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Sample records for patterned subwavelength apertures

  1. Extraordinary optical transmission through patterned subwavelength apertures.

    SciTech Connect

    Kemme, Shanalyn A.; El-Kady, Ihab Fathy; Hadley, G. Ronald; Peters, David William; Lanes, Chris E.

    2004-12-01

    Light propagating through a subwavelength aperture can be dramatically increased by etching a grating in the metal around the hole. Moreover, light that would typically broadly diverge when passing through an unpatterned subwavelength hole can be directed into a narrow beam by utilizing a specific pattern around the aperture. While the increased transmission and narrowed angular emission appear to defy far-field diffraction theory, they are consistent with a fortuitous plasmon/photon coupling. In addition, the coupling between photons and surface plasmons affects the emissivity of a surface comprised of such structures. These properties are useful across several strategic areas of interest to Sandia. A controllable emission spectrum could benefit satellite and military application areas. Photolithography and near-field microscopy are natural applications for a system that controls light beyond the diffraction limit in a manner that is easily parallelizable. Over the one year of this LDRD, we have built or modified the numerical tools necessary to model such structures. These numerical codes and the knowledge base for using them appropriately will be available in the future for modeling work on surface plasmons or other optical modeling at Sandia. Using these tools, we have designed and optimized structures for various transmission or emission properties. We demonstrate the ability to design a metallic skin with an emissivity peak at a pre-determined wavelength in the spectrum. We optimize structures for maximum light transmission and show transmitted beams that beat the far-field diffraction limit.

  2. A half wave retarder made of bilayer subwavelength metallic apertures

    SciTech Connect

    Marset, zsolt; Chan, Ho Bun; Carr, D. W.; Cirelli, R. A.

    2011-01-01

    The paper describes the fabrication of a half wave plate where the retardation in one polarization is achieved through tailoring the evanescent field coupling between two metal layers with arrays of subwavelength apertures. The main advantages of this design include versatility in the operational wavelength, compactness and potential integration with other optical components, as well as the possibility of dynamical control of the polarization of the transmitted light through lateral nanomechanical motion between the two metal layers.

  3. Control of Surface Plasmons Emitted from Arrays of Subwavelength Apertures

    NASA Astrophysics Data System (ADS)

    Blumberg, Girsh; Dennis, Brian; Egorov, Dimitri; Haftel, Michael

    2004-03-01

    We demonstrate that surface plasmons (SPs) can be emitted in the form of long and coherent jets whose intensity and propagation direction can be manipulated by varying the wavelength, incidence angle, and polarization of the excitation light as well as through adjustment periodicity of 2D structures and dielectric properties of the interfaces. We also demonstrate the reverse conversion of SPs back into free propagating light and observe controllable and highly directional beaming. We use for sample gold films on a fused silica substrates with fabricated arrays of subwavelength apertures illuminated by a tunable laser. We image coherent SP modes by a near-field scanning optical microscope (NSOM) and demonstrate emission of SP jets in controlled propagation direction. By adding mirrors and lenses we demonstrate SP standing waves and focusing which concentrates high local density of electromagnetic energy on the gold-air interface. By performing NSOM scans as a function of distance from the gold-air interface we map out the volume distribution of light intensity above the array and confirm highly directional nature of light emitted from periodic 2D structure of subwavelength apertures down to a few microns away from the surface.

  4. Anomalous light absorption around subwavelength apertures in metal films.

    PubMed

    Lozan, O; Perrin, M; Ea-Kim, B; Rampnoux, J M; Dilhaire, S; Lalanne, P

    2014-05-16

    In this Letter, we study the heat dissipated at metal surfaces by the electromagnetic field scattered by isolated subwavelength apertures in metal screens. In contrast to the common belief that the intensity of waves created by local sources should decrease with the distance from the sources, we reveal that the dissipated heat at the surface remains constant over a broad spatial interval. This behavior that occurs for noble metals at near infrared wavelengths is observed with nonintrusive thermoreflectance measurements and is explained with an analytical model, which underlines the intricate role played by quasicylindrical waves in the phenomenon. Additionally, we show that, by monitoring the phase of the quasicylindrical waves, the total heat dissipated at the metal surface can be rendered substantially smaller than the heat dissipated by the launched plasmon. This interesting property offers an alternative to amplification for overcoming the loss issue in miniaturized plasmonic devices. PMID:24877942

  5. Anomalous light absorption around subwavelength apertures in metal films.

    PubMed

    Lozan, O; Perrin, M; Ea-Kim, B; Rampnoux, J M; Dilhaire, S; Lalanne, P

    2014-05-16

    In this Letter, we study the heat dissipated at metal surfaces by the electromagnetic field scattered by isolated subwavelength apertures in metal screens. In contrast to the common belief that the intensity of waves created by local sources should decrease with the distance from the sources, we reveal that the dissipated heat at the surface remains constant over a broad spatial interval. This behavior that occurs for noble metals at near infrared wavelengths is observed with nonintrusive thermoreflectance measurements and is explained with an analytical model, which underlines the intricate role played by quasicylindrical waves in the phenomenon. Additionally, we show that, by monitoring the phase of the quasicylindrical waves, the total heat dissipated at the metal surface can be rendered substantially smaller than the heat dissipated by the launched plasmon. This interesting property offers an alternative to amplification for overcoming the loss issue in miniaturized plasmonic devices.

  6. Spectral light separator based on deep-subwavelength resonant apertures in a metallic film

    SciTech Connect

    Büyükalp, Yasin; Catrysse, Peter B. Shin, Wonseok; Fan, Shanhui

    2014-07-07

    We propose to funnel, select, and collect light spectrally by exploiting the unique properties of deep-subwavelength resonant apertures in a metallic film. In our approach, each aperture has an electromagnetic cross section that is much larger than its physical size while the frequency of the collected light is controlled by its height through the Fabry-Pérot resonance mechanism. The electromagnetic crosstalk between apertures remains low despite physical separations in the deep-subwavelength range. The resulting device enables an extremely efficient, subwavelength way to decompose light into its spectral components without the loss of photons and spatial coregistration errors. As a specific example, we show a subwavelength-size structure with three deep-subwavelength slits in a metallic film designed to operate in the mid-wave infrared range between 3 and 5.5 μm.

  7. Enhanced transmission of transverse electric waves through periodic arrays of structured subwavelength apertures.

    PubMed

    Xiao, Sanshui; Peng, Liang; Mortensen, Niels Asger

    2010-03-15

    Transmission through sub-wavelength apertures in perfect metals is expected to be strongly suppressed. However, by structural engineering of the apertures, we numerically demonstrate that the transmission of transverse electric waves through periodic arrays of subwavelength apertures in a thin metallic film can be significantly enhanced. Based on equivalent circuit theory analysis, periodic arrays of square structured subwavelength apertures are obtained with a 1900-fold transmission enhancement factor when the side length a of the apertures is 10 times smaller than the wavelength (a/lambda =0.1). By examining the induced surface currents and investigating the influence of the lattice constant and the incident angle to the resonant frequency, we show that the enhancement is due to the excitation of the strong localized resonant modes of the structured apertures.

  8. Molecular recognition with nanostructures fabricated by photopolymerization within metallic subwavelength apertures

    NASA Astrophysics Data System (ADS)

    Urraca, J. L.; Barrios, C. A.; Canalejas-Tejero, V.; Orellana, G.; Moreno-Bondi, M. C.

    2014-07-01

    The first demonstration of fabrication of submicron lateral resolution molecularly imprinted polymer (MIP) patterns by photoinduced local polymerization within metal subwavelength apertures is reported. The size of the photopolymerized MIP features is finely tuned by the dose of 532 nm radiation. Rhodamine 123 (R123) has been selected as a fluorescent model template to prove the recognition capability of the MIP nanostructures, which has been evaluated by fluorescence lifetime imaging microscopy (FLIM) with single photon timing measurements. The binding selectivity provided by the imprinting effect has been confirmed in the presence of compounds structurally related to R123. These results pave the way to the development of nanomaterial architectures with biomimetic artificial recognition properties for environmental, clinical and food testing.The first demonstration of fabrication of submicron lateral resolution molecularly imprinted polymer (MIP) patterns by photoinduced local polymerization within metal subwavelength apertures is reported. The size of the photopolymerized MIP features is finely tuned by the dose of 532 nm radiation. Rhodamine 123 (R123) has been selected as a fluorescent model template to prove the recognition capability of the MIP nanostructures, which has been evaluated by fluorescence lifetime imaging microscopy (FLIM) with single photon timing measurements. The binding selectivity provided by the imprinting effect has been confirmed in the presence of compounds structurally related to R123. These results pave the way to the development of nanomaterial architectures with biomimetic artificial recognition properties for environmental, clinical and food testing. Electronic supplementary information (ESI) available: Fig. SI.1: chemical structure and acronyms of the different fluorescent dyes; optimization of polymer composition; Table SI.1. Template recovery after polymerization; determination of the binding capacity by equilibrium rebinding

  9. Transmission enhancement through deep subwavelength apertures using connected split ring resonators.

    PubMed

    Ates, Damla; Cakmak, Atilla Ozgur; Colak, Evrim; Zhao, Rongkuo; Soukoulis, C M; Ozbay, Ekmel

    2010-02-15

    We report astonishingly high transmission enhancement factors through a subwavelength aperture at microwave frequencies by placing connected split ring resonators in the vicinity of the aperture. We carried out numerical simulations that are consistent with our experimental conclusions. We experimentally show higher than 70,000-fold extraordinary transmission through a deep subwavelength aperture with an electrical size of lambda/31 x lambda/12 (width x length), in terms of the operational wavelength. We discuss the physical origins of the phenomenon. Our numerical results predict that even more improvements of the enhancement factors are attainable. Theoretically, the approach opens up the possibility for achieving very large enhancement factors by overcoming the physical limitations and thereby minimizes the dependence on the aperture geometries.

  10. Polarization-dependent transmission through subwavelength anisotropic aperture arrays.

    PubMed

    Dimaio, Jeffrey R; Ballato, John

    2006-03-20

    The use of polarized light as an approach to further control the extraordinary transmission (EOT) through nanostructured metallic films has recently gained attention. In this work, it is shown that aperture shape and orientation not only determine the intensity of the polarized light emitted, corroborating the previous work of others, but also can be used to spectrally tune the relative peak intensity of surface plasmon polaritons modes. The high extinction ratio of high aspect ratio apertures lends itself to the creation of micron sized structures that emit at different wavelengths depending upon the orientation of linearly polarized incident light. This has many potential applications including the prospect of color shifting pixels for high definition television (HDTV) and thin film electroluminescent (TFEL) devices as well as novel polarization mode dispersion control components.

  11. Diffracted Evanescent Wave Model for Enhanced, Suppressed and Directional Transmission through Subwavelength Apertures

    NASA Astrophysics Data System (ADS)

    Lezec, Henri

    2005-03-01

    The transmission spectrum of an array of subwavelength apertures in a metal film displays a set of peaks related to the periodicity. Extraordinary transmission efficiencies at these positions have been claimed and associated with discrete grating-coupling conditions that excite surface-plasmon polaritons (SPPs). In this talk, we re-evaluate the magnitude and origin of the effect by proper normalization of the as-collected transmission spectrum of the array to that of the corresponding isolated hole. The normalized spectrum then reveals a sequence of both enhancements and suppressions of modest and similar magnitude (less than a factor of ten). This continuous modulation is inconsistent with an SPP-based interpretation, but rather suggests an underlying mechanism based on interference. A subwavelength aperture couples inefficiently to a specific surface mode such as an SPP because it diffracts light into a continuum of evanescent surface waves with a large distribution of in-plane k-vectors. We show however that these components sum to form an effective surface wave which is coherent over a short range and phase-shifted with respect to the source. We confirm the presence of this composite diffracted evanescent wave (CDEW) via interferometric experiments involving pairs of subwavelength apertures. We propose a new model for the anomalous transmission of hole arrays in which enhancement and suppression result from the interference of light directly incident upon (or emerging from) a given hole with CDEWs launched by neighboring holes. This model successfully predicts equivalent effects in non-metallic systems. In addition, it accounts for the salient optical properties of single apertures surrounded by surface corrugations, such as efficient, low-divergence beaming.

  12. High-precision three-dimensional coordinate measurement with subwavelength-aperture-fiber point diffraction interferometer

    NASA Astrophysics Data System (ADS)

    Wang, Daodang; Xu, Yangbo; Chen, Xixi; Wang, Fumin; Kong, Ming; Zhao, Jun

    2014-11-01

    To overcome the accuracy limitation due to the machining error of standard parts in measurement system, a threedimensional coordinate measurement method with subwavelength-aperture-fiber point diffraction interferometer (PDI) is proposed, in which the high-precision measurement standard is obtained from the ideal point-diffracted spherical wavefront instead of standard components. On the basis of the phase distribution demodulated from point-diffraction interference field, high-precision three-dimensional coordinate measurement is realized with numerical iteration optimization algorithm. The subwavelength-aperture fiber is used as point-diffraction source to get precise and highenergy spherical wavefront within high aperture angle range, by which the conflict between diffraction wave angle and energy in traditional PDI can be avoided. Besides, a double-iterative method based on Levenbery-Marquardt algorithm is proposed to realize precise reconstruct three-dimensional coordinate. The analysis shows that the proposed method can reach the measurement precision better than microns within a 200×200×300 (in unit of mm) working volume. This measurement method does not rely on the initial iteration value in numerical coordinate reconstruction, and also has high measurement precision, large measuring range, fast processing speed and preferable anti-noise ability. It is of great practicality for measurement of three-dimensional coordinate and calibration of measurement system.

  13. Dual-band-enhanced Transmission through a Subwavelength Aperture by Coupled Metamaterial Resonators

    PubMed Central

    Guo, Yunsheng; Zhou, Ji

    2015-01-01

    In classical mechanics, it is well known that a system consisting of two identical pendulums connected by a spring will steadily oscillate with two modes: one at the fundamental frequency of a single pendulum and one in which the frequency increases with the stiffness of the spring. Inspired by this physical concept, we present an analogous approach that uses two metamaterial resonators to realize dual-band-enhanced transmission of microwaves through a subwavelength aperture. The metamaterial resonators are formed by the periodically varying and strongly localized fields that occur in the two metal split-ring resonators, which are placed gap-to-gap on either side of the aperture. The dual-band frequency separation is determined by the coupling strength between the two resonators. Measured transmission spectra, simulated field distributions, and theoretical analyses verify our approach. PMID:25634496

  14. Super sub-wavelength patterns in photon coincidence detection

    NASA Astrophysics Data System (ADS)

    Liu, Ruifeng; Zhang, Pei; Zhou, Yu; Gao, Hong; Li, Fuli

    2014-02-01

    High-precision measurements implemented with light are desired in all fields of science. However, light acts as a wave, and the Rayleigh criterion in classical optics yields a diffraction limit that prevents obtaining a resolution smaller than the wavelength. Sub-wavelength interference has potential application in lithography because it beats the classical Rayleigh resolution limit. Here, we carefully study second-order correlation theory to establish the physics behind sub-wavelength interference in photon coincidence detection. A Young's double slit experiment with pseudo-thermal light is performed to test the second-order correlation pattern. The results show that when two point detectors are scanned in different ways, super sub-wavelength interference patterns can be obtained. We then provide a theoretical explanation for this surprising result, and demonstrate that this explanation is also suitable for the results found for entangled light. Furthermore, we discuss the limitations of these types of super sub-wavelength interference patterns in quantum lithography.

  15. Super sub-wavelength patterns in photon coincidence detection

    PubMed Central

    Liu, Ruifeng; Zhang, Pei; Zhou, Yu; Gao, Hong; Li, Fuli

    2014-01-01

    High-precision measurements implemented with light are desired in all fields of science. However, light acts as a wave, and the Rayleigh criterion in classical optics yields a diffraction limit that prevents obtaining a resolution smaller than the wavelength. Sub-wavelength interference has potential application in lithography because it beats the classical Rayleigh resolution limit. Here, we carefully study second-order correlation theory to establish the physics behind sub-wavelength interference in photon coincidence detection. A Young's double slit experiment with pseudo-thermal light is performed to test the second-order correlation pattern. The results show that when two point detectors are scanned in different ways, super sub-wavelength interference patterns can be obtained. We then provide a theoretical explanation for this surprising result, and demonstrate that this explanation is also suitable for the results found for entangled light. Furthermore, we discuss the limitations of these types of super sub-wavelength interference patterns in quantum lithography. PMID:24531057

  16. Super sub-wavelength patterns in photon coincidence detection.

    PubMed

    Liu, Ruifeng; Zhang, Pei; Zhou, Yu; Gao, Hong; Li, Fuli

    2014-02-17

    High-precision measurements implemented with light are desired in all fields of science. However, light acts as a wave, and the Rayleigh criterion in classical optics yields a diffraction limit that prevents obtaining a resolution smaller than the wavelength. Sub-wavelength interference has potential application in lithography because it beats the classical Rayleigh resolution limit. Here, we carefully study second-order correlation theory to establish the physics behind sub-wavelength interference in photon coincidence detection. A Young's double slit experiment with pseudo-thermal light is performed to test the second-order correlation pattern. The results show that when two point detectors are scanned in different ways, super sub-wavelength interference patterns can be obtained. We then provide a theoretical explanation for this surprising result, and demonstrate that this explanation is also suitable for the results found for entangled light. Furthermore, we discuss the limitations of these types of super sub-wavelength interference patterns in quantum lithography.

  17. Experimental and numerical confirmation of composite diffracted evasnescent-wave (CDEW) model for enhanced transmission of subwavelength apertures

    NASA Astrophysics Data System (ADS)

    Lezec, Henri J.; Thio, Tineke

    2006-03-01

    When a subwavelength aperture in an opaque film is surrounded by periodic surface corrugations, its optical transmission can be enhanced or suppressed with respect to that of an identical aperture without surface corrugations. We have proposed a model in which the subwavelength surface structure scatters the incident light into evanescent waves: The total, or composite, diffracted evanescent waves (CDEWs) travel along the surface and their interference with the light directly falling on the aperture leads to the transmission modulation. The CDEW model is valid for metallic as well as non-metallic surfaces, and thus differs qualitatively from the surface plasmon model, which requires a metallic surface. We show that the optical transmission of an embedded periodic array of dots, where the surface is absent altogether, is related to the transmission of hole arrays by Babinet’s principle, underscoring the importance of diffraction. Furthermore, numerical calculations on small- area corrugations verify the functional form of the CDEWs.

  18. Total broadband transmission of microwaves through a subwavelength aperture by localized E-field coupling of split-ring resonators.

    PubMed

    Guo, Yunsheng; Zhou, Ji

    2014-11-01

    Resonance coupling of two resonators with the same resonant frequency is a highly efficient energy transfer approach in physics. Here we report total broadband transmission of microwaves through a metallic subwavelength aperture using the coupled resonances of the strongly localized electric fields at the gaps of two split-ring resonators (SRRs) placed on either side of the aperture. At the center frequency of the broad band, the phase difference between the two localized time-varying electric fields is 90°, which is consistent with the critical coupling state that is a sufficient condition for the two-resonator system to realize total transmission if the resonators are assumed to be lossless.

  19. Design and fabrication of sub-wavelength annular apertures for femtosecond laser machining

    NASA Astrophysics Data System (ADS)

    Hsu, Kuan-Yu; Tung, Yen-Chun; Chung, Ming-Han; Lee, Chih-Kung

    2015-03-01

    Many research teams have begun pursuing optical micromachining technology in recent years due to its associated noncontact and fast speed characteristics. However, the focal spot sizes and the depth of focus (DOF) strongly influenced the design requirements of the micromachining system. The focal spot size determines the minimum features can be fabricated, which is inversely proportional to the DOF. That is, smaller focal spot size led to shorter DOF. However, the DOF of the emitted visible or near-infrared light beam is typically limited to tens of nanometers for traditional optic system. The disadvantages of using nanosecond laser for micromachining such as burrs formation and surface roughness were found to further influence the accuracy of machined surfaces. To alleviate all of the above-mentioned problems, sub-wavelength annular aperture (SAA) illuminated with 780 nm femtosecond laser were integrated to develop the new laser micromachining system presented in this paper. We first optimized the parameters for high transmittance associated with the SAA structure for the 780 nm femtosecond laser used by adopting the finite difference time domain simulations method. A lateral microscope was modified from a traditional microscope to facilitate the measurement of the emitted light beam optical energy distribution. To verify the newly developed system performance the femtosecond laser was used to illuminate the SAA fabricated on the metallic film to produce the Bessel light beam so as to perform micromachining and process on silicon, PCB board and glass. Experimental results were found to match the original system design goals reasonably well.

  20. Geometrical isotropy in perforated plates with subwavelength holes decorated with Archimedean patterns

    NASA Astrophysics Data System (ADS)

    Gómez-Lozano, V.; Rubio, C.; Candelas, P.; Belmar, F.; Uris, A.

    2015-08-01

    The design and use of small apertures perforated in opaque plates to control the transmission of ultrasonic waves has been widely studied in recent years. The ultrasonic transmission response of brass plates perforated with Archimedean patterns of subwavelength hole arrays immersed in water is reported, both numerically and experimentally, in this work. It is shown that an increase in the geometrical isotropy of the elementary cells of the Archimedean patterns gives rise to a suppression of both minimum and maximum transmission corresponding to the destructive and constructive interferences, leading to uniformity within the angle-dependent transmitted sound power coefficient. The experimental results are in close agreement with the calculated ones. This property can be used to design ultrasonic devices such as filters and sensors.

  1. Coherent patterning of matter waves with subwavelength localization

    NASA Astrophysics Data System (ADS)

    Mompart, J.; Ahufinger, V.; Birkl, G.

    2009-05-01

    We propose the subwavelength localization via adiabatic passage (SLAP) technique to coherently achieve state-selective patterning of matter waves well beyond the diffraction limit. The SLAP technique consists in coupling two partially overlapping and spatially structured laser fields to three internal levels of the matter wave yielding state-selective localization at those positions where the adiabatic passage process does not occur. We show that by means of this technique matter wave localization down to the single nanometer scale can be achieved. We analyze in detail the potential implementation of the SLAP technique for nanolithography with an atomic beam of metastable Ne∗ and for coherent patterning of a two-component R87b Bose-Einstein condensate.

  2. Direct laser writing of pyramidal plasmonic structures with apertures and asymmetric gratings towards efficient subwavelength light focusing.

    PubMed

    Mu, Jiajia; Liu, Zhiguang; Li, Jiafang; Hao, Tingting; Wang, Yujin; Sun, Shengsheng; Li, Zhi-Yuan; Li, Junjie; Li, Wuxia; Gu, Changzhi

    2015-08-24

    Efficient confining of photons into subwavelength scale is of great importance in both fundamental researches and engineering applications, of which one major challenge lies in the lack of effective and reliable on-chip nanofabrication techniques. Here we demonstrate the efficient subwavelength light focusing with carefully engineered pyramidal structures fabricated by direct laser writing and surface metallization. The important effects of the geometry and symmetry are investigated. Apertures with various sizes are flexibly introduced at the apex of the pyramids, the focusing spot size and center-to-sidelobe ratio of which could be improved a factor of ~4 and ~3, respectively, compared with the conical counterparts of identical size. Moreover, two pairs of asymmetric through-nanogratings are conceptually introduced onto the top end of the pyramids, showing significantly improved focusing characteristics. The studies provide a novel methodology for the design and realization of 3D plasmonic focusing with low-noise background and high energy transfer.

  3. Tunable subwavelength photonic lattices and solitons in periodically patterned graphene monolayer.

    PubMed

    Huang, Changming; Ye, Fangwei; Sun, Zhipei; Chen, Xianfeng

    2014-12-01

    We study linear and nonlinear mode properties in a periodically patterned graphene sheet. We demonstrate that a subwavelength one-dimensional photonic lattice can be defined across the graphene monolayer, with its modulation depth and correspondingly the associated photonic band structures being controlled rapidly, by an external gate voltage. We find the existences of graphene lattice solitons at the deep-subwavelength scales in both dimensions, thanks to the combination of graphene intrinsic self-focusing nonlinearity and the graphene plasmonic confinement effects.

  4. Fraunhofer Diffraction Patterns from Apertures Illuminated with Nonparallel Light.

    ERIC Educational Resources Information Center

    Klingsporn, Paul E.

    1979-01-01

    Discusses several aspects of Fraunhofer diffraction patterns from apertures illuminated by diverging light. Develops a generalization to apertures of arbitrary shape which shows that the sizes of the pattern are related by a simple scale factor. Uses the Abbe theory of image formation by diffraction to discuss the intensity of illumination of the…

  5. Sub-wavelength imaging of photo-induced refractive index pattern in chalcogenide glass films

    NASA Astrophysics Data System (ADS)

    Yang, Zhiyong; Anheier, Norman C.; Qiao, Hong A.; Lucas, Pierre

    2009-11-01

    Mapping of refractive index patterns with sub-wavelength resolution is achieved using Near-field Scanning Optical Microscopy (NSOM) in reflection mode. Imaging of index pattern is performed on surface gratings photo-imprinted in As 2S 3 films. The NSOM is adapted with a near infrared laser which wavelength (785 nm) is chosen to be within the transparency window of the glass film therefore allowing consistent measure of reflected light. Quantitative measurements of photo-induced index changes can then be obtained from knowledge of the initial film index. Images of gratings with a period of 0.5 micron are easily collected therefore demonstrating sub-wavelength spatial resolution. The technique permits to concurrently obtain a topographic image and index image of the gratings thereby permitting to quantify the extent of photodarkening and photoexpansion simultaneously. It is shown that relief gratings tend to vanish in films aged in air for several months however the index gratings remain.

  6. Optical properties of subwavelength patterned metal gratings for photonic device application and an alternative proposal

    NASA Astrophysics Data System (ADS)

    Lyu, Hong-Kun; Woo, Sungho; Jo, Sung-Hyun; Shin, Jang-Kyoo

    2013-09-01

    We investigated optical properties of subwavelength patterned metal gratings for photonic device application. It was known that optical transmittance of metal films with subwavelength periodic hole arrays can be controlled by applying a dielectric overlay to the film and the films can act as wavelength or frequency selective filters. Following advancement in lithography technology it could be applied up to complementary metal oxide semiconductor (CMOS) image sensors (CIS) by patterning metal layers placed on each pixel's photo detective device. However it is not easy to replace organic color filters applied on CIS up to date because the standard CIS structure has multi-metal layers, thick dielectric layers, and too thick metal layers. In this work, we explore possibility to integrate the metal film into a CIS chip and present an alternative proposal by computer simulation utilizing finite-difference time-domain (FDTD) method. We applied aluminum (Al) for the metal film and the dispersion information associated with Al was derived from the Lorentz-Drude model. We expect that this work could contribute to search to apply subwavelength patterned metal gratings to photonic devices.

  7. Diffraction patterns from multiple tilted laser apertures: numerical analysis

    NASA Astrophysics Data System (ADS)

    Kovalev, Anton V.; Polyakov, Vadim M.

    2016-03-01

    We propose a Rayleigh-Sommerfeld based method for numerical calculation of multiple tilted apertures near and far field diffraction patterns. Method is based on iterative procedure of fast Fourier transform based circular convolution of the initial field complex amplitudes distribution and impulse response function modified in order to account aperture and observation planes mutual tilt. The method is computationally efficient and has good accordance with the results of experimental diffraction patterns and can be applied for analysis of spatial noises occurring in master oscillator power amplifier laser systems. The example of diffraction simulation for a Phobos-Ground laser rangefinder amplifier is demonstrated.

  8. Transmittance enhancement of sapphires with antireflective subwavelength grating patterned UV polymer surface structures by soft lithography.

