Science.gov

Sample records for active laser illumination

  1. Near infrared laser illuminator for very long-range flash active imaging applications

    NASA Astrophysics Data System (ADS)

    Lutz, Yves; Metzger, Nicolas

    2011-10-01

    For very long-range flash active imaging applications, a powerful and narrow beam divergence pulsed laser illuminator is needed. Conventional high fill factor 1-centimeter diode bars are not well suited to produce a homogeneous and narrow beam divergence in an easy way. In the present paper, a concept based on a QCW mini-bars laser diode stack, focusing lenses and beam homogenisation is presented. With fifteen 1.5 mm conductively cooled fast axis collimated mini-bars, a peak power of 803 Watt at a wavelength of 810 nm is achieved with a maximum duty cycle of 2 percent. After collimation, the laser beam on the scene shows very homogeneous rectangular illumination geometry with a ratio of 4:3 well adapted for active imaging purposes. The beam divergence is reduced to 3.35 × 2.53 mrd with a two lenses objective of focal length f = 573 mm and f-number f# = 4.8.

  2. Laser sources for object illumination

    SciTech Connect

    Albrecht, G.F.

    1994-11-15

    The considerations which formulate the specifications for a laser illuminator are explained, using the example of an underwater object. Depending on the parameters which define the scenario, widely varying laser requirements result.

  3. Scanned Laser Illuminator/Receiver

    DTIC Science & Technology

    1976-11-01

    illustrate parallel development of the PIN diode /CCD sensor hybrid and the 100W laser . Al- though a detailed cost analysis for procurement of this large...pmww^^W .m^n.m .,** ■ —ssa^ AFAL-TR-76-184 \\ SCANNED LASER ILLUMINATOR/RECEIVER ^ R. A. Honzik and F. B. Warren ^•Martin Marietta...NUMBER 4. TITLE (and Sublille) SCANNED LASER ILLUMINATOR/RECEIVER 5, TYPE OF REPORT & PERIOD COVERED Final Technical Report Dec 75

  4. Laser illuminated flat panel display

    SciTech Connect

    Veligdan, J.T.

    1995-12-31

    A 10 inch laser illuminated flat panel Planar Optic Display (POD) screen has been constructed and tested. This POD screen technology is an entirely new concept in display technology. Although the initial display is flat and made of glass, this technology lends itself to applications where a plastic display might be wrapped around the viewer. The display screen is comprised of hundreds of planar optical waveguides where each glass waveguide represents a vertical line of resolution. A black cladding layer, having a lower index of refraction, is placed between each waveguide layer. Since the cladding makes the screen surface black, the contrast is high. The prototype display is 9 inches wide by 5 inches high and approximately I inch thick. A 3 milliwatt HeNe laser is used as the illumination source and a vector scanning technique is employed.

  5. Atmospheric effects on active illumination

    NASA Astrophysics Data System (ADS)

    Shaw, Scot E. J.; Kansky, Jan E.

    2005-08-01

    For some beam-control applications, we can rely on the cooperation of the target when gathering information about the target location and the state of the atmosphere between the target and the beam-control system. The typical example is a cooperative point-source beacon on the target. Light from such a beacon allows the beam-control system to track the target accurately, and, if higher-order adaptive optics is to be employed, to make wave-front measurements and apply appropriate corrections with a deformable mirror. In many applications, including directed-energy weapons, the target is not cooperative. In the absence of a cooperative beacon, we must find other ways to collect the relevant information. This can be accomplished with an active-illumination system. Typically, this means shining one or more lasers at the target and observing the reflected light. In this paper, we qualitatively explore a number of difficulties inherent to active illumination, and suggest some possible mitigation techniques.

  6. Long-range laser-illuminated imaging

    NASA Astrophysics Data System (ADS)

    Dayton, David C.; Browne, Stephen L.; Sandven, Steven C.; Gonglewski, John D.; Gallegos, Joe; Shilko, Michael L., Sr.

    2000-11-01

    We demonstrate the utility of laser illuminated imaging for clandestine night time surveillance from a simulated airborne platform at standoff ranges in excess 20 km. In order to reduce the necessary laser per pulse energy required for illumination at such long ranges, and to mitigate atmospheric turbulence effects on image resolution, we have investigated a unique multi-frame post-processing technique. It is shown that in the presence of atmospheric turbulence and coherent speckle effects, this approach can produce superior results to conventional scene flood illumination.

  7. Pulsed Laser Illumination of Photovoltaic Cells

    NASA Technical Reports Server (NTRS)

    Yater, Jane A.; Lowe, Roland; Jenkins, Philip; Landis, Geoffrey A.

    1994-01-01

    In future space missions, free electron lasers (FEL) may be used to illuminate photovoltaic array receivers to provide remote power. The induction FEL and the radio-frequency (RF) FEL both produce pulsed rather than continuous output. In this work, we investigate cell response to pulsed laser light which simulates the RF FEL format, producing 50 ps pulses at a frequency of 78 MHz. A variety of Si, GaAs, CaSb and CdInSe2 (CIS) solar cells are tested at average incident powers between 4 mW/sq cm and 425 mW/sq cm. The results indicate that if the pulse repetition is high, cell efficiencies are only slightly reduced by using a pulsed laser source compared to constant illumination at the same wavelength. Because the pulse separation is less than or approximately equal to the minority carrier lifetime, the illumination conditions are effectively those of a continuous wave laser. The time dependence of the voltage and current response of the cells are also measured using a sampling oscilloscope equipped with a high frequency voltage probe and current transformer. The frequency response of the cells is weak, with both voltage and current outputs essentially dc in nature. Comparison with previous experiments shows that the RF FEL pulse format yields much more efficient photovoltaic conversion of light than does an induction FEL pulse format.

  8. Pulsed laser illumination of photovoltaic cells

    NASA Technical Reports Server (NTRS)

    Yater, Jane A.; Lowe, Roland A.; Jenkins, Phillip P.; Landis, Geoffrey A.

    1994-01-01

    In future space missions, free electron lasers (FEL) may be used to illuminate photovoltaic array receivers to provide remote power. Both the radio-frequency (RF) and induction FEL provide FEL produce pulsed rather than continuous output. In this work we investigate cell response to pulsed laser light which simulates the RF FEL format. The results indicate that if the pulse repetition is high, cell efficiencies are only slightly reduced compared to constant illumination at the same wavelength. The frequency response of the cells is weak, with both voltage and current outputs essentially dc in nature. Comparison with previous experiments indicates that the RF FEL pulse format yields more efficient photovoltaic conversion than does an induction FEL pulse format.

  9. Pulsed laser illumination of photovoltaic cells

    NASA Technical Reports Server (NTRS)

    Yater, Jane A.; Lowe, Roland A.; Jenkins, Phillip P.; Landis, Geoffrey A.

    1995-01-01

    In future space missions, free electron lasers (FEL) may be used to illuminate photovoltaic receivers to provide remote power. Both the radio-frequency (RF) and induction FEL produce pulsed rather than continuous output. In this work we investigate cell response to pulsed laser light which simulates the RF FEL format. The results indicate that if the pulse repetition is high, cell efficiencies are only slightly reduced compared to constant illumination at the same wavelength. The frequency response of the cells is weak, with both voltage and current outputs essentially dc in nature. Comparison with previous experiments indicates that the RF FEL pulse format yields more efficient photovoltaic conversion than does an induction FEL format.

  10. Compact laser illumination system for endoscopic interventions.

    PubMed

    Blase, Bastian

    2015-08-01

    External cold light sources as well as LEDs are commonly used for abdominal illumination in minimally invasive surgery. Still, both feature certain disadvantages. A new illumination system for endoscopes based on laser diodes is placed in the handle. No external light cables are needed. High conversion and coupling efficiencies and small package size allow for several diodes to be integrated, enabling color mixing and the adjustment of color temperatures. An optical module to collimate and combine the light is described. The heat to be dissipated is stored in a passive latent heat storage based on phase change materials surrounding the optical module. Thereby, operation time is considerably extended, as the handle's temperature is stabilized. To reduce the negative effect of coherent light on optical rough surfaces leading to patterns of spots, several devices for speckle reduction are developed and tested. By combining these components, an assembly of a powerful RGB laser light module for the integration in standard sized endoscopes is formed.

  11. Moonbase night power by laser illumination

    NASA Technical Reports Server (NTRS)

    Landis, Geoffrey A.

    1992-01-01

    Moonbase solar-power concepts must somehow address the energy storage problem posed by the 354-hour lunar night. Attention is presently given to the feasibility of laser-array illumination of a lunar base, using technology that is projected to be available in the near term. Beam-spreading due to atmospheric distortions could be reduced through the use of adaptive optics to compensate for atmospheric turbulence.

  12. 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.

  13. Space power by laser illumination of PV arrays

    NASA Technical Reports Server (NTRS)

    Landis, Geoffrey A.

    1991-01-01

    There has recently been a resurgence of interest in the use of beamed power to support space exploration activities. The utility is examined of photovoltaics and problem and research areas are identified for photovoltaics in two beamed-power applications: to convert incident laser radiation to power at a remote receiving station, and as a primary power source on space based power station transmitting power to a remote user. A particular application of recent interest is to use a ground-based free electron laser as a power source for space applications. Specific applications include: night power for a moonbase by laser illumination of the moonbase solar arrays; use of a laser to provide power for satellites in medium and geosynchronous Earth orbit, and a laser powered system for an electrical propulsion orbital transfer vehicle. These and other applications are currently being investigated at NASA Lewis as part of a new program to demonstrate the feasibility of laser transmission of power for space.

  14. Active illuminated space object imaging and tracking simulation

    NASA Astrophysics Data System (ADS)

    Yue, Yufang; Xie, Xiaogang; Luo, Wen; Zhang, Feizhou; An, Jianzhu

    2016-10-01

    Optical earth imaging simulation of a space target in orbit and it's extraction in laser illumination condition were discussed. Based on the orbit and corresponding attitude of a satellite, its 3D imaging rendering was built. General simulation platform was researched, which was adaptive to variable 3D satellite models and relative position relationships between satellite and earth detector system. Unified parallel projection technology was proposed in this paper. Furthermore, we denoted that random optical distribution in laser-illuminated condition was a challenge for object discrimination. Great randomicity of laser active illuminating speckles was the primary factor. The conjunction effects of multi-frame accumulation process and some tracking methods such as Meanshift tracking, contour poid, and filter deconvolution were simulated. Comparison of results illustrates that the union of multi-frame accumulation and contour poid was recommendable for laser active illuminated images, which had capacities of high tracking precise and stability for multiple object attitudes.

  15. Fiber Coupled Laser Diodes with Even Illumination Pattern

    NASA Technical Reports Server (NTRS)

    Howard, Richard T. (Inventor)

    2007-01-01

    An optical fiber for evenly illuminating a target. The optical fiber is coupled to a laser emitting diode and receives laser light. The la ser light travels through the fiber optic and exits at an exit end. T he exit end has a diffractive optical pattern formed thereon via etch ing, molding or cutting, to reduce the Gaussian profile present in co nventional fiber optic cables The reduction of the Gaussian provides an even illumination from the fiber optic cable.

  16. Illuminating Northern California's Active Faults

    NASA Astrophysics Data System (ADS)

    Prentice, Carol S.; Crosby, Christopher J.; Whitehill, Caroline S.; Arrowsmith, J. Ramón; Furlong, Kevin P.; Phillips, David A.

    2009-02-01

    Newly acquired light detection and ranging (lidar) topographic data provide a powerful community resource for the study of landforms associated with the plate boundary faults of northern California (Figure 1). In the spring of 2007, GeoEarthScope, a component of the EarthScope Facility construction project funded by the U.S. National Science Foundation, acquired approximately 2000 square kilometers of airborne lidar topographic data along major active fault zones of northern California. These data are now freely available in point cloud (x, y, z coordinate data for every laser return), digital elevation model (DEM), and KMZ (zipped Keyhole Markup Language, for use in Google Earth™ and other similar software) formats through the GEON OpenTopography Portal (http://www.OpenTopography.org/data). Importantly, vegetation can be digitally removed from lidar data, producing high-resolution images (0.5- or 1.0-meter DEMs) of the ground surface beneath forested regions that reveal landforms typically obscured by vegetation canopy (Figure 2).

  17. Infrared laser diode with visible illuminator for biomedical stimulation

    NASA Astrophysics Data System (ADS)

    Strek, Wieslaw; Podbielska, Halina; Szafranski, C.; Kuzmin, Andrei N.; Ges, J. A.; Ryabtsev, Gennadii I.

    1995-02-01

    The special laser diode device (LDD) leasing in the near infrared region (IR) with two wavelengths: (lambda) 1 equals 850 nm and (lambda) 2 equals 1000 nm, designed for laser therapy, is presented. This device is characterized by a unique feature, namely a separate built-in illuminator, operating in 670 nm. The special construction of LDD and the illuminator enables the user to visualize exactly the surface irradiated by IR radiation. The exposure time and the output of laser power are also controlled and can be displayed on the LED monitor at the front panel. This new device, described here, is compact, low cost, and user friendly.

  18. Illuminating the Hazards of Powerful Laser Products

    MedlinePlus

    ... the laser and the potential to pose serious danger if used improperly. The labeling for Classes II– ... to Keep Kids Safe More in Consumer Updates Animal & Veterinary Children's Health Cosmetics Dietary Supplements Drugs Food ...

  19. Response of silicon solar cell to pulsed laser illumination

    NASA Technical Reports Server (NTRS)

    Willowby, D.; Alexander, D.; Edge, T.; Herren, K.

    1993-01-01

    The response of silicon solar cell(s) to pulsed laser illumination is discussed. The motivation was due to the interest of Earth to space/Moon power beaming applications. When this work began, it was not known if solar cells would respond to laser light with pulse lengths in the nanosecond range and a repetition frequency in the kHz range. This is because the laser pulse would be shorter than the minority carrier lifetime of silicon. A 20-nanosecond (ns) full width half max (FWHM) pulse from an aluminum-gallium/arsenide (Al-Ga-As) diode laser was used to illuminate silicon solar cells at a wavelength of 885 nanometers (nm). Using a high-speed digital oscilloscope, the response of the solar cells to individual pulses across various resistive loads was observed and recorded.

  20. Even Illumination from Fiber-Optic-Coupled Laser Diodes

    NASA Technical Reports Server (NTRS)

    Howard, Richard T.

    2006-01-01

    A method of equipping fiber-optic-coupled laser diodes to evenly illuminate specified fields of view has been proposed. The essence of the method is to shape the tips of the optical fibers into suitably designed diffractive optical elements. One of the main benefits afforded by the method would be more nearly complete utilization of the available light. Diffractive optics is a relatively new field of optics in which laser beams are shaped by use of diffraction instead of refraction.

  1. Standoff Hyperspectral Imaging of Explosives Residues Using Broadly Tunable External Cavity Quantum Cascade Laser Illumination

    SciTech Connect

    Bernacki, Bruce E.; Phillips, Mark C.

    2010-05-01

    We describe experimental results on the detection of explosives residues using active hyperspectral imaging by illumination of the target surface using an external cavity quantum cascade laser (ECQCL) and imaging using a room temperature microbolometer camera. The active hyperspectral imaging technique forms an image hypercube by recording one image for each tuning step of the ECQCL. The resulting hyperspectral image contains the full absorption spectrum produced by the illumination laser at each pixel in the image which can then be used to identify the explosive type and relative quantity using spectral identification approaches developed initially in the remote sensing community.

  2. Color digital lensless holographic microscopy: laser versus LED illumination.

    PubMed

    Garcia-Sucerquia, Jorge

    2016-08-20

    A comparison of the performance of color digital lensless holographic microscopy (CDLHM) as utilized for illumination of RGB lasers or a super-bright white-light LED with a set of spectral filters is presented. As the use of lasers in CDLHM conceals the possibility of having a compact, lightweight, portable, and low cost microscope, and additionally the limited available laser radiation wavelengths limit a real multispectral imaging microscope, here we present the use of super-bright white-light LED and spectral filters for illuminating the sample. The performance of RGB laser-CDLHM and LED-CDLHM is evaluated on imaging a section of the head of a Drosophila melanogaster fly. This comparison shows that there is trade-off between the spatial resolution of the microscope and the light sources utilized, which can be understood with regard to the coherence properties of the illuminating light. Despite the smaller spatial coherence features of LED-CDLHM in comparison with laser-CDLHM, the former shows promise as a portable RGB digital lensless holographic microscope that could be extended to other wavelengths by the use of different spectral filters.

  3. Random laser illumination: an ideal source for biomedical polarization imaging?

    NASA Astrophysics Data System (ADS)

    Carvalho, Mariana T.; Lotay, Amrit S.; Kenny, Fiona M.; Girkin, John M.; Gomes, Anderson S. L.

    2016-03-01

    Imaging applications increasingly require light sources with high spectral density (power over spectral bandwidth. This has led in many cases to the replacement of conventional thermal light sources with bright light-emitting diodes (LEDs), lasers and superluminescent diodes. Although lasers and superluminescent diodes appear to be ideal light sources due to their narrow bandwidth and power, however, in the case of full-field imaging, their spatial coherence leads to coherent artefacts, such as speckle, that corrupt the image. LEDs, in contrast, have lower spatial coherence and thus seem the natural choice, but they have low spectral density. Random Lasers are an unconventional type of laser that can be engineered to provide low spatial coherence with high spectral density. These characteristics makes them potential sources for biological imaging applications where specific absorption and reflection are the characteristics required for state of the art imaging. In this work, a Random Laser (RL) is used to demonstrate speckle-free full-field imaging for polarization-dependent imaging in an epi-illumination configuration. We compare LED and RL illumination analysing the resulting images demonstrating that the RL illumination produces an imaging system with higher performance (image quality and spectral density) than that provided by LEDs.

  4. Wide-field Fourier ptychographic microscopy using laser illumination source

    PubMed Central

    Chung, Jaebum; Lu, Hangwen; Ou, Xiaoze; Zhou, Haojiang; Yang, Changhuei

    2016-01-01

    Fourier ptychographic (FP) microscopy is a coherent imaging method that can synthesize an image with a higher bandwidth using multiple low-bandwidth images captured at different spatial frequency regions. The method’s demand for multiple images drives the need for a brighter illumination scheme and a high-frame-rate camera for a faster acquisition. We report the use of a guided laser beam as an illumination source for an FP microscope. It uses a mirror array and a 2-dimensional scanning Galvo mirror system to provide a sample with plane-wave illuminations at diverse incidence angles. The use of a laser presents speckles in the image capturing process due to reflections between glass surfaces in the system. They appear as slowly varying background fluctuations in the final reconstructed image. We are able to mitigate these artifacts by including a phase image obtained by differential phase contrast (DPC) deconvolution in the FP algorithm. We use a 1-Watt laser configured to provide a collimated beam with 150 mW of power and beam diameter of 1 cm to allow for the total capturing time of 0.96 seconds for 96 raw FPM input images in our system, with the camera sensor’s frame rate being the bottleneck for speed. We demonstrate a factor of 4 resolution improvement using a 0.1 NA objective lens over the full camera field-of-view of 2.7 mm by 1.5 mm. PMID:27896016

  5. Design and evaluation of laser spot illuminator for a laser projection engine design

    NASA Astrophysics Data System (ADS)

    Dwivedi, Ashish; Khan, Gufran Sayeed; Sharma, Anurag

    2016-11-01

    An easily implementable illumination optical element enabling collection and redirection of multiple precollimated laser beams to be used as a laser spot illuminator (LSI) is proposed. Unlike the lenses, this element is free from any aberration and focusing/defocusing effects which may arise due to curved surfaces. The nonfocusing nature of beams reduces risk of the thermal instability at the target spot if compared with focused beam, especially for high brightness applications where multiple laser beams are used. Further, the illuminating spot is more uniform and pupil filling is higher which can help in the reduction of speckle contrast for imaging applications. In this research, we present two designs of LSI named biprism and sleek design, suitable for conventional grinding-polishing and molding methods of fabrication, respectively. It is shown that the proposed spot illuminator is suitable for conversion of lamp/LED-based projection engine design into a laser projector engine without any modification in its relay and imaging optics. Display performance parameters such as efficiency and uniformity across the modulator plane are reported and found acceptable for the projection engine designs using light tunnels as well as lenslet arrays for homogenization. Further, a prototype of a biprism laser illuminator for 2×4 laser arrays has been fabricated and evaluated to demonstrate its manufacturability.

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

    SciTech Connect

    Mark, J.W.K.

    1985-12-12

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

  7. Target tracking using infrared measurements and laser illumination

    NASA Astrophysics Data System (ADS)

    Maybeck, Peter S.; Herrera, Theodore D.; Evans, Roger J.

    1994-07-01

    A missile target tracker is designed using a filter/correlator (with adaptive target shape identification) based on forward-looking infrared (FLIR) sensor measurements to track the center-of-intensity of the hardbody/plume combination, and another filter using Doppler and/or speckle information in the return from a low-power laser illuminator to estimate the offset between the intensity centroid and the hardbody center-of-mass. The Doppler information is shown to yield smaller bias and error variance from the tracker than the speckle information. Performance of trackers based on just Doppler or both Doppler and speckle information from the laser return is portrayed as a function of important parameters in the tracking environment.

  8. Directed energy active illumination for near-Earth object detection

    NASA Astrophysics Data System (ADS)

    Riley, Jordan; Lubin, Philip; Hughes, Gary B.; O'Neill, Hugh; Meinhold, Peter; Suen, Jonathan; Bible, Johanna; Johansson, Isabella E.; Griswold, Janelle; Cook, Brianna

    2014-09-01

    On 15 February 2013, a previously unknown ~20 m asteroid struck Earth near Chelyabinsk, Russia, releasing kinetic energy equivalent to ~570 kt TNT. Detecting objects like the Chelyabinsk impactor that are orbiting near Earth is a difficult task, in part because such objects spend much of their own orbits in the direction of the Sun when viewed from Earth. Efforts aimed at protecting Earth from future impacts will rely heavily on continued discovery. Ground-based optical observatory networks and Earth-orbiting spacecraft with infrared sensors have dramatically increased the pace of discovery. Still, less than 5% of near-Earth objects (NEOs) >=100 m/~100 Mt TNT have been identified, and the proportion of known objects decreases rapidly for smaller sizes. Low emissivity of some objects also makes detection by passive sensors difficult. A proposed orbiting laser phased array directed energy system could be used for active illumination of NEOs, enhancing discovery particularly for smaller and lower emissivity objects. Laser fiber amplifiers emit very narrow-band energy, simplifying detection. Results of simulated illumination scenarios are presented based on an orbiting emitter array with specified characteristics. Simulations indicate that return signals from small and low emissivity objects is strong enough to detect. The possibility for both directed and full sky blind surveys is discussed, and the resulting diameter and mass limits for objects in different observational scenarios. The ability to determine both position and speed of detected objects is also discussed.

  9. Eye-safe laser illuminators as less-than-lethal weapons

    NASA Astrophysics Data System (ADS)

    German, John D.; Adler, Dean S.

    1997-01-01

    Law enforcement and military forces are often faced with situations requiring less-than-lethal response options. Low- power, eye-safe laser illuminators have been shown to be effective, non-lethal weapons for a variety of law enforcement and other-than-war military applications. Through the effects of illumination, glare, and psychological impact; lasers can provide unequivocal warning, threat assessment based on reaction to the warning, hesitation, distraction, and reductions in combat and functional effectiveness. This paper discusses ongoing research and development by Science and Engineering Associates into laser illuminator concepts for civilian and military use. Topics include fundamental design and safety issues, laser diode requirements, and laser illuminator concepts, including a grenade shell laser system that converts a standard 40-mm grenade launcher into a laser illuminator.

  10. Imaging of gaseous oxygen through DFB laser illumination

    NASA Astrophysics Data System (ADS)

    Cocola, L.; Fedel, M.; Tondello, G.; Poletto, L.

    2016-05-01

    A Tunable Diode Laser Absorption Spectroscopy setup with Wavelength Modulation has been used together with a synchronous sampling imaging sensor to obtain two-dimensional transmission-mode images of oxygen content. Modulated laser light from a 760nm DFB source has been used to illuminate a scene from the back while image frames were acquired with a high dynamic range camera. Thanks to synchronous timing between the imaging device and laser light modulation, the traditional lock-in approach used in Wavelength Modulation Spectroscopy was replaced by image processing techniques, and many scanning periods were averaged together to allow resolution of small intensity variation over the already weak absorption signals from oxygen absorption band. After proper binning and filtering, the time-domain waveform obtained from each pixel in a set of frames representing the wavelength scan was used as the single detector signal in a traditional TDLAS-WMS setup, and so processed through a software defined digital lock-in demodulation and a second harmonic signal fitting routine. In this way the WMS artifacts of a gas absorption feature were obtained from each pixel together with intensity normalization parameter, allowing a reconstruction of oxygen distribution in a two-dimensional scene regardless from broadband transmitted intensity. As a first demonstration of the effectiveness of this setup, oxygen absorption images of similar containers filled with either oxygen or nitrogen were acquired and processed.

  11. Laser illumination of multiple capillaries that form a waveguide

    DOEpatents

    Dhadwal, Harbans S.; Quesada, Mark A.; Studier, F. William

    1998-08-04

    A system and method are disclosed for efficient laser illumination of the interiors of multiple capillaries simultaneously, and collection of light emitted from them. Capillaries in a parallel array can form an optical waveguide wherein refraction at the cylindrical surfaces confines side-on illuminating light to the core of each successive capillary in the array. Methods are provided for determining conditions where capillaries will form a waveguide and for assessing and minimizing losses due to reflection. Light can be delivered to the arrayed capillaries through an integrated fiber optic transmitter or through a pair of such transmitters aligned coaxially at opposite sides of the array. Light emitted from materials within the capillaries can be carried to a detection system through optical fibers, each of which collects light from a single capillary, with little cross talk between the capillaries. The collection ends of the optical fibers can be in a parallel array with the same spacing as the capillary array, so that the collection fibers can all be aligned to the capillaries simultaneously. Applicability includes improving the efficiency of many analytical methods that use capillaries, including particularly high-throughput DNA sequencing and diagnostic methods based on capillary electrophoresis.

  12. Laser illumination of multiple capillaries that form a waveguide

    DOEpatents

    Dhadwal, H.S.; Quesada, M.A.; Studier, F.W.

    1998-08-04

    A system and method are disclosed for efficient laser illumination of the interiors of multiple capillaries simultaneously, and collection of light emitted from them. Capillaries in a parallel array can form an optical waveguide wherein refraction at the cylindrical surfaces confines side-on illuminating light to the core of each successive capillary in the array. Methods are provided for determining conditions where capillaries will form a waveguide and for assessing and minimizing losses due to reflection. Light can be delivered to the arrayed capillaries through an integrated fiber optic transmitter or through a pair of such transmitters aligned coaxially at opposite sides of the array. Light emitted from materials within the capillaries can be carried to a detection system through optical fibers, each of which collects light from a single capillary, with little cross talk between the capillaries. The collection ends of the optical fibers can be in a parallel array with the same spacing as the capillary array, so that the collection fibers can all be aligned to the capillaries simultaneously. Applicability includes improving the efficiency of many analytical methods that use capillaries, including particularly high-throughput DNA sequencing and diagnostic methods based on capillary electrophoresis. 35 figs.

  13. Waveform agile high-power fiber laser illuminators for directed-energy weapon systems

    NASA Astrophysics Data System (ADS)

    Engin, Doruk; Lu, Wei; Kimpel, Frank; Gupta, Shantanu

    2012-06-01

    A kW-class fiber-amplifier based laser illuminator system at 1030nm is demonstrated. At 125 kHz pulse repetition rate, 1.9mJ energy per pulse (235W average power) is achieved for 100nsec pulses with >72% optical conversion efficiency, and at 250kHz repetition, >350W average power is demonstrated, limited by the available pumps. Excellent agreement is established between the experimental results and dynamic fiber amplifier simulation, for predicting the pulse shape, spectrum and ASE accumulation throughout the fiber-amplifier chain. High pulse-energy, high power fiber-amplifier operation requires careful engineering - minimize ASE content throughout the pre-amplifier stages, use of large mode area gain fiber in the final power stage for effective pulse energy extraction, and pulse pre-shaping to compensate for the laser gain-saturation induced intra-pulse and pulse-pattern dependent distortion. Such optimization using commercially available (VLMA) fibers with core size in the 30-40μm range is estimated to lead to >4mJ pulse energy for 100nsec pulse at 50kHz repetition rate. Such waveform agile high-power, high-energy pulsed fiber laser illuminators at λ=1030nm satisfies requirements for active-tracking/ranging in high-energy laser (HEL) weapon systems, and in uplink laser beacon for deep space communication.

  14. Light pipe design method and stepper experimentation for interference effects reduction in laser illumination

    NASA Astrophysics Data System (ADS)

    Poyet, Jean-Michel; Lutz, Yves

    2016-07-01

    The use of light pipes is an efficient and low-cost technique to get a homogeneous illumination for laser-gated viewing systems. However, this technique suffers from drawbacks when used with coherent sources like solid-state lasers. Compacting light pipe-based laser illuminators involves working with small light pipe sections, and experiments show that interference fringes appear on the laser illumination profiles. The principle of light pipe homogenization has been reviewed using geometrical optics to understand the phenomenon better, and a pragmatic light pipe design method, based on laser-gated viewing system parameters, is proposed. Another original solution based on optical stepper is studied to reduce both interference fringes and speckle noise to increase the homogeneity of laser illumination profiles.

  15. EO/IR/Laser illumination sensors for perimeter security

    NASA Astrophysics Data System (ADS)

    Natelson, David

    2007-04-01

    The integration of varied types of EO, IR, and Laser Illumination sensors used for perimeter security greatly improves the data that is available to the process of classifying potential threats. A key component of the design of layered sets of sensors is to understand the method in which detection, recognition, and identification distances are defined by each vendor. Historically, it has been challenging to compare each vendor's stated values as each type of sensor has unique characteristics that hinder the process of performing a so called "apples to apples" comparison. This results in more costly field testing and software simulations that attempt to model real world deployments. What we do know is that solutions are desired where multiple sensors are used to provide information to the Detection, Recognition through Identification process, as well as, associated human or software-based threat assessment and reaction processes. Perimeter security typically involves several layers of detection and investigation. Many entities have invested in detection sensors only to find out that they lack integrated or queued investigative sensors that provide a better return on investment for their systems. When you add night vision sensors to the mix, the challenges increase. This paper will examine sensor technologies and integration/command control/analytics technologies that are attempting to tie things together. The latest technologies including queued sensors and advances in detection/analytics using PTZ sensors will be covered.

  16. Illuminating Northern California’s Active Faults

    USGS Publications Warehouse

    Prentice, Carol S.; Crosby, Christopher J.; Whitehill, Caroline S.; Arrowsmith, J. Ramon; Furlong, Kevin P.; Philips, David A.

    2009-01-01

    Newly acquired light detection and ranging (lidar) topographic data provide a powerful community resource for the study of landforms associated with the plate boundary faults of northern California (Figure 1). In the spring of 2007, GeoEarthScope, a component of the EarthScope Facility construction project funded by the U.S. National Science Foundation, acquired approximately 2000 square kilometers of airborne lidar topographic data along major active fault zones of northern California. These data are now freely available in point cloud (x, y, z coordinate data for every laser return), digital elevation model (DEM), and KMZ (zipped Keyhole Markup Language, for use in Google EarthTM and other similar software) formats through the GEON OpenTopography Portal (http://www.OpenTopography.org/data). Importantly, vegetation can be digitally removed from lidar data, producing high-resolution images (0.5- or 1.0-meter DEMs) of the ground surface beneath forested regions that reveal landforms typically obscured by vegetation canopy (Figure 2)

  17. Laser agile illumination for object tracking and classification - Feasibility study

    NASA Technical Reports Server (NTRS)

    Scholl, Marija S.; Vanzyl, Jakob J.; Meinel, Aden B.; Meinel, Marjorie P.; Scholl, James W.

    1988-01-01

    The 'agile illumination' concept for discrimination between ICBM warheads and decoys involves a two-aperture illumination with coherent light, diffraction of light by propagation, and a resulting interference pattern on the object surface. A scanning two-beam interference pattern illuminates one object at a time; depending on the shape, momentum, spinning, and tumbling characteristics of the interrogated object, different temporal signals will be obtained for different classes of objects.

  18. Standoff hyperspectral imaging of explosives residues using broadly tunable external cavity quantum cascade laser illumination

    NASA Astrophysics Data System (ADS)

    Bernacki, Bruce E.; Phillips, Mark C.

    2010-04-01

    We describe experimental results on the detection of explosives residues with active hyperspectral imaging by illumination of the target surface using an external cavity quantum cascade laser (ECQCL) and imaging using an uncooled microbolometer camera. Explosives have rich absorption features in the molecular fingerprint region that spans 1500 to 500 wavenumbers and is easily probed by the wavelength range of quantum cascade lasers (QCL), which can be fabricated to emit from 3300 to 400 wavenumbers. Our laboratory-built ECQCL consists of a Fabry-Pérot laser with anti-reflection coated front facet that is arranged in a Littman-Metcalf configuration. The ECQCL was operated quasi-CW with a 100 kHz repetition rate, 50% duty cycle drive signal and tuning range from 1102.95 to 983.8 wavenumbers. The active hyperspectral imaging technique forms an image hypercube by recording one image for each tuning step of the ECQCL. For the experiments reported here, each wavelength band was 2 wavenumbers wide and 60 bands of image data were acquired in 2 seconds. The resulting hyperspectral image contains the full absorption spectrum produced by the illumination laser at each pixel in the image which can then be used to identify the explosive type and relative quantity using the rich library of spectral identification approaches developed initially in the remote sensing community. These techniques include spectral feature fitting, matched filtering, and mixture tuned matched filtering. Mixtures of materials can be evaluated using linear spectral unmixing approaches and matched filtering or mixture tuned matched filtering. We provide examples of these methods using ENVI, a commercial spectral image processing software package.

  19. An inexpensive programmable illumination microscope with active feedback

    PubMed Central

    Tompkins, Nathan; Fraden, Seth

    2016-01-01

    We have developed a programmable illumination system capable of tracking and illuminating numerous objects simultaneously using only low-cost and reused optical components. The active feedback control software allows for a closed-loop system that tracks and perturbs objects of interest automatically. Our system uses a static stage where the objects of interest are tracked computationally as they move across the field of view allowing for a large number of simultaneous experiments. An algorithmically determined illumination pattern can be applied anywhere in the field of view with simultaneous imaging and perturbation using different colors of light to enable spatially and temporally structured illumination. Our system consists of a consumer projector, camera, 35-mm camera lens, and a small number of other optical and scaffolding components. The entire apparatus can be assembled for under $4,000. PMID:27642182

  20. Digital micromirror device-based laser-illumination Fourier ptychographic microscopy

    PubMed Central

    Kuang, Cuifang; Ma, Ye; Zhou, Renjie; Lee, Justin; Barbastathis, George; Dasari, Ramachandra R.; Yaqoob, Zahid; So, Peter T. C.

    2015-01-01

    We report a novel approach to Fourier ptychographic microscopy (FPM) by using a digital micromirror device (DMD) and a coherent laser source (532 nm) for generating spatially modulated sample illumination. Previously demonstrated FPM systems are all based on partially-coherent illumination, which offers limited throughput due to insufficient brightness. Our FPM employs a high power coherent laser source to enable shot-noise limited high-speed imaging. For the first time, a digital micromirror device (DMD), imaged onto the back focal plane of the illumination objective, is used to generate spatially modulated sample illumination field for ptychography. By coding the on/off states of the micromirrors, the illumination plane wave angle can be varied at speeds more than 4 kHz. A set of intensity images, resulting from different oblique illuminations, are used to numerically reconstruct one high-resolution image without obvious laser speckle. Experiments were conducted using a USAF resolution target and a fiber sample, demonstrating high-resolution imaging capability of our system. We envision that our approach, if combined with a coded-aperture compressive-sensing algorithm, will further improve the imaging speed in DMD-based FPM systems. PMID:26480361

  1. Keck Laser Illuminates AGN in the Distant Universe.

    NASA Astrophysics Data System (ADS)

    Melbourne, J.; Wright, S.; Le Mignant, D.; Barczys, M.; Larkin, J.; Max, C.; Koo, D.

    2004-12-01

    The Center for Adaptive Optics Treasury Survey (CATS) aims to combine deep HST images in the optical with deep Keck adaptive optics (AO) data in the near-infrared (NIR) to study distant galaxies, AGN, and supernovae. We recently achieved an important new milestone by securing the first high quality Keck laser guide star (LGS) AO image of faint galaxies. Six galaxies with redshifts ranging from 0.3-1.0 were targeted in one pointing in the GOODS-S field. Two are Chandra sources with complex morphologies suggestive of recent merger activity. Substructures seen in the NIR AO image, including the double nucleus of one Chandra source and multiple tight knots in another, are confirmed in the optical HST images (both about 0.1" FWHM) but are undetected in very deep, ground-based NIR images from ESO with seeing about 0.5" FWHM. We will present results on the stellar populations of the substructures as derived from photometry of the galaxy subcomponents using the NIR AO data and the optical HST data taken with four ACS filters.

  2. A Practical Laser Projector with New Illumination Optics for Reduction of Speckle Noise

    NASA Astrophysics Data System (ADS)

    Kasazumi, Ken'ichi; Kitaoka, Yasuo; Mizuuchi, Kiminori; Yamamoto, Kazuhisa

    2004-08-01

    We have developed illumination optics for image projection systems. It realizes uniform illumination and suppression of speckle and diffraction noises by using a diffuser and integrator optics. By optimizing the diffusing angle of the diffuser, optical power loss was less than 10%. A proto type of a laser projector with a red wide-stripe semiconductor laser and green and blue second-harmonic generation lasers was realized by using the developed illumination optics and twisted nematic liquid-crystal panels. Still images from a personal computer and video images from a digital versatile disk (DVD) player were displayed with the system and a wide colour gamut and smooth images without diffraction noise nor speckle noise were confirmed.

  3. Universal threshold for femtosecond laser ablation with oblique illumination

    NASA Astrophysics Data System (ADS)

    Liu, Xiao-Long; Cheng, Weibo; Petrarca, Massimo; Polynkin, Pavel

    2016-10-01

    We quantify the dependence of the single-shot ablation threshold on the angle of incidence and polarization of a femtosecond laser beam, for three dissimilar solid-state materials: a metal, a dielectric, and a semiconductor. Using the constant, linear value of the index of refraction, we calculate the laser fluence transmitted through the air-material interface at the point of ablation threshold. We show that, in spite of the highly nonlinear ionization dynamics involved in the ablation process, the so defined transmitted threshold fluence is universally independent of the angle of incidence and polarization of the laser beam for all three material types. We suggest that angular dependence of ablation threshold can be utilized for profiling fluence distributions in ultra-intense femtosecond laser beams.

  4. Low Power Ground-Based Laser Illumination for Electric Propulsion Applications

    NASA Technical Reports Server (NTRS)

    Lapointe, Michael R.; Oleson, Steven R.

    1994-01-01

    A preliminary evaluation of low power, ground-based laser powered electric propulsion systems is presented. A review of available and near-term laser, photovoltaic, and adaptive optic systems indicates that approximately 5-kW of ground-based laser power can be delivered at an equivalent one-sun intensity to an orbit of approximately 2000 km. Laser illumination at the proper wavelength can double photovoltaic array conversion efficiencies compared to efficiencies obtained with solar illumination at the same intensity, allowing a reduction in array mass. The reduced array mass allows extra propellant to be carried with no penalty in total spacecraft mass. The extra propellant mass can extend the satellite life in orbit, allowing additional revenue to be generated. A trade study using realistic cost estimates and conservative ground station viewing capability was performed to estimate the number of communication satellites which must be illuminated to make a proliferated system of laser ground stations economically attractive. The required number of satellites is typically below that of proposed communication satellite constellations, indicating that low power ground-based laser beaming may be commercially viable. However, near-term advances in low specific mass solar arrays and high energy density batteries for LEO applications would render the ground-based laser system impracticable.

  5. Laser illuminator and optical system for disk patterning

    DOEpatents

    Hackel, Lloyd A.; Dane, C. Brent; Dixit, Shamasundar N.; Everett, Mathew; Honig, John

    2000-01-01

    Magnetic recording media are textured over areas designated for contact in order to minimize friction with data transducing heads. In fabricating a hard disk, an aluminum nickel-phosphorous substrate is polished to a specular finish. A mechanical means is then used to roughen an annular area intended to be the head contact band. An optical and mechanical system allows thousands of spots to be generated with each laser pulse, allowing the textured pattern to be rapidly generated with a low repetition rate laser and an uncomplicated mechanical system. The system uses a low power laser, a beam expander, a specially designed phase plate, a prism to deflect the beam, a lens to transmit the diffraction pattern to the far field, a mechanical means to rotate the pattern and a trigger system to fire the laser when sections of the pattern are precisely aligned. The system generates an annular segment of the desired pattern with which the total pattern is generated by rotating the optical system about its optic axis, sensing the rotational position and firing the laser as the annular segment rotates into the next appropriate position. This marking system can be integrated into a disk sputtering system for manufacturing magnetic disks, allowing for a very streamlined manufacturing process.

  6. Cutting edge science: Laser surgery illuminates viscoelasticity of merotelic kinetochores

    PubMed Central

    Cabello, Simon

    2016-01-01

    Increasing evidence in eukaryotic cells suggests that mechanical forces are essential for building a robust mitotic apparatus and correcting inappropriate chromosome attachments. In this issue, Cojoc et al. (2016. J. Cell Biol., http://dx.doi.org/10.1083/jcb.201506011) use laser microsurgery in vivo to measure and study the viscoelastic properties of kinetochores. PMID:27002164

  7. Versatile illumination platform and fast optical switch to give standard observation camera gated active imaging capacity

    NASA Astrophysics Data System (ADS)

    Grasser, R.; Peyronneaudi, Benjamin; Yon, Kevin; Aubry, Marie

    2015-10-01

    CILAS, subsidiary of Airbus Defense and Space, develops, manufactures and sales laser-based optronics equipment for defense and homeland security applications. Part of its activity is related to active systems for threat detection, recognition and identification. Active surveillance and active imaging systems are often required to achieve identification capacity in case for long range observation in adverse conditions. In order to ease the deployment of active imaging systems often complex and expensive, CILAS suggests a new concept. It consists on the association of two apparatus working together. On one side, a patented versatile laser platform enables high peak power laser illumination for long range observation. On the other side, a small camera add-on works as a fast optical switch to select photons with specific time of flight only. The association of the versatile illumination platform and the fast optical switch presents itself as an independent body, so called "flash module", giving to virtually any passive observation systems gated active imaging capacity in NIR and SWIR.

  8. Waveguide generated mitigation of speckle and scintillation on an actively illuminated target

    NASA Astrophysics Data System (ADS)

    Moore, Trevor D.; Raynor, Robert A.; Spencer, Mark F.; Schmidt, Jason D.

    2016-09-01

    Active illumination is often used when passive illumination cannot produce enough signal intensity to be a reliable imaging method. However, an increase in signal intensity is often achieved by using highly coherent laser sources, which produce undesirable effects such as speckle and scintillation. The deleterious effects of speckle and scintillation are often so immense that the imaging camera cannot receive intelligible data, thereby rendering the active illumination technique useless. By reducing the spatial coherence of the laser beam that is actively illuminating the object, it is possible to reduce the corruption of the received data caused by speckle and scintillation. The waveguide method discussed in this paper reduces spatial coherence through multiple total internal reflections, which create multiple virtual sources of diverse path lengths. The differing path lengths between the virtual sources and the target allow for the temporal coherence properties of the laser to be translated into spatial coherence properties. The resulting partial spatial coherence helps to mitigate the self-interference of the beam as it travels through the atmosphere and reflects off of optically rough targets. This mitigation method results in a cleaner, intelligible image that may be further processed for the intended use, unlike its unmitigated counterpart. Previous research has been done to independently reduce speckle or scintillation by way of spatial incoherence, but there has been no focus on modeling the waveguide, specifically the image plane the waveguide creates. Utilizing a ray-tracing method we can determine the coherence length of the source necessary to create incoherent spots in the image plane, as well as accurately modeling the image plane.

  9. Trans-illuminated laser speckle imaging of collateral artery blood flow in ischemic mouse hindlimb.

    PubMed

    Meisner, Joshua K; Niu, Jacqueline; Sumer, Suna; Price, Richard J

    2013-09-01

    The mouse ischemic hindlimb model is used widely for studying collateral artery growth (i.e., arteriogenesis) in response to increased shear stress. Nonetheless, precise measurements of regional shear stress changes along individual collateral arteries are lacking. Our goal is to develop and verify trans-illumination laser speckle flowmetry (LSF) for this purpose. Studies of defibrinated bovine blood flow through tubes embedded in tissue-mimicking phantoms indicate that trans-illumination LSF better maintains sensitivity with an increasing tissue depth when compared to epi-illumination, with an ∼50% reduction in the exponential decay of the speckle velocity signal. Applying trans-illuminated LSF to the gracilis muscle collateral artery network in vivo yields both improved sensitivity and reduced noise when compared to epi-illumination. Trans-illuminated LSF images reveal regional differences in collateral artery blood velocity after femoral artery ligation and are used to measure an ∼2-fold increase in the shear stress at the entrance regions to the muscle. We believe these represent the first direct measurements of regional shear stress changes in individual mouse collateral arteries. The ability to capture deeper vascular signals using a trans-illumination configuration for LSF may expand the current applications for LSF, which could have bearing on determining how shear stress magnitude and direction regulate arteriogenesis.

  10. Simulation of the temperature increase in porcine cadaver iris during direct illumination by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Sun, Hui; Kurtz, Ronald M.; Juhasz, Tibor

    2012-03-01

    As a model for laser exposure of the iris during femtosecond corneal surgery, we simulated the temperature rise in porcine cadaver iris during direct illumination by the femtosecond laser. The temperature increase induced by a 60 kHz iFS Advanced Femtosecond Laser (AMO Inc., Santa Ana, CA) in porcine cadaver iris was simulated using COMSOL (Comsol Inc., Burlington, MA) finite element software. Temperature increases up to 2.45 °C (corresponding to 2 μJ laser pulse energy and 24 second illumination) were observed in the porcine cadaver iris from the simulation with little variation in temperature profiles compared with specimens for the same laser energy illumination in experiment. : The commercial iFS Advanced Femtosecond Laser operating with pulse energies at approximately the lower limit of the range evaluated in this study would be expected to result in a 1.23 °C temperature increase and, therefore, does not present a safety hazard to the iris.

  11. CLEANSPACE 'Small Debris Removal By Laser Illumination And Complementary Technologies'

    SciTech Connect

    Esmiller, Bruno; Jacquelard, Christophe

    2011-11-10

    Studies show that the number of debris in Low Earth Orbit is exponentially growing despite future debris release mitigation measures considered. Especially, the already existing population of small and medium debris (between 1 cm and several dozens of cm) is today a concrete threat to operational satellites. A ground based laser solution which can remove at low expense and in a non-destructive way hazardous debris of decimetric size around selected space assets appears as one highly promising answer. This solution will be studied in the frame of CLEANSPACE project which is a part of the FP7 space theme. The overall CLEANSPACE objective is threefold: to propose an efficient and affordable global system architecture, to tackle safety regulation aspects, political implications and future collaborations, to develop affordable technological bricks and to establish roadmap for the development and the future implantation of a fully functional laser protection system. This paper will present the CLEANSPACE project.

  12. Illumination of 3 and 4 hole spherical laser driven hohlraums

    SciTech Connect

    Wilson, D.C.; Wingate, C.A.; Mead, W.C.; McLeod, J.

    1990-01-01

    We have considered what laser beam orientations entering static spherical hohlraums through three or four holes are needed to uniformly distribute the incident laser energy on the hohlraum wall. Each incident beam is characterized by its angle of incidence, i, with respect to the normal to the laser entrance hole. In the set of beams needed to cover the hohlraum interior, let i{sub min} be the minimum angle of incidence of beams in this set, i.e. the beam which most closely approaches the center. Let i{sub max} be the beam which passes most obliquely through the entrance hole. To leave the maximum unexposed central volume we desire the largest i{sub min}. To minimize the entrance hole diameter i{sub max} should be minimized. For a hohlraum with three holes located 120{degree} apart in a plane through the hohlraum center, the wall can be covered uniformly by a set of beams with i{sub min} = 30{degree} and i{sub max} = 60{degree}. For a hohlraum with four holes located at the corners of a tetrahedron there exist two sets, one with i{sub min} = 27.3{degree} and i{sub max} = 54.6{degree}, and another with i{sub min} = 35.4{degree} and i{sub max} = 62.6{degree}.

  13. Method for controlling a laser additive process using intrinsic illumination

    NASA Astrophysics Data System (ADS)

    Tait, Robert; Cai, Guoshuang; Azer, Magdi; Chen, Xiaobin; Liu, Yong; Harding, Kevin

    2015-05-01

    One form of additive manufacturing is to use a laser to generate a melt pool from powdered metal that is sprayed from a nozzle. The laser net-shape machining system builds the part a layer at a time by following a predetermined path. However, because the path may need to take many turns, maintaining a constant melt pool may not be easy. A straight section may require one speed and power while a sharp bend would over melt the metal at the same settings. This paper describes a process monitoring method that uses the intrinsic IR radiation from the melt pool along with a process model configured to establish target values for the parameters associated with the manufacture or repair. This model is based upon known properties of the metal being used as well as the properties of the laser beam. An adaptive control technique is then employed to control process parameters of the machining system based upon the real-time weld pool measurement. Since the system uses the heat radiant from the melt pool, other previously deposited metal does not confuse the system as only the melted material is seen by the camera.

  14. Active polarimeter optical system laser hazard analysis.

    SciTech Connect

    Augustoni, Arnold L.

    2005-07-01

    A laser hazard analysis was performed for the SNL Active Polarimeter Optical System based on the ANSI Standard Z136.1-2000, American National Standard for Safe Use of Lasers and the ANSI Standard Z136.6-2000, American National Standard for Safe Use of Lasers Outdoors. The Active Polarimeter Optical System (APOS) uses a pulsed, near-infrared, chromium doped lithium strontium aluminum fluoride (Cr:LiSAF) crystal laser in conjunction with a holographic diffuser and lens to illuminate a scene of interest. The APOS is intended for outdoor operations. The system is mounted on a height adjustable platform (6 feet to 40 feet) and sits atop a tripod that points the beam downward. The beam can be pointed from nadir to as much as 60 degrees off of nadir producing an illuminating spot geometry that can vary from circular (at nadir) to elliptical in shape (off of nadir). The JP Innovations crystal Cr:LiSAF laser parameters are presented in section II. The illuminating laser spot size is variable and can be adjusted by adjusting the separation distance between the lens and the holographic diffuser. The system is adjusted while platform is at the lowest level. The laser spot is adjusted for a particular spot size at a particular distance (elevation) from the laser by adjusting the separation distance (d{sub diffuser}) to predetermined values. The downward pointing angle is also adjusted before the platform is raised to the selected operation elevation.

  15. High-speed compressive range imaging based on active illumination.

    PubMed

    Sun, Yangyang; Yuan, Xin; Pang, Shuo

    2016-10-03

    We report a compressive imaging method based on active illumination, which reconstructs a 3D scene at a frame rate beyond the acquisition speed limit of the camera. We have built an imaging prototype that projects temporally varying illumination pattern and demonstrated a joint reconstruction algorithm that iteratively retrieves both the range and high-temporal-frequency information from the 2D low-frame rate measurement. The reflectance and depth-map videos have been reconstructed at 1000 frames per second (fps) from the measurement captured at 200 fps. The range resolution is in agreement with the resolution calculated from the triangulation methods based on the same system geometry. We expect such an imaging method could become a simple solution to a wide range of applications, including industrial metrology, 3D printing, and vehicle navigations.

  16. Color difference amplification between gold nanoparticles in colorimetric analysis with actively controlled multiband illumination.

    PubMed

    Cheng, Xiaodong; Dai, Dinggui; Yuan, Zhiqin; Peng, Lan; He, Yan; Yeung, Edward S

    2014-08-05

    Spectral chemical sensing with digital color analysis by using consumer imaging devices could potentially revolutionize personalized healthcare. However, samples with small spectral variations often cannot be differentiated in color due to the nonlinearity of color appearance. In this study, we address this problem by exploiting the color image formation mechanism in digital photography. A close examination of the color image processing pipeline emphasizes that although the color can be represented digitally, it is still a reproducible subjective perception rather than a measurable physical property. That makes it possible to physically manage the color appearance of a nonradiative specimen through engineered illumination. By using scattering light imaging of gold nanoparticles (GNPs) as a model system, we demonstrated via simulation that enlarged color difference between spectrally close samples could be achieved with actively controlled illumination of multiple narrow-band light sources. Experimentally, darkfield imaging results indicate that color separation of single GNPs with various sizes can be significantly improved and the detection limit of GNP aggregation-based colorimetric assays can be much reduced when the conventional spectrally continuous white light was replaced with three independently intensity-controlled laser beams, even though the laser lines were uncorrelated with the LSPR maxima of the GNPs. With low-cost narrow-band light sources widely available today, this actively controlled illumination strategy could be utilized to replace the spectrometer in many spectral sensing applications.

  17. Optimal speckle noise reduction filter for range gated laser illuminated imaging

    NASA Astrophysics Data System (ADS)

    Dayton, David; Gonglewski, John; Lasche, James; Hassall, Arthur

    2016-09-01

    Laser illuminated imaging has a number of applications in the areas of night time air-to-ground target surveillance, ID, and pointing and tracking. Using a laser illuminator, the illumination intensity and thus the signal to noise ratio can be controlled. With the advent of high performance range gated cameras in the short-wave infra-red band, higher spatial resolution can be achieved over passive thermal night imaging cameras in the mid-wave infra-red due to the shorter wave-length. If a coherent illuminator is used the resulting imagery often suffers from speckle noise due to the scattering off of a rough target surface, which gives it a grainy "salt and pepper" appearance. The probability density function for the intensity of focal plane speckle is well understood to follow a negative exponential distribution. This can be exploited to develop a Bayesian speckle noise filter. The filter has the advantage over simple frame averaging approaches in that it preserves target features and motion while reducing speckle noise without smearing or blurring the images. The resulting filtered images have the appearance of passive imagery and so are more amenable to sensor fusion with simultaneous mid-wave infra-red thermal images for enhanced target ID. The noise filter improvement is demonstrated using examples from real world laser imaging tests on tactical targets.

  18. Contrast- and illumination-invariant object recognition from active sensation.

    PubMed

    Rentschler, Ingo; Osman, Erol; Jüttner, Martin

    2009-01-01

    It has been suggested that the deleterious effect of contrast reversal on visual recognition is unique to faces, not objects. Here we show from priming, supervised category learning, and generalization that there is no such thing as general invariance of recognition of non-face objects against contrast reversal and, likewise, changes in direction of illumination. However, when recognition varies with rendering conditions, invariance may be restored and effects of continuous learning may be reduced by providing prior object knowledge from active sensation. Our findings suggest that the degree of contrast invariance achieved reflects functional characteristics of object representations learned in a task-dependent fashion.

  19. Quantitative comparison of organic photovoltaic bulk heterojunction photostability under laser illumination

    SciTech Connect

    Lesoine, Michael D.; Bobbitt, Jonathan M.; Carr, John A.; Elshobaki, Moneim; Chaudhary, Sumit; Smith, Emily A.

    2014-11-20

    The photostability of bulk heterojunction organic photovoltaic films containing a polymer donor and a fullerene-derivative acceptor was examined using resonance Raman spectroscopy and controlled laser power densities. The polymer donors were poly(3-hexylthiophene-2,5-diyl) (P3HT), poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl] (PCDTBT), or poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}) (PTB7). Four sample preparation methods were studied: (i) thin or (ii) thick films with fast solvent evaporation under nitrogen, (iii) thick films with slow solvent evaporation under nitrogen, and (iv) thin films dried under nitrogen followed by thermal annealing. Polymer order was assessed by monitoring a Raman peak’s full width at half-maximum and location as a function of illumination time and laser power densities from 2.5 × 103 to 2.5 × 105 W cm–2. Resonance Raman spectroscopy measurements show that before prolonged illumination, PCDTBT and PTB7 have the same initial order for all preparation conditions, while P3HT order improves with slow solvent drying or thermal annealing. All films exhibited changes to bulk heterojunction structure with 2.5 × 105 Wcm–2 laser illumination as measured by resonance Raman spectroscopy, and atomic force microscopy images show evidence of sample heating that affects the polymer over an area greater than the illumination profile. Furthermore, photostability data are important for proper characterization by techniques involving illumination and the development of devices suitable for real-world applications.

  20. Quantitative comparison of organic photovoltaic bulk heterojunction photostability under laser illumination

    DOE PAGES

    Lesoine, Michael D.; Bobbitt, Jonathan M.; Carr, John A.; ...

    2014-11-20

    The photostability of bulk heterojunction organic photovoltaic films containing a polymer donor and a fullerene-derivative acceptor was examined using resonance Raman spectroscopy and controlled laser power densities. The polymer donors were poly(3-hexylthiophene-2,5-diyl) (P3HT), poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl] (PCDTBT), or poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}) (PTB7). Four sample preparation methods were studied: (i) thin or (ii) thick films with fast solvent evaporation under nitrogen, (iii) thick films with slow solvent evaporation under nitrogen, and (iv) thin films dried under nitrogen followed by thermal annealing. Polymer order was assessed by monitoring a Raman peak’s full width at half-maximum and location as a function of illumination time and laser powermore » densities from 2.5 × 103 to 2.5 × 105 W cm–2. Resonance Raman spectroscopy measurements show that before prolonged illumination, PCDTBT and PTB7 have the same initial order for all preparation conditions, while P3HT order improves with slow solvent drying or thermal annealing. All films exhibited changes to bulk heterojunction structure with 2.5 × 105 Wcm–2 laser illumination as measured by resonance Raman spectroscopy, and atomic force microscopy images show evidence of sample heating that affects the polymer over an area greater than the illumination profile. Furthermore, photostability data are important for proper characterization by techniques involving illumination and the development of devices suitable for real-world applications.« less

  1. Investigation into the electromagnetic impulses from long-pulse laser illuminating solid targets inside a laser facility

    NASA Astrophysics Data System (ADS)

    Yi, Tao; Yang, Jinwen; Yang, Ming; Wang, Chuanke; Yang, Weiming; Li, Tingshuai; Liu, Shenye; Jiang, Shaoen; Ding, Yongkun; Xiao, Shaoqiu

    2016-09-01

    Emission of the electromagnetic pulses (EMP) due to laser-target interaction in laser facility had been evaluated using a cone antenna in this work. The microwave in frequencies ranging from several hundreds of MHz to 2 GHz was recorded when long-pulse lasers with several thousands of joules illuminated the solid targets, meanwhile the voltage signals from 1 V to 4 V were captured as functions of laser energy and backlight laser, where the corresponding electric field strengths were obtained by simulating the cone antenna in combination with conducting a mathematical process (Tiknohov Regularization with L curve). All the typical coupled voltage oscillations displayed multiple peaks and had duration of up to 80 ns before decaying into noise and mechanisms of the EMP generation was schematically interpreted in basis of the practical measuring environments. The resultant data were expected to offer basic know-how to achieve inertial confinement fusion.

  2. Miniature solid-state lasers for pointing, illumination, and warning devices

    NASA Astrophysics Data System (ADS)

    Brown, D. C.; Singley, J. M.; Yager, E.; Kowalewski, K.; Lotito, B.; Guelzow, J.; Hildreth, J.; Kuper, J. W.

    2008-04-01

    In this paper we review the current status of and progress towards higher power and more wavelength diverse diode-pumped solid-state miniature lasers. Snake Creek Lasers now offers unprecedented continuous wave (CW) output power from 9.0 mm and 5.6 mm TO type packages, including the smallest green laser in the world, the MicroGreen TM laser, and the highest density green laser in the world, the MiniGreen TM laser. In addition we offer an infrared laser, the MiniIR TM, operating at 1064 nm, and have just introduced a blue Mini laser operating at 473 nm in a 9.0 mm package. Recently we demonstrated over 1 W of output power at 1064 nm from a 12 mm TO type package, and green output power from 300-500 mW from the same 12 mm package. In addition, the company is developing a number of other innovative new miniature CW solid-state lasers operating at 750 nm, 820 nm, 458 nm, and an eye-safe Q-switched laser operating at 1550 nm. We also review recently demonstrated combining volume Bragg grating (VBG) technology has been combined with automatic power control (APC) to produce high power MiniGreen TM lasers whose output is constant to +/- 10 % over a wide temperature range, without the use of a thermoelectric cooler (TEC). This technology is expected to find widespread application in military and commercial applications where wide temperature operation is particularly important. It has immediate applications in laser pointers, illuminators, and laser flashlights, and displays.

  3. A Radio System for Avoiding Illuminating Aircraft with a Laser Beam

    NASA Astrophysics Data System (ADS)

    Coles, W. A.; Murphy, T. W.; Melser, J. F.; Tu, J. K.; White, G. A.; Kassabian, K. H.; Bales, K.; Baumgartner, B. B.

    2012-01-01

    When scientific experiments require transmission of powerful laser or radio beams through the atmosphere, the Federal Aviation Administration (FAA) requires that precautions be taken to avoid inadvertent illumination of aircraft. At present, the FAA requires that laser operators use human spotters to protect against accidental illumination. Here, we describe a simple, inexpensive, and highly reliable electronic system for detecting aircraft entering the vicinity of a laser beam that makes use of the air traffic control (ATC) radio transponders required on most aircraft. The radio system uses two antennas, both aligned with the laser beam. One antenna has a broad beam and the other has a narrow beam. The ratio of the transponder power received in the narrow beam to that received in the broad beam gives a measure of the angular distance of the aircraft from the axis that is independent of the range or the transmitter power. This ratio is easily measured and can be used to shutter the laser when the aircraft is too close to the beam. Comparisons of prototype systems operating at both the Apache Point and W. M. Keck Observatory with an FAA database indicate successful identification of commercial airplanes passing near the telescope boresight.

  4. PITBUL: a physics-based modeling package for imaging and tracking of airborne targets for HEL applications including active illumination

    NASA Astrophysics Data System (ADS)

    Van Zandt, Noah R.; McCrae, Jack E.; Fiorino, Steven T.

    2013-05-01

    Aimpoint acquisition and maintenance is critical to high energy laser (HEL) system performance. This study demonstrates the development by the AFIT/CDE of a physics-based modeling package, PITBUL, for tracking airborne targets for HEL applications, including atmospheric and sensor effects and active illumination, which is a focus of this work. High-resolution simulated imagery of the 3D airborne target in-flight as seen from the laser position is generated using the HELSEEM model, and includes solar illumination, laser illumination, and thermal emission. Both CW and pulsed laser illumination are modeled, including the effects of illuminator scintillation, atmospheric backscatter, and speckle, which are treated at a first-principles level. Realistic vertical profiles of molecular and aerosol absorption and scattering, as well as optical turbulence, are generated using AFIT/CDE's Laser Environmental Effects Definition and Reference (LEEDR) model. The spatially and temporally varying effects of turbulence are calculated and applied via a fast-running wave optical method known as light tunneling. Sensor effects, for example blur, sampling, read-out noise, and random photon arrival, are applied to the imagery. Track algorithms, including centroid and Fitts correlation, as a part of a closed loop tracker are applied to the degraded imagery and scored, to provide an estimate of overall system performance. To gauge performance of a laser system against a UAV target, tracking results are presented as a function of signal to noise ratio. Additionally, validation efforts to date involving comparisons between simulated and experimental tracking of UAVs are presented.

  5. Comparison of cap lamp and laser illumination for detecting visual escape cues in smoke

    PubMed Central

    Lutz, T.J.; Sammarco, J.J.; Srednicki, J.R.; Gallagher, S.

    2015-01-01

    The Illuminating Engineering Society of North America reports that an underground mine is the most difficult environment to illuminate (Rea, 2000). Researchers at the U.S. National Institute for Occupational Safety and Health (NIOSH) Office of Mine Safety and Health Research (OMSHR) are conducting ongoing studies designed to explore different lighting technologies for improving mine safety. Underground miners use different visual cues to escape from a smoke-filled environment. Primary and secondary escapeways are marked with reflective ceiling tags of various colors. Miners also look for mine rail tracks. The main objective of this paper is to compare different lighting types and ceiling tag colors to differentiate what works best in a smoke-filled environment. Various cap lamps (LED and incandescent) and lasers (red, blue, green) were compared to see which options resulted in the longest detection distances for red, green and blue reflective markers and a section of mine rail track. All targets advanced toward the human subject inside of a smoke-filled room to simulate the subject walking in a mine environment. Detection distances were recorded and analyzed to find the best cap lamp, laser color and target color in a smoke environment. Results show that cap lamp, laser color and target color do make a difference in detection distances and are perceived differently based on subject age. Cap lamps were superior to lasers in all circumstances of ceiling tag detection, with the exception of the green laser. The incandescent cap lamp worked best in the simulated smoke compared to the LED cap lamps. The green laser was the best color for detecting the tags and track compared to the red and blue lasers. The green tags were the easiest color to detect on the ceiling. On average, the track was easier for the subjects to detect than the ceiling tags. PMID:26236146

  6. Numerical analysis of the direct drive illumination uniformity for the Laser MegaJoule facility

    NASA Astrophysics Data System (ADS)

    Temporal, M.; Canaud, B.; Garbett, W. J.; Ramis, R.

