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Sample records for green-to-orange light based

  1. A Strategy to enhance Eu3+ emission from LiYF4:Eu nanophosphors and green-to-orange multicolor tunable, transparent nanophosphor-polymer composites

    PubMed Central

    Kim, Su Yeon; Won, Yu-Ho; Jang, Ho Seong

    2015-01-01

    LiYF4:Eu nanophosphors with a single tetragonal phase are synthesized, and various strategies to enhance the Eu3+ emission from the nanophosphors are investigated. The optimized Eu3+ concentration is 35 mol%, and the red emission peaks due to the 5D0 →7FJ (J = 1 and 2) transitions of Eu3+ ions are further enhanced by energy transfer from a sensitizer pair of Ce3+ and Tb3+. The triple doping of Ce, Tb, and Eu into the LiYF4 host more effectively enhances the Eu3+ emission than the core/shell strategies of LiYF4:Eu(35%)/LiYF4:Ce(15%), Tb(15%) and LiYF4:Ce(15%), Tb(15%)/LiYF4:Eu(35%) architectures. Efficient energy transfer from Ce3+ to Eu3+ through Tb3+ results in three times higher Eu3+ emission intensity from LiYF4:Ce(15%), Tb(15%), Eu(1%) nanophosphors compared with LiYF4:Eu(35%), which contains the optimized Eu3+ concentration. Owing to the energy transfer of Ce3+ → Tb3+ and Ce3+ → Tb3+ → Eu3+, intense green and red emission peaks are observed from LiYF4:Ce(13%), Tb(14%), Eu(1-5%) (LiYF4:Ce, Tb, Eu) nanophosphors, and the intensity ratio of green to red emission is controlled by adjusting the Eu3+ concentration. With increasing Eu3+ concentration, the LiYF4:Ce, Tb, Eu nanophosphors exhibit multicolor emission from green to orange. In addition, the successful incorporation of LiYF4:Ce, Tb, Eu nanophosphors into polydimethylsiloxane (PDMS) facilitates the preparation of highly transparent nanophosphor-PDMS composites that present excellent multicolor tunability. PMID:25597900

  2. Carbon Nanotube Based Light Sensor

    NASA Technical Reports Server (NTRS)

    Wincheski, russell A. (Inventor); Smits, Jan M. (Inventor); Jordan, Jeffrey D. (Inventor); Watkins, Anthony Neal (Inventor); Ingram, JoAnne L. (Inventor)

    2006-01-01

    A light sensor substrate comprises a base made from a semi-conductive material and topped with a layer of an electrically non-conductive material. A first electrode and a plurality of carbon nanotube (CNT)-based conductors are positioned on the layer of electrically non-conductive material with the CNT-based conductors being distributed in a spaced apart fashion about a periphery of the first electrode. Each CNT-based conductor is coupled on one end thereof to the first electrode and extends away from the first electrode to terminate at a second free end. A second or gate electrode is positioned on the non-conductive material layer and is spaced apart from the second free end of each CNT-based conductor. Coupled to the first and second electrode is a device for detecting electron transfer along the CNT-based conductors resulting from light impinging on the CNT-based conductors.

  3. The International Year of Light and Light-based Technologies

    NASA Astrophysics Data System (ADS)

    Pendrill, Ann-Marie

    2015-05-01

    I report on the opening ceremony of the International Year of Light and Light-based Technologies 2015 (IYL2015), which took place at the UNESCO headquarters in Paris, France, on 19-20 January 2015. Over the two days, more than 1000 participants from all over the world learned more about the fundamental properties of light and advanced photonics applications, the history of optics and its applications through the centuries, light poverty and light pollution, and light for everyday life, health and research.

  4. Light pollution simulations for planar ground-based light sources.

    PubMed

    Kocifaj, Miroslav

    2008-02-20

    The light pollution model is employed to analyze spatial behavior of luminance at the night sky under cloudless and overcast conditions. Enhanced light excess is particularly identified at cloudy skies, because the clouds efficiently contribute to the downward luminous flux. It is evident that size of ground-based light sources can play an important role in the case of overcast sky conditions. Nevertheless, the realistically sized light sources are rarely embedded into light pollution modeling, and rather they are replaced by simple point sources. We discuss the discrepancies between sky luminance distributions when at first the planar light sources are considered and at second the point-source approximation is accepted. The found differences are noticeable if the size of the light source, distance to the observer, and altitude of a cloudy layer are comparable one to the other. Compared with point-source approximation, an inclusion of the size factor into modeling the light sources leads to partial elimination of the steep changes of sky luminance (typical for point sources of light). The narrow and sharp light pillars normally presented on the sky illuminated by point light sources can disappear or fuse together when two or more nearby light sources are considered with their real sizes. Sky elements situated close to the horizon will glow efficiently if luminous flux originates from two-dimensional ground-based entities (such as cities or villages). PMID:18288228

  5. Eu{sup 2+}, Mn{sup 2+} co-doped Ba{sub 9}Y{sub 2}Si{sub 6}O{sub 24} phosphors based on near-UV-excitable LED lights

    SciTech Connect

    Kim, Yoejin; Park, Sangmoon

    2014-01-01

    Graphical abstract: - Highlights: • New near-ultraviolet (NUV)-excitable materials composed of Ba{sub 9}Eu{sub m}Mn{sub n}Y{sub 2}Si{sub 6}O{sub 24} (m = 0.01–0.5, n = 0–0.7) were prepared. • High energy-transfer from Eu{sup 2+} to Mn{sup 2+} and their energy-transfer mechanism were discussed. • The co-doping of Eu{sup 2+} and Mn{sup 2+} in the orthosilicate structure resulted in the emission of white light under NUV LED light. - Abstract: New single-phase and near-ultraviolet (NUV)-excitable materials composed of Ba{sub 9}Eu{sub m}Mn{sub n}Y{sub 2}Si{sub 6}O{sub 24} (m = 0.01–0.5, n = 0–0.7) were prepared via a solid-state reaction in reducing atmosphere. X-ray diffraction patterns of the obtained phosphors were examined to index the peak positions. After doping the host structure with Eu{sup 2+} and Mn{sup 2+} emitters, the intense green, white, and orange emission lights that were observed in the photoluminescence spectra under NUV excitation were monitored. The dependence of the luminescent intensity of the Mn{sup 2+} co-doped (n = 0.1–0.7) host lattices on the fixed Eu{sup 2+} content (m = 0.1, 0.3, 0.5) is also investigated. Co-doping Mn{sup 2+} into the Eu{sup 2+}-doped host structure enabled a high energy-transfer from Eu{sup 2+} to Mn{sup 2+} and their energy-transfer mechanism were discussed. Using these phosphors, the desired CIE values including emissions throughout the green to orange regions of the spectra were achieved. Efficient white-light light-emitting diodes (LEDs) were fabricated using Eu{sup 2+} and Mn{sup 2+} co-doped phosphors based on NUV-excitable LED lights.

  6. Optical Receiver Based On Luminescent Light Trapping

    NASA Technical Reports Server (NTRS)

    Perry, Joseph W.; Cole, Terry; Zewail, Ahmed H.

    1991-01-01

    Experiment demonstrates feasibility of optical-communication receiver based on luminescent light trapping. Light-gathering element plate of transparent material impregnated with laser dye. Light from distant laser transmitter falls on plate and absorbed by dye molecules, which become excited and reradiate. Reradiated light confined within plate by total internal reflection as it propagates toward edge of plate. Light arriving at edge escapes from plate and detected by small, high-speed, high-gain photomultiplier tubes or other photosensitive devices. Simple, inexpensive, and accepts light from almost any angle. Receiver of this configuration supports reception of data at rate of 13 MHz and higher.

  7. Visible light communication based motion detection.

    PubMed

    Sewaiwar, Atul; Tiwari, Samrat Vikramaditya; Chung, Yeon-Ho

    2015-07-13

    In this paper, a unique and novel visible light communication based motion detection is presented. The proposed motion detection is performed based on white light LEDs and an array of photodetectors from existing visible light communication (VLC) links, thus providing VLC with three functionalities of illumination, communication and motion detection. The motion is detected by observing the pattern created by intentional obstruction of the VLC link. Experimental and simulation results demonstrate the validity of the proposed VLC based motion detection technique. The VLC based motion detection can benefit smart devices control in VLC based smart home environments. PMID:26191937

  8. A web-based virtual lighting simulator

    SciTech Connect

    Papamichael, Konstantinos; Lai, Judy; Fuller, Daniel; Tariq, Tara

    2002-05-06

    This paper is about a web-based ''virtual lighting simulator,'' which is intended to allow architects and lighting designers to quickly assess the effect of key parameters on the daylighting and lighting performance in various space types. The virtual lighting simulator consists of a web-based interface that allows navigation through a large database of images and data, which were generated through parametric lighting simulations. At its current form, the virtual lighting simulator has two main modules, one for daylighting and one for electric lighting. The daylighting module includes images and data for a small office space, varying most key daylighting parameters, such as window size and orientation, glazing type, surface reflectance, sky conditions, time of the year, etc. The electric lighting module includes images and data for five space types (classroom, small office, large open office, warehouse and small retail), varying key lighting parameters, such as the electric lighting system, surface reflectance, dimming/switching, etc. The computed images include perspectives and plans and are displayed in various formats to support qualitative as well as quantitative assessment. The quantitative information is in the form of iso-contour lines superimposed on the images, as well as false color images and statistical information on work plane illuminance. The qualitative information includes images that are adjusted to account for the sensitivity and adaptation of the human eye. The paper also includes a section on the major technical issues and their resolution.

  9. Broadband light based optoelectric tweezers

    NASA Astrophysics Data System (ADS)

    Mishra, Avanish; Clayton, Katherine; Wereley, Steve

    2015-11-01

    Trapping, sorting and transport of particles are fundamental operations in microfluidic platforms. However, very few methods exist that can dynamically trap and manipulate particles with high spatial resolution and accuracy. Recently, a new set of methods have emerged that can trap and sort particles by optically controlling electrokinetic effects. Rapid Electrokinetic Patterning (REP) is such an emerging optoelectric technique. It utilizes a laser activated electrothermal (ET) vortex and particle-electrode interactions for trapping particles. Trapped particles can be translated by optically steering the laser or by moving the trapping chamber. Previously demonstrated applications of REP have utilized a 1064 nm infrared laser, integrated in an inverted microscope, to create the necessary temperature rise for producing the ET flow. Use of an external laser for REP trapping is expensive and time intensive to integrate, making it difficult to design a portable REP system. Using experiments and simulations, we show that a non-coherent incandescent broadband light source can be used for REP trapping and manipulation. This allows for a microscope with a broadband lamp to be used for REP trapping without integrating an external laser.

  10. The Specter of Fuel-Based Light

    SciTech Connect

    Mills, Evan

    2005-05-16

    Contemporary questions about sustainable energy and development converge in unexpected ways around a technology that is at once an echo of the past and yet very much a part of the present: fuel-based lighting in the developing world. An emerging opportunity for reducing the global costs and greenhouse-gas emissions associated with this highly inefficient form of lighting energy use is to replace fuel-based lamps with white solid-state (''LED'') lighting, described in this Policy Forum, which can be affordably solar-powered. Doing so would allow those without access to electricity in developing world to affordably leapfrog over the prevailing incandescent and fluorescent lighting technologies in use today through the electrified world.

  11. Light sources based on semiconductor current filaments

    DOEpatents

    Zutavern, Fred J.; Loubriel, Guillermo M.; Buttram, Malcolm T.; Mar, Alan; Helgeson, Wesley D.; O'Malley, Martin W.; Hjalmarson, Harold P.; Baca, Albert G.; Chow, Weng W.; Vawter, G. Allen

    2003-01-01

    The present invention provides a new type of semiconductor light source that can produce a high peak power output and is not injection, e-beam, or optically pumped. The present invention is capable of producing high quality coherent or incoherent optical emission. The present invention is based on current filaments, unlike conventional semiconductor lasers that are based on p-n junctions. The present invention provides a light source formed by an electron-hole plasma inside a current filament. The electron-hole plasma can be several hundred microns in diameter and several centimeters long. A current filament can be initiated optically or with an e-beam, but can be pumped electrically across a large insulating region. A current filament can be produced in high gain photoconductive semiconductor switches. The light source provided by the present invention has a potentially large volume and therefore a potentially large energy per pulse or peak power available from a single (coherent) semiconductor laser. Like other semiconductor lasers, these light sources will emit radiation at the wavelength near the bandgap energy (for GaAs 875 nm or near infra red). Immediate potential applications of the present invention include high energy, short pulse, compact, low cost lasers and other incoherent light sources.

  12. Plasma-based EUV light source

    DOEpatents

    Shumlak, Uri; Golingo, Raymond; Nelson, Brian A.

    2010-11-02

    Various mechanisms are provided relating to plasma-based light source that may be used for lithography as well as other applications. For example, a device is disclosed for producing extreme ultraviolet (EUV) light based on a sheared plasma flow. The device can produce a plasma pinch that can last several orders of magnitude longer than what is typically sustained in a Z-pinch, thus enabling the device to provide more power output than what has been hitherto predicted in theory or attained in practice. Such power output may be used in a lithography system for manufacturing integrated circuits, enabling the use of EUV wavelengths on the order of about 13.5 nm. Lastly, the process of manufacturing such a plasma pinch is discussed, where the process includes providing a sheared flow of plasma in order to stabilize it for long periods of time.

  13. New light field camera based on physical based rendering tracing

    NASA Astrophysics Data System (ADS)

    Chung, Ming-Han; Chang, Shan-Ching; Lee, Chih-Kung

    2014-03-01

    Even though light field technology was first invented more than 50 years ago, it did not gain popularity due to the limitation imposed by the computation technology. With the rapid advancement of computer technology over the last decade, the limitation has been uplifted and the light field technology quickly returns to the spotlight of the research stage. In this paper, PBRT (Physical Based Rendering Tracing) was introduced to overcome the limitation of using traditional optical simulation approach to study the light field camera technology. More specifically, traditional optical simulation approach can only present light energy distribution but typically lack the capability to present the pictures in realistic scenes. By using PBRT, which was developed to create virtual scenes, 4D light field information was obtained to conduct initial data analysis and calculation. This PBRT approach was also used to explore the light field data calculation potential in creating realistic photos. Furthermore, we integrated the optical experimental measurement results with PBRT in order to place the real measurement results into the virtually created scenes. In other words, our approach provided us with a way to establish a link of virtual scene with the real measurement results. Several images developed based on the above-mentioned approaches were analyzed and discussed to verify the pros and cons of the newly developed PBRT based light field camera technology. It will be shown that this newly developed light field camera approach can circumvent the loss of spatial resolution associated with adopting a micro-lens array in front of the image sensors. Detailed operational constraint, performance metrics, computation resources needed, etc. associated with this newly developed light field camera technique were presented in detail.

  14. Forecasting Urban Expansion Based on Night Lights

    NASA Astrophysics Data System (ADS)

    Stathakis, D.

    2016-06-01

    Forecasting urban expansion models are a very powerful tool in the hands of urban planners in order to anticipate and mitigate future urbanization pressures. In this paper, a linear regression forecasting urban expansion model is implemented based on the annual composite night lights time series available from National Oceanic and Atmospheric Administration (NOAA). The product known as 'stable lights' is used in particular, after it has been corrected with a standard intercalibration process to reduce artificial year-to-year fluctuations as much as possible. Forecasting is done for ten years after the end of the time series. Because the method is spatially explicit the predicted expansion trends are relatively accurately mapped. Two metrics are used to validate the process. The first one is the year-to-year Sum of Lights (SoL) variation. The second is the year-to-year image correlation coefficient. Overall it is evident that the method is able to provide an insight on future urbanization pressures in order to be taken into account in planning. The trends are quantified in a clear spatial manner.

  15. A universal, easy-to-apply light-quality index based on natural light spectrum resemblance

    NASA Astrophysics Data System (ADS)

    Jou, Jwo-Huei; Chou, Kun-Yi; Yang, Fu-Chin; Agrawal, Abhishek; Chen, Sun-Zen; Tseng, Jing-Ru; Lin, Ching-Chiao; Chen, Po-Wei; Wong, Ken-Tsung; Chi, Yun

    2014-05-01

    Light-quality is extremely crucial for any light source to be used for illumination. However, a proper light-quality index is still missing although numerous electricity-driven lighting measures have been introduced since past 150 yr. We present in this communication a universal and easy-to-apply index for quantifying the quality of any given lighting source, which is based on direct comparison of its lumen spectrum with the natural light counterpart having the same color temperature. A general principle for creating high quality pseudo-natural light is accordingly derived. By using organic light-emitting diode technology, for example, daylight-style emission with a 96% natural light resemblance is obtained as a high number of organic emitters with diffused colors spanning throughout the entire visible range are employed. The same principle can be extended to other lighting technology such as light-emitting diode to generate natural light-style emission.

  16. Light Based Cellular Interactions: hypotheses and perspectives

    NASA Astrophysics Data System (ADS)

    Laager, Frederic

    2015-08-01

    This work investigates the theoretical possibility of interactions between cells via light. We first take a brief look at the previous research done in the past to have a better understanding of the field and the origins of the concept of cellular interactions. Then we identify the different elements essential for interactions between two parties. We then compare the required elements with the known and studied elements and characteristics which are well defined in biology, chemistry and physics. This way we are able to set up four postulates required for cell interactions: I. A signal is present and subject to secondary modulation by the emitter cells. II. There is a plastic information medium that reacts directly to the metabolic state of the emitter and therefore carries information about the emitter. III. An optical signal can be perceived by cells on a molecular level by a multitude of different receptors. IV. The information can in theory be processed by cells and metabolic changes in reaction to the signals can be observed. We demonstrate that all required elements have been observed. Most of them have important and well-known roles in cells. Therefore we suggest that our hypothetical model is a good explanation for light based cellular interactions.

  17. 6. DETAIL VIEW SHOWING BASE OF LIGHT TOWER, LOOKING SOUTHEAST ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    6. DETAIL VIEW SHOWING BASE OF LIGHT TOWER, LOOKING SOUTHEAST - Monomoy Point Light Station, Approximately 3500 feet Northeast Powder Hole Pond, Monomoy National Wildlife Refuge, Chatham, Barnstable County, MA

  18. Headlamps for light based driver assistance

    NASA Astrophysics Data System (ADS)

    Götz, M.; Kleinkes, M.

    2008-04-01

    Driving at night is dangerous. Although only 25% of all driving tasks are performed at night, nearly half of all fatal accidents happen in this time. In order to increase safety when driving under poor visibility conditions, automotive front lighting systems have undergone a strong development in the last fifteen years. One important milestone was the introduction of Xenon headlamps in 1992, which provide more and brighter light for road illumination than ever before. Since then the paradigm of simply providing more light has changed toward providing optimised light distributions, which support the driver's perception. A first step in this direction was the introduction of dynamic bend lighting and cornering light in 2003. In 2006 the first full AFS headlamp (Adaptive Front Lighting System) allowed an optimised adoption of the light distribution to the driving situation. These systems use information provided by vehicle sensors and an intelligent algorithm to guide light towards those areas where needed. Nowadays, even more information about the vehicle's environment is available. Image processing systems, for example, allow to detect other traffic participants, their speed and their driving directions. In future headlamp systems these data will be used to constantly regulate the reach of the light distribution thus allowing a maximal reach without providing glare. Moreover, technologies that allow to constantly use a high-beam light distribution are under development. These systems will illuminate the whole traffic area only excluding other traffic participants. LED light sources will play a significant role in these scenarios, since they allow to precisely illuminate certain areas of the road, while neighbouring parts will be left in dark.

  19. Challenges and opportunities in LED based lighting

    NASA Astrophysics Data System (ADS)

    Panahi, Allen

    2013-05-01

    Solid state lighting technology has made great advances over the last decade and has become the technology of choice to displace legacy incandescent and as well as the more efficient fluorescent lights. While efficiencies have been improved and cost of the LEDs has been steadily lowered still many challenges exist in the thermal, electrical, optical, and packaging implementations.

  20. Optical design and lighting application of an LED-based sports lighting system

    NASA Astrophysics Data System (ADS)

    Boxler, Larry

    2011-10-01

    This paper describes both the optical development of an LED-based sports lighting system and the results of the application of the system to an actual sport field. A traditional sport lighting fixture is generally composed of a single 1500 watt High Intensity Discharge (HID) light source with reflectors used to control the light distribution. The efficacy of the HID light source is equivalent or nearly equivalent to most LED light sources, putting LEDs at a large cost disadvantage in a high light output application such as sports lighting due to the number of LEDs and supporting components required to run an LED system. To assess the feasibility and applicability of LEDs in a sports lighting application, an LED-based sport light has been developed and installed on a small soccer field specified to have an average maintained illuminance level of 30 footcandles. An existing HID sport lighting system was also installed on the same size soccer field adjacent to the LED field with the same average footcandle level for comparison. Results indicate that LEDs can provide equivalent average illumination; however the LED source and system component cost is substantially higher. Despite the high cost, it was found that improved optical control afforded by the optical design used in the system provides a significant improvement in offsite wasted spill light, glare control, and on field uniformity. This could provide an advantage for LED systems.

  1. Polymer and small molecule based hybrid light source

    DOEpatents

    Choong, Vi-En; Choulis, Stelios; Krummacher, Benjamin Claus; Mathai, Mathew; So, Franky

    2010-03-16

    An organic electroluminescent device, includes: a substrate; a hole-injecting electrode (anode) coated over the substrate; a hole injection layer coated over the anode; a hole transporting layer coated over the hole injection layer; a polymer based light emitting layer, coated over the hole transporting layer; a small molecule based light emitting layer, thermally evaporated over the polymer based light emitting layer; and an electron-injecting electrode (cathode) deposited over the electroluminescent polymer layer.

  2. Light-based therapies in acne treatment

    PubMed Central

    Pei, Susan; Inamadar, Arun C.; Adya, Keshavmurthy A.; Tsoukas, Maria M.

    2015-01-01

    The use of light and laser in the treatment of acne is increasing as these modalities are safe, effective, and associated with no or minimal complications when used appropriately. These light and laser sources are also being used in combination with pharmacological and/or physical measures to synergize their effects and optimize the therapeutic outcome. This review focuses on optical devices used in treating acne and serves to delineate the current application of various methods, including their utility and efficacy. PMID:26009707

  3. Light-field-based phase imaging

    NASA Astrophysics Data System (ADS)

    Liu, Jingdan; Xu, Tingfa; Yue, Weirui; Situ, Guohai

    2014-10-01

    Phase contains important information about the diffraction or scattering property of an object, and therefore the imaging of phase is vital to many applications including biomedicine and metrology, just name a few. However, due to the limited bandwidth of image sensors, it is not possible to directly detect the phase of an optical field. Many methods including the Transport of Intensity Equation (TIE) have been well demonstrated for quantitative and non-interferometric imaging of phase. The TIE offers an experimentally simple technique for computing phase quantitatively from two or more defocused images. Usually, the defocused images were experimentally obtained by shifting the camera along the optical axis with slight intervals. Note that light field imaging has the capability to take an image stack focused at different depths by digital refocusing the captured light field of a scene. In this paper, we propose to combine Light Field Microscopy and the TIE method for phase imaging, taking the digital-refocusing advantage of Light Field Microscopy. We demonstrate the propose technique by simulation results. Compare with the traditional camera-shifting technique, light-field imaging allows the capturing the defocused images without any mechanical instability and therefore demonstrate advantage in practical applications.

  4. Slow-light-based optical frequency shifter

    NASA Astrophysics Data System (ADS)

    Li, Qian; Bao, Yupan; Thuresson, Axel; Nilsson, Adam N.; Rippe, Lars; Kröll, Stefan

    2016-04-01

    We demonstrate experimentally and theoretically a controllable way of shifting the frequency of an optical pulse by using a combination of spectral hole burning, slow light effect, and linear Stark effect in a rare-earth-ion-doped crystal. We claim that the solid angle of acceptance of a frequency shift structure can be close to 2 π , which means that the frequency shifter could work not only for optical pulses propagating in a specific spatial mode but also for randomly scattered light. As the frequency shift is controlled solely by an external electric field, it works also for weak coherent light fields and can be used, for example, as a frequency shifter for quantum memory devices in quantum communication.

  5. Camera array based light field microscopy

    PubMed Central

    Lin, Xing; Wu, Jiamin; Zheng, Guoan; Dai, Qionghai

    2015-01-01

    This paper proposes a novel approach for high-resolution light field microscopy imaging by using a camera array. In this approach, we apply a two-stage relay system for expanding the aperture plane of the microscope into the size of an imaging lens array, and utilize a sensor array for acquiring different sub-apertures images formed by corresponding imaging lenses. By combining the rectified and synchronized images from 5 × 5 viewpoints with our prototype system, we successfully recovered color light field videos for various fast-moving microscopic specimens with a spatial resolution of 0.79 megapixels at 30 frames per second, corresponding to an unprecedented data throughput of 562.5 MB/s for light field microscopy. We also demonstrated the use of the reported platform for different applications, including post-capture refocusing, phase reconstruction, 3D imaging, and optical metrology. PMID:26417490

  6. Camera array based light field microscopy.

    PubMed

    Lin, Xing; Wu, Jiamin; Zheng, Guoan; Dai, Qionghai

    2015-09-01

    This paper proposes a novel approach for high-resolution light field microscopy imaging by using a camera array. In this approach, we apply a two-stage relay system for expanding the aperture plane of the microscope into the size of an imaging lens array, and utilize a sensor array for acquiring different sub-apertures images formed by corresponding imaging lenses. By combining the rectified and synchronized images from 5 × 5 viewpoints with our prototype system, we successfully recovered color light field videos for various fast-moving microscopic specimens with a spatial resolution of 0.79 megapixels at 30 frames per second, corresponding to an unprecedented data throughput of 562.5 MB/s for light field microscopy. We also demonstrated the use of the reported platform for different applications, including post-capture refocusing, phase reconstruction, 3D imaging, and optical metrology. PMID:26417490

  7. High Brightness GaN-Based Light-Emitting Diodes

    NASA Astrophysics Data System (ADS)

    Lee, Ya-Ju; Lu, Tien-Chang; Kuo, Hao-Chung; Wang, Shing-Chung

    2007-06-01

    This paper reviews our recent progress of GaN-based high brightness light-emitting diodes (LEDs). Firstly, by adopting chemical wet etching patterned sapphire substrates in GaN-based LEDs, not only could increase the extraction quantum efficiency, but also improve the internal quantum efficiency. Secondly, we present a high light-extraction 465-nm GaN-based vertical light-emitting diode structure with double diffuse surfaces. The external quantum efficiency was demonstrated to be about 40%. The high performance LED was achieved mainly due to the strong guided-light scattering efficiency while employing double diffuse surfaces.

  8. Immunoassay control method based on light scattering

    NASA Astrophysics Data System (ADS)

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

    1999-11-01

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

  9. Visible light metasurfaces based on gallium nitride high contrast gratings

    NASA Astrophysics Data System (ADS)

    Wang, Zhenhai; He, Shumin; Liu, Qifa; Wang, Wei

    2016-05-01

    We propose visible-light metasurfaces (VLMs) capable of serving as lens and beam deflecting element based on gallium nitride (GaN) high contrast gratings (HCGs). By precisely manipulating the wavefront of the transmitted light, we theoretically demonstrate an HCG focusing lens with transmissivity of 86.3%, and a VLM with beam deflection angle of 6.09° and transmissivity as high as 91.4%. The proposed all-dielectric metasurfaces are promising for GaN-based visible light-emitting diodes (LEDs), which would be robust and versatile for controlling the output light propagation and polarization, as well as enhancing the extraction efficiency of the LEDs.

  10. Qualifying lighting remodelling in a Hungarian city based on light pollution effects

    NASA Astrophysics Data System (ADS)

    Kolláth, Z.; Dömény, A.; Kolláth, K.; Nagy, B.

    2016-09-01

    The public lighting system has been remodelled in several Hungarian cities. In some cases the majority of the old luminaries were fitted with high pressure sodium lamps and they were replaced with white LED lighting with a typical correlated colour temperature of about 4500 K. Therefore, these remodelling works provide a testbed for methods in measurements and modelling. We measured the luminance of the light domes of selected cities by DSLR photometry before and after the remodelling. Thanks to the full cut off design of the new lighting fixtures we obtained a slight decrease even in the blue part of the sky dome spectra of a tested city. However, we have to note that this positive change is the result of the bad geometry (large ULR) of the previous lighting system. Based on Monte Carlo radiative transfer calculations we provide a comparison of different indicators that can be used to qualify the remodelling, and to predict the possible changes in light pollution.

  11. Homeostasis lighting control based on relationship between lighting environment and human behavior

    NASA Astrophysics Data System (ADS)

    Ueda, Risa; Mita, Akira

    2015-03-01

    Although each person has own preferences, living spaces which can respond to various preferences and needs have not become reality. Focusing on the lighting environments which influence on the impression of living spaces, this research aims to offer comfortable lighting environments for each resident by a flexible control. This research examines the relationship between lighting environments and human behaviors considering colored lights. In accord with the relationship, this research proposes an illuminance-color control system which flexibly changes spatial environments responding to human conditions. Firstly, the psychological evaluation was conducted in order to build human models for various environments. As a result, preferred lighting environments for each examinee were determined for particular behaviors. Moreover, satisfaction levels of lighting environments were calculated by using seven types of impression of the environments as parameters. The results were summarized as human models. Secondly, this research proposed "Homeostasis Lighting Control System", which employs the human models. Homeostasis lighting control system embodies the algorithm of homeostasis, which is one of the functions of the physiological adaptation. Human discomfort feelings are obtained automatically by the sensor agent robot. The system can offer comfortable lighting environments without controlling environments by residents autonomously based on the information from the robot. This research takes into accounts both illuminance and color. The robot communicates with the server which contains human models, then the system corresponds to individuals. Combining these three systems, the proposed system can effectively control the lighting environment. At last, the feasibility of the proposed system was verified by simulation experiments.

  12. Improved Slow Light Capacity In Graphene-based Waveguide

    PubMed Central

    Hao, Ran; Peng, Xi-Liang; Li, Er-Ping; Xu, Yang; Jin, Jia-Min; Zhang, Xian-Min; Chen, Hong-Sheng

    2015-01-01

    We have systematically investigated the wideband slow light in two-dimensional material graphene, revealing that graphene exhibits much larger slow light capability than other materials. The slow light performances including material dispersion, bandwidth, dynamic control ability, delay-bandwidth product, propagation loss, and group-velocity dispersion are studied, proving graphene exhibits significant advantages in these performances. A large delay-bandwidth product has been obtained in a simple yet functional grating waveguide with slow down factor c/vg at 163 and slow light bandwidth Δω at 94.4 nm centered at 10.38 μm, which is several orders of magnitude larger than previous results. Physical explanation of the enhanced slow light in graphene is given. Our results indicate graphene is an excellent platform for slow light applications, promoting various future slow light devices based on graphene. PMID:26478563

  13. Semiconductor Nanocrystals-Based White Light Emitting Diodes

    SciTech Connect

    Dai, Quanqin; Hu, Michael Z.; Duty, Chad E

    2010-01-01

    In response to the demands for energy and the concerns of global warming and climate change, energy efficient and environmentally friendly solid state lighting, such as white light emitting diodes (WLEDs), is considered to be the most promising and suitable light source. Because of their small size, high efficiency, and long lifetime, WLEDs based on colloidal semiconductor nanocrystals (or quantum dots) are emerging as a completely new technology platform for the development of flat-panel displays and solid state lighting, exhibiting the potential to replace the conventionally used incandescent and fluorescent lamps. This replacement could cut the ever-increasing energy consumption, solve the problem of rapidly depleting fossil fuel reserves, and improve the quality of the global environment. In this review, we highlight the recent progress in semiconductor nanocrystals-based WLEDs, compare different approaches for generating white light, and discuss the benefits and challenges of the solid state lighting technology.

  14. Optical bidirectional beacon based visible light communications.

    PubMed

    Tiwari, Samrat Vikramaditya; Sewaiwar, Atul; Chung, Yeon Ho

    2015-10-01

    In an indoor bidirectional visible light communications (VLC), a line-of-sight (LOS) transmission plays a major role in obtaining adequate performance of a VLC system. Signals are often obstructed in the LOS transmission path, causing an effect called optical shadowing. In the absence of LOS, the performance of the VLC system degrades significantly and, in particular, at uplink transmission this degradation becomes severe due to design constraints and limited power at uplink devices. In this paper, a novel concept and design of an optical bidirectional beacon (OBB) is presented as an efficient model to counter the performance degradation in a non-line-of-sight (NLOS) VLC system. OBB is an independent operating bidirectional transceiver unit installed on walls, composed of red, green, and blue (RGB) light emitting diodes (LEDs), photodetectors (PDs) and color filters. OBB improves the coverage area in the form of providing additional or alternate paths for transmission and enhances the performance of the VLC system in terms of bit error rate (BER). To verify the effectiveness of the proposed system, simulations were carried out under optical shadowing conditions at various locations in an indoor environment. The simulation results and analysis show that the implementation of OBB improves the performance of the VLC system significantly, especially when the LOS bidirectional transmission paths are completely or partially obstructed. PMID:26480168

  15. Fiber based generation of azimuthally polarized light

    NASA Astrophysics Data System (ADS)

    Jocher, Christoph; Jauregui, Cesar; Voigtländer, Christian; Stutzki, Fabian; Nolte, Stefan; Limpert, Jens; Tünnermann, Andreas

    2012-02-01

    We report on a novel approach for the generation of radially and azimuthally polarized light employing a fiber mode filter. The mode filter consists of a Fiber Bragg Grating written in a strongly guiding fiber with lifted modal degeneracy. These kinds of fibers guide radially and azimuthally polarized modes with non-degenerated, i.e. distinct, effective refractive indexes. The Fiber Bragg Grating reflects light only if the Bragg condition is fulfilled. In case of strongly guiding fibers the radially and azimuthally polarized modes are guided with different effective refractive indices and, consequently, the Bragg condition is fulfilled at different wavelengths. If the reflection bandwidth of the Fiber Bragg Grating is narrow enough, the radially and azimuthally polarized modes are spectrally separated. Thus, with such a mode filter it is possible to filter the radially or azimuthally polarized mode. This filter is suitable for its integration in a resonator for stable, compact and high polarization purity azimuthally and radially polarized all-fiber oscillators. In a first experiment an azimuthally polarized mode filter consisting of a commercially available step index fiber and a femtosecond written Fiber Bragg Grating was fabricated. The experimental results are presented and discussed.

  16. A lighting assembly based on red and blue light-emitting diodes as a lighting source for space agriculture

    NASA Astrophysics Data System (ADS)

    Avercheva, Olga; Berkovich, Yuliy A.; Smolyanina, Svetlana; Bassarskaya, Elizaveta; Zhigalova, Tatiana; Ptushenko, Vasiliy; Erokhin, Alexei

    Light-emitting diodes (LEDs) are a promising lighting source for space agriculture due to their high efficiency, longevity, safety, and other factors. Assemblies based on red and blue LEDs have been recommended in literature, although not all plants show sufficient productivity in such lighting conditions. Adding of green LEDs proposed in some works was aimed at psychological support for the crew, and not at the improvement of plant growth. We studied the growth and the state of the photosynthetic apparatus in Chinese cabbage (Brassica chinensis L.) plants grown under red (650 nm) and blue (470 nm) light-emitting diodes (LEDs). Plants grown under a high-pressure sodium lamp (HPS lamp) were used as a control. The plants were illuminated with two photosynthetic photon flux levels: nearly 400 µE and about 100 µE. Plants grown under LEDs with 400 µE level, as compared to control plants, showed lower fresh weight, edible biomass, growth rate, and sugar content. The difference in fresh weight and edible biomass was even more pronounced in plants grown with 100 µE level; the data indicate that the adaptability of the test plants to insufficient lighting decreased. Under LEDs, we observed the decreasing of root growth and the absence of transition to the flowering stage, which points to a change in the hormonal balance in plants grown in such lighting conditions. We also found differences in the functioning of the photosynthetic apparatus and its reaction to a low lighting level. We have concluded that a lighting assembly with red and blue LEDs only is insufficient for the plant growth and productivity, and can bring about alterations in their adaptive and regulatory mechanisms. Further studies are needed to optimize the lighting spectrum for space agriculture, taking into account the photosynthetic, phototropic and regulatory roles of light. Using white LEDs or adding far-red and green LEDs might be a promising approach.

  17. Filter selection based on light source for multispectral imaging

    NASA Astrophysics Data System (ADS)

    Xu, Peng; Xu, Haisong

    2016-07-01

    In multispectral imaging, it is necessary to select a reduced number of filters to balance the imaging efficiency and spectral reflectance recovery accuracy. Due to the combined effect of filters and light source on reflectance recovery, the optimal filters are influenced by the employed light source in the multispectral imaging system. By casting the filter selection as an optimization issue, the selection of optimal filters corresponding to the employed light source proceeds with respect to a set of target samples utilizing one kind of genetic algorithms, regardless of the detailed spectral characteristics of the light source, filters, and sensor. Under three light sources with distinct spectral power distributions, the proposed filter selection method was evaluated on a filter-wheel based multispectral device with a set of interference filters. It was verified that the filters derived by the proposed method achieve better spectral and colorimetric accuracy of reflectance recovery than the conventional one under different light sources.

  18. Beacon system based on light-emitting diode sources for runways lighting

    NASA Astrophysics Data System (ADS)

    Montes, Mario González; Vázquez, Daniel; Fernandez-Balbuena, Antonio A.; Bernabeu, Eusebio

    2014-06-01

    New aeronautical ground lighting techniques are becoming increasingly important to ensure the safety and reduce the maintenance costs of the plane's tracks. Until recently, tracks had embedded lighting systems whose sources were based on incandescent lamps. But incandescent lamps have several disadvantages: high energy consumption and frequent breakdowns that result in high maintenance costs (lamp average life-time is ˜1500 operating hours) and the lamp's technology has a lack of new lighting functions, such as signal handling and modification. To solve these problems, the industry has developed systems based on light-emitting diode (LED) technology with improved features: (1) LED lighting consumes one tenth the power, (2) it improves preventive maintenance (an LED's lifetime range is between 25,000 and 100,000 hours), and (3) LED lighting technology can be controlled remotely according to the needs of the track configuration. LEDs have been in use for more than three decades, but only recently, around 2002, have they begun to be used as visual aids, representing the greatest potential change for airport lighting since their inception in the 1920s. Currently, embedded LED systems are not being broadly used due to the specific constraints of the rules and regulations of airports (beacon dimensions, power system technology, etc.). The fundamental requirements applied to embedded lighting systems are to be hosted on a volume where the dimensions are usually critical and also to integrate all the essential components for operation. An embedded architecture that meets the lighting regulations for airport runways is presented. The present work is divided into three main tasks: development of an optical system to optimize lighting according to International Civil Aviation Organization, manufacturing prototype, and model validation.

  19. Spectral matching research for light-emitting diode-based neonatal jaundice therapeutic device light source

    NASA Astrophysics Data System (ADS)

    Gan, Ruting; Guo, Zhenning; Lin, Jieben

    2015-09-01

    To decrease the risk of bilirubin encephalopathy and minimize the need for exchange transfusions, we report a novel design for light source of light-emitting diode (LED)-based neonatal jaundice therapeutic device (NJTD). The bilirubin absorption spectrum in vivo was regarded as target. Based on spectral constructing theory, we used commercially available LEDs with different peak wavelengths and full width at half maximum as matching light sources. Simple genetic algorithm was first proposed as the spectral matching method. The required LEDs number at each peak wavelength was calculated, and then, the commercial light source sample model of the device was fabricated to confirm the spectral matching technology. In addition, the corresponding spectrum was measured and the effect was analyzed finally. The results showed that fitted spectrum was very similar to the target spectrum with 98.86 % matching degree, and the actual device model has a spectrum close to the target with 96.02 % matching degree. With higher fitting degree and efficiency, this matching algorithm is very suitable for light source matching technology of LED-based spectral distribution, and bilirubin absorption spectrum in vivo will be auspicious candidate for the target spectrum of new LED-based NJTD light source.

  20. Berkeley Accelerator Space Effects (BASE) Light Ion FacilityUpgrade

    SciTech Connect

    Johnson, Michael B.; McMahan, Margaret A.; Gimpel, Thomas L.; Tiffany, William S.

    2006-07-07

    The BASE Light Ion Facility upgrades have been completed. All proton beams are now delivered to Cave 4A. New control software, a larger diameter beam window, and improved quality assurance measures have been added.

  1. What future for quantum dot-based light emitters?

    NASA Astrophysics Data System (ADS)

    Nurmikko, Arto

    2015-12-01

    Synthesis of semiconductor colloidal quantum dots by low-cost, solution-based methods has produced an abundance of basic science. Can these materials be transformed to high-performance light emitters to disrupt established photonics technologies, particularly semiconductor lasers?

  2. Context-based presets for lighting setup in residential space.

    PubMed

    Choi, Kyungah; Lee, Jeongmin; Suk, Hyeon-Jeong

    2016-01-01

    This study aims to derive context-based lighting setup presets in residential space by exploring the multilateral relationships among household activities, affects, and lighting setups. Three procedures were involved: First, sixty affective words were evaluated through which seven affect factors were extracted to facilitate the evaluation of colored illumination in the subsequent experiment. Second, in the user study, seven affect factors and thirty household activities were used to evaluate 147 lighting setups extracted from combinations of twelve hues, six illuminance levels, and three purity levels. As a result, twenty lighting setup presets were derived that were not only activity-based, but affect-based as well. Lastly, the twenty presets were prototyped as a set of testbed to further explore potentials and limitations. This study demonstrates that intuitive, context-based presets can help users explore the effects of colored illumination in creating a diverse range of user experiences. PMID:26360214

  3. Semiconductor-Nanocrystals-Based White Light-Emitting Diodes

    SciTech Connect

    Dai, Quanqin; Duty, Chad E; Hu, Michael Z.

    2010-01-01

    In response to the demands for energy and the concerns of global warming and climate change, energy efficient and environmentally friendly solid-state lighting, such as white lightemitting diodes (WLEDs), is considered to be the most promising and suitable light source. Because of their small size, high efficiency, and long lifetime, WLEDs based on colloidal semiconductor nanocrystals (or quantum dots) are emerging as a completely new technology platform for the development of flat-panel displays and solid-state lighting, exhibiting the potential to replace the conventionally used incandescent and fluorescent lamps. This replacement can cut the ever-increasing level of energy consumption, solve the problem of rapidly depleting fossil fuel reserves, and improve the quality of the global environment. In this review, the recent progress in semiconductor-nanocrystals-based WLEDs is highlighted, the different approaches for generating white light are compared, and the benefits and challenges of the solid-state lighting technology are discussed.

  4. Cherenkov Light-based Beam Profiling for Ultrarelativistic Electron Beams

    SciTech Connect

    Adli, E.; Gessner, S. J.; Corde, S.; Hogan, M. J.; Bjerke, H. H.

    2015-02-09

    We describe a beam profile monitor design based on Cherenkov light emitted from a charged particle beam in an air gap. The main components of the profile monitor are silicon wafers used to reflect Cherenkov light onto a camera lens system. The design allows for measuring large beam sizes, with large photon yield per beam charge and excellent signal linearity with beam charge. Furthermore, the profile monitor signal is independent of the particle energy for ultrarelativistic particles. Different design and parameter considerations are discussed. A Cherenkov light-based profile monitor has been installed at the FACET User Facility at SLAC. Finally, we report on the measured performance of this profile monitor.

  5. A ratiometric fluorescent probe based on boron dipyrromethene and rhodamine Förster resonance energy transfer platform for hypochlorous acid and its application in living cells.

    PubMed

    Liu, Ying; Zhao, Zhi-Min; Miao, Jun-Ying; Zhao, Bao-Xiang

    2016-05-19

    We have developed a ratiometric fluorescent probe BRT based on boron dipyrromethene (BODIPY) and rhodamine-thiohydrazide Förster resonance energy transfer (FRET) platform for sensing hypochlorous acid (HOCl) with high selectivity and sensitivity. The probe can detect HOCl in 15 s with the detection limit of 38 nM. Upon mixing with HOCl the fluorescence colour of probe BRT changed from green to orange. Moreover, probe BRT was applied to successfully monitor HOCl in living RAW 264.7 cells. PMID:27126792

  6. A review on visible light active perovskite-based photocatalysts.

    PubMed

    Kanhere, Pushkar; Chen, Zhong

    2014-01-01

    Perovskite-based photocatalysts are of significant interest in the field of photocatalysis. To date, several perovskite material systems have been developed and their applications in visible light photocatalysis studied. This article provides a review of the visible light (λ > 400 nm) active perovskite-based photocatalyst systems. The materials systems are classified by the B site cations and their crystal structure, optical properties, electronic structure, and photocatalytic performance are reviewed in detail. Titanates, tantalates, niobates, vanadates, and ferrites form important photocatalysts which show promise in visible light-driven photoreactions. Along with simple perovskite (ABO3) structures, development of double/complex perovskites that are active under visible light is also reviewed. Various strategies employed for enhancing the photocatalytic performance have been discussed, emphasizing the specific advantages and challenges offered by perovskite-based photocatalysts. This review provides a broad overview of the perovskite photocatalysts, summarizing the current state of the work and offering useful insights for their future development. PMID:25532834

  7. Light weight cellular structures based on aluminium

    SciTech Connect

    Prakash, O.; Embury, J.D.; Sinclair, C.; Sang, H.; Silvetti, P.

    1997-02-01

    An interesting form of lightweight material which has emerged in the past 2 decades is metallic foam. This paper deals with the basic concepts of making metallic foams and a detailed study of foams produced from Al-SiC. In addition, some aspects of cellular solids based on honeycomb structures are outlined including the concept of producing both two-phase foams and foams with composite walls.

  8. Improved spring model-based collaborative indoor visible light positioning

    NASA Astrophysics Data System (ADS)

    Luo, Zhijie; Zhang, WeiNan; Zhou, GuoFu

    2016-03-01

    Gaining accuracy with indoor positioning of individuals is important as many location-based services rely on the user's current position to provide them with useful services. Many researchers have studied indoor positioning techniques based on WiFi and Bluetooth. However, they have disadvantages such as low accuracy or high cost. In this paper, we propose an indoor positioning system in which visible light radiated from light-emitting diodes is used to locate the position of receivers. Compared with existing methods using light-emitting diode light, we present a high-precision and simple implementation collaborative indoor visible light positioning system based on an improved spring model. We first estimate coordinate position information using the visible light positioning system, and then use the spring model to correct positioning errors. The system can be employed easily because it does not require additional sensors and the occlusion problem of visible light would be alleviated. We also describe simulation experiments, which confirm the feasibility of our proposed method.

  9. Improved spring model-based collaborative indoor visible light positioning

    NASA Astrophysics Data System (ADS)

    Luo, Zhijie; Zhang, WeiNan; Zhou, GuoFu

    2016-06-01

    Gaining accuracy with indoor positioning of individuals is important as many location-based services rely on the user's current position to provide them with useful services. Many researchers have studied indoor positioning techniques based on WiFi and Bluetooth. However, they have disadvantages such as low accuracy or high cost. In this paper, we propose an indoor positioning system in which visible light radiated from light-emitting diodes is used to locate the position of receivers. Compared with existing methods using light-emitting diode light, we present a high-precision and simple implementation collaborative indoor visible light positioning system based on an improved spring model. We first estimate coordinate position information using the visible light positioning system, and then use the spring model to correct positioning errors. The system can be employed easily because it does not require additional sensors and the occlusion problem of visible light would be alleviated. We also describe simulation experiments, which confirm the feasibility of our proposed method.

  10. Broadband visible light source based on AllnGaN light emitting diodes

    DOEpatents

    Crawford, Mary H.; Nelson, Jeffrey S.

    2003-12-16

    A visible light source device is described based on a light emitting diode and a nanocluster-based film. The light emitting diode utilizes a semiconductor quantum well structure between n-type and p-type semiconductor materials on the top surface a substrate such as sapphire. The nanocluster-based film is deposited on the bottom surface of the substrate and can be derived from a solution of MoS.sub.2, MoSe.sub.2, WS.sub.2, and WSe.sub.2 particles of size greater than approximately 2 nm in diameter and less than approximately 15 nm in diameter, having an absorption wavelength greater than approximately 300 nm and less than approximately 650 nm.

  11. Optical characterization of nitride-based light-emitting diodes for solid-state lighting applications

    NASA Astrophysics Data System (ADS)

    Masui, Hisashi

    This dissertation describes research dedicated to the solid-state lighting technology based on III-nitride light-emitting diodes (LEDs). Nitride semiconductors are rather an immature material system compared to conventional III-V semiconductors. As the solid-state lighting technology based on nitride optoelectronic devices becomes widely accepted in the market, solid-state technology is required to compete with the conventional vacuum lighting technology, especially in energy efficiency. In addition to such energy-efficiency requirements, solid-state optoelectronic devices have the potential to explore new applications based on their unique properties. The research was conducted as a way of optical characterization of LEDs with a strong emphasis on electroluminescence. Device-packaging techniques were introduced in the early stage of the research to evaluate performances of discrete LEDs including phosphor-combined white-light emitting devices. Light extraction and white-LED fabrication were of direct interest in terms of solid-state lighting, which occupies a large part of the present dissertation. The suspended-LED technique was introduced to improve light extraction and the sphere package was invented as a result of the technique. A phosphor-combined sphere LED achieved as high as 117 lm/W of luminous efficacy. Low-temperature characterization is important to evaluate light-emission efficiency of LEDs, especially the internal quantum efficiency. It was a generally known problem that electroluminescence efficiency deteriorates drastically at low temperature where photoluminescence efficiency remains high. High-quality LEDs prepared on GaN bulk substrates that became available during the present project contributed to the low-temperature study, largely to address the problem. Electroluminescence is related to carrier generation processes via low-temperature measurements on such high-quality LEDs. This study produced a model to explain electroluminescence

  12. Overview of Light Hydrogen-Based Low Energy Nuclear Reactions

    NASA Astrophysics Data System (ADS)

    Miley, George H.; Shrestha, Prajakti J.

    This paper reviews light water and hydrogen-based low-energy nuclear reactions (LENRs) including the different methodologies used to study these reactions and the results obtained. Reports of excess heat production, transmutation reactions, and nuclear radiation emission are cited. An aim of this review is to present a summary of the present status of light water LENR research and provide some insight into where this research is heading.

  13. Advances and prospects in nitrides based light-emitting-diodes

    NASA Astrophysics Data System (ADS)

    Jinmin, Li; Zhe, Liu; Zhiqiang, Liu; Jianchang, Yan; Tongbo, Wei; Xiaoyan, Yi; Junxi, Wang

    2016-06-01

    Due to their low power consumption, long lifetime and high efficiency, nitrides based white light-emitting-diodes (LEDs) have long been considered to be a promising technology for next generation illumination. In this work, we provide a brief review of the development of GaN based LEDs. Some pioneering and significant experiment results of our group and the overview of the recent progress in this field are presented. We hope it can provide some meaningful information for the development of high efficiency GaN based LEDs and solid-state-lighting. Project supported by the National High Technology Research and Development Program of China (No. 2013AA03A101).

  14. Lighting.

    SciTech Connect

    United States. Bonneville Power Administration.

    1992-09-01

    Since lighting accounts for about one-third of the energy used in commercial buildings, there is opportunity to conserve. There are two ways to reduce lighting energy use: modify lighting systems so that they used less electricity and/or reduce the number of hours the lights are used. This booklet presents a number of ways to do both. Topics covered include: reassessing lighting levels, reducing lighting levels, increasing bulb & fixture efficiency, using controls to regulate lighting, and taking advantage of daylight.

  15. Light: an experiments based learning approach with primary school children

    NASA Astrophysics Data System (ADS)

    Abreu, Cátia; Noversa, Silvana; Varela, Paulo; Costa, Manuel F.

    2014-07-01

    A pedagogical intervention project was carried out at a primary school in the municipality of Vila Verde, Braga in Portugal. In a class of the 3rd grade, composed of 16 students, a practice of inquiry-based science teaching was implemented, addressing the curricular topic "Light Experiments". Various experimental activities were planned within this topic, including: What is light? How does light travel? Does light travel through every material? How is light reflected by a mirror? This project adopted an action research methodology and had as its main objectives: a) to promote a practical and experimental approach to the science component of the Environmental Studies curricular area; b) to describe the scientific meaning construction process inherent to the topics addressed in the classroom with the children, c) to assess the learning steps and children' achievements. Class diaries were prepared, based on field notes and audio recordings taken in the classroom. Through the analysis of the class diary concerning the topic "materials that let light travel through them" we intend to illustrate the process of construction of scientific meanings promoted in the classroom with our approach.

  16. Semiconductor-nanocrystals-based white light-emitting diodes.

    PubMed

    Dai, Quanqin; Duty, Chad E; Hu, Michael Z

    2010-08-01

    In response to the demands for energy and the concerns of global warming and climate change, energy efficient and environmentally friendly solid-state lighting, such as white light-emitting diodes (WLEDs), is considered to be the most promising and suitable light source. Because of their small size, high efficiency, and long lifetime, WLEDs based on colloidal semiconductor nanocrystals (or quantum dots) are emerging as a completely new technology platform for the development of flat-panel displays and solid-state lighting, exhibiting the potential to replace the conventionally used incandescent and fluorescent lamps. This replacement can cut the ever-increasing level of energy consumption, solve the problem of rapidly depleting fossil fuel reserves, and improve the quality of the global environment. In this review, the recent progress in semiconductor-nanocrystals-based WLEDs is highlighted, the different approaches for generating white light are compared, and the benefits and challenges of the solid-state lighting technology are discussed. PMID:20602425

  17. Light Field Imaging Based Accurate Image Specular Highlight Removal

    PubMed Central

    Wang, Haoqian; Xu, Chenxue; Wang, Xingzheng; Zhang, Yongbing; Peng, Bo

    2016-01-01

    Specular reflection removal is indispensable to many computer vision tasks. However, most existing methods fail or degrade in complex real scenarios for their individual drawbacks. Benefiting from the light field imaging technology, this paper proposes a novel and accurate approach to remove specularity and improve image quality. We first capture images with specularity by the light field camera (Lytro ILLUM). After accurately estimating the image depth, a simple and concise threshold strategy is adopted to cluster the specular pixels into “unsaturated” and “saturated” category. Finally, a color variance analysis of multiple views and a local color refinement are individually conducted on the two categories to recover diffuse color information. Experimental evaluation by comparison with existed methods based on our light field dataset together with Stanford light field archive verifies the effectiveness of our proposed algorithm. PMID:27253083

  18. Laser and Light-Based Aesthetics in Men.

    PubMed

    Green, Jeremy B; Metelitsa, Andrei I; Kaufman, Joely; Keaney, Terrence

    2015-09-01

    Men represent an important evolving segment of the cosmetic market. With the growing acceptability of cosmetic procedures along with societal and workplace pressure to maintain youthfulness, men increasingly seek the advice of aesthetic practitioners. Despite this so-called "Menaissance," there is a paucity of published literature regarding laser and light treatments of male skin. Herein the differences in male cutaneous physiology are addressed, followed by a review of light-based treatment of conditions largely unique to male skin, pseudofolliculitis barbae, and rhinophyma. Next, the publications related to laser treatment of male skin specifically are examined. We conclude with a discussion of personal observations derived from clinical experience with laser and light-based treatments in men. PMID:26355628

  19. Cherenkov Light-based Beam Profiling for Ultrarelativistic Electron Beams

    DOE PAGESBeta

    Adli, E.; Gessner, S. J.; Corde, S.; Hogan, M. J.; Bjerke, H. H.

    2015-02-09

    We describe a beam profile monitor design based on Cherenkov light emitted from a charged particle beam in an air gap. The main components of the profile monitor are silicon wafers used to reflect Cherenkov light onto a camera lens system. The design allows for measuring large beam sizes, with large photon yield per beam charge and excellent signal linearity with beam charge. Furthermore, the profile monitor signal is independent of the particle energy for ultrarelativistic particles. Different design and parameter considerations are discussed. A Cherenkov light-based profile monitor has been installed at the FACET User Facility at SLAC. Finally,more » we report on the measured performance of this profile monitor.« less

  20. GaN-based light-emitting diodes suitable for white light

    NASA Astrophysics Data System (ADS)

    Mukai, Takashi; Yamada, Motokazu; Mitani, Tomotsugu; Narukawa, Yukio; Shioji, Shuji; Niki, Isamu; Sonobe, Shin-ya; Izuno, Kunihiro; Suenaga, Ryoma

    2003-07-01

    High-efficient light emitting diodes (LEDs) emitting red, amber, green, blue and ultraviolet light have been obtained through the use of an InGaN active layers. The localized energy states caused by In composition fluctuation in the InGaN active layer seem to be related to the high efficiency of the InGaN-based emitting devices in spite of having a large number of threading dislocations (TDs). InGaN single-quantum-well-structure blue LEDs were grown on epitaxially laterally overgrown GaN (ELOG) and sapphire substrates. The characteristics of both LEDs was almost same. These results indicate that the dislocation doesn't affect the efficiency practically. Recently, the development of high-power light source using GaN-based LEDs has become active. In such high-power LEDs, the density of forward current is much higher than that of past LEDs. Therefore, an advantage of carrier localization in InGaN active layer becomes small, because of band filling under high injection level. This means that reducing the density of TDs becomes important, just like GaN-based laser diodes. Also, we show recent results of GaN-based LEDs.

  1. Bright light-emitting diodes based on organometal halide perovskite

    NASA Astrophysics Data System (ADS)

    Tan, Zhi-Kuang; Moghaddam, Reza Saberi; Lai, May Ling; Docampo, Pablo; Higler, Ruben; Deschler, Felix; Price, Michael; Sadhanala, Aditya; Pazos, Luis M.; Credgington, Dan; Hanusch, Fabian; Bein, Thomas; Snaith, Henry J.; Friend, Richard H.

    2014-09-01

    Solid-state light-emitting devices based on direct-bandgap semiconductors have, over the past two decades, been utilized as energy-efficient sources of lighting. However, fabrication of these devices typically relies on expensive high-temperature and high-vacuum processes, rendering them uneconomical for use in large-area displays. Here, we report high-brightness light-emitting diodes based on solution-processed organometal halide perovskites. We demonstrate electroluminescence in the near-infrared, green and red by tuning the halide compositions in the perovskite. In our infrared device, a thin 15 nm layer of CH3NH3PbI3-xClx perovskite emitter is sandwiched between larger-bandgap titanium dioxide (TiO2) and poly(9,9‧-dioctylfluorene) (F8) layers, effectively confining electrons and holes in the perovskite layer for radiative recombination. We report an infrared radiance of 13.2 W sr-1 m-2 at a current density of 363 mA cm-2, with highest external and internal quantum efficiencies of 0.76% and 3.4%, respectively. In our green light-emitting device with an ITO/PEDOT:PSS/CH3NH3PbBr3/F8/Ca/Ag structure, we achieved a luminance of 364 cd m-2 at a current density of 123 mA cm-2, giving external and internal quantum efficiencies of 0.1% and 0.4%, respectively. We show, using photoluminescence studies, that radiative bimolecular recombination is dominant at higher excitation densities. Hence, the quantum efficiencies of the perovskite light-emitting diodes increase at higher current densities. This demonstration of effective perovskite electroluminescence offers scope for developing this unique class of materials into efficient and colour-tunable light emitters for low-cost display, lighting and optical communication applications.

  2. Thermal Performance of III-Nitride Light Emitting Diodes and Developments in Laser Based White Lighting

    NASA Astrophysics Data System (ADS)

    Pfaff, Nathan Andrew

    Light emitting diodes, LEDs, have two distinct reductions in their efficiency. Efficiency droop which is a decrease in efficiency with increasing current density, and thermal droop, a reduction in efficiency with increasing temperature. Although there has been extensive work on efficiency droop and research into both the mitigation and causes of efficiency droop, comparably little research has been done on thermal droop. Since the early years of III-Nitride LEDs, have shown better performance than other materials systems used in visible light emitters when operated at increased temperatures. Due to the push for increased electrical efficiency thermal droop has been largely ignored or dealt with at a packaging level. Now LEDs are increasingly used in general illumination applications requiring high-current and high-flux operation resulting in elevated operating temperatures. In such high power applications LEDs can reach temperatures of over 100 °C where the performance can be significantly degraded. By altering the internal structure both below and within the active region the thermal droop of LEDs was reduced while preserving or enhancing electrical efficiency. Increased high temperature performance was observed on both blue c-plane and m-plane LEDs. Electrical droop which adversely affects LEDs in general illumination applications is difficult to mitigate. As an alternative to high-current, high-luminous flux LEDs for general illumination, phosphor converted laser, pc-LD, based white lighting is demonstrated. pc-LD shows virtually droop free performance over a wide range of high current densities with high luminous flux levels. The ability to achieve efficiencies on par with pc-LEDs, with significantly reduced substrate use and extremely high current operation, suggests that pc-LD white lighting has potential for entry into select white lighting applications in the near future. First demonstrations of pc-LD white lighting with general illumination level fluxes

  3. Absorbance Based Light Emitting Diode Optical Sensors and Sensing Devices

    PubMed Central

    O'Toole, Martina; Diamond, Dermot

    2008-01-01

    The ever increasing demand for in situ monitoring of health, environment and security has created a need for reliable, miniaturised sensing devices. To achieve this, appropriate analytical devices are required that possess operating characteristics of reliability, low power consumption, low cost, autonomous operation capability and compatibility with wireless communications systems. The use of light emitting diodes (LEDs) as light sources is one strategy, which has been successfully applied in chemical sensing. This paper summarises the development and advancement of LED based chemical sensors and sensing devices in terms of their configuration and application, with the focus on transmittance and reflectance absorptiometric measurements.

  4. Laser wakefield accelerator based light sources: potential applications and requirements

    SciTech Connect

    Albert, F.; Thomas, A. G.; Mangles, S. P.D.; Banerjee, S.; Corde, S.; Flacco, A.; Litos, M.; Neely, D.; Viera, J.; Najmudin, Z.; Bingham, R.; Joshi, C.; Katsouleas, T.

    2015-01-15

    In this article we review the prospects of laser wakefield accelerators as next generation light sources for applications. This work arose as a result of discussions held at the 2013 Laser Plasma Accelerators Workshop. X-ray phase contrast imaging, X-ray absorption spectroscopy, and nuclear resonance fluorescence are highlighted as potential applications for laser-plasma based light sources. We discuss ongoing and future efforts to improve the properties of radiation from plasma betatron emission and Compton scattering using laser wakefield accelerators for these specific applications.

  5. Asynchronous indoor positioning system based on visible light communications

    NASA Astrophysics Data System (ADS)

    Zhang, Weizhi; Chowdhury, M. I. Sakib; Kavehrad, Mohsen

    2014-04-01

    Indoor positioning has become an attractive research topic within the past two decades. However, no satisfying solution has been found with consideration of both accuracy and system complexity. Recently, research on visible light communications (VLC) offer new opportunities in realizing accurate indoor positioning with relatively simple system configuration. An indoor positioning system based on VLC technology is introduced, with no synchronization requirement on the transmitters. Simulation results show that, with over 95% confidence, the target receiver can be located with an accuracy of 5.9 cm, assuming indirect sunlight exposure and proper installation of light-emitting diode bulbs.

  6. Light-pollution model for cloudy and cloudless night skies with ground-based light sources.

    PubMed

    Kocifaj, Miroslav

    2007-05-20

    The scalable theoretical model of light pollution for ground sources is presented. The model is successfully employed for simulation of angular behavior of the spectral and integral sky radiance and/or luminance during nighttime. There is no restriction on the number of ground-based light sources or on the spatial distribution of these sources in the vicinity of the measuring point (i.e., both distances and azimuth angles of the light sources are configurable). The model is applicable for real finite-dimensional surface sources with defined spectral and angular radiating properties contrary to frequently used point-source approximations. The influence of the atmosphere on the transmitted radiation is formulated in terms of aerosol and molecular optical properties. Altitude and spectral reflectance of a cloud layer are the main factors introduced for simulation of cloudy and/or overcast conditions. The derived equations are translated into numerically fast code, and it is possible to repeat the entire set of calculations in real time. The parametric character of the model enables its efficient usage by illuminating engineers and/or astronomers in the study of various light-pollution situations. Some examples of numerical runs in the form of graphical results are presented. PMID:17514252

  7. Wheel pose measurement based on cross structure light

    NASA Astrophysics Data System (ADS)

    Zhao, Qiancheng; Ding, Xun; Wang, Xian; Zhao, Yafeng

    2016-01-01

    It's necessary for automobile to detect and adjust four-wheel alignment parameters regularly, due to the significant effect on improving stability, enhancing security and reducing tire wear of automobiles. In order to measure the parameters that determined by relative position and posture of four wheels to the automobile cab, this paper proposes a method which applies monocular vision of linear structure light to wheel pose measurement. Firstly, space coordinates of feature point cloud are calculated out from the principle of structured light. Then, an algorithm is designed to determine the normal vector of wheel tangent plane and measure the wheel pose. Finally, actual experiments that by evaluation of adjusted wheel angle measurement are carried out to verify the system accuracy. The corresponding studies can be applied in designing and developing 3D four-wheel alignment system that based on structured light.

