate in sea and estuarine waters

NASA Technical Reports Server (NTRS)

Bandy, A. R.

1973-01-01

Laser-Raman light scattering is a technique for determining sulfate concentrations in sea and estuarine waters with apparently none of the interferences inherent in the gravimetric and titrametric methods. The Raman measurement involved the ratioing of the peak heights of an unknown sulfate concentration and a nitrate internal standard. This ratio was used to calculate the unknown sulfate concentration from a standard curve. The standard curve was derived from the Raman data on prepared nitrate-sulfate solutions. At the 99.7% confidence level, the accuracy of the Raman technique was 7 to 8.6 percent over the concentration range of the standard curve. The sulfate analyses of water samples collected at the mouth of the James River, Hampton, Virginia, demonstrated that in most cases sulfate had a constant concentration relative to salinity in this area.

Determination of molecular weight of membrane proteins by the use of low-angle laser light scattering combined with high-performance gel chromatography in the presence of a non-ionic surfactant.

PubMed

Maezawa, S; Hayashi, Y; Nakae, T; Ishii, J; Kameyama, K; Takagi, T

1983-09-28

An assessment study was carried out to evaluate the performance of the low-angle laser light scattering technique combined with high-performance gel chromatography in the presence of a nonionic surfactant, octaethyleneglycol n-dodecyl ether, precision differential refractometry and ultraviolet photometry. It was found that the combined technique is highly promising as a method for the determination of the molecular weight of a membrane protein solubilized by the surfactant. For trial, molecular weights of the following membrane proteins of Escherichia coli, both solubilized in oligomeric forms, were measured; porin that forms the transmembrane diffusion pore in the outer membrane, and lambda-receptor protein that facilitates the diffusion of maltose-maltodextrins across the outer membrane. The result obtained indicates that both porin and lambda-receptor protein exist as trimers in the surfactant solution.

Investigation of light source and scattering medium related to vapor-screen flow visualization in a supersonic wind tunnel

NASA Technical Reports Server (NTRS)

Snow, W. L.; Morris, O. A.

1984-01-01

Methods for increasing the radiant in light sheets used for vapor screen set-ups were investigated. Both high-pressure mercury arc lamps and lasers were considered. Pulsed operation of the air-cooled 1-kW lamps increased the light output but decreased reliability. An ellipsoidal mirror improved the output of the air-cooled lamps by concentrating the light but increased the complexity of the housing. Water-cooled-4-kW lamps coupled with high-aperture Fresnel lenses provided reasonable improvements over the air-cooled lamps. Fanned laser beams measurements of scattered light versus dew point made in conjunction with successful attempts to control the fluid injection. A number of smoke generators are described and test results comparing smoke and vapor screens are shown. Finally, one test included a periscope system to relay the image to a camera outside the flow.

Numerical study on trapping and guiding of nanoparticles in a flow using scattering field of laser light

NASA Astrophysics Data System (ADS)

Yokoi, Naomichi; Aizu, Yoshihisa

2018-01-01

Optical trapping and guiding using laser have been proven to be useful for non-contact and non-invasive manipulation of small objects such as biological cells, organelles within cells, and dielectric particles. We have numerically investigated so far the motion of a Brownian particle suspended in still water under the illumination of a speckle pattern generated by the interference of coherent light scattered by a rough object. In the present study, we investigate numerically the motion of a particle in a water flow under the illumination of a speckle pattern that is at rest or in motion. Trajectory of the particle is simulated in relation with its size, flow velocity, maximum irradiance, and moving velocity of the speckle pattern to confirm the feasibility of the present method for performing optical trapping and guiding of the particle in the flow.

Lamb wave propagation in a restricted geometry composite pi-joint specimen

NASA Astrophysics Data System (ADS)

Blackshire, James L.; Soni, Som

2012-05-01

The propagation of elastic waves in a material can involve a number of complex physical phenomena, resulting in both subtle and dramatic effects on detected signal content. In recent years, the use of advanced methods for characterizing and imaging elastic wave propagation and scattering processes has increased, where for example the use of scanning laser vibrometry and advanced computational models have been used very effectively to identify propagating modes, scattering phenomena, and damage feature interactions. In the present effort, the propagation of Lamb waves within a narrow, constrained geometry composite pi-joint structure are studied using 3D finite element models and scanning laser vibrometry measurements, where the effects of varying sample thickness, complex joint curvatures, and restricted structure geometries are highlighted, and a direct comparison of computational and experimental results are provided for simulated and realistic geometry composite pi-joint samples.

