Spie Newsroom最新文献

{"title":"Liquid crystal composites as a route to 3D nanoparticle assembly","authors":"L. Hirst, Sheida T. Riahinasab, C. Melton","doi":"10.1117/2.1201702.006865","DOIUrl":"https://doi.org/10.1117/2.1201702.006865","url":null,"abstract":"","PeriodicalId":22075,"journal":{"name":"Spie Newsroom","volume":"29 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85154087","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Novel semiconductor membrane external-cavity surface-emitting laser","authors":"H. Kahle, C. Mateo, U. Brauch, R. Bek, M. Jetter, T. Graf, P. Michler","doi":"10.1117/2.1201703.006864","DOIUrl":"https://doi.org/10.1117/2.1201703.006864","url":null,"abstract":"Optically pumped semiconductor vertical external-cavity surfaceemitting lasers (VECSELs) exhibit many desirable properties1, 2 and have therefore become an important stand-alone class of solid-state lasers over the last 20 years. For example, VECSELs can be used nowadays to reach 100W-level continuous wave output.3 However, a large quantum defect (resulting from the energy difference between pump and laser photons) means that heat is incorporated into the active region of VECSELs. This gives rise to a strongly temperature-dependent performance4 caused by the interplay of gain and cavity resonance and the limited charge-carrier confinement. The limited charge-carrier confinement is a particular challenge in the aluminum gallium indium phosphide (AlGaInP) material system, i.e., in which the thermal conductivity5, 6 is low and the laser structure is based on a thick distributed Bragg reflector (DBR). Indeed, the thermal conductivity of this type of DBR is an order of magnitude lower than well-conducting metals (i.e., which are often used as backside heatsinks) and two orders of magnitude worse than diamond (commonly used for the backside or as an intracavity heat spreader).7 In addition, the semiconductor structure itself—with a thickness of several micrometers (for the active region and the DBR)—and the substrate (with a typical thickness of 350 m) impede the heat flow out of the active region. To overcome the heat flow problems and to improve the performance of VECSELs, numerous thermal management strategies have been previously proposed. Such approaches include changes to the heat spreader arrangement,8 removing the substrate,1 flip-chip processes,9 or the insertion of compound mirrors.10 According to the natural progression of these Figure 1. Picture of the semiconductor membrane external-cavity surface-emitting laser (MECSEL) in operation. From left to right, the out-coupling/resonator mirror, diamond-sandwiched semiconductor gain membrane (integrated into a brass mount), birefringent filter, and pump optics with a 532nm pump laser beam (behind the birefringent filter), and a highly reflective resonator can be seen (as illustrated schematically in Figure 2).","PeriodicalId":22075,"journal":{"name":"Spie Newsroom","volume":"86 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73051374","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Monitoring short-lived climate pollutants by laser absorption spectroscopy","authors":"Weidong Chen, Gaoxuan Wang, Dong Chen, Fengjiao Shen, H. Yi, R. Maamary, P. Augustin, M. Fourmentin, E. Fertein, M. Sigrist","doi":"10.1117/2.1201704.006896","DOIUrl":"https://doi.org/10.1117/2.1201704.006896","url":null,"abstract":"","PeriodicalId":22075,"journal":{"name":"Spie Newsroom","volume":"68 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77325035","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hydrogen production with holes: what we learn from operando studies","authors":"A. Braun, R. Toth, Kelebogile Maabong, M. Diale","doi":"10.1117/2.1201704.006793","DOIUrl":"https://doi.org/10.1117/2.1201704.006793","url":null,"abstract":"As we become more aware of the limited amount of energy available from traditional sources, we are increasingly turning to solar power as a viable alternative.1, 2 Of the total worldwide energy consumption, 20% is electrical, with an increasing share being produced by photovoltaics. Scientists, engineers, technologists, and investors are now working towards a renewable alternative for the remaining 80%, which is currently obtained from fossil fuels, nuclear fuels, and biomass.3–5 Photoelectrochemical cells (PECs), which use sunlight to convert water into solar-hydrogen fuel, represent one route to achieving a renewable energy source. PECs are based on semiconductor photoelectrodes,6 but their principles of energy conversion and storage are analogous to photosynthesis. The photoelectrodes within PECs are comprised of two electrodes. At least one contains a light absorber (which is applied as a coating on a transparent conducting oxide, TCO) and one has an electrocatalytic surface (e.g., an aqueous-electrolyte coating). When light strikes the absorber, photoelectrons and holes are created. The electrons then migrate through the TCO, which acts as a current collector, and enter the electric circuit. The holes diffuse to the electrode surface, where they chemically react with water molecules and cause them to electrochemically split into oxygen gas. This gas evolves at the photoanode and can be collected in a container for any potential further use. Protons migrate through the electrolyte to the counter electrode, where they combine with electrons to form hydrogen gas, which is collected as fuel. We have designed a PEC reactor (a prototype of which is shown in Figure 1) that has a large (10 10cm) iron oxide Figure 1. The photoelectrochemical cell (PEC) reactor prototype. The device has an active area of 100cm2 and is comprised of glass coated with an iron-oxide photoelectrode. The design incorporates an oxygen gas outlet (top left). The white compartment on the right of the device holds the