  8. Laser and light-based treatment options for hidradenitis suppurativa.

    PubMed

    Hamzavi, Iltefat H; Griffith, James L; Riyaz, Farhaad; Hessam, Schapoor; Bechara, Falk G

    2015-11-01

    Hidradenitis suppurativa (HS) is a chronic inflammatory disease that commonly develops painful, deep dermal abscesses and chronic, draining sinus tracts. Classically, pharmacologic and surgical therapies have been effective for reducing lesion activity and inflammation, but provide only modest success in the prevention of future recurrences and disease progression. Adjunctive therapies, such as laser and light-based therapies, have become more commonly used in the management of HS. These therapies work to reduce the occurrence of painful HS flare-ups by decreasing the number of hair follicles, sebaceous glands, and bacteria in affected areas, and by ablatively debulking chronic lesions. The best results are seen when treatment is individualized, taking disease severity into consideration when selecting specific energy-based approaches. This article will discuss various light-based therapies and the evidence supporting their use in the management of HS. PMID:26470622

  9. Performance of light-emitting-diode based on quantum dots

    NASA Astrophysics Data System (ADS)

    Kim, Sungwoo; Im, Sang Hyuk; Kim, Sang-Wook

    2013-05-01

    Light-emitting diodes (LEDs) based on colloidal quantum dots (QDs) have attracted considerable attention due to their potential in applications such as color-saturated displays and white light with high color-rendering index. However, cadmium-based QD-LEDs are strictly regulated in industrial applications because of the high toxicity of cadmium. As an alternative, InP-based cadmium-free QDs are recommended owing to their wide emission range that is comparable to that of CdSe, and their environmentally friendly properties when applied to QD-LEDs and white QD-LEDs. This feature article provides an overview of QDs' merits in display and light-emitting applications as well as a discussion of their color tunability, photo-stability, and high luminescence efficiency. We will include optical down-conversion devices using various QDs, electroluminescent devices based on organic and inorganic charge-transporting layers, and printing methods using cadmium based and cadmium free QDs.

  10. High-Efficiency Nitride-Based Solid-State Lighting

    SciTech Connect

    Paul T. Fini; Shuji Nakamura

    2005-07-30

    In this final technical progress report we summarize research accomplished during Department of Energy contract DE-FC26-01NT41203, entitled ''High-Efficiency Nitride-Based Solid-State Lighting''. Two teams, from the University of California at Santa Barbara (Principle Investigator: Dr. Shuji Nakamura) and the Lighting Research Center at Rensselaer Polytechnic Institute (led by Dr. N. Narendran), pursued the goals of this contract from thin film growth, characterization, and packaging/luminaire design standpoints. The UCSB team initially pursued the development of blue gallium nitride (GaN)-based vertical-cavity surface-emitting lasers, as well as ultraviolet GaN-based light emitting diodes (LEDs). In Year 2, the emphasis shifted to resonant-cavity light emitting diodes, also known as micro-cavity LEDs when extremely thin device cavities are fabricated. These devices have very directional emission and higher light extraction efficiency than conventional LEDs. Via the optimization of thin-film growth and refinement of device processing, we decreased the total cavity thickness to less than 1 {micro}m, such that micro-cavity effects were clearly observed and a light extraction efficiency of over 10% was reached. We also began the development of photonic crystals for increased light extraction, in particular for so-called ''guided modes'' which would otherwise propagate laterally in the device and be re-absorbed. Finally, we pursued the growth of smooth, high-quality nonpolar a-plane and m-plane GaN films, as well as blue light emitting diodes on these novel films. Initial nonpolar LEDs showed the expected behavior of negligible peak wavelength shift with increasing drive current. M-plane LEDs in particular show promise, as unpackaged devices had unsaturated optical output power of {approx} 3 mW at 200 mA drive current. The LRC's tasks were aimed at developing the subcomponents necessary for packaging UCSB's light emitting diodes, and packaging them to produce a white

  11. III V nitride based light-emitting devices

    NASA Astrophysics Data System (ADS)

    Nakamura, Shuji

    1997-04-01

    High brightness InGaN single-quantum-well structure (SQW) blue and green light-emitting diodes (LEDs) with luminous intensities of 2 cd and 10 cd have been achieved and commercialized. By combining these high-power and high-brightness blue InGaN SQW LED, green InGaN SQW LED and red AlInGaP LED, many kinds of applications, such as LED full-color displays and LED white lamps for use in place of incandescent or fluorescent lamps, are now possible with characteristics of high reliability, high durability and low energy consumption. Also, very recently, III-V nitride based laser diodes (LDs) were fabricated for the first time. These LDs emitted coherent light at 390-440 nm from an InGaN based multi-quantum-well structure at room temperature. The emission wavelength is the shortest one ever generated by a semiconductor laser diode.

  12. Versatile multispectral microscope based on light emitting diodes

    NASA Astrophysics Data System (ADS)

    Brydegaard, Mikkel; Merdasa, Aboma; Jayaweera, Hiran; Ålebring, Jens; Svanberg, Sune

    2011-12-01

    We describe the development of a novel multispectral microscope, based on light-emitting diodes, capable of acquiring megapixel images in thirteen spectral bands from the ultraviolet to the near infrared. The system captures images and spectra in transmittance, reflectance, and scattering modes. We present as examples of applications ground truth measurements for remote sensing and parasitology diagnostics. The system is a general purpose scientific instrument that could be used to develop dedicated simplified instruments with optimal bands and mode selection.

  13. Penning plasma based simultaneous light emission source of visible and VUV lights

    NASA Astrophysics Data System (ADS)

    Vyas, G. L.; Prakash, R.; Pal, U. N.; Manchanda, R.; Halder, N.

    2016-06-01

    In this paper, a laboratory-based penning plasma discharge source is reported which has been developed in two anode configurations and is able to produce visible and VUV lights simultaneously. The developed source has simultaneous diagnostics facility using Langmuir probe and optical emission spectroscopy. The two anode configurations, namely, double ring and rectangular configurations, have been studied and compared for optimum use of the geometry for efficient light emissions and recording. The plasma is produced using helium gas and admixture of three noble gases including helium, neon, and argon. The source is capable to produce eight spectral lines for pure helium in the VUV range from 20 to 60 nm and total 24 spectral lines covering the wavelength range 20-106 nm for the admixture of gases. The large range of VUV lines is generated from gaseous admixture rather from the sputtered materials. The recorded spectrum shows that the plasma light radiations in both visible and VUV range are larger in double ring configuration than that of the rectangular configurations at the same discharge operating conditions. To clearly understand the difference, the imaging of the discharge using ICCD camera and particle-in-cell simulation using VORPAL have also been carried out. The effect of ion diffusion, metastable collision with the anode wall and the nonlinear effects are correlated to explain the results.

  14. Controlled-phase gate for photons based on stationary light

    NASA Astrophysics Data System (ADS)

    Iakoupov, Ivan; Borregaard, Johannes; Sørensen, Anders S.

    We propose a controlled-phase gate for optical photons based on an atomic ensemble coupled to a one-dimensional waveguide. When an ensemble of Λ-type atoms is subject to a standing wave control field, it creates a stationary light effect where the ensemble develops a band gap for light propagation. For frequencies close to the band gap, the light-matter interactions are enhanced due to the reduced group velocity of the light pulses. Changing the internal state of one of the atoms, such that it behaves as an absorbing two-level atom instead of a transparent Λ-type atom, can change the scattering properties of the whole ensemble, switching it from being completely transmissive to being completely reflective. To realize a controlled-phase gate between photons, we store one of the photons inside the atomic ensemble (thereby changing the internal state of one of the atoms), scatter a second photon off the ensemble, and retrieve the first photon. Finally, we consider an application of the proposed controlled-phase gate - a quantum repeater.

  15. Carbon nanotube-based organic light emitting diodes

    NASA Astrophysics Data System (ADS)

    Bansal, Malti; Srivastava, Ritu; Lal, C.; Kamalasanan, M. N.; Tanwar, L. S.

    2009-11-01

    Carbon nanotubes; revolutionary and fascinating from the materials point of view and exceedingly sensational from a research point of view; are standing today at the threshold between inorganic electronics and organic electronics and posing a serious challenge to the big daddies of these two domains in electronics i.e., silicon and indium tin oxide (ITO). In the field of inorganic electronics, carbon nanotubes offer advantages such as high current carrying capacity, ballistic transport, absence of dangling bonds, etc. and on the other hand, in the field of organic electronics, carbon nanotubes offer advantages such as high conductivity, high carrier mobility, optical transparency (in visible and IR spectral ranges), flexibility, robustness, environmental resistance, etc. and hence, they are seriously being considered as contenders to silicon and ITO. This review traces the origin of carbon nanotubes in the field of organic electronics (with emphasis on organic light emitting diodes) and moves on to cover the latest advances in the field of carbon nanotube-based organic light emitting diodes. Topics that are covered within include applications of multi-wall nanotubes and single-wall nanotubes in organic light emitting diodes. Applications of carbon nanotubes as hole-transport layers, as electron-transport layers, as transparent electrodes, etc. in organic light emitting diodes are discussed and the daunting challenges facing this progressive field today are brought into the limelight.

  16. HIGH-EFFICIENCY NITRIDE-BASED SOLID-STATE LIGHTING

    SciTech Connect

    Dr. Paul T. Fini; Prof. Shuji Nakamura

    2002-09-01

    In this annual report we summarize the progress obtained in the first year with the support of DoE contract No.DE-FC26-01NT41203, entitled ''High-Efficiency Nitride-Based Solid-State Lighting''. The two teams, from the University of California at Santa Barbara (Principle Investigator: Dr. Shuji Nakamura) and Rensselaer Polytechnic Institute (led by Dr. N. Narendran), are pursuing the goals of this contract from thin film growth, characterization, and packaging standpoints. The UCSB team has made significant progress in the development of GaN vertical cavity surface-emitting lasers (VCSELs) as well as light-emitting diodes (LEDs) with AlGaN active regions emitting in the ultraviolet (UV). The Rensselaer team has developed target specifications for some of the key parameters for the proposed solid-state lighting system, including a luminous flux requirement matrix for various lighting applications, optimal spectral power distributions, and the performance characteristics of currently available commercial LEDs for eventual comparisons to the devices developed in the scope of this project.

  17. HIGH-EFFICIENCY NITRIDE-BASED SOLID-STATE LIGHTING

    SciTech Connect

    Dr. Paul T. Fini; Prof. Shuji Nakamura

    2002-04-30

    In this semiannual report we summarize the progress obtained in the first six months with the support of DoE contract No.DE-FC26-01NT41203, entitled ''High-Efficiency Nitride-Based Solid-State Lighting''. The two teams, from the University of California at Santa Barbara (Principle Investigator: Dr. Shuji Nakamura) and Rensselaer Polytechnic Institute (led by Dr. N. Narendran), are pursuing the goals of this contract from thin film growth, characterization, and packaging standpoints. The UCSB team has made significant progress in the development of GaN vertical cavity surface-emitting lasers (VCSELs) as well as light-emitting diodes (LEDs) with AlGaN active regions emitting in the ultraviolet (UV). The Rensselaer team has developed target specifications for some of the key parameters for the proposed solid-state lighting system, including a luminous flux requirement matrix for various lighting applications, optimal spectral power distributions, and the performance characteristics of currently available commercial LEDs for eventual comparisons to the devices developed in the scope of this project.

  18. Development of Key Technologies for White Lighting Based on Light-Emitting Diodes (LEDs)

    SciTech Connect

    Werner Goetz; Bill Imler; James Kim; Junko Kobayashi; Andrew Kim; Mike Krames; Rick Mann; Gerd Mueller-Mach; Anneli Munkholm; Jonathan Wierer

    2004-03-31

    This program was organized to focus on materials development issues critical to the acceleration of solid-state lighting, and was split into three major thrust areas: (1) study of dislocation density reduction for GaN grown on sapphire using 'cantilever epitaxy', and the impact of dislocation density on the performance of state-of-the-art high-power LEDs; (2) the evaluation of in situ techniques for monitoring gas phase chemistry and the properties of GaN-based layers during metal-organic vapor phase epitaxy (MOCVD), and (3) feasibility for using semiconductor nanoparticles ('quantum dots') for the down-conversion of blue or ultraviolet light to generate white light. The program included a partnership between Lumileds Lighting (epitaxy and device fabrication for high power LEDs) and Sandia National Laboratories (cantilever epitaxy, gas phase chemistry, and quantum dot synthesis). Key findings included: (1) cantilever epitaxy can provide dislocation density reduction comparable to that of more complicated approaches, but all in one epitaxial growth step; however, further improvements are required to realize significant gains in LED performance at high drive currents, (2) in situ tools can provide detailed knowledge about gas phase chemistry, and can be used to monitor and control epitaxial layer composition and temperature to provide improved yields (e.g., a fivefold increase in color targeting is demonstrated for 540nm LEDs), and (3) quantum efficiency for quantum dots is improved and maintained up to 70% in epoxy thin films, but further work is necessary to increase densification (absorption) and robustness before practical application to LEDs.

  19. Light extraction analysis of GaN-based light-emitting diodes with surface texture and/or patterned substrate.

    PubMed

    Lee, Tsung-Xian; Gao, Ko-Fon; Chien, Wei-Ting; Sun, Ching-Cherng

    2007-05-28

    Light extraction analysis of GaN-based light-emitting diodes (LEDs) with Monte Carlo ray tracing is presented. To obtain high light extraction efficiency, periodic structures introduced on the top surface and/or on the substrate of various types of LED are simulated, including wire bonding, flip chip and Thin GaN. Micro pyramid array with an apex angle from 20o to 70o is shown to effectively improve the light extraction efficiency. In addition, for an LED encapsulated within an epoxy lens, the patterned substrate with pyramid array is found to be a more effective way to increase light extraction efficiency than the surface texture. PMID:19546977

  20. Novel light emissive yttrium-based nanoparticles and composites

    NASA Astrophysics Data System (ADS)

    Hill, Laura Burka

    Yttrium-based inorganic optical materials generally are of practical interest for three applications: solid state lighting/displays, lasers, and scintillators. Solid-state lighting is particularly desirable commercially for its efficiency and lifetime compared to traditional incandescent alternatives. This type of lighting technology is of increasing interest as incandescent light bulbs are being gradually phased-out due to government regulations on maximum wattage of these devices. Additionally, shortcomings in the current state of the art have driven the need for a more thermally stable material for use in this area. In this dissertation, we develop and characterize a novel composite material consisting of optically active yttrium-based nanoparticles doped into silica sol-gels. For lighting and display applications, low-cost, low-temperature synthesis methods for materials that meet or exceed the quality of the materials currently on the market are highly desirable. During the course of this work, we discuss the characterization of yttrium-based nanoparticles with respect to their incorporation in a sol-gel matrix composite. We then prepared these composite materials using a variety of methods and assess their quality according to a set of selection criteria and for lighting/display applications. Novel light-emitting composites consisting of Ce:YAG or Eu:Y2O 3 (yttria) nanoparticles in an inorganic medium were successfully developed and characterized. The optical properties of the nanoparticles were maintained when incorporated into the sol-gel medium and were shown to be comparable with the current state of the art. Comparison was made between the nanoparticle emission and the composite emission and, in the case of the Ce:YAG, the CIE coordinates, showing no change between the emission intensities or peak locations. We successfully demonstrated the conversion of fluoride-based particles into Y2O3 during sol-gel processing and demonstrated that no reaction took

  1. Silicon-based structures for IR light emission

    NASA Astrophysics Data System (ADS)

    Hansson, Göran V.; Ni, Wei-Xin; Joelsson, Kenneth B.; Buyanova, I. A.

    1997-01-01

    There is a lot of interest in obtaining efficient infra-red (IR) light emission from Si-based structures for use in optoelectronics. Although it has been theoretically predicted that Sim/Gen atomic layer superlattices can have a quasi-direct bandgap, the experimental studies have not yet given very high luminescence intensities, particularly at room temperature, from such structures. So far, the most efficient method to have IR light emission at room temperature is to process Si/Si1-xGex superlattices or quantum well structures into narrow (<60nm diameter) columnar structures. After planarization with insulating material it has been possible to fabricate LEDs using these columns. While the results are very promising there are also a number of unsolved problems concerning the mechanism allowing for efficient light emission and concerning the passivation of the surfaces of the columns to have a long-term stability of the emission. Another way to have IR light emission at room temperature and possibly obtain a Si-based laser is to use Er-doped material. For Er-doped LEDs, most of the work has been done on ion-implanted structures. It has been found that to have the Er-related emission at 1.54 μm it is necessary to also have co-dopants like O or F to activate the Er. Since a high temperature step is necessary to anneal out implantation damage it has been difficult to have high concentrations of Er/O without precipitation, as the required concentration for useful devices is far above the solid solubility of Er in Si. Low temperature growth using MBE is a promising method to achieve high Er/O or Er/F concentrations without precipitation and intense room-temperature electroluminescence has very recently been reported from a reverse biased Er/O-doped LED grown by MBE.

  2. Integrated LED-based luminare for general lighting

    DOEpatents

    Dowling, Kevin J.; Lys, Ihor A.; Roberge, Brian; Williamson, Ryan C.; Roberts, Ron; Datta, Michael; Mollnow, Tomas; Morgan, Frederick M.

    2013-03-05

    Lighting apparatus and methods employing LED light sources are described. The LED light sources are integrated with other components in the form of a luminaire or other general purpose lighting structure. Some of the lighting structures are formed as Parabolic Aluminum Reflector (PAR) luminaires, allowing them to be inserted into conventional sockets. The lighting structures display beneficial operating characteristics, such as efficient operation, high thermal dissipation, high output, and good color mixing.

  3. Integrated LED-based luminaire for general lighting

    DOEpatents

    Dowling, Kevin J.; Lys, Ihor A.; Williamson, Ryan C.; Roberge, Brian; Roberts, Ron; Morgan, Frederick; Datta, Michael Jay; Mollnow, Tomas Jonathan

    2016-08-30

    Lighting apparatus and methods employing LED light sources are described. The LED light sources are integrated with other components in the form of a luminaire or other general purpose lighting structure. Some of the lighting structures are formed as Parabolic Aluminum Reflector (PAR) luminaires, allowing them to be inserted into conventional sockets. The lighting structures display beneficial operating characteristics, such as efficient operation, high thermal dissipation, high output, and good color mixing.

  4. Quantum repeater based on cavity QED evolutions and coherent light

    NASA Astrophysics Data System (ADS)

    Gonţa, Denis; van Loock, Peter

    2016-05-01

    In the framework of cavity QED, we propose a quantum repeater scheme that uses coherent light and chains of atoms coupled to optical cavities. In contrast to conventional repeater schemes, in our scheme there is no need for an explicit use of two-qubit quantum logical gates by exploiting solely the cavity QED evolution. In our previous work (Gonta and van Loock in Phys Rev A 88:052308, 2013), we already proposed a quantum repeater in which the entanglement between two neighboring repeater nodes was distributed using controlled displacements of input coherent light, while the produced low-fidelity entangled pairs were purified using ancillary (four-partite) entangled states. In the present work, the entanglement distribution is realized using a sequence of controlled phase shifts and displacements of input coherent light. Compared to previous coherent-state-based distribution schemes for two-qubit entanglement, our scheme here relies only upon a simple discrimination of two coherent states with opposite signs, which can be performed in a quantum mechanically optimal fashion via a beam splitter and two on-off detectors. For the entanglement purification, we employ a method that avoids the use of extra entangled ancilla states. Our repeater scheme exhibits reasonable fidelities and repeater rates providing an attractive platform for long-distance quantum communication.

  5. Light-responsive viscoelastic fluids based on anionic wormlike micelles.

    PubMed

    Lu, Yechang; Zhou, Tengfei; Fan, Qing; Dong, Jinfeng; Li, Xuefeng

    2013-12-15

    A new class of light-responsive viscoelastic fluids based on anionic wormlike micelles is reported. The key components are sodium oleate (NaOA) and a cationic azobenzene dye, 1-[2-(4-phenylazo-phenoxy)-ethyl]-3-methylimidazolium bromide (C0AZOC2IMB). These binary systems are gel-like fluids at certain concentration ratios of [C0AZOC2IMB]/[NaOA], e.g. 35/100, owing to the formation of long, entangled wormlike micelles. The viscosity of these fluids can be controlled reversibly by light due to photo isomerization between trans-C0AZOC2IMB and cis-C0AZOC2IMB. For example, the zero-shear viscosity (η0) of an originally gel-like sample is high up to ~1300 Pa s when C0AZOC2IMB is in its trans from, whereas the mixture becomes a Newtonian fluid with η0 about 0.01 Pa s after UV light irradiation. For the post-irradiated cis-C0AZOC2IMB, short cylindrical micelles form, hence accounting for the lower viscosity. Evidence for the structural transition is provided by UV-vis spectra, rheology, (1)H NMR and cryo-transmission electronic microscopy measurements. PMID:24144381

  6. A structured light-based system for human heads

    NASA Astrophysics Data System (ADS)

    Wu, XianFeng; Li, Dehua; Gang, Jin; Zhou, Zhu

    2004-07-01

    The 3-D modeling of heads by using optical triangulation techniques is of great interest in the context of virtual reality, telecommunication and computer animation. This paper presents a structured light-based system mainly for human heads. It is named "3-D Laser Color Scanner" (3DLCS). A 3-D model is obtained with a cylindrical scan. The laser beam is switched on and off using a "light valve" and two successive CCD frames are captured, one with the laser line showing and one without. We can simplify the laser line extracting by subtracting these two images. In this system, two CCD cameras are used to avoid occlusion problems. Color information is read from the CCD when the laser light is absent. Since traditional laser scanner will miss the range data in the low-reflectance areas such as the hair area of human head, a shape from silhouette algorithm is presented to overcome this problem. Finally, we give some results using our system. The resulting model is suitable for many applications.

  7. Light programmable organic transistor memory device based on hybrid dielectric

    NASA Astrophysics Data System (ADS)

    Ren, Xiaochen; Chan, Paddy K. L.

    2013-09-01

    We have fabricated the transistor memory devices based on SiO2 and polystyrene (PS) hybrid dielectric. The trap states densities with different semiconductors have been investigated and a maximum 160V memory window between programming and erasing is realized. For DNTT based transistor, the trapped electron density is limited by the number of mobile electrons in semiconductor. The charge transport mechanism is verified by light induced Vth shift effect. Furthermore, in order to meet the low operating power requirement of portable electronic devices, we fabricated the organic memory transistor based on AlOx/self-assembly monolayer (SAM)/PS hybrid dielectric, the effective capacitance of hybrid dielectric is 210 nF cm-2 and the transistor can reach saturation state at -3V gate bias. The memory window in transfer I-V curve is around 1V under +/-5V programming and erasing bias.

  8. High-Efficiency Nitride-Base Photonic Crystal Light Sources

    SciTech Connect

    James Speck; Evelyn Hu; Claude Weisbuch; Yong-Seok Choi; Kelly McGroddy; Gregor Koblmuller; Elison Matioli; Elizabeth Rangel; Fabian Rol; Dobri Simeonov

    2010-01-31

    The research activities performed in the framework of this project represent a major breakthrough in the demonstration of Photonic Crystals (PhC) as a competitive technology for LEDs with high light extraction efficiency. The goals of the project were to explore the viable approaches to manufacturability of PhC LEDS through proven standard industrial processes, establish the limits of light extraction by various concepts of PhC LEDs, and determine the possible advantages of PhC LEDs over current and forthcoming LED extraction concepts. We have developed three very different geometries for PhC light extraction in LEDs. In addition, we have demonstrated reliable methods for their in-depth analysis allowing the extraction of important parameters such as light extraction efficiency, modal extraction length, directionality, internal and external quantum efficiency. The information gained allows better understanding of the physical processes and the effect of the design parameters on the light directionality and extraction efficiency. As a result, we produced LEDs with controllable emission directionality and a state of the art extraction efficiency that goes up to 94%. Those devices are based on embedded air-gap PhC - a novel technology concept developed in the framework of this project. They rely on a simple and planar fabrication process that is very interesting for industrial implementation due to its robustness and scalability. In fact, besides the additional patterning and regrowth steps, the process is identical as that for standard industrially used p-side-up LEDs. The final devices exhibit the same good electrical characteristics and high process yield as a series of test standard LEDs obtained in comparable conditions. Finally, the technology of embedded air-gap patterns (PhC) has significant potential in other related fields such as: increasing the optical mode interaction with the active region in semiconductor lasers; increasing the coupling of the incident

  9. Determination of impurities in crude light pyridine bases

    SciTech Connect

    Novikov, E.G.; Tsaur, A.G.; Lisina, L.A.; Dybkin, P.A.

    1981-01-01

    Hydrogen cyanide, hydrogen sulfide, ammonia and phenols are always products of coal pyrolysis. In addition the coke oven gas contains carbon disulfide. The simultaneous presence of ammonia and carbon disulfide leads inevitably to the formation of thiocyanates in the entire recovery system before the saturator, and particularly in the ammonia liquor. All these compounds may be expected to be present in the crude light pyridine bases (CLPB). This causes corrosion of the equipment and reduces the photostability of the final process products. The ability of the phenols to form high boiling point azeotropes with the bases reduces the ..beta..-picoline fraction yield. For these reasons the presence of the stated impurities in the CLPB is undesirable. In the present work an estimate has been made of the average annual concentration of phenols, cyanides, thiocyanates and chlorides in the crude light pyridine bases of all the plants supplying this material in the Eastern USSR. The table shows only the mean values of the concentrations for each component in the samples of the individual plants, and also those for water.

  10. Virtual reality 3D headset based on DMD light modulators

    SciTech Connect

    Bernacki, Bruce E.; Evans, Allan; Tang, Edward

    2014-06-13

    We present the design of an immersion-type 3D headset suitable for virtual reality applications based upon digital micro-mirror devices (DMD). Our approach leverages silicon micro mirrors offering 720p resolution displays in a small form-factor. Supporting chip sets allow rapid integration of these devices into wearable displays with high resolution and low power consumption. Applications include night driving, piloting of UAVs, fusion of multiple sensors for pilots, training, vision diagnostics and consumer gaming. Our design is described in which light from the DMD is imaged to infinity and the user’s own eye lens forms a real image on the user’s retina.

  11. Cellular Bases of Light-regulated Gravity Responses

    NASA Technical Reports Server (NTRS)

    Roux, Stanley J.

    2003-01-01

    This report summarizes the most significant research accomplished in our NAG2-1347 project on the cellular bases of light-regulated gravity responses, It elaborates mainly on our discovery of the role of calcium currents in gravity-directed polar development in single germinating spore cells of the fern Ceratopteris, our development of RNA silencing as a viable method of suppressing the expression of specific genes in Ceratopteris, and on the structure, expression and distribution of members of the annexin family in flowering plants, especially Arabidopsis.

  12. Fast and accurate line scanner based on white light interferometry

    NASA Astrophysics Data System (ADS)

    Lambelet, Patrick; Moosburger, Rudolf

    2013-04-01

    White-light interferometry is a highly accurate technology for 3D measurements. The principle is widely utilized in surface metrology instruments but rarely adopted for in-line inspection systems. The main challenges for rolling out inspection systems based on white-light interferometry to the production floor are its sensitivity to environmental vibrations and relatively long measurement times: a large quantity of data needs to be acquired and processed in order to obtain a single topographic measurement. Heliotis developed a smart-pixel CMOS camera (lock-in camera) which is specially suited for white-light interferometry. The demodulation of the interference signal is treated at the level of the pixel which typically reduces the acquisition data by one orders of magnitude. Along with the high bandwidth of the dedicated lock-in camera, vertical scan-speeds of more than 40mm/s are reachable. The high scan speed allows for the realization of inspection systems that are rugged against external vibrations as present on the production floor. For many industrial applications such as the inspection of wafer-bumps, surface of mechanical parts and solar-panel, large areas need to be measured. In this case either the instrument or the sample are displaced laterally and several measurements are stitched together. The cycle time of such a system is mostly limited by the stepping time for multiple lateral displacements. A line-scanner based on white light interferometry would eliminate most of the stepping time while maintaining robustness and accuracy. A. Olszak proposed a simple geometry to realize such a lateral scanning interferometer. We demonstrate that such inclined interferometers can benefit significantly from the fast in-pixel demodulation capabilities of the lock-in camera. One drawback of an inclined observation perspective is that its application is limited to objects with scattering surfaces. We therefore propose an alternate geometry where the incident light is

  13. MOCVD growth of GaN nanopyramid and nanopillar LED with emission in green to orange color

    NASA Astrophysics Data System (ADS)

    Kuo, Hao-Chung; Cheng, Yuh-Jen

    2012-10-01

    We report the fabrication and demonstration of electrically driven green, yellow-green, and amber color nanopyramid LEDs. The quantum wells were grown on nanopyramid facets, which have low polarization field and allow high In incorporation.

  14. Virtual reality 3D headset based on DMD light modulators

    NASA Astrophysics Data System (ADS)

    Bernacki, Bruce E.; Evans, Allan; Tang, Edward

    2014-06-01

    We present the design of an immersion-type 3D headset suitable for virtual reality applications based upon digital micromirror devices (DMD). Current methods for presenting information for virtual reality are focused on either polarizationbased modulators such as liquid crystal on silicon (LCoS) devices, or miniature LCD or LED displays often using lenses to place the image at infinity. LCoS modulators are an area of active research and development, and reduce the amount of viewing light by 50% due to the use of polarization. Viewable LCD or LED screens may suffer low resolution, cause eye fatigue, and exhibit a "screen door" or pixelation effect due to the low pixel fill factor. Our approach leverages a mature technology based on silicon micro mirrors delivering 720p resolution displays in a small form-factor with high fill factor. Supporting chip sets allow rapid integration of these devices into wearable displays with high-definition resolution and low power consumption, and many of the design methods developed for DMD projector applications can be adapted to display use. Potential applications include night driving with natural depth perception, piloting of UAVs, fusion of multiple sensors for pilots, training, vision diagnostics and consumer gaming. Our design concept is described in which light from the DMD is imaged to infinity and the user's own eye lens forms a real image on the user's retina resulting in a virtual retinal display.

  15. Invisibility Cloaking Based on Geometrical Optics for Visible Light

    NASA Astrophysics Data System (ADS)

    Ichikawa, H.; Oura, M.; Taoda, T.

    2013-06-01

    Optical cloaking has been one of unattainable dreams and just a subject in fiction until recently. Several different approaches to cloaking have been proposed and demonstrated: stealth technology, active camouflage and transformation optics. The last one would be the most formal approach modifying electromagnetic field around an object to be cloaked with metamaterials. While cloaking based on transformation optics, though valid only at single frequency, is experimentally demonstrated in microwave region, its operation in visible spectrum is still distant from realisation mainly owing to difficulty in fabricating metamaterial structure whose elements are much smaller than wavelength of light. Here we show that achromatic optical cloaking in visible spectrum is possible with the mere principle based on geometrical optics. In combining a pair of polarising beam splitters and right-angled prisms, rays of light to be obstructed by an object can make a detour to an observer, while unobstructed rays go straight through two polarising beam splitters. What is observed eventually through the device is simply background image as if nothing exists in between.

  16. Continuous-wave optical fiber based supercontinuum light source

    NASA Astrophysics Data System (ADS)

    Lu, Z. G.; Song, Y.; Liu, J. R.; Zhang, X. P.

    2007-11-01

    We have demonstrated a continuum-wave (CW) supercontinuum (SC) fiber light source with over 1000 nm bandwidth based on a low-cost erbium/ytterbium co-doped double-cladding fiber ring cavity laser. Based on the observation to the SC evolvement, we have experimentally analyzed the detailed contributions of several nonlinear effects within highly nonlinear dispersion-shifted fiber (HNLF). Our experimental results have clearly indicated that four-wave mixing (FWM) and stimulated Raman scattering (SRS) play key roles in CW-pumped SC generation. At the same time, self-phase modulation (SPM) mainly contributes to generate new frequency components near the peaks that appear in the form of the spectra broadening while cross-phase modulation (XPM) enhances the broadening of peaks.

  17. Autofocusing system for spatial light modulator-based maskless lithography.

    PubMed

    Schlangen, Sebastian; Ihme, Maximilian; Rahlves, Maik; Roth, Bernhard

    2016-03-10

    To produce diffractive or holographic structures in a photolithographic process, an optical projection system enabling structure resolution in the submicrometer range is highly desirable. To ensure that the optical focus of such a system lies on the substrate surface during the whole lithographic fabrication process, an autofocus system able to focus on a depth of field of a few hundred nanometers is usually required. In this work, we developed an autofocus system for spatial light modulator (SLM)-based maskless photolithographic applications. The system is capable of high-precision focusing without affecting the photoresist performance. It is based on contrast measurement combined with focus-pattern illumination to ensure high contrast at the substrate surface. In addition, we evaluated various autofocus algorithms with respect to time efficiency and accuracy to determine suitable focus-pattern and focus-algorithm combinations. PMID:26974774

  18. Performance characterization of structured light-based fingerprint scanner

    NASA Astrophysics Data System (ADS)

    Hassebrook, Laurence G.; Wang, Minghao; Daley, Raymond C.

    2013-05-01

    Our group believes that the evolution of fingerprint capture technology is in transition to include 3-D non-contact fingerprint capture. More specifically we believe that systems based on structured light illumination provide the highest level of depth measurement accuracy. However, for these new technologies to be fully accepted by the biometric community, they must be compliant with federal standards of performance. At present these standards do not exist for this new biometric technology. We propose and define a set of test procedures to be used to verify compliance with the Federal Bureau of Investigation's image quality specification for Personal Identity Verification single fingerprint capture devices. The proposed test procedures include: geometric accuracy, lateral resolution based on intensity or depth, gray level uniformity and flattened fingerprint image quality. Several 2-D contact analogies, performance tradeoffs and optimization dilemmas are evaluated and proposed solutions are presented.

  19. Hemithioindigo-based photoswitches as ultrafast light trigger in chromopeptides

    NASA Astrophysics Data System (ADS)

    Cordes, T.; Weinrich, D.; Kempa, S.; Riesselmann, K.; Herre, S.; Hoppmann, C.; Rück-Braun, K.; Zinth, W.

    2006-09-01

    The spectroscopy and dynamics of a novel hemithioindigo-based photoswitch forming a ω-amino acid derivative are presented. Light absorption in the visible spectral range induces photoisomerization between Z and E configurations with quantum yields in the 10% range. The Z isomer is thermally stable, while the E isomer relaxes back to the Z form within several hours. The E isomers provides a distinct spectral range, where the photoisomerization process can be initiated selectively. Both directions of the photoisomerization are investigated by transient absorption spectroscopy and time constants for the formation of the photoproduct in the 10-30 ps range are observed. The ability of the hemithioindigo-based photoswitch to drive structural dynamics in peptides and proteins is tested for two ω-amino acid derivatives forming linear and cyclic structures.

  20. Future Synchrotron Light Sources Based on Ultimate Storage Rings

    SciTech Connect

    Cai, Yunhai; /SLAC

    2012-04-09

    The main purpose of this talk is to describe how far one might push the state of the art in storage ring design. The talk will start with an overview of the latest developments and advances in the design of synchrotron light sources based on the concept of an 'ultimate' storage ring. The review will establish how bright a ring based light source might be, where the frontier of technological challenges are, and what the limits of accelerator physics are. Emphasis will be given to possible improvements in accelerator design and developments in technology toward the goal of achieving an ultimate storage ring. An ultimate storage ring (USR), defined as an electron ring-based light source having an emittance in both transverse planes at the diffraction limit for the range of X-ray wavelengths of interest for a scientific community, would provide very high brightness photons having high transverse coherence that would extend the capabilities of X-ray imaging and probe techniques beyond today's performance. It would be a cost-effective, high-coherence 4th generation light source, competitive with one based on energy recovery linac (ERL) technology, serving a large number of users studying material, chemical, and biological sciences. Furthermore, because of the experience accumulated over many decades of ring operation, it would have the great advantage of stability and reliability. In this paper we consider the design of an USR having 10-pm-rad emittance. It is a tremendous challenge to design a storage ring having such an extremely low emittance, a factor of 100 smaller than those in existing light sources, especially such that it has adequate dynamic aperture and beam lifetime. In many ultra-low emittance designs, the injection acceptances are not large enough for accumulation of the electron beam, necessitating on-axis injection where stored electron bunches are completely replaced with newly injected ones. Recently, starting with the MAX-IV 7-bend achromatic cell, we

  1. A novel amblyopia treatment system based on LED light source

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoqing; Chen, Qingshan; Wang, Xiaoling

    2011-05-01

    A novel LED (light emitting diode) light source of five different colors (white, red, green, blue and yellow) is adopted instead of conventional incandescent lamps for an amblyopia treatment system and seven training methods for rectifying amblyopia are incorporated so as for achieving an integrated therapy. The LED light source is designed to provide uniform illumination, adjustable light intensity and alterable colors. Experimental tests indicate that the LED light source operates steadily and fulfills the technical demand of amblyopia treatment.

  2. A novel amblyopia treatment system based on LED light source

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoqing; Chen, Qingshan; Wang, Xiaoling

    2010-12-01

    A novel LED (light emitting diode) light source of five different colors (white, red, green, blue and yellow) is adopted instead of conventional incandescent lamps for an amblyopia treatment system and seven training methods for rectifying amblyopia are incorporated so as for achieving an integrated therapy. The LED light source is designed to provide uniform illumination, adjustable light intensity and alterable colors. Experimental tests indicate that the LED light source operates steadily and fulfills the technical demand of amblyopia treatment.

  3. Development of ultraviolet nitride-based light emitting diodes

    NASA Astrophysics Data System (ADS)

    Katona, Thomas Matthew

    2003-10-01

    Deep ultraviolet light emitting diodes, with emission wavelengths shorter than 360 nm, have attracted interest due to their potential applications as replacement white light sources, in non-line of sight communication, for chemical and biological weapons detection, medical applications, water purification, and counterfeit detection. Light emitters in this wavelength range require AlGaN based active regions with increasing Al composition as the wavelength is decreased. High Al composition AlGaN based devices have been challenged by difficulty in growth, low electron and hole mobilities, and deep dopant levels resulting in low carrier concentrations. The combination of these factors has resulted in UV optoelectronic devices with quantum efficiency several orders of magnitude lower than their GaN/InGaN based visible counterparts. This work will details studies on alternative selective area growth techniques for dislocation reduction and the development of ultraviolet LEDs ranging from 292--340 nm. Lateral overgrowth of GaN on patterned Si (111) substrates was developed with the hope of developing seed material for bulk GaN growth. The effect of growth conditions on both the crystallographic wing tilt and crack density in the AlN/GaN films was studied. By controlling the lateral to vertical growth rate at the beginning of lateral overgrowth, the wing tilt can be effectively eliminated. We also demonstrate the first lateral overgrowth of AlN to create low threading dislocation density AlN template layers for optoelectronic device development. Deep UV quantum wells grown on this material were studied with cathodoluminescence to study the effect of dislocations on radiative recombination in deep UV devices. In addition to work on lateral overgrowth of GaN and AlN, 292, 340 nm LEDs were grown on AlN on sapphire and GaN on sapphire respectively. AlN strain relief interlayers were developed to prevent cracking of the 340 nm AlGaN based LEDs that were grown in tension on Ga

  4. High-output LED-based light engine for profile lighting fixtures with high color uniformity using freeform reflectors.

    PubMed

    Gadegaard, Jesper; Jensen, Thøger Kari; Jørgensen, Dennis Thykjær; Kristensen, Peter Kjær; Søndergaard, Thomas; Pedersen, Thomas Garm; Pedersen, Kjeld

    2016-02-20

    In the stage lighting and entertainment market, light engines (LEs) for lighting fixtures are often based on high-intensity discharge (HID) bulbs. Switching to LED-based light engines gives possibilities for fast switching, additive color mixing, a longer lifetime, and potentially, more energy-efficient systems. The lumen output of a single LED is still not sufficient to replace an HID source in high-output profile fixtures, but combining multiple LEDs can create an LE with a similar output, but with added complexity. This paper presents the results of modeling and testing such a light engine. Custom ray-tracing software was used to design a high-output red, green and blue LED-based light engine with twelve CBT-90 LEDs using a dual-reflector principle. The simulated optical system efficiency was 0.626 with a perfect (R=1) reflector coating for light delivered on a target surface through the entire optical system. A profile lighting fixture prototype was created, and provided an output of 6744 lumen and an efficiency of 0.412. The lower efficiency was mainly due to a non-optimal reflector coating, and the optimized design is expected to reach a significantly higher efficiency. PMID:26906589

  5. A Light Scattering Layer for Internal Light Extraction of Organic Light-Emitting Diodes Based on Silver Nanowires.

    PubMed

    Lee, Keunsoo; Shin, Jin-Wook; Park, Jun-Hwan; Lee, Jonghee; Joo, Chul Woong; Lee, Jeong-Ik; Cho, Doo-Hee; Lim, Jong Tae; Oh, Min-Cheol; Ju, Byeong-Kwon; Moon, Jaehyun

    2016-07-13

    We propose and fabricate a random light scattering layer for light extraction in organic light-emitting diodes (OLEDs) with silver nanodots, which were obtained by melting silver nanowires. The OLED with the light scattering layer as an internal light extraction structure was enhanced by 49.1% for the integrated external quantum efficiency (EQE). When a wrinkle structure is simultaneously used for an external light extraction structure, the total enhancement of the integrated EQE was 65.3%. The EQE is maximized to 65.3% at a current level of 2.0 mA/cm(2). By applying an internal light scattering layer and wrinkle structure to an OLED, the variance in the emission spectra was negligible over a broad viewing angle. Power mode analyses with finite difference time domain (FDTD) simulations revealed that the use of a scattering layer effectively reduced the waveguiding mode while introducing non-negligible absorption. Our method offers an effective yet simple approach to achieve both efficiency enhancement and spectral stability for a wide range of OLED applications. PMID:27314500

  6. Experimental Study of Red-, Green-, and Blue-Based Light Emitting Diodes Visible Light Communications for Micro-Projector Application

    NASA Astrophysics Data System (ADS)

    Chou, H.-H.; Liaw, S.-K.; Jiang, J.-S.; Teng, C.

    2016-05-01

    In this research, an experimental short-range visible light communication link using red-, green-, and blue-based light-emitting diodes (LEDs) for portable micro-projector applications is presented. A Reconfigurable design of a post-equalizer aimed to improve the inherent narrow modulation bandwidth of red-, green-, and blue-based LEDs has been experimentally implemented, and its effectiveness with optical filters at the receiver is investigated. Reflective liquid-crystal-on-silicon-based micro-projection architecture, widely used in portable micro-projectors, was set up to evaluate the proposed visible light communication system. The measurement results demonstrated that a significant aggregative bandwidth improvement of 162 MHz as well as an aggregative data transmission rate of nearly 400 Mb/s can be achieved by using a non-return-to-zero-on-off keying (NRZ-OOK) modulation scheme based on only one polarization state of incident light without any offline signal processing.

  7. Ultrafast image-based dynamic light scattering for nanoparticle sizing

    SciTech Connect

    Zhou, Wu; Zhang, Jie; Liu, Lili; Cai, Xiaoshu

    2015-11-15

    An ultrafast sizing method for nanoparticles is proposed, called as UIDLS (Ultrafast Image-based Dynamic Light Scattering). This method makes use of the intensity fluctuation of scattered light from nanoparticles in Brownian motion, which is similar to the conventional DLS method. The difference in the experimental system is that the scattered light by nanoparticles is received by an image sensor instead of a photomultiplier tube. A novel data processing algorithm is proposed to directly get correlation coefficient between two images at a certain time interval (from microseconds to milliseconds) by employing a two-dimensional image correlation algorithm. This coefficient has been proved to be a monotonic function of the particle diameter. Samples of standard latex particles (79/100/352/482/948 nm) were measured for validation of the proposed method. The measurement accuracy of higher than 90% was found with standard deviations less than 3%. A sample of nanosilver particle with nominal size of 20 ± 2 nm and a sample of polymethyl methacrylate emulsion with unknown size were also tested using UIDLS method. The measured results were 23.2 ± 3.0 nm and 246.1 ± 6.3 nm, respectively, which is substantially consistent with the transmission electron microscope results. Since the time for acquisition of two successive images has been reduced to less than 1 ms and the data processing time in about 10 ms, the total measuring time can be dramatically reduced from hundreds seconds to tens of milliseconds, which provides the potential for real-time and in situ nanoparticle sizing.

  8. Ultrafast image-based dynamic light scattering for nanoparticle sizing.

    PubMed

    Zhou, Wu; Zhang, Jie; Liu, Lili; Cai, Xiaoshu

    2015-11-01

    An ultrafast sizing method for nanoparticles is proposed, called as UIDLS (Ultrafast Image-based Dynamic Light Scattering). This method makes use of the intensity fluctuation of scattered light from nanoparticles in Brownian motion, which is similar to the conventional DLS method. The difference in the experimental system is that the scattered light by nanoparticles is received by an image sensor instead of a photomultiplier tube. A novel data processing algorithm is proposed to directly get correlation coefficient between two images at a certain time interval (from microseconds to milliseconds) by employing a two-dimensional image correlation algorithm. This coefficient has been proved to be a monotonic function of the particle diameter. Samples of standard latex particles (79/100/352/482/948 nm) were measured for validation of the proposed method. The measurement accuracy of higher than 90% was found with standard deviations less than 3%. A sample of nanosilver particle with nominal size of 20 ± 2 nm and a sample of polymethyl methacrylate emulsion with unknown size were also tested using UIDLS method. The measured results were 23.2 ± 3.0 nm and 246.1 ± 6.3 nm, respectively, which is substantially consistent with the transmission electron microscope results. Since the time for acquisition of two successive images has been reduced to less than 1 ms and the data processing time in about 10 ms, the total measuring time can be dramatically reduced from hundreds seconds to tens of milliseconds, which provides the potential for real-time and in situ nanoparticle sizing. PMID:26628172

  9. Ultrafast image-based dynamic light scattering for nanoparticle sizing

    NASA Astrophysics Data System (ADS)

    Zhou, Wu; Zhang, Jie; Liu, Lili; Cai, Xiaoshu

    2015-11-01

    An ultrafast sizing method for nanoparticles is proposed, called as UIDLS (Ultrafast Image-based Dynamic Light Scattering). This method makes use of the intensity fluctuation of scattered light from nanoparticles in Brownian motion, which is similar to the conventional DLS method. The difference in the experimental system is that the scattered light by nanoparticles is received by an image sensor instead of a photomultiplier tube. A novel data processing algorithm is proposed to directly get correlation coefficient between two images at a certain time interval (from microseconds to milliseconds) by employing a two-dimensional image correlation algorithm. This coefficient has been proved to be a monotonic function of the particle diameter. Samples of standard latex particles (79/100/352/482/948 nm) were measured for validation of the proposed method. The measurement accuracy of higher than 90% was found with standard deviations less than 3%. A sample of nanosilver particle with nominal size of 20 ± 2 nm and a sample of polymethyl methacrylate emulsion with unknown size were also tested using UIDLS method. The measured results were 23.2 ± 3.0 nm and 246.1 ± 6.3 nm, respectively, which is substantially consistent with the transmission electron microscope results. Since the time for acquisition of two successive images has been reduced to less than 1 ms and the data processing time in about 10 ms, the total measuring time can be dramatically reduced from hundreds seconds to tens of milliseconds, which provides the potential for real-time and in situ nanoparticle sizing.

  10. A low emittance and high efficiency visible light photocathode for high brightness accelerator-based X-ray light sources

    SciTech Connect

    Vecchione, T.; Ben-Zvi, I.; Dowell, D.H.; Feng, J.; Rao, T.; Smedley, J.; Wan, W.; Padmore, H.A.

    2011-07-21

    Free-electron lasers and energy recovery linacs represent a new generation of ultra-high brightness electron accelerator based x-ray sources. Photocathodes are a critical performance-limiting component of these systems. Here, we describe the development of photocathodes based on potassium-cesium-antimonide that satisfy many of the key requirements of future light sources, such as robustness, high quantum efficiency when excited with visible light, and low transverse emittance.

  11. A low emittance and high efficiency visible light photocathode for high brightness accelerator-based X-ray light sources

    SciTech Connect

    Vecchione, T.; Feng, J.; Wan, W.; Padmore, H. A.; Ben-Zvi, I.; Dowell, D. H.; Rao, T.; Smedley, J.

    2011-07-18

    Free-electron lasers and energy recovery linacs represent a new generation of ultra-high brightness electron accelerator based x-ray sources. Photocathodes are a critical performance-limiting component of these systems. Here, we describe the development of photocathodes based on potassium-cesium-antimonide that satisfy many of the key requirements of future light sources, such as robustness, high quantum efficiency when excited with visible light, and low transverse emittance.

  12. Nitride and Oxynitride Based Phosphors for Solid State Lighting

    SciTech Connect

    Tian, Yongchi

    2011-10-15

    The objective of the project is to advance the technology of the Lightscape Materials Inc. (Lightscape) proprietary nitride and oxynitride phosphors for solid state lighting (SSL) from the current level of maturity of applied research to advanced engineering development. This objective will be accomplished by optimizing the novel nitride and oxynitride phosphors, whose formulations are listed in Table 1, and establishing cost-effective preparation processes for the phosphors. The target performances of the phosphors are: • High luminescence efficiency: Quantum Yield = 90%. • Superior thermal stability of luminescence: Thermal Quenching Loss <10% at 150 °C. • Superior environmental stability: Luminescence Maintenance >90% after 5,000 hours at 85 °C and 85% relative humidity. • Scattering loss <10%. • Cost-effective preparation processes. The resulting phosphor materials and their preparation processes are anticipated to be a drop-in component for product development paths undertaken by LED lamp makers in the SSL industry. Upon program completion, Lightscape will target market insertion that enables high efficacy, high color rendering index (CRI), high thermal stability and long lifetime LED-based lighting products for general illumination that realizes substantial energy savings.

  13. Ellipse-based DCO-OFDM for visible light communications

    NASA Astrophysics Data System (ADS)

    Mao, Tianqi; Wang, Zhaocheng; Wang, Qi; Dai, Linglong

    2016-02-01

    Ellipse-based DC-biased optical orthogonal frequency division multiplexing (E-DCO-OFDM) is proposed for visible light communications (VLC), which achieves a significant peak-to-average power ratio (PAPR) reduction, thus enhancing the overall performance when light-emitting diode (LED) nonlinearity is considered. In E-DCO-OFDM, the real-valued output of OFDM is modulated onto an ellipse, whereby only the imaginary part of the complex point on the ellipse is transmitted. Although the PAPR of E-DCO-OFDM decreases as the ratio of major radius to minor radius becomes larger, it may be more vulnerable to the effect of noise, leading to the performance loss. Therefore, the relationship between the system performance and the critical parameters in E-DCO-OFDM, such as the ratio between the major and minor radius of the ellipse, is investigated. Meanwhile, simulations demonstrate that E-DCO-OFDM adopting the optimal parameters achieves a considerable signal-to-noise ratio (SNR) gain over the conventional DCO-OFDM.

  14. HIGH-EFFICIENCY NITRIDE-BASED SOLID-STATE LIGHTING

    SciTech Connect

    Paul T. Fini; Shuji Nakamura

    2003-10-30

    In this second annual report we summarize the progress in the second-year period of Department of Energy contract DE-FC26-01NT41203, entitled ''High- Efficiency Nitride-Based Solid-State Lighting''. The two teams, from the University of California at Santa Barbara (Principle Investigator: Dr. Shuji Nakamura) and Rensselaer Polytechnic Institute (led by Dr. N. Narendran), are pursuing the goals of this contract from thin film growth, characterization, and packaging standpoints. The UCSB team has recently made significant progress in the development of light-emitting diodes (LEDs) with AlGaN active regions emitting in the ultraviolet (UV), resonant-cavity LEDs (RCLEDs), as well as lateral epitaxial overgrowth (LEO) techniques to obtain large-area non-polar GaN films with low average dislocation density. The Rensselaer team has benchmarked the performance of commercially available LED systems and has also conducted efforts to develop an optimized RCLED packaging scheme, including development of advanced epoxy encapsulant chemistries.

  15. Contrasting trends in light pollution across Europe based on satellite observed night time lights.

    PubMed

    Bennie, Jonathan; Davies, Thomas W; Duffy, James P; Inger, Richard; Gaston, Kevin J

    2014-01-01

    Since the 1970s nighttime satellite images of the Earth from space have provided a striking illustration of the extent of artificial light. Meanwhile, growing awareness of adverse impacts of artificial light at night on scientific astronomy, human health, ecological processes and aesthetic enjoyment of the night sky has led to recognition of light pollution as a significant global environmental issue. Links between economic activity, population growth and artificial light are well documented in rapidly developing regions. Applying a novel method to analysis of satellite images of European nighttime lights over 15 years, we show that while the continental trend is towards increasing brightness, some economically developed regions show more complex patterns with large areas decreasing in observed brightness over this period. This highlights that opportunities exist to constrain and even reduce the environmental impact of artificial light pollution while delivering cost and energy-saving benefits. PMID:24445659

  16. Contrasting trends in light pollution across Europe based on satellite observed night time lights

    NASA Astrophysics Data System (ADS)

    Bennie, Jonathan; Davies, Thomas W.; Duffy, James P.; Inger, Richard; Gaston, Kevin J.

    2014-01-01

    Since the 1970s nighttime satellite images of the Earth from space have provided a striking illustration of the extent of artificial light. Meanwhile, growing awareness of adverse impacts of artificial light at night on scientific astronomy, human health, ecological processes and aesthetic enjoyment of the night sky has led to recognition of light pollution as a significant global environmental issue. Links between economic activity, population growth and artificial light are well documented in rapidly developing regions. Applying a novel method to analysis of satellite images of European nighttime lights over 15 years, we show that while the continental trend is towards increasing brightness, some economically developed regions show more complex patterns with large areas decreasing in observed brightness over this period. This highlights that opportunities exist to constrain and even reduce the environmental impact of artificial light pollution while delivering cost and energy-saving benefits.

  17. Contrasting trends in light pollution across Europe based on satellite observed night time lights

    PubMed Central

    Bennie, Jonathan; Davies, Thomas W.; Duffy, James P.; Inger, Richard; Gaston, Kevin J.

    2014-01-01

    Since the 1970s nighttime satellite images of the Earth from space have provided a striking illustration of the extent of artificial light. Meanwhile, growing awareness of adverse impacts of artificial light at night on scientific astronomy, human health, ecological processes and aesthetic enjoyment of the night sky has led to recognition of light pollution as a significant global environmental issue. Links between economic activity, population growth and artificial light are well documented in rapidly developing regions. Applying a novel method to analysis of satellite images of European nighttime lights over 15 years, we show that while the continental trend is towards increasing brightness, some economically developed regions show more complex patterns with large areas decreasing in observed brightness over this period. This highlights that opportunities exist to constrain and even reduce the environmental impact of artificial light pollution while delivering cost and energy-saving benefits. PMID:24445659

  18. Optomechanics based on angular momentum exchange between light and matter

    NASA Astrophysics Data System (ADS)

    Shi, H.; Bhattacharya, M.

    2016-08-01

    The subject of optomechanics involves interactions between optical and mechanical degrees of freedom, and is currently of great interest as an enabler of fundamental investigations in quantum mechanics, as well as a platform for ultrasensitive measurement devices. The majority of optomechanical configurations rely on the exchange of linear momentum between light and matter. We will begin this tutorial with a brief description of such systems. Subsequently, we will introduce optomechanical systems based on angular momentum exchange. In this context, optical fields carrying polarization and orbital angular momentum will be considered, while for the mechanics, torsional and free rotational motion will be of relevance. Our overall aims will be to supply basic analyses of some of the existing theoretical proposals, to provide functional descriptions of some of the experiments conducted thus far, and to consider some directions for future research. We hope this tutorial will be useful to both theorists and experimentalists interested in the subject.

  19. Directed light fabrication of iron-based materials

    SciTech Connect

    Thoma, D.J.; Charbon, C.; Lewis, G.K.; Nemec, R.B.

    1995-01-01

    Directed light fabrication (DLF) is a process that fuses gas delivered metal powders within a focal zone of a laser beam to produce fully dense, 3-dimensional metal components. From a computer generated solid model, deposition ``tool paths`` are constructed that command the laser movement to fabricate near net shape parts a layer at a time. Among potential candidate systems to study, iron-based alloys are particularly attractive for rapid prototyping. To evaluate the processing parameters in the DLF process, studies have been performed on the microstructural development in 1-dimensional and 2-dimensional Fe-based components. For example, continuous microstructural features are evident, implying a continuous liquid/solid interface during processing. In addition, solidification cooling rates have been determined based upon secondary dendrite arm spacings in Fe-25wt. % Ni and 316 stainless steel. Cooling rates vary from 10{sup 1}{minus}10{sup 5} K s{sup {minus}1}, and the solidification behavior has been simulated using macroscopic heat transfer analyses.

  20. Enabling a blue-hazard free general lighting based on candle light-style OLED.

    PubMed

    Jou, Jwo-Huei; Kumar, Sudhir; An, Chih-Chia; Singh, Meenu; Yu, Huei-Huan; Hsieh, Chun-Yu; Lin, You-Xing; Sung, Chao-Feng; Wang, Ching-Wu

    2015-06-01

    Increasing studies report blue light to possess a potential hazard to the retina of human eyes, secretion of melatonin and artworks. To devise a human- and artwork-friendly light source and to also trigger a "Lighting Renaissance", we demonstrate here how to enable a quality, blue-hazard free general lighting source on the basis of low color-temperature organic light emitting diodes. With the use of multiple candlelight complementary emitters, the sensationally warm candle light-style emission is proven to be also drivable by electricity. To be energy-saving, highly efficient candle-light emission is demanded. The device shows, at 100 cd m-2 for example, an efficacy of 85.4 lm W-1, an external quantum efficiency of 27.4%, with a 79 spectrum resemblance index and 2,279 K color temperature. The high efficiency may be attributed to the candlelight emitting dyes with a high quantum yield, and the host molecules facilitating an effective host-to-guest energy transfer, as well as effective carrier injection balance. PMID:26072882

  1. Light emitting diode-based nanosecond ultraviolet light source for fluorescence lifetime measurements

    NASA Astrophysics Data System (ADS)

    Araki, Tsutomu; Misawa, Hiroaki

    1995-12-01

    A compact pulsed-light source is devised from an InGaN/AlGaN double heterostructure light-emitting diode (LED). The LED emits a 450-nm (blue) light under conventional dc operation below 30 mA. When a current larger than 50 mA is applied, the intensity of the 450-nm light saturates, but that of the 380-nm light due to the InGaN component continues to increase. This phenomenon is utilized to realize a nanosecond ultraviolet (UV) light source. Under repetitive, large current pulsing (frequency=10 kHz, pulse width=4 ns, peak current=2 A), the peak LED emission shifts from 450 to 380 nm. Intense light pulses (peak value=40 mW) of 4-ns duration were generated. To evaluate the potential of the pulsed LED as an excitation source, the fluorescence lifetime of a quinine-sulfate solution was measured. The observed lifetime characteristics agreed well with the generally accepted behavior.

  2. Light based anti-infectives: ultraviolet C irradiation, photodynamic therapy, blue light, and beyond

    PubMed Central

    Yin, Rui; Dai, Tianhong; Avci, Pinar; Jorge, Ana Elisa Serafim; de Melo, Wanessa CMA; Vecchio, Daniela; Huang, Ying-Ying; Gupta, Asheesh; Hamblin, Michael R

    2013-01-01

    Owing to the worldwide increase in antibiotic resistance, researchers are investigating alternative anti-infective strategies to which it is supposed microorganisms will be unable to develop resistance. Prominent among these strategies, is a group of approaches which rely on light to deliver the killing blow. As is well known, ultraviolet light, particularly UVC (200–280nm), is germicidal, but it has not been much developed as an anti-infective approach until recently, when it was realized that the possible adverse effects to host tissue were relatively minor compared to its high activity in killing pathogens. Photodynamic therapy is the combination of non-toxic photosensitizing dyes with harmless visible light that together produce abundant destructive reactive oxygen species (ROS). Certain cationic dyes or photosensitizers have good specificity for binding to microbial cells while sparing host mammalian cells and can be used for treating many localized infections, both superficial and even deep-seated by using fiber optic delivered light. Many microbial cells are highly sensitive to killing by blue light (400–470 nm) due to accumulation of naturally occurring photosensitizers such as porphyrins and flavins. Near infrared light has also been shown to have antimicrobial effects against certain species. Clinical applications of these technologies include skin, dental, wound, stomach, nasal, toenail and other infections which are amenable to effective light delivery. PMID:24060701

  3. Light scattering in opal-based photonic crystals

    NASA Astrophysics Data System (ADS)

    Limonov, M. F.

    2010-05-01

    We present a new light scattering pattern in low-contrast opal-based photonic crystals (PhCs). The structure of real opals is always imperfect because of the a-SiO2 particles being inherently inhomogeneous and nonuniform in size and average dielectric permittivity. We found that opals possess all predictable properties of multi-component PhCs, which we define as periodic structures consisting of inhomogeneous or multiple (three or more) components. By theory, by properly tuning the permittivity of one of the components in ordered, low-contrast multi-component PhCs (for instance, of the filler ɛf in an opal), one can produce selective disappearance of any non-resonant (hkl) stop band. A study of transmission spectra of opals revealed that stop bands exhibit different (including resonant) behavior under variation of ɛf. Experiment did not, however, substantiate complete disappearance of stop bands predicted by theory for an ordered PhC. In the region of the predicted disappearance, a new effect has been observed, namely flip-over of the Bragg band, i.e., transformation of the Bragg dip into a Bragg rise. The flip-over effect, which has been studied in considerable detail in the particular example of the (111) stop band, originates from the nonuniformity of a-SiO2 particles. This nonuniformity leads to additional broad-band light scattering, the character of which is determined by Mie scattering. Thus, Mie scattering is responsible for two components in opal transmission spectra, more specifically, narrow Bragg bands and broad-band background. Their interference gives rise to formation of the Fano resonance, which in opal spectra becomes manifest, first, in a Bragg band asymmetry, and, second, in the flip-over effect, i.e., transformation of a photonic stop band into a photonic pass band.

  4. Lifelog-based lighting design for biofied building

    NASA Astrophysics Data System (ADS)

    Kake, Fumika; Mita, Akira

    2016-04-01

    A design tool is proposed for lighting control system that reflects histories of residents' past life using a genetic mechanism. There are many previous researches which show the preference of lighting design differs depending on people and their behaviors. And recently, due to the appearance of LED which can change light color easily, the number of lighting scenes have drastically increased. It is difficult for residents to grasp all patterns of lighting and understand what pattern of lighting design fits for their behaviors. So if we can extract lighting preferences and demands of each resident from histories of past life and reflect these information in next lighting control, it's possible to make living space more comfortable. An evolutionally adaptation mechanism learnt from living organisms is proposed in this research to extract the information from lifelog, especially focusing on methylation and mutation. Methylation is one of the epigenetic algorithms making a difference in phenotype without changing DNA sequence. Mutation is one of the genetic algorithms making a difference in phenotype by changing DNA sequence. Those two mechanisms are applied in the system. First, the lifelog of residents and using hysteresis of lighting equipment are collected. Then the lifelog is converted into the genetic information and stored. When the lifelog is stored enough, the superior genes will be picked up from the stored genetic information to be reflected in lighting control in next generation. Simulations to verify the versatility of the system were conducted.

  5. Beam-based Feedback for the Linac Coherent Light Source

    SciTech Connect

    Fairley, D.; Allison, S.; Chevtsov, S.; Chu, P.; Decker, F.J.; Emma, P.; Frisch, J.; Himel, T.; Kim, K.; Krejcik, P.; Loos, H.; Lahey, T.; Natampalli, P.; Peng, S.; Rogind, D.; Shoaee, H.; Straumann, T.; Williams, E.; White, G.; Wu, J.; Zelazney, M.; /SLAC

    2010-02-11

    Beam-based feedback control loops are required by the Linac Coherent Light Source (LCLS) program in order to provide fast, single-pulse stabilization of beam parameters. Eight transverse feedback loops, a 6 x 6 longitudinal feedback loop, and a loop to maintain the electron bunch charge were successfully prototyped in MATLAB for the LCLS, and have been maintaining stability of the LCLS electron beam at beam rates up to 30Hz. In the final commissioning phase of LCLS the beam will be operating at up to 120Hz. In order to run the feedback loops at beam rate, the feedback loops will be implemented in EPICS IOCs with a dedicated ethernet multi-cast network. This paper will discuss the design of the beam-based Fast Feedback System for LCLS. Topics include MATLAB feedback prototyping, algorithm for 120Hz feedback, network design for fast data transport, actuator and sensor design for single-pulse control and sensor readback, and feedback configuration and runtime control.

  6. High light extraction efficiency in bulk-GaN based volumetric violet light-emitting diodes

    SciTech Connect

    David, Aurelien Hurni, Christophe A.; Aldaz, Rafael I.; Cich, Michael J.; Ellis, Bryan; Huang, Kevin; Steranka, Frank M.; Krames, Michael R.

    2014-12-08

    We report on the light extraction efficiency of III-Nitride violet light-emitting diodes with a volumetric flip-chip architecture. We introduce an accurate optical model to account for light extraction. We fabricate a series of devices with varying optical configurations and fit their measured performance with our model. We show the importance of second-order optical effects like photon recycling and residual surface roughness to account for data. We conclude that our devices reach an extraction efficiency of 89%.

  7. Light-Harvesting Antennae Based on Silicon Nanocrystals.

    PubMed

    Romano, Francesco; Yu, Yixuan; Korgel, Brian A; Bergamini, Giacomo; Ceroni, Paola

    2016-08-01

    Silicon (Si) nanocrystals are relatively strong light emitters, but are weak light absorbers as a result of their indirect band gap. One way to enhance light absorption is to functionalize the nanocrystals with chromophores that are strong light absorbers. By designing systems that enable efficient energy transfer from the chromophore to the Si nanocrystal, the brightness of the nanocrystals can be significantly increased. There have now been a few experimental systems in which covalent attachment of chromophores, efficient energy transfer and significantly increased brightness have been demonstrated. This review discusses progress on these systems and the remaining challenges. PMID:27573405

  8. Lighting

    SciTech Connect

    Audin, L.

    1994-12-31

    EPAct covers a vast territory beyond lighting and, like all legislation, also contains numerous {open_quotes}favors,{close_quotes} compromises, and even some sleight-of-hand. Tucked away under Title XIX, for example, is an increase from 20% to 28% tax on gambling winnings, effective January 1, 1993 - apparently as a way to help pay for new spending listed elsewhere in the bill. Overall, it is a landmark piece of legislation, about a decade overdue. It remains to be seen how the Federal Government will enforce upgrading of state (or even their own) energy codes. There is no mention of funding for {open_quotes}energy police{close_quotes} in EPAct. Merely creating such a national standard, however, provides a target for those who sincerely wish to create an energy-efficient future.

  9. Light Pollution: A Threat to Ground-based Astronomy

    NASA Astrophysics Data System (ADS)

    Davis, D. R.

    1999-09-01

    Light pollution that accompanies population growth has reduced the effectiveness of several world class observing sites and threatens most others in the world. Recent decades have seen an activist approach to dealing with light pollution issues, led by a few members of the astronomical community. The principal tool for combating light pollution is the local outdoor lighting ordinance designed to protect dark skies by requiring some combination of: a) shielding outdoor lighting so that none of the light is emitted above the horizontal plane, 2) encouraging the use of "astronomy friendly" light sources such as low pressure sodium, and 3) limiting the total amount of outdoor light that is produced. Such measures have been effective in the past, however, in some areas, development is rapidly moving close to world-class observatories; the Canoa Ranch development near Mt. Hopkins in southern Arizona is the most recent highly visible example. More effective measures are needed to protect existing sites in the future. The astronomical community needs to become more aware of the increasing threat to many prime observing sites and become more active in developing effective programs for preserving the dark sky. This is needed not only for the benefit of our profession but also for preserving the heritage of the night sky for future generations.

  10. Structured Light-Based 3D Reconstruction System for Plants.

    PubMed

    Nguyen, Thuy Tuong; Slaughter, David C; Max, Nelson; Maloof, Julin N; Sinha, Neelima

    2015-01-01

    Camera-based 3D reconstruction of physical objects is one of the most popular computer vision trends in recent years. Many systems have been built to model different real-world subjects, but there is lack of a completely robust system for plants. This paper presents a full 3D reconstruction system that incorporates both hardware structures (including the proposed structured light system to enhance textures on object surfaces) and software algorithms (including the proposed 3D point cloud registration and plant feature measurement). This paper demonstrates the ability to produce 3D models of whole plants created from multiple pairs of stereo images taken at different viewing angles, without the need to destructively cut away any parts of a plant. The ability to accurately predict phenotyping features, such as the number of leaves, plant height, leaf size and internode distances, is also demonstrated. Experimental results show that, for plants having a range of leaf sizes and a distance between leaves appropriate for the hardware design, the algorithms successfully predict phenotyping features in the target crops, with a recall of 0.97 and a precision of 0.89 for leaf detection and less than a 13-mm error for plant size, leaf size and internode distance. PMID:26230701

  11. Glass-based confined structures enabling light control

    SciTech Connect

    Chiappini, Andrea; Normani, Simone; Chiasera, Alessandro; Vasilchenko, Iustyna; Ristic, Davor; Boulard, Brigitte; Dorosz, Dominik; Scotognella, Francesco; Vaccari, Alessandro; Taccheo, Stefano; Pelli, Stefano; Righini, Giancarlo C.; Conti, Gualtiero Nunzi; Ramponi, Roberta; and others

    2015-04-24

    When a luminescent ion is confined in a system characterized by one or more specific properties such as spatial size, geometrical dimension and shape, refractive index, local crystal field, cut-off vibrational energy and so on, it's possible to control its emission. The control of branching ratios as a function of the composition, the luminescence enhancement induced by a photonic crystal, or the laser action in a microresonator, are well known examples of light control. Photonic glass-based structures are extremely viable systems to exploit the above mentioned properties and in our research team we have successfully fabricated luminescent photonic structures by different techniques, including sol-gel, rf sputtering, drawing, melting, and physical vapour deposition. Here we will discuss some of them with the aim to make the reader aware of the chemical-physical properties related to each specific system. We will demonstrate that glass ceramic waveguides in some cases present superior spectroscopic properties in respect to the parent glass, that compositional properties can play a positive role in reducing luminescence quenching and in developing novel planar waveguides and fibers, that colloids allow to obtain high internal quantum efficiency and that photonic crystals, microcavities and microresonators can enable the handling of the rare earth luminescence. Finally, the pros and cons of the systems and of the different techniques employed for their fabrication will be discussed and some perspectives concerning the glass photonics will be proposed looking at both possible applications and investigation of physical properties.

  12. Scheduling for indoor visible light communication based on graph theory.

    PubMed

    Tao, Yuyang; Liang, Xiao; Wang, Jiaheng; Zhao, Chunming

    2015-02-01

    Visible light communication (VLC) has drawn much attention in the field of high-rate indoor wireless communication. While most existing works focused on point-to-point VLC technologies, few studies have concerned multiuser VLC, where multiple optical access points (APs) transmit data to multiple user receivers. In such scenarios, inter-user interference constitutes the major factor limiting the system performance. Therefore, a proper scheduling scheme has to be proposed to coordinate the interference and optimize the whole system performance. In this work, we aim to maximize the sum rate of the system while taking into account user fairness by appropriately assigning LED lamps to multiple users. The formulated scheduling problem turns out to be a maximum weighted independent set problem. We then propose a novel and efficient resource allocation method based on graph theory to achieve high sum rates. Moreover, we also introduce proportional fairness into our scheduling scheme to ensure the user fairness. Our proposed scheduling scheme can, with low complexity, achieve more multiplexing gains, higher sum rate, and better fairness than the existing works. PMID:25836136

  13. Structured Light-Based 3D Reconstruction System for Plants

    PubMed Central

    Nguyen, Thuy Tuong; Slaughter, David C.; Max, Nelson; Maloof, Julin N.; Sinha, Neelima

    2015-01-01

    Camera-based 3D reconstruction of physical objects is one of the most popular computer vision trends in recent years. Many systems have been built to model different real-world subjects, but there is lack of a completely robust system for plants.This paper presents a full 3D reconstruction system that incorporates both hardware structures (including the proposed structured light system to enhance textures on object surfaces) and software algorithms (including the proposed 3D point cloud registration and plant feature measurement). This paper demonstrates the ability to produce 3D models of whole plants created from multiple pairs of stereo images taken at different viewing angles, without the need to destructively cut away any parts of a plant. The ability to accurately predict phenotyping features, such as the number of leaves, plant height, leaf size and internode distances, is also demonstrated. Experimental results show that, for plants having a range of leaf sizes and a distance between leaves appropriate for the hardware design, the algorithms successfully predict phenotyping features in the target crops, with a recall of 0.97 and a precision of 0.89 for leaf detection and less than a 13-mm error for plant size, leaf size and internode distance. PMID:26230701

  14. Glass-based confined structures enabling light control

    NASA Astrophysics Data System (ADS)

    Chiappini, Andrea; Lukowiak, Anna; Vasilchenko, Iustyna; Ristic, Davor; Normani, Simone; Chiasera, Alessandro; Boulard, Brigitte; Dorosz, Dominik; Scotognella, Francesco; Vaccari, Alessandro; Taccheo, Stefano; Pelli, Stefano; Conti, Gualtiero Nunzi; Ramponi, Roberta; Righini, Giancarlo C.; Gonçalves, Rogeria R.; Rahman, M. Kamil Abd; Ferrari, Maurizio

    2015-04-01

    When a luminescent ion is confined in a system characterized by one or more specific properties such as spatial size, geometrical dimension and shape, refractive index, local crystal field, cut-off vibrational energy and so on, it's possible to control its emission. The control of branching ratios as a function of the composition, the luminescence enhancement induced by a photonic crystal, or the laser action in a microresonator, are well known examples of light control. Photonic glass-based structures are extremely viable systems to exploit the above mentioned properties and in our research team we have successfully fabricated luminescent photonic structures by different techniques, including sol-gel, rf sputtering, drawing, melting, and physical vapour deposition. Here we will discuss some of them with the aim to make the reader aware of the chemical-physical properties related to each specific system. We will demonstrate that glass ceramic waveguides in some cases present superior spectroscopic properties in respect to the parent glass, that compositional properties can play a positive role in reducing luminescence quenching and in developing novel planar waveguides and fibers, that colloids allow to obtain high internal quantum efficiency and that photonic crystals, microcavities and microresonators can enable the handling of the rare earth luminescence. Finally, the pros and cons of the systems and of the different techniques employed for their fabrication will be discussed and some perspectives concerning the glass photonics will be proposed looking at both possible applications and investigation of physical properties.

  15. GPGPU-based surface inspection from structured white light

    NASA Astrophysics Data System (ADS)

    Bordallo López, Miguel; Niemelä, Karri; Silvén, Olli

    2012-03-01

    Automatic surface inspection has been used in the industry to reliably detect all kinds of surface defects and to measure the overall quality of a produced piece. Structured light systems (SLS) are based on the reconstruction of the 3D information of a selected area by projecting several phase-shifted sinusoidal patterns onto a surface. Due to the high speed of production lines, surface inspection systems require extremely fast imaging methods and lots of computational power. The cost of such systems can easily become considerable. The use of standard PCs and Graphics Processing Units (GPUs) for data processing tasks facilitates the construction of cost-effective systems. We present a parallel implementation of the required algorithms written in C with CUDA extensions. In our contribution, we describe the challenges of the design on a GPU, compared with a traditional CPU implementation. We provide a qualitative evaluation of the results and a comparison of the algorithm speed performance on several platforms. The system is able to compute two megapixels height maps with 100 micrometers spatial resolution in less than 200ms on a mid-budget laptop. Our GPU implementation runs about ten times faster than our previous C code implementation.

  16. Dynamic Light Scattering Based Microelectrophoresis: Main Prospects and Limitations

    PubMed Central

    Uskoković, Vuk

    2013-01-01

    Microelectrophoresis based on the dynamic light scattering (DLS) effect has been a major tool for assessing and controlling the conditions for stability of colloidal systems. However, both the DLS methods for characterization of the hydrodynamic size of dispersed submicron particles and the theory behind the electrokinetic phenomena are associated with fundamental and practical approximations that limit their sensitivity and information output. Some of these fundamental limitations, including the spherical approximation of DLS measurements and an inability of microelectrophoretic analyses of colloidal systems to detect discrete charges and differ between differently charged particle surfaces due to rotational diffusion and particle orientation averaging, are revisited in this work. Along with that, the main prospects of these two analytical methods are mentioned. A detailed review of the role of zeta potential in processes of biochemical nature is given too. It is argued that although zeta potential has been used as one of the main parameters in controlling the stability of colloidal dispersions, its application potentials are much broader. Manipulating surface charges of interacting species in designing complex soft matter morphologies using the concept of zeta potential, intensively investigated recently, is given as one of the examples. Branching out from the field of colloid chemistry, DLS and zeta potential analyses are now increasingly finding application in drug delivery, biotechnologies, physical chemistry of nanoscale phenomena and other research fields that stand on the frontier of the contemporary science. Coupling the DLS-based microelectrophoretic systems with complementary characterization methods is mentioned as one of the prosperous paths for increasing the information output of these two analytical techniques. PMID:23904690

  17. A low-cost low-maintenance ultraviolet lithography light source based on light-emitting diodes.

    PubMed

    Erickstad, M; Gutierrez, E; Groisman, A

    2015-01-01

    A source of collimated ultraviolet (UV) light is a central piece of equipment needed for lithographic fabrication of microfluidic devices. Conventional UV light sources based on high-pressure mercury lamps require considerable maintenance and provide broad-band illumination with intensity that often changes with time. Here we present a source of narrow-band UV light based on an array of nine 365 nm light-emitting diodes (LEDs). Each LED has two dedicated converging lenses, reducing the divergence of light emanating from it to 5.4°. Partial overlap of the areas illuminated by individual LEDs provides UV illumination with a mean intensity of ~1.7 mW cm(-2) and coefficient of variation <3% over a 90 × 90 mm target area. The light source was used to lithographically fabricate micro-reliefs with thicknesses from ~25 to 311 μm with SU8 photoresists. A cumulative irradiation of 370 mJ cm(-2) (4 min exposure) produced reliefs of good quality for all SU8 thicknesses. Polydimethylsiloxane (PDMS) replicas of the SU8 reliefs had microchannels with nearly rectangular cross-sections that were highly consistent over the entire target area, and partitions between the channels had depth to width ratios up to 5. The UV light source has also been successfully used for photolithography with positive photoresists, AZ40XT and SPR-220. The proposed light source is built with a total cost of <$1000, consumes a minimal amount of power, is expected to last for ~50,000 exposures, is maintenance-free, and is particularly appealing for small research-and-development microfluidic fabrication. PMID:25322205

  18. Modulation based cells distribution for visible light communication.

    PubMed

    Wu, Yongsheng; Yang, Aiying; Feng, Lihui; Zuo, Lin; Sun, Yu-Nan

    2012-10-22

    Cells distribution for visible light communication can enhance the capacity of the data transmission by the reuse of optical spectrum. In this paper, we adopt three modulation formats as OOK, PPM and PWM for neighboring cells A, B and C respectively. The prototype experiment results demonstrate the error free transmission of 1.0 Mbit/s and 6.25 Mbit/s visible light communication system with our scheme. With the available LED, we can expect that the data rate of a visible light communication system with seamless connectivity can be up to 71.4 Mbit/s. PMID:23187182

  19. Carbonitride based phosphors and light emitting devices using the same

    DOEpatents

    Li, Yuanqiang; Tian, Yongchi; Romanelli, Michael Dennis

    2013-08-20

    Disclosed herein is a novel group of carbidonitride phosphors and light emitting devices which utilize these phosphors. In certain embodiments, the present invention is directed to a novel family of carbidonitride-based phosphors expressed as follows: Ca.sub.1-xAl.sub.x-xySi.sub.1-x+xyN.sub.2-x-xyC.sub.xy:A; (1) Ca.sub.1-x-zNa.sub.zM(III).sub.x-xy-zSi.sub.1-x+xy+zN.sub.2-x-xyC.sub.xy:- A; (2) M(II).sub.1-x-zM(I).sub.zM(III).sub.x-xy-zSi.sub.1-x+xy+zN.sub.2-x- -xyC.sub.xy:A; (3) M(II).sub.1-x-zM(I).sub.zM(III).sub.x-xy-zSi.sub.1-x+xy+zN.sub.2-x-xy-2w/- 3C.sub.xyO.sub.w-v/2H.sub.v:A; and (4) M(II).sub.1-x-zM(I).sub.zM(III).sub.x-xy-zSi.sub.1-x+xy+zN.sub.2-x-xy-2w/- 3-v/3C.sub.xyO.sub.wH.sub.v:A, (4a) wherein 0xy+z, and 0

  20. Three-dimension reconstruction based on spatial light modulator

    NASA Astrophysics Data System (ADS)

    Deng, Xuejiao; Zhang, Nanyang; Zeng, Yanan; Yin, Shiliang; Wang, Weiyu

    2011-02-01

    Three-dimension reconstruction, known as an important research direction of computer graphics, is widely used in the related field such as industrial design and manufacture, construction, aerospace, biology and so on. Via such technology we can obtain three-dimension digital point cloud from a two-dimension image, and then simulate the three-dimensional structure of the physical object for further study. At present, the obtaining of three-dimension digital point cloud data is mainly based on the adaptive optics system with Shack-Hartmann sensor and phase-shifting digital holography. Referring to surface fitting, there are also many available methods such as iterated discrete fourier transform, convolution and image interpolation, linear phase retrieval. The main problems we came across in three-dimension reconstruction are the extraction of feature points and arithmetic of curve fitting. To solve such problems, we can, first of all, calculate the relevant surface normal vector information of each pixel in the light source coordinate system, then these vectors are to be converted to the coordinates of image through the coordinate conversion, so the expectant 3D point cloud get arise. Secondly, after the following procedures of de-noising, repairing, the feature points can later be selected and fitted to get the fitting function of the surface topography by means of Zernike polynomial, so as to reconstruct the determinand's three-dimensional topography. In this paper, a new kind of three-dimension reconstruction algorithm is proposed, with the assistance of which, the topography can be estimated from its grayscale at different sample points. Moreover, the previous stimulation and the experimental results prove that the new algorithm has a strong capability to fit, especially for large-scale objects .

  1. LED-based endoscopic light source for spectral imaging

    NASA Astrophysics Data System (ADS)

    Browning, Craig M.; Mayes, Samuel; Favreau, Peter; Rich, Thomas C.; Leavesley, Silas J.

    2016-03-01

    Colorectal cancer is the United States 3rd leading cancer in death rates.1 The current screening for colorectal cancer is an endoscopic procedure using white light endoscopy (WLE). There are multiple new methods testing to replace WLE, for example narrow band imaging and autofluorescence imaging.2 However, these methods do not meet the need for a higher specificity or sensitivity. The goal for this project is to modify the presently used endoscope light source to house 16 narrow wavelength LEDs for spectral imaging in real time while increasing sensitivity and specificity. The process to do such was to take an Olympus CLK-4 light source, replace the light and electronics with 16 LEDs and new circuitry. This allows control of the power and intensity of the LEDs. This required a larger enclosure to house a bracket system for the solid light guide (lightpipe), three new circuit boards, a power source and National Instruments hardware/software for computer control. The results were a successfully designed retrofit with all the new features. The LED testing resulted in the ability to control each wavelength's intensity. The measured intensity over the voltage range will provide the information needed to couple the camera for imaging. Overall the project was successful; the modifications to the light source added the controllable LEDs. This brings the research one step closer to the main goal of spectral imaging for early detection of colorectal cancer. Future goals will be to connect the camera and test the imaging process.

  2. Yttrium oxide based three dimensional metamaterials for visible light cloaking

    NASA Astrophysics Data System (ADS)

    Rai, Pratyush; Kumar, Prashanth S.; Varadan, Vijay K.; Ruffin, Paul; Brantley, Christina; Edwards, Eugene

    2014-04-01

    Metamaterial with negative refractive index is the key phenomenon behind the concept of a cloaking device to hide an object from light in visible spectrum. Metamaterials made of two and three dimensional lattices of periodically placed electromagnetic resonant cells can achieve absorption and propagation of incident electromagnetic radiation as confined electromagnetic fields confined to a waveguide as surface plasmon polaritons, which can be used for shielding an object from in-tune electromagnetic radiation. The periodicity and dimensions of resonant cavity determine the frequency, which are very small as compared to the wavelength of incident light. Till now the phenomena have been demonstrated only for lights in near infrared spectrum. Recent advancements in fabrication techniques have made it possible to fabricate array of three dimensional nanostructures with cross-sections as small as 25 nm that are required for negative refractive index for wavelengths in visible light spectrum of 400-700 nm and for wider view angle. Two types of metamaterial designs, three dimensional concentric split ring and fishnet, are considered. Three dimensional structures consisted of metal-dielectric-metal stacks. The metal is silver and dielectric is yttrium oxide, other than conventional materials such as FR4 and Duroid. High κ dielectric and high refractive index as well as large crystal symmetry of Yttrium oxide has been investigated as encapsulating medium. Dependence of refractive index on wavelength and bandwidth of negative refractive index region are analyzed for application towards cloaking from light in visible spectrum.

  3. Gold Nanorods Based Platforms for Light-Mediated Theranostics

    PubMed Central

    Zhang, Zhenjiang; Wang, Jing; Chen, Chunying

    2013-01-01

    Due to their tunable surface plasmon and photothermal effects, gold nanorods (AuNRs) have proved to be promising in a wide range of biomedical applications such as imaging, hyperthermia therapy and drug delivery. All these applications can be remotely controlled by near infrared (NIR) light which can penetrate deep into human tissues with minimal lateral invasion. AuNRs thus hold the potential to combine both imaging diagnosis and therapeutic treatment into one single system and function as a NIR light-mediated theranostic platform. Herein we review recent progress in diagnostic and therapeutic applications of AuNRs with a highlight on combined applications for theranostic purposes. PMID:23471510

  4. Photo-actuating waveguiding fibers based on light responsive hydrogels

    NASA Astrophysics Data System (ADS)

    Zhou, Ying; Hauser, Adam; Rasmussen, Nathan; Kuzyk, Mark; Hayward, Ryan

    2015-03-01

    The combination of light-absorbing nanoparticles with thermally sensitive hydrogels has been widely explored as a strategy for photo-thermal actuation. Here, we employ a system of photo-crosslinkable copolymers containing pendent benzophenone units to prepare planar waveguiding polymethylmethacrylate(PMMA) fibers patterned with poly(N-isopropyl acrylamide) (PNIPAM) copolymer hydrogels containing Au nanoparticles. These structures show both thermally- and photo-actuated bending behavior due to swelling stresses developed in the PNIPAM gel layer. Further, we establish that light can be successfully guided into micro-patterned fibers, yielding a route to remotely controlled micro-actuators.

  5. Preliminary study for improving the VIIRS DNB low light calibration accuracy with ground based active light source

    NASA Astrophysics Data System (ADS)

    Cao, Changyong; Zong, Yuqing; Bai, Yan; Shao, Xi

    2015-09-01

    There is a growing interest in the science and user community in the Visible Infrared Imaging Radiometer Suite (VIIRS) Day/Night Band (DNB) low light detection capabilities at night for quantitative applications such as airglow, geophysical retrievals under lunar illumination, light power estimation, search and rescue, energy use, urban expansion and other human activities. Given the growing interest in the use of the DNB data, a pressing need arises for improving the calibration stability and absolute accuracy of the DNB at low radiances. Currently the low light calibration accuracy was estimated at a moderate 15%-100% while the long-term stability has yet to be characterized. This study investigates selected existing night light point sources from Suomi NPP DNB observations and evaluates the feasibility of SI traceable nightlight source at radiance levels near 3 nW·cm-2·sr-1, that potentially can be installed at selected sites for VIIRS DNB calibration/validation. The illumination geometry, surrounding environment, as well as atmospheric effects are also discussed. The uncertainties of the ground based light source are estimated. This study will contribute to the understanding of how the Earth's atmosphere and surface variability contribute to the stability of the DNB measured radiances, and how to separate them from instrument calibration stability. It presents the need for SI traceable active light sources to monitor the calibration stability, radiometric and geolocation accuracy, and point spread functions of the DNB. Finally, it is also hoped to address whether or not active light sources can be used for detecting environmental changes, such as aerosols.

  6. Photonic crystal fibre-based light source for STED lithography

    SciTech Connect

    Glubokov, D A; Sychev, V V; Vitukhnovsky, Alexey G; Korol'kov, A E

    2013-06-30

    A light source having a relative noise level in the order of 10{sup -6} and sufficient stability for application in STED lithography has been obtained using the generation of Cherenkov peaks in a supercontinuum spectrum. (laser applications and other topics in quantum electronics)

  7. Characterization of the KID-Based Light Detectors of CALDER

    NASA Astrophysics Data System (ADS)

    Casali, N.; Bellini, F.; Cardani, L.; Castellano, M. G.; Colantoni, I.; Coppolecchia, A.; Cosmelli, C.; Cruciani, A.; D'Addabbo, A.; Di Domizio, S.; Martinez, M.; Tomei, C.; Vignati, M.

    2016-07-01

    The aim of the Cryogenic wide-Area Light Detectors with Excellent Resolution (CALDER) project is the development of light detectors with active area of 5 × 5 cm2 and noise energy resolution smaller than 20 eV RMS, implementing phonon-mediated kinetic inductance detectors. The detectors are developed to improve the background suppression in large-mass bolometric experiments such as CUORE, via the double read-out of the light and the heat released by particles interacting in the bolometers. In this work, we present the characterization of the first light detectors developed by CALDER. We describe the analysis tools to evaluate the resonator parameters (resonant frequency and quality factors) taking into account simultaneously all the resonance distortions introduced by the read-out chain (as the feed-line impedance and its mismatch) and by the power stored in the resonator itself. We detail the method for the selection of the optimal point for the detector operation (maximizing the signal-to-noise ratio). Finally, we present the response of the detector to optical pulses in the energy range of 0{-}30 keV.

  8. Characterization of the KID-Based Light Detectors of CALDER

    NASA Astrophysics Data System (ADS)

    Casali, N.; Bellini, F.; Cardani, L.; Castellano, M. G.; Colantoni, I.; Coppolecchia, A.; Cosmelli, C.; Cruciani, A.; D'Addabbo, A.; Di Domizio, S.; Martinez, M.; Tomei, C.; Vignati, M.

    2015-11-01

    The aim of the Cryogenic wide-Area Light Detectors with Excellent Resolution (CALDER) project is the development of light detectors with active area of 5 × 5 cm2 and noise energy resolution smaller than 20 eV RMS, implementing phonon-mediated kinetic inductance detectors. The detectors are developed to improve the background suppression in large-mass bolometric experiments such as CUORE, via the double read-out of the light and the heat released by particles interacting in the bolometers. In this work, we present the characterization of the first light detectors developed by CALDER. We describe the analysis tools to evaluate the resonator parameters (resonant frequency and quality factors) taking into account simultaneously all the resonance distortions introduced by the read-out chain (as the feed-line impedance and its mismatch) and by the power stored in the resonator itself. We detail the method for the selection of the optimal point for the detector operation (maximizing the signal-to-noise ratio). Finally, we present the response of the detector to optical pulses in the energy range of 0{-}30 keV.

  9. Nanocluster-based white-light-emitting material employing surface tuning

    DOEpatents

    Wilcoxon, Jess P.; Abrams, Billie L.; Thoma, Steven G.

    2007-06-26

    A method for making a nanocrystal-based material capable of emitting light over a sufficiently broad spectral range to appear white. Surface-modifying ligands are used to shift and broaden the emission of semiconductor nanocrystals to produce nanoparticle-based materials that emit white light.

  10. Using an ethernet based relay to remotely control lights at CFHT

    NASA Astrophysics Data System (ADS)

    Barrick, Gregory

    2011-03-01

    Prior to observatory automation, all the lights at the summit were controlled using local light switches. Lights that were inadvertently left on during the day that impact observing can previously could be turned off by the night staff. Likewise, the night staff could turn on lights as needed for troubleshooting. Remote observing will make this impossible. The use of WebRelays provided a means for remotely turning on or off critical lights as needed. WebRelays are an Ethernet based relay that can be controlled either using network commands or by supplying voltage to an optically isolated input on the WebRelay.

  11. LiteVis: Integrated Visualization for Simulation-Based Decision Support in Lighting Design.

    PubMed

    Sorger, Johannes; Ortner, Thomas; Luksch, Christian; Schwärzler, Michael; Gröller, Eduard; Piringer, Harald

    2016-01-01

    State-of-the-art lighting design is based on physically accurate lighting simulations of scenes such as offices. The simulation results support lighting designers in the creation of lighting configurations, which must meet contradicting customer objectives regarding quality and price while conforming to industry standards. However, current tools for lighting design impede rapid feedback cycles. On the one side, they decouple analysis and simulation specification. On the other side, they lack capabilities for a detailed comparison of multiple configurations. The primary contribution of this paper is a design study of LiteVis, a system for efficient decision support in lighting design. LiteVis tightly integrates global illumination-based lighting simulation, a spatial representation of the scene, and non-spatial visualizations of parameters and result indicators. This enables an efficient iterative cycle of simulation parametrization and analysis. Specifically, a novel visualization supports decision making by ranking simulated lighting configurations with regard to a weight-based prioritization of objectives that considers both spatial and non-spatial characteristics. In the spatial domain, novel concepts support a detailed comparison of illumination scenarios. We demonstrate LiteVis using a real-world use case and report qualitative feedback of lighting designers. This feedback indicates that LiteVis successfully supports lighting designers to achieve key tasks more efficiently and with greater certainty. PMID:26529708

  12. White organic light-emitting diodes based on tandem structures

    NASA Astrophysics Data System (ADS)

    Guo, Fawen; Ma, Dongge

    2005-10-01

    White organic light-emitting diodes made of two electroluminescent (EL) units connected by a charge generation layer were fabricated. Thus, with a tandem structure of indium tin oxide/N ,N'-di(naphthalene-1-yl)-N ,N'-diphenyl-benzidine (NPB)/9,10-bis-(β-naphthyl)-anthrene (ADN)/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP)/tris(8-hydroxyquinoline) aluminum (Alq3)/BCP:Li/V2O5/NPB/Alq3:4-(dicyanomethylene)-2-t-butyle-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)4H-pyran (DCJTB)/Alq3/LiF/Al, a stable white light with Commission Internationale De L'Eclairage chromaticity coordinates from (0.35, 0.32) at 18V to (0.36, 0.36) at 50V was generated. It was clearly seen that the EL spectra consist of red band at 600nm due to DCJTB, green band at 505nm due to Alq3, and blue band at 435nm due to ADN, and the current efficiency and brightness equal basically to the sum of the two EL units. As a result, the tandem devices showed white light emission with a maximum brightness of 10200cd /m2 at a bias of 40V and a maximum current efficiency of 10.7cd/A at a current density of 3.5mA/cm2.

  13. Cell light scattering characteristic research based on FDTD algorithm

    NASA Astrophysics Data System (ADS)

    Lin, Xiaogang; Zhu, Hao; Li, Wenchao; Ye, Changbin

    2015-10-01

    As with the number of cancer increases year by year, so it is important to be found and treated earlier. With biological cells and tissues are sensitive to infrared and visible light, cell morphology and physical structure of the optical properties can easily obtain, we can provide theoretical basis for the early diagnosis of cancer by observing the difference of optical properties between normal and cancerous cells. Compared with Mie scattering theory, finite difference time domain (FDTD) algorithm can analyze any complex structure model. In this paper we use mathematical modeling method to establish the single cell mathematical model and with finite difference time domain algorithm to simulate the propagation and scattering of light in the biological cells, you can calculate the scattering of electromagnetic field distribution at anytime and anywhere. With radar cross section (RCS) to measure the results of the scattering characteristics. Due to the difference between normal cells and cancerous cells are embodied in cell shape, size and the refractive index, through the simulation we can get different cell parameters of light scattering information, Find out the cell parameters change the changing rule of the influence on the scattering characteristics and find out change regularity of scattering characteristics. These data can judge very accurate of the cells is normal or cancerous cells.

  14. Multifocal multiphoton microscopy based on a spatial light modulator

    PubMed Central

    Shao, Y.; Qin, W.; Liu, H.; Peng, X.; Niu, H.

    2013-01-01

    We present a new multifocal multiphoton microscope that employs a programmable spatial light modulator to generate dynamic multifocus arrays which can be rapidly scanned by changing the incident angle of the laser beam using a pair of galvo scanners. Using this microscope, we can rapidly select the number and the spatial density of focal points in a multifocus array, as well as the locations and shapes of arrays according to the features of the areas of interest in the field of view without any change to the hardware. PMID:23894222

  15. Metal Organic Vapor Phase Epitaxy of Monolithic Two-Color Light-Emitting Diodes Using an InGaN-Based Light Converter

    NASA Astrophysics Data System (ADS)

    Damilano, Benjamin; Kim-Chauveau, Hyonju; Frayssinet, Eric; Brault, Julien; Hussain, Sakhawat; Lekhal, Kaddour; Vennéguès, Philippe; De Mierry, Philippe; Massies, Jean

    2013-09-01

    Monolithic InGaN-based light-emitting diodes (LEDs) using a light converter fully grown by metal organic vapor phase epitaxy are demonstrated. The light converter, consisting of 10-40 InGaN/GaN quantum wells, is grown first, followed by a violet pump LED. The structure and growth conditions of the pump LED are specifically adapted to avoid thermal degradation of the light converter. Electroluminescence analysis shows that part of the pump light is absorbed by the light converter and reemitted at longer wavelength. Depending on the emission wavelength of the light converter, different LED colors are achieved. In particular, for red-emitting light converters, a color temperature of 2100 K corresponding to a tint between warm white and candle light is demonstrated.

  16. Ejecta from Hypervelocity Dust Impacts Based on Light Flash Measurements

    NASA Astrophysics Data System (ADS)

    Drake, Keith; Sternovsky, Z.; Horányi, M.; Kempf, S.; Srama, R.

    2013-10-01

    Ejecta from hypervelocity dust impacts have been shown to depend on the impinging particles’ velocity, mass, composition, etc. (J. Friichtenicht 1965, G. Eichhorn 1976). Ejecta is thought to be responsible for developing rings and dusty atmospheres of moons throughout the solar system. In order for rings to be produced, dust velocities must be greater than the moon’s escape speed. To understand the dust impact yield; impact ejecta parameters (velocities, masses, angular distributions) must be well understood. Laboratory experiments provide direct information about the ejecta production rates and impactor fluxes. Using hypervelocity (1-60km/s) iron dust at the University of Colorado dust accelerator in Boulder, Colorado we measured the time characteristics and intensities of light flashes produced on a quartz disc from primary and secondary impacts. The flashes were measured with a photomultiplier tube at varying distances and angles. By analyzing the light flashes produced by such impacts we show that this method is a viable technique for measuring these parameters. These measurements provide detailed information about the secondary mass and velocity profiles, leading to insights into the formation of dusty rings and atmospheres.

  17. Light-triggered thermoelectric conversion based on a carbon nanotube-polymer hybrid gel.

    PubMed

    Miyako, Eijiro; Nagata, Hideya; Funahashi, Ryoji; Hirano, Ken; Hirotsu, Takahiro

    2009-01-01

    Lights? Nanotubes? Action! A hydrogel comprising lysozymes, poly(ethylene glycol), phospholipids, and functionalized single-walled carbon nanotubes is employed for light-driven thermoelectric conversion. A photoinduced thermoelectric conversion module based on the hydrogel functions as a novel electric power generator (see image). This concept may find application in various industries, such as robotics and aerospace engineering. PMID:19455558

  18. Synthesis of quinoline based heterocyclic compounds for blue lighting application

    NASA Astrophysics Data System (ADS)

    Kumar, Vinod; Gohain, Mukut; Van Tonder, Johannes H.; Ponra, S.; Bezuindenhoudt, B. C. B.; Ntwaeaborwa, O. M.; Swart, H. C.

    2015-12-01

    2,4-Diphenylquinoline (DPQ), derivatives 6-chloro-2,4-diphenylquinoline (DPQ-Cl) and 4‧,6-dichloro-2,4-diphenylquinoline (DPQ-Cl2) were synthesized using a three-component domino reaction. The DPQ, DPQ-Cl and DPQ-Cl2 were characterized by nuclear magnetic resonance spectroscopy, scanning electron microscopy, thermogravimetric analysis (TGA). Fourier transformed infra-red spectroscopy, X-ray photoelectron spectroscopy (XPS), Ultraviolet-visible (UV-vis) spectroscopy and photoluminescence spectroscopy. The TGA results showed that the DPQ was more thermally stable with respect to the DPQ-Cl and DPQ-Cl2. The synthesized organic phosphors showed bright emission in the blue region under an UV excitation wavelength of 325 nm with the power of 18 mW. These organic phosphors were found to be efficient candidate and may be used in organic blue light emitting devices.

  19. Visible light responsive systems based on metastable-state photoacids

    NASA Astrophysics Data System (ADS)

    Liao, Yi

    2015-09-01

    Proton transfer is one of the most fundamental processes in nature. Metastable-state photoacids can reversibly generate a large proton concentration under visible light with moderate intensity. which provides a general approach to control various proton transfer processes. Several applications of mPAHs have been demonstrated recently including control of acid-catalyzed reactions, volume-change of hydrogels, polymer conductivity, bacteria killing, odorant release, and color change of materials. They have also been utilized to control supramolecular assemblies, molecular switches, microbial fuel cells and cationic sensors. In this talk, the mechanism, structure design, and applications of metastable-state photoacids are introduced. Recent development of different types of metastable-state photoacids is presented. Challenges and future work are also discussed.

  20. Multilayer light emitting diodes using a PPV based copolymer

    NASA Astrophysics Data System (ADS)

    Nguyen, T. P.; Chen, L. C.; Wang, X.; Huang, Z.

    1998-01-01

    We have investigated the electrical and optical properties of poly((2,5-(dimethoxy) p-phenylene vinylene)- p-phenylene vinylene) (PDMeOPV/PPV) copolymer used as an emitting layer in light emitting diodes. With p-phenylene vinylene (PPV) used as a hole transport layer and polyphenylquinoxaline (PPQ) as an electron transport layer, the emission intensity of the devices has substantially increased without alteration of the transport property. The different conduction mechanisms in the diodes were examined and discussed in terms of the energy band diagrams of the polymer layers. A balance of the injected charge carriers confined in the copolymer could explain the enhancement of the performance of the multilayer diodes.

  1. Automultiscopic displays based on orbital angular momentum of light

    NASA Astrophysics Data System (ADS)

    Li, Xuefeng; Chu, Jiaqi; Smithwick, Quinn; Chu, Daping

    2016-08-01

    Orbital angular momentum (OAM) of light has drawn increasing attention due to its intriguingly rich physics and potential for a variety of applications. Having an unbounded set of orthogonal states, OAM has been used to enhance the channel capacity of data transmission. We propose and demonstrate the viability of using OAM to create an automultiscopic 3D display. Multi-view image information is encoded using an OAM beam array, then sorted into different view directions using coordinate transformation elements. A three-view demonstration was achieved to encode and decode 9 × 9 pixel images. These demonstrations suggest that OAM could potentially serve as an additional platform for future 3D display systems.

  2. Characterizing Scitillation and Cherenkov Light Yield in Water-Based Liquid Scintillators

    NASA Astrophysics Data System (ADS)

    Land, B. J.; Caravaca, J.; Descamps, F. B.; Orebi Gann, G. D.

    2016-03-01

    The recent development of Water-based Liquid Scintillator (WbLS) has made it possible to produce scintillating materials with highly tunable light yields and excellent optical clarity. This allows for a straightforward combination of the directional properties of Cherenkov light with the greater energy resolution afforded by the typically brighter scintillation light, which lends itself well to a broad program of neutrino physics. Here we explore the light yields and optical properties of WbLS materials in development for Theia (formerly ASDC) as measured in our benchtop Theia R&D at Berkeley Lab and extrapolate to larger detectors.

  3. Catalytic oxidation of light alkanes in presence of a base

    DOEpatents

    Bhinde, Manoj V.; Bierl, Thomas W.

    1998-01-01

    The presence of a base in the reaction mixture in a metal-ligand catalyzed partial oxidation of alkanes results in sustained catalyst activity, and in greater percent conversion as compared with oxidation in the absence of base, while maintaining satisfactory selectivity for the desired oxidation, for example the oxidation of isobutane to isobutanol.

  4. Catalytic oxidation of light alkanes in presence of a base

    DOEpatents

    Bhinde, M.V.; Bierl, T.W.

    1998-03-03

    The presence of a base in the reaction mixture in a metal-ligand catalyzed partial oxidation of alkanes results in sustained catalyst activity, and in greater percent conversion as compared with oxidation in the absence of base, while maintaining satisfactory selectivity for the desired oxidation, for example the oxidation of isobutane to isobutanol. 1 fig.

  5. Design and implementation of green intelligent lights based on the ZigBee

    NASA Astrophysics Data System (ADS)

    Gan, Yong; Jia, Chunli; Zou, Dongyao; Yang, Jiajia; Guo, Qianqian

    2013-03-01

    By analysis of the low degree of intelligence of the traditional lighting control methods, the paper uses the singlechip microcomputer for the control core, and uses a pyroelectric infrared technology to detect the existence of the human body, light sensors to sense the light intensity; the interface uses infrared sensor module, photosensitive sensor module, relay module to transmit the signal, which based on ZigBee wireless network. The main function of the design is to realize that the lighting can intelligently adjust the brightness according to the indoor light intensity when people in door, and it can turn off the light when people left. The circuit and program design of this system is flexible, and the system achieves the effect of intelligent energy saving control.

  6. Influences of colorful LED emissions on spectrophotometric properties of a LED based white light source

    NASA Astrophysics Data System (ADS)

    Sametoglu, F.; Celikel, O.

    2011-05-01

    A LED based white light source (WLS) is designed and constructed to determine the color characteristics of the samples having specular and diffuse reflectance properties at the standard measurement conditions of 0/45 and d/8. The light source is composed of high power cool white and ultraviolet light emitting diodes (LEDs) which are operable in adjustable current levels. In order to combine the light beams emerging from two LED sources, a 1x2 fiber optic combiner is used. Optical characterizations of the light source designed and influences of several colorful LEDs called Royal-Blue, Blue, Cyan, Green, Amber, Red-Orange and Red on spectrophotometric properties of the light source are investigated.

  7. Smell sensing and visualizing based on multi-quantum wells spatial light modulator

    NASA Astrophysics Data System (ADS)

    Tian, Fengchun; Zhao, Zhenzhen; Jia, Pengfei; Liao, Hailin; Chen, Danyu; Liu, Shouqiong

    2014-09-01

    For the existing drawbacks of traditional detecting methods which use gratings or prisms to detect light intensity distribution at each wavelength of polychromatic light, a novel method based on multi-quantum wells spatial light modulator (MQWs-SLM) has been proposed in this paper. In the proposed method, MQWs-SLM serves as a distribution features detector of the signal light. It is on the basis of quantum-confine Stark effect (QCSE) that the vertical applied voltage can change the absorption features of exciton in multi-quantum wells, and further change the distribution features of the readout polychromatic light of MQWs-SLM. It can be not only an universal detecting method, but also especially recommended to use in the Electronic nose system for features detecting of signal light so as to realize smell sensing and visualizing. The feasibility of the proposed method has been confirmed by mathematical modeling and analysis, simulation experiments and research status analysis.

  8. Controlling the light distribution through turbid media with wavefront shaping based on volumetric optoacoustic feedback

    NASA Astrophysics Data System (ADS)

    Deán-Ben, X. Luís.; Estrada, Héctor; Özbek, Ali; Razansky, Daniel

    2016-03-01

    Wavefront shaping based on optoacoustic (photoacoustic) feedback has recently emerged as a promising tool to control the light distribution in optically-scattering media. In this approach, the phase of a short-pulsed light beam is spatially-modulated to create constructive light interference (focusing) at specific locations in the speckle pattern of the scattered wavefield. The optoacoustic signals generated by light absorption provide a convenient feedback mechanism to optimize the phase mask of the spatial light modulator in order to achieve the desired light intensity distribution. The optimization procedure can be done by directly considering the acquired signals or the reconstructed images of the light absorption distribution. Recently, our group has introduced a volumetric (three-dimensional) optoacoustic wavefront shaping platform that enables monitoring the distribution of light absorption in an entire volume with frame rates of tens of Hz. With this approach, it is possible to simultaneously control the volumetric light distribution through turbid media. Experiments performed with absorbing microparticles distributed in a three-dimensional region showcase the feasibility of enhancing the light intensity at specific points, where the size of particles is also essential to maximize the signal enhancement. The advantages provided by optoacoustic imaging in terms of spatial and temporal resolution anticipate new capabilities of wavefront shaping techniques in biomedical optics.

  9. Dynamic light scattering (DLS)-based immunoassay for ultra-sensitive detection of tumor marker protein.

    PubMed

    Li, Chao; Ma, Jiehua; Fan, Qiongxuan; Tao, Yaqin; Li, Genxi

    2016-06-14

    A novel dynamic light scattering (DLS)-based immunoassay that utilizes manganese dioxide nanosheet-modified gold nanoparticles (MnO2-GNPs) as an activatable nanoprobe has been developed to detect tumor markers down to femtomolar levels. PMID:27247980

  10. DNA-Based Oligochromophores as Light-Harvesting Systems.

    PubMed

    Ensslen, Philipp; Brandl, Fabian; Sezi, Sabrina; Varghese, Reji; Kutta, Roger-Jan; Dick, Bernhard; Wagenknecht, Hans-Achim

    2015-06-22

    The chromophores ethynyl pyrene as blue, ethynyl perylene as green and ethynyl Nile red as red emitter were conjugated to the 5-position of 2'-deoxyuridine via an acetylene bridge. Using phosphoramidite chemistry on solid phase labelled DNA duplexes were prepared that bear single chromophore modifications, and binary and ternary combinations of these chromophore modifications. The steady-state and time-resolved fluorescence spectra of all three chromophores were studied in these modified DNA duplexes. An energy-transfer cascade occurs from ethynyl pyrene over ethynyl perylene to ethynyl Nile red and subsequently an electron-transfer cascade in the opposite direction (from ethynyl Nile red to ethynyl perylene or ethynyl pyrene, but not from ethynyl perylene to ethynyl pyrene). The electron-transfer processes finally provide charge separation. The efficiencies by these energy and electron-transfer processes can be tuned by the distances between the chromophores and the sequences. Most importantly, excitation at any wavelength between 350 and 700 nm finally leads to charge separated states which make these DNA samples promising candidates for light-harvesting systems. PMID:26069203

  11. Optoelectrofluidic field separation based on light-intensity gradients

    PubMed Central

    Lee, Sanghyun; Park, Hyun Jin; Yoon, Jin Sung; Kang, Kwan Hyoung

    2010-01-01

    Optoelectrofluidic field separation (OEFS) of particles under light -intensity gradient (LIG) is reported, where the LIG illumination on the photoconductive layer converts the short-ranged dielectrophoresis (DEP) force to the long-ranged one. The long-ranged DEP force can compete with the hydrodynamic force by alternating current electro-osmosis (ACEO) over the entire illumination area for realizing effective field separation of particles. In the OEFS system, the codirectional illumination and observation induce the levitation effect, compensating the attenuation of the DEP force under LIG illumination by slightly floating particles from the surface. Results of the field separation and concentration of diverse particle pairs (0.82–16 μm) are well demonstrated, and conditions determining the critical radius and effective particle manipulation are discussed. The OEFS with codirectional LIG strategy could be a promising particle manipulation method in many applications where a rapid manipulation of biological cells and particles over the entire working area are of interest. PMID:20697461

  12. Toward user mobility for OFDM-based visible light communications.

    PubMed

    Hong, Yang; Chen, Lian-Kuan

    2016-08-15

    We propose and experimentally demonstrate a mobile visible light communications (mobi-VLC) transmission system. The impact of user mobility on the performance of the mobi-VLC system is characterized, and we propose the use of the channel-independent orthogonal circulant matrix transform (OCT) precoding to combat the packet loss performance degradation induced by mobility. A mobile user terminal is used to detect the signal from a blue laser placed at 1 m away from the moving track. Various moving speeds (20, 40, 60, and 80  cm/s) and lateral moving distances (30, 40, and 50 cm) of the user terminal are investigated. The effectiveness of the OCT precoding is evaluated by the comparison with the conventional orthogonal frequency division multiplexing (OFDM) scheme and the adaptive-loaded discrete multi-tone (DMT) scheme. Experimental results show that the system performance degrades with the increase in user mobility speed and in moving distance. Furthermore, the OCT precoding provides performance improvement that is superior over that of conventional OFDM schemes, and it exhibits lower packet loss rate than that of adaptive-loaded DMT. No packet loss for 300  Mb/s transmission is achieved with a 30 cm lateral moving distance at 20  cm/s. PMID:27519083

  13. Research on spaceborne low light detection based on EMCCD and CMOS

    NASA Astrophysics Data System (ADS)

    Wu, Xingxing; Liu, Jinguo; Zhou, Huaide; Zhang, Boyan

    2015-10-01

    Electron Multiplying Charge Coupled Device(EMCCD) can realize read out noise of less than 1e- by promoting gain of charges with the charge multiplication principle and is suitable for low light imaging. With the development of back Illuminated CMOS technology CMOS with high quantum efficiency and less than 1.5e- read noise has been developed by Changchun Institute of Optics, Fine Mechanics and Physics(CIOMP). Spaceborne low light detection cameras based on EMCCD CCD201 and based on CMOS were respectively established and system noise models were founded. Low light detection performance as well as principle of spaceborne camera based on EMCCD and spaceborne camera based on CMOS were compared and analyzed. Results of analysis indicated that signal to noise(SNR) of spaceborne low light detection camera based on EMCCD would be 23.78 as radiance at entrance pupil of the camera was as low as 10-9 W/cm2/sr/μm at the focal plane temperature of 20°C. Spaceborne low light detection camera worked in starring mode and the integration time was 2 second. SNR of low light detection camera based on CMOS would be 27.42 under the same conditions. If cooling systems were used and the temperature was lowered from 20°C to -20°C, SNR of low light detection camera based on EMCCD would be improved to 27.533 while SNR of low light detection camera based on CMOS would be improved to 27.79.

  14. GENERIC, COMPONENT FAILURE DATA BASE FOR LIGHT WATER AND LIQUID SODIUM REACTOR PRAs

    SciTech Connect

    S. A. Eide; S. V. Chmielewski; T. D. Swantz

    1990-02-01

    A comprehensive generic component failure data base has been developed for light water and liquid sodium reactor probabilistic risk assessments (PRAs) . The Nuclear Computerized Library for Assessing Reactor Reliability (NUCLARR) and the Centralized Reliability Data Organization (CREDO) data bases were used to generate component failure rates . Using this approach, most of the failure rates are based on actual plant data rather than existing estimates .

  15. Graphene-Based Ultra-Light Batteries for Aircraft

    NASA Technical Reports Server (NTRS)

    Calle, Carlos I.; Kaner, Richard B.

    2014-01-01

    Develop a graphene-based ultracapacitor prototype that is flexible, thin, lightweight, durable, low cost, and safe and that will demonstrate the feasibility for use in aircraft center dot These graphene-based devices store charge on graphene sheets and take advantage of the large accessible surface area of graphene (2,600 m2/g) to increase the electrical energy that can be stored. center dot The proposed devices should have the electrical storage capacity of thin-film-ion batteries but with much shorter charge/discharge cycle times as well as longer lives center dot The proposed devices will be carbon-based and so will not have the same issues with flammability or toxicity as the standard lithium-based storage cells There are two main established methods for the storage and delivery of electrical energy: center dot Batteries - Store energy with electrochemical reactions - High energy densities - Slow charge/discharge cycles - Used in applications requiring large amounts of energy ? aircraft center dot Electrochemical capacitors - Store energy in electrochemical double layers - Fast charge/discharge cycles - Low energy densities - Used in electronics devices - Large capacitors are used in truck engine cranking

  16. Stray light correction for diode-array-based spectrometers using a monochromator.

    PubMed

    Salim, Saber G R; Fox, Nigel P; Hartree, William S; Woolliams, Emma R; Sun, Tong; Grattan, Kenneth T V

    2011-09-10

    Photodiode-array-based spectrometers are increasingly being used in a wide variety of applications. However, the signal measured by this type of instrument often is not what is anticipated by the user and is often subject to contamination from stray light. This paper describes an efficient and low-cost stray light correction approach based on a relatively simple system using a monochromator-based source. The paper further discusses the limitations of using a monochromator instead of a laser, as used by previous researchers, and its impact on the quality of the stray light correction. The reliability and robustness of the stray light correction matrix generated have been studied and are also reported. PMID:21946995

  17. Enhancing the light extraction efficiency of GaN-based LEDs

    NASA Astrophysics Data System (ADS)

    Niu, Pingjuan; Li, Yanling; Li, Xiaoyun; Liu, Hongwei; Tian, Haitao; Gao, Tiecheng; Yang, Guanghua

    2007-11-01

    GaN-based light-emitting diode (LED) has been widely used in recent years, and tremendous progress has been achieved in GaN-based semiconductor materials and relevant process. However, owing to the large refractive index contrast between GaN-based semiconductor materials and air, light can be easily totally internally reflected at the semiconductor/air interface, and the critical angle for light to escape from the semiconductor is small. Therefore, the light extraction efficiency for GaN-based LED is still low and needs improving. Some of the leading approaches to enhance light extraction efficiency of GaN-based LED such as surface texturing or roughening, omnidirectional reflectors, photonic crystals, laser liftoff, transparent electrode, patterned substrate and so on are introduced in detail. For each approach, how the variation in device structure or material improves the light extraction efficiency is analyzed thoroughly. At last, some of mentioned approaches that are promising are evaluated and viewed briefly.

  18. VLC-based indoor location awareness using LED light and image sensors

    NASA Astrophysics Data System (ADS)

    Lee, Seok-Ju; Yoo, Jong-Ho; Jung, Sung-Yoon

    2012-11-01

    Recently, indoor LED lighting can be considered for constructing green infra with energy saving and additionally providing LED-IT convergence services such as visible light communication (VLC) based location awareness and navigation services. For example, in case of large complex shopping mall, location awareness to navigate the destination is very important issue. However, the conventional navigation using GPS is not working indoors. Alternative location service based on WLAN has a problem that the position accuracy is low. For example, it is difficult to estimate the height exactly. If the position error of the height is greater than the height between floors, it may cause big problem. Therefore, conventional navigation is inappropriate for indoor navigation. Alternative possible solution for indoor navigation is VLC based location awareness scheme. Because indoor LED infra will be definitely equipped for providing lighting functionality, indoor LED lighting has a possibility to provide relatively high accuracy of position estimation combined with VLC technology. In this paper, we provide a new VLC based positioning system using visible LED lights and image sensors. Our system uses location of image sensor lens and location of reception plane. By using more than two image sensor, we can determine transmitter position less than 1m position error. Through simulation, we verify the validity of the proposed VLC based new positioning system using visible LED light and image sensors.

  19. Recognition of Banknote Fitness Based on a Fuzzy System Using Visible Light Reflection and Near-infrared Light Transmission Images

    PubMed Central

    Kwon, Seung Yong; Pham, Tuyen Danh; Park, Kang Ryoung; Jeong, Dae Sik; Yoon, Sungsoo

    2016-01-01

    Fitness classification is a technique to assess the quality of banknotes in order to determine whether they are usable. Banknote classification techniques are useful in preventing problems that arise from the circulation of substandard banknotes (such as recognition failures, or bill jams in automated teller machines (ATMs) or bank counting machines). By and large, fitness classification continues to be carried out by humans, and this can cause the problem of varying fitness classifications for the same bill by different evaluators, and requires a lot of time. To address these problems, this study proposes a fuzzy system-based method that can reduce the processing time needed for fitness classification, and can determine the fitness of banknotes through an objective, systematic method rather than subjective judgment. Our algorithm was an implementation to actual banknote counting machine. Based on the results of tests on 3856 banknotes in United States currency (USD), 3956 in Korean currency (KRW), and 2300 banknotes in Indian currency (INR) using visible light reflection (VR) and near-infrared light transmission (NIRT) imaging, the proposed method was found to yield higher accuracy than prevalent banknote fitness classification methods. Moreover, it was confirmed that the proposed algorithm can operate in real time, not only in a normal PC environment, but also in an embedded system environment of a banknote counting machine. PMID:27294940

  20. Recognition of Banknote Fitness Based on a Fuzzy System Using Visible Light Reflection and Near-infrared Light Transmission Images.

    PubMed

    Kwon, Seung Yong; Pham, Tuyen Danh; Park, Kang Ryoung; Jeong, Dae Sik; Yoon, Sungsoo

    2016-01-01

    Fitness classification is a technique to assess the quality of banknotes in order to determine whether they are usable. Banknote classification techniques are useful in preventing problems that arise from the circulation of substandard banknotes (such as recognition failures, or bill jams in automated teller machines (ATMs) or bank counting machines). By and large, fitness classification continues to be carried out by humans, and this can cause the problem of varying fitness classifications for the same bill by different evaluators, and requires a lot of time. To address these problems, this study proposes a fuzzy system-based method that can reduce the processing time needed for fitness classification, and can determine the fitness of banknotes through an objective, systematic method rather than subjective judgment. Our algorithm was an implementation to actual banknote counting machine. Based on the results of tests on 3856 banknotes in United States currency (USD), 3956 in Korean currency (KRW), and 2300 banknotes in Indian currency (INR) using visible light reflection (VR) and near-infrared light transmission (NIRT) imaging, the proposed method was found to yield higher accuracy than prevalent banknote fitness classification methods. Moreover, it was confirmed that the proposed algorithm can operate in real time, not only in a normal PC environment, but also in an embedded system environment of a banknote counting machine. PMID:27294940

  1. Reflected-light-source-based three-dimensional display with high brightness.

    PubMed

    Lv, Guo-Jiao; Wu, Fei; Zhao, Wu-Xiang; Fan, Jun; Zhao, Bai-Chuan; Wang, Qiong-Hua

    2016-05-01

    A reflected-light-source (RLS)-based 3D display is proposed. This display consists of an RLS and a 2D display panel. The 2D display panel is located in front of the RLS. The RLS consists of a light source, a light guide plate (LGP), and a reflection cavity. The light source and the LGP are located in the reflection cavity. Light from the light source can enter into the LGP and reflect continuously in the reflection cavity. The reflection cavity has a series of slits, and light can exit only from these slits. These slits can work as a postpositional parallax barrier, so when they modulate the parallax images on the 2D display, 3D images are formed. Different from the conventional 3D display based on a parallax barrier, this RLS has less optical loss, so it can provide higher brightness. A prototype of this display is developed. Experimental results show that this RLS-based 3D display can provide higher brightness than the conventional one. PMID:27140355

  2. Exploring the performance of indoor localization systems based on VLC-RSSI, including the effect of NLOS components using two light-emitting diode lighting systems

    NASA Astrophysics Data System (ADS)

    Elkarim, Mohammed Abd; Mohammed, Nazmi A.; Aly, Moustafa H.

    2015-10-01

    We analyze the effect of diffuse reflection on indoor localization systems based on visible light communication. The target position is estimated using a received signal strength indication technique. Two lighting systems are considered: distinct and uniform lighting systems. Each utilizes commercially available light-emitting diodes and photodiodes with an illumination level conforming to standards. We introduce a comparative study between the two lighting systems through different transmitter (Tx) and receiver (Rx) essential parameters. The results show that the uniform lighting system achieves less localization error (≤20.43 cm) than a distinct lighting system (≤45.9 cm). The uniform lighting system is well adapted to low-Rx field of view (FOV) and narrow radiation angle (error=1 mm when semiradiation angle=5 deg). In the case of a distinct lighting system, low-Rx FOV is also required, while the Tx semiradiation angle needs to be determined carefully (error≤3.08 cm when semiradiation angle=20 deg). Finally, the uniform lighting system shows flexibility in the process of Tx and Rx designs. A uniform lighting system can utilize Rxs with narrow FOVs (≥8.6 deg), while a distinct lighting system is limited to Rx with a wide FOV (≥53.96 deg).

  3. Comparative Sensitivities of Gravitational Wave Detectors Based on Atom Interferometers and Light Interferometers

    NASA Technical Reports Server (NTRS)

    Baker, John G.; Thorpe, J. I.

    2012-01-01

    We consider a class of proposed gravitational wave detectors based on multiple atomic interferometers separated by large baselines and referenced by common laser systems. We compute the sensitivity limits of these detectors due to intrinsic phase noise of the light sources, non-inertial motion of the light sources, and atomic shot noise and compare them to sensitivity limits for traditional light interferometers. We find that atom interferometers and light interferometers are limited in a nearly identical way by intrinsic phase noise and that both require similar mitigation strategies (e.g. multiple arm instruments) to reach interesting sensitivities. The sensitivity limit from motion of the light sources is slightly different and favors the atom interferometers in the low-frequency limit, although the limit in both cases is severe. Whether this potential advantage outweighs the additional complexity associated with including atom interferometers will require further study.

  4. Comparison of Atom Interferometers and Light Interferometers as Space-Based Gravitational Wave Detectors

    NASA Technical Reports Server (NTRS)

    Baker, John G.

    2012-01-01

    We consider a class of proposed gravitational wave detectors based on multiple atomic interferometers separated by large baselines and referenced by common laser systems. We compute the sensitivity limits of these detectors due to intrinsic phase noise of the light sources, non-inertial motion of the light sources, and atomic shot noise and compare them to sensitivity limits for traditional light interferometers. We find that atom interferometers and light interferometers are limited in a nearly identical way by intrinsic phase noise and that both require similar mitigation strategies (e.g. multiple arm instruments) to reach interesting sensitivities. The sensitivity limit from motion of the light sources is slightly different and favors the atom interferometers in the low-frequency limit, although the limit in both cases is severe.

  5. Comparison of atom interferometers and light interferometers as space-based gravitational wave detectors.

    PubMed

    Baker, John G; Thorpe, J I

    2012-05-25

    We consider a class of proposed gravitational-wave detectors based on multiple atomic interferometers separated by large baselines and referenced by common laser systems. We compute the sensitivity limits of these detectors due to intrinsic phase noise of the light sources, noninertial motion of the light sources, and atomic shot noise and compare them to sensitivity limits for traditional light interferometers. We find that atom interferometers and light interferometers are limited in a nearly identical way by intrinsic phase noise and that both require similar mitigation strategies (e.g., multiple-arm instruments) to reach interesting sensitivities. The sensitivity limit from motion of the light sources is slightly different and, in principle, favors the atom interferometers in the low-frequency limit, although the limit in both cases is severe. PMID:23003235

  6. A Red-Light Running Prevention System Based on Artificial Neural Network and Vehicle Trajectory Data

    PubMed Central

    Li, Pengfei; Li, Yan; Guo, Xiucheng

    2014-01-01

    The high frequency of red-light running and complex driving behaviors at the yellow onset at intersections cannot be explained solely by the dilemma zone and vehicle kinematics. In this paper, the author presented a red-light running prevention system which was based on artificial neural networks (ANNs) to approximate the complex driver behaviors during yellow and all-red clearance and serve as the basis of an innovative red-light running prevention system. The artificial neural network and vehicle trajectory are applied to identify the potential red-light runners. The ANN training time was also acceptable and its predicting accurate rate was over 80%. Lastly, a prototype red-light running prevention system with the trained ANN model was described. This new system can be directly retrofitted into the existing traffic signal systems. PMID:25435870

  7. Light-curing considerations for resin-based composite materials: a review. Part I.

    PubMed

    Malhotra, Neeraj; Mala, Kundabala

    2010-09-01

    There has been a continual advent of improved technologies in dentistry. Among these are the material sciences of resin-based composites (RBCs). Since the introduction of light-cured RBCs, the problem of polymerization shrinkage and the methods used to overcome this have concerned clinicians and researchers. Types of curing light and modes of curing have been shown to affect the degree of polymerization and related shrinkage of RBCs. This review, which is divided into two parts, discusses the contemporary light-curing units. Part I explores the evolution in light-curing units and different curing modes. Part II highlights the clinical considerations regarding light curing of RBCs that are important for achieving optimal curing and maximum polymerization of RBCs in a clinical setting. PMID:20879203

  8. Space-based visible all-reflective stray light telescope

    NASA Astrophysics Data System (ADS)

    Wang, Dexter; Gardner, Leo R.; Wong, Wallace K.; Hadfield, Peter

    1991-08-01

    A 6-inch diameter aperture space-based visible telescope has been optimized to perform surveillance against the space background with earth albedo as a primary source of straylight. A three mirror off-axis anastigmat has been designed to cover a 1.4 degree(s) by 6.6 degree(s) field- of-view with 60 (mu) radian spatial resolution. The telescope body and optics are constructed of 6061-T6 aluminum to provide a thermally stable optical system. The optical elements are 'superfinished' to minimize scatter. Extensive baffles and stops are utilized to further reduce straylight. The telescope will be used on the Midcourse Space Experiment platform.

  9. Massively parallel spatial light modulation-based optical signal processing

    NASA Astrophysics Data System (ADS)

    Li, Yao

    1993-03-01

    A new optical parallel arithmetic processing scheme using a nonholographic optoelectronic content-addressable memory (CAM) was proposed. The design of a four-bit CAM-based optical carry look-ahead adder was studied. Compared with existing optoelectronic binary addition approaches, this nonholographic CAM Scheme offers a number of practical advantages, such as faster processing speed and ease of optical implementation and alignment. For an addition of numbers longer than four bits, by incorporating the previous stage's carry, a number of four-bit CLA's can be cascaded. Experimental results were also demonstrated. One paper to the Optics Letters was published.

  10. Classification and thermal history of petroleum based on light hydrocarbons

    NASA Astrophysics Data System (ADS)

    Thompson, K. F. M.

    1983-02-01

    Classifications of oils and kerogens are described. Two indices are employed, termed the Heptane and IsoheptaneValues, based on analyses of gasoline-range hydrocarbons. The indices assess degree of paraffinicity. and allow the definition of four types of oil: normal, mature, supermature, and biodegraded. The values of these indices measured in sediment extracts are a function of maximum attained temperature and of kerogen type. Aliphatic and aromatic kerogens are definable. Only the extracts of sediments bearing aliphatic kerogens having a specific thermal history are identical to the normal oils which form the largest group (41%) in the sample set. This group was evidently generated at subsurface temperatures of the order of 138°-149°C, (280°-300°F) defined under specific conditions of burial history. It is suggested that all other petroleums are transformation products of normal oils.

  11. IC-BASED CONTROLS FOR ENERGY-EFFICIENT LIGHTING

    SciTech Connect

    Richard Zhang

    2005-03-01

    A new approach for driving high frequency energy saving ballasts is developed and documented in this report. The developed approach utilizes an IC-based platform that provides the benefits of reduced system cost, reduced ballast size, and universal application to a wide range of lamp technologies, such as linear fluorescent lamps (LFL), compact fluorescent lamps (CFL) and high intensity discharge lamps (HID). The control IC chip set developed for the platform includes dual low voltage (LV) IC gate drive that provides gate drive for high and low side power switches in typical ballast circuits, and ballast controller IC that provides control functionalities optimal for different lamps and digital interface for future extension to more sophisticated control and communication.

  12. Automatic illumination compensation device based on a photoelectrochemical biofuel cell driven by visible light.

    PubMed

    Yu, You; Han, Yanchao; Xu, Miao; Zhang, Lingling; Dong, Shaojun

    2016-04-28

    Inverted illumination compensation is important in energy-saving projects, artificial photosynthesis and some forms of agriculture, such as hydroponics. However, only a few illumination adjustments based on self-powered biodetectors that quantitatively detect the intensity of visible light have been reported. We constructed an automatic illumination compensation device based on a photoelectrochemical biofuel cell (PBFC) driven by visible light. The PBFC consisted of a glucose dehydrogenase modified bioanode and a p-type semiconductor cuprous oxide photocathode. The PBFC had a high power output of 161.4 μW cm(-2) and an open circuit potential that responded rapidly to visible light. It adjusted the amount of illumination inversely irrespective of how the external illumination was changed. This rational design of utilizing PBFCs provides new insights into automatic light adjustable devices and may be of benefit to intelligent applications. PMID:27076202

  13. Three-visible-light wave combiner based on photonic crystal waveguides.

    PubMed

    Liu, Dingwen; Sun, Yiling; Ouyang, Zhengbiao

    2014-07-20

    We present a three-visible-light wave combiner based on two-dimensional photonic crystal waveguides whose widths are not integral multiples of the lattice period. The proposed device consists of two cascaded directional couplers. It combines three visible light waves with different wavelengths from three input ports into a single output port. As an example, a combiner for combining light waves of 635, 532, and 488 nm, which are commonly used as the three primary colors in laser display systems, is designed and demonstrated through the finite-difference time-domain method. The results show that the proposed device can perform efficient synthesis for three visible light waves with transmittance exceeding 89% for each wavelength and high ability in preventing the backward coupling of waves from different waveguides. The method for designing the combiner is useful for designing other waveguide couplers based on photonic crystals made of dispersion materials. PMID:25090219

  14. Light controlled drug delivery containers based on spiropyran doped liquid crystal micro spheres

    PubMed Central

    Petriashvili, Gia; Devadze, Lali; Zurabishvili, Tsisana; Sepashvili, Nino; Chubinidze, Ketevan

    2016-01-01

    We have developed a novel, light activated drug delivery containers, based on spiropyran doped liquid crystal micro spheres. Upon exposure to UV/violet light, the spiropyran molecules entrapped inside the nematic liquid crystal micro spheres, interconvert from the hydrophobic, oil soluble form, to the hydrophilic, water soluble merocyanine one, which stimulates the translocation of the merocyanine molecules across the nematic liquid crystal-water barrier and results their homogeneous distribution throughout in an aqueous environment. Light controllable switching property and extremely high solubility of spiropyran in the nematic liquid crystal, promise to elaborate a novel and reliable vehicles for the drug delivery systems. PMID:26977353

  15. Light controlled drug delivery containers based on spiropyran doped liquid crystal micro spheres.

    PubMed

    Petriashvili, Gia; Devadze, Lali; Zurabishvili, Tsisana; Sepashvili, Nino; Chubinidze, Ketevan

    2016-02-01

    We have developed a novel, light activated drug delivery containers, based on spiropyran doped liquid crystal micro spheres. Upon exposure to UV/violet light, the spiropyran molecules entrapped inside the nematic liquid crystal micro spheres, interconvert from the hydrophobic, oil soluble form, to the hydrophilic, water soluble merocyanine one, which stimulates the translocation of the merocyanine molecules across the nematic liquid crystal-water barrier and results their homogeneous distribution throughout in an aqueous environment. Light controllable switching property and extremely high solubility of spiropyran in the nematic liquid crystal, promise to elaborate a novel and reliable vehicles for the drug delivery systems. PMID:26977353

  16. Multilayered Organic Light Emitting Diodes Based on Polyfluorenes

    NASA Astrophysics Data System (ADS)

    Bozano, Luisa; Marsitzky, Dirk; Carter, Kenneth; Swanson, Sally; Lee, Victor; Salem, Jesse; Miller, Robert; Scott, Campbell; Carter, Sue

    2001-03-01

    The electroluminescence of polyfluorene homopolymers and various arylene copolymers is in the deep blue, with peak emission wavelengths as small as 420 nm. These materials are therefore of great interest for use in full-color OLED displays both as emitters for blue subpixels and as hosts for red and green emitting dopants or comonomers. In this work, we compare the properties of single and multilayer diode structures based on dihexyl and di(2-ethylexyl) substituted polyfluorenes. A cross-linkable polymeric arylamine hole transport polymer and/or a polyquinoline electron transport layer are introduced to better balance the charge injection from the electrodes and optimize the recombination in the fluorene emitter layer. External quantum efficiencies increase from about 0.1layer devices to well over 1The electrical and optical response is determined by steady state and transient measurements. The effects on efficiency, emission spectrum and electrical response resulting from the introduction of dopant dyes into the emitter layer are also presented.

  17. SPIM-fluid: open source light-sheet based platform for high-throughput imaging.

    PubMed

    Gualda, Emilio J; Pereira, Hugo; Vale, Tiago; Estrada, Marta Falcão; Brito, Catarina; Moreno, Nuno

    2015-11-01

    Light sheet fluorescence microscopy has recently emerged as the technique of choice for obtaining high quality 3D images of whole organisms/embryos with low photodamage and fast acquisition rates. Here we present an open source unified implementation based on Arduino and Micromanager, which is capable of operating Light Sheet Microscopes for automatized 3D high-throughput imaging on three-dimensional cell cultures and model organisms like zebrafish, oriented to massive drug screening. PMID:26601007

  18. SPIM-fluid: open source light-sheet based platform for high-throughput imaging

    PubMed Central

    Gualda, Emilio J.; Pereira, Hugo; Vale, Tiago; Estrada, Marta Falcão; Brito, Catarina; Moreno, Nuno

    2015-01-01

    Light sheet fluorescence microscopy has recently emerged as the technique of choice for obtaining high quality 3D images of whole organisms/embryos with low photodamage and fast acquisition rates. Here we present an open source unified implementation based on Arduino and Micromanager, which is capable of operating Light Sheet Microscopes for automatized 3D high-throughput imaging on three-dimensional cell cultures and model organisms like zebrafish, oriented to massive drug screening. PMID:26601007

  19. Quantum memory for nonstationary light fields based on controlled reversible inhomogeneous broadening

    SciTech Connect

    Kraus, B.; Tittel, W.; Gisin, N.; Nilsson, M.; Kroell, S.; Cirac, J. I.

    2006-02-15

    We propose a method for efficient storage and recall of arbitrary nonstationary light fields, such as, for instance, single photon time-bin qubits or intense fields, in optically dense atomic ensembles. Our approach to quantum memory is based on controlled, reversible, inhomogeneous broadening and relies on a hidden time-reversal symmetry of the optical Bloch equations describing the propagation of the light field. We briefly discuss experimental realizations of our proposal.

  20. Automatic illumination compensation device based on a photoelectrochemical biofuel cell driven by visible light

    NASA Astrophysics Data System (ADS)

    Yu, You; Han, Yanchao; Xu, Miao; Zhang, Lingling; Dong, Shaojun

    2016-04-01

    Inverted illumination compensation is important in energy-saving projects, artificial photosynthesis and some forms of agriculture, such as hydroponics. However, only a few illumination adjustments based on self-powered biodetectors that quantitatively detect the intensity of visible light have been reported. We constructed an automatic illumination compensation device based on a photoelectrochemical biofuel cell (PBFC) driven by visible light. The PBFC consisted of a glucose dehydrogenase modified bioanode and a p-type semiconductor cuprous oxide photocathode. The PBFC had a high power output of 161.4 μW cm-2 and an open circuit potential that responded rapidly to visible light. It adjusted the amount of illumination inversely irrespective of how the external illumination was changed. This rational design of utilizing PBFCs provides new insights into automatic light adjustable devices and may be of benefit to intelligent applications.Inverted illumination compensation is important in energy-saving projects, artificial photosynthesis and some forms of agriculture, such as hydroponics. However, only a few illumination adjustments based on self-powered biodetectors that quantitatively detect the intensity of visible light have been reported. We constructed an automatic illumination compensation device based on a photoelectrochemical biofuel cell (PBFC) driven by visible light. The PBFC consisted of a glucose dehydrogenase modified bioanode and a p-type semiconductor cuprous oxide photocathode. The PBFC had a high power output of 161.4 μW cm-2 and an open circuit potential that responded rapidly to visible light. It adjusted the amount of illumination inversely irrespective of how the external illumination was changed. This rational design of utilizing PBFCs provides new insights into automatic light adjustable devices and may be of benefit to intelligent applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00759g

  1. Structurally Integrated Photoluminescence-Based Lactate Sensor Using Organic Light Emitting Devices (OLEDs) as the Light Source

    SciTech Connect

    Chengliang Qian

    2006-08-09

    Multianalyte bio(chemical) sensors are extensively researched for monitoring analytes in complex systems, such as blood serum. As a step towards developing such multianalyte sensors, we studied a novel, structurally integrated, organic light emitting device (OLED)-based sensing platform for detection of lactate. Lactate biosensors have attracted numerous research efforts, due to their wide applications in clinical diagnosis, athletic training and food industry. The OLED-based sensor is based on monitoring the oxidation reaction of lactate, which is catalyzed by the lactate oxidase (LOX) enzyme. The sensing component is based on an oxygen-sensitive dye, Platinum octaethyl porphyrin (PtOEP), whose photoluminescence (PL) lifetime {tau} decreases as the oxygen level increases. The PtOEP dye was embedded in a thin film polystyrene (PS) matrix; the LOX was dissolved in solution or immobilized in a sol-gel matrix. {tau} was measured as a function of the lactate concentration; as the lactate concentration increases, {tau} increases due to increased oxygen consumption. The sensors performance is discussed in terms of the detection sensitivity, dynamic range, and response time. A response time of {approx}32 sec was achieved when the LOX was dissolved in solution and kept in a closed cell. Steps towards development of a multianalyte sensor array using an array of individually addressable OLED pixels were also presented.

  2. AlGaInN-based light emitting diodes with a transparent p-contact based on thin ITO films

    SciTech Connect

    Smirnova, I. P. Markov, L. K.; Pavlyuchenko, A. S.; Kukushkin, M. V.

    2012-03-15

    A method for obtaining transparent conductive ITO (indium-tin oxide) films aimed for use in light emitting diodes of the blue spectral range is developed. The peak external quantum efficiency of light-emitting diodes with a p-contact based on the obtained films reaches 25%, while for similar light-emitting diodes with a standard semitransparent metal contact, it is <10%. An observed increase in the direct voltage drop from 3.15 to 3.37 V does not significantly affect the possibility of applying these films in light-emitting diodes since the optical power of light-emitting diodes with a transparent p-contact based on ITO films exceeds that of chips with metal semitransparent p-contacts with a working current of 20 mA by a factor of almost 2.5. Light-emitting diodes with p-contacts based on ITO films successfully withstand a pumping current that exceeds their calculated working current by a factor of 5 without the appearance of any signs of degradation.

  3. Development of Advanced LED Phosphors by Spray-based Processes for Solid State Lighting

    SciTech Connect

    Cabot Corporation

    2007-09-30

    The overarching goal of the project was to develop luminescent materials using aerosol processes for making improved LED devices for solid state lighting. In essence this means improving white light emitting phosphor based LEDs by improvement of the phosphor and phosphor layer. The structure of these types of light sources, displayed in Figure 1, comprises of a blue or UV LED under a phosphor layer that converts the blue or UV light to a broad visible (white) light. Traditionally, this is done with a blue emitting diode combined with a blue absorbing, broadly yellow emitting phosphor such as Y{sub 3}Al{sub 5}O{sub 12}:Ce (YAG). A similar result may be achieved by combining a UV emitting diode and at least three different UV absorbing phosphors: red, green, and blue emitting. These emitted colors mix to make white light. The efficiency of these LEDs is based on the combined efficiency of the LED, phosphor, and the interaction between the two. The Cabot SSL project attempted to improve the over all efficiency of the LED light source be improving the efficiency of the phosphor and the interaction between the LED light and the phosphor. Cabot's spray based process for producing phosphor powders is able to improve the brightness of the powder itself by increasing the activator (the species that emits the light) concentration without adverse quenching effects compared to conventional synthesis. This will allow less phosphor powder to be used, and will decrease the cost of the light source; thus lowering the barrier of entry to the lighting market. Cabot's process also allows for chemical flexibility of the phosphor particles, which may result in tunable emission spectra and so light sources with improved color rendering. Another benefit of Cabot's process is the resulting spherical morphology of the particles. Less light scattering results when spherical particles are used in the phosphor layer (Figure 1) compared to when conventional, irregular shaped phosphor particles

  4. Light interaction in sapphire/MgF2/Al triple-layer omnidirectional reflectors in AlGaN-based near ultraviolet light-emitting diodes

    PubMed Central

    Lee, Keon Hwa; Moon, Yong-Tae; Song, June-O; Kwak, Joon Seop

    2015-01-01

    This study examined systematically the mechanism of light interaction in the sapphire/MgF2/Al triple-layer omnidirectional reflectors (ODR) and its effects on the light output power in near ultraviolet light emitting diodes (NUV-LEDs) with the ODR. The light output power of NUV-LEDs with the triple-layer ODR structure increased with decreasing surface roughness of the sapphire backside in the ODR. Theoretical modeling of the roughened surface suggests that the dependence of the reflectance of the triple-layer ODR structure on the surface roughness can be attributed mainly to light absorption by the Al nano-structures and the trapping of scattered light in the MgF2 layer. Furthermore, the ray tracing simulation based upon the theoretical modeling showed good agreement with the measured reflectance of the ODR structure in diffuse mode. PMID:26010378

  5. A Light Switch Based on Protein S-Nitrosylation Fine-Tunes Photosynthetic Light Harvesting in Chlamydomonas.

    PubMed

    Berger, Hanna; De Mia, Marcello; Morisse, Samuel; Marchand, Christophe H; Lemaire, Stéphane D; Wobbe, Lutz; Kruse, Olaf

    2016-06-01

    Photosynthetic eukaryotes are challenged by a fluctuating light supply, demanding for a modulated expression of nucleus-encoded light-harvesting proteins associated with photosystem II (LHCII) to adjust light-harvesting capacity to the prevailing light conditions. Here, we provide clear evidence for a regulatory circuit that controls cytosolic LHCII translation in response to light quantity changes. In the green unicellular alga Chlamydomonas reinhardtii, the cytosolic RNA-binding protein NAB1 represses translation of certain LHCII isoform mRNAs. Specific nitrosylation of Cys-226 decreases NAB1 activity and could be demonstrated in vitro and in vivo. The less active, nitrosylated form of NAB1 is found in cells acclimated to limiting light supply, which permits accumulation of light-harvesting proteins and efficient light capture. In contrast, elevated light supply causes its denitrosylation, thereby activating the repression of light-harvesting protein synthesis, which is needed to control excitation pressure at photosystem II. Denitrosylation of recombinant NAB1 is efficiently performed by the cytosolic thioredoxin system in vitro. To our knowledge, NAB1 is the first example of stimulus-induced denitrosylation in the context of photosynthetic acclimation. By identifying this novel redox cross-talk pathway between chloroplast and cytosol, we add a new key element required for drawing a precise blue print of the regulatory network of light harvesting. PMID:27208221

  6. Ultra High p-doping Material Research for GaN Based Light Emitters

    SciTech Connect

    Vladimir Dmitriev

    2007-06-30

    The main goal of the Project is to investigate doping mechanisms in p-type GaN and AlGaN and controllably fabricate ultra high doped p-GaN materials and epitaxial structures. Highly doped p-type GaN-based materials with low electrical resistivity and abrupt doping profiles are of great importance for efficient light emitters for solid state lighting (SSL) applications. Cost-effective hydride vapor phase epitaxial (HVPE) technology was proposed to investigate and develop p-GaN materials for SSL. High p-type doping is required to improve (i) carrier injection efficiency in light emitting p-n junctions that will result in increasing of light emitting efficiency, (ii) current spreading in light emitting structures that will improve external quantum efficiency, and (iii) parameters of Ohmic contacts to reduce operating voltage and tolerate higher forward currents needed for the high output power operation of light emitters. Highly doped p-type GaN layers and AlGaN/GaN heterostructures with low electrical resistivity will lead to novel device and contact metallization designs for high-power high efficiency GaN-based light emitters. Overall, highly doped p-GaN is a key element to develop light emitting devices for the DOE SSL program. The project was focused on material research for highly doped p-type GaN materials and device structures for applications in high performance light emitters for general illumination P-GaN and p-AlGaN layers and multi-layer structures were grown by HVPE and investigated in terms of surface morphology and structure, doping concentrations and profiles, optical, electrical, and structural properties. Tasks of the project were successfully accomplished. Highly doped GaN materials with p-type conductivity were fabricated. As-grown GaN layers had concentration N{sub a}-N{sub d} as high as 3 x 10{sup 19} cm{sup -3}. Mechanisms of doping were investigated and results of material studies were reported at several International conferences providing

  7. Reanalysis of the Near-infrared Extragalactic Background Light Based on the IRTS Observations

    NASA Astrophysics Data System (ADS)

    Matsumoto, T.; Kim, M. G.; Pyo, J.; Tsumura, K.

    2015-07-01

    We reanalyze data of the near-infrared background taken by IRTS using up-to-date observational results of zodiacal light (ZL), integrated star light, and diffuse Galactic light. We confirm the existence of residual isotropic emission, which is slightly lower but almost the same as previously reported. At wavelengths longer than 2 μm, the result is fairly consistent with the recent observation with AKARI. We also perform the same analysis using a different ZL model by Wright and detect residual isotropic emission that is slightly lower than that based on the original Kelsall model. Both models show residual isotropic emission that is significantly brighter than the integrated light of galaxies.

  8. A novel autonomous real-time position method based on polarized light and geomagnetic field

    PubMed Central

    Wang, Yinlong; Chu, Jinkui; Zhang, Ran; Wang, Lu; Wang, Zhiwen

    2015-01-01

    Many animals exploit polarized light in order to calibrate their magnetic compasses for navigation. For example, some birds are equipped with biological magnetic and celestial compasses enabling them to migrate between the Western and Eastern Hemispheres. The Vikings' ability to derive true direction from polarized light is also widely accepted. However, their amazing navigational capabilities are still not completely clear. Inspired by birds' and Vikings' ancient navigational skills. Here we present a combined real-time position method based on the use of polarized light and geomagnetic field. The new method works independently of any artificial signal source with no accumulation of errors and can obtain the position and the orientation directly. The novel device simply consists of two polarized light sensors, a 3-axis compass and a computer. The field experiments demonstrate device performance. PMID:25851793

  9. A novel autonomous real-time position method based on polarized light and geomagnetic field

    NASA Astrophysics Data System (ADS)

    Wang, Yinlong; Chu, Jinkui; Zhang, Ran; Wang, Lu; Wang, Zhiwen

    2015-04-01

    Many animals exploit polarized light in order to calibrate their magnetic compasses for navigation. For example, some birds are equipped with biological magnetic and celestial compasses enabling them to migrate between the Western and Eastern Hemispheres. The Vikings' ability to derive true direction from polarized light is also widely accepted. However, their amazing navigational capabilities are still not completely clear. Inspired by birds' and Vikings' ancient navigational skills. Here we present a combined real-time position method based on the use of polarized light and geomagnetic field. The new method works independently of any artificial signal source with no accumulation of errors and can obtain the position and the orientation directly. The novel device simply consists of two polarized light sensors, a 3-axis compass and a computer. The field experiments demonstrate device performance.

  10. A novel autonomous real-time position method based on polarized light and geomagnetic field.

    PubMed

    Wang, Yinlong; Chu, Jinkui; Zhang, Ran; Wang, Lu; Wang, Zhiwen

    2015-01-01

    Many animals exploit polarized light in order to calibrate their magnetic compasses for navigation. For example, some birds are equipped with biological magnetic and celestial compasses enabling them to migrate between the Western and Eastern Hemispheres. The Vikings' ability to derive true direction from polarized light is also widely accepted. However, their amazing navigational capabilities are still not completely clear. Inspired by birds' and Vikings' ancient navigational skills. Here we present a combined real-time position method based on the use of polarized light and geomagnetic field. The new method works independently of any artificial signal source with no accumulation of errors and can obtain the position and the orientation directly. The novel device simply consists of two polarized light sensors, a 3-axis compass and a computer. The field experiments demonstrate device performance. PMID:25851793

  11. Light-curing considerations for resin-based composite materials: a review. Part II.

    PubMed

    Malhotra, Neeraj; Mala, Kundabala

    2010-10-01

    As discussed in Part I, the type of curing light and curing mode impact the polymerization kinetics of resin-based composite (RBC) materials. Major changes in light-curing units and curing modes have occurred. The type of curing light and mode employed affects the polymerization shrinkage and associated stresses, microhardness, depth of cure, degree of conversion, and color change of RBCs. These factors also may influence the microleakage in an RBC restoration. Apart from the type of unit and mode used, the polymerization of RBCs is also affected by how a light-curing unit is used and handled, as well as the aspects associated with RBCs and the environment. Part II discusses the various clinical issues that should be considered while curing RBC restorations in order to achieve the best possible outcome. PMID:20960988

  12. Comparative efficiency analysis of GaN-based light-emitting diodes and laser diodes

    NASA Astrophysics Data System (ADS)

    Piprek, Joachim

    2016-07-01

    Nobel laureate Shuji Nakamura predicted in 2014 that GaN-based laser diodes are the future of solid state lighting. However, blue GaN-lasers still exhibit less than 40% wall-plug efficiency, while some GaN-based blue light-emitting diodes exceed 80%. This paper investigates non-thermal reasons behind this difference. The inherently poor hole conductivity of the Mg-doped waveguide cladding layer of laser diodes is identified as main reason for their low electrical-to-optical energy conversion efficiency.

  13. Method to produce nanocrystalline powders of oxide-based phosphors for lighting applications

    DOEpatents

    Loureiro, Sergio Paulo Martins; Setlur, Anant Achyut; Williams, Darryl Stephen; Manoharan, Mohan; Srivastava, Alok Mani

    2007-12-25

    Some embodiments of the present invention are directed toward nanocrystalline oxide-based phosphor materials, and methods for making same. Typically, such methods comprise a steric entrapment route for converting precursors into such phosphor material. In some embodiments, the nanocrystalline oxide-based phosphor materials are quantum splitting phosphors. In some or other embodiments, such nanocrystalline oxide based phosphor materials provide reduced scattering, leading to greater efficiency, when used in lighting applications.

  14. Generic component failure data base for light water and liquid sodium reactor PRAs (probabilistic risk assessments)

    SciTech Connect

    Eide, S.A.; Chmielewski, S.V.; Swantz, T.D.

    1990-02-01

    A comprehensive generic component failure data base has been developed for light water and liquid sodium reactor probabilistic risk assessments (PRAs). The Nuclear Computerized Library for Assessing Reactor Reliability (NUCLARR) and the Centralized Reliability Data Organization (CREDO) data bases were used to generate component failure rates. Using this approach, most of the failure rates are based on actual plant data rather than existing estimates. 21 refs., 9 tabs.

  15. Light-based therapy on wound healing : a review

    NASA Astrophysics Data System (ADS)

    Pik Suan, Lau; Bidin, Noriah; Cherng, Chong Jia; Hamid, Asmah

    2014-08-01

    Wound healing is a complex matrix and overlapping process. In order to accelerate the healing process and minimize bacterial infection, light-based therapy was applied to stimulate bio-reaction to improve healing. The aim of this paper is to review the effects induced by light source (laser and incoherent light like LED) on different biological targets. The light-based therapy techniques were categorized according to the wavelength, energy density, type of irradiance and activity of tissues in the healing process. Out of 80 cases, 77% were animal studies, 5% were human studies and 18% were cell studies. Around 75% of light-based therapy has an advantage on tissue interaction and 25% has no effect or inhibition on the healing process. The appropriate dose appears to be between 1 and 5 J cm-2. At shorter wavelength, photobiostimulation would be effective with a high frequently administrated low-energy dose. On the other hand, for longer wavelength it is the reverse, i.e., more effective with a low frequent treated schedule and a high-energy dose.

  16. Laser and Light-based Treatment of Keloids – A Review

    PubMed Central

    Mamalis, A.D.; Lev-Tov, H.; Nguyen, D.H.; Jagdeo, J.R.

    2015-01-01

    Keloids are an overgrowth of fibrotic tissue outside the original boundaries of an injury and occur secondary to defective wound healing. Keloids often have a functional, aesthetic, or psychosocial impact on patients as highlighted by quality-of-life studies. Our goal is to provide clinicians and scientists an overview of the data available on laser and light-based therapies for treatment of keloids, and highlight emerging light-based therapeutic technologies and the evidence available to support their use. We employed the following search strategy to identify the clinical evidence reported in the biomedical literature: in November 2012, we searched PubMed.gov, Ovid MEDLINE, Embase, and Cochrane Reviews (1980-present) for published randomized clinical trials, clinical studies, case series, and case reports related to the treatment of keloids. The search terms we utilized were ‘keloid(s)’ AND ‘laser’ OR ‘light-emitting diode’ OR ‘photodynamic therapy’ OR ‘intense pulsed light’ OR ‘low level light’ OR ‘phototherapy.’ Our search yielded 347 unique articles. Of these, 33 articles met our inclusion and exclusion criteria. We qualitatively conclude that laser and light-based treatment modalities may achieve favorable patient outcomes. Clinical studies using CO2 laser are more prevalent in current literature and a combination regimen may be an adequate ablative approach. Adding light-based treatments, such as LED phototherapy or photodynamic therapy, to laser treatment regimens may enhance patient outcomes. Lasers and other light-based technology have introduced new ways to manage keloids that may result in improved aesthetic and symptomatic outcomes and decreased keloid recurrence. PMID:24033440

  17. Recent Progress in Quantum Dot Based White Light-Emitting Devices.

    PubMed

    Su, Liang; Zhang, Xiaoyu; Zhang, Yu; Rogach, Andrey L

    2016-08-01

    Colloidal semiconductor quantum dots (QDs) have been widely employed as components of white light-emitting diodes (WLEDs) due to their excellent optical properties (highly saturated emission color, high luminescence quantum yield) as well as thermal and chemical stability. Much effort has been devoted to realize efficient QD-based WLEDs, including the synthesis of superior luminescent nanomaterials with excellent stabilities, and the design of advanced devices structures. In this paper, after introducing photometric parameters of the contemporary QD-based WLEDs, we highlight the recent progress in these devices grouped according to three main mechanisms for white light generation: optical excitation, direct charge carrier injection, and Förster resonance energy transfer. The methods to generate white light, the design of QD emitters and QD-based devices, as well as their fabrication techniques are considered, and the key scientific and technological challenges in the QD-based WLEDs are highlighted. Novel light-emitting materials for WLEDs such as carbon-based nanoparticles are also considered. PMID:27573394

  18. Angle-resolved light scattering of individual rod-shaped bacteria based on Fourier transform light scattering

    PubMed Central

    Jo, YoungJu; Jung, JaeHwang; Lee, Jee Woong; Shin, Della; Park, HyunJoo; Nam, Ki Tae; Park, Ji-Ho; Park, YongKeun

    2014-01-01

    Two-dimensional angle-resolved light scattering maps of individual rod-shaped bacteria are measured at the single-cell level. Using quantitative phase imaging and Fourier transform light scattering techniques, the light scattering patterns of individual bacteria in four rod-shaped species (Bacillus subtilis, Lactobacillus casei, Synechococcus elongatus, and Escherichia coli) are measured with unprecedented sensitivity in a broad angular range from −70° to 70°. The measured light scattering patterns are analyzed along the two principal axes of rod-shaped bacteria in order to systematically investigate the species-specific characteristics of anisotropic light scattering. In addition, the cellular dry mass of individual bacteria is calculated and used to demonstrate that the cell-to-cell variations in light scattering within bacterial species is related to the cellular dry mass and growth. PMID:24867385

  19. Angle-resolved light scattering of individual rod-shaped bacteria based on Fourier transform light scattering

    NASA Astrophysics Data System (ADS)

    Jo, Youngju; Jung, Jaehwang; Lee, Jee Woong; Shin, Della; Park, Hyunjoo; Nam, Ki Tae; Park, Ji-Ho; Park, Yongkeun

    2014-05-01

    Two-dimensional angle-resolved light scattering maps of individual rod-shaped bacteria are measured at the single-cell level. Using quantitative phase imaging and Fourier transform light scattering techniques, the light scattering patterns of individual bacteria in four rod-shaped species (Bacillus subtilis, Lactobacillus casei, Synechococcus elongatus, and Escherichia coli) are measured with unprecedented sensitivity in a broad angular range from -70° to 70°. The measured light scattering patterns are analyzed along the two principal axes of rod-shaped bacteria in order to systematically investigate the species-specific characteristics of anisotropic light scattering. In addition, the cellular dry mass of individual bacteria is calculated and used to demonstrate that the cell-to-cell variations in light scattering within bacterial species is related to the cellular dry mass and growth.

  20. Indoor anti-occlusion visible light positioning systems based on particle filtering

    NASA Astrophysics Data System (ADS)

    Jiang, Meng; Huang, Zhitong; Li, Jianfeng; Zhang, Ruqi; Ji, Yuefeng

    2015-04-01

    As one of the most popular categories of mobile services, a rapid growth of indoor location-based services has been witnessed over the past decades. Indoor positioning methods based on Wi-Fi, radio-frequency identification or Bluetooth are widely commercialized; however, they have disadvantages such as low accuracy or high cost. An emerging method using visible light is under research recently. The existed visible light positioning (VLP) schemes using carrier allocation, time allocation and multiple receivers all have limitations. This paper presents a novel mechanism using particle filtering in VLP system. By this method no additional devices are needed and the occlusion problem in visible light would be alleviated which will effectively enhance the flexibility for indoor positioning.

  1. Detection of UV light based on chemically stimulated luminescence of crystal phosphors

    NASA Astrophysics Data System (ADS)

    Grankin, D. V.; Grankin, V. P.; Martysh, M. A.

    2016-06-01

    High-efficiency accommodation of heterogeneous-reaction energy via an electronic channel and the possibility of using this effect to design an ionizing (UV) radiation detector based on chemically stimulated luminescence have been investigated. Preliminary irradiation of a ZnS sample by UV light is found to cause a luminescence flash under subsequent exposure of the sample surface to a flux of hydrogen atoms. The flash intensity depends on the UV excitation level and increases by several orders of magnitude in comparison with an unirradiated sample. It is shown that a new method for detecting UV light using chemically stimulated luminescence of crystal phosphors accumulating light yield can be developed based on this effect.

  2. Capacity analyze of WDM indoor visible light communication based on LED for standard illumination

    NASA Astrophysics Data System (ADS)

    Huang, Heqing; Tang, Yi; Cui, Lu; Zhu, Qingwei; Luo, Jiabin

    2015-08-01

    For indoor visible light communication (VLC) systems aim to achieve communication and illumination simultaneously, the channel capacity are significantly affected by illumination demands in actual scenarios. To enhance the system performance, the wavelength division multiplex (WDM) technique can be introduced. In this letter, we analyzed the demands of illuminance and chromaticity's influence on indoor WDM visible light communication system based on color light emitting diodes (LED). The spectra distribution, crosstalk and noise of WDM VLC system were analyzed and the relative optimal total channel capacity was obtained by optimizing the number of sub-channels and their intensity at standard illumination scenario. It's shown that by applying WDM technique, the total channel capacity of LED based VLC system can be about 4 times than the situation of single sub-channel, even with indoor illumination constraints. What's more, the system performance can be improved by adjusting appropriate number of sub-channels and their intensity accordingly.

  3. Tailoring the chirality of light emission with spherical Si-based antennas.

    PubMed

    Zambrana-Puyalto, Xavier; Bonod, Nicolas

    2016-05-21

    Chirality of light is of fundamental importance in several enabling technologies with growing applications in life sciences, chemistry and photodetection. Recently, some attention has been focused on chiral quantum emitters. Consequently, optical antennas which are able to tailor the chirality of light emission are needed. Spherical nanoresonators such as colloids are of particular interest to design optical antennas since they can be synthesized at a large scale and they exhibit good optical properties. Here, we show that these colloids can be used to tailor the chirality of a chiral emitter. To this purpose, we derive an analytic formalism to model the interaction between a chiral emitter and a spherical resonator. We then compare the performances of metallic and dielectric spherical antennas to tailor the chirality of light emission. It is seen that, due to their strong electric dipolar response, metallic spherical nanoparticles spoil the chirality of light emission by yielding achiral fields. In contrast, thanks to the combined excitation of electric and magnetic modes, dielectric Si-based particles feature the ability to inhibit or to boost the chirality of light emission. Finally, it is shown that dual modes in dielectric antennas preserve the chirality of light emission. PMID:27141982

  4. Photocapacitive light sensor based on metal-YMnO3-insulator-semiconductor structures

    NASA Astrophysics Data System (ADS)

    Bogusz, A.; Choudhary, O. S.; Skorupa, I.; Bürger, D.; Lawerenz, A.; Lei, Y.; Zeng, H.; Abendroth, B.; Stöcker, H.; Schmidt, O. G.; Schmidt, H.

    2016-02-01

    Technology of light sensors, due to the wide range of applications, is a dynamically developing branch of both science and industry. This work presents concept of photodetectors based on a metal-ferroelectric-insulator-semiconductor, a structure which has not been thoroughly explored in the field of photodetectors. Functionality of the presented light sensor exploits the effects of photocapacitive phenomena, ferroelectric polarization, and charge trapping. This is accomplished by an interplay between polarization alignment, subsequent charge distribution, and charge trapping processes under given illumination condition and gate voltage. Change of capacitance serves as a read out parameter indicating the wavelength and intensity of the illuminating light. The operational principle of the proposed photocapacitive light sensor is demonstrated in terms of capacitance-voltage and capacitance-time characteristics of an Al/YMnO3/SiNx/p-Si structure exposed to green, red, and near infrared light. Obtained results are discussed in terms of optical properties of YMnO3 and SiNx layers contributing to the performance of photodetectors. Presented concept of light sensing might serve as the basis for the development of more advanced photodetectors.

  5. Highly Transparent, Visible-Light Photodetector Based on Oxide Semiconductors and Quantum Dots.

    PubMed

    Shin, Seung Won; Lee, Kwang-Ho; Park, Jin-Seong; Kang, Seong Jun

    2015-09-01

    Highly transparent phototransistors that can detect visible light have been fabricated by combining indium-gallium-zinc oxide (IGZO) and quantum dots (QDs). A wide-band-gap IGZO film was used as a transparent semiconducting channel, while small-band-gap QDs were adopted to absorb and convert visible light to an electrical signal. Typical IGZO thin-film transistors (TFTs) did not show a photocurrent with illumination of visible light. However, IGZO TFTs decorated with QDs showed enhanced photocurrent upon exposure to visible light. The device showed a responsivity of 1.35×10(4) A/W and an external quantum efficiency of 2.59×10(4) under illumination by a 635 nm laser. The origin of the increased photocurrent in the visible light was the small band gap of the QDs combined with the transparent IGZO films. Therefore, transparent phototransistors based on IGZO and QDs were fabricated and characterized in detail. The result is relevant for the development of highly transparent photodetectors that can detect visible light. PMID:26293387

  6. Moisture-insensitive optical fingerprint scanner based on polarization resolved in-finger scattered light.

    PubMed

    Back, Seon-Woo; Lee, Yong-Geon; Lee, Sang-Shin; Son, Geun-Sik

    2016-08-22

    A moisture-insensitive optical fingerprint scanner (FPS) that is based on polarization resolved in-finger light is proposed and realized. Incident visible light, which is selectively fed to a fingerprint sample via a polarization beam splitter (PBS), is deemed to be partially scattered backward by tissues associated with the skin of the finger. The backscattered light is mostly index-guided in the ridge comprising the fingerprint, which has a higher refractive index, and is drastically dispersed in the valley, which is typically filled with water or air and so has a lower index. However, when light reflects directly off the surface of the finger skin, it fundamentally prevents the scanned image from being determined. The proposed FPS produces bright and dark intensity patterns that are alternately created on the surface of the PBS and correspond to the ridges and valleys, respectively. Thus, this method can especially distinguish between a fake synthetic fingerprint and a genuine fingerprint due to its use of in-finger scattered light. The scanner has been rigorously designed by carrying out ray-optic simulations depending on the wavelength, with tissue-induced scattering taken into account. The device was constructed by incorporating a wire-grid type PBS in conjunction with visible LED sources, including blue, green and red. The scanner adopting a blue LED, which exhibits the strongest light scattering, resulted in the best fingerprint image, enabling enhanced fidelity under the wet and dry situations. Finally, a fake synthetic fingerprint could be successfully discriminated. PMID:27557199

  7. Tailoring the chirality of light emission with spherical Si-based antennas

    NASA Astrophysics Data System (ADS)

    Zambrana-Puyalto, Xavier; Bonod, Nicolas

    2016-05-01

    Chirality of light is of fundamental importance in several enabling technologies with growing applications in life sciences, chemistry and photodetection. Recently, some attention has been focused on chiral quantum emitters. Consequently, optical antennas which are able to tailor the chirality of light emission are needed. Spherical nanoresonators such as colloids are of particular interest to design optical antennas since they can be synthesized at a large scale and they exhibit good optical properties. Here, we show that these colloids can be used to tailor the chirality of a chiral emitter. To this purpose, we derive an analytic formalism to model the interaction between a chiral emitter and a spherical resonator. We then compare the performances of metallic and dielectric spherical antennas to tailor the chirality of light emission. It is seen that, due to their strong electric dipolar response, metallic spherical nanoparticles spoil the chirality of light emission by yielding achiral fields. In contrast, thanks to the combined excitation of electric and magnetic modes, dielectric Si-based particles feature the ability to inhibit or to boost the chirality of light emission. Finally, it is shown that dual modes in dielectric antennas preserve the chirality of light emission.

  8. The numerical simulation and goniometric measurements of cells light scattering based on Mie theory

    NASA Astrophysics Data System (ADS)

    Lin, Xiaogang; Ye, Changbin; Zhu, Hao; Li, Wenchao; Wu, Jie

    2015-10-01

    Optical diagnostic technique, due to its rapid and non-invasive for the diagnosis diseases at the cellular level, can be performed in vivo and allow for real-time diagnosis. While light scattering method is capable of characterizing the structural properties of tissue at the cellular and subcellular scale. In this paper, the spherical models of cells light scattering were established based on Mie, and the distribution curves of scattering intensity in the range of 0~180 degrees were got to explore change rule of cells light scattering information at the molecular level. Also, a platform for experiments used to measure the light scattering information of cells was built to get the change rule of cells light scattering information in wide angular range. And the particle size distribution (PSD) of cells was got by the inversion algorithm. A comparative analysis between numerical simulation and goniometric measurements revealed that the forward-scattering and side-scattering were influenced by the particle size of cells and relative index of refraction between cells and surrounding media. It could also be concluded that it was necessary to get and analyze the light scattering information of larger scattering angle range, which may be related to the intracellular organelles and nucleus.

  9. Effect of LED-LCU light irradiance distribution on mechanical properties of resin based materials.

    PubMed

    Magalhães Filho, T R; Weig, K M; Costa, M F; Werneck, M M; Barthem, R B; Costa Neto, C A

    2016-06-01

    The objective of this study is to analyze the light power distribution along the tip end of the light guide of three LED-LCUs (Light Curing Units) and to evaluate its effect on the mechanical properties of a polymer based dental composite. Firstly, the light power distribution over the whole area of LED-LCU light guide surface was analyzed by three methods: visual projection observation, spectral measurement and optical spectral analysis (OSA). The light power distribution and the total irradiance were different for the three LEDs used, but the wavelength was within the camphorquinone absorption spectrum. The use of a blank sheet was quite on hand to make a qualitative analysis of a beam, and it is costless. Secondly, specimens of a hybrid composite with approximately 8mm diameter and 2mm thickness were produced and polymerized by 20s exposition time to each LED-LCU. Thirdly, the elastic modulus (E) and hardness (HV) were measured throughout the irradiated area by instrumented micro-indentation test (IIT), allowing to correlate localized power and mechanical properties. Both E and HV showed to be very sensitive to local power and wavelength dependent, but they followed the beam power profile. It was also shown that the mechanical properties could be directly correlated to the curing process. Very steep differences in mechanical properties over very short distances may impair the material performance, since residual stresses can easily be built over it. PMID:27040223

  10. Hybrid light transport model based bioluminescence tomography reconstruction for early gastric cancer detection

    NASA Astrophysics Data System (ADS)

    Chen, Xueli; Liang, Jimin; Hu, Hao; Qu, Xiaochao; Yang, Defu; Chen, Duofang; Zhu, Shouping; Tian, Jie

    2012-03-01

    Gastric cancer is the second cause of cancer-related death in the world, and it remains difficult to cure because it has been in late-stage once that is found. Early gastric cancer detection becomes an effective approach to decrease the gastric cancer mortality. Bioluminescence tomography (BLT) has been applied to detect early liver cancer and prostate cancer metastasis. However, the gastric cancer commonly originates from the gastric mucosa and grows outwards. The bioluminescent light will pass through a non-scattering region constructed by gastric pouch when it transports in tissues. Thus, the current BLT reconstruction algorithms based on the approximation model of radiative transfer equation are not optimal to handle this problem. To address the gastric cancer specific problem, this paper presents a novel reconstruction algorithm that uses a hybrid light transport model to describe the bioluminescent light propagation in tissues. The radiosity theory integrated with the diffusion equation to form the hybrid light transport model is utilized to describe light propagation in the non-scattering region. After the finite element discretization, the hybrid light transport model is converted into a minimization problem which fuses an l1 norm based regularization term to reveal the sparsity of bioluminescent source distribution. The performance of the reconstruction algorithm is first demonstrated with a digital mouse based simulation with the reconstruction error less than 1mm. An in situ gastric cancer-bearing nude mouse based experiment is then conducted. The primary result reveals the ability of the novel BLT reconstruction algorithm in early gastric cancer detection.

  11. Influence of light-curing mode on the cytotoxicity of resin-based surface sealants

    PubMed Central

    2014-01-01

    Background Surface sealants have been successfully used in the prevention of erosive tooth wear. However, when multiple tooth surfaces should be sealed, the light-curing procedure is very time-consuming. Therefore, the aim of this study was to investigate whether reduced light-curing time (while maintaining similar energy density) has an influence on resin-based surface sealant cytotoxicity. Methods Bovine dentine discs were treated as follows: group 1: untreated, groups 2–5: Seal&Protect and groups 6–9: experimental sealer. Groups 2 and 6 were light-cured (VALO LED light-curing device) for 40 s (1000 mW/cm2), groups 3 and 7 for 10 s (1000 mW/cm2), groups 4 and 8 for 7 s (1400 mW/cm2) and groups 5 and 9 for 3 s (3200 mW/cm2). Later, materials were extracted in culture medium for 24 h, and released lactate dehydrogenase (LDH) activity as a measure of cytotoxicity was determined photometrically after cells (dental pulp cells and gingival fibroblasts) were exposed to the extracts for 24 h. Three independent experiments, for both sample preparation and cytotoxicity testing, were performed. Results Overall, lowest cytotoxicity was observed for the unsealed control group. No significant influence of light-curing settings on the cytotoxicity was observed (p = 0.537 and 0.838 for pulp cells and gingival fibroblasts, respectively). No significant difference in the cytotoxicity of the two sealants was observed after light-curing with same light-curing settings (group 2 vs. 6, 3 vs. 7, 4 vs. 8 and 5 vs. 9: p > 0.05, respectively). Conclusions Shortening the light-curing time, while maintaining constant energy density, resulted in no higher cytotoxicity of the investigated sealants. PMID:24885810

  12. Lighting: Green Light.

    ERIC Educational Resources Information Center

    Maniccia, Dorine

    2003-01-01

    Explains that by using sustainable (green) building practices, schools and universities can make their lighting systems more efficient, noting that embracing green design principles can help schools attract students. Discusses lighting-control technologies (occupancy sensing technology, daylighting technology, and scheduling based technologies),…

  13. Exploring light rain in the trades as observed by satellite- and ground-based remote sensing

    NASA Astrophysics Data System (ADS)

    Burdanowitz, Jörg; Nuijens, Louise; Klepp, Christian; Stevens, Bjorn

    2013-04-01

    Satellite climatologies are usually expected to have difficulties to properly capture light rain from shallow marine clouds due to limited spatiotemporal resolution. In order to evaluate this, ground-based radar data from the RICO (Rain in Cumulus clouds over the Ocean) campaign is compared with rainfall estimates of three different satellite climatologies over the subtropical North Atlantic. In particular, these satellite products are the Hamburg Ocean Atmosphere Parameters and fluxes from Satellite data (HOAPS), the Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA) and the Global Precipitation Climatology Project (GPCP). Different footprint sizes and temporal resolutions among the used satellite products require an up-scaling of the data to facilitate a fair comparison. Apart from that, recent micro rain radar data from the Barbados Cloud Observatory (BCO) is analyzed to further explore the nature of light rain over the subtropical ocean at a higher temporal resolution. In the trades, the dominance of light rain, i.e. low rain intensities, is ubiquitous as previously observed in several field studies. However, some of them even seem to be conservative in their estimation of light rain contribution to total rainfall according to recent BCO measurements. For active and passive satellite sensors the light rain detection still remains a challenging task. However, as main result, satellite products showed to be partly able to resolve light rain events from shallow clouds during RICO. HOAPS detects most and GPCP least of them while TMPA performs similarly to HOAPS. But along a mean trade-wind trajectory starting at the Canaries, TMPA detects less light rainfall compared to HOAPS, especially in the Caribbean region. Currently collected ship-based rain data sets will be used to further evaluate the performance of HOAPS and TMPA over larger areas of the subtropical Atlantic.

  14. SearchLight: a freely available web-based quantitative spectral analysis tool (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Prabhat, Prashant; Peet, Michael; Erdogan, Turan

    2016-03-01

    In order to design a fluorescence experiment, typically the spectra of a fluorophore and of a filter set are overlaid on a single graph and the spectral overlap is evaluated intuitively. However, in a typical fluorescence imaging system the fluorophores and optical filters are not the only wavelength dependent variables - even the excitation light sources have been changing. For example, LED Light Engines may have a significantly different spectral response compared to the traditional metal-halide lamps. Therefore, for a more accurate assessment of fluorophore-to-filter-set compatibility, all sources of spectral variation should be taken into account simultaneously. Additionally, intuitive or qualitative evaluation of many spectra does not necessarily provide a realistic assessment of the system performance. "SearchLight" is a freely available web-based spectral plotting and analysis tool that can be used to address the need for accurate, quantitative spectral evaluation of fluorescence measurement systems. This tool is available at: http://searchlight.semrock.com/. Based on a detailed mathematical framework [1], SearchLight calculates signal, noise, and signal-to-noise ratio for multiple combinations of fluorophores, filter sets, light sources and detectors. SearchLight allows for qualitative and quantitative evaluation of the compatibility of filter sets with fluorophores, analysis of bleed-through, identification of optimized spectral edge locations for a set of filters under specific experimental conditions, and guidance regarding labeling protocols in multiplexing imaging assays. Entire SearchLight sessions can be shared with colleagues and collaborators and saved for future reference. [1] Anderson, N., Prabhat, P. and Erdogan, T., Spectral Modeling in Fluorescence Microscopy, http://www.semrock.com (2010).

  15. Simplification of a light-based model for estimating final internode length in greenhouse cucumber canopies

    PubMed Central

    Kahlen, Katrin; Stützel, Hartmut

    2011-01-01

    Background and Aims Light quantity and quality affect internode lengths in cucumber (Cucumis sativus), whereby leaf area and the optical properties of the leaves mainly control light quality within a cucumber plant community. This modelling study aimed at providing a simple, non-destructive method to predict final internode lengths (FILs) using light quantity and leaf area data. Methods Several simplifications of a light quantity and quality sensitive model for estimating FILs in cucumber have been tested. The direct simplifications substitute the term for the red : far-red (R : FR) ratios, by a term for (a) the leaf area index (LAI, m2 m−2) or (b) partial LAI, the cumulative leaf area per m2 ground, where leaf area per m2 ground is accumulated from the top of each plant until a number, n, of leaves per plant is reached. The indirect simplifications estimate the input R : FR ratio based on partial leaf area and plant density. Key Results In all models, simulated FILs were in line with the measured FILs over various canopy architectures and light conditions, but the prediction quality varied. The indirect simplification based on leaf area of ten leaves revealed the best fit with measured data. Its prediction quality was even higher than of the original model. Conclusions This study showed that for vertically trained cucumber plants, leaf area data can substitute local light quality data for estimating FIL data. In unstressed canopies, leaf area over the upper ten ranks seems to represent the feedback of the growing architecture on internode elongation with respect to light quality. This highlights the role of this domain of leaves as the primary source for the specific R : FR signal controlling the final length of an internode and could therefore guide future research on up-scaling local processes to the crop level. PMID:21642233

  16. An azobenzene-based photochromic liquid crystalline amphiphile for a remote-controllable light shutter.

    PubMed

    Kim, Dae-Yoon; Lee, Sang-A; Kim, Huisu; Min Kim, Soo; Kim, Namil; Jeong, Kwang-Un

    2015-07-14

    By considering intramolecular conformations and intermolecular interactions, an azobenzene-based photochromic liquid crystalline amphiphile is synthesized for demonstrating a remote-controllable light shutter by the photo-induced isothermal phase transition between the highly ordered crystal phase and the isotropic liquid phase. PMID:26067781

  17. Methods for gully characterization in agricultural croplands using ground-based light detection and ranging

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Gullies constitute an important source of sediment from agricultural fields. In order to properly understand gully formation and evolution over time, as well as, sediment yield, detailed topographic representations of agricultural fields are required. New technologies such as ground-based Light Dete...

  18. Light-induced resistive switching in silicon-based metal-insulator-semiconductor structures

    NASA Astrophysics Data System (ADS)

    Tikhov, S. V.; Gorshkov, O. N.; Koryazhkina, M. N.; Antonov, I. N.; Kasatkin, A. P.

    2016-05-01

    We have studied light-induced resistive switching in metal-insulator-semiconductor structures based on silicon covered with a tunneling-thin SiO2 layer and nanometer-thick layer of antimony. The role of an insulator was played by yttria-stabilized zirconia.

  19. Calibration method for line-structured light vision sensor based on a single ball target

    NASA Astrophysics Data System (ADS)

    Liu, Zhen; Li, Xiaojing; Li, Fengjiao; Zhang, Guangjun

    2015-06-01

    Profile feature imaging for ball targets is unaffected by the position of the target. On this basis, this study proposes a method for the rapid calibration of a line-structured light system based on a single ball target. The calibration process is as follows: the ball target is placed at least once and is illuminated by the light stripe from the laser projector. The vision sensor captures an image of this target. The laser stripe and profile images of the ball target are then extracted. Based on these extracted features and the optical centre of the camera, the spatial equations of the ball target and a cone profile are calculated. The plane on which the intersection line of the two equations lies is the light plane. Finally, the optimal solution for the light plane equation is obtained through nonlinear optimization under a maximum likelihood criterion. The validity of the proposed method is demonstrated through simulation and physical experiments. In the physical experiment, the field of view of the structured light vision sensor measures 300 mm×250 mm. A calibration accuracy of 0.04 mm can be achieved using the proposed method. This accuracy is comparable to that of the calibration method which utilizes planar targets.

  20. Development of White-Light Emitting Active Layers in Nitride Based Heterostructures for Phosphorless Solid State Lighting

    SciTech Connect

    Jan Talbot; Kailash Mishra

    2007-12-31

    This report provides a summary of research activities carried out at the University of California, San Diego and Central Research of OSRAM SYLVANIA in Beverly, MA partially supported by a research contract from US Department of Energy, DE-FC26-04NT422274. The main objective of this project was to develop III-V nitrides activated by rare earth ions, RE{sup 3+}, which could eliminate the need for phosphors in nitride-based solid state light sources. The main idea was to convert electron-hole pairs injected into the active layer in a LED die to white light directly through transitions within the energy levels of the 4f{sup n}-manifold of RE{sup 3+}. We focused on the following materials: Eu{sup 3+}(red), Tb{sup 3+}(green), Er{sup 3+}(green), Dy{sup 3+}(yellow) and Tm{sup 3+}(blue) in AlN, GaN and alloys of AlN and GaN. Our strategy was to explore candidate materials in powder form first, and then study their behavior in thin films. Thin films of these materials were to be deposited on sapphire substrates using pulsed laser deposition (PLD) and metal organic vapor phase epitaxy (MOVPE). The photo- and cathode-luminescence measurements of these materials were used to investigate their suitability for white light generation. The project proceeded along this route with minor modifications needed to produce better materials and to expedite our progress towards the final goal. The project made the following accomplishments: (1) red emission from Eu{sup 3+}, green from Tb{sup 3+}, yellow from Dy{sup 3+} and blue from Tm{sup 3+} in AlN powders; (2) red emission from Eu{sup 3+} and green emission from Tb{sup 3+} in GaN powder; (3) red emission from Eu{sup 3+} in alloys of GaN and AlN; (4) green emission from Tb{sup 3+} in GaN thin films by PLD; (5) red emission from Eu{sup 3+} and Tb{sup 3+} in GaN thin films deposited by MOVPE; (6) energy transfer from host to RE{sup 3+}; (7) energy transfer from Tb{sup 3+} to Eu{sup 3+} in AlN powders; (8) emission from AlN powder samples

  1. Optical asymmetric cryptography based on elliptical polarized light linear truncation and a numerical reconstruction technique.

    PubMed

    Lin, Chao; Shen, Xueju; Wang, Zhisong; Zhao, Cheng

    2014-06-20

    We demonstrate a novel optical asymmetric cryptosystem based on the principle of elliptical polarized light linear truncation and a numerical reconstruction technique. The device of an array of linear polarizers is introduced to achieve linear truncation on the spatially resolved elliptical polarization distribution during image encryption. This encoding process can be characterized as confusion-based optical cryptography that involves no Fourier lens and diffusion operation. Based on the Jones matrix formalism, the intensity transmittance for this truncation is deduced to perform elliptical polarized light reconstruction based on two intensity measurements. Use of a quick response code makes the proposed cryptosystem practical, with versatile key sensitivity and fault tolerance. Both simulation and preliminary experimental results that support theoretical analysis are presented. An analysis of the resistance of the proposed method on a known public key attack is also provided. PMID:24979424

  2. Enhanced light emission in vertical-structured GaN-based light-emitting diodes with trench etching and arrayed p-electrodes

    NASA Astrophysics Data System (ADS)

    Lin, Tseng-Hsing; Wang, Shui-Jinn; Tu, Yung-Chun; Hung, Chien-Hsiung; Lin, Che-An; Lin, Yung-Cheng; You, Zong-Sian

    2015-05-01

    We investigate the effect of trench etching and arrayed p-electrodes in improving current spreading and the efficiency of light extraction of GaN-based vertical-structured light-emitting diodes (VLEDs). Both simulated and experimental results on the uniformities of current distribution and light emission are presented and discussed. For a 2 × 2 array VLED with a die size of 1020 × 1020 μm2, enhancements in light output power by 0.38% (6.03%) and wall-plug efficiency by 2.79% (2.32%) at 364.4 mA/mm2 (728.9 mA/mm2) as compared with that of regular VLED are achieved experimentally, which are attributed to improved current spreading from the arrayed p-electrode and trench designs as well as enhanced light emission from the trench region.

  3. Phase grating wavefront curvature sensor based on liquid crystal spatial light modulator

    NASA Astrophysics Data System (ADS)

    Chen, Bo; Li, Xiaoyang; Yang, Xu

    2015-08-01

    The phase grating wavefront curvature sensor based on liquid crystal spatial light modulator is introduced. A close-loop phase retrieval method based on Eigen functions of Laplacian is proposed, and its accuracy and efficiency are analyzed through numerical experiments of atmospheric phase retrieval. The results show that the close-loop phase retrieval method has a high accuracy. Moreover, it is stable regardless of modal cross coupling.

  4. Polarized electroabsorption spectra and light soaking of solar cells based on hydrogenated amorphous silicon

    NASA Astrophysics Data System (ADS)

    Jiang, Lin; Wang, Qi; Schiff, E. A.; Guha, S.; Yang, J.

    1998-03-01

    We present grazing-incidence measurements of polarized electroabsorption spectra in p-i-n solar cells based on hydrogenated amorphous silicon (a-Si:H). We find a significantly stronger polarization dependence in the present measurements compared with earlier work based on electroabsorption detected using coplanar electrodes on a-Si:H thin films. We do not find any significant dependence of the polarized electroabsorption upon light soaking, although this effect was found in previous work with coplanar electrodes.

  5. Panorama of new generation of accelerator based short wavelength coherent light sources

    NASA Astrophysics Data System (ADS)

    Couprie, M. E.

    2015-12-01

    The newly developed intense short wavelength light sources (from Extreme Ultra-Violet (EUV) to X-rays) have open the path to the exploration of matter for revealing structures and electronic processes and for following their evolution in time. After drawing the panorama of existing accelerator based short wavelength light sources, the new trends of evolution of short wavelengths FEL are described, with some illustrations with the example of the LUNEX5 (free electron Laser a New accelerator for the Exploitation of X-ray radiation of 5th generation) demonstrator project of advanced compact Free Electron Laser.

  6. Shaping of spherical light intensity based on the interference of tightly focused beams with different polarizations

    NASA Astrophysics Data System (ADS)

    Khonina, Svetlana N.; Ustinov, Andrey V.; Volotovsky, Sergey G.

    2014-08-01

    We consider the shaping of spherical intensity distributions based on the interference of counter-propagating tightly focused vortex beams with different polarizations. The formation of 3D distributions is performed using a simple method of optimization of the width and position of the single annular aperture. The optimum parameters for the narrow aperture are calculated analytically. In addition the wide aperture parameters are numerically adjusted. It is shown that depending on the polarization, the additional vortex phase and/or phase shift in the beams allow to form either solid light balls or light spheres of subwavelength radius. They consist of the various electric field components.

  7. Self-Action of Light Fields in Waveguide Photon Structures Based on Electro-Optic Crystals

    NASA Astrophysics Data System (ADS)

    Shandarov, V. M.

    2016-02-01

    Special features of spatial self-action of light fields in nonlinear optical photonic waveguide structures formed in strontium barium niobate and lithium niobate electro-optic crystals are discussed. The main methods of forming such structures including photorefractive waveguide elements and systems are briefly considered. The formation of spatial optical solitons in planar waveguides based on lithium niobate and strontium barium niobate crystals as well as in one-dimensional photonic lattices in lithium niobate is demonstrated experimentally for light beams of microwatt power. In regimes of spatial optical solitons, channel optical waveguides are formed not only in the planar waveguides, but also in the volume of photorefractive lithium niobate.

  8. Physics Holographic Recording Device Based on LCoS Spatial Light Modulator

    NASA Astrophysics Data System (ADS)

    Bulanovs, A.; Tamanis, E.; Mihailova, I.

    2011-01-01

    A PC-controlled holographic recording device has been developed in which a LC-R-2500 Spatial Light Modulator (SLM) based on reflective Liquid Crystal on Silicone (LCoS) display was used. The device allows the amplitude and phase modu-lation of coherent light wave fronts. In the optical scheme, a DPSS (Diode Pumped Solid State) laser with nanosecond pulse duration and wavelength 532 nm was applied. The holographic recording was made and tested in the amplitude and phase wave front modulation modes on a chalcogenide semiconductor photoresist As40S15S45. The experimental results are presented.

  9. Study of SBS slow light based on nano-material doped fiber

    NASA Astrophysics Data System (ADS)

    Zhang, Ying; Lang, Pei-Lin; Zhang, Ru

    2009-03-01

    A novel optical fiber doped with nano material InP is manufactured by the modified chemical vapor deposition (MCVD). The slow light based on stimulated Brillouin scattering (SBS) in the optical fiber is studied. The results show that a time delay of ˜738 ps is obtained when the input Stokes pulse is 900 ps(FWHM) and the SBS gain is ˜15. It shows that a considerable time delay and an amplification of the input light can be achieved by this novel optical fiber.

  10. Optimal control of light storage in atomic ensemble based on photon echoes

    NASA Astrophysics Data System (ADS)

    Wu, Tingwan; Chen, Qinzhi

    2009-11-01

    This paper presents a simple quantum memory method for efficient storage and retrieve of light. The technique is based on the principle of controlled reversible inhomogeneous broadening for which the information of the quantum state light is imprinted in a two-level atoms ensemble and recalled by flipping the external nonuniform electric field. In present work, the induced Stark shift varied linearly with position, and a numerical analysis for this protocol has been studied. It shows that the storage efficiency can nearly reach 100% with a large enough optical depth, and the optimal broadening for a given pulse width is also analyzed.