Method for pulse control in a laser including a stimulated brillouin scattering mirror system

DOEpatents

Dane, C. Brent; Hackel, Lloyd; Harris, Fritz B.

2007-10-23

A laser system, such as a master oscillator/power amplifier system, comprises a gain medium and a stimulated Brillouin scattering SBS mirror system. The SBS mirror system includes an in situ filtered SBS medium that comprises a compound having a small negative non-linear index of refraction, such as a perfluoro compound. An SBS relay telescope having a telescope focal point includes a baffle at the telescope focal point which blocks off angle beams. A beam splitter is placed between the SBS mirror system and the SBS relay telescope, directing a fraction of the beam to an alternate beam path for an alignment fiducial. The SBS mirror system has a collimated SBS cell and a focused SBS cell. An adjustable attenuator is placed between the collimated SBS cell and the focused SBS cell, by which pulse width of the reflected beam can be adjusted.

Numerical study on trapping and guiding of nanoparticles in a flow using scattering field of laser light

NASA Astrophysics Data System (ADS)

Yokoi, Naomichi; Aizu, Yoshihisa

2018-06-01

Optical trapping and guiding using laser have been proven to be useful for non-contact and non-invasive manipulation of small objects such as biological cells, organelles within cells, and dielectric particles. We have numerically investigated so far the motion of a Brownian particle suspended in still water under the illumination of a speckle pattern generated by the interference of coherent light scattered by a rough object. In the present study, we investigate numerically the motion of a particle in a water flow under the illumination of a speckle pattern that is at rest or in motion. Trajectory of the particle is simulated in relation with its size, flow velocity, maximum irradiance, and moving velocity of the speckle pattern to confirm the feasibility of the present method for performing optical trapping and guiding of the particle in the flow.

Enhancing resolution in coherent x-ray diffraction imaging.

PubMed

Noh, Do Young; Kim, Chan; Kim, Yoonhee; Song, Changyong

2016-12-14

Achieving a resolution near 1 nm is a critical issue in coherent x-ray diffraction imaging (CDI) for applications in materials and biology. Albeit with various advantages of CDI based on synchrotrons and newly developed x-ray free electron lasers, its applications would be limited without improving resolution well below 10 nm. Here, we review the issues and efforts in improving CDI resolution including various methods for resolution determination. Enhancing diffraction signal at large diffraction angles, with the aid of interference between neighboring strong scatterers or templates, is reviewed and discussed in terms of increasing signal-to-noise ratio. In addition, we discuss errors in image reconstruction algorithms-caused by the discreteness of the Fourier transformations involved-which degrade the spatial resolution, and suggest ways to correct them. We expect this review to be useful for applications of CDI in imaging weakly scattering soft matters using coherent x-ray sources including x-ray free electron lasers.

Laser scattering in a hanging drop vapor diffusion apparatus for protein crystal growth in a microgravity environment

NASA Technical Reports Server (NTRS)

Casay, G. A.; Wilson, W. W.

1992-01-01

One type of hardware used to grow protein crystals in the microgravity environment aboard the U.S. Space Shuttle is a hanging drop vapor diffusion apparatus (HDVDA). In order to optimize crystal growth conditions, dynamic control of the HDVDA is desirable. A critical component in the dynamically controlled system is a detector for protein nucleation. We have constructed a laser scattering detector for the HDVDA capable of detecting the nucleation stage. The detector was successfully tested for several scatterers differing in size using dynamic light scattering techniques. In addition, the ability to detect protein nucleation using the HDVDA was demonstrated for lysozyme.