    2014-01-01

    The illumination uniformity provided during the initial imprinting phase of the laser foot pulse in a direct drive scenario at the Laser MegaJoule facility has been analyzed. This study analyzes the quality of the illumination of a spherical capsule and concerns the uniformity of the first shock generate in the absorber of an Inertial Confinement Fusion capsule. Four configurations making use of all or some of the 80 laser beams organized in the 20 quads of the cones at 49° and 131° with respect to the polar axis have been considered in order to assemble the foot pulse. Elliptical and circular super-gaussian laser intensity profiles taking into account beam-to-beam power imbalance (10%), pointing error (50 μm), and target positioning (20 μm) have been considered. It has been found that the use of the Polar Direct Drive technique can in some cases reduce the irradiation non-uniformity by a factor as high as 50%. In all cases, elliptical profile provides better results in comparison with the circular one and it is shown that the minimum of the non-uniformity is also a function of the capsule radius.

  7. Numerical analysis of the direct drive illumination uniformity for the Laser MegaJoule facility

    SciTech Connect

    Temporal, M.; Canaud, B.; Garbett, W. J.; Ramis, R.

    2014-01-15

    The illumination uniformity provided during the initial imprinting phase of the laser foot pulse in a direct drive scenario at the Laser MegaJoule facility has been analyzed. This study analyzes the quality of the illumination of a spherical capsule and concerns the uniformity of the first shock generate in the absorber of an Inertial Confinement Fusion capsule. Four configurations making use of all or some of the 80 laser beams organized in the 20 quads of the cones at 49° and 131° with respect to the polar axis have been considered in order to assemble the foot pulse. Elliptical and circular super-gaussian laser intensity profiles taking into account beam-to-beam power imbalance (10%), pointing error (50 μm), and target positioning (20 μm) have been considered. It has been found that the use of the Polar Direct Drive technique can in some cases reduce the irradiation non-uniformity by a factor as high as 50%. In all cases, elliptical profile provides better results in comparison with the circular one and it is shown that the minimum of the non-uniformity is also a function of the capsule radius.

  8. Frictional Properties of UV illuminated ZnO Thin Films Grown by Pulsed Laser Deposition

    NASA Astrophysics Data System (ADS)

    Chiu, Hsiang-Chih; Chang, Huan-Pu; Lo, Fang-Yu; Yeh, Yu-Ting; Department of Physics, National Taiwan Normal University Collaboration

    Zinc Oxide (ZnO) nanostructures have potential applications in nano-electro-mechanical systems (NEMS) due to their unique physical properties. ZnO is also an excellent lubricant and hence a promising candidate for protective coatings in NEMS. By means of atomic force microscopy (AFM), we have investigated the frictional properties of ZnO thin films prepared by pulsed laser deposition technique. In addition, UV illumination is used to convert the surface wettability of ZnO thin films from being more hydrophobic to superhydrophilic via the photo-catalyst effect. We found that the frictional properties of the UV illuminated, superhydrophilic ZnO surface are strongly dependent on the environment humidity. While for hydrophobic ZnO, no such dependence is found. The observed frictional behaviors can be explained by the interplay between the surface roughness, environmental humidity and the presence of nanoscale capillary condensation forming between surface asperities at the tip-ZnO contact. Our results might find applications in future ZnO related NEMS. Frictional Properties of UV illuminated ZnO Thin Films Grown by Pulsed Laser Deposition.

  9. Variable FOV optical illumination system with constant aspect ratio for 2-D array lasers diodes

    NASA Astrophysics Data System (ADS)

    Arasa, J.; de la Fuente, M. C.; Ibañez, C.

    2008-09-01

    In this contribution we present a compact system to create an illumination distribution with a constant aspect ratio 3:4 and FOV from 0.4 to 1 degree. Besides, the system must delivery 40 W from 170 individual laser diodes placed in a regular 2-D array distribution of 10 x 20 mm. The main problem that must be solved is the high asymmetry of the individual sources; emission divergence's ratio 3:73 (0.3 vs. 7.4 degree) combined with the flux holes due to the laser's heat drain. In one axis (divergence of 0.3º) the best design strategy approach is a Galileo telescope but in the other axis a collimator configuration is the best solution. To manage both solutions at the same time is the aim of this contribution. Unfortunately for the Galileo strategy, source dimensions are too large so aspheric surfaces are needed, and the collimator configuration requires an EFL that must change from 573 to 1432 mm. The presented solution uses a set of three fixed anamorphic lenses, two of them pure cylinders, combined with a wheel of anamorphic lenses that have the function to change the FOV of the system. The most important contribution of the design is to obtain a constant final ratio 3:4 from an initial ratio of 3:73 with no losses of energy. The proposed solution produces an illumination pattern with peaks and valleys lower than 40%. This pattern distribution might be unacceptable for a standard illumination solution. However, the actual FOV is used to illuminate far away targets thus air turbulence is enough to homogenize the distribution on the target.

  10. Large-solid-angle illuminators for extreme ultraviolet lithography with laser plasmas

    SciTech Connect

    Kubiak, G.D.; Tichenor, D.A.; Sweatt, W.C.; Chow, W.W.

    1995-06-01

    Laser Plasma Sources (LPSS) of extreme ultraviolet radiation are an attractive alternative to synchrotron radiation sources for extreme ultraviolet lithography (EUVL) due to their modularity, brightness, and modest size and cost. To fully exploit the extreme ultraviolet power emitted by such sources, it is necessary to capture the largest possible fraction of the source emission half-sphere while simultaneously optimizing the illumination stationarity and uniformity on the object mask. In this LDRD project, laser plasma source illumination systems for EUVL have been designed and then theoretically and experimentally characterized. Ellipsoidal condensers have been found to be simple yet extremely efficient condensers for small-field EUVL imaging systems. The effects of aberrations in such condensers on extreme ultraviolet (EUV) imaging have been studied with physical optics modeling. Lastly, the design of an efficient large-solid-angle condenser has been completed. It collects 50% of the available laser plasma source power at 14 nm and delivers it properly to the object mask in a wide-arc-field camera.

  11. Diffraction characteristics of a Fresnel zone plate illuminated by 10 fs laser pulses.

    PubMed

    Zhang, HaiFeng; Li, JianChao; Doerr, David W; Alexander, Dennis R

    2006-11-20

    Results of experimental and theoretical work performed to compare diffraction patterns and focal distributions of a Fresnel zone plate illuminated by ultrashort 10 fs pulsed and cw laser beams are presented. It is shown that the foci intensities of 10 fs pulses are considerably lower than those of cw beams while the focal widths in the axial and radial directions are broadened. Calculations also indicate the spectral modulation along the center of the diffraction patterns. These phenomena are explained by the coherent superposition of the composing frequency content.

  12. Multiple free electron laser pulse illumination of a carbon coated silicon substrate

    NASA Astrophysics Data System (ADS)

    Siemer, Björn; Hoger, Tim; Rutkowski, Marco; Menneken, Martina; Düsterer, Stefan; Zacharias, Helmut

    2013-05-01

    The fourth generation of XUV-, soft x-ray- and x-ray-light sources, like the free electron lasers FLASH and FERMI@Elettra, leads to new seminal scientific findings and technical challenges. For the facilities the question of the beam transport is of utmost importance. To provide a good reflectivity over a large range of photon energies up to about 300 eV mostly carbon coated silicon mirrors illuminated under gracing incidence angle are mostly chosen. Thereby the coating for the mirrors must tolerate high light intensities at high photon energies and also high repetition rates. In the present experiment an amorphous carbon coated silicon substrate was illuminated at photon energies of 21 nm (58 eV) and an average pulse energy of ~27 μJ. The ellipsoidal spot size of 300 μm × 600 μm at FLASH leads to a fluence of 0.019 J/cm2. The influence of multiple (100 - 20.000) light pulses to the coated surface is analyzed. Depending on the number of pulses a change in reflectivity is visible under a light microscope. Both an AFM profile and measurements with a profilometer yield no topological changes. The investigation of the illuminated spots with a microfocus Raman spectrometer shows a decrease of the carbon signal at higher pulse repetition rates.

  13. Laser illumination and EO systems for covert surveillance from NIR to SWIR and beyond

    NASA Astrophysics Data System (ADS)

    Dvinelis, Edgaras; Žukauskas, Tomas; Kaušylas, Mindaugas; Vizbaras, Augustinas; Vizbaras, Kristijonas; Vizbaras, Dominykas

    2016-10-01

    One of the most important factor of success in battlefield is the ability to remain undetected by the opposing forces while also having an ability to detect all possible threats. Illumination and pointing systems working in NIR and SWIR bands are presented. Wavelengths up to 1100 nm can be registered by newest generation image intensifier tubes, CCD and EMCCD sensors. Image intensifier tubes of generation III or older are only limited up to wavelength of 900 nm [1]. Longer wavelengths of 1550 nm and 1625 nm are designed to be used with SWIR electro-optical systems and they cannot be detected by any standard night vision system. Long range SWIR illuminators and pointers have beam divergences down to 1 mrad and optical powers up to 1.5 W. Due to lower atmospheric scattering SWIR illuminators and pointers can be used at extremely long distances up to 10s of km and even further during heavy weather conditions. Longer wavelengths of 2100 nm and 2450 nm are also presented, this spectrum band is of great interest for direct infrared countermeasure (DIRCM) applications. State-of-the-art SWIR and LWIR electro-optical systems are presented. Sensitive InGaAs sensors coupled with "fast" (low F/#) optical lenses can provide complete night vision, detection of all NIR and SWIR laser lines, penetration through smoke, dust and fog. Finally beyond-state-of-the-art uncooled micro-bolometer LWIR systems are presented featuring ultra-high sensor sensitivities of 20 mK.

  14. Initiation of vacuum insulator surface high-voltage flashover with electrons produced by laser illumination

    SciTech Connect

    Krasik, Ya. E.; Leopold, J. G.

    2015-08-15

    In this paper, experiments are described in which cylindrical vacuum insulator samples and samples inclined at 45° relative to the cathode were stressed by microsecond timescale high-voltage pulses and illuminated by focused UV laser beam pulses. In these experiments, we were able to distinguish between flashover initiated by the laser producing only photo-electrons and when plasma is formed. It was shown that flashover is predominantly initiated near the cathode triple junction. Even dense plasma formed near the anode triple junction does not necessarily lead to vacuum surface flashover. The experimental results directly confirm our conjecture that insulator surface breakdown can be avoided by preventing its initiation [J. G. Leopold et al., Phys. Rev. ST Accel. Beams 10, 060401 (2007)] and complement our previous experimental results [J. Z. Gleizer et al., IEEE Trans. Dielectr. Electr. Insul. 21, 2394 (2014) and J. Z. Gleizer et al., J. Appl. Phys. 117, 073301 (2015)].

  15. Bright illumination reduces parietal EEG alpha activity during a sustained attention task.

    PubMed

    Min, Byoung-Kyong; Jung, Young-Chul; Kim, Eosu; Park, Jin Young

    2013-11-13

    The influence of the illumination condition on our cognitive-performance seems to be more critical in the modern life, wherein, most people work in an office under a specific illumination condition. However, neurophysiological changes in a specific illumination state and their cognitive interpretation still remain unclear. Thereby, in the present study, the effect of different illumination conditions on the same cognitive performance was evaluated particularly by EEG wavelet analyses. During a sustained attention task, we observed that the higher illumination condition yielded significantly lower parietal tonic electroencephalogram (EEG) alpha activity before the presentation of the probe digit and longer reaction times, than that of the other illumination conditions. Although previous studies suggest that lower prestimulus EEG alpha activity is related to higher performance in an upcoming task, the reduced prestimulus alpha activity under higher illumination was associated with delayed reaction times in the present study. Presumably, the higher background illumination condition seems to be too bright for normal attentional processing and distracted participants' attention during a sustained attention task. Such a bottom-up effect by stimulus salience seemed to overwhelm a prestimulus top-down effect reflected in prestimulus alpha power during the bright background condition. This finding might imply a dynamic competition between prestimulus top-down and poststimulus bottom-up processes. Our findings provide compelling evidence that the illumination condition substantially modulates our attentional processing. Further refinement of the illumination parameters and subsequent exploration of cognitive-modulation are necessary to facilitate our cognitive performance.

  16. High direct drive illumination uniformity achieved by multi-parameter optimization approach: a case study of Shenguang III laser facility.

    PubMed

    Tian, Chao; Chen, Jia; Zhang, Bo; Shan, Lianqiang; Zhou, Weimin; Liu, Dongxiao; Bi, Bi; Zhang, Feng; Wang, Weiwu; Zhang, Baohan; Gu, Yuqiu

    2015-05-04

    The uniformity of the compression driver is of fundamental importance for inertial confinement fusion (ICF). In this paper, the illumination uniformity on a spherical capsule during the initial imprinting phase directly driven by laser beams has been considered. We aim to explore methods to achieve high direct drive illumination uniformity on laser facilities designed for indirect drive ICF. There are many parameters that would affect the irradiation uniformity, such as Polar Direct Drive displacement quantity, capsule radius, laser spot size and intensity distribution within a laser beam. A novel approach to reduce the root mean square illumination non-uniformity based on multi-parameter optimizing approach (particle swarm optimization) is proposed, which enables us to obtain a set of optimal parameters over a large parameter space. Finally, this method is applied to improve the direct drive illumination uniformity provided by Shenguang III laser facility and the illumination non-uniformity is reduced from 5.62% to 0.23% for perfectly balanced beams. Moreover, beam errors (power imbalance and pointing error) are taken into account to provide a more practical solution and results show that this multi-parameter optimization approach is effective.

  17. Measurement of the temperature increase in the porcine cadaver iris during direct illumination by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Sun, Hui; Kurtz, Ronald M.; Juhasz, Tibor

    2010-02-01

    Multiple femtosecond lasers have now been cleared for use for ophthalmic surgery, including for creation of corneal flaps in LASIK surgery. Preliminary measurements indicated that during typical surgical use, 50-60% of laser energy may pass beyond the cornea with potential effects on the iris. To further evaluate iris laser exposure during femtosecond corneal surgery, we measured the temperature increase in porcine cadaver iris in situ during direct illumination by the iFS Advanced Femtoosecond Laser (AMO Inc. Santa Ana, CA) with an infrared thermal imaging camera. To replicate the illumination geometry of the eye during the surgery, an excised porcine cadaver iris was placed 1.5 mm from the flat glass contact lens. The temperature field was observed in twenty cadaver iris at laser pulse energy levels ranging from 1 to 2 μJ (corresponding approximately to surgical energies of 2 to 4 μJ per pulse). Temperature increases up to 2.3 °C (corresponding to 2 μJ per pulse and 24 second procedure time) were observed in the cadaver iris with little variation in temperature profiles between specimens for the same laser energy illumination. For laser pulse energy and procedure time characteristic to the iFS Advanced Femtoosecond Laser the temperature increase was measured to be 1.2 °C. Our studies suggest that the magnitude of iris heating that occurs during such femtosecond laser corneal surgery is small and does not present a safety hazard to the iris.

  18. Comparison of LASER and LED illumination for fiber optic fringe projection

    NASA Astrophysics Data System (ADS)

    Matthias, Steffen; Kästner, Markus; Reithmeier, Eduard

    2016-04-01

    The inspection of functional elements is a crucial part of modern production cycles. However, with higher integration of production machinery and products, the accessibility for measurement systems is more and more limited. A solution for this problem can be found in endoscopy techniques, which are able to transport the image information for optical measurement methods. In this paper, an optical inspection system based on the fringe projection profilometry technique is presented. The fiber-optic fringe projection system uses two high-resolution image fibers to connect a compact sensor head to the pattern generation and camera unit. In order to keep inspection times low, the system is developed with particular focus on fast projection times. This can be achieved by using a digital micro-mirror device, which is capable of projecting grey-scale patterns at a rate of more than 10 images per second. However, due to the low numerical aperture of the optical fibers, a limiting factor for the pattern rate is the illumination path of the pattern generator. Two different designs of the illumination path are presented, which are based on a LASER light source as well as a LED light source. Due to low beam divergence and high intensities LASERs are well suited for fiber coupling. Unfortunately, the coherent property of the light has negative effects in certain measurement applications, as interference patterns, the so called speckle, appear on rough surfaces. Although speckle reducing methods are employed in the LASER beam path, the emergence of interference cannot be prevented completely. As an alternative, an illumination path based on a LED light source is demonstrated. To compare the effects of the speckle, based on measurements on a planar calibration standard both designs are compared in terms of phase noise, which is directly related to the noise in the reconstructed 3-D point data. Additionally, optical power measurements of both methods are compared to give an

  19. Ramp-wave compression experiment with direct laser illumination on Shen Guang III prototype Laser facility

    NASA Astrophysics Data System (ADS)

    Wang, Feng; Xu, Tao; Optical Team Collaboration

    2016-10-01

    Ramp-wave compression (RWC) experiment to balance the high compression pressure generation in aluminum and x-ray blanking effect in transparent window was demonstrated on Shen Guang-III prototype laser facility. A new target concept was proposed to develop a laser-driven shocks-RWC technique for studying material behavior under dynamic, high pressure conditions. As the ``little shocks'' in our experiment cannot be avoided, the effort to diminish the shock under a special level has been demonstrated with Al/Au/Al/LiF target. The highest pressure is about 500GPa after using the multilayer target design Al/Au/Al/LiF and about 1013W/cm2 laser pulse incident on the planer Al target, instantaneously affecting ablation layer located 500 μm away. As the x-ray generated by Al layer had been prevented by the Au layer, the width abrupt onset of strong absorption of an optical probe beam (λ = 532 nm) in LiF window may be the limitation for this kind if RWC experiment during the experiment time scale for 30 μm thick step. With the design laser shape and target structure of Al/Au/Al/LiF, 500GPa may be the highest pressure after balance the preheat effect and ablation efficiency for laser direct-drive experiment.

  20. X-ray lasers and methods utilizing two component driving illumination provided by optical laser means of relatively low energy and small physical size

    DOEpatents

    Rosen, Mordecai D.; Matthews, Dennis L.

    1991-01-01

    An X-ray laser (10), and related methodology, are disclosed wherein an X-ray laser target (12) is illuminated with a first pulse of optical laser radiation (14) of relatively long duration having scarcely enough energy to produce a narrow and linear cool plasma of uniform composition (38). A second, relatively short pulse of optical laser radiation (18) is uniformly swept across the length, from end to end, of the plasma (38), at about the speed of light, to consecutively illuminate continuously succeeding portions of the plasma (38) with optical laser radiation having scarcely enough energy to heat, ionize, and invert them into the continuously succeeding portions of an X-ray gain medium. This inventive double pulse technique results in a saving of more than two orders of magnitude in driving optical laser energy, when compared to the conventional single pulse approach.

  1. Terahertz emission from InSb illuminated by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Arlauskas, A.; Subačius, L.; Krotkus, A.; Malevich, V. L.

    2017-02-01

    Athough terahertz (THz) radiation from semiconductor surfaces illuminated by femtosecond laser pulses was observed a long time ago, the mechanisms responsible for this radiation still remains questionable, especially in narrow band gap semiconductors. Four different crystallographic orientation {(1 0 0), (1 1 0), (1 1 1) and (1 1 2)} InSb samples were analyzed in this investigation. THz amplitude dependences on the excitation wavelength and azimuthal angle are presented in this paper. We have shown that the second order nonlinear effect—optical rectification—is responsible for THz radiation in InSb. The microscopic origin of this effect is related to the orientation of electrons momenta by the optical radiation and anisotropy of the conduction band at high energies. Monte Carlo simulations have shown that electric field screening by intrinsic carriers diminishes the contribution of the third order nonlinear effect in this material.

  2. Quantitative imaging of a non-combusting diesel spray using structured laser illumination planar imaging

    NASA Astrophysics Data System (ADS)

    Berrocal, E.; Kristensson, E.; Hottenbach, P.; Aldén, M.; Grünefeld, G.

    2012-12-01

    Due to its transient nature, high atomization process, and rapid generation of fine evaporating droplets, diesel sprays have been, and still remain, one of the most challenging sprays to be fully analyzed and understood by means of non-intrusive diagnostics. The main limitation of laser techniques for quantitative measurements of diesel sprays concerns the detection of the multiple light scattering resulting from the high optical density of such a scattering medium. A second limitation is the extinction of the incident laser radiation as it crosses the spray, as well as the attenuation of the signal which is to be detected. All these issues have strongly motivated, during the past decade, the use of X-ray instead of visible light for dense spray diagnostics. However, we demonstrate in this paper that based on an affordable Nd:YAG laser system, structured laser illumination planar imaging (SLIPI) can provide accurate quantitative description of a non-reacting diesel spray injected at 1,100 bar within a room temperature vessel pressurized at 18.6 bar. The technique is used at λ = 355 nm excitation wavelength with 1.0 mol% TMPD dye concentration, for simultaneous LIF/Mie imaging. Furthermore, a novel dual-SLIPI configuration is tested with Mie scattering detection only. The results confirm that a mapping of both the droplet Sauter mean diameter and extinction coefficient can be obtained by such complementary approaches. These new insights are provided in this article at late times after injection start. It is demonstrated that the application of SLIPI to diesel sprays provides valuable quantitative information which was not previously accessible.

  3. Laser Illumination of Helicopters: A Comparative Analysis With Fixed-Wing Aircraft for the Period 1980 - 2011

    DTIC Science & Technology

    2013-04-01

    Aircraft for the Period 1980 – 2011 April 2013 6. Performing Organization Code 7. Author(s) 8. Performing Organization Report No...Agency Code 15. Supplemental Notes 16. Abstract INTRODUCTION. Laser illuminations of aircraft have resulted in pilots reporting...the level of exposure (4). A sharp rise in the number of laser incidents reported in the mid-1990s resulted in a revision of FAA Order 7400.2

  4. Tunable Broadband Radiation Generated Via Ultrafast Laser Illumination of an Inductively Charged Superconducting Ring

    PubMed Central

    Bulmer, John; Bullard, Thomas; Dolasinski, Brian; Murphy, John; Sparkes, Martin; Pangovski, Krste; O’Neill, William; Powers, Peter; Haugan, Timothy

    2015-01-01

    An electromagnetic transmitter typically consists of individual components such as a waveguide, antenna, power supply, and an oscillator. In this communication we circumvent complications associated with connecting these individual components and instead combine them into a non-traditional, photonic enabled, compact transmitter device for tunable, ultrawide band (UWB) radiation. This device is a centimeter scale, continuous, thin film superconducting ring supporting a persistent super-current. An ultrafast laser pulse (required) illuminates the ring (either at a point or uniformly around the ring) and perturbs the super-current by the de-pairing and recombination of Cooper pairs. This generates a microwave pulse where both ring and laser pulse geometry dictates the radiated spectrum’s shape. The transmitting device is self contained and completely isolated from conductive components that are observed to interfere with the generated signal. A rich spectrum is observed that extends beyond 30 GHz (equipment limited) and illustrates the complex super-current dynamics bridging optical, THz, and microwave wavelengths. PMID:26659022

  5. Intravascular low-power laser light illumination: a new method in restenosis prevention

    NASA Astrophysics Data System (ADS)

    Derkacz, Arkadiusz; Bialy, Dariusz; Protasiewicz, Marcin; Beres-Pawlik, Elzbieta M.; Abramski, Krzysztof M.

    2004-07-01

    The procedure of percutaneous coronary intervention is associated with the 30% risk of restenosis in the dilatated coronary artery. in order to minimize its occurrence we developed the method of intracoronary low power laser irradiation and called it the photoremodling. We developed and constructed at total set-up for the intravascular illumination. It consists of the laser diode connected with a multimode step-index silica fiber 200/270 μm terminated with a special fiber diffuser, which allows to irradiate homogeneously a coronary vessel in the place of dilatation. The diffuser is inserted into the coronary vessel by a modificated angioplasty catheter. Till now PTCA plus photoremodeling procedures have been carried out in 40 patients (28 with stent implantation and 12 with balloon angioplasty). We did not observed any side effects and complications of the procedure. All patients were qualified for 6 months follow-up, which was terminated in 19 cases with a control coronarography. We did not find any case of restenosis in the stent group. In the group of patients after balloon angioplasty restenosis rate was 25%. The new method of treatment is safe. The preliminary results seem to be beneficial especially in the case of stent implantation.

  6. Safety Guidelines for Laser Illumination on Exposed High Explosives and Metals in Contact with High Explosives with Calculational Results

    SciTech Connect

    Benterou, J; Roeske, F; Wilkins, P; Carpenter, K H

    2002-04-17

    Experimental tests have been undertaken to determine safe levels of laser exposure on bare high explosive (HE) samples and on common metals used in intimate contact with HE. Laser light is often focused on bare HE and upon metals in contact with HE during alignment procedures and experimental metrology experiments. This paper looks at effects caused by focusing laser beams at high energy densities directly onto the surface of various bare HE samples. Laser energy densities (fluence) exceeding 19 kilowatts/cm{sup 2} using a 5-milliwatt, 670 nm, cw laser diode were generated by focusing the laser down to a spot size diameter of 4 microns. Upon careful inspection, no laser damage was observed in any of the HE samples illuminated at this fluence level. Direct laser exposure of metals directly contacting HE surfaces was also tested. Laser energy densities (fluence) varying from 188 Watts/cm{sup 2} to 12.7 KW/cm{sup 2} were generated using an 11-Watt, 532 nm frequency-doubled Nd:YAG cw laser with focal spot size diameters as small as 100 microns. These measurements look at the temperature rise of the surface of the metal in contact with HE when laser energy is incident on the opposite side of the metal. The temperature rise was experimentally measured as a function of incident laser power, spot size, metal composition and metal thickness. Numerical simulations were also performed to solve the two-dimensional heat flow problem for this experimental geometry. In order to simplify the numerical simulation to allow representation of a large number of physical cases, the equations used in the simulation are expressed in terms of dimensionless variables. The normalized numerical solutions are then compared to the various experimental configurations utilized. Calculations and experiment agree well over the range measured. Safety guidelines for alignment laser illumination upon bare HE are outlined.

  7. An automated aircraft detection system to prevent illumination from the laser guide star beacons at the MMT and LBT

    NASA Astrophysics Data System (ADS)

    Newman, Kevin; Hart, Michael

    2011-10-01

    High powered guide star laser beams are a potential hazard for aircraft. Currently at the MMT telescope located on Mt. Hopkins in Southern Arizona, five Rayleigh guide stars create a total of 25 W of power at 532 nm wavelength. The ARGOS laser guide star for the Large Binocular Telescope (LBT) located on Mt. Graham in Southern Arizona will generate six Rayleigh guide stars with a total of 108 W at 532 nm. We present an automated system for use at the MMT and the LBT designed to detect aircraft and shutter the lasers when aircraft illumination is pending. The detection system at the MMT uses a single wide-angle CCD camera mounted to the optical support structure of the telescope. The LBT system employs two of the same CCD cameras, and an additional bore-sighted thermal infrared camera. The visible cameras integrate frames for 0.5 s to produce streaks from anti-collision beacons required for all aircraft. The IR camera serves as a backup and to protect unlighted aircraft. In each case, adjacent frames are compared using image processing software to detect streaks and movement in the field. If an aircraft is detected, the position and projected trajectory are calculated and compared to the position of the laser beams. If an aircraft illumination appears likely, the laser safety shutter is closed and a message is sent to the laser operator. As a safety precaution, a heartbeat signal from the control computer is required to keep the laser shutter open.

  8. Analysis of multiple scattering suppression using structured laser illumination planar imaging in scattering and fluorescing media.

    PubMed

    Kristensson, E; Araneo, L; Berrocal, E; Manin, J; Richter, M; Aldén, M; Linne, M

    2011-07-04

    The accuracy, precision and limitations of the imaging technique named Structured Laser Illumination Planar Imaging (SLIPI) have been investigated. SLIPI, which allows multiply scattered light to be diminished, has previously demonstrated improvements in image quality and contrast for spray imaging. In the current study the method is applied to a controlled confined environment consisting of a mixture of water and monodisperse polystyrene microspheres. Elastic scattering and fluorescence are studied and the results obtained when probing different particle concentrations and diameters conclusively show the advantages of SLIPI for imaging within moderately turbid media. Although the technique presents both good repeatability and agreement with the Beer-Lambert law, discrepancies in its performance were, however, discovered. Photons undergoing scattering without changing their incident trajectory cannot be discriminated and, owing to differences in scattering phase functions, probing larger particles reduces the suppression of multiply scattered light. However, in terms of visibility such behavior is beneficial as it allows denser media to be probed. It is further demonstrated that the suppression of diffuse light performs equally well regardless of whether photons propagate along the incident direction or towards the camera. In addition, this filtering process acts independently on the spatial distribution of the multiply scattered light but is limited by the finite dynamic range and unavoidable signal noise of the camera.

  9. Active focus stabilization for upright selective plane illumination microscopy

    PubMed Central

    Hedde, Per Niklas; Gratton, Enrico

    2015-01-01

    Due to its sectioning capability, large field of view, and minimal light exposure, selective plane illumination microscopy has become the preferred choice for 3D time lapse imaging. Single cells in a dish can be conveniently imaged using an upright/inverted configuration. However, for measurements on long time scales (hours to days), mechanical drift is a problem; especially for studies of mammalian cells that typically require heating to 37°C which causes a thermal gradient across the instrument. Since the light sheet diverges towards the edges of the field of view, such a drift leads to a decrease in axial resolution over time. Or, even worse, the specimen could move out of the imaging volume. Here, we present a simple, cost-effective way to stabilize the axial position using the microscope camera to track the sample position. Thereby, sample loss is prevented and an optimal axial resolution is maintained by keeping the sample at the position where the light sheet is at its thinnest. We demonstrate the virtue of our approach by measurements of the light sheet thickness and 3D time lapse imaging of a cell monolayer at physiological conditions. PMID:26072829

  10. Active focus stabilization for upright selective plane illumination microscopy.

    PubMed

    Hedde, Per Niklas; Gratton, Enrico

    2015-06-01

    Due to its sectioning capability, large field of view, and minimal light exposure, selective plane illumination microscopy has become the preferred choice for 3D time lapse imaging. Single cells in a dish can be conveniently imaged using an upright/inverted configuration. However, for measurements on long time scales (hours to days), mechanical drift is a problem; especially for studies of mammalian cells that typically require heating to 37°C which causes a thermal gradient across the instrument. Since the light sheet diverges towards the edges of the field of view, such a drift leads to a decrease in axial resolution over time. Or, even worse, the specimen could move out of the imaging volume. Here, we present a simple, cost-effective way to stabilize the axial position using the microscope camera to track the sample position. Thereby, sample loss is prevented and an optimal axial resolution is maintained by keeping the sample at the position where the light sheet is at its thinnest. We demonstrate the virtue of our approach by measurements of the light sheet thickness and 3D time lapse imaging of a cell monolayer at physiological conditions.

  11. Transient microwave bandwidth measurements of illuminated silicon switches for optical pulse-shape control of laser-fusion drivers

    SciTech Connect

    Green, K.; Donaldson, W.R.; Sobolewski, R.; Okishev, A.; Skeldon, M.D.; Letzring, S.; Seka, W.

    1995-12-31

    The microwave transmission properties of a high-purity ({>=}40 k{Omega}{center_dot}cm) single-crystal-silicon, photoconductive (PC) switch were measured while the switch was optically activated. The switch was 2.3 mm wide (the width of the microstrip electrode), 2 mm long, and 0.5 mm thick with a 0.5-mm photoconductive gap and was mounted in a 50-{Omega} microstrip transmission line. The switch was irradiated uniformly with a 150-ns FWHM pulse from a ND:YAG laser (wavelength = 1.064 {micro}m). The insertion loss of the optically activated PC switch was a nearly constant {minus}0.7 dB across the measurement system bandwidth (9 GHz). Under these illumination conditions, the switch exhibited negligible bandwidth limitations. The microstrip structure by itself had an insertion loss that increased from {minus}0.4 dB at 1 GHz to {minus}1.4 dB at 9 GHz.

  12. Image processing for non-ratiometric measurement of membrane voltage using fluorescent reporters and pulsed laser illumination.

    PubMed

    Silve, Aude; Rocke, Sarah; Frey, Wolfgang

    2015-06-01

    The measurement of transmembrane voltages induced by pulsed electric field exposure can be achieved by using fluorescent dyes like ANNINE-6. Such approach requires a quantitative determination of the fluorescence intensity along the cell's membrane by image processing. When high temporal resolution is required, the illumination source is frequently a dye-laser which causes high fluctuations in the intensity of illumination which in turn affects the fluorescence intensity and thus the quality of the results. We propose an image processing technique that allows to overcome the fluctuations and to produce quantitative data. It uses the optical background noise as a correcting factor. Standard deviation in the fluctuations is thus efficiently reduced by at least a factor of 2.5. Additionally we draw attention to the fact that the parasitic component of the laser radiation (ASE) can also suppress fluctuations although it deteriorates wavelength precision.

  13. Widefield imaging of upconverting nanoparticles on epifluorescence microscopes adapted for laser illumination with top-hat profile

    NASA Astrophysics Data System (ADS)

    Mrazek, Jiri; Pospisilova, Martina; Svozil, Vit; Cadek, Ondrej; Nesporova, Kristina; Sulakova, Romana; Brandejsova, Martina; Vranova, Jana; Velebny, Vladimir

    2016-05-01

    We describe a modification of epifluorescence microscopes that allows quantitative widefield imaging of samples labeled by upconverting nanoparticles (UCNP). A top-hat illumination profile on the sample was achieved with a 980-nm laser diode by using tandem microlens arrays, a moving diffuser and a telescope, which adjusts the top-hat area to the field of view. Illumination homogeneity is a critical factor for imaging of UCNP since the intensity of their luminescence typically scales with the second power of the excitation intensity. Our illuminator is combined with the epifluorescence attachment of the microscope, allowing easy switching between observation of UCNP and traditional fluorescent dyes. Illumination profile homogeneity of about 98% was measured for objectives with magnification from 4× to 100×, and the top-hat profile was also obtained with phase contrast objectives. We demonstrate capability of the illuminator by evaluating in vitro uptake of UCNP encapsulated in oleyl-hyaluronan micelles into breast cancer cells. Micelles bearing the targeting peptide were about an order of magnitude more efficient than nontargeted micelles.

  14. Full-order Mueller matrix polarimeter using liquid-crystal phase retarders and active illumination

    NASA Astrophysics Data System (ADS)

    Dayton, David C.; Hoover, Brian G.; Gonglewski, John D.

    2003-03-01

    Full order Stokes polarimeters are often composed of an analyzer consisting of a rotating quarter wave plate in front of a horizontal polarizer. A number of measurements are then made with the wave-plate oriented at different angle. The four-element Stokes vector is then computed from a linear combination of these measurements. A disadvantage of this device is that only a limited range of analyzer states can be generated. As a result a large number of measurements may be required to reduce the noise gain in the Stokes vector reconstructor. In this paper we describe a polarimeter based on a linear polarizer and two variable wave plates. It can be shown that such a device can produce an arbitrary polarization state. An active polarimeter consists of a generator stage, which transmits a laser illuminator with different polarization states and a receiver with a polarization analyzer stage. In our system both generator and analyzer stages consist of a horizontal polarizer and two variable wave-plates. A sixteen element Mueller matrix of resolved images is then formed for target characterization.

  15. Strategy for introducing antibacterial activity under ambient illumination in titania nanoparticles

    NASA Astrophysics Data System (ADS)

    Hsu, Alexander; Liu, Fangzhou; Leung, Yu Hang; Ma, Angel P. Y.; Djurišić, Aleksandra B.; Leung, Frederick C. C.

    2014-03-01

    Titanium dioxide (TiO2) is a wide bandgap (~3.4 eV) semiconductor material which is commonly used as a photocatalyst and antibacterial material. UV illumination with energy similar to the bandgap is often needed to make the material active. It would be favorable for practical applications, if its action can also be activated under ambient. Recently, robust antibacterial action was demonstrated on ZnO nanoparticles under ambient illumination. In this study, we demonstrated robust antibacterial activity of TiO2 nanoparticles induced by annealing under ambient illumination. It was found that the antibacterial activity could be significantly changed by tuning the annealing temperatures and using different crucibles containing the nanoparticles. Bacterium Escherichia coli was used as the model organism in the test. It was observed that although no significant antibacterial activity was observed on the starting material (untreated commercial TiO2 nanoparticles), the activity increases significantly if the nanoparticles were annealed above 650 °C with crucible lined with copper foil. The survival rate of E. coli bacteria approaches to zero if the nanoparticles annealing temperature reaches 850 °C. Under optimized conditions, three different titania nanoparticle samples exhibited antibacterial activity under ambient illumination. This work sheds light on the development of ambient-active antibacterial coating and in particular, on the modification of any TiO2 material to become ambient-active with a suitable treatment.

  16. Multispectral illumination and image processing techniques for active millimeter-wave concealed object detection.

    PubMed

    Zhang, Lixiao; Stiens, Johan; Elhawil, Amna; Vounckx, Roger

    2008-12-01

    Active millimeter-wave imaging systems for concealed object detection offer the possibility of much higher image contrast than passive systems, especially in indoor applications. By studying active millimeter-wave images of different test objects derived in the W band, we show that multispectral illumination is critical to the detectability of targets. We also propose to use image change detection techniques, including image differencing, normalized difference vegetation index, and principle component analysis to process the multispectral millimeter-wave images. The results demonstrate that multispectral illumination can significantly reveal the object features hidden by image artifacts and improve the appearance of the objects.

  17. UV-laser-based longitudinal illuminated diffuser (LID) incorporating diffractive and Lambertian reflectance for the disinfection of beverages

    NASA Astrophysics Data System (ADS)

    Lizotte, Todd

    2010-08-01

    A novel laser beam shaping system was designed to demonstrate the potential of using high power UV laser sources for large scale disinfection of liquids used in the production of food products, such as juices, beer, milk and other beverage types. The design incorporates a patented assembly of optical components including a diffractive beam splitting/shaping element and a faceted pyramidal or conically shaped Lambertian diffuser made from a compression molded PTFE compounds. When properly sintered to an appropriate density, as an example between 1.10 and 1.40 grams per cubic centimeter, the compressed PTFE compounds show a ~99% reflectance at wavelengths ranging from 300 nm to 1500 nm, and a ~98.5% refection of wavelengths from 250 nm to 2000 nm [1]. The unique diffuser configuration also benefits from the fact that the PTFE compounds do not degrade when exposed to ultraviolet radiation as do barium sulfate materials and silver or aluminized mirror coatings [2]. These components are contained within a hermetically sealed quartz tube. Once assembled a laser beam is directed through one end of the tube. This window takes the form of a computer generated diffractive splitter or other diffractive shaper element to split the laser beam into a series of spot beamlets, circular rings or other geometric shapes. As each of the split beamlets or rings cascade downward, they illuminate various points along the tapered PTFE cone or faceted pyramidal form. As they strike the surface they each diffuse in a Lambertian reflectance pattern creating a pseudo-uniform circumferential illuminator along the length of the quartz tube enclosing the assembly. The compact tubular structure termed Longitudinal Illuminated Diffuser (LID) provides a unique UV disinfection source that can be placed within a centrifugal reactor or a pipe based reactor chamber. This paper will review the overall design principle, key component design parameters, preliminary analytic and bench operational testing

  18. Excess carrier generation in femtosecond-laser processed sulfur doped silicon by means of sub-bandgap illumination

    SciTech Connect

    Guenther, Kay-Michael; Gimpel, Thomas; Ruibys, Augustinas; Kontermann, Stefan; Tomm, Jens W.; Winter, Stefan; Schade, Wolfgang

    2014-01-27

    With Fourier-transform photocurrent spectroscopy and spectral response measurements, we show that silicon doped with sulfur by femtosecond laser irradiation generates excess carriers, when illuminated with infrared light above 1100 nm. Three distinct sub-bandgap photocurrent features are observed. Their onset energies are in good agreement with the known sulfur levels S{sup +}, S{sup 0}, and S{sub 2}{sup 0}. The excess carriers are separated by a pn-junction to form a significant photocurrent. Therefore, this material likely demonstrates the impurity band photovoltaic effect.

  19. Digital holographic interferometry with CO2 lasers and diffuse illumination applied to large space reflector metrology [Invited].

    PubMed

    Georges, Marc P; Vandenrijt, Jean-François; Thizy, Cédric; Stockman, Yvan; Queeckers, Patrick; Dubois, Frank; Doyle, Dominic

    2013-01-01

    Digital holographic interferometry in the long-wave infrared domain has been developed by combining a CO(2) laser and a microbolometer array. The long wavelength allows large deformation measurements, which are of interest in the case of large space reflectors undergoing thermal changes when in orbit. We review holography at such wavelengths and present some specific aspects related to this spectral range on our measurements. For the design of our digital holographic interferometer, we studied the possibility of illuminating specular objects by a reflective diffuser. We discuss the development of the interferometer and the results obtained on a representative space reflector, first in the laboratory and then during vacuum cryogenic test.

  20. Single-shot, volumetrically illuminated, three-dimensional, tomographic laser-induced-fluorescence imaging in a gaseous free jet.

    PubMed

    Halls, Benjamin R; Thul, Daniel J; Michaelis, Dirk; Roy, Sukesh; Meyer, Terrence R; Gord, James R

    2016-05-02

    Single-shot, tomographic imaging of the three-dimensional concentration field is demonstrated in a turbulent gaseous free jet in co-flow using volumetrically illuminated laser-induced fluorescence. The fourth-harmonic output of an Nd:YAG laser at 266 nm is formed into a collimated 15 × 20 mm2 beam to excite the ground singlet state of acetone seeded into the central jet. Subsequent fluorescence is collected along eight lines of sight for tomographic reconstruction using a combination of stereoscopes optically coupled to four two-stage intensified CMOS cameras. The performance of the imaging system is evaluated and shown to be sufficient for recording instantaneous three-dimensional features with high signal-to-noise (130:1) and nominal spatial resolution of 0.6-1.5 mm at x/D = 7-15.5.

  1. Photoresistances of semi-insulating GaAs photoconductive switch illuminated by 1.064 μm laser pulse

    NASA Astrophysics Data System (ADS)

    Wu, Minghe; Zheng, Xiaoming; Ruan, Chengli; Yang, Hongchun; Sun, Yunqing; Wang, Shan; Zhang, Kedi; Liu, Hong

    2009-07-01

    The Shockley-Read-Hall model (SRHM) and its simplified model (SSRHM) were used to describe the characteristics of a photoconductive semiconductor switch (PCSS) made from a semi-insulating (SI) gallium arsenide (GaAs) chip, biased at low voltage, and illuminated by a 1.064 μm laser pulse. These characteristics include the free carrier densities, dynamic photoresistance, and time evolution of output pulses of the PCSS. The deep donor EL2 centers in SI GaAs play a dominant role in both the SRHM and SSRHM as electrons at EL2 unionized centers are strongly excited by the subband-gap photons at the wavelength of 1.064 μm. Theoretical modeling on the evolution of the experimental measured output pulses led to a two-step micromechanism of electron excitation process within the GaAs chip. The minimum photoresistances predicted by the SSRHM are in good agreement with experimental measurements, which confirms the dominant role of EL2 in the generation of electric pulses from a SI GaAs photoconductivity switch on which the 1064 nm laser pulse is illuminated.

  2. The Effects of Laser Illumination on Operational and Visual Performance of Pilots During Final Approach

    DTIC Science & Technology

    2004-06-01

    astronomical and atmospheric research, deep- space communications, orbital satellite imaging , and defense systems designed to track, target, and destroy...can sometimes be diffi cult. For instance, prolonged exposure to darkness can result in “night myopia ” (i.e., the inability to see distant objects...illumination has been removed. 3. Afterimage – A transient image left in the visual fi eld after an exposure to a bright light. The demands on a pilot’s

  3. Effects of Laser Illumination on Operational and Visual Performance of Pilots Conducting Terminal Operations

    DTIC Science & Technology

    2003-08-01

    astronomical research, deep-space communications, orbital satellite imaging , and defense systems designed to target, track, and destroy airborne...in night myopia (i.e., the inability to see distant objects or fine detail due to the loss of cone receptor func- tion). Furthermore, exposure to...effect that persists after the source of illumination has been removed. 3. Afterimage – A transient image left in the visual field after an

  4. Target detection in active polarization images perturbed with additive noise and illumination nonuniformity.

    PubMed

    Bénière, Arnaud; Goudail, François; Dolfi, Daniel; Alouini, Mehdi

    2009-07-01

    Active imaging systems that illuminate a scene with polarized light and acquire two images in two orthogonal polarizations yield information about the intensity contrast and the orthogonal state contrast (OSC) in the scene. Both contrasts are relevant for target detection. However, in real systems, the illumination is often spatially or temporally nonuniform. This creates artificial intensity contrasts that can lead to false alarms. We derive generalized likelihood ratio test (GLRT) detectors, for which intensity information is taken into account or not and determine the relevant expressions of the contrast in these two situations. These results are used to determine in which cases considering intensity information in addition to polarimetric information is relevant or not.

  5. Laser controlled deposition of metal microstructures via nondiffracting Bessel beam illumination

    NASA Astrophysics Data System (ADS)

    Drampyan, Rafael; Leonov, Nikita; Vartanyan, Tigran

    2016-04-01

    The technique of the laser controlled deposition of sodium and rubidium deposits on the sapphire substrate is presented. The metals were deposited on the clean sapphire substrate from the vapor phase contained in the evacuated and sealed cell. We use an axicon to produce a non-diffracting Bessel beam out of the beam got from the cw diode laser with 200 mW power at the wavelength of 532 nm. After 30 minutes of the laser-controlled deposition the substrates were examined in the optical microscope. The obtained metal deposits form the sharp-cut circles with the pitch of 10 μm, coincident with the tens of dark rings of the Bessel beam. Reduction of the laser power leads to the build up of the continuous metal film over the whole substrate.

  6. Multi-user 3D display using a head tracker and RGB laser illumination source

    NASA Astrophysics Data System (ADS)

    Surman, Phil; Sexton, Ian; Hopf, Klaus; Bates, Richard; Lee, Wing Kai; Buckley, Edward

    2007-05-01

    A glasses-free (auto-stereoscopic) 3D display that will serve several viewers who have freedom of movement over a large viewing region is described. This operates on the principle of employing head position tracking to provide regions referred to as exit pupils that follow the positions ofthe viewers' eyes in order for appropriate left and right images to be seen. A non-intrusive multi-user head tracker controls the light sources of a specially designed backlight that illuminates a direct-view LCD.

  7. Post shot analysis of plasma conditions of Gold Spheres illuminated by the URLLE Omega laser, as measured via Thomson scattering

    NASA Astrophysics Data System (ADS)

    Rosen, M. D.; Ross, J. S.; Scott, H. A.; Landen, N.; Froula, D.; Dewald, E.; May, M.; Widmann, K.

    2013-10-01

    Recently there was a follow up to the 2006 campaign to illuminate 1 mm diameter gold spheres using the Omega laser at LLE. The 2013 campaign uses Thomson scattering to diagnose the plasma conditions as a function of time, at various radial positions in the coronal, laser heated, blow-off region. Laser irradiances were 1, 5, and 10 × 1014 W/sqcm, usually in a 1 ns pulse duration. Depleted uranium and Ag spheres were also tested. We compare the predictions of plasma conditions using various non-LTE computational models of atomic physics and electron transport (as implemented into the rad-hydro code Lasnex) to this data. The ``high flux model (HFM)'' (DCA atomic physics and non local transport) compares well for some of experiments, while an intermediate model that radiates a bit less total x-ray fluence than the HFM, does better on other experiments. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  8. Research of target uniform illumination on SG-III laser facility

    NASA Astrophysics Data System (ADS)

    Zhang, Rui; Jia, Huaiting; Geng, Yuanchao; Li, Ping; Liu, Lanqin; Tian, Xiaocheng; Yuan, Haoyu; Fan, Chen; Su, Jingqin; Hu, Dongxia; Zhu, Qihua; Zheng, Wanguo

    2016-10-01

    In the research of inertial confinement fusion, laser plasma interaction (LPI) is becoming a key problem that affects ignition. Here, multi-frequency modulation (Multi-FM) smoothing by spectral dispersion (SSD), continuous phase plate (CPP) and polarization smoothing (PS) were experimentally studied and equipped on SG-III laser facility. After using these technologies, the focal spots of SG-III laser facility can be adjusted, controlled and repeated accurately. Experiments on SG-III laser facility indicate when the number of color cycles adopts 1, imposing SSD with 3.3 times diffraction limit (TDL) did not lead to pinhole closure in the spatial filters of the preamplifier and the main amplifier with 30-TDL pinhole size. The nonuniformity of the focal spots using Multi-FM SSD, CPP and PS drops to 0.18, comparing to 0.26 with CPP+SSD, and 0.84 with CPP and wedged lens. Polarization smoothing using flat birefringent plate in the convergent beam of final optics assembly (FOA) was studied.

  9. Value added cleaning and disinfection of the root canal: laser-activated irrigation and laser-induced photoporation

    NASA Astrophysics Data System (ADS)

    De Moor, Roeland J. G.; Meire, Maarten A.

    2016-03-01

    Among present-day marketed systems ultrasonic activation appears to be the best way to activate and potentiate endodontic irrigants. An alternative for ultrasonic activation of irrigants is laser activated irrigation (LAI) or photoninitiated acoustic streaming. Based on present-day research it appears that LAI (especially with Erbium lasers) can be more efficient for debris removal out of root canals and interaction with the endodontic biofilms thanks to the induction of specific cavitation phenomena and acoustic streaming. Other wavelengths are now explored to be used for LAI. Another way to interact with biofilms is to rely on laser-induced photoporation in combination with gold nanoparticles ( AuNPs). The latter is an alternative physical method for delivering macromolecules in cells. Nanosized membrane pores can be created upon pulsed laser illumination. Depending on the laser energy, pores are created through either direct heating of the AuNPs or by vapour nanobubbles that can emerge around the AuNPs.

  10. Measurements of blood flow and blood concentration change using laser speckle in fiber illumination and its application to estimation of stress condition

    NASA Astrophysics Data System (ADS)

    Yokoi, Naomichi; Shinohara, Tomomi; Funamizu, Hideki; Kyoso, Masaki; Shimatani, Yuichi; Yuasa, Tomonori; Aizu, Yoshihisa

    2016-11-01

    Speckle imaging method is useful for monitoring of blood flow in living bodies. We have proposed so far the method for simultaneous imaging of blood flow and blood concentration change using laser speckle patterns at two wavelengths. However, our conventional measurement system has difficulty in adjusting the illuminating optical axis of two laser sources. Therefore, we introduce a novel arrangement using a coaxial fiber illumination in the detection of speckle patterns in two wavelengths. By this arrangement, the blood flow can be stably analyzed with a frame rate using an estimation parameter proposed by the authors based on the spatial contrast of speckle patterns. This parameter is useful for estimating an autonomic nervous function which reflects stress conditions caused by tension and excitement. In this study, we present measurements of the blood flow and blood concentration change in the fiber illumination, and its application to estimation of stress condition.

  11. Carrier emission of n-type gallium nitride illuminated by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Li, Runze; Zhu, Pengfei; Chen, Jie; Cao, Jianming; Rentzepis, Peter M.; Zhang, Jie

    2016-12-01

    The carrier emission efficiency of light emitting diodes is of fundamental importance for many technological applications, including the performance of GaN and other semiconductor photocathodes. We have measured the evolution of the emitted carriers and the associated transient electric field after femtosecond laser excitation of n-type GaN single crystals. These processes were studied using sub-picosecond, ultrashort, electron pulses and explained by means of a "three-layer" analytical model. We find that for pump laser intensities on the order of 1011 W/cm2, the electrons that escaped from the crystal surface have a charge of ˜2.7 pC and a velocity of ˜1.8 μm/ps. The associated transient electrical field evolves at intervals ranging from picoseconds to nanoseconds. These results provide a dynamic perspective on the photoemission properties of semiconductor photocathodes.

  12. Remote Bridge Deflection Measurement Using an Advanced Video Deflectometer and Actively Illuminated LED Targets.

    PubMed

    Tian, Long; Pan, Bing

    2016-08-23

    An advanced video deflectometer using actively illuminated LED targets is proposed for remote, real-time measurement of bridge deflection. The system configuration, fundamental principles, and measuring procedures of the video deflectometer are first described. To address the challenge of remote and accurate deflection measurement of large engineering structures without being affected by ambient light, the novel idea of active imaging, which combines high-brightness monochromatic LED targets with coupled bandpass filter imaging, is introduced. Then, to examine the measurement accuracy of the proposed advanced video deflectometer in outdoor environments, vertical motions of an LED target with precisely-controlled translations were measured and compared with prescribed values. Finally, by tracking six LED targets mounted on the bridge, the developed video deflectometer was applied for field, remote, and multipoint deflection measurement of the Wuhan Yangtze River Bridge, one of the most prestigious and most publicized constructions in China, during its routine safety evaluation tests. Since the proposed video deflectometer using actively illuminated LED targets offers prominent merits of remote, contactless, real-time, and multipoint deflection measurement with strong robustness against ambient light changes, it has great potential in the routine safety evaluation of various bridges and other large-scale engineering structures.

  13. Remote Bridge Deflection Measurement Using an Advanced Video Deflectometer and Actively Illuminated LED Targets

    PubMed Central

    Tian, Long; Pan, Bing

    2016-01-01

    An advanced video deflectometer using actively illuminated LED targets is proposed for remote, real-time measurement of bridge deflection. The system configuration, fundamental principles, and measuring procedures of the video deflectometer are first described. To address the challenge of remote and accurate deflection measurement of large engineering structures without being affected by ambient light, the novel idea of active imaging, which combines high-brightness monochromatic LED targets with coupled bandpass filter imaging, is introduced. Then, to examine the measurement accuracy of the proposed advanced video deflectometer in outdoor environments, vertical motions of an LED target with precisely-controlled translations were measured and compared with prescribed values. Finally, by tracking six LED targets mounted on the bridge, the developed video deflectometer was applied for field, remote, and multipoint deflection measurement of the Wuhan Yangtze River Bridge, one of the most prestigious and most publicized constructions in China, during its routine safety evaluation tests. Since the proposed video deflectometer using actively illuminated LED targets offers prominent merits of remote, contactless, real-time, and multipoint deflection measurement with strong robustness against ambient light changes, it has great potential in the routine safety evaluation of various bridges and other large-scale engineering structures. PMID:27563901

  14. Local electric field enhancement at the heterojunction of Si/SiGe axially heterostructured nanowires under laser illumination

    NASA Astrophysics Data System (ADS)

    Pura, Jose Luis; Anaya, Julián; Souto, Jorge; Carmelo Prieto, Ángel; Rodríguez, Andrés; Rodríguez, Tomás; Jiménez, Juan

    2016-11-01

    We present a phenomenon concerning electromagnetic enhancement at the heterojunction region of axially heterostructured Si/SiGe nanowires when the nanowire is illuminated by a focused laser beam. The local electric field is sensed by micro Raman spectroscopy, which allows the enhancement of the Raman signal arising from the heterojunction region to be revealed; the Raman signal per unit volume increases at least ten times with respect to the homogeneous Si and SiGe nanowire segments. In order to explore the physical meaning of this phenomenon, a three-dimensional solution of the Maxwell equations of the interaction between the focused laser beam and the nanowire was carried out by finite element methods. A local enhancement of the electric field at the heterojunction was deduced. However, the magnitude of the electromagnetic field enhancement only approaches the experimental one when the free carriers are considered, showing enhanced absorption at the carrier depleted heterojunction region. The existence of this effect promises a way of improving photon harvesting using axially heterostructured semiconductor nanowires.

  15. In vitro photodynamic properties of methylene blue in a combination with laser illumination at 630 nm concerning Candida albicans.

    PubMed

    Pasyechnikova, Nataliya; Zborovskaya, Olexandra; Kustrin, Taras

    2009-01-01

    The study had to define influence of combined applications of laser radiation and methylene blue (MB) on pathogenic culture of Candida albicans in vitro. The experimental study was done at standard techniques of method of cultivations in a broth. The laser irradiation of cultures was done at once after addition of MB in concentration 0.05%, 0.1% and 0.2%. During studying action of MB in dark, influence of MB to the growth of test-shtam without laser radiation, were prepared fluid Gissa's broth with glucose without Andrede's indicator. Activation of MB was done by laser with wave length 630 nm during 3 or 5 min. All experiments were passed in 4 parallels and 3 repeats. Maximal suppression of growth of microorganisms was noted in group with using 0.1% MB with laser radiation 3 minutes without centrifugation after 24 hours. Maximal suppression of growth was noted in group after centrifugation with 0.05% MB with exposure of laser 3 min. after 48 hours. Sensitivity of pathogenic culture of Candida albicans to application of B and laser raises accordingly to increase of concentration of MB.

  16. Photocatalytic activity of Zr:SrTiO 3 under UV illumination

    NASA Astrophysics Data System (ADS)

    Chen, Liang; Zhang, Shouchen; Wang, Liqiu; Xue, Dongfeng; Yin, Shu

    2009-01-01

    SrTiO 3 is a well-known efficient photocatalyst and has various industrial applications such as water or air purification antibacterial agents and self-cleaning surfaces. In this work, pure SrTiO 3 and Zr:SrTiO 3 photocatalysts were prepared by the sol-gel method and then tested by scanning electron microscopy (SEM) and X-ray diffraction, respectively. The crystal phase of Zr:SrTiO 3 shows a typical perovskite structure, in which Ti sites are substituted by Zr atoms. The as-prepared yellow Zr:SrTiO 3 powders were then used as UV photocatalysts. Photocatalytic degradation activity of methylene blue over zirconium-doped SrTiO 3 catalysts was tested under UV illumination. The high activity of Zr:SrTiO 3 was due to the defects of its crystal lattice, thus the energy needed by the semiconductor photoproduction electron transition to the conduction band was smaller than the intrinsic absorption band. The optimal conditions of our experiments are as follows: under 8% doping density of Zr, 10 mg/l initial concentration of methylene blue, 0.15 g photocatalyst dosage, 6.5 of pH value and 4 h of UV illumination time, the degradation rate of methylene blue can reach 93.6%.

  17. 2PE-STED microscopy with a single Ti:sapphire laser for reduced illumination.

    PubMed

    Li, Qifeng; Wang, Yang; Chen, Da; Wu, Sherry S H

    2014-01-01

    We reported a new effective approach to carry out two-photon excitation stimulated emission depletion (2PE-STED) microscopy using a single Ti:sapphire laser system. With an acoustic-optic Bragg cell, the modulated-CW 2PE STED microscope had the benefits of both CW and pulse approaches: lower input power, simple optical scheme and no complicated synchronization. Additionally, it also took advantages of fluorescence yield increasing. The sub-diffraction-limit resolution was demonstrated using ATTO 425-tagged clathrin-coated vesicles.

  18. Compact active mirror laser (CAMIL)

    NASA Astrophysics Data System (ADS)

    Vetrovec, John

    2002-03-01

    This work presents concept and scaling considerations for a solid-state laser with a gain medium disk operating in the active mirror mode. The disk is of composite construction formed by bonding undoped optical medium to the peripheral edges of a gain medium disk. Pump diode arrays are placed around the perimeter of the composite disk and pump light is injected into the undoped edge. With proper choice of lasant doping, diode placement and diode divergence, a uniform laser gain can be achieved across large portions of the disk. To mitigate thermal deformations, the gain medium disk is pressure-clamped to a rigid, cooled substrate. Effective reduction of thermo-optical distortions makes this laser suitable for operation at high-average power.

  19. Active debris removal: Aspects of trajectories, communication and illumination during final approach

    NASA Astrophysics Data System (ADS)

    Deloo, J. A. F.; Mooij, E.

    2015-12-01

    The aim of this research is to investigate a debris-remediation technique where a chaser performs a rendezvous with the debris, establishes a rigid-link connection, and actively de-orbits the debris. ESA's satellite Envisat has been used as a design case. The research assessed passive safety aspects of the final-approach manoeuvres by analysing the resulting trajectories after thrust inhibit. Next, the research explored the possibility for continuous ground communication by considering the chain of European space tracking (ESTRACK) ground stations (located mainly in Europe). Furthermore, obstruction of the communication signal by the target was studied. Last, the research studies the illumination conditions encountered by the chaser, where obscuration of the Sun by the target was taken into account. Each of these elements are studied for the final approach only. In the topic of passive safety, the results confirm that manoeuvres on H-bar are passively unsafe, and indicate this also for the fly-around manoeuvres along the natural orbital motion. It can be concluded from the communication analysis that the maximum duration of the uninterrupted window varies between 22 and 32 min, using the chain of core ESTRACK ground stations. However, the study on communication blockage shows that frequent communication gaps can occur, with the longest gaps being in the order of one minute in duration. In the field of illumination, it can be concluded that correct target illumination and sensor visibility cannot be guaranteed. Furthermore, the average solar-array area available during final approach varies between 35% and 75%, due to both incorrect pointing of the solar array by the chaser and obscuration by the target.

  20. Investigation on Raman spectral features of a coated tablet under variation of its orientation respective to laser illumination and measurement of nominal coating thickness of packed tablets.

    PubMed

    Kim, Jaejin; Hwang, Jinyoung; Woo, Young-Ah; Chung, Hoeil

    2016-11-30

    To investigate Raman spectral features of a coated biconvex tablet under variation of its orientation respective to laser illumination, spectra of the tablet were collected by illuminating laser on 12 different locations on the tablet with 3 different illumination angles of 45, 75 and 90°. The spectral variations were more substantial when the tablet faces with engraved letters and greater surface curvature were measured, since the sampled volume of coating relative to that of a core tablet changed significantly under these circumstances as the illumination angle varied. The preliminary examination confirmed that the acquisition of tablet-representative spectra was the requisite for reliable measurement of coating thickness. Then, to mimic real monitoring of coating process, Raman spectra were directly collected on a packing of 30 tablets with repetition of random tablet packing up to 15 times and univariate models utilizing the intensity of coating peak at 638cm(-1) were developed using the cumulatively averaged spectra with an average weight of the 30 tablets as a reference. To acquire less tablet orientation-sensitive spectra, a wide area illumination (WAI) scheme providing a large sampling area (28.3mm(2)) on a tablet with a long focal length (∼25cm) was employed. The averaging of the first to seventh spectra, equivalently utilizing more packing-representative spectra for quantitative analysis, made the measurement of nominal coating thickness of packed tablets accurate.

  1. Laser scanning confocal microscope with programmable amplitude, phase, and polarization of the illumination beam.

    PubMed

    Boruah, B R; Neil, M A A

    2009-01-01

    We describe the design and construction of a laser scanning confocal microscope with programmable beam forming optics. The amplitude, phase, and polarization of the laser beam used in the microscope can be controlled in real time with the help of a liquid crystal spatial light modulator, acting as a computer generated hologram, in conjunction with a polarizing beam splitter and two right angled prisms assembly. Two scan mirrors, comprising an on-axis fast moving scan mirror for line scanning and an off-axis slow moving scan mirror for frame scanning, configured in a way to minimize the movement of the scanned beam over the pupil plane of the microscope objective, form the XY scan unit. The confocal system, that incorporates the programmable beam forming unit and the scan unit, has been implemented to image in both reflected and fluorescence light from the specimen. Efficiency of the system to programmably generate custom defined vector beams has been demonstrated by generating a bottle structured focal volume, which in fact is the overlap of two cross polarized beams, that can simultaneously improve both the lateral and axial resolutions if used as the de-excitation beam in a stimulated emission depletion confocal microscope.

  2. Characteristics of cytochrome oxidase activity in visual system neurons in kittens reared in conditions of flashing illumination.

    PubMed

    Merkul'eva, N S; Makarov, F N

    2005-10-01

    The studies reported here addressed the effects of flashing (15 Hz) lights on the metabolic activity of visual system neurons in animals reared in condition of crepuscular illumination. Activity of the respiratory enzyme cytochrome oxidase was detected in the cortex of visual areas 17 and 18 and in the lateral geniculate body in kittens. The results showed that kittens subjected to this stimulation, unlike intact kittens and kittens reared in conditions of crepuscular illumination, showed a change in the pattern of cytochrome oxidase distribution in cortical field 17 consisting of the appearance of alternating areas of increased and decreased enzyme activity in layers III and IV. In cortical field 18 and the lateral geniculate body, experimental kittens showed no changes in the cytochrome oxidase activity distribution pattern. It is suggested that flashing illumination leads to disturbance of the balance in activity in the Y and X conducting channels of the visual system.

  3. Laser Fluorescence Illuminates the Soft Tissue and Life Habits of the Early Cretaceous Bird Confuciusornis

    PubMed Central

    Falk, Amanda R.; Kaye, Thomas G.; Zhou, Zhonghe; Burnham, David A.

    2016-01-01

    In this paper we report the discovery of non-plumage soft tissues in Confuciusornis, a basal beaked bird from the Early Cretaceous Jehol Biota in northeastern China. Various soft tissues are visualized and interpreted through the use of laser-stimulated fluorescence, providing much novel anatomical information about this early bird, specifically reticulate scales covering the feet, and the well-developed and robust pro- and postpatagium. We also include a direct comparison between the forelimb soft tissues of Confuciusornis and modern avian patagia. Furthermore, apparently large, fleshy phalangeal pads are preserved on the feet. The reticulate scales, robust phalangeal pads as well as the highly recurved pedal claws strongly support Confuciusornis as an arboreal bird. Reticulate scales are more rounded than scutate scales and do not overlap, thus allowing for more flexibility in the toe. The extent of the pro- and postpatagium and the robust primary feather rachises are evidence that Confuciusornis was capable of powered flight, contrary to previous reports suggesting otherwise. A unique avian wing shape is also reconstructed based on plumage preserved. These soft tissues combined indicate an arboreal bird with the capacity for short-term (non-migratory) flight, and suggest that, although primitive, Confuciusornis already possessed many relatively advanced avian anatomical characteristics. PMID:27973609

  4. [Peculiarities of cytochrome oxidase activity in the visual cortex neurons of kittens reared under the conditions of flickering illumination].

    PubMed

    Merkul'eva, N S; Makarov, F N

    2004-01-01

    The objective of this study was to analyze the influence of the light flickering with the frequency of 15 Hz, on the neuronal metabolic activity in kittens reared under the conditions of mesopic illumination. The method for demonstration of a respiratory enzyme cytochrome oxidase was used to study the visual cortex areas 17 and 18 and the lateral geniculate nucleus. It was shown that in kittens that were subjected to this stimulation as opposed to intact animals and to kittens reared under the conditions of mesopic illumination, specific changes in pattern of cytochrome oxidase distribution in area 17 took place. This change was manifested by the appearance of alternating zones of increased and decreased enzyme activity in layers III and IV. Within the cortical area 18 and lateral geniculate nucleus, no changes in the pattern of cytochrome oxidase activity distribution were detected in experimental kittens. It is suggested that flickering illumination results in disequilibrium of Y- and X-visual pathway activity.

  5. Bactericidal activity of copper-deposited TiO2 thin film under weak UV light illumination.

    PubMed

    Sunada, Kayano; Watanabe, Toshiya; Hashimoto, Kazuhito

    2003-10-15

    The bactericidal activity of copper-deposited titanium dioxide thin film (Cu/TiO2) was investigated under very weak ultraviolet (UV) light illumination. To elucidate the roles of the film photocatalyst and the deposited copper in the bactericidal activity, cells from a copper-resistant Escherichia coli (E. coli) strain were utilized. A decrease in survival rate was not observed with the copper-resistant cells under dark conditions, but when illuminated with a very weak UV intensity of 1 microW/cm2, the survival rate decreased, suggesting photocatalytic bactericidal activity. The decay curve of survival on the Cu/TiO2 film under very weak UV light illumination consisted of two steps, similar to the survival change of normal E. coli on TiO2 films under rather strong UV illumination. The first step is due to the partial decomposition of the outer membrane in the cell envelope by a photocatalytic process, followed by permeation of the copper ions into the cytoplasmic membrane. The second step is due to a disorder of the cytoplasmic membrane caused by the copper ions, which results in a loss of the cell's integrity. These processes explain why the Cu/TiO2 film system shows an effective bactericidal activity even under very weak UV light illumination.

  6. Comparison of chemiluminescence from luminol solution and luminol-TiO₂ suspension after illumination of a 355 nm pulse laser.

    PubMed

    Min, Lingyue; Chen, Xueming; Wu, Xing-Zheng

    2010-01-01

    Chemiluminescence (CL) from luminol solution and luminol-TiO₂ suspension after illumination of a 355 nm pulse laser is compared. Both the CL systems showed the CL spectra with maximum wavelength of 430 nm, suggesting that the emission was from the excite state of 3-aminophthalate ion. The TiO₂ photocatalytically induced luminol CL could be separately detected either when the pulse laser power was smaller than 0.15 mJ/pulse or a slit was placed beyond -2-2 mm in the vertical direction of the laser beam. The TiO₂ photocatalytically induced luminol CL intensity was linear to the laser power, while that of the 355 nm pulse laser-induced was nonlinear. A log-log plot between the 355 nm pulse laser-induced luminol CL intensity and laser power showed a near-linear regression fit with a slope of 2.11, suggesting that a two-photon absorption process of luminol was present in the 355 nm pulse laser-induced luminol CL. Adsorbed oxygen on the surface of TiO₂ seemed to greatly contribute to the photocatalytically induced CL.

  7. Transparent selective illumination means suitable for use in optically activated electrical switches and optically activated electrical switches constructed using same

    DOEpatents

    Wilcox, R.B.

    1991-09-10

    A planar transparent light conducting means and an improved optically activated electrical switch made using the novel light conducting means are disclosed. The light conducting means further comprise light scattering means on one or more opposite planar surfaces thereof to transmit light from the light conducting means into adjacent media and reflective means on other surfaces of the light conducting means not containing the light scattering means. The optically activated electrical switch comprises at least two stacked photoconductive wafers, each having electrodes formed on both surfaces thereof, and separated by the planar transparent light conducting means. The light scattering means on the light conducting means face surfaces of the wafers not covered by the electrodes to transmit light from the light conducting means into the photoconductive wafers to uniformly illuminate and activate the switch. 11 figures.

  8. Transparent selective illumination means suitable for use in optically activated electrical switches and optically activated electrical switches constructed using same

    DOEpatents

    Wilcox, Russell B.

    1991-01-01

    A planar transparent light conducting means and an improved optically activated electrical switch made using the novel light conducting means are disclosed. The light conducting means further comprise light scattering means on one or more opposite planar surfaces thereof to transmit light from the light conducting means into adjacent media and reflective means on other surfaces of the light conducting means not containing the light scattering means. The optically activated electrical switch comprises at least two stacked photoconductive wafers, each having electrodes formed on both surfaces thereof, and separated by the planar transparent light conducting means. The light scattering means on the light conducting means face surfaces of the wafers not covered by the electrodes to transmit light from the light conducting means into the photoconductive wafers to uniformly illuminate and activate the switch.

  9. Elimination of speckle and target orientation requirements in millimeter-wave active imaging by modulated multimode mixing illumination.

    PubMed

    Patrick, Mark A; Holt, Jennifer A; Joye, Colin D; De Lucia, Frank C

    2012-12-01

    Active imaging can provide significantly larger signal margins in the millimeter-wave spectral region than passive imaging, especially indoors-an important application for which there is no cold sky illumination. However, coherent effects, such as speckle, negate much of this advantage by destroying image clarity and target recognition. Moreover, active imaging demonstrations often use strategically chosen target orientations to optimally reflect power from the active illuminator back to the imaging receiver. In this paper we will discuss and show experimental results for a new active imaging approach that largely eliminates coherent effects and the need for optimized target orientation. The work described uses a synthesized harmonic multiplier chain to drive a 5 W extended interaction klystron at 218.4 GHz, a mechanical mode mixer to illuminate and modulate many modes, and a heterodyne receiver coupled into a 60 cm scanning mirror. Large signal margins were obtained in this ~50 m range work, showing paths to imaging at ~1 km, imaging with considerably less powerful illuminators, and the use of focal plane arrays.

  10. Effect of Laser Irradiation on Enzyme Activity

    NASA Astrophysics Data System (ADS)

    Murakami, Satoshi; Kashii, Masafumi; Kitano, Hiroshi; Adachi, Hiroaki; Takano, Kazufumi; Matsumura, Hiroyoshi; Inoue, Tsuyoshi; Mori, Yusuke; Doi, Masaaki; Sugamoto, Kazuomi; Yoshikawa, Hideki; Sasaki, Takatomo

    2005-11-01

    We previously developed a protein crystallization technique using a femtosecond laser and protein crystal processing and detaching techniques using a pulsed UV laser. In this study, we examine the effect of laser irradiation on protein integrity. After several kinds of laser were irradiated on part of a solution of glycerol-6-phosphate dehydrogenase from Leuconostoc mesenteroides, we measured the enzyme activity. Femtosecond and deep-UV laser irradiations have little influence on the whole enzyme activity, whereas the enzyme lost its activity upon high-power near-infrared laser irradiation at a wavelength of 1547 nm. These results suggest that suitable laser irradiation has no remarkable destructive influence on protein crystallization or crystal processing.

  11. Visualisation of plasma induced processes in interelectrode gap of micropinch installation using laser illuminator on molecular nitrogen

    NASA Astrophysics Data System (ADS)

    Filippov, E.; Sarantsev, S.; Raevsky, I.; Savjolov, A.

    2016-11-01

    The paper presents the results of researched processes in the interelectrode gap of High-current low-inductance vacuum spark (HLIV) on the "PION" system [1] by means of active laser diagnostics with visualisation of radiation field. The influence of the cathode geometry and position of the trigger system on the plasma dynamics of HLIV is considered. The regularities of the discharge for different initial conditions are established. The conditions under which the most stable plasma point is formed in space and time are determined.

  12. Multi-wavelength Spatial LED illumination based detector for in vitro detection of Botulinum Neurotoxin A Activity

    PubMed Central

    Sun, Steven; Francis, Jesse; Sapsford, Kim E.; Kostov, Yordan; Rasooly, Avraham

    2010-01-01

    A portable and rapid detection system for the activity analysis of Botulinum Neurotoxins (BoNT) is needed for food safety and bio-security applications. To improve BoNT activity detection, a previously designed portable charge-coupled device (CCD) based detector was modified and equipped with a higher intensity more versatile multi-wavelength spatial light-emitting diode (LED) illumination, a faster CCD detector and the capability to simultaneously detect 30 samples. A FITC/DABCYL Förster Resonance Energy Transfer (FRET)-labeled peptide substrate (SNAP-25), with BoNT-A target cleavage site sequence was used to measure BoNT-A light chain (LcA) activity through the FITC fluorescence increase that occurs upon peptide substrate cleavage. For fluorescence excitation, a multi-wavelength spatial LED illuminator was used and compared to our previous electroluminescent (EL) strips. The LED illuminator was equipped with blue, green, red and white LEDs, covering a spectrum of 450-680 nm (red 610-650 nm, green 492-550 nm, blue 450-495 nm, and white LED 440-680 nm). In terms of light intensity, the blue LED was found to be ~80 fold higher than the previously used blue EL strips. When measuring the activity of LcA the CCD detector limit of detection (LOD) was found to be 0.08 nM LcA for both the blue LED (2 s exposure) and the blue EL (which require ≥60 s exposure) while the limits of quantitation (LOQ) is about 1 nM. The LOD for white LED was higher at 1.4 nM while the white EL was not used for the assay due to a high variable background. Unlike the weaker intensity EL illumination the high intensity LED illumination enabled shorter exposure times and allowed multi-wavelength illumination without the need to physically change the excitation strip, thus making spectrum excitation of multiple fluorophores possible increasing the versatility of the detector platform for a variety of optical detection assays. PMID:20498728

  13. High speed video shooting with continuous-wave laser illumination in laboratory modeling of wind - wave interaction

    NASA Astrophysics Data System (ADS)

    Kandaurov, Alexander; Troitskaya, Yuliya; Caulliez, Guillemette; Sergeev, Daniil; Vdovin, Maxim

    2014-05-01

    Three examples of usage of high-speed video filming in investigation of wind-wave interaction in laboratory conditions is described. Experiments were carried out at the Wind - wave stratified flume of IAP RAS (length 10 m, cross section of air channel 0.4 x 0.4 m, wind velocity up to 24 m/s) and at the Large Air-Sea Interaction Facility (LASIF) - MIO/Luminy (length 40 m, cross section of air channel 3.2 x 1.6 m, wind velocity up to 10 m/s). A combination of PIV-measurements, optical measurements of water surface form and wave gages were used for detailed investigation of the characteristics of the wind flow over the water surface. The modified PIV-method is based on the use of continuous-wave (CW) laser illumination of the airflow seeded by particles and high-speed video. During the experiments on the Wind - wave stratified flume of IAP RAS Green (532 nm) CW laser with 1.5 Wt output power was used as a source for light sheet. High speed digital camera Videosprint (VS-Fast) was used for taking visualized air flow images with the frame rate 2000 Hz. Velocity air flow field was retrieved by PIV images processing with adaptive cross-correlation method on the curvilinear grid following surface wave profile. The mean wind velocity profiles were retrieved using conditional in phase averaging like in [1]. In the experiments on the LASIF more powerful Argon laser (4 Wt, CW) was used as well as high-speed camera with higher sensitivity and resolution: Optronics Camrecord CR3000x2, frame rate 3571 Hz, frame size 259×1696 px. In both series of experiments spherical 0.02 mm polyamide particles with inertial time 7 ms were used for seeding airflow. New particle seeding system based on utilization of air pressure is capable of injecting 2 g of particles per second for 1.3 - 2.4 s without flow disturbance. Used in LASIF this system provided high particle density on PIV-images. In combination with high-resolution camera it allowed us to obtain momentum fluxes directly from

  14. Hotsphere illumination

    NASA Astrophysics Data System (ADS)

    Razavi, Bahar S.; Kuzyakov, Yakov

    2016-04-01

    Soils are the most heterogeneous parts of the biosphere, with an extremely high differentiation of properties and processes at all spatial and temporal scales. Importance of the hotspheres such as rhizosphere, detritusphere, porosphere (including drilosphere and biopores), hyphasphere and spermosphere, calls for spatially explicit methods to illuminate distribution of microbial activities in these hotspheres (Kuzyakov and Blagodatskaya, 2015). Zymography technique has previously been adapted to visualize the spatial dynamics of enzyme activities in rhizosphere (Spohn and Kuzyakov, 2014). Here, we further developed soil zymography to obtain a higher resolution of enzyme activities by enabling direct contact of substrate-saturated membranes with soil. For the first time, we aimed at quantitative imaging of enzyme activities in various hotspheres. We calculated and compared percentage of enzymatic hotspots of five hotspheres: spermosphere, rhizosphere, detritusphere, drilosphere and biopores. Spatial distribution of activities of two enzymes: β-glucosidase and leucine amino peptidase were analyzed in the spermosphere, rhizosphere and detritusphere of maize and lentil. Zymography has been done 3 days (spermosphere), 14 days (rhizosphere) after sowing and 21 days after cutting plant (detritusphere). Spatial resolution of fluorescent images was improved by direct application fluorogenically labelled substrates on the soil surface. Such improvement enabled to visualize enzyme distribution of mycorrhiza hypha on the rhizobox surface. Further, to visualize the 2D distribution of the enzyme activities in porosphere, we placed earthworms (Lumbricus terrestris), (drilosphere) and ground beetle species Platynus dorsalis Pont. (Coleoptera; Carabidae), (biopore), in transparent boxes for 2weeks. The developed in situ zymography visualized the heterogeneity of enzyme activities along and across the roots. Spatial patterns of enzyme activities as a function of distance along the

  15. A six-junction GaAs laser power converter with different sizes of active aperture

    NASA Astrophysics Data System (ADS)

    Sun, Yu-run; Dong, Jian-rong; He, Yang; Zhao, Yong-ming; Yu, Shu-zhen; Xue, Ji-ping; Xue, Chi; Wang, Jin; Lu, Yun-qing; Ding, Yan-wen

    2017-01-01

    We investigate a novel GaAs-based laser power converters (LPCs) grown by metal-organic chemical vapor deposition (MOCVD), which uses a single monolithic structure with six junctions connected by tunnel junctions to obtain a high output voltage. The LPCs with diameters of active aperture of 2 mm and 4 mm were fabricated and tested. The test results show that under an 808 nm laser, two LPCs both show an open circuit voltage of above 6.5 V. A maximum power conversion efficiency of 50.2% is obtained by 2 mm sample with laser power of 0.256 W, and an output electric power of 1.9 W with laser power of 4.85 W is obtained by 4 mm sample. The performances of the LPCs are deteriorated under illumination of high flux, and the 4 mm sample shows a higher laser power tolerance.

  16. Nonlinear Structured Illumination Using a Fluorescent Protein Activating at the Readout Wavelength

    PubMed Central

    Hou, Wenya; Kielhorn, Martin; Arai, Yoshiyuki; Nagai, Takeharu; Kessels, Michael M.; Qualmann, Britta; Heintzmann, Rainer

    2016-01-01

    Structured illumination microscopy (SIM) is a wide-field technique in fluorescence microscopy that provides fast data acquisition and two-fold resolution improvement beyond the Abbe limit. We observed a further resolution improvement using the nonlinear emission response of a fluorescent protein. We demonstrated a two-beam nonlinear structured illumination microscope by introducing only a minor change into the system used for linear SIM (LSIM). To achieve the required nonlinear dependence in nonlinear SIM (NL-SIM) we exploited the photoswitching of the recently introduced fluorophore Kohinoor. It is particularly suitable due to its positive contrast photoswitching characteristics. Contrary to other reversibly photoswitchable fluorescent proteins which only have high photostability in living cells, Kohinoor additionally showed little degradation in fixed cells over many switching cycles. PMID:27783656

  17. Finite element model of the temperature increase in excised porcine cadaver iris during direct illumination by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Sun, Hui; Kurtz, Ronald M.; Juhasz, Tibor

    2012-07-01

    In order to model the thermal effect of laser exposure of the iris during laser corneal surgery, we simulated the temperature increase in porcine cadaver iris. The simulation data for the 60 kHz FS60 Laser showed that the temperature increased up to 1.23°C and 2.45°C (at laser pulse energy 1 and 2 µJ, respectively) by the 24 second procedure time. Calculated temperature profiles show good agreement with data obtained from ex vivo experiments using porcine cadaver iris. Simulation results of different types of femtosecond lasers indicate that the Laser in situ keratomileusis procedure does not present a safety hazard to the iris.

  18. Simulation of the temperature increase in human cadaver retina during direct illumination by 150-kHz femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Sun, Hui; Hosszufalusi, Nora; Mikula, Eric R.; Juhasz, Tibor

    2011-10-01

    We have developed a two-dimensional computer model to predict the temperature increase of the retina during femtosecond corneal laser flap cutting. Simulating a typical clinical setting for 150-kHz iFS advanced femtosecond laser (0.8- to 1-μJ laser pulse energy and 15-s procedure time at a laser wavelength of 1053 nm), the temperature increase is 0.2°C. Calculated temperature profiles show good agreement with data obtained from ex vivo experiments using human cadaver retina. Simulation results obtained for different commercial femtosecond lasers indicate that during the laser in situ keratomileusis procedure the temperature increase of the retina is insufficient to induce damage.

  19. An automated airplane detection system for the safeguard against airplane illumination from the laser guide star beacons at the MMT

    NASA Astrophysics Data System (ADS)

    Snyder, Miguel; Lloyd-Hart, Michael

    2007-09-01

    Laser beams for guide star generation are a potential hazard for aircraft. At the MMT telescope located on Mt. Hopkins in Southern Arizona, a constellation of five Rayleigh guide stars is created with a total of 25 W of projected power at 532 nm wavelength. We report operational results from an automatic system deployed at the MMT that is designed to detect aircraft and shut down the lasers if a collision with the beams appears likely. The system, building on a previous prototype, uses a wide-angle CCD camera mounted with a minimally unobstructed view to the optical support structure at the top of the telescope. A computer program reads the camera once every two seconds and calculates the difference between adjacent image pairs. The anti-collision beacons required on all aircraft by the Federal Aviation Administration appear as streaks in the field. If an airplane is detected, it is located in the field relative to the laser beam and its path is projected. If aircraft are detected near or appear that they will approach the beam, the laser's safety shutter is closed and warning messages are sent to the laser operator. Failsafe operation is assured by a "heart beat" signal continuously sent from the detection system to the laser controller, and by the fact that the safety shutter must be energized to open. In the event of a power failure, the system must be manually reset by the Laser Safety Officer before the laser beam can again be propagated.

  20. Laser activated diffuse discharge switch

    DOEpatents

    Christophorou, Loucas G.; Hunter, Scott R.

    1988-01-01

    The invention is a gas mixture for a diffuse discharge switch which is capable of changing from a conducting state to an insulating state in the presence of electrons upon the introduction of laser light. The mixture is composed of a buffer gas such as nitrogen or argon and an electron attaching gas such as C.sub.6 H.sub.5 SH, C.sub.6 H.sub.5 SCH.sub.3, CH.sub.3 CHO and CF.sub.3 CHO wherein the electron attachment is brought on by indirect excitation of molecules to long-lived states by exposure to laser light.

  1. [Methods for Reducing Laser Speckles to Achieve Even Illumination of the Microscope Field of View in Biophysical Studies].

    PubMed

    Barsky, V E; Lysov, Yu P; Yegorov, E E; Yurasov, D A; Mamaev, D D; Yurasov, R A; Cherepanov, A V; Chudinov, A V; Smoldovskaya, O V; Arefieva, A S; Rubina, A Yu; Zasedatelev, A S

    2015-01-01

    The aim of this work was to compare different speckle reduction techniques. It was shown that the use of devices based on liquid crystals only leads to partial reduction of speckle contrast. In quantitative luminescent microscopy an application of the mechanical devices when a laser beam is spread within the field of view turned out to be more efficient. Laser speckle noise was virtually eliminated with the developed and manufactured mechanical device comprising a fiber optic ring light guide and the vibrator that permits movement of optical fiber ends towards the laser diode during measurements. The method developed for the analysis of microarrays was successfully applied to the problem of speckle reduction.

  2. Distinguished Lectureship Award on the Applications of Physics: Illuminating My Career - From Flash Gordon to Laser Surgery

    NASA Astrophysics Data System (ADS)

    Wynne, James

    2015-03-01

    As a child, I was fascinated by television programs about Flash Gordon. His partner in conquering the universe was Dr. Alexis Zarkov, a physicist, who had invented, among other things, a death ray gun. My personal ``death ray'' was a magnifying glass, focusing sunlight on unsuspecting insects, like crawling ants. I also practiced sneaking up on resting, flying, stinging insects and burning their wings before they could take off and attack me. So I understood something about the power of sunlight. In my senior year of high school, I had a fabulous physics teacher, Lewis E. Love, and I knew after one week that I wanted to be a physicist, not a medical doctor, which is the career my parents wanted me to pursue. It turns out that the first laser functioned on May 16, 1960, just one month before I graduated from high school, and it was inevitable that I would pursue a career working with lasers. My first job as a physicist, during the summer of 1963, was working with lasers at TRG, Inc. a small company whose guru was Gordon Gould, now recognized as the inventor of the laser. After three summers at TRG, I spent three years working on nonlinear optics for my PhD thesis, under the guidance of Prof. Nicolaas Bloembergen, who later won the Nobel Prize in Physics for codifying nonlinear optics. Following completion of my PhD research in 1969, I joined IBM Research, where I have worked ever since. Upon joining the Quantum Electronics group in the Physical Sciences Dept. of the T.J. Watson Research Center, my management told me to ``do something great'' with lasers. After working on atomic spectroscopy with dye lasers through the 1970s, I had the inspiration to acquire an excimer laser for the Laser Physics and Chemistry group. Using this laser, my colleagues and I discovered excimer laser surgery, capable of removing human and animal tissue with great precision, while leaving the underlying and adjacent tissue free of collateral damage. This discovery laid the foundation for

  3. Comparison of polar cap electron density enhancement due to solar illumination and geomagnetic activity as measured by IMAGE/RPI

    NASA Astrophysics Data System (ADS)

    Nsumei, P.; Reinisch, B.; Song, P.; Tu, J.; Huang, X.

    2007-12-01

    Polar cap electron density (Ne) measurements made between the years 2000 - 2005 by the radio plasma imager (RPI) on board the IMAGE spacecraft are used to study the density enhancements resulting from changes in solar illumination and geomagnetic activity level. This study covers a geocentric distance, R = 1.4 - 5.0 RE and the polar cap is defined by an empirical boundary model that takes into account the dynamic nature of the location and size of the polar cap. The average polar cap electron density profile depends on geomagnetic activity level e.g., measured by the Kp index and solar illumination (solar zenith angle) at the footprints of the geomagnetic field lines. Our analysis of RPI Ne data shows that increase in geomagnetic activity leads to an enhancement in Ne. This enhancement in Ne is found to increase with altitude. At geocentric distance of R = 4.5 RE, an increase in the geomagnetic activity level from Kp < 2 to ~5 results in an Ne increase by a factor of ~5. On the other hand, a strong solar illumination control of Ne at lower altitudes, and not at higher is observed. At geocentric distance of ~ 2 RE, the average Ne is larger on the sunlit side than on the dark side by a factor of 3 - 4 both for quiet and disturbed conditions. At geocentric distance of about 2.5 RE the effects of these two factors on Ne appear to be comparable. Similar to previous polar cap density models, a functional representation of RPI Ne that takes the form of a power law is proposed. While in the previous Ne functional representations the power index is a constant, the power index in our representation of Ne distribution is found to correlate with (and hence is a function of) the Kp index and the solar zenith angle (SZA).

  4. Research on range-gated laser active imaging seeker

    NASA Astrophysics Data System (ADS)

    You, Mu; Wang, PengHui; Tan, DongJie

    2013-09-01

    Compared with other imaging methods such as millimeter wave imaging, infrared imaging and visible light imaging, laser imaging provides both a 2-D array of reflected intensity data as well as 2-D array of range data, which is the most important data for use in autonomous target acquisition .In terms of application, it can be widely used in military fields such as radar, guidance and fuse. In this paper, we present a laser active imaging seeker system based on range-gated laser transmitter and sensor technology .The seeker system presented here consist of two important part, one is laser image system, which uses a negative lens to diverge the light from a pulse laser to flood illuminate a target, return light is collected by a camera lens, each laser pulse triggers the camera delay and shutter. The other is stabilization gimbals, which is designed to be a rotatable structure both in azimuth and elevation angles. The laser image system consists of transmitter and receiver. The transmitter is based on diode pumped solid-state lasers that are passively Q-switched at 532nm wavelength. A visible wavelength was chosen because the receiver uses a Gen III image intensifier tube with a spectral sensitivity limited to wavelengths less than 900nm.The receiver is image intensifier tube's micro channel plate coupled into high sensitivity charge coupled device camera. The image has been taken at range over one kilometer and can be taken at much longer range in better weather. Image frame frequency can be changed according to requirement of guidance with modifiable range gate, The instantaneous field of views of the system was found to be 2×2 deg. Since completion of system integration, the seeker system has gone through a series of tests both in the lab and in the outdoor field. Two different kinds of buildings have been chosen as target, which is located at range from 200m up to 1000m.To simulate dynamic process of range change between missile and target, the seeker system has

  5. Photocatalytic activity of titania coatings synthesised by a combined laser/sol–gel technique

    SciTech Connect

    Adraider, Y.; Pang, Y.X.; Nabhani, F.; Hodgson, S.N.; Sharp, M.C.; Al-Waidh, A.

    2014-06-01

    Highlights: • Sol–gel method was used to prepare titania coatings. • Titania thin films were coated on substrate surface by dip coating. • Fibre laser was employed to irradiate the titania coated surfaces. • Photocatalytic efficiency of titania coatings was significantly improved after laser processing. - Abstract: Titania coatings were prepared using sol–gel method and then applied on the substrate surface by dip coating. Fibre laser (λ = 1064 nm) in continuous wave mode was used to irradiate the titania coated surfaces at different specific energies. The ATR-FTIR, XRD, SEM, EDS and contact angle measurement were employed to analyse surface morphology, phase composition and crystalline structure of laser-irradiated titania coatings, whilst the photocatalytic activity was evaluated by measuring the decomposition of methylene blue (MB) after exposure to the visible light for various illumination times. Results showed that the laser-irradiated titania coatings demonstrate significant different composition and microstructure in comparison with the as-coated from the same sol–gel titania. Photocatalytic efficiency of titania coatings was significantly improved after laser processing. The photocatalytic activity of laser-irradiated titania coatings was higher than that of the as-coated titania. The titania coating processed at laser specific energy of 6.5 J/mm{sup 2} exhibited the highest photocatalytic activity among all titania samples.

  6. Appearance of radial breathing modes in Raman spectra of multi-walled carbon nanotubes upon laser illumination

    NASA Astrophysics Data System (ADS)

    Rai, Padmnabh; Mohapatra, Dipti R.; Hazra, K. S.; Misra, D. S.; Ghatak, Jay; Satyam, P. V.

    2008-03-01

    The Raman spectra of the multi-walled carbon nanotubes are studied with the laser power of 5-20 mW. We observe the Raman bands at ˜1352, 1581, 1607, and 2700 cm -1 with 5 mW laser power. As the laser power is increased to 10, 15 and 20 mW, the radial breathing modes (RBMs) of the single wall carbon nanotubes (SWNTs) appear in the range 200-610 cm -1. The diameter corresponding to the highest RBM is ˜0.37 nm, the lowest reported so far. The RBMs are attributed to the local synthesis of the SWNTs at the top surface of the samples at higher laser power.

  7. Photocatalytic activity of SrTiO3 codoped with nitrogen and lanthanum under visible light illumination.

    PubMed

    Miyauchi, Masahiro; Takashio, Minoru; Tobimatsu, Hiroki

    2004-01-06

    Yellow SrTiO3 powders codoped with nitrogen and lanthanum (STO:N,La) were studied as visible light photocatalysts. The crystal phase of STO:N,La exhibited a pure perovskite phase, and O and Sr sites atoms were substitutionally doped with N and La atoms, respectively. The first principle calculation of STO:N,La indicated that the edge of the N(2p) band is situated above the valence band, which consisted of O(2p) orbitals, and the La orbitals did not exist in the band gap of SrTiO3. STO:N,La exhibited a higher oxidation activity of gaseous 2-propanol under vis illumination than SrTiO3 doped only with nitrogen (STO:N). The high activity of STO:N,La was due to the decrease in the oxygen vacancies, which acted as electron-hole recombination centers, because codoping with La3+ and N3- ions maintained the charge balance. The optimum doping density of N and La for visible light activity was 0.5%, and STO:N,La(0.5%) had an activity under UV illumination similar to pure SrTiO3.

  8. Aftershocks illuminate the 2011 Mineral, Virginia, earthquake causative fault zone and nearby active faults

    USGS Publications Warehouse

    Horton, Jr., J. Wright; Shah, Anjana K.; McNamara, Daniel E.; Snyder, Stephen L.; Carter, Aina M

    2015-01-01

    Deployment of temporary seismic stations after the 2011 Mineral, Virginia (USA), earthquake produced a well-recorded aftershock sequence. The majority of aftershocks are in a tabular cluster that delineates the previously unknown Quail fault zone. Quail fault zone aftershocks range from ~3 to 8 km in depth and are in a 1-km-thick zone striking ~036° and dipping ~50°SE, consistent with a 028°, 50°SE main-shock nodal plane having mostly reverse slip. This cluster extends ~10 km along strike. The Quail fault zone projects to the surface in gneiss of the Ordovician Chopawamsic Formation just southeast of the Ordovician–Silurian Ellisville Granodiorite pluton tail. The following three clusters of shallow (<3 km) aftershocks illuminate other faults. (1) An elongate cluster of early aftershocks, ~10 km east of the Quail fault zone, extends 8 km from Fredericks Hall, strikes ~035°–039°, and appears to be roughly vertical. The Fredericks Hall fault may be a strand or splay of the older Lakeside fault zone, which to the south spans a width of several kilometers. (2) A cluster of later aftershocks ~3 km northeast of Cuckoo delineates a fault near the eastern contact of the Ordovician Quantico Formation. (3) An elongate cluster of late aftershocks ~1 km northwest of the Quail fault zone aftershock cluster delineates the northwest fault (described herein), which is temporally distinct, dips more steeply, and has a more northeastward strike. Some aftershock-illuminated faults coincide with preexisting units or structures evident from radiometric anomalies, suggesting tectonic inheritance or reactivation.

  9. Study of timing properties of multi-pixel-photon-counter's illuminated by 630 nm and 405 nm PiLas laser light

    SciTech Connect

    Ronzhin, Anatoly; Demarteau, Marcel; Los, Sergey; Ramberg, Erik; /Fermilab

    2009-04-01

    Timing measurements of Multy-Pixel-Photon Counters (MPPC's) at the picosecond level were performed at Fermilab. The core timing resolution of the amplifiers, discriminators and TAC/ADC combination to perform these measurements is approximately 2 picoseconds. The single photoelectron time resolution (SPTR) was measured for the signals coming from the MPPC's. An SPTR of about one hundred picoseconds was obtained for MPPC's illuminated by picosecond laser pulses. The SPTR depends on applied bias voltage and on the wavelength of the light. A simple model is proposed to explain the difference in the SPTR for blue and red light. Finally, requirements for the MPPC's temperature and bias voltage stability to maintain the time resolution are discussed.

  10. Characterization of microwave MESFET circuits under laser illumination. Applications to phased array radar, microwave communications, and digital clock control

    NASA Astrophysics Data System (ADS)

    Genco, Sheryl M.

    1994-10-01

    Optical injection of MESFET's directly affects the operating characteristics of the devices. The MESFET properties, induced by optical injection, can stabilize oscillator operating frequency, control amplifier gain, and open the door for feasible integrated microwave-optical devices. The optical injection of DC MESFET's, oscillators, and amplifiers is explored. Systems applications, including phased array radar, wave division multiplexing (WDM), and computer clock control, are provided. The main contributions of this research are analyzing the modulation properties of the locked laser subsystem, using the locked laser system to inject MESFET devices and characterizing the photo-effects in MESFET circuits, reducing the phase noise in a microwave oscillator via optical injection, and developing a theoretical description of the injection properties of oscillators that can be used to describe an injection locked laser and a microwave oscillator with a change of constants.

  11. Characterization of Microwave Mesfet Circuits Under Laser Illumination: Applications to Phased Array Radar, Microwave Communications and Digital Clock Control.

    NASA Astrophysics Data System (ADS)

    Genco, Sheryl Marie

    Optical injection of MESFETs directly affects the operating characteristics of the devices. The MESFET properties, induced by optical injection, can stabilize oscillator operating frequency, control amplifier gain and open the door for feasible integrated microwave-optical devices. The optical injection of DC MESFETs, oscillators, and amplifiers, is explored. Systems applications, including phased array radar, wave division multiplexing (WDM) and computer clock control, are provided. The main contributions of this research are analyzing the modulation properties of the locked laser subsystem, using the locked laser system to inject MESFET devices and characterizing the photo-effects in MESFET circuits, reducing the phase noise in a microwave oscillator via optical injection and developing a theoretical description of the injection properties of oscillators that can be used to describe an injection locked laser and a microwave oscillator with a change of constants.

  12. [Illumination's effect on the growth and nitrate reductase activity of typical red-tide algae in the East China Sea].

    PubMed

    Li, Hong-mei; Shi, Xiao-yong; Ding, Yan-yan; Tang, Hong-jie

    2013-09-01

    Two typical red-tide algae, Skeletonema costatum and Prorocentrum donghaiense were selected as studied objects. The nitrate reductase activity (NRA) and the growth of the two algae under different illuminations through incubation experiment were studied. The illumination condition was consistent with in situ. Results showed that P. donghaiense and S. costatum could grow normally in the solar radiation ranged from 30-60 W x m(-2), and the growth curve was "S" type. However, when solar radiation was below 9 W x m(-2), the two alga could hardly grow. In the range of 0-60 W x m(-2), three parameters (NRAmax, micro(max), Bf) increased with the increasing of light intensity, indicating that the light intensity can influence the grow of alga indirectly through influencing the nitrate reductase activity. The micro(max) and NRAmax in unite volume of Skeletonema costatum were higher than those of Prorocentrum donghaiense, indicating that Skeletonema costatum can better utilize the nitrate than Prorocentrum donghaiense.

  13. The illuminating role of laser scanning digital elevation models in precision agriculture experimental designs - an agro-ecology perspective

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Laser scanning data streams, when linked with multi-spectral, hyperspectral, apparent soil electro-conductivity (ECa), or other kinds of geo-referenced data streams, aid in the creation of maps that allow useful applications in agricultural systems. These combinations of georeferenced information p...

  14. Characterization of a Low-Cost Optical Flow Sensor When Using an External Laser as a Direct Illumination Source

    PubMed Central

    Font, Davinia; Tresanchez, Marcel; Pallejà, Tomàs; Teixidó, Mercè; Palacín, Jordi

    2011-01-01

    In this paper, a low cost optical flow sensor is combined with an external laser device to measure surface displacements and mechanical oscillations. The measurement system is based on applying coherent light to a diffuser surface and using an optical flow sensor to analyze the reflected and transferred light to estimate the displacement of the surface or the laser spot. This work is focused on the characterization of this measurement system, which can have the optical flow sensor placed at different angles and distances from the diffuser surface. The results have shown that the displacement of the diffuser surface is badly estimated when the optical mouse sensor is placed in front of the diffuser surface (angular orientation >150°) while the highest sensitivity is obtained when the sensor is located behind the diffuser surface and on the axis of the laser source (angular orientation 0°). In this case, the coefficient of determination of the measured displacement, R2, was very high (>0.99) with a relative error of less than 1.29%. Increasing the distance between the surface and the sensor also increased the sensitivity which increases linearly, R2 = 0.99. Finally, this measurement setup was proposed to measure very low frequency mechanical oscillations applied to the laser device, up to 0.01 Hz in this work. The results have shown that increasing the distance between the surface and the optical flow sensor also increases the sensitivity and the measurement range. PMID:22247696

  15. An active solid state ring laser gyroscope

    SciTech Connect

    Valle, T.J.

    1992-01-01

    The properties of an active, solid state ring laser gyroscope were investigated. Two laser diode pumped monolithic nonplanar ring oscillators (NPRO), forced to lase in opposite directions, formed the NPRO-Gyro. It was unique in being an active ring laser gyroscope with a homogeneously broadened gain medium. This work examined sources of technical and fundamental noise. Associated calculations accounted for aspects of the NPRO-Gyro performance, suggested design improvements, and outlined limitations. The work brought out the need to stabilize the NPRO environment in order to achieve performance goals. Two Nd:YAG NPROs were mounted within an environment short term stabilized to microdegrees Celsius. The Allan variance of the NPRO-Gyro beat note was 500 Hz for a one second time delay. Unequal treatment of the NPROs appeared as noise on the beat frequency, therefore reducing its rotation sensitivity. The sensitivity to rotation was limited by technical noise sources.

  16. High resolution three dimensional microscopy of biological microstructures using zone plate lenses with x-ray laser illumination

    SciTech Connect

    Trebes, J.

    1990-12-12

    One of the goals of biomedical research is the development of imaging techniques capable of producing high resolution ({approximately}300{Angstrom}) three dimensional images of structures within live cells. Recent developments in zone plate lenses at LBL and in x-ray lasers at LLNL indicate that flash three dimensional x-ray microscopy of live biological objects can be achieved in the near term. This concept for a microscope utilizes an x-ray laser to backlit immunogold labeled biological objects. These backlit objects are then imaged with low f-number, high resolution zone plate lenses. Backlighting and imaging along several different directions allows a three dimensional image to be obtained using tomographic techniques.

  17. Synthesis of BiVO4/TiO2 composites and evaluation of their photocatalytic activity under indoor illumination.

    PubMed

    Longo, Giulia; Fresno, Fernando; Gross, Silvia; Štangar, Urška Lavrenčič

    2014-10-01

    BiVO4/TiO2 composites with different weight ratios have been prepared by coprecipitation-based reactions followed by either thermal or hydrothermal treatment with the aim of evaluating the TiO2 photosensitization by BiVO4. The obtained materials present in all cases the desired monoclinic phase of BiVO4 and anatase phase of TiO2. Visible light absorption increased with increasing amount of bismuth vanadate. XPS results reveal the surface enrichment of Ti with respect to the bulk composition in samples characterised by a higher content of BiVO4. The photocatalytic activity of the prepared materials was tested for the degradation of isopropanol in the gas phase under indoor illumination conditions. Although none of the composites was able to improve the activity of TiO2, the low BiVO4 containing samples appear as more suitable for further synthesis tuning.

  18. Re-examining our inhibitions: A speculative re-analysis of data from gold spheres illuminated by the URLLE Omega laser

    NASA Astrophysics Data System (ADS)

    Rosen, Mordecai; Ross, Steven; Thomas, Cliff

    2015-11-01

    A 2006 campaign, that illuminated 1 mm diameter gold spheres using the Omega laser at LLE, required the simulations to use a ``liberal'' flux limiter of f =0.15 (or equivalently a non-local model) in order to match the high levels of measured x-ray emission. In 2013, Thomson Scattering (TS) diagnosed the plasma conditions in the Au sphere's laser heated corona at various radial positions as a function of time. The simulation model using non-local transport compared well for some of the TS data (for ZTe) but not for all of it. Meanwhile, using this model for hohlraums, led to discrepancies with data (such as drive) when applied to some hohlraums, though less-so for others. As a result, hohlraum models with a more restrictive flux limiter, including a ``two-stream-instability (TSI)'' flux limit model (which, when operative, is effectively f =0.015) are being considered. Here we invoke the possibility that the same ion acoustic turbulence (an outgrowth of the TSI), which acts like an effective scatterer to inhibit electron transport, can, by the same token, also increase absorption. This increase in absorption, applied (speculatively) close by the critical surface, can begin to match the Au sphere x-ray emission, as well as a preponderance of the ZTe data. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  19. Natural light illumination system.

    PubMed

    Whang, Allen Jong-Woei; Chen, Yi-Yung; Yang, Shu-Hua; Pan, Po-Hsuan; Chou, Kao-Hsu; Lee, Yu-Chi; Lee, Zong-Yi; Chen, Chi-An; Chen, Cheng-Nan

    2010-12-10

    In recent years, green energy has undergone a lot of development and has been the subject of many applications. Many research studies have focused on illumination with sunlight as a means of saving energy and creating healthy lighting. Natural light illumination systems have collecting, transmitting, and lighting elements. Today, most daylight collectors use dynamic concentrators; these include Sun tracking systems. However, this design is too expensive to be cost effective. To create a low-cost collector that can be easily installed on a large building, we have designed a static concentrator, which is prismatic and cascadable, to collect sunlight for indoor illumination. The transmission component uses a large number of optical fibers. Because optical fibers are expensive, this means that most of the cost for the system will be related to transmission. In this paper, we also use a prismatic structure to design an optical coupler for coupling n to 1. With the n-to-1 coupler, the number of optical fibers necessary can be greatly reduced. Although this new natural light illumination system can effectively guide collected sunlight and send it to the basement or to other indoor places for healthy lighting, previously there has been no way to manage the collected sunlight when lighting was not desired. To solve this problem, we have designed an optical switch and a beam splitter to control and separate the transmitted light. When replacing traditional sources, the lighting should have similar characteristics, such as intensity distribution and geometric parameters, to those of traditional artificial sources. We have designed, simulated, and optimized an illumination lightpipe with a dot pattern to redistribute the collected sunlight from the natural light illumination system such that it equals the qualities of a traditional lighting system. We also provide an active lighting module that provides lighting from the natural light illumination system or LED auxiliary

  20. Resonant activation in bistable semiconductor lasers

    SciTech Connect

    Lepri, Stefano; Giacomelli, Giovanni

    2007-08-15

    We theoretically investigate the possibility of observing resonant activation in the hopping dynamics of two-mode semiconductor lasers. We present a series of simulations of a rate-equation model under random and periodic modulation of the bias current. In both cases, for an optimal choice of the modulation time scale, the hopping times between the stable lasing modes attain a minimum. The simulation data are understood by means of an effective one-dimensional Langevin equation with multiplicative fluctuations. Our conclusions apply to both edge-emitting and vertical cavity lasers, thus opening the way to several experimental tests in such optical systems.

  1. Observation of nanoscale cooling effects by substrates and the surrounding media for single gold nanoparticles under CW-laser illumination.

    PubMed

    Setoura, Kenji; Okada, Yudai; Werner, Daniel; Hashimoto, Shuichi

    2013-09-24

    Understanding the nanoscale heating-induced local thermal response is important but hampered by lack of information on temperatures at such small scales. This paper reports laser-induced heating and thermal equilibration of metal nanoparticles supported on different substrates and immersed in several media. We use single-particle spectroscopy to monitor nanoparticle temperature rises due to laser excitation. Because of changes in the refractive index of the surrounding medium, the scattering spectrum of the gold nanoparticles undergoes a shift that is related to the temperature of the system. We find that the temperature increase depends on both the surrounding medium and the supporting substrate. We furthermore model the nanoparticle temperature using a simplified 1-D heat conduction model with an effective thermal conductivity that takes both substrate and environment into account. The results from this model are also compared to a more detailed 2-D heat transfer analysis. The results presented here are quite new and important to many plasmonic nanoparticle applications where the strong absorption cross section of the nanoparticles leads to a significant temperature rise. In particular, the current work introduces an analysis that can be easily implemented to model the temperature of a nanoparticle supported on a substrate, as is the case in many single-particle measurements.

  2. Ultrafast Dynamics of a Nucleobase Analogue Illuminated by a Short Intense X-ray Free Electron Laser Pulse

    NASA Astrophysics Data System (ADS)

    Nagaya, K.; Motomura, K.; Kukk, E.; Fukuzawa, H.; Wada, S.; Tachibana, T.; Ito, Y.; Mondal, S.; Sakai, T.; Matsunami, K.; Koga, R.; Ohmura, S.; Takahashi, Y.; Kanno, M.; Rudenko, A.; Nicolas, C.; Liu, X.-J.; Zhang, Y.; Chen, J.; Anand, M.; Jiang, Y. H.; Kim, D.-E.; Tono, K.; Yabashi, M.; Kono, H.; Miron, C.; Yao, M.; Ueda, K.

    2016-04-01

    Understanding x-ray radiation damage is a crucial issue for both medical applications of x rays and x-ray free-electron-laser (XFEL) science aimed at molecular imaging. Decrypting the charge and fragmentation dynamics of nucleobases, the smallest units of a macro-biomolecule, contributes to a bottom-up understanding of the damage via cascades of phenomena following x-ray exposure. We investigate experimentally and by numerical simulations the ultrafast radiation damage induced on a nucleobase analogue (5-iodouracil) by an ultrashort (10 fs) high-intensity radiation pulse generated by XFEL at SPring-8 Angstrom Compact free electron Laser (SACLA). The present study elucidates a plausible underlying radiosensitizing mechanism of 5-iodouracil. This mechanism is independent of the exact composition of 5-iodouracil and thus relevant to other such radiosensitizers. Furthermore, we found that despite a rapid increase of the net molecular charge in the presence of iodine, and of the ultrafast release of hydrogen, the other atoms are almost frozen within the 10-fs duration of the exposure. This validates single-shot molecular imaging as a consistent approach, provided the radiation pulse used is brief enough.

  3. Actively mode-locked Raman fiber laser.

    PubMed

    Yang, Xuezong; Zhang, Lei; Jiang, Huawei; Fan, Tingwei; Feng, Yan

    2015-07-27

    Active mode-locking of Raman fiber laser is experimentally investigated for the first time. An all fiber connected and polarization maintaining loop cavity of ~500 m long is pumped by a linearly polarized 1120 nm Yb fiber laser and modulated by an acousto-optic modulator. Stable 2 ns width pulse train at 1178 nm is obtained with modulator opening time of > 50 ns. At higher power, pulses become longer, and second order Raman Stokes could take place, which however can be suppressed by adjusting the open time and modulation frequency. Transient pulse evolution measurement confirms the absence of relaxation oscillation in Raman fiber laser. Tuning of repetition rate from 392 kHz to 31.37 MHz is obtained with harmonic mode locking.

  4. OPTICAL SYSTEMS: Calculation of the illuminance distribution in the focal spot of a focusing system taking into account aberrations in this system and divergence of a focused laser beam

    NASA Astrophysics Data System (ADS)

    Gitin, Andrey V.

    2007-03-01

    The dependence of the focal-spot size of a 'deep' parabolic mirror reflector on the laser-beam divergence is analysed by the method of elementary reflections. The dependence of the focal-beam diameter of an ideal focusing optical system on the laser-beam parameters is described. The expression is obtained for calculating the illumination distribution in the focal spot of a 'deep' mirror reflector which takes into account both aberrations and light-gathering power of the reflector and the divergence of a focused laser beam.

  5. Enhanced photocatalytic activity of ZnO/CuO nanocomposite for the degradation of textile dye on visible light illumination.

    PubMed

    Saravanan, R; Karthikeyan, S; Gupta, V K; Sekaran, G; Narayanan, V; Stephen, A

    2013-01-01

    The photocatalytic degradation of organic dyes such as methylene blue and methyl orange in the presence of various percentages of composite catalyst under visible light irradiation was carried out. The catalyst ZnO nanorods and ZnO/CuO nanocomposites of different weight ratios were prepared by new thermal decomposition method, which is simple and cost effective. The prepared catalysts were characterized by different techniques such as X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, Fourier transform infrared spectroscopy and UV-visible absorption spectroscopy. Further, the most photocatalytically active composite material was used for degradation of real textile waste water under visible light illumination. The irradiated samples were analysed by total organic carbon and chemical oxygen demand. The efficiency of the catalyst and their photocatalytic mechanism has been discussed in detail.

  6. Study Illuminates K-Ras4B Activation, Which May Help Predict Drug Resistance | Poster

    Cancer.gov

    Until recently, researchers studying RAS, a family of proteins involved in transmitting signals within cells, believed that the exchange of guanosine 5’-diphosphate (GDP) by guanosine triphosphate (GTP) was sufficient to activate the protein. Once activated, RAS can cause unintended and overactive signaling in cells, which can lead to cell division and, ultimately, cancer.

  7. First-Hand Participation: Illuminating Teachers' Self-Perceptions of Physical Activity Delivery

    ERIC Educational Resources Information Center

    Till, Jude; Ferkins, Lesley

    2014-01-01

    The study examines school-based physical activity in investigating teachers' perceptions of a physical activity-related professional development (PD) intervention in New Zealand primary schools. Eighteen semi-structured interviews with six teachers from two schools was the primary data collection method. Using a selected programme, teachers'…

  8. Effects of intracerebroventricular histamine injection on circadian activity phase entrainment during rapid illumination changes.

    PubMed

    Itowi, N; Yamatodani, A; Mochizuki, T; Wada, H

    1991-02-11

    Histamine is reported to have different effects on shifting the circadian activity phase depending on its circadian administration time (CT). The delay-sensitive period is CT 12-15, and the advance-sensitive period is CT 0-3. The activity phase of rats was entrained by a new light-dark cycle within a week in groups treated with either saline or i.c.v. histamine at CT 12-15. However, on treatment at CT 0-3 the activity phase of the group treated with histamine was entrained by the new light-dark cycle in half the period required for entrainment in the control group.

  9. Effect of surface plasmon resonance on the photocatalytic activity of Au/TiO2 under UV/visible illumination.

    PubMed

    Tseng, Yao-Hsuan; Chang, I-Guo; Tai, Yian; Wu, Kung-Wei

    2012-01-01

    In this study, gold-loaded titanium dioxide was prepared by an impregnation method to investigate the effect of surface plasmon resonance (SPR) on photoactivity. The deposited gold nanoparticles (NPs) absorb visible light because of SPR. The effects of both the gold content and the TiO2 size of Au/TiO2 on SPR and the photocatalytic efficiency were investigated. The morphology, crystal structure, light absorption, emission from the recombination of a photoexcited electron and hole, and the degree of aggregation were investigated using transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-visible-diffuse reflectance spectra (UV-VIS-DRS), photoluminescence (PL) spectroscopy, and turbidimetry, respectively. Photocatalytic activity was evaluated by the decolorization of methyl orange solution over modified titania under UV and UV/GLED (green light emitting diode) illumination. Au/TiO2 NPs exhibited an absorption peak (530-570 nm) because of SPR. The results of our photocatalytic experiments indicated that the UV-inducedly photocatalytic reaction rate was improved by simultaneously using UV and green light illumination; this corresponds to the adsorption region of SPR. Au/TiO2 could use the enhanced electric field amplitude on the surface of the Au particle in the spectral vicinity of its plasmon resonance and thus improve the photoactivity. Experimental results show that the synergistic effect between UV and green light for the improvement of photoactivity increases with increasing the SPR absorption, which in turn is affected by the Au content and TiO2 size.

  10. Functional Safety of Hybrid Laser Safety Systems - How can a Combination between Passive and Active Components Prevent Accidents?

    NASA Astrophysics Data System (ADS)

    Lugauer, F. P.; Stiehl, T. H.; Zaeh, M. F.

    Modern laser systems are widely used in industry due to their excellent flexibility and high beam intensities. This leads to an increased hazard potential, because conventional laser safety barriers only offer a short protection time when illuminated with high laser powers. For that reason active systems are used more and more to prevent accidents with laser machines. These systems must fulfil the requirements of functional safety, e.g. according to IEC 61508, which causes high costs. The safety provided by common passive barriers is usually unconsidered in this context. In the presented approach, active and passive systems are evaluated from a holistic perspective. To assess the functional safety of hybrid safety systems, the failure probability of passive barriers is analysed and added to the failure probability of the active system.

  11. Photobleaching and phototoxicity of KillerRed in tumor spheroids induced by continuous wave and pulsed laser illumination.

    PubMed

    Kuznetsova, Daria S; Shirmanova, Marina V; Dudenkova, Varvara V; Subochev, Pavel V; Turchin, Ilya V; Zagaynova, Elena V; Lukyanov, Sergey A; Shakhov, Boris E; Kamensky, Vladislav A

    2015-11-01

    The purpose of this study was to evaluate photobleaching of the genetically encoded photosensitizer KillerRed in tumor spheroids upon pulsed and continuous wave (CW) laser irradiation and to analyze the mechanisms of cancer cell death after the treatment. We observed the light-dose dependent mechanism of KillerRed photobleaching over a wide range of fluence rates. Loss of fluorescence was limited to 80% at light doses of 150 J/cm(2) and more. Based on the bleaching curves, six PDT regimes were applied for irradiation using CW and pulsed regimes at a power density of 160 mW/cm(2) and light doses of 140 J/cm(2) , 170 J/cm(2) and 200 J/cm(2). Irradiation of KillerRed-expressing spheroids in the pulsed mode (pulse duration 15 ns, pulse repetition rate 10 Hz) induced predominantly apoptotic cell death, while in the case of CW mode the cancer cells underwent necrosis. In general, these results improve our understanding of photobleaching mechanisms in GFP-like proteins and show the importance of appropriate selection of treatment mode for PDT with KillerRed. Representative fluorescence image of two KillerRed-expressing spheroids before and immediately after CW irradiation.

  12. Demand illumination control apparatus

    NASA Technical Reports Server (NTRS)

    Warren, Carl (Inventor); Arline, Jimmie (Inventor); LaPalme, Julius (Inventor)

    1981-01-01

    Solar illuminating compensating apparatus is disclosed whereby the interior of a building is illuminated to a substantially constant, predetermined level of light intensity by a combination of natural illumination from the sun and artificial illumination from electricity wherein the intensity of said artificial illumination is controlled by fully electronic means which increases the level of artificial illumination when the natural illumination is inadequate and vice versa.

  13. Light illuminated α-Fe2O3/Pt nanoparticles as water activation agent for photoelectrochemical water splitting.

    PubMed

    Li, Xiaodong; Wang, Zhi; Zhang, Zemin; Chen, Lulu; Cheng, Jianli; Ni, Wei; Wang, Bin; Xie, Erqing

    2015-03-16

    The photoelectrochemical (PEC) water splitting is hampered by strong bonds of H2O molecules and low ionic conductivity of pure water. The photocatalysts dispersed in pure water can serve as a water activation agent, which provides an alternative pathway to overcome such limitations. Here we report that the light illuminated α-Fe2O3/Pt nanoparticles may produce a reservoir of reactive intermediates including H2O2, ·OH, OH(-) and H(+) capable of promoting the pure water reduction/oxidation half-reactions at cathode and highly photocatalytic-active TiO2/In2S3/AgInS2 photoanode, respectively. Remarkable photocurrent enhancement has been obtained with α-Fe2O3/Pt as water activation agent. The use of α-Fe2O3/Pt to promote the reactivity of pure water represents a new paradigm for reproducible hydrogen fuel provision by PEC water splitting, allowing efficient splitting of pure water without adding of corrosive chemicals or sacrificial agent.

  14. Microwave accelerated synthesis of zinc oxide nanoplates and their enhanced photocatalytic activity under UV and solar illuminations

    NASA Astrophysics Data System (ADS)

    Anas, S.; Rahul, S.; Babitha, K. B.; Mangalaraja, R. V.; Ananthakumar, S.

    2015-11-01

    Photoactive zinc based nanoplates were developed through a rapid microwave synthesis. A low temperature thermolysis reaction in a surfactant medium was initially performed for producing microwave active zinc based polar precursors. Using these precursors, the zinc oxide nanopowder having platelet morphologies were prepared. The nanoplatelets exhibited random growth with non-polar (1 0 1) surface as the major growth plane. The structural and functional features of the resultant zinc oxide samples were monitored using XRD, FTIR, TEM and PL. The photocatalytic activities of the samples were investigated through the standard photoreduction kinetics using the methylene blue dye. The catalytic efficiencies of the samples were checked both under UV and sunlight. A comparative study was also performed with the standard TiO2 sample. The analyses revealed that the microwave derived zinc oxide have higher catalytic efficiency, than the standard titania samples, both under UV and sunlight illuminations. The unique nature of the zinc oxide non-polar surfaces can be attributed due to the presence of more active two dimensional open surfaces and the higher content of oxygen defect concentrations.

  15. A chloroplast "wake up" mechanism: Illumination with weak light activates the photosynthetic antenna function in dark-adapted plants.

    PubMed

    Janik, Ewa; Bednarska, Joanna; Zubik, Monika; Luchowski, Rafal; Mazur, Radoslaw; Sowinski, Karol; Grudzinski, Wojciech; Garstka, Maciej; Gruszecki, Wieslaw I

    2017-03-01

    The efficient and fluent operation of photosynthesis in plants relies on activity of pigment-protein complexes called antenna, absorbing light and transferring excitations toward the reaction centers. Here we show, based on the results of the fluorescence lifetime imaging analyses of single chloroplasts, that pigment-protein complexes, in dark-adapted plants, are not able to act effectively as photosynthetic antennas, due to pronounced, adverse excitation quenching. It appeared that the antenna function could be activated by a short (on a minute timescale) illumination with light of relatively low intensity, substantially below the photosynthesis saturation threshold. The low-light-induced activation of the antenna function was attributed to phosphorylation of the major accessory light-harvesting complex LHCII, based on the fact that such a mechanism was not observed in the stn7 Arabidopsis thaliana mutant, with impaired LHCII phosphorylation. It is proposed that the protein phosphorylation-controlled change in the LHCII clustering ability provides mechanistic background for this regulatory process.

  16. Influences of acute ethanol exposure on locomotor activities of zebrafish larvae under different illumination.

    PubMed

    Guo, Ning; Lin, Jia; Peng, Xiaolan; Chen, Haojun; Zhang, Yinglan; Liu, Xiuyun; Li, Qiang

    2015-11-01

    Larval zebrafish present unique opportunities to study the behavioral responses of a model organism to environmental challenges during early developmental stages. The purpose of the current study was to investigate the locomotor activities of AB strain zebrafish larvae at 5 and 7 days post-fertilization (dpf) in response to light changes under the influence of ethanol, and to explore potential neurological mechanisms that are involved in ethanol intoxication. AB strain zebrafish larvae at both 5 and 7 dpf were treated with ethanol at 0% (control), 0.1%, 0.25%, 0.5%, 1%, and 2% (v/v%). The locomotor activities of the larvae during alternating light-dark challenges, as well as the locomotor responses immediately following the light transitions, were investigated. The levels of various neurotransmitters were also measured in selected ethanol-treated groups. The larvae at 5 and 7 dpf demonstrated similar patterns of locomotor responses to ethanol treatment. Ethanol treatment at 1% increased the swimming distances of the zebrafish larvae in the dark periods, but had no effect on the swimming distances in the light periods. In contrast, ethanol treatment at 2% increased the swimming distances in the light periods, but did not potentiate the swimming activity in the dark periods, compared to controls. Differences in the levels of neurotransmitters that are involved in norepinephrine, dopamine, and serotonin pathways were also observed in groups with different ethanol treatments. These results indicated the behavioral studies concerning the ethanol effects on locomotor activities of zebrafish larvae could be carried out as early as 5 dpf. The 1% and 2% ethanol-treated zebrafish larvae modeled ethanol effects at different intoxication states, and the differences in neurotransmitter levels suggested the involvement of various neurotransmitter pathways in different ethanol intoxication states.

  17. Laser Initiated Ordnance (LIO) activities in NASA

    NASA Technical Reports Server (NTRS)

    Schulze, Norman R.

    1994-01-01

    This technical report presents the summary of the 2nd NASA Aerospace Pyrotechnic Systems Workshop's discussion on Laser Initiated Ordnance (LIO). Laser initiated ordnance benefits, applications, advantage of laser ordnance, and disadvantage of laser diode initiated ordnance are discussed. In addition, the three LIO programs: NASA standard laser diode safe and arm, NASA standard laser detonators, and laser diode safe/arm performance are reviewed. Steps for the LIO implementation are also presented.

  18. X-ray structures of AMPA receptor-cone snail toxin complexes illuminate activation mechanism.

    PubMed

    Chen, Lei; Dürr, Katharina L; Gouaux, Eric

    2014-08-29

    AMPA-sensitive glutamate receptors are crucial to the structural and dynamic properties of the brain, to the development and function of the central nervous system, and to the treatment of neurological conditions from depression to cognitive impairment. However, the molecular principles underlying AMPA receptor activation have remained elusive. We determined multiple x-ray crystal structures of the GluA2 AMPA receptor in complex with a Conus striatus cone snail toxin, a positive allosteric modulator, and orthosteric agonists, at 3.8 to 4.1 angstrom resolution. We show how the toxin acts like a straightjacket on the ligand-binding domain (LBD) "gating ring," restraining the domains via both intra- and interdimer cross-links such that agonist-induced closure of the LBD "clamshells" is transduced into an irislike expansion of the gating ring. By structural analysis of activation-enhancing mutants, we show how the expansion of the LBD gating ring results in pulling forces on the M3 helices that, in turn, are coupled to ion channel gating.

  19. Rapid High Spatial Resolution Chemical Characterization of Soil Structure to Illuminate Nutrient Distribution Mechanisms Related to Carbon Cycling Using Laser Ablation Aerosol Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Hicks, R. K.; Alexander, M. L. L.; Newburn, M. K.

    2015-12-01

    Soils contain approximately half of Earth's terrestrial carbon. As such, it is important to understand the factors that control the cycling of this soil organic carbon between the land and the atmosphere. Models that attribute the persistence of soil organic carbon to the intrinsic properties of the molecules themselves are inconsistent with recent observations— for example, materials that are more thermodynamically stable have been found to have a shorter lifetime in soils than ones that are less stable, and vice versa. A new explanation has therefore been posited that invokes ecosystem properties as a whole, and not just intrinsic molecular properties, as the kinetic factor controlling soil carbon dynamics. Because soil dynamics occur on a small scale, techniques with high spatial resolution are required for their study. Existing techniques such as TOF-SIMS require preparation of the sample and introduction into a high vacuum system, and do not address the need to examine large numbers of sample systems without perturbation of chemical and physical properties. To address this analytical challenge, we have coupled a laser ablation (LA) module to an Aerodyne aerosol mass spectrometer (AMS), thereby enabling sample introduction and subsequent measurement of small amounts of soil organic matter by the laser ablation aerosol mass spectrometer (LA-AMS). Due to the adjustable laser beam width, the LA-AMS can probe spot sizes ranging from 1-150 μm in diameter, liberating from 10-100 ng/pulse. With a detection limit of 1 pM, the AMS allows for chemical characterization of the ablated material in terms of elemental ratios, compound classes, and TOC/TOM ratios. Furthermore, the LA-AMS is capable of rapid, in-situ sampling under ambient conditions, thereby eliminating the need for sample processing or transport before analysis. Here, we will present the first results from systematic studies aimed at validating the LA-AMS method as well as results from initial measurements

  20. Bias-illumination stress effect in thin film transistors with a nitrogen low-doped IZO active layer

    NASA Astrophysics Data System (ADS)

    Cheremisin, Alexander B.; Kuznetsov, Sergey N.; Stefanovich, Genrikh B.

    2016-10-01

    The effect of ZnO and IZO moderate nitridation on the performance of thin film transistors (TFTs) has been studied by methods of transfer and capacitance-voltage characteristics, isochronal annealing and computer modeling. Layers of ZnO:N and IZO:N were prepared by reactive sputtering. It is shown that nitridation of the ZnO matrix up to a concentration of 9 at.% results in the deterioration of transistor parameters. However, nitridation of the IZO matrix does not impair a transistor’s static parameters and also provides enhanced performance reproducibility. An additional positive effect is manifested in the electrical stress stability of transistor characteristics at negative bias and positive bias in darkness. Negative bias illumination stress (NBIS) of IZO:N structures also causes TFTs’ degradation similar to that for IGZO devices. However, our observations of the NBIS effect have revealed the following important features. Holes trapped under NBIS could not be neutralized by electrons in the channel in the accumulation regime, thus indicating negligible interaction between positively-charged defects and the conduction band. In addition, trapped holes’ depopulation was performed by thermal activation with an isochronal annealing method. An activation energy of ˜0.8 eV was revealed which is interpreted as the energy level of defects above the valence-band maximum. The specified features do not correlate with the assumption of the key role of oxygen vacancies in NBIS that is extensively presented in literature.

  1. Discovery of an Active RAG Transposon Illuminates the Origins of V(D)J Recombination.

    PubMed

    Huang, Shengfeng; Tao, Xin; Yuan, Shaochun; Zhang, Yuhang; Li, Peiyi; Beilinson, Helen A; Zhang, Ya; Yu, Wenjuan; Pontarotti, Pierre; Escriva, Hector; Le Petillon, Yann; Liu, Xiaolong; Chen, Shangwu; Schatz, David G; Xu, Anlong

    2016-06-30

    Co-option of RAG1 and RAG2 for antigen receptor gene assembly by V(D)J recombination was a crucial event in the evolution of jawed vertebrate adaptive immunity. RAG1/2 are proposed to have arisen from a transposable element, but definitive evidence for this is lacking. Here, we report the discovery of ProtoRAG, a DNA transposon family from lancelets, the most basal extant chordates. A typical ProtoRAG is flanked by 5-bp target site duplications and a pair of terminal inverted repeats (TIRs) resembling V(D)J recombination signal sequences. Between the TIRs reside tail-to-tail-oriented, intron-containing RAG1-like and RAG2-like genes. We demonstrate that ProtoRAG was recently active in the lancelet germline and that the lancelet RAG1/2-like proteins can mediate TIR-dependent transposon excision, host DNA recombination, transposition, and low-efficiency TIR rejoining using reaction mechanisms similar to those used by vertebrate RAGs. We propose that ProtoRAG represents a molecular "living fossil" of the long-sought RAG transposon.

  2. Illumination influences working memory: an EEG study.

    PubMed

    Park, Jin Young; Min, Byoung-Kyong; Jung, Young-Chul; Pak, Hyensou; Jeong, Yeon-Hong; Kim, Eosu

    2013-09-05

    Illumination conditions appear to influence working efficacy in everyday life. In the present study, we obtained electroencephalogram (EEG) correlates of working-memory load, and investigated how these waveforms are modulated by illumination conditions. We hypothesized that illumination conditions may affect cognitive performance. We designed an EEG study to monitor and record participants' EEG during the Sternberg working memory task under four different illumination conditions. Illumination conditions were generated with a factorial design of two color-temperatures (3000 and 7100 K) by two illuminance levels (150 and 700 lx). During a working memory task, we observed that high illuminance led to significantly lower frontal EEG theta activity than did low illuminance. These differences persisted despite no significant difference in task performance between illumination conditions. We found that the latency of an early event-related potential component, such as N1, was significantly modulated by the illumination condition. The fact that the illumination condition affects brain activity but not behavioral performance suggests that the lighting conditions used in the present study did not influence the performance stage of behavioral processing. Nevertheless, our findings provide objective evidence that illumination conditions modulate brain activity. Further studies are necessary to refine the optimal lighting parameters for facilitating working memory.

  3. Green laser light activates the inner ear

    NASA Astrophysics Data System (ADS)

    Wenzel, Gentiana I.; Balster, Sven; Zhang, Kaiyin; Lim, Hubert H.; Reich, Uta; Massow, Ole; Lubatschowski, Holger; Ertmer, Wolfgang; Lenarz, Thomas; Reuter, Guenter

    2009-07-01

    The hearing performance with conventional hearing aids and cochlear implants is dramatically reduced in noisy environments and for sounds more complex than speech (e. g. music), partially due to the lack of localized sensorineural activation across different frequency regions with these devices. Laser light can be focused in a controlled manner and may provide more localized activation of the inner ear, the cochlea. We sought to assess whether visible light with parameters that could induce an optoacoustic effect (532 nm, 10-ns pulses) would activate the cochlea. Auditory brainstem responses (ABRs) were recorded preoperatively in anesthetized guinea pigs to confirm normal hearing. After opening the bulla, a 50-μm core-diameter optical fiber was positioned in the round window niche and directed toward the basilar membrane. Optically induced ABRs (OABRs), similar in shape to those of acoustic stimulation, were elicited with single pulses. The OABR peaks increased with energy level (0.6 to 23 μJ/pulse) and remained consistent even after 30 minutes of continuous stimulation at 13 μJ, indicating minimal or no stimulation-induced damage within the cochlea. Our findings demonstrate that visible light can effectively and reliably activate the cochlea without any apparent damage. Further studies are in progress to investigate the frequency-specific nature and mechanism of green light cochlear activation.

  4. Muscle activity characterization by laser Doppler Myography

    NASA Astrophysics Data System (ADS)

    Scalise, Lorenzo; Casaccia, Sara; Marchionni, Paolo; Ercoli, Ilaria; Primo Tomasini, Enrico

    2013-09-01

    Electromiography (EMG) is the gold-standard technique used for the evaluation of muscle activity. This technique is used in biomechanics, sport medicine, neurology and rehabilitation therapy and it provides the electrical activity produced by skeletal muscles. Among the parameters measured with EMG, two very important quantities are: signal amplitude and duration of muscle contraction, muscle fatigue and maximum muscle power. Recently, a new measurement procedure, named Laser Doppler Myography (LDMi), for the non contact assessment of muscle activity has been proposed to measure the vibro-mechanical behaviour of the muscle. The aim of this study is to present the LDMi technique and to evaluate its capacity to measure some characteristic features proper of the muscle. In this paper LDMi is compared with standard superficial EMG (sEMG) requiring the application of sensors on the skin of each patient. sEMG and LDMi signals have been simultaneously acquired and processed to test correlations. Three parameters has been analyzed to compare these techniques: Muscle activation timing, signal amplitude and muscle fatigue. LDMi appears to be a reliable and promising measurement technique allowing the measurements without contact with the patient skin.

  5. Actively Q-switched Raman fiber laser

    NASA Astrophysics Data System (ADS)

    Kuznetsov, A. G.; Podivilov, E. V.; Babin, S. A.

    2015-03-01

    A new scheme providing actively Q-switched operation of a Raman fiber laser (RFL) has been proposed and tested. The RFL consists of a 1 km single-mode fiber with a switchable loop mirror at one end and an angled cleaved output end. An 1080 nm pulse with microsecond duration is generated at the output by means of acousto-optic switching of the mirror at ~30 kHz in the presence of 6 W backward pumping at 1030 nm. In the proposed scheme, the generated pulse energy is defined by the pump energy distributed along the passive fiber, which amounts to 30 μJ in our case. The available pump energy may be increased by means of fiber lengthening. Pulse shortening is also expected.

  6. NASA'S Earth Science Enterprise Embraces Active Laser Remote Sensing from Space

    NASA Technical Reports Server (NTRS)

    Luther, Michael R.; Paules, Granville E., III

    1999-01-01

    Several objectives of NASA's Earth Science Enterprise are accomplished, and in some cases, uniquely enabled by the advantages of earth-orbiting active lidar (laser radar) sensors. With lidar, the photons that provide the excitation illumination for the desired measurement are both controlled and well known. The controlled characteristics include when and where the illumination occurs, the wavelength, bandwidth, pulse length, and polarization. These advantages translate into high signal levels, excellent spatial resolution, and independence from time of day and the sun's position. As the lidar technology has rapidly matured, ESE scientific endeavors have begun to use lidar sensors over the last 10 years. Several more lidar sensors are approved for future flight. The applications include both altimetry (rangefinding) and profiling. Hybrid missions, such as the approved Geoscience Laser Altimeter System (GLAS) sensor to fly on the ICESat mission, will do both at the same time. Profiling applications encompass aerosol, cloud, wind, and molecular concentration measurements. Recent selection of the PICASSO Earth System Science Pathfinder mission and the complementary CLOUDSAT radar-based mission, both flying in formation with the EOS PM mission, will fully exploit the capabilities of multiple sensor systems to accomplish critical science needs requiring such profiling. To round out the briefing a review of past and planned ESE missions will be presented.

  7. Lunar South Pole Illumination

    NASA Video Gallery

    Simulated illumination conditions over the lunar South Pole region, from ~80°S to the pole. The movie runs for 28 days, centered on the LCROSS impact date on October 9th, 2009. The illumination ca...

  8. Lights illuminate surfaces superluminally

    NASA Astrophysics Data System (ADS)

    Nemiroff, Robert J.; Zhong, Qi; Lilleskov, Elias

    2016-07-01

    When a light bulb is turned on, light moves away from it at speed c, by definition. When light from this bulb illuminates a surface, however, this illumination front is not constrained to move at speed c. A simple proof is given that this illumination front always moves faster than c. Generalized, when any compact light source itself varies, this information spreads across all of the surfaces it illuminates at speeds faster than light.

  9. Multiple-illumination photoacoustic tomography

    NASA Astrophysics Data System (ADS)

    Barber, Quinn M.; Zemp, Roger J.

    2016-03-01

    Previously we described the potential for multiple illumination photoacoustic tomography to provide quantitative reconstructions, however this work used only simulated data. We have developed a custom photoacoustic-ultrasound tomography system capable of multiple illuminations and parallel acquisition from a 256 element 5 MHz transducer ring array with 8-cm diameter. The multiple illumination scheme uses a free-space light delivery geometry where a rotational stage scans a pulsed laser beam onto different incident locations around the sample. For each illumination location a photoacoustic image is reconstructed using a modified backprojection algorithm. Images from different source locations have the potential to be combined to form an improved deep-tissue image using our previously developed iterative algorithms. We complement the photoacoustic imaging data with unique ultrasound imaging data. Most previous ultrasound tomography methods have used migration algorithms, iterative ray-based analysis, wave-equation modeling, or frequency-based algorithms that all demand large amounts of data and computational power. We propose a new UST method that offers isotropic resolution, provides scattering contrast, as well as the potential for measuring ultrasound scattering anisotropy and decoupling density and compressibility contributions. The imaging system is driven by a Verasonics scan engine and programmed for both ultrasound and photoacoustic imaging modes. Resolution has been measured to be 150 μm for ultrasound and 200 μm for photoacoustic images. Imaging capabilities are demonstrated on phantoms with custom-tailored ultrasound scattering and optical properties, as well as in murine models.

  10. Active coherent laser spectrometer for remote detection and identification of chemicals

    NASA Astrophysics Data System (ADS)

    MacLeod, Neil A.; Weidmann, Damien

    2012-10-01

    Currently, there exists a capability gap for the remote detection and identification of threat chemicals. We report here on the development of an Active Coherent Laser Spectrometer (ACLaS) operating in the thermal infrared and capable of multi-species stand-off detection of chemicals at sub ppm.m levels. A bench top prototype of the instrument has been developed using distributed feedback mid-infrared quantum cascade lasers as spectroscopic sources. The instrument provides active eye-safe illumination of a topographic target and subsequent spectroscopic analysis through optical heterodyne detection of the diffuse backscattered field. Chemical selectivity is provided by the combination of the narrow laser spectral bandwidth (typically < 2 MHz) and frequency tunability that allows the recording of the full absorption spectrum of any species within the instrument line of sight. Stand-off detection at distances up to 12 m has been demonstrated on light molecules such as H2O, CH4 and N2O. A physical model of the stand-off detection scenario including ro-vibrational molecular absorption parameters was used in conjunction with a fitting algorithm to retrieve quantitative mixing ratio information on multiple absorbers.

  11. The reversal of the laser-beam-induced-current contrast with varying illumination density in a Cu{sub 2}ZnSnSe{sub 4} thin-film solar cell

    SciTech Connect

    Chen, Qiong; Zhang, Yong

    2013-12-09

    We apply an array of correlated spatially-resolved techniques, including μ-Raman/photoluminescence/reflectance/laser-beam-induced-current in conjunction with scanning electron microscopy and atomic force microscopy, to study the impact of the microscopic-scale thickness inhomogeneity of CdS layer in a Cu{sub 2}ZnSnSe{sub 4} thin-film solar cell. Thicker CdS regions are found to cause more light reflecting loss thus yield lower external quantum efficiencies and energy conversion efficiencies than the general area. However, these regions show much less efficiency degradation at high illumination intensity, leading to an inversion of laser-beam-induced-current contrast in the area mapping. While improving the CdS layer uniformity can boost the device performance, the finding further points out the possibility of operating thin-film photovoltaic devices based on the similar materials (such as CuInGaSe{sub 2}, CdTe, Cu{sub 2}ZnSn(S,Se){sub 4}) under a substantially higher illumination density for concentrated photovoltaic and photo-detection.

  12. Small high-speed dynamic target at close range laser active imaging system

    NASA Astrophysics Data System (ADS)

    Yao, Jun; Wang, Du-yue; Zhang, Zheng; Zhang, Yue; Dai, Qin

    2016-11-01

    In the shooting range measuring, all-weather, high speed, unattended, the new concepts such as the remote control is gradually applied. In this paper, a new type of low cost range measurement system, using FPGA + MCU as electronic control system of laser active illumination and high-speed CMOS camera, data to the rear zone by using optical fiber communications, transmission and realizes the remote control of unmanned, due to the low cost of front-end equipment, can be used as consumables replacement at any time, combined with distributed layout principle, can maximum limit close to the measured with mutilate ability goal, thus to achieve the goal of small high-speed dynamic imaging from close range.

  13. Laser stimulation can activate autophagy in HeLa cells

    SciTech Connect

    Wang, Yisen; Hu, Minglie; Wang, Chingyue; Lan, Bei; Cao, Youjia; He, Hao

    2014-10-27

    For decades, lasers have been a daily tool in most biological research for fluorescent excitation by confocal or multiphoton microscopy. More than 20 years ago, cell photodamage caused by intense laser stimulation was noticed by generating reactive oxygen species, which was then thought as the main damage effect by photons. In this study, we show that laser stimulation can induce autophagy, an important cell lysosomal pathway responding to immune stimulation and starvation, without any biochemical treatment. Two different types of laser stimulations are found to be capable of activating autophagy: continuous scanning by continuous-wave visible lasers and a short-time flash of femtosecond laser irradiation. The autophagy generation is independent from wavelength, power, and scanning duration of the visible lasers. In contrast, the power of femtosecond laser is very critical to autophagy because the multiphoton excited Ca{sup 2+} dominates autophagy signaling. In general, we show here the different mechanisms of autophagy generation by such laser stimulation, which correspond to confocal microscopy and cell surgery, respectively. Those results can help further understanding of photodamage and autophagy signaling.

  14. Laser stimulation can activate autophagy in HeLa cells

    NASA Astrophysics Data System (ADS)

    Wang, Yisen; Lan, Bei; He, Hao; Hu, Minglie; Cao, Youjia; Wang, Chingyue

    2014-10-01

    For decades, lasers have been a daily tool in most biological research for fluorescent excitation by confocal or multiphoton microscopy. More than 20 years ago, cell photodamage caused by intense laser stimulation was noticed by generating reactive oxygen species, which was then thought as the main damage effect by photons. In this study, we show that laser stimulation can induce autophagy, an important cell lysosomal pathway responding to immune stimulation and starvation, without any biochemical treatment. Two different types of laser stimulations are found to be capable of activating autophagy: continuous scanning by continuous-wave visible lasers and a short-time flash of femtosecond laser irradiation. The autophagy generation is independent from wavelength, power, and scanning duration of the visible lasers. In contrast, the power of femtosecond laser is very critical to autophagy because the multiphoton excited Ca2+ dominates autophagy signaling. In general, we show here the different mechanisms of autophagy generation by such laser stimulation, which correspond to confocal microscopy and cell surgery, respectively. Those results can help further understanding of photodamage and autophagy signaling.

  15. Active skin cooling in conjunction with laser dermatologic surgery.

    PubMed

    Nelson, J S; Majaron, B; Kelly, K M

    2000-12-01

    The clinical objective in the laser treatment of patients with specific dermatoses is to maximize thermal damage to the target chromophore while minimizing injury to the normal skin. Unfortunately, for some lesions, the threshold incident light dosage for epidermal injury can be very close to the threshold for permanent removal of the target chromophore, thus precluding the use of higher light dosages. An important method of overcoming the aforementioned problem is to selectively cool the most superficial layers of the skin. Although melanin absorption will result in heat production during laser exposure, cooling the epidermis can prevent its temperature elevation from exceeding the threshold for thermal injury. Spatially selective cooling can be achieved by active cooling using a cryogen spray or cold sapphire contact handpieces. These devices promote rapid and spatially selective epidermal cooling to low temperatures without affecting the target chromophore temperature before the laser pulse is delivered. Cooling has become an Integral part in the emerging discipline of laser dermatologic surgery. Attend almost any academic dermatology conference and you are likely to find many lectures that relate to cooling during dermatologic laser surgery. Although cooling in conjunction with laser therapy has become the clinical standard for many laser procedures, considerable controversy surrounds this methodology. We present herewith an overview of currently used techniques for active cooling of human skin and explore their advantages and disadvantages in relationship to specific dermatoses amenable to laser therapy.

  16. [Effect of vernalization and red light illumination of seedlings of bread wheat (Triticum aestivum L.) on the temperature profile of the cAMP phosphodiesterase activity].

    PubMed

    Fedenko, E P; Koksharova, T A; Agamalova, S R; Beliaeva, E V

    2004-01-01

    Phenotypic manifestations of Vrn (vernalization) and Ppd (photoperiodism) genes responsible for transition of bread wheat Triticum aestivum L. to generative growth (flowering) are mutually related. Since the mechanism of phytochrome-induced photoperiodism involves the enzymes of cyclic adenosine monophosphate metabolism and phosphodiesterase in particular, we tested involvement of phosphodiesterase in the process of winter wheat vernalization and formation of flowering competence in alternate wheat requiring a long day but no vernalization for the transition to flowering. We studied temperature dependence of phosphodiesterase activity in vernalized and unvernalized winter wheat on the one hand and in etiolated and red light illuminated seedlings of alternate wheat on the other hand. Short-term experiments demonstrated that vernalization and red light illumination are similar to long day by the effect on the long-day plants. Both influences induced a pronounced inversion of the temperature profile of phosphodiesterase activity in the 28-45 degrees C range. We propose that phosphodiesterase is involved in vernalization processes and can serve as a sensor of low temperature in winter wheat. Changed temperature profile is a radical control mechanism of phosphodiesterase activity in response to the influences (red light and vernalizing temperatures) responsible for competence of various bread wheat forms for generative growth.

  17. Low intensity laser therapy speeds wound healing in hemophilia by enhancing platelet procoagulant activity.

    PubMed

    Hoffman, Maureane; Monroe, Dougald M

    2012-01-01

    Our group has previously shown that cutaneous wound healing is delayed and histologically abnormal in a mouse model of hemophilia. Hemostasis is not only required to stop bleeding at the time of wounding, but also produces bioactive substances that promote appropriate inflammatory and proliferative responses during healing. Low intensity laser therapy (LILT) has been reported to enhance impaired wound healing in a variety of animal and human studies. The current studies were conducted to test the hypothesis that LILT can improve healing in a hemophilia B mouse model. Three daily treatments with 12 J/sq cm of 650 nm laser illumination reduced the time to closure of a 3-mm cutaneous punch biopsy wound in the hemophilic mice. All wounds were closed at 13 days in the sham-treated hemophilic mice, compared with 10 days in the LILT-treated hemophilic mice, and 9 days in wild-type mice. While LILT can speed healing by enhancing proliferation of cutaneous cells, we found that an additional mechanism likely contributes to the efficacy of LILT in the hemophilic mice. LILT enhanced the mechanical rigidity and platelet activity of clots formed from human platelet-rich plasma. Illumination of isolated platelets increased the mitochondrial membrane potential and enhanced binding of coagulation factors to the surface of activated platelets. Thus, while LILT can directly promote proliferative responses during healing, it also appears to enhance hemostasis in an animal model with impaired coagulation. These data suggest that trials of LILT as an adjunct to the usual hemostatic therapies in hemophilia are warranted.

  18. Effect of illumination on the content of melatonin, phenolic compounds, and antioxidant activity during germination of lentils (Lens culinaris L.) and kidney beans (Phaseolus vulgaris L.).

    PubMed

    Aguilera, Yolanda; Liébana, Rosa; Herrera, Teresa; Rebollo-Hernanz, Miguel; Sanchez-Puelles, Carlos; Benítez, Vanesa; Martín-Cabrejas, María A

    2014-11-05

    This study reports the effects of two different illumination conditions during germination (12 h light/12 h dark vs 24 h dark) in lentils (Lens culinaris L.) and kidney beans (Phaseolus vulgaris L.) on the content of melatonin and phenolic compounds, as well as the antioxidant activity. Germination led to relative increase in melatonin content and significant antioxidant activity, while the content of phenolic compounds decreased. The highest melatonin content was obtained after 6 days of germination under 24 h dark for both legumes. These germinated legume seeds with improved levels of melatonin might play a protective role against free radicals. Thus, considering the potent antioxidant activity of melatonin, these sprouts can be consumed as direct foods and be offered as preventive food strategies in combating chronic diseases through the diet.

  19. Illumination Under Trees

    SciTech Connect

    Max, N

    2002-08-19

    This paper is a survey of the author's work on illumination and shadows under trees, including the effects of sky illumination, sun penumbras, scattering in a misty atmosphere below the trees, and multiple scattering and transmission between leaves. It also describes a hierarchical image-based rendering method for trees.

  20. Grouping Illumination Frameworks

    ERIC Educational Resources Information Center

    Zdravkovic, Suncica; Economou, Elias; Gilchrist, Alan

    2012-01-01

    According to Koffka (1935), the lightness of a target surface is determined by the relationship between the target and the illumination frame of reference to which it belongs. However, each scene contains numerous illumination frames, and judging each one separately would lead to an enormous amount of computing. Grouping those frames that are in…

  1. Substrate-emitting semiconductor laser with a trapezoidal active region

    SciTech Connect

    Dikareva, N V; Nekorkin, S M; Karzanova, M V; Zvonkov, B N; Aleshkin, V Ya; Dubinov, A A; Afonenko, A A

    2014-04-28

    Semiconductor lasers with a narrow (∼2°) directional pattern in the planes both parallel and perpendicular to the p–n junction are fabricated. To achieve a low radiation divergence in the p–n junction plane, the active region in this plane was designed in the form of a trapezium. The narrow directional pattern in the plane perpendicular to the p–n junction was ensured by the use of a leaky mode, through which more than 90% of laser power was coupled out. (lasers)

  2. Post-illumination activity of SnO2 nanoparticle-decorated Cu2O nanocubes by H2O2 production in dark from photocatalytic “memory”

    PubMed Central

    Liu, Lingmei; Sun, Wuzhu; Yang, Weiyi; Li, Qi; Shang, Jian Ku

    2016-01-01

    Most photocatalysts only function under illumination, while many potential applications require continuous activities in dark. Thus, novel photocatalysts should be developed, which could store part of their photoactivity in “memory” under illumination and then be active from this “memory” after the illumination is turned off for an extended period of time. Here a novel composite photocatalyst of SnO2 nanoparticle-decorated Cu2O nanocubes is developed. Their large conduction band potential difference and the inner electrostatic field formed in the p-n heterojunction provide a strong driving force for photogenerated electrons to move from Cu2O to SnO2 under visible light illumination, which could then be released to react with O2 in dark to produce H2O2 for its post-illumination activity. This work demonstrates that the selection of decoration components for photocatalysts with the post-illumination photocatalytic “memory” could be largely expanded to semiconductors with conduction band potentials less positive than the two-electron reduction potential of O2. PMID:26879006

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  4. Solid state active/passive night vision imager using continuous-wave laser diodes and silicon focal plane arrays

    NASA Astrophysics Data System (ADS)

    Vollmerhausen, Richard H.

    2013-04-01

    Passive imaging offers covertness and low power, while active imaging provides longer range target acquisition without the need for natural or external illumination. This paper describes a focal plane array (FPA) concept that has the low noise needed for state-of-the-art passive imaging and the high-speed gating needed for active imaging. The FPA is used with highly efficient but low-peak-power laser diodes to create a night vision imager that has the size, weight, and power attributes suitable for man-portable applications. Video output is provided in both the active and passive modes. In addition, the active mode is Class 1 eye safe and is not visible to the naked eye or to night vision goggles.

  5. Activity of respiratory system during laser irradiation of brain structures

    NASA Astrophysics Data System (ADS)

    Merkulova, N. A.; Sergeyeva, L. I.

    1984-06-01

    The performance of one of the principal links of the respiratory system, the respiratory center, was studied as a function of the exposure of the medulla oblongata and the sensomotor zone of the cerebral hemisphere cortex to low level laser irradiation in the red wavelength of the spectrum. Experiments were done on white rats under barbital anesthesia. Under such conditions a substantial effect was observed on the activity of the respiratory center. Laser light may display activating or inhibitory influences, in some cases the bilateral symmetry of the activity of the respiratory center is affected indicating deep changes in the integrative mechanism of the functioning of the right and left sides of the hemispheres. The laser beam effect depends on many factors: specific light properties, duration of the exposure, repetition of exposures, initial functional state of the CNS, etc.

  6. Laser Initiated Ordnance (LIO) activities in NASA

    NASA Technical Reports Server (NTRS)

    Schulze, Norman R.

    1994-01-01

    Laser initiated ordnance appears to offer the advantages of greater reliability, enhanced safety, lighter, less costly products, and improvements in spacecraft system designs which can lead to higher operational efficiency. But the lack of flight demonstrations has prevented the application of this new technology into new programs. Hence, a three-phase technology program was initiated by NASA to provide flight proof of their technical and programmatic feasibility: flight demonstration aboard an unmanned commercial vehicle (Pegasus), use as a Space Shuttle payload, and the most demanding of applications, namely, solid rocket motor vehicle ignition and flight termination. The programs investigate, via flight demonstrations the use of fully solid state laser diode systems to reduce potential hazards imposed by stray electrical signals. Inadvertent ignition has proven to cause serious problems. While the current electromechanical have been made safe, the result has been complex systems. Now is the time to take advantage of this new technology to further enhance safety and reliability of spacecraft systems. Two of the three phases are underway; an announcement of opportunity for the third, a sounding rocket flight demonstration, was made at the workshop.

  7. Environmental stability of actively mode locked fibre lasers

    NASA Astrophysics Data System (ADS)

    Hill, Calum H.; Lee, Stephen T.; Reid, Derryck T.; Baili, Ghaya; Davies, John

    2016-10-01

    Lasers developed for defence related applications typically encounter issues with reliability and meeting desired specification when taken from the lab to the product line. In particular the harsh environmental conditions a laser has to endure can lead to difficulties. This paper examines a specific class of laser, namely actively mode-locked fibre lasers (AMLFLs), and discusses the impact of environmental perturbations. Theoretical and experimental results have assisted in developing techniques to improve the stability of a mode-locked pulse train for continuous operation. Many of the lessons learned in this research are applicable to a much broader category of lasers. The AMLFL consists of a fibre ring cavity containing a semiconductor optical amplifier (SOA), an isolator, an output coupler, a circulator, a bandpass filter and a modulator. The laser produces a train of 6-ps pulses at 800 nm with a repetition rate in the GHz regime and a low-noise profile. This performance is realisable in a laboratory environment. However, even small changes in temperature on the order of 0.1 °C can cause a collapse of mode-locked dynamics such that the required stability cannot be achieved without suitable feedback. Investigations into the root causes of this failure were performed by changing the temperature of components that constitute the laser resonator and observing their properties. Several different feedback mechanisms have been investigated to improve laser stability in an environment with dynamic temperature changes. Active cavity length control will be discussed along with DC bias control of the Mach-Zehnder modulator (MZM).

  8. Microscope illumination systems for 157 nm

    NASA Astrophysics Data System (ADS)

    Pesch, Alexander; Uhlendorf, Kristina; Deparnay, Arnaud; Erdmann, Lars; Kuschnerus, Peter; Engel, Thomas; Brunner, Robert

    2003-05-01

    The image quality of an inspection microscope depends strongly on the performance of the illumination system. Especially in the case of laser-based illumination it is necessary to transform the original beam profile into a homogeneous light spot with a flat top field distribution. Simultaneously, speckles caused by the coherence of the laser have to be reduced. Here we discuss different ways to homogenize the multi mode beam profile of a pulsed compact 157 nm excimer laser. A variety of setups, combining dynamic acting diffusers, microlens arrays and primary lenses were realized and characterized in several geometrical arrangements. The homogenizers were evaluated and characterized especially with respect to the statistical behavior on the integrated pulse number.

  9. Lasers.

    ERIC Educational Resources Information Center

    Schewe, Phillip F.

    1981-01-01

    Examines the nature of laser light. Topics include: (1) production and characteristics of laser light; (2) nine types of lasers; (3) five laser techniques including holography; (4) laser spectroscopy; and (5) laser fusion and other applications. (SK)

  10. Exploring a new phenomenon in the bactericidal response of TiO2 thin films by Fe doping: Exerting the antimicrobial activity even after stoppage of illumination

    NASA Astrophysics Data System (ADS)

    Naghibi, Sanaz; Vahed, Shohreh; Torabi, Omid; Jamshidi, Amin; Golabgir, Mohammad Hossein

    2015-02-01

    Antibacterial properties of Fe-doped TiO2 thin films prepared on glass by the sol-gel hot-dipping technique were studied. The films were characterized by X-ray diffraction, field emission scanning electron microscopy, scanning probe microscopy and X-ray photoelectron spectroscopy. The photocatalytic activities were evaluated by measuring the decomposition rate of methylene blue under ultra violet and visible light. The antibacterial properties of the coatings were investigated against Escherichia coli, Staphylococcus aureus, Saccharomyces cerevisia and Aspergillus niger. The principle of incubation methods was also discussed. The results indicated that Fe doping of thin films eventuated in high antibacterial properties under visible light and this performance remained even after stoppage of illumination. This article tries to provide some explanation for this fact.

  11. Active Laser Ranging Along with Lasercom: Field Emulation

    NASA Technical Reports Server (NTRS)

    Chen, Y.; Birnbaum, K.; Hemmati, H.

    2011-01-01

    In summary, this work has: (1) Demonstrated the real-time active laser ranging using a method applicable to interplanetary distances (2) Sub-millimeter ranging accuracy has been achieved with the systems built from off-the-shelf commercial components, demonstrating the robustness of the scheme (3) The experimental results indicate that active laser ranging can be implemented for interplanetary distances to meet the goal of 1mm ranging accuracy, including the effects of the Earth's atmosphere (4) Paves the way for advances in the study of fundamental physics and solar system dynamics.

  12. Chemical Bond Activation Observed with an X-ray Laser.

    PubMed

    Beye, Martin; Öberg, Henrik; Xin, Hongliang; Dakovski, Georgi L; Dell'Angela, Martina; Föhlisch, Alexander; Gladh, Jörgen; Hantschmann, Markus; Hieke, Florian; Kaya, Sarp; Kühn, Danilo; LaRue, Jerry; Mercurio, Giuseppe; Minitti, Michael P; Mitra, Ankush; Moeller, Stefan P; Ng, May Ling; Nilsson, Anders; Nordlund, Dennis; Nørskov, Jens; Öström, Henrik; Ogasawara, Hirohito; Persson, Mats; Schlotter, William F; Sellberg, Jonas A; Wolf, Martin; Abild-Pedersen, Frank; Pettersson, Lars G M; Wurth, Wilfried

    2016-09-15

    The concept of bonding and antibonding orbitals is fundamental in chemistry. The population of those orbitals and the energetic difference between the two reflect the strength of the bonding interaction. Weakening the bond is expected to reduce this energetic splitting, but the transient character of bond-activation has so far prohibited direct experimental access. Here we apply time-resolved soft X-ray spectroscopy at a free-electron laser to directly observe the decreased bonding-antibonding splitting following bond-activation using an ultrashort optical laser pulse.

  13. Shackleton Crater Illumination

    NASA Video Gallery

    Simulated illumination conditions near the lunar South Pole. The 30km x 30km region highlights the Shackleton crater. The movie runs for 28 days, centered on the LCROSS impact date on October 9th, ...

  14. Wood's lamp illumination (image)

    MedlinePlus

    A Wood's lamp emits ultraviolet light and can be a diagnostic aid in determining if someone has a fungal ... is an infection on the area where the Wood's lamp is illuminating, the area will fluoresce. Normally ...

  15. Illuminating black holes

    NASA Astrophysics Data System (ADS)

    Barr, Ian A.; Bull, Anne; O'Brien, Eileen; Drillsma-Milgrom, Katy A.; Milgrom, Lionel R.

    2016-07-01

    Two-dimensional shadows formed by illuminating vortices are shown to be visually analogous to the gravitational action of black holes on light and surrounding matter. They could be useful teaching aids demonstrating some of the consequences of general relativity.

  16. Effects of Near-Infrared Laser on Neural Cell Activity

    NASA Astrophysics Data System (ADS)

    Mochizuki-Oda, Noriko; Kataoka, Yosky; Yamada, Hisao; Awazu, Kunio

    2004-08-01

    Near-infrared laser has been used to relieve patients from various kinds of pain caused by postherpetic neuralgesia, myofascial dysfunction, surgical and traumatic wound, cancer, and rheumatoid arthritis. Clinically, He-Ne (λ=632.8 nm, 780 nm) and Ga-Al-As (805 ± 25 nm) lasers are used to irradiate trigger points or nerve ganglion. However the precise mechanisms of such biological actions of the laser have not yet been resolved. Since laser therapy is often effective to suppress the pain caused by hyperactive excitation of sensory neurons, interactions with laser light and neural cells are suggested. As neural excitation requires large amount of energy liberated from adenosine triphosphate (ATP), we examined the effect of 830-nm laser irradiation on the energy metabolism of the rat central nervous system and isolated mitochondria from brain. The diode laser was applied for 15 min with irradiance of 4.8 W/cm2 on a 2 mm-diameter spot at the brain surface. Tissue ATP content of the irradiated area in the cerebral cortex was 19 % higher than that of the non-treated area (opposite side of the cortex), whereas the ADP content showed no significant difference. Irradiation at another wavelength (652 nm) had no effect on either ATP or ADP contents. The temperature of the brain tissue was increased 4.5 - 5.0 °C during the irradiation of both 830-nm and 652-nm laser light. Direct irradiation of the mitochondrial suspension did not show any wavelength-dependent acceleration of respiration rate nor ATP synthesis. These results suggest that the increase in tissue ATP content did not result from the thermal effect, but from specific effect of the laser operated at 830 nm. Electrophysiological studies showed the hyperpolarization of membrane potential of isolated neurons and decrease in membrane resistance with irradiation of the laser, suggesting an activation of potassium channels. Intracellular ATP is reported to regulate some kinds of potassium channels. Possible mechanisms

  17. Overview of the laser activities at Rheinmetall Waffe Munition

    NASA Astrophysics Data System (ADS)

    Ludewigt, Klaus; Riesbeck, Thomas; Schünemann, B.; Graf, A.; Jung, Markus; Schreiber, Th.; Eberhardt, Ramona; Tünnermann, A.

    2012-11-01

    The paper will give an overview over the laser weapon activities at RWM (Rheinmetall Waffe Munition) over the last years. Starting from the actual scenarios for laser weapon applications as: CRAM (Counter Rocket Artillery Mortar), Air Defence and UXO (unexploded ordnance) clearing. The basic requirements of a future laser weapon as beam diameter, beam quality, tracking capability, adaptive optics were deduced. For the UXO scenario a mobile directed energy laser demonstrator for humanitarian mine and UXO clearing based on fiber lasers is presented. Based on the parameters the system concept including the cooling system, power supply and the integration into the armoured vehicle TM 170 are explained. The contribution show first experiments of UXO and IED clearing. Different technical approaches to achieve laser power in the 100 kW regime combined with very good beam quality are discussed to fulfil the requirements of the CRAM and Air Defence scenario. Spectral coupling and the beam superimposing both are performed by Rheinmetall Waffe Munition. At the spectral coupling the basic technology parameters for the fiber laser and the dielectric grating as the latest results were put into context with the power levels reached at other groups. For the beam super imposing technology the basic experiments regarding the tracking capability and compensation of the atmosphere on the test range at Unterlüß will be explained. A generic 10 kW Laser Weapon Demonstrator based on 2 Laser Weapon Modules (LWM) from RWM each 5 kW fiber Laser with beam forming and tracking integrate by the team of RWM and RAD (Rheinmetall Air Defense) into a Ground based Air Defend system consisting of Skyguard and Millenium turret are presented. The flight path of the UAV within the valley of the life firing range at Ochsenboden Switzerland is shown. Selected results of the successful tests against UAV's are presented. It shows the capability of the generic 10 kW Laser Weapon Demonstrator to track and

  18. Illumination in diverse codimensions

    NASA Technical Reports Server (NTRS)

    Banks, David C.

    1994-01-01

    This paper derives a model of diffuse and specular illumination in arbitrarily large dimensions, based on a few characteristics of material and light in three-space. It then describes how to adjust for the anomaly of excess brightness in large codimensions. If a surface is grooved or furry, it can be illuminated with a hybrid model that incorporates both the one dimensional geometry (the grooves or fur) and the two dimensional geometry (the surface).

  19. Excited states in the active media of oxygen - iodine lasers

    SciTech Connect

    Azyazov, V N

    2009-11-30

    A review of investigations of kinetic processes in active media oxygen - iodine lasers (OILs) performed in the last decade is presented. The mechanisms of pumping and quenching of electronically and vibrationally excited O{sub 2} and I{sub 2} molecules are considered, and dissociation mechanisms of I{sub 2} in the active medium of the OIL are analysed. The values of kinetic constants of processes proceeding in the active media of OILs are recommended. (review)

  20. In vitro perforation of human epithelial carcinoma cell with antibody-conjugated biodegradable microspheres illuminated by a single 80 femtosecond near-infrared laser pulse.

    PubMed

    Terakawa, Mitsuhiro; Tsunoi, Yasuyuki; Mitsuhashi, Tatsuki

    2012-01-01

    Pulsed laser interaction with small metallic and dielectric particles has been receiving attention as a method of drug delivery to many cells. However, most of the particles are attended by many risks, which are mainly dependent upon particle size. Unlike other widely used particles, biodegradable particles have advantages of being broken down and eliminated by innate metabolic processes. In this paper, the perforation of cell membrane by a focused spot with transparent biodegradable microspheres excited by a single 800 nm, 80 fs laser pulse is demonstrated. A polylactic acid (PLA) sphere, a biodegradable polymer, was used. Fluorescein isothiocyanate (FITC)-dextran and short interfering RNA were delivered into many human epithelial carcinoma cells (A431 cells) by applying a single 80 fs laser pulse in the presence of antibody-conjugated PLA microspheres. The focused intensity was also simulated by the three-dimensional finite-difference time-domain method. Perforation by biodegradable spheres compared with other particles has the potential to be a much safer phototherapy and drug delivery method for patients. The present method can open a new avenue, which is considered an efficient adherent for the selective perforation of cells which express the specific antigen on the cell membrane.

  1. Optics, illumination, and image sensing for machine vision III; Proceedings of the Meeting, Cambridge, MA, Nov. 8, 9, 1988

    SciTech Connect

    Svetkoff, D.J.

    1989-01-01

    Various papers on optics, illumination, and image sensing for machine vision are presented. Some of the optics discussed include: illumination and imaging of moving objects, strobe illumination systems for machine vision, optical collision timer, new electrooptical coordinate measurement system, flexible and piezoresistive touch sensing array, selection of cameras for machine vision, custom fixed-focal length versus zoom lenses, performance of optimal phase-only filters, minimum variance SDF design using adaptive algorithms, Ho-Kashyap associative processors, component spaces for invariant pattern recognition, grid labeling using a marked grid, illumination-based model of stochastic textures, color-encoded moire contouring, noise measurement and suppression in active 3-D laser-based imaging systems, structural stereo matching of Laplacian-of-Gaussian contour segments for 3D perception, earth surface recovery from remotely sensed images, and shape from Lambertian photometric flow fields.

  2. Infrared Beam Induced Contrast With Double Illumination

    NASA Astrophysics Data System (ADS)

    Castaldini, A.; Cavallini, A.

    1988-07-01

    Over the last few years scanning optical microscopy (SOM) has been largely developed as a tool to explore the physical properties of materials. In particular the optical beam induced current (OBIC) mode of the SOM has been used to map the electronic properties of semiconducting devices. A new type of scanning microscopy method, as well as some results obtained by it, will be reported in this paper. Though similar, to a certain extent, to the standard scanning optical microscopy, this new investigation technique, from now on refered to as infrared beam induced contrast (IRBIC), differs from it in substance. The chopped light from a quartz halogen lamp is focused by a conventional microscope rearranged on the specimen surface, and a pin-hole is positioned so as to reduce the probe size (not the resolving power) to 1.5um. The resulting beam power density is of the order of 1mW*cm-2. Such a low power density presents some disadvantages in comparison with the traditional laser sources, but, on the other hand, it allows a very high sensitivity in the investigation of the defect electrical activity. With this experimental set-up the specimen front surface is probed with band-gap radiation. Its back surface is illuminated by continuous light in the infrared, coming through a monochromator from a glow-bar. The radiation wavelength can be selected continuously so as the photon energy ranges over the whole valence-to-conduction energy gap. When the specimen is probed, the photoinduced carriers are separated by the built-in field due to the depletion zone of a p-n junction or a Schottky barrier, and the photocurrent is amplified by the lock-in technique. The application of a back-surface radiation of less than the band-gap energy modifies, in some way, the photoconductive response to the band-gap probe since the secondary illumination changes the occupancy of the traps in the forbidden gap active in the photoconductive process. This phenomenon, known as "quenching" of

  3. Scaling of strontium-vapor laser active volume

    NASA Astrophysics Data System (ADS)

    Soldatov, A. N.; Polunin, Yu. P.

    2008-01-01

    Variations in the energy performance of a self-terminating Sr-vapor laser (SrVL) are examined. The active laser volume is varied between 20 and 650 cm 3. A linear relation is revealed between the average power delivered by the SrVL and its active volume. The SrVL efficiency is found to increase with active volume and to be comparable with that of a copper-vapor laser for an active volume V = 650 cm 3 (0.45 %). As the volume is increased, the total lasing pulse duration increases from 30 to 120 ns. The beam divergence problems associated with the use of a Fabry-Perot cavity or an unstable resonator of the telescopic type are discussed. A total average power of 13.5 W is obtained from V = 650 cm 3 at a lasing PRR F = 19 kHz. The output power generated at different laser wavelengths is as follows: 10.4 W at λ = 6.456 μm, 2.6 W at λ = 3 μm, and 0.5 W at λ = 1 μm. The wavelength dependence of the lasing pulse duration is considered.

  4. Tetravalent chromium (Cr(4+)) as laser-active ion for tunable solid-state lasers

    NASA Technical Reports Server (NTRS)

    Seas, A.; Petricevic, V.; Alfano, Robert R.

    1992-01-01

    Generation of femtosecond pulses from a continuous-wave mode-locked chromium-doped forsterite (Cr(4+):Mg2SiO4) laser has been accomplished. The forsterite laser was actively mode-locked using an acousto-optic modulator operating at 78 MHz with two Brewster high-dispersion glass prisms for intra-cavity chirp compensation. Transform-limited sub-100-fs pulses were routinely generated in the TEM(sub 00) mode with 85 mW of continuous power (with 1 percent output coupler), tunable over 1230-1280 nm. The shortest pulses of 60-fs pulsewidth were measured.

  5. Toward a Descriptive Science of Teaching: How the TDOP Illuminates the Multidimensional Nature of Active Learning in Postsecondary Classrooms

    ERIC Educational Resources Information Center

    Hora, Matthew T.

    2015-01-01

    Detailed accounts of teaching can shed light on the nature and prevalence of active learning, yet common approaches reduce teaching to unidimensional descriptors or binary categorizations. In this paper, I use the instructional systems-of-practice framework and the Teaching Dimensions Observation Protocol (TDOP) to advance an approach to thinking…

  6. Illumination from light-emitting diodes (LEDs) disrupts pathological cytokines expression and activates relevant signal pathways in primary human retinal pigment epithelial cells.

    PubMed

    Shen, Ye; Xie, Chen; Gu, Yangshun; Li, Xiuyi; Tong, Jianping

    2016-04-01

    Age-related macular degeneration (AMD) is the leading cause of blindness in the aged people. The latest systemic review of epidemiological investigations revealed that excessive light exposure increases the risk of AMD. With the drastically increasing use of high-energy light-emitting diodes (LEDs) light in our domestic environment nowadays, it is supposed to pose a potential oxidative threat to ocular health. Retinal pigment epithelium (RPE) is the major ocular source of pathological cytokines, which regulate local inflammation and angiogenesis. We hypothesized that high-energy LED light might disrupt the pathological cytokine expression of retinal pigment epithelium (RPE), contributing to the pathogenesis of AMD. Primary human RPE cells were isolated from eyecups of normal eye donors and seeded into plate wells for growing to confluence. Two widely used multichromatic white light-emitting diodes (LEDs) with correlated color temperatures (CCTs) of 2954 and 7378 K were used in this experiment. The confluent primary RPE cells were under white LEDs light exposure until 24 h. VEGF-A, IL-6, IL-8 and MCP-1 proteins and mRNAs were measured using an ELISA kit and RT-PCR, respectively. Activation of mitogen-activated protein kinases (MAPKs), Akt, Janus kinase (JAK)2 and Nuclear factor (NF)-κB signal pathways after LEDs illumination were evaluated by western blotting analysis. The level of reactive oxygen species (ROS) using chloromethyl- 2',7'-dichlorodihydrofluorescein diacetate. Inhibitors of relevant signal pathways and anti-oxidants were added to the primary RPE cells before LEDs illumination to evaluate their biological functions. We found that 7378 K light, but not 2954 K upregulated the VEGF-A, IL-6, IL-8 and downregulated MCP-1 proteins and mRNAs levels in a time-dependent manner. In parallel, initial activation of MAPKs and NF-κB signal pathways were also observed after 7378 K light exposure. Mechanistically, antioxidants for eliminating reactive oxygen

  7. Active media for tunable lasers based on hybrid polymers

    SciTech Connect

    Kopylova, T N; Eremina, N S; Vaitulevich, E A; Samsonova, L G; Maier, G V; Tel'minov, E N; Solodova, T A; Solodov, A M

    2008-02-28

    The lasing properties of rhodamine 6G (chloride and perchlorate) in synthesised hybrid polymers based on an organic polymer (methyl methacrylate with hydroxyethyl methacrylate) and an inorganic precursor (tetraethoxysilane) are studied. Rhodamine 6G samples were transversely pumped by the second harmonic of a Nd{sup 3+}:YAG laser. It is found that the active media based on hybrid polymers have a considerably longer service life compared to the active media based on organic polymers. The structure of the hybrid polymer is studied by the methods of IR Fourier spectroscopy, X-ray diffraction, and thermogravimetry. It is shown that the longer service life of hybrid-polymer active media is explained by the formation of an inorganic nanostructure network in them, which improves the thermooptic properties of the material and reduces the efficiency of thermal decomposition of active molecules. (lasers. amplifiers)

  8. Bright field illumination system

    NASA Technical Reports Server (NTRS)

    Huber, Edward D. (Inventor)

    1998-01-01

    A Bright Field Illumination system for inspecting a range of characteristically different kinds of defects, depressions, and ridges in a selected material surface. The system has an illumination source placed near a first focus of an elliptical reflector. In addition, a camera facing the inspected area is placed near the illumination source and the first focus. The second focus of the elliptical reflector is located at a distance approximately twice the elliptical reflector's distance above the inspected surface. The elliptical reflector directs the light from the source onto the inspected surface. Due to the shape of the elliptical reflector, light that is specularly reflected from the inspected surface is directed into the camera is which located at the position of the reflected second focus of the ellipse. This system creates a brightly lighted background field against which damage sites appear as high contrast dark objects which can be easily detected by a person or an automated inspection system. In addition, the Bright Field Illumination system and method can be used in combination with a vision inspection system providing for multiplexed illumination and data handling of multiple kinds of surface characteristics including abrupt and gradual surface variations and differences between measured characteristics of different kinds and prior instruments.

  9. Preparation, characterization of the Ta-doped ZnO nanoparticles and their photocatalytic activity under visible-light illumination

    SciTech Connect

    Kong Jizhou; Li Aidong; Zhai Haifa; Gong Youpin; Li Hui; Wu Di

    2009-08-15

    This paper describes a novel catalyst of the Ta-doped ZnO nanocrystals prepared by a modified polymerizable complex method using the water-soluble tantalum precursor as the sources of Ta. The catalysts were characterized by means of various analytical techniques as a function of Ta content (x=0-4 mol%) systematically. A remarkable advantage of the results was confirmed that dopant Ta enhanced the visible-light absorption of ZnO and the low-solubility tantalum doping could restrain the growth of crystal and minish the particle size. The relationship between the physicochemical property and the photocatalytic performance was discussed, and it was found that the photocatalytic activity in the photochemical degradation of methylene blue under visible-light irradiation (lambda>=420 nm) was dependent on the contents of the dopant, which could affect the particle size, concentration of surface hydroxyl groups and active hydrogen-related defect sites, and the visible-light absorption. The highest photocatalytic activity was obtained for the 1.0 mol% Ta-doped ZnO sample. - Graphical abstract: The addition of the tantalum into ZnO prepared by a modified polymerizable complex method not only restrains the growth of crystal, minish the particle size, but also changes the nanocrystal morphology.

  10. Active imaging system with Faraday filter

    DOEpatents

    Snyder, James J.

    1993-01-01

    An active imaging system has a low to medium powered laser transmitter and receiver wherein the receiver includes a Faraday filter with an ultranarrow optical bandpass and a bare (nonintensified) CCD camera. The laser is locked in the vicinity of the passband of the Faraday filter. The system has high sensitivity to the laser illumination while eliminating solar background.

  11. Active imaging system with Faraday filter

    DOEpatents

    Snyder, J.J.

    1993-04-13

    An active imaging system has a low to medium powered laser transmitter and receiver wherein the receiver includes a Faraday filter with an ultranarrow optical bandpass and a bare (nonintensified) CCD camera. The laser is locked in the vicinity of the passband of the Faraday filter. The system has high sensitivity to the laser illumination while eliminating solar background.

  12. Laser active thermography for non-destructive testing

    NASA Astrophysics Data System (ADS)

    Semerok, A.; Grisolia, C.; Fomichev, S. V.; Thro, P.-Y.

    2013-11-01

    Thermography methods have found their applications in different fields of human activity. The non-destructive feature of these methods along with the additional advantage by automated remote control and tests of nuclear installations without personnel attendance in the contaminated zone are of particular interest. Laser active pyrometry and laser lock-in thermography for in situ non-destructive characterization of micrometric layers on graphite substrates from European tokamaks were under extensive experimental and theoretical studies in CEA (France). The studies were aimed to obtain layer characterization with cross-checking the layer thermal contact coefficients determined by active laser pyrometry and lock-in thermography. The experimental installation comprised a Nd-YAG pulsed repetition rate laser (1 Hz - 10 kHz repetition rate frequency, homogeneous spot) and a home-made pyrometer system based on two pyrometers for the temperature measurements in 500 - 2600 K range. For both methods, the layer characterization was provided by the best fit of the experimental results and simulations. The layer thermal contact coefficients determined by both methods were quite comparable. Though there was no gain in the measurements accuracy, lock-in measurements have proved their advantage as being much more rapid. The obtained experimental and theoretical results are presented. Some practical applications and possible improvements of the methods are discussed.

  13. Photodecolorisation of melanoidins in vinasse with illuminated TiO2-ZnO/activated carbon composite.

    PubMed

    Otieno, Benton O; Apollo, Seth O; Naidoo, Bobby E; Ochieng, Aoyi

    2017-03-10

    A hybrid photo-catalyst, TiO2-ZnO, was synthesized by immobilizing ZnO on commercial TiO2 (aeroxide P25). Activated carbon (AC) was subsequently used to support the hybrid, thus forming a TiO2-ZnO/AC composite catalyst. Fourier transform infrared (FTIR) analysis and scanning electron microscopy integrated with energy-dispersive X-ray spectroscopy (SEM-EDX) investigations revealed successful catalyst synthesis. Optical properties of the hybrid determined from photoluminescence (PL) and Ultraviolet-visible (UV-vis) spectroscopy confirmed a restrained recombination of electron-hole pairs and reduced energy band gap due to a successful heterojunction formation. The prepared catalysts were used to photodecolorise vinasse in a 12-W UVC batch photoreactor. TiO2-ZnO had improved photocatalytic activity compared with TiO2 and ZnO separately. On supporting the hybrid onto AC, both adsorption and photocatalytic activities were further enhanced with improved overall color removal of 86% from 68%. Photodecolorisation followed the pseudo-first-order reaction model with the rate constant ([Formula: see text]) observed decreasing from 0.0701 to 0.0436 min(-1) on increasing the initial concentration from 5,000 to 14,000 ppm. The UV process was found to be 33-fold less energy intensive for color reduction as compared to total organic carbon (TOC) reduction. Formation of nitrates during the photodecolorisation process was attributed to the mineralization of nitrogen heteroatoms in the color-causing melanoidin compounds.

  14. Laser activated nanothermolysis of leukemia cells monitored by photothermal microscopy

    NASA Astrophysics Data System (ADS)

    Lapotko, Dmitri; Lukianova, Ekaterina; Shnip, Alexander; Zheltov, George; Potapnev, Michail; Savitsky, Valeriy; Klimovich, Olga; Oraevsky, Alexander

    2005-04-01

    We are developing new diagnostic and therapeutic technologies for leukemia based on selective targeting of leukemia cells with gold nanoparticles and thermomechanical destruction of the tumor cells with laser-induced microbubbles. Clusters of spherical gold nanoparticles that have strong optical absorption of laser pulses at 532 nm served as nucleation sites of vapor microbubbles. The nanoparticles were targeted selectively to leukemia cells using leukemia-specific surface receptors and a set of two monoclonal antibodies. Application of a primary myeloid-specific antibody to tumor cells followed by targeting the cells with 30-nm nanoparticles conjugated with a secondary antibody (IgG) resulted in formation of nanoparticulate clusters due to aggregation of IgGs. Formation of clusters resulted in substantial decrease of the damage threshold for target cells. The results encourage development of Laser Activated Nanothermolysis as a Cell Elimination Therapy (LANCET) for leukemia. The proposed technology can be applied separately or in combination with chemotherapy for killing leukemia cells without damage to other blood cells. Potential applications include initial reduction of concentration of leukemia cells in blood prior to chemotherapy and treatment of residual tumor cells after the chemotherapy. Laser-induced bubbles in individual cells and cell damage were monitored by analyzing profile of photothermal response signals over the entire cell after irradiation with a single 10-ns long laser pulse. Photothermal microscopy was utilized for imaging formation of microbubbles around nanoparticulate clusters.

  15. OLED area illumination source

    DOEpatents

    Foust, Donald Franklin; Duggal, Anil Raj; Shiang, Joseph John; Nealon, William Francis; Bortscheller, Jacob Charles

    2008-03-25

    The present invention relates to an area illumination light source comprising a plurality of individual OLED panels. The individual OLED panels are configured in a physically modular fashion. Each OLED panel comprising a plurality of OLED devices. Each OLED panel comprises a first electrode and a second electrode such that the power being supplied to each individual OLED panel may be varied independently. A power supply unit capable of delivering varying levels of voltage simultaneously to the first and second electrodes of each of the individual OLED panels is also provided. The area illumination light source also comprises a mount within which the OLED panels are arrayed.

  16. Nonimaging optical illumination system

    DOEpatents

    Winston, R.; Ries, H.

    1996-12-17

    A nonimaging illumination optical device for producing a selected far field illuminance over an angular range. The optical device includes a light source, a light reflecting surface, and a family of light edge rays defined along a reference line with the reflecting surface defined in terms of the reference line as a parametric function R(t) where t is a scalar parameter position and R(t)=k(t)+Du(t) where k(t) is a parameterization of the reference line, and D is a distance from a point on the reference line to the reflection surface along the desired edge ray through the point. 35 figs.

  17. Nonimaging optical illumination system

    DOEpatents

    Winston, R.; Ries, H.

    1998-10-06

    A nonimaging illumination optical device for producing a selected far field illuminance over an angular range. The optical device includes a light source a light reflecting surface, and a family of light edge rays defined along a reference line with the reflecting surface defined in terms of the reference lines a parametric function R(t) where t is a scalar parameter position and R(t)=k(t)+Du(t) where k(t) is a parameterization of the reference line, and D is a distance from a point on the reference line to the reflection surface along the desired edge ray through the point. 35 figs.

  18. Illumination-compensated non-contact imaging photoplethysmography via dual-mode temporally coded illumination

    NASA Astrophysics Data System (ADS)

    Amelard, Robert; Scharfenberger, Christian; Wong, Alexander; Clausi, David A.

    2015-03-01

    Non-contact camera-based imaging photoplethysmography (iPPG) is useful for measuring heart rate in conditions where contact devices are problematic due to issues such as mobility, comfort, and sanitation. Existing iPPG methods analyse the light-tissue interaction of either active or passive (ambient) illumination. Many active iPPG methods assume the incident ambient light is negligible to the active illumination, resulting in high power requirements, while many passive iPPG methods assume near-constant ambient conditions. These assumptions can only be achieved in environments with controlled illumination and thus constrain the use of such devices. To increase the number of possible applications of iPPG devices, we propose a dual-mode active iPPG system that is robust to changes in ambient illumination variations. Our system uses a temporally-coded illumination sequence that is synchronized with the camera to measure both active and ambient illumination interaction for determining heart rate. By subtracting the ambient contribution, the remaining illumination data can be attributed to the controlled illuminant. Our device comprises a camera and an LED illuminant controlled by a microcontroller. The microcontroller drives the temporal code via synchronizing the frame captures and illumination time at the hardware level. By simulating changes in ambient light conditions, experimental results show our device is able to assess heart rate accurately in challenging lighting conditions. By varying the temporal code, we demonstrate the trade-off between camera frame rate and ambient light compensation for optimal blood pulse detection.

  19. Probing Planetary Bodies for Subsurface Volatiles: GEANT4 Models of Gamma Ray, Fast, Epithermal, and Thermal Neutron Response to Active Neutron Illumination

    NASA Astrophysics Data System (ADS)

    Chin, G.; Sagdeev, R.; Su, J. J.; Murray, J.

    2014-12-01

    Using an active source of neutrons as an in situ probe of a planetary body has proven to be a powerful tool to extract information about the presence, abundance, and location of subsurface volatiles without the need for drilling. The Dynamic Albedo of Neutrons (DAN) instrument on Curiosity is an example of such an instrument and is designed to detect the location and abundance of hydrogen within the top 50 cm of the Martian surface. DAN works by sending a pulse of neutrons towards the ground beneath the rover and detecting the reflected neutrons. The intensity and time of arrival of the reflection depends on the proportion of water, while the time the pulse takes to reach the detector is a function of the depth at which the water is located. Similar instruments can also be effective probes at the polar-regions of the Moon or on asteroids as a way of detecting sequestered volatiles. We present the results of GEANT4 particle simulation models of gamma ray, fast, epithermal, and thermal neutron responses to active neutron illumination. The results are parameterized by hydrogen abundance, stratification and depth of volatile layers, versus the distribution of neutron and gamma ray energy reflections. Models will be presented to approximate Martian, lunar, and asteroid environments and would be useful tools to assess utility for future NASA exploration missions to these types of planetary bodies.

  20. Efficient illumination for microsecond tracking microscopy.

    PubMed

    Dulin, David; Barland, Stephane; Hachair, Xavier; Pedaci, Francesco

    2014-01-01

    The possibility to observe microsecond dynamics at the sub-micron scale, opened by recent technological advances in fast camera sensors, will affect many biophysical studies based on particle tracking in optical microscopy. A main limiting factor for further development of fast video microscopy remains the illumination of the sample, which must deliver sufficient light to the camera to allow microsecond exposure times. Here we systematically compare the main illumination systems employed in holographic tracking microscopy, and we show that a superluminescent diode and a modulated laser diode perform the best in terms of image quality and acquisition speed, respectively. In particular, we show that the simple and inexpensive laser illumination enables less than 1 μs camera exposure time at high magnification on a large field of view without coherence image artifacts, together with a good hologram quality that allows nm-tracking of microscopic beads to be performed. This comparison of sources can guide in choosing the most efficient illumination system with respect to the specific application.

  1. Coupled-resonator vertical-cavity lasers with two active gain regions

    DOEpatents

    Fischer, Arthur J.; Choquette, Kent D.; Chow, Weng W.

    2003-05-20

    A new class of coupled-resonator vertical-cavity semiconductor lasers has been developed. These lasers have multiple resonant cavities containing regions of active laser media, resulting in a multi-terminal laser component with a wide range of novel properties.

  2. Tetravalent chromium (Cr(4+)) as laser-active ion for tunable solid-state lasers

    NASA Technical Reports Server (NTRS)

    Seas, A.; Petricevic, V.; Alfano, Robert R.

    1993-01-01

    Major accomplishments under NASA grant NAG-1-1346 are summarized. (1) numerical modeling of the four mirror astigmatically compensated, Z-fold cavity was performed and several design parameters to be used for the construction of a femtosecond forsterite laser were revealed by simulation. (2) femtosecond pulses from a continuous wave mode-locked chromium doped forsterite laser were generated. The forsterite laser was actively mode-locked using an acousto-optic modulator operating at 78 MHz with two Brewster high dispersion glass prisms for intra-cavity chirp compensation. Transform-limited sub-100-fs pulses were routinely generated in the TEM(sub 00) mode with 85 mW of continuous power tunable over 1230-1280 nm. The shortest pulses of 60-fs pulsewidth were measured. (3) Self-mode-locked operation of the Cr:forsterite laser was achieved. Synchronous pumping was used to mode lock the forsterite laser resulting in picosecond pulses, which in turn provided the starting mechanism for self-mode-locking. The pulses generated had an FWHM of 105 fs and were tunable between 1230-1270 nm. (4) Numerical calculations indicated that the pair of SF 14 prisms used in the cavity compensated for quadratic phase but introduced a large cubic phase term. Further calculations of other optical glasses indicated that a pair of SFN 64 prisms can introduce the same amount of quadratic phase as SF 14 prisms but introduce a smaller cubic phase. When the SF 14 prisms were replaced by SFN 64 prisms the pulsewidth was reduced to 50 fs. Great improvement was observed in the stability of the self mode-locked forsterite laser and in the ease of achieving mode locking. Using the same experimental arrangement and a new forsterite crystal with improved FOM the pulse width was reduced to 36 fs.

  3. Pulsed laser linescanner for a backscatter absorption gas imaging system

    DOEpatents

    Kulp, Thomas J.; Reichardt, Thomas A.; Schmitt, Randal L.; Bambha, Ray P.

    2004-02-10

    An active (laser-illuminated) imaging system is described that is suitable for use in backscatter absorption gas imaging (BAGI). A BAGI imager operates by imaging a scene as it is illuminated with radiation that is absorbed by the gas to be detected. Gases become "visible" in the image when they attenuate the illumination creating a shadow in the image. This disclosure describes a BAGI imager that operates in a linescanned manner using a high repetition rate pulsed laser as its illumination source. The format of this system allows differential imaging, in which the scene is illuminated with light at least 2 wavelengths--one or more absorbed by the gas and one or more not absorbed. The system is designed to accomplish imaging in a manner that is insensitive to motion of the camera, so that it can be held in the hand of an operator or operated from a moving vehicle.

  4. Craniofacial dysmorphology in 22q11.2 deletion syndrome by 3D laser surface imaging and geometric morphometrics: Illuminating the developmental relationship to risk for psychosis

    PubMed Central

    Prasad, Sarah; Katina, Stanislav; Hennessy, Robin J.; Murphy, Kieran C.; Bowman, Adrian W.

    2015-01-01

    Persons with 22q11.2 deletion syndrome (22q11.2DS) are characterized inter alia by facial dysmorphology and greatly increased risk for psychotic illness. Recent studies indicate facial dysmorphology in adults with schizophrenia. This study evaluates the extent to which the facial dysmorphology of 22q11.2DS is similar to or different from that evident in schizophrenia. Twenty‐one 22q11.2DS‐sibling control pairs were assessed using 3D laser surface imaging. Geometric morphometrics was applied to 30 anatomical landmarks, 480 geometrically homologous semi‐landmarks on curves and 1720 semi‐landmarks interpolated on each 3D facial surface. Principal component (PC) analysis of overall shape space indicated PC2 to strongly distinguish 22q11.2DS from controls. Visualization of PC2 indicated 22q11.2DS and schizophrenia to be similar in terms of overall widening of the upper face, lateral displacement of the eyes/orbits, prominence of the cheeks, narrowing of the lower face, narrowing of nasal prominences and posterior displacement of the chin; they differed in terms of facial length (increased in 22q11.2DS, decreased in schizophrenia), mid‐face and nasal prominences (displaced upwards and outwards in 22q11.2DS, less prominent in schizophrenia); lips (more prominent in 22q11.2DS; less prominent in schizophrenia) and mouth (open mouth posture in 22q11.2DS; closed mouth posture in schizophrenia). These findings directly implicate dysmorphogenesis in a cerebral‐craniofacial domain that is common to 22q11.2DS and schizophrenia and which may repay further clinical and genetic interrogation in relation to the developmental origins of psychotic illness. © 2015 The Authors. American Journal of Medical Genetics Part A Published by Wiley Periodicals, Inc. PMID:25691406

  5. Insight in the Chemistry of Laser-Activated Dental Bleaching

    PubMed Central

    De Moor, Roeland Jozef Gentil; Meire, Maarten August; De Coster, Peter Jozef; Walsh, Laurence James

    2015-01-01

    The use of optical radiation for the activation of bleaching products has not yet been completely elucidated. Laser light is suggested to enhance the oxidizing effect of hydrogen peroxide. Different methods of enhancing hydrogen peroxide based bleaching are possible. They can be classified into six groups: alkaline pH environment, thermal enhancement and photothermal effect, photooxidation effect and direct photobleaching, photolysis effect and photodissociation, Fenton reaction and photocatalysis, and photodynamic effect. PMID:25874251

  6. Insight in the chemistry of laser-activated dental bleaching.

    PubMed

    De Moor, Roeland Jozef Gentil; Verheyen, Jeroen; Diachuk, Andrii; Verheyen, Peter; Meire, Maarten August; De Coster, Peter Jozef; Keulemans, Filip; De Bruyne, Mieke; Walsh, Laurence James

    2015-01-01

    The use of optical radiation for the activation of bleaching products has not yet been completely elucidated. Laser light is suggested to enhance the oxidizing effect of hydrogen peroxide. Different methods of enhancing hydrogen peroxide based bleaching are possible. They can be classified into six groups: alkaline pH environment, thermal enhancement and photothermal effect, photooxidation effect and direct photobleaching, photolysis effect and photodissociation, Fenton reaction and photocatalysis, and photodynamic effect.

  7. Influence of Saline on Temperature Profile of Laser Lithotripsy Activation

    PubMed Central

    Silva, Igor N.; Donalisio da Silva, Rodrigo; Gustafson, Diedra; Sehrt, David; Kim, Fernando J.

    2015-01-01

    Abstract Purpose: We established an ex vivo model to evaluate the temperature profile of the ureter during laser lithotripsy, the influence of irrigation on temperature, and thermal spread during lithotripsy with the holmium:yttrium-aluminum-garnet (Ho:YAG) laser. Materials and Methods: Two ex vivo models of Ovis aries urinary tract and human calcium oxalate calculi were used. The Open Ureteral Model was opened longitudinally to measure the thermal profile of the urothelium. On the Clinical Model, anterograde ureteroscopy was performed in an intact urinary system. Temperatures were measured on the external portion of the ureter and the urothelium during lithotripsy and intentional perforation. The lithotripsy group (n=20) was divided into irrigated (n=10) and nonirrigated (n=10), which were compared for thermal spread length and values during laser activation. The intentional perforation group (n=10) was evaluated under saline flow. The Ho:YAG laser with a 365 μm laser fiber and power at 10W was used (1J/Pulse at 10 Hz). Infrared Fluke Ti55 Thermal Imager was used for evaluation. Maximum temperature values were recorded and compared. Results: On the Clinical Model, the external ureteral wall obtained a temperature of 37.4°C±2.5° and 49.5°C±2.3° (P=0.003) and in the Open Ureteral Model, 49.7°C and 112.4°C with and without irrigation, respectively (P<0.05). The thermal spread along the external ureter wall was not statically significant with or without irrigation (P=0.065). During intentional perforation, differences in temperatures were found between groups (opened with and without irrigation): 81.8°±8.8° and 145.0°±15.0°, respectively (P<0.005). Conclusion: There is an increase in the external ureteral temperature during laser activation, but ureteral thermal values decreased when saline flow was applied. Ureter thermal spread showed no difference between irrigated and nonirrigated subgroups. This is the first laser lithotripsy thermography study

  8. Image Correlation Microscopy for Uniform Illumination

    PubMed Central

    Gaborski, Thomas R.; Sealander, Michael N.; Ehrenberg, Morton; Waugh, Richard E.; McGrath, James L.

    2011-01-01

    Image cross-correlation microscopy (ICM) is a technique that quantifies the motion of fluorescent features in an image by measuring the temporal autocorrelation function decay in a time-lapse image sequence. ICM has traditionally employed laser-scanning microscopes because the technique emerged as an extension of laser-based fluorescence correlation spectroscopy (FCS). In this work, we show that image correlation can also be used to measure fluorescence dynamics in uniform illumination or wide-field imaging systems and we call our new approach uniform illumination image correlation microscopy (UI-ICM). Wide-field microscopy is not only a simpler, less expensive imaging modality, but it offers the capability of greater temporal resolution over laser-scanning systems. In traditional laser-scanning ICM, lateral mobility is calculated from the temporal de-correlation of an image, where the characteristic length is the illuminating laser beam width. In wide-field microscopy, the diffusion length is defined by the feature size using the spatial autocorrelation function (SACF). Correlation function decay in time occurs as an object diffuses from its original position. We show that theoretical and simulated comparisons between Gaussian and uniform features indicate the temporal autocorrelation function (TACF) depends strongly on particle size and not particle shape. In this report, we establish the relationships between the SACF feature size, TACF characteristic time and the diffusion coefficient for UI-ICM using analytical, Monte-Carlo and experimental validation with particle tracking algorithms. Additionally, we demonstrate UI-ICM analysis of adhesion molecule domain aggregation and diffusion on the surface of human neutrophils. PMID:20055917

  9. Preparation and characterization of mesoporous N-doped and sulfuric acid treated anatase TiO{sub 2} catalysts and their photocatalytic activity under UV and Vis illumination

    SciTech Connect

    Kun, Robert; Tarjan, Sandor; Oszko, Albert; Seemann, Torben; Zoellmer, Volker; Busse, Matthias; Dekany, Imre

    2009-11-15

    Nitrogen-doped TiO{sub 2} catalysts were prepared by a precipitation method. The samples were calcined at 400 deg. C for 4 h in air. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), low temperature N{sub 2}-adsorption was used for structural characterization and UV-diffuse reflectance (UV-DR) was applied to investigate the optical properties of the as-prepared samples. It was found that microporous N-doped catalysts have solely anatase crystalline structure. Acidic treatment of the calcined samples was performed using sulfuric acid agitation. The crystalline structure remained unchanged due to surface treatment, while the porosity and the surface areas (a{sub BET}{sup S}) were decreased dramatically. Optical characterization of the doped catalysts showed that they could be excited by visible light photons in the 400-500 nm wavelength range (lambda{sub g,1}={approx}390 nm, lambda{sub g,2}={approx}510 nm). It was also established that surface treatment enhances the Vis-light absorption of the N-TiO{sub 2} powders. Finally the catalysts were tested in the photocatalytic degradation of phenol in aqueous suspensions. Two different light sources were used; one of them was a UV-rich high pressure Hg-lamp, while the other was a tubular visible light source. We found that using visible light illumination N-doped, acid treated TiO{sub 2} samples were more catalytically active than non-doped TiO{sub 2} catalysts. - Graphical abstract: The effect of the acid treatment on the visible-light-driven photocatalytic activity of the N-doped, anatase TiO{sub 2} catalysts.

  10. Photocatalytic degradation of phenol in natural seawater using visible light active carbon modified (CM)-n-TiO2 nanoparticles under UV light and natural sunlight illuminations.

    PubMed

    Shaban, Yasser A; El Sayed, Mohamed A; El Maradny, Amr A; Al Farawati, Radwan Kh; Al Zobidi, Mousa I

    2013-04-01

    The photocatalytic degradation of phenol in seawater was investigated under UV and natural sunlight using visible light active carbon modified (CM)-n-TiO2 nanoparticles, synthesized via a sol-gel method. Carbon modification of n-TiO2 was performed using titanium butoxide, carbon-containing precursor, as a source of both carbon and titanium. For comparison, unmodified n-TiO2 was also synthesized by hydrolysis and oxidation of titanium trichloride in the absence of any carbon source. The presence of carbon in CM-n-TiO2 nanoparticles was confirmed by energy dispersive spectroscopy (EDS) analysis. Carbon modification was found to be responsible for lowering the bandgap energy from 3.14eV for n-TiO2 to 1.86eV for CM-n-TiO2 which in turn enhanced the photocatalytic activity of CM-n-TiO2 towards the degradation of phenol in seawater under illumination of UV light as well as natural sunlight. This enhanced photoresponse of CM-n-TiO2 is in agreement with the UV-Vis spectroscopic results that showed higher absorption of light in both UV and visible regions. The effects of catalyst dose, initial concentration of phenol, and pH were studied. The highest degradation rate was obtained at pH 3 and catalyst dose of 1.0gL(-1). The data photocatalytic degradation of phenol in seawater using CM-n-TiO2 were successfully fitted to Langmuir-Hinshelwood model, and can be described by pseudo-first order kinetics.

  11. Nonimaging Optical Illumination System

    DOEpatents

    Winston, Roland

    1994-02-22

    A nonimaging illumination or concentration optical device. An optical device is provided having a light source, a light reflecting surface with an opening and positioned partially around the light source which is opposite the opening of the light reflecting surface. The light reflecting surface is disposed to produce a substantially uniform intensity output with the reflecting surface defined in terms of a radius vector R.sub.i in conjunction with an angle .phi..sub.i between R.sub.i, a direction from the source and an angle .theta..sub.i between direct forward illumination and the light ray reflected once from the reflecting surface. R.sub.i varies as the exponential of tan (.phi..sub.i -.theta..sub.i)/2 integrated over .phi..sub.i.

  12. Nonimaging optical illumination system

    DOEpatents

    Winston, Roland; Ries, Harald

    1996-01-01

    A nonimaging illumination optical device for producing a selected far field illuminance over an angular range. The optical device includes a light source 102, a light reflecting surface 108, and a family of light edge rays defined along a reference line 104 with the reflecting surface 108 defined in terms of the reference line 104 as a parametric function R(t) where t is a scalar parameter position and R(t)=k(t)+Du(t) where k(t) is a parameterization of the reference line 104, and D is a distance from a point on the reference line 104 to the reflection surface 108 along the desired edge ray through the point.

  13. Nonimaging optical illumination system

    DOEpatents

    Winston, Roland; Ries, Harald

    1998-01-01

    A nonimaging illumination optical device for producing a selected far field illuminance over an angular range. The optical device includes a light source 102, a light reflecting surface 108, and a family of light edge rays defined along a reference line 104 with the reflecting surface 108 defined in terms of the reference line 104 as a parametric function R(t) where t is a scalar parameter position and R(t)=k(t)+Du(t) where k(t) is a parameterization of the reference line 104, and D is a distance from a point on the reference line 104 to the reflection surface 108 along the desired edge ray through the point.

  14. Nonimaging optical illumination system

    DOEpatents

    Winston, Roland; Ries, Harald

    2000-01-01

    A nonimaging illumination optical device for producing a selected far field illuminance over an angular range. The optical device includes a light source 102, a light reflecting surface 108, and a family of light edge rays defined along a reference line 104 with the reflecting surface 108 defined in terms of the reference line 104 as a parametric function R(t) where t is a scalar parameter position and R(t)=k(t)+Du(t) where k(t) is a parameterization of the reference line 104, and D is a distance from a point on the reference line 104 to the reflection surface 108 along the desired edge ray through the point.

  15. Graphene active plasmonic metamaterials for new types of terahertz lasers

    NASA Astrophysics Data System (ADS)

    Otsuji, Taiichi; Watanabe, Takayuki; Satou, Akira; Popov, Vyacheslav; Ryzhii, Victor

    2013-05-01

    This paper reviews recent advances in graphene active plasmonic metamaterials for new types of terahertz lasers. We theoretically discovered that when the population of Dirac Fermionic carriers in graphene are inverted by optical or electrical pumping the excitation of graphene plasmons by the THz photons results in propagating surface plasmon polaritons with giant gain in a wide THz range. Furthermore, when graphene is patterned in a micro- or nano-ribbon array by grating gate metallization, the structure acts as an active plasmonic metamaterial, providing a super-radiant plasmonic lasing with giant gain at the plasmon modes in a wide THz frequency range.

  16. Active Control of Laser Wavefronts in Atom Interferometers

    NASA Astrophysics Data System (ADS)

    Trimeche, A.; Langlois, M.; Merlet, S.; Pereira Dos Santos, F.

    2017-03-01

    Wavefront aberrations are identified as a major limitation in quantum sensors. They are today the main contribution in the uncertainty budget of the best cold-atom interferometers based on two-photon laser beam splitters and constitute an important limit for their long-term stability, impeding these instruments from reaching their full potential. Moreover, they will also remain a major obstacle in future experiments based on large-momentum beam splitters. In this article, we tackle this issue by using a deformable mirror to control actively the laser wavefronts in atom interferometry. In particular, we demonstrate in an experimental proof of principle the efficient correction of wavefront aberrations in an atomic gravimeter.

  17. LASER APPLICATIONS AND OTHER TOPICS IN LASER TECHNOLOGY: Xenon and hydrogen gas mixtures as laser active media

    NASA Astrophysics Data System (ADS)

    Zuev, V. S.; Kanaev, A. V.; Mikheev, L. D.

    1988-08-01

    It is suggested that gaseous mixtures of xenon and molecular hydrogen may be used as active media of Xe2 (172 nm) and XeH ( ~ 250 nm) photochemical lasers. By adding more than 3 Torr of hydrogen to xenon, amplification can be achieved in the 172 nm range as a result of quenching of the 1u/0u- absorbing state under optical pumping conditions. The hydrogen atoms produced by the quenching process can be utilized to populate XeH* by three-body recombination with Xe* ( 3P1/2) atoms.

  18. Critical illumination condenser for x-ray lithography

    DOEpatents

    Cohen, S.J.; Seppala, L.G.

    1998-04-07

    A critical illumination condenser system is disclosed, particularly adapted for use in extreme ultraviolet (EUV) projection lithography based on a ring field imaging system and a laser produced plasma source. The system uses three spherical mirrors and is capable of illuminating the extent of the mask plane by scanning either the primary mirror or the laser plasma source. The angles of radiation incident upon each mirror of the critical illumination condenser vary by less than eight (8) degrees. For example, the imaging system in which the critical illumination condenser is utilized has a 200 {micro}m source and requires a magnification of 26. The three spherical mirror system constitutes a two mirror inverse Cassegrain, or Schwarzschild configuration, with a 25% area obstruction (50% linear obstruction). The third mirror provides the final pupil and image relay. The mirrors include a multilayer reflective coating which is reflective over a narrow bandwidth. 6 figs.

  19. Critical illumination condenser for x-ray lithography

    DOEpatents

    Cohen, Simon J.; Seppala, Lynn G.

    1998-01-01

    A critical illumination condenser system, particularly adapted for use in extreme ultraviolet (EUV) projection lithography based on a ring field imaging system and a laser produced plasma source. The system uses three spherical mirrors and is capable of illuminating the extent of the mask plane by scanning either the primary mirror or the laser plasma source. The angles of radiation incident upon each mirror of the critical illumination condenser vary by less than eight (8) degrees. For example, the imaging system in which the critical illumination condenser is utilized has a 200 .mu.m source and requires a magnification of 26.times.. The three spherical mirror system constitutes a two mirror inverse Cassegrain, or Schwarzschild configuration, with a 25% area obstruction (50% linear obstruction). The third mirror provides the final pupil and image relay. The mirrors include a multilayer reflective coating which is reflective over a narrow bandwidth.

  20. Quantum dots as active material for quantum cascade lasers: comparison to quantum wells

    NASA Astrophysics Data System (ADS)

    Michael, Stephan; Chow, Weng W.; Schneider, Hans Christian

    2016-03-01

    We review a microscopic laser theory for quantum dots as active material for quantum cascade lasers, in which carrier collisions are treated at the level of quantum kinetic equations. The computed characteristics of such a quantum-dot active material are compared to a state-of-the-art quantum-well quantum cascade laser. We find that the current requirement to achieve a comparable gain-length product is reduced compared to that of the quantum-well quantum cascade laser.

  1. Ti : sapphire laser synchronised with femtosecond Yb pump laser via nonlinear pulse coupling in Ti : sapphire active medium

    NASA Astrophysics Data System (ADS)

    Didenko, N. V.; Konyashchenko, A. V.; Konyashchenko, D. A.; Kostryukov, P. V.; Kuritsyn, I. I.; Lutsenko, A. P.; Mavritskiy, A. O.

    2017-02-01

    A laser system utilising the method of synchronous pumping of a Ti : sapphire laser by a high-power femtosecond Yb3+-doped laser is described. The pulse repetition rate of the Ti : sapphire laser is successfully locked to the repetition rate of the Yb laser for more than 6 hours without the use of any additional electronics. The measured timing jitter is shown to be less than 1 fs. A simple qualitative model addressing the synchronisation mechanism utilising the cross-phase modulation of oscillation and pump pulses within a Ti : sapphire active medium is proposed. Output parameters of the Ti : sapphire laser as functions of its cavity length are discussed in terms of this model.

  2. ACTIVE MEDIA: Dynamics of growth of inhomogeneities in the active medium of a liquid laser

    NASA Astrophysics Data System (ADS)

    Barikhin, B. A.; Ivanov, A. Yu; Kudryavkin, E. V.; Nedolugov, V. I.

    1991-07-01

    Fast cinematography of holograms and of shadow and interference patterns was combined with an acoustic method in a study of the dynamics of growth of inhomogeneities in the active medium of a coaxially pumped dye laser. The main mechanism of the formation of these inhomogeneities was related to acoustic waves created by the deformation of the walls of a dye cell created by electrical pulses applied to the pump flashlamp. Multipulse operation of this laser could be achieved and the off-duty factor could be reduced if the active medium was excited by the strongest possible pump pulses.

  3. Nonimaging Optical Illumination System

    DOEpatents

    Winston, Roland

    1994-08-02

    A nonimaging illumination optical device for producing selected intensity output over an angular range. The device includes a light reflecting surface (24, 26) around a light source (22) which is disposed opposite the aperture opening of the light reflecting surface (24, 26). The light source (22) has a characteristic dimension which is small relative to one or more of the distance from the light source (22) to the light reflecting surface (24, 26) or the angle subtended by the light source (22) at the light reflecting surface (24, 26).

  4. Ellipticus CW Illumination System

    DTIC Science & Technology

    2012-08-07

    conceived the idea of making the antenna out of coaxial cable instead of wire and loading the outer conductor with resis- tively damped ferrite ...radiat- ing gap and match the impedance of the antenna as shown in Figure 4. The ferrite bead design, as well as that of the balun, was quite a...Illuminator at Patuxent River NAS. 3.2.1 Wormhole feed concept. The method chosen for driving the radiat- ing gap at the top of the antenna was what Dr

  5. Photonic crystal lasers using wavelength-scale embedded active region

    NASA Astrophysics Data System (ADS)

    Matsuo, Shinji; Sato, Tomonari; Takeda, Koji; Shinya, Akihiko; Nozaki, Kengo; Kuramochi, Eiichi; Taniyama, Hideaki; Notomi, Masaya; Fujii, Takuro; Hasebe, Koichi; Kakitsuka, Takaaki

    2014-01-01

    Lasers with ultra-low operating energy are desired for use in chip-to-chip and on-chip optical interconnects. If we are to reduce the operating energy, we must reduce the active volume. Therefore, a photonic crystal (PhC) laser with a wavelength-scale cavity has attracted a lot of attention because a PhC provides a large Q-factor with a small volume. To improve this device's performance, we employ an embedded active region structure in which the wavelength-scale active region is buried with an InP PhC slab. This structure enables us to achieve effective confinement of both carriers and photons, and to improve the thermal resistance of the device. Thus, we have obtained a large external differential quantum efficiency of 55% and an output power of -10 dBm by optical pumping. For electrical pumping, we use a lateral p-i-n structure that employs Zn diffusion and Si ion implantation for p-type and n-type doping, respectively. We have achieved room-temperature continuous-wave operation with a threshold current of 7.8 µA and a maximum 3 dB bandwidth of 16.2 GHz. The results of an experimental bit error rate measurement with a 10 Gbit s-1 NRZ signal reveal the minimum operating energy for transferring a single bit of 5.5 fJ. These results show the potential of this laser to be used for very short reach interconnects. We also describe the optimal design of cavity quality (Q) factor in terms of achieving a large output power with a low operating energy using a calculation based on rate equations. When we assume an internal absorption loss of 20 cm-1, the optimized coupling Q-factor is 2000.

  6. Laser-activated shape memory polymer intravascular thrombectomy device

    NASA Astrophysics Data System (ADS)

    Small, Ward, IV; Wilson, Thomas S.; Benett, William J.; Loge, Jeffrey M.; Maitland, Duncan J.

    2005-10-01

    A blood clot (thrombus) that becomes lodged in the arterial network supplying the brain can cause an ischemic stroke, depriving the brain of oxygen and often resulting in permanent disability. As an alternative to conventional clot-dissolving drug treatment, we are developing an intravascular laser-activated therapeutic device using shape memory polymer (SMP) to mechanically retrieve the thrombus and restore blood flow to the brain. Thermal imaging and computer simulation were used to characterize the optical and photothermal behavior of the SMP microactuator. Deployment of the SMP device in an in vitro thrombotic vascular occlusion model demonstrated the clinical treatment concept.

  7. Parallel hierarchical global illumination

    SciTech Connect

    Snell, Quinn O.

    1997-10-08

    Solving the global illumination problem is equivalent to determining the intensity of every wavelength of light in all directions at every point in a given scene. The complexity of the problem has led researchers to use approximation methods for solving the problem on serial computers. Rather than using an approximation method, such as backward ray tracing or radiosity, the authors have chosen to solve the Rendering Equation by direct simulation of light transport from the light sources. This paper presents an algorithm that solves the Rendering Equation to any desired accuracy, and can be run in parallel on distributed memory or shared memory computer systems with excellent scaling properties. It appears superior in both speed and physical correctness to recent published methods involving bidirectional ray tracing or hybrid treatments of diffuse and specular surfaces. Like progressive radiosity methods, it dynamically refines the geometry decomposition where required, but does so without the excessive storage requirements for ray histories. The algorithm, called Photon, produces a scene which converges to the global illumination solution. This amounts to a huge task for a 1997-vintage serial computer, but using the power of a parallel supercomputer significantly reduces the time required to generate a solution. Currently, Photon can be run on most parallel environments from a shared memory multiprocessor to a parallel supercomputer, as well as on clusters of heterogeneous workstations.

  8. Laser-enhanced high-intensity focused ultrasound heating in an in vivo small animal model

    NASA Astrophysics Data System (ADS)

    Jo, Janggun; Yang, Xinmai

    2016-11-01

    The enhanced heating effect during the combination of high-intensity focused ultrasound (HIFU) and low-optical-fluence laser illumination was investigated by using an in vivo murine animal model. The thighs of murine animals were synergistically irradiated by HIFU and pulsed nano-second laser light. The temperature increases in the target region were measured by a thermocouple under different HIFU pressures, which were 6.2, 7.9, and 9.8 MPa, in combination with 20 mJ/cm2 laser exposures at 532 nm wavelength. In comparison with conventional laser therapies, the laser fluence used here is at least one order of magnitude lower. The results showed that laser illumination could enhance temperature during HIFU applications. Additionally, cavitation activity was enhanced when laser and HIFU irradiation were concurrently used. Further, a theoretical simulation showed that the inertial cavitation threshold was indeed decreased when laser and HIFU irradiation were utilized concurrently.

  9. Low level laser therapy reduces inflammation in activated Achilles tendinitis

    NASA Astrophysics Data System (ADS)

    Bjordal, Jan M.; Iversen, Vegard; Lopes-Martins, Rodrigo Alvaro B.

    2006-02-01

    Objective: Low level laser therapy (LLLT) has been forwarded as therapy for osteoarthritis and tendinopathy. Results in animal and cell studies suggest that LLLT may act through a biological mechanism of inflammatory modulation. The current study was designed to investigate if LLLT has an anti-inflammatory effect on activated tendinitis of the Achilles tendon. Methods: Seven patients with bilateral Achilles tendonitis (14 tendons) who had aggravated symptoms by pain-inducing activity immediately prior to the study. LLLT (1.8 Joules for each of three points along the Achilles tendon with 904nm infrared laser) and placebo LLLT were administered to either Achilles tendons in a random order to which patients and therapist were blinded. Inflammation was examined by 1) mini-invasive microdialysis for measuring the concentration of inflammatory marker PGE II in the peritendinous tissue, 2) ultrasound with Doppler measurement of peri- and intratendinous blood flow, 3) pressure pain algometry and 4) single hop test. Results: PGE 2- levels were significantly reduced at 75, 90 and 105 minutes after active LLLT compared both to pre-treatment levels (p=0.026) and to placebo LLLT (p=0.009). Changes in pressure pain threshold (PPT) were significantly different (P=0.012) between groups. PPT increased by a mean value of 0.19 kg/cm2 [95%CI:0.04 to 0.34] after treatment in the active LLLT group, while pressure pain threshold was reduced by -0.20 kg/cm2 [95%CI:-0.45 to 0.05] after placebo LLLT. Conclusion: LLLT can be used to reduce inflammatory musculskeletal pain as it reduces inflammation and increases pressure pain threshold levels in activity-induced pain episodes of Achilles tendinopathy.

  10. A Terminal Guidance Model for Smart Projectiles Employing a Semi-Active Laser Seeker

    DTIC Science & Technology

    2011-08-01

    A Terminal Guidance Model for Smart Projectiles Employing a Semi-Active Laser Seeker by Luke S. Strohm ARL-TR-5654 August 2011...Terminal Guidance Model for Smart Projectiles Employing a Semi-Active Laser Seeker Luke S. Strohm Weapons and Materials Research Directorate...January 2010–31 March 2011 4. TITLE AND SUBTITLE A Terminal Guidance Model for Smart Projectiles Employing a Semi-Active Laser Seeker 5a. CONTRACT

  11. Experimental study on rat NK cell activity improvement by laser acupoint irradiation

    NASA Astrophysics Data System (ADS)

    Yang, Dongxiao; Chen, Xiufeng; Ruan, Buqing; Yang, Feng

    1998-08-01

    To study the improvement of the natural killer (NK) cell activity by semiconductor laser acupoint irradiation, rats were used in this experiment and were injected immunosuppressant in their abdomen. The immunoassay was made after the surface irradiation and inner irradiation at Baihui point by semiconductor laser. The NK cell activity is an important index of immunologic function. The results showed that the NK cell activity after laser acupoint irradiation was enhanced. This enhancement is relatively important in the clinical therapy of tumor.

  12. Active, LCoS based laser interferometer for microelements studies

    NASA Astrophysics Data System (ADS)

    Kacperski, Jacek; Kujawinska, Malgorzata

    2006-10-01

    The modification of classical Twyman-Green interferometer by implementation of Liquid Crystal on Silicon (LCoS) spatial light modulator as the reference mirror allows introducing arbitrary phase in the reference wavefront. This special capability is applied to facilitate the measurements of shape and deformation of active microelements and extend the range of such measurement. This can be realized by introducing linear or circular spatial carrier frequency into interferogram or by compensating object wavefront deformation. Moreover LCoS display can be used as an accurate phase shifter if the proper calibration is introduced. The analysis of sources of measurement errors introduced by LCoS display is presented and the ways of their elimination are discussed. The possible application of LCoS based laser interferometer for initial microelement shape determination and transient deformation monitoring as well as active reference phase modification are shown and experimentally confirmed during silicon micromembranes studies.

  13. Active, LCoS based laser interferometer for microelements studies.

    PubMed

    Kacperski, Jacek; Kujawinska, Malgorzata

    2006-10-16

    The modification of classical Twyman-Green interferometer by implementation of Liquid Crystal on Silicon (LCoS) spatial light modulator as the reference mirror allows introducing arbitrary phase in the reference wavefront. This special capability is applied to facilitate the measurements of shape and deformation of active microelements and extend the range of such measurement. This can be realized by introducing linear or circular spatial carrier frequency into interferogram or by compensating object wavefront deformation. Moreover LCoS display can be used as an accurate phase shifter if the proper calibration is introduced. The analysis of sources of measurement errors introduced by LCoS display is presented and the ways of their elimination are discussed. The possible application of LCoS based laser interferometer for initial microelement shape determination and transient deformation monitoring as well as active reference phase modification are shown and experimentally confirmed during silicon micromembranes studies.

  14. 29 CFR 1926.56 - Illumination.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Illumination. (a) General. Construction areas, ramps, runways, corridors, offices, shops, and storage areas... tunnel heading.) 10 General construction plant and shops (e.g., batch plants, screening plants, mechanical and electrical equipment rooms, carpenter shops, rigging lofts and active storerooms, barracks...

  15. Split-illumination electron holography

    SciTech Connect

    Tanigaki, Toshiaki; Aizawa, Shinji; Suzuki, Takahiro; Park, Hyun Soon; Inada, Yoshikatsu; Matsuda, Tsuyoshi; Taniyama, Akira; Shindo, Daisuke; Tonomura, Akira

    2012-07-23

    We developed a split-illumination electron holography that uses an electron biprism in the illuminating system and two biprisms (applicable to one biprism) in the imaging system, enabling holographic interference micrographs of regions far from the sample edge to be obtained. Using a condenser biprism, we split an electron wave into two coherent electron waves: one wave is to illuminate an observation area far from the sample edge in the sample plane and the other wave to pass through a vacuum space outside the sample. The split-illumination holography has the potential to greatly expand the breadth of applications of electron holography.

  16. Measuring the size of biological nanostructures with spatially modulated illumination microscopy.

    PubMed

    Martin, Sonya; Failla, Antonio Virgilio; Spöri, Udo; Cremer, Christoph; Pombo, Ana

    2004-05-01

    Spatially modulated illumination fluorescence microscopy can in theory measure the sizes of objects with a diameter ranging between 10 and 200 nm and has allowed accurate size measurement of subresolution fluorescent beads ( approximately 40-100 nm). Biological structures in this size range have so far been measured by electron microscopy. Here, we have labeled sites containing the active, hyperphosphorylated form of RNA polymerase II in the nucleus of HeLa cells by using the antibody H5. The spatially modulated illumination-microscope was compared with confocal laser scanning and electron microscopes and found to be suitable for measuring the size of cellular nanostructures in a biological setting. The hyperphosphorylated form of polymerase II was found in structures with a diameter of approximately 70 nm, well below the 200-nm resolution limit of standard fluorescence microscopes.

  17. Novel mid-infrared lasers with compressively strained InAsSb active regions

    SciTech Connect

    Kurtz, S.R.; Biefeld, R.M.; Allerman, A.A.

    1997-02-01

    Mid-infrared lasers grown by MOCVD with AlAsSb claddings and strained InAsSb active regions are reported. A 3.8--3.9 {micro}m injection laser with a pseudomorphic InAsSb multiple quantum well active region lased at 210 K under pulsed operation. A semi-metal layer acts as an internal electron source for the injection laser. An optically pumped laser with an InAsSb/InAsP strained-layer superlattice active region was demonstrated at 3.7 {micro}m, 240 K.

  18. Silicate-matrix active media for tunable solid-state lasers

    SciTech Connect

    Kuznetsova, Rimma T; Mayer, G V; Manekina, Yu A; Tel'minov, E N; Arabei, S M; Pavich, T A; Solovyov, Konstantin N

    2007-08-31

    The lasing characteristics of solid active media based on laser dyes (rhodamines, coumarin 2, paraterphenyl) doped into silicate bulk matrices and thin films of different compositions are studied upon optical excitation. The lasing efficiency, photostability, and spectral parameters of laser media are investigated as functions of the excitation wavelength and intensity. Variations in these parameters due to the interaction of organic luminophores with a silicate matrix and radiation are discussed. (active media. lasers)

  19. Low-power laser irradiation enhance macrophage phagocytic capacity through Src activation

    NASA Astrophysics Data System (ADS)

    Wu, Shengnan; Zhou, Feifan; Xing, Da

    2012-03-01

    Phagocytosis and subsequent degradation of pathogens by macrophages play a pivotal role in host innate immunity in mammals. Laser irradiation has been found to produce photobiological effects with evidence of interference with organic functions. In this study, we focused our attention on the effects of He-Ne laser on the phagocytic activity of macrophages, the regulation mechanism of phagocytosis was also discussed. Our results indicated that Low-power laser irradiation can enhance the phagocytosis of macrophage through activation of Src.

  20. Active mode locking of lasers by piezoelectrically induced diffraction modulation

    NASA Astrophysics Data System (ADS)

    Krausz, F.; Turi, L.; Kuti, Cs.; Schmidt, A. J.

    1990-04-01

    A new amplitude-modulation mode-locking technique is presented. Acoustic waves are generated directly on the faces of a resonant photoelastic medium. The created standing waves cause a highly efficient diffraction modulation of light. The modulation depth of standing-wave mode lockers is related to material and drive parameters and a figure of merit is introduced. With a lithium niobate crystal modulation depths over 10 are achieved at 1.054 μm and 1 W of radio frequency power. Using this device for the active mode locking of a continuous-wave Nd:glass laser pulses as short as 3.8 ps are produced at a repetition rate of 66 MHz. Limitations of amplitude-modulation mode locking by standing acoustic waves are discussed.

  1. Active/passive mode-locked laser oscillator

    DOEpatents

    Fountain, William D.; Johnson, Bertram C.

    1977-01-01

    A Q-switched/mode-locked Nd:YAG laser oscillator employing simultaneous active (electro-optic) and passive (saturable absorber) loss modulation within the optical cavity is described. This "dual modulation" oscillator can produce transform-limited pulses of duration ranging from about 30 psec to about 5 nsec with greatly improved stability compared to other mode-locked systems. The pulses produced by this system lack intrapulse frequency or amplitude modulation, and hence are idealy suited for amplification to high energies and for other applications where well-defined pulses are required. Also, the pulses of this system have excellent interpulse characteristics, wherein the optical noise between the individual pulses of the pulse train has a power level well below the power of the peak pulse of the train.

  2. Efficient active depth sensing by laser speckle projection system

    NASA Astrophysics Data System (ADS)

    Yin, Xuanwu; Wang, Guijin; Shi, Chenbo; Liao, Qingmin

    2014-01-01

    An active depth sensing approach by laser speckle projection system is proposed. After capturing the speckle pattern with an infrared digital camera, we extract the pure speckle pattern using a direct-global separation method. Then the pure speckles are represented by Census binary features. By evaluating the matching cost and uniqueness between the real-time image and the reference image, robust correspondences are selected as support points. After that, we build a disparity grid and propose a generative graphical model to compute disparities. An iterative approach is designed to propagate the messages between blocks and update the model. Finally, a dense depth map can be obtained by subpixel interpolation and transformation. The experimental evaluations demonstrate the effectiveness and efficiency of our approach.

  3. On the modified active region design of interband cascade lasers

    SciTech Connect

    Motyka, M.; Ryczko, K.; Dyksik, M.; Sęk, G.; Misiewicz, J.; Weih, R.; Dallner, M.; Kamp, M.; Höfling, S.

    2015-02-28

    Type II InAs/GaInSb quantum wells (QWs) grown on GaSb or InAs substrates and designed to be integrated in the active region of interband cascade lasers (ICLs) emitting in the mid infrared have been investigated. Optical spectroscopy, combined with band structure calculations, has been used to probe their electronic properties. A design with multiple InAs QWs has been compared with the more common double W-shaped QW and it has been demonstrated that it allows red shifting the emission wavelength and enhancing the transition oscillator strength. This can be beneficial for the improvements of the ICLs performances, especially when considering their long-wavelength operation.

  4. Modeling and optimization of actively Q-switched Nd-doped quasi-three-level laser

    NASA Astrophysics Data System (ADS)

    Yan, Renpeng; Yu, Xin; Li, Xudong; Chen, Deying; Gao, Jing

    2013-09-01

    The energy transfer upconversion and the ground state absorption are considered in solving the rate equations for an active Q-switched quasi-three-level laser. The dependence of output pulse characters on the laser parameters is investigated by solving the rate equations. The influence of the energy transfer upconversion on the pulsed laser performance is illustrated and discussed. By this model, the optimal parameters could be achieved for arbitrary quasi-three-level Q-switched lasers. An acousto-optical Q-switched Nd:YAG 946 nm laser is constructed and the reliability of the theoretical model is demonstrated.

  5. Actively mode-locked fiber laser using acousto-optic modulator

    NASA Astrophysics Data System (ADS)

    Nikodem, Michal P.; Sergeant, Hendrik; Kaczmarek, Pawel; Abramski, Krzysztof M.

    2008-12-01

    In recent years we have observed growing interest in mode-locked fiber lasers. Development of erbium doped fiber (EDF) amplifiers and WDM technique made 3rd telecommunication window extremely interesting region for ultrafast optics. The main advantages of fiber lasers i.e. narrow linewidth and wide gain bandwidth make them very attractive sources in various applications. In this paper we present an actively mode-locked erbium doped fiber ring laser. Modelocking is obtained using an acousto-optic modulator (AOM) coupled into the laser cavity. The impact of different parameters (e.g. light polarization, modulation frequency) is investigated. We study mechanisms of controlling the wavelength of the laser.

  6. Optimizing ultrafast illumination for multiphoton-excited fluorescence imaging

    PubMed Central

    Stoltzfus, Caleb R.; Rebane, Aleksander

    2016-01-01

    We study the optimal conditions for high throughput two-photon excited fluorescence (2PEF) and three-photon excited fluorescence (3PEF) imaging using femtosecond lasers. We derive relations that allow maximization of the rate of imaging depending on the average power, pulse repetition rate, and noise characteristics of the laser, as well as on the size and structure of the sample. We perform our analysis using ~100 MHz, ~1 MHz and 1 kHz pulse rates and using both a tightly-focused illumination beam with diffraction-limited image resolution, as well loosely focused illumination with a relatively low image resolution, where the latter utilizes separate illumination and fluorescence detection beam paths. Our theoretical estimates agree with the experiments, which makes our approach especially useful for optimizing high throughput imaging of large samples with a field-of-view up to 10x10 cm2. PMID:27231620

  7. Temperature activated absorption during laser-induced damage: The evolution of laser-supported solid-state absorption fronts

    SciTech Connect

    Carr, C W; Bude, J D; Shen, N; Demange, P

    2010-10-26

    Previously we have shown that the size of laser induced damage sites in both KDP and SiO{sub 2} is largely governed by the duration of the laser pulse which creates them. Here we present a model based on experiment and simulation that accounts for this behavior. Specifically, we show that solid-state laser-supported absorption fronts are generated during a damage event and that these fronts propagate at constant velocities for laser intensities up to 4 GW/cm{sup 2}. It is the constant absorption front velocity that leads to the dependence of laser damage site size on pulse duration. We show that these absorption fronts are driven principally by the temperature-activated deep sub band-gap optical absorptivity, free electron transport, and thermal diffusion in defect-free silica for temperatures up to 15,000K and pressures < 15GPa. In addition to the practical application of selecting an optimal laser for pre-initiation of large aperture optics, this work serves as a platform for understanding general laser-matter interactions in dielectrics under a variety of conditions.

  8. Illuminated push-button switch

    NASA Astrophysics Data System (ADS)

    Iwagiri, T.

    1983-05-01

    An illuminated push-button switch is described. It is characterized by the fact that is consists of a switch group, an operator button opening and closing the switch group, and a light-emitting element which illuminates the face of the operator button.

  9. Optical tomography with structured illumination.

    PubMed

    Lukic, Vladimir; Markel, Vadim A; Schotland, John C

    2009-04-01

    We consider the image reconstruction problem for optical tomography with structured illumination. A fast image reconstruction algorithm is proposed that reduces the required number of measurements of the optical field compared to methods that utilize point-source illumination. The results are illustrated with numerical simulations.

  10. Methanogenic activity tests by Infrared Tunable Diode Laser Absorption Spectroscopy.

    PubMed

    Martinez-Cruz, Karla; Sepulveda-Jauregui, Armando; Escobar-Orozco, Nayeli; Thalasso, Frederic

    2012-10-01

    Methanogenic activity (MA) tests are commonly carried out to estimate the capability of anaerobic biomass to treat effluents, to evaluate anaerobic activity in bioreactors or natural ecosystems, or to quantify inhibitory effects on methanogenic activity. These activity tests are usually based on the measurement of the volume of biogas produced by volumetric, pressure increase or gas chromatography (GC) methods. In this study, we present an alternative method for non-invasive measurement of methane produced during activity tests in closed vials, based on Infrared Tunable Diode Laser Absorption Spectroscopy (MA-TDLAS). This new method was tested during model acetoclastic and hydrogenotrophic methanogenic activity tests and was compared to a more traditional method based on gas chromatography. From the results obtained, the CH(4) detection limit of the method was estimated to 60 ppm and the minimum measurable methane production rate was estimated to 1.09(.)10(-3) mg l(-1) h(-1), which is below CH(4) production rate usually reported in both anaerobic reactors and natural ecosystems. Additionally to sensitivity, the method has several potential interests compared to more traditional methods among which short measurements time allowing the measurement of a large number of MA test vials, non-invasive measurements avoiding leakage or external interferences and similar cost to GC based methods. It is concluded that MA-TDLAS is a promising method that could be of interest not only in the field of anaerobic digestion but also, in the field of environmental ecology where CH(4) production rates are usually very low.

  11. Short wavelength laser

    DOEpatents

    Hagelstein, P.L.

    1984-06-25

    A short wavelength laser is provided that is driven by conventional-laser pulses. A multiplicity of panels, mounted on substrates, are supported in two separated and alternately staggered facing and parallel arrays disposed along an approximately linear path. When the panels are illuminated by the conventional-laser pulses, single pass EUV or soft x-ray laser pulses are produced.

  12. Spatial homogeneity criteria for active media of cataphoresis repetitively pulsed metal vapour lasers

    SciTech Connect

    Chebotarev, Gennady D; Prutsakov, Oleg O; Latush, Evgeny L

    2005-07-31

    The formation of the transverse distribution of the metal vapour concentration in repetitively pulsed lasers is analysed. The criterion for the homogeneity of this distribution is found. The optimal conditions for excitation of the active media of cataphoresis repetitively pulsed metal vapour lasers are determined under which a high degree of both longitudinal and transverse homogeneity is achieved. (active media)

  13. Laser-activated gold catalysts for liquid-phase growth of cadmium selenide nanowires.

    PubMed

    Huang, C; Mao, J; Chen, X M; Yang, J; Du, X W

    2015-02-07

    A laser-activated-catalyst (LAC) technique was developed to grow CdSe nanowires in liquid medium at room temperature. The gold catalysts dispersed in the precursor solution were activated by a pulsed laser so as to decompose the precursor and catalyse the nanowire growth simultaneously. The LAC technique can achieve accurate positioning of nanowires, which is beneficial for device fabrication.

  14. Effect of laser irradiation of nanoparticles in aqueous uranium salt solutions on nuclide activity

    SciTech Connect

    Simakin, Aleksandr V; Shafeev, Georgii A

    2011-07-31

    This paper presents an experimental study of the effect of laser irradiation of aqueous uranyl chloride solutions containing gold nanoparticles on the activity of the uranium series radionuclides {sup 234}Th, {sup 234m}Pa, and {sup 235}U. The solutions were exposed to femtosecond Ti:sapphire laser pulses and to the second or third harmonic of a Nd:YAG laser (150-ps pulses) at a peak intensity in the medium of {approx}10{sup 12} W cm{sup -2}. The activities of the radionuclides in the irradiated solutions were shown to differ markedly from their equilibrium values. The sign of the deviation depends on the laser wavelength. The measured activity deviations can be interpreted as evidence that laser exposure of nanoparticles accelerates the alpha and beta decays of the radionuclides. The observed effects are accounted for in terms of a mechanism that involves resonant enhancement of optical waves by metallic nanoparticles. (interaction of laser radiation with matter)

  15. Do humans discount the illuminant?

    NASA Astrophysics Data System (ADS)

    McCann, John J.

    2005-03-01

    In constancy experiments, humans report very small changes in appearance with substantial illumination changes. Hermann von Helmholtz introduced the term "discounting the illuminant" to describe 19th century thinking about underlying mechanisms of constancy. It uses an indirect approach. Since observers see objects as constant, observers "must" be able to detect the spatial and spectral changes in illumination and automatically compensate by altering the signals from the quanta catches of retinal receptors. Instead of solving the problem directly by calculating an object"s reflectance from the array of scene radiances, Helmholtz chose to solve the problem of identifying the illumination. Twentieth century experiments by Hubel and Wiesel, Campbell, Land, and Gibson demonstrate the power of mechanisms using spatial comparisons. This paper analyses a series of different experiments looking for unequivocal evidence that either supports "discounting the illuminant" or supports spatial comparisons as the underlying mechanism of constancy.

  16. Insulator Surface Flashover Due to UV Illumination

    SciTech Connect

    Javedani, J B; Houck, T L; Lahowe, D A; Vogtlin, G E; Goerz, D A

    2009-07-27

    The surface of an insulator under vacuum and under electrical charge will flashover when illuminated by a critical dose of ultra-violet (UV) radiation - depending on the insulator size and material, insulator cone angle, the applied voltage and insulator shot-history. A testbed comprised of an excimer laser (KrF, 248 nm, {approx}16 MW, 30 ns FWHM,), a vacuum chamber, and a negative polarity dc high voltage power supply ({le} -60 kV) were assembled to test 1.0 cm thick angled insulators for surface-flashover. Several candidate insulator materials, e.g. High Density Polyethylene (HDPE), Rexolite{reg_sign} 1400, Macor{trademark} and Mycalex, of varying cone angles were tested against UV illumination. Commercial energy meters were used to measure the UV fluence of the pulsed laser beam. In-house designed and fabricated capacitive probes (D-dots, >12 GHz bandwidth) were embedded in the anode electrode underneath the insulator to determine the time of UV arrival and time of flashover. Of the tested insulators, the +45 degree Rexolite insulator showed more resistance to UV for surface flashover; at UV fluence level of less than 13 mJ/cm{sup 2}, it was not possible to induce a flashover for up to -60 kV of DC potential across the insulator's surface. The probes also permitted the electrical charge on the insulator before and after flashover to be inferred. Photon to electron conversion efficiency for the surface of Rexolite insulator was determined from charge-balance equation. In order to understand the physical mechanism leading to flashover, we further experimented with the +45 degree Rexolite insulator by masking portions of the UV beam to illuminate only a section of the insulator surface; (1) the half nearest the cathode and subsequently, (2) the half nearest the anode. The critical UV fluence and time to flashover were measured and the results in each case were then compared with the base case of full-beam illumination. It was discovered that the time for the

  17. Research on laser protection: an overview of 20 years of activities at Fraunhofer IOSB

    NASA Astrophysics Data System (ADS)

    Ritt, G.; Walter, D.; Eberle, B.

    2013-10-01

    Since the advent of the laser in 1960, the protection of human eyes and sensors against intended or unintended damage by laser radiation is a hot research topic. As long as the parameters of a laser source such as the wavelength and the output power are known, adequate laser safety can be ensured simply by utilizing conventional laser protection filters which are based on absorption or interference effects. This is typically the case in cooperative environments like a laboratory or industrial facilities. A very different situation prevails in military defense or civil security. There, the parameters of encountering laser threats are usually unknown. Protection measures, helping against all types of laser threats, are the long desired objective of countless research activities. The biggest challenge in finding an effective measure arises from single laser pulses of unknown wavelength. The problem demands for a passive protection concept and may be based for example on intensity dependent effects. Moreover, the requested solutions shall comprise add-on possibilities like thin films to be put on existing optics, windshields or glasses. Unfortunately, such an all-embracing solution is still far out of reach. The Fraunhofer IOSB has been working on the evaluation and development of non-conventional laser protection methods for more than 20 years. An overview of the past and present research activities shall be presented, comprising protection measures against laser damaging and laser dazzling.

  18. Lighting with laser diodes

    NASA Astrophysics Data System (ADS)

    Basu, Chandrajit; Meinhardt-Wollweber, Merve; Roth, Bernhard

    2013-08-01

    Contemporary white light-emitting diodes (LEDs) are much more efficient than compact fluorescent lamps and hence are rapidly capturing the market for general illumination. LEDs are also replacing halogen lamps or even newer xenon based lamps in automotive headlamps. Because laser diodes are inherently much brighter and often more efficient than corresponding LEDs, there is great research interest in developing laser diode based illumination systems. Operating at higher current densities and with smaller form factors, laser diodes may outperform LEDs in the future. This article reviews the possibilities and challenges in the integration of visible laser diodes in future illumination systems.

  19. Application of copper vapour lasers for controlling activity of uranium isotopes

    SciTech Connect

    Barmina, E V; Sukhov, I A; Lepekhin, N M; Priseko, Yu S; Filippov, V G; Simakin, Aleksandr V; Shafeev, Georgii A

    2013-06-30

    Beryllium nanoparticles are generated upon ablation of a beryllium target in water by a copper vapour laser. The average size of single crystalline nanoparticles is 12 nm. Ablation of a beryllium target in aqueous solutions of uranyl chloride leads to a significant (up to 50 %) decrease in the gamma activity of radionuclides of the uranium-238 and uranium-235 series. Data on the recovery of the gamma activity of these nuclides to new steady-state values after laser irradiation are obtained. The possibility of application of copper vapour lasers for radioactive waste deactivation is discussed. (laser applications and other topics in quantum electronics)

  20. Picosecond pulse measurements using the active laser medium

    NASA Technical Reports Server (NTRS)

    Bernardin, James P.; Lawandy, N. M.

    1990-01-01

    A simple method for measuring the pulse lengths of synchronously pumped dye lasers which does not require the use of an external nonlinear medium, such as a doubling crystal or two-photon fluorescence cell, to autocorrelate the pulses is discussed. The technique involves feeding the laser pulses back into the dye jet, thus correlating the output pulses with the intracavity pulses to obtain pulse length signatures in the resulting time-averaged laser power. Experimental measurements were performed using a rhodamine 6G dye laser pumped by a mode-locked frequency-doubled Nd:YAG laser. The results agree well with numerical computations, and the method proves effective in determining lengths of picosecond laser pulses.

  1. Matching illumination of solid objects.

    PubMed

    Pont, Sylvia C; Koenderink, Jan J

    2007-04-01

    The appearance of objects is determined by their surface reflectance and roughness and by the light field. Conversely, human observers might derive properties of the light field from the appearance of objects. The inverse problem has no unique solution, so perceptual interactions between reflectance, roughness, and lightfield are to be expected. In two separate experiments, we tested whether observers are able to match the illumination of spheres under collimated illumination only (matching of illumination direction) and under more or less diffuse illumination (matching of illumination direction and directedness of the beam). We found that observers are quite able to match collimated illumination directions of two rendered Lambertian spheres. Matching of the collimated beam directions of a Lambertian sphere and that of a real object with arbitrary reflectance and roughness properties resulted in similar results for the azimuthal angle, but in higher variance for the polar angle. Translucent objects and a tennis ball were found to be systematic outliers. If the directedness of the beam was also varied, the direction settings showed larger variance for more diffuse illumination. The directedness settings showed an overall quite large variance and, interestingly, interacted with the polar angle settings. We discuss possible photometrical mechanisms behind these effects.

  2. Equivalence between free-electron-laser oscillators and actively-mode-locked lasers: Detailed studies of temporal, spatiotemporal, and spectrotemporal dynamics

    SciTech Connect

    Bruni, C.; Legrand, T.; Szwaj, C.; Bielawski, S.; Couprie, M. E.

    2011-12-15

    We show experimentally and numerically that free-electron-laser (FEL) oscillators behave in a very similar way to conventional actively-mode-locked lasers. This stems from the similar structures of their underlying Haus equations. A comparative study of the temporal evolutions of the pulse train shapes and spatiotemporal regimes is performed on a Nd:YVO{sub 4} laser and a storage-ring free-electron laser. Furthermore, since direct observations of time-resolved pulse shapes and spectra are more accessible on free-electron lasers, the analogy also potentially enables one to investigate mode-locked laser dynamics using existing FEL facilities.

  3. Diffuse-Illumination Systems for Growing Plants

    NASA Technical Reports Server (NTRS)

    May, George; Ryan, Robert

    2010-01-01

    Agriculture in both terrestrial and space-controlled environments relies heavily on artificial illumination for efficient photosynthesis. Plant-growth illumination systems require high photon flux in the spectral range corresponding with plant photosynthetic active radiation (PAR) (400 700 nm), high spatial uniformity to promote uniform growth, and high energy efficiency to minimize electricity usage. The proposed plant-growth system takes advantage of the highly diffuse reflective surfaces on the interior of a sphere, hemisphere, or other nearly enclosed structure that is coated with highly reflective materials. This type of surface and structure uniformly mixes discrete light sources to produce highly uniform illumination. Multiple reflections from within the domelike structures are exploited to obtain diffuse illumination, which promotes the efficient reuse of photons that have not yet been absorbed by plants. The highly reflective surfaces encourage only the plant tissue (placed inside the sphere or enclosure) to absorb the light. Discrete light sources, such as light emitting diodes (LEDs), are typically used because of their high efficiency, wavelength selection, and electronically dimmable properties. The light sources are arranged to minimize shadowing and to improve uniformity. Different wavelengths of LEDs (typically blue, green, and red) are used for photosynthesis. Wavelengths outside the PAR range can be added for plant diagnostics or for growth regulation

  4. Structured illumination temporal compressive microscopy

    PubMed Central

    Yuan, Xin; Pang, Shuo

    2016-01-01

    We present a compressive video microscope based on structured illumination with incoherent light source. The source-side illumination coding scheme allows the emission photons being collected by the full aperture of the microscope objective, and thus is suitable for the fluorescence readout mode. A 2-step iterative reconstruction algorithm, termed BWISE, has been developed to address the mismatch between the illumination pattern size and the detector pixel size. Image sequences with a temporal compression ratio of 4:1 were demonstrated. PMID:27231586

  5. Thin-disk laser based on an Yb:YAG / YAG composite active element

    SciTech Connect

    Kuznetsov, I I; Mukhin, I B; Vadimova, O L; Palashov, O V

    2015-03-31

    A thin-disk laser module based on an Yb:YAG / YAG composite active element is developed with a small-signal gain of 1.25 and a stored energy of 400 mJ under cw pumping. The gain and thermally induced phase distortions in the module are studied experimentally. Based on this module, a thin-disk laser with an average power of 300 W and a slope efficiency of 42% is designed. (lasers)

  6. Active stabilization of a diode laser injection lock.

    PubMed

    Saxberg, Brendan; Plotkin-Swing, Benjamin; Gupta, Subhadeep

    2016-06-01

    We report on a device to electronically stabilize the optical injection lock of a semiconductor diode laser. Our technique uses as discriminator the peak height of the laser's transmission signal on a scanning Fabry-Perot cavity and feeds back to the diode current, thereby maintaining maximum optical power in the injected mode. A two-component feedback algorithm provides constant optimization of the injection lock, keeping it robust to slow thermal drifts and allowing fast recovery from sudden failures such as temporary occlusion of the injection beam. We demonstrate the successful performance of our stabilization method in a diode laser setup at 399 nm used for laser cooling of Yb atoms. The device eases the requirements on passive stabilization and can benefit any diode laser injection lock application, particularly those where several such locks are employed.

  7. Active stabilization of a diode laser injection lock

    NASA Astrophysics Data System (ADS)

    Saxberg, Brendan; Plotkin-Swing, Benjamin; Gupta, Subhadeep

    2016-06-01

    We report on a device to electronically stabilize the optical injection lock of a semiconductor diode laser. Our technique uses as discriminator the peak height of the laser's transmission signal on a scanning Fabry-Perot cavity and feeds back to the diode current, thereby maintaining maximum optical power in the injected mode. A two-component feedback algorithm provides constant optimization of the injection lock, keeping it robust to slow thermal drifts and allowing fast recovery from sudden failures such as temporary occlusion of the injection beam. We demonstrate the successful performance of our stabilization method in a diode laser setup at 399 nm used for laser cooling of Yb atoms. The device eases the requirements on passive stabilization and can benefit any diode laser injection lock application, particularly those where several such locks are employed.

  8. Hourly Illumination of Shackleton Crater

    NASA Video Gallery

    Illumination of Shackleton crater, a 21-km-diameter (12.5 mile-diameter) structure situated adjacent to the Moon’s south pole. The resolution is 30 meters (approximately 100 feet) per pixel. Fra...

  9. Laser-activated remote phosphor conversion with ceramic phosphors

    NASA Astrophysics Data System (ADS)

    Lenef, Alan; Kelso, John; Tchoul, Maxim; Mehl, Oliver; Sorg, Jörg; Zheng, Y.

    2014-09-01

    Direct laser activation of a remote phosphor, or LARP, is a highly effective approach for producing very high luminance solid-state light sources. Such sources have much smaller étendue than LEDs of similar power, thereby greatly increasing system luminous fluxes in projection and display applications. While several commercial products now employ LARP technology, most current configurations employ phosphor powders in a silicone matrix deposited on rotating wheels. These provide a low excitation duty cycle that helps limit quenching and thermal overload. These systems already operate close to maximum achievable pump powers and intensities. To further increase power scaling and eliminate mechanical parts to achieve smaller footprints, OSRAM has been developing static LARP systems based on high-thermal conductivity monolithic ceramic phosphors. OSRAM has recently introduced a static LARP product using ceramic phosphor for endoscopy and also demonstrated a LARP concept for automotive forward lighting1. We first discuss the basic LARP concept with ceramic phosphors, showing how their improved thermal conductivity can achieve both high luminous fluxes and luminance in a static configuration. Secondly, we show the importance of scattering and low optical losses to achieving high overall efficiency and light extraction. This is shown through experimental results and radiation transport calculations. Finally, we discuss some of the fundamental factors which limit the ultimate luminance achievable with ceramic converted LARP, including optical pumping effects and thermal quenching.

  10. Optical Properties of Active Regions in Terahertz Quantum Cascade Lasers

    NASA Astrophysics Data System (ADS)

    Dyksik, M.; Motyka, M.; Rudno-Rudziński, W.; Sęk, G.; Misiewicz, J.; Pucicki, D.; Kosiel, K.; Sankowska, I.; Kubacka-Traczyk, J.; Bugajski, M.

    2016-07-01

    In this work, AlGaAs/GaAs superlattice, with layers' sequence and compositions imitating the active and injector regions of a quantum cascade laser designed for emission in the terahertz spectral range, was investigated. Three independent absorption-like optical spectroscopy techniques were employed in order to study the band structure of the minibands formed within the conduction band. Photoreflectance measurements provided information about interband transitions in the investigated system. Common transmission spectra revealed, in the target range of intraband transitions, mainly a number of lines associated with the phonon-related processes, including two-phonon absorption. In contrast, differential transmittance realized by means of Fourier-transform spectroscopy was utilized to probe the confined states of the conduction band. The obtained energy separation between the second and third confined electron levels, expected to be predominantly contributing to the lasing, was found to be ~9 meV. The optical spectroscopy measurements were supported by numerical calculations performed in the effective mass approximation and XRD measurements for layers' width verification. The calculated energy spacings are in a good agreement with the experimental values.

  11. Fiber-laser pumped actively Q-switched Er:LuYAG laser at 1648 nm

    NASA Astrophysics Data System (ADS)

    Yang, X. F.; Wang, Y.; Zhao, T.; Zhu, H. Y.; Shen, D. Y.

    2016-02-01

    We demonstrated an acousto-optic Q-switched 1648 nm Er:LuYAG laser resonantly pumped by a cladding-pumped Er,Yb fiber laser at 1532 nm. Stable Q-switching operation was obtained with the pulse repetition rate (PRR) varying from 200 Hz to 10 kHz. At PRR of 200 Hz, the laser yielded Q-switched pulses with 3.3 mJ pulse energy and 65 ns pulse duration, corresponding to a peak power of 50.7 kW for 10.4 W of incident pump power.

  12. Image plane sweep volume illumination.

    PubMed

    Sundén, Erik; Ynnerman, Anders; Ropinski, Timo

    2011-12-01

    In recent years, many volumetric illumination models have been proposed, which have the potential to simulate advanced lighting effects and thus support improved image comprehension. Although volume ray-casting is widely accepted as the volume rendering technique which achieves the highest image quality, so far no volumetric illumination algorithm has been designed to be directly incorporated into the ray-casting process. In this paper we propose image plane sweep volume illumination (IPSVI), which allows the integration of advanced illumination effects into a GPU-based volume ray-caster by exploiting the plane sweep paradigm. Thus, we are able to reduce the problem complexity and achieve interactive frame rates, while supporting scattering as well as shadowing. Since all illumination computations are performed directly within a single rendering pass, IPSVI does not require any preprocessing nor does it need to store intermediate results within an illumination volume. It therefore has a significantly lower memory footprint than other techniques. This makes IPSVI directly applicable to large data sets. Furthermore, the integration into a GPU-based ray-caster allows for high image quality as well as improved rendering performance by exploiting early ray termination. This paper discusses the theory behind IPSVI, describes its implementation, demonstrates its visual results and provides performance measurements.

  13. Secure communication via quantum illumination

    NASA Astrophysics Data System (ADS)

    Shapiro, Jeffrey H.; Zhang, Zheshen; Wong, Franco N. C.

    2014-10-01

    In the quantum illumination protocol for secure communication, Alice prepares entangled signal and idler beams via spontaneous parametric downconversion. She sends the signal beam to Bob, while retaining the idler. Bob imposes message modulation on the beam he receives from Alice, amplifies it, and sends it back to her. Alice then decodes Bob's information by making a joint quantum measurement on the light she has retained and the light she has received from him. The basic performance analysis for this protocol—which demonstrates its immunity to passive eavesdropping, in which Eve can only listen to Alice and Bob's transmissions—is reviewed, along with the results of its first proof-of-principle experiment. Further analysis is then presented, showing that secure data rates in excess of 1 Gbps may be possible over 20-km-long fiber links with technology that is available or under development. Finally, an initial scheme for thwarting active eavesdropping, in which Eve injects her own light into Bob's terminal, is proposed and analyzed.

  14. Active Interrogation of Sensitive Nuclear Material Using Laser Driven Neutron Beams

    SciTech Connect

    Favalli, Andrea; Roth, Markus

    2015-05-01

    An investigation of the viability of a laser-driven neutron source for active interrogation is reported. The need is for a fast, movable, operationally safe neutron source which is energy tunable and has high-intensity, directional neutron production. Reasons for the choice of neutrons and lasers are set forth. Results from the interrogation of an enriched U sample are shown.

  15. Ultra-intense Laser Applications to the Industries at GPI

    SciTech Connect

    Kitagawa, Yoneyoshi; Mori, Yoshitaka; Ootsuka, Shuji; Makino, Takahiro; Ohta, Mari; Suzuki, Tetsuya; Kuwabara, Hajime

    2009-01-22

    The laser accelerator provides us not only ultra high field, but also extremely short pulse radiation sources, the laser-produced X-rays. Using a 1.2 TW table-top Ti:sap laser, we are pursuing the activities for the industrial application. First we proposed a new injection acceleration scheme using the ultra short beat-wave accelerator for the economical radiation source. Then we proposed two applications both on the backward see-through vision of distant objects using the laser X-rays, and on the X-ray illumination on Aspergillus awamori spores, which is 100 times effective of the current X-ray tube cases.

  16. generation of picosecond pulses in solid-state lasers using new active media

    SciTech Connect

    Lisitsyn, V.N.; Matrosov, V.N.; Pestryakov, E.V.; Trunov, V.I.

    1986-07-01

    Results are reported of investigations aimed at generating nanosecond radiation pulses in solid-state lasers using new active media having broad gain lines. Passive mode locking is accomplished for the first time in a BeLa:Nd/sup 3/ laser at a wavelength 1.354 microm, and in a YAG:Nd/sup 3/ laser on a 1.32-microm transition. The free lasing and mode-locking regimes were investigated in an alexandrite (BeA1/sub 2/O/sub 4/:Cr/sup 3/) laser in the 0.72-0.78-microm range and in a synchronously pumped laser on F/sub 2//sup -/ centers in LiF in the 1.12-1.24-microm region. The features of nonlinear perception of IR radiation by the eye, using a developed picosecond laser on F/sub 2//sup -/ centers, are investigated for the first time.

  17. Active mode locking of quantum cascade lasers in an external ring cavity

    PubMed Central

    Revin, D. G.; Hemingway, M.; Wang, Y.; Cockburn, J. W.; Belyanin, A.

    2016-01-01

    Stable ultrashort light pulses and frequency combs generated by mode-locked lasers have many important applications including high-resolution spectroscopy, fast chemical detection and identification, studies of ultrafast processes, and laser metrology. While compact mode-locked lasers emitting in the visible and near infrared range have revolutionized photonic technologies, the systems operating in the mid-infrared range where most gases have their strong absorption lines, are bulky and expensive and rely on nonlinear frequency down-conversion. Quantum cascade lasers are the most powerful and versatile compact light sources in the mid-infrared range, yet achieving their mode-locked operation remains a challenge, despite dedicated effort. Here we report the demonstration of active mode locking of an external-cavity quantum cascade laser. The laser operates in the mode-locked regime at room temperature and over the full dynamic range of injection currents. PMID:27147409

  18. Tetravalent Chromium (Cr(4+)) as Laser-Active Ion for Tunable Solid-State Lasers

    NASA Technical Reports Server (NTRS)

    Seas, A.; Petricevic, V.; Alfano, Robert R.

    1993-01-01

    During 10/31/92 - 3/31/93, the following summarizes our major accomplishments: (1) the self-mode-locked operation of the Cr:forsterite laser was achieved; (2) synchronous pumping was used to mode lock the forsterite laser resulting in picosecond pulses, which in turn provided the starting mechanism for self-mode-locking; and (3) the pulses generated had a FWHW of 105 fs and were tunable between 1230 - 1270 nm.

  19. NEW ACTIVE MEDIA AND ELEMENTS OF LASER SYSTEMS: Laser with resonators coupled by a dynamic hologram

    NASA Astrophysics Data System (ADS)

    Gerasimov, V. B.; Golyanov, A. V.; Luk'yanchuk, B. S.; Ogluzdin, Valerii E.; Rubtsova, I. L.; Sugrobov, V. A.; Khizhnyak, A. I.

    1987-11-01

    The nature of operation of a laser with a phase-conjugate mirror utilizing multibeam interaction was found to have a considerable influence on the coupling of its resonator to the resonator of a laser used to pump the mirror. A system of this kind with resonators coupled by a dynamic hologram exhibited "soft" lasing in the presence of a self-pumped phase-conjugate mirror.

  20. Laser ion source activities at Brookhaven National Laboratory

    DOE PAGES

    Kanesue, Takeshi; Okamura, Masahiro

    2015-07-31

    In Brookhaven National Laboratory (BNL), we have been developing laser ion sources for diverse accelerators. Tabletop Nd:YAG lasers with up to several Joules of energy are mainly used to create ablation plasmas for stable operations. The obtained charge states depend on laser power density and target species. Two types of ion extraction schemes, Direct Plasma Injection Scheme (DPIS) and conventional static extraction, are used depending on application. We optimized and select a suitable laser irradiation condition and a beam extraction scheme to meet the requirement of the following accelerator system. We have demonstrated to accelerate more than 5 x 1010more » of C6+ ions using the DPIS. We successfully commissioned low charge ion beam provider to the user facilities in BNL. As a result, to achieve higher current, higher charge state and lower emittance, further studies will continue.« less

  1. Laser ion source activities at Brookhaven National Laboratory

    SciTech Connect

    Kanesue, Takeshi; Okamura, Masahiro

    2015-07-31

    In Brookhaven National Laboratory (BNL), we have been developing laser ion sources for diverse accelerators. Tabletop Nd:YAG lasers with up to several Joules of energy are mainly used to create ablation plasmas for stable operations. The obtained charge states depend on laser power density and target species. Two types of ion extraction schemes, Direct Plasma Injection Scheme (DPIS) and conventional static extraction, are used depending on application. We optimized and select a suitable laser irradiation condition and a beam extraction scheme to meet the requirement of the following accelerator system. We have demonstrated to accelerate more than 5 x 1010 of C6+ ions using the DPIS. We successfully commissioned low charge ion beam provider to the user facilities in BNL. As a result, to achieve higher current, higher charge state and lower emittance, further studies will continue.

  2. Active imaging system with Faraday filter

    SciTech Connect

    Snyder, J.J.

    1992-12-31

    This invention is comprised of an active imaging system which has a low to medium powered laser transmitter and a receiver wherein the receiver includes a Faraday filter with an ultranarrow optical bandpass and a bare (nonintensified) CCD camera. The laser is locked in the vicinity of the passband of the Faraday filter. The system has high sensitivity to the laser illumination wile eliminating solar background.

  3. Passive and Active Protective Clothing against High-Power Laser Radiation

    NASA Astrophysics Data System (ADS)

    Hennigs, C.; Hustedt, M.; Kaierle, S.; Wenzel, D.; Markstein, S.; Hutter, A.

    The main objective of the work described in this paper was the development of passive and active protective clothing for the protection of the human skin against accidental laser irradiation and of active protective curtains. Here, the passive systems consist of functional multi-layer textiles, providing a high level of passive laser resistance. In addition, the active functional multi-layer textiles incorporate sensors that detect laser exposure and are, by means of a safety control, able to deactivate the laser beam automatically.Due to the lack of regulations for testing and qualifying textiles to be used as laser PPE, test methods were defined and validated. Additionally, corresponding testing set-ups were developed.Finally, the gap with respect to standardization was bridged by the definition of a test procedure and the requirements with respect to laser PPE.The developments were demonstrated by a set of tailored functional passive and active laser-protective clothing prototypes (gloves, jackets, aprons, trousers) and active curtains as well as by a prototype testing rig, providing the possibility to perform the specified low-power and high-power textile test procedure.

  4. Laser light induced modulations in metabolic activities in human brain cancer

    NASA Astrophysics Data System (ADS)

    Tata, Darrell B.; Waynant, Ronald W.

    2008-03-01

    The role of low visible or near infra-red laser intensity in suppressing metabolic activity of malignant human brain cancer (glioblastoma) cells was investigated through the application of either a continuous wave 633nm HeNe or a pulsed picosecond 1,552nm wavelength laser. Human glioblastomas were exposed in their growth culture medium with serum for several energy doses. For both types of laser exposures the glioblastomas exhibited a maximal decline in the metabolic activity relative to their respective sham control counterparts at 10 J/cm2. The cellular metabolic activities for various treatment doses were measured through the colorimetric MTS metabolic assay after the laser exposure. Interestingly, addition of (the enzyme) catalase in the growth medium prior to the laser exposure was found to diminish the laser induced metabolic suppression for all fluence treatment conditions, thus suggesting a functional role of H IIO II in the metabolic suppression. Taken together, our findings reveal that visible or near infra-red low level light exposures could potentially be a viable tool in reducing the metabolic activity of cancers; evidence at hand implicates a role of light induced H IIO II in bringing about in part, suppression in the metabolic activity. Due to the cellular "biphasic" response to the laser exposure, further research needs to be undertaken to determine exposure parameters which would optimize metabolic and cellular growth suppression in-vivo.

  5. Development of mid-IR lasers for Laser Remote Sensing

    NASA Technical Reports Server (NTRS)

    Soibel, Alexander; Mansour, Kamjou; Spiers, Gary; Forouhar, Siamak

    2005-01-01

    There is an existing need in JPL and in NASA for development of mid-IR lasers, such as Quantum Cascade (QC) lasers, for in-situ and remote laser spectrometers. Mid-IR, compact, low power consumption laser spectrometers have a great potential for detection and measurements of planetary gases and biological important biomarker molecules such as H20, H202, CH4, and many additional chemical species on Mars and other Solar system planets. Another potential application of QC lasers for future NASA mission is in high power remote Laser Reflectance Spectrometers (LRS). In LSR instrument, mid-infrared lasers will act as the illumination source for conducting active mid-IR reflectance spectroscopy of solid-surfaced objects in the outer Solar System. These spectrometers have the potential to provide an incredible amount of information about the compositions of surfaces in the outer Solar System. In this work, we will discuss our current effort at JPL to advance QC lasers to a level that the laser performance, operational requirements and reliability be compatible with the instruments demands for space exploration applications.

  6. Specimen illumination apparatus with optical cavity for dark field illumination

    DOEpatents

    Pinkel, Daniel; Sudar, Damir; Albertson, Donna

    1999-01-01

    An illumination apparatus with a specimen slide holder, an illumination source, an optical cavity producing multiple reflection of illumination light to a specimen comprising a first and a second reflective surface arranged to achieve multiple reflections of light to a specimen is provided. The apparatus can further include additional reflective surfaces to achieve the optical cavity, a slide for mounting the specimen, a coverslip which is a reflective component of the optical cavity, one or more prisms for directing light within the optical cavity, antifading solutions for improving the viewing properties of the specimen, an array of materials for analysis, fluorescent components, curved reflective surfaces as components of the optical cavity, specimen detection apparatus, optical detection equipment, computers for analysis of optical images, a plane polarizer, fiberoptics, light transmission apertures, microscopic components, lenses for viewing the specimen, and upper and lower mirrors above and below the specimen slide as components of the optical cavity. Methods of using the apparatus are also provided.

  7. Continuous-wave and actively Q-switched Nd:LSO crystal lasers

    NASA Astrophysics Data System (ADS)

    Zhuang, S.; Li, D.; Xu, X.; Wang, Z.; Yu, H.; Xu, J.; Chen, L.; Zhao, Y.; Guo, L.; Xu, X.

    2012-04-01

    With a fiber coupled laser diode array as the pump source, Nd-doped Lu2SiO5 (Nd:LSO) crystal lasers at 4F3/2→4I11/2 and 4F3/2→4I13/2 transitions were demonstrated. The active Q-switched dual-wavelength lasers at about 1.08 μm, as well as continuous-wave (CW) and active Q-switched lasers at 1357 nm are reported for the first time, to the best of our knowledge. Considering the small emission cross-sections and long fluorescence lifetime, this material possesses large energy storage ability and excellent Q-switched properties. The special emission wavelength at 1357 nm will have promising applications to be used in many fields, such as THz generation, pumping of Cr3+:LiSAF, repumping of strontium optical clock, laser Doppler velocimeter and distributed fiber sensor.

  8. Kinetic Monte Carlo simulations of boron activation in implanted Si under laser thermal annealing

    NASA Astrophysics Data System (ADS)

    Fisicaro, Giuseppe; Pelaz, Lourdes; Aboy, Maria; Lopez, Pedro; Italia, Markus; Huet, Karim; Cristiano, Filadelfo; Essa, Zahi; Yang, Qui; Bedel-Pereira, Elena; Quillec, Maurice; La Magna, Antonino

    2014-02-01

    We investigate the correlation between dopant activation and damage evolution in boron-implanted silicon under excimer laser irradiation. The dopant activation efficiency in the solid phase was measured under a wide range of irradiation conditions and simulated using coupled phase-field and kinetic Monte Carlo models. With the inclusion of dopant atoms, the presented code extends the capabilities of a previous version, allowing its definitive validation by means of detailed comparisons with experimental data. The stochastic method predicts the post-implant kinetics of the defect-dopant system in the far-from-equilibrium conditions caused by laser irradiation. The simulations explain the dopant activation dynamics and demonstrate that the competitive dopant-defect kinetics during the first laser annealing treatment dominates the activation phenomenon, stabilizing the system against additional laser irradiation steps.

  9. The DESI shutter with integrated fiber illumination system

    NASA Astrophysics Data System (ADS)

    Derwent, Mark A.; O'Brien, Thomas P.; Pappalardo, Daniel P.; Martini, Paul; Coker, Carl T.; Pogge, Richard W.

    2016-08-01

    The Dark Energy Spectroscopic Instrument (DESI) is under construction to measure the expansion history of the Universe using the Baryon Acoustic Oscillation technique. The spectra of 40 million galaxies over 14,000 sq deg will be measured during the life of the experiment. A new prime focus corrector for the KPNO Mayall telescope will deliver light to 5000 fiber optic positioners. The fibers in turn feed ten broad-band spectrographs. We describe the unique shutter design that incorporates a fiber illumination system into the shutter blade. When activated, the fiber illumination system directs intense 430-480nm wavelength light at the instrument's fiber slit in order to back-illuminate the telescope's focal plane and verify the location of the robotic fiber positioners. The back-illumination is typically active during science exposure read-outs and therefore requires the shutter to attenuate light by a factor of at least 107. This paper describes how we have integrated the fiber illumination system into the shutter blade, as well as incorporated an inflatable seal around the shutter aperture to achieve the light attenuation requirement. We also present lab results that characterize the fiber illumination and shutter attenuation. Finally, we discuss the control scheme that executes exposure and fiber illumination modes, and meets the shutter timing requirements.

  10. Active waveguides written by femtosecond laser irradiation in an erbium-doped phospho-tellurite glass.

    PubMed

    Fernandez, T Toney; Della Valle, G; Osellame, R; Jose, G; Chiodo, N; Jha, A; Laporta, P

    2008-09-15

    We report on fs-laser micromachining of active waveguides in a new erbium-doped phospho-tellurite glass by means of a compact cavity-dumped Yb-based writing system. The spectroscopic properties of the glass were investigated, and the fs-laser written waveguides were characterized in terms of passive as well as active performance. In particular, internal gain was demonstrated in the whole C+L band of optical communications (1530- 1610 nm).

  11. Digital in-line holographic microscope based on the grating illumination with improved resolution by interpolation

    NASA Astrophysics Data System (ADS)

    Feng, Shaodong; Wang, Mingjun; Wu, Jigang

    2016-10-01

    High resolution is always a pursuing target in the imaging field, as a new prospective technique in imaging applications, digital in-line holography has become a very active field for compactness, more information and low-cost. However, for compact system, the resolution is often limited by sensor pixel size. To overcome this problem, we propose an iterative reconstruction method with data interpolation based on the grating illumination. In our method, the Talbot self-image of a Ronchi grating is exerted in the sample plane as a priori constraint which lead to the convergence of the iteration, the iteration between the sample plane and the sensor plane can provide some extra information with interpolation in the sensor plane based on the a priori constraint, furthermore, the iteration reconstruction can also eliminates the twin-image to improve the image quality. Numerical simulation has been conducted to show the effectiveness of this method. In order to make a further verification, we have developed a lensless in-line holographic microscope with a compact and wide field-of-view design. In our setup, the sample was under the Talbot image illumination of the Ronchi grating, which was illuminated by a collimated laser beam, and holograms were recorded by a digital imaging sensor. We can shift the grating laterally to get a wide-field image. We demonstrated the resolution of our imaging system by using the USAF resolution target as a sample, and the results shown the resolution improvement of the image.

  12. Effect of the active-ion concentration on the lasing dynamics of holmium fibre lasers

    SciTech Connect

    Kurkov, Andrei S; Sholokhov, E M; Marakulin, A V; Minashina, L A

    2010-12-09

    The lasing dynamics of fibre lasers with a core based on quartz glass doped with holmium ions to concentrations in the range of 10{sup 19}-10{sup 20} cm{sup -3} is investigated. It is shown that fibre lasers with a high concentration of active holmium ions generate pulses, but a decrease in the holmium concentration changes the lasing from pulsed to cw regime. At the same time, a decrease in the active-ion concentration and the corresponding increase in the fibre length in the cavity reduce the lasing efficiency. (lasers)

  13. Prismatic louver active façades for natural illumination and thermal energy gain in high-rise and commercial buildings

    NASA Astrophysics Data System (ADS)

    Vlachokostas, A.; Volkmann, C.; Madamopoulos, N.

    2013-06-01

    High-rise and commercial buildings in urban centers present a great challenge in terms of their energy consumption. Due to maximization of rentable square footage, the preferred urban façade system over the past 50 years has been the "curtain wall", only a few inches thick and comprised of modular steel or aluminum framing and predominant glass infills. The perceived Achilles heel of these modern glass façade systems is their thermal inefficiency: They are inadequate thermal barriers and exhibit excessive solar gain. The excessive solar gain has a negative impact on lighting and cooling loads of the entire building. This negative impact will be further exacerbated with rising energy costs. However, rather than view the glass façade's uncontrolled solar gain merely as a weakness contributing to higher energy consumption, the condition could indeed be considered as related to an energy solution. These glass façades can be retrofitted to operate as a provider of daylight and energy for the rest of the building, taking advantage of the overexposure to the sun. With today's technology, the sun's abundant renewable energy can be the driving force for the energy transition of these building envelopes. Illumination, thermal energy, and electricity production can be directly supplied from the sun, and when correctly and efficiently managed, they can lead to a significantly less energy-intensive building stock. We propose a multi-purpose, prismatic, louver-based façade to perform both daylight and thermal energy harvesting with a goal of offering a better daylight environment for the occupants, and reduce the energy consumption and carbon footprint of the building. While decentralized air-conditioning units are commonly accepted as façade "plug-ins", such decentralization could be utilized with more benefits by passively managing the interior space conditions, without using any extra power. Just as living organisms respond and adapt to the environmental changes in

  14. Laparoscopic applications of laser-activated tissue glues

    NASA Astrophysics Data System (ADS)

    Bass, Lawrence S.; Oz, Mehmet C.; Auteri, Joseph S.; Williams, Matthew R.; Rosen, Jeffrey; Libutti, Steven K.; Eaton, Alexander M.; Lontz, John F.; Nowygrod, Roman; Treat, Michael R.

    1991-07-01

    The rapid growth of laparoscopic cholecystectomy and other laparoscopic procedures has created the need for simple, secure techniques for laparoscopic closure without sutures. While laser tissue welding offers one solution to this problem, concerns about adequacy of weld strength and watertightness remain. Tissue solders are proteinaceous materials which are placed on coapted tissue edges of the tissue to be closed or sealed. Laser energy is then applied to fix the glue in place completing the closure. Closure of the choledochotomy following a laparoscopic common duct exploration is one potential application of this technique. Canine longitudinal choledochotomies 5 mm in length were sealed using several laser glues and using the 808 nm diode laser. Saline was then infused until rupture of the closure and peak bursting strength recorded. Fibrinogen glue provided moderately good adhesion but poor burst strength. Handling characteristics were variable. A viscosity adjusted fibrinogen preparation produced good adherence with mean weld strength 264 +/- 7 mm Hg. The clinical endpoint for welding was a whitening and drying of the tissue. New laser solders can provide a watertight choledochotomy closure of adequate immediate strength. This would allow reliable, technically feasible common bile duct exploration via a laparoscopic approach.

  15. Clinical and Spectrophotometric Evaluation of LED and Laser Activated Teeth Bleaching

    PubMed Central

    Lo Giudice, R.; Pantaleo, G.; Lizio, A.; Romeo, U.; Castiello, G.; Spagnuolo, G.; Giudice, G. Lo

    2016-01-01

    Background: Auxiliary power sources (LED and laser) are used in in-office teeth bleaching techniques to accelerate the redox reaction of the whitening gel to increase ease of use, to improve comfort and safety, and to decrease the procedure time. Objective: The aim this study is to evaluate the efficiency of the teeth whitening procedures performed with hydrogen peroxide and carbamide peroxide, LED or Laser activated. Method: 18 patients, affected by exogenous dyschromia, were treated with a bleaching agent composed by 35% hydrogen peroxide and 10% carbamide peroxide. They were divided into two groups: in the first group the bleaching agent was activated by a LED lamp; in the second group it was activated by a Laser diode lamp. Both groups were subjected to 3 bleaching cycle of 15’ each. The chromatic evaluations were performed before and after one week from the treatment, using a chromatic scale and a spectrophotometer. The mean value of pre, post bleaching and follow-up were analyzed using a T-test, with results statistically significant for P<0,05. Results: Results showed that the variations in brightness, chroma and hue are significantly influenced by the interaction between the whitening agent and the original colour of the teeth. Laser-activation has marginally improved the bleaching effectiveness. All patients treated with laser activation complained an increase in dental sensitivity. Conclusion: The use of laser-activating systems did not improve the efficacy of bleaching. PMID:27386010

  16. Deformation of partially pumped active mirrors for high average-power diode-pumped solid-state lasers.

    PubMed

    Albach, Daniel; LeTouzé, Geoffroy; Chanteloup, Jean-Christophe

    2011-04-25

    We discuss the deformation of a partially pumped active mirror amplifier as a free standing disk, as implemented in several laser systems. We rely on the Lucia laser project to experimentally evaluate the analytical and numerical deformation models.

  17. Biological activity of photoproducts of merocyanine 540 generated by laser-light activation

    NASA Astrophysics Data System (ADS)

    Gulliya, Kirpal S.; Chanh, Tran C.; Pervaiz, Shazib; Harriman, Anthony; Matthews, James Lester

    1992-08-01

    Controlled exposure of photoactive compounds to light prior to their use in biological targets results in the formation of heretofore unknown photoproducts. This process of photoproduct generation, termed "preactivation," renders the photactive compound capable of systemic use without further dependence on light. Preactivation of mercyanin 540 (MC540) and several other photoactive compounds is achievable by exposure to CW and pulse laser radiation. The singlet oxygen generated at excited states attacks the dye molucule itself, resulting in the formation of biologically active photoproducts. For preactivated MC540 (photoproducts of MC540) generated by exposure to argon laser light (514 nm) and light from free-electron laser, we have demonstrated its effectiveness in selective killing of certain types of cultured tumor cells as well as human immunodeficiency virus type 1 (HIV-1) with very low, if any, damage to normal cells and tisues. For example, approximately 90% of the Burkitt's lymphoma Daudi cells and HL-60 leukemic cells are killed by preactivated MC540 at a concentration of 120 μg/ml. A two-hour treatment of cultured cells with buthionine sulfoxamine followed by the treatement with preactivated MC540 reults in 99.99% inhibition of clonogenic tumor stem cell growth. We also have demonstrated that preactivated MC540 is very effective in killing cell-free and cell-associated HIV-1. It also is very effective in killing HIV-1 and simian immunodeficiency virus (SIV) in virus-infected blood in vitro as determined by reverse transcriptase, P24, P17, core antigen expression and synctium formation. Treatment of HIV-1 with preactivated MC540 renders the treated HIV-1 incapable of binding to CD4 target molecules on T cells as determined by immunofluorescence and radioimmunoprecipitation assays. In vivo toxicology studies show that preactivated MC540 is very well tolerated and does not produce any signs of adverse reaction at the therapeutic doses, as determined by

  18. Modulation of cardiomyocyte activity using pulsed laser irradiated gold nanoparticles

    PubMed Central

    Gentemann, Lara; Kalies, Stefan; Coffee, Michelle; Meyer, Heiko; Ripken, Tammo; Heisterkamp, Alexander; Zweigerdt, Robert; Heinemann, Dag

    2016-01-01

    Can photothermal gold nanoparticle mediated laser manipulation be applied to induce cardiac contraction? Based on our previous work, we present a novel concept of cell stimulation. A 532 nm picosecond laser was employed to heat gold nanoparticles on cardiomyocytes. This leads to calcium oscillations in the HL-1 cardiomyocyte cell line. As calcium is connected to the contractility, we aimed to alter the contraction rate of native and stem cell derived cardiomyocytes. A contraction rate increase was particularly observed in calcium containing buffer with neonatal rat cardiomyocytes. Consequently, the study provides conceptual ideas for a light based, nanoparticle mediated stimulation system. PMID:28101410

  19. Lasers.

    PubMed

    Passeron, T

    2012-12-01

    Lasers are a very effective approach for treating many hyperpigmented lesions. They are the gold standard treatment for actinic lentigos and dermal hypermelanocytosis, such as Ota nevus. Becker nevus, hyperpigmented mosaicisms, and lentigines can also be successfully treated with lasers, but they could be less effective and relapses can be observed. However, lasers cannot be proposed for all types of hyperpigmentation. Thus, freckles and café-au-lait macules should not be treated as the relapses are nearly constant. Due to its complex pathophysiology, melasma has a special place in hyperpigmented dermatoses. Q-switched lasers (using standard parameters or low fluency) should not be used because of consistent relapses and the high risk of post-inflammatory hyperpigmentation. Paradoxically, targeting the vascular component of the melasma lesion with lasers could have a beneficial effect. However, these results have yet to be confirmed. In all cases, a precise diagnosis of the type of hyperpigmentation is mandatory before any laser treatment, and the limits and the potential side effects of the treatment must be clearly explained to patients.

  20. [Lasers].

    PubMed

    Passeron, T

    2012-11-01

    Lasers are a very effective approach for treating many hyperpigmented lesions. They are the gold standard treatment for actinic lentigos and dermal hypermelanocytosis, such as Ota nevus. Becker nevus, hyperpigmented mosaicisms, and lentigines can also be successfully treated with lasers, but they could be less effective and relapses can be observed. However, lasers cannot be proposed for all types of hyperpigmentation. Thus, freckles and café-au-lait macules should not be treated as the relapses are nearly constant. Due to its complex pathophysiology, melasma has a special place in hyperpigmented dermatoses. Q-switched lasers (using standard parameters or low fluency) should not be used because of consistent relapses and the high risk of post-inflammatory hyperpigmentation. Paradoxically, targeting the vascular component of the melasma lesion with lasers could have a beneficial effect. However, these results have yet to be confirmed. In all cases, a precise diagnosis of the type of hyperpigmentation is mandatory before any laser treatment, and the limits and the potential side effects of the treatment must be clearly explained to patients.

  1. Tetravalent Chromium (Cr(4+)) as Laser-Active Ion for Tunable Solid-State Lasers

    NASA Technical Reports Server (NTRS)

    Seas, A.; Petricevic, V.; Alfano, Robert R.

    1992-01-01

    During 10/31/91 - 3/31/92, the following summarizes are major accomplishments: (1) numerical modeling of the four mirror astigmatically compensated, Z-fold cavity was performed; and (2) the simulation revealed several design parameters to be used for the construction of a femtosecond forsterite laser.

  2. Activation of VEGF and FGF induced angiogenesis under influence of low level laser radiation in vitro

    NASA Astrophysics Data System (ADS)

    Gasparyan, Levon; Brill, Grigory; Makela, Anu

    2006-02-01

    One of the feasible explanations for long-term treatment effects of laser therapy of diseases connected with tissue ischemia and altered blood circulation is activation of angiogenesis after low level laser irradiation. The aim of the current study was to investigate if laser irradiation can enhance vascular endothelial growth factor (VEGF) or basic fibroblast growth factor (FGF) induced angiogenesis in vitro. The study was conducted on rat thoracic aortal rings. Samples of group 1 served as control, samples of groups 2 and 3 were incubated with VEGF or FGF, group 4 samples were irradiated with laser (660 nm, 20 mW) during 10 min, samples of groups 5 and 6 were incubated with VEGF or FGF accordingly and received 10 min of laser irradiation. In the control group no noticeable angiogenesis occurred. The application of VEGF activated angiogenesis: the area covered by new vessels was 1,3+/-0,24 mm2 and the maximal length of vessels was 0,93+/-0,11 mm. Laser light irradiation (group 4) activated angiogenesis (1,9+/-0,29 mm2 and 0,75+/-0,10 mm). The combined influence of laser light and VEGF on angiogenesis (group 5) was significantly stronger (p <0,001), than each of the factors separately (6,98+/-0,88 mm2 and 1,7+/-0,23 mm). Application of FGF also activated angiogenesis: the area covered by new vessels was 2,76+/-0,22 mm2 and the maximal length of vessels was 1,19+/-0,12 mm. Combined influence of laser light and FGF on angiogenesis (group 6) was again significantly stronger (p <0,001), than each of the factors separately (5,43+/-0,28 mm2 and 1,99+/-0,10 mm). Studies show that laser irradiation can intensify effects of growth factors in vitro.

  3. Illumination analysis of LAPAN's IR micro bolometer

    NASA Astrophysics Data System (ADS)

    Bustanul, A.; Irwan, P.; Andi M., T.

    2016-10-01

    We have since 2 years ago been doing a research in term of an IR Micrometer Bolometer which aims to fulfill our office, LAPAN, desire to put it as one of payloads into LAPAN's next micro satellite project, either at LAPAN A4 or at LAPAN A5. Due to the lack of experience on the subject, everything had been initiated by spectral radiance analysis adjusted by catastrophes sources in Indonesia, mainly wild fire (forest fire) and active volcano. Based on the result of the appropriate spectral radiance wavelength, 3.8 - 4 μm, and field of view (FOV), we, then, went through the further analysis, optical analysis. Focusing in illumination matter, the process was done by using Zemax software. Optical pass Interference and Stray light were two things that become our concern throughout the work. They could also be an evaluation of the performance optimization of illumination analysis of our optical design. The results, graphs, show that our design performance is close diffraction limited and the image blur of the geometrical produced by Lapan's IR Micro Bolometer lenses is in the pixel area range. Therefore, our optical design performance is relatively good and will produce image with high quality. In this paper, the Illumination analysis and process of LAPAN's Infra Red (IR) Micro Bolometer is presented.

  4. Role of ROS-mediated TGF beta activation in laser photobiomodulation

    NASA Astrophysics Data System (ADS)

    Arany, Praveen R.; Chen, Aaron Chih-Hao; Hunt, Tristan; Mooney, David J.; Hamblin, Michael

    2009-02-01

    The ability of laser light to modulate specific biological processes has been well documented but the precise mechanism mediating these photobiological interactions remains an area of intense investigation. We recently published the results of our clinical trial with 30 patients in an oral tooth-extraction wound healing model using a 904nm GaAs laser (Oralaser 1010, Oralia, Konstnaz, Germany), assessing healing parameters using routine histopathology and immunostaining (Arany et al Wound Rep Regen 2007, 15, 866). We observed a better organized healing response in laser irradiated oral tissues that correlated with an increased expression of TGF-beta1 immediately post laser irradiation. Our data suggested the source of latent TGF-beta1 might be from the degranulating platelets in the serum, an abundant source of in vivo latent TGF-beta, in the freshly wounded tissues. Further, we also demonstrated the ability of the low power near-infrared laser irradiation to activate the latent TGF-beta complexes in vitro at varying fluences from 10sec (0.1 J/cm2) to 600secs (6 J/cm2). Using serum we observed two isoforms, namely TGF-beta1 and TGF-beta3, were capable of being activated by laser irradiation using an isoform-specific ELISA and a reporter based (p3TP) assay system. We are presently pursuing the precise photomolecular mechanisms focusing on potential chromophores, wavelength and fluence parameters affecting the Latent TGF-beta activation process in serum. As ROS mediated TGF-beta activation has been previously demonstrated and we are also exploring the role of Laser generated-ROS in this activation process. In summary, we present evidence of a potential molecular mechanism for laser photobiomodulation in its ability to activate latent TGF-beta complexes.

  5. Illumination Conditions of the Lunar Polar Regions Using LOLA Topography

    NASA Technical Reports Server (NTRS)

    Mazarico, E.; Neumann, G. A.; Smith, D. E.; Zuber, M. T.; Torrence, M. H.

    2011-01-01

    We use high-resolution altimetry data obtained by the Lunar Orbiter Laser Altimeter instrument onboard the Lunar Reconnaissance Orbiter to characterize present illumination conditions in the polar regions of the Moon. Compared to previous studies, both the spatial and temporal extent of the simulations are increased significantly, as well as the coverage (fill ratio) of the topographic maps used, thanks to the 28 Hz firing rate of the five-beam instrument. We determine the horizon elevation in a number of directions based on 240 m-resolution polar digital elevation models reaching down to 75 latitude. The illumination of both polar regions extending to 80 can be calculated for any geometry from those horizon longitudinal profiles. We validated our modeling with recent Lunar Reconnaissance Orbiter Wide-Angle Camera images. We assessed the extent of permanently shadowed regions (PSRs, defined as areas that never receive direct solar illumination), and obtained total areas generally larger than previous studies (12,866 and 16,055 km2, in the north and south respectively). We extended our direct illumination model to account for singly-scattered light, and found that every PSR does receive some amount of scattered light during the year. We conducted simulations over long periods (several 18.6-years lunar precession cycles) with a high temporal resolution (6 h), and identified the most illuminated locations in the vicinity of both poles. Because of the importance of those sites for exploration and engineering considerations, we characterized their illumination more precisely over the near future. Every year, a location near the Shackleton crater rim in the south polar region is sunlit continuously for 240 days, and its longest continuous period in total darkness is about 1.5 days. For some locations small height gains ( 10 m) can dramatically improve their average illumination and reduce the night duration, rendering some of those particularly attractive energy-wise as

  6. Diode-pumped actively Q-switched thulium laser

    NASA Astrophysics Data System (ADS)

    Jabczynski, J. K.; Zendzian, W.; Kwiatkowski, J.; Jelinkova, H.; Sulc, J.; Nemec, M.

    2007-06-01

    The properties of several Tm doped crystals regarding application in Q-switched tunable laser were analyzed theoretically. The acousto-optically Q-switched Tm:YLF laser is described in experimental part. The fiber coupled (0.4-mm core diameter) laser diode bar at 792-nm wavelength was deployed for pumping. The uncoated, with 3.5% dopant of thulium YLF rod of ø3x8mm size wrapped with indium foil was mounted in copper heat-sink maintaining 293 K temperature of coolant water. Above 6 W of output power and near 50% slope efficiency with respect to absorbed pump power was demonstrated in free-running mode for a short, 40-mm long resonator. The quartz acousto-optic modulator with above 80% diffraction efficiency for 25-W power of RF was taken as the Q-switch for such a laser. In the best case of Q-switching mode up to 2-mJ output energy with 15-ns pulse duration corresponding to 100-kW peak power was demonstrated for rep. rate of a few Hz. Emission wavelength was around 1904 nm for both free-running and Q-switching regimes

  7. Effect of active-ion concentration on holmium fibre laser efficiency

    SciTech Connect

    Kurkov, Andrei S; Sholokhov, E M; Marakulin, A V; Minashina, L A

    2010-08-03

    We have measured the fraction of holmium ions that relax nonradiatively to the ground level as a result of interaction at a metastable level in optical fibres with a silica-based core doped with holmium ions to 2 x 10{sup 19} - 2 x 10{sup 20} cm{sup -3}. The percentage of such ions has been shown to depend on the absolute active-ion concentration. The fibres have been used to make a number of 2.05-{mu}m lasers, and their slope efficiency has been measured. The laser efficiency decreases with increasing holmium concentration in the fibres (lasers)

  8. Laser-ablated active doping technique for visible spectroscopy measurements on Z.

    SciTech Connect

    Gomez, Matthew Robert

    2013-09-01

    Visible spectroscopy is a powerful diagnostic, allowing plasma parameters ranging from temperature and density to electric and magnetic fields to be measured. Spectroscopic dopants are commonly introduced to make these measurements. On Z, dopants are introduced passively (i.e. a salt deposited on a current-carrying surface); however, in some cases, passive doping can limit the times and locations at which measurements can be made. Active doping utilizes an auxiliary energy source to disperse the dopant independently from the rest of the experiment. The objective of this LDRD project was to explore laser ablation as a method of actively introducing spectroscopic dopants. Ideally, the laser energy would be delivered to the dopant via fiber optic, which would eliminate the need for time-intensive laser alignments in the Z chamber. Experiments conducted in a light lab to assess the feasibility of fibercoupled and open-beam laser-ablated doping are discussed.

  9. Active thermography inspection of protective glass contamination on laser scanning heads.

    PubMed

    Skala, J; Svantner, M; Tesar, J; Franc, A

    2016-12-01

    Industrial lasers are an expanding technology of welding and other materials processing. Lasers with optical scanning heads are often used, as these provide more versatility, accuracy, and speed. The output part of the scanning head is covered by a protective glass, which might get contaminated by various particles from the laser processing. This decreases the transmissivity of the glass, and it can affect the production quality. The contamination needs to be checked regularly, but a visual inspection might not always be effective. This paper proposes two alternative methods of inspecting the protective glass: flash-pulse active thermography, and laser active thermography. They are based on the thermal excitation of the glass and measuring the response with an infrared camera. The experimental setup and practical results are described and the advantages and disadvantages are discussed. The presented methods are proven to be effective in detecting the contamination of the glass.

  10. The power of the bubble: comparing ultrasonic and laser activated irrigation

    NASA Astrophysics Data System (ADS)

    De Moor, Roeland J. G.; Meire, Maarten A.; Verdaasdonk, Rudolf M.

    2014-01-01

    The major problem of irrigation is the fluid motion within the confined geometry of the root canal : efficient dispersion of the liquid is difficult, conventional irrigation is limited due to the absence of turbulence over much of the canal volume, vapour lock may limit apical cleaning and disinfection, there is also a stagnation plane beyond the needle tip. The best way to improve irrigant penetration and biofilm removal is achieved by means of the agitation of the fluid. Today ultrasonic activation appears to be the best way to activate and potentiate irrigants among the present-day used means and marketed systems. Another way to activate irrigation solutions is the use of lasers: laser activated irrigation or photon-initiated acoustic streaming have been investigated. Based on present-day research it appears that the efficacy of laser activation (especially with Erbium lasers) can be more efficient thanks to the induction of specific cavitation phenomena and acoustic streaming. Other wavelengths are now explored to be used for laser activated irrigation.

  11. Visualization of the Drosophila dKeap1-CncC interaction on chromatin illumines cooperative, xenobiotic-specific gene activation.

    PubMed

    Deng, Huai; Kerppola, Tom K

    2014-08-01

    Interactions among transcription factors control their physiological functions by regulating their binding specificities and transcriptional activities. We implement a strategy to visualize directly the genomic loci that are bound by multi-protein complexes in single cells in Drosophila. This method is based on bimolecular fluorescence complementation (BiFC) analysis of protein interactions on polytene chromosomes. Drosophila Keap1 (dKeap1)-CncC complexes localized to the nucleus and bound chromatin loci that were not bound preferentially by dKeap1 or CncC when they were expressed separately. dKeap1 and CncC binding at these loci was enhanced by phenobarbital, but not by tert-butylhydroquinone (tBHQ) or paraquat. Endogenous dKeap1 and CncC activated transcription of the Jheh (Jheh1, Jheh2, Jheh3) and dKeap1 genes at these loci, whereas CncC alone activated other xenobiotic response genes. Ectopic dKeap1 expression increased CncC binding at the Jheh and dKeap1 gene loci and activated their transcription, whereas dKeap1 inhibited CncC binding at other xenobiotic response gene loci and suppressed their transcription. The combinatorial chromatin-binding specificities and transcriptional activities of dKeap1-CncC complexes mediated the selective activation of different sets of genes by different xenobiotic compounds, in part through feed-forward activation of dKeap1 transcription.

  12. Laser-activated nano-biomaterials for tissue repair and controlled drug release

    SciTech Connect

    Matteini, P; Ratto, F; Rossi, F; Pini, R

    2014-07-31

    We present recent achievements of minimally invasive welding of biological tissue and controlled drug release based on laser-activated nano-biomaterials. In particular, we consider new advancements in the biomedical application of near-IR absorbing gold nano-chromophores as an original solution for the photothermal repair of surgical incisions and as nanotriggers of controlled drug release from hybrid biopolymer scaffolds. (laser biophotonics)

  13. Emerging concepts of laser-activated nanoparticles for tissue bonding

    NASA Astrophysics Data System (ADS)

    Matteini, Paolo; Ratto, Fulvio; Rossi, Francesca; Pini, Roberto

    2012-01-01

    We report recent achievements and future perspectives of minimally invasive bonding of biological tissues triggered by laser light. In particular, we review new advancements in the biomedical exploitation of near-infrared absorbing gold nanoparticles as an original solution for the photothermal closure of surgical incisions. Advanced concepts of laser tissue bonding involving the application of hybrid nanocomposites obtained by inclusion of nanochromophores into biopolymer scaffolds are also introduced. The perspectives of tissue bonding are discussed in the following aspects: (1) tissue bonding with highly-stabilized nanochromophores, (2) enhanced tissue bonding with patterned nanocomposites, (3) real-time monitoring of temperature distributions, (4) tracking of tissue regeneration based on the optical resonances of gold nanoparticles.

  14. Optimized geometric configuration of active ring laser gyroscopes

    NASA Astrophysics Data System (ADS)

    Gormley, John; Salloum, Tony

    2016-05-01

    We present a thorough derivation of the Sagnac effect for a ring laser gyroscope of any arbitrary polygonal configuration. We determine optimized alternative geometric configurations for the mirrors. The simulations incur the implementation of a lasing medium with the standard square system, triangular, pentagonal, and oblongated square configuration (diamond). Simulations of possible new geometric configurations are considered, as well as the possibility of adjusting the concavity of the mirrors.

  15. Laser-activated remote phosphor light engine for projection applications

    NASA Astrophysics Data System (ADS)

    Daniels, Martin; Mehl, Oliver; Hartwig, Ulrich

    2015-09-01

    Recent developments in blue emitting laser diodes enable attractive solutions in projection applications using phosphors for efficient light conversion with very high luminance levels. Various commercially available projectors incorporating this technology have entered the market in the past years. While luminous flux levels are still comparable to lamp-based systems, lifetime expectations of classical lamp systems are exceeded by far. OSRAM GmbH has been exploring this technology for several years and has introduced the PHASER® brand name (Phosphor + laser). State-of-the-art is a rotating phosphor wheel excited by blue laser diodes to deliver the necessary primary colors, either sequentially for single-imager projection engines, or simultaneously for 3-panel systems. The PHASER® technology enables flux and luminance scaling, which allows for smaller imagers and therefore cost-efficient projection solutions. The resulting overall efficiency and ANSI lumen specification at the projection screen of these systems is significantly determined by the target color gamut and the light transmission efficiency of the projection system. With increasing power and flux level demand, thermal issues, especially phosphor conversion related, dominate the opto-mechanical system design requirements. These flux levels are a great challenge for all components of an SSL-projection system (SSL:solid-state lighting). OSRAḾs PHASER® light engine platform is constantly expanded towards higher luminous flux levels as well as higher luminance levels for various applications. Recent experiments employ blue laser pump powers of multiple 100 Watts to excite various phosphors resulting in luminous flux levels of more than 40 klm.

  16. Study of Shallow Backside Junctions for Backside Illumination of CMOS Image Sensors

    NASA Astrophysics Data System (ADS)

    Choi, Chung Seok; Yeo, Sang Chul; Kim, Dohwan; Kim, Jongchae; Yoo, Kyung Dong; Lee, Hyuck Mo

    2014-11-01

    Backside illumination complementary metal oxide semiconductor image sensors (BSI CISs) represent an advanced technology that produces high-quality image sensors. However, BSI CISs are limited by high dark signals and noise signals on the backside. To address these problems, backside junctions are commonly used. High-dose backside junctions effectively reduce dark signals and noise signals. The depth of the implantation profile is a key factor in determining the junction depth. A laser thermal annealing process is conducted only near the surface to the activation, and thus broader doping profiles are limitations to be activation of dopants. Changing the dopant from B to BF2 can decrease the implant projected range. However, there are abnormal activation rates for BF2 in applications involving laser thermal annealing processes for shallow junctions. Although the need for BF2 is increasing, a mechanism for its slow activation and low activation rates has not yet been confirmed. Here, we identify the mechanism by which BF2 undergoes low activation after a melting threshold temperature and explain why this phenomenon occurs. In addition, we confirm a condition that provides high activation rates of BF2 and show the reduction of dark signals and noise signals at the high density BSI CISs.

  17. Active cooling solutions for high power laser diodes stacks

    NASA Astrophysics Data System (ADS)

    Karni, Yoram; Klumel, Genady; Levy, Moshe; Berk, Yuri; Openhaim, Yaki; Gridish, Yaakov; Elgali, Asher; Avisar, Meir; Blonder, Moshe; Sagy, Hila; Gertsenshtein, Alex

    2008-02-01

    High power water cooled diode lasers find increasing demand in biomedical, cosmetic and industrial applications, where very high brightness and power are required. The high brightness is achieved either by increasing the power of each bar or by reducing the emitting area of the stacks. Two new products will be presented: Horizontal CW stacks with output power as high as 1kW using 80 W bars with emitting area width as low as 50 μm Vertical QCW stacks with output power as high as 1.2kW using 120 W bars. Heat removal from high power laser stacks often requires microchannel coolers operated with finely filtered deionized (DI) water. However, for certain industrial applications the reliability of this cooling method is widely considered insufficient due to leakage failures caused the highly corrosive DI water. Two solutions to the above problem will be discussed. A microchannel cooler-based package, which vastly reduces the corrosion problem, and a novel high-power laser diode stack that completely eliminates it. The latter solution is especially effective for pulsed applications in high duty cycle range.

  18. Influence of lasing parameters on the cleaning efficacy of laser-activated irrigation with pulsed erbium lasers.

    PubMed

    Meire, Maarten A; Havelaerts, Sophie; De Moor, Roeland J

    2016-05-01

    Laser-activated irrigation (LAI) using erbium lasers is an irrigant agitation technique with great potential for improved cleaning of the root canal system, as shown in many in vitro studies. However, lasing parameters for LAI vary considerably and their influence remains unclear. Therefore, this study sought to investigate the influence of pulse energy, pulse frequency, pulse length, irradiation time and fibre tip shape, position and diameter on the cleaning efficacy of LAI. Transparent resin blocks containing standardized root canals (apical diameter of 0.4 mm, 6% taper, 15 mm long, with a coronal reservoir) were used as the test model. A standardized groove in the apical part of each canal wall was packed with stained dentin debris. The canals were filled with irrigant, which was activated by an erbium: yttrium aluminium garnet (Er:YAG) laser (2940 nm, AT Fidelis, Fotona, Ljubljana, Slovenia). In each experiment, one laser parameter was varied, while the others remained constant. In this way, the influence of pulse energy (10-40 mJ), pulse length (50-1000 μs), frequency (5-30 Hz), irradiation time (5-40 s) and fibre tip shape (flat or conical), position (pulp chamber, canal entrance, next to groove) and diameter (300-600 μm) was determined by treating 20 canals per parameter. The amount of debris remaining in the groove after each LAI procedure was scored and compared among the different treatments. The parameters significantly (P < 0.05, Kruskal-Wallis) affecting debris removal from the groove were fibre tip position, pulse length, pulse energy, irradiation time and frequency. Fibre tip shape and diameter had no significant influence on the cleaning efficacy.

  19. CONTROL OF LASER RADIATION PARAMETERS: Excitation of dynamic chaos in a monolithic ring chip laser upon periodic modulation of mechanical stresses in the active element

    NASA Astrophysics Data System (ADS)

    Kravtsov, Nikolai V.; Sidorov, S. S.; Pashinin, Pavel P.; Firsov, V. V.; Chekina, S. N.

    2004-04-01

    The peculiarities of nonlinear dynamics of solid-state bidirectional ring Nd:YAG chip lasers are studied theoretically and experimentally during periodic modulation of mechanical stresses in the active element. It is shown that modulation of mechanical stresses is an effective method for exciting dynamic chaos in a monolithic chip laser.

  20. PHYSICAL EFFECTS OCCURRING DURING GENERATION AND AMPLIFICATION OF LASER RADIATION: Kinetic model of the active medium of an XeCl laser pumped by an electron beam

    NASA Astrophysics Data System (ADS)

    Boĭchenko, A. M.; Derzhiev, V. I.; Zhidkov, A. G.; Yakovlenko, Sergei I.

    1989-02-01

    Kinetic models of active media of an XeCl laser are developed for the case when these media are diluted by various buffer gases (helium, neon, argon) and the laser is pumped by an electron beam. The results of the calculations are in satisfactory agreement with experimental data.

  1. Evaluation of impacts of laser parameters on laser cell efficiencies

    NASA Astrophysics Data System (ADS)

    Zhang, Yichen; Zhao, Changming; Yang, Suhui; Wang, Yunshi; Zhu, Qihai; Ke, Jieyao; Xu, Peng; Guan, Zhe; Zhang, Haiyang

    2015-08-01

    Wireless laser power supply to long-distance devices is drawing more and more interest in recent years. As power receivers, laser cells are adhered on these devices. Relatively high laser cell efficiency could be obtained under a monochromatic illumination. In order to study the most efficient laser illumination conditions to the laser cell, the efficiencies of circular and rectangular cells illuminated by laser with fundamental mode are compared. The simulations show that the cell efficiency increases slowly with the increase of the laser power, and decreases with the increase of the spot size. When the rectangular cell and the circular cell have the same area, and the diameter of the circular cell and that of the laser spot are equal, the efficiency of the circular cell is higher than the rectangular cell.

  2. In vivo carotid artery closure by laser activation of hyaluronan-embedded gold nanorods

    NASA Astrophysics Data System (ADS)

    Matteini, Paolo; Ratto, Fulvio; Rossi, Francesca; Rossi, Giacomo; Esposito, Giuseppe; Puca, Alfredo; Albanese, Alessio; Maira, Giulio; Pini, Roberto

    2010-07-01

    We prove the first application of near-infrared-absorbing gold nanorods (GNRs) for in vivo laser closure of a rabbit carotid artery. GNRs are first functionalized with a biopolymeric shell and then embedded in hyaluronan, which gives a stabilized and handy laser-activable formulation. Four rabbits undergo closure of a 3-mm longitudinal incision performed on the carotid artery by means of a 810-nm diode laser in conjunction with the topical application of the GNRs composite. An effective surgery is obtained by using a 40-W/cm2 laser power density. The histological and electron microscopy evaluation after a 30-day follow-up demonstrates complete healing of the treated arteries with full re-endothelization at the site of GNRs application. The absence of microgranuloma formation and/or dystrophic calcification is evidence that no host reaction to nanoparticles interspersed through the vascular tissue occurred. The observation of a reshaping and associated blue shift of the NIR absorption band of GNRs after laser treatment supports the occurrence of a self-terminating process, and thus of additional safety of the minimally invasive laser procedure. This study underlines the feasibility of using GNRs for in vivo laser soldering applications, which represents a step forward toward the introduction of nanotechnology-based therapies in minimally invasive clinical practices.

  3. DARK-FIELD ILLUMINATION SYSTEM

    DOEpatents

    Norgren, D.U.

    1962-07-24

    A means was developed for viewing objects against a dark background from a viewing point close to the light which illuminates the objects and under conditions where the back scattering of light by the objects is minimal. A broad light retro-directing member on the opposite side of the objects from the light returns direct light back towards the source while directing other light away from the viewing point. The viewing point is offset from the light and thus receives only light which is forwardly scattered by an object while returning towards the source. The object is seen, at its true location, against a dark background. The invention is particularly adapted for illuminating and viewing nuclear particle tracks in a liquid hydrogen bubble chamber through a single chamber window. (AEC)

  4. Structured line illumination Raman microscopy

    PubMed Central

    Watanabe, Kozue; Palonpon, Almar F.; Smith, Nicholas I.; Chiu, Liang-da; Kasai, Atsushi; Hashimoto, Hitoshi; Kawata, Satoshi; Fujita, Katsumasa

    2015-01-01

    In the last couple of decades, the spatial resolution in optical microscopy has increased to unprecedented levels by exploiting the fluorescence properties of the probe. At about the same time, Raman imaging techniques have emerged as a way to image inherent chemical information in a sample without using fluorescent probes. However, in many applications, the achievable resolution is limited to about half the wavelength of excitation light. Here we report the use of structured illumination to increase the spatial resolution of label-free spontaneous Raman microscopy, generating highly detailed spatial contrast from the ensemble of molecular information in the sample. Using structured line illumination in slit-scanning Raman microscopy, we demonstrate a marked improvement in spatial resolution and show the applicability to a range of samples, including both biological and inorganic chemical component mapping. This technique is expected to contribute towards greater understanding of chemical component distributions in organic and inorganic materials. PMID:26626144

  5. Lunar-illuminated outdoor hologram

    NASA Astrophysics Data System (ADS)

    Jepsen, Mary Lou; Dawson, Paula H.

    1992-05-01

    The first step in the construction of a very deep, large source size, white light illuminated hologram is discussed. We outline the steps taken thus far in the creation of our computer- generated master hologram slit. Our goal is to computer generate a 2 meter master slit for optical transfer via Benton rainbow holography technique. The transfer hologram will ultimately be re-illuminated by the moon and fill a space of approximately 8000 cubic meters. Discussion of the relative merits of synthetic stereographic methods and CGH methods is presented as well as several novel hybrid techniques. The CGH test prints thus far created are evaluated for several types of aberrations and methods of pre-distortion and distortion correction are proposed.

  6. Illumination box and camera system

    DOEpatents

    Haas, Jeffrey S.; Kelly, Fredrick R.; Bushman, John F.; Wiefel, Michael H.; Jensen, Wayne A.; Klunder, Gregory L.

    2002-01-01

    A hand portable, field-deployable thin-layer chromatography (TLC) unit and a hand portable, battery-operated unit for development, illumination, and data acquisition of the TLC plates contain many miniaturized features that permit a large number of samples to be processed efficiently. The TLC unit includes a solvent tank, a holder for TLC plates, and a variety of tool chambers for storing TLC plates, solvent, and pipettes. After processing in the TLC unit, a TLC plate is positioned in a collapsible illumination box, where the box and a CCD camera are optically aligned for optimal pixel resolution of the CCD images of the TLC plate. The TLC system includes an improved development chamber for chemical development of TLC plates that prevents solvent overflow.

  7. Active lamp pulse driver circuit. [optical pumping of laser media

    NASA Technical Reports Server (NTRS)

    Logan, K. E. (Inventor)

    1983-01-01

    A flashlamp drive circuit is described which uses an unsaturated transistor as a current mode switch to periodically subject a partially ionized gaseous laser excitation flashlamp to a stable, rectangular pulse of current from an incomplete discharge of an energy storage capacitor. A monostable multivibrator sets the pulse interval, initiating the pulse in response to a flash command by providing a reference voltage to a non-inverting terminal of a base drive amplifier; a tap on an emitter resistor provides a feedback signal sensitive to the current amplitude to an inverting terminal of amplifier, thereby controlling the pulse amplitude. The circuit drives the flashlamp to provide a squarewave current flashlamp discharge.

  8. Synthesis of mesoporous TiO(2-x)N(x) spheres by template free homogeneous co-precipitation method and their photo-catalytic activity under visible light illumination.

    PubMed

    Parida, K M; Naik, Brundabana

    2009-05-01

    The article presents preparation, characterization and catalytic activity evaluation of an efficient nitrogen doped mesoporous titania sphere photo-catalyst for degradation of methylene blue (MB) and methyl orange (MO) under visible light illumination. Nitrogen doped titania was prepared by soft chemical route i.e. template free, slow and controlled homogeneous co-precipitation from titanium oxysulfate sulfuric acid complex hydrate, urea, ethanol and water. The molar composition of TiOSO(4) to urea was varied to prepare different atomic % nitrogen doped titania. Mesoporous anatase TiO(2-x)N(x) spheres with average crystallite size of 10 nm and formation of titanium oxynitride center were confirmed from HRTEM, XRD and XPS study. UV-vis DRS showed a strong absorption in the range of 400-500 nm which supports its use in visible spectrum of light. Nitrogen adsorption-desorption study supports the porous nature of the doped material. All the TiO(2-x)N(x) samples showed higher photo-catalytic activity than Degussa P(25) and undoped mesoporous titania. Sample containing around one atomic % nitrogen showed highest activity among the TiO(2-x)N(x) samples.

  9. Active cooling of pulse compression diffraction gratings for high energy, high average power ultrafast lasers.

    PubMed

    Alessi, David A; Rosso, Paul A; Nguyen, Hoang T; Aasen, Michael D; Britten, Jerald A; Haefner, Constantin

    2016-12-26

    Laser energy absorption and subsequent heat removal from diffraction gratings in chirped pulse compressors poses a significant challenge in high repetition rate, high peak power laser development. In order to understand the average power limitations, we have modeled the time-resolved thermo-mechanical properties of current and advanced diffraction gratings. We have also developed and demonstrated a technique of actively cooling Petawatt scale, gold compressor gratings to operate at 600W of average power - a 15x increase over the highest average power petawatt laser currently in operation. Combining this technique with low absorption multilayer dielectric gratings developed in our group would enable pulse compressors for petawatt peak power lasers operating at average powers well above 40kW.

  10. Delivery of molecules into cells using carbon nanoparticles activated by femtosecond laser pulses.

    PubMed

    Chakravarty, Prerona; Qian, Wei; El-Sayed, Mostafa A; Prausnitz, Mark R

    2010-08-01

    A major barrier to drug and gene delivery is crossing the cell's plasma membrane. Physical forces applied to cells via electroporation, ultrasound and laser irradiation generate nanoscale holes in the plasma membrane for direct delivery of drugs into the cytoplasm. Inspired by previous work showing that laser excitation of carbon nanoparticles can drive the carbon-steam reaction to generate highly controlled shock waves, we show that carbon black nanoparticles activated by femtosecond laser pulses can facilitate the delivery of small molecules, proteins and DNA into two types of cells. Our initial results suggest that interaction between the laser energy and carbon black nanoparticles may generate photoacoustic forces by chemical reaction to create transient holes in the membrane for intracellular delivery.

  11. Fully automated hybrid diode laser assembly using high precision active alignment

    NASA Astrophysics Data System (ADS)

    Böttger, Gunnar; Weber, Daniel; Scholz, Friedemann; Schröder, Henning; Schneider-Ramelow, Martin; Lang, Klaus-Dieter

    2016-03-01

    Fraunhofer IZM, Technische Universität Berlin and eagleyard Photonics present various implementations of current micro-optical assemblies for high quality free space laser beam forming and efficient fiber coupling. The laser modules shown are optimized for fast and automated assembly in small form factor packages via state-of-the-art active alignment machinery, using alignment and joining processes that have been developed and established in various industrial research projects. Operational wavelengths and optical powers ranging from 600 to 1600 nm and from 1 mW to several W respectively are addressed, for application in high-resolution laser spectroscopy, telecom and optical sensors, up to the optical powers needed in industrial and medical laser treatment.

  12. Extraction and quantitation of coumarin from cinnamon and its effect on enzymatic browning in fresh apple juice: a bioinformatics approach to illuminate its antibrowning activity.

    PubMed

    Thada, Rajarajeshwari; Chockalingam, Shivashri; Dhandapani, Ramesh Kumar; Panchamoorthy, Rajasekar

    2013-06-05

    Enzymatic browning by polyphenoloxidase (PPO) affects food quality and taste in fruits and vegetables. Thus, the study was designed to reduce browning in apple juice by coumarin. The ethanolic extract of cinnamon was prepared and its coumarin content was quantitated by HPLC, using authentic coumarin (AC) as standard. The effect of cinnamon extract (CE) and AC on enzymatic browning, its time dependent effects, and the specific activity of PPO and peroxidase (POD) were studied in apple juice. The docking of coumarin with PPO and POD was also performed to elucidate its antibrowning mechanism. The CE (73%) and AC (82%) showed better reduction in browning, maintained its antibrowning effect at all time points, and significantly (p < 0.05) reduced the specific activity of PPO and POD when compared with controls. Coumarin showed strong interaction with binding pockets of PPO and POD, suggesting its potential use as inhibitor to enzyme mediated browning in apple juice.

  13. Short wavelength laser

    DOEpatents

    Hagelstein, Peter L.

    1986-01-01

    A short wavelength laser (28) is provided that is driven by conventional-laser pulses (30, 31). A multiplicity of panels (32), mounted on substrates (34), are supported in two separated and alternately staggered facing and parallel arrays disposed along an approximately linear path (42). When the panels (32) are illuminated by the conventional-laser pulses (30, 31), single pass EUV or soft x-ray laser pulses (44, 46) are produced.

  14. A Superradiant Raman Laser as a Hybrid Active/Passive Atomic Sensor

    NASA Astrophysics Data System (ADS)

    Bohnet, Justin; Weiner, Joshua; Cox, Kevin; Chen, Zilong; Thompson, James

    2013-05-01

    We have realized an atomic sensor that combines active, wideband sensing with passive measurement periods using dynamic control of a cold-atom, superradiant Raman laser. In a superradiant laser, collective emission of the atomic ensemble maps the quantum phase stored in the atoms onto the detected cavity field. We discuss the fundamental precision of the superradiant mapping and show theoretically that the precision of the non-demolition measurement is only a factor of two worse than the standard quantum limit on phase estimation for a coherent spin state. Using the superradiant readout, we experimentally demonstrate a repeated, non-demolition conditional Ramsey sequence that has the potential to combine the benefit of a high-bandwidth active frequency reference with a high-accuracy passive device. We also present an experimental realization of a superradiant Raman laser operated as a hybrid active/passive atomic magnetometer.

  15. The decoding system of semi-active laser guidance based on FPGA

    NASA Astrophysics Data System (ADS)

    Qi, Chang; Feng, Longling; Feng, Yimin; Wang, Benguo; Chen, Bo; Luo, Xiong

    2011-11-01

    In this paper, we describe a new design of semi-active laser guided decoding system based on FPGA. The system is designed to receive the echo pulse through a 4-qundrant laser sensor and process the digital laser pulses through analogdigital conversion, which are some fixed interval encoding signal reflected from the target. The decoding system improve the adjustment accuracy of the laser seeker, which reach 0.1us about 50 times in theory compared to current technology. State machine is used to address complicated laser signal, including how to hand of the identification and trapping of the correct laser pulses, how to hand of a state of anti-jamming, how to hand of capturing the laser pulses again after signal missing. And a real-time gate signal is adopted to enhance the ability of anti-interference[1]. Processed signal is used to monitor and control, the processed result is transmitted to a electric actuator and subsequently be sent to laser seeker as a guidance signal or to a PC to simulate and monitor or to be stored in Flash that can extract whenever needed. The whole performance of the system is oprated in laboratory and decoding model is simulated with Modelsim module in detail. The testing results show that the design can reduce the span of decoding time effectively, identify and track the echo pulses from target correctly even to the missed codes or interferential codes. The feasible technique wins the time for laser guidance, and has some theoretical and military value.

  16. Active laser radar (lidar) for measurement of corresponding height and reflectance images

    NASA Astrophysics Data System (ADS)

    Froehlich, Christoph; Mettenleiter, M.; Haertl, F.

    1997-08-01

    For the survey and inspection of environmental objects, a non-tactile, robust and precise imaging of height and depth is the basis sensor technology. For visual inspection,surface classification, and documentation purposes, however, additional information concerning reflectance of measured objects is necessary. High-speed acquisition of both geometric and visual information is achieved by means of an active laser radar, supporting consistent 3D height and 2D reflectance images. The laser radar is an optical-wavelength system, and is comparable to devices built by ERIM, Odetics, and Perceptron, measuring the range between sensor and target surfaces as well as the reflectance of the target surface, which corresponds to the magnitude of the back scattered laser energy. In contrast to these range sensing devices, the laser radar under consideration is designed for high speed and precise operation in both indoor and outdoor environments, emitting a minimum of near-IR laser energy. It integrates a laser range measurement system and a mechanical deflection system for 3D environmental measurements. This paper reports on design details of the laser radar for surface inspection tasks. It outlines the performance requirements and introduces the measurement principle. The hardware design, including the main modules, such as the laser head, the high frequency unit, the laser beam deflection system, and the digital signal processing unit are discussed.the signal processing unit consists of dedicated signal processors for real-time sensor data preprocessing as well as a sensor computer for high-level image analysis and feature extraction. The paper focuses on performance data of the system, including noise, drift over time, precision, and accuracy with measurements. It discuses the influences of ambient light, surface material of the target, and ambient temperature for range accuracy and range precision. Furthermore, experimental results from inspection of buildings, monuments

  17. Fast functional imaging of multiple brain regions in intact zebrafish larvae using selective plane illumination microscopy.

    PubMed

    Panier, Thomas; Romano, Sebastián A; Olive, Raphaël; Pietri, Thomas; Sumbre, Germán; Candelier, Raphaël; Debrégeas, Georges

    2013-01-01

    The optical transparency and the small dimensions of zebrafish at the larval stage make it a vertebrate model of choice for brain-wide in-vivo functional imaging. However, current point-scanning imaging techniques, such as two-photon or confocal microscopy, impose a strong limit on acquisition speed which in turn sets the number of neurons that can be simultaneously recorded. At 5 Hz, this number is of the order of one thousand, i.e., approximately 1-2% of the brain. Here we demonstrate that this limitation can be greatly overcome by using Selective-plane Illumination Microscopy (SPIM). Zebrafish larvae expressing the genetically encoded calcium indicator GCaMP3 were illuminated with a scanned laser sheet and imaged with a camera whose optical axis was oriented orthogonally to the illumination plane. This optical sectioning approach was shown to permit functional imaging of a very large fraction of the brain volume of 5-9-day-old larvae with single- or near single-cell resolution. The spontaneous activity of up to 5,000 neurons was recorded at 20 Hz for 20-60 min. By rapidly scanning the specimen in the axial direction, the activity of 25,000 individual neurons from 5 different z-planes (approximately 30% of the entire brain) could be simultaneously monitored at 4 Hz. Compared to point-scanning techniques, this imaging strategy thus yields a ≃20-fold increase in data throughput (number of recorded neurons times acquisition rate) without compromising the signal-to-noise ratio (SNR). The extended field of view offered by the SPIM method allowed us to directly identify large scale ensembles of neurons, spanning several brain regions, that displayed correlated activity and were thus likely to participate in common neural processes. The benefits and limitations of SPIM for functional imaging in zebrafish as well as future developments are briefly discussed.

  18. Generating Submillimeter-Wave Frequencies From Laser Pulses

    NASA Technical Reports Server (NTRS)

    Spencer, Michael G.; Maserjian, Joseph

    1994-01-01

    Semiconductor photoconductive switches generate electrical pulses containing submillimeter-wavelength carrier signals (frequency between 300 and 3,000 GHz) and harmonics thereof when illuminated with short-rise-time pulses from lasers. Device of this type used as local oscilator in heterodyne submillimeter-wave receiver. Electrical output of device coupled via transmission line, waveguide, or antenna to mixer circuitry of receiver. Phase delays between optically activated semiconductor switches determine output carrier frequencies. N electrical pulses generated by each laser pulse. Thus, fundamental output frequency is N times laser-pulse-repetition rate.

  19. 2.6 W diode-pumped actively mode-locked Tm:YLF laser

    NASA Astrophysics Data System (ADS)

    Mužík, J.; Jelínek, M., Jr.; Vyhlídal, D.; Kubeček, V.

    2015-03-01

    We have experimentally demonstrated an actively mode-locked laser with a Tm3+-doped yttrium lithium fluoride crystal (YLF). A continuous mode-locked regime was achieved using an acousto-optic modulator and a stable train of pulses with 149.3 MHz repetition rate, 170 ps pulse width and 2.6 W average output power at 1.91 µm in a nearly diffraction-limited beam was obtained. To the best of our knowledge, this is the first report on a diode-pumped actively mode-locked bulk thulium laser with a stable output.

  20. A method for pulsed scannerless laser imaging using focal plane array

    NASA Astrophysics Data System (ADS)

    Zhang, Zhi-peng; Wang, Ke-yong; Deng, Jia-hao; Hai, Yan

    2011-06-01

    Laser imaging techniques have advantages for EMI (Electro Magnetic Interference) immunity and abundant image information. This contribution describes the research activity on the scannerless laser imaging detection technique using direct detection aimed at laser fuze applications. The technique using a pulsed laser to illuminate the target and a focal plane array can be used as a receiver. The range information is achieved by means of a direct time of light measurement. Information about the reflectivity of the target is gathered by recording the amplitude of the received pulse. In this paper a high-repetition-frequency, narrow pulse semiconductor laser floodlight emitting system is designed; corresponding optics is used to generate the homogenously illuminated FOI (field of illumination). The echo of laser is collected by receiving optical system fed to focal plane array. Some experiments were done with the emitting and receiving systems that had been designed. Experiments show the validity and rationality of this method. The scannerless structure is robust and provides instantaneous snapshot-type imaging. Avoiding any moving mechanical parts, scannerless laser imaging system have distinct characteristics such as small, compact, high frame rate, wide field of view and high reliability. It is an optimal approach to realize laser imaging fuze.

  1. Nanoengineered InAs quantum dot active medium for laser diodes

    NASA Astrophysics Data System (ADS)

    Tokranov, Vadim E.; Yakimov, Michael; Katsnelson, Alex; Lamberti, Matthew; Agnello, Gabriel; Oktyabrsky, Serge

    2004-05-01

    Nanoengineering approach was used to develop an efficient active medium based on self-assembled InAs/GaAs quantum dots (QDs) for laser diodes operating at elevated temperatures. Photoluminescence (PL), transmission electron microscopy, and electroluminescence were used to study the influence of an overgrowth procedure on the properties of multiple-layer QDs. Optical properties of QDs were optimized by the adjustment of a GaAs overlayer thickness prior to a heating step, responsible for the truncation of the pyramid-shaped QDs. Triple-layer QD edge-emitting lasers with 1220 nm emitting wavelength exhibited a maximum saturated modal gain of 16 cm-1. To use truncated QD active medium for vertical cavity surface emitting lasers, seven layers of QDs with 20 nm of short period superlattice barriers between layers was developed. A wavelength of 1190 nm edge-emitting lasers with 120 nm total thickness 7xQDs active medium showed almost two times higher maximum saturated gain, 31 cm-1. Unfortunately, these lasers with closer distance between QD layers in active medium demonstrated stronger temperature dependence (with To = 110 K) of threshold current density and lasing wavelength. A record high characteristic temperature for lasing threshold, To = 380 K up to 55 C, was measured for edge-emitting laser diodes, which contained triple-layer truncated QD active medium. We believe that AlAs capping in combination with truncation procedure result in significant suppression of carrier transport between QDs within the layer as well as between QD layers.

  2. Complex Active Optical Networks as a New Laser Concept

    NASA Astrophysics Data System (ADS)

    Lepri, Stefano; Trono, Cosimo; Giacomelli, Giovanni

    2017-03-01

    Complex optical networks containing one or more gain sections are investigated, and the evidence of lasing action is reported; the emission spectrum reflects the topological disorder induced by the connections. A theoretical description compares well with the measurements, mapping the networks to directed graphs and showing the analogies with the problem of quantum chaos on graphs. We show that the interplay of chaotic diffusion and amplification leads to an emission statistic with characteristic heavy tails: for different topologies, an unprecedented experimental demonstration of Lévy statistics expected for random lasers is here provided for a continuous-wave pumped system. This result is also supported by a Monte Carlo simulation based on the ray random walk on the graph.

  3. Bubble-cell interactions with laser-activated polymeric microcapsules

    NASA Astrophysics Data System (ADS)

    Versluis, Michel; Lajoinie, Guillaume; van Rooij, Tom; Skachkov, Ilya; Kooiman, Klazina; de Jong, Nico; Physics of Fluids Group, University of Twente Team; Biomedical Engineering, Erasmus MC Team

    2015-11-01

    Polymeric microcapsules that are made light-absorbing by the addition of a dye in their shell can generate cavitation microbubbles with spatiotemporal control when irradiated by a pulsed laser. These particles less than 3 μm in size can circulate through the body, bind to tissues and are expected to be readily detected, even if a single cavitation bubble is produced. In this paper, we study the impact of such cavitation bubbles on a cell monolayer and quantify it in terms of cell poration and cell viability. Two capsules formulations were used; the first one encapsulates a low boiling point oil and induced less cell damage than the second that was loaded with a high boiling point oil. We also report the generation of stable bubbles by the first capsule formulation that completely absorb the cells in their close vicinity. Physics of Fluid group MIRA Institute for Biomedical Technology and Technical Medicine MESA+ Institute for Nanotechnology.

  4. Apparatus and method for generating partially coherent illumination for photolithography

    DOEpatents

    Sweatt, William C.

    2001-01-01

    The present invention introduces a novel scatter plate into the optical path of source light used for illuminating a replicated object. The scatter plate has been designed to interrupt a focused, incoming light beam by introducing between about 8 to 24 diffraction zones blazed onto the surface of the scatter plate which intercept the light and redirect it to a like number of different positions in the condenser entrance pupil each of which is determined by the relative orientation and the spatial frequency of the diffraction grating in each of the several zones. Light falling onto the scatter plate, therefore, generates a plurality of unphased sources of illumination as seen by the back half of the optical system. The system comprises a high brightness source, such as a laser, creating light which is taken up by a beam forming optic which focuses the incoming light into a condenser which in turn, focuses light into a field lens creating Kohler illumination image of the source in a camera entrance pupil. The light passing through the field lens illuminates a mask which interrupts the source light as either a positive or negative image of the object to be replicated. Light passing by the mask is focused into the entrance pupil of the lithographic camera creating an image of the mask onto a receptive media.

  5. Active and passive multispectral scanner for earth resources applications: An advanced applications flight experiment

    NASA Technical Reports Server (NTRS)

    Hasell, P. G., Jr.; Peterson, L. M.; Thomson, F. J.; Work, E. A.; Kriegler, F. J.

    1977-01-01

    The development of an experimental airborne multispectral scanner to provide both active (laser illuminated) and passive (solar illuminated) data from a commonly registered surface scene is discussed. The system was constructed according to specifications derived in an initial programs design study. The system was installed in an aircraft and test flown to produce illustrative active and passive multi-spectral imagery. However, data was not collected nor analyzed for any specific application.

  6. Mirror with a variable amplitude - phase reflectance. 2. Modelling of a laser resonator with an active output mirror

    SciTech Connect

    Kiiko, V V; Kislov, V I; Ofitserov, Evgenii N

    2011-03-31

    We present the operator model of the laser resonator with an active output mirror based on the Fabry - Perot interferometer with nonflat (spherical and aspherical) mirrors and an adjustable gap. The results of numerical simulation of a microchip laser with a thermal lens and an active output interferometer-based mirror are given. It is shown that the use of an active interferometer as the output cavity mirror allows one to control the number of transverse modes of laser radiation and its power; in this case, the beam divergence can be reduced by a factor of 1.5 - 2.5. (laser resonators)

  7. Image recombination transform algorithm for superresolution structured illumination microscopy

    NASA Astrophysics Data System (ADS)

    Zhou, Xing; Lei, Ming; Dan, Dan; Yao, Baoli; Yang, Yanlong; Qian, Jia; Chen, Guangde; Bianco, Piero R.

    2016-09-01

    Structured illumination microscopy (SIM) is an attractive choice for fast superresolution imaging. The generation of structured illumination patterns made by interference of laser beams is broadly employed to obtain high modulation depth of patterns, while the polarizations of the laser beams must be elaborately controlled to guarantee the high contrast of interference intensity, which brings a more complex configuration for the polarization control. The emerging pattern projection strategy is much more compact, but the modulation depth of patterns is deteriorated by the optical transfer function of the optical system, especially in high spatial frequency near the diffraction limit. Therefore, the traditional superresolution reconstruction algorithm for interference-based SIM will suffer from many artifacts in the case of projection-based SIM that possesses a low modulation depth. Here, we propose an alternative reconstruction algorithm based on image recombination transform, which provides an alternative solution to address this problem even in a weak modulation depth. We demonstrated the effectiveness of this algorithm in the multicolor superresolution imaging of bovine pulmonary arterial endothelial cells in our developed projection-based SIM system, which applies a computer controlled digital micromirror device for fast fringe generation and multicolor light-emitting diodes for illumination. The merit of the system incorporated with the proposed algorithm allows for a low excitation intensity fluorescence imaging even less than 1 W/cm2, which is beneficial for the long-term, in vivo superresolved imaging of live cells and tissues.

  8. Antibody and markers of T-cell activation illuminate the pathogenesis of HCV immune restoration disease in HIV/HCV co-infected patients commencing ART.

    PubMed

    Yunihastuti, Evy; Lee, Silvia; Gani, Rino A; Saraswati, Henny; Sundaru, Heru; Lesmana, L A; Sukmana, Nanang; Price, Patricia

    2011-04-01

    Some HIV/hepatitis C virus co-infected patients beginning ART experience Immune Restoration Disease (IRD) manifested as a rise in serum alanine transaminase. This was investigated in HIV/HCV co-infected individuals (n=50) commencing ART in Jakarta (Indonesia). Samples were collected at weeks 0, 4, 8, 12, 24 and at HCV IRD. Nine patients experienced HCV IRD (incidence=9.2 per 1000 person-weeks). These resolved without changing treatment. Markers of T-cell activation (sCD26, sCD30) and immune recruitment (CXCL10) increased in many HCV IRD cases, so T-cells may mediate HCV IRD. Total anti-HCV antibody (core, NS3, NS4) remained lower in HCV IRD cases, but levels of antibody to core were not lower in HCV IRD cases. Rises in HCV RNA on ART were independent of HCV IRD, but there was a negative correlation between baseline HCV RNA and total anti-HCV antibody. High levels of antibody may protect against HCV IRD, via lower HCV antigen loads.

  9. Fabrication and In Vitro Deployment of a Laser-Activated Shape Memory Polymer Vascular Stent

    SciTech Connect

    Baer, G M; Small IV, W; Wilson, T S; Benett, W J; Matthews, D L; Hartman, J; Maitland, D J

    2007-04-25

    Vascular stents are small tubular scaffolds used in the treatment of arterial stenosis (narrowing of the vessel). Most vascular stents are metallic and are deployed either by balloon expansion or by self-expansion. A shape memory polymer (SMP) stent may enhance flexibility, compliance, and drug elution compared to its current metallic counterparts. The purpose of this study was to describe the fabrication of a laser-activated SMP stent and demonstrate photothermal expansion of the stent in an in vitro artery model. A novel SMP stent was fabricated from thermoplastic polyurethane. A solid SMP tube formed by dip coating a stainless steel pin was laser-etched to create the mesh pattern of the finished stent. The stent was crimped over a fiber-optic cylindrical light diffuser coupled to an infrared diode laser. Photothermal actuation of the stent was performed in a water-filled mock artery. At a physiological flow rate, the stent did not fully expand at the maximum laser power (8.6 W) due to convective cooling. However, under zero flow, simulating the technique of endovascular flow occlusion, complete laser actuation was achieved in the mock artery at a laser power of {approx}8 W. We have shown the design and fabrication of an SMP stent and a means of light delivery for photothermal actuation. Though further studies are required to optimize the device and assess thermal tissue damage, photothermal actuation of the SMP stent was demonstrated.

  10. Axicon-based annular laser trap for studies on sperm activity

    NASA Astrophysics Data System (ADS)

    Shao, Bing; Vinson, Jaclyn M.; Botvinick, Elliot L.; Esener, Sadik C.; Berns, Michael W.

    2005-08-01

    As a powerful and noninvasive tool, laser trapping has been widely applied for the confinement and physiological study of biological cells and organelles. Researchers have used the single spot laser trap to hold individual sperm and quantitatively evaluated the motile force generated by a sperm. Early studies revealed the relationship between sperm motility and swimming behavior and helped the investigations in medical aspects of sperm activity. As sperm chemotaxis draws more and more interest in fertilization research, the studies on sperm-egg communication may help to explain male or female infertility and provide exciting new approaches to contraception. However, single spot laser trapping can only be used to investigate an individual target, which has limits in efficiency and throughput. To study the chemotactic response of sperm to eggs and to characterize sperm motility, an annular laser trap with a diameter of several hundred microns is designed, simulated with ray tracing tool, and implemented. An axicon transforms the wavefront such that the laser beam is incident on the microscope objective from all directions while filling the back aperture completely for high efficiency trapping. A trapping experiment with microspheres is carried out to evaluate the system performance. The power requirement for annular sperm trapping is determined experimentally and compared with theoretical calculations. With a chemo-attractant located in the center and sperm approaching from all directions, the annular laser trapping could serve as a speed bump for sperm so that motility characterization and fertility sorting can be performed efficiently.

  11. Quantification of the activity of biomolecules in microarrays obtained by direct laser transfer.

    PubMed

    Dinca, V; Ranella, A; Farsari, M; Kafetzopoulos, D; Dinescu, M; Popescu, A; Fotakis, C

    2008-10-01

    The direct-writing technique laser-induced forward transfer has been employed for the micro-array printing of liquid solutions of the enzyme horseradish peroxidase and the protein Titin on nitrocellulose solid surfaces. The effect of two UV laser pulse lengths, femtosecond and nanosecond has been studied in relation with maintaining the activity of the transferred biomolecules. The quantification of the active biomolecules after transfer has been carried out using Bradford assay, quantitative colorimetric enzymatic assay and fluorescence techniques. Spectrophotometric measurements of the HRP and the Titin activity as well as chromatogenic and fluorescence assay studies have revealed a connection between the properties of the deposited, biologically active biomolecules, the experimental conditions and the target composition. The bioassays have shown that up to 78% of the biomolecules remained active after femtosecond laser transfer, while this value reduced to 54% after nanosecond laser transfer. The addition of glycerol in a percentage up to 70% in the solution to be transferred has contributed to the stabilization of the micro-array patterns and the increase of their resolution.

  12. Extraterrestrial applications of solar optics for interior illumination

    NASA Technical Reports Server (NTRS)

    Eijadi, David A.; Williams, Kyle D.

    1992-01-01

    Solar optics is a terrestrial technology that has potential extraterrestrial applications. Active solar optics (ASO) and passive solar optics (PSO) are two approaches to the transmission of sunlight to remote interior spaces. Active solar optics is most appropriate for task illumination, while PSO is most appropriate for general illumination. Research into solar optics, motivated by energy conservation, has produced lightweight and low-cost materials, products that have applications to NASA's Controlled Ecological Life Support System (CELSS) program and its lunar base studies. Specifically, prism light guides have great potential in these contexts. Several applications of solar optics to lunar base concepts are illustrated.

  13. Low-level Ga-Al-As laser irradiation enhances osteoblast proliferation through activation of Hedgehog signaling pathway

    NASA Astrophysics Data System (ADS)

    Li, Qiushi; Qu, Zhou; Chen, Yingxin; Liu, Shujie; Zhou, Yanmin

    2014-12-01

    Low-level laser irradiation has been reported to promote bone formation, but the molecular mechanism is still unclear. Hedgehog signaling pathway has been reported to play an important role in promoting bone formation. The aim of the present study was to examine whether low-level Ga-Al-As laser (808 nm) irradiation could have an effect on Hedgehog signaling pathway during osteoblast proliferation in vitro. Mouse osteoblastic cell line MC3T3-E1 was cultured in vitro. The cultures after laser irradiation (3.75J/cm2) were treated with recombinant N-terminals Sonic Hedgehog (N-Shh)or Hedgehog inhibitor cyclopamine (cy). The experiment was divided into 4 group, group 1:laser irradiation, group 2: laser irradiation and N-Shh, group 3: laser irradiation and cy, group 4:control with no laser irradiation. On day 1,2 and 3,cell proliferation was determined by cell counting, Cell Counting Kit-8.On 12 h and 24 h, cell cycle was detected by flow cytometry. Proliferation activity of laser irradiation and N-Shh group was remarkably increased compared with those of laser irradiation group. Proliferation activity of laser irradiation and cy group was remarkably decreased compared with those of laser irradiation group, however proliferation activity of laser irradiation and cy group was remarkably increased compared with those of control group. These results suggest that low-level Ga-Al-As laser irradiation activate Hedgehog signaling pathway during osteoblast proliferation in vitro. Hedgehog signaling pathway is one of the signaling pathways by which low-level Ga-Al-As laser irradiation regulates osteoblast proliferation.

  14. Noninvasive diode laser activation of transient receptor potential proteins and nociceptors

    NASA Astrophysics Data System (ADS)

    Jiang, Nan; Cooper, Brian Y.; Nemenov, Michael I.

    2007-02-01

    We investigated diode laser (980 nm) evoked activation of transient receptor potential proteins (TRPV1 and TRPV2). C and A-delta (Aδ) nociceptor families are primarily responsible for pain mediation in the peripheral nervous system. TRPV1 proteins have been associated with heat evoked pain in C fibers while Aδ fibers have been associated with TRPV2. Diode laser stimulation allows a margin of safety between non-invasive activation and damage 19, 22, 34. Laser pulses (20-50 ms, 0.1-10 W, 980 nm) were used to stimulate: A) in vitro: excised patches from HEK293 cells expressing TRPV1; B) in vitro: rat DRG nociceptors expressing either TRPV1 or TRPV2; and C) in vivo: C-fibers of the rat saphenous nerve (SN) trunk. Cell currents were recorded using standard patch clamp methods. The SN was also stimulated electrically with bipolar electrodes. Stimulation (20-50 ms) of HEK and DRG cells expressing TRPV1 was highly reproducible. Activation and peak currents were achieved at estimated peak temperatures of 55°C and 70°C. Threshold activation was also observed in DRG neurons expressing TRPV2. The conduction velocity for laser-activated saphenous nerve afferents was in the C fiber range (0.5-1 m/s). Electrically stimulated nerve contained stimulation artifacts and complex neural components with conduction velocities ranging from 0.3-30 m/s. Diode laser activation of TRPV1 protein is a reproducible and effective means to probe TRP activity in both in vivo and in vitro preparations

  15. Weakened negative effect of Au/TiO2 photocatalytic activity by CdS quantum dots deposited under UV-vis light illumination at different intensity ratios.

    PubMed

    Song, Kang; Wang, Xiaohong; Xiang, Qun; Xu, Jiaqiang

    2016-10-26

    Herein, we demonstrate experimentally the coexistence of photocatalytic dual opposite roles of Au nanoparticles in a UV-vis light irradiated Au/TiO2 system. We have investigated that the photocatalytic performance curves of Au/TiO2 and CdS/Au/TiO2 for degradation of methylene blue (MB) all present a V-shape with different radiation power ratios. However, through the comparison of photocatalytic activities of Au/TiO2 and CdS/Au/TiO2 by statistics and mathematical simulation, we propose qualitatively that the deposition of CdS used as a photosensitizer could extend the Au/TiO2 light absorption range and weaken the negative effect of Au/TiO2. Compared with Au/TiO2, it is proven indirectly that the photo-excited electrons of CdS/Au/TiO2 transfer from CdS to Au, and then to TiO2. Furthermore, we discuss the photocatalytic dual opposite roles of Au nanoparticles between CdS and TiO2, the positive effect includes localized surface plasmon resonance (LSPR) and Schottky barrier (SB), and the negative effect is that Au nanoparticles can be used as a new charge-carrier recombination center. In addition, we have analyzed that the dual opposite relationship of Au/TiO2 under the irradiation of mixed-light could be regulated by changing the intensity ratio of visible to UV light as well.

  16. Applications of TM polarized illumination

    NASA Astrophysics Data System (ADS)

    Smith, Bruce; Zhou, Jianming; Xie, Peng

    2008-03-01

    The use of transverse electric (TE) polarization has dominated illumination schemes as selective polarization is used for high-NA patterning. The benefits of TE polarization are clear - the interference of diffracted beams remains absolute at oblique angles. Transverse magnetic (TM) polarization is usually considered less desirable as imaging modulation from interference at large angle falls off rapidly as the 1/cosθ. Significant potential remains, however, for the use of TM polarization at large angles when its reflection component is utilized. By controlling the resist/substrate interface reflectivity, high modulation for TM polarization can be maintained for angles up to 90° in the resist. This can potentially impact the design of illumination away from most recent TE-only schemes for oblique imaging angles (high NA). We demonstrate several cases of TM illumination combined with tuned substrate reflectivity for 0.93NA, 1.20NA, and 1.35NA and compare results to TE and unpolarized cases. The goal is to achieve a flat response through polarization at large imaging angles. An additional application of TM illumination is its potential use for double patterning. As double patterning and double exposure approaches are sought in order to meet the needs of 32nm device generations and beyond, materials and process engineering challenges become prohibitive. We have devised a method for frequency doubling in a single exposure using an unconventional means of polarization selection and by making use of the reflective component produced at the photoresist/substrate interface. In doing so, patterns can be deposited into a photoresist film with double density. As an example, using a projection system numerical aperture of 1.20, with water as an immersion fluid, and a conventional polyacrylate 193nm photoresist, pattern resolution at 20nm half-pitch are obtainable (which is 0.125lambda/NA). The process to transfer this geometry into a hardmask layer uses conventional materials

  17. Synchrotron-based EUV lithography illuminator simulator

    DOEpatents

    Naulleau, Patrick P.

    2004-07-27

    A lithographic illuminator to illuminate a reticle to be imaged with a range of angles is provided. The illumination can be employed to generate a pattern in the pupil of the imaging system, where spatial coordinates in the pupil plane correspond to illumination angles in the reticle plane. In particular, a coherent synchrotron beamline is used along with a potentially decoherentizing holographic optical element (HOE), as an experimental EUV illuminator simulation station. The pupil fill is completely defined by a single HOE, thus the system can be easily modified to model a variety of illuminator fill patterns. The HOE can be designed to generate any desired angular spectrum and such a device can serve as the basis for an illuminator simulator.

  18. Modification of graphene oxide by laser irradiation: a new route to enhance antibacterial activity

    NASA Astrophysics Data System (ADS)

    Buccheri, Maria A.; D'Angelo, Daniele; Scalese, Silvia; Spanò, Simon F.; Filice, Simona; Fazio, Enza; Compagnini, Giuseppe; Zimbone, Massimo; Brundo, Maria V.; Pecoraro, Roberta; Alba, Anna; Sinatra, Fulvia; Rappazzo, Giancarlo; Privitera, Vittorio

    2016-06-01

    The antibacterial activity and possible toxicity of graphene oxide and laser-irradiated graphene oxide (iGO) were investigated. Antibacterial activity was tested on Escherichia coli and shown to be higher for GO irradiated for at least three hours, which seems to be correlated to the resulting morphology of laser-treated GO and independent of the kind and amount of oxygen functionalities. X-ray photoelectron spectroscopy, Raman spectroscopy, dynamic light scattering and scanning electron microscopy (SEM) show a reduction of the GO flakes size after visible laser irradiation, preserving considerable oxygen content and degree of hydrophilicity. SEM images of the bacteria after the exposure to the iGO flakes confirm membrane damage after interaction with the laser-modified morphology of GO. In addition, a fish embryo toxicity test on zebrafish displayed that neither mortality nor sublethal effects were caused by the different iGO solutions, even when the concentration was increased up to four times higher than the one effective in reducing the bacteria survival. The antibacterial properties and the absence of toxicity make the visible laser irradiation of GO a promising option for water purification applications.

  19. Low level laser therapy modulates viability, alkaline phosphatase and matrix metalloproteinase-2 activities of osteoblasts.

    PubMed

    Oliveira, Flávia Amadeu de; Matos, Adriana Arruda; Matsuda, Sandra Satiko; Buzalaf, Marília Afonso Rabelo; Bagnato, Vanderley Salvador; Machado, Maria Aparecida de Andrade Moreira; Damante, Carla Andreotti; Oliveira, Rodrigo Cardoso de; Peres-Buzalaf, Camila

    2017-04-01

    Low level laser therapy (LLLT) has been shown to stimulate bone cell metabolism but their impact on the matrix metalloproteinase (MMP) expression and activity is little explored. This study evaluated the influence of LLLT at two different wavelengths, red and infrared, on MC3T3-E1 preosteoblast viability, alkaline phosphatase (ALP) and MMP-2 and -9 activities. To accomplish this, MC3T3-E1 cells were irradiated with a punctual application of either red (660nm; InGaAIP active medium) or infrared (780nm; GaAlAs active medium) lasers both at a potency of 20mW, energy dose of 0.08 or 0.16J, and energy density of 1.9J/cm(2) or 3.8J/cm(2), respectively. The control group received no irradiation. Cellular viability, ALP and MMP-2 and -9 activities were assessed by MTT assay, enzymatic activity and zymography, respectively, at 24, 48 and 72h. The treatment of cells with both red and infrared lasers significantly increased the cellular viability compared to the non-irradiated control group at 24 and 48h. The ALP activity was also up modulated in infrared groups at 24 and 72h, depending on the energy densities. In addition, the irradiation with red laser at the energy density of 1.9J/cm(2) promoted an enhancement of MMP-2 activity at 48 and 72h. However, no differences were observed for the MMP-9 activity. In conclusion, when used at these specific parameters, LLL modulates both preosteoblast viability and differentiation highlighted by the increased ALP and MMP-2 activities induced by irradiation.

  20. Micromilled optical elements for edge-lit illumination panels

    NASA Astrophysics Data System (ADS)

    Ronny, Rahima Afrose; Knopf, George K.; Bordatchev, Evgueni; Nikumb, Suwas

    2013-04-01

    Edge-lit light guide panels (LGPs) with micropatterned surfaces represent a new technology for developing small- and medium-sized illumination sources for application such as automotive, residential lighting, and advertising displays. The shape, density, and spatial distribution of the micro-optical structures (MOSs) imprinted on the transparent LGP must be selected to achieve high brightness and uniform luminance over the active surface. We examine how round-tip cylindrical MOSs fabricated by precision micromilling can be used to create patterned surfaces on low-cost transparent polymethyl-methacrylate substrates for high-intensity illumination applications. The impact of varying the number, pitch, spatial distribution, and depth of the optical microstructures on lighting performance is initially investigated using LightTools™ simulation software. To illustrate the microfabrication process, several 100×100×6 mm3 LGP prototypes are constructed and tested. The prototypes include an "optimized" array of MOSs that exhibit near-uniform illumination (approximately 89%) across its active light-emitting surface. Although the average illumination was 7.3% less than the value predicted from numerical simulation, it demonstrates how LGPs can be created using micromilling operations. Customized MOS arrays with a bright rectangular pattern near the center of the panel and a sequence of MOSs that illuminate a predefined logo are also presented.

  1. Optics, illumination, and image sensing for machine vision VI; Proceedings of the Meeting, Boston, MA, Nov. 14, 15, 1991

    NASA Astrophysics Data System (ADS)

    Svetkoff, Donald J.

    Recent advances in research on imaging technologies and practical application of numerous techniques are reported. Consideration is given to illumination and sensing methods and systems, image and instrument models, optical processing and data manipulation, and 3D imaging techniques and systems. Particular attention is given to light source design for machine vision, multisource and color lighting for detection of small protuberances, VLSI sensor/processor circuitry for autonomous robots, calibration of an active stereoscopic imaging system, image processor development with synthetic images, optical morphological processing of disordered structures, a high-speed coherent optical correlator based on two MOSLMs, 3D line-scan intensity ratio sensing, pulsed time-of-flight laser range-finding techniques for industrial applications, and a comparison of continuous-wave and pulsed time-of-flight laser range-finding techniques.

  2. Active mode locking of a p-Ge hot hole laser

    SciTech Connect

    Hovenier, J.N.; Muravjov, A.V.; Pavlov, S.G.; Shastin, V.N.; Strijbos, R.C.; Wenckebach, W.T.

    1997-07-01

    The generation of 200 picosecond pulses of far-infrared radiation from a p-Ge hot hole laser (50{endash}140 cm{sup {minus}1}) was achieved due to active mode locking by electrical intracavity modulation of the gain. {copyright} {ital 1997 American Institute of Physics.}

  3. 3D fluorescence anisotropy imaging using selective plane illumination microscopy

    PubMed Central

    Hedde, Per Niklas; Ranjit, Suman; Gratton, Enrico

    2015-01-01

    Fluorescence anisotropy imaging is a popular method to visualize changes in organization and conformation of biomolecules within cells and tissues. In such an experiment, depolarization effects resulting from differences in orientation, proximity and rotational mobility of fluorescently labeled molecules are probed with high spatial resolution. Fluorescence anisotropy is typically imaged using laser scanning and epifluorescence-based approaches. Unfortunately, those techniques are limited in either axial resolution, image acquisition speed, or by photobleaching. In the last decade, however, selective plane illumination microscopy has emerged as the preferred choice for three-dimensional time lapse imaging combining axial sectioning capability with fast, camera-based image acquisition, and minimal light exposure. We demonstrate how selective plane illumination microscopy can be utilized for three-dimensional fluorescence anisotropy imaging of live cells. We further examined the formation of focal adhesions by three-dimensional time lapse anisotropy imaging of CHO-K1 cells expressing an EGFP-paxillin fusion protein. PMID:26368202

  4. Lasers in aviation

    NASA Astrophysics Data System (ADS)

    Goncharov, I. N.; Dezhin, V. N.; Kutakhov, V. P.; Petukhov, A. V.; Sidorin, V. M.; Sukhar, I. M.

    The way in which lasers are being incorporated into the military aircraft of the United States and the countries of Western Europe is discussed. Descriptions are given of laser weapons-guiding systems (including ranger finders and systems for target illumination), laser systems for navigation and flight-safety assurance (gyroscopes, velocity gauges, altimeters, systems providing meteorological data, proximity warning systems), and laser systems for air reconnaissance, communications, and control. Attention is also given to the Glissada laser guide path system, developed in the USSR. The physics of the systems is emphasized in the description and the principles underlying the operation of a laser are discussed in the introduction.

  5. Active spectral imaging and mapping

    NASA Astrophysics Data System (ADS)

    Steinvall, Ove

    2014-04-01

    Active imaging and mapping using lasers as illumination sources have been of increasing interest during the last decades. Applications range from defense and security, remote sensing, medicine, robotics, and others. So far, these laser systems have mostly been based on a fix wavelength laser. Recent advances in lasers enable emission of tunable, multiline, or broadband emission, which together with the development of array detectors will extend the capabilities of active imaging and mapping. This paper will review some of the recent work on active imaging mainly for defense and security and remote sensing applications. A short survey of basic lidar relations and present fix wavelength laser systems is followed by a review of the benefits of adding the spectral dimension to active and/or passive electro-optical systems.

  6. Short cavity active mode locking fiber laser for optical sensing and imaging

    NASA Astrophysics Data System (ADS)

    Lee, Hwi Don; Han, Ga Hee; Jeong, Syung Won; Jeong, Myung Yung; Kim, Chang-Seok; Shin, Jun Geun; Lee, Byeong Ha; Eom, Tae Joong

    2014-05-01

    We demonstrate a highly linear wavenumber- swept active mode locking (AML) fiber laser for optical sensing and imaging without any wavenumber-space resampling process. In this all-electric AML wavenumber-swept mechanism, a conventional wavelength selection filter is eliminated and, instead, the suitable programmed electric modulation signal is directly applied to the gain medium. Various types of wavenumber (or wavelength) tunings can be implemented because of the filter-less cavity configuration. Therefore, we successfully demonstrate a linearly wavenumber-swept AML fiber laser with 26.5 mW of output power to obtain an in-vivo OCT image at the 100 kHz swept rate.

  7. A history of semi-active laser dome and window materials

    NASA Astrophysics Data System (ADS)

    Sullivan, Roger M.

    2014-05-01

    Semi-Active Laser (SAL) guidance systems were developed starting in the mid-1960's and today form an important class of precision guided weapons. The laser wavelengths generally fall in the short wave infrared region of the spectrum. Relative to passive, image based, infrared seekers the optical demands placed on the domes or windows of SAL seekers is very modest, allowing the use of low cost, easily manufactured materials, such as polycarbonate. This paper will examine the transition of SAL window and dome science and technology from the laboratory to battlefield, with special emphasis on the story of polycarbonate domes.

  8. Evaluation of metal vapor laser designs with radial separation of the active medium

    NASA Astrophysics Data System (ADS)

    Soldatov, Anatoly N.; Polunin, Yu. P.; Chausova, L. N.

    1995-08-01

    Recent advances in self-terminating metal-vapor lasers have largely resulted from the feasibility of scaling laser characteristics in the cylindrical configuration of the active medium and longitudinal pulsed discharge, which makes it possible to provide the average power W > 100W from a large bore laser tube. Increasing the active volume, however, at the expense of a larger bore for this geometry of the gas discharge channel substantially reduces the specific energy Esp and the average specific power Wsp. Notably, the best laser characteristics have been realized with a low average specific input power Psp. The latter ranged between 1.5 and 0.5 W/cm3 for 6-12 cm bore tubes. As Psp was increased above a certain value, Wsp and W were found to decrease. As that took place, there appeared high radial inhomogeneities in the laser power distribution. Among the things which interfere with further increase of W, Wsp, and Esp as the input energy is increased, are radially nonuniform overheating of the active medium and very high degree of ionization. Given high input energies, these factors will give rise to a substantial deficit of ground state metal atoms N(O) at the center of the laser tube. As Psp is increased, the valley in the radial thermal distribution N(R) gets deeper due to ambipolar diffusion. The N(R) variation with excitation conditions has been studied experimentally for cylindrical laser tubes. The primary processes involved have been examined by means of the saturated power model. In this work we have studied laser action from Cu, I, and AuI in a tube whose configuration allows us to ameliorate the effect of a number of limiting factors on the output energy performance, on the one hand, and provides transversely separated excitation zones on the other, which, in turn, makes it possible to realize optimal thermophysical characteristics of the active medium, manipulate the spatial distribution of metal vapor, including the case of simultaneous excitation of

  9. Segmentation and estimation of spatially varying illumination.

    PubMed

    Lin Gu; Huynh, Cong Phuoc; Robles-Kelly, Antonio

    2014-08-01

    In this paper, we present an unsupervised method for segmenting the illuminant regions and estimating the illumination power spectrum from a single image of a scene lit by multiple light sources. Here, illuminant region segmentation is cast as a probabilistic clustering problem in the image spectral radiance space. We formulate the problem in an optimization setting, which aims to maximize the likelihood of the image radiance with respect to a mixture model while enforcing a spatial smoothness constraint on the illuminant spectrum. We initialize the sample pixel set under each illuminant via a projection of the image radiance spectra onto a low-dimensional subspace spanned by a randomly chosen subset of spectra. Subsequently, we optimize the objective function in a coordinate-ascent manner by updating the weights of the mixture components, sample pixel set under each illuminant, and illuminant posterior probabilities. We then estimate the illuminant power spectrum per pixel making use of these posterior probabilities. We compare our method with a number of alternatives for the tasks of illumination region segmentation, illumination color estimation, and color correction. Our experiments show the effectiveness of our method as applied to one hyperspectral and three trichromatic image data sets.

  10. Apparatus and method for generating partially coherent illumination for photolithography

    DOEpatents

    Sweatt, W.C.

    1999-07-06

    The present invention relates an apparatus and method for creating a bright, uniform source of partially coherent radiation for illuminating a pattern, in order to replicate an image of said pattern with a high degree of acuity. The present invention introduces a novel scatter plate into the optical path of source light used for illuminating a replicated object. The scatter plate has been designed to interrupt a focused, incoming light beam by introducing between about 8 to 24 diffraction zones blazed onto the surface of the scatter plate which intercept the light and redirect it to a like number of different positions in the condenser entrance pupil each of which is determined by the relative orientation and the spatial frequency of the diffraction grating in each of the several zones. Light falling onto the scatter plate, therefore, generates a plurality of unphased sources of illumination as seen by the back half of the optical system. The system includes a high brightness source, such as a laser, creating light which is taken up by a beam forming optic which focuses the incoming light into a condenser which in turn, focuses light into a field lens creating Kohler illumination image of the source in a camera entrance pupil. The light passing through the field lens illuminates a mask which interrupts the source light as either a positive or negative image of the object to be replicated. Light passing by the mask is focused into the entrance pupil of the lithographic camera creating an image of the mask onto a receptive media. 7 figs.

  11. Apparatus and method for generating partially coherent illumination for photolithography

    DOEpatents

    Sweatt, William C.

    1999-01-01

    The present invention relates an apparatus and method for creating a bright, uniform source of partially coherent radiation for illuminating a pattern, in order to replicate an image of said pattern with a high degree of acuity. The present invention introduces a novel scatter plate into the optical path of source light used for illuminating a replicated object. The scatter plate has been designed to interrupt a focused, incoming light beam by introducing between about 8 to 24 diffraction zones blazed onto the surface of the scatter plate which intercept the light and redirect it to a like number of different positions in the condenser entrance pupil each of which is determined by the relative orientation and the spatial frequency of the diffraction grating in each of the several zones. Light falling onto the scatter plate, therefore, generates a plurality of unphased sources of illumination as seen by the back half of the optical system. The system includes a high brightness source, such as a laser, creating light which is taken up by a beam forming optic which focuses the incoming light into a condenser which in turn, focuses light into a field lens creating Kohler illumination image of the source in a camera entrance pupil. The light passing through the field lens illuminates a mask which interrupts the source light as either a positive or negative image of the object to be replicated. Light passing by the mask is focused into the entrance pupil of the lithographic camera creating an image of the mask onto a receptive media.

  12. Transillumination spatially modulated illumination microscopy for human chromosome imaging

    NASA Astrophysics Data System (ADS)

    Pitris, Costas; Heracleous, Peter; Patsalis, Philippos

    2005-03-01

    Human chromosome analysis is an essential task in cytogenetics, especially in prenatal screening, genetic syndrome diagnosis, cancer pathology research and mutagen dosimetry. Chromosomal analysis begins with the creation of a karyotype, which is a layout of chromosome images organized by decreasing size in pairs. Both manual and automatic classification of chromosomes are limited by the resolution of the microscope and imaging system used. One way to improve the results of classification and even detect subtleties now remaining undetected, is to enhance the resolution of the images. It is possible to achieve lateral resolution beyond the classical limit, by using spatially modulated illumination (SMI) in a wide-field, non-confocal microscope. In this case, the sample is illuminated with spatially modulated light, which makes normally inaccessible high-resolution information visible in the observed image by shifting higher frequencies within the OTF limits of the microscope. Although, SMI microscopes have been reported in the past, this manuscript reports the development of a transillumination microscope for opaque, non-fluorescent samples. The illumination path consisted of a light source illuminating a ruled grating which was subsequently imaged on the sample. The grating was mounted on a rotating and translating stage so that the magnification and rotation of the pattern could be adjusted. The imaging lens was a 1.25 NA oil immersion objective. Test samples showed resolution improvement, as judged from a comparison of the experimentally obtained FWHM. Further studies using smaller fringe distance or laser interference pattern illumination will be evaluated to further optimize the SMI results.

  13. Wavelength-tunable actively mode-locked erbium-doped fiber ring laser using a distributed feedback semiconductor laser as mode locker and tunable filter

    NASA Astrophysics Data System (ADS)

    Li, Shenping; Chan, K. T.

    1999-07-01

    A wavelength-tunable actively mode-locked erbium fiber ring laser was demonstrated using a distributed feedback semiconductor laser as an intensity mode locker and a tunable optical filter. Very stable optical pulse trains at gigabit repetition rates were generated using harmonica mode locking. The supermode noise was suppressed to 60 dB below the signal level and the root-mean-square timing jitter (0.45 kHz-1 MHz) was found to be about 1% of the pulse duration. A continuous wavelength tuning range of 1.8 nm was achieved by changing the semiconductor laser temperature from 11.4 to 30 °C.

  14. Active protein and calcium hydroxyapatite bilayers grown by laser techniques for therapeutic applications.

    PubMed

    Motoc, M M; Axente, E; Popescu, C; Sima, L E; Petrescu, S M; Mihailescu, I N; Gyorgy, E

    2013-09-01

    Active protein and bioceramic calcium hydroxyapatite (HA) bilayers were grown by combining conventional pulsed laser deposition (PLD) and matrix-assisted pulsed laser evaporation (MAPLE) techniques. A pulsed UV KrF* excimer laser was used for the irradiations. The HA layers were grown by PLD. Proteins with antimicrobial action were attached to the bioceramic layers using MAPLE. The composite MAPLE targets were obtained by dissolving the proteins powder in distilled water. The crystalline status and chemical composition of the obtained structures were studied by X-ray diffractometry and Fourier transform infrared spectroscopy. The layers were grown for the design of advanced future metal implants coatings, ensuring both enhanced bone formation and localized antimicrobial therapy. Our results demonstrated that protein coatings improve bone cell proliferation in vitro. Immunofluorescence experiments show that actin filaments stretch throughout bone cells and sustain their optimal spreading.

  15. Activation of molecular oxygen by infrared laser radiation in pigment-free aerobic systems.

    PubMed

    Krasnovsky, A A; Drozdova, N N; Ivanov, A V; Ambartsumian, R V

    2003-09-01

    With the goal of mimicking the mechanisms of the biological effects of low energy laser irradiation, we have shown that infrared low intensity laser radiation causes oxygenation of the chemical traps of singlet oxygen dissolved in organic media and water saturated by air at normal atmospheric pressure. The photooxygenation rate was directly proportional to the oxygen concentration and strongly inhibited by the singlet oxygen quenchers. The maximum of the photooxygenation action spectrum coincided with the maximum of the oxygen absorption band at 1270 nm. The data provide unambiguous evidence that photooxygenation is determined by the reactive singlet (1)Delta(g )state formed as a result of direct laser excitation of molecular oxygen. Hence, activation of oxygen caused by its direct photoexcitation may occur in natural systems.

  16. Middle infrared active coherent laser spectrometer for standoff detection of chemicals.

    PubMed

    Macleod, Neil A; Rose, Rebecca; Weidmann, Damien

    2013-10-01

    Using a quantum cascade laser emitting at 7.85 μm, a middle infrared active coherent laser spectrometer has been developed for the standoff detection of vapor phase chemicals. The first prototype has been tested using diffuse target backscattering at ranges up to ~30 m. Exploiting the continuous frequency tuning of the laser source, spectra of water vapor, methane, nitrous oxide, and hydrogen peroxide were recorded. A forward model of the instrument was used to perform spectral unmixing and retrieve line-of-sight integrated concentrations and their one-sigma uncertainties. Performance was found to be limited by speckle noise originating from topographic targets. For absorbers with large absorption cross sections such as nitrous oxide (>10(-19) cm(2)·molecule(-1)), normalized detection sensitivities range between 14 and 0.3 ppm·m·Hz(-1/2), depending on the efficiency of the speckle reduction scheme implemented.

  17. Promotion of protein crystal growth by actively switching crystal growth mode via femtosecond laser ablation

    NASA Astrophysics Data System (ADS)

    Tominaga, Yusuke; Maruyama, Mihoko; Yoshimura, Masashi; Koizumi, Haruhiko; Tachibana, Masaru; Sugiyama, Shigeru; Adachi, Hiroaki; Tsukamoto, Katsuo; Matsumura, Hiroyoshi; Takano, Kazufumi; Murakami, Satoshi; Inoue, Tsuyoshi; Yoshikawa, Hiroshi Y.; Mori, Yusuke

    2016-11-01

    Large single crystals with desirable shapes are essential for various scientific and industrial fields, such as X-ray/neutron crystallography and crystalline devices. However, in the case of proteins the production of such crystals is particularly challenging, despite the efforts devoted to optimization of the environmental, chemical and physical parameters. Here we report an innovative approach for promoting the growth of protein crystals by directly modifying the local crystal structure via femtosecond laser ablation. We demonstrate that protein crystals with surfaces that are locally etched (several micrometers in diameter) by femtosecond laser ablation show enhanced growth rates without losing crystal quality. Optical phase-sensitive microscopy and X-ray topography imaging techniques reveal that the local etching induces spiral growth, which is energetically advantageous compared with the spontaneous two-dimensional nucleation growth mode. These findings prove that femtosecond laser ablation can actively switch the crystal growth mode, offering flexible control over the size and shape of protein crystals.

  18. Active and passive sensing of collective atomic coherence in a superradiant laser

    NASA Astrophysics Data System (ADS)

    Bohnet, Justin G.; Chen, Zilong; Weiner, Joshua M.; Cox, Kevin C.; Thompson, James K.

    2013-07-01

    We study the nondemolition mapping of collective quantum coherence onto a cavity light field in a superradiant, cold-atom 87Rb Raman laser. We show theoretically that the fundamental precision of the mapping is near the standard quantum limit on phase estimation for a coherent spin state, Δϕ=1/N, where N is the number of atoms. The associated characteristic measurement time scale τW∝1/N is collectively enhanced. The nondemolition nature of the measurement is characterized by only 0.5 photon recoils deposited per atom due to optical repumping in a time τW. We experimentally realize conditional Ramsey spectroscopy in our superradiant Raman laser, compare the results to the predicted precision, and study the mapping in the presence of decoherence, far from the steady-state conditions previously considered. Finally, we demonstrate a hybrid mode of operation in which the laser is repeatedly toggled between active and passive sensing.

  19. Characterization and control of tunable quantum cascade laser beam parameters for stand-off spectroscopy

    NASA Astrophysics Data System (ADS)

    Furstenberg, Robert; Kendziora, Christopher A.; Papantonakis, Michael R.; Nguyen, Viet; McGill, R. Andrew

    2016-05-01

    Infrared active stand-off detection techniques often employ high power tunable quantum cascade lasers (QCLs) for target illumination. Due to the distances involved, any fluctuation of the laser beam direction and/or beam profile is amplified at the sample position. If not accounted for, this leads to diminished performance (both sensitivity and selectivity) of the detection technique as a direct result of uncertainties in laser irradiance at each imaged pixel of the sample. This is especially true for detection approaches which illuminate a relatively small footprint at the target since the laser beam profile spatial fluctuations are often comparable to the (focused) laser spot size. Also, there is often a necessary trade-off between high output QCL power and beam quality. Therefore, precise characterization of the laser beam profile and direction as a function of laser properties (tuning wavelength, current and operating mode: pulsed or CW) is imperative. We present detailed measurements of beam profiles, beam wander and power fluctuations and their reproducibility as function of laser wavelength and stand-off distance for a commercially available tunable quantum cascade laser. We present strategies for improving beam quality by compensating for fluctuations using a motorized mirror and a pair of motorized lenses. We also investigate QCL mode hops and how they affect laser beam properties at the sample. Detailed mode-hop stability maps were measured.

  20. Rapid prototyping of reflectors for vehicle lighting using laser activated remote phosphor

    NASA Astrophysics Data System (ADS)

    Lachmayer, Roland; Kloppenburg, Gerolf; Wolf, Alexander

    2015-03-01

    Bright white light sources are of significant importance for automotive front lighting systems. Today's upper class vehicles mainly use HID or LED as light source. As a further step in this development laser diode based systems offer high luminance, efficiency and allow the realization of new styling concepts and new dynamic lighting functions. These white laser diode systems can either be realized by mixing different spectral sources or by combining diodes with specific phosphors. Based on the approach of generating light using a laser and remote phosphor, lighting modules are manufactured. Four blue laser diodes (450 nm) are used to activate a phosphor coating and thus to achieve white light. A segmented paraboloid reflector generates the desired light distribution for an additional car headlamp. We use high speed milling and selective laser melting to build the reflector system for this lighting module. We compare the spectral reflection grade of these materials. Furthermore the generated modules are analyzed regarding their efficiency and light distribution. The use of Rapid Prototyping technologies allows an early validation of the chosen concept and is supposed to reduce cost and time in the product development process significantly. Therefor we discuss costs and times of the applied manufacturing technologies.

  1. Activity of retinal ganglion cells following intense, nanosecond laser flashes. Final report, 1983-1986

    SciTech Connect

    Glickman, R.D.

    1989-01-01

    The effects of intense, but nonlesion-producing, laser exposures of 20-ns duration were determined on the light responses and spontaneous activity of retinal ganglion cells recorded in situ from the rhesus monkey. (Following a single, 20-ns exposure centered on its receptive field, a ganglion cell produced an 'afterdischarge' of maintained action potentials). The duration of the afterdischarge depended on the diameter of the laser beam on the retina and on the beam's intensity. Laser exposures subtending 0.5 to 2.0 deg, and delivering 45 to 60% of the maximum permissible exposure, elicited afterdischarges that lasted up to 80 s. When the beam diameter was decreased to 0.25 deg, the afterdischarge was reduced to 30 s, and to less than 5 s with the 0.12-deg beam. Light sensitivity after the laser exposure recovered rapidly during the first 10 s and then more slowly, but exponentially, until it reached the preflash level. Color-opponent ganglion cells exhibited a phenomenon called 'response-reversal' after the laser exposure, presumably due to selective adaptation of a mid-wavelength cone-input. Because a 20-ns exposure, regardless of intensity, is likely to photoregenerate more than half of the available visual pigment, the effects of ganglion cell response described here are not likely to be due solely to pigment bleaching.

  2. Influence of different illumination profiles on the on-state resistances of silicon carbide photoconductive semiconductor switches

    SciTech Connect

    Wang, Langning Xun, Tao; Yang, Hanwu; Liu, Jinliang; Zhang, Yu

    2014-04-15

    Characteristics of a silicon-carbide (SiC) photoconductive switch under different illumination profiles are presented. We triggered a V-doped semi-insulated 6H-SiC switch with lateral geometry using a laser beam of 532-nm wavelength. Photoconductivity tests for different spot profiles and locations show that such switches achieve a minimum on-state resistance when the switching gap is illuminated. The differences between on-state resistances are small for various partial illuminations of the switching gap. Semiconductor modeling is used to simulate the electric field and current profiles for different partial illuminations. The simulation results show poor on-state switch performance when partially illuminated. Based on these results, a more revealing circuit model for the switch matches well with experimental results for partial illuminations.

  3. Influence of different illumination profiles on the on-state resistances of silicon carbide photoconductive semiconductor switches.

    PubMed

    Wang, Langning; Xun, Tao; Yang, Hanwu; Liu, Jinliang; Zhang, Yu

    2014-04-01

    Characteristics of a silicon-carbide (SiC) photoconductive switch under different illumination profiles are presented. We triggered a V-doped semi-insulated 6H-SiC switch with lateral geometry using a laser beam of 532-nm wavelength. Photoconductivity tests for different spot profiles and locations show that such switches achieve a minimum on-state resistance when the switching gap is illuminated. The differences between on-state resistances are small for various partial illuminations of the switching gap. Semiconductor modeling is used to simulate the electric field and current profiles for different partial illuminations. The simulation results show poor on-state switch performance when partially illuminated. Based on these results, a more revealing circuit model for the switch matches well with experimental results for partial illuminations.

  4. Background illumination and automated perimetry.

    PubMed

    Klewin, K M; Radius, R L

    1986-03-01

    Visual field function in the right and left eyes of 31 normal volunteers was evaluated with an automated projection perimeter (OCTOPUS). Serial visual field evaluations were repeated in these same eyes with neutral filters of increasing optical density. We compared the results of threshold determinations with the different neutral filters in place before the examined eye. Significant reduction in threshold sensitivity at several test spots throughout the central 30 degrees visual field was seen with neutral density filters of 0.5 log units or greater. The low level of background illumination of the OCTOPUS perimeter (4.0 apostilbs) may allow relatively minor reduction in light transmission by the ocular media to produce significant changes in the recorded level of threshold sensitivity during visual field evaluation.

  5. Fully depleted back illuminated CCD

    DOEpatents

    Holland, Stephen Edward

    2001-01-01

    A backside illuminated charge coupled device (CCD) is formed of a relatively thick high resistivity photon sensitive silicon substrate, with frontside electronic circuitry, and an optically transparent backside ohmic contact for applying a backside voltage which is at least sufficient to substantially fully deplete the substrate. A greater bias voltage which overdepletes the substrate may also be applied. One way of applying the bias voltage to the substrate is by physically connecting the voltage source to the ohmic contact. An alternate way of applying the bias voltage to the substrate is to physically connect the voltage source to the frontside of the substrate, at a point outside the depletion region. Thus both frontside and backside contacts can be used for backside biasing to fully deplete the substrate. Also, high resistivity gaps around the CCD channels and electrically floating channel stop regions can be provided in the CCD array around the CCD channels. The CCD array forms an imaging sensor useful in astronomy.

  6. Free-form illumination optics

    NASA Astrophysics Data System (ADS)

    Mohedano, Rubén; Chaves, Julio; Hernández, Maikel

    2016-04-01

    In many illumination problems, the beam pattern needed and/or some geometrical constraints lead to very asymmetric design conditions. These asymmetries have been solved in the past by means of arrangements of rotationally symmetric or linear lamps aimed in different directions whose patterns overlap to provide the asymmetric prescriptions or by splitting one single lamp into several sections, each one providing a part of the pattern. The development of new design methods yielding smooth continuous free-form optical surfaces to solve these challenging design problems, combined with the proper CAD modeling tools plus the development of multiple axes diamond turn machines, give birth to a new generation of optics. These are able to offer the performance and other advanced features, such as efficiency, compactness, or aesthetical advantages, and can be manufactured at low cost by injection molding. This paper presents two examples of devices with free-form optical surfaces, a camera flash, and a car headlamp.

  7. Activators of photoluminescence in calcite: evidence from high-resolution, laser-excited luminescence spectroscopy

    USGS Publications Warehouse

    Pedone, V.A.; Cercone, K.R.; Burruss, R.C.

    1990-01-01

    Laser-excited luminescence spectroscopy of a red-algal, biogenic calcite and a synthetic Mn-calcite can make the distinction between organic and trace-element activators of photoluminescence. Organic-activated photoluminescence in biogenic calcite is characterized by significant peak shifts and increasing intensity with shorter-wavelength excitation and by significant decreases in intensity after heating to ??? 400??C. In contrast, Mn-activated photoluminescence shows no peak shift, greatest intensity under green excitation and limited changes after heating. Examination of samples with a high-sensitivity spectrometer using several wavelengths of exciting light is necessary for identification of photoluminescence activators. ?? 1990.

  8. Laser optical disk position encoder with active heads

    NASA Technical Reports Server (NTRS)

    Osborne, Eric P.

    1991-01-01

    An angular position encoder that minimizes the effects of eccentricity and other misalignments between the disk and the read stations by employing heads with beam steering optics that actively track the disk in directions along the disk radius and normal to its surface is discussed. The device adapts features prevalent in optical disk technology to the application of angular position sensing.

  9. Pathway illuminated: visualizing protein kinase C signaling.

    PubMed

    Violin, Jonathan D; Newton, Alexandra C

    2003-12-01

    Protein kinase C has been at the center of cell signaling since the discovery 25 years ago that it transduces signals that promote phospholipid hydrolysis. In recent years, the use of genetically encoded fluorescent reporters has enabled studies of the regulation of protein kinase C signaling in living cells. Advances in imaging techniques have unveiled unprecedented detail of the signal processing mechanics of protein kinase C, from the second messengers calcium and diacylglycerol that regulate protein kinase C activity, to the locations and kinetics of different protein kinase C isozymes, to the spatial and temporal dynamics of substrate phosphorylation by this key enzyme. This review discusses how fluorescence imaging studies have illuminated the fidelity with which protein kinase C transduces rapidly changing extracellular information into intracellular phosphorylation signals.

  10. Active eye-tracking for an adaptive optics scanning laser ophthalmoscope.

    PubMed

    Sheehy, Christy K; Tiruveedhula, Pavan; Sabesan, Ramkumar; Roorda, Austin

    2015-07-01

    We demonstrate a system that combines a tracking scanning laser ophthalmoscope (TSLO) and an adaptive optics scanning laser ophthalmoscope (AOSLO) system resulting in both optical (hardware) and digital (software) eye-tracking capabilities. The hybrid system employs the TSLO for active eye-tracking at a rate up to 960 Hz for real-time stabilization of the AOSLO system. AOSLO videos with active eye-tracking signals showed, at most, an amplitude of motion of 0.20 arcminutes for horizontal motion and 0.14 arcminutes for vertical motion. Subsequent real-time digital stabilization limited residual motion to an average of only 0.06 arcminutes (a 95% reduction). By correcting for high amplitude, low frequency drifts of the eye, the active TSLO eye-tracking system enabled the AOSLO system to capture high-resolution retinal images over a larger range of motion than previously possible with just the AOSLO imaging system alone.

  11. A laser-induced repetitive fast neutron source applied for gold activation analysis

    SciTech Connect

    Lee, Sungman; Park, Sangsoon; Lee, Kitae; Cha, Hyungki

    2012-12-15

    A laser-induced repetitively operated fast neutron source was developed for applications in laser-driven nuclear physics research. The developed neutron source, which has a neutron yield of approximately 4 Multiplication-Sign 10{sup 5} n/pulse and can be operated up to a pulse repetition rate of 10 Hz, was applied for a gold activation analysis. Relatively strong delayed gamma spectra of the activated gold were measured at 333 keV and 355 keV, and proved the possibility of the neutron source for activation analyses. In addition, the nuclear reactions responsible for the measured gamma spectra of gold were elucidated by the 14 MeV fast neutrons resulting from the D(t,n)He{sup 4} nuclear reaction, for which the required tritium originated from the primary fusion reaction, D(d,p)T{sup 3}.

  12. Doubly active Q switching and mode locking of an all-fiber laser.

    PubMed

    Cuadrado-Laborde, Christian; Díez, Antonio; Cruz, Jose L; Andrés, Miguel V

    2009-09-15

    Simultaneous and independent active Q switching and active mode locking of an erbium-doped fiber laser is demonstrated using all-fiber modulation techniques. A magnetostrictive rod attached to the output fiber Bragg grating modulates the Q factor of the Fabry-Perot cavity, whereas active mode locking is achieved by amplitude modulation with a Bragg-grating-based acousto-optic device. Fully modulated Q-switched mode-locked trains of optical pulses were obtained for a wide range of pump powers and repetition rates. For a Q-switched repetition rate of 500 Hz and a pump power of 100 mW, the laser generates trains of 12-14 mode-locked pulses of about 1 ns each, within an envelope of 550 ns, an overall energy of 0.65 microJ, and a peak power higher than 250 W for the central pulses of the train.

  13. Active eye-tracking for an adaptive optics scanning laser ophthalmoscope

    PubMed Central

    Sheehy, Christy K.; Tiruveedhula, Pavan; Sabesan, Ramkumar; Roorda, Austin

    2015-01-01

    We demonstrate a system that combines a tracking scanning laser ophthalmoscope (TSLO) and an adaptive optics scanning laser ophthalmoscope (AOSLO) system resulting in both optical (hardware) and digital (software) eye-tracking capabilities. The hybrid system employs the TSLO for active eye-tracking at a rate up to 960 Hz for real-time stabilization of the AOSLO system. AOSLO videos with active eye-tracking signals showed, at most, an amplitude of motion of 0.20 arcminutes for horizontal motion and 0.14 arcminutes for vertical motion. Subsequent real-time digital stabilization limited residual motion to an average of only 0.06 arcminutes (a 95% reduction). By correcting for high amplitude, low frequency drifts of the eye, the active TSLO eye-tracking system enabled the AOSLO system to capture high-resolution retinal images over a larger range of motion than previously possible with just the AOSLO imaging system alone. PMID:26203370

  14. Off-axis illumination of lithography tool

    NASA Astrophysics Data System (ADS)

    Xing, Han; Lin, Li; Bin, Ma

    2013-12-01

    Lithography tool is a necessary part for LSI and VLSI. The illumination system design is an important part in the lithography optical system design. Off-axis illumination technology is an effective way to reducing resolution of lithography. The paper introduction the basic components of lithography tool, the principle of off-axis illumination reducing the resolution of lithography and focus on the two implementations of OAI technology, finally point out advantages and disadvantage of the two implementations.

  15. Light induced modulation instability of surfaces under intense illumination

    SciTech Connect

    Burlakov, V. M. Goriely, A.; Foulds, I.

    2013-12-16

    We show that a flat surface of a polymer in rubber state illuminated with intense electromagnetic radiation is unstable with respect to periodic modulation. Initial periodic perturbation is amplified due to periodic thermal expansion of the material heated by radiation. Periodic heating is due to focusing-defocusing effects caused by the initial surface modulation. The surface modulation has a period longer than the excitation wavelength and does not require coherent light source. Therefore, it is not related to the well-known laser induced periodic structures on polymer surfaces but may contribute to their formation and to other phenomena of light-matter interaction.

  16. Laser barometer

    DOEpatents

    Abercrombie, Kevin R.; Shiels, David; Rash, Tim

    2001-02-06

    A pressure measuring instrument that utilizes the change of the refractive index of a gas as a function of pressure and the coherent nature of a laser light to determine the barometric pressure within an environment. As the gas pressure in a closed environment varies, the index of refraction of the gas changes. The amount of change is a function of the gas pressure. By illuminating the gas with a laser light source, causing the wavelength of the light to change, pressure can be quantified by measuring the shift in fringes (alternating light and dark bands produced when coherent light is mixed) in an interferometer.

  17. Field trial of active remote sensing using a high-power short-wave infrared supercontinuum laser.

    PubMed

    Alexander, Vinay V; Shi, Zhennan; Islam, Mohammed N; Ke, Kevin; Kalinchenko, Galina; Freeman, Michael J; Ifarraguerri, Agustin; Meola, Joseph; Absi, Anthony; Leonard, James; Zadnik, Jerome A; Szalkowski, Anthony S; Boer, Gregory J

    2013-09-20

    Field trial results of a 5 W all-fiber broadband supercontinuum (SC) laser covering the short-wave infrared (SWIR) wavelength bands from ~1.55 to 2.35 μm are presented. The SC laser is kept on a 12 story tower at the Wright Patterson Air Force Base and propagated through the atmosphere to a target 1.6 km away. Beam quality of the SC laser after propagating through 1.6 km is studied using a SWIR camera and show a near diffraction limited beam with an M(2) value of <1.3. The SC laser is used as the illumination source to perform spectral reflectance measurements of various samples at 1.6 km, and the results are seen to be in good agreement with in-lab measurements using a conventional lamp source. Spectral stability measurements are performed after atmospheric propagation through 1.6 km and show a relative variability of ~4%-8% across the spectrum depending on the atmospheric turbulence effects. Spectral stability measurements are also performed in-lab and show a relative variability of <0.6% across the spectrum.

  18. Improved Interference configuration for structured illumination microscopy

    NASA Astrophysics Data System (ADS)

    Chen, Houkai; Wei, Shibiao; Wu, Xiaojing; Yang, Yong; Zhang, Yuquan; Du, Luping; Liu, Jun; Zhu, Siwei; Yuan, Xiaocong

    2017-02-01

    We present an improved structured illumination configuration for structured illumination microscopy (SIM) based on spatial light modulator. Precise phase shifts and rotation of illumination fringes can be dynamically controlled using a spatial light modulator. The method is different from the conventional illumination configuration that are based on interference of ±1 diffractive order light. The experimental setup requires less optical elements making it compact, reliable, and suitable for integration. The method has been applied in the standing-wave total internal reflection fluorescent microscopy. High lateral resolution of sub-100 nm was achieved in single directional resolution enhancement experiments.

  19. Polarimetric target detection under uneven illumination.

    PubMed

    Huang, Bingjing; Liu, Tiegen; Han, Jiahui; Hu, Haofeng

    2015-09-07

    In polarimetric imaging, the uneven illumination could cause the significant spatial intensity fluctuations in the scene, and thus hampers the target detection. In this paper, we propose a method of illumination compensation and contrast optimization for Stokes polarimetric imaging, which allows significantly increasing the performance of target detection under uneven illumination. We show with numerical simulation and real-world experiment that, based on the intensity information contained in the polarization information, the contrast can be effectively enhanced by proper approach, which is of particular importance in practical applications with spatial illumination fluctuations, such as remote sensing.

  20. Illumination system characterization for hyperspectral imaging

    NASA Astrophysics Data System (ADS)

    Katrašnik, Jaka; Pernuš, Franjo; Likar, Boštjan

    2011-03-01

    Near-infrared hyperspectral imaging is becoming a popular tool in the biomedical field, especially for detection and analysis of different types of cancers, analysis of skin burns and bruises, imaging of blood vessels and for many other applications. As in all imaging systems, proper illumination is crucial to attain optimal image quality that is needed for best performance of image analysis algorithms. In hyperspectral imaging based on filters (AOTF, LCTF and filter wheel) the acquired spectral signature has to be representative in all parts of the imaged object. Therefore, the whole object must be equally well illuminated - without shadows and specular reflections. As there are no restrictions imposed on the material and geometry of the object, the desired object illumination can only be achieved with completely diffuse illumination. In order to minimize shadows and specular reflections in diffuse illumination the light illuminating the object must be spatially, angularly and spectrally uniform. We present and test two diffuse illumination system designs that try to achieve optimal uniformity of the above mentioned properties. The illumination uniformity properties were measured with an AOTF based hyperspectral imaging system utilizing a standard white diffuse reflectance target and a specially designed calibration target for estimating the spatial and angular illumination uniformity.

  1. Structured illumination fluorescence Fourier ptychographic microscopy

    NASA Astrophysics Data System (ADS)

    Xiu, Peng; Chen, Youhua; Kuang, Cuifang; Fang, Yue; Wang, Yifan; Fan, Jiannan; Xu, Yingke; Liu, Xu

    2016-12-01

    We apply a Fourier ptychographic algorithm for fluorescent samples using structured illumination. The samples are illuminated with structured light patterns and the raw imaging data using traditional structured illumination fluorescence microscopy (SIM) are acquired. We then extract equivalent oblique illuminated images of fluorescent samples from the SIM images. An optimized Fourier ptychography algorithm is proposed, which ensures the fidelity of the reconstructed the super-resolution results. This method can break the diffraction limit to a resolution of λ/4, and has a better signal-to-noise ratio (SNR) than SIM, especially when the background noise is high.

  2. Illumination discrimination in real and simulated scenes

    PubMed Central

    Radonjić, Ana; Pearce, Bradley; Aston, Stacey; Krieger, Avery; Dubin, Hilary; Cottaris, Nicolas P.; Brainard, David H.; Hurlbert, Anya C.

    2016-01-01

    Characterizing humans' ability to discriminate changes in illumination provides information about the visual system's representation of the distal stimulus. We have previously shown that humans are able to discriminate illumination changes and that sensitivity to such changes depends on their chromatic direction. Probing illumination discrimination further would be facilitated by the use of computer-graphics simulations, which would, in practice, enable a wider range of stimulus manipulations. There is no a priori guarantee, however, that results obtained with simulated scenes generalize to real illuminated scenes. To investigate this question, we measured illumination discrimination in real and simulated scenes that were well-matched in mean chromaticity and scene geometry. Illumination discrimination thresholds were essentially identical for the two stimulus types. As in our previous work, these thresholds varied with illumination change direction. We exploited the flexibility offered by the use of graphics simulations to investigate whether the differences across direction are preserved when the surfaces in the scene are varied. We show that varying the scene's surface ensemble in a manner that also changes mean scene chromaticity modulates the relative sensitivity to illumination changes along different chromatic directions. Thus, any characterization of sensitivity to changes in illumination must be defined relative to the set of surfaces in the scene.

  3. High-efficiency high-energy Ka source for the critically-required maximum illumination of x-ray optics on Z using Z-petawatt-driven laser-breakout-afterburner accelerated ultrarelativistic electrons LDRD .

    SciTech Connect

    Sefkow, Adam B.; Bennett, Guy R.

    2010-09-01

    Under the auspices of the Science of Extreme Environments LDRD program, a <2 year theoretical- and computational-physics study was performed (LDRD Project 130805) by Guy R Bennett (formally in Center-01600) and Adam B. Sefkow (Center-01600): To investigate novel target designs by which a short-pulse, PW-class beam could create a brighter K{alpha} x-ray source than by simple, direct-laser-irradiation of a flat foil; Direct-Foil-Irradiation (DFI). The computational studies - which are still ongoing at this writing - were performed primarily on the RedStorm supercomputer at Sandia National Laboratories Albuquerque site. The motivation for a higher efficiency K{alpha} emitter was very clear: as the backlighter flux for any x-ray imaging technique on the Z accelerator increases, the signal-to-noise and signal-to-background ratios improve. This ultimately allows the imaging system to reach its full quantitative potential as a diagnostic. Depending on the particular application/experiment this would imply, for example, that the system would have reached its full design spatial resolution and thus the capability to see features that might otherwise be indiscernible with a traditional DFI-like x-ray source. This LDRD began FY09 and ended FY10.

  4. Effect of temperature and illumination of streamer discharges in cadmium sulfide and cadmium selenide single crystals

    SciTech Connect

    Gladyshchuk, A.A.; Gurskii, A.L.; Parashchuk, V.V.; Yablonskii, G.P.

    1986-12-01

    The excitation conditions, the orientation, the radiation spectra of streamer discharges and the effect of laser illumination and temperature on the properties of streamers in cadmium sulfide single crystals has appeared in previous studies. Light generation in CdSe single crystals and in the mixed compounds CdS/sub x/Se/sub 1-x/ was obtained with streamer excitation through detailed information on the crystallographic orientation of the streamers and radiation spectra of these crystals. In this paper, the authors present new data on the effect of the temperature and illumination in the region 77-520/sup 0/K on the probability of excitation and the orientation of streamer discharges in cadmium sulfide crystals; the characteristic features of excitation, orientation, and luminescence spectra of streamer discharges in CdS/sub x/Se/sub 1-x/. The crystals were illuminated with radiation from an incandescent lamp with controllable intensity in the spectral range 560-580 nm and by impulsive radiation from an LGT-21 nitrogen laser (wavelength = 337.1 nm and I/sub e/ = 30 kW/cm/sup 2/. The resistivity of the crystalline plates as a function of the illumination intensity was determined from measurements of the photoconductivity. The streamer illumination of the discharge was separated from the illumination background by interference light filters.

  5. A Low-Level Carbon Dioxide Laser Promotes Fibroblast Proliferation and Migration through Activation of Akt, ERK, and JNK

    PubMed Central

    Shingyochi, Yoshiaki; Kanazawa, Shigeyuki; Tajima, Satoshi; Tanaka, Rica; Mizuno, Hiroshi; Tobita, Morikuni

    2017-01-01

    Background Low-level laser therapy (LLLT) with various types of lasers promotes fibroblast proliferation and migration during the process of wound healing. Although LLLT with a carbon dioxide (CO2) laser was also reported to promote wound healing, the underlying mechanisms at the cellular level have not been previously described. Herein, we investigated the effect of LLLT with a CO2 laser on fibroblast proliferation and migration. Materials and Methods Cultured human dermal fibroblasts were prepared. MTS and cell migration assays were performed with fibroblasts after LLLT with a CO2 laser at various doses (0.1, 0.5, 1.0, 2.0, or 5.0 J/cm2) to observe the effects of LLLT with a CO2 laser on the proliferation and migration of fibroblasts. The non-irradiated group served as the control. Moreover, western blot analysis was performed using fibroblasts after LLLT with a CO2 laser to analyze changes in the activities of Akt, extracellular signal-regulated kinase (ERK), and Jun N-terminal kinase (JNK), which are signaling molecules associated with cell proliferation and migration. Finally, the MTS assay, a cell migration assay, and western blot analysis were performed using fibroblasts treated with inhibitors of Akt, ERK, or JNK before LLLT with a CO2 laser. Results In MTS and cell migration assays, fibroblast proliferation and migration were promoted after LLLT with a CO2 laser at 1.0 J/cm2. Western blot analysis revealed that Akt, ERK, and JNK activities were promoted in fibroblasts after LLLT with a CO2 laser at 1.0 J/cm2. Moreover, inhibition of Akt, ERK, or JNK significantly blocked fibroblast proliferation and migration. Conclusions These findings suggested that LLLT with a CO2 laser would accelerate wound healing by promoting the proliferation and migration of fibroblasts. Activation of Akt, ERK, and JNK was essential for CO2 laser-induced proliferation and migration of fibroblasts. PMID:28045948

  6. Masked illumination scheme for a galvanometer scanning high-speed confocal fluorescence microscope.

    PubMed

    Kim, Dong Uk; Moon, Sucbei; Song, Hoseong; Kwon, Hyuk-Sang; Kim, Dug Young

    2011-01-01

    High-speed beam scanning and data acquisition in a laser scanning confocal microscope system are normally implemented with a resonant galvanometer scanner and a frame grabber. However, the nonlinear scanning speed of a resonant galvanometer can generate nonuniform photobleaching in a fluorescence sample as well as image distortion near the edges of a galvanometer scanned fluorescence image. Besides, incompatibility of signal format between a frame grabber and a point detector can lead to digitization error during data acquisition. In this article, we introduce a masked illumination scheme which can effectively decrease drawbacks in fluorescence images taken by a laser scanning confocal microscope with a resonant galvanometer and a frame grabber. We have demonstrated that the difference of photobleaching between the center and the edge of a fluorescence image can be reduced from 26 to 5% in our confocal laser scanning microscope with a square illumination mask. Another advantage of our masked illumination scheme is that the zero level or the lowest input level of an analog signal in a frame grabber can be accurately set by the dark area of a mask in our masked illumination scheme. We have experimentally demonstrated the advantages of our masked illumination method in detail.

  7. Laser clock

    SciTech Connect

    Facklam, R.L.

    1983-05-26

    A laser clock includes a linear laser in one embodiment of the clock and a ring laser gyro in the other embodiment. The linear laser is frequency stabilized and utilizes a single active medium in the form of a low pressure gas, such as He-Ne, with a Doppler broadened gain curve. The ring laser gyro is a four frequency laser with a Faraday rotor. Detector and electronic circuitry associated with the laser of each embodiment detects a beat frequency and convert it to a clock signal.

  8. Creation of Cu2O@TiO2 composite photocatalysts with p-n heterojunctions formed on exposed Cu2O facets, their energy band alignment study, and their enhanced photocatalytic activity under illumination with visible light.

    PubMed

    Liu, Lingmei; Yang, Weiyi; Sun, Wuzhu; Li, Qi; Shang, Jian Ku

    2015-01-28

    The creation of photocatalysts with controlled facets has become an important approach to enhance their activity. However, how the formation of heterojunctions on exposed facets could affect their photocatalytic performance ranking had not yet been investigated. In this study, Cu2O@TiO2 core-shell structures were created, and Cu2O/TiO2 p-n heterojunctions were formed on various exposed facets of Cu2O cubes, Cu2O cuboctahedra, and Cu2O octahedra, respectively. These Cu2O@TiO2 polyhedra demonstrated an enhanced photocatalytic degradation effect on Methylene Blue (MB) and 4-nitrophenol (4-NP) under visible light illumination, because of the enhanced charge carrier separation by the formation of Cu2O@TiO2 p-n heterojunctions. It was further found that their photocatalytic performance was also facet-dependent as pure Cu2O polyhedra, while the photocatalytic performance ranking of these Cu2O@TiO2 polyhedra was different with that of their corresponding Cu2O polyhedron cores. By the combination of optical property measurement and XPS analysis, the energy band alignments of these Cu2O@TiO2 polyhedra were determined, which demonstrated that Cu2O@TiO2 octahedra had the highest band offset for the separation of charge carriers. Thus, the charge-carrier-separation-driven force in Cu2O@TiO2 polyhedra was different from their corresponding Cu2O polyhedron cores, which resulted in their different surface photovoltage spectrum (SPS) responses and different photocatalytic performance rankings.

  9. Six-color solid state illuminator for cinema projector

    NASA Astrophysics Data System (ADS)

    Huang, Junejei; Wang, Yuchang

    2014-09-01

    Light source for cinema projector requires reliability, high brightness, good color and 3D for without silver screens. To meet these requirements, a laser-phosphor based solid state illuminator with 6 primary colors is proposed. The six primary colors are divided into two groups and include colors of R1, R2, G1, G2, B1 and B2. Colors of B1, B2 and R2 come from lasers of wavelengths 440 nm, 465 nm and 639 nm. Color of G1 comes from G-phosphor pumped by B2 laser. Colors of G2 and R1 come from Y-phosphor pumped by B1 laser. Two groups of colors are combined by a multiband filter and working by alternately switching B1 and B2 lasers. The combined two sequences of three colors are sent to the 3-chip cinema projector and synchronized with frame rate of 120Hz. In 2D mode, the resulting 6 primary colors provide a very wide color gamut. In 3D mode, two groups of red, green and blue primary colors provide two groups of images that received by left and right eyes.

  10. Photomodulation of cellular and subcellular activities by He-Ne laser

    NASA Astrophysics Data System (ADS)

    Moro, Loredana; Greco, Margherita; Marra, Ersilia; Passarella, Salvatore

    2003-12-01

    In hepatocytes, proliferation of tetraploid and binuclear cells and an increase in cytosolic and mitochondrial protein synthesis are caused by He-Ne laser irradiation. To gain some insight into the mechanism of photomodulation of cellular and subcellular activities in isolated hepatocytes, intracellular mediators of cell photostimulation were investigated in intact cells and isolated mitochondria. Irradiation of isolated hepatocytes and isolated rat liver mitochondria was carried out with He-Ne laser (wavelength: 632.8 nm; fluence: 0.24 J cm-2; fluence rate: 12 mW cm-2). Changes in cytosolic [(Ca2+)c] and mitochondrial [(Ca2+)m] calcium concentration, and in mitochondrial (Δψm) and plasma (Δψc) membrane potential were, monitored using either colorimetric or fluorescent probes. C-fos expression was studied by Northern and immunoblotting analysis. As a result of irradiation, an increase in (Ca2+)c and a calcium-dependent increase in Δψc were found. The increase in (Ca2+)c, in turn, caused an increase in c-fos expression. Finally, an increase in (Ca2+)m, probably owing to the increase in Δψm, was found. Increase in (Ca2+)c, leading to activation of gene expression, and a general activation of mitochondrial metabolism, could play a major role in the mechanism of photostimulation of cellular activities by He-Ne laser.

  11. Fourier Transform Infrared (FTIR) Observation Of Catalytically Active Intermediates Produced By Laser Photolysis Of Iron Pentacarbonyl

    NASA Astrophysics Data System (ADS)

    Paquette, Michael S.

    1984-05-01

    The pulsed laser excitation of iron pentacarbonyl in solutions of 1-pentene photoinitiates a highly active catalytic process for isomerization of the olefin. This process is observed in situ by rapid scanning FTIR spectroscopy, allowing subsecond acquisition of spectra. These are deconvoluted into discrete spectral components which are assigned molecular formulas. Specific activities have been obtained for two catalytically significant complexes from a correlation of catalytic activity with compositional changes. A similar interpretation of multipulse and cw experiments allowed development of a comprehensive cycle of thermal and photochemical interconversions among components.

  12. Oscillation regimes of a solid-state ring laser with active beat-note stabilization: From a chaotic device to a ring-laser gyroscope

    SciTech Connect

    Schwartz, Sylvain; Feugnet, Gilles; Pocholle, Jean-Paul; Lariontsev, Evguenii

    2007-08-15

    We report an experimental and theoretical study of a rotating diode-pumped Nd-YAG ring laser with active beat-note stabilization. Our experimental setup is described in the usual Maxwell-Bloch formalism. We analytically derive a stability condition and some frequency response characteristics for the solid-state ring-laser gyroscope, illustrating the important role of mode coupling effects on the dynamics of such a device. Experimental data are presented and compared with the theory on the basis of realistic laser parameters, showing very good agreement. Our results illustrate the duality between the very rich nonlinear dynamics of the diode-pumped solid-state ring laser (including chaotic behavior) and the possibility to obtain a very stable beat note, resulting in a potentially new kind of rotation sensor.

  13. Loop laser cavities with self-pumped phase-conjugate mirrors in low-gain active media for phase-locked multichannel laser systems

    SciTech Connect

    Basiev, Tasoltan T; Gavrilov, A V; Ershkov, M N; Smetanin, Sergei N; Fedin, Aleksandr V; Bel'kov, K A; Boreysho, A S; Lebedev, V F

    2011-03-31

    It is proved that lasers with different loop cavities with self-pumped phase-conjugate mirrors in low-gain active media can operate under injection of external laser radiation and can be used for the development of diode-pumped phase-locked multichannel neodymium laser systems operating both on the fundamental laser transition with the wavelength {lambda} = 1.06 {mu}m and on the transition with {lambda} = 1.34 {mu}m. The phase-conjugate oscillation thresholds in the case of injection of an external signal are determined for a multiloop cavity configuration and an increased number of active elements in the cavity. It is shown that phase-conjugate oscillation can occur even if the single-pass gain of the active element is as low as only {approx}2. Under high-power side diode pumping of a multiloop Nd:YAG laser, single-mode output radiation was achieved at {lambda} = 1.064 {mu}m with a pulse energy up to 0.75 J, a pulse repetition rate up to 25 Hz, an average power up to 18.3 W, and an efficiency up to 20%. In a multiloop Nd:YAG laser with three active elements in the cavity, single-mode radiation at {lambda} = 1.34 {mu}m was obtained with a pulse energy up to 0.96 J, a pulse repetition rate up to 10 Hz, and an average power up to 8.5 W. (control of laser radiation parameters)

  14. Effect of distorted illumination waves on coherent diffraction microscopy

    SciTech Connect

    Kohmura, Yoshiki; Nishino, Yoshinori; Ishikawa, Tetsuya; Miao Jianwei

    2005-12-15

    Coherent diffraction microscopy requires a well-defined illumination wave such as a plane wave on a specimen. Experimentally, a small pinhole or a focused beam is often used to reduce the illumination area but they unavoidably distort the waves. The distortion of the illumination wave causes artifacts in the phase retrieval of oversampled diffraction patterns. Using computer simulations, we searched for the conditions where strong artifacts arise by changing the Fresnel number, pinhole size, alignment error and photon statistics. The experimental setup with Fresnel number of around 1 and smaller than 1 realized a small reconstruction error when the pinhole radius is larger than a few times the specimen size. These conditions are suitable for the rotation of specimens for the three-dimensional (3D) observations. Such investigation will have an impact in the design of coherent diffraction microscopes for the 3D characterization of nanoscale materials and biological systems using the third generation synchrotron radiation and future x-ray free-electron lasers.

  15. Firsthand in situ observation of active fine laser tuning by combining a temperature gradient and a CLC wedge cell structure.

    PubMed

    Jeong, Mi-Yun; Cha, Jihun

    2015-08-10

    In situ direct observation of the lasing process in a cholesteric liquid crystal (CLC) laser array using a CMOS camera was used to investigate discontinuous laser tuning in a parallel CLC cell. In accordance with the discontinuous pitch change by thermal energy transfer, at the same time the laser wavelength undergoes an immediate and discontinuous shift. And we found out the reason why the CLC phase has domain textures. And this work develops a simple active tunable laser array by forming a spatial temperature gradient along a wedge CLC cell. With this new strategy, only just about 7 nm laser tuning range at room temperature is extremely widened over the 105 nm wavelength range with about 0.2 nm tuning resolution. Furthermore, there is no aging effect because the employed CLC array has only one chiral molecular concentration. This strategy could be used in a practical CLC laser device application.

  16. Optimization of nuclear-pumped laser active media by electron beam

    SciTech Connect

    Tarasenko, V.F.; Fedenev, A.V.

    1996-05-01

    In present report there are assumed the results of nuclear pumped laser (NPL) active media experimental studying with electron beam excitation and the analysis is made for emission characteristics and kinetic processes of more perspective lasers, which are operating at low pumping power close to NPL excitation conditions. Basic attention is paying to experimental data, obtained for e-beam pumped low-threshold active media, which have allowed to accelerate the understanding of the inversion population creation processes in NPL and which have predetermined new future experiments with NPL. It has been shown that in spit of same differences in plasma creation processes for e-beam pumping and fission fragment excitation, operating level and inversion population creation processes in nonequilibrium recombinant plasma are similar for both types of excitation at compatible pumping power and pulse duration. {copyright} {ital 1996 American Institute of Physics.}

  17. Antimicrobial activity of biopolymer-antibiotic thin films fabricated by advanced pulsed laser methods

    NASA Astrophysics Data System (ADS)

    Cristescu, R.; Popescu, C.; Dorcioman, G.; Miroiu, F. M.; Socol, G.; Mihailescu, I. N.; Gittard, S. D.; Miller, P. R.; Narayan, R. J.; Enculescu, M.; Chrisey, D. B.

    2013-08-01

    We report on thin film deposition by matrix assisted pulsed laser evaporation (MAPLE) of two polymer-drug composite thin film systems. A pulsed KrF* excimer laser source (λ = 248 nm, τ = 25 ns, ν = 10 Hz) was used to deposit composite thin films of poly(D,L-lactide) (PDLLA) containing several gentamicin concentrations. FTIR spectroscopy was used to demonstrate that MAPLE-transferred materials exhibited chemical structures similar to those of drop cast materials. Scanning electron microscopy data indicated that MAPLE may be used to fabricate thin films of good morphological quality. The activity of PDLLA-gentamicin composite thin films against Staphylococcus aureus bacteria was demonstrated using drop testing. The influence of drug concentration on microbial viability was also assessed. Our studies indicate that polymer-drug composite thin films prepared by MAPLE may be used to impart antimicrobial activity to implants, medical devices, and other contact surfaces.

  18. A novel active disturbance rejection based tracking design for laser system with quadrant photodetector

    NASA Astrophysics Data System (ADS)

    Manojlović, Stojadin M.; Barbarić, Žarko P.; Mitrović, Srđan T.

    2015-06-01

    A new tracking design for laser systems with different arrangements of a quadrant photodetector, based on the principle of active disturbance rejection control is suggested. The detailed models of quadrant photodetector with standard add-subtract, difference-over-sum and diagonal-difference-over-sum algorithms for displacement signals are included in the control loop. Target moving, non-linearity of a photodetector, parameter perturbations and exterior disturbances are treated as a total disturbance. Active disturbance rejection controllers with linear extended state observers for total disturbance estimation and rejection are designed. Proposed methods are analysed in frequency domain to quantify their stability characteristics and disturbance rejection performances. It is shown through simulations, that tracking errors are effectively compensated, providing the laser spot positioning in the area near the centre of quadrant photodetector where the mentioned algorithms have the highest sensitivity, which provides tracking of the manoeuvring targets with high accuracy.

  19. Imaging of Phase Objects using Partially Coherent Illumination

    SciTech Connect

    Ravizza, F. L.

    2013-01-01

    Screening high-power laser optics for light intensifying phase objects that cause laserinduced damage on downstream optics is critical to sustaining laser operation. Identifying such flaws on large-apertures is quite challenging since they are relatively small and invisible to conventional inspection methods. A Linescan Phase Differential Imaging (LPDI) system was developed to rapidly identify these flaws on large-aperture optics within a single full-aperture dark-field image. We describe a two-step production phase object screening process consisting of LPDI mapping and image analysis, followed by high-resolution interferometry and propagation based evaluation of the downstream damage potential of identified flaws. An image simulation code capable of modeling the LPDI partially coherent illumination was used to optimize its phase object sensitivity.

  20. ACTIVE MEDIA: Photoprocesses in laser-active media operating in the 400 nm range. II. Photochemical processes

    NASA Astrophysics Data System (ADS)

    Kuznetsova, Rimma T.; Kopylova, T. N.; Degtyarenko, K. M.; Sergeev, A. K.; Nesterenko, S. N.; Mayer, G. V.; Afanas'ev, N. B.; Vereskun, V. N.

    1996-09-01

    The quantum yield of phototransformations, the relative yields of photoproducts, and the half-life of active media based on 2-4(pyridyl)-5-(4-methophenyl) oxazole (4PyPO) and of the substituted derivatives of dipyrazolinylbenzene (PDPDP) were investigated as a function of the concentration of the solution, the length of the active medium, and the parameters of the pump pulses generated by an XeCl laser. The results obtained are interpreted with the help of the data on the lasing efficiency and on the induced-absorption spectra.

  1. Illumination preference, illumination constancy and colour discrimination by bumblebees in an environment with patchy light.

    PubMed

    Arnold, Sarah E J; Chittka, Lars

    2012-07-01

    Patchy illumination presents foraging animals with a challenge, as the targets being sought may appear to vary in colour depending on the illumination, compromising target identification. We sought to explore how the bumblebee Bombus terrestris copes with tasks involving flower colour discrimination under patchy illumination. Light patches varied between unobscured daylight and leaf-shade, as a bee might encounter in and around woodland. Using a flight arena and coloured filters, as well as one or two different colours of artificial flower, we quantified how bees chose to forage when presented with foraging tasks under patchy illumination. Bees were better at discriminating a pair of similar colours under simulated unobscured daylight illumination than when foraging under leaf-shade illumination. Accordingly, we found that bees with prior experience of simulated daylight but not leaf-shade illumination initially preferred to forage in simulated daylight when all artificial flowers contained rewards as well as when only one colour was rewarding, whereas bees with prior experience of both illuminants did not exhibit this preference. Bees also switched between illuminants less than expected by chance. This means that bees prefer illumination conditions with which they are familiar, and in which rewarding flower colours are easily distinguishable from unrewarding ones. Under patchy illumination, colour discrimination performance was substantially poorer than in homogenous light. The bees' abilities at coping with patchy light may therefore impact on foraging behaviour in the wild, particularly in woodlands, where illumination can change over short spatial scales.

  2. 3D structured illumination microscopy

    NASA Astrophysics Data System (ADS)

    Dougherty, William M.; Goodwin, Paul C.

    2011-03-01

    Three-dimensional structured illumination microscopy achieves double the lateral and axial resolution of wide-field microscopy, using conventional fluorescent dyes, proteins and sample preparation techniques. A three-dimensional interference-fringe pattern excites the fluorescence, filling in the "missing cone" of the wide field optical transfer function, thereby enabling axial (z) discrimination. The pattern acts as a spatial carrier frequency that mixes with the higher spatial frequency components of the image, which usually succumb to the diffraction limit. The fluorescence image encodes the high frequency content as a down-mixed, moiré-like pattern. A series of images is required, wherein the 3D pattern is shifted and rotated, providing down-mixed data for a system of linear equations. Super-resolution is obtained by solving these equations. The speed with which the image series can be obtained can be a problem for the microscopy of living cells. Challenges include pattern-switching speeds, optical efficiency, wavefront quality and fringe contrast, fringe pitch optimization, and polarization issues. We will review some recent developments in 3D-SIM hardware with the goal of super-resolved z-stacks of motile cells.

  3. Extinction-Optimized Volume Illumination.

    PubMed

    Ament, Marco; Zirr, Tobias; Dachsbacher, Carsten

    2016-05-16

    We present a novel method to optimize the attenuation of light for the single scattering model in direct volume rendering. A common problem of single scattering is the high dynamic range between lit and shadowed regions due to the exponential attenuation of light along a ray. Moreover, light is often attenuated too strong between a sample point and the camera, hampering the visibility of important features. Our algorithm employs an importance function to selectively illuminate important structures and make them visible from the camera. With the importance function, more light can be transmitted to the features of interest, while contextual structures cast shadows which provide visual cues for perception of depth. At the same time, more scattered light is transmitted from the sample point to the camera to improve the primary visibility of important features. We formulate a minimization problem that automatically determines the extinction along a view or shadow ray to obtain a good balance between sufficient transmittance and attenuation. In contrast to previous approaches, we do not require a computationally expensive solution of a global optimization, but instead provide a closed-form solution for each sampled extinction value along a view or shadow ray and thus achieve interactive performance.

  4. Field Demonstrations of Active Laser Ranging with Sub-mm Precision

    NASA Technical Reports Server (NTRS)

    Chen, Yijiang; Birnbaum, Kevin M.; Hemmati, Hamid

    2011-01-01

    Precision ranging between planets will provide valuable information for scientific studies of the solar system and fundamental physics. Current passive ranging techniques using retro-reflectors are limited to the Earth-Moon distance due to the 1/R? losses. We report on a laboratory realization and field implementation of active laser ranging in real-time with two terminals, emulating interplanetary distance. Sub-millimeter accuracy is demonstrated.

  5. AN ACTIVE NITROGEN PLASMA ATOM RESERVOIR FOR LASER-INDUCED IONIZATION SPECTROMETRY

    DTIC Science & Technology

    1988-01-01

    An active nitrogen plasma was generat-J using a laboratory - constructed Beenakker type microwave cavity. 2 5 The microwave power oscillator (Micro...exhausting of ozone. Microarc Atomizer A laboratory -constructed microarc atomizer was positioned at the rear of the Beenakker cavity in direct line with the...the regions of interest, the laser- induced ionization signal was monitored. A laboratory -constructed etalon system of very low finesse was used to

  6. Passive feedback control of actively mode-locked pulsed Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Buchvarov, Ivan C.; Saltiel, Solomon M.

    1992-11-01

    A passive feedback control in an actively mode-locked pulsed Nd:YAG laser was used to shorten the pulse duration or obtain millisecond trains of ultra-short light pulses. The intracavity second harmonic generation in a crystal situated at proper distance from the output mirror served as a positive or negative feedback. When negative feedback was used, the length of the train was limited by the length of the flash lamp pumping pulse.

  7. 29 CFR 1926.56 - Illumination.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... shall be lighted to not less than the minimum illumination intensities listed in Table D-3 while any work is in progress: Table D-3—Minimum Illumination Intensities in Foot-Candles Foot-candles Area or... drilling, mucking, and scaling. Bureau of Mines approved cap lights shall be acceptable for use in...

  8. 29 CFR 1926.56 - Illumination.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... shall be lighted to not less than the minimum illumination intensities listed in Table D-3 while any work is in progress: Table D-3—Minimum Illumination Intensities in Foot-Candles Foot-candles Area or... drilling, mucking, and scaling. Bureau of Mines approved cap lights shall be acceptable for use in...

  9. Translating Rimbaud's "Illuminations": Games with Words

    ERIC Educational Resources Information Center

    Slote, Daniel

    1978-01-01

    Rimbaud's "Illuminations," one vast word-game, is used as an example of one of the most interesting challenges in translation--the rendering of plays on words. The process is discussed and illustrated by the analysis of numerous segments from "Illuminations." It is concluded that a satisfactory translation is almost impossible.…

  10. Reflectance and Illumination Recovery in the Wild.

    PubMed

    Lombardi, Stephen; Nishino, Ko

    2016-01-01

    The appearance of an object in an image encodes invaluable information about that object and the surrounding scene. Inferring object reflectance and scene illumination from an image would help us decode this information: reflectance can reveal important properties about the materials composing an object; the illumination can tell us, for instance, whether the scene is indoors or outdoors. Recovering reflectance and illumination from a single image in the real world, however, is a difficult task. Real scenes illuminate objects from every visible direction and real objects vary greatly in reflectance behavior. In addition, the image formation process introduces ambiguities, like color constancy, that make reversing the process ill-posed. To address this problem, we propose a Bayesian framework for joint reflectance and illumination inference in the real world. We develop a reflectance model and priors that precisely capture the space of real-world object reflectance and a flexible illumination model that can represent real-world illumination with priors that combat the deleterious effects of image formation. We analyze the performance of our approach on a set of synthetic data and demonstrate results on real-world scenes. These contributions enable reliable reflectance and illumination inference in the real world.

  11. A chitosan based, laser activated thin film surgical adhesive, 'SurgiLux': preparation and demonstration.

    PubMed

    Foster, L John R; Karsten, Elizabeth

    2012-10-23

    Sutures are a 4,000 year old technology that remain the 'gold-standard' for wound closure by virtue of their repair strength (~100 KPa). However, sutures can act as a nidus for infection and in many procedures are unable to effect wound repair or interfere with functional tissue regeneration.(1) Surgical glues and adhesives, such as those based on fibrin and cyanoacrylates, have been developed as alternatives to sutures for the repair of such wounds. However, current commercial adhesives also have significant disadvantages, ranging from viral and prion transfer and a lack of repair strength as with the fibrin glues, to tissue toxicity and a lack of biocompatibility for the cyanoacrylate based adhesives. Furthermore, currently available surgical adhesives tend to be gel-based and can have extended curing times which limit their application.(2) Similarly, the use of UV lasers to facilitate cross-linking mechanisms in protein-based or albumin 'solders' can lead to DNA damage while laser tissue welding (LTW) predisposes thermal damage to tissues.(3) Despite their disadvantages, adhesives and LTW have captured approximately 30% of the wound closure market reported to be in excess of US $5 billion per annum, a significant testament to the need for sutureless technology.(4) In the pursuit of sutureless technology we have utilized chitosan as a biomaterial for the development of a flexible, thin film, laser-activated surgical adhesive termed 'SurgiLux'. This novel bioadhesive uses a unique combination of biomaterials and photonics that are FDA approved and successfully used in a variety of biomedical applications and products. SurgiLux overcomes all the disadvantages associated with sutures and current surgical adhesives (see Table 1). In this presentation we report the relatively simple protocol for the fabrication of SurgiLux and demonstrate its laser activation and tissue weld strength. SurgiLux films adhere to collagenous tissue without chemical modification such as

  12. Regulation of cytochrome C peroxidase activity by nitric oxide and laser irradiation.

    PubMed

    Osipov, A N; Stepanov, G O; Vladimirov, Yu A; Kozlov, A V; Kagan, V E

    2006-10-01

    Apoptosis can be induced by activation of so-called "death receptors" (extrinsic pathway) or multiple apoptotic factors (intrinsic pathway), which leads to release of cytochrome c from mitochondria. This event is considered to be a point of no return in apoptosis. One of the most important events in the development of apoptosis is the enhancement of cytochrome c peroxidase activity upon its interaction with cardiolipin, which modifies the active center of cytochrome c. In the present work, we have investigated the effects of nitric oxide on the cytochrome c peroxidase activity when cytochrome c is bound to cardiolipin or sodium dodecyl sulfate. We have observed that cytochrome c peroxidase activity, distinctly increased due to the presence of anionic lipids, is completely suppressed by nitric oxide. At the same time, nitrosyl complexes of cytochrome c, produced in the interaction with nitric oxide, demonstrated sensitivity to laser irradiation (441 nm) and were photolyzed during irradiation. This decomposition led to partial restoration of cytochrome c peroxidase activity. Finally, we conclude that nitric oxide and laser irradiation may serve as effective instruments for regulating the peroxidase activity of cytochrome c, and, probably, apoptosis.

  13. Imaging of Endogenous Metabolites of Plant Leaves by Mass Spectrometry Based on Laser Activated Electron Tunneling.

    PubMed

    Huang, Lulu; Tang, Xuemei; Zhang, Wenyang; Jiang, Ruowei; Chen, Disong; Zhang, Juan; Zhong, Hongying

    2016-04-07

    A new mass spectrometric imaging approach based on laser activated electron tunneling (LAET) was described and applied to analysis of endogenous metabolites of plant leaves. LAET is an electron-directed soft ionization technique. Compressed thin films of semiconductor nanoparticles of bismuth cobalt zinc oxide were placed on the sample plate for proof-of-principle demonstration because they can not only absorb ultraviolet laser but also have high electron mobility. Upon laser irradiation, electrons are excited from valence bands to conduction bands. With appropriate kinetic energies, photoexcited electrons can tunnel away from the barrier and eventually be captured by charge deficient atoms present in neutral molecules. Resultant unpaired electron subsequently initiates specific chemical bond cleavage and generates ions that can be detected in negative ion mode of the mass spectrometer. LAET avoids the co-crystallization process of routinely used organic matrix materials with analyzes in MALDI (matrix assisted-laser desorption ionization) analysis. Thus uneven distribution of crystals with different sizes and shapes as well as background peaks in the low mass range resulting from matrix molecules is eliminated. Advantages of LAET imaging technique include not only improved spatial resolution but also photoelectron capture dissociation which produces predictable fragment ions.

  14. Method of laser activated nano-thermolysis for elimination of tumor cells.

    PubMed

    Lapotko, Dmitri; Lukianova, Ekaterina; Potapnev, Michail; Aleinikova, Olga; Oraevsky, Alexander

    2006-07-28

    We describe novel ex vivo method for elimination of tumor cells from cell suspension, Laser Activated Nanothermolysis and propose this method for purging of bone marrow and blood transplants. K562 and human lympholeukemia cells were eliminated in experiments by laser-induced micro-bubbles that emerge inside individual target cells around selectively formed clusters of light-absorbing gold nanoparticles. Pretreatment of tumor cells with specific monoclonal antibodies and Ig-conjugated 30-nm gold particles allowed the formation of clusters of 10-20 on the surface of cell membrane. Electron microscopy found the nanoparticulate clusters inside the cells. Total (100%) elimination of K562 cells targeted with specific antibodies was achieved with single laser pulses with optical fluence of 5J/cm(2) at the wavelength of 532 nm without damage to the same cells targeted without specific antibodies. Total elimination of human lymphoblasts from suspension of normal stem cells was achieved by a single laser pulse with the optical fluence of 1.7J/cm(2), while the damage level of normal cells was 16%.

  15. Imaging of Endogenous Metabolites of Plant Leaves by Mass Spectrometry Based on Laser Activated Electron Tunneling

    PubMed Central

    Huang, Lulu; Tang, Xuemei; Zhang, Wenyang; Jiang, Ruowei; Chen, Disong; Zhang, Juan; Zhong, Hongying

    2016-01-01

    A new mass spectrometric imaging approach based on laser activated electron tunneling (LAET) was described and applied to analysis of endogenous metabolites of plant leaves. LAET is an electron-directed soft ionization technique. Compressed thin films of semiconductor nanoparticles of bismuth cobalt zinc oxide were placed on the sample plate for proof-of-principle demonstration because they can not only absorb ultraviolet laser but also have high electron mobility. Upon laser irradiation, electrons are excited from valence bands to conduction bands. With appropriate kinetic energies, photoexcited electrons can tunnel away from the barrier and eventually be captured by charge deficient atoms present in neutral molecules. Resultant unpaired electron subsequently initiates specific chemical bond cleavage and generates ions that can be detected in negative ion mode of the mass spectrometer. LAET avoids the co-crystallization process of routinely used organic matrix materials with analyzes in MALDI (matrix assisted-laser desorption ionization) analysis. Thus uneven distribution of crystals with different sizes and shapes as well as background peaks in the low mass range resulting from matrix molecules is eliminated. Advantages of LAET imaging technique include not only improved spatial resolution but also photoelectron capture dissociation which produces predictable fragment ions. PMID:27053227

  16. Chemical imaging of latent fingerprints by mass spectrometry based on laser activated electron tunneling.

    PubMed

    Tang, Xuemei; Huang, Lulu; Zhang, Wenyang; Zhong, Hongying

    2015-03-03

    Identification of endogenous and exogenous chemicals contained in latent fingerprints is important for forensic science in order to acquire evidence of criminal identities and contacts with specific chemicals. Mass spectrometry has emerged as a powerful technique for such applications without any derivatization or fluorescent tags. Among these techniques, MALDI (Matrix Assisted Laser Desorption Ionization) provides small beam size but has interferences with MALDI matrix materials, which cause ion suppressions as well as limited spatial resolution resulting from uneven distribution of MALDI matrix crystals with different sizes. LAET (Laser Activated Electron Tunneling) described in this work offers capabilities for chemical imaging through electron-directed soft ionization. A special film of semiconductors has been designed for collection of fingerprints. Nanoparticles of bismuth cobalt zinc oxide were compressed on a conductive metal substrate (Al or Cu sticky tape) under 10 MPa pressure. Resultant uniform thin films provide tight and shining surfaces on which fingers are impressed. Irradiation of ultraviolet laser pulses (355 nm) on the thin film instantly generates photoelectrons that can be captured by adsorbed organic molecules and subsequently cause electron-directed ionization and fragmentation. Imaging of latent fingerprints is achieved by visualization of the spatial distribution of these molecular ions and structural information-rich fragment ions. Atomic electron emission together with finely tuned laser beam size improve spatial resolution. With the LAET technique, imaging analysis not only can identify physical shapes but also reveal endogenous metabolites present in females and males, detect contacts with prohibited substances, and resolve overlapped latent fingerprints.

  17. Ultraviolet light and laser irradiation enhances the antibacterial activity of glucosamine-functionalized gold nanoparticles

    PubMed Central

    Govindaraju, Saravanan; Ramasamy, Mohankandhasamy; Baskaran, Rengarajan; Ahn, Sang Jung; Yun, Kyusik

    2015-01-01

    Here we report a novel method for the synthesis of glucosamine-functionalized gold nanoparticles (GlcN-AuNPs) using biocompatible and biodegradable glucosamine for antibacterial activity. GlcN-AuNPs were prepared using different concentrations of glucosamine. The synthesized AuNPs were characterized for surface plasmon resonance, surface morphology, fluorescence spectroscopy, and antibacterial activity. The minimum inhibitory concentrations (MICs) of the AuNPs, GlcN-AuNPs, and GlcN-AuNPs when irradiated by ultraviolet light and laser were investigated and compared with the MIC of standard kanamycin using Escherichia coli by the microdilution method. Laser-irradiated GlcN-AuNPs exhibited significant bactericidal activity against E. coli. Flow cytometry and fluorescence microscopic analysis supported the cell death mechanism in the presence of GlcN-AuNP-treated bacteria. Further, morphological changes in E. coli after laser treatment were investigated using atomic force microscopy and transmission electron microscopy. The overall results of this study suggest that the prepared nanoparticles have potential as a potent antibacterial agent for the treatment of a wide range of disease-causing bacteria. PMID:26345521

  18. Colour constancy and conscious perception of changes of illuminant.

    PubMed

    Barbur, John L; Spang, Karoline

    2008-02-12

    A sudden change in illuminant (e.g., the outcome of turning on a tungsten light in a room illuminated with dim, natural daylight) causes a "global" change in perceived colour which subjects often recognise as a change of illuminant. In spite of this distinct, global change in the perceptual appearance of the scene caused by significant changes in the wavelength composition of the light reflected from different objects under the new illuminant, the perceived colour of the objects remains largely unchanged and this cornerstone property of human vision is often described as instantaneous colour constancy (ICC). ICC mechanisms are often difficult to study. The generation of appropriate stimuli to isolate ICC mechanisms remains a difficult task since the extraction of colour signals is also confounded in the processing of spatial chromatic context that leads to ICC. The extraction of differences in chromaticity that describe spatial changes in the wavelength composition of the light on the retina is a necessary operation that must precede colour constancy computations. A change of illuminant or changes in the spectral reflectance of the elements that make up the scene under a constant illuminant cause spatial changes in chromatic context and are likely to drive colour constancy mechanisms, but not exclusively. The same stimulus changes also cause differences in local luminance contrast and overall light flux changes, stimulus attributes that can activate different areas of the visual cortex. In order to address this problem we carried out a series of dichoptic experiments designed to investigate how the colour signals from the two eyes are combined in dichoptically viewed Mondrians and the extent to which the processing of chromatic context in monocularly driven neurons contributes to ICC. The psychophysical findings show that normal levels of ICC can be achieved in dichoptic experiments, even when the subject remains unaware of any changes of illuminant. Functional MRI

  19. Illuminant spectrum estimation at a pixel.

    PubMed

    Ratnasingam, Sivalogeswaran; Hernández-Andrés, Javier

    2011-04-01

    In this paper, an algorithm is proposed to estimate the spectral power distribution of a light source at a pixel. The first step of the algorithm is forming a two-dimensional illuminant invariant chromaticity space. In estimating the illuminant spectrum, generalized inverse estimation and Wiener estimation methods were applied. The chromaticity space was divided into small grids and a weight matrix was used to estimate the illuminant spectrum illuminating the pixels that fall within a grid. The algorithm was tested using a different number of sensor responses to determine the optimum number of sensors for accurate colorimetric and spectral reproduction. To investigate the performance of the algorithm realistically, the responses were multiplied with Gaussian noise and then quantized to 10 bits. The algorithm was tested with standard and measured data. Based on the results presented, the algorithm can be used with six sensors to obtain a colorimetrically good estimate of the illuminant spectrum at a pixel.

  20. New photocathode using ZnSe substrates with GaAs active layer

    NASA Astrophysics Data System (ADS)

    Jin, Xiuguang; Takeda, Yoshikazu; Fuchi, Shingo

    2017-03-01

    GaAs active layers were successfully fabricated on ZnSe substrates using a metalorganic vapor phase epitaxy system. As a photocathode, a GaAs active layer shows a high quantum efficiency (QE) of 9% at 532 nm laser light illumination, which is comparable to a QE of 11% from GaAs bulk. In addition, a photoemission current of 10 µA was obtained from this photocathode. One more important point is that this photocathode could realize back-side illumination of 532 nm laser light, and thus its widespread applications are expected in microscopy and accelerator fields.

  1. The relationship between ambient illumination and psychological factors in viewing of display Images

    NASA Astrophysics Data System (ADS)

    Iwanami, Takuya; Kikuchi, Ayano; Kaneko, Takashi; Hirai, Keita; Yano, Natsumi; Nakaguchi, Toshiya; Tsumura, Norimichi; Yoshida, Yasuhiro; Miyake, Yoichi

    2009-01-01

    In this paper, we have clarified the relationship between ambient illumination and psychological factors in viewing of display images. Psychological factors were obtained by the factor analysis with the results of the semantic differential (SD) method. In the psychological experiments, subjects evaluated the impressions of displayed images with changing ambient illuminating conditions. The illumination conditions were controlled by a fluorescent ceiling light and a color LED illumination which was located behind the display. We experimented under two kinds of conditions. One was the experiment with changing brightness of the ambient illumination. The other was the experiment with changing the colors of the background illumination. In the results of the experiment, two factors "realistic sensation, dynamism" and "comfortable," were extracted under different brightness of the ambient illumination of the display surroundings. It was shown that the "comfortable" was improved by the brightness of display surroundings. On the other hand, when the illumination color of surroundings was changed, three factors "comfortable," "realistic sensation, dynamism" and "activity" were extracted. It was also shown that the value of "comfortable" and "realistic sensation, dynamism" increased when the display surroundings were illuminated by the average color of the image contents.

  2. Emerging liquid crystal waveguide technology for low SWaP active short-wave infrared imagers

    NASA Astrophysics Data System (ADS)

    Keller, Sean D.; Uyeno, Gerald P.; Lynch, Ted; Davis, Scott R.; Rommel, Scott D.; Pino, Juan

    2015-03-01

    Raytheon's innovative active short wave infrared (SWIR) imager uses Vescent Photonic's emerging liquid crystal waveguide (LCWG) technology to continuously steer the illumination laser beam over the imager field of view (FOV). This approach instantly illuminates a very small fraction of the FOV, which significantly reduces the laser power compared to flash illumination. This reduced laser power directly leads to a reduction in the size, weight and power (SWaP) of the laser. The reduction in laser power reduces the input power and thermal rejection, which leads to additional reduction in the SWaP of the power supplies and thermal control. The high-speed steering capability of the LCWG enables the imager's SWaP reduction. The SWaP reduction is possible using either global or rolling shutter detectors. In both cases, the LCWG steers the laser beam over the entire FOV while the detector is integrating. For a rolling shutter detector, the LCWG synchronizes the steering with the rolling shutter to illuminate only regions currently integrating. Raytheon's approach enables low SWaP active SWIR imagers without compromising image quality. This paper presents the results of Raytheon's active SWIR imager demonstration including steering control and synchronization with the detector integration.

  3. Structured white-light illumination for diagnostic investigations

    NASA Astrophysics Data System (ADS)

    Schau, P.; Brandes, A.; Frenner, K.; Kienle, A.; Osten, W.

    2013-04-01

    The optical coherence tomography (OCT) is an important technology for non-invasive, in vivo medical diagnostics. It enables the high-resolution recording of two-dimensional tomograms or three-dimensional volumes of biological tissue. Two mechanisms help separating the signal from the scattering background. First, reflected or backscattered light from outside the focal spot is suppressed by confocal discrimination. Additionally, the signal modulation is enhanced due to identical optical path lengths of both branches of the white light interferometry setup. Since the OCT relies on the interference between reference light and scattered light, this method cannot be readily extended for fluorescence measurements. An alternative approach is the confocal fluorescence microscopy, which uses confocal microscopy to suppress the fluorescent light from outside the focal spot. Hence, only the fluorescent light in the focal plane, which is 3 to 4 magnitudes lower in intensity than the excitation light, is detected. However, the surrounding area is illuminated with full intensity, which might cause photo-bleaching. There are also other promising approaches such as the two-photon excitation microscopy or fluorescence lifetime microscopy, which we will not cover in more detail. For fluorescence measurements of strongly-scattering samples such as biological tissue but also for technical surfaces, we propose a structured white-light illumination. We present two different approaches for the sample illumination utilizing a white light laser or a white light LED, respectively. We show first simulations of the individual illumination setups and their impact on the scattering within the sample. Furthermore, we investigated the distribution of the fluorescent light that reaches the detection part of the device when excited within a scattering medium, for this purpose we implemented a novel fast-converging algorithm for conditional fluence rate in our Monte Carlo algorithm.

  4. Vertically illuminated TW-UTC photodiodes for terahertz generation

    NASA Astrophysics Data System (ADS)

    Barrientos Z., Claudio M.; Calle G., Victor H.; Alvarez, Jaime A.; Mena, F. Patricio; Vukusic, Josip; Stake, Jan; Michael, Ernest A.

    2012-09-01

    More efficient and powerful continuous-wave photonic mixers as terahertz sources are motivated by the need of more versatile local oscillators for submillimeter/terahertz receiver systems. Uni-Travelling Carrier (UTC) photodiodes are very prospective candidates for reaching this objective, but so far only have been reported as lumped-elements or as edge-illuminated optical-waveguide travelling-wave (TW) devices. To overcome the associated power limitations of those implementations, we are developing a novel implementation of the UTC photodiodes which combines a travelingwave photomixer with vertical velocity-matched illumination in a distributed structure. In this implementation called velocity-matched travelling-wave uni-travelling carrier photodiode, it is possible to obtain in-situ velocity matching of the beat-fringes of the two angled laser beams with the submm/THz-wave on the stripline. In this way, minimum frequency roll-off is achieved by tuning the angle between the two laser beams. A first design of these TW-UTC PDs from our Terahertz Photonics Laboratory at University of Chile has been micro-fabricated at the MC2 cleanroom facility at Chalmers Technical University.

  5. Photochromic film texturing with speckle illumination: application to goods authentication

    NASA Astrophysics Data System (ADS)

    Crespo-Monteiro, Nicolas; Destouches, Nathalie; Fournel, Thierry

    2012-10-01

    Thanks to the localized surface plasmon resonance of silver nanoparticles, mesoporous titania films loaded with silver salts manifest a photochromic behavior that can be used to perform updatable laser microinscriptions. Under UV illumination, the silver salts are reduced into silver nanoparticles and the illuminated areas become grey-brown. This coloration can be completely erased by oxidizing the silver nanoparticles with a polychromatic or monochromatic visible light whose spectrum lies in the resonance band of silver nanoparticles. The paper investigates the usage of such photochromic Ag/TiO2 films for creating an updatable random texturing. Random textures are produced on coated glass samples, initially homogeneous, by exposing them to speckle patterns resulting from the scattering of a UV laser beam from an optically rough surface. The stability of such textures under homogeneous UV post-exposures is investigated as a function of the speckle exposure time. Under optimized exposure conditions, the textures remain stable enough for a long time and the differences between textures are sufficiently discriminative to use the texturing process for goods authentication. This is demonstrated by calculating the correlation coefficient of thousands of couples of texture images. The numerical treatment of images has the advantage to be robust to changes in the sample repositioning between different image records. The rewritability of the samples is characterized through the comparison of different textures successively erased and written at the same place on multiple samples.

  6. Selective Metallization Induced by Laser Activation: Fabricating Metallized Patterns on Polymer via Metal Oxide Composite.

    PubMed

    Zhang, Jihai; Zhou, Tao; Wen, Liang

    2017-02-28

    Recently, metallization on polymer substrates has been given more attention due to its outstanding properties of both plastics and metals. In this study, the metal oxide composite of copper-chromium oxide (CuO·Cr2O3) was incorporated into the polymer matrix to design a good laser direct structuring (LDS) material, and the well-defined copper pattern (thickness =10 μm) was successfully fabricated through selective metallization based on 1064 nm near-infrared pulsed laser activation and electroless copper plating. We also prepared polymer composites incorporated with CuO and Cr2O3; however, these two polymer composites both had very poor capacity of selective metallization, which has no practical value for LDS technology. In our work, the key reasons causing the above results were systematically studied and elucidated using XPS, UV-vis-IR, optical microscopy, SEM, contact angle, ATR FTIR, and so on. The results showed that 54.0% Cu(2+) in the polymer composite of CuO·Cr2O3 (the amount =5 wt %) is reduced to Cu(0) (elemental copper) after laser activation (irradiation); however, this value is only 26.8% for the polymer composite of CuO (the amount =5 wt %). It was confirmed that to achieve a successful selective metallization after laser activation, not only was the new formed Cu(0) (the catalytic seeds) the crucial factor, but the number of generated Cu(0) catalytic seeds was also important. These two factors codetermined the final results of the selective metallization. The CuO·Cr2O3 is very suitable for applications of fabricating metallic patterns (e.g., metal decoration, circuit) on the inherent pure black or bright black polymer materials via LDS technology, which has a prospect of large-scale industrial applications.

  7. Stand-off detection of HMX traces by active spectral imaging with a tunable CO{sub 2} laser

    SciTech Connect

    Pavlenko, A A; Maksimenko, E V; Chernyshova, L V

    2014-04-28

    Experimental results on stand-off detection of HMX traces at various surfaces using the method of active spectral imaging in the IR region are reported. (laser applications and other topics in quantum electronics)

  8. Active mode-locked lasers and other photonic devices using electro-optic whispering gallery mode resonators

    NASA Technical Reports Server (NTRS)

    Matsko, Andrey B. (Inventor); Ilchenko, Vladimir (Inventor); Savchenkov, Anatoliy (Inventor); Maleki, Lutfollah (Inventor)

    2006-01-01

    Techniques and devices using whispering gallery mode (WGM) optical resonators, where the optical materials of the WGM resonators exhibit an electro-optical effect to perform optical modulation. Examples of actively mode-locked lasers and other devices are described.

  9. Chromatic illumination discrimination ability reveals that human colour constancy is optimised for blue daylight illuminations.

    PubMed

    Pearce, Bradley; Crichton, Stuart; Mackiewicz, Michal; Finlayson, Graham D; Hurlbert, Anya

    2014-01-01

    The phenomenon of colour constancy in human visual perception keeps surface colours constant, despite changes in their reflected light due to changing illumination. Although colour constancy has evolved under a constrained subset of illuminations, it is unknown whether its underlying mechanisms, thought to involve multiple components from retina to cortex, are optimised for particular environmental variations. Here we demonstrate a new method for investigating colour constancy using illumination matching in real scenes which, unlike previous methods using surface matching and simulated scenes, allows testing of multiple, real illuminations. We use real scenes consisting of solid familiar or unfamiliar objects against uniform or variegated backgrounds and compare discrimination performance for typical illuminations from the daylight chromaticity locus (approximately blue-yellow) and atypical spectra from an orthogonal locus (approximately red-green, at correlated colour temperature 6700 K), all produced in real time by a 10-channel LED illuminator. We find that discrimination of illumination changes is poorer along the daylight locus than the atypical locus, and is poorest particularly for bluer illumination changes, demonstrating conversely that surface colour constancy is best for blue daylight illuminations. Illumination discrimination is also enhanced, and therefore colour constancy diminished, for uniform backgrounds, irrespective of the object type. These results are not explained by statistical properties of the scene signal changes at the retinal level. We conclude that high-level mechanisms of colour constancy are biased for the blue daylight illuminations and variegated backgrounds to which the human visual system has typically been exposed.

  10. Chromatic Illumination Discrimination Ability Reveals that Human Colour Constancy Is Optimised for Blue Daylight Illuminations

    PubMed Central

    Pearce, Bradley; Crichton, Stuart; Mackiewicz, Michal; Finlayson, Graham D.; Hurlbert, Anya

    2014-01-01

    The phenomenon of colour constancy in human visual perception keeps surface colours constant, despite changes in their reflected light due to changing illumination. Although colour constancy has evolved under a constrained subset of illuminations, it is unknown whether its underlying mechanisms, thought to involve multiple components from retina to cortex, are optimised for particular environmental variations. Here we demonstrate a new method for investigating colour constancy using illumination matching in real scenes which, unlike previous methods using surface matching and simulated scenes, allows testing of multiple, real illuminations. We use real scenes consisting of solid familiar or unfamiliar objects against uniform or variegated backgrounds and compare discrimination performance for typical illuminations from the daylight chromaticity locus (approximately blue-yellow) and atypical spectra from an orthogonal locus (approximately red-green, at correlated colour temperature 6700 K), all produced in real time by a 10-channel LED illuminator. We find that discrimination of illumination changes is poorer along the daylight locus than the atypical locus, and is poorest particularly for bluer illumination changes, demonstrating conversely that surface colour constancy is best for blue daylight illuminations. Illumination discrimination is also enhanced, and therefore colour constancy diminished, for uniform backgrounds, irrespective of the object type. These results are not explained by statistical properties of the scene signal changes at the retinal level. We conclude that high-level mechanisms of colour constancy are biased for the blue daylight illuminations and variegated backgrounds to which the human visual system has typically been exposed. PMID:24586299

  11. Thermal conductivity tensors of the cladding and active layers of interband cascade lasers

    NASA Astrophysics Data System (ADS)

    Zhou, Chuanle; Cui, Boya; Vurgaftman, I.; Canedy, C. L.; Kim, C. S.; Kim, M.; Bewley, W. W.; Merritt, C. D.; Abell, J.; Meyer, J. R.; Grayson, M.

    2014-12-01

    The cross-plane and in-plane thermal conductivities of the W-active stages and InAs/AlSb superlattice optical cladding layer of an interband cascade laser (ICL) were characterized for temperatures ranging from 15 K to 324 K. The in-plane thermal conductivity of the active layer is somewhat larger than the cross-plane value at temperatures above about 30 K, while the thermal conductivity tensor becomes nearly isotropic at the lowest temperatures studied. These results will improve ICL performance simulations and guide the optimization of thermal management.

  12. Low level laser therapy activates NF-kB via generation of reactive oxygen species in mouse embryonic fibroblasts

    NASA Astrophysics Data System (ADS)

    Chen, Aaron Chih-Hao; Arany, Praveen R.; Huang, Ying-Ying; Tomkinson, Elizabeth M.; Saleem, Taimur; Yull, Fiona E.; Blackwell, Timothy S.; Hamblin, Michael R.

    2009-02-01

    Despite over forty years of investigation on low-level light therapy (LLLT), the fundamental mechanisms underlying photobiomodulation remain unclear. In this study, we isolated murine embryonic fibroblasts (MEF) from transgenic NF-kB luciferase reporter mice and studied their response to 810-nm laser radiation. Significant activation of NFkB was observed for fluences higher than 0.003 J/cm2. NF-kB activation by laser was detectable at 1-hour time point. Moreover, we demonstrated that laser phosphorylated both IKK α/β and NF-kB 15 minutes after irradiation, which implied that laser activates NF-kB via phosphorylation of IKK α/β. Suspecting mitochondria as the source of NF-kB activation signaling pathway, we demonstrated that laser increased both intracellular reactive oxygen species (ROS) by fluorescence microscopy with dichlorodihydrofluorescein and ATP synthesis by luciferase assay. Mitochondrial inhibitors, such as antimycin A, rotenone and paraquat increased ROS and NF-kB activation but had no effect on ATP. The ROS quenchers N-acetyl-L-cysteine and ascorbic acid abrogated laser-induced NF-kB and ROS but not ATP. These results suggested that ROS might play an important role in the signaling pathway of laser induced NF-kB activation. However, the western blot showed that antimycin A, a mitochondrial inhibitor, did not activate NF-kB via serine phosphorylation of IKK α/β as the laser did. On the other hand, LLLT, unlike mitochondrial inhibitors, induced increased cellular ATP levels, which indicates that light also upregulates mitochondrial respiration. ATP upregulation reached a maximum at 0.3 J/cm2 or higher. We conclude that LLLT not only enhances mitochondrial respiration, but also activates the redox-sensitive transcription factor NF-kB by generating ROS as signaling molecules.

  13. Nd:YAG laser with passive-active mode-locking

    NASA Astrophysics Data System (ADS)

    Zhao, Weijiang; Chen, Zhenlei; Ren, Deming; Qu, Yanchen; Mo, Shuang; Huang, Jinjer; Andreev, Yury M.; Gorobets, Vadim A.; Petukhov, Vladimir O.; Zemlyanov, Aleksei A.

    2008-03-01

    All solid-state flash-lamp pumped passive-active mode-locked Nd3+:YAG laser is designed and experimentally studded. Saturation absorber Cr4+:YAG with initial transparency 25 and 47% are used as a passive Q-switcher and acousto-optical fused quartz modulator as an active mode-locker. Efficient length of the laser cavity with fixed mirror positions (1.45 m spaced) is droved by changes of 100% flat mirror for concave mirrors with different focus lengths. Changeable output mirrors with transparencies of 15 and 50% are used. Driving of the cavity parameters, laser and acousto-optical modulator power supply voltages let us to control output pulse train and single pulse parameters. As it goes from the analyses of oscillograms fixed with pyroelectric detector (τ=0.5 ns) and 1 GHz oscilloscope, over 95% of pulse output energy has been mode-locked. Average duration of the pulse train envelope of 5 to 50 single pulses at FWHM has been droved within 50 to 600 ns. When this single pulse duration is controlled but did not exceed 2 ns.

  14. Photo-catalytic Activities of Plant Hormones on Semiconductor Nanoparticles by Laser-Activated Electron Tunneling and Emitting

    PubMed Central

    Tang, Xuemei; Huang, Lulu; Zhang, Wenyang; Jiang, Ruowei; Zhong, Hongying

    2015-01-01

    Understanding of the dynamic process of laser-induced ultrafast electron tunneling is still very limited. It has been thought that the photo-catalytic reaction of adsorbents on the surface is either dependent on the number of resultant electron-hole pairs where excess energy is lost to the lattice through coupling with phonon modes, or dependent on irradiation photon wavelength. We used UV (355 nm) laser pulses to excite electrons from the valence band to the conduction band of titanium dioxide (TiO2), zinc oxide (ZnO) and bismuth cobalt zinc oxide (Bi2O3)0.07(CoO)0.03(ZnO)0.9 semiconductor nanoparticles with different photo catalytic properties. Photoelectrons are extracted, accelerated in a static electric field and eventually captured by charge deficient atoms of adsorbed organic molecules. A time-of-flight mass spectrometer was used to detect negative molecules and fragment ions generated by un-paired electron directed bond cleavages. We show that the probability of electron tunneling is determined by the strength of the static electric field and intrinsic electron mobility of semiconductors. Photo-catalytic dissociation or polymerization reactions of adsorbents are highly dependent on the kinetic energy of tunneling electrons as well as the strength of laser influx. By using this approach, photo-activities of phytohormones have been investigated. PMID:25749635

  15. Photo-catalytic activities of plant hormones on semiconductor nanoparticles by laser-activated electron tunneling and emitting.

    PubMed

    Tang, Xuemei; Huang, Lulu; Zhang, Wenyang; Jiang, Ruowei; Zhong, Hongying

    2015-03-09

    Understanding of the dynamic process of laser-induced ultrafast electron tunneling is still very limited. It has been thought that the photo-catalytic reaction of adsorbents on the surface is either dependent on the number of resultant electron-hole pairs where excess energy is lost to the lattice through coupling with phonon modes, or dependent on irradiation photon wavelength. We used UV (355 nm) laser pulses to excite electrons from the valence band to the conduction band of titanium dioxide (TiO₂), zinc oxide (ZnO) and bismuth cobalt zinc oxide (Bi₂O₃)₀.₀₇(CoO)₀.₀₃(ZnO)₀.₉ semiconductor nanoparticles with different photo catalytic properties. Photoelectrons are extracted, accelerated in a static electric field and eventually captured by charge deficient atoms of adsorbed organic molecules. A time-of-flight mass spectrometer was used to detect negative molecules and fragment ions generated by un-paired electron directed bond cleavages. We show that the probability of electron tunneling is determined by the strength of the static electric field and intrinsic electron mobility of semiconductors. Photo-catalytic dissociation or polymerization reactions of adsorbents are highly dependent on the kinetic energy of tunneling electrons as well as the strength of laser influx. By using this approach, photo-activities of phytohormones have been investigated.

  16. Photo-catalytic Activities of Plant Hormones on Semiconductor Nanoparticles by Laser-Activated Electron Tunneling and Emitting

    NASA Astrophysics Data System (ADS)

    Tang, Xuemei; Huang, Lulu; Zhang, Wenyang; Jiang, Ruowei; Zhong, Hongying

    2015-03-01

    Understanding of the dynamic process of laser-induced ultrafast electron tunneling is still very limited. It has been thought that the photo-catalytic reaction of adsorbents on the surface is either dependent on the number of resultant electron-hole pairs where excess energy is lost to the lattice through coupling with phonon modes, or dependent on irradiation photon wavelength. We used UV (355 nm) laser pulses to excite electrons from the valence band to the conduction band of titanium dioxide (TiO2), zinc oxide (ZnO) and bismuth cobalt zinc oxide (Bi2O3)0.07(CoO)0.03(ZnO)0.9 semiconductor nanoparticles with different photo catalytic properties. Photoelectrons are extracted, accelerated in a static electric field and eventually captured by charge deficient atoms of adsorbed organic molecules. A time-of-flight mass spectrometer was used to detect negative molecules and fragment ions generated by un-paired electron directed bond cleavages. We show that the probability of electron tunneling is determined by the strength of the static electric field and intrinsic electron mobility of semiconductors. Photo-catalytic dissociation or polymerization reactions of adsorbents are highly dependent on the kinetic energy of tunneling electrons as well as the strength of laser influx. By using this approach, photo-activities of phytohormones have been investigated.

  17. Automated co-alignment of coherent fiber laser arrays via active phase-locking.

    PubMed

    Goodno, Gregory D; Weiss, S Benjamin

    2012-07-02

    We demonstrate a novel closed-loop approach for high-precision co-alignment of laser beams in an actively phase-locked, coherently combined fiber laser array. The approach ensures interferometric precision by optically transducing beam-to-beam pointing errors into phase errors on a single detector, which are subsequently nulled by duplication of closed-loop phasing controls. Using this approach, beams from five coherent fiber tips were simultaneously phase-locked and position-locked with sub-micron accuracy. Spatial filtering of the sensed light is shown to extend the control range over multiple beam diameters by recovering spatial coherence despite the lack of far-field beam overlap.

  18. Quantum cascade laser based active hyperspectral imaging for standoff detection of chemicals on surfaces

    NASA Astrophysics Data System (ADS)

    Hugger, S.; Fuchs, F.; Jarvis, J.; Yang, Q. K.; Rattunde, M.; Ostendorf, R.; Schilling, C.; Driad, R.; Bronner, W.; Aidam, R.; Wagner, J.; Tybussek, T.; Rieblinger, K.

    2016-02-01

    We employ active hyperspectral imaging using tunable mid-infrared (MIR) quantum cascade lasers for contactless identification of solid and liquid contaminations on surfaces. By collecting the backscattered laser radiation with a camera, a hyperspectral data cube, containing the spatially resolved spectral information of the scene is obtained. Data is analyzed using appropriate algorithms to find the target substances even on substrates with a priori unknown spectra. Eye-save standoff detection of residues of explosives and precursors over extended distances is demonstrated and the main purpose of our system. However, it can be applied to any substance with characteristic reflectance / absorbance spectrum. As an example, we present first results of monitoring food quality by distinguishing fresh and mold contaminated peanuts by their MIR backscattering spectrum.

  19. Active fiber polymer cladding temperature measurement under conditions of laser generation and amplification

    NASA Astrophysics Data System (ADS)

    Sypin, V. E.; Prusakov, K. Y.; Ryabushkin, O. A.

    2016-04-01

    Polymer cladding temperature of active fiber in lasing regime is important parameter as it allows determination of fiber core temperature that in turn effects laser generation and amplification efficiency. Besides polymer cladding has much lower temperature damage threshold comparing to fused silica. For example, 200 degrees Kelvin overheating of the polymer cladding can result in fiber degradation. In present paper we introduce novel and simple method for precise temperature measurement of active fibers cladding under conditions of laser generation and amplification. Dependence of longitudinal temperature distribution along active fibers on optical pump power can be determined. This method employs measurement of temperature dependent electrical resistance of the metal wire being in thermal contact with fiber polymer cladding. The wire is reeled on the active fiber segment. Under lasing or amplification conditions the polymer cladding of the active fiber is heated together with coiled metal wire resulting in its electrical resistance change. By measuring resistance variation one can determine the temperature of the given fiber section.

  20. Delivery of Molecules into Human Corneal Endothelial Cells by Carbon Nanoparticles Activated by Femtosecond Laser.

    PubMed

    Jumelle, Clotilde; Mauclair, Cyril; Houzet, Julien; Bernard, Aurélien; He, Zhiguo; Forest, Fabien; Peoc'h, Michel; Acquart, Sophie; Gain, Philippe; Thuret, Gilles

    2015-01-01

    Corneal endothelial cells (CECs) form a monolayer at the innermost face of the cornea and are the engine of corneal transparency. Nevertheless, they are a vulnerable population incapable of regeneration in humans, and their diseases are responsible for one third of corneal grafts performed worldwide. Donor corneas are stored in eye banks for security and quality controls, then delivered to surgeons. This period could allow specific interventions to modify the characteristics of CECs in order to increase their proliferative capacity, increase their resistance to apoptosis, or release immunosuppressive molecules. Delivery of molecules specifically into CECs during storage would therefore open up new therapeutic perspectives. For clinical applications, physical methods have a more favorable individual and general benefit/risk ratio than most biological vectors, but are often less efficient. The delivery of molecules into cells by carbon nanoparticles activated by femtosecond laser pulses is a promising recent technique developed on non-adherent cells. The nanoparticles are partly consummated by the reaction releasing CO and H2 gas bubbles responsible for the shockwave at the origin of cell transient permeation. Our aim was to develop an experimental setting to deliver a small molecule (calcein) into the monolayer of adherent CECs. We confirmed that increased laser fluence and time exposure increased uptake efficiency while keeping cell mortality below 5%. We optimized the area covered by the laser beam by using a motorized stage allowing homogeneous scanning of the cell culture surface using a spiral path. Calcein uptake reached median efficiency of 54.5% (range 50.3-57.3) of CECs with low mortality (0.5%, range (0.55-1.0)). After sorting by flow cytometry, CECs having uptaken calcein remained viable and presented normal morphological characteristics. Delivery of molecules into CECs by carbon nanoparticles activated by femtosecond laser could prove useful for future