platinum counter electrode for hydrogen gas evolution and collection. One molar mass of potassium hydroxide, acting as the electrolyte, is supplied continuously.","PeriodicalId":22075,"journal":{"name":"Spie Newsroom","volume":"93 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90261821","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multi-projection 3D displays using multiplexing techniques in autostereoscopic displays","authors":"Byoungho Lee, Soon-gi Park, Keehoon Hong, Jisoo Hong","doi":"10.1117/2.2201705.03","DOIUrl":"https://doi.org/10.1117/2.2201705.03","url":null,"abstract":"","PeriodicalId":22075,"journal":{"name":"Spie Newsroom","volume":"111 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88876099","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A new signal-amplification mechanism discovered in semiconductors","authors":"Y. Lo, Yu-hsin Liu, D. Hall, Ifikhar Ahmad Niaz, Mohammad Abu Raihan Miah","doi":"10.1117/2.1201701.006843","DOIUrl":"https://doi.org/10.1117/2.1201701.006843","url":null,"abstract":"Preamplifiers (i.e., electronic devices that amplify signals) are required in optical imaging and detection systems to increase weak current signals.1 If the detector itself can produce sufficient gain, however, the sensitivity of such devices may be able to overcome the limitations that are imposed by the thermal noise of electronics. An internal amplification mechanism (i.e., impact ionization) has been used in photodetection for decades. In an avalanche photodiode—a reverse-biased p-n junction device that is operated at a voltage close to breakdown voltage,2, 3 APD—an ionization collision with the lattice—occurs when the photogenerated primary carriers acquire enough energy: see Figure 1(a). Secondary electron-hole (e-h) pairs are produced from this collision, which in turn cause additional ionization collisions as the pairs cross the depletion region (i.e., the ‘avalanche’ process). APD-based photoreceivers achieve sufficient sensitivity for fiber-optic communications. However, they require a high operation voltage (over 20V) and suffer from high excess noise with increasing gain. In devices with internal gain, interference originates mainly from shot noise that is amplified with the signal.4 The noise of these systems is best characterized by the excess noise factor (ENF), which is calculated from the fluctuation of the amplification gain. In our work, we are proposing a new internal amplification mechanism called the cycling excitation process (CEP). This process relies on the transitions involving localized states, which are formed via dopant compensation within a p-n junction diode. The Coulomb interactions that occur between energetic carriers and these localized states have stronger efficiency Figure 1. Schematic illustration of (a) the avalanche process and (b) the cycling excitation process (CEP). The former is based on impact ionization between the hot and the bound electron in the valance band. In contrast, CEP occurs as a result of the Auger process between a hot electron and an electron in the localized state in the dopant within the n-type region. Eg : Energy bandgap. 0: Primary carrier from direct photo absorption. 1: Carrier produced by Auger excitation.","PeriodicalId":22075,"journal":{"name":"Spie Newsroom","volume":"67 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77119335","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Microscopic intracellular lasers tag individual cells over several generations","authors":"M. Schubert, M. Gather","doi":"10.1117/2.1201704.006899","DOIUrl":"https://doi.org/10.1117/2.1201704.006899","url":null,"abstract":"The ability to track individual cells among the trillions that are present in the human body is critical to advancing our understanding of many important biomedical questions. For example, tracking individual cells could enable us to study the function of neuronal networks, follow the inflammation response of immune cells, and unravel the way in which circulating tumor cells contribute to the formation of cancer metastasis. Among the techniques that have recently been developed to achieve single-cell resolution in tissue samples or whole animals, light sheet microscopy,1 transgenic labeling of cellular subsets,2 and genetic barcodes3 hold particular promise. However, as powerful as these methods are, they either rely critically on highly transparent samples, are strongly limited by the total number of unique cell tags, or are highly invasive. We recently developed a radically different approach to track large populations of cells over extended periods of time.4 Our method is based on tiny fluorescent plastic beads that are placed inside of each cell. These beads have diameters of about 15 m and are made of polystyrene doped with a brightly fluorescent green dye. Natural phagocytosis has proven very efficient for transferring the beads into immune cells (macrophages), where they act as microresonators (that is, they trap and amplify light by forcing it onto a circular path along the circumference of the bead).4, 5 When optically pumped, the green dye in the beads provides optical gain that leads to the emission of laser light within the living cell, thus enabling their detection. Furthermore, because the emitted laser frequency depends critically on the size of the bead, inherent size variations create unique, barcode-like laser spectra (see Figure 1) that allow the identification of Figure 1. Representative montage showing the operation of our microscopic intracellular lasers. Microlasers (green spheres) located inside live cells provide optical barcodes that can be used to identify and track individual cells within large populations of cells.","PeriodicalId":22075,"journal":{"name":"Spie Newsroom","volume":"48 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86407890","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Computationally inexpensive simulations for nanoimprint lithography","authors":"H. Taylor","doi":"10.1117/2.1201703.006887","DOIUrl":"https://doi.org/10.1117/2.1201703.006887","url":null,"abstract":"Among emerging nanopatterning techniques, nanoimprint lithography (NIL) is especially promising because the equipment required is relatively inexpensive. In NIL, a patterned template mechanically deforms a polymer film or resin on the surface of a semiconductor wafer (as shown in Figure 1) to transfer features and create an etching mask for subsequent processing. The prospect of reduced patterning costs enabled by this technique (compared with, for example, extreme-UV lithography) is particularly attractive to manufacturers of NAND flash memory, i.e., the predominant form of non-volatile memory used in electronic devices today. NAND flash memory does not require power to store data and is the key component of solidstate hard disk drives and camera memory cards. Nonetheless, to increase its adoption, it is crucial to reduce the cost per bit and, for this reason, there is an exceptionally strong incentive to reduce manufacturing costs. NIL is a promising approach for realizing a reduction in NAND flash manufacturing costs, but there are a number of associated challenges. For example, it is particularly difficult to achieve good inter-layer alignment and template lifetimes, and to minimize the pattern defectivity. Defectivity is the issue most in need of process modeling. There are two contributors to defectivity: random contributions (including particles or spatial errors in the dispensing of resin droplets onto the wafer); and systematic contributions, e.g., incomplete template-cavity filling, variation of the resin’s residual-layer thickness (between the template and the substrate), and template–resin adhesion. To ensure the successful use of NIL for fabricating NAND flash memory, it is necessary to predict any voids that may arise beneath the template after the dispensed droplets have spread Figure 1. Schematic illustration of nanoimprint lithography, using a droplet-dispensed resin.6 (1) A patterned quartz template is bowed and brought into contact with inkjet-dispensed pL-volume resin droplets on the wafer. (2) The curvature of the template is then relaxed to spread droplets and fill cavities. (3) After a dwell period (to enable residual layer homogenization), the resin is cured by UV exposure through the template.","PeriodicalId":22075,"journal":{"name":"Spie Newsroom","volume":"931 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77059296","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Design considerations for full-color e-paper","authors":"Bo‐Ru Yang, Yu-Cheng Wang, Li Wang","doi":"10.1117/2.1201704.006820","DOIUrl":"https://doi.org/10.1117/2.1201704.006820","url":null,"abstract":"","PeriodicalId":22075,"journal":{"name":"Spie Newsroom","volume":"6 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91495331","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Phase diagram for investigating the scattering properties of passive scatterers","authors":"Jeng-Yi Lee, Ray-Kuang Lee","doi":"10.1117/2.1201703.006854","DOIUrl":"https://doi.org/10.1117/2.1201703.006854","url":null,"abstract":"The study of scattering (i.e., how a single receiver or scatterer responds to an external stimulus) is relevant to a wide range of subjects that are, in some way, related to wave physics (e.g., electromagnetic radiation, elastic waves, thermal diffusion, and quantum physics). Inspired by the recent developments of metamaterials and state-of-the-art nano-optical technologies, the design of functional scatterers has attracted much attention over the last decade (both experimentally and theoretically). For instance, unusual scattering states (including invisible cloaking, resonant scattering, coherent perfect absorption, superscattering, and superabsorbers) have been demonstrated when specific materials are used in the configuration of multilayered structures.1–5 Devices in which these scattering states are used have great potential for applications in biochemistry, greenenergy generation, ultrasensitive detection sensors, and optical microscopy. To obtain the exotic electromagnetic properties at a subwavelength scale, however, a variety of specific conditions need to be satisfied and a better understanding of scattering coefficients is thus required. The study of light radiation being scattered from small particles can be traced back to Lord Rayleigh’s explanation for the color of the sky.6 Furthermore, an exact solution for spherical scatterers was derived by Mie and Lorenz more than a century ago.7 This solution is valid for particles with any geometrical size, and for possible permittivity and permeability values. Nonetheless, although a basic understanding of the recently discovered unusual scattering states can be derived from existing scattering theory, a unified understanding of all these exotic states is still lacking. Figure 1. Phase diagram for a passive scatterer defined by the magnitude, jC .TE;TM/ n j, and the phase, .TE;TM/ n , of the transverse electric (TE) and transverse magnetic (TM) modes of electromagnetic radiation (where n denotes the order of the harmonic channel). The colored region represents the allowable solutions of C .TE;TM/ n and the white region represents the forbidden states for passive scatterers. The value (i.e., color) of the contours represents the normalized absorption cross section ( abs) for the TE or TM modes. : Wavelength of electromagnetic radiation.8","PeriodicalId":22075,"journal":{"name":"Spie Newsroom","volume":"24 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75865653","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}