Semiconductor laser insert with uniform illumination for use in photodynamic therapy

NASA Astrophysics Data System (ADS)

Charamisinau, Ivan; Happawana, Gemunu; Evans, Gary; Rosen, Arye; Hsi, Richard A.; Bour, David

2005-08-01

A low-cost semiconductor red laser light delivery system for esophagus cancer treatment is presented. The system is small enough for insertion into the patient's body. Scattering elements with nanoscale particles are used to achieve uniform illumination. The scattering element optimization calculations, with Mie theory, provide scattering and absorption efficiency factors for scattering particles composed of various materials. The possibility of using randomly deformed spheres and composite particles instead of perfect spheres is analyzed using an extension to Mie theory. The measured radiation pattern from a prototype light delivery system fabricated using these design criteria shows reasonable agreement with the theoretically predicted pattern.

Calibration of Thomson scattering system on VEST

NASA Astrophysics Data System (ADS)

Kim, Y.-G.; Lee, J.-H.; Kim, D.; Yoo, M.-G.; Lee, H.; Hwang, Y. S.; Na, Y.-S.

2017-12-01

The Thomson scattering system has been recently installed on Versatile Experiment Spherical Torus (VEST) to measure the electron temperature and the density of the core plasmas. Since the calibration of the system is required for the accurate measurement of these parameters, a polychromator and the system efficiency are calibrated. The bias voltage of the detector is optimized and the relative responsivity of the polychromator is measured to analyse the spectral broadening. The tendency of decreasing responsivity because of the ambient temperature change is addressed together. The efficiencies of the alignments using HeNe laser and Nd:YAG laser are compared. After the alignment using Rayleigh scattering, it is improved ~ 7 times while the peak signal of the stray light is decreased. To evaluate the efficiencies of the alignment using HeNe laser, it is compared with the efficiency of the fine alignment by Rayleigh scattering. After absolute calibration is done, the Thomson scattering signal is estimated theoretically. The Bayesian analysis is tried using the synthetic data, and the results show that the input temperature and the density are inside the contour of the 90% confident level. The calibrated Thomson scattering system will provide the meaningful information of the core plasma of the VEST.

Point-spread imaging for measurement of skin translucency and scattering.

PubMed

Jiang, Zhi-xing; Kaplan, Peter D

2008-08-01

The translucency of skin has long been identified as an important cue for healthy and youthful looking skin. There is currently no universal definition for skin translucency let alone a measurement method. We propose that skin translucency is the light scattering beneath skin surface. We demonstrate the use of polarization gated point spreading imaging for non-invasive, in vivo measurement of the translucency and the reduced scattering coefficient m's of skin. We developed a polarization-gated point-spread imaging system to measure the spread of the incident pencil-thin laser beam on the skin. Skin translucency was calculated as the spread of the laser beam. From the measurement of the shift of the light diffuse center from the light injection point, the reduced scattering coefficient m's of the skin was calculated. We validated the measurement technique with milk as an in vitro model for skin. The measured m's of milk solution was found to be linearly proportional to the milk concentration, in agreement with Beer's law. The calculated translucency decreased as the milk concentration increased or as the reduced scattering coefficient m's increased. It was also found that the translucency decreased as the absorption coefficient of the milk solution increased. The measured translucency of a set of custom made clay tiles correlated well with the consumer perception of the incremental ranking of the translucency. In vivo measurement of skin translucency and the reduced scattering coefficient m's were carried out on several volunteers. The measured reduced scattering coefficient m's was in agreement with those in the literature. The measured skin translucency for different skin ethnicities of Caucasian, North Asian, South Asian and African American were in line with the expectation that skin translucency decreases as the skin color gets darker.

A technique to measure the size of particles in laser Doppler velocimetry applications

NASA Technical Reports Server (NTRS)

Hess, C. F.

1985-01-01

A method to measure the size of particles in Laser Doppler Velocimeter (LDV) applications is discussed. Since in LDV the velocity of the flow is assocated with the velocity of particles to establish how well they follow the flow, in the present method the interferometric probe volume is surrounded by a larger beam of different polarization or wavelength. The particle size is then measured from the absolute intensity scattered from the large beam by particles crossing the fringes. Experiments using polystrene particles between 1.1 and 3.3 microns and larger glass beads are reported. It is shown that the method has an excellent size resolution and its accuracy is better than 10% for the particle size studied.

Optical correlation techniques in fluid dynamics

NASA Astrophysics Data System (ADS)

Schätzel, K.; Schulz-Dubois, E. O.; Vehrenkamp, R.

1981-04-01

Three flow measurement techniques make use of fast digital correlators. The most widely spread is photon correlation velocimetry using crossed laser beams, and detecting Doppler shifted light scattered by small particles in the flow. Depending on the processing of the photon correlation output, this technique yields mean velocity, turbulence level, and even the detailed probability distribution of one velocity component. An improved data processing scheme is demonstrated on laminar vortex flow in a curved channel. In the second method, rate correlation based upon threshold crossings of a high pass filtered laser Doppler signal can be used to obtain velocity correlation functions. The most powerful set-up developed in our laboratory uses a phase locked loop type tracker and a multibit correlator to analyze time-dependent Taylor vortex flow. With two optical systems and trackers, cross-correlation functions reveal phase relations between different vortices. The last method makes use of refractive index fluctuations (eg in two phase flows) instead of scattering particles. Interferometry with bidirectional counting, and digital correlation and probability analysis, constitutes a new quantitative technique related to classical Schlieren methods. Measurements on a mixing flow of heated and cold air contribute new ideas to the theory of turbulent random phase screens.

High resolution x-ray Thomson scattering measurements from cryogenic hydrogen jets using the linac coherent light source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fletcher, L. B., E-mail: lbfletch@slac.stanford.edu; Galtier, E.; Gamboa, E. J.

2016-11-15

We present the first spectrally resolved measurements of x-rays scattered from cryogenic hydrogen jets in the single photon counting limit. The 120 Hz capabilities of the LCLS, together with a novel hydrogen jet design [J. B. Kim et al., Rev. Sci. Instrum. (these proceedings)], allow for the ability to record a near background free spectrum. Such high-dynamic-range x-ray scattering measurements enable a platform to study ultra-fast, laser-driven, heating dynamics of hydrogen plasmas. This measurement has been achieved using two highly annealed pyrolytic graphite crystal spectrometers to spectrally resolve 5.5 keV x-rays elastically and inelastically scattered from cryogenic hydrogen and focusedmore » on Cornell-SLAC pixel array detectors [S. Herrmann et al., Nucl. Instrum. Methods Phys. Res., Sect. A 718, 550 (2013)].« less

Pulsed Laser Ablation-Induced Green Synthesis of TiO2 Nanoparticles and Application of Novel Small Angle X-Ray Scattering Technique for Nanoparticle Size and Size Distribution Analysis.

PubMed

Singh, Amandeep; Vihinen, Jorma; Frankberg, Erkka; Hyvärinen, Leo; Honkanen, Mari; Levänen, Erkki

2016-12-01

This paper aims to introduce small angle X-ray scattering (SAXS) as a promising technique for measuring size and size distribution of TiO 2 nanoparticles. In this manuscript, pulsed laser ablation in liquids (PLAL) has been demonstrated as a quick and simple technique for synthesizing TiO 2 nanoparticles directly into deionized water as a suspension from titanium targets. Spherical TiO 2 nanoparticles with diameters in the range 4-35 nm were observed with transmission electron microscopy (TEM). X-ray diffraction (XRD) showed highly crystalline nanoparticles that comprised of two main photoactive phases of TiO 2 : anatase and rutile. However, presence of minor amounts of brookite was also reported. The traditional methods for nanoparticle size and size distribution analysis such as electron microscopy-based methods are time-consuming. In this study, we have proposed and validated SAXS as a promising method for characterization of laser-ablated TiO 2 nanoparticles for their size and size distribution by comparing SAXS- and TEM-measured nanoparticle size and size distribution. SAXS- and TEM-measured size distributions closely followed each other for each sample, and size distributions in both showed maxima at the same nanoparticle size. The SAXS-measured nanoparticle diameters were slightly larger than the respective diameters measured by TEM. This was because SAXS measures an agglomerate consisting of several particles as one big particle which slightly increased the mean diameter. TEM- and SAXS-measured mean diameters when plotted together showed similar trend in the variation in the size as the laser power was changed which along with extremely similar size distributions for TEM and SAXS validated the application of SAXS for size distribution measurement of the synthesized TiO 2 nanoparticles.

Demonstration of x-ray Thomson scattering using picosecond K-α x-ray sources in the characterization of dense heated matter

DOE PAGES

Kritcher, A. L.; Neumayer, P.; Lee, H. J.; ...

2008-10-31

Here, we present K-α x-ray Thomson scattering from shock compressed matter for use as a diagnostic in determining the temperature, density, and ionization state with picosecond resolution. The development of this source as a diagnostic as well as stringent requirements for successful K-α x-ray Thomson scattering are addressed. Here, the first elastic and inelastic scattering measurements on a medium size laser facility have been observed. We present scattering data from solid density carbon plasmas with >1X 10 5 photons in the elastic peak that validate the capability of single shot characterization of warm dense matter and the ability to usemore » this scattering source at future free electron lasers and for fusion experiments at the National Ignition Facility (NIF), LLNL.« less

Thomson-scattering measurements in the collective and noncollective regimes in laser produced plasmas (invited).

PubMed

Ross, J S; Glenzer, S H; Palastro, J P; Pollock, B B; Price, D; Tynan, G R; Froula, D H

2010-10-01

We present simultaneous Thomson-scattering measurements of light scattered from ion-acoustic and electron-plasma fluctuations in a N(2) gas jet plasma. By varying the plasma density from 1.5×10(18) to 4.0×10(19) cm(-3) and the temperature from 100 to 600 eV, we observe the transition from the collective regime to the noncollective regime in the high-frequency Thomson-scattering spectrum. These measurements allow an accurate local measurement of fundamental plasma parameters: electron temperature, density, and ion temperature. Furthermore, experiments performed in the high densities typically found in laser produced plasmas result in scattering from electrons moving near the phase velocity of the relativistic plasma waves. Therefore, it is shown that even at low temperatures relativistic corrections to the scattered power must be included.

Non-equilibrium Green's function calculation for GaN-based terahertz-quantum cascade laser structures

NASA Astrophysics Data System (ADS)

Yasuda, H.; Kubis, T.; Hosako, I.; Hirakawa, K.

2012-04-01

We theoretically investigated GaN-based resonant phonon terahertz-quantum cascade laser (QCL) structures for possible high-temperature operation by using the non-equilibrium Green's function method. It was found that the GaN-based THz-QCL structures do not necessarily have a gain sufficient for lasing, even though the thermal backfilling and the thermally activated phonon scattering are effectively suppressed. The main reason for this is the broadening of the subband levels caused by a very strong interaction between electrons and longitudinal optical (LO) phonons in GaN.

Modified stimulated Raman scattering of a laser induced by trapped electrons in a plasma

NASA Astrophysics Data System (ADS)

Baliyan, Sweta; Rafat, Mohd.; Ahmad, Nafis; Sajal, Vivek

2017-10-01

The plasma wave, generated in stimulated Raman scattering process by an intense laser in the plasmas, traps a significant number of electrons in its potential energy minima. These electrons travel with the phase velocity of plasma wave and oscillate with bounce frequency. When the bounce frequency of electrons becomes equal to the growth rate of Raman process, resonance takes place. Now, Raman scattering gets modified by parametrically exciting a trapped electron mode and an electromagnetic sideband. The ponderomotive force due to the pump and sideband drives the plasma wave, whereas the density perturbation due to the trapped electron mode couples with the oscillating velocity of electrons due to the laser to produce a nonlinear current, driving the sideband.

Probing scattering mechanisms with symmetric quantum cascade lasers.

PubMed

Deutsch, Christoph; Detz, Hermann; Zederbauer, Tobias; Andrews, Aaron M; Klang, Pavel; Kubis, Tillmann; Klimeck, Gerhard; Schuster, Manfred E; Schrenk, Werner; Strasser, Gottfried; Unterrainer, Karl

2013-03-25

A characteristic feature of quantum cascade lasers is their unipolar carrier transport. We exploit this feature and realize nominally symmetric active regions for terahertz quantum cascade lasers, which should yield equal performance with either bias polarity. However, symmetric devices exhibit a strongly bias polarity dependent performance due to growth direction asymmetries, making them an ideal tool to study the related scattering mechanisms. In the case of an InGaAs/GaAsSb heterostructure, the pronounced interface asymmetry leads to a significantly better performance with negative bias polarity and can even lead to unidirectionally working devices, although the nominal band structure is symmetric. The results are a direct experimental proof that interface roughness scattering has a major impact on transport/lasing performance.

Studies of central interactions of Si ions at 14.5 x A GeV/c in Au and Cu

NASA Astrophysics Data System (ADS)

Eiseman, S. E.; Etkin, A.; Foley, K. J.; Hackenburg, R. W.; Longacre, R. S.; Love, W. A.; Morris, T. W.; Platner, E. D.; Saulys, A. C.; Lindenbaum, S. J.

Understanding the growth and saturation of parametric instabilities in laser-produced plasmas requires knowledge of the nonlinear properties of the instabilities and their interaction with each other. Nonlinear behavior of parametric instabilities, which are usually associated with unique optical features, were evidenced in numerous experiments on a variety of laser facilities. Four examples of nonlinear behavior in laser-produced plasmas are discussed: nonlinear stimulated Brillouin scattering spectra, suppression of stimulated Raman scattering by stimulated Brillouin scattering, the parametric decay instability and the onset of turbulence, and the transition to bursting behavior of the two-plasmon decay instability. Experiments are discussed that demonstrate the nonlinear effects which occur as a consequence.

Multipurpose end-station for coherent diffraction imaging and scattering at FERMI@Elettra free-electron laser facility.

PubMed

Capotondi, Flavio; Pedersoli, Emanuele; Bencivenga, Filippo; Manfredda, Michele; Mahne, Nicola; Raimondi, Lorenzo; Svetina, Cristian; Zangrando, Marco; Demidovich, Alexander; Nikolov, Ivaylo; Danailov, Miltcho; Masciovecchio, Claudio; Kiskinova, Maya

2015-05-01

The Diffraction and Projection Imaging (DiProI) beamline at FERMI, the Elettra free-electron laser (FEL), hosts a multi-purpose station that has been opened to users since the end of 2012. This paper describes the core capabilities of the station, designed to make use of the unique features of the FERMI-FEL for performing a wide range of static and dynamic scattering experiments. The various schemes for time-resolved experiments, employing both soft X-ray FEL and seed laser IR radiation are presented by using selected recent results. The ongoing upgrade is adding a reflection geometry setup for scattering experiments, expanding the application fields by providing both high lateral and depth resolution.

Narrow bandwidth Laser-Plasma Accelerator driven Thomson photon source development

NASA Astrophysics Data System (ADS)

Geddes, C. G. R.; Tsai, H.-E.; Otero, G.; Liu, X.; van Tilborg, J.; Toth, Cs.; Vay, J.-L.; Lehe, R.; Schroeder, C. B.; Esarey, E.; Friedman, A.; Grote, D. P.; Leemans, W. P.

2017-10-01

Compact, high-quality photon sources at MeV energies can be provided by Thomson scattering of a laser from the electron beam of a Laser-Plasma Accelerator (LPA). Recent experiments and simulations demonstrate controllable LPAs in the energy range appropriate to MeV sources. Simulations indicate that high flux with narrow energy spread can be achieved via control of the scattering laser pulse shape and laser guiding, and that undesired background bremsstrahlung can be mitigated by plasma based deceleration of the electron beam after photon production. Construction of experiments and laser capabilities to combine these elements will be presented, along with initial operations, towards a compact photon source system. Work supported by US DOE NNSA DNN R&D and by Sc. HEP under contract DE-AC02-05CH11231.

Quantifying time-of-flight-resolved optical field dynamics in turbid media with interferometric near-infrared spectroscopy (iNIRS) (Conference Presentation)

NASA Astrophysics Data System (ADS)

Borycki, Dawid; Kholiqov, Oybek; Zhou, Wenjun; Srinivasan, Vivek J.

2017-03-01

Sensing and imaging methods based on the dynamic scattering of coherent light, including laser speckle, laser Doppler, and diffuse correlation spectroscopy quantify scatterer motion using light intensity (speckle) fluctuations. The underlying optical field autocorrelation (OFA), rather than being measured directly, is typically inferred from the intensity autocorrelation (IA) through the Siegert relationship, by assuming that the scattered field obeys Gaussian statistics. In this work, we demonstrate interferometric near-infrared spectroscopy (iNIRS) for measurement of time-of-flight (TOF) resolved field and intensity autocorrelations in fluid tissue phantoms and in vivo. In phantoms, we find a breakdown of the Siegert relationship for short times-of-flight due to a contribution from static paths whose optical field does not decorrelate over experimental time scales, and demonstrate that eliminating such paths by polarization gating restores the validity of the Siegert relationship. Inspired by these results, we developed a method, called correlation gating, for separating the OFA into static and dynamic components. Correlation gating enables more precise quantification of tissue dynamics. To prove this, we show that iNIRS and correlation gating can be applied to measure cerebral hemodynamics of the nude mouse in vivo using dynamically scattered (ergodic) paths and not static (non-ergodic) paths, which may not be impacted by blood. More generally, correlation gating, in conjunction with TOF resolution, enables more precise separation of diffuse and non-diffusive contributions to OFA than is possible with TOF resolution alone. Finally, we show that direct measurements of OFA are statistically more efficient than indirect measurements based on IA.

Overview of Optical and Thermal Laser-Tissue Interaction and Nomenclature

NASA Astrophysics Data System (ADS)

Welch, Ashley J.; van Gemert, Martin J. C.

The development of a unified theory for the optical and thermal response of tissue to laser radiation is no longer in its infancy, though it is still not fully developed. This book describes our current understanding of the physical events that can occur when light interacts with tissue, particularly the sequence of formulations that estimate the optical and thermal responses of tissue to laser radiation. This overview is followed by an important chapter that describes the basic interactions of light with tissue. Part I considers basic tissue optics. Tissue is treated as an absorbing and scattering medium and methods are presented for calculating and measuring light propagation, including polarized light. Also, methods for estimating tissue optical properties from measurements of reflection and transmission are discussed. Part II concerns the thermal response of tissue owing to absorbed light, and rate reactions are presented for predicting the extent of laser induced thermal damage. Methods for measuring temperature, thermal properties, rate constants, pulsed ablation and laser tissue interactions are detailed. Part III is devoted to examples that use the theory presented in Parts I and II to analyze various medical applications of lasers. Discussions of Optical Coherence Tomography (OCT), forensic optics, and light stimulation of nerves are also included.

Frequency shift measurement in shock-compressed materials

DOEpatents

Moore, David S.; Schmidt, Stephen C.

1985-01-01

A method for determining molecular vibrational frequencies in shock-compressed transparent materials. A single laser beam pulse is directed into a sample material while the material is shock-compressed from a direction opposite that of the incident laser beam. A Stokes beam produced by stimulated Raman scattering is emitted back along the path of the incident laser beam, that is, in the opposite direction to that of the incident laser beam. The Stokes beam is separated from the incident beam and its frequency measured. The difference in frequency between the Stokes beam and the incident beam is representative of the characteristic frequency of the Raman active mode of the sample. Both the incident beam and the Stokes beam pass perpendicularly through the shock front advancing through the sample, thereby minimizing adverse effects of refraction.

ISTC projects devoted to improving laser beam quality

NASA Astrophysics Data System (ADS)

Malakhov, Yu. I.

2007-05-01

Short overview is done about the activity of ISTC in a direction concerned with improving powerful laser beam quality by means of nonlinear and linear adaptive optics methods. Completed projects #0591 and #1929 resulted in the development of a stimulated Brillouin scattering (SBS) phase conjugation mirror of superhigh fidelity employing the kinoform optical elements (rasters of small lenses) of new generation designed for pulsed or pulse-periodic lasers with nanosecond scale pulse duration. Project #2631 is devoted to development of an adaptive optical system for phase registration and correction of laser beams with wave front vortices. The principles of operation of conventional adaptive systems are based on the assumption that the phase is a smooth continuous function in space. Therefore the solution of the Project tasks will assume a new step in adaptive optics.