    PubMed

    Lee, Soo Hyun; Leem, Jung Woo; Yu, Jae Su

    2013-12-01

    We report the total and diffuse transmission enhancement of sapphires with the ultraviolet curable SU8 polymer surface structures consisting of conical subwavelength gratings (SWGs) at one- and both-side surfaces for different periods. The SWGs patterns on the silicon templates were transferred into the SU8 polymer film surface on sapphires by a simple and cost-effective soft lithography technique. For the fabricated samples, the surface morphologies, wetting behaviors, and optical characteristics were investigated. For theoretical optical analysis, a rigorous coupled-wave analysis method was used. At a period of 350 nm, the sample with SWGs on SU8 film/sapphire exhibited a hydrophobic surface and higher total transmittance compared to the bare sapphire over a wide wavelength of 450-1000 nm. As the period of SWGs was increased, the low total transmittance region of < 85% was shifted towards the longer wavelengths and became broader while the diffuse transmittance was increased (i.e., larger haze ratio). For the samples with SWGs at both-side surfaces, the total and diffuse transmittance spectra were further enhanced compared to the samples with SWGs at one-side surface. The theoretical optical calculation results showed a similar trend to the experimentally measured data. PMID:24514482

  9. Transmittance enhancement of sapphires with antireflective subwavelength grating patterned UV polymer surface structures by soft lithography.

    PubMed

    Lee, Soo Hyun; Leem, Jung Woo; Yu, Jae Su

    2013-12-01

    We report the total and diffuse transmission enhancement of sapphires with the ultraviolet curable SU8 polymer surface structures consisting of conical subwavelength gratings (SWGs) at one- and both-side surfaces for different periods. The SWGs patterns on the silicon templates were transferred into the SU8 polymer film surface on sapphires by a simple and cost-effective soft lithography technique. For the fabricated samples, the surface morphologies, wetting behaviors, and optical characteristics were investigated. For theoretical optical analysis, a rigorous coupled-wave analysis method was used. At a period of 350 nm, the sample with SWGs on SU8 film/sapphire exhibited a hydrophobic surface and higher total transmittance compared to the bare sapphire over a wide wavelength of 450-1000 nm. As the period of SWGs was increased, the low total transmittance region of < 85% was shifted towards the longer wavelengths and became broader while the diffuse transmittance was increased (i.e., larger haze ratio). For the samples with SWGs at both-side surfaces, the total and diffuse transmittance spectra were further enhanced compared to the samples with SWGs at one-side surface. The theoretical optical calculation results showed a similar trend to the experimentally measured data.

  10. Resonant optical transmission through sub-wavelength annular apertures caused by a plasmonic transverse electromagnetic (TEM) mode

    NASA Astrophysics Data System (ADS)

    Ndao, A.; Salvi, J.; Salut, R.; Bernal, M.-P.; Alaridhee, T.; Belkhir, A.; Baida, F. I.

    2014-12-01

    We demonstrate enhanced transmission through annular aperture arrays (AAA) by the excitation of the transverse electromagnetic (TEM) guided mode. A complete numerical study is performed to correctly design the structure before it is experimentally characterized. Actually, the challenge was to get efficient TEM-based transmission in the visible range. It turned out to be a hard task because of the strong absorption associated with this guided mode. Nevertheless, we have succeeded to experimentally prove its excitation thanks to the enhanced transmission measured in the far-field. This is the first time we demonstrate experimental evidence of this phenomenon with such AAA structure illuminated at oblique incidence in the visible range. This increases the potential applications of such structures as well, single molecule spectroscopy, photovoltaic, spectral filtering, optical trapping, etc...

  11. Fresnel diffraction and fractal patterns from polygonal apertures.

    PubMed

    Huang, J G; Christian, J M; McDonald, G S

    2006-11-01

    Two compact analytical descriptions of Fresnel diffraction patterns from polygonal apertures under uniform illumination are detailed. In particular, a simple expression for the diffracted field from constituent edges is derived. These results have fundamental importance as well as specific applications, and they promise new physical insights into diffraction-related phenomena. The usefulness of the formulations is illuminated in the context of a virtual source theory that accounts for two transverse dimensions. This application permits calculation of fractal unstable-resonator modes of arbitrary order and unprecedented accuracy. PMID:17047703

  12. Ultrafast rotating dipole or propeller-shaped patterns: subwavelength shaping of a beam of light on a femtosecond time scale.

    PubMed

    Khonina, Svetlana N; Golub, Ilya

    2016-04-01

    We report on a remarkable property of azimuthally (radially) polarized light beams containing a vortex or an orbital angular momentum: upon tight focusing of a first-order vortex beam, the subwavelength spot has a shape of an electric (magnetic) dipole rotating at an optical frequency. For beams with a vortex of order m, the generated pattern is propeller-shaped and rotates at a 1/m fraction of the optical frequency. The applications include petahertz control of electrical or optical conductance between two electrodes or waveguides of two-terminal junctions.

  13. Large-Area Sub-Wavelength Optical Patterning via Long-Range Ordered Polymer Lens Array.

    PubMed

    Wu, Jin; Liow, Chihao; Tao, Kai; Guo, Yuanyuan; Wang, Xiaotian; Miao, Jianmin

    2016-06-29

    Fabrication of large-area, highly orderly, and high-resolution nanostructures in a cost-effective fashion prompts advances in nanotechnology. Herein, for the first time, we demonstrate a unique strategy to prepare a long-range highly regular polymer lens from photoresist nanotrenches based templates, which are obtained from underexposure. The relationship between exposure dose and the cross-sectional morphology of produced photoresist nanostructures is revealed for the first time. The polymer lens arrays are repeatedly used for rapid generation of sub-100 nm nanopatterns across centimeter-scale areas. The light focusing properties of the nanoscale polymer lens are investigated by both simulation and experiment. It is found that the geometry, size of the lens, and the exposure dose can be deployed to adjust the produced feature size, spacing, and shapes. Because the polymer lenses are derived from top-down photolithography, the nearly perfect long-range periodicity of produced nanopatterns is ensured, and the feature shapes can be flexibly designed. Because this nanolithographic strategy enables subwavelength periodical nanopatterns with controllable feature size, geometry, and composition in a cost-effective manner, it can be optimized as a viable and potent nanofabrication tool for various technological applications. PMID:27301636

  14. Simultaneous displacement and slope measurement in electronic speckle pattern interferometry using adjustable aperture multiplexing.

    PubMed

    Lu, Min; Wang, Shengjia; Aulbach, Laura; Koch, Alexander W

    2016-08-01

    This paper suggests the use of adjustable aperture multiplexing (AAM), a method which is able to introduce multiple tunable carrier frequencies into a three-beam electronic speckle pattern interferometer to measure the out-of-plane displacement and its first-order derivative simultaneously. In the optical arrangement, two single apertures are located in the object and reference light paths, respectively. In cooperation with two adjustable mirrors, virtual images of the single apertures construct three pairs of virtual double apertures with variable aperture opening sizes and aperture distances. By setting the aperture parameter properly, three tunable spatial carrier frequencies are produced within the speckle pattern and completely separate the information of three interferograms in the frequency domain. By applying the inverse Fourier transform to a selected spectrum, its corresponding phase difference distribution can thus be evaluated. Therefore, we can obtain the phase map due to the deformation as well as its slope of the test surface from two speckle patterns which are recorded at different loading events. By this means, simultaneous and dynamic measurements are realized. AAM has greatly simplified the measurement system, which contributes to improving the system stability and increasing the system flexibility and adaptability to various measurement requirements. This paper presents the AAM working principle, the phase retrieval using spatial carrier frequency, and preliminary experimental results. PMID:27505365

  15. Large-area electromagnetic enhancement by a resonant excitation of surface waves on a metallic surface with periodic subwavelength patterns.

    PubMed

    Zhang, Xin; Liu, Haitao; Zhong, Ying

    2013-10-01

    We theoretically investigate the electromagnetic enhancement on a metallic surface patterned with periodic subwavelength structures. Fully-vectorial calculations show a large-area electromagnetic enhancement (LAEE) on the surface, which strongly contrasts with the previously reported "hot spots" that occur in specific tiny regions and which relieves the rigorous requirement of the nano-scale location of sample molecules. The LAEE allows for designing more practicable substrates for many enhanced-spectra applications. By building up microscopic models, the LAEE is shown due to a resonant excitation of surface waves that include both the surface plasmon polariton (SPP) and a quasi-cylindrical wave (QCW). The surface waves propagate on the substrate over a long distance and thus greatly enlarge the area of electromagnetic enhancement compared to the nano-sized hot spots caused by localized modes. Gain medium is introduced to further strengthen the large-area surface-wave resonance, with which an enhancement factor (EF) of electric-field intensity up to a few thousands is achieved.

  16. Design and fabrication of antireflective GaN subwavelength grating structures using periodic silica sphere monolayer array patterning

    NASA Astrophysics Data System (ADS)

    Ko, Yeong Hwan; Yu, Jae Su

    2013-12-01

    We designed and fabricated gallium nitride (GaN) subwavelength grating (SWG) structures on GaN/sapphire via patterning using the periodic silica sphere monolayer array as an etch mask and a subsequent dry etching for efficient antireflection coatings. Theoretical optimization of GaN SWG structures was performed in terms of their geometrical parameters by the rigorous coupled-wave analysis simulation using a theoretical structural model. The bullet-like parabola-shaped SWGs with a large height-to-diameter ratio ( R H/D) yielded good broadband and wide-angle antireflective surface properties. Considering the R H/D, the GaN SWG structure using 320-nm silica spheres theoretically and experimentally exhibited the most efficient antireflection property because it provided a linearly graded effective refractive index profile with relatively long relaxation length. For various geometries of the fabricated GaN SWGs on GaN/sapphire, the calculated reflectance results showed a similar tendency with the experimental results.

  17. A novel method of calculating far-field patterns of large aperture antennas

    NASA Technical Reports Server (NTRS)

    Bailey, M. C.

    1986-01-01

    A method is described for calculation of the radiation pattern of large aperture antennas. A piece-wise linear approximation of the aperture field using overlapping pyramidal basis functions allows the radiation pattern of an aperture antenna to be calculated as though it were a two-dimensional array. The calculation of radiation pattern data versus theta and phi, suitable for 3-D or contour plot algorithms, is achieved by locating the array in the yz-plane and performing a summation over the aperture field data sampled on a square grid. A FORTRAN subroutine is provided for performing radiation pattern calculations. Numerical results are included to demonstrate the accuracy and convergence of the method. These numerical results indicate that typical accuracies of + or - 0.1 dB for Directivity, + or - dB for the 1st Sidelobe Level, and + - 2dB for the 2nd Sidelobe Level can be obtained with an aperture grid of 45x45 points and requires approximately 0.02 seconds CPU time per far-field data point on a VAX 11/750 with a floating point accelerator.

  18. Nano patterning with a single high-transmission nano-metal aperture system

    NASA Astrophysics Data System (ADS)

    Kim, Yongwoo; Park, Sinjeung; Lee, Eungman; Hahn, Jae W.

    2008-03-01

    We design a C-shaped aperture which overcomes the diffraction limit of light to produce a high-brightness nano-size light spot. For optical nano lithography, we construct a nano patterning system using an optical probe which adopts a solid immersion lens (SIL), the 120 nm thickness aluminum film on the bottom surface of the SIL and the C-shaped aperture engraved in the metal film. Light source is a diode laser of 405nm wavelength to expose h-line photoresist(PR). A linear stage holding the optical probe makes the nano aperture contact with the PR coated on silicon wafer. Using this patterning system, we obtain sub 100nm array patterns and measure the system performance in various exposure conditions to verify the feasibility of plasmonic lithography.

  19. Stacked subwavelength gratings for imaging polarimetry

    NASA Astrophysics Data System (ADS)

    Deguzman, Panfilo Castro

    The stacking of subwavelength gratings (SWG) in an integrated structure is presented for an application in imaging polarimetry. Imaging polarimetry extends the capability of conventional imaging by providing polarization information about a scene, in addition to variations in intensity. In this dissertation, a novel approach is introduced to develop a real-time imaging polarimeter. Subwavelength gratings are implemented as linear and circular polarization filters that are directly mounted onto the focal plane array of an infrared (IR) camera. Wire grid polarizers are used as linear polarization filters. The stacked structure, consisting of a wire grid polarizer and a form birefringent quarter-wave plate (QWP), implements the circular polarization filter and is the focus of this dissertation. Initial investigations of the development of the individual SWG components and their integration are presented. Rigorous Coupled Wave Analysis (RCWA) was used to design the SWG structures. A broadband form birefringent quarter-wave plate for the 3.5 to 5 μm wavelength range was designed as a grating structure patterned directly into the substrate. Two fabrication methods for the wire grid polarizer were investigated. A 0.5 μm period polarizer was patterned by interference lithography. A 1 μm period polarizer was patterned by contact printing. The stacking of the subwavelength grating structures was analyzed using the Jones Matrix calculus and a new RCWA method (developed by fellow graduate student Jianhua Jiang). Stacked SWG's were fabricated as large area (1.3 cm x 1.3 cm) filters and as a 256 x 256 array of small aperture (15 μm x 15 μm) pixels. Two stack designs were investigated, referred to as Stack I and Stack II. Stack I consisted of the 0.5 μm period polarizer and the form birefringent QWP. Stack II consisted of the I μm grid period polarizer and the form birefringent QWP. Simulation and measured results are presented to compare the cases of samples with and

  20. Fraunhofer diffraction patterns from uniformly illuminated square output apertures with noncentered square obscurations.

    PubMed

    Sutton, G W; Weiner, M M; Mani, S A

    1976-09-01

    Theoretical Fraunhofer diffraction patterns are presented for uniformly illuminated square apertures with noncentered square obscurations. The energy within a given subtended solid angle in the far field is calculated. It is shown that the cornered-off-axis obscuration provides much more far-field energy in a given spot size than the centered obscuration for the same clear aperture area and total energy, for example, 82% more far-field energy in the first Airy square for 50% obscuration, thus providing superior performance for practical systems.

  1. Enhanced Etching, Surface Damage Recovery, and Submicron Patterning of Hybrid Perovskites using a Chemically Gas-Assisted Focused-Ion Beam for Subwavelength Grating Photonic Applications.

    PubMed

    Alias, Mohd S; Yang, Yang; Ng, Tien K; Dursun, Ibrahim; Shi, Dong; Saidaminov, Makhsud I; Priante, Davide; Bakr, Osman M; Ooi, Boon S

    2016-01-01

    The high optical gain and absorption of organic-inorganic hybrid perovskites have attracted attention for photonic device applications. However, owing to the sensitivity of organic moieties to solvents and temperature, device processing is challenging, particularly for patterning. Here, we report the direct patterning of perovskites using chemically gas-assisted focused-ion beam (GAFIB) etching with XeF2 and I2 precursors. We demonstrate etching enhancement in addition to controllability and marginal surface damage compared to focused-ion beam (FIB) etching without precursors. Utilizing the GAFIB etching, we fabricated a uniform and periodic submicron perovskite subwavelength grating (SWG) absorber with broadband absorption and nanoscale precision. Our results demonstrate the use of FIB as a submicron patterning tool and a means of providing surface treatment (after FIB patterning to minimize optical loss) for perovskite photonic nanostructures. The SWG absorber can be patterned on perovskite solar cells to enhance the device efficiency through increasing light trapping and absorption. PMID:26688008

  2. Enhanced Etching, Surface Damage Recovery, and Submicron Patterning of Hybrid Perovskites using a Chemically Gas-Assisted Focused-Ion Beam for Subwavelength Grating Photonic Applications.

    PubMed

    Alias, Mohd S; Yang, Yang; Ng, Tien K; Dursun, Ibrahim; Shi, Dong; Saidaminov, Makhsud I; Priante, Davide; Bakr, Osman M; Ooi, Boon S

    2016-01-01

    The high optical gain and absorption of organic-inorganic hybrid perovskites have attracted attention for photonic device applications. However, owing to the sensitivity of organic moieties to solvents and temperature, device processing is challenging, particularly for patterning. Here, we report the direct patterning of perovskites using chemically gas-assisted focused-ion beam (GAFIB) etching with XeF2 and I2 precursors. We demonstrate etching enhancement in addition to controllability and marginal surface damage compared to focused-ion beam (FIB) etching without precursors. Utilizing the GAFIB etching, we fabricated a uniform and periodic submicron perovskite subwavelength grating (SWG) absorber with broadband absorption and nanoscale precision. Our results demonstrate the use of FIB as a submicron patterning tool and a means of providing surface treatment (after FIB patterning to minimize optical loss) for perovskite photonic nanostructures. The SWG absorber can be patterned on perovskite solar cells to enhance the device efficiency through increasing light trapping and absorption.

  3. Computation of scalar far-field patterns of large-aperture antennas

    NASA Technical Reports Server (NTRS)

    Omalley, T. A.

    1976-01-01

    In computer programs used for evaluating the performance of high-gain antennas, efficient numerical methods for calculating the far-field patterns must be used since the majority of computer time and storage requirements may be attributed to this phase of the program. The numerical method most frequently used is the Fast Fourier Transform (FFT), which computes the far field as the Fourier transform of the field distribution in the antenna aperture. A new numerical method that in many applications is superior to the FFT in terms of reducing computer time and storage requirements is described.

  4. Realizable feed-element patterns and optimum aperture efficiency in multibeam antenna systems

    NASA Technical Reports Server (NTRS)

    Yngvesson, K. S.; Rahmat-Samii, Y.; Johansson, J. F.; Kim, Y. S.

    1988-01-01

    The results of an earlier paper by Rahmat-Samii et al. (1981), regarding realizable patterns from feed elements that are part of an array that feeds a reflector antenna, are extended. The earlier paper used a cos exp q theta model for the element radiation pattern, whereas here a parametric study is performed, using a model that assumes a central beam of cos exp q theta shape, with a constant sidelobe level outside the central beam. Realizable q-values are constrained by the maximum directivity based on feed element area. The optimum aperture efficiency (excluding array feed network losses) in an array-reflector system is evaluated as a function of element spacing using this model as well as the model of the earlier paper. Experimental data for tapered slot antenna (TSA) arrays are in agreement with the conclusions based on the model.

  5. Synchronized moving aperture radiation therapy (SMART): improvement of breathing pattern reproducibility using respiratory coaching

    NASA Astrophysics Data System (ADS)

    Neicu, Toni; Berbeco, Ross; Wolfgang, John; Jiang, Steve B.

    2006-02-01

    Recently, at Massachusetts General Hospital (MGH) we proposed a new treatment technique called synchronized moving aperture radiation therapy (SMART) to account for tumour motion during radiotherapy. The basic idea of SMART is to synchronize the moving radiation beam aperture formed by a dynamic multileaf collimator with the tumour motion induced by respiration. The two key requirements for being able to successfully use SMART in clinical practice are the precise and fast detection of tumour position during the simulation/treatment and the good reproducibility of the tumour motion pattern. To fulfil the first requirement, an integrated radiotherapy imaging system is currently being developed at MGH. The results of a previous study show that breath coaching techniques are required to make SMART an efficient technique in general. In this study, we investigate volunteer and patient respiratory coaching using a commercial respiratory gating system as a respiration coaching tool. Five healthy volunteers, observed during six sessions, and 33 lung cancer patients, observed during one session when undergoing 4D CT scans, were investigated with audio and visual promptings, with free breathing as a control. For all five volunteers, breath coaching was well tolerated and the intra- and inter-session reproducibility of the breathing pattern was greatly improved. Out of 33 patients, six exhibited a regular breathing pattern and needed no coaching, four could not be coached at all due to the patient's medical condition or had difficulty following the instructions, 13 could only be coached with audio instructions and 10 could follow the instructions of and benefit from audio-video coaching. We found that, for all volunteers and for those patients who could be properly coached, breath coaching improves the duty cycle of SMART treatment. However, about half of the patients could not follow both audio and video instructions simultaneously, suggesting that the current coaching

  6. Statistical approach for subwavelength measurements with a conventional light microscope

    PubMed Central

    Palanker, Daniel; Lewis, Aaron

    1991-01-01

    A method is developed theoretically that will permit subwavelength measurements of objects that differ from the surroundings by any contrast enhancing parameter, such as fluorescence, second harmonic generation, reflection et cetera, using a statistical analysis of a picture obtained with a conventional light microscope through a set of subwavelength apertures or by repeated scanning of a laser beam over a defined area. It is demonstrated that with this methodology information can be obtained on microdomains that are thirty times less than the diameter of the aperture. For example, for apertures that are 0.3 μm in diameter it is possible to measure the dimension of objects that are ∼10 nm. A technology is described by which it is possible to produce masks with the appropriate apertures. Instrumentation is described that would allow for the realization of these statistical methodologies with either apertures or scanning laser beams. ImagesFIGURE 2FIGURE 6FIGURE 7 PMID:19431808

  7. Subwavelength focusing of terahertz waves in silicon hyperbolic metamaterials.

    PubMed

    Kannegulla, Akash; Cheng, Li-Jing

    2016-08-01

    We theoretically demonstrate the subwavelength focusing of terahertz (THz) waves in a hyperbolic metamaterial (HMM) based on a two-dimensional subwavelength silicon pillar array microstructure. The silicon microstructure with a doping concentration of at least 1017  cm-3 offers a hyperbolic dispersion at terahertz frequency range and promises the focusing of terahertz Gaussian beams. The results agree with the simulation based on effective medium theory. The focusing effect can be controlled by the doping concentration, which determines the real part of the out-of-plane permittivity and, therefore, the refraction angles in HMM. The focusing property in the HMM structure allows the propagation of terahertz wave through a subwavelength aperture. The silicon-based HMM structure can be realized using microfabrication technologies and has the potential to advance terahertz imaging with subwavelength resolution. PMID:27472613

  8. Subwavelength nanopatterning of photochromic diarylethene films

    SciTech Connect

    Cantu, Precious; Brimhall, Nicole; Menon, Rajesh; Andrew, Trisha L.; Castagna, Rossella; Bertarelli, Chiara

    2012-04-30

    The resolution of optical patterning is constrained by the far-field diffraction limit. In this letter, we describe an approach that exploits the unique photo- and electro-chemistry of diarylethene photochromic molecules to overcome this diffraction limit and achieve sub-wavelength nanopatterning.

  9. Subwavelength nanopatterning of photochromic diarylethene films

    NASA Astrophysics Data System (ADS)

    Cantu, Precious; Brimhall, Nicole; Andrew, Trisha L.; Castagna, Rossella; Bertarelli, Chiara; Menon, Rajesh

    2012-04-01

    The resolution of optical patterning is constrained by the far-field diffraction limit. In this letter, we describe an approach that exploits the unique photo- and electro-chemistry of diarylethene photochromic molecules to overcome this diffraction limit and achieve sub-wavelength nanopatterning.

  10. Scale-dependent Patterns in One-dimensional Fracture Spacing and Aperture Data

    NASA Astrophysics Data System (ADS)

    Roy, A.; Perfect, E.

    2013-12-01

    One-dimensional scanline data about fracture spacing and size attributes such as aperture or length are mostly considered in separate studies that compute the cumulative frequency of these attributes without regard to their actual spatial sequence. In a previous study, we showed that spacing data can be analyzed using lacunarity to identify whether fractures occur in clusters. However, to determine if such clusters also contain the largest fractures in terms of a size attribute such as aperture, it is imperative that data about the size attribute be integrated with information about fracture spacing. While for example, some researchers have considered aperture in conjunction with spacing, their analyses were either applicable only to a specific type of data (e.g. multifractal) or failed to characterize the data at different scales. Lacunarity is a technique for analyzing multi-scale non-binary data and is ideally-suited for characterizing scanline data with spacing and aperture values. We present a technique that can statistically delineate the relationship between size attributes and spatial clustering. We begin by building a model scanline that has complete partitioning of fractures with small and large apertures between the intercluster regions and clusters. We demonstrate that the ratio of lacunarity for this model to that of its counterpart for a completely randomized sequence of apertures can be used to determine whether large-aperture fractures preferentially occur next to each other. The technique is then applied to two natural fracture scanline datasets, one with most of the large apertures occurring in fracture clusters, and the other with more randomly-spaced fractures, without any specific ordering of aperture values. The lacunarity ratio clearly discriminates between these two datasets and, in the case of the first example, it is also able to identify the range of scales over which the widest fractures are clustered. The technique thus developed for

  11. Fabrication of Nanoscale Oxide Aperture under the Influence of Electron Beam Exposure

    NASA Astrophysics Data System (ADS)

    Jung, M. Y.; Kim, D. W.; Choi, Seong S.

    2004-03-01

    Recently there have been tremendous interests about near field optical lithographic techniques for the next generation gigabyte information storage devices. The near field optical lithographic technique will circumvent the classical diffraction limit and can provide the sub-wavelength size patterns less than 100 nm and the parallel data processing has been examined. Therefore, several parallel processing techniques such as multi-cantilever array and the nano-size aperture array have been previously reported. In this work, the nano-fabrication technique for the sub-wavelength size aperture array is presented. Initially, the (50× 50) dot array was patterned on the SiO2 thermally grown on Si (100) substrate. Each dot has (5× 5) μ m^2 pattern size. The anisotropic TMAH etching of the Si substrate was performed and followed by anisotropic stress-dependent thermal oxidation at 1000 r C and backside Si etching using TMAH solution. The opening of the nano-size aperture on the oxide pyramid array was carried out using water-diluted (50:1) HF solution. The uniformity of the (50× 50) nano-size aperture array was examined carefully on the four corners of the array patterns. The average diameter of the aperture was ˜ 260 nm and its deviation was found to be ˜ 10%. The opening rate of the nano-oxide aperture presented the slightly higher that the expected data. The increased opening rate was attributed to the large amount of electron accumulation during FE-SEM measurements. The increased opening rate can be attributed to the Fermi level shift from electron accumulation on the nanoscale aperture area..

  12. Stopping potential and ion beamlet control for micro-resistive patterning through sub-Debye length plasma apertures

    NASA Astrophysics Data System (ADS)

    Chowdhury, Abhishek; Chatterjee, Sanghamitro; Dutta, Apurba; Bhattacharjee, Sudeep

    2014-12-01

    Focused multiple ion beamlets from a microwave plasma source is investigated for localized micron-scale modification of substrates in a patterned manner. Plasma electrodes (PE) with an array of through apertures having aperture diameters of the order of plasma Debye length are investigated for generating the beamlets. Extraction through sub-Debye length apertures becomes possible when the PE is kept at floating potential. It is found that the current - voltage characteristics of the extracted beamlets exhibits interesting features such as a space-charge-limited region that has a different behaviour than the conventional Child-Langmuir's law and an extraction-voltage-limited region that does not undergo saturation but exhibits a Schottky-like behaviour similar to that of a vacuum diode. A switching technique to control the motion of individual beamlets is developed and the stopping potential determined. The beamlets are thereafter used to create localized micro-resistive patterns. The experimental results are compared with simulations and reasonably good agreement is obtained.

  13. Stopping potential and ion beamlet control for micro-resistive patterning through sub-Debye length plasma apertures

    SciTech Connect

    Chowdhury, Abhishek; Chatterjee, Sanghamitro; Dutta, Apurba; Bhattacharjee, Sudeep

    2014-12-15

    Focused multiple ion beamlets from a microwave plasma source is investigated for localized micron-scale modification of substrates in a patterned manner. Plasma electrodes (PE) with an array of through apertures having aperture diameters of the order of plasma Debye length are investigated for generating the beamlets. Extraction through sub-Debye length apertures becomes possible when the PE is kept at floating potential. It is found that the current – voltage characteristics of the extracted beamlets exhibits interesting features such as a space-charge-limited region that has a different behaviour than the conventional Child-Langmuir’s law and an extraction-voltage-limited region that does not undergo saturation but exhibits a Schottky-like behaviour similar to that of a vacuum diode. A switching technique to control the motion of individual beamlets is developed and the stopping potential determined. The beamlets are thereafter used to create localized micro-resistive patterns. The experimental results are compared with simulations and reasonably good agreement is obtained.

  14. Predicting dissolution patterns in variable aperture fractures: 1. Development and evaluation of an enhanced depth-averaged computational model

    SciTech Connect

    Detwiler, R L; Rajaram, H

    2006-04-21

    Water-rock interactions within variable-aperture fractures can lead to dissolution of fracture surfaces and local alteration of fracture apertures, potentially transforming the transport properties of the fracture over time. Because fractures often provide dominant pathways for subsurface flow and transport, developing models that effectively quantify the role of dissolution on changing transport properties over a range of scales is critical to understanding potential impacts of natural and anthropogenic processes. Dissolution of fracture surfaces is controlled by surface-reaction kinetics and transport of reactants and products to and from the fracture surfaces. We present development and evaluation of a depth-averaged model of fracture flow and reactive transport that explicitly calculates local dissolution-induced alterations in fracture apertures. The model incorporates an effective mass transfer relationship that implicitly represents the transition from reaction-limited dissolution to transport-limited dissolution. We evaluate the model through direct comparison to previously reported physical experiments in transparent analog fractures fabricated by mating an inert, transparent rough surface with a smooth single crystal of potassium dihydrogen phosphate (KDP), which allowed direct measurement of fracture aperture during dissolution experiments using well-established light transmission techniques [Detwiler, et al., 2003]. Comparison of experiments and simulations at different flow rates demonstrate the relative impact of the dimensionless Peclet and Damkohler numbers on fracture dissolution and the ability of the computational model to simulate dissolution. Despite some discrepancies in the small-scale details of dissolution patterns, the simulations predict the evolution of large-scale features quite well for the different experimental conditions. This suggests that our depth-averaged approach to simulating fracture dissolution provides a useful approach for

  15. Nonlocal effects in double fishnet metasurfaces nanostructured at deep subwavelength level as a path toward simultaneous sensing of multiple chemical analytes

    NASA Astrophysics Data System (ADS)

    Tanasković, Dragan; Obradov, Marko; Jakšić, Olga; Jakšić, Zoran

    2016-01-01

    Nanoplasmonic devices are among the most sensitive chemical sensors, with sensitivities reaching the single-molecule level. An especially convenient class of such sensors is that based on metasurfaces with subwavelength nanoholes, examples being extraordinary optical transmission arrays and double fishnet structures. Such structures ensure operation both in transmission and reflection mode and ensure high sensitivities and excellent coupling with external readout. In this paper we consider the possibility to tailor the response of aperture-based sensor structures by modifying the geometry of nanoholes at the deep subwavelength level through ensuring controlled use of nonlocal effects. We investigate the case where nonlocality is achieved by modifying the basic metamaterial fishnet structure (a metal-dielectric-metal sandwich with rectangular openings) by superposing additional subwavelength patterns, ensuring the appearance of new optical modes. The obtained unit cell superstructure will have multiple tailorable spectral peaks that will increase the selectivity at different wavelengths. The finite elements method was used for simulations of the proposed structures. As an example, we applied our results to the case of a benzene sensor, showing that its spectral properties and selectivity can be tuned by modifying geometry at a deep subwavelength scale. The obtained custom-designed spectral selectivity is convenient for multianalyte chemical sensing using a single structure.

  16. Coupling polariton quantum boxes in sub-wavelength grating microcavities

    SciTech Connect

    Zhang, Bo; Wang, Zhaorong; Deng, Hui; Brodbeck, Sebastian; Kamp, Martin; Schneider, Christian; Höfling, Sven

    2015-02-02

    We report the construction of decoupled, coupled, and quasi-one dimensional polariton systems from zero dimensional polariton quantum boxes using microcavities with sub-wavelength gratings as the top mirror. By designing the tethering patterns around the suspended sub-wavelength gratings, we control the coupling between individual quantum boxes through different optical potentials. Energy levels and real-space or momentum space distributions of the confined modes were measured, which agreed well with simulations.

  17. Subwavelength hybrid terahertz waveguides.

    PubMed

    Nam, Sung Hyun; Taylor, Antoinette J; Efimov, Anatoly

    2009-12-01

    We introduce and present general properties of hybrid terahertz waveguides. Weakly confined Zenneck waves on a metal-dielectric interface at terahertz frequencies can be transformed to a strongly confined yet low-loss subwavelength mode through coupling with a photonic mode of a nearby high-index dielectric strip. We analyze confinement, attenuation, and dispersion properties of this mode. The proposed design is suitable for planar integration and allows easy fabrication on chip scale. The superior waveguiding properties at terahertz frequencies could enable the hybrid terahertz waveguides as building blocks for terahertz integrated circuits.

  18. Retrieving two-dimensional information of the subwavelength variation from far-field irradiance.

    PubMed

    Chu, Shu-Chun; Chern, Jyh-Long

    2006-10-01

    An eigenvalue-problem approach of blind deconvolution is developed to retrieve the information of two-dimensional subwavelength variation from far-field irradiance with an embedded-aperture configuration with three detectors. A reference signal has been implemented to determine the scaling issue, and hence it allows the exact order of magnitude of the retrieved signals to be estimated correctly. It is shown that the subwavelength variations of a two-dimensional aperture can be identified with a precision of better than a 1% error ratio.

  19. Gain and Loss Factor for Conical Horns, and Impact of Ground Plane Edge Diffractions on Radiation Patterns of Uncoated and Coated Circular Aperture Antennas

    NASA Astrophysics Data System (ADS)

    Aboserwal, Nafati Abdasallam

    Horn antennas have been used for over a hundred years. They have a wide variety of uses where they are a basic and popular microwave antenna for many practical applications, such as feed elements for communication reflector dishes on satellite or point-to-point relay antennas. They are also widely utilized as gain standards for calibration and gain measurement of other antennas. The gain and loss factor of conical horns are revisited in this dissertation based on spherical and quadratic aperture phase distributions. The gain is compared with published classical data in an attempt to confirm their validity and accuracy and to determine whether they were derived based on spherical or quadratic aperture phase distributions. In this work, it is demonstrated that the gain of a conical horn antenna obtained by using a spherical phase distribution is in close agreement with published classical data. Moreover, more accurate expressions for the loss factor, to account for amplitude and phase tapers over the horn aperture, are derived. New formulas for the design of optimum gain conical horns, based on the more accurate spherical aperture phase distribution, are derived. To better understand the impact of edge diffractions on aperture antenna performance, an extensive investigation of the edge diffractions impact is undertaken in this dissertation for commercial aperture antennas. The impact of finite uncoated and coated PEC ground plane edge diffractions on the amplitude patterns in the principal planes of circular apertures is intensively examined. Similarly, aperture edge diffractions of aperture antennas without ground planes are examined. Computational results obtained by the analytical model are compared with experimental and HFSS-simulated results for all cases studied. In addition, the impact of the ground plane size, coating thickness, and relative permittivity of the dielectric layer on the radiation amplitude in the back region has been examined. This

  20. Resonant Effects in Nanoscale Bowtie Apertures

    NASA Astrophysics Data System (ADS)

    Ding, Li; Qin, Jin; Guo, Songpo; Liu, Tao; Kinzel, Edward; Wang, Liang

    2016-06-01

    Nanoscale bowtie aperture antennas can be used to focus light well below the diffraction limit with extremely high transmission efficiencies. This paper studies the spectral dependence of the transmission through nanoscale bowtie apertures defined in a silver film. A realistic bowtie aperture is numerically modeled using the Finite Difference Time Domain (FDTD) method. Results show that the transmission spectrum is dominated by Fabry-Pérot (F-P) waveguide modes and plasmonic modes. The F-P resonance is sensitive to the thickness of the film and the plasmonic resonant mode is closely related to the gap distance of the bowtie aperture. Both characteristics significantly affect the transmission spectrum. To verify these numerical results, bowtie apertures are FIB milled in a silver film. Experimental transmission measurements agree with simulation data. Based on this result, nanoscale bowtie apertures can be optimized to realize deep sub-wavelength confinement with high transmission efficiency with applications to nanolithography, data storage, and bio-chemical sensing.

  1. A new sparse Bayesian learning method for inverse synthetic aperture radar imaging via exploiting cluster patterns

    NASA Astrophysics Data System (ADS)

    Fang, Jun; Zhang, Lizao; Duan, Huiping; Huang, Lei; Li, Hongbin

    2016-05-01

    The application of sparse representation to SAR/ISAR imaging has attracted much attention over the past few years. This new class of sparse representation based imaging methods present a number of unique advantages over conventional range-Doppler methods, the basic idea behind these works is to formulate SAR/ISAR imaging as a sparse signal recovery problem. In this paper, we propose a new two-dimensional pattern-coupled sparse Bayesian learning(SBL) method to capture the underlying cluster patterns of the ISAR target images. Based on this model, an expectation-maximization (EM) algorithm is developed to infer the maximum a posterior (MAP) estimate of the hyperparameters, along with the posterior distribution of the sparse signal. Experimental results demonstrate that the proposed method is able to achieve a substantial performance improvement over existing algorithms, including the conventional SBL method.

  2. A unidirectional subwavelength focusing near-field plate

    SciTech Connect

    Imani, Mohammadreza F.; Grbic, Anthony

    2014-01-28

    Near-field plates consist of non-periodically patterned surfaces that can overcome the diffraction limit and confine electromagnetic fields to subwavelength dimensions. Previous near-field plates experimentally demonstrated extreme field tailoring capabilities. However, their performance suffered from radiation/reflection in undesired directions, those other than the subwavelength focus. This issue can limit the practical use of near-field plates. In this paper, we address this issue by designing a unidirectional near-field plate that can form a subwavelength focal pattern, while suppressing the field radiated/reflected in other directions. The design and operation of the proposed unidirectional near-field plate are verified through full-wave simulation. The unidirectional near-field plate may find application in high resolution imaging and probing, high density data storage, and wireless power transfer systems. As an example, its utility as a high resolution probe is demonstrated through full-wave electromagnetic simulation.

  3. Spatial optical phase-modulating metadevice with subwavelength pixelation.

    PubMed

    Cencillo-Abad, Pablo; Plum, Eric; Rogers, Edward T F; Zheludev, Nikolay I

    2016-08-01

    Dynamic control over optical wavefronts enables focusing, diffraction and redirection of light on demand, however, sub-wavelength resolution is required to avoid unwanted diffracted beams that are present in commercial spatial light modulators. Here we propose a realistic metadevice that dynamically controls the optical phase of reflected beams with sub-wavelength pixelation in one dimension. Based on reconfigurable metamaterials and nanomembrane technology, it consists of individually moveable metallic nanowire actuators that control the phase of reflected light by modulating the optical path length. We demonstrate that the metadevice can provide on-demand optical wavefront shaping functionalities of diffraction gratings, beam splitters, phase-gradient metasurfaces, cylindrical mirrors and mirror arrays - with variable focal distance and numerical aperture - without unwanted diffraction.

  4. Spatial optical phase-modulating metadevice with subwavelength pixelation.

    PubMed

    Cencillo-Abad, Pablo; Plum, Eric; Rogers, Edward T F; Zheludev, Nikolay I

    2016-08-01

    Dynamic control over optical wavefronts enables focusing, diffraction and redirection of light on demand, however, sub-wavelength resolution is required to avoid unwanted diffracted beams that are present in commercial spatial light modulators. Here we propose a realistic metadevice that dynamically controls the optical phase of reflected beams with sub-wavelength pixelation in one dimension. Based on reconfigurable metamaterials and nanomembrane technology, it consists of individually moveable metallic nanowire actuators that control the phase of reflected light by modulating the optical path length. We demonstrate that the metadevice can provide on-demand optical wavefront shaping functionalities of diffraction gratings, beam splitters, phase-gradient metasurfaces, cylindrical mirrors and mirror arrays - with variable focal distance and numerical aperture - without unwanted diffraction. PMID:27505842

  5. Improved near field lithography by surface plasmon resonance in groove-patterned masks

    NASA Astrophysics Data System (ADS)

    Zeng, Beibei; Pan, Li; Liu, Ling; Fang, Liang; Wang, Changtao; Luo, Xiangang

    2009-12-01

    Near field lithography (NFL) provides an effective way for obtaining lithography features' sizes far beyond the diffraction limit. However, optical transmission through isolated subwavelength apertures is very low in the lithography process. It also makes it difficult to obtain a uniform lithography pattern where isolated and arrayed slit structures coexist because of different optical transmission through these two kinds of structures. It is proposed in this paper that using appropriately designed groove structures around subwavelength metallic slits could solve this problem. Numerical calculations performed by the finite-difference time-domain (FDTD) method demonstrate that about ten times transmission enhancement could be obtained. This occurs as a surface plasmon is resonantly excited and light is concentrated into nanometer scale apertures, resulting in not only greatly enhanced NFL efficiency but also uniform distribution of light intensity for isolated and arrayed slit patterns. Also discussed is the enhancement dependence on the structural parameters of NFL masks.

  6. Focussed ion beam machined cantilever aperture probes for near-field optical imaging.

    PubMed

    Jin, E X; Xu, X

    2008-03-01

    Near-field optical probe is the key element of a near-field scanning optical microscopy (NSOM) system. The key innovation in the first two NSOM experiments (Pohl et al., 1984; Lewis et al., 1984) is the fabrications of a sub-wavelength optical aperture at the apex of a sharply pointed transparent probe tip with a thin metal coating. This paper discusses the routine use of focussed ion beam (FIB) to micro-machine NSOM aperture probes from the commercial silicon nitride cantilevered atomic force microscopy probes. Two FIB micro-machining approaches are used to form a nanoaperture of controllable size and shape at the apex of the tip. The FIB side slicing produces a silicon nitride aperture on the flat-end tips with controllable sizes varying from 120 nm to 30 nm. The FIB head-on drilling creates holes on the aluminium-coated tips with sizes down to 50 nm. Nanoapertures in C and bow tie shapes can also be patterned using the FIB head-on milling method to possibly enhance the optical transmission. A transmission-collection NSOM system is constructed from a commercial atomic force microscopy to characterize the optical resolution of FIB-micro-machined aperture tips. The optical resolution of 78 nm is demonstrated by an aperture probe fabricated by FIB head-on drilling. Simultaneous topography imaging can also be realized using the same probe. By mapping the optical near-field from a bow-tie aperture, optical resolution as small as 59 nm is achieved by an aperture probe fabricated by the FIB side slicing method. Overall, high resolution and reliable optical imaging of routinely FIB-micro-machined aperture probes are demonstrated.

  7. Near-Field Spectroscopy and Imaging of Subwavelength Plasmonic Terahertz Resonators

    DOE PAGESBeta

    Mitrofanov, Oleg; Khromova, Irina; Siday, Thomas; Thompson, Robert J.; Ponomarev, Andrey N.; Brener, Igal; Reno, John L.

    2016-04-22

    We describe the temporal evolution of the terahertz (THz) field leading to the excitation of plasmonic resonances in carbon microfibers. The field evolution is mapped in space and time for the 3/2 wavelength resonance using a subwavelength aperture THz near-field probe with an embedded THz photoconductive detector. The excitation of surface waves at the fiber tips leads to the formation of a standing wave along the fiber. Local THz time-domain spectroscopy at one of the standing wave crests shows a clear third-order resonance peak at 1.65 THz, well described by the Lorentz model. Lastly, this application of the subwavelength aperturemore » THz near-field microscopy for mode mapping and local spectroscopy demonstrates the potential of near-field methods for studies of subwavelength plasmonic THz resonators.« less

  8. Analysis of line-and-space resist patterns with sub-20 nm half-pitch fabricated using high-numerical-aperture exposure tool of extreme ultraviolet lithography

    NASA Astrophysics Data System (ADS)

    Kozawa, Takahiro; Santillan, Julius Joseph; Itani, Toshiro

    2016-09-01

    The resolution of resist processes for extreme ultraviolet (EUV) lithography has been steadily improved and has reached the sub-20 nm half-pitch region. Currently, the resist materials capable of resolving 11 nm half-pitch line-and-space patterns are being developed in industrial fields. In this study, the line-and-space resist patterns with sub-20 nm half-pitches were fabricated using a high-numerical-aperture (NA) EUV exposure tool and analyzed by the Monte Carlo simulation. The scanning electron microscopy (SEM) images of resist patterns after their development were compared with the latent images calculated on the basis of the sensitization and reaction mechanisms of chemically amplified EUV resists. The approximate relationship between resist patterns and latent images was clarified for the sub-20 nm half-pitch region. For the realization of 11 nm half-pitch fabrication, the suppression of the stochastic effects in the development process is an important consideration.

  9. Subwavelength focusing and guiding of surface plasmons.

    PubMed

    Yin, Leilei; Vlasko-Vlasov, Vitali K; Pearson, John; Hiller, Jon M; Hua, Jiong; Welp, Ulrich; Brown, Dennis E; Kimball, Clyde W

    2005-07-01

    The constructive interference of surface plasmon polaritons (SPP) launched by nanometric holes allows us to focus SPP into a spot of high near-field intensity having subwavelength width. Near-field scanning optical microscopy is used to map the local SPP intensity. The resulting SPP patterns and their polarization dependence are accurately described in model calculations based on a dipolar model for the SPP emission at each hole. Furthermore, we show that the high SPP intensity in the focal spot can be launched and propagated on a Ag strip guide with a 250 x 50 nm2 cross section, thus overcoming the diffraction limit of conventional optics. The combination of focusing arrays and nano-waveguides may serve as a basic element in planar nano-photonic circuits.

  10. Mosaic of coded aperture arrays

    DOEpatents

    Fenimore, Edward E.; Cannon, Thomas M.

    1980-01-01

    The present invention pertains to a mosaic of coded aperture arrays which is capable of imaging off-axis sources with minimum detector size. Mosaics of the basic array pattern create a circular on periodic correlation of the object on a section of the picture plane. This section consists of elements of the central basic pattern as well as elements from neighboring patterns and is a cyclic version of the basic pattern. Since all object points contribute a complete cyclic version of the basic pattern, a section of the picture, which is the size of the basic aperture pattern, contains all the information necessary to image the object with no artifacts.

  11. Wave front engineering from an array of thin aperture antennas.

    PubMed

    Kang, Ming; Feng, Tianhua; Wang, Hui-Tian; Li, Jensen

    2012-07-01

    We propose an ultra-thin metamaterial constructed by an ensemble of the same type of anisotropic aperture antennas with phase discontinuity for wave front manipulation across the metamaterial. A circularly polarized light is completely converted to the cross-polarized light which can either be bent or focused tightly near the diffraction limit. It depends on a precise control of the optical-axis profile of the antennas on a subwavelength scale, in which the rotation angle of the optical axis has a simple linear relationship to the phase discontinuity. Such an approach enables effective wave front engineering within a subwavelength scale.

  12. Resonant Effects in Nanoscale Bowtie Apertures.

    PubMed

    Ding, Li; Qin, Jin; Guo, Songpo; Liu, Tao; Kinzel, Edward; Wang, Liang

    2016-01-01

    Nanoscale bowtie aperture antennas can be used to focus light well below the diffraction limit with extremely high transmission efficiencies. This paper studies the spectral dependence of the transmission through nanoscale bowtie apertures defined in a silver film. A realistic bowtie aperture is numerically modeled using the Finite Difference Time Domain (FDTD) method. Results show that the transmission spectrum is dominated by Fabry-Pérot (F-P) waveguide modes and plasmonic modes. The F-P resonance is sensitive to the thickness of the film and the plasmonic resonant mode is closely related to the gap distance of the bowtie aperture. Both characteristics significantly affect the transmission spectrum. To verify these numerical results, bowtie apertures are FIB milled in a silver film. Experimental transmission measurements agree with simulation data. Based on this result, nanoscale bowtie apertures can be optimized to realize deep sub-wavelength confinement with high transmission efficiency with applications to nanolithography, data storage, and bio-chemical sensing. PMID:27250995

  13. Resonant Effects in Nanoscale Bowtie Apertures

    PubMed Central

    Ding, Li; Qin, Jin; Guo, Songpo; Liu, Tao; Kinzel, Edward; Wang, Liang

    2016-01-01

    Nanoscale bowtie aperture antennas can be used to focus light well below the diffraction limit with extremely high transmission efficiencies. This paper studies the spectral dependence of the transmission through nanoscale bowtie apertures defined in a silver film. A realistic bowtie aperture is numerically modeled using the Finite Difference Time Domain (FDTD) method. Results show that the transmission spectrum is dominated by Fabry-Pérot (F-P) waveguide modes and plasmonic modes. The F-P resonance is sensitive to the thickness of the film and the plasmonic resonant mode is closely related to the gap distance of the bowtie aperture. Both characteristics significantly affect the transmission spectrum. To verify these numerical results, bowtie apertures are FIB milled in a silver film. Experimental transmission measurements agree with simulation data. Based on this result, nanoscale bowtie apertures can be optimized to realize deep sub-wavelength confinement with high transmission efficiency with applications to nanolithography, data storage, and bio-chemical sensing. PMID:27250995

  14. Spin-dependent diffraction of evanescent waves by subwavelength gratings.

    PubMed

    Wu, Kedi; Wang, Guo Ping

    2015-08-15

    We present a way to observe the spin-to-orbital conversion phenomenon. A spinning evanescent wave can be asymmetrically transformed into propagation waves through one certain diffraction order by a periodical subwavelength grating. By detecting diffraction field distribution behind the grating, we observed spin-dependent diffraction patterns. Furthermore, replacing the periodical grating by a Fibonacci grating, we can simultaneously observe multiple order diffractions of a spin evanescent wave. In this case, the multiple diffraction beams can interfere with each other behind the quasi-periodical grating to form asymmetric interference patterns. Our work provides another way toward the realization of spin-to-orbital conversion of light. PMID:26274640

  15. Subwavelength micropillar array terahertz lasers.

    PubMed

    Krall, Michael; Brandstetter, Martin; Deutsch, Christoph; Detz, Hermann; Andrews, Aaron Maxwell; Schrenk, Werner; Strasser, Gottfried; Unterrainer, Karl

    2014-01-13

    We report on micropillar-based terahertz lasers with active pillars that are much smaller than the emission wavelength. These micropillar array lasers correspond to scaled-down band-edge photonic crystal lasers forming an active photonic metamaterial. In contrast to photonic crystal lasers which use significantly larger pillar structures, lasing emission is not observed close to high-symmetry points in the photonic band diagram, but in the effective medium regime. We measure stimulated emission at 4 THz for micropillar array lasers with pillar diameters of 5 µm. Our results not only demonstrate the integration of active subwavelength optics in a terahertz laser, but are also an important step towards the realization of nanowire-based terahertz lasers.

  16. Dexterous acoustic trapping and patterning of particles assisted by phononic crystal plate

    NASA Astrophysics Data System (ADS)

    Wang, Tian; Ke, Manzhu; Xu, Shengjun; Feng, Junheng; Qiu, Chunyin; Liu, Zhengyou

    2015-04-01

    In this letter, we present experimental demonstration of multi-particles trapping and patterning by the artificially engineered acoustic field of phononic crystal plate. Polystyrene particles are precisely trapped and patterned in two dimensional arrays, for example, the square, triangular, or quasi-periodic arrays, depending on the structures of the phononic crystal plates with varying sub-wavelength holes array. Analysis shows that the enhanced acoustic radiation force, induced by the resonant transmission field highly localized near the sub-wavelength apertures, accounts for the particles self-organizing. It can be envisaged that this kind of simple design of phononic crystal plates would pave an alternative route for self-assembly of particles and may be utilized in the lab-on-a-chip devices.

  17. Dexterous acoustic trapping and patterning of particles assisted by phononic crystal plate

    SciTech Connect

    Wang, Tian; Ke, Manzhu Xu, Shengjun; Feng, Junheng; Qiu, Chunyin; Liu, Zhengyou

    2015-04-20

    In this letter, we present experimental demonstration of multi-particles trapping and patterning by the artificially engineered acoustic field of phononic crystal plate. Polystyrene particles are precisely trapped and patterned in two dimensional arrays, for example, the square, triangular, or quasi-periodic arrays, depending on the structures of the phononic crystal plates with varying sub-wavelength holes array. Analysis shows that the enhanced acoustic radiation force, induced by the resonant transmission field highly localized near the sub-wavelength apertures, accounts for the particles self-organizing. It can be envisaged that this kind of simple design of phononic crystal plates would pave an alternative route for self-assembly of particles and may be utilized in the lab-on-a-chip devices.

  18. Evidence for subwavelength imaging with positive refraction

    NASA Astrophysics Data System (ADS)

    Gui Ma, Yun; Sahebdivan, Sahar; Ong, C. K.; Tyc, Tomáš; Leonhardt, Ulf

    2011-03-01

    The resolution of lenses is normally limited by the wave nature of light. Imaging with perfect resolution was believed to rely on negative refraction, but here we present experimental evidence for subwavelength imaging with positive refraction.

  19. Aperture excited dielectric antennas

    NASA Technical Reports Server (NTRS)

    Crosswell, W. F.; Chatterjee, J. S.; Mason, V. B.; Tai, C. T.

    1974-01-01

    The results of a comprehensive experimental and theoretical study of the effect of placing dielectric objects over the aperture of waveguide antennas are presented. Experimental measurements of the radiation patterns, gain, impedance, near-field amplitude, and pattern and impedance coupling between pairs of antennas are given for various Plexiglas shapes, including the sphere and the cube, excited by rectangular, circular, and square waveguide feed apertures. The waveguide excitation of a dielectric sphere is modeled using the Huygens' source, and expressions for the resulting electric fields, directivity, and efficiency are derived. Calculations using this model show good overall agreement with experimental patterns and directivity measurements. The waveguide under an infinite dielectric slab is used as an impedance model. Calculations using this model agree qualitatively with the measured impedance data. It is concluded that dielectric loaded antennas such as the waveguide excited sphere, cube, or sphere-cylinder can produce directivities in excess of that obtained by a uniformly illuminated aperture of the same cross section, particularly for dielectric objects with dimensions of 2 wavelengths or less. It is also shown that for certain configurations coupling between two antennas of this type is less than that for the same antennas without dielectric loading.

  20. Novel large aperture EBCCD

    NASA Astrophysics Data System (ADS)

    Suzuki, Atsumu; Aoki, Shigeki; Haba, Junji; Sakuda, Makoto; Suyama, Motohiro

    2011-02-01

    A novel large aperture electron bombardment charge coupled device (EBCCD) has been developed. The diameter of its photocathode is 10 cm and it is the first EBCCD with such a large aperture. Its gain shows good linearity as a function of applied voltage up to -12 kV, where the gain is 2400. The spatial resolution was measured using ladder pattern charts. It is better than 2 line pairs/mm, which corresponds to 3.5 times the CCD pixel size. The spatial resolution was also measured with a copper foil pattern on a fluorescent screen irradiated with X-rays (14 and 18 keV) and a 60 keV gamma-ray from an americium source. The result was consistent with the measurement using ladder pattern charts. The output signal as a function of input light intensity shows better linearity than that of image intensifier tubes (IIT) as expected. We could detect cosmic rays passing through a scintillating fiber block and a plastic scintillator as a demonstration for a practical use in particle physics experiments. This kind of large aperture EBCCD can, for example, be used as an image sensor for a detector with a large number of readout channels and is expected to be additionally applied to other physics experiments.

  1. Centimeter-scale subwavelength photolithography using metal-coated elastomeric photomasks with modulated light intensity at the oblique sidewalls.

    PubMed

    Wu, Jin; Liu, Yayuan; Guo, Yuanyuan; Feng, Shuanglong; Zou, Binghua; Mao, Hui; Yu, Cheng-han; Tian, Danbi; Huang, Wei; Huo, Fengwei

    2015-05-01

    By coating polydimethylsiloxane (PDMS) relief structures with a layer of opaque metal such as gold, the incident light is strictly allowed to pass through the nanoscopic apertures at the sidewalls of PDMS reliefs to expose underlying photoresist at nanoscale regions, thus producing subwavelength nanopatterns covering centimeter-scale areas. It was found that the sidewalls were a little oblique, which was the key to form the nanoscale apertures. Two-sided and one-sided subwavelength apertures can be constructed by employing vertical and oblique metal evaporation directions, respectively. Consequently, two-line and one-line subwavelength nanopatterns with programmable feature shapes, sizes, and periodicities could be produced using the obtained photomasks. The smallest aperture size and line width of 80 nm were achieved. In contrast to the generation of raised positive photoresist nanopatterns in phase shifting photolithography, the recessed positive photoresist nanopatterns produced in this study provide a convenient route to transfer the resist nanopatterns to metal nanopatterns. This nanolithography methodology possesses the distinctive advantages of simplicity, low cost, high throughput, and nanoscale feature size and shape controllability, making it a potent nanofabrication technique to enable functional nanostructures for various potential applications.

  2. Subwavelength Lattice Optics by Evolutionary Design

    PubMed Central

    2015-01-01

    This paper describes a new class of structured optical materials—lattice opto-materials—that can manipulate the flow of visible light into a wide range of three-dimensional profiles using evolutionary design principles. Lattice opto-materials are based on the discretization of a surface into a two-dimensional (2D) subwavelength lattice whose individual lattice sites can be controlled to achieve a programmed optical response. To access a desired optical property, we designed a lattice evolutionary algorithm that includes and optimizes contributions from every element in the lattice. Lattice opto-materials can exhibit simple properties, such as on- and off-axis focusing, and can also concentrate light into multiple, discrete spots. We expanded the unit cell shapes of the lattice to achieve distinct, polarization-dependent optical responses from the same 2D patterned substrate. Finally, these lattice opto-materials can also be combined into architectures that resemble a new type of compound flat lens. PMID:25380062

  3. Metalenses at visible wavelengths: Diffraction-limited focusing and subwavelength resolution imaging

    NASA Astrophysics Data System (ADS)

    Khorasaninejad, Mohammadreza; Chen, Wei Ting; Devlin, Robert C.; Oh, Jaewon; Zhu, Alexander Y.; Capasso, Federico

    2016-06-01

    Subwavelength resolution imaging requires high numerical aperture (NA) lenses, which are bulky and expensive. Metasurfaces allow the miniaturization of conventional refractive optics into planar structures. We show that high-aspect-ratio titanium dioxide metasurfaces can be fabricated and designed as metalenses with NA = 0.8. Diffraction-limited focusing is demonstrated at wavelengths of 405, 532, and 660 nm with corresponding efficiencies of 86, 73, and 66%. The metalenses can resolve nanoscale features separated by subwavelength distances and provide magnification as high as 170×, with image qualities comparable to a state-of-the-art commercial objective. Our results firmly establish that metalenses can have widespread applications in laser-based microscopy, imaging, and spectroscopy.

  4. Routing of deep-subwavelength optical beams without reflection and diffraction using infinitely anisotropic metamaterials

    NASA Astrophysics Data System (ADS)

    Catrysse, Peter B.; Fan, Shanhui

    2015-03-01

    Media that are described by extreme electromagnetic parameters, such as very large/small permittivity/permeability, have generated significant fundamental and applied interest in recent years. Notable examples include epsilon-near-zero, ultra-low refractive-index, and ultra-high refractive-index materials. Many photonic structures, such as waveguides, lenses, and photonic band gap materials, benefit greatly from the large index contrast provided by such media. In this paper, I discuss our recent work on media with infinite anisotropy, i.e., infinite permittivity (permeability) in one direction and finite in the other directions. As an illustration of the unusual optical behaviors that result from infinite anisotropy, I describe efficient light transport in deep-subwavelength apertures filled with infinitely anisotropic media. I then point out some of the opportunities that exist for controlling light at the nano-scale using infinitely anisotropic media by themselves. First, I show that a single medium with infinite anisotropy enables diffraction-free propagation of deep-subwavelength beams. Next, I demonstrate interfaces between two infinitely anisotropic media that are impedancematched for complete deep-subwavelength beams and enable reflection-free routing with zero bend radius that is entirely free from diffraction effects even when deep-subwavelength information is encoded on the beams. These behaviors indicate an unprecedented possibility to use media with infinite anisotropy to manipulate beams with deepsubwavelength features, including complete images. To illustrate physical realizability, I demonstrate a metamaterial design using existing materials in a planar geometry, which can be implemented using well-established nanofabrication techniques. This approach provides a path to deep-subwavelength routing of information-carrying beams and far-field imaging unencumbered by diffraction and reflection.

  5. Broadband chirality-coded meta-aperture for photon-spin resolving

    PubMed Central

    Du, Luping; Kou, Shan Shan; Balaur, Eugeniu; Cadusch, Jasper J.; Roberts, Ann; Abbey, Brian; Yuan, Xiao-Cong; Tang, Dingyuan; Lin, Jiao

    2015-01-01

    The behaviour of light transmitted through an individual subwavelength aperture becomes counterintuitive in the presence of surrounding ‘decoration', a phenomenon known as the extraordinary optical transmission. Despite being polarization-sensitive, such an individual nano-aperture, however, often cannot differentiate between the two distinct spin-states of photons because of the loss of photon information on light-aperture interaction. This creates a ‘blind-spot' for the aperture with respect to the helicity of chiral light. Here we report the development of a subwavelength aperture embedded with metasurfaces dubbed a ‘meta-aperture', which breaks this spin degeneracy. By exploiting the phase-shaping capabilities of metasurfaces, we are able to create specific meta-apertures in which the pair of circularly polarized light spin-states produces opposite transmission spectra over a broad spectral range. The concept incorporating metasurfaces with nano-apertures provides a venue for exploring new physics on spin-aperture interaction and potentially has a broad range of applications in spin-optoelectronics and chiral sensing. PMID:26628047

  6. Deep subwavelength waveguiding and focusing based on designer surface plasmons.

    PubMed

    Zhao, Wangshi; Eldaiki, Omar M; Yang, Ruoxi; Lu, Zhaolin

    2010-09-27

    We experimentally demonstrate focusing and guiding electromagnetic (EM) waves in a designer surface plasmonic waveguide with deep subwavelength mode cross section. Our experiments show that a metal grating with suitable parameters, functioning as a designer surface plasmonic waveguide, can support deep subwavelength surface modes and the width of the modes can be squeezed also into deep subwavelength by tapering the width of the waveguide. The results provide a new insight into deep subwavelength waveguiding and focusing.

  7. Generation and subwavelength focusing of longitudinal magnetic fields in a metallized fiber tip.

    PubMed

    Ploss, Daniel; Kriesch, Arian; Pfeifer, Hannes; Banzer, Peter; Peschel, Ulf

    2014-06-01

    We demonstrate experimentally and numerically that in fiber tips as they are used in NSOMs azimuthally polarized electrical fields (|E(azi)|2 / |E(tot)|2 ≈55% ± 5% for λ0 = 1550 nm), respectively subwavelength confined (FWHM ≈450 nm ≈λ0/3.5) magnetic fields, are generated for a certain tip aperture diameter (d = 1.4 μm). We attribute the generation of this field distribution in metal-coated fiber tips to symmetry breaking in the bend and subsequent plasmonic mode filtering in the truncated conical taper. PMID:24921567

  8. Extraordinary transmission-based super-resolved axial imaging using subwavelength metallic nanoaperture arrays

    NASA Astrophysics Data System (ADS)

    Lee, Wonju; Oh, Youngjin; Choi, Jong-ryul; Kim, Kyujung; Kim, Donghyun

    2015-03-01

    A super-resolved axial imaging technique was investigated based on extraordinary transmission (EOT) of light using metallic gradient nanoaperture arrays. Light through subwavelength nanoapertures at thick metal film can be transmitted and amplified by several orders of magnitude due to plasmonic coupling. Here, the feasibility of EOT-based axial imaging with super resolution is explored. Since light penetration of EOT is much deeper than that of evanescent waves, the axial range to obtain the distance information of fluorescence signals can be extended by EOT. The axial distribution of ganglioside in mouse macrophage cells was measured with sub-diffraction-limited resolution after reconstruction using differential fluorescence excitation on gradient aperture arrays.

  9. Optical addressing at the subwavelength scale

    PubMed

    Weeber; Dereux; Girard; Colas Des Francs G; Krenn; Goudonnet

    2000-11-01

    The Green dyadic formalism is applied to the study of the optical properties of dielectric subwavelength structures integrated in coplanar geometry. We first consider homogeneous wires with high refractive index featuring subwavelength cross sections. We show that such wires may have guiding properties and that they may be coupled with a local illumination produced by a focused Gaussian beam totally reflected at the substrate interface. When excited by the focused beam, these subwavelength optical waveguides (SOW's) provide a confined source of light that could be used to excite a single nanoscopic object. Well designed heteregeneous wires resulting from the alignment of dielectric particles separated from each other by a subwavelength distance are also found to propagate a Gaussian beam excitation over several micrometers. This propagation occurs with reasonable damping for incident beams in the visible frequency range. The computed transmission spectra of these heterowires may exhibit narrow gaps. Finally, we discuss the relation between the optical properties of the SOW and the calculated electromagnetic local density of states. PMID:11102099

  10. A systematic review of aperture shapes

    NASA Astrophysics Data System (ADS)

    Schultz, A. B.; Frazier, T. V.

    The paper discusses the application of apodization to reflecting telescopes. The diffraction pattern of a telescope, which is the image of a star, can be changed considerably by using different aperture shapes in combination with appropriately shaped occulting masks on the optical axis. Aperture shapes studied were the circular, square, and hexagonal. Polaris (α-UMin) was used as the test system.

  11. Evaluation of GLOCK 9 mm Firing Pin Aperture Shear Mark Individuality Based On 1,632 Different Pistols by Traditional Pattern Matching and IBIS Pattern Recognition.

    PubMed

    Hamby, James E; Norris, Stephen; Petraco, Nicholas D K

    2016-01-01

    Over a period of 21 years, a number of fired GLOCK cartridge cases have been evaluated. A total of 1632 GLOCK firearms were used to generate a sample of the same size. Our research hypothesis was that no cartridge cases fired from different 9-mm semiautomatic GLOCK pistols would be mistaken as coming from the same gun. Using optical comparison microscopy, two separate experiments were carried out to test this hypothesis. A subsample of 617 test-fired cases were subjected to algorithmic comparison by the Integrated Ballistics Identification System (IBIS). The second experiment subjected the full set of 1632 cases to manual comparisons using traditional pattern matching. None of the cartridge cases were "matched" by either of these two experiments. Using these empirical findings, an established Bayesian probability model was used to estimate the chance that a 9-mm cartridge case, fired from a GLOCK, could be mistaken as coming from the same firearm when in fact it did not (i.e., the random match probability). PMID:26390232

  12. Approximate model for surface-plasmon generation at slit apertures.

    PubMed

    Lalanne, P; Hugonin, J P; Rodier, J C

    2006-07-01

    We present a semianalytical model that quantitatively predicts the scattering of light by a single subwavelength slit in a thick metal screen. In contrast to previous theoretical works related to the transmission properties of the slit, the analysis emphasizes the generation of surface plasmons at the slit apertures. The model relies on a two-stage scattering mechanism, a purely geometric diffraction problem in the immediate vicinity of the slit aperture followed by the launching of a bounded surface-plasmon wave on the flat interfaces surrounding the aperture. By comparison with a full electromagnetic treatment, the model is shown to provide accurate formulas for the plasmonic generation strength coefficients, even for metals with a low conductivity. Limitations are outlined for large slit widths (>lambda) or oblique incidence (>30 degrees ) when the slit is illuminated by a plane wave. PMID:16783423

  13. High power laser antireflection subwavelength grating on fused silica by colloidal lithography

    NASA Astrophysics Data System (ADS)

    Ye, Xin; Huang, Jin; Geng, Feng; Liu, Hongjie; Sun, Laixi; Yan, Lianghong; Jiang, Xiaodong; Wu, Weidong; Zheng, Wanguo

    2016-07-01

    In this study we report on an efficient and simple method to fabricate an antireflection subwavelength grating on a fused silica substrate using two-step reactive ion etching with monolayer polystyrene colloidal crystals as masks. We show that the period and spacing of the obtained subwavelength grating were determined by the initial diameter of polystyrene microspheres and the oxygen ion etching duration. The height of pillar arrays can be adjusted by tuning the second-step fluorine ion etching duration. These parameters are proved to be useful in tailoring the antireflection properties of subwavelength grating using a finite-difference time-domain (FDTD) method and effective medium theory. The subwavelength grating exhibits excellent antireflection properties. The near-field distribution of the SWG which is directly patterned into the substrate material is performed by a 3D-FDTD method. It is found that the near-field distribution is strongly dependent on the periodicity of surface structure, which has the potential to promote the ability of anti-laser-induced damage. For 10 ns pulse duration and 1064 nm wavelength, we experimentally determined their laser induced damage threshold to 32 J cm-2, which is nearly as high as bulk fused silica with 31.5 J cm-2.

  14. High power laser antireflection subwavelength grating on fused silica by colloidal lithography

    NASA Astrophysics Data System (ADS)

    Ye, Xin; Huang, Jin; Geng, Feng; Liu, Hongjie; Sun, Laixi; Yan, Lianghong; Jiang, Xiaodong; Wu, Weidong; Zheng, Wanguo

    2016-07-01

    In this study we report on an efficient and simple method to fabricate an antireflection subwavelength grating on a fused silica substrate using two-step reactive ion etching with monolayer polystyrene colloidal crystals as masks. We show that the period and spacing of the obtained subwavelength grating were determined by the initial diameter of polystyrene microspheres and the oxygen ion etching duration. The height of pillar arrays can be adjusted by tuning the second-step fluorine ion etching duration. These parameters are proved to be useful in tailoring the antireflection properties of subwavelength grating using a finite-difference time-domain (FDTD) method and effective medium theory. The subwavelength grating exhibits excellent antireflection properties. The near-field distribution of the SWG which is directly patterned into the substrate material is performed by a 3D-FDTD method. It is found that the near-field distribution is strongly dependent on the periodicity of surface structure, which has the potential to promote the ability of anti-laser-induced damage. For 10 ns pulse duration and 1064 nm wavelength, we experimentally determined their laser induced damage threshold to 32 J cm‑2, which is nearly as high as bulk fused silica with 31.5 J cm‑2.

  15. Subwavelength structured surfaces and their applications

    NASA Technical Reports Server (NTRS)

    Raguin, Daniel H.; Morris, G. Michael

    1993-01-01

    The term subwavelength structured (SWS) surface describes any surface that contains a subwavelength-period grating or gratings. The grating may be of any type provided the period is sufficiently fine so that, unlike conventional gratings, no diffraction orders propagate other than the zeroth orders. Because of the fine periods involved, the fabrication of such surfaces for applications in the visible and infrared portions of the spectral regime have only recently been considered. With refinements in holographic procedures and the push of the semiconductor industry for submicron lithography, production of SWS surfaces is becoming increasingly viable. The topics covered include the following: analytic approaches to analyze SWS surfaces, 1D periodic stratification and effective medium theory, design of waveplates using form birefringence, and 2D binary antireflection structured surfaces.

  16. Physical and timing verification of subwavelength-scale designs: I. Lithography impact on MOSFETs

    NASA Astrophysics Data System (ADS)

    Pack, Robert C.; Axelrad, Valery; Shibkov, Andrei; Boksha, Victor V.; Huckabay, Judy A.; Salik, Rachid; Staud, Wolfgang; Wang, Ruoping; Grobman, Warren D.

    2003-07-01

    Subwavelength lithography at low contrast, or low-k1 factor, leads to new requirements for design, design analysis, and design verification techniques. These techniques must account for inherent physical circuit feature distortions resulting from layout pattern-dependent design-to-silicon patterning processes in this era. These distortions are unavoidable, even in the presence of sophisticated Resolution Enhancement Technologies (RET), and are a 'fact-of-life" for the designer implementing nanometer-scale designs for the foreseeable low-k1 future. The consequence is that fabricated silicon feature shapes and dimensions are in general printed with far less fidelity in comparison to the designer"s desired layout than in past generations and that the designer must consider design within significantly different margins of geometry tolerance. Traditional (Mead-Conway originated) WYSIWYG (what you see is what you get) design methodologies, assume that the designer"s physical circuit element shapes are accurate in comparison to the corresponding shapes on the real fabricated IC, and uses design rules to verify satisfactory fabrication compliance, as the input for both interconnect parasitic loading calculations and to transistor models used for performance simulation. However, these assumptions are increasingly poor ones as k1 decreases to unprecidented levels -- with concomitant increase in patterned feature distortion and fabrication yield failure modes. This paper explores a new paradigm for nanometer-scale design, one in which more advanced models of critical low-k1 lithographic printing effects are incorporated into the design flow to improve upon yield and performance verification accuracy. We start with an analysis of a complex 32-bit adder block circuit design to determine systematic changes in gate length, width and shape variations for each MOSFET in the circuit due to optical proximity effects. The physical gate dimensions for all, as predicted by the

  17. Subwavelength optical microscopy in the far field

    SciTech Connect

    Sun Qingqing; Zubairy, M. Suhail; Al-Amri, M.; Scully, Marlan O.

    2011-06-15

    We present a procedure for subwavelength optical microscopy. The identical atoms are distributed on a plane and shined with a standing wave. We rotate the plane to different angles and record the resonant fluorescence spectra in the far field, from which we can obtain their distance and location information. This procedure also works for atomic separation above one wavelength and therefore provides a seamless microscopy.

  18. Metamaterial coatings for subwavelength-resolution imaging

    NASA Astrophysics Data System (ADS)

    Zapata-Rodríguez, Carlos J.; Pastor, David; Miret, Juan J.

    2011-05-01

    Coating lenses are membranes made of materials exhibiting negative index of refraction and deposited on other media with high dielectric constant ɛ3. Unfortunately far-field imaging suffers from centrosymmetric aberrations. We propose a simple procedure to compensate partially deviations from ray-tracing perfect imaging in asymmetric metamaterial lenses. We also show that, under some circumstances, coating superlens may recover subwavelength information transmitted in a relative spatial spectrum ranging from 1 to √ɛ3.

  19. Subwavelength films for standoff radiation dosimetry

    SciTech Connect

    Alvine, Kyle J.; Bernacki, Bruce E.; Bennett, Wendy D.; Schemer-Kohrn, Alan L.; Suter, Jonathan D.

    2015-05-22

    We present optical subwavelength nanostructure architecture suitable for standoff radiation dosimetry with remote optical readout in the visible or infrared spectral regions. To achieve this, films of subwavelength structures are fabricated over several square inches via the creation of a 2D non-close packed (NCP) array template of radiation-sensitive polymeric nanoparticles, followed by magnetron sputtering of a metallic coating to form a 2D array of separated hemispherical nanoscale metallic shells. The nanoshells are highly reflective at resonance in the visible or infrared depending on design. These structures and their behavior are based on the open ring resonator (ORR) architecture and have their analog in resonant inductive-capacitive (LC) circuits, which display a resonance wavelength that is inversely proportional to the square root of the product of the inductance and capacitance. Therefore, any modification of the nanostructure material properties due to radiation alters the inductive or capacitive behavior of the subwavelength features, which in turn changes their optical properties resulting in a shift in the optical resonance. This shift in resonance may be remotely interrogated actively using either laser illumination or passively by hyperspectral or multispectral sensing with broadband illumination. These structures may be designed to be either anisotropic or isotropic, which can also offer polarization-sensitive interrogation. We present experimental measurements of a radiation induced shift in the optical resonance of a subwavelength film after exposure to an absorbed dose of gamma radiation from 2 Mrad up to 62 Mrad demonstrating the effect. Interestingly the resonance shift is non-monotonic for this material system and possible radiation damage mechanisms to the nanoparticles are discussed.

  20. Subwavelength films for standoff radiation dosimetry

    NASA Astrophysics Data System (ADS)

    Alvine, Kyle J.; Bernacki, Bruce E.; Bennett, Wendy D.; Schemer-Kohrn, Alan; Suter, Jonathan D.

    2015-05-01

    We present optical subwavelength nanostructure architecture suitable for standoff radiation dosimetry with remote optical readout in the visible or infrared spectral regions. To achieve this, films of subwavelength structures are fabricated over several square inches via the creation of a 2D non-close packed (NCP) array template of radiationsensitive polymeric nanoparticles, followed by magnetron sputtering of a metallic coating to form a 2D array of separated hemispherical nanoscale metallic shells. The nanoshells are highly reflective at resonance in the visible or infrared depending on design. These structures and their behavior are based on the open ring resonator (ORR) architecture and have their analog in resonant inductive-capacitive (LC) circuits, which display a resonance wavelength that is inversely proportional to the square root of the product of the inductance and capacitance. Therefore, any modification of the nanostructure material properties due to radiation alters the inductive or capacitive behavior of the subwavelength features, which in turn changes their optical properties resulting in a shift in the optical resonance. This shift in resonance may be remotely interrogated actively using either laser illumination or passively by hyperspectral or multispectral sensing with broadband illumination. These structures may be designed to be either anisotropic or isotropic, which can also offer polarization-sensitive interrogation. We present experimental measurements of a radiation induced shift in the optical resonance of a subwavelength film after exposure to an absorbed dose of gamma radiation from 2 Mrad up to 62 Mrad demonstrating the effect. Interestingly the resonance shift is non-monotonic for this material system and possible radiation damage mechanisms to the nanoparticles are discussed.

  1. Terahertz waveguide emitter with subwavelength confinement

    NASA Astrophysics Data System (ADS)

    Martl, Michael; Darmo, Juraj; Dietze, Daniel; Unterrainer, Karl; Gornik, Erich

    2010-01-01

    The generation of broadband terahertz pulses on the facet of waveguides is presented as an alternative to widely used coupling techniques. Dielectric loaded subwavelength waveguide structures with lateral confinement are investigated with respect to propagating modes and waveguide losses. The results show the terahertz waveguide emitter to be a promising tool for terahertz spectroscopy in the near field and for the probing of microstructured devices such as quantum cascade lasers.

  2. Subwavelength resonant nanostructured films for sensing

    SciTech Connect

    Alvine, Kyle J.; Bernacki, Bruce E.; Suter, Jonathan D.; Bennett, Wendy D.; Edwards, Daniel L.; Mendoza, Albert

    2013-05-29

    We present a novel subwavelength nanostructure architecture that may be utilized for optical standoff sensing applications. The subwavelength structures are fabricated via a combination of nanoimprint lithography and metal sputtering to create metallic nanostructured films encased within a transparent media. The structures are based on the open ring resonator (ORR) architecture and have their analog in resonant LC circuits, which display a resonance frequency that is inversely proportional to the square root of the product of the inductance and capacitance. Therefore, any perturbation of the nanostructured films due to chemical or environmental effects can alter the inductive or capacitive behavior of the subwavelength features, which can shift the resonant frequency and provide an indication of the external stimulus. This shift in resonance can be interrogated remotely either actively using either laser illumination or passively using hyperspectral or multispectral sensing. These structures may be designed to be either anisotropic or isotropic, which can also provide polarization-sensitive interrogation. Due to the nanometer-scale of the structures, they can be tailored to be optically responsive in the visible or near infrared spectrum with a highly reflective resonant peak that is dependent solely on structural dimensions and material characteristics. We present experimental measurements of the optical response of these structures as a function of wavelength, polarization, and incident angle demonstrating the resonant effect in the near infrared region. Numerical modeling data showing the effect of different fabrication parameters such as structure parameters are also discussed.

  3. Subwavelength nanobrush target to collimate fast electrons

    NASA Astrophysics Data System (ADS)

    Zhao, Zongqing; Cao, Lihua; Cao, Leifeng; Zhou, Weimin; Wu, Yuchi; Zhu, Bin; Dong, Kegong; Zhang, Baohan; Ding, Yongkun; Gu, Yuqiu

    2011-10-01

    A subwavelength nanobrush target was proposed to collimate fast electrons in laser plasma interaction, which consists of a 5 μm copper underlay covered with a 20 μm thick layer of metallic fibers. The diameter of the individual fibers is about 200 nm and the spacing between them is about 150 nm. The experiment was hold at SILEX-I laser facility (10 J, 31 fs, 300 TW). When a subwavelength nanobrush target interacts with ultraintense laser of 7.9*1018/cm2, highly collimated fast electron beam with divergence angle nearly zero whereas the divergence of the plane target is 40 degree. Two-dimensional particle-in-cell (PIC) simulations show that the fast electrons will be accelerated and guided by strong transient electromagnetic fields created at the wall surfaces of nanobrushs. Both experiment and simulation show that the subwavelength nanobrush target can indeed generate fast electrons more efficiency and collimate them. The scheme should be useful for fast ignition and K α source research in inertial confinement fusion.

  4. Extreme output sensitivity to subwavelength boundary deformation in microcavities

    NASA Astrophysics Data System (ADS)

    Ge, Li; Song, Qinghai; Redding, Brandon; Cao, Hui

    2013-02-01

    We demonstrate a generic and robust mechanism that leads to an extreme output sensitivity to a deep subwavelength boundary perturbation in wavelength-scale microcavities. A deformation of the cavity boundary on the order of ten-thousandth of a wavelength may flip the output directions by 180∘, corresponding to a variation of 0.1 nm for a 1-μm-radius cavity. Our analysis based on a perturbation theory reveals that such tiny structural change can cause a strong mixing of nearly degenerate cavity resonances with different angular momenta, and their interference is greatly enhanced to have a radical influence on the far-field pattern. Our finding opens the possibility of utilizing carefully designed wavelength-scale microcavities for fast beam steering and high-resolution detection.

  5. Using subwavelength diffraction gratings to design open electromagnetic cavities.

    PubMed

    Dupré, Matthieu; Fink, Mathias; Lerosey, Geoffroy

    2014-01-31

    In this Letter we propose to use subwavelength diffraction gratings as very good semitransparent mirrors for electromagnetic waves to design open cavities. To do so, we replace part of the walls of a cavity by such a grating. We numerically and analytically link the grating characteristics to the spectral properties of the realized open cavity. Then we demonstrate that the eigenmodes of the cavity can be transmitted perfectly through the grating to the exterior, thereby turning a point source inside the cavity into a very directive source. We investigate the effect of disorder, which leads to isotropic radiation patterns, and perform experiments in the microwave domain in order to support our claims. Finally, we present an example of application of the concept in fundamental physics, by measuring from outside the eigenmodes of a disordered microwave cavity.

  6. Sub-wavelength terahertz beam profiling of a THz source via an all-optical knife-edge technique

    NASA Astrophysics Data System (ADS)

    Phing, Sze Ho; Mazhorova, Anna; Shalaby, Mostafa; Peccianti, Marco; Clerici, Matteo; Pasquazi, Alessia; Ozturk, Yavuz; Ali, Jalil; Morandotti, Roberto

    2015-02-01

    Terahertz technologies recently emerged as outstanding candidates for a variety of applications in such sectors as security, biomedical, pharmaceutical, aero spatial, etc. Imaging the terahertz field, however, still remains a challenge, particularly when sub-wavelength resolutions are involved. Here we demonstrate an all-optical technique for the terahertz near-field imaging directly at the source plane. A thin layer (<100 nm-thickness) of photo carriers is induced on the surface of the terahertz generation crystal, which acts as an all-optical, virtual blade for terahertz near-field imaging via a knife-edge technique. Remarkably, and in spite of the fact that the proposed approach does not require any mechanical probe, such as tips or apertures, we are able to demonstrate the imaging of a terahertz source with deeply sub-wavelength features (<30 μm) directly in its emission plane.

  7. Grating-flanked plasmonic coaxial apertures for efficient fiber optical tweezers.

    PubMed

    Saleh, Amr A E; Sheikhoelislami, Sassan; Gastelum, Steven; Dionne, Jennifer A

    2016-09-01

    Subwavelength plasmonic apertures have been foundational for direct optical manipulation of nanoscale specimens including sub-100 nm polymeric beads, metallic nanoparticles and proteins. While most plasmonic traps result in two-dimensional localization, three-dimensional manipulation has been demonstrated by integrating a plasmonic aperture on an optical fiber tip. However, such 3D traps are usually inefficient since the optical mode of the fiber and the subwavelength aperture only weakly couple. In this paper we design more efficient optical-fiber-based plasmonic tweezers combining a coaxial plasmonic aperture with a plasmonic grating coupler at the fiber tip facet. Using full-field finite difference time domain analysis, we optimize the grating design for both gold and silver fiber-based coaxial tweezers such that the optical transmission through the apertures is maximized. With the optimized grating, we show that the maximum transmission efficiency increases from 2.5% to 19.6% and from 1.48% to 16.7% for the gold and silver structures respectively. To evaluate their performance as optical tweezers, we calculate the optical forces and the corresponding trapping potential on dielectric particles interacting with the apertures. We demonstrate that the enahncement in the transmission translates into an equivalent increase in the optical forces. Consequently, the optical power required to achieve stable optical trapping is significantly reduced allowing for efficient localization and 3D manipulation of sub-30 nm dielectric particles. PMID:27607663

  8. Designer plasmonic structures and metamaterials for subwavelength photonics

    NASA Astrophysics Data System (ADS)

    Capasso, Federico

    2011-03-01

    Plasmonic structures and metamaterials have opened up new opportunities for manipulating light at subwavelength scales thus opening up new frontiers in optical materials design and photonics in such areas as imaging, sensing and new optical sources. In this talk I will present recent research from our group in this area. Through innovative use of plasmonic structures we have demonstrated how one can design the far field and near field of state of the art semiconductor lasers and optical fibers. Examples are plasmonic laser antennas creating ultrahigh intense near field nanospots in the near infrared, mid-infrared semiconductor lasers with very low divergence and control of polarization (linear/circular) as well as multibeam lasers. Metamaterials have created unique opportunities for nanophotonics. Recently we have shown that by patterning the facet of Terahertz quantum cascade lasers with subwavelength periodic structures one can dramatically modify the surface plasmon dispersion curve which leads to a highly collimated THz beam with divergence reduced from 180 deg to 5 deg. I will also discuss work on new clusters of colloidal core-shell metallic nanoparticles using self-assembly techniques. Magnetic activity in trimers at near infrared wavelengths and strikingly pronounced Fano-like resonances in heptamers are among the exciting new findings from light scattering experiments. Such building blocks are an important stepping stone towards novel designer metamaterials synthesized bottom up. Finally experiments with gold plasmonic nanocavity gratings have shown that the latter can dramatically enhance surface nonlinear optical processes. The four-wave mixing signal was enhanced by a factor up to 2000, two orders of magnitude higher than previously reported.

  9. Interferometric characterization of subwavelength lamellar gratings.

    PubMed

    Lalanne, P; Pichon, P; Chavel, P; Cambril, E; Launois, H

    1999-08-10

    We propose a new, to our knowledge, method for determining the two main critical parameters of periodic one-dimensional lamellar structures, namely, linewidths and etched depths. The method is simple and requires only two measurements for the phase of the zero-transmitted order under two orthogonal polarizations. It is inspired by the analogy between subwavelength gratings and anisotropic homogeneous thin films. The method is tested with experimental data obtained with a Mach-Zehnder interferometer. Etched depths and linewidths derived from the interferograms and electromagnetic theory are compared with scanning-electron-microscope observations. PMID:18323987

  10. Scalar wave diffraction from a circular aperture

    SciTech Connect

    Cerjan, C.

    1995-01-25

    The scalar wave theory is used to evaluate the expected diffraction patterns from a circular aperture. The standard far-field Kirchhoff approximation is compared to the exact result expressed in terms of oblate spheroidal harmonics. Deviations from an expanding spherical wave are calculated for circular aperture radius and the incident beam wavelength using suggested values for a recently proposed point diffractin interferometer. The Kirchhoff approximation is increasingly reliable in the far-field limit as the aperture radius is increased, although significant errors in amplitude and phase persist.

  11. Coded aperture imaging for fluorescent x-rays

    SciTech Connect

    Haboub, A.; MacDowell, A. A.; Marchesini, S.; Parkinson, D. Y.

    2014-06-15

    We employ a coded aperture pattern in front of a pixilated charge couple device detector to image fluorescent x-rays (6–25 KeV) from samples irradiated with synchrotron radiation. Coded apertures encode the angular direction of x-rays, and given a known source plane, allow for a large numerical aperture x-ray imaging system. The algorithm to develop and fabricate the free standing No-Two-Holes-Touching aperture pattern was developed. The algorithms to reconstruct the x-ray image from the recorded encoded pattern were developed by means of a ray tracing technique and confirmed by experiments on standard samples.

  12. Debuncher Momentum Aperture Measurements

    SciTech Connect

    O'Day, S.

    1991-01-01

    During the November 1990 through January 1991 {bar p} studies period, the momentum aperture of the beam in the debuncher ring was measured. The momentum aperture ({Delta}p/p) was found to be 4.7%. The momentum spread was also measured with beam bunch rotation off. A nearly constant particle population density was observed for particles with {Delta}p/p of less than 4.3%, indicating virtually unobstructed orbits in this region. The population of particles with momenta outside this aperture was found to decrease rapidly. An absolute or 'cut-off' momentum aperture of {Delta}p/p = 5.50% was measured.

  13. Subwavelength resonant nanostructured films for sensing

    NASA Astrophysics Data System (ADS)

    Alvine, K. J.; Bernacki, B. E.; Suter, J. D.; Bennett, W. D.; Edwards, D. J.; Mendoza, A.

    2013-05-01

    We present a novel subwavelength nanostructure architecture that may be utilized for optical standoff sensing applications. The subwavelength structures are fabricated via a combination of nanoimprint lithography and metal sputtering to create metallic nanostructured films encased within a transparent media. The structures are based on the open ring resonator (ORR) architecture which has a characteristic resonance frequency. Any perturbation of the nanostructured films due to chemical or environmental effects can shift the resonant frequency and provide an indication of the external stimulus. This shift in resonance can be interrogated remotely either actively using either laser illumination or passively using hyperspectral or multispectral sensing. These structures may be designed to be either anisotropic or isotropic, which can also provide polarization-sensitive interrogation. Due to the nanometer scale of the structures, they can be tailored to be optically responsive in the visible or near infrared spectrum with a highly reflective resonant peak that is dependent solely on structural dimensions and material characteristics. We present experimental measurements of the optical response of these structures as a function of wavelength, polarization, and incident angle demonstrating the resonant effect in the near infrared region. Numerical modeling data showing the effect of different fabrication parameters such as structure parameters are also discussed.

  14. Variable-aperture screen

    DOEpatents

    Savage, George M.

    1991-01-01

    Apparatus for separating material into first and second portions according to size including a plurality of shafts, a plurality of spaced disks radiating outwardly from each of the shafts to define apertures and linkage interconnecting the shafts for moving the shafts toward or away from one another to vary the size of the apertures while the apparatus is performing the separating function.

  15. Rotating Aperture System

    DOEpatents

    Rusnak, Brian; Hall, James M.; Shen, Stewart; Wood, Richard L.

    2005-01-18

    A rotating aperture system includes a low-pressure vacuum pumping stage with apertures for passage of a deuterium beam. A stator assembly includes holes for passage of the beam. The rotor assembly includes a shaft connected to a deuterium gas cell or a crossflow venturi that has a single aperture on each side that together align with holes every rotation. The rotating apertures are synchronized with the firing of the deuterium beam such that the beam fires through a clear aperture and passes into the Xe gas beam stop. Portions of the rotor are lapped into the stator to improve the sealing surfaces, to prevent rapid escape of the deuterium gas from the gas cell.

  16. Theory of light scattering in subwavelength metallic slot antenna array fabricated on subwavelength thin film

    NASA Astrophysics Data System (ADS)

    Choi, S. B.; Park, D. J.

    2015-10-01

    We demonstrate an analytic model that describes the near-field electromagnetic field profile near a subwavelength-sized metallic slot antenna fabricated on a thin dielectric substrate having a subwavelength thickness reaching λ/1000 in the terahertz frequency region. We found two-dimensional light diffraction induced by the two-dimensional nature of the slot antenna, and back-reflected waves interfered with each other in a complicated manner, resulting in a coupling of the Fourierdecomposed field amplitudes between the diffraction orders along the x and the y directions. We applied these findings to our model by modifying a previously developed model [D. J. Park et al., J. Korean Phys. Soc. 65, 1390 (2014)], and we monitor the effect on far-field transmission. This coupling effect was found to contribute to removal of physically-meaningless spikes or divergences in the transmission spectra, especially for relatively thick substrates.

  17. Extraordinary terahertz transmission through a copper film perforated with circular and rectangular apertures

    NASA Astrophysics Data System (ADS)

    Hu, Dan; Chen, Bing

    2015-11-01

    The extraordinary transmission (ET) due to localized surface plasmon (LSP) and propagating surface plasmon (PSP) resonances of terahertz wave through a copper film perforated with circular and rectangular apertures is investigated theoretically and experimentally. Considering that the field distributions of LSP and PSP resonances are determined by the shape and periods of the apertures on the film, the relations between extraordinary and the geometrical parameters of the apertures are investigated. The intensities of the ETs induced by the PSP resonances mode [1, 1] are much stronger than the fundamental ones [1, 0] and [0, 1]. Our finds provide another effective method to tailor the extraordinary THz transmission in sub-wavelength metallic aperture structures.

  18. GHz Electroluminescence Modulation in Nanoscale Subwavelength Emitters.

    PubMed

    Rossella, Francesco; Piazza, Vincenzo; Rocci, Mirko; Ercolani, Daniele; Sorba, Lucia; Beltram, Fabio; Roddaro, Stefano

    2016-09-14

    We investigate light emission from nanoscale point-sources obtained in hybrid metal-GaAs nanowires embedding two sharp axial Schottky barriers. Devices are obtained via the formation of Ni-rich metallic alloy regions in the nanostructure body thanks to a technique of controlled thermal annealing of Ni/Au electrodes. In agreement with recent findings, visible-light electroluminescence can be observed upon suitable voltage biasing of the junctions. We investigate the time-resolved emission properties of our devices and demonstrate an electrical modulation of light generation up to 1 GHz. We explore different drive configurations and discuss the intrinsic bottlenecks of the present device architecture. Our results demonstrate a novel technique for the realization of fast subwavelength light sources with possible applications in sensing and microscopy beyond the diffraction limit. PMID:27532324

  19. Subwavelength total acoustic absorption with degenerate resonators

    NASA Astrophysics Data System (ADS)

    Yang, Min; Meng, Chong; Fu, Caixing; Li, Yong; Yang, Zhiyu; Sheng, Ping

    2015-09-01

    We report the experimental realization of perfect sound absorption by sub-wavelength monopole and dipole resonators that exhibit degenerate resonant frequencies. This is achieved through the destructive interference of two resonators' transmission responses, while the matching of their averaged impedances to that of air implies no backscattering, thereby leading to total absorption. Two examples, both using decorated membrane resonators (DMRs) as the basic units, are presented. The first is a flat panel comprising a DMR and a pair of coupled DMRs, while the second one is a ventilated short tube containing a DMR in conjunction with a sidewall DMR backed by a cavity. In both examples, near perfect absorption, up to 99.7%, has been observed with the airborne wavelength up to 1.2 m, which is at least an order of magnitude larger than the composite absorber. Excellent agreement between theory and experiment is obtained.

  20. Canalization of subwavelength images by electromagnetic crystals

    NASA Astrophysics Data System (ADS)

    Belov, Pavel A.; Simovski, Constantin R.; Ikonen, Pekka

    2005-05-01

    The original regime of operation for flat superlenses formed by electromagnetic crystals is proposed. This regime does not involve negative refraction and amplification of evanescent waves in contrast to the perfect lenses formed by left-handed media. The subwavelength spatial spectrum of a source is canalized by the eigenmodes of the crystal having the same longitudinal components of wave vector and group velocities directed across the slab. The regime is implemented at low frequencies with respect to the crystal period by using capacitively loaded wire media. The resolution of λ/6 is demonstrated. The thickness of the superlens is not related with the distance to the source and the lens can be made thick enough.

  1. Temperature-independent silicon subwavelength grating waveguides.

    PubMed

    Schmid, J H; Ibrahim, M; Cheben, P; Lapointe, J; Janz, S; Bock, P J; Densmore, A; Lamontagne, B; Ma, R; Ye, W N; Xu, D-X

    2011-06-01

    We demonstrate, by experiment and numerical calculations, temperature-independent subwavelength grating waveguides with a periodic composite core composed of alternating regions of silicon and SU-8 polymer. The polymer has a negative thermo-optic (TO) material coefficient that cancels the large positive TO effect of the silicon. Measurements and Bloch mode calculations were carried out over a range of silicon-polymer duty ratios. The lowest measured TO coefficient at a wavelength of 1550 nm is 1.8×10(-6) K(-1); 2 orders of magnitude smaller than a conventional silicon photonic wire waveguide. Calculations predict the possibility of complete cancellation of the silicon waveguide temperature dependence. PMID:21633465

  2. Measuring subwavelength spatial coherence with plasmonic interferometry

    NASA Astrophysics Data System (ADS)

    Morrill, Drew; Li, Dongfang; Pacifici, Domenico

    2016-10-01

    Optical interferometry has enabled quantification of the spatial and temporal correlations of electromagnetic fields, which laid the foundations for the theory of optical coherence. Despite significant advances in fundamental theories and applications, the measurement of nanoscale coherence lengths for highly incoherent optical fields has remained elusive. Here, we employ plasmonic interferometry (that is, optical interferometry with surface plasmons) to characterize the spatial degree of coherence of light beams down to subwavelength scales, with measured coherence lengths as low as ∼330 nm for an incident wavelength of 500 nm. Furthermore, we demonstrate a compact coherence meter that integrates this method with an image sensor. Precise determination of spatial coherence can advance high-resolution imaging and tomographic schemes, and provide an experimental platform for the development and testing of optical coherence theories at the nanoscale.

  3. Liquid crystal on subwavelength metal gratings

    NASA Astrophysics Data System (ADS)

    Palto, S. P.; Barnik, M. I.; Artemov, V. V.; Shtykov, N. M.; Geivandov, A. R.; Yudin, S. G.; Gorkunov, M. V.

    2015-06-01

    Optical and electrooptical properties of a system consisting of subwavelength metal gratings and nematic liquid crystal layer are studied. Aluminium gratings that also act as interdigitated electrodes are produced by focused ion beam lithography. It is found that a liquid crystal layer strongly influences both the resonance and light polarization properties characteristic of the gratings. Enhanced transmittance is observed not only for the TM-polarized light in the near infrared spectral range but also for the TE-polarized light in the visible range. Although the electrodes are separated by nanosized slits, and the electric field is strongly localized near the surface, a pronounced electrooptical effect is registered. The effect is explained in terms of local reorientation of liquid crystal molecules at the grating surface and propagation of the orientational deformation from the surface into the bulk of the liquid crystal layer.

  4. Liquid crystal on subwavelength metal gratings

    SciTech Connect

    Palto, S. P.; Barnik, M. I.; Artemov, V. V.; Shtykov, N. M.; Geivandov, A. R.; Yudin, S. G.; Gorkunov, M. V.

    2015-06-14

    Optical and electrooptical properties of a system consisting of subwavelength metal gratings and nematic liquid crystal layer are studied. Aluminium gratings that also act as interdigitated electrodes are produced by focused ion beam lithography. It is found that a liquid crystal layer strongly influences both the resonance and light polarization properties characteristic of the gratings. Enhanced transmittance is observed not only for the TM-polarized light in the near infrared spectral range but also for the TE-polarized light in the visible range. Although the electrodes are separated by nanosized slits, and the electric field is strongly localized near the surface, a pronounced electrooptical effect is registered. The effect is explained in terms of local reorientation of liquid crystal molecules at the grating surface and propagation of the orientational deformation from the surface into the bulk of the liquid crystal layer.

  5. Sub-Aperture Interferometers

    NASA Technical Reports Server (NTRS)

    Zhao, Feng

    2010-01-01

    Sub-aperture interferometers -- also called wavefront-split interferometers -- have been developed for simultaneously measuring displacements of multiple targets. The terms "sub-aperture" and "wavefront-split" signify that the original measurement light beam in an interferometer is split into multiple sub-beams derived from non-overlapping portions of the original measurement-beam aperture. Each measurement sub-beam is aimed at a retroreflector mounted on one of the targets. The splitting of the measurement beam is accomplished by use of truncated mirrors and masks, as shown in the example below

  6. Coded Aperture Imaging for Fluorescent X-rays-Biomedical Applications

    SciTech Connect

    Haboub, Abdel; MacDowell, Alastair; Marchesini, Stefano; Parkinson, Dilworth

    2013-06-01

    Employing a coded aperture pattern in front of a charge couple device pixilated detector (CCD) allows for imaging of fluorescent x-rays (6-25KeV) being emitted from samples irradiated with x-rays. Coded apertures encode the angular direction of x-rays and allow for a large Numerical Aperture x- ray imaging system. The algorithm to develop the self-supported coded aperture pattern of the Non Two Holes Touching (NTHT) pattern was developed. The algorithms to reconstruct the x-ray image from the encoded pattern recorded were developed by means of modeling and confirmed by experiments. Samples were irradiated by monochromatic synchrotron x-ray radiation, and fluorescent x-rays from several different test metal samples were imaged through the newly developed coded aperture imaging system. By choice of the exciting energy the different metals were speciated.

  7. Sub-wavelength antenna enhanced bilayer graphene tunable photodetector

    DOEpatents

    Beechem, III, Thomas Edwin; Howell, Stephen W.; Peters, David W.; Davids, Paul; Ohta, Taisuke

    2016-03-22

    The integration of bilayer graphene with an absorption enhancing sub-wavelength antenna provides an infrared photodetector capable of real-time spectral tuning without filters at nanosecond timescales.

  8. Stand-off explosive detection utilizing low power stimulated emission nuclear quadrupole resonance detection and subwavelength focusing wideband super lens

    NASA Astrophysics Data System (ADS)

    Apostolos, John; Mouyos, William; Feng, Judy; Chase, Walter

    2015-05-01

    The need for advanced techniques to detect improvised explosive devices (IED) at stand-off distances greater than ten (10) meters has driven AMI Research and Development (AMI) to develop a solution to detect and identify the threat utilizing a forward looking Synthetic Aperture Radar (SAR) combined with our CW radar technology Nuclear Quadrupole Resonance (NQR) detection system. The novel features include a near-field sub-wavelength focusing antenna, a wide band 300 KHz to 300 MHz rapidly scanning CW radar facilitated by a high Q antenna/tuner, and an advanced processor utilizing Rabi transitions where the nucleus oscillates between states under the time dependent incident electromagnetic field and alternately absorbs energy from the incident field while emitting coherent energy via stimulated emission. AMI's Sub-wavelength Focusing Wide Band Super Lens uses a Near-Field SAR, making detection possible at distances greater than ten (10) meters. This super lens is capable of operating on the near-field and focusing electromagnetic waves to resolutions beyond the diffraction limit. When applied to the case of a vehicle approaching an explosive hazard the methodologies of synthetic aperture radar is fused with the array based super resolution and the NQR data processing detecting the explosive hazard.

  9. Variable-aperture screen

    DOEpatents

    Savage, G.M.

    1991-10-29

    Apparatus is described for separating material into first and second portions according to size including a plurality of shafts, a plurality of spaced disks radiating outwardly from each of the shafts to define apertures and linkage interconnecting the shafts for moving the shafts toward or away from one another to vary the size of the apertures while the apparatus is performing the separating function. 10 figures.

  10. APT: Aperture Photometry Tool

    NASA Astrophysics Data System (ADS)

    Laher, Russ

    2012-08-01

    Aperture Photometry Tool (APT) is software for astronomers and students interested in manually exploring the photometric qualities of astronomical images. It has a graphical user interface (GUI) which allows the image data associated with aperture photometry calculations for point and extended sources to be visualized and, therefore, more effectively analyzed. Mouse-clicking on a source in the displayed image draws a circular or elliptical aperture and sky annulus around the source and computes the source intensity and its uncertainty, along with several commonly used measures of the local sky background and its variability. The results are displayed and can be optionally saved to an aperture-photometry-table file and plotted on graphs in various ways using functions available in the software. APT is geared toward processing sources in a small number of images and is not suitable for bulk processing a large number of images, unlike other aperture photometry packages (e.g., SExtractor). However, APT does have a convenient source-list tool that enables calculations for a large number of detections in a given image. The source-list tool can be run either in automatic mode to generate an aperture photometry table quickly or in manual mode to permit inspection and adjustment of the calculation for each individual detection. APT displays a variety of useful graphs, including image histogram, and aperture slices, source scatter plot, sky scatter plot, sky histogram, radial profile, curve of growth, and aperture-photometry-table scatter plots and histograms. APT has functions for customizing calculations, including outlier rejection, pixel “picking” and “zapping,” and a selection of source and sky models. The radial-profile-interpolation source model, accessed via the radial-profile-plot panel, allows recovery of source intensity from pixels with missing data and can be especially beneficial in crowded fields.

  11. Subwavelength Sensing Using Nonlinear Feedback in a Wave-Chaotic Cavity

    NASA Astrophysics Data System (ADS)

    Cohen, Seth D.

    Typical imaging systems rely on the interactions of matter with electromagnetic radiation, which can lead to scattered waves that are radiated away from the imaging area. The goal such an imaging device is to collect these radiated waves and focus them onto a measurement detector that is sensitive to the wave's properties such as wavelength (or color) and intensity. The detector's measurements of the scattered fields are then used to reconstruct spatial information about the original matter such as its shape or location. However, when a scattered wave is collected by the imaging device, it diffracts and inteferes with itself. The resulting interference pattern can blur spatial information of the reconstructed image. This leads to a so-called diffraction limit, which describes the minimum sizes of spatial features on a scatterer that can be resolved using conventional imaging techniques. The diffraction limit scales with the wavelength lambda of the illuminating field, where the limit for conventional imaging with visible light is approximately 200 nm. Investigating subwavelength objects (< lambda) requires more advanced measurement techniques, and improving the resolving capabilities of imaging devices continues to be an active area of research. Here, I describe a new sensing technique for resolving the position of a subwavelength scatterer (< lambda) with vastly subwavelength resolution (<< lambda). My approach combines two separate fields of scientific inquiry: time-delayed nonlinear feedback and wave chaos. In typical time-delayed nonlinear feedback systems, the output of a nonlinear device is delayed and fed back to its input. In my experiment, the output of a radio-frequency (lambda ~ 15 cm) nonlinear circuit is injected into a complex scattering environment known as a wave-chaotic cavity. Inside the cavity, the field interacts with a subwavelength dielectric object from all sides, and a portion of the scattered waves are coupled out of the cavity, amplified

  12. Ultra-Small Imaging and Spectrometry Elements with Subwavelength Performance

    SciTech Connect

    Kevin J. Webb; Shivanand

    2007-07-26

    Silver/silicon dioxide and gold/silicon multilayer imaging structures are shown to have subwavelength imaging performance. The influence of the duty cycle is presented. Imaging possibilities with a slab having isotropic negative effective dielectric constant is also explored. This system may be worthy of an experimental program to establish that subwavelength resolution is practical. Success will lead to a new class of imaging, memory, and interconnection structures.

  13. Theoretical study for aerial image intensity in resist in high numerical aperture projection optics and experimental verification with one-dimensional patterns

    NASA Astrophysics Data System (ADS)

    Shibuya, Masato; Takada, Akira; Nakashima, Toshiharu

    2016-04-01

    In optical lithography, high-performance exposure tools are indispensable to obtain not only fine patterns but also preciseness in pattern width. Since an accurate theoretical method is necessary to predict these values, some pioneer and valuable studies have been proposed. However, there might be some ambiguity or lack of consensus regarding the treatment of diffraction by object, incoming inclination factor onto image plane in scalar imaging theory, and paradoxical phenomenon of the inclined entrance plane wave onto image in vector imaging theory. We have reconsidered imaging theory in detail and also phenomenologically resolved the paradox. By comparing theoretical aerial image intensity with experimental pattern width for one-dimensional pattern, we have validated our theoretical consideration.

  14. UAVSAR Phased Array Aperture

    NASA Technical Reports Server (NTRS)

    Chamberlain, Neil; Zawadzki, Mark; Sadowy, Greg; Oakes, Eric; Brown, Kyle; Hodges, Richard

    2009-01-01

    This paper describes the development of a patch antenna array for an L-band repeat-pass interferometric synthetic aperture radar (InSAR) instrument that is to be flown on an unmanned aerial vehicle (UAV). The antenna operates at a center frequency of 1.2575 GHz and with a bandwidth of 80 MHz, consistent with a number of radar instruments that JPL has previously flown. The antenna is designed to radiate orthogonal linear polarizations in order to facilitate fully-polarimetric measurements. Beam-pointing requirements for repeat-pass SAR interferometry necessitate electronic scanning in azimuth over a range of -20degrees in order to compensate for aircraft yaw. Beam-steering is accomplished by transmit/receive (T/R) modules and a beamforming network implemented in a stripline circuit board. This paper, while providing an overview of phased array architecture, focuses on the electromagnetic design of the antenna tiles and associated interconnects. An important aspect of the design of this antenna is that it has an amplitude taper of 10dB in the elevation direction. This is to reduce multipath reflections from the wing that would otherwise be detrimental to interferometric radar measurements. This taper is provided by coupling networks in the interconnect circuits as opposed to attenuating the output of the T/R modules. Details are given of material choices and fabrication techniques that meet the demanding environmental conditions that the antenna must operate in. Predicted array performance is reported in terms of co-polarized and crosspolarized far-field antenna patterns, and also in terms of active reflection coefficient.

  15. Graphene based metamaterials for terahertz cloaking and subwavelength imaging

    NASA Astrophysics Data System (ADS)

    Forouzmand, Seyedali

    Graphene is a two-dimensional carbon crystal that became one of the most controversial topics of research in the last few years. The intense interest in graphene stems from recent demonstrations of their potentially revolutionary electromagnetic applications -- including negative refraction, subdiffraction imaging, and even invisibility -- which have suggested a wide range of new devices for communications, sensing, and biomedicine. In addition, it has been shown that graphene is amenable to unique patterning schemes such as cutting, bending, folding, and fusion that are predicted to lead to interesting properties. A recent proposed application of graphene is in engineering the scattering properties of objects, which may be leveraged in applications such as radar-cross-section management and stealth, where it may be required to make one object look like another object or render an object completely invisible. We present the analytical formulation for the analysis of electromagnetic interaction with a finite conducting wedge covered with a cylindrically shaped nanostructured graphene metasurface, resulting in the scattering cancellation of the dominant scattering mode for all the incident and all the observation angles. Following this idea, the cylindrical graphene metasurface is utilized for cloaking of several concentric finite conducting wedges. In addition, a wedge shaped metasurface is proposed as an alternative approach for cloaking of finite wedges. The resolution of the conventional imaging lenses is restricted by the natural diffraction limit. Artificially engineered metamaterials now offer the possibility of creating a superlens that overcomes this restriction. We demonstrate that a wire medium (WM) slab loaded with graphene sheets enables the enhancement of the near field for subwavelength imaging at terahertz (THz) frequencies. The analysis is based on the nonlocal homogenization model for WM with the additional boundary condition in the connection of

  16. Fraunhofer diffraction of Laguerre-Gaussian beam caused by a dynamic superposed dual-triangular aperture

    NASA Astrophysics Data System (ADS)

    Li, Xinzhong; Tai, Yuping; Nie, Zhaogang; Wang, Hui; Li, Hehe; Wang, Jingge; Tang, Jie; Wang, Yishan

    2015-12-01

    We investigate the Fraunhofer diffraction of a Laguerre-Gaussian (LG) beam incident on a dynamic superposed dual-triangular aperture. The evolution of the diffraction pattern from this aperture is analyzed experimentally and theoretically. A special aperture, called the hex-star triangular aperture, demonstrates interesting diffraction patterns. Further, the diffraction properties of integer, half-integer, and fractional orders of topological charges at the Fraunhofer zone are studied by using the hex-star triangular aperture. This study can provide additional information to enhance the understanding of the diffraction properties of the LG beam transmitted through a complex aperture.

  17. Differential Synthetic Aperture Ladar

    SciTech Connect

    Stappaerts, E A; Scharlemann, E

    2005-02-07

    We report a differential synthetic aperture ladar (DSAL) concept that relaxes platform and laser requirements compared to conventional SAL. Line-of-sight translation/vibration constraints are reduced by several orders of magnitude, while laser frequency stability is typically relaxed by an order of magnitude. The technique is most advantageous for shorter laser wavelengths, ultraviolet to mid-infrared. Analytical and modeling results, including the effect of speckle and atmospheric turbulence, are presented. Synthetic aperture ladars are of growing interest, and several theoretical and experimental papers have been published on the subject. Compared to RF synthetic aperture radar (SAR), platform/ladar motion and transmitter bandwidth constraints are especially demanding at optical wavelengths. For mid-IR and shorter wavelengths, deviations from a linear trajectory along the synthetic aperture length have to be submicron, or their magnitude must be measured to that precision for compensation. The laser coherence time has to be the synthetic aperture transit time, or transmitter phase has to be recorded and a correction applied on detection.

  18. Acoustic transmission through compound subwavelength slit arrays

    NASA Astrophysics Data System (ADS)

    Ward, G. P.; Hibbins, A. P.; Sambles, J. R.; Smith, J. D.

    2016-07-01

    The angular dependence of the transmission of sound in air through four types of two-dimensional slit arrays formed of aluminium slats is explored, both experimentally and numerically. For a simple, subwavelength periodic slit array, it is well known that Fabry-Perot-like waveguide resonances, supported by the slit cavities, coupled to diffracted evanescent waves, result in enhanced acoustic transmission at frequencies determined by the length, width, and separation of each slit cavity. We demonstrate that altering the spacing or width of some of the slits to form a compound array (i.e., an array having a basis comprised of more than one slit) results in sharp dips in the transmission spectra, which may have a strong angular dependence. These features correspond to phase resonances, which have been studied extensively in the electromagnetic case. This geometry allows for additional near-field configurations compared to the simple array, whereby the field in adjacent cavities can be out of phase. Several types of compound slit arrays are investigated; one such structure is optimized to minimize the effect of boundary-layer loss mechanisms present in each slit cavity, thereby achieving a deep, sharp transmission minimum in a broad maximum.

  19. Plasmon transmission through excitonic subwavelength gaps.

    PubMed

    Sukharev, Maxim; Nitzan, Abraham

    2016-04-14

    We study the transfer of electromagnetic energy across a subwavelength gap separating two co-axial metal nanorods. In the absence of spacer in the gap separating the rods, the system exhibits strong coupling behavior between longitudinal plasmons in the two rods. The nature and magnitude of this coupling are studied by varying various geometrical parameters. As a function of frequency, the transmission is dominated by a split longitudinal plasmon peak. The two hybrid modes are the dipole-like "bonding" mode characterized by a peak intensity in the gap and a quadrupole-like "antibonding" mode whose amplitude vanishes at the gap center. When the length of one rod is varied, this mode spectrum exhibits the familiar anti-crossing behavior that depends on the coupling strength determined by the gap width. When off-resonant 2-level emitters are placed in the gap, almost no effect on the frequency dependent transmission is observed. In contrast, when the molecular system is resonant with the plasmonic line shape, the transmission is strongly modified, showing characteristics of strong exciton-plasmon coupling. Most strongly modified is the transmission near the lower frequency "bonding" plasmon mode. The presence of resonant molecules in the gap affects not only the molecule-field interaction but also the spatial distribution of the field intensity and the electromagnetic energy flux across the junction. PMID:27083741

  20. Characterization of fracture aperture for groundwater flow and transport

    NASA Astrophysics Data System (ADS)

    Sawada, A.; Sato, H.; Tetsu, K.; Sakamoto, K.

    2007-12-01

    This paper presents experiments and numerical analyses of flow and transport carried out on natural fractures and transparent replica of fractures. The purpose of this study was to improve the understanding of the role of heterogeneous aperture patterns on channelization of groundwater flow and dispersion in solute transport. The research proceeded as follows: First, a precision plane grinder was applied perpendicular to the fracture plane to characterize the aperture distribution on a natural fracture with 1 mm of increment size. Although both time and labor were intensive, this approach provided a detailed, three dimensional picture of the pattern of fracture aperture. This information was analyzed to provide quantitative measures for the fracture aperture distribution, including JRC (Joint Roughness Coefficient) and fracture contact area ratio. These parameters were used to develop numerical models with corresponding synthetic aperture patterns. The transparent fracture replica and numerical models were then used to study how transport is affected by the aperture spatial pattern. In the transparent replica, transmitted light intensity measured by a CCD camera was used to image channeling and dispersion due to the fracture aperture spatial pattern. The CCD image data was analyzed to obtain the quantitative fracture aperture and tracer concentration data according to Lambert-Beer's law. The experimental results were analyzed using the numerical models. Comparison of the numerical models to the transparent replica provided information about the nature of channeling and dispersion due to aperture spatial patterns. These results support to develop a methodology for defining representative fracture aperture of a simplified parallel fracture model for flow and transport in heterogeneous fractures for contaminant transport analysis.

  1. Tunable ultra-deep subwavelength photolithography using a surface plasmon resonant cavity.

    PubMed

    Ge, Weihao; Wang, Chinhua; Xue, Yinfei; Cao, Bing; Zhang, Baoshun; Xu, Ke

    2011-03-28

    Using numerical simulations, we report an observation of a novel tunable ultra-deep subwavelength nanolithography technique using a surface plasmon resonant cavity formed by a metallic grating and a metallic thin-film layer separated by a photoresist layer. The tuning capability is implemented by varying the cavity length, from which surface plasmon interferometric patterns with inherently higher optical resolution than that of conventional surface plasmon techniques are generated in the cavity of photoresist layer. The physical origin of the tunability is analytically confirmed by the dispersion relation derived from the cavity system.

  2. Sub-wavelength surface gratings for light redirection in transparent substrates

    NASA Astrophysics Data System (ADS)

    Buß, Thomas; Smith, Cameron L. C.; Brøkner Christiansen, Mads; Marie, Rodolphe; Kristensen, Anders

    2012-07-01

    We demonstrate sub-wavelength grating couplers patterned on glass surfaces which are designed to convert incident free-space radiation into guided modes along the glass material. The devices are fabricated by nanoimprint lithography and the measured optical performance is compared to a simple model based on diffraction and ray-optics, and complemented by numerical simulations. We show that our approach is suitable for redirecting and guiding light over a broad range of incident angles and wavelengths in transparent substrates. The technique has potential applications for solar harvesting in window panes and display applications with minimal influence on vision quality.

  3. In-line metrology setup for periodic nanostructures based on sub-wavelength diffraction

    NASA Astrophysics Data System (ADS)

    Kreuzer, Martin; Gomis Bresco, Jordi; Sledzinska, Marianna; Sotomayor Torres, Clivia M.

    2015-09-01

    The analysis of diffracted light from periodic structures is shown to be a versatile metrology technique applicable to inline metrology for periodic nanostructures. We show that 10 nm changes in periodic structures can be traced optically by means of sub-wavelength diffraction. Polymer gratings were fabricated by electron beam lithography. The gratings have a common periodicity of 6 μm, but different line width, ranging from 370 to 550 nm in 10 nm steps. A comparison between the resulting diffraction patterns shows marked differences in intensity which are used to sense nanometre scale deviations in periodic structures.

  4. Young's experiment with a double slit of sub-wavelength dimensions.

    PubMed

    Lee, Kanghee; Lim, Jongseok; Ahn, Jaewook

    2013-08-12

    We report that the interference pattern of Young's double-slit experiment changes as a function of polarization in the sub-wavelength diffraction regime. Experiments carried out with terahertz time-domain spectroscopy reveal that diffracted waves from sub-wavelength-scale slits exhibit either positive or negative phase shift with respect to Gouy phase depending on the polarization. Theoretical explanation based on the induction of electric current and magnetic dipole in the vicinity of the slits shows an excellent agreement with the experimental results.

  5. Holographic polymer-dispersed liquid crystal memory for optically reconfigurable gate array using subwavelength grating mask.

    PubMed

    Ogiwara, Akifumi; Watanabe, Minoru; Mabuchi, Takayuki; Kobayashi, Fuminori

    2011-12-01

    Holographic polymer-dispersed liquid crystal (HPDLC) memory formed by a subwavelength grating (SWG) mask is presented for new optical information processing. The SWG structure in a photomask is formed on the SiO(2) plate using the anisotropic reactive ion etching technique. The configuration contexts for optically reconfigurable gate arrays (ORGAs) are stored in the HPDLC memory by polarization modulation property based on the form birefringence of the SWG plate. The configuration context pattern in the HPDLC memory is reconstructed to write it for the ORGAs under parallel programmability. PMID:22192988

  6. Diffractive optics based on modulated subwavelength-domain V-ridge gratings

    NASA Astrophysics Data System (ADS)

    Bose, Gaurav; Verhoeven, Antonie; Vartiainen, Ismo; Roussey, Matthieu; Kuittinen, Markku; Tervo, Jani; Turunen, Jari

    2016-08-01

    We study the properties of reflection-type V-ridge gratings in the subwavelength domain and describe a method to realize diffractive optical elements by using such gratings as signal carriers. In particular, we utilize a coding scheme based on position modulation of a high-frequency V-ridge carrier grating. We design and demonstrate beam splitting elements using this coding scheme, electron-beam lithography, anisotropic wet etching of silicon, hot embossing of polymer, and metal deposition. These elements have the outstanding property of operating over a large spectral range from 406 to 520 nm. The measured diffraction patterns show excellent agreement with theoretical results given by rigorous diffraction theory.

  7. Confocal coded aperture imaging

    DOEpatents

    Tobin, Jr., Kenneth William; Thomas, Jr., Clarence E.

    2001-01-01

    A method for imaging a target volume comprises the steps of: radiating a small bandwidth of energy toward the target volume; focusing the small bandwidth of energy into a beam; moving the target volume through a plurality of positions within the focused beam; collecting a beam of energy scattered from the target volume with a non-diffractive confocal coded aperture; generating a shadow image of said aperture from every point source of radiation in the target volume; and, reconstructing the shadow image into a 3-dimensional image of the every point source by mathematically correlating the shadow image with a digital or analog version of the coded aperture. The method can comprise the step of collecting the beam of energy scattered from the target volume with a Fresnel zone plate.

  8. Motion compensation on synthetic aperture sonar images

    NASA Astrophysics Data System (ADS)

    Heremans, R.; Acheroy, M.; Dupont, Y.

    2006-09-01

    High resolution sonars are required to detect and classify mines on the sea-bed. Synthetic aperture sonar increases the sonar cross range resolution by several orders of magnitudes while maintaining or increasing the area search rate. The resolution is however strongly dependent on the precision with which the motion errors of the platform can be estimated. The term micro-navigation is used to describe this very special requirement for sub-wavelength relative positioning of the platform. Therefore algorithms were designed to estimate those motion errors and to correct for them during the (ω, k)-reconstruction phase. To validate the quality of the motion estimation algorithms a single transmitter/multiple receiver simulator was build, allowing to generate multiple point targets with or without surge and/or sway and/or yaw motion errors. The surge motion estimation is shown on real data, which were taken during a sea trial in November of 2003 with the low frequency (12 kHz) side scan sonar (LFSS) moving on a rail positioned on the sea-bed near Marciana Marina on the Elba Island, Italy.

  9. Aperture Photometry Tool

    NASA Astrophysics Data System (ADS)

    Laher, Russ R.; Gorjian, Varoujan; Rebull, Luisa M.; Masci, Frank J.; Fowler, John W.; Helou, George; Kulkarni, Shrinivas R.; Law, Nicholas M.

    2012-07-01

    Aperture Photometry Tool (APT) is software for astronomers and students interested in manually exploring the photometric qualities of astronomical images. It is a graphical user interface (GUI) designed to allow the image data associated with aperture photometry calculations for point and extended sources to be visualized and, therefore, more effectively analyzed. The finely tuned layout of the GUI, along with judicious use of color-coding and alerting, is intended to give maximal user utility and convenience. Simply mouse-clicking on a source in the displayed image will instantly draw a circular or elliptical aperture and sky annulus around the source and will compute the source intensity and its uncertainty, along with several commonly used measures of the local sky background and its variability. The results are displayed and can be optionally saved to an aperture-photometry-table file and plotted on graphs in various ways using functions available in the software. APT is geared toward processing sources in a small number of images and is not suitable for bulk processing a large number of images, unlike other aperture photometry packages (e.g., SExtractor). However, APT does have a convenient source-list tool that enables calculations for a large number of detections in a given image. The source-list tool can be run either in automatic mode to generate an aperture photometry table quickly or in manual mode to permit inspection and adjustment of the calculation for each individual detection. APT displays a variety of useful graphs with just the push of a button, including image histogram, x and y aperture slices, source scatter plot, sky scatter plot, sky histogram, radial profile, curve of growth, and aperture-photometry-table scatter plots and histograms. APT has many functions for customizing the calculations, including outlier rejection, pixel "picking" and "zapping," and a selection of source and sky models. The radial-profile-interpolation source model

  10. Beam focusing characteristics of diffractive lenses with binary subwavelength structures

    NASA Astrophysics Data System (ADS)

    Feng, Di; Yan, Yingbai; Jin, Guofan; Fan, Shoushan

    2004-09-01

    The diffractive optical elements with binary subwavelength structures have the ability for monolithic integration and can require only single step fabrication, but the subwavelength and aperiodic nature of the diffractive optical elements prevent the use of scalar diffraction theory and the use of coupled-wave theory. To overcome these limitations, we present the rigorous vector analysis and design of diffractive lenses that are finite in extent and have binary subwavelength structures by using a two-dimensional finite-difference time-domain method. By using these effective analysis tools, we analyze the focusing characteristics of continuous profile lenses and binary subwavelength diffractive lenses obtained by generalizing the design approach presented by Farn, for different incidence polarization waves (TE polarization and TM polarization) and for different f-numbers of lenses. The comparative results have shown that the focusing characteristics, including the focal shift, the focal depth, the focal spot size, and the diffractive efficiency, of binary subwavelength diffractive lenses are different from those of continuous profile lenses and are more sensitive to the polarization of incidence wave.

  11. Fabrication of resonant subwavelength grating based on thiol-ene

    NASA Astrophysics Data System (ADS)

    Zhang, Man; Deng, Qiling; Shi, Lifang; Li, Zhiwei; Pang, Hui; Zhang, Yukun; Yu, Jinqing; Hu, Song

    2014-08-01

    This paper presents an approach used to fabricate resonant subwavelength grating based on thiol-ene material. First of all, polydimethylsiloxane soft imprint stamp with opposite structure of the subwavelength grating master mold is made by casting. Then, the desired subwavelength grating with UV-curable thiol-ene material grating structure is fabricated using the polydimethylsioxane soft stamp by UV-curable soft-lithography. Here, we fabricate a subwavelength grating with period of 300nm using the approach, which could reflect blue light with wavelength ranging from 448nm to 482nm at a specific angle and presents the excellent resonant characteristic. The experimental results are consistent with the simulation results, demonstrating that the approach proposed in this paper could effectively fabricate the thiol-ene material resonant subwavelength grating structure. The thiol-ene material is a new green UV-curable polymer material, including a number of advantages such as rapid UV-curing in the natural environment, low-cost, high resolution, and regulative performance characteristic. The fabrication technique in this paper is simple, low-cost, and easy to high throughput, which has broad application prospects in the preparation of micro and nano structures.

  12. Dynamic metamaterial aperture for microwave imaging

    SciTech Connect

    Sleasman, Timothy; Imani, Mohammadreza F.; Gollub, Jonah N.; Smith, David R.

    2015-11-16

    We present a dynamic metamaterial aperture for use in computational imaging schemes at microwave frequencies. The aperture consists of an array of complementary, resonant metamaterial elements patterned into the upper conductor of a microstrip line. Each metamaterial element contains two diodes connected to an external control circuit such that the resonance of the metamaterial element can be damped by application of a bias voltage. Through applying different voltages to the control circuit, select subsets of the elements can be switched on to create unique radiation patterns that illuminate the scene. Spatial information of an imaging domain can thus be encoded onto this set of radiation patterns, or measurements, which can be processed to reconstruct the targets in the scene using compressive sensing algorithms. We discuss the design and operation of a metamaterial imaging system and demonstrate reconstructed images with a 10:1 compression ratio. Dynamic metamaterial apertures can potentially be of benefit in microwave or millimeter wave systems such as those used in security screening and through-wall imaging. In addition, feature-specific or adaptive imaging can be facilitated through the use of the dynamic aperture.

  13. Optical synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Ilovitsh, Asaf; Zach, Shlomo; Zalevsky, Zeev

    2013-06-01

    A method is proposed for increasing the resolution of an object and overcoming the diffraction limit of an optical system installed on top of a moving imaging system, such as an airborne platform or satellite. The resolution improvement is obtained via a two-step process. First, three low resolution differently defocused images are captured and the optical phase is retrieved using an improved iterative Gershberg-Saxton based algorithm. The phase retrieval allows numerical back propagation of the field to the aperture plane. Second, the imaging system is shifted and the first step is repeated. The obtained optical fields at the aperture plane are combined and a synthetically increased lens aperture is generated along the direction of movement, yielding higher imaging resolution. The method resembles a well-known approach from the microwave regime called the synthetic aperture radar in which the antenna size is synthetically increased along the platform propagation direction. The proposed method is demonstrated via Matlab simulation as well as through laboratory experiment.

  14. Apodizer aperture for lasers

    DOEpatents

    Jorna, Siebe; Siebert, Larry D.; Brueckner, Keith A.

    1976-11-09

    An aperture attenuator for use with high power lasers which includes glass windows shaped and assembled to form an annulus chamber which is filled with a dye solution. The annulus chamber is shaped such that the section in alignment with the axis of the incident beam follows a curve which is represented by the equation y = (r - r.sub.o).sup.n.

  15. Synthetic Aperture Radar Interferometry

    NASA Technical Reports Server (NTRS)

    Rosen, P. A.; Hensley, S.; Joughin, I. R.; Li, F.; Madsen, S. N.; Rodriguez, E.; Goldstein, R. M.

    1998-01-01

    Synthetic aperture radar interferometry is an imaging technique for measuring the topography of a surface, its changes over time, and other changes in the detailed characteristics of the surface. This paper reviews the techniques of interferometry, systems and limitations, and applications in a rapidly growing area of science and engineering.

  16. 1D fast coded aperture camera.

    PubMed

    Haw, Magnus; Bellan, Paul

    2015-04-01

    A fast (100 MHz) 1D coded aperture visible light camera has been developed as a prototype for imaging plasma experiments in the EUV/X-ray bands. The system uses printed patterns on transparency sheets as the masked aperture and an 80 channel photodiode array (9 V reverse bias) as the detector. In the low signal limit, the system has demonstrated 40-fold increase in throughput and a signal-to-noise gain of ≈7 over that of a pinhole camera of equivalent parameters. In its present iteration, the camera can only image visible light; however, the only modifications needed to make the system EUV/X-ray sensitive are to acquire appropriate EUV/X-ray photodiodes and to machine a metal masked aperture. PMID:25933861

  17. 1D fast coded aperture camera.

    PubMed

    Haw, Magnus; Bellan, Paul

    2015-04-01

    A fast (100 MHz) 1D coded aperture visible light camera has been developed as a prototype for imaging plasma experiments in the EUV/X-ray bands. The system uses printed patterns on transparency sheets as the masked aperture and an 80 channel photodiode array (9 V reverse bias) as the detector. In the low signal limit, the system has demonstrated 40-fold increase in throughput and a signal-to-noise gain of ≈7 over that of a pinhole camera of equivalent parameters. In its present iteration, the camera can only image visible light; however, the only modifications needed to make the system EUV/X-ray sensitive are to acquire appropriate EUV/X-ray photodiodes and to machine a metal masked aperture.

  18. Extreme stiffness hyperbolic elastic metamaterial for total transmission subwavelength imaging

    NASA Astrophysics Data System (ADS)

    Lee, Hyuk; Oh, Joo Hwan; Seung, Hong Min; Cho, Seung Hyun; Kim, Yoon Young

    2016-04-01

    Subwavelength imaging by metamaterials and extended work to pursue total transmission has been successfully demonstrated with electromagnetic and acoustic waves very recently. However, no elastic counterpart has been reported because earlier attempts suffer from considerable loss. Here, for the first time, we realize an elastic hyperbolic metamaterial lens and experimentally show total transmission subwavelength imaging with measured wave field inside the metamaterial lens. The main idea is to compensate for the decreased impedance in the perforated elastic metamaterial by utilizing extreme stiffness, which has not been independently actualized in a continuum elastic medium so far. The fabricated elastic lens is capable of directly transferring subwavelength information from the input to the output boundary. In the experiment, this intriguing phenomenon is confirmed by scanning the elastic structures inside the lens with laser scanning vibrometer. The proposed elastic metamaterial lens will bring forth significant guidelines for ultrasonic imaging techniques.

  19. Transfer of orbital angular momentum through sub-wavelength waveguides.

    PubMed

    Wang, Yanqin; Ma, Xiaoliang; Pu, Mingbo; Li, Xiong; Huang, Cheng; Pan, Wenbo; Zhao, Bo; Cui, Jianhua; Luo, Xiangang

    2015-02-01

    Data capacity of optical communication is achieving its limit owing to the non-linear effect of optical fiber. As an effective alternative, light carrying orbital angular momentum can greatly increase the capacity for its unprecedented degree of freedom. We demonstrate the propagation of orbital angular momentum with topological charge of 1 and 2 in plasmonic circular waveguide with sub-wavelength diameter with little propagation loss of 2.73 dB/μm, which has never been observed in optical fibers with sub-wavelength diameter. We also confirm that lights carrying orbital angular momentum can be maintained in sharp bended sub-wavelength waveguide. This plasmonic waveguide may serve as a key component in on-chip systems involving OAM.

  20. Extreme stiffness hyperbolic elastic metamaterial for total transmission subwavelength imaging

    PubMed Central

    Lee, Hyuk; Oh, Joo Hwan; Seung, Hong Min; Cho, Seung Hyun; Kim, Yoon Young

    2016-01-01

    Subwavelength imaging by metamaterials and extended work to pursue total transmission has been successfully demonstrated with electromagnetic and acoustic waves very recently. However, no elastic counterpart has been reported because earlier attempts suffer from considerable loss. Here, for the first time, we realize an elastic hyperbolic metamaterial lens and experimentally show total transmission subwavelength imaging with measured wave field inside the metamaterial lens. The main idea is to compensate for the decreased impedance in the perforated elastic metamaterial by utilizing extreme stiffness, which has not been independently actualized in a continuum elastic medium so far. The fabricated elastic lens is capable of directly transferring subwavelength information from the input to the output boundary. In the experiment, this intriguing phenomenon is confirmed by scanning the elastic structures inside the lens with laser scanning vibrometer. The proposed elastic metamaterial lens will bring forth significant guidelines for ultrasonic imaging techniques. PMID:27040762

  1. Acoustic subwavelength imaging of subsurface objects with acoustic resonant metalens

    SciTech Connect

    Cheng, Ying; Liu, XiaoJun; Zhou, Chen; Wei, Qi; Wu, DaJian

    2013-11-25

    Early research into acoustic metamaterials has shown the possibility of achieving subwavelength near-field acoustic imaging. However, a major restriction of acoustic metamaterials is that the imaging objects must be placed in close vicinity of the devices. Here, we present an approach for acoustic imaging of subsurface objects far below the diffraction limit. An acoustic metalens made of holey-structured metamaterials is used to magnify evanescent waves, which can rebuild an image at the central plane. Without changing the physical structure of the metalens, our proposed approach can image objects located at certain distances from the input surface, which provides subsurface signatures of the objects with subwavelength spatial resolution.

  2. Subwavelength-grating-assisted broadband polarization-independent directional coupler.

    PubMed

    Liu, Lu; Deng, Qingzhong; Zhou, Zhiping

    2016-04-01

    This Letter presents both numerical and experimental results of a polarization-independent directional coupler based on slot waveguides with a subwavelength grating. The measured coupling efficiency is 97.4% for TE and 96.7% for TM polarization at a wavelength of 1550 nm. Further analysis shows that the proposed subwavelength grating directional coupler has a fabrication tolerance of ±20  nm for the grating structure and that the coupling efficiencies for the two polarizations are both higher than -0.5  dB (∼89%), exceeding the entire C-band (1525-1570 nm) experimentally. PMID:27192309

  3. Aperture center energy showcase

    SciTech Connect

    Torres, J. J.

    2012-03-01

    Sandia and Forest City have established a Cooperative Research and Development Agreement (CRADA), and the partnership provides a unique opportunity to take technology research and development from demonstration to application in a sustainable community. A project under that CRADA, Aperture Center Energy Showcase, offers a means to develop exhibits and demonstrations that present feedback to community members, Sandia customers, and visitors. The technologies included in the showcase focus on renewable energy and its efficiency, and resilience. These technologies are generally scalable, and provide secure, efficient solutions to energy production, delivery, and usage. In addition to establishing an Energy Showcase, support offices and conference capabilities that facilitate research, collaboration, and demonstration were created. The Aperture Center project focuses on establishing a location that provides outreach, awareness, and demonstration of research findings, emerging technologies, and project developments to Sandia customers, visitors, and Mesa del Sol community members.

  4. Configurable Aperture Space Telescope

    NASA Technical Reports Server (NTRS)

    Ennico, Kimberly; Bendek, Eduardo

    2015-01-01

    In December 2014, we were awarded Center Innovation Fund to evaluate an optical and mechanical concept for a novel implementation of a segmented telescope based on modular, interconnected small sats (satlets). The concept is called CAST, a Configurable Aperture Space Telescope. With a current TRL is 2 we will aim to reach TLR 3 in Sept 2015 by demonstrating a 2x2 mirror system to validate our optical model and error budget, provide straw man mechanical architecture and structural damping analyses, and derive future satlet-based observatory performance requirements. CAST provides an alternative access to visible and/or UV wavelength space telescope with 1-meter or larger aperture for NASA SMD Astrophysics and Planetary Science community after the retirement of HST

  5. Integrated electrochromic aperture diaphragm

    NASA Astrophysics Data System (ADS)

    Deutschmann, T.; Oesterschulze, E.

    2014-05-01

    In the last years, the triumphal march of handheld electronics with integrated cameras has opened amazing fields for small high performing optical systems. For this purpose miniaturized iris apertures are of practical importance because they are essential to control both the dynamic range of the imaging system and the depth of focus. Therefore, we invented a micro optical iris based on an electrochromic (EC) material. This material changes its absorption in response to an applied voltage. A coaxial arrangement of annular rings of the EC material is used to establish an iris aperture without need of any mechanical moving parts. The advantages of this device do not only arise from the space-saving design with a thickness of the device layer of 50μm. But it also benefits from low power consumption. In fact, its transmission state is stable in an open circuit, phrased memory effect. Only changes of the absorption require a voltage of up to 2 V. In contrast to mechanical iris apertures the absorption may be controlled on an analog scale offering the opportunity for apodization. These properties make our device the ideal candidate for battery powered and space-saving systems. We present optical measurements concerning control of the transmitted intensity and depth of focus, and studies dealing with switching times, light scattering, and stability. While the EC polymer used in this study still has limitations concerning color and contrast, the presented device features all functions of an iris aperture. In contrast to conventional devices it offers some special features. Owing to the variable chemistry of the EC material, its spectral response may be adjusted to certain applications like color filtering in different spectral regimes (UV, optical range, infrared). Furthermore, all segments may be switched individually to establish functions like spatial Fourier filtering or lateral tunable intensity filters.

  6. Electric and magnetic response in dielectric dark states for low loss subwavelength optical meta atoms

    SciTech Connect

    Jain, Aditya; Moitra, Parikshit; Koschny, Thomas; Valentine, Jason; Soukoulis, Costas M.

    2015-07-14

    Artificially created surfaces or metasurfaces, composed of appropriately shaped subwavelength structures, namely, meta-atoms, control light at subwavelength scales. Historically, metasurfaces have used radiating metallic resonators as subwavelength inclusions. However, while resonant optical metasurfaces made from metal have been sufficiently subwavelength in the propagation direction, they are too lossy for many applications. Metasurfaces made out of radiating dielectric resonators have been proposed to solve the loss problem, but are marginally subwavelength at optical frequencies. We designed subwavelength resonators made out of nonradiating dielectrics. The resonators are decorated with appropriately placed scatterers, resulting in a meta-atom with an engineered electromagnetic response. A metasurface that yields an electric response is fabricated, experimentally characterized, and a method to obtain a magnetic response at optical frequencies is theoretically demonstrated. In conclusion, this design methodology paves the way for metasurfaces that are simultaneously subwavelength and low loss.

  7. Electric and magnetic response in dielectric dark states for low loss subwavelength optical meta atoms

    DOE PAGESBeta

    Jain, Aditya; Moitra, Parikshit; Koschny, Thomas; Valentine, Jason; Soukoulis, Costas M.

    2015-07-14

    Artificially created surfaces or metasurfaces, composed of appropriately shaped subwavelength structures, namely, meta-atoms, control light at subwavelength scales. Historically, metasurfaces have used radiating metallic resonators as subwavelength inclusions. However, while resonant optical metasurfaces made from metal have been sufficiently subwavelength in the propagation direction, they are too lossy for many applications. Metasurfaces made out of radiating dielectric resonators have been proposed to solve the loss problem, but are marginally subwavelength at optical frequencies. We designed subwavelength resonators made out of nonradiating dielectrics. The resonators are decorated with appropriately placed scatterers, resulting in a meta-atom with an engineered electromagnetic response. Amore » metasurface that yields an electric response is fabricated, experimentally characterized, and a method to obtain a magnetic response at optical frequencies is theoretically demonstrated. In conclusion, this design methodology paves the way for metasurfaces that are simultaneously subwavelength and low loss.« less

  8. Ultra-broadband and efficient surface plasmon polariton launching through metallic nanoslits of subwavelength period

    PubMed Central

    Li, Guangyuan; Zhang, Jiasen

    2014-01-01

    Ultra-broadband, efficient and unidirectional surface plasmon polariton (SPP) launching is of great concern in plasmonic devices and circuits. To address this challenge, a novel method adopting deep-subwavelength slits of subwavelength period (λSPP/4 ~ λSPP/3) in a thick metal film and under backside illumination is proposed. A new band pattern featuring broadband and wide angular characteristics, which is due to the coupling of the zeroth-order SPP resonance at the superstrate–metal interface and the first-order SPP resonance at the metal–substrate interface, is observed for the first time in the dispersion diagram. Unidirectional SPP launching efficiency of ~50%, ultra-broad bandwidth of up to 780 nm, covering the entire optical fiber communication bands, and relatively wide angular range of 7° are achieved. This remarkable efficient, ultra-broadband and wide angular performance is demonstrated by carefully designed experiments in the near infrared regime, showing good agreement with numerical results. PMID:25081812

  9. Subwavelength-scale tailoring of surface phonon polaritons by focused ion-beam implantation.

    PubMed

    Ocelic, N; Hillenbrand, R

    2004-09-01

    Recent advances in optical nanotechnologies by controlling surface plasmon polaritons in metallic nanostructures demonstrate high potential for subwavelength-scale waveguiding of light, data storage, microscopy or biophotonics. Surprisingly, surface phonon polaritons-infrared counterparts to surface plasmon polaritons-have not been widely explored for nanophotonic applications. As they rely on the infrared or terahertz excitation of lattice vibrations in polar crystals they offer totally different material classes for nanophotonic applications, such as semiconductors and insulators. In an initial step towards nanoscale surface phonon photonics we show evidence that the local properties of surface phonon polaritons can be tailored at a subwavelength-scale by focused ion-beam modification of the crystal structure, even without significant alteration of the surface topography. Such single-step-fabricated, monolithic structures could be used for controlling electromagnetic energy transport by surface phonon polaritons in miniaturized integrated devices operating at infrared or terahertz frequencies. We verify the polaritonic properties of an ion-beam-patterned SiC surface by infrared near-field microscopy. The near-field images also demonstrate nanometre-scale resolved infrared mapping of crystal quality useful in semiconductor processing or crystal growth.

  10. Optical filter including a sub-wavelength periodic structure and method of making

    DOEpatents

    Kaushik, S.; Stallard, B.R.

    1998-03-10

    An optical filter includes a dielectric layer formed within a resonant optical cavity, with the dielectric layer having formed therein a sub-wavelength periodic structure to define, at least in part, a wavelength for transmission of light through the resonant optical cavity. The sub-wavelength periodic structure can be formed either by removing material from the dielectric layer (e.g. by etching through an electron-beam defined mask), or by altering the composition of the layer (e.g. by ion implantation). Different portions of the dielectric layer can be patterned to form one or more optical interference filter elements having different light transmission wavelengths so that the optical filter can filter incident light according to wavelength and/or polarization. For some embodiments, the optical filter can include a detector element in optical alignment with each optical interference filter element to quantify or measure the filtered light for analysis thereof. The optical filter has applications to spectrometry, colorimetry, and chemical sensing. 17 figs.

  11. Optical filter including a sub-wavelength periodic structure and method of making

    DOEpatents

    Kaushik, Sumanth; Stallard, Brian R.

    1998-01-01

    An optical filter includes a dielectric layer formed within a resonant optical cavity, with the dielectric layer having formed therein a sub-wavelength periodic structure to define, at least in part, a wavelength for transmission of light through the resonant optical cavity. The sub-wavelength periodic structure can be formed either by removing material from the dielectric layer (e.g. by etching through an electron-beam defined mask), or by altering the composition of the layer (e.g. by ion implantation). Different portions of the dielectric layer can be patterned to form one or more optical interference filter elements having different light transmission wavelengths so that the optical filter can filter incident light according to wavelength and/or polarization. For some embodiments, the optical filter can include a detector element in optical alignment with each optical interference filter element to quantify or measure the filtered light for analysis thereof. The optical filter has applications to spectrometry, colorimetry, and chemical sensing.

  12. Integrated circuit layout design methodology for deep sub-wavelength processes

    NASA Astrophysics Data System (ADS)

    Torres Robles, Juan Andres

    One of the critical aspects of semiconductor fabrication is the patterning of multiple design layers onto silicon wafers. Since 180nm processes came online, the semiconductor industry has operated under conditions in which the critical features are smaller than the wavelength of light used during the patterning process. Such sub-wavelength conditions present many challenges because topology, rather than feature width and space, defines the yield characteristics of the devices. Pattern variability can contribute as much as 80% of the total timing margins defined by traditional SPICE corner models. Because feature variability is undesirable from electrical considerations, this work proposes a physical design verification methodology that emphasizes pattern robustness to process variations. This new method is based on a framework composed of manufacturability objects, operators and guidelines, which permits the definition of a scoring system ranking the manufacturing process and the manufacturability of the designs. This framework is intended to alleviate circuit design and verification challenges and it based on three new concepts: the first relates to compact process model requirements. The second involves the definition of a new design object, called pv-Band, which reflects layout sensitivity to process variations. The third is the specification of two manufacturability metrics that, when optimized, can improve yield by accounting layout sensitivities across multiple design levels (e.g., Active, polysilicon, contact, metal 1, etc.). By integrating these new concepts (process models, pv-Bands and manufacturability metrics) with existing knowledge, this work moves forward the state-of-the-art of physical design and verification of integrated circuits subject to sub-wavelength effects.

  13. Differential Optical Synthetic Aperture Radar

    DOEpatents

    Stappaerts, Eddy A.

    2005-04-12

    A new differential technique for forming optical images using a synthetic aperture is introduced. This differential technique utilizes a single aperture to obtain unique (N) phases that can be processed to produce a synthetic aperture image at points along a trajectory. This is accomplished by dividing the aperture into two equal "subapertures", each having a width that is less than the actual aperture, along the direction of flight. As the platform flies along a given trajectory, a source illuminates objects and the two subapertures are configured to collect return signals. The techniques of the invention is designed to cancel common-mode errors, trajectory deviations from a straight line, and laser phase noise to provide the set of resultant (N) phases that can produce an image having a spatial resolution corresponding to a synthetic aperture.

  14. Real-time and Sub-wavelength Ultrafast Coherent Diffraction Imaging in the Extreme Ultraviolet

    PubMed Central

    Zürch, M.; Rothhardt, J.; Hädrich, S.; Demmler, S.; Krebs, M.; Limpert, J.; Tünnermann, A.; Guggenmos, A.; Kleineberg, U.; Spielmann, C.

    2014-01-01

    Coherent Diffraction Imaging is a technique to study matter with nanometer-scale spatial resolution based on coherent illumination of the sample with hard X-ray, soft X-ray or extreme ultraviolet light delivered from synchrotrons or more recently X-ray Free-Electron Lasers. This robust technique simultaneously allows quantitative amplitude and phase contrast imaging. Laser-driven high harmonic generation XUV-sources allow table-top realizations. However, the low conversion efficiency of lab-based sources imposes either a large scale laser system or long exposure times, preventing many applications. Here we present a lensless imaging experiment combining a high numerical aperture (NA = 0.8) setup with a high average power fibre laser driven high harmonic source. The high flux and narrow-band harmonic line at 33.2 nm enables either sub-wavelength spatial resolution close to the Abbe limit (Δr = 0.8λ) for long exposure time, or sub-70 nm imaging in less than one second. The unprecedented high spatial resolution, compactness of the setup together with the real-time capability paves the way for a plethora of applications in fundamental and life sciences. PMID:25483626

  15. Compounding in synthetic aperture imaging.

    PubMed

    Hansen, Jens Munk; Jensen, Jørgen Arendt

    2012-09-01

    A method for obtaining compound images using synthetic aperture data is investigated using a convex array transducer. The new approach allows spatial compounding to be performed for any number of angles without reducing the frame rate or temporal resolution. This important feature is an intrinsic property of how the compound images are constructed using synthetic aperture data and an improvement compared with how spatial compounding is obtained using conventional methods. The synthetic aperture compound images are created by exploiting the linearity of delay-and-sum beamformation for data collected from multiple spherical emissions to synthesize multiple transmit and receive apertures, corresponding to imaging the tissue from multiple directions. The many images are added incoherently, to produce a single compound image. Using a 192-element, 3.5-MHz, λ-pitch transducer, it is demonstrated from tissue-phantom measurements that the speckle is reduced and the contrast resolution improved when applying synthetic aperture compound imaging. At a depth of 4 cm, the size of the synthesized apertures is optimized for lesion detection based on the speckle information density. This is a performance measure for tissue contrast resolution which quantifies the tradeoff between resolution loss and speckle reduction. The speckle information density is improved by 25% when comparing synthetic aperture compounding to a similar setup for compounding using dynamic receive focusing. The cystic resolution and clutter levels are measured using a wire phantom setup and compared with conventional application of the array, as well as to synthetic aperture imaging without compounding. If the full aperture is used for synthetic aperture compounding, the cystic resolution is improved by 41% compared with conventional imaging, and is at least as good as what can be obtained using synthetic aperture imaging without compounding. PMID:23007781

  16. Broadband subwavelength imaging using a tunable graphene-lens.

    PubMed

    Li, Peining; Taubner, Thomas

    2012-11-27

    Graphene as a one-atom-thick planar sheet can support surface plasmons at infrared (IR) and terahertz (THz) frequencies, opening up exciting possibilities for the emerging research field of graphene plasmonics. Here, we theoretically report that a layered graphene-lens (GL) enables the enhancement of evanescent waves for near-field subdiffractive imaging. Compared to other resonant imaging devices like superlenses, the nonresonant operation of the GL provides the advantages of a broad intrinsic bandwidth and a low sensitivity to losses, while still maintaining a good subwavelength resolution of better than λ/10. Most importantly, thanks to the large tunability of the graphene, we show that our GL is a continuously frequency-tunable subwavelength-imaging device in the IR and THz regions, thus allowing for ultrabroadband spectral applications. PMID:23046079

  17. Realization of deep subwavelength resolution with singular media

    PubMed Central

    Xu, Su; Jiang, Yuyu; Xu, Hongyi; Wang, Junxia; Lin, Shisheng; Chen, Hongsheng; Zhang, Baile

    2014-01-01

    The record of imaging resolution has kept being refreshed in the past decades and the best resolution of hyperlenses and superlenses so far is about one out of tens in terms of wavelength. In this paper, by adopting a hybrid concept of transformation optics and singular media, we report a broadband meta-lens design methodology with ultra-high resolution. The meta-lens is made of subwavelength metal/air layers, which exhibit singular medium property over a broad band. As a proof of concept, the subwavelength imaging ability is demonstrated over a broad frequency band from 1.5–10 GHz with the resolution varying from 1/117 to 1/17 wavelength experimentally. PMID:24909738

  18. Left-handed metamaterial coatings for subwavelength-resolution imaging.

    PubMed

    Zapata-Rodríguez, Carlos J; Pastor, David; Martínez, Luis E; Miret, Juan J

    2012-09-01

    We report on a procedure to improve the resolution of far-field imaging by using a neighboring high-index medium that is coated with a left-handed metamaterial. The resulting plot can also exhibit an enhanced transmission by considering proper conditions to retract backscattering. Based on negative refraction, geometrical aberrations are considered in detail since they may cause a great impact in this sort of diffraction-unlimited imaging by reducing its resolution power. We employ a standard aberration analysis to refine the asymmetric configuration of metamaterial superlenses. We demonstrate that low-order centrosymmetric aberrations can be fully corrected for a given object plane. For subwavelength-resolution imaging, however, high-order aberrations become of relevance, which may be balanced with defocus. Not only the point spread function but also numerical simulations based on the finite-element method support our theoretical analysis, and subwavelength resolution is verified in the image plane.

  19. Transmission resonances of metallic compound gratings with subwavelength slits.

    PubMed

    Skigin, Diana C; Depine, Ricardo A

    2005-11-18

    Transmission metallic gratings with subwavelength slits are known to produce enhanced transmitted intensity for certain resonant wavelengths. One of the mechanisms that produce these resonances is the excitation of waveguide modes inside the slits. We show that by adding slits to the period, the transmission maxima are widened and, simultaneously, this generates phase resonances that appear as sharp dips in the transmission response. These resonances are characterized by a significant enhancement of the interior field.

  20. Optical pulling using evanescent mode in sub-wavelength channels.

    PubMed

    Zhu, Tongtong; Mahdy, M R C; Cao, Yongyin; Lv, Haiyi; Sun, Fangkui; Jiang, Zehui; Ding, Weiqiang

    2016-08-01

    Optical evanescent wave in total internal reflection has been widely used in efficient optical manipulation, where the object is trapped by the intrinsic intensity gradient of the evanescent wave while transported by the scattering force along the orthogonal direction. Here, we propose a distinct optical manipulation scheme using the attenuated modes in subwavelength optical channels, where both the trapping and transportation forces are along the channel direction. We create such a mode in a sub-wavelength photonic crystal waveguide and quantitatively obtain the net pushing and pulling forces, which can overcome the Brownian motion within a critical length. Due to the presence of the physical channel, subwavelength trapping on the transverse direction is natural, and manipulation along bend trajectories is also possible without the assistance of the self-acceleration beams provided a channel is adopted. This optical manipulation method can be extended to any other channels that support attenuation mode, and may provide an alternate way for flexible optical manipulation. PMID:27505807

  1. Optica aperture synthesis

    NASA Astrophysics Data System (ADS)

    van der Avoort, Casper

    2006-05-01

    Optical long baseline stellar interferometry is an observational technique in astronomy that already exists for over a century, but is truly blooming during the last decades. The undoubted value of stellar interferometry as a technique to measure stellar parameters beyond the classical resolution limit is more and more spreading to the regime of synthesis imaging. With optical aperture synthesis imaging, the measurement of parameters is extended to the reconstruction of high resolution stellar images. A number of optical telescope arrays for synthesis imaging are operational on Earth, while space-based telescope arrays are being designed. For all imaging arrays, the combination of the light collected by the telescopes in the array can be performed in a number of ways. In this thesis, methods are introduced to model these methods of beam combination and compare their effectiveness in the generation of data to be used to reconstruct the image of a stellar object. One of these methods of beam combination is to be applied in a future space telescope. The European Space Agency is developing a mission that can valuably be extended with an imaging beam combiner. This mission is labeled Darwin, as its main goal is to provide information on the origin of life. The primary objective is the detection of planets around nearby stars - called exoplanets- and more precisely, Earth-like exoplanets. This detection is based on a signal, rather than an image. With an imaging mode, designed as described in this thesis, Darwin can make images of, for example, the planetary system to which the detected exoplanet belongs or, as another example, of the dust disk around a star out of which planets form. Such images will greatly contribute to the understanding of the formation of our own planetary system and of how and when life became possible on Earth. The comparison of beam combination methods for interferometric imaging occupies most of the pages of this thesis. Additional chapters will

  2. Fast-neutron, coded-aperture imager

    NASA Astrophysics Data System (ADS)

    Woolf, Richard S.; Phlips, Bernard F.; Hutcheson, Anthony L.; Wulf, Eric A.

    2015-06-01

    This work discusses a large-scale, coded-aperture imager for fast neutrons, building off a proof-of concept instrument developed at the U.S. Naval Research Laboratory (NRL). The Space Science Division at the NRL has a heritage of developing large-scale, mobile systems, using coded-aperture imaging, for long-range γ-ray detection and localization. The fast-neutron, coded-aperture imaging instrument, designed for a mobile unit (20 ft. ISO container), consists of a 32-element array of 15 cm×15 cm×15 cm liquid scintillation detectors (EJ-309) mounted behind a 12×12 pseudorandom coded aperture. The elements of the aperture are composed of 15 cm×15 cm×10 cm blocks of high-density polyethylene (HDPE). The arrangement of the aperture elements produces a shadow pattern on the detector array behind the mask. By measuring of the number of neutron counts per masked and unmasked detector, and with knowledge of the mask pattern, a source image can be deconvolved to obtain a 2-d location. The number of neutrons per detector was obtained by processing the fast signal from each PMT in flash digitizing electronics. Digital pulse shape discrimination (PSD) was performed to filter out the fast-neutron signal from the γ background. The prototype instrument was tested at an indoor facility at the NRL with a 1.8-μCi and 13-μCi 252Cf neutron/γ source at three standoff distances of 9, 15 and 26 m (maximum allowed in the facility) over a 15-min integration time. The imaging and detection capabilities of the instrument were tested by moving the source in half- and one-pixel increments across the image plane. We show a representative sample of the results obtained at one-pixel increments for a standoff distance of 9 m. The 1.8-μCi source was not detected at the 26-m standoff. In order to increase the sensitivity of the instrument, we reduced the fastneutron background by shielding the top, sides and back of the detector array with 10-cm-thick HDPE. This shielding configuration led

  3. Hybrid nanowedge plasmonic waveguide for low loss propagation with ultra-deep-subwavelength mode confinement.

    PubMed

    Ma, Youqiao; Farrell, Gerald; Semenova, Yuliya; Wu, Qiang

    2014-02-15

    In this Letter, a novel waveguide based on hybrid surface plasmon polaritons (HSPPs) is proposed and numerically analyzed. This waveguide consists of two dielectric nanowires placed on both sides of a nanowedge-patterned metal film, which can confine light in the ultra-deep-subwavelength region (ranging from λ²/4000 to λ²/400) with a long propagation length (ranging from 1200 to 3500 μm). Compared to a previous HSPPs waveguide without the nanowedges, with the same propagation length, our proposed structure has much higher mode confinement with 1 order of magnitude smaller normalized mode area. An investigation of the effect of structural perturbations indicates that our proposed waveguide also has good tolerance of fabrication errors. The proposed waveguide could be an interesting alternative structure to realize nanolasers and optical trapping.

  4. Tailoring Dispersion for Broadband Low-loss Optical Metamaterials Using Deep-subwavelength Inclusions

    PubMed Central

    Jiang, Zhi Hao; Yun, Seokho; Lin, Lan; Bossard, Jeremy A.; Werner, Douglas H.; Mayer, Theresa S.

    2013-01-01

    Metamaterials have the potential to create optical devices with new and diverse functionalities based on novel wave phenomena. Most practical optical systems require that the device properties be tightly controlled over a broad wavelength range. However, optical metamaterials are inherently dispersive, which limits operational bandwidths and leads to high absorption losses. Here, we show that deep-subwavelength inclusions can controllably tailor the dispersive properties of an established metamaterial structure thereby producing a broadband low-loss optical device with a desired response. We experimentally verify this by optimizing an array of nano-notch inclusions, which perturb the mode patterns and strength of the primary and secondary fishnet nanostructure resonances and give an optically thin mid-wave-infrared filter with a broad transmissive pass-band and near-constant group delay. This work outlines a powerful new strategy for realizing a wide range of broadband optical devices that exploit the unique properties of metamaterials. PMID:23535875

  5. Left handed dispersion of a stack of subwavelength hole metal arrays at terahertz frequencies

    NASA Astrophysics Data System (ADS)

    Croënne, Charles; Garet, Frédéric; Lheurette, Éric; Coutaz, Jean-Louis; Lippens, Didier

    2009-03-01

    We report on the electromagnetic response of a stack of subwavelength hole metal arrays. The samples were designed for exhibiting left handed dispersion branches under normal incidence, and their transmissivities were optimized via the fabrication of elliptical-shaped holes. They are constituted of benzocyclobutene layers with tens of micron thicknesses and submicron-thick gold films patterned by photolithography. Experimental evidence, achieved by time-domain terahertz spectroscopy and supported by full wave simulations, of a ground left handed dispersion branch is found around 0.45 THz. The insertion losses are -3 dB for a five-layer structure, this good level being explained by the matching of the impedance.

  6. Eyeglass: A Very Large Aperture Diffractive Space Telescope

    SciTech Connect

    Hyde, R; Dixit, S; Weisberg, A; Rushford, M

    2002-07-29

    Eyeglass is a very large aperture (25-100 meter) space telescope consisting of two distinct spacecraft, separated in space by several kilometers. A diffractive lens provides the telescope's large aperture, and a separate, much smaller, space telescope serves as its mobile eyepiece. Use of a transmissive diffractive lens solves two basic problems associated with very large aperture space telescopes; it is inherently fieldable (lightweight and flat, hence packagable and deployable) and virtually eliminates the traditional, very tight, surface shape tolerances faced by reflecting apertures. The potential drawback to use of a diffractive primary (very narrow spectral bandwidth) is eliminated by corrective optics in the telescope's eyepiece. The Eyeglass can provide diffraction-limited imaging with either single-band, multiband, or continuous spectral coverage. Broadband diffractive telescopes have been built at LLNL and have demonstrated diffraction-limited performance over a 40% spectral bandwidth (0.48-0.72 {micro}m). As one approach to package a large aperture for launch, a foldable lens has been built and demonstrated. A 75 cm aperture diffractive lens was constructed from 6 panels of 1 m thick silica; it achieved diffraction-limited performance both before and after folding. This multiple panel, folding lens, approach is currently being scaled-up at LLNL. We are building a 5 meter aperture foldable lens, involving 72 panels of 700 {micro}m thick glass sheets, diffractively patterned to operate as coherent f/50 lens.

  7. Fracture-aperture alteration induced by calcite precipitation

    NASA Astrophysics Data System (ADS)

    Jones, T.; Detwiler, R. L.

    2013-12-01

    within variable-aperture fields will investigate the dependency of growth patterns on heterogeneous aperture distributions. (a) Aperture strain (Δb/bi) after 14 days. Precipitation is concentrated near the inlet and decreases in the flow direction. (b) Width-averaged profiles of the initial and final aperture field show changes in aperture and smoothing that results from calcite precipitation between the initial discrete crystals.

  8. Sparse aperture endoscope

    DOEpatents

    Fitch, Joseph P.

    1999-07-06

    An endoscope which reduces the volume needed by the imaging part thereof, maintains resolution of a wide diameter optical system, while increasing tool access, and allows stereographic or interferometric processing for depth and perspective information/visualization. Because the endoscope decreases the volume consumed by imaging optics such allows a larger fraction of the volume to be used for non-imaging tools, which allows smaller incisions in surgical and diagnostic medical applications thus produces less trauma to the patient or allows access to smaller volumes than is possible with larger instruments. The endoscope utilizes fiber optic light pipes in an outer layer for illumination, a multi-pupil imaging system in an inner annulus, and an access channel for other tools in the center. The endoscope is amenable to implementation as a flexible scope, and thus increases the utility thereof. Because the endoscope uses a multi-aperture pupil, it can also be utilized as an optical array, allowing stereographic and interferometric processing.

  9. Sparse aperture endoscope

    DOEpatents

    Fitch, J.P.

    1999-07-06

    An endoscope is disclosed which reduces the volume needed by the imaging part, maintains resolution of a wide diameter optical system, while increasing tool access, and allows stereographic or interferometric processing for depth and perspective information/visualization. Because the endoscope decreases the volume consumed by imaging optics such allows a larger fraction of the volume to be used for non-imaging tools, which allows smaller incisions in surgical and diagnostic medical applications thus produces less trauma to the patient or allows access to smaller volumes than is possible with larger instruments. The endoscope utilizes fiber optic light pipes in an outer layer for illumination, a multi-pupil imaging system in an inner annulus, and an access channel for other tools in the center. The endoscope is amenable to implementation as a flexible scope, and thus increases it's utility. Because the endoscope uses a multi-aperture pupil, it can also be utilized as an optical array, allowing stereographic and interferometric processing. 7 figs.

  10. DAVINCI: Dilute Aperture VIsible Nulling Coronagraphic Imager

    NASA Technical Reports Server (NTRS)

    Shao, Michael; Levine, B. M.; Vasisht, G.; Lane, B. F.; Woodruff, R.; Vasudevan, G.; Samuele, R.; Lloyd, C. A.; Clampin, M.; Lyon, R.; Guyon, O.

    2008-01-01

    This slide presentation gives an overview of DAVINCI (Dilute Aperture VIsible Nulling Coronagraphic Imager). The presentation also includes information about dilute aperture coronagraph, and lyot efficiency.

  11. Bistatic synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Yates, Gillian

    Synthetic aperture radar (SAR) allows all-weather, day and night, surface surveillance and has the ability to detect, classify and geolocate objects at long stand-off ranges. Bistatic SAR, where the transmitter and the receiver are on separate platforms, is seen as a potential means of countering the vulnerability of conventional monostatic SAR to electronic countermeasures, particularly directional jamming, and avoiding physical attack of the imaging platform. As the receiving platform can be totally passive, it does not advertise its position by RF emissions. The transmitter is not susceptible to jamming and can, for example, operate at long stand-off ranges to reduce its vulnerability to physical attack. This thesis examines some of the complications involved in producing high-resolution bistatic SAR imagery. The effect of bistatic operation on resolution is examined from a theoretical viewpoint and analytical expressions for resolution are developed. These expressions are verified by simulation work using a simple 'point by point' processor. This work is extended to look at using modern practical processing engines for bistatic geometries. Adaptations of the polar format algorithm and range migration algorithm are considered. The principal achievement of this work is a fully airborne demonstration of bistatic SAR. The route taken in reaching this is given, along with some results. The bistatic SAR imagery is analysed and compared to the monostatic imagery collected at the same time. Demonstrating high-resolution bistatic SAR imagery using two airborne platforms represents what I believe to be a European first and is likely to be the first time that this has been achieved outside the US (the UK has very little insight into US work on this topic). Bistatic target characteristics are examined through the use of simulations. This also compares bistatic imagery with monostatic and gives further insight into the utility of bistatic SAR.

  12. Coded aperture compressive temporal imaging.

    PubMed

    Llull, Patrick; Liao, Xuejun; Yuan, Xin; Yang, Jianbo; Kittle, David; Carin, Lawrence; Sapiro, Guillermo; Brady, David J

    2013-05-01

    We use mechanical translation of a coded aperture for code division multiple access compression of video. We discuss the compressed video's temporal resolution and present experimental results for reconstructions of > 10 frames of temporal data per coded snapshot.

  13. Optically resonant subwavelength films for tamper-indicating tags and seals

    SciTech Connect

    Alvine, Kyle J.; Suter, Jonathan D.; Bernacki, Bruce E.; Bennett, Wendy D.

    2015-05-23

    We present the design, modeling and performance of a proof-of-concept tamper indicating approach that exploits newly-developed subwavelength-patterned films. These films have a nanostructure-dependent resonant optical reflection that is wavelength, angle, and polarization dependent. As such, they can be tailored to fabricate overlay transparent films for tamper indication and authentication of sensitive or controlled materials not possible with currently-known technologies. An additional advantage is that the unique optical signature is dictated by the geometry and fabrication process of the nanostructures in the film, rather than on the material used. The essential structure unit in the subwavelength resonant coating is a nanoscale Open-Ring Resonator (ORR). This building block is fabricated by coating a dielectric nanoscale template with metal to form a hemispherical shell-like structure. This curved metallic shell structure has a cross-section with an intrinsic capacitance and inductance and is thus the optical equivalent to the well-known “LC” circuit where the capacitance and inductance are determined by the nanoshell dimensions. For structures with sub 100 nm scale, this resonance occurs in the visible electromagnetic spectrum, and in the IR for larger shells. Tampering of the film would be visible though misalignment of the angular dependence of the features in the film. It is additionally possible to add in intrinsic oxidation and strain sensitive matrix materials to further complicate tamper repair and counterfeiting. Cursory standoff readout would be relatively simple using a combination of a near-infrared (or visible) LED flashlight and polarizer or passively using room lighting illumination and a dispersive detector.

  14. Optically resonant subwavelength films for tamper-indicating tags and seals

    NASA Astrophysics Data System (ADS)

    Alvine, Kyle J.; Suter, Jonathan D.; Bernacki, Bruce E.; Bennett, Wendy D.

    2015-05-01

    We present the design, modeling and performance of a proof-of-concept tamper indicating approach that exploits newlydeveloped subwavelength-patterned films. These films have a nanostructure-dependent resonant optical reflection that is wavelength, angle, and polarization dependent. As such, they can be tailored to fabricate overlay transparent films for tamper indication and authentication of sensitive or controlled materials not possible with currently-known technologies. An additional advantage is that the unique optical signature is dictated by the geometry and fabrication process of the nanostructures in the film, rather than on the material used. The essential structure unit in the subwavelength resonant coating is a nanoscale Open-Ring Resonator (ORR). This building block is fabricated by coating a dielectric nanoscale template with metal to form a hemispherical shell-like structure. This curved metallic shell structure has a cross-section with an intrinsic capacitance and inductance and is thus the optical equivalent to the well-known "LC" circuit where the capacitance and inductance are determined by the nanoshell dimensions. For structures with sub 100 nm scale, this resonance occurs in the visible electromagnetic spectrum, and in the IR for larger shells. Tampering of the film would be visible though misalignment of the angle-sensitive features in the film. It is additionally possible to add in intrinsic oxidation and strain sensitive matrix materials to further complicate tamper repair and counterfeiting. Cursory standoff readout would be relatively simple using a combination of a near-infrared (or visible) LED flashlight and polarizer or passively using room lighting illumination and a dispersive detector.

  15. Superresolution and Synthetic Aperture Radar

    SciTech Connect

    DICKEY,FRED M.; ROMERO,LOUIS; DOERRY,ARMIN W.

    2001-05-01

    Superresolution concepts offer the potential of resolution beyond the classical limit. This great promise has not generally been realized. In this study we investigate the potential application of superresolution concepts to synthetic aperture radar. The analytical basis for superresolution theory is discussed. The application of the concept to synthetic aperture radar is investigated as an operator inversion problem. Generally, the operator inversion problem is ill posed. A criterion for judging superresolution processing of an image is presented.

  16. Vision aided inertial navigation system augmented with a coded aperture

    NASA Astrophysics Data System (ADS)

    Morrison, Jamie R.

    Navigation through a three-dimensional indoor environment is a formidable challenge for an autonomous micro air vehicle. A main obstacle to indoor navigation is maintaining a robust navigation solution (i.e. air vehicle position and attitude estimates) given the inadequate access to satellite positioning information. A MEMS (micro-electro-mechanical system) based inertial navigation system provides a small, power efficient means of maintaining a vehicle navigation solution; however, unmitigated error propagation from relatively noisy MEMS sensors results in the loss of a usable navigation solution over a short period of time. Several navigation systems use camera imagery to diminish error propagation by measuring the direction to features in the environment. Changes in feature direction provide information regarding direction for vehicle movement, but not the scale of movement. Movement scale information is contained in the depth to the features. Depth-from-defocus is a classic technique proposed to derive depth from a single image that involves analysis of the blur inherent in a scene with a narrow depth of field. A challenge to this method is distinguishing blurriness caused by the focal blur from blurriness inherent to the observed scene. In 2007, MIT's Computer Science and Artificial Intelligence Laboratory demonstrated replacing the traditional rounded aperture with a coded aperture to produce a complex blur pattern that is more easily distinguished from the scene. A key to measuring depth using a coded aperture then is to correctly match the blur pattern in a region of the scene with a previously determined set of blur patterns for known depths. As the depth increases from the focal plane of the camera, the observable change in the blur pattern for small changes in depth is generally reduced. Consequently, as the depth of a feature to be measured using a depth-from-defocus technique increases, the measurement performance decreases. However, a Fresnel zone

  17. Optically pumped subwavelength-scale metallodielectric nanopatch resonators.

    PubMed

    Kwon, Kyungmok; You, Jong-Bum; Shim, Jaeho; Jung, Youngho; Yu, Kyoungsik

    2016-01-01

    We discuss subwavelength-scale semiconductor metal-optic resonators placed on the metal substrate with various top metal plate sizes. Albeit with large optical losses, addition of metal layers converts a leaky semiconductor nano-block into a highly-confined optical cavity. Optically pumped lasing action is observed with the extended top metal layer that can significantly suppress the radiation losses. Careful investigation of self-heating effects during the optical carrier injection process shows the importance of temperature-dependent material properties in the laser rate equation model and the overall laser performances. PMID:27549640

  18. Optically pumped subwavelength-scale metallodielectric nanopatch resonators

    NASA Astrophysics Data System (ADS)

    Kwon, Kyungmok; You, Jong-Bum; Shim, Jaeho; Jung, Youngho; Yu, Kyoungsik

    2016-08-01

    We discuss subwavelength-scale semiconductor metal-optic resonators placed on the metal substrate with various top metal plate sizes. Albeit with large optical losses, addition of metal layers converts a leaky semiconductor nano-block into a highly-confined optical cavity. Optically pumped lasing action is observed with the extended top metal layer that can significantly suppress the radiation losses. Careful investigation of self-heating effects during the optical carrier injection process shows the importance of temperature-dependent material properties in the laser rate equation model and the overall laser performances.

  19. Optically pumped subwavelength-scale metallodielectric nanopatch resonators

    PubMed Central

    Kwon, Kyungmok; You, Jong-bum; Shim, Jaeho; Jung, Youngho; Yu, Kyoungsik

    2016-01-01

    We discuss subwavelength-scale semiconductor metal-optic resonators placed on the metal substrate with various top metal plate sizes. Albeit with large optical losses, addition of metal layers converts a leaky semiconductor nano-block into a highly-confined optical cavity. Optically pumped lasing action is observed with the extended top metal layer that can significantly suppress the radiation losses. Careful investigation of self-heating effects during the optical carrier injection process shows the importance of temperature-dependent material properties in the laser rate equation model and the overall laser performances. PMID:27549640

  20. Subwavelength position sensing using nonlinear feedback and wave chaos.

    PubMed

    Cohen, Seth D; Cavalcante, Hugo L D de S; Gauthier, Daniel J

    2011-12-16

    We demonstrate a position-sensing technique that relies on the inherent sensitivity of chaos, where we illuminate a subwavelength object with a complex structured radio-frequency field generated using wave chaos and nonlinear feedback. We operate the system in a quasiperiodic state and analyze changes in the frequency content of the scalar voltage signal in the feedback loop. This allows us to extract the object's position with a one-dimensional resolution of ~λ/10,000 and a two-dimensional resolution of ~λ/300, where λ is the shortest wavelength of the illuminating source.

  1. Simulations of waveguide Bragg grating filters based on subwavelength grating waveguide

    NASA Astrophysics Data System (ADS)

    Čtyroký, Jiří; Kwiecien, Pavel; Wang, Junjia; Richter, Ivan; Glesk, Ivan; Chen, Lawrence

    2015-05-01

    Subwavelength grating waveguides represent a flexible and perspective alternative to standard silicon-on-insulator nanophotonic waveguides. In such structures, waves propagate in the form of Bloch modes, in contrast to standard longitudinally uniform waveguides. Tunability of parameters of subwavelength grating structures possesses a great advantage of a broad variability of the (effective) refractive index and its dispersion, without significantly increasing fabrication complexity. A subwavelength grating structure is based on a (quasi)-periodic arrangement of two different materials, i.e. rectangular nanoblocks of silicon, embedded into a lower-index superstrate, with a period (much) smaller than the operational wavelength of the optical radiation. Clearly, by changing the filling factor, i.e., the duty-cycle of the subwavelength grating structure, its effective refractive index can be varied essentially between that of the superstrate and that of silicon. Our contribution is devoted to a detailed numerical analysis of Bloch modes in subwavelength grating waveguides and Bragg gratings based on subwavelength grating waveguides. Two independent versions of 3D Fourier modal methods developed within last years in our laboratories are used as our standard numerical tools. By comparison with results obtained with a 2D FDTD commercially available method we show that for reliable design of subwavelength grating waveguide devices of this kind, full-vector 3D methods have to be used. It is especially the case of Bragg gratings based on subwavelength grating waveguides, as analyzed in this paper. We discuss two options of a subwavelength grating modulation - designed by changing the subwavelength grating duty cycle, and by misplacement of Si blocks, and compare their properties from the point of view of fabrication feasibility.

  2. High performance absorber structure using subwavelength multi-branch dimers

    NASA Astrophysics Data System (ADS)

    He, Kebo; Su, Guangyao; Liu, Chuanhong; Gou, Fangwang; Zhang, Zhaoyu

    2012-11-01

    As the desire growing of the thin film absorption structure for various sub-wavelength applications such as photo detector, thin-film thermal emitters, thermo photovoltaic cells, and multi-color filters, we proposed a type of subwavelength multi-branch dimers which exhibit several tunable dipole-dipole-like plasmonic resonances and integrated it into metal-insulator-metal structure as the top layer. The structures are studied through numerical calculation by finite element method. When normal incident is considered, the novel structure shows three absorption peaks in the considered wavelength range. One peak has near-perfect absorption and the other two also show excellent absorption.. When different angle oblique incident is considered, the absorption only has slight change, which is useful to an ultrathin absorber structure. In addition, we find that the thickness of the dielectric layer can tune the absorption rates for each absorption peak. In general, the multi-branch dimers can easily tune its absorption rates and spectrum via the change of their geometric parameters such as branch lengths, branch angles, and dielectric layer thickness.

  3. Magnetically controlled planar hyperbolic metamaterials for subwavelength resolution

    NASA Astrophysics Data System (ADS)

    Cheng, Bo Han; Chen, Hong Wen; Chang, Kai Jiun; Lan, Yung-Chiang; Tsai, Din Ping

    2015-12-01

    Breaking diffraction limitation is one of the most important issues and still remains to be solved for the demand of high-density optoelectronic components, especially for the photolithography industry. Since the scattered signals of fine feature (i.e. the size is smaller than half of the illuminating wavelength λ) are evanescent, these signals cannot be captured by using conventional glass- or plastic-based optical lens. Hence the corresponding fine feature is lost. In this work, we propose and analyze a magnetically controlled InSb-dielectric multi-layered structure with ability of subwavelength resolution at THz region. This layered structure can resolve subwavelength structures at different frequencies merely changing the magnitude of external magnetic field. Furthermore, the resolving power for a fixed incident frequency can be increased by only increasing the magnitude of applied external magnetic field. By using transfer matrix method and effective medium approach, the mechanism of achieving super resolution is elucidated. The electromagnetic numerical simulation results also prove the rationality and feasibility of the proposed design. Because the proposed device can be dynamically reconfigured by simply changing the magnitude of external magnetic field, it would provide a practical route for multi-functional material, real-time super-resolution imaging, and photolithography.

  4. Terahertz spectroscopy of two-dimensional subwavelength plasmonic structures

    SciTech Connect

    Azad, Abul K; Chen, Houtong; Taylor, Antoinette; O' Hara, John F; Han, Jiaguang; Lu, Xinchao; Zhang, Weili

    2009-01-01

    The fascinating properties of plasmonic structures have had significant impact on the development of next generation ultracompact photonic and optoelectronic components. We study two-dimensional plasmonic structures functioning at terahertz frequencies. Resonant terahertz response due to surface plasmons and dipole localized surface plasmons were investigated by the state-of-the-art terahertz time domain spectroscopy (THz-TDS) using both transmission and reflection configurations. Extraordinary terahertz transmission was demonstrated through the subwavelength metallic hole arrays made from good conducting metals as well as poor metals. Metallic arrays m!lde from Pb, generally a poor metal, and having optically thin thicknesses less than one-third of a skin depth also contributed in enhanced THz transmission. A direct transition of a surface plasmon resonance from a photonic crystal minimum was observed in a photo-doped semiconductor array. Electrical controls of the surface plasmon resonances by hybridization of the Schottkey diode between the metallic grating and the semiconductor substrate are investigated as a function of the applied reverse bias. In addition, we have demonstrated photo-induced creation and annihilation of surface plasmons with appropriate semiconductors at room temperature. According to the Fano model, the transmission properties are characterized by two essential contributions: resonant excitation of surface plasmons and nonresonant direct transmission. Such plasmonic structures may find fascinating applications in terahertz imaging, biomedical sensing, subwavelength terahertz spectroscopy, tunable filters, and integrated terahertz devices.

  5. Active resonant subwavelength grating devices for high speed spectroscopic sensing

    NASA Astrophysics Data System (ADS)

    Gin, A. V.; Kemme, S. A.; Boye, R. R.; Peters, D. W.; Ihlefeld, J. F.; Briggs, R. D.; Wendt, J. R.; Marshall, L. H.; Carter, T. R.; Samora, S.

    2009-02-01

    In this paper, we describe progress towards a multi-color spectrometer and radiometer based upon an active resonant subwavelength grating (RSG). This active RSG component acts as a tunable high-speed optical filter that allows device miniaturization and ruggedization not realizable using current sensors with conventional bulk optics. Furthermore, the geometrical characteristics of the device allow for inherently high speed operation. Because of the small critical dimensions of the RSG devices, the fabrication of these sensors can prove challenging. However, we utilize the state-of-the-art capabilities at Sandia National Laboratories to realize these subwavelength grating devices. This work also leverages previous work on passive RSG devices with greater than 98% efficiency and ~1nm FWHM. Rigorous coupled wave analysis has been utilized to design RSG devices with PLZT, PMN-PT and BaTiO3 electrooptic thin films on sapphire substrates. The simulated interdigitated electrode configuration achieves field strengths around 3×107 V/m. This translates to an increase in the refractive index of 0.05 with a 40V bias potential resulting in a 90% contrast of the modulated optical signal. We have fabricated several active RSG devices on selected electro-optic materials and we discuss the latest experimental results on these devices with variable electrostatic bias and a tunable wavelength source around 1.5μm. Finally, we present the proposed data acquisition hardware and system integration plans.

  6. [Intercross cascaded dual-layer resonant sub-wavelength gratings].

    PubMed

    Chen, Yong-li; Zhao, Da-zun

    2009-04-01

    A security grating structure, intercross cascaded dual-layer resonant sub-wavelength grating structure, is presented. It can broaden the resonant wavelength width of resonant sub-wavelength gratings and obtain the better optical variable effect. The full-width-at half-maximum (FWHM) broadening mechanism of security grating structures is analyzed. The FWHM is dependent on the energy coupled into the grating waveguide layer. The grating structure parameters are optimized and designed. The resonance performance and grating fabrication tolerances are also studied numerically using the vector diffraction theory (the rigorous coupled wave theory). Simulation results indicate that the value of the spectral resonant peak for the security grating structure is not decreased as the incident angle increases or decreases and the maximum FWHM of different depth of grating grooves is about seven times that of the basic resonant grating structure. The resonant dual grating waveguide structure is a kind of security grating configuration with the potential to achieve higher industry application value and its resonance performance is not sensitive to manufacture errors. PMID:19626922

  7. Magnetically controlled planar hyperbolic metamaterials for subwavelength resolution

    PubMed Central

    Cheng, Bo Han; Chen, Hong Wen; Chang, Kai Jiun; Lan, Yung-Chiang; Tsai, Din Ping

    2015-01-01

    Breaking diffraction limitation is one of the most important issues and still remains to be solved for the demand of high-density optoelectronic components, especially for the photolithography industry. Since the scattered signals of fine feature (i.e. the size is smaller than half of the illuminating wavelength λ) are evanescent, these signals cannot be captured by using conventional glass- or plastic-based optical lens. Hence the corresponding fine feature is lost. In this work, we propose and analyze a magnetically controlled InSb-dielectric multi-layered structure with ability of subwavelength resolution at THz region. This layered structure can resolve subwavelength structures at different frequencies merely changing the magnitude of external magnetic field. Furthermore, the resolving power for a fixed incident frequency can be increased by only increasing the magnitude of applied external magnetic field. By using transfer matrix method and effective medium approach, the mechanism of achieving super resolution is elucidated. The electromagnetic numerical simulation results also prove the rationality and feasibility of the proposed design. Because the proposed device can be dynamically reconfigured by simply changing the magnitude of external magnetic field, it would provide a practical route for multi-functional material, real-time super-resolution imaging, and photolithography. PMID:26656499

  8. Active resonant subwavelength grating for scannerless range imaging sensors.

    SciTech Connect

    Kemme, Shanalyn A.; Nellums, Robert O.; Boye, Robert R.; Peters, David William

    2006-11-01

    In this late-start LDRD, we will present a design for a wavelength-agile, high-speed modulator that enables a long-term vision for the THz Scannerless Range Imaging (SRI) sensor. It takes the place of the currently-utilized SRI micro-channel plate which is limited to photocathode sensitive wavelengths (primarily in the visible and near-IR regimes). Two of Sandia's successful technologies--subwavelength diffractive optics and THz sources and detectors--are poised to extend the capabilities of the SRI sensor. The goal is to drastically broaden the SRI's sensing waveband--all the way to the THz regime--so the sensor can see through image-obscuring, scattering environments like smoke and dust. Surface properties, such as reflectivity, emissivity, and scattering roughness, vary greatly with the illuminating wavelength. Thus, objects that are difficult to image at the SRI sensor's present near-IR wavelengths may be imaged more easily at the considerably longer THz wavelengths (0.1 to 1mm). The proposed component is an active Resonant Subwavelength Grating (RSG). Sandia invested considerable effort on a passive RSG two years ago, which resulted in a highly-efficient (reflectivity greater than gold), wavelength-specific reflector. For this late-start LDRD proposal, we will transform the passive RSG design into an active laser-line reflector.

  9. Graphene-loaded wire medium for tunable broadband subwavelength imaging

    NASA Astrophysics Data System (ADS)

    Forouzmand, Ali; Bernety, Hossein M.; Yakovlev, Alexander B.

    2015-08-01

    In this paper, we demonstrate that a wire medium (WM) slab loaded with graphene sheets enables the enhancement of the near field for subwavelength imaging at terahertz frequencies. The analysis is based on the nonlocal homogenization model for WM with the additional boundary condition at the connection of wires to graphene. The principle of the operation of the proposed lens depends on the enhancement of evanescent waves, wherein the excited surface plasmons at the lower and upper graphene interfaces are coupled by an array of metallic wires. The resolution and the operating frequency of the subwavelength imaging device are mainly determined by the tunability of graphene and the structural parameters of the WM slab. The proposed structure has a resolution better than λ /10 with the advantages of broad bandwidth, low sensitivity to losses, and tunability with respect to the chemical potential even if the distance between two graphene sheets is a significant fraction of wavelength. Severe challenges in the fabrication of the lens have been studied in-depth, and a promising approach for a practical realization has been proposed.

  10. Optical characterization of subwavelength-scale solid immersion lenses

    NASA Astrophysics Data System (ADS)

    Kim, Myun-Sik; Scharf, Toralf; Haq, Mohammad Tahdiul; Nakagawa, Wataru; Herzig, Hans Peter

    2012-03-01

    We present the fabrication and optical characterization of nano-scale solid immersion lenses (nano-SILs) with sizes down to a subwavelength range. Submicron-scale cylinders fabricated by electron-beam lithography (EBL) are thermally reflowed to form a spherical shape. Subsequent soft lithography leads to nano-SILs on transparent substrates, i.e. glass, for optical characterization with visible light. The optical characterization is performed using a high-resolution interference microscope (HRIM) with illumination at 642 nm wavelength. The measurements of the 3D amplitude and phase fields provide information on the spot size and the peak intensity. In particular, the phase measurement is a more convincing proof of the Airy disc size reduction rather than the full-width at half maximum (FWHM) spot size. The focal spots produced by the nano-SILs show both spot-size reduction and enhanced optical intensity, which are consistent with the immersion effect. In this way, we experimentally confirm the immersion effect of a subwavelength-size SIL (d = 530 nm and h = 45 nm) with a spot reduction ratio of 1.35, which is less than the expected value of 1.5, most likely due to the slightly non-ideal shape of the nano-SIL.

  11. Cavity-excited Huygens' metasurface antennas for near-unity aperture illumination efficiency from arbitrarily large apertures

    NASA Astrophysics Data System (ADS)

    Epstein, Ariel; Wong, Joseph P. S.; Eleftheriades, George V.

    2016-01-01

    One of the long-standing problems in antenna engineering is the realization of highly directive beams using low-profile devices. In this paper, we provide a solution to this problem by means of Huygens' metasurfaces (HMSs), based on the equivalence principle. This principle states that a given excitation can be transformed to a desirable aperture field by inducing suitable electric and (equivalent) magnetic surface currents. Building on this concept, we propose and demonstrate cavity-excited HMS antennas, where the single-source-fed cavity is designed to optimize aperture illumination, while the HMS facilitates the current distribution that ensures phase purity of aperture fields. The HMS breaks the coupling between the excitation and radiation spectra typical to standard partially reflecting surfaces, allowing tailoring of the aperture properties to produce a desirable radiation pattern, without incurring edge-taper losses. The proposed low-profile design yields near-unity aperture illumination efficiencies from arbitrarily large apertures, offering new capabilities for microwave, terahertz and optical radiators.

  12. Cavity-excited Huygens' metasurface antennas for near-unity aperture illumination efficiency from arbitrarily large apertures

    PubMed Central

    Epstein, Ariel; Wong, Joseph P. S.; Eleftheriades, George V.

    2016-01-01

    One of the long-standing problems in antenna engineering is the realization of highly directive beams using low-profile devices. In this paper, we provide a solution to this problem by means of Huygens' metasurfaces (HMSs), based on the equivalence principle. This principle states that a given excitation can be transformed to a desirable aperture field by inducing suitable electric and (equivalent) magnetic surface currents. Building on this concept, we propose and demonstrate cavity-excited HMS antennas, where the single-source-fed cavity is designed to optimize aperture illumination, while the HMS facilitates the current distribution that ensures phase purity of aperture fields. The HMS breaks the coupling between the excitation and radiation spectra typical to standard partially reflecting surfaces, allowing tailoring of the aperture properties to produce a desirable radiation pattern, without incurring edge-taper losses. The proposed low-profile design yields near-unity aperture illumination efficiencies from arbitrarily large apertures, offering new capabilities for microwave, terahertz and optical radiators. PMID:26790605

  13. Cavity-excited Huygens' metasurface antennas for near-unity aperture illumination efficiency from arbitrarily large apertures.

    PubMed

    Epstein, Ariel; Wong, Joseph P S; Eleftheriades, George V

    2016-01-21

    One of the long-standing problems in antenna engineering is the realization of highly directive beams using low-profile devices. In this paper, we provide a solution to this problem by means of Huygens' metasurfaces (HMSs), based on the equivalence principle. This principle states that a given excitation can be transformed to a desirable aperture field by inducing suitable electric and (equivalent) magnetic surface currents. Building on this concept, we propose and demonstrate cavity-excited HMS antennas, where the single-source-fed cavity is designed to optimize aperture illumination, while the HMS facilitates the current distribution that ensures phase purity of aperture fields. The HMS breaks the coupling between the excitation and radiation spectra typical to standard partially reflecting surfaces, allowing tailoring of the aperture properties to produce a desirable radiation pattern, without incurring edge-taper losses. The proposed low-profile design yields near-unity aperture illumination efficiencies from arbitrarily large apertures, offering new capabilities for microwave, terahertz and optical radiators.

  14. Cavity-excited Huygens' metasurface antennas for near-unity aperture illumination efficiency from arbitrarily large apertures.

    PubMed

    Epstein, Ariel; Wong, Joseph P S; Eleftheriades, George V

    2016-01-01

    One of the long-standing problems in antenna engineering is the realization of highly directive beams using low-profile devices. In this paper, we provide a solution to this problem by means of Huygens' metasurfaces (HMSs), based on the equivalence principle. This principle states that a given excitation can be transformed to a desirable aperture field by inducing suitable electric and (equivalent) magnetic surface currents. Building on this concept, we propose and demonstrate cavity-excited HMS antennas, where the single-source-fed cavity is designed to optimize aperture illumination, while the HMS facilitates the current distribution that ensures phase purity of aperture fields. The HMS breaks the coupling between the excitation and radiation spectra typical to standard partially reflecting surfaces, allowing tailoring of the aperture properties to produce a desirable radiation pattern, without incurring edge-taper losses. The proposed low-profile design yields near-unity aperture illumination efficiencies from arbitrarily large apertures, offering new capabilities for microwave, terahertz and optical radiators. PMID:26790605

  15. A Ploidy-Sensitive Mechanism Regulates Aperture Formation on the Arabidopsis Pollen Surface and Guides Localization of the Aperture Factor INP1

    PubMed Central

    Reeder, Sarah H.; Lee, Byung Ha; Fox, Ronald; Dobritsa, Anna A.

    2016-01-01

    Pollen presents a powerful model for studying mechanisms of precise formation and deposition of extracellular structures. Deposition of the pollen wall exine leads to the generation of species-specific patterns on pollen surface. In most species, exine does not develop uniformly across the pollen surface, resulting in the formation of apertures–openings in the exine that are species-specific in number, morphology and location. A long time ago, it was proposed that number and positions of apertures might be determined by the geometry of tetrads of microspores–the precursors of pollen grains arising via meiotic cytokinesis, and by the number of last-contact points between sister microspores. We have tested this model by characterizing Arabidopsis mutants with ectopic apertures and/or abnormal geometry of meiotic products. Here we demonstrate that contact points per se do not act as aperture number determinants and that a correct geometric conformation of a tetrad is neither necessary nor sufficient to generate a correct number of apertures. A mechanism sensitive to pollen ploidy, however, is very important for aperture number and positions and for guiding the aperture factor INP1 to future aperture sites. In the mutants with ectopic apertures, the number and positions of INP1 localization sites change depending on ploidy or ploidy-related cell size and not on INP1 levels, suggesting that sites for aperture formation are specified before INP1 is brought to them. PMID:27177036

  16. Large area and deep sub-wavelength interference lithography employing odd surface plasmon modes

    PubMed Central

    Liu, Liqin; Luo, Yunfei; Zhao, Zeyu; Zhang, Wei; Gao, Guohan; Zeng, Bo; Wang, Changtao; Luo, Xiangang

    2016-01-01

    In this paper, large area and deep sub-wavelength interference patterns are realized experimentally by using odd surface plasmon modes in the metal/insulator/metal structure. Theoretical investigation shows that the odd modes possesses much higher transversal wave vector and great inhibition of tangential electric field components, facilitating surface plasmon interference fringes with high resolution and contrast in the measure of electric field intensity. Interference resist patterns with 45 nm (∼λ/8) half-pitch, 50 nm depth, and area size up to 20 mm × 20 mm were obtained by using 20 nm Al/50 nm photo resist/50 nm Al films with greatly reduced surface roughness and 180 nm pitch exciting grating fabