Science.gov

Sample records for active laser illumination

  1. Quantification of the atmospheric scintillation for laser illumination in active imaging.

    PubMed

    Poyet, Jean-Michel; Meyer, Olivier; Christnacher, Frank

    2014-05-01

    Most of the analytical scintillation models used by experts to simulate the illumination performances of active imaging systems are based on the use of monochromatic, punctual, and coherent sources. These analytical models seem pessimistic regarding lightpipe-based illumination techniques. Outdoor trials have been made with 1.57 μm laser illuminators with and without lightpipe to record illumination maps and associated refractive index structure parameter C(n)2 with a propagation distance of 1 km. Analysis shows a reduction of the scintillation by a factor of 2.5 comparing analytical models and laser illumination with lightpipe.

  2. Fiber optic illumination by laser activated remote phosphor

    NASA Astrophysics Data System (ADS)

    Hartwig, Ulrich

    2012-10-01

    For some fiber optic applications, like high-end endoscopy, light sources with high luminance are necessary. Currently, short arc discharge lamps are being used. However, more and more LED solutions are trying to compete, but they can not yet reach the performance obtainable by 300 W Xenon short arc discharge lamps. To make this field of application accessible for solid state light sources, a new approach is necessary. Diode lasers have rapidly advanced in the past years. This is particularly true for multimode laser diodes emitting at around 445 nm wavelength. Single diodes emitting more than 1 W of optical power are already available. These laser sources exhibit extremely high radiance, thus they can be focused onto very small areas. Phosphors placed near the focus can result in high luminance sources. On the basis of this idea, a device has been developed to match the performance of a state of the art 300 W Xenon lamp system. An array of laser diodes is used to illuminate a phosphor plate which converts the blue pump light into yellow light. The converted light is collected and adapted to the application by a tapered TIR rod. To achieve a color point on the Planckian locus at 6000 K, the light of an LED emitting at around 460 nm is superimposed to the converted light.

  3. 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.

  4. Beam uniformity analysis of infrared laser illuminators

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

  5. 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.

  6. 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.

  7. 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.

  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. 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.

  10. Excimer laser processing of backside-illuminated CCDS

    NASA Technical Reports Server (NTRS)

    Russell, S. D.

    1993-01-01

    An excimer laser is used to activate previously implanted dopants on the backside of a backside-illuminated CCD. The controlled ion implantation of the backside and subsequent thin layer heating and recrystallization by the short wavelength pulsed excimer laser simultaneously activates the dopant and anneals out implant damage. This improves the dark current response, repairs defective pixels and improves spectral response. This process heats a very thin layer of the material to high temperatures on a nanosecond time scale while the bulk of the delicate CCD substrate remains at low temperature. Excimer laser processing backside-illuminated CCD's enables salvage and utilization of otherwise nonfunctional components by bringing their dark current response to within an acceptable range. This process is particularly useful for solid state imaging detectors used in commercial, scientific and government applications requiring a wide spectral response and low light level detection.

  11. 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. PMID:26737628

  12. Optical device for intravascular low-power laser illumination

    NASA Astrophysics Data System (ADS)

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

    2003-04-01

    The treatment method presented in this paper is an adjunct to coronary angioplasty. It consists in irradiating a previously dilated artery with laser light which stimulates endothelium proliferation and reduces local inflammation. The influence of 808 nm laser light on the endothelium was studied in vitro. Because of the location of atherosclerotic plaques, illumination of the endothelium poses a problem. To overcome it, we have designed and built a laser set-up for homogeneous intravascular illumination in vivo.

  13. 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.

  14. Multipass laser cavity for efficient transverse illumination of an elongated volume.

    PubMed

    Vogelsang, Jan; Diepold, Marc; Antognini, Aldo; Dax, Andreas; Götzfried, Johannes; Hänsch, Theodor W; Kottmann, Franz; Krauth, Julian J; Liu, Yi-Wei; Nebel, Tobias; Nez, Francois; Schuhmann, Karsten; Taqqu, David; Pohl, Randolf

    2014-06-01

    A multipass laser cavity is presented which can be used to illuminate an elongated volume from a transverse direction. The illuminated volume can also have a very large transverse cross section. Convenient access to the illuminated volume is granted. The multipass cavity is very robust against misalignment, and no active stabilization is needed. The scheme is suitable for example in beam experiments, where the beam path must not be blocked by a laser mirror, or if the illuminated volume must be very large. This cavity was used for the muonic-hydrogen experiment in which 6 μm laser light illuminated a volume of 7 × 25 × 176 mm3, using mirrors that are only 12 mm in height. We present our measurement of the intensity distribution inside the multipass cavity and show that this is in good agreement with our simulation. PMID:24921502

  15. 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.

  16. Laser Illumination Modality of Photoacoustic Imaging Technique for Prostate Cancer

    NASA Astrophysics Data System (ADS)

    Peng, Dong-qing; Peng, Yuan-yuan; Guo, Jian; Li, Hui

    2016-02-01

    Photoacoustic imaging (PAI) has recently emerged as a promising imaging technique for prostate cancer. But there was still a lot of challenge in the PAI for prostate cancer detection, such as laser illumination modality. Knowledge of absorbed light distribution in prostate tissue was essential since the distribution characteristic of absorbed light energy would influence the imaging depth and range of PAI. In order to make a comparison of different laser illumination modality of photoacoustic imaging technique for prostate cancer, optical model of human prostate was established and combined with Monte Carlo simulation method to calculate the light absorption distribution in the prostate tissue. Characteristic of light absorption distribution of transurethral and trans-rectal illumination case, and of tumor at different location was compared with each other.The relevant conclusions would be significant for optimizing the light illumination in a PAI system for prostate cancer detection.

  17. Illuminating the Hazards of Powerful Laser Products

    MedlinePlus

    ... the sun. The startling effect of a bright beam of light can cause serious accidents when aimed ... for Devices and Radiological Health. “A green laser beam could cause a larger startling or flash-blinding ...

  18. 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.

  19. 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.

  20. 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. PMID:27556985

  1. 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.

  2. Confocal laser scanning microscopy with spatiotemporal structured illumination.

    PubMed

    Gao, Peng; Nienhaus, G Ulrich

    2016-03-15

    Confocal laser scanning microscopy (CLSM), which is widely utilized in the biological and biomedical sciences, is limited in spatial resolution due to diffraction to about half the light wavelength. Here we have combined structured illumination with CLSM to enhance its spatial resolution. To this end, we have used a spatial light modulator (SLM) to generate fringe patterns of different orientations and phase shifts in the excitation spot without any mechanical movement. We have achieved 1.8 and 1.7 times enhanced lateral and axial resolutions, respectively, by synthesizing the object spectrum along different illumination directions. This technique is thus a promising tool for high-resolution morphological or fluorescence imaging, especially in deep tissue. PMID:26977667

  3. 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.

  4. 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.

  5. Use of a laser stripe illuminator for enhanced underwater viewing

    NASA Astrophysics Data System (ADS)

    Tetlow, Steve; Allwood, Robert L.

    1994-10-01

    A laser-based illumination system that can be incorporated into the existing underwater viewing system of current remotely operated vehicles (ROVs) has been investigated. A stripe of projected laser light is scanned over the target and resultant image frames are processed and combined to produce a computer generated composite image. Initially, the system was characterized through trials in the underwater optical test facility at Cranfield where water conditions are easily controlled. Subsequently, further work was carried out on a self- contained underwater unit at a flooded quarry in Leicestershire. Several advantages of this technique have been identified from the laboratory and field trials. Scanning the laser source allows greater control of the lighting envelope resulting in more optically uniform images. Contrast improvements of 300% and range improvements of 50% over orthodox systems have been measured. The use of image processing allows a greater degree of flexibility in image presentation and because this methodology is based on a standard underwater camera, it is complementary and can be fitted retrospectively at relatively low cost.

  6. 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.

  7. 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.

  8. 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.

  9. Design of a silicon avalanche photodiode pixel with integrated laser diode using back-illuminated crystallographically etched silicon-on-sapphire with monolithically integrated microlens for dual-mode passive and active imaging arrays

    NASA Astrophysics Data System (ADS)

    Stern, Alvin G.

    2010-08-01

    There is a growing need in scientific research applications for dual-mode, passive and active 2D and 3D LADAR imaging methods. To fill this need, an advanced back-illuminated silicon avalanche photodiode (APD) design is presented using a novel silicon-on-sapphire substrate incorporating a crystalline aluminum nitride (AlN) antireflective layer between the silicon and R-plane sapphire. This allows integration of a high quantum efficiency silicon APD with a gallium nitride (GaN) laser diode in each pixel. The pixel design enables single photon sensitive, solid-state focal plane arrays (FPAs) with wide dynamic range, supporting passive and active imaging capability in a single FPA. When (100) silicon is properly etched with TMAH solution, square based pyramidal frustum or mesa arrays result with the four mesa sidewalls of the APD formed by (111) silicon planes that intersect the (100) planes at a crystallographic angle, φ c = 54.7°. The APD device is fabricated in the mesa using conventional silicon processing technology. The GaN laser diode is fabricated by epitaxial growth inside of an inverted, etched cavity in the silicon mesa. Microlenses are fabricated in the thinned, and AR-coated sapphire substrate. The APDs share a common, front-side anode contact, and laser diodes share a common cathode. A low resistance (Al) or (Cu) metal anode grid fills the space between pixels and also inhibits optical crosstalk. SOS-APD arrays are flip-chip bump-bonded to CMOS readout ICs to produce hybrid FPAs. The square 27 μm emitter-detector pixel achieves SNR > 1 in active detection mode for Lambert surfaces at 1,000 meters.

  10. 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.

  11. 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)

  12. 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.

  13. Wide-area SWIR arrays and active illuminators

    NASA Astrophysics Data System (ADS)

    MacDougal, Michael; Hood, Andrew; Geske, Jon; Wang, Chad; Renner, Daniel; Follman, David; Heu, Paula

    2012-01-01

    We describe the factors that go into the component choices for a short wavelength (SWIR) imager, which include the SWIR sensor, the lens, and the illuminator. We have shown the factors for reducing dark current, and shown that we can achieve well below 1.5 nA/cm2 for 15 μm devices at 7°C. We have mated our InGaAs detector arrays to 640x512 readout integrated integrated circuits (ROICs) to make focal plane arrays (FPAs). In addition, we have fabricated high definition 1920x1080 FPAs for wide field of view imaging. The resulting FPAs are capable of imaging photon fluxes with wavelengths between 1 and 1.6 microns at low light levels. The dark current associated with these FPAs is extremely low, exhibiting a mean dark current density of 0.26 nA/cm2 at 0°C. FLIR has also developed a high definition, 1920x1080, 15 um pitch SWIR sensor. In addition, FLIR has developed laser arrays that provide flat illumination in scenes that are normally light-starved. The illuminators have 40% wall-plug efficiency and provide low-speckle illumination, provide artifact-free imagery versus conventional laser illuminators.

  14. 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.

  15. An inexpensive programmable illumination microscope with active feedback

    NASA Astrophysics Data System (ADS)

    Tompkins, Nathan; Fraden, Seth

    2016-02-01

    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. Supplemental matlab code is available to assist in the setup of the active feedback software.

  16. 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.

  17. 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

  18. Efficient vertical-cavity surface-emitting lasers for infrared illumination applications

    NASA Astrophysics Data System (ADS)

    Seurin, Jean-Francois; Xu, Guoyang; Guo, Baiming; Miglo, Alexander; Wang, Qing; Pradhan, Prachi; Wynn, James D.; Khalfin, Viktor; Zou, Wei-Xiong; Ghosh, Chuni; Van Leeuwen, Robert

    2011-03-01

    Infrared illumination is used in the commercial and defense markets for surveillance and security, for high-speed imaging, and for military covert operations. Vertical-cavity surface-emitting lasers (VCSELs) are an attractive candidate for IR illumination applications as they offer advantageous properties such as efficiency, intrinsically low diverging circular beam, low-cost manufacturing, narrow emission spectrum, and high reliability. VCSELs can also operate at high temperatures, thereby meeting the harsh environmental requirements of many illuminators. The efficiency and brightness of these VCSELs also reduce the requirements of the power supply compared to, for example, an LED approach. We present results on VCSEL arrays for illumination applications, as well as results on VCSEL-based illumination experiments. These VCSELs are used in illuminators emitting from a few Watts up to several hundred Watts. The emission of these VCSEL-based illuminators is speckle-free with no interference patterns. Infra-red illumination at up to 1,600ft (500m) from the source has been demonstrated using VCSEL-based illumination, without any optics.

  19. Resolution enhancement of two-photon microscopy via intensity-modulated laser scanning structured illumination.

    PubMed

    Yeh, Chia-Hua; Chen, Szu-Yu

    2015-03-20

    Conventional structured illumination microscopy (SIM) with wide-field illumination is an applicable tool to provide resolution enhancement. And yet its applications in thick specimens are still full of challenges. By combing the structured illumination concept with two-photon excitation, a laser scanning two-photon structured illumination microscope (LSTP-SIM) was constructed to gain ∼1.42-fold lateral resolution enhancement in contrast to two-photon fluorescence microscopy. With a point-scanning geometry, an acoustic-optical modulator was used to modulate temporally the excitation intensity in order to produce the structured illumination pattern. The theoretical models of image formation and image reconstruction were clearly established. Simulation and experiments were both performed to show the capability of this system to enhance the lateral resolution. Combined with the inherent optical sectioning power of the two-photon excitation, LSTP-SIM would have the potential for applications in optically-thick specimens. PMID:25968516

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

    PubMed

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

    2015-10-19

    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. 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

  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. A laser beam shaper for homogeneous rectangular illumination based on freeform micro lens array

    NASA Astrophysics Data System (ADS)

    Chen, En-guo; Huang, Jia-min; Guo, Tai-liang; Wu, Reng-mao

    2016-07-01

    An effective design method of freeform micro lens array is presented for shaping varied laser beams into prescribed rectangular illumination. The variable separation mapping is applied to design concave freeform surfaces for constructing a freeform lens array. Several dedicated examples show that the designed freeform optical lens array can achieve a prescribed rectangular illumination pattern, especially without considering the initial states of incident laser beams. Both high collection efficiency and good spatial uniformity can be available simultaneously. Tolerance analysis is also performed to demonstrate that this optical device can well avoid fabricating difficulty in actual applications.

  4. 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.

  5. 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.

  6. Four-color laser white illuminant demonstrating high color-rendering quality

    SciTech Connect

    Neumann, A.; Wierer, J. J.; Davis, W.; Ohno, Y.; Brueck, S. R.; Tsao, J.Y.

    2011-07-01

    Solid-state lighting is currently based on light-emitting diodes (LEDs) and phosphors. Solid-state lighting based on lasers would offer significant advantages including high potential efficiencies at high current densities. Light emitted from lasers, however, has a much narrower spectral line-width than light emitted from LEDs or phosphors. Therefore it is a common belief that white light produced by a set of lasers of different colors would not be of high enough quality for general illumination. We tested this belief experimentally, and found the opposite to be true. This result paves the way for the use of lasers in solid-state lighting.

  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. 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

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

    PubMed

    Cabello, Simon; Gachet, Yannick; Tournier, Sylvie

    2016-03-28

    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.

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

    PubMed Central

    Meisner, Joshua K.; Niu, Jacqueline; Sumer, Suna

    2013-01-01

    Abstract. 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. PMID:24045691

  11. Fast continuous tuning of terahertz quantum-cascade lasers by rear-facet illumination

    NASA Astrophysics Data System (ADS)

    Hempel, Martin; Röben, Benjamin; Schrottke, Lutz; Hübers, Heinz-Wilhelm; Grahn, Holger T.

    2016-05-01

    GaAs-based terahertz quantum-cascade lasers (QCLs) are continuously tuned in their emission frequency by illuminating the rear facet with a near-infrared, high-power diode laser. For QCLs emitting around 3.1 THz, the maximum tuning range amounts to 2.8 GHz for continuous-wave operation at a heat sink temperature of 55 K, while in pulsed mode 9.1 and 8.0 GHz are achieved at 35 and 55 K, respectively.

  12. 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.

  13. Improved background oriented schlieren imaging using laser speckle illumination

    NASA Astrophysics Data System (ADS)

    Meier, Alexander H.; Roesgen, Thomas

    2013-06-01

    A new variant of the background oriented schlieren technique is presented. Using a laser to generate a speckle reference pattern, several shortcomings of the conventional technique can be overcome. The arrangement decouples the achievable sensitivity from the placement constraint on the reference screen, facilitating the design of compact, high-sensitivity configurations. A new dual-pass imaging mode is introduced which further improves system performance and permits focusing on the target scene. Examples are presented that confirm the theoretical predictions.

  14. Mask inspection microscopy with 13.2 nm table-top laser illumination

    SciTech Connect

    Brizuela, Fernando; Wang, Yong; Brewer, Courtney A.; Pedaci, Francesco; Chao, Weilun; Anderson, Erik H.; Liu, Yanwei; Goldberg, Kenneth A.; Naulleau, Patrick; Wachulak, Przemyslaw; Marconi, Mario C.; Attwood, David T.; Rocca, Jorge J.; Menoni, Carmen S.

    2008-10-14

    We report the demonstration of a reflection microscope that operates at 13.2-nm wavelength with a spatial resolution of 55 {+-} 3 nm. The microscope uses illumination from a table-top EUV laser to acquire aerial images of photolithography masks with a 20 second exposure time. The modulation transfer function of the optical system was characterized.

  15. 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.

  16. 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.

  17. Laser illuminated etched track scattering (LITES) dosimetry system.

    PubMed

    Moore, M E; Gepford, H J; Hermes, R E; Hertel, N E; Devine, R T

    2002-01-01

    Los Alamos National Labs (LANL) has developed an etched track foil (CR-39) reader for neutron dose between 0 and 50.0 mSv. Currently, the US Department of Energy mandates general employee annual exposure not to exceed 50.0 mSv (5 rem). At LANL, due to a non-linear response at higher exposures. accepted practice only uses an Autoscan 60 system up to 3 mSv. The LITES system, however, has demonstrated linear response to 50 mSv, where the proprietary design measures the amount of laser light scattered by the etched tracks, proportional to dose. A collection of calibrated foils was counted by an Autoscan 60 and the LITES prototype, and the Autoscan 60 showed good linearity when counting exposure up to about 15 mSv, but not for higher exposures. From 0 to 50 mSv, the Autoscan 60 had a correlation coefficient of R2 = 0.941 and the LITES system had R2 = 0.991. PMID:12382702

  18. Laser induced breakdown spectroscopy and hyper-spectral imaging analysis of pigments on an illuminated manuscript

    NASA Astrophysics Data System (ADS)

    Melessanaki, K.; Papadakis, V.; Balas, C.; Anglos, D.

    2001-12-01

    Laser induced breakdown spectroscopy (LIBS) was used for the first time in the in-situ identification of pigments in an illuminated manuscript dated from the 12th-13th century AD. Spectral data are presented from the analysis performed on the illumination of an initial letter ‘T’ and on the gold paint used in several parts of the writing. Identification of most pigments, in a nearly non-destructive way, was achieved. In parallel to LIBS, hyper-spectral imaging analysis was performed, which enabled the mapping of the pigments’ spatial distribution on the basis of their characteristic, visible and near infrared absorption spectral features. The identification of the red pigment based on hyper-spectral imaging analysis is demonstrated. Identification of pigments and inks is of great importance for the dating and systematic characterization of illuminated manuscripts and, as shown in this work, a combined analytical approach can provide important and useful information.

  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.; 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 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. Measurement of repetitive surface displacement modulation induced by illuminating femto-second laser pulses

    NASA Astrophysics Data System (ADS)

    Tozawa, Ryoma; Barada, Daisuke; Kawata, Shigeo

    2015-09-01

    In this study, a light-driven deformable mirror is fabricated by electron beam lithography. The mirror is consisted of a deformation layer and a micromirror array. The deformation layer is made of an azobenzene polymer and the micromirro array is deposited on the deformation layer. The deformation of azobenzene polymer is induced by illuminating a continuum wave beam or femto-second pulse laser beam. Then, the micromirror is displaced. The displacement modulation is experimentally confirmed by interference measurement.

  2. 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.

  3. 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

    2016-06-01

    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.

  4. 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.

  5. 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.

  6. First Results from Laser-Driven MagLIF Experiments on OMEGA: Optimization of Illumination Uniformity

    NASA Astrophysics Data System (ADS)

    Chang, P.-Y.; Barnak, D. H.; Betti, R.; Davies, J. R.; Fiksel, G.

    2015-11-01

    The physics principles of magnetic liner inertial fusion (MagLIF) are investigated on the Omega Laser Facility using 40 beams for compression and 1 beam for preheating a small (300- μm-radius, 1-mm-long) cylindrical plastic shell. Here we report of the first implosion experiments to optimize the illumination uniformity. These initial experiments do not include laser preheat. The beams in ring 3 and ring 4 around the symmetric axis are used to implode a cylindrical target. Beams in different rings illuminate the target surface with different incident angles, leading to different energy-coupling efficiencies. The beams in ring 3 have a shallower angle of incident than ring 4. When implosion velocities are compared for targets driven by either ring 3 or ring 4, we find that ring 3 couples ~ 40 % less kinetic energy than ring 4. One- and two-dimensional simulations using LILAC (1-D) and FLASH (2-D) are used to compare to the experimental results and to optimize the illumination uniformity. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and by DE-FG02-04ER54786 and DE-FC02-04ER54789 (Fusion Science Center).

  7. Direct Phasing of Finite Crystals Illuminated with a Free-Electron Laser

    NASA Astrophysics Data System (ADS)

    Kirian, Richard A.; Bean, Richard J.; Beyerlein, Kenneth R.; Barthelmess, Miriam; Yoon, Chun Hong; Wang, Fenglin; Capotondi, Flavio; Pedersoli, Emanuele; Barty, Anton; Chapman, Henry N.

    2015-01-01

    It has been suggested that the extended intensity profiles surrounding Bragg reflections that arise when a series of finite crystals of varying size and shape are illuminated by the intense, coherent illumination of an x-ray free-electron laser may enable the crystal's unit-cell electron density to be obtained ab initio via well-established iterative phasing algorithms. Such a technique could have a significant impact on the field of biological structure determination since it avoids the need for a priori information from similar known structures, multiple measurements near resonant atomic absorption energies, isomorphic derivative crystals, or atomic-resolution data. Here, we demonstrate this phasing technique on diffraction patterns recorded from artificial two-dimensional microcrystals using the seeded soft x-ray free-electron laser FERMI. We show that the technique is effective when the illuminating wavefront has nonuniform phase and amplitude, and when the diffraction intensities cannot be measured uniformly throughout reciprocal space because of a limited signal-to-noise ratio.

  8. 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.

  9. 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.

  10. 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)].

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    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)].

  12. Induction of beta-glucosidase activity in maize coleoptiles by blue light illumination.

    PubMed

    Jabeen, Riffat; Yamada, Kosumi; Shigemori, Hideyuki; Hasegawa, Tsuyoshi; Hara, Masakazu; Kuboi, Toru; Hasegawa, Koji

    2006-03-01

    The role of beta-glucosidase during the phototropic response in maize (Zea mays) coleoptiles was investigated. Unilateral blue light illumination abruptly up-regulated the activity of beta-glucosidase in the illuminated halves, 10 min after the onset of illumination, peaking after 30 min and decreasing thereafter. The level of 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA), which is released from DIMBOA glucoside (DIMBOA-Glc) by beta-glucosidase, and its degradation compound 6-methoxy-benzoxazolinone (MBOA) were elevated within 30 min in the illuminated halves as compare to the shaded halves, prior to the phototropic curvature. Furthermore, beta-glucosidase inhibitor treatment significantly decreased the phototropic curvature and decreased growth suppression in the illuminated sides. These results suggest that blue light induces the activity of beta-glucosidase in the illuminated halves of coleoptiles causing an increase in DIMBOA biosynthesis and the growth inhibition that leads to a phototropic curvature. PMID:16473658

  13. 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

    2015-05-01

    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.

  14. 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.

  15. An epiiluminator/detector unit permitting arc lamp illumination for fluorescence activated cell sorters.

    PubMed

    Koper, G J; Bonnet, J; Christiaanse, J G; Ploem, J S

    1982-07-01

    The application of arc lamps to flow cytometers is discussed and epiillumination for jet-in-air cell sorters is introduced. An epiilluminator/detector unit equipped with a mercury arc lamp constructed for a commercially available cell sorter is described. Experiments in which laser and mercury arc lamp illumination were compared show that the signal-to-noise ratio for the arc lamp illumination is predominantly limited by shot noise from constant light backgrounds due to reflected excitation light and ambient light. Arc lamp illumination can be used for the sorting of highly fluorescent objects such as cells stained for DNA by for example: ethidium bromide, propidium iodide, or the Hoechst dyes. The simultaneous employment of mercury arc and laser light sources as an inexpensive dual wavelength system is discussed.

  16. Growth of spontaneous periodic surface structures on solids during laser illumination

    NASA Astrophysics Data System (ADS)

    Guosheng, Zhou; Fauchet, P. M.; Siegman, A. E.

    1982-11-01

    Spontaneous periodic surface structures, or ripples, are frequently observed after illumination of metals, semiconductors, and dielectrics by intense laser pulses. We develop a theory which predicts the observed spacing, polarization, and growth properties of these ripples. In this model, one or several Fourier components of a random surface disturbance scatter light from the incident beam very nearly along the surface. The interference of this diffracted optical wave with the incident beam then gives rise to optical interference fringes which can reinforce the initial disturbance. Sinusoidal corrugations on either metallic or molten surfaces seem to provide strong positive feedback for ripple growth, whereas sinusoidal gratings in temperature, electron-hole density, or dielectric constant seem much less well correlated with observations.

  17. 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.

  18. 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.

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

    PubMed

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

    2015-12-11

    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.

  20. 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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    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.

  2. 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.

  3. 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.

  4. Pineal melatonin and locomotor activity of rats under gradual illuminance transitions.

    PubMed

    Laakso, M L; Leinonen, L; Joutsiniemi, S L; Porkka-Heiskanen, T; Stenberg, D

    1992-10-01

    The locomotor activity and pineal melatonin patterns of adult male rats were compared under two different lighting regimes. The animals were kept 8 days under 12/12 h light/dark cycles with abrupt or slowly decreasing and increasing transitions (twilight periods about 2 h). The onsets of high activity and melatonin rise were phase-locked in the two conditions and related to about half-maximal illuminance level of the gradual dusk. The high activity of the control rats stopped 30-60 min before the abrupt light onset and the rats under the gradual lighting transitions ceased the locomotor activity at about 1 hour before the half-maximal illuminance. The melatonin peak levels were found 4 h before the abrupt lights-on time. Under the slow illuminance transitions the average melatonin peak was related to the illuminance level between maximum and minimum in the morning. Thus, both the melatonin rhythm and the rest-activity rhythm under the gradual dawn and dusk were adjusted according to about half-maximal illuminances in the present conditions.

  5. Operational specifications of the laser illuminated track etch scattering dosemeter reader.

    PubMed

    Moore, M E; Gepford, H J; Hoffman, J M; McKeever, R J; Devine, R T

    2006-01-01

    The personnel dosimetry operations team at the Los Alamos National Laboratory (LANL) has accepted the laser illuminated track etch scattering (LITES) dosemeter reader into its suite of radiation dose measurement instruments. The LITES instrument transmits coherent light from a He-Ne laser through the pertinent track etch foil and a photodiode measures the amount of light scattered by the etched tracks. A small beam stop blocks the main laser light, while a lens refocuses the scattered light into the photodiode. Three stepper motors in the current LITES system are used to position a carousel that holds 36 track etch dosemeters (TEDs). Preliminary work with the LITES system demonstrated the device had a linear response in counting foils subjected to exposures up to 50 mSv (5.0 rem). The United States Department of Energy requires that the annual general employee dose not exceed 50 mSv (5.0 rem). On a regular basis, LANL uses the Autoscan-60 reader system (Thermo Electron Corp.) for counting track etch dosemeters. However, LANL uses a 15 h etch process for CR-39 dosemeters, and this produces more and larger track etch pits than the 6 h etch used by many institutions. Therefore, LANL only uses the Autoscan-60 for measuring neutron dose equivalent up to exposure levels of approximately 3 mSv (300 mrem). The LITES system has a measured lower limit of detection of approximately 0.6 mSv (60 mrem), and it has a correlation coefficient of R (2) = 0.99 over an exposure range up to 500 mSv (50.0 rem). A series of blind studies were done using three methods: the Autoscan-60 system, manual counting by optical microscope and the LITES instrument. A collection of track etch dosemeters of unknown neutron dose equivalent (NDE) were analysed using the three methods, and the performance coefficient (PC) was calculated when the NDE became known. The Autoscan-60 and optical microscope methods had a combined PC = 0.171, and the LITES instrument had a PC = 0.194, where a PC less than or

  6. 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.

  7. 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.

  8. 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

  9. Effect of illuminance and color temperature on lowering of physiological activity.

    PubMed

    Noguchi, H; Sakaguchi, T

    1999-07-01

    To investigate how illuminance and color temperature in illumination affect the autonomic nervous system and central nervous system in conditions tending to lower physiological activity, and with an ordinary residential setting in mind, we performed an experiment on 8 healthy male subjects. The experimental conditions consisted of 4 conditions provided by a combination of 2 levels of color temperature (3000 K, 5000 K) and 2 levels of illuminance (30 lx, 150 lx). Physiological measurement was carried out during a process of 22 minutes of light exposure followed by 20 minutes of sleep in darkness. Heart rate variability (HRV) was used as an index of the autonomic nervous system, and alpha attenuation coefficient (AAC) and mean frequency of EEG were used as indices of the central nervous system. Subjective evaluation of drowsiness during the experiment was also carried out immediately following the 20 minutes sleep. No effect on HRV from illumination was noted, but significantly (p < 0.05) lower values for AAC were obtained under 3000 K conditions than 5000 K conditions in measurements during the first half of light exposure (Session 1). During alpha attenuation testing, significantly (p < 0.05) lower values for mean frequency in the theta-beta EEG bandwidth were also obtained under 3000 K conditions than 5000 K conditions, but that pattern persisted in measurement during the second half of light exposure (Session 2). Subjective drowsiness was also higher under 3000 K conditions than 5000 K conditions. These results suggest that low color temperature light creates a smooth lowering of central nervous system activity, and that low color temperature illumination can be used effectively in a bedroom or other such environment where it is desirable to facilitate lowered physiological activity.

  10. Turbulence-induced scintillation on Gaussian-beam waves: theoretical predictions and observations from a laser-illuminated satellite

    NASA Astrophysics Data System (ADS)

    Shelton, John D.

    1995-10-01

    Expressions for the variance and the power spectral density of turbulence-induced log-amplitude fluctuations are derived for Gaussian-beam waves in the regime of weak scattering. This formulation includes effects that are due to turbulence strength variations along the propagation path, offset of the observation point from the beam axis, and sensitivity to focus and beam diameter. Comparison of theoretical results with observed scintillation during experiments with a laser-illuminated satellite reveals good agreement. Copyright (c) 1995 Optical Society of America

  11. 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.

  12. Finite element modeling of bulk ultrasonic waves generated by ring-shaped laser illumination in a diamond anvil cell.

    PubMed

    Feng, Wen; Yang, Dexing; Guo, Yuning; Chang, Ying

    2012-03-12

    Thermoelastic finite element models are established to study the bulk ultrasonic waves of an aluminum film generated by ring-shaped laser illumination in a diamond anvil cell. By analyzing the amplitudes of bulk ultrasonic waves arrived at the rear surface of film in detail, it shows that there exists strong enhancement effects on the central axis of the ring due to the constructive interference among the waves created by different parts of the ring source. The displacement distributions along the central axis indicate that the focal depth of shear wave is mainly determined by its directivity induced by a point-like laser source in a DAC system while it is more complicated to determine the focal depth of longitudinal wave. In particular, through changing the ring radius, we quantitatively demonstrate that the signal amplitudes generated by a ring source are far greater than those generated by a point-like source.

  13. A new microscope optics for laser dark-field illumination applied to high precision two dimensional measurement of specimen displacement

    NASA Astrophysics Data System (ADS)

    Noda, Naoki; Kamimura, Shinji

    2008-02-01

    With conventional light microscopy, precision in the measurement of the displacement of a specimen depends on the signal-to-noise ratio when we measure the light intensity of magnified images. This implies that, for the improvement of precision, getting brighter images and reducing background light noise are both inevitably required. For this purpose, we developed a new optics for laser dark-field illumination. For the microscopy, we used a laser beam and a pair of axicons (conical lenses) to get an optimal condition for dark-field observations. The optics was applied to measuring two dimensional microbead displacements with subnanometer precision. The bandwidth of our detection system overall was 10kHz. Over most of this bandwidth, the observed noise level was as small as 0.1nm/√Hz.

  14. Effects of snap-freezing and near-infrared laser illumination on porcine prostate tissue as measured by Raman spectroscopy.

    PubMed

    Candefjord, Stefan; Ramser, Kerstin; Lindahl, Olof A

    2009-09-01

    Most Raman spectroscopic studies on tissue are performed in vitro. To assure that the results are applicable to in vivo examinations, preparation protocols and measurement procedures of tissue for in vitro studies should preserve tissue characteristics close to the native state. This study had two aims. The first was to elucidate if photoinduced effects arise during 5 minutes' continuous illumination of tissue with an 830 nm laser at an irradiance of approximately 3 x 10(10) W/m2. The second was to investigate the effects of snap-freezing of porcine prostate tissue in liquid nitrogen and subsequent storage at -80 degrees C, by means of multivariate analysis. 830 nm laser illumination of the specified irradiance did not affect the Raman spectra. A decrease of the spectral background was observed, likely due to photobleaching of tissue fluorophores. Snap-freezing and subsequent storage at -80 degrees C gave rise to subtle but significant alterations in Raman spectra, most likely related to changes in the protein conformations.

  15. Estimation of the cooling times for a metallic tip under laser illumination

    SciTech Connect

    Vurpillot, F.; Gault, B.; Vella, A.; Bouet, M.; Deconihout, B.

    2006-02-27

    The temperature evolution at the apex of a sharply pointed needle submitted to ultrafast pulsed-laser irradiation was determined using a pump-probe method. The laser pulse acts as a pump pulse whereas the probe pulse is a fast high-voltage pulse. Then cooling times are consistent with a heating zone of a few microns with a laser beam polarized along the tip axis and a spot size of 0.8 mm.

  16. Coaxial monitoring of the fibre laser lap welding of Zn-coated steel sheets using an auxiliary illuminant

    NASA Astrophysics Data System (ADS)

    Zhang, Yi; Zhang, Chenglei; Tan, Lipeng; Li, Shichun

    2013-09-01

    In the laser welding process, weld defects are often caused by many factors, such as variations in the laser power, welding speed and gaps between two workpieces. In an auto-welding system, the on-line monitoring of the welding quality is very important in avoiding weld defects. In this paper, an on-line coaxial monitoring system with an auxiliary illuminant was built for the fibre laser welding of galvanised steel; images of the weld pool were taken during the welding process. Profiles of the weld pool and the keyhole were obtained by processing the images using the region-growing algorithm and the Canny algorithm. In this research, we used the on-line monitored weld pool width to monitor the weld surface width. The weld penetration status was divided into the three categories of incompletely penetrated, moderately penetrated and over-penetrated using the value of d (diameter at the bottom of the keyhole)/D (diameter at the top of the keyhole). Thus, the weld width and weld penetration status of fibre laser welding can be monitored on-line.

  17. Laser-driven phosphor-converted white light source for solid-state illumination.

    PubMed

    George, Anthony F; Al-waisawy, Sara; Wright, Jason T; Jadwisienczak, Wojciech M; Rahman, Faiz

    2016-03-10

    Energy efficiency and lighting quality considerations are driving research into laser-pumped white light sources. Laser diodes as pump sources for downconversion phosphors promise freedom from "droop" that adversely affects the efficiency of light-emitting diodes (LEDs). High-intensity laser diode-pumped light sources for applications such as search lights and automobile headlights have been demonstrated recently. Our paper describes the design and construction of a domestic/office-type solid-state luminaire driven by light from an integrated violet laser-diode module. A trichromatic phosphor made from a blend of separate europium-containing rare-earth phosphors was used as the downconversion medium. Mechanical and optical design of the reflector and the phosphor plate are described. Characteristics of both the pump light and the downconverted light are also described. Our studies also looked at the variation of chromaticity coordinates with variation in pump power and the effect of laser speckle on the lamp's light output. Finally, there is a brief discussion of energy conversion efficiency and longevity considerations, comparing pumping with LEDs versus pumping with laser diodes. PMID:26974780

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

    PubMed

    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

  19. 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

  20. Diffraction rings obtained from a suspension of skeletal myofibrils by laser light illumination. Study of internal structure of sarcomeres.

    PubMed Central

    Ishiwata, S; Okamura, N

    1989-01-01

    Diffraction rings corresponding to the first, second, and third order were obtained by laser light illumination from a suspension of rabbit glycerinated psoas myofibrils (diameter, 1-2 microns; average length of the straight region, 44 microns; average sarcomere length, 2.2-2.6 microns) of which the optical thickness was appropriately chosen. Dispersed myofibrils were nearly randomly oriented in two dimensions, so that the effects of muscle volume were minimized; these effects usually interfere significantly with a quantitative analysis of laser optical diffraction in the fiber system. The diameters of diffraction rings represented the average sarcomere length. By using this system, we confirmed the ability of the unit cell (sarcomere) structure model to explain the intensity change of diffraction lines accompanying the dissociation from both ends of thick filaments in a high salt solution. The length of an A-band estimated from the relative intensity of diffraction rings and that directly measured on phase-contrast micrographs coincided well with each other. Also, we found that myofibrils with a long sarcomere length shorten to a slack length accompanying the decrease in overlap between thick and thin filaments produced by the dissociation of thick filaments. Images FIGURE 4 FIGURE 1 FIGURE 8 PMID:2692720

  1. 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.

  2. 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.

  3. Thermal effects of laser illumination on coated quartz crystal microbalance surfaces

    NASA Astrophysics Data System (ADS)

    Keller, Benjamin; Stevens, Keeley; Pan, Liming; Krim, Jacqueline

    2013-03-01

    Prior work on the thermal sensitivity of quartz crystal microbalances (QCM) has shown them to be powerful tools, capable of measuring milli-Kelvin temperature impulses while also presenting a well-understood response to steady state heating. This has been demonstrated for physical contact to the QCM surface via a STM tip with a temperature differential; here we present a novel application wherein a laser is focused onto the coated QCM, thus applying a non-contact thermal pulse. By applying variable length (second to minute) exposures from a laser source we can isolate the thermal shock, time decay and gross heating effects. The system is sensitive to the coating used, showing significant differences in heating for absorbative and reflective coatings. This method is unique in that the QCM measures energy lost into the substrate, unlike standard techniques which focus primarily on material efficiency. This has potential to characterize various coatings used in solar cells and thermal collectors, as well as in photovoltaic materials. Funding provided by NSF DMR.

  4. Short-wavelength infrared imaging using low dark current InGaAs detector arrays and vertical-cavity surface-emitting laser illuminators

    NASA Astrophysics Data System (ADS)

    Macdougal, Michael; Geske, Jon; Wang, Chad; Follman, David

    2011-06-01

    We describe the factors that go into the component choices for a short wavelength IR (SWIR) imager, which include the SWIR sensor, the lens, and the illuminator. We have shown the factors for reducing dark current, and shown that we can achieve well below 1.5 nA/cm2 for 15 μm devices at 7 °C. In addition, we have mated our InGaAs detector arrays to 640×512 readout integrated integrated circuits to make focal plane arrays (FPAs). The resulting FPAs are capable of imaging photon fluxes with wavelengths between 1 and 1.6 μm at low light levels. The dark current associated with these FPAs is extremely low, exhibiting a mean dark current density of 0.26 nA/cm2 at 0 °C. Noise due to the readout can be reduced from 95 to 57 electrons by using off-chip correlated double sampling. In addition, Aerius has developed laser arrays that provide flat illumination in scenes that are normally light-starved. The illuminators have 40% wall-plug efficiency and provide low-speckle illumination, and provide artifact-free imagery versus conventional laser illuminators.

  5. Photothermovoltaic effects induced by CO2 laser illumination of PbTe-metal junctions

    NASA Astrophysics Data System (ADS)

    Asmontas, Steponas P.; Dashevsky, Z.; Dariel, M. P.; Gradauskas, Jonas; Jarashneli, A.; Shusterman, S.; Suziedelis, Algirdas; Valusis, Gintaras

    2001-03-01

    Our study is concerned with the photo-thermovoltaic effects caused by the absorption of CO2 laser light in narrow gap AIVBVI semiconductors. We report on results of experimental study of photoresponse induced in n-type and p- type lead telluride with Ni contacts. We show that in the case of ohmic contacts (n-PbTe-Ni and p-PbTe-Ni at 300K) the detected signal originated from thermoemf due to created crystal lattice temperature gradient. In the case of p- PbTe-Ni at 80K we have Schottky contacts and the photoresponse consists at least of two components: fast and great in value photoemf- due to carrier generation resulting from two-photon absorption, and slow as well as of lower magnitude thermoemf.

  6. Impact of a distance estimation error inducing a visualized zone gap on the target illuminance in range-gated active imaging.

    PubMed

    Matwyschuk, Alexis

    2014-01-01

    Some stand-alone airborne systems of target reconnaissance such as a missile seeker head use range-gated laser active imaging to visualize a target in the scene. To center the visualized zone on the target, it is important to know the distance between the active imaging system and the target. However, as this exact distance is not known before the detection of the target, it can be only estimated. This estimated distance can be erroneous (max≈500  m) with some technological drifts (gyrometric drift, accelerometric drift, missile position error, etc.). To be able to evaluate the impact of a distance estimation error on target illuminance in active imaging, the expressions of the illuminance attenuation ratio according to the decentered target position with regard to the visualized zone were determined. These different equations will be used to determine, in future stand-alone reconnaissance systems, the target signal-to-noise ratio as a function of the localization error. Generally speaking, two modes of visualization were used: first by using a fixed width of the visualized zone, and second by increasing the width of the visualized zone as a function of the distance. The defined different expressions allowed us to study the illuminance behavior of the target with regard to the value of the gap (difference between the estimated distance and the real distance) for each mode of visualization. The results showed that from a target distance of about 1 km, the visualization mode with variable zone width allowed us to decrease the target illuminance less during a gap caused by an estimation error of the target distance.

  7. Low-cost vehicle-mounted enhanced vision system comprised of a laser illuminator and range-gated camera

    NASA Astrophysics Data System (ADS)

    Pencikowski, Paul S.

    1996-05-01

    Considerable research has been done regarding the use of enhanced vision as a means to enable a vehicle operator to `see' through bad weather or obscuration such as smoke and dust. This research has generally emphasized Forward-looking infra-red (Flir) and millimeter-wave (radar) technologies. Flir is an acceptable approach if modest performance is all that is required. Millimeter wave radar has distinct advantages over Flir in certain cases, but generally requires operator training to interpret various display-screen presentations. The Northrop Grumman Corporation has begun a major sensor-development program to develop a prototype (eye-safe) laser-illuminator/range-gated camera system. The near-term goal is to field a system that would deliver a minimum of 3000 foot penetration of worst-case fog/obscurant. This image would appear on a display as a high resolution monochromatic image. This paper will explore the concept, the proposed automotive application, and the projected cost.

  8. Deep trap, laser activated image converting system

    NASA Technical Reports Server (NTRS)

    Maserjian, J. (Inventor)

    1975-01-01

    Receiving an optical image on the surface of a photoconducting semiconductor is presented, storing the image in deep traps of the semiconductor, and later scanning the semiconductor with a laser beam to empty the deep traps, thereby producing a video signal. The semiconductor is illuminated with photons of energy greater than the band gap producing electron-hole pairs in the semiconductor which subsequently fill traps in energy from the band edges. When the laser beam of low energy photons excites the trapped electrons and holes out of the traps into the conduction and valence bands, a photoconductivity can be observed.

  9. 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.

  10. 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.

  11. [Chronobiological approach to the treatment of patients with erectile dysfunction using a combination of local negative pressure and laser illumination].

    PubMed

    Moskvin, S V; Ivanchenko, L P

    2014-01-01

    It is shown that the synchronization of energetic, spectral, frequency, and temporal parameters of technique with biorhythms of physiological processes in the organ, which is target of impact, and in the human body as a whole, allows to significantly improve efficiency, and achieve stable and reproducible results of treatment. The article presents the results of study including 62 patients with vasculogenic ED. The study design included the randomization of patients into 3 groups depending on the complex of the therapy with the use of combined techniques, including negative pressure and laser illumination (LLNP) as a part of combined therapy and as monotherapy. Significant increase in the peak flow velocity after a course of treatment was observed in all three groups of patients. Improvement in erectile function was observed in all groups; according to IIEF score, erectile function has increased by 22.3 +/- 0.05% in group 1, by 34 +/- 1.5% in the group 2, and by 19 +/- 1.7% in the group 3, indicating the best results of treatment in the group receiving combined therapy. Combination of LLNP with the administration of PDE5 inhibitors significantly increases the effectiveness of treatment of vasculogenic ED due to the influence of physical factors on the stabilization of hemodynamics in the main arteries of the penis. After a course of therapy, increase in systemic vascular elasticity by 39.8 +/- 1.5% was also noted. The efficiency of the LLNP methodology in the treatment of patients with vasculogenic ED is demonstrated. The best results were obtained in the group of patients treated with combined therapy, including the use of LLNP and PDE-5 inhibitor. PMID:25211927

  12. 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

  13. 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

  14. 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

  15. Laser and optics activities at CREOL

    SciTech Connect

    Stickley, C.M.

    1995-06-01

    CREOL is an interdisciplinary institute with a mission to foster and support research and education in the optical and laser sciences and engineering. CREOL`s principal members are its 21-strong faculty. The faculty are encouraged and supported in developing, maintaining, and expanding innovative and sponsored research programs, especially ones that are coupled to industry`s needs. The CREOL Director and Assistant Director, through empowerment by the CREOL faculty, coordinate and oversee the interactive, interdisciplinary projects of the faculty, the 85 graduate students and the 39 research staff. CREOL integrates these research efforts with the general educational mission and goals of the university, develops comprehensive course work in the optical and laser sciences and engineering, provides guidance and instruction to graduate students, administers MS and PhD programs, and provides facilities, funds, and administrative support to assist the faculty in carrying out CREOL`s mission and obtaining financial support for the research projects. CREOL`s specific areas of research activity include the following: IR systems; nonlinear optics; crystal growth; nonlinear integrated optics; new solid-state lasers; tunable far-infrared lasers; thin-film optics; theory; semiconductor lasers; x-ray/optical scattering; laser-induced damage; free-electron lasers; solid-state spectroscopy; x-ray sources and applications; laser propagation; laser processing of materials; optical design; optical limiting/sensor protection; diffractive optics; quantum well optoelectronics; dense plasmas/high-field physics; laser radar and remote sensing; diode-based lasers; and glass science.

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

    PubMed Central

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

    2011-01-01

    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. PMID:22029369

  17. 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.

  18. The research of multi-frame target recognition based on laser active imaging

    NASA Astrophysics Data System (ADS)

    Wang, Can-jin; Sun, Tao; Wang, Tin-feng; Chen, Juan

    2013-09-01

    Laser active imaging is fit to conditions such as no difference in temperature between target and background, pitch-black night, bad visibility. Also it can be used to detect a faint target in long range or small target in deep space, which has advantage of high definition and good contrast. In one word, it is immune to environment. However, due to the affect of long distance, limited laser energy and atmospheric backscatter, it is impossible to illuminate the whole scene at the same time. It means that the target in every single frame is unevenly or partly illuminated, which make the recognition more difficult. At the same time the speckle noise which is common in laser active imaging blurs the images . In this paper we do some research on laser active imaging and propose a new target recognition method based on multi-frame images . Firstly, multi pulses of laser is used to obtain sub-images for different parts of scene. A denoising method combined homomorphic filter with wavelet domain SURE is used to suppress speckle noise. And blind deconvolution is introduced to obtain low-noise and clear sub-images. Then these sub-images are registered and stitched to combine a completely and uniformly illuminated scene image. After that, a new target recognition method based on contour moments is proposed. Firstly, canny operator is used to obtain contours. For each contour, seven invariant Hu moments are calculated to generate the feature vectors. At last the feature vectors are input into double hidden layers BP neural network for classification . Experiments results indicate that the proposed algorithm could achieve a high recognition rate and satisfactory real-time performance for laser active imaging.

  19. 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

  20. Shadowgraph illumination techniques for framing cameras

    SciTech Connect

    Malone, R.M.; Flurer, R.L.; Frogget, B.C.; Sorenson, D.S.; Holmes, V.H.; Obst, A.W.

    1997-06-01

    Many pulse power applications in use at the Pegasus facility at the Los Alamos National Laboratory require specialized imaging techniques. Due to the short event duration times, visible images are recorded by high speed electronic framing cameras. Framing cameras provide the advantages of high speed movies of back light experiments. These high speed framing cameras require bright illumination sources to record images with 10 ns integration times. High power lasers offer sufficient light for back illuminating the target assemblies; however, laser speckle noise lowers the contrast in the image. Laser speckle noise also limits the effective resolution. This discussion focuses on the use of telescopes to collect images 50 feet away. Both light field and dark field illumination techniques are compared. By adding relay lenses between the assembly target and the telescope, a high resolution magnified image can be recorded. For dark field illumination, these relay lenses can be used to separate the object field from the illumination laser. The illumination laser can be made to focus onto the opaque secondary of a Schmidt telescope. Thus, the telescope only collects scattered light from the target assembly. This dark field illumination eliminates the laser speckle noise and allows high resolution images to be recorded. Using the secondary of the telescope to block the illumination laser makes dark field illumination an ideal choice for the framing camera.

  1. 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.

  2. 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.

  3. [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.

  4. [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. PMID:24288981

  5. 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

  6. 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.

  7. 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.

  8. 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...

  9. Laser remote monitoring of plant photosynthetic activity

    NASA Astrophysics Data System (ADS)

    Barbini, Roberto; Colao, Francesco; Fantoni, Roberta; Palucci, Antonio; Ribezzo, Sergio

    1995-11-01

    Laboratory measurements of laser induced chlorophyll fluorescence kinetics (Kautsky effect) on dark-adapted vegetation targets (maize, pine-tree) have been performed with a lidar fluorosensor by superimposing probe pulses upon an actinic light. The collected induction curves (fast rise and slow decline) have been used to reveal the occurrence of stresses and the damage produced by a pine-tree parasite. A new two-pulse LIF (laser induced fluorescence) methodology has been investigated both theoretically and experimentally, in view of remotely monitoring the plant photosynthetic activity. This technique may yield information upon the in-vivo photosynthetic processes of plants, revealing a possible stress status (nutrients depletion, presence of herbicides, photoinhibition, etc.). The lidar apparatus used contains two laser sources in order to differentially measure the chlorophyll fluorescence by means of a laser pump-and-probe technique. In fact LIF signals in the red chlorophyll band 690 nm may provide in-vivo information upon photosynthesis process in high order plants and algae. Laser pump-and-probe experimental tests, with excitation 355 nm or 532 nm, already detect the presence of herbicides, and the effects of plant exposure to thermal stresses and to low levels of gaseous pollutants. Laser measured fluorescence yields (Y) have been found to be consistent with those obtained by an in-situ fluorimeter (PAM). With proper choices of experimental parameters (pump and probe laser intensities), Y approaches the theoretical value expected for a healthy dark-adapted plant.

  10. Responsivity uniformity enhancements for Backside-Illuminated Charge-Coupled Devices (BICCDs) by excimer laser-assisted etching

    NASA Astrophysics Data System (ADS)

    Russell, Stephen D.; Sexton, Douglas A.

    1991-05-01

    BICCDs are solid-state electronic imaging devices which read out image charges from wells in an array of pixels. The substrate below the pixel array is typically thinned by chemically etching (100)-oriented silicon using a potassium hydroxide (KOH) etch. The potassium hydroxide anisotropically etches to the (111) crystallographic plane in silicon, leaving smooth sidewalls at an angle of 54.7 deg to the image plane. This smooth surface acts as a mirror to reflect extraneous light onto the image plane of the BICCD, causing spurious images and reducing the responsivity uniformity (RU) of the devices. We have developed a noncontact excimer laser-assisted process to promote a chemical reaction between a halocarbon ambient and the silicon. The laser-assisted chemical reaction results in a roughened (textured) surface which behaves as a light sink. The use of a nonreactive ambient allows us to texture the sidewalls of prepackaged and pretested devices. The sidewalls of fully functional BICCD die have been textured in a Freon-115 (chloropentafluoroethane) ambient by directing 5000 pulses with laser fluence of about 0.75 J/sq cm upon them. The RU of the devices as well as the background level (fat-zero) are dramatically improved.

  11. 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

  12. Laser line illumination scheme allowing the reduction of background signal and the correction of absorption heterogeneities effects for fluorescence reflectance imaging.

    PubMed

    Fantoni, Frédéric; Hervé, Lionel; Poher, Vincent; Gioux, Sylvain; Mars, Jérôme I; Dinten, Jean-Marc

    2015-10-01

    Intraoperative fluorescence imaging in reflectance geometry is an attractive imaging modality as it allows to noninvasively monitor the fluorescence targeted tumors located below the tissue surface. Some drawbacks of this technique are the background fluorescence decreasing the contrast and absorption heterogeneities leading to misinterpretations concerning fluorescence concentrations. We propose a correction technique based on a laser line scanning illumination scheme. We scan the medium with the laser line and acquire, at each position of the line, both fluorescence and excitation images. We then use the finding that there is a relationship between the excitation intensity profile and the background fluorescence one to predict the amount of signal to subtract from the fluorescence images to get a better contrast. As the light absorption information is contained both in fluorescence and excitation images, this method also permits us to correct the effects of absorption heterogeneities. This technique has been validated on simulations and experimentally. Fluorescent inclusions are observed in several configurations at depths ranging from 1 mm to 1 cm. Results obtained with this technique are compared with those obtained with a classical wide-field detection scheme for contrast enhancement and with the fluorescence by an excitation ratio approach for absorption correction. PMID:26442963

  13. 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.

  14. 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. PMID:25428048

  15. 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.

  16. 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,…

  17. Steerable diffraction limited line illumination system using deformable mirror

    NASA Astrophysics Data System (ADS)

    Taniguchi, Koichi; Kim, Dae Wook; Shimura, Kei; Burge, James H.

    2013-09-01

    Many scientific and industrial applications often require high performance optical systems utilizing spatially shaped illumination patterns of laser beams. Precisely shaped line illumination can be used for various line scanning systems or surface inspection devices. In order to achieve the highest resolution or superior signal to noise ratio limited by the fundamental theory, a diffraction limited illumination optical system (e.g. <0.8 Strehl ratio) gives the narrowest illumination line width determined by the system's NA (Numerical Aperture) value. For high precision and in-factory industrial applications, the Diffraction Limited Line Illumination (DLLI) needs to be controlled in three dimensional space rapidly as the target object under the illumination may not be always aligned with respect to the illumination system. A steerable DLLI system with three degrees of freedom (i.e. axial displacement, rotation, and tilt) is developed using an adaptive optics system. By electronically controlling the Zernike based surface shapes of the deformable mirror, the DLLI in free space is actively positioned and oriented with high accuracy. The geometrical optics based mathematical model to control the Zernike modes of the deformable mirror and the performance of a bench-top proof-ofconcept system will be presented with experimental data and analysis results.

  18. 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.

  19. 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.

  20. 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.

  1. Optical trapping/modification of nano-(micro)particles by gradient and photorefractive forces during laser illumination

    NASA Astrophysics Data System (ADS)

    Kukhtarev, N.; Kukhtareva, T.; Okafor, F.

    2010-08-01

    In this paper we describe photo-induced trapping/redistribution of silver nano-(micro) particles near the surface of photorefractive crystal LiNbO3:Fe. This type of optical trapping is due to combined forces of direct gradient-force trapping and asymmetric photorefractive forces of electro-phoresis and dielectro-phoresis. The silver nanoparticles were produced through extracellular biosynthesis on exposure to the fungus, Fusarium oxysporum (FO) and to the plant extracts. Pulsed and CW visible laser radiation lead to significant modification of nanoparticle clusters. This study indicates that extracellular biosynthesis can constitute a possible viable alternative method for the production of nanoparticles. In addition, the theoretical modeling of asymmetric photorefractive electric field grating has been presented and compared with the experimental results.

  2. Fiber optic illumination of a poly(dimethylsiloxane) sheath flow cuvette for diode laser induced fluorescence detection in capillary electrophoresis.

    PubMed

    Skinner, Cameron D

    2015-02-01

    A Tee configuration sheath flow cuvette with square cross-section channels has been produced in PDMS for CE detection. The output of a 1.4 W laser diode operating at 450 nm was focused onto the 300 μm core of a 370 μm od fiber optic whose end was inserted into one arm of the Tee for LIF. The optimal configuration had the fiber optic positioned 500 μm downstream from the intersection and the end of the 35 cm 50 μm id 365 μm od capillary just outside the intersection and in the leg of the Tee, resulting in a 90° configuration. Detection limits of 50 and 3 pM and linear calibrations of at least three orders of magnitude were obtained for Lucifer Yellow and fluorescein, respectively.

  3. 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.

  4. 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.

  5. 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. PMID:26384924

  6. 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.

  7. Operational specifications of the L.I.T.E.S. (Laser Illuminated Track Etch Scattering) dosemeter reader.

    SciTech Connect

    Moore, M. E.; Devine, R. T.; Gepford, H. J.; McKeever, R. J.; Hoffman, J. M.

    2004-01-01

    The Personnel Dosimetry Operations Team at the Los Alamos National Laboratory (LANL) has accepted the LITES dosimeter reader into its suite of radiation dose measurement instruments. The LITES instrument transmits coherent light from a HeNe laser through the pertinent track etch foil and a photodiode measures the amount of light scattered by the etched tracks. A small beam stop blocks the main laser light, while a lens refocuses the scattered light into the photodiode. Three stepper motors in the current LITES system are used to position a carousel that holds 36 track etch dosimeters. Preliminary work with the LITES system demonstrated the device had a linear response in counting foils subjected to exposures up to 50 mSv (5.0 rem). The United States Department of Energy requires that annual general employee dose not exceed 50 mSv (5.0 rem). On a regular basis, LANL uses the Autoscan 60 reader system (Thermo Electron Corp.) for counting track etch dosimeters. However, LANL uses a 15 hour etch process for CR39 dosimeters, and this produces more and larger track etch pits than the 6 hour etch used by many institutions. Therefore, LANL only uses the Autoscan 60 for measuring neutron dose equivalent up to exposure levels of about 3 mSv (300 mrem). The LITES system has a measured lower limit of detection (LLD) of about 0.6 mSv (60 mrem), and it has a correlation coefficient of R{sup 2} = 0.99 over an exposure range up to 500 mSv (50.0 rem). A series of blind studies were done using three methods: the Autoscan 60 system, manual counting by optical microscope, and the LITES instrument. A collection of track etch dosimeters of unknown NDE (neutron dose equivalent) were analyzed using the three methods, and the (PC) performance coefficient was calculated when the NDE became known. The Autoscan 60 and optical microscope methods had a combined PC = 0.171, and the LITES instrument had a PC = 0.194, where a PC less than or equal to 0.300 is considered satisfactory.

  8. 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. PMID:26367642

  9. 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. PMID:25103405

  10. 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.

  11. 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.

  12. A novel optical apparatus for the study of rolling contact wear/fatigue based on a high-speed camera and multiple-source laser illumination.

    PubMed

    Bodini, I; Sansoni, G; Lancini, M; Pasinetti, S; Docchio, F

    2016-08-01

    Rolling contact wear/fatigue tests on wheel/rail specimens are important to produce wheels and rails of new materials for improved lifetime and performance, which are able to operate in harsh environments and at high rolling speeds. This paper presents a novel non-invasive, all-optical system, based on a high-speed video camera and multiple laser illumination sources, which is able to continuously monitor the dynamics of the specimens used to test wheel and rail materials, in a laboratory test bench. 3D macro-topography and angular position of the specimen are simultaneously performed, together with the acquisition of surface micro-topography, at speeds up to 500 rpm, making use of a fast camera and image processing algorithms. Synthetic indexes for surface micro-topography classification are defined, the 3D macro-topography is measured with a standard uncertainty down to 0.019 mm, and the angular position is measured on a purposely developed analog encoder with a standard uncertainty of 2.9°. The very small camera exposure time enables to obtain blur-free images with excellent definition. The system will be described with the aid of end-cycle specimens, as well as of in-test specimens. PMID:27587125

  13. A novel optical apparatus for the study of rolling contact wear/fatigue based on a high-speed camera and multiple-source laser illumination.

    PubMed

    Bodini, I; Sansoni, G; Lancini, M; Pasinetti, S; Docchio, F

    2016-08-01

    Rolling contact wear/fatigue tests on wheel/rail specimens are important to produce wheels and rails of new materials for improved lifetime and performance, which are able to operate in harsh environments and at high rolling speeds. This paper presents a novel non-invasive, all-optical system, based on a high-speed video camera and multiple laser illumination sources, which is able to continuously monitor the dynamics of the specimens used to test wheel and rail materials, in a laboratory test bench. 3D macro-topography and angular position of the specimen are simultaneously performed, together with the acquisition of surface micro-topography, at speeds up to 500 rpm, making use of a fast camera and image processing algorithms. Synthetic indexes for surface micro-topography classification are defined, the 3D macro-topography is measured with a standard uncertainty down to 0.019 mm, and the angular position is measured on a purposely developed analog encoder with a standard uncertainty of 2.9°. The very small camera exposure time enables to obtain blur-free images with excellent definition. The system will be described with the aid of end-cycle specimens, as well as of in-test specimens.

  14. A novel optical apparatus for the study of rolling contact wear/fatigue based on a high-speed camera and multiple-source laser illumination

    NASA Astrophysics Data System (ADS)

    Bodini, I.; Sansoni, G.; Lancini, M.; Pasinetti, S.; Docchio, F.

    2016-08-01

    Rolling contact wear/fatigue tests on wheel/rail specimens are important to produce wheels and rails of new materials for improved lifetime and performance, which are able to operate in harsh environments and at high rolling speeds. This paper presents a novel non-invasive, all-optical system, based on a high-speed video camera and multiple laser illumination sources, which is able to continuously monitor the dynamics of the specimens used to test wheel and rail materials, in a laboratory test bench. 3D macro-topography and angular position of the specimen are simultaneously performed, together with the acquisition of surface micro-topography, at speeds up to 500 rpm, making use of a fast camera and image processing algorithms. Synthetic indexes for surface micro-topography classification are defined, the 3D macro-topography is measured with a standard uncertainty down to 0.019 mm, and the angular position is measured on a purposely developed analog encoder with a standard uncertainty of 2.9°. The very small camera exposure time enables to obtain blur-free images with excellent definition. The system will be described with the aid of end-cycle specimens, as well as of in-test specimens.

  15. 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.

  16. 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. PMID:27293192

  17. Hα Emission in Post-Common-Envelope Binaries: White Dwarf Illumination vs. Chromospheric Activity

    NASA Astrophysics Data System (ADS)

    Spiewak, Renée; Pomerantz, B.; Strelnitski, V.; Walker, G. E.; Krajci, T.

    2013-01-01

    We revisit and augment the narrow-band photometry of two post-common-envelope close binary systems, V471 Tau and DE CVn, composed of a white dwarf (WD) and a red dwarf (RD). The photometry was accomplished using the 24-inch telescope of the Maria Mitchell Observatory and the 0.35-m telescope of the Astrokolkhoz Observatory. The filters allowed us to separate the temporal behavior of the Hα emission and the adjacent continuum. The latter shows in both binaries the well-known double wave with maxima around phases 0.25 and 0.75 and with an amplitude of several percent, which has been ascribed to the ellipsoidal shape of the red dwarf. We confirm our previous, preliminary conclusion that the phase curves of Hα emission in these two stars are different: in DE CVn, it is similar to the two-peak curve of the continuum, whereas in V471 Tau it has only one maximum - at phase 0.5. We interpret this difference by the difference in the WD temperature, previously determined as 34,500 and 8,000 K, for V471 Tau and DE CVn respectively. We show that the sub-WD area of the RD in V471 Tau intercepts enough ionizing photons from the hot WD to produce the observed Hα luminosity, whereas the relatively cold WD in DE CVn lacks several orders of magnitude in UV luminosity to create the observed Hα luminosity, which therefore should be ascribed to the chromospheric activity of the RD. This project was supported by NSF/REU grant AST-0851892 and the Nantucket Maria Mitchell Association.

  18. Flexible structured illumination microscope with a programmable illumination array.

    PubMed

    Křížek, Pavel; Raška, Ivan; Hagen, Guy M

    2012-10-22

    Structured illumination microscopy (SIM) has grown into a family of methods which achieve optical sectioning, resolution beyond the Abbe limit, or a combination of both effects in optical microscopy. SIM techniques rely on illumination of a sample with patterns of light which must be shifted between each acquired image. The patterns are typically created with physical gratings or masks, and the final optically sectioned or high resolution image is obtained computationally after data acquisition. We used a flexible, high speed ferroelectric liquid crystal microdisplay for definition of the illumination pattern coupled with widefield detection. Focusing on optical sectioning, we developed a unique and highly accurate calibration approach which allowed us to determine a mathematical model describing the mapping of the illumination pattern from the microdisplay to the camera sensor. This is important for higher performance image processing methods such as scaled subtraction of the out of focus light, which require knowledge of the illumination pattern position in the acquired data. We evaluated the signal to noise ratio and the sectioning ability of the reconstructed images for several data processing methods and illumination patterns with a wide range of spatial frequencies. We present our results on a thin fluorescent layer sample and also on biological samples, where we achieved thinner optical sections than either confocal laser scanning or spinning disk microscopes. PMID:23187221

  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. 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.

  1. Active laser tweezers microrheometry of microbial biofilms

    NASA Astrophysics Data System (ADS)

    Osterman, N.; Slapar, V.; Boric, M.; Stopar, D.; Babič, D.; Poberaj, I.

    2010-08-01

    Microbial biofilms are present on biotic and abiotic surfaces and have a significant impact on many fields in industry, health care and technology. Thus, a better understanding of processes that lead to development of biofilms and their chemical and mechanical properties is needed. In the following paper we report the results of active laser tweezers microrheology study of optically inhomogeneous extracellular matrix secreted by Visbrio sp. bacteria. One particle and two particle active microrheology were used in experiments. Both methods exhibited high enough sensitivity to detect viscosity changes at early stages of bacterial growth. We also showed that both methods can be used in mature samples where optical inhomogeneity becomes significant.

  2. 29 CFR 1917.123 - Illumination. 9

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... CFR 126.15(1) and (n), and 33 CFR 154.570 sets out requirements for illumination at “designated... illuminated. Unless conditions described in the regulations of the United States Coast Guard (33 CFR 126.15(1) and (n), and 33 CFR 154.570) exist in the case of specific operations, illumination in active...

  3. 29 CFR 1917.123 - Illumination. 9

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... illuminated. Unless conditions described in the regulations of the United States Coast Guard (33 CFR 126.15(1) and (n), and 33 CFR 154.570) exist in the case of specific operations, illumination in active work... CFR 126.15(1) and (n), and 33 CFR 154.570 sets out requirements for illumination at...

  4. 29 CFR 1917.123 - Illumination. 9

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... illuminated. Unless conditions described in the regulations of the United States Coast Guard (33 CFR 126.15(1) and (n), and 33 CFR 154.570) exist in the case of specific operations, illumination in active work... CFR 126.15(1) and (n), and 33 CFR 154.570 sets out requirements for illumination at...

  5. 29 CFR 1917.123 - Illumination. 9

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... illuminated. Unless conditions described in the regulations of the United States Coast Guard (33 CFR 126.15(1) and (n), and 33 CFR 154.570) exist in the case of specific operations, illumination in active work... CFR 126.15(1) and (n), and 33 CFR 154.570 sets out requirements for illumination at...

  6. 29 CFR 1917.123 - Illumination. 9

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... illuminated. Unless conditions described in the regulations of the United States Coast Guard (33 CFR 126.15(1) and (n), and 33 CFR 154.570) exist in the case of specific operations, illumination in active work... CFR 126.15(1) and (n), and 33 CFR 154.570 sets out requirements for illumination at...

  7. Illumination influences working memory: an EEG study.

    PubMed

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

    2013-09-01

    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.

  8. Transport of biologically active material in laser cutting.

    PubMed

    Frenz, M; Mathezloic, F; Stoffel, M H; Zweig, A D; Romano, V; Weber, H P

    1988-01-01

    The transport of biologically active material during laser cutting with CO2 and Er lasers is demonstrated. This transport mechanism removes particles from the surface of gelatin, agar, and liver samples into the depth of the laser-formed craters. The transport phenomenon is explained by a contraction and condensation of enclosed hot water vapor. We show by cultivating transported bacteria in agar that biological particles can survive the shock of the transport. Determination of the numbers of active cells evidences a more pronounced activity of the cultivated bacteria after impact with an Er laser than with a CO2 laser.

  9. Illuminating Engineering Research Institute Annual Report 1967. A Review of Project Activities and a Roundup of IERI Research Interests.

    ERIC Educational Resources Information Center

    Illuminating Engineering Research Inst., New York, NY.

    Presented in this report are the Illuminating Engineering Research Institute's fundamental scientific concepts in a new frame of realism while relating them to an up-to-date accounting of the search for new basic knowledge. In addition to being an annual accounting, it is also intended to provide orientation. Its presented in dramatic and…

  10. Conformational dynamics of the active site loop of S-adenosylmethionine synthetase illuminated by site-directed spin labeling.

    PubMed

    Taylor, John C; Markham, George D

    2003-07-15

    S-adenosylmethionine synthetase (ATP: L-methionine S-adenosyltransferase, methionine adenosyltransferase, a.k.a. MAT) is one of numerous enzymes that have a flexible polypeptide loop that moves to gate access to the active site in a motion that is closely coupled to catalysis. Crystallographic studies of this tetrameric enzyme have shown that the loop is closed in the absence of bound substrates. However, the loop must open to allow substrate binding and a variety of data indicate that the loop is closed during the catalytic steps. Previous kinetic studies indicate that during turnover loop motion occurs on a time scale of 10(-2)s, ca. 10-fold faster than chemical transformations and turnover. Site-directed spin labeling has been used to introduce nitroxide groups at two positions in the loop to illuminate how the motion of the loop is affected by substrate binding. The two loop mutants constructed, G105C and D107C, retain wild type levels of MAT activity; attachment of a methanethiosulfonate spin label to convert the cysteine to the "R1" residue reduced the k(cat) only for the labeled D107R1 form (7-fold). The K(m) value for methionine increased 2- to 4-fold for the cysteine mutants and 2- to 7-fold for the labeled proteins, whereas the K(m) for ATP was changed by at most 2-fold. EPR spectra for both labeled proteins are nearly identical and show the presence of two major spin label environments with rotational diffusion rates differing by approximately 10-fold; the slower rate is ca. 4-fold faster than the estimated protein rotational rate. The spectra are not altered by addition of substrates or products. At both positions the less mobile conformation constitutes ca. 65% of the total species, indicating an equilibrium that only slightly favors one form, that in which the label is more immobilized. The equilibrium constant that relates the two forms is comparable to the equilibrium constant of 1.5 for a conformational change that was previously deduced from the

  11. Comparison of radiometric scaling laws and detailed wave-optics simulations for designing ground-based laser satellite-illumination and receiver systems

    NASA Astrophysics Data System (ADS)

    Bush, Keith A.

    2002-12-01

    Ground-based optical transmitter and receiver systems designed for active imaging, active tracking and laser ranging of satellites in Earth orbit are very sensitive to physical conditions limiting the radiometric returns for achieving these measurements. The initial design of these systems is often based on simple radiometric scaling laws that provide estimates of average radiometric returns and are derived from experimental data or from more complex theoretical calculations. While these laws are quite useful, it is often easy to lose sight of the initial assumptions made in their formulation, and hence, the limits of their accuracy for designing certain systems. The objective of this paper is to review some of the commonly used radiometric scaling laws for active systems and to establish guidelines for their use based on comparisons of their predictions with results from detailed wave-optics simulations for different system design requirements and physical conditions. The combined effects of laser and transmitter beam parameters, wave-front aberrations, atmospheric turbulence, and satellite optical cross-section are considered.

  12. 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.

  13. 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...

  14. Light intensity independence during dynamic laser speckle analysis

    NASA Astrophysics Data System (ADS)

    Reis, Renan Oliveira; Rabal, Hector J.; Braga, Roberto A.

    2016-05-01

    We explore some different normalizations of current dynamic laser speckle activity measures searching for their performance with respect to the illumination inhomogeneity of the samples. Inertia Moment and Average Value of Differences of the co-occurrence matrix are compared using a paint-drying case study on a uniform sample where attenuation in a portion of the illuminated area is introduced using a neutral density filter. In this way, all environmental conditions being equal but non-uniform illumination permits the comparison on a better approximation to objectivity. The results presented show that it is possible to mitigate the effects of the illumination in the activities measured by the dynamic laser speckle.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Optodynamic Phenomena During Laser-Activated Irrigation Within Root Canals

    NASA Astrophysics Data System (ADS)

    Lukač, Nejc; Gregorčič, Peter; Jezeršek, Matija

    2016-07-01

    Laser-activated irrigation is a powerful endodontic treatment for smear layer, bacteria, and debris removal from the root canal. In this study, we use shadow photography and the laser-beam-transmission probe to examine the dynamics of laser-induced vapor bubbles inside a root canal model and compare ultrasonic needle irrigation to the laser method. Results confirm important phenomenological differences in the two endodontic methods with the laser method resulting in much deeper irrigation. Observations of simulated debris particles show liquid vorticity effects which in our opinion represents the major cleaning mechanism.

  20. Spatio-temporal patterns of photosystem II activity and plasma-membrane proton flows in Chara corallina cells exposed to overall and local illumination.

    PubMed

    Bulychev, Alexander; Vredenberg, Wim

    2003-11-01

    Pulse-amplitude modulated microfluorometry and an extracellular pH microprobe were used to examine light-induced spatial heterogeneity of photosynthetic and H(+)-transporting activities in cells of Chara corallina Klein ex Willd. Subcellular domains featuring different PSII photochemical activities were found to conform to alternate alkaline and acid zones produced near the cell surface, with peaks of PSII activity correlating with the position of acid zones. Buffers eliminated pH variations near the cell surface but did not destroy the variations in PSII photochemical yield (deltaF/Fm'). When a dark-adapted cell was exposed to actinic light, the PSII effective yield decreased within 5-15 min in the alkaline regions but rose after the initial decline in the acid regions. The light-induced decrease in deltaF/Fm' in the alkaline regions occurred prior to or synchronously with the steep rise in local pH. The kinetics of deltaF/Fm', Fm', and F observed in alkaline regions under overall illumination of Chara cells were replaced by those typical of acid regions, when the illumination area size was restricted to 1.5-2 mm. The data show that photoinduced patterns in photosynthetic activity are not predetermined by the particular structural organization of alkaline and acid cell regions but are subject to dynamic changes.

  1. Active hyperspectral imaging using a quantum cascade laser (QCL) array and digital-pixel focal plane array (DFPA) camera.

    PubMed

    Goyal, Anish; Myers, Travis; Wang, Christine A; Kelly, Michael; Tyrrell, Brian; Gokden, B; Sanchez, Antonio; Turner, George; Capasso, Federico

    2014-06-16

    We demonstrate active hyperspectral imaging using a quantum-cascade laser (QCL) array as the illumination source and a digital-pixel focal-plane-array (DFPA) camera as the receiver. The multi-wavelength QCL array used in this work comprises 15 individually addressable QCLs in which the beams from all lasers are spatially overlapped using wavelength beam combining (WBC). The DFPA camera was configured to integrate the laser light reflected from the sample and to perform on-chip subtraction of the passive thermal background. A 27-frame hyperspectral image was acquired of a liquid contaminant on a diffuse gold surface at a range of 5 meters. The measured spectral reflectance closely matches the calculated reflectance. Furthermore, the high-speed capabilities of the system were demonstrated by capturing differential reflectance images of sand and KClO3 particles that were moving at speeds of up to 10 m/s.

  2. 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.

  3. 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.

  4. Laser based on dye-activated silica gel

    SciTech Connect

    Altshuler, G.B.; Bakhanov, V.A.; Dulneva, E.G.; Erofeev, A.V.; Mazurin, O.V.; Roskova, G.P.; Tsekhomskaya, T.S.

    1987-06-01

    Silica gel activated by a dye is used as a new laser medium. The lasin characteristics of rhodamine 6G in silica gel are reported. An important characteristic of the dye laser is its long service life, which is determined by the photostability of the dye in silic gel.(AIP)

  5. Active-region designs in quantum cascade lasers

    SciTech Connect

    Zasavitskii, I I

    2012-10-31

    This paper analyses the development of active-region designs in quantum cascade lasers. Active-region designs have been demonstrated to date that employ various radiative transitions (vertical, diagonal, interminiband and interband). The lower laser level is depopulated through nonradiative transitions, such as one- or two-phonon (and even three-phonon) relaxation or bound state {yields} continuum transitions. Advances in active-region designs and energy diagram optimisation in the past few years have led to significant improvements in important characteristics of quantum cascade lasers, such as their output power, emission bandwidth, characteristic temperature and efficiency. (invited paper)

  6. The effect of night illumination, red and infrared light, on locomotor activity, behaviour and melatonin of Senegalese sole (Solea senegalensis) broodstock.

    PubMed

    Carazo, I; Norambuena, F; Oliveira, C; Sánchez-Vázquez, F J; Duncan, N J

    2013-06-13

    The present study aimed to determine a non-invasive nocturnal lighting system for the behavioural observation of a highly light sensitive species, Senegalese sole (Solea senegalensis). Locomotor activity, four types of behaviour and plasma melatonin were analysed in groups of 12 adult Senegalese sole (Solea senegalensis) reared in captivity and held under four night illumination treatments: total darkness (control), high 50lux intensity red light (group RH), low 5lux intensity red light (group RL) and infrared light (group IR). All groups experienced the same conditions during the day (lights on from 07:00 to 19:00) with white lighting of 125lux. Clarity of video images taken at night for the observation of fish behaviour were ranked as follows: group RH>RL>IR>control. All treatments presented a daily rhythm in locomotor activity with high activity from 14:00 to 18:00 and low activity from 21:00 to 12:00. The sole exposed to the high intensity red light at night appeared to be disturbed as during the low nocturnal locomotor activity period group RH presented higher activity and significantly higher nocturnal behaviour related to escape or fear than was observed in the other groups. The groups control, RL and IR exhibited similar levels of nocturnal locomotor activity and nocturnal behaviour related to escape or fear. Plasma melatonin, at mid-dark was not significantly different between the control and groups RL and IR, while melatonin was significantly lower in group RH compared to the control. The authors recommended low intensity red night illumination for the non-invasive study of nocturnal behaviour of Senegalese sole adults.

  7. 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

    2014-11-01

    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.

  8. 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

    2014-11-01

    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. PMID:25310717

  9. Frequency Conversion Activation on the Mercury Laser

    SciTech Connect

    Bayramian, A J; Beach, R J; Bibeau, C; Campbell, R; Ebbers, C A; Freitas, B L; Kent, R; Van Lue, D; Liao, Z; Landron, T; Payne, S A; Schaffers, K I; Sutton, S; Fei, Y; Chai, B

    2004-09-24

    High efficiency frequency conversion while operating at average power is critical for the Mercury laser. We will demonstrate average power frequency conversion of face-cooled DKDP and YCOB crystals using a sapphire heat spreader approach.

  10. High-energy laser activities at MBDA Germany

    NASA Astrophysics Data System (ADS)

    Mohring, Bernd; Dietrich, Stephan; Tassini, Leonardo; Protz, Rudolf; Geidek, Franz; Zoz, Jürgen

    2013-05-01

    At MBDA Germany a concept for a high-energy laser weapon system is investigated, which is based on existing industrial laser sources. Due to the enormous progress in the field of high-power fiber lasers, commercial industrial fiber lasers are now available delivering a nearly-diffraction limited beam quality with power levels of up to 10 kW. By using a geometric beam coupling scheme, a number of individual high-power fiber laser beams are combined together using one common beam director telescope. A total laser beam power of more than 100 kW can be achieved, which is sufficient for an operational laser weapon system. The individual beams from the different lasers are steered by servo-loops using fast tip-tilt mirrors. This principle enables the concentration of the total laser beam power at one common focal point on a distant target, also allowing fine tracking of target movements and first-order compensation of turbulence effects on laser beam propagation. The proposed beam combination concept was demonstrated by using different experimental set-ups. A number of experiments were performed successfully to investigate laser beam target interaction and target fine tracking, also at large distances and at moving targets. Content and results of these investigations are reported, which demonstrate the complete engagement sequence for a C-RAM scenario. This includes subsequent steps of target acquisition by radar and IR optics, followed by large angle coarse tracking, active fine tracking and destruction of the target by the laser system. This successful implementation of geometric beam combining is an important step for the realization of a laser weapon system in the near future.

  11. 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.

  12. Illuminance of neonatal units.

    PubMed

    Robinson, J; Moseley, M J; Fielder, A R

    1990-07-01

    We have measured the illuminance (brightness) of seven neonatal units during both the day and the night. When the units were lit solely by fluorescent tubes the mean illuminance was 348 lux (range 192-690). During the day the mean illuminance was 470 lux (range 236-905). The high dependency regions in four of the seven units were significantly brighter than the corresponding low dependency nurseries at all times. In two of these units there is a policy of reducing the amount of artificial light in the low dependency areas at night, and in these the normal mean illuminance was 50 lux. We have measured the general levels of illumination to which a neonate might be exposed; the ocular exposure to light of a neonate depends, however, on both physical and biological factors and more research is required before an accurate estimate can be made.

  13. 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.

  14. 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.

  15. 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

  16. Effects of forward and backward transitions in light intensities in tau-illuminance curves of the rat motor activity rhythm under constant dim light.

    PubMed

    Cambras, Trinitat; Díez-Noguera, Antoni

    2012-07-01

    Circadian rhythms are strongly influenced by light intensity, the effects of which may persist beyond the duration of light exposure (aftereffects). Here, the authors constructed period-illuminance curves for the motor activity circadian rhythm of male and female rats by recording the effects of a series of small upward and downward steps in light intensity (illuminance ranging between .01 lux of dim red light and 1 lux of white light) on their activity. In all cases, stepwise changes were made in five logarithmic steps (irradiance: dim red light: .692 µW/cm(2) and white light: .006, .016, .044, .12, and .315 µW/cm(2), corresponding, respectively, to .02, .05, .14, .13, and 1 lux measured at cage level), with changes in intensity every 2 wks. One group of rats (DLD) started in dim red light, moved up to 1 lux white light, and then back down to the original light intensity. Another group (LDL) started at 1 lux, moved down to .01 lux, and then back up to the original intensity. Motor activity data were recorded throughout the experiment and tau values, the percentage of variance explained by the rhythm, and the mean motor activity for each stage and group were calculated. The results show differences in the dynamics of tau values between the DLD and LDL groups and between males and females. In the LDL group, the tau values of both males and females were dependent on light intensity, and were similar for the forward and backward transitions. In other words, no aftereffects were found, and no differences were detected between males and females. In the DLD group, however, differences were found between males and females. Males had a tau value of 24 h 20 min under dim red light, 25 h 40 min under 1 lux, and 24 h 50 min on return to dim red light. It is noticeable that the tau values of the backward branch of the illuminance curve contradicted classical predictions, since at .38 and .14 lux the tau values were shorter than those found under the same intensities after

  17. Selective plane illumination microscopy on a chip.

    PubMed

    Paiè, Petra; Bragheri, Francesca; Bassi, Andrea; Osellame, Roberto

    2016-04-26

    Selective plane illumination microscopy can image biological samples at a high spatiotemporal resolution. Complex sample preparation and system alignment normally limit the throughput of the method. Using femtosecond laser micromachining, we created an integrated optofluidic device that allows obtaining continuous flow imaging, three-dimensional reconstruction and high-throughput analysis of large multicellular spheroids at a subcellular resolution.

  18. Research on long-range laser active imaging system applied in adverse weather conditions

    NASA Astrophysics Data System (ADS)

    Gai, Zhi-gang; Liu, Meng-de; Yang, Li; Kabanov, V. V.; Shi, Lei; Zhao, Jie; Chu, Shi-bo; Yang, Jun-xian; Zhou, Yang

    2013-09-01

    A low-light level night vision device or thermal infrared imager belonging to passive imaging system is generally used in daily target detection and identification. But in adverse weather conditions of dark of night, poor atmospheric transmission characteristics or strong backscattering (fog, dust, rain, snow, etc.), even the most sensitive low-light level night vision could not provide enough image resolution for detecting and identifying targets, and the thermal infrared imager is also limited by low temperature contrast. A long-range laser active imaging system, in combination with high-power semiconductor pulsed lasers with collimation technology, receiving objective lens of large diameter, long focal length and narrow viewing angle, high-gain image intensifier CCD (ICCD) camera and range-gated synchronization control technology, is developed for long distance target detection and high resolution imaging in adverse weather conditions. The system composition and operating principle are introduced. The extremely powerful and efficient illuminators with collimation technology are able to deliver uniform beams, which are essential for illuminating targets at a distance and generating high-quality images. The particular receiving objective lens, ICCD camera and range-gated synchronization control technology could reduce strong backscattering signal and improve imaging signal-to-noise ratio. The laboratory and outfield experiments have been done to validate imaging effect and imaging quality. The results show that the minimum resolution is about 3-5cm, 10cm, and greater than 20 cm for target far from 1100m, 4700m, and 6700m respectively in dark of night. Furthermore, the minimum resolution could reach to 10cm and 20cm for target far from 2500m and 4800m respectively and the image is too blurred to accurately identify the target when observing the target far from 7200m in rainy condition.

  19. 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.

  20. 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 ...

  1. 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.

  2. 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, ...

  3. 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)

  4. Envelope evolution of a laser pulse in an active medium

    SciTech Connect

    Fisher, D.L.; Tajima, T.; Downer, M.C.; Siders, C.W.

    1994-11-01

    The authors show that the envelope velocity, v{sub env}, of a short laser pulse can, via propagation in an active medium, be made less than, equal to, or even greater than c, the vacuum phase velocity of light. Simulation results, based on moving frame propagation equations coupling the laser pulse, active medium and plasma, are presented, as well as equations that determines the design value of super- and sub-luminous v{sub env}. In this simulation the laser pulse evolves in time in a moving frame as opposed to their earlier work where the profile was fixed. The elimination of phase slippage and pump depletion effects in the laser wakefield accelerator is discussed as a particular application. Finally they discuss media properties necessary for an experimental realization of this technique.

  5. 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).

  6. Design of a back-illuminated, crystallographically etched, silicon-on-sapphire avalanche photodiode with monolithically integrated microlens, for dual-mode passive & active imaging arrays

    NASA Astrophysics Data System (ADS)

    Stern, Alvin G.; Cole, Daniel C.

    2008-12-01

    There is a growing need in space and environmental research applications for dual-mode, passive and active 2D and 3D ladar imaging methods. To fill this need, an advanced back-illuminated avalanche photodiode (APD) design is presented based on crystallographically etched (100) epitaxial silicon on R-plane sapphire (SOS), enabling single photon sensitive, solid-state focal plane arrays (FPAs) with wide dynamic range, supporting passive and active imaging capability in a single FPA. When (100) silicon is properly etched with KOH:IPA:H2O solution through a thermally grown oxide mask, square based pyramidal frustum or mesa arrays result with the four mesa sidewalls of the APD formed by (111) silicon planes that intersect the (100) planes at a crystallographic angle, Φc = 54.7°. The APD device is fabricated in the mesa using conventional silicon processing technology. Detectors are back-illuminated through light focusing microlenses fabricated in the thinned, AR-coated sapphire substrate. The APDs share a common, front-side anode contact, made locally at the base of each device mesa. A low resistance (Al) or (Cu) metal anode grid fills the space between pixels and also inhibits optical cross-talk. SOS-APD arrays are indium bump-bonded to CMOS readout ICs to produce hybrid FPAs. The quantum efficiency for the square 27 µm pixels exceeds 50% for 250 nm < λ < 400 nm and exceeds 80% for 400 nm < λ < 700 nm. The sapphire microlenses compensate detector quantum efficiency loss resulting from the mesa geometry and yield 100% sensitive-area-fill-factor arrays, limited in size only by the wafer diameter.

  7. Lasers. Technology Learning Activity. Teacher Edition. Technology Education Series.

    ERIC Educational Resources Information Center

    Oklahoma State Dept. of Vocational and Technical Education, Stillwater. Curriculum and Instructional Materials Center.

    This document contains the materials required for presenting an 8-day competency-based technology learning activity (TLA) designed to introduce students in grades 6-10 to advances and career opportunities in the field of laser technology. The guide uses a series of hands-on exploratory experiences into which activities to help students develop…

  8. 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.

  9. 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.

  10. 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…

  11. Field-Testing of an Active Laser Tracking System

    NASA Astrophysics Data System (ADS)

    Markov, V.; Khiznyak, A.; Woll, D.; Liu, S.

    Comprehensive space surveillance demands a more accurate technique in tracking multi-dimensional state vector (3D coordinate, velocity, vibration, etc.) of the space objects. RF radiometric techniques typically can not provide the needed accuracy, while passive optical (and laser) tracking systems can provide distance to the object and its angular position, but not a direct reading of velocity, the parameter of primary importance for space object tracking and characterization. Addressing this problem with active optical tracking techniques is challenging because of the great distances involved, the high velocity of the satellites, and the optical aberrations induced by the atmosphere. We have proposed a phase conjugation based laser tracking concept, and accomplished the first version of design and engineering of a prototype for an Active Laser Tracking System (ALTS). In its current state the ALTS is capable to demonstrate the very basics operational principles of the proposed active tracking technique. We then performed a number of experiments to prove operational capabilities of this prototype both at MetroLaser's lab environment and at Edwards AFB Test Range. In its current architecture the ALTS is comprised of two laser cavities, Master and Slave that are coupled through a Phase Conjugate Mirror (PCM) formed in a non-linear medium (NLM) set at Master laser cavity. By pumping NLM and forming PCM, Master laser establishes the cavities coupling mode and injects the photons in the slave cavity. It is essential that the specific features of the PCM not only serve to couple ALTS cavities, but also serves to compensate optical aberrations of the ALTS (gain media and optical elements of the laser resonator). Due to its ability to compensate optical aberrations, phase conjugate resonators are capable of sustaining oscillation with a remote target as an output coupler. The entire system comprises of several modules, including a laser, emitting/receiving telescope, gimbal

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. High-average-power actively-mode-locked Tm3+ fiber lasers

    NASA Astrophysics Data System (ADS)

    Eckerle, Michael; Kieleck, Christelle; Hübner, Philipp; Świderski, Jacek; Jackson, Stuart D.; Mazé, Gwenael; Eichhorn, Marc

    2012-02-01

    Fiber lasers emitting in the 2 μm wavelength range doped with thulium ions can be used as highly efficient pump sources for nonlinear converters to generate mid-infrared radiation. For spectroscopic purposes, illumination and countermeasures, a broad mid-infrared emission spectrum is advantageous. This can be reached by supercontinuum generation in fibers, e.g. fluoride fibers, which up to now has, however, only been presented with either low average power, complex Raman-shifted 1.55 μm pump sources or multi-stage amplifier pump schemes. Here we present recent results of a new actively-mode-locked single-oscillator scheme that can provide the high-repetition rate sub-ns pump pulses needed for pumping supercontinuum generators. A thulium-doped silica fiber laser is presented that provides > 11 W of average power CW-mode-locked pulses at 38 MHz repetition rate at ~ 38 ps pulse width. Upgrading the setup to allow Q-switched mode-locked operation yields mode-locked 40 MHz pulses arranged in 60 kHz bunched Q-switch envelopes and thus increases further the available peak power. In this Q-switched mode-locked regime over 5 W of average power has been achieved.

  17. 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. PMID:27584914

  18. 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

  19. 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

  20. Activation mechanism of AMPA receptors illuminated by complexes with cone snail toxin, allosteric potentiator and orthosteric agonists

    PubMed Central

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

    2014-01-01

    AMPA-sensitive glutamate receptors are crucial to the structural and dynamical 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. Here we determine 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 – 4.1 Å resolution. We show how the toxin acts like a ‘straight jacket’ 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 iris-like 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. PMID:25103405

  1. Active annular-beam laser autocollimator system.

    PubMed

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

    1975-08-01

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

  2. 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)

  3. 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.

  4. 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.

  5. 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.

  6. Practical structured illumination microscopy.

    PubMed

    Rego, E Hesper; Shao, Lin

    2015-01-01

    Structured illumination microscopy (SIM) is a method that can double the spatial resolution of wide-field fluorescence microscopy in three dimensions by using spatially structured illumination light. In this chapter, we introduce the basic principles of SIM and describe in detail several different implementations based on either a diffraction grating or liquid crystal spatial light modulators. We also describe nonlinear SIM, a method that in theory can achieve unlimited resolution. In addition, we discuss a number of key points important for high-resolution imaging. PMID:25391800

  7. Tailored reflectors for illumination.

    PubMed

    Jenkins, D; Winston, R

    1996-04-01

    We report on tailored reflector design methods that allow the placement of general illumination patterns onto a target plane. The use of a new integral design method based on the edge-ray principle of nonimaging optics gives much more compact reflector shapes by eliminating the need for a gap between the source and the reflector profile. In addition, the reflectivity of the reflector is incorporated as a design parameter. We show the performance of design for constant irradiance on a distant plane, and we show how a leading-edge-ray method may be used to achieve general illumination patterns on nearby targets. PMID:21085288

  8. Laser-heating-based active optics for synchrotron radiation applications.

    PubMed

    Yang, Fugui; Li, Ming; Gao, Lidan; Sheng, Weifan; Liu, Peng; Zhang, Xiaowei

    2016-06-15

    Active optics has attracted considerable interest from researchers in synchrotron radiation facilities because of its capacity for x-ray wavefront correction. Here, we report a novel and efficient technique for correcting or modulating a mirror surface profile based on laser-heating-induced thermal expansion. An experimental study of the characteristics of the surface thermal deformation response indicates that the power of a milliwatt laser yields a bump height as low as the subnanometer scale and that the variation of the spot size modulates the response function width effectively. In addition, the capacity of the laser-heating technique for free-form surface modulation is demonstrated via a one-dimensional surface correction experiment. The developed method is a promising new approach toward effective x-ray active optics coupled with at-wavelength metrology techniques.

  9. Stories from Laser Camp: outreach activities for kids

    NASA Astrophysics Data System (ADS)

    Tourangeau, Derek; Simoneau, James

    2010-08-01

    Often in the ever-expanding community of Optics and Photonics, what we do remains a mystery to the outside world. The technology created by our community permeates the lives of every citizen yet is taken for granted due to unfamiliarity. At Three Rivers Community College (TRCC), we have taken steps to rectify that situation. The college's Laser and Fiber Optic Technology program (LFOT) and the TRCC student chapter of SPIE run many outreach activities, the most successful of which is Laser Camp. This paper will present a comprehensive overview of Laser Camp from the students' aspect with testimonials, discussion of the optics themed activities and provide a view of the SPIE members' journey.

  10. Laser-heating-based active optics for synchrotron radiation applications.

    PubMed

    Yang, Fugui; Li, Ming; Gao, Lidan; Sheng, Weifan; Liu, Peng; Zhang, Xiaowei

    2016-06-15

    Active optics has attracted considerable interest from researchers in synchrotron radiation facilities because of its capacity for x-ray wavefront correction. Here, we report a novel and efficient technique for correcting or modulating a mirror surface profile based on laser-heating-induced thermal expansion. An experimental study of the characteristics of the surface thermal deformation response indicates that the power of a milliwatt laser yields a bump height as low as the subnanometer scale and that the variation of the spot size modulates the response function width effectively. In addition, the capacity of the laser-heating technique for free-form surface modulation is demonstrated via a one-dimensional surface correction experiment. The developed method is a promising new approach toward effective x-ray active optics coupled with at-wavelength metrology techniques. PMID:27304296

  11. 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.

  12. Dopamine and Full-Field Illumination Activate D1 and D2–D5-Type Receptors in Adult Rat Retinal Ganglion Cells

    PubMed Central

    Ogata, Genki; Stradleigh, Tyler W.; Partida, Gloria J.; Ishida, Andrew T.

    2012-01-01

    Dopamine can regulate signal generation and transmission by activating multiple receptors and signaling cascades, especially in striatum, hippocampus, and cerebral cortex. Dopamine modulates an even larger variety of cellular properties in retina, yet has been reported to do so by only D1 receptor-driven cyclic adenosine monophosphate (cAMP) increases or D2 receptor-driven cAMP decreases. Here, we test the possibility that dopamine operates differently on retinal ganglion cells, because the ganglion cell layer binds D1 and D2 receptor ligands, and displays changes in signaling components other than cAMP under illumination that should release dopamine. In adult rat retinal ganglion cells, based on patch-clamp recordings, Ca2+ imaging, and immunohistochemistry, we find that 1) spike firing is inhibited by dopamine and SKF 83959 (an agonist that does not activate homomeric D1 receptors or alter cAMP levels in other systems); 2) D1 and D2 receptor antagonists (SCH 23390, eticlopride, raclopride) counteract these effects; 3) these antagonists also block light-induced rises in cAMP, light-induced activation of Ca2+/calmodulin-dependent protein kinase II, and dopamine-induced Ca2+ influx; and 4) the Ca2+ rise is markedly reduced by removing extracellular Ca2+ and by an IP3 receptor antagonist (2-APB). These results provide the first evidence that dopamine activates a receptor in adult mammalian retinal neurons that is distinct from classical D1 and D2 receptors, and that dopamine can activate mechanisms in addition to cAMP and cAMP-dependent protein kinase to modulate retinal ganglion cell excitability. PMID:22678972

  13. 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)

  14. 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.

  15. A study of the feasibility and performance of an active/passive imager using silicon focal plane arrays and incoherent continuous wave laser diodes

    NASA Astrophysics Data System (ADS)

    Vollmerhausen, Richard H.

    This dissertation describes an active/passive imager (API) that provides reliable, nighttime, target acquisition in a man-portable package with effective visual range of about 4 kilometers. The reflective imagery is easier to interpret than currently used thermal imagery. Also, in the active mode, the API provides performance equivalent to the big-aperture, thermal systems used on weapons platforms like tanks and attack helicopters. This dissertation describes the research needed to demonstrate both the feasibility and utility of the API. Part of the research describes implementation of a silicon focal plane array (SFPA) capable of both active and passive imaging. The passive imaging mode exceeds the nighttime performance of currently fielded, man-portable sensors. Further, when scene illumination is insufficient for passive imaging, the low dark current of SFPA makes it possible to use continuous wave laser diodes (CWLD) to add an active imaging mode. CWLD have advantages of size, efficiency, and improved eye safety when compared to high peak-power diodes. Because of the improved eye safety, the API provides user-demanded features like video output and extended range gates in the active as well as passive imaging modes. Like any other night vision device, the API depends on natural illumination of the scene for passive operation. Although it has been known for decades that "starlight" illumination is actually from diffuse airglow emissions, the research described in this dissertation provides the first estimates of the global and temporal variation of ground illumination due to airglow. A third related element of the current research establishes the impact of atmospheric aerosols on API performance. We know from day experience that atmospheric scattering of sunlight into the imager line-of-sight can blind the imager and drastically degrade performance. Atmospheric scattering of sunlight is extensively covered in the literature. However, previous literature did not

  16. Illumination optimization for 65nm technology node

    NASA Astrophysics Data System (ADS)

    Wang, Ching-Heng; Liu, Qingwei; Zhang, Liguo; Hung, Chi-Yuan

    2006-10-01

    The most important task of the microlithography process is to make the manufacturable process latitude/window, including dose latitude and Depth of Focus, as wide as possible. Thus, to perform a thorough source optimization during process development is becoming more critical as moving to high NA technology nodes. Furthermore, Optical proximity correction (OPC) are always used to provide a common process window for structures that would, otherwise, have no overlapping windows. But as the critical dimension of the IC design shrinks dramatically, the flexibility for applying OPC also decreases. So a robust microlithography process should also be OPC-friendly. This paper demonstrates our work on the illumination optimization during the process development. The Calibre ILO (Illumination Optimization) tool was used to perform the illumination optimization and provided plots of DOF vs. various parametric illumination settings. This was used to screen the various illumination settings for the one with optimum process margins. The resulting illumination conditions were then implemented and analyzed at a real wafer level on our 90/65nm critical layers, such as Active, Poly, Contact and Metal. In conclusion, based on these results, a summary is provided highlighting how OPC can get benefit from proper illumination optimization.

  17. Development of a compact vertical-cavity surface-emitting laser end-pumped actively Q-switched laser for laser-induced breakdown spectroscopy.

    PubMed

    Li, Shuo; Liu, Lei; Chen, Rongzhang; Nelsen, Bryan; Huang, Xi; Lu, Yongfeng; Chen, Kevin

    2016-03-01

    This paper reports the development of a compact and portable actively Q-switched Nd:YAG laser and its applications in laser-induced breakdown spectroscopy (LIBS). The laser was end-pumped by a vertical-cavity surface-emitting laser (VCSEL). The cavity lases at a wavelength of 1064 nm and produced pulses of 16 ns with a maximum pulse energy of 12.9 mJ. The laser exhibits a reliable performance in terms of pulse-to-pulse stability and timing jitter. The LIBS experiments were carried out using this laser on NIST standard alloy samples. Shot-to-shot LIBS signal stability, crater profile, time evolution of emission spectra, plasma electron density and temperature, and limits of detection were studied and reported in this paper. The test results demonstrate that the VCSEL-pumped solid-state laser is an effective and compact laser tool for laser remote sensing applications. PMID:27036765

  18. Development of a compact vertical-cavity surface-emitting laser end-pumped actively Q-switched laser for laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Shuo; Liu, Lei; Chen, Rongzhang; Nelsen, Bryan; Huang, Xi; Lu, Yongfeng; Chen, Kevin

    2016-03-01

    This paper reports the development of a compact and portable actively Q-switched Nd:YAG laser and its applications in laser-induced breakdown spectroscopy (LIBS). The laser was end-pumped by a vertical-cavity surface-emitting laser (VCSEL). The cavity lases at a wavelength of 1064 nm and produced pulses of 16 ns with a maximum pulse energy of 12.9 mJ. The laser exhibits a reliable performance in terms of pulse-to-pulse stability and timing jitter. The LIBS experiments were carried out using this laser on NIST standard alloy samples. Shot-to-shot LIBS signal stability, crater profile, time evolution of emission spectra, plasma electron density and temperature, and limits of detection were studied and reported in this paper. The test results demonstrate that the VCSEL-pumped solid-state laser is an effective and compact laser tool for laser remote sensing applications.

  19. Predicting Ground Illuminance

    NASA Astrophysics Data System (ADS)

    Lesniak, Michael V.; Tregoning, Brett D.; Hitchens, Alexandra E.

    2015-01-01

    Our Sun outputs 3.85 x 1026 W of radiation, of which roughly 37% is in the visible band. It is directly responsible for nearly all natural illuminance experienced on Earth's surface, either in the form of direct/refracted sunlight or in reflected light bouncing off the surfaces and/or atmospheres of our Moon and the visible planets. Ground illuminance, defined as the amount of visible light intercepting a unit area of surface (from all incident angles), varies over 7 orders of magnitude from day to night. It is highly dependent on well-modeled factors such as the relative positions of the Sun, Earth, and Moon. It is also dependent on less predictable factors such as local atmospheric conditions and weather.Several models have been proposed to predict ground illuminance, including Brown (1952) and Shapiro (1982, 1987). The Brown model is a set of empirical data collected from observation points around the world that has been reduced to a smooth fit of illuminance against a single variable, solar altitude. It provides limited applicability to the Moon and for cloudy conditions via multiplicative reduction factors. The Shapiro model is a theoretical model that treats the atmosphere as a three layer system of light reflectance and transmittance. It has different sets of reflectance and transmittance coefficients for various cloud types.In this paper we compare the models' predictions to ground illuminance data from an observing run at the White Sands missile range (data was obtained from the United Kingdom's Meteorology Office). Continuous illuminance readings were recorded under various cloud conditions, during both daytime and nighttime hours. We find that under clear skies, the Shapiro model tends to better fit the observations during daytime hours with typical discrepancies under 10%. Under cloudy skies, both models tend to poorly predict ground illuminance. However, the Shapiro model, with typical average daytime discrepancies of 25% or less in many cases

  20. Dual-wavelength polymer laser based on an active/inactive/active sandwich-like structure

    NASA Astrophysics Data System (ADS)

    Zhai, Tianrui; Wu, Xiaofeng; Wang, Meng; Tong, Fei; Li, Songtao; Ma, Yanbin; Deng, Jinxiang; Zhang, Xinping

    2016-09-01

    Dual-wavelength laser emission is achieved by using an active/inactive/active sandwich-like structure, which can be conveniently fabricated using spin coating technique. Poly [(9, 9-dioctylfluorenyl-2, 7-diyl)-alt-co-(1, 4-benzo-(2, 1', 3) -thiadiazole)] and polyvinyl alcohol are employed as the active and the inactive materials, respectively. Two laser wavelengths are simultaneously observed, which are attributed to the difference of the surrounding refractive index of two active waveguides in the sandwich-like structure. Each wavelength is controlled by the respective waveguide structure, meaning that multi-wavelength laser can be designed by stacking the active/inactive layer pair. These results provide more flexibility to design compact laser sources.

  1. Quantitative phase imaging with programmable illumination

    NASA Astrophysics Data System (ADS)

    Kim, Taewoo; Edwards, Chris; Goddard, Lynford L.; Popescu, Gabriel

    2015-03-01

    Even with the recent rapid advances in the field of microscopy, non-laser light sources used for light microscopy have not been developing significantly. Most current optical microscopy systems use halogen bulbs as their light sources to provide a white-light illumination. Due to the confined shapes and finite filament size of the bulbs, little room is available for modification in the light source, which prevents further advances in microscopy. By contrast, commercial projectors provide a high power output that is comparable to the halogen lamps while allowing for great flexibility in patterning the illumination. In addition to their high brightness, the illumination can be patterned to have arbitrary spatial and spectral distributions. Therefore, commercial projectors can be adopted as a flexible light source to an optical microscope by careful alignment to the existing optical path. In this study, we employed a commercial projector source to a quantitative phase imaging system called spatial light interference microscopy (SLIM), which is an outside module for an existing phase contrast (PC) microscope. By replacing the ring illumination of PC with a ring-shaped pattern projected onto the condenser plane, we were able to recover the same result as the original SLIM. Furthermore, the ring illumination is replaced with multiple dots aligned along the same ring to minimize the overlap between the scattered and unscattered fields. This new method minimizes the halo artifact of the imaging system, which allows for a halo-free high-resolution quantitative phase microscopy system.

  2. Frequency signature of water activity by biospeckle laser

    NASA Astrophysics Data System (ADS)

    Cardoso, Rafael Rodrigues; Costa, Anderson Gomide; Nobre, Cassia Marques Batista; Braga, Roberto Alves

    2011-04-01

    Biospeckle laser technique has become an important tool to investigate biological activity in several areas of science. However, due to the complexity of biological materials it is necessary to develop research processes that ensure greater efficiency in isolating areas of different activities in the same material using the biospeckle. Thus, alternative techniques, such as those related to spectral domain, allow approaches that provide a means for frequency and isolation marking of various observed phenomena. The possibility of creating frequency markers related to physical or chemical phenomena under biospeckle laser monitoring opens the way for important applications in the analysis of biological materials. In seeds, for example, one research challenge is the creation of a methodology to analyze their vigor undermining the influence of water activity. This study aimed to use wavelet transform to create maps in frequency of biological material, particularly from maize and bean seeds, seeking to isolate water activity. Wavelet transform was used in conjunction with traditional biospeckle laser methods, Fujii, Generalized Differences and Time History Speckle Patterns. The data analysis allowed access of information in different frequencies, making it possible to map activities that only occur at certain frequencies in the seeds associated to particular areas they operate, as in the case of activities present in the embryo as well as those present in the endosperm. Thus the work enabled the identification of frequency bands where water activity may be operating creating a signature useful in further works.

  3. 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.

  4. 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.

  5. 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.

  6. 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)

  7. Active Wavelength Control of an External Cavity Quantum Cascade Laser

    PubMed Central

    Tsai, Tracy; Wysocki, Gerard

    2012-01-01

    We present an active wavelength control system for grating-based external cavity lasers that increases the accuracy of predicting the lasing wavelength based on the grating equation and significantly improves scan-to-scan wavelength/frequency repeatability. The ultimate 3σ precision of a frequency scan is determined by the scan-to-scan repeatability of 0.042 cm−1. Since this control method can be applied to any external cavity laser with little to no modification, such a precision provides an excellent opportunity for spectroscopic applications that target molecular absorption lines at standard atmospheric conditions. PMID:23483850

  8. Dissipative soliton in actively mode-locked fiber laser.

    PubMed

    Wang, Ruixin; Dai, Yitang; Yan, Li; Wu, Jian; Xu, Kun; Li, Yan; Lin, Jintong

    2012-03-12

    A dissipative soliton in an all-normal-dispersion actively mode-locked ytterbium-doped fiber laser is reported for the first time. Pulses with 10-ps duration and edge-to-edge bandwidth of 9 nm are generated, and then extra-cavity compressed down to 560 fs due to the large chirp. Widely wavelength tuning between 1031 and 1080 nm is achieved by adjusting the driving frequency only. Our simulation shows that the proposed laser operates in the dissipative soliton shaping regime.

  9. Taming random lasers through active spatial control of the pump.

    PubMed

    Bachelard, N; Andreasen, J; Gigan, S; Sebbah, P

    2012-07-20

    Active control of the spatial pump profile is proposed to exercise control over random laser emission. We demonstrate numerically the selection of any desired lasing mode from the emission spectrum. An iterative optimization method is employed, first in the regime of strong scattering where modes are spatially localized and can be easily selected using local pumping. Remarkably, this method works efficiently even in the weakly scattering regime, where strong spatial overlap of the modes precludes spatial selectivity. A complex optimized pump profile is found, which selects the desired lasing mode at the expense of others, thus demonstrating the potential of pump shaping for robust and controllable single mode operation of a random laser.

  10. Taming Random Lasers through Active Spatial Control of the Pump

    NASA Astrophysics Data System (ADS)

    Bachelard, N.; Andreasen, J.; Gigan, S.; Sebbah, P.

    2012-07-01

    Active control of the spatial pump profile is proposed to exercise control over random laser emission. We demonstrate numerically the selection of any desired lasing mode from the emission spectrum. An iterative optimization method is employed, first in the regime of strong scattering where modes are spatially localized and can be easily selected using local pumping. Remarkably, this method works efficiently even in the weakly scattering regime, where strong spatial overlap of the modes precludes spatial selectivity. A complex optimized pump profile is found, which selects the desired lasing mode at the expense of others, thus demonstrating the potential of pump shaping for robust and controllable single mode operation of a random laser.

  11. 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.

  12. Predicting Ground Illuminance

    NASA Astrophysics Data System (ADS)

    Lesniak, Michael V.

    2014-01-01

    Our Sun outputs 3.85 × 1026 W of radiation, of which ≈37% is in the visible band. It is directly responsible for nearly all natural illuminance experienced on Earth's surface, either in the form of direct/refracted sunlight or in reflected light bouncing off the surfaces and/or atmospheres of our Moon and the visible planets. Ground illuminance, defined as the amount of visible light intercepting a unit area of surface (from all incident angles), varies over 7 orders of magnitude from day to night. It is highly dependent on well-modeled factors such as the relative positions of the Sun, Earth, and Moon. It is also dependent on less predictable factors such as local atmospheric conditions and weather. Several models have been proposed to predict ground illuminance, including Brown (1952) and Shapiro (1982, 1987). The Brown model is a set of empirical data collected from observation points around the world that has been reduced to a smooth fit of illuminance against a single variable, solar altitude. It provides limited applicability to the Moon and for cloudy conditions via multiplicative reduction factors. The Shapiro model is a theoretical model that treats the atmosphere as a three layer system of light reflectance and transmittance. It has different sets of reflectance and transmittance coefficients for various cloud types. Ground illuminance data from an observing run at the White Sands missile range were obtained from the United Kingdom Meteorology Office. Based on available weather reports, five days of clear sky observations were selected. These data are compared to the predictions of the two models. We find that neither of the models provide an accurate treatment during twilight conditions when the Sun is at or a few degrees below the horizon. When the Sun is above the horizon, the Shapiro model straddles the observed data, ranging between 90% and 120% of the recorded illuminance. During the same times, the Brown model is between 70% and 90% of the

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Laser light triggered-activated carbon nanosystem for cancer therapy.

    PubMed

    Chu, Maoquan; Peng, Jinliang; Zhao, Jiajia; Liang, Shanlu; Shao, Yuxiang; Wu, Qiang

    2013-02-01

    Among carbon-based nanomaterials, activated carbon (AC) may be an ideal candidate as a carrier for tumor therapeutic agents. Here we found a new property of nanoscale activated carbon (NAC) with narrow size distribution, namely the rapid conversion of light to thermal energy both in vitro and in vivo. An aqueous suspension of 200 μL of NAC (1 mg/mL) exhibited a rapid temperature increase of more than 35 °C after irradiation for 20 min with a 655-nm laser; this was within the temperature range for effective tumor treatment. We demonstrated that lung cancer cells (H-1299) incubated with bamboo nano-AC (BNAC) were killed with high efficiency after laser irradiation. In addition, mouse tumors with sizes smaller than the laser spot that had been injected with BNAC disappeared after irradiation. For tumors larger than the laser spot area, the incorporation of the photosensitizer ZnPc obviously increased the tumor growth inhibition efficiency of BNAC. BNAC-ZnPc was found to exhibit a synergistic effect when photothermal and photodynamic therapies were administered in combination. These results indicated that NAC can be used for high efficiency cancer phototherapy.

  20. 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.

  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.

    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.

  2. 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.

  3. 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

  4. 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.

  5. Activities of developing high-power KrF lasers and studying laser plasmas interaction physics at CIAE

    NASA Astrophysics Data System (ADS)

    Wang, Naiyan; Shan, Yusheng; Ma, Weiyi; Yang, Dawei; Kun, Gong; Wang, Xiaojun; Tang, Xiuzhang; Tao, Yezheng; Ma, Jinglong; Jiang, Xingdong

    2002-01-01

    This report reviews the scientific activities on high power laser and laser plasma physics at CIAE. A 6-beam KrF excimer laser system (100 J/23 ns/248 nm/1013 W/cm2, 15 min/shot) has been built, the Raman technologies used to upgrade it to 1014 W/cm2 has been studied. A UV femtosecond Ti:sapphire/KrF hybrid laser (50 mJ/220 fs/248 nm/1017 W/cm2) has been developed also, hot electron generation research has been carried out in the fs laser. In the near future, the fs laser will be amplified in six-beam laser system to produce ultra-high intensity to do fundamental researches on Fast Ignition of ICF.

  6. 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.

  7. 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.

  8. 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

  9. Sutureless cataract incision closure using laser-activated tissue glues

    NASA Astrophysics Data System (ADS)

    Eaton, Alexander M.; Bass, Lawrence S.; Libutti, Steven K.; Schubert, Herman D.; Treat, Michael R.

    1991-06-01

    With the advent of phacoemulsification and foldable intraocular lenses, there is renewed interest in sutureless cataract wound. We report the use of laser activated tissue glues for the closure of scleral tunnel cataract incisions. Two glue mixtures were tested in enucleated porcine eyes. Glue A was composed of hyaluronic acid, human albumin, and indocyanine green dye. Glue B contained hyaluronic acid, chondroitin sulfate, human albumin, and indocyanine green dye. A Spectra Physics diode laser (808 nm) with a power density of 7-1 1 watts/cm2 was used for glue activation. Wound bursting pressures, as determined by the presence of fluid at the wound margin, was significantly higher with both glue combinations than without the glue (Plaser activated tissue glues may be an alternative to suture closure of scleral tunnel cataract incisions.

  10. ILLUMINATION RESPONSE OF CDZNTE

    SciTech Connect

    Teague, L.; Washington, A.; Duff, M.

    2011-08-02

    CdZnTe (CZT) semiconducting crystals are of interest for use as room temperature X- and {gamma}-ray spectrometers. Several studies have focused on understanding the various electronic properties of these materials, such as the surface and bulk resistivities and the distribution of the electric field within the crystal. Specifically of interest is how these properties are influenced by a variety of factors including structural heterogeneities, such as secondary phases (SPs) and line defects as well as environmental effects. Herein, we report the bulk current, surface current, electric field distribution and performance of a spectrometer-grade CZT crystal exposed to above band-gap energy illumination.

  11. Evaluation of activity through dynamic laser speckle using the absolute value of the differences

    NASA Astrophysics Data System (ADS)

    Braga, R. A.; Nobre, C. M. B.; Costa, A. G.; Sáfadi, T.; da Costa, F. M.

    2011-01-01

    When a material is illuminated with a laser beam, it is possible to verify a phenomenon known as dynamic speckle or biospeckle. It exhibits an interference image that contains lots of information about the process being analyzed, and one of its most important applications is determining the activity quantity from the materials under study. The numerical analysis of the dynamic speckle images can be carried out by means of a co-occurrence matrix (COM) that assembles the intensity distributions of a speckle pattern with regard to time. An operational method that is widely used on the biospeckle COMs is the inertia moment (IM). Some studies demonstrate that IM is more sensitive on analyzing processes that involve high activities or high frequencies if considering the spectral analysis of the phenomena. However, when this variation is not so intense, this method is less efficient. For low variations on the activity or low frequencies, qualitative methods such as wavelet based entropy and cross-spectrum analysis have presented better results; however, processes that are in the intermediate range of activity are not well covered for any of these techniques mentioned earlier. The contribution of this research is to present an alternative approach, based on the absolute value of the differences (AVD) when handling the biospeckle COM. By using AVD on the seed-drying process, was found that it is efficient on verifying the behavior of the intermediate frequencies. Accumulated sum test (Coates and Diggle) showed that AVD and IM are generated from the same stochastic process. Thus, AVD is useful as an alternative method in some cases or even as a complementary tool for analyzing the dynamic speckle, mainly when the information of the activity is not present on high frequencies.

  12. Three-dimensional imaging simulation of active laser detection based on DLOS method

    NASA Astrophysics Data System (ADS)

    Zhang, Chuanxin; Zhou, Honghe; Chen, Xiang; Yuan, Yuan; Shuai, Yong; Tan, Heping

    2016-07-01

    The technology of active laser detection is widely used in many different fields nowadays. With the development of computer technology, programmable software simulation can provide reference for the design of active laser detection. The characteristics of the active laser detecting systems also can be judged more visual. Based on the features of the active laser detection, an improved method of radiative transfer calculation (Double Line Of Sight) was developed, and the simulation models of complete active laser detecting imaging were founded. Compared with the results calculated by the Monte Carlo method, the correctness of the improved method was verified. The results of active laser detecting imaging of complex three-dimensional targets in different atmospheric scenes were compared. The influence of different atmospheric dielectric property were analyzed, which provides effective reference for the design of active laser detection.

  13. Laser beam active brazing of metal ceramic joints

    NASA Astrophysics Data System (ADS)

    Haferkamp, Heinz; Bach, Friedrich W.; von Alvensleben, Ferdinand; Kreutzburg, K.

    1996-04-01

    The use of engineering ceramics is becoming more and more important. Reasons for this are the specific properties of these materials, such as high strength, corrosion resistance and wear resistance. To apply the advantages of ceramics, joining techniques of metal ceramic parts are required. In this paper, joining of metal ceramic joints by laser beam brazing is presented. This joining technique is characterized by local heat input, and the minimal thermal stress of the brazed components. During the investigations, an Nd:YAG laser and a vacuum chamber were applied. The advantages of Nd:YAG lasers are the simple mechanical construction, and laser beam guidance via quartz glass fibers, which leads to high handling flexibility. In addition, most of the materials show a high absorption rate for this kind of radiation. As materials, ceramic Al2O3 with a purity of 99.4% and metals such as X5CrNi189 and Fe54Ni29Co17 were used. As a filler material, commercially available silver and silver- copper brazes with chemically active elements like titanium were employed. During this study, the brazing wetting behavior and the formation of diffusion layers in dependence on processing parameters were investigated. The results have shown that high brazing qualities can be achieved by means of the laser beam brazing process. Crack-free joining of metal ceramic parts is currently only possible by the use of metals such as Fe54Ni29Co17 because of its low thermal expansion coefficient, which reduces thermal stresses within the joining zone.

  14. 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.

  15. THz quantum cascade lasers with wafer bonded active regions.

    PubMed

    Brandstetter, M; Deutsch, C; Benz, A; Cole, G D; Detz, H; Andrews, A M; Schrenk, W; Strasser, G; Unterrainer, K

    2012-10-01

    We demonstrate terahertz quantum-cascade lasers with a 30 μm thick double-metal waveguide, which are fabricated by stacking two 15 μm thick active regions using a wafer bonding process. By increasing the active region thickness more optical power is generated inside the cavity, the waveguide losses are decreased and the far-field is improved due to a larger facet aperture. In this way the output power is increased by significantly more than a factor of 2 without reducing the maximum operating temperature and without increasing the threshold current.

  16. Microwave quantum illumination.

    PubMed

    Barzanjeh, Shabir; Guha, Saikat; Weedbrook, Christian; Vitali, David; Shapiro, Jeffrey H; Pirandola, Stefano

    2015-02-27

    Quantum illumination is a quantum-optical sensing technique in which an entangled source is exploited to improve the detection of a low-reflectivity object that is immersed in a bright thermal background. Here, we describe and analyze a system for applying this technique at microwave frequencies, a more appropriate spectral region for target detection than the optical, due to the naturally occurring bright thermal background in the microwave regime. We use an electro-optomechanical converter to entangle microwave signal and optical idler fields, with the former being sent to probe the target region and the latter being retained at the source. The microwave radiation collected from the target region is then phase conjugated and upconverted into an optical field that is combined with the retained idler in a joint-detection quantum measurement. The error probability of this microwave quantum-illumination system, or quantum radar, is shown to be superior to that of any classical microwave radar of equal transmitted energy.

  17. Microwave quantum illumination.

    PubMed

    Barzanjeh, Shabir; Guha, Saikat; Weedbrook, Christian; Vitali, David; Shapiro, Jeffrey H; Pirandola, Stefano

    2015-02-27

    Quantum illumination is a quantum-optical sensing technique in which an entangled source is exploited to improve the detection of a low-reflectivity object that is immersed in a bright thermal background. Here, we describe and analyze a system for applying this technique at microwave frequencies, a more appropriate spectral region for target detection than the optical, due to the naturally occurring bright thermal background in the microwave regime. We use an electro-optomechanical converter to entangle microwave signal and optical idler fields, with the former being sent to probe the target region and the latter being retained at the source. The microwave radiation collected from the target region is then phase conjugated and upconverted into an optical field that is combined with the retained idler in a joint-detection quantum measurement. The error probability of this microwave quantum-illumination system, or quantum radar, is shown to be superior to that of any classical microwave radar of equal transmitted energy. PMID:25768743

  18. Parallel hierarchical global illumination

    SciTech Connect

    Snell, Q.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.

  19. Analysis of the restricting factors of laser countermeasure active detection technology

    NASA Astrophysics Data System (ADS)

    Zhang, Yufa; Sun, Xiaoquan

    2016-07-01

    The detection effect of laser active detection system is affected by various kinds of factors. In view of the application requirement of laser active detection, the influence factors for laser active detection are analyzed. The mathematical model of cat eye target detection distance has been built, influence of the parameters of laser detection system and the environment on detection range and the detection efficiency are analyzed. Various parameters constraint detection performance is simulated. The results show that the discovery distance of laser active detection is affected by the laser divergence angle, the incident angle and the visibility of the atmosphere. For a given detection range, the laser divergence angle and the detection efficiency are mutually restricted. Therefore, in view of specific application environment, it is necessary to select appropriate laser detection parameters to achieve optimal detection effect.

  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. 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.

  2. 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.

  3. Active linewidth-narrowing of a mid-infrared quantum cascade laser without optical reference.

    PubMed

    Tombez, L; Schilt, S; Hofstetter, D; Südmeyer, T

    2013-12-01

    We report on a technique for frequency noise reduction and linewidth-narrowing of a distributed-feedback mid-IR quantum cascade laser (QCL) that does not involve any optical frequency reference. The voltage fluctuations across the QCL are sensed, amplified and fed back to the temperature of the QCL at a fast rate using a near-IR laser illuminating the top of the QCL chip. A locking bandwidth of 300 kHz and a reduction of the frequency noise power spectral density by a factor of 10 with respect to the free-running laser are achieved. From 2 MHz for the free-running QCL, the linewidth is narrowed below 700 kHz (10 ms observation time).

  4. An active alignment method for post launch co-alignment of laser beam combiner systems

    NASA Technical Reports Server (NTRS)

    Yu, A. W.; Green, J. W.; Maynard, W. L.; Minott, P. O.; Krainak, M. A.

    1992-01-01

    A laser transmitter for high bandwidth geosynchronous satellite communications is described. High optical power is achieved by combining semiconductor laser diodes. An active alignment scheme is proposed for achieving the +/- 20 microrad post launch multiple laser angular co-alignment requirement.

  5. 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.

  6. Laser Technology.

    ERIC Educational Resources Information Center

    Gauger, Robert

    1993-01-01

    Describes lasers and indicates that learning about laser technology and creating laser technology activities are among the teacher enhancement processes needed to strengthen technology education. (JOW)

  7. Reflectance and illuminant estimation for digital cameras

    NASA Astrophysics Data System (ADS)

    Dicarlo, Jeffrey Michael

    Several important problems in color imaging can be traced to differences in how cameras and humans sample the spectral properties of light. Color processing within the imaging pipeline, loosely referred to as color correction, transforms the sampled camera responses to a form that matches the human responses. The accuracy of the color correction transformation is limited for two reasons. First, the human visual system and most color acquisition devices critically undersample the spectral information, making the differences in their sampling functions quite significant. Second, the human visual system derives a relatively constant surface color appearance despite variations in the illuminant, complicating color correction with the need to estimate the illuminant. Assuming complete knowledge of the illuminant, we formulate color correction as an input-referred estimation problem. In particular, we analyze how a small number of camera measurements can be used to estimate a complete spectral surface reflectance function. We introduce conventional linear color transformations, and then extend these transformations using forms of local linear regression that we refer to as submanifold estimation methods. These methods are based on the observation that for many data sets the deviations between the signal and the linear estimate is systematic; submanifold methods incorporate knowledge of these systematic deviations to improve upon linear estimation methods. We describe the geometric intuition of these methods and evaluate the submanifold method on printed material data and hyperspectral image data. Next, we discard the assumption of complete knowledge of the illuminant and analyze a technique to estimate the illuminant. Conventional algorithms rely on statistical assumptions about the scene properties (surface reflectance functions and geometry) to estimate the ambient illuminant. We introduce a new illuminant estimation paradigm that uses an active imaging method to

  8. Active optics, adaptive optics, and laser guide stars.

    PubMed

    Hubin, N; Noethe, L

    1993-11-26

    Optical astronomy is crucial to our understanding of the universe, but the capabilities of ground-based telescopes are severely limited by the effects of telescope errors and of the atmosphere on the passage of light. Recently, it has become possible to construct inbuilt corrective devices that can compensate for both types of degradations as observations are conducted. For full use of the newly emerged class of 8-meter telescopes, such active corrective capabilities, known as active and adaptive optics, are essential. Some physical limitations in the adaptive optics field can be overcome by artificially created reference stars, called laser guide stars. These new technologies have lately been applied with success to some medium and very large telescopes. PMID:17736819

  9. Illuminated push-button switch

    NASA Technical Reports Server (NTRS)

    Iwagiri, T.

    1983-01-01

    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.

  10. 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.

  11. Dual-illumination planar Doppler velocimetry using a single camera

    NASA Astrophysics Data System (ADS)

    Charrett, Tom O. H.; Ford, Helen D.; Nobes, David S.; Tatam, Ralph P.

    2003-11-01

    A Planar Doppler Velocimetry (PDV) illumination system has been designed which is able to generate two beams, separated in frequency by about 600 MHz. This allows a common-path imaging head to be constructed, using a single imaging camera instead of the usual camera pair. Both illumination beams can be derived from a single laser, using acousto-optic modulators to effect the frequency shifts. One illumination frequency lies on an absorption line of gaseous iodine, and the other just off the absorption line. The beams sequentially illuminate a plane within a seeded flow and Doppler-shifted scattered light passes through an iodine vapor cell onto the camera. The beam that lies at an optical frequency away from the absorption line is not affected by passage through the cell, and provides a reference image. The other beam, the frequency of which coincides with an absorption line, encodes the velocity information as a variation in transmission dependent upon the Doppler shift. Images of the flow under both illumination frequencies are formed on the same camera, ensuring registration of the reference and signal images. This removes a major problem of a two-camera imaging head, and cost efficiency is also improved by the simplification of the system. The dual illumination technique has been shown to operate successfully with a spinning disc as a test object. The benefits of combining the dual illumination system with a three-component, fiber-linked imaging head developed at Cranfield will be discussed.

  12. Optimizing ultrafast illumination for multiphoton-excited fluorescence imaging.

    PubMed

    Stoltzfus, Caleb R; Rebane, Aleksander

    2016-05-01

    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 cm(2). PMID:27231620

  13. 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

  14. 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

  15. Application of covert illumination to intrusion surveillance, assessment, and detection

    NASA Astrophysics Data System (ADS)

    Maki, Melvin C.; Scherbarth, Stefan

    1995-05-01

    Covert illumination is an important element in providing surveillance, detection, and assessment for security applications. IR illumination is increasingly providing this function; however, conventional filament-based illuminators have limited performance and life. A new variety of light emitting diode (LED) illuminators is described that provides long life at low power. A further advance is to use a planar array of LED's with lenses to optimize the uniformity of scene illumination and maximize the illumination range. Modern CCD cameras have an inherently high IR sensitivity so are well matched to work with this illumination. Further enhancements are to integrate the combination of low-light camera and LED illuminator in a discrete column type package to make the overall illumination and assessment system unobtrusive. Finally, these components can be further combined with automated assessment aids to turn the surveillance device into a true detection sensor that can operate stand-alone without active personnel monitoring. A review of the major IR design considerations is included, along with several examples of systems to illustrate potential applications.

  16. Backward reflection analysis of transmitting channel of active laser ranging optics

    NASA Astrophysics Data System (ADS)

    Hong, Jinsuk; Koh, Hae Seog

    2013-09-01

    The designed Active LDR(Laser Detection and Ranging) System contains high-power Laser and its diameter is approximately 24mm. Although the laser transmitting channel and receiving optic channel are completely separated from each other and doesn't share any of the optical components in design, each channel shares 4 wedge scanners, which are to overcome the narrow FOV(Field of View) of the optical system. Any backward reflection back to the fiber laser end must be carefully studied since it can damage the LD(Laser Diodes), the inner components of the laser unit because of the high amplification factor of the laser unit. In this study, the stray light caused by the transmitting channel's laser and inner reflection by optical components were analyzed by ASAP(Advanced System Analysis Program) software. We also can confirm the operability and stability of the system by more than 6 months of operation of the system.

  17. Active Laser Guide Star refocusing system for EAGLE instrument

    NASA Astrophysics Data System (ADS)

    Hugot, Emmanuel; Madec, Fabrice; Vives, Sébastien; Chardin, Elodie; Ferrari, Marc; Le Mignant, David; Gimenez, Jean Luc; Mazzanti, Silvio; Vola, Pascal; Cuby, Jean Gabriel

    We detail the study of a laser guide star (LGS) refocusing system based on an variable curvature mirror (VCM) of high dynamic, in the frame of the EAGLE instrument for the E-ELT. From the top level requirements, an on axis optical design based on an active component is optimised to ensure maximal performance in terms of encircled energy. The refocusing is operated by the VCM, which shape varies with the distance of the sodium layer to the telescope. The VCM system concept is based on an embedded metrology. We detail the finite element analysis (FEA) of the VCM, allowing an optimization of the thickness profile to get an optical quality better than λ/5 RMS at each curvature. Mechanical design and manufacturing of prototypes are also presented.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. 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.

  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. Photoactivation and optogenetics with micro mirror enhanced illumination

    NASA Astrophysics Data System (ADS)

    Rückerl, F.; Berndt, D.; Heber, J.; Shorte, S.

    2014-05-01

    Photoactivation and "optogenetics" require the precise control of the illumination path in optical microscopes. It is equally important to shape the illumination spatially as well as to have control over the intensity and the duration of the illumination. In order to achieve these goals we use programmable, diffractive Micro Mirror Arrays (MMA) as fast spatial light modulators for beam steering. By combining two MMAs with 256×256 mirrors each, our illumination setup allows for fast angular and spatial control at a wide spectral range (260-1000 nm). Illumination pulses can be as short as 50 μs, or can also extend to several seconds. The specific illumination modes of the individual areas results in a precise control over the light dose to the sample, giving significant advantage when investigating dosage dependent activation inasmuch as both the duration and the intensity can be controlled distinctly. The setup is integrated to a microscope and allows selective illumination of regions in the sample, enabling the precise, localized activation of fluorescent probes and the activation and deactivation of cellular and subcellular signaling cascades using photo activated ion channels. The high reflectivity in the UV range (up to 260nm) further allows gene silencing using UV activated constructs (e.g. caged morpholinos).

  5. 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.

  6. 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...

  7. 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)

  8. Comparative bactericidal activities of lasers operating at seven different wavelengths

    NASA Astrophysics Data System (ADS)

    Watson, Ian A.; Ward, Glenn D.; Wang, RuiKang K.; Sharp, James H.; Budgett, David M.; Stewart-Tull, Duncan E.; Wardlaw, Alastair C.; Chatwin, Christopher R.

    1996-10-01

    Seven laser instruments, delivering radiation at a selection of wavelengths in the range of 0.355 to 118 micrometers , we investigated for their ability to kill Escherichia coli as a lawn of the bacteria on nutrient agar culture plates. Easily the most effective was a 600-W CO2 laser operating at 10.6 micrometers , which produced 1.2-cm2 circular zones of sterilization at energy densities of around 8 J cm-2 in a 30-msec exposure. Circular zones with an area of 0.7 cm2 were achieved with 200 W from a Nd:YAG laser delivering 8-ms, 10-J pulses of 1.06 micrometers radiation at 20 Hz. The exposure time, however, was 16 s and the energy density was more than 240 times higher than with the CO2 laser. This difference is believed to be partly due to the much higher absorption of radiation at 10.6 micrometers , by water in the bacterial cells and the surrounding medium. Sterilization was observed after exposure to frequency- tripled Nd:YAG laser radiation at 355 nm. Lasers that were totally ineffective in killing Escherichia coli were the far infrared laser, the laser diode array, and the argon ion laser. The speed at which laser sterilization can be achieved is particularly attractive to the medical and food industries.

  9. 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.

  10. Illuminating the life of GPCRs

    PubMed Central

    Böhme, Ilka; Beck-Sickinger, Annette G

    2009-01-01

    The investigation of biological systems highly depends on the possibilities that allow scientists to visualize and quantify biomolecules and their related activities in real-time and non-invasively. G-protein coupled receptors represent a family of very dynamic and highly regulated transmembrane proteins that are involved in various important physiological processes. Since their localization is not confined to the cell surface they have been a very attractive "moving target" and the understanding of their intracellular pathways as well as the identified protein-protein-interactions has had implications for therapeutic interventions. Recent and ongoing advances in both the establishment of a variety of labeling methods and the improvement of measuring and analyzing instrumentation, have made fluorescence techniques to an indispensable tool for GPCR imaging. The illumination of their complex life cycle, which includes receptor biosynthesis, membrane targeting, ligand binding, signaling, internalization, recycling and degradation, will provide new insights into the relationship between spatial receptor distribution and function. This review covers the existing technologies to track GPCRs in living cells. Fluorescent ligands, antibodies, auto-fluorescent proteins as well as the evolving technologies for chemical labeling with peptide- and protein-tags are described and their major applications concerning the GPCR life cycle are presented. PMID:19602276

  11. Patterning of nanostructured thin films by structured light illumination

    SciTech Connect

    Haro-Poniatowski, E.; Fort, E.; Lacharme, J.P.; Ricolleau, C.

    2005-10-03

    Light-induced reshaping of silver nanostructured films near the percolation threshold are investigated using a KrF excimer laser emitting at 248 nm. Depending on the laser intensity and the number of pulses, striking effects are observed for which the irregular particles melt and transform into spherical shaped particles. We show that the laser-induced modifications can be spatially designed by irradiating through masks and gratings taking advantage of their respective diffractive properties. This permits an easy and well controlled way to produce a variety of submicron patterning. The induced patterns accurately coincide with the intensity variations of the illumination field.

  12. 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)

  13. Gas dynamics of the active medium of a supersonic cw HF chemical laser

    SciTech Connect

    Fedorov, Igor' A; Rotinyan, Mikhail A; Krivitskii, A M

    2000-12-31

    Gas-dynamic characteristics of a 5-kW supersonic cw HF chemical laser with a nozzle array of size 25 cm x 2.8 cm and the nozzle - nozzle mixing scheme were experimentally studied. The distributions of Mach numbers, static pressure, total pressure behind the normal shock, and the loss of total pressure were measured in the flow of an active medium in wide ranges of variation of the flow rate of secondary fuel (hydrogen) and pressure in the atomic-fluorine generator. The energy parameters of the laser were found to be interrelated with the gas dynamics and the optical quality of the active laser medium. (lasers)

  14. Spiral wobbling beam illumination uniformity in HIF fuel target implosion

    NASA Astrophysics Data System (ADS)

    Kawata, S.; Kurosaki, T.; Koseki, S.; Hisatomi, Y.; Barada, D.; Ma, Y. Y.; Ogoyski, A. I.

    2013-11-01

    A few % wobbling-beam illumination nonuniformity is realized in heavy ion inertial confinement fusion (HIF) throughout the heavy ion beam (HIB) driver pulse by a newly introduced spiraling beam axis motion in the first two rotations. The wobbling HIB illumination was proposed to realize a uniform implosion in HIF. However, the initial imprint of the wobbling HIBs was a serious problem and introduces a large unacceptable energy deposition nonuniformity. In the wobbling HIBs illumination, the illumination nonuniformity oscillates in time and space. The oscillating-HIB energy deposition may produce a time-dependent implosion acceleration, which reduces the Rayleigh-Taylor (R-T) growth [Laser Part. Beams 11, 757 (1993), Nuclear Inst. Methods in Phys. Res. A 606, 152 (2009), Phys. Plasmas 19, 024503 (2012)] and the implosion nonuniformity. The wobbling HIBs can be generated in HIB accelerators and the oscillating frequency may be several 100 MHz ˜ 1 GHz [Phys. Rev. Lett. 104, 254801 (2010)]. Three-dimensional HIBs illumination computations present that the few % wobbling HIBs illumination nonuniformity oscillates with the same wobbling HIBs frequency.

  15. Broadband tunable external cavity quantum cascade lasers for standoff detection of explosives

    NASA Astrophysics Data System (ADS)

    Hugger, S.; Fuchs, F.; Jarvis, J.; Kinzer, M.; Yang, Q. K.; Bronner, W.; Driad, R.; Aidam, R.; Degreif, K.; Schnürer, F.

    2012-06-01

    We demonstrate contactless detection of solid residues of explosives using mid-infrared laser spectroscopy. Our detection scheme relies on active laser illumination, synchronized with the collection of the backscattered radiation by an infrared camera. The key component of the system is an external cavity quantum cascade laser with a tuning range of 300 cm-1 centered at 1220 cm-1. Residues of TNT (trinitrotoluene), PETN (pentaerythritol tetranitrate) and RDX (cyclotrimethylenetrinitramine) could be identified and discriminated against non-hazardous materials by scanning the illumination wavelength over several of the characteristic absorption features of the explosives.

  16. 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.

  17. Laser-activated protein solder for peripheral nerve repair

    NASA Astrophysics Data System (ADS)

    Trickett, Rodney I.; Lauto, Antonio; Dawes, Judith M.; Owen, Earl R.

    1995-05-01

    A 100 micrometers core optical fiber-coupled 75 mW diode laser operating at a wavelength of 800 nm has been used in conjunction with a protein solder to stripe weld severed rat tibial nerves, reducing the long operating time required for microsurgical nerve repair. Welding is produced by selective laser denaturation of the albumin based solder which contains the dye indocyanine green. Operating time for laser soldering was 10 +/- 5 min. (n equals 20) compared to 23 +/- 9 min. (n equals 10) for microsuturing. The laser solder technique resulted in patent welds with a tensile strength of 15 +/- 5 g, while microsutured nerves had a tensile strength of 40 +/- 10 g. Histopathology of the laser soldered nerves, conducted immediately after surgery, displayed solder adhesion to the outer membrane with minimal damage to the inner axons of the nerves. An in vivo study is under way comparing laser solder repaired tibial nerves to conventional microsuture repair. At the time of submission 15 laser soldered nerves and 7 sutured nerves were characterized at 3 months and showed successful regeneration with compound muscle action potentials of 27 +/- 8 mV and 29 +/- 8 mW respectively. A faster, less damaging and long lasting laser based anastomotic technique is presented.

  18. 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.

  19. 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.

  20. 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. PMID:27370428

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. Laser-activated protein bands for peripheral nerve repair

    NASA Astrophysics Data System (ADS)

    Lauto, Antonio; Trickett, Rodney I.; Malik, Richard; Dawes, Judith M.; Owen, Earl R.

    1996-01-01

    A 100 micrometer core optical fiber-coupled 75 mW diode laser operating at a wavelength of 800 nm has been used in conjunction with a protein solder to stripe weld severed rat tibial nerves, reducing the long operating time required for microsurgical nerve repair. Welding is produced by selective laser denaturation of the protein based solder which contains the dye indocyanine green. Operating time for laser soldering was 10 plus or minus 5 min. (n equals 24) compared to 23 plus or minus 9 min (n equals 13) for microsuturing. The laser solder technique resulted in patent welds with a tensile strength of 15 plus or minus 5 g, while microsutured nerves had a tensile strength of 40 plus or minus 10 g. Histopathology of the laser soldered nerves, conducted immediately after surgery, displayed solder adhesion to the outer membrane with minimal damage to the inner axons of the nerves. An in vivo study, with a total of fifty-seven adult male wistar rats, compared laser solder repaired tibial nerves to conventional microsuture repair. Twenty-four laser soldered nerves and thirteen sutured nerves were characterized at three months and showed successful regeneration with average compound muscle action potentials (CMAP) of 2.4 plus or minus 0.7 mV and 2.7 plus or minus 0.8 mV respectively. Histopathology of the in vivo study, confirmed the comparable regeneration of axons in laser and suture operated nerves. A faster, less damaging and long lasting laser based anastomotic technique is presented.

  6. Changes of electric cochlea activity of guinea pigs during argon laser stapedotomy

    NASA Astrophysics Data System (ADS)

    Michalski, Wojciech; Pres, Krzysztof; Dziewiszek, Wojciech; Pospiech, Lucyna

    2000-11-01

    Small electric signals appear on surface of a cochlea when the ear is stimulated by sound. A level of the signals can be measured of the electric activity of cochlea. The aim of the experiments was recording of changes of the cochlear potentials during argon laser stapedotomy. On the base of the recording the limits of the safe argon laser stapedotomy have been preliminary estimated. The series of argon laser pulses lasting 0.2-0.5 s and of 16 s interval between the pulses are preferable for safety of argon laser stapedotomy. The pulse peak power should be below 1 W.

  7. A course in illumination engineering

    NASA Astrophysics Data System (ADS)

    Koshel, R. John

    2007-09-01

    Illumination engineering is the novel field of more general field of optical design and engineering. A seminar, project-based course has been started at the College of Optical Science, The Univ. of Arizona. Topics include lightpipes, sources, sampling, modeling methods, reflectors, and displays. Guest lecturers from industry provide a wealth of additional content. The goal is to education our next generation of optical designers about this intriguing, complex, yet understudied field. Other goals are to provide training in nonsequential optical design software, connections between experimental data and modeling, and the non-technical aspects of the illumination field.

  8. Statistical characterization of real-world illumination.

    PubMed

    Dror, Ron O; Willsky, Alan S; Adelson, Edward H

    2004-09-28

    Although studies of vision and graphics often assume simple illumination models, real-world illumination is highly complex, with reflected light incident on a surface from almost every direction. One can capture the illumination from every direction at one point photographically using a spherical illumination map. This work illustrates, through analysis of photographically acquired, high dynamic range illumination maps, that real-world illumination possesses a high degree of statistical regularity. The marginal and joint wavelet coefficient distributions and harmonic spectra of illumination maps resemble those documented in the natural image statistics literature. However, illumination maps differ from typical photographs in that illumination maps are statistically nonstationary and may contain localized light sources that dominate their power spectra. Our work provides a foundation for statistical models of real-world illumination, thereby facilitating the understanding of human material perception, the design of robust computer vision systems, and the rendering of realistic computer graphics imagery. PMID:15493972

  9. 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.

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

    PubMed

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

    2016-05-05

    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.

  11. 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

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. Ultrafast vapourization dynamics of laser-activated polymeric microcapsules

    NASA Astrophysics Data System (ADS)

    Lajoinie, Guillaume; Gelderblom, Erik; Chlon, Ceciel; Böhmer, Marcel; Steenbergen, Wiendelt; de Jong, Nico; Manohar, Srirang; Versluis, Michel

    2014-04-01

    Precision control of vapourization, both in space and time, has many potential applications; however, the physical mechanisms underlying controlled boiling are not well understood. The reason is the combined microscopic length scales and ultrashort timescales associated with the initiation and subsequent dynamical behaviour of the vapour bubbles formed. Here we study the nanoseconds vapour bubble dynamics of laser-heated single oil-filled microcapsules using coupled optical and acoustic detection. Pulsed laser excitation leads to vapour formation and collapse, and a simple physical model captures the observed radial dynamics and resulting acoustic pressures. Continuous wave laser excitation leads to a sequence of vapourization/condensation cycles, the result of absorbing microcapsule fragments moving in and out of the laser beam. A model incorporating thermal diffusion from the capsule shell into the oil core and surrounding water reveals the mechanisms behind the onset of vapourization. Excellent agreement is observed between the modelled dynamics and experiment.

  19. Photovoltaic receivers for laser beamed power in space

    NASA Technical Reports Server (NTRS)

    Landis, Geoffrey A.

    1991-01-01

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

  20. 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.

  1. Actively mode-locked all fiber laser with cylindrical vector beam output.

    PubMed

    Zhou, Yong; Wang, Anting; Gu, Chun; Sun, Biao; Xu, Lixin; Li, Feng; Chung, Dick; Zhan, Qiwen

    2016-02-01

    We demonstrated an all fiber actively mode-locked laser that emits a cylindrical vector beam. An intra-cavity few-mode fiber Bragg grating inscribed in a short section of four-mode fiber is employed to provide mode selection and spectrum filtering functions. Mode coupling is achieved by offset splicing between the single-mode fiber and the four-mode fiber in the laser cavity. A LiNbO3 Mach-Zehnder modulator is used to achieve active mode-locking in the laser. The laser operates at 1547 nm with 30 dB spectrum width of 0.2 nm. The mode-locked pulses have a duration of 2 ns and repetition of 12.06 MHz. Through adjusting the polarization state in the laser cavity, both radially and azimuthally polarized beams have been obtained with high mode purity.

  2. Actively mode-locked all fiber laser with cylindrical vector beam output.

    PubMed

    Zhou, Yong; Wang, Anting; Gu, Chun; Sun, Biao; Xu, Lixin; Li, Feng; Chung, Dick; Zhan, Qiwen

    2016-02-01

    We demonstrated an all fiber actively mode-locked laser that emits a cylindrical vector beam. An intra-cavity few-mode fiber Bragg grating inscribed in a short section of four-mode fiber is employed to provide mode selection and spectrum filtering functions. Mode coupling is achieved by offset splicing between the single-mode fiber and the four-mode fiber in the laser cavity. A LiNbO3 Mach-Zehnder modulator is used to achieve active mode-locking in the laser. The laser operates at 1547 nm with 30 dB spectrum width of 0.2 nm. The mode-locked pulses have a duration of 2 ns and repetition of 12.06 MHz. Through adjusting the polarization state in the laser cavity, both radially and azimuthally polarized beams have been obtained with high mode purity. PMID:26907420

  3. All fiber actively mode-locked fiber laser emitting cylindrical vector beam

    NASA Astrophysics Data System (ADS)

    Zhou, Yong; Wang, Anting; Gu, Chun; Xu, Lixin; Zhan, Qiwen

    2015-08-01

    We demonstrated an all fiber actively mode-locked laser emitting cylindrical vector beam. A few-mode fiber Bragg grating is adopted to achieve mode selecting and spectrum filtering. An offset splicing of single-mode fiber with fourmode fiber is utilized as a mode coupler in the laser cavity. A LiNbO3 Mach-Zehnder modulator is used to achieve active mode locking in the laser. The laser operates at 1547nm with 30 dB spectrum width of 0.3nm. The emitted modelocked pulses have a duration of 1ns and repetition of 12.06MHz. Both radially and azimuthally polarized beams have been obtained with very good modal symmetry by adjusting the polarization in the laser cavity.

  4. 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

  5. Quasi-Bessel beams from asymmetric and astigmatic illumination sources.

    PubMed

    Müller, Angelina; Wapler, Matthias C; Schwarz, Ulrich T; Reisacher, Markus; Holc, Katarzyna; Ambacher, Oliver; Wallrabe, Ulrike

    2016-07-25

    We study the spatial intensity distribution and the self-reconstruction of quasi-Bessel beams produced from refractive axicon lenses with edge emitting laser diodes as asymmetric and astigmatic illumination sources. Comparing these to a symmetric mono-mode fiber source, we find that the asymmetry results in a transition of a quasi-Bessel beam into a bow-tie shaped pattern and eventually to a line shaped profile at a larger distance along the optical axis. Furthermore, we analytically estimate and discuss the effects of astigmatism, substrate modes and non-perfect axicons. We find a good agreement between experiment, simulation and analytic considerations. Results include the derivation of a maximal axicon angle related to astigmatism of the illuminating beam, impact of laser diode beam profile imperfections like substrate modes and a longitudinal oscillation of the core intensity and radius caused by a rounded axicon tip. PMID:27464190

  6. 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.

  7. 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).

  8. 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)

  9. Monolithically integrated active waveguides and lasers using rare-earth doped spin-on glass

    SciTech Connect

    Ashby, C.I.H.; Sullivan, C.T.; Vawter, G.A.

    1996-09-01

    This LDRD program No. 3505.230 explored a new approach to monolithic integration of active waveguides and rare-earth solid state lasers directly onto III-V substrates. It involved selectively incorporating rare-earth ions into spin-on glasses (SOGs) that could be solvent cast and then patterned with conventional microelectronic processing. The patterned, rare-earth spin-on glasses (RESOGs) were to be photopumped by laser diodes prefabricated on the wafer and would serve as directly integrated active waveguides and/or rare-earth solid state lasers.

  10. 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

  11. Study on illuminance and visual properties of flammable illumination.

    PubMed

    Yamasaki, K; Nagai, Y

    1997-09-01

    In order to investigate the physical, economical, physiological and psychological aspects regarding ancient lighting, two series of experiment were performed. At first a darkroom (1.3 x 4.5 m, Ht: 2.7 m) was constructed. In experiment I, illuminance and consumption rate of fuel were measured. The Japanese classic candle, plant oil and animal fat yield 1.12, 0.30-0.62 and 0.05 lux at 1.0 m distance, respectively. The illuminance was reduced to about 50% by and on which was a lighting tool of folkcraft. The burning duration of plant oil was about two weeks to 180 ml when it burned 4 hours per one day. In experiment II, 15 young females were examined regarding the visual properties such as visual acuity, readability of newspaper and discrimination of color under the simulated illumination of candle. The visual acuity was 0.42 under 0.16 lux. It needed more than 1.44 lux to read a newspaper. In the color discrimination test, yellowish green was most difficult, silver or long wave range colors were easy.

  12. 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

  13. 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. PMID:21643092

  14. Laser micromachining of through via interconnects in active die for 3-D multichip module

    NASA Astrophysics Data System (ADS)

    Chu, D.; Miller, W. D.

    One method to increase density in integrated circuits (IC) is to stack die to create a 3-D multichip module (MCM). In the past, special post wafer processing was done to bring interconnects out to the edge of the die. The die were sawed, glued, and stacked. Special processing was done to create interconnects on the edge to provide for interconnects to each of the die. These processes require an IC type fabrication facility (fab) and special processing equipment. In contrast, we have developed packaging assembly methods to create vertical through vias in bond pads of active silicon die, isolate these vias, and metal fill these vias without the use of a special IC fab. These die with through vias can then be joined and stacked to create a 3-D MCM. Vertical through vias in active die are created by laser micromachining using a Nd:YAG laser. Besides the fundamental 1064 nm (infrared) laser wavelength of a Nd:YAG laser, modifications to our Nd:YAG laser allowed us to generate the second harmonic 532 nm (green) laser wavelength and fourth harmonic 266 nm (ultraviolet) laser wavelength in laser micromachining for these vias. Experiments were conducted to determine the best laser wavelengths to use for laser micromachining of vertical through vias in order to minimize damage to the active die. Via isolation experiments were done in order to determine the best method in isolating the bond pads of the die. Die thinning techniques were developed to allow for die thickness as thin as 50 microns. This would allow for high 3-D density when the die are stacked. A method was developed to metal fill the vias with solder using a wire bonder with solder wire.

  15. Laser micromachining of through via interconnects in active die for 3-D multichip module

    SciTech Connect

    Chu, D.; Miller, W.D.

    1995-09-01

    One method to increase density in integrated circuits (IC) is to stack die to create a 3-D multichip module (MCM). In the past, special post wafer processing was done to bring interconnects out to the edge of the die. The die were sawed, glued, and stacked. Special processing was done to create interconnects on the edge to provide for interconnects to each of the die. These processes require an IC type fabrication facility (fab) and special processing equipment. In contrast, we have developed packaging assembly methods to created vertical through vias in bond pads of active silicon die, isolate these vias, and metal fill these vias without the use of a special IC fab. These die with through vias can then be joined and stacked to create a 3-D MCM. Vertical through vias in active die are created by laser micromachining using a Nd:YAG laser. Besides the fundamental 1064 nm (infra-red) laser wavelength of a Nd:YAG laser, modifications to our Nd:YAG laser allowed us to generate the second harmonic 532 nm (green) laser wavelength and fourth harmonic 266nm (ultra violet) laser wavelength in laser micromachining for these vias. Experiments were conducted to determine the best laser wavelengths to use for laser micromachining of vertical through vias in order to minimize damage to the active die. Via isolation experiments were done in order to determine the best method in isolating the bond pads of the die. Die thinning techniques were developed to allow for die thickness as thin as 50 {mu}m. This would allow for high 3-D density when the die are stacked. A method was developed to metal fill the vias with solder using a wire bonder with solder wire.

  16. Active mode-locking of mid-infrared quantum cascade lasers with short gain recovery time.

    PubMed

    Wang, Yongrui; Belyanin, Alexey

    2015-02-23

    We investigate the dynamics of actively modulated mid-infrared quantum cascade lasers (QCLs) using space- and time-domain simulations of coupled density matrix and Maxwell equations with resonant tunneling current taken into account. We show that it is possible to achieve active mode locking and stable generation of picosecond pulses in high performance QCLs with a vertical laser transition and a short gain recovery time by bias modulation of a short section of a monolithic Fabry-Perot cavity. In fact, active mode locking in QCLs with a short gain recovery time turns out to be more robust to the variation of parameters as compared to previously studied lasers with a long gain recovery time. We investigate the effects of spatial hole burning and phase locking on the laser output.

  17. High illumination uniformity scheme with 32 beams configuration for direct-drive inertial confinement fusion

    NASA Astrophysics Data System (ADS)

    Li, Li; Gu, Chun; Xu, Lixin; Zhou, Shenlei

    2016-04-01

    The self-adapting algorithms are improved to optimize a beam configuration in the direct drive laser fusion system with the solid state lasers. A configuration of 32 laser beams is proposed for achieving a high uniformity illumination, with a root-mean-square deviation at 10-4 level. In our optimization, the parameters such as beam number, beam arrangement, and beam intensity profile are taken into account. The illumination uniformity robustness versus the parameters such as intensity profile deviations, power imbalance, intensity profile noise, the pointing error, and the target position error is also discussed. In this study, the model is assumed a solid-sphere illumination, and refraction effects of incident light on the corona are not considered. Our results may have a potential application in the design of the direct-drive laser fusion of the Shen Guang-II Upgrading facility (SG-II-U, China).

  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.

    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.

  19. 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.

  20. 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.

  1. 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

  2. Structured line illumination Raman microscopy

    NASA Astrophysics Data System (ADS)

    Watanabe, Kozue; Palonpon, Almar F.; Smith, Nicholas I.; Chiu, Liang-Da; Kasai, Atsushi; Hashimoto, Hitoshi; Kawata, Satoshi; Fujita, Katsumasa

    2015-12-01

    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.

  3. Laser Holography. High Tech with High Potential for Learning Activities.

    ERIC Educational Resources Information Center

    Schlegel, Ronald D.

    1986-01-01

    This article discusses the procedure, historical development, and applications of holography, and discusses the feasibility and value of implementing a unit or course of study of laser holography into an existing photography laboratory and curriculum. An equipment and supplies list, giving supplies and cost, is included. (CT)

  4. Light-induced cooling of active medium of CW TEA CO2 laser

    NASA Astrophysics Data System (ADS)

    Azharonok, Viktor V.; Filatova, Irina I.; Shimanovich, Vladimir D.

    2003-10-01

    In the present paper a gas kinetic temperature change of active medium of high-power TEA CO2 laser that is conditioned by a self-influence of laser radiation on plasma parameters, is investigated. The active medium was pumped by a self-sustained transverse glow discharge. The gas kinetic temperature Tg of plasma has been deduced from the half-width of rotationally unresolved spectral bands of the (2+)N2. It is shown that the laser radiation propagation through the inverse medium causes a cooling of the active medium. The degree of the gas mixture cooling δTg~5K at W~2.2 W/2.2 W/cm3 and δTg~60 K at W~4.4 W/cm3. We suppose that the effect of the active medium cooling is connected with the change of a kinetic of V-T relaxation in asymmetrical mode of the active medium cooling is connected with the change of a kinetic of V-T relaxation in asymmetrical mode of the active medium cooling is connected with with the change of a kinetic of V-T relaxation in asymmetrical mode of vibrationally-excited CO2 molecule when the lasing takes place in the laser resonator. Analytical estimation of light-induced temperature change δT*g of fast-flow TEA CO2-laser active medium are compared with the experimental ones.

  5. 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

    2013-06-01

    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.

  6. 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

    2013-06-01

    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. PMID:23683299

  7. [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.

  8. 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.

  9. Activation of ethylenediaminetetraacetic acid by a 940 nm diode laser for enhanced removal of smear layer.

    PubMed

    Lagemann, Manfred; George, Roy; Chai, Lei; Walsh, Laurence J

    2014-08-01

    Laser enhancement of ethylenediaminetetraacetic acid with cetrimide (EDTAC) has previously been shown to increase removal of smear layer, for middle-infrared erbium lasers. This study evaluated the efficiency of EDTAC activation using a near-infrared-pulsed 940 nm laser delivered by plain fibre tips into 15% EDTAC or 3% hydrogen peroxide. Root canals in 4 groups of 10 single roots were prepared using rotary files, with controls for the presence and absence of smear layer. After laser treatment (80 mJ pulse(-1) , 50 Hz, 6 cycles of 10 s), roots were split and the apical, middle and coronal thirds of the canal were examined using scanning electron microscopy, with the area of dentine tubules determined by a validated quantitative image analysis method. Lasing EDTAC considerably improved smear layer removal, while lasing into peroxide gave minimal smear layer removal. The laser protocol used was more effective for smear layer removal than the 'gold standard' protocol using EDTAC with sodium hypochlorite (NaOCl). In addition, lasers may also provide a benefit through photothermal disinfection. Further research is needed to optimise irrigant activation protocols using near-infrared diode lasers of other wavelengths.

  10. 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)

  11. Direct laser writing for active and passive high-Q polymer microdisks on silicon.

    PubMed

    Grossmann, Tobias; Schleede, Simone; Hauser, Mario; Beck, Torsten; Thiel, Michael; von Freymann, Georg; Mappes, Timo; Kalt, Heinz

    2011-06-01

    We report the fabrication of high-Q polymeric microdisks on silicon via direct laser writing utilizing two-photon absorption induced polymerization. The quality factors of the passive cavities are above 10(6) in the 1300 nm wavelength region. The flexible three-dimensional (3D) lithography method allows for the fabrication of different cavity thicknesses on the same substrate, useful for rapid prototyping of active and passive optical microcavities. Microdisk lasers are realized by doping the resist with dye, resulting in laser emission at visible wavelengths.

  12. 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.

  13. Waterproof active paper via laser surface micropatterning of magnetic nanoparticles.

    PubMed

    Chitnis, G; Ziaie, B

    2012-09-26

    Paper is one of the oldest and most abundant materials known to man. Recently, there has been a considerable interest in creating paper devices by combining paper with other functional materials. In this letter, we demonstrate a simple fabrication technique to create water-resistant ferro-patterns on wax paper using CO(2) laser ablation. A resolution of about 100 μm is achieved which is mostly limited by the cellulose fiber size (~50 μm) in the wax paper and can be improved by using a smaller cellulose matrix. Laser ablation results in modification of surface morphology and chemistry, leading to a change in surface energy. We also present a 2D model for ferrofluid deposition relating the size of the pattern to the amount of ferroparticles deposited on the surface. Finally, a paper gripper is presented to demonstrate advantages of our technique, which allows microscale patterning and machining in a single step. PMID:22939525

  14. 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)

  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. Laser Activated Flow Regulator for Glaucoma Drainage Devices

    PubMed Central

    Olson, Jeffrey L.; Velez-Montoya, Raul; Bhandari, Ramanath

    2014-01-01

    Purpose To assess the capabilities of a new glaucoma drainage device regulator in controlling fluid flow as well as to demonstrate that this effect may be titratable by noninvasive means. Methods A rigid eye model with two main ports was used. On the first port, we placed a saline solution column. On the second, we placed a glaucoma shunt. We then measured the flow and flow rate through the system. After placing the regulator device on the tip of the tube, we measured again with the intact membrane and with the membrane open 50% and 100%. For the ex vivo testing we used a similar setting, using a cadaveric porcine eye, we measured again the flow and flow rate. However, this time we opened the membrane gradually using laser shots. A one-way analysis of variance and a Fisher's Least Significant Difference test were used for statistical significance. We also calculated the correlation between the numbers of laser shots applied and the main outcomes. Results The flow through the system with the glaucoma drainage device regulator (membrane intact and 50% open) was statistically lower than with the membrane open 100% and without device (P < 0.05). The flow was successfully controlled by the number of laser shots applied, and showed a positive correlation (+ 0.9). The flow rate was almost doubled every 10 shots and statistically lower than without device at all time (P < 0.05). Conclusions The glaucoma drainage device regulator can be controlled noninvasively with laser, and allows titratable control of aqueous flow. Translational Relevance Initial results and evidence from this experiment will justify the initiation of in vivo animal trials with the glaucoma drainage device regulator; which brings us closer to possible human trials and the chance to significantly improve the existing technology to treat glaucoma surgically. PMID:25374772

  17. 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.

  18. Design and simulation of two-section DFB lasers with short active-section lengths.

    PubMed

    Zhao, Gongyuan; Sun, Junqiang; Xi, Yanping; Gao, Dingshan; Lu, Qiaoyin; Guo, Weihua

    2016-05-16

    Distributed feedback lasers comprised of a reflection section and an active section have been proposed for high direct-modulation bandwidth. The reflection section has the same core layer as the active section so butt-joint re-growth is avoided. Without current injection the reflection section will be pumped to near transparency by the emission from the laser itself so high reflection (> 0.75) can still be achieved as confirmed by the simulation. Therefore a short (150 µm) active section can be used, which enables a low threshold current (~5 mA) and a high direct modulation bandwidth (>30 GHz) as demonstrated by the simulation. PMID:27409881

  19. 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.

  20. Enhanced weak-signal sensitivity in two-photon microscopy by adaptive illumination.

    PubMed

    Chu, Kengyeh K; Lim, Daryl; Mertz, Jerome

    2007-10-01

    We describe a technique to enhance both the weak-signal relative sensitivity and the dynamic range of a laser scanning optical microscope. The technique is based on maintaining a fixed detection power by fast feedback control of the illumination power, thereby transferring high measurement resolution to weak signals while virtually eliminating the possibility of image saturation. We analyze and demonstrate the benefits of adaptive illumination in two-photon fluorescence microscopy.

  1. 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.

  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. 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.

  4. LED uniform illumination system for DMD-based confocal microscopy

    NASA Astrophysics Data System (ADS)

    Xiao, Kaimin; Hou, Wenmei; Xu, Qixin; Peng, Bofang

    2013-10-01

    Due to the coherence of laser light source it could produce coherent noise in parallel confocal microscopy based on Digital Micromirror Device (DMD) and thus affect the resolution. LED light source instead of the laser light source can give full play because of its incoherence characterization. In this paper, free-form surface lens is used for LED secondary optics design. According to the LED characteristics and the law of refraction, we have established differential equations of free-form surface. We solved equations with the method of Runge-Kutta by Matlab and the model was built in Tracepro for optical simulation. The results show that the uniformity on the DMD is better than 90% and the lighting efficiency is higher than before. The measured data show us a much more uniform illumination on DMD and LED uniform illumination system successfully avoided the gray error which was caused by the uneven illumination. The LED driver circuit using DC power supply provides us a more stable light source. The axial optical tomography is more accurate and the reconstruction of three-dimensional image is more clearer.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. Active-medium inhomogeneities and optical quality of radiation of supersonic chemical oxygen-iodine lasers

    SciTech Connect

    Boreysho, A S; Druzhinin, S L; Lobachev, V V; Savin, A V; Strakhov, S Yu; Trilis, A V

    2007-09-30

    Optical inhomogeneities of the active medium of a supersonic chemical oxygen-iodine laser (COIL) and their effect on the radiation parameters are studied in the case when an unstable resonator is used. Classification of optical inhomogeneities and the main factors affecting the quality of COIL radiation are considered. The results of numerical simulation of a three-dimensional gas-dynamic active medium and an unstable optical resonator in the diffraction approximation are presented. The constraints in the fabrication of large-scale COILs associated with a deterioration of the optical quality of radiation are determined. (lasers)

  13. Corneal aldehyde dehydrogenase and glutathione S-transferase activity after excimer laser keratectomy in guinea pigs

    PubMed Central

    Bilgihan, K.; Bilgihan, A.; Turkozkan, N.

    1998-01-01

    BACKGROUND—The free radical balance of the eye may be changed by excimer laser keratectomy. Previous studies have demonstrated that excimer laser keratectomy increases the corneal temperature, decreases the superoxide dismutase activity of the aqueous, and induces lipid peroxidation in the superficial corneal stroma. Aldehyde dehydrogenase (ALDH) and glutathione S-transferase (GST) are known to play an important role in corneal metabolism, particularly in detoxification of aldehydes, which are generated from free radical reactions.
METHODS—In three groups of guinea pigs mechanical corneal de-epithelialisation was performed in group I, superficial corneal photoablation in group II, and deep corneal photoablation in group III, and the corneal ALDH and GST activities measured after 48 hours.
RESULTS—The mean ALDH and GST activities of group I and II showed no differences compared with the controls (p>0.05). The corneal ALDH activities were found to be significantly decreased (p<0.05) and GST activities increased (p<0.05) in group III.
CONCLUSION—These results suggest that excimer laser treatment of high myopia may change the ALDH and GST activities, metabolism, and free radical balance of the cornea.

 Keywords: excimer laser keratectomy; aldehyde dehydrogenase; glutathione S-transferase PMID:9602629

  14. Structured illumination microscopy using random intensity incoherent reflectance.

    PubMed

    Hoffman, Zachary R; DiMarzio, Charles A; DiMazrio, Charles A

    2013-06-01

    Depth information is resolved from thick specimens using a modification of structured illumination. By projecting a random projection pattern with varied spatial frequencies that is rotated while capturing images, sectioning can be performed using an incoherent light source in reflectance only. This provides a low-cost solution to obtaining information similar to that produced in confocal microscopy and other methods of structured illumination, without the requirement of complex or elaborate equipment, coherent light sources, or fluorescence. The broad line width of the light emitting diode minimizes artifacts associated with speckle from the laser while also increasing the safety of the instrument. Single diffusers and cascaded diffusers are compared to provide the most efficient method for sectioning at depth. By using reflectance only, in vivo images are produced on a human subject, generating high-contrast images and providing depth information about subsurface objects.

  15. 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

  16. 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.

  17. Efficacy of laser-based irrigant activation methods in removing debris from simulated root canal irregularities.

    PubMed

    Deleu, Ellen; Meire, Maarten A; De Moor, Roeland J G

    2015-02-01

    In root canal therapy, irrigating solutions are essential to assist in debridement and disinfection, but their spread and action is often restricted by canal anatomy. Hence, activation of irrigants is suggested to improve their distribution in the canal system, increasing irrigation effectiveness. Activation can be done with lasers, termed laser-activated irrigation (LAI). The purpose of this in vitro study was to compare the efficacy of different irrigant activation methods in removing debris from simulated root canal irregularities. Twenty-five straight human canine roots were embedded in resin, split, and their canals prepared to a standardized shape. A groove was cut in the wall of each canal and filled with dentin debris. Canals were filled with sodium hypochlorite and six irrigant activation procedures were tested: conventional needle irrigation (CI), manual-dynamic irrigation with a tapered gutta percha cone (manual-dynamic irrigation (MDI)), passive ultrasonic irrigation, LAI with 2,940-nm erbium-doped yttrium aluminum garnet (Er:YAG) laser with a plain fiber tip inside the canal (Er-flat), LAI with Er:YAG laser with a conical tip held at the canal entrance (Er-PIPS), and LAI with a 980-nm diode laser moving the fiber inside the canal (diode). The amount of remaining debris in the groove was scored and compared among the groups using non-parametric tests. Conventional irrigation removed significantly less debris than all other groups. The Er:YAG with plain fiber tip was more efficient than MDI, CI, diode, and Er:YAG laser with PIPS tip in removing debris from simulated root canal irregularities.

  18. 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)

  19. 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.

  20. 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.

  1. 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.

  2. Infrared Laser Activation of Soluble and Membrane Protein Assemblies in the Gas Phase.

    PubMed

    Mikhailov, Victor A; Liko, Idlir; Mize, Todd H; Bush, Matthew F; Benesch, Justin L P; Robinson, Carol V

    2016-07-19

    Collision-induced dissociation (CID) is the dominant method for probing intact macromolecular complexes in the gas phase by means of mass spectrometry (MS). The energy obtained from collisional activation is dependent on the charge state of the ion and the pressures and potentials within the instrument: these factors limit CID capability. Activation by infrared (IR) laser radiation offers an attractive alternative as the radiation energy absorbed by the ions is charge-state-independent and the intensity and time scale of activation is controlled by a laser source external to the mass spectrometer. Here we implement and apply IR activation, in different irradiation regimes, to study both soluble and membrane protein assemblies. We show that IR activation using high-intensity pulsed lasers is faster than collisional and radiative cooling and requires much lower energy than continuous IR irradiation. We demonstrate that IR activation is an effective means for studying membrane protein assemblies, and liberate an intact V-type ATPase complex from detergent micelles, a result that cannot be achieved by means of CID using standard collision energies. Notably, we find that IR activation can be sufficiently soft to retain specific lipids bound to the complex. We further demonstrate that, by applying a combination of collisional activation, mass selection, and IR activation of the liberated complex, we can elucidate subunit stoichiometry and the masses of specifically bound lipids in a single MS experiment.

  3. 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.

  4. 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.

  5. Different Brain Network Activations Induced by Modulation and Nonmodulation Laser Acupuncture

    PubMed Central

    Hsieh, Chang-Wei; Wu, Jih-Huah; Hsieh, Chao-Hsien; Wang, Qwa-Fun; Chen, Jyh-Horng

    2011-01-01

    The aim of this study is to compare the distinct cerebral activation with continued wave (CW) and 10 Hz-modulated wave (MW) stimulation during low-level laser acupuncture. Functional magnetic resonance imaging (fMRI) studies were performed to investigate the possible mechanism during laser acupuncture stimulation at the left foot's yongquan (K1) acupoint. There are 12 healthy right-handed volunteers for each type of laser stimulation (10-Hz-Modulated wave: 8 males and 4 females; continued wave: 9 males and 3 females). The analysis of multisubjects in this experiment was applied by random-effect (RFX) analysis. In CW groups, significant activations were found within the inferior parietal lobule, the primary somatosensory cortex, and the precuneus of left parietal lobe. Medial and superior frontal gyrus of left frontal lobe were also aroused. In MW groups, significant activations were found within the primary motor cortex and middle temporal gyrus of left hemisphere and bilateral cuneus. Placebo stimulation did not show any activation. Most activation areas were involved in the functions of memory, attention, and self-consciousness. The results showed the cerebral hemodynamic responses of two laser acupuncture stimulation modes and implied that its mechanism was not only based upon afferent sensory information processing, but that it also had the hemodynamic property altered during external stimulation. PMID:20953400

  6. 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.

  7. 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.

  8. 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.

  9. Laser-activated solder weld repair of the inferior alveolar nerve in rats

    NASA Astrophysics Data System (ADS)

    Curtis, Nigel J.; Lauto, Antonio; Trickett, Rodney I.; Owen, Earl R.; Walker, D. M.

    1997-05-01

    A new laser activated solder weld technique is described for the microsurgical repair of the inferior alveolar nerve in rats. The laser weld technique used an albumin based solder, containing indocyanine cardiogreen, plus an infrared diode laser. Seven animals had inferior alveolar nerve repairs performed using the laser weld technique and these were compared against corresponding unoperated controls plus three cases of nerve section without repair. Histochemical analysis was performed utilizing neuron counts and horseradish peroxidase tracer (HRP) uptake in the trigeminal ganglion following sacrifice and staining of frozen sections with cresyl violet and diaminobenzidene. The results of this analysis showed comparable mean neuron counts and mean HRP uptake by neurons for the unoperated control and laser weld groups with considerable reduction of mean values in cases of nerve section with no repair. Sections of the repaired inferior alveolar nerves, stained with Masson's trichrome, showed no adverse reactions by axons or epineurium to the coagulative repair with the solder and demonstrated regeneration of myelinated axons at the time of sacrifice. In summary a new technique of laser weld repair of the inferior alveolar nerve is described which, on initial analysis, appears to be a reliable alternative to traditional techniques.

  10. Fabrication and in vitro deployment of a laser-activated shape memory polymer vascular stent

    PubMed Central

    Baer, Géraldine M; Small, Ward; Wilson, Thomas S; Benett, William J; Matthews, Dennis L; Hartman, Jonathan; Maitland, Duncan J

    2007-01-01

    Background 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. Methods 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. Results 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 ~8 W. Conclusion 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. PMID:18042294

  11. Activation energy study of electron transport in high performance short wavelengths quantum cascade lasers.

    PubMed

    Pflügl, Christian; Diehl, Laurent; Lyakh, Arkadiy; Wang, Qi Jie; Maulini, Richard; Tsekoun, Alexei; Patel, C Kumar N; Wang, Xiaojun; Capasso, Federico

    2010-01-18

    We present a method to study current paths through quantum cascade lasers (QCLs). The temperature dependence of the current is measured at a fixed voltage. At low temperatures we find activation energies that correspond to the energy difference between the injector ground state and the upper laser level. At higher temperatures additional paths with larger activation energies are found. Application of this method to high performance QCLs based on strained InGaAs/InAlAs quantum wells and barriers with different band-offsets allows us to identify individual parasitic current paths through the devices. The results give insight into the transport properties of quantum cascade lasers thus providing a useful tool for device optimization.

  12. Bandwidth enhancement of injection-locked distributed reflector lasers with wirelike active regions.

    PubMed

    Lee, SeungHun; Parekh, Devang; Shindo, Takahiko; Yang, Weijian; Guo, Peng; Takahashi, Daisuke; Nishiyama, Nobuhiko; Chang-Hasnain, Connie J; Arai, Shigehisa

    2010-08-01

    The modulation bandwidth enhancement of distributed reflector (DR) lasers with wirelike active regions utilizing optical injection locking is demonstrated both theoretically and experimentally. By the rate equation analysis, it is shown that DR lasers with wirelike active regions realize a low optical injection power and a large bandwidth enhancement under small operation currents. Experimentally, the small-signal bandwidth is increased to >15 GHz at a bias current of 5 mA, which is 4 times smaller than that for conventional edge-emitting lasers. A large signal modulation at 10 Gbps is also performed at the same bias current of 5 mA and voltage swing of 0.4 V(pp), and error-free detection was confirmed under the low-power conditions.

  13. Application of laser radiation in decoration and marking of ceramic products

    NASA Astrophysics Data System (ADS)

    Chmielewska, D.; Gebel, R.; Szamałek, K.; Olszyna, A.; Marczak, J.; Sarzyński, A.; Strzelec, M.

    2013-01-01

    In cooperation with the Institute of Optoelectronics MUT, the Institute of Ceramics and Building Materials conducts work on laser decoration of ceramic products. Two methods are under development: laser activation and laser sintering. The activation method is based on change of color of specially prepared ceramic material due only to illumination by laser beam. Laser sintering is a deposition welding process in which a layer of ceramic powder is deposited on the substrate material, and the two ceramic materials are fused through the application of laser beam, in turn creating any desired color pattern. The paper describes the influence of some physical phenomena on the progress of the laser process as well as sample experimental results.

  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. Non-invasive diode laser activation of transient receptor potential proteins in nociceptors.

    PubMed

    Jiang, Nan; Cooper, Brian Y; Nemenov, Michael I

    2007-02-21

    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.

  16. 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.

  17. Heart rate estimation from facial photoplethysmography during dynamic illuminance changes.

    PubMed

    Dongseok Lee; Jeehoon Kim; Sungjun Kwon; Kwangsuk Park

    2015-08-01

    Camera-based remote photoplethysmography (rPPG) enables low-cost, non-contact cardiovascular activity monitoring. However, applying rPPG to practical use has some limitations caused from the artifacts by illuminance changes. During watching a video in a dark room, for example, watching a TV at night without illuminance, there is a high correlation between the brightness changes of a video and the illuminance variation on the skin of the viewer's face. In this study, we propose an artifact reduction method in rPPG, which is caused by the variation of the illuminance. The method subtracts the artifacts from the raw facial rPPG signal by applying multi-order curve fitting between the illuminance information from the facial rPPG signal and the brightness information from a video. On average, the results showed that signal-to-noise ratio (SNR) increased from -11.74 to -4.19 dB and from -15.27 to 7.99 dB for low-dynamic-brightness and high-dynamic-brightness video, respectively. In addition, the root-mean-square-error (RMSE) of estimated heart rate decreased from 11.00 to 1.82 bpm and from 9.88 to 4.65 bpm for the videos, respectively. PMID:26736863

  18. Heart rate estimation from facial photoplethysmography during dynamic illuminance changes.

    PubMed

    Dongseok Lee; Jeehoon Kim; Sungjun Kwon; Kwangsuk Park

    2015-08-01

    Camera-based remote photoplethysmography (rPPG) enables low-cost, non-contact cardiovascular activity monitoring. However, applying rPPG to practical use has some limitations caused from the artifacts by illuminance changes. During watching a video in a dark room, for example, watching a TV at night without illuminance, there is a high correlation between the brightness changes of a video and the illuminance variation on the skin of the viewer's face. In this study, we propose an artifact reduction method in rPPG, which is caused by the variation of the illuminance. The method subtracts the artifacts from the raw facial rPPG signal by applying multi-order curve fitting between the illuminance information from the facial rPPG signal and the brightness information from a video. On average, the results showed that signal-to-noise ratio (SNR) increased from -11.74 to -4.19 dB and from -15.27 to 7.99 dB for low-dynamic-brightness and high-dynamic-brightness video, respectively. In addition, the root-mean-square-error (RMSE) of estimated heart rate decreased from 11.00 to 1.82 bpm and from 9.88 to 4.65 bpm for the videos, respectively.

  19. XRX-Köhler optical design and illumination optimization

    NASA Astrophysics Data System (ADS)

    Coughenour, Blake; Angel, Roger

    2014-12-01

    This paper describes the optical and illumination design of a CPV solar energy system. The challenges of creating a highly efficient yet low-cost system architecture come from many sources, but are primarily limited by the photoelectron conversion efficiency of the cells and the illumination performance of the system for on-axis and off-axis pointing scenarios. Furthermore, the need for high solar spectral throughput, evenly concentrated sunlight, and tolerance to offaxis pointing places strict illumination requirements on the optical design. To be commercially viable, the cost associated with all components must be minimized so that when taken together, the absolute installed cost of the system in kWh is lower than any other solar energy method. We present two low-cost optical design embodiments of a dishbased concentration photovoltaic (CPV) system that utilize Köhler illumination to achieve good illumination uniformity across an array of solar cells. Further optimization for active shadowing compensation and compound electrical I-V curve modeling for the solar cell array is performed that allows realistic off-axis performance scenarios to be modeled with the correct power response sensitivity.

  20. Physiological effects of sudden change in illuminance during dark-adapted state.

    PubMed

    Noguchi, H; Sakaguchi, T; Sato, M

    1999-05-01

    To derive an optimal illuminance of nighttime illumination, we conducted an experiment with 7 healthy young individuals and 7 healthy elderly individuals as subjects. After 20 minutes of adaptation to darkness, subjects were exposed to illumination under 5 conditions comprising 0.5 lx, 1 lx, 3 lx, 10 lx, or 30 lx vertical illuminance of the facial region, and heart rate variability (HRV) and electroencephalogram (EEG) were measured, and discomfort was evaluated by subjective report. Results of LF/(LF + HF) (LF = low frequency, HF = high frequency) demonstrated a V-shaped trend for the young groups beginning during exposure and ending post exposure, with 3 lx conditions representing the minimum value, a value markedly lower than that for 30 lx conditions. From these results we inferred that approximately 3 lx illuminance could best suppress physiological stress. Evaluation of discomfort by subjective report also demonstrated an increase in discomfort evaluation scores under high illuminance conditions. The alpha-wave proportion of EEG during exposure fell markedly on 3 lx or higher illuminance conditions, and we inferred that visual sensory information and cortical activity level were adequately attained in 3 lx or higher illuminance conditions. These results suggest that the optimal illuminance of nighttime illumination is approximately 3 lx.

  1. 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.

  2. Modification of graphene oxide by laser irradiation: a new route to enhance antibacterial activity.

    PubMed

    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

    2016-06-17

    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. PMID:27158973

  3. Effects of changing illuminance on somatosensory function.

    PubMed

    Yoshinaga, Naoki; Fujita, Mizuho; Tanaka, Yuji L; Nemoto, Seiji

    2011-01-01

    Artificial sources of illumination can be easily used, regardless of the time and place, to improve visibility at night and in dark places. Illuminance and color temperature are particularly important factors since they are known to elicit physiological effects. However, the relationship between changes in illuminance and somatosensory function has not been sufficiently clarified. Thus, the purpose of this study was to construct a laboratorial model to examine the effects of lowering or raising illuminance on somatosensory function. Three illuminance levels (200 lx, 50 lx, and 0 lx), which were changed using all combinations, and an artificial sensory stimulus maintained at a constant intensity were presented to the subjects of this study. Objective sensory function in response to the sensory stimulus was investigated by somatosensory evoked potential (SEP), and subjective sensory evaluation in response to the stimulus was investigated using a visual analogue scale (VAS) and by interview. In many cases, the SEP amplitude and VAS value tended to decrease when illuminance was lowered and tended to increase when illuminance was raised. However, in a few cases, SEP amplitude and VAS value tended to increase in spite of the low illuminance. The occurrence of attention responses and unpleasant emotional responses caused by lowering the illuminance seems to be related to this study finding.

  4. Ray tracing analysis of inclined illumination techniques.

    PubMed

    Sinkó, József; Szabó, Gábor; Erdélyi, Miklós

    2014-08-11

    The reduction of out of focus signal is a general task in fluorescence microscopy and is especially important in the recently developed super-resolution techniques because of the degradation of the final image. Several illumination methods have been developed to provide decreased out of focus signal level relative to the common epifluorescent illumination. In this paper we examine the highly inclined and the total internal reflection illumination techniques using the ray tracing method. Two merit functions were introduced for the quantitative description of the excitation of the selected region. We studied the feasibility of illumination methods, and the required corrections arising from the imperfections of the optical elements.

  5. 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.

  6. 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.

  7. Measurement of pressure changes during laser-activated irrigant by an erbium, chromium: yttrium, scandium, gallium, garnet laser.

    PubMed

    Peeters, Harry Huiz; De Moor, Roeland J G

    2015-07-01

    The use of Er,Cr:YSGG laser to activate irrigants results in the creation of vapour bubbles and shockwaves. The present study evaluated the magnitude of pressure changes in the root canal during laser-activated irrigation. The root canal of a single extracted maxillary canine was enlarged to a size 40/0.06 file. A pressure sensor was inserted apically into the root canal. The tooth was processed as follows. In the EDTA condition, the tooth was irrigated with 17 % EDTA; in the NaOCl condition, the tooth was irrigated with 3 % NaOCl. In all conditions, the irrigants were activated at 0.75 and 1.75 W for 60 s using RFT2 and MZ2 tips; to analyse the effect of tip placement, the tip was activated at the orifice and after inserting the tip 5 mm deeper than the orifice. Data showed no significant difference between irrigation regimens (p > 0.05). There were no significant differences of the pressure between RFT2 and MZ2 tips (p > 0.05). The placement of tips closer to the apex resulted in significantly higher pressure than at the orifice (p < 0.001). The use of 1.75 W power resulted in a significantly higher increase of pressure compared to 0.75 W (p < 0.001), regardless either the type of solutions or tips used. The magnitude of the pressure changes in the root canal at 0.75 W was significantly lower than 1.75 W regardless of either type of tips or solutions used. The closer the insertion of the tip to the apex, the higher the pressure.

  8. 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.

  9. 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.

  10. Illuminating Asset Value through New Seismic Technology

    NASA Astrophysics Data System (ADS)

    Brandsberg-Dahl, S.

    2007-05-01

    evaluate technologies and subsequently encourage vendor activity to develop and deploy a commercial system. The 3D seismic method exploded into general usage in the 1990's. Our industry delivered 3D cheaper and faster, improving quality through improved acquisition specifications and new processing technology. The need to mitigate business risks in highly material subsalt plays led BP to explore the technical limits of the seismic method, testing novel acquisition techniques to improve illumination and signal to noise ratio. These were successful and are applicable to analogue seismic quality problems globally providing breakthroughs in illuminating previously hidden geology and hydrocarbon reservoirs. A focused business challenge, smart risk taking, investment in people and computing capability, partnerships, and rapid implementation are key themes that will be touched on through out the talk.

  11. 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.

  12. Measuring of object vibration using sinusoidal-modulation laser-diode active interferometer

    NASA Astrophysics Data System (ADS)

    Ai, Yong; Cao, Qinfeng; Lu, Su

    1996-09-01

    Using the character that the emitting optical frequency of the laser diode is controlled by the injected current, the ability of eliminating environmental disturbance of the sinusoidal modulation laser diode active interferometer will be raised by more than one hundred times through putting the disturbed interference signal produced by the environment into the interferometer. When vibrating frequency of objects is different from that of the sinusoidol modulation, 'beat- frequency' will be produced in the interfere signal, which can be analyzed to get the vibrating frequency of objects. This paper described the operation principle and theoretical delusion of the 'beat-frequency' method.

  13. 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.

  14. Effects of Cr2O3 Activating Flux on the Plasma Plume in Pulsed Laser Welding

    NASA Astrophysics Data System (ADS)

    Yi, Luo; Yunfei, Du; Xiaojian, Xie; Rui, Wan; Liang, Zhu; Jingtao, Han

    2016-08-01

    The effects of Cr2O3 activating flux on pulsed YAG laser welding of stainless steel and, particularly, on the behavior of the plasma plume in the welding process were investigated. According to the acoustic emission (AE) signals detected in the welding process, the possible mechanism for the improvement in penetration depth was discussed. The results indicated that the AE signals detected in the welding process reflected the behavior of the plasma plume as pulsed laser energy affecting the molten pool. The root-mean-square (RMS) waveform, AE count, and power spectrum of AE signals were three effective means to characterize the behavior of the plasma plume, which indicated the characteristics of energy released by the plasma plume. The activating flux affected by the laser beam helped to increase the duration and intensity of energy released by the plasma plume, which improved the recoil force and thermal effect transferred from the plasma plume to the molten pool. These results were the main mechanism for Cr2O3 activating flux addition improving the penetration depth in pulsed YAG laser welding.

  15. Effects of Cr2O3 Activating Flux on the Plasma Plume in Pulsed Laser Welding

    NASA Astrophysics Data System (ADS)

    Yi, Luo; Yunfei, Du; Xiaojian, Xie; Rui, Wan; Liang, Zhu; Jingtao, Han

    2016-11-01

    The effects of Cr2O3 activating flux on pulsed YAG laser welding of stainless steel and, particularly, on the behavior of the plasma plume in the welding process were investigated. According to the acoustic emission (AE) signals detected in the welding process, the possible mechanism for the improvement in penetration depth was discussed. The results indicated that the AE signals detected in the welding process reflected the behavior of the plasma plume as pulsed laser energy affecting the molten pool. The root-mean-square (RMS) waveform, AE count, and power spectrum of AE signals were three effective means to characterize the behavior of the plasma plume, which indicated the characteristics of energy released by the plasma plume. The activating flux affected by the laser beam helped to increase the duration and intensity of energy released by the plasma plume, which improved the recoil force and thermal effect transferred from the plasma plume to the molten pool. These results were the main mechanism for Cr2O3 activating flux addition improving the penetration depth in pulsed YAG laser welding.

  16. Radiation-induced defects in Pr3+-activated LiYF4 laser host

    NASA Astrophysics Data System (ADS)

    Dhoble, S. J.; Deshpande, S. P.; Pode, R. B.; Dhoble, N. S.; Gundurao, T. K.

    2004-11-01

    Rare earth doped fluorides have been used in laser applications. Not much is known about the effect of ionizing radiation on the lasing and other properties of fluorides. Therefore, in recent years much attention has been paid to the study of radiation-induced defects in laser materials, as they affect the optical and stimulated emission properties. The defect formation by gamma-ray irradiation in Pr3+ activated LiYF4, powder prepared by melt method, have been studied by thermoluminescence and electron spin resonance techniques and are reported in this paper. It is shown that LiYF4:Pr3+ is sensitive to gamma-ray radiation. Characterization of this laser material using ESR and photoluminescence techniques is also described.

  17. Broadband standoff detection of large molecules by mid-infrared active coherent laser spectrometry.

    PubMed

    Macleod, Neil A; Molero, Francisco; Weidmann, Damien

    2015-01-26

    A widely tunable active coherent laser spectrometer (ACLaS) has been demonstrated for standoff detection of broadband absorbers in the 1280 to 1318 cm-1 spectral region using an external cavity quantum cascade laser as a mid-infrared source. The broad tuning range allows detection and quantification of vapor phase molecules, such as dichloroethane, ethylene glycol dinitrate, and tetrafluoroethane. The level of confidence in molecular mixing ratios retrieved from interfering spectral measurements is assessed in a quantitative manner. A first qualitative demonstration of condensed phase chemical detection on nitroacetanilide has also been conducted. Detection performances of the broadband ACLaS have been placed in the context of explosive detection and compared to that obtained using distributed feedback quantum cascade lasers.

  18. Generation of dissipative solitons in an actively mode-locked ultralong fibre laser

    SciTech Connect

    Koliada, N A; Nyushkov, B N; Ivanenko, A V; Kobtsev, Sergey M; Harper, Paul; Turitsyn, Sergei K; Denisov, Vladimir I; Pivtsov, V S

    2013-02-28

    A single-pulse actively mode-locked fibre laser with a cavity length exceeding 1 km has been developed and investigated for the first time. This all-fibre erbium-doped laser has a normal intracavity dispersion and generates dissipative 8-ns solitons with a fundamental repetition rate of 163.8 kHz; the energy per pulse reaches 34 nJ. The implemented mode locking, based on the use of intracavity intensity modulator, provides self-triggering and high stability of pulsed lasing. A possibility of continuous tuning of the centre lasing wavelength in the range of 1558 - 1560 nm without any tunable spectral selective elements in the cavity is demonstrated. The tuning occurs when controlling the modulation signal frequency due to the forced change in the pulse repetition time (group delay) under the conditions of intracavity chromatic dispersion. (laser optics 2012)

  19. 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.

  20. Aspects of illumination system optimization

    NASA Astrophysics Data System (ADS)

    Koshel, R. John

    2004-09-01

    This paper focuses on the facets of illumination system optimization, in particular parameterization of objects, the number of rays that must be traced to sample properly its properties, and the optimization algorithm with the associated merit function designation. Non-interference ensures that the parameterized objects do not erroneously intersect each other or leave gaps during the steps of the optimization procedure. The required number of rays is based on a model developed for television cameras during their initial days of development. Using signal to noise ratio, it provides the number of rays based on the desired contrast, feature size, and allowed error probability. A lightpipe is used to highlight the nuances of this model. The utility of using system symmetry to increase ray count is also discussed. A modified simplex method of optimization is described. This algorithm provides quicker convergence than the standard simplex method, while it is also robust, accurate, and convergent. A previous example using a compound parabolic concentrator highlights the utility of this improvement.

  1. 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.

  2. 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. PMID:21809349

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Laser optical disk position encoder with active heads

    NASA Astrophysics Data System (ADS)

    Osborne, Eric P.

    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. 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.

  10. 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.

  11. Effect of distorted illumination waves on coherent diffraction microscopy

    NASA Astrophysics Data System (ADS)

    Kohmura, Yoshiki; Nishino, Yoshinori; Ishikawa, Tetsuya; Miao, Jianwei

    2005-12-01

    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.

  12. Lensless in-line holographic microscope with Talbot grating illumination.

    PubMed

    Feng, Shaodong; Wang, Mingjun; Wu, Jigang

    2016-07-15

    We have developed a wide field-of-view lensless in-line holographic microscope (LIHM) capable of acquiring microscopic images with a compact design. In our imaging system, a Ronchi grating was illuminated by a collimated laser beam to generate a Talbot self-imaging grating illumination on the sample, and the in-line holograms were recorded by a CMOS imaging sensor behind the sample. An iterative reconstruction algorithm was then applied to reconstruct the sample image while eliminating the twin-image background that appears in traditional in-line holography. In the algorithm, the dark areas of the illumination grating were used as a known constraint to define the sample support that led to convergence of the iteration. The whole-sample image can be acquired by laterally shifting the grating. We demonstrated the performance of our iteration algorithm and imaging system by successfully acquiring images of polystyrene microspheres with 5 μm diameter and the wing of a green lacewing. PMID:27420484

  13. 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.

  14. 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.

  15. 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}.

  16. A laser-induced repetitive fast neutron source applied for gold activation analysis.

    PubMed

    Lee, Sungman; Park, Sangsoon; Lee, Kitae; Cha, Hyungki

    2012-12-01

    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 × 10(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(4) nuclear reaction, for which the required tritium originated from the primary fusion reaction, D(d,p)T(3). PMID:23277984

  17. 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

  18. 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.

  19. Laser optical disk position encoder with active heads

    NASA Astrophysics Data System (ADS)

    Osborne, Eric P.

    1992-04-01

    An angular position encoder is provided that minimizes the effects of eccentricity and other misalignments between the disk and the read stations by employing heads which incorporate beam steering optics with the ability to actively track the disk in directions along the disk radius and normal to its surface. The device adapts features prevalent in optical disk technology toward the application of angular position sensing. A reflective disk and the principles of interferometry are employed. The servo-controlled steering optics move so as to acquire a track on the disk lying at a predetermined radius and distance below the head, and then adjust position and orientation in order to maintain the view of the disk track as required. Thus, the device is actively self-aligning.

  20. Laser optical disk position encoder with active heads

    NASA Astrophysics Data System (ADS)

    Osborne, Eric P.

    1990-03-01

    An angular position encoder is provided that minimizes the effects of eccentricity and other misalignments between the disk and the read stations by employing heads which incorporate beam steering optics with the ability to actively track the disk in directions along the disk radius and normal to its surface. The device adapts features prevalent in optical disk technology toward the application of angular position sensing. A reflective disk and the principles of interferometry are employed. The servo-controlled steering optics move so as to acquire a track on the disk lying at a predetermined radius and distance below the head, and then adjust position and orientation in order to maintain the view of the disk track as required. Thus, the device is actively self-aligning.

  1. 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.

  2. 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. PMID:24085183

  3. 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.

  4. Illuminance, Subjective Sleep Quality, and Psychosomatic Health in Elderly Individuals Requiring Care: A Survey of Japan's Hokuriku Region in Winter.

    PubMed

    Ichimori, Akie; Tsukasaki, Keiko; Koyama, Emi

    2015-01-01

    We measured the illuminance exposure for 3 days in winter of a convenience sample of 44 elderly people certified as requiring support in Japan's Hokuriku region. We calculated the illuminance ratio per minute during activity and while in bed and analyzed the relationship between illuminance, subjective sleep quality, and psychosomatic health. There was a significant negative correlation between illuminance and 15-item Geriatric Depression Scale scores. Multiple regression analysis indicated that depression scores were significantly related to age, level of required support, and illuminance. The findings suggest that environments without light and dark cycles increase depression scores in frail elderly people. PMID:25970104

  5. Illuminance, Subjective Sleep Quality, and Psychosomatic Health in Elderly Individuals Requiring Care: A Survey of Japan's Hokuriku Region in Winter.

    PubMed

    Ichimori, Akie; Tsukasaki, Keiko; Koyama, Emi

    2015-01-01

    We measured the illuminance exposure for 3 days in winter of a convenience sample of 44 elderly people certified as requiring support in Japan's Hokuriku region. We calculated the illuminance ratio per minute during activity and while in bed and analyzed the relationship between illuminance, subjective sleep quality, and psychosomatic health. There was a significant negative correlation between illuminance and 15-item Geriatric Depression Scale scores. Multiple regression analysis indicated that depression scores were significantly related to age, level of required support, and illuminance. The findings suggest that environments without light and dark cycles increase depression scores in frail elderly people.

  6. 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.

  7. 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.

  8. 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

  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

    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. Disruption of cell membranes via laser-activated, acoustically active, carbon nanoparticles

    NASA Astrophysics Data System (ADS)

    Holguin, Stefany; Prausnitz, Mark; Thadhani, Naresh

    2015-06-01

    Physical drug delivery methods provide an avenue to overcome the selectivity of the cell membrane via physical forces that disrupt cell membranes and drive drug molecules into the cytosol. When carbon black nanoparticles in suspension with cells and drug molecules are exposed to nanosecond-pulsed laser light, high uptake and cell viability are observed. This laser-carbon nanoparticle interaction causes thermal expansion and local vaporization that results in the release of acoustic waves into the surrounding medium. These combined energy transduction mechanisms, phenomena called transient nanoparticle energy transduction (TNET), are responsible for disruption of the cell membrane and subsequent efficient intracellular drug uptake while maintaining high cell viability. The overall objective of this work is to investigate TNET and the bioeffects associated with physical disruption of cell membranes for drug delivery via laser-carbon nanoparticle interactions. For example, varying and quantifying energy input to carbon nanoparticles by way of laser beam manipulation, assists in the understanding and assessment of subsequent bioeffects. Results of work performed to date will be presented. National Science Foundation Graduate Research Fellowship under Grant No. 0946809, Georgia Tech University Center of Exemplary Mentoring (UCEM) & the Alfred P. Sloan Foundation.

  12. Illuminance and egg production in broiler breeders.

    PubMed

    Lewis, P D; Danisman, R; Gous, R M

    2009-03-01

    1. Ross broiler breeders were reared at a nominal illuminance of 15, 20 or 45 lux and transferred to a nominal illuminance of 25, 55 or 70 lux at 20 weeks. 2. There were no significant interactions between the response to illuminance during rearing and in lay. This means that it matters not whether illuminance is increased, decreased or held constant on transfer to the laying house, provided it equals or exceeds the biological optimum for satisfactory egg production. 3. Whilst there were no significant effects of illuminance in either the rearing period or laying periods on egg numbers, peak rate of lay, terminal rate of lay, egg mass output or liveability, meta-analyses of these and other data indicated biological optima of 15 lux during rearing and 7 lux in the laying period. Birds reared at 45 lux had a lower mean egg weight (and earlier sexual maturity) than birds reared at 15 lux, and hens illuminated at 25 lux in the laying period laid more eggs on the floor than at either 55 or 70 lux. 4. Typical primary breeder recommendations of 10-20 lux during rearing and 30-60 lux in lay are appropriate for floor-housed birds; however, an illuminance of 7 lux could be used for caged birds, subject to welfare-code compliance.

  13. LED illuminant on the ambient light

    NASA Astrophysics Data System (ADS)

    Liu, Anqing; Sandipan, Mishra; Shur, Michael

    2014-09-01

    We develop an approach for combining illuminance and spectral power distribution of the LED and ambient light and apply our technique for developing an LED camera flashlight balancing the illuminance contrast between object and background. Our method uses the closed loop, multiobjective optimization comprising: (1) characterizing the lighting task by illuminance, correlated color temperature (CCT), and statistical color quality indices that include a set of Statistical Color Quality Metrics and the Color Rendition Index (CRI) implemented with indexes of S (saturation) or D (dulling); (2) measuring the illuminance and the spectrum of the ambient light on the target lighting surface, which might depend on all the sources proving illumination and on the reflected light; (3) determining the desired illuminance of the LED source on the target lighting surface; (4) calculating the desired luminous flux of the LED source according to the desired illuminance; (5) constituting the SPD of the LED source; (6) calculating the relative spectra counts of the LED source and the ambient light on the target lighting surface (7) calculating the CCT and statistical color quality indexes of the combined light; (8) repeating the above steps until the resulting SPD is close enough to the expectation. Using the above method, an LED camera flashlight has been designed, which works together with usual fluorescent ambient light and generates working lighting environment with high fidelity and high CCT (6000K). The spectrum and luminous flux of the LED lamp is automatically tunable with a change of the ambient light.

  14. Efficiency of continuous-wave solar pumped semiconductor lasers

    NASA Astrophysics Data System (ADS)

    Johnson, Stanley; Küppers, Franko; Pau, Stanley

    2013-04-01

    We report the results of an efficient solar pumped semiconductor laser system that uses high efficiency multi-junction photovoltaic cells and laser diodes in order to achieve the sunlight to laser light conversion efficiency of over 10% without any active cooling and concentration optics. Semiconductor lasers with wavelength from 445 nm to 1550 nm are powered directly by an array of photovoltaic (PV) cells under one sun illumination (100 mW/cm2). The maximum energy efficiency reaches 10.34% at 976 nm with an output power of 4.31 W. This system is inherently more efficient than direct solar pumped lasers that have been studied in the past and could play a key role in future renewable energy production and power beaming applications.

  15. 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.

  16. Active/passive scanning. [airborne multispectral laser scanners for agricultural and water resources applications

    NASA Technical Reports Server (NTRS)

    Woodfill, J. R.; Thomson, F. J.

    1979-01-01

    The paper deals with the design, construction, and applications of an active/passive multispectral scanner combining lasers with conventional passive remote sensors. An application investigation was first undertaken to identify remote sensing applications where active/passive scanners (APS) would provide improvement over current means. Calibration techniques and instrument sensitivity are evaluated to provide predictions of the APS's capability to meet user needs. A preliminary instrument design was developed from the initial conceptual scheme. A design review settled the issues of worthwhile applications, calibration approach, hardware design, and laser complement. Next, a detailed mechanical design was drafted and construction of the APS commenced. The completed APS was tested and calibrated in the laboratory, then installed in a C-47 aircraft and ground tested. Several flight tests completed the test program.

  17. Rapid laser nephelometric determination of amylase activity in serum and urine.

    PubMed

    Liu, T Z; Wei, J S

    1991-03-01

    We describe herein a rapid and sensitive laser nephelometric method for the determination of serum and urinary amylase activities. Our data showed that the change in relative light scattering (RLS) of an amylopectin substrate measured by a laser nephelometer related directly with amylolytic activity of amylase from 50 to 600 IU/L. Within-run variations at 293 and 769 IU/L sera showed CV's of 5.0% and 3.1%, respectively. Day-to-day variation for the same sera showed CV's of 7.2% and 4.7%, respectively. Correlation studies using the manual Phadebas dye-starch complex method and with the Roche amylochrome method showed correlation coefficients of 0.99 and 0.95, respectively. Using urine specimens, the correlation studies also showed a correlation coefficient of 0.98. These studies indicated that the proposed method was sensitive, fast, economical and easily adaptable to emergency and routine applications.

  18. 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.

  19. Organic solid-state lasers based on sexiphenyl as active chromophore

    NASA Astrophysics Data System (ADS)

    Schneider, D.; Rabe, T.; Riedl, T.; Dobbertin, T.; Kröger, M.; Becker, E.; Johannes, H.-H.; Kowalsky, W.; Weimann, T.; Wang, J.; Hinze, P.

    2005-08-01

    We report on various sexiphenyl derivatives as gain media in organic solid-state lasers. The molecules involved in this research are simple p-sexiphenyl, the laser dye molecule 2,5,2""',5""'-tetra-t-butyl-p-sexiphenyl (TBS) and the spirolinked sexiphenyl-derivative 2,7-bis(biphenyl-4-yl)-2',7'-di-tert-butyl-9,9'-spirobifluorene. It appears that the morphology of vacuum-deposited thin films is highly dependent on the sterical dimensions of the respective molecules. Whereas thin films based on simple p-sexiphenyl comprise large clusters which significantly deteriorate their waveguiding properties; films formed by TBS, and the spiroderivative show a dramatically improved morphology with reduced surface roughness. Therefore amplified spontaneous emission (ASE) and lasing are demonstrated in both of the last but not in films based on p-sexiphenyl. Second-order distributed-feedback lasers with TBS as the active medium have been prepared with an emission between 390 and 435 nm depending on the grating period of the Bragg reflector. While the ASE characteristics are similar in films formed by TBS and the spiroderivative, TBS exhibits even superior laser threshold densities which are as low as 45μJ/cm2 at a wavelength of 396 nm.

  20. 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

  1. Imaging of Endogenous Metabolites of Plant Leaves by Mass Spectrometry Based on Laser Activated Electron Tunneling

    NASA Astrophysics Data System (ADS)

    Huang, Lulu; Tang, Xuemei; Zhang, Wenyang; Jiang, Ruowei; Chen, Disong; Zhang, Juan; Zhong, Hongying

    2016-04-01

    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.

  2. Chemical imaging of latent fingerprints by mass spectrometry based on laser activated electron tunneling.

    PubMed

    Tang, Xuemei; Huang, Lulu; Zhang, Wenyang; Zhong, Hongying

    2015-03-01

    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. PMID:25647159

  3. Chemical imaging of latent fingerprints by mass spectrometry based on laser activated electron tunneling.

    PubMed

    Tang, Xuemei; Huang, Lulu; Zhang, Wenyang; Zhong, Hongying

    2015-03-01

    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.

  4. 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

  5. Study of dopant activation in biaxially compressively strained SiGe layers using excimer laser annealing

    NASA Astrophysics Data System (ADS)

    Luong, G. V.; Wirths, S.; Stefanov, S.; Holländer, B.; Schubert, J.; Conde, J. C.; Stoica, T.; Breuer, U.; Chiussi, S.; Goryll, M.; Buca, D.; Mantl, S.

    2013-05-01

    Excimer Laser Annealing (ELA) with a wavelength of 248 nm is used to study doping of biaxialy compressively strained Si1-xGex/Si heterostructures. The challenge is to achieve a high activation of As in SiGe, while conserving the elastic strain and suppressing dopant diffusion. Doping of 20 nm Si0.64Ge0.36 layers by ion implantation of 1 × 1015 As+/cm2 and subsequent laser annealing using single 20 ns pulse with an energy density of 0.6 J/cm2 leads to an As activation of about 20% and a sheet resistance of 650 Ω/sq. At this laser energy density, the entire SiGe layer melts and the subsequent fast recrystallization on a nanosecond time scale allows high As incorporation into the lattice. Moreover, using these annealing parameters, the SiGe layer exhibits epitaxial regrowth with negligible strain relaxation. ELA at energy densities greater than 0.6 J/cm2 resembles Pulsed Lased Induced Epitaxy, leading to an intermixing of the SiGe layer with the Si substrate, thus to thicker single-crystalline strained SiGe layers with sheet resistance down to 62 Ω/sq. Effects of energy densities on composition, crystal quality, activation of As and co-doping with B are discussed and related to the spatial and temporal evolution of the temperature in the irradiated zone, as simulated by Finite Element Methods.

  6. 29 CFR 1918.92 - Illumination.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) Walking, working, and climbing areas. Walking, working, and climbing areas shall be illuminated. Unless conditions described in the regulations of the U.S. Coast Guard (33 CFR 154.570) exist for...

  7. Hyperspectral face recognition under variable outdoor illumination

    NASA Astrophysics Data System (ADS)

    Pan, Zhihong; Healey, Glenn E.; Prasad, Manish; Tromberg, Bruce J.

    2004-08-01

    We examine the performance of illumination-invariant face recognition in outdoor hyperspectral images using a database of 200 subjects. The hyperspectral camera acquires 31 bands over the 700-1000nm spectral range. Faces are represented by local spectral information for several tissue types. Illumination variation is modeled by low-dimensional spectral radiance subspaces. Invariant subspace projection over multiple tissue types is used for recognition. The experiments consider various face orientations and expressions. The analysis includes experiments for images synthesized using face reflectance images of 200 subjects and a database of over 7,000 outdoor illumination spectra. We also consider experiments that use a set of face images that were acquired under outdoor illumination conditions.

  8. Confocal imaging with orthogonally polarized illumination beams

    NASA Astrophysics Data System (ADS)

    Kalita, Ranjan; Boruah, Bosanta R.

    2016-03-01

    In confocal microscopy the polarization of the illumination beam plays an important role in determining the orientation of the fluorescent molecules being illuminated. The efficiency of the excitation depends on the angle between the excitation electric field and the direction of the molecular dipole. In order to determine the orientation of the fluorescent molecules in the focal plane the molecules are to be excited using two mutually orthogonal electric fields. In this paper we show how a computer generated holography technique can be implemented using a ferroelectric liquid crystal spatial light modulator to conveniently obtain two images of the same target once with an X polarized illumination beam and another with a Y polarized illumination beam.

  9. Illumination control apparatus for compensating solar light

    NASA Technical Reports Server (NTRS)

    Owens, L. J. (Inventor)

    1978-01-01

    An illumination control apparatus is presented for supplementing light from solar radiation with light from an artificial light source to compensate for periods of insufficient levels of solar light. The apparatus maintains a desired illumination level within an interior space comprising an artificial light source connected to an electrical power source with a switch means for selectively energizing said light source. An actuator means for controlling the on-off operation of the switch means is connected to a light sensor which responses to the illumination level of the interior space. A limit switch carried adjacent to the actuator limits the movement of the actuator within a predetermined range so as to prevent further movement thereof during detection of erroneous illumination conditions.

  10. An illuminated flute needle for vitreoretinal surgery.

    PubMed

    Davison, C N; Rosen, P H

    1994-06-01

    We have developed a simple self-illuminated flute needle for internal drainage of subretinal fluid during three-port vitrectomy. This instrument facilitates visualization and drainage through peripheral retinal breaks.

  11. 10 CFR 431.202 - Definitions concerning illuminated exit signs.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... COMMERCIAL AND INDUSTRIAL EQUIPMENT Illuminated Exit Signs § 431.202 Definitions concerning illuminated exit... sign. Illuminated exit sign means a sign that— (1) Is designed to be permanently fixed in place...

  12. 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)

  13. 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.

  14. Response of Spirogyra chloroplast to local illumination.

    PubMed

    Ohiwa, T

    1977-01-01

    1. The chloroplast of Spirogyra grows diffusively over its entire length even when irradiated only locally. Illumination of a disconnected chloroplast fragment also enhances the growth of other disconnected, non-illuminated fragments in the same cell. -2. When irradiated locally, the chloroplast becomes deformed to bring a greater part of it into the lighted area. Deformation caused by local illumination occurs only in the vicinity of the light-dark boundary. The chloroplast ribbon in this region shifts toward the lighted area not in parallel with the cell axis but obliquely to it. -3. Only light from the blue region induces the deformation. -4. The ability of the chloroplast to be centrifuged decreases in the illuminated region and increases in the shadowed region close to the light-dark boundary. -5. In a cell in which only the longitudinal half is illuminated, the chloroplast helix deforms to allow a greater part of the green ribbon to come into the illuminated half without changing its helical pitch.

  15. Laser light scattering spectroscopy: a new method to measure tracheobronchial mucociliary activity.

    PubMed Central

    Svartengren, K; Wiman, L G; Thyberg, P; Rigler, R

    1989-01-01

    Laser light scattering spectroscopy is based on the evaluation of the frequency shift of coherent light scattered by moving particles. This makes it particularly suitable for use in light guiding systems. In this study laser light scattering spectroscopy was assessed for its ability to provide information on the motility of respiratory cilia. In vitro and in vivo measurements were undertaken with animal tracheal mucosa. The intensity fluctuations of laser light scattered from moving cilia were analysed in terms of their autocorrelation functions to provide information on the frequency and synchrony of beating cilia. In vitro measurements were performed on fresh bovine trachea to estimate a safe laser power level for mucosal exposure and to test the method by defining the temperature dependence of the ciliary beat frequency. Power densities not exceeding 0.3 kW/cm2 were found to be the upper limit for long term exposure of the mucosa in vitro. Ciliary beat frequency showed a pronounced temperature dependence, ranging from 5.8 to 28.3 Hz over the temperature range 20-43.5 degrees C. A maximum frequency was found at 41.5 degrees C. In vivo measurements of ciliary activity were performed in six pigs by means of optical fibres for light transmission combined with fibreoptic bronchoscopy. A ciliary beat frequency of 5 Hz was obtained; heart and breathing frequencies could be separated and identified. These results suggest that laser light scattering spectroscopy might provide a convenient method of studying the mucociliary system of the lower airways. PMID:2772854

  16. Illumination of mesospheric irregularity by lightning discharge

    NASA Astrophysics Data System (ADS)

    Füllekrug, Martin; Mezentsev, Andrew; Soula, Serge; Velde, Oscar; Evans, Adrian

    2013-12-01

    Theoretical model calculations recently predicted the existence of mesospheric irregularities which assist the initiation of sprites. Here we report the experimental detection of a ˜3-19 km3 large mesospheric irregularity at ˜80-85 km height which is illuminated by the electromagnetic field of an intense positive cloud-to-ground lightning discharge. While the lightning discharge causes a prompt group of four sprites above the lightning discharge, the mesospheric irregularity is found at a horizontal distance at least ˜15-20 km away from the sprite group and it rebrightens ˜40-60 ms after the sprite group occurrence. This rebrightening is driven by a local quasi-static electric field enhancement with a charge moment ˜4-20 Ckm which causes the irregularity to develop a downward descending luminous column from ˜75-85 km height. The quasi-static electric field enhancement is caused by the reorganization of residual charge inside the thundercloud during a high-level activity of intracloud discharges with ˜10-20 pulses per ms. Such mesospheric irregularities might have an effect on the wave propagation of 100 kHz radio waves which are used for atomic time transfer and marine navigation.

  17. Spectral and generating properties of active laser media based on dye-doped elastomers

    NASA Astrophysics Data System (ADS)

    Bezrodnyi, Vladimir; Derevyanko, N.; Ishchenko, Alexander A.; Slobodin, Valeriy V.; Karabanova, Ludmila V.

    2002-12-01

    The advantages of a polyurethane matrix over other polymers, which are widely used as active media for dye lasers, are analzyed. This matrix exhibits the photostability, service life, radiation resistance, conversion efficiency, and homogeneity of the dye distribution that surpass these properties for active media based on polyurethane acrylate, which has close physical and operation properties. These advantages result not only from the milder polymerization conditions but also from a lower probability of the formation of ion pairs and dye aggregates. A substantial suppression of these processes in polyurethane is explained by its greater polarity and solvation ability compared to polyurathane acrylate.

  18. Generation of picosecond pulses and frequency combs in actively mode locked external ring cavity quantum cascade lasers

    SciTech Connect

    Wójcik, Aleksander K.; Belyanin, Alexey; Malara, Pietro; Blanchard, Romain; Mansuripur, Tobias S.; Capasso, Federico

    2013-12-02

    We propose a robust and reliable method of active mode locking of mid-infrared quantum cascade lasers and develop its theoretical description. Its key element is the use of an external ring cavity, which circumvents fundamental issues undermining the stability of mode locking in quantum cascade lasers. We show that active mode locking can give rise to the generation of picosecond pulses and phase-locked frequency combs containing thousands of the ring cavity modes.

  19. 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.

  20. Illuminating a dialectical transformative activist stance in education

    NASA Astrophysics Data System (ADS)

    Ritchie, Stephen M.

    2008-07-01

    In this essay I comment on Stetsenko's (2008) essay that draws together the work of Vygotsky, Piaget and Dewey, as she attempts to counter the `new' reductionist synthesis in public educational policy. While this theoretical work is helpful, it could be enhanced further by illuminating everyday practices of learners. I pose some questions that might provoke ongoing discussions by researchers as they transform collaboratively cultural-historical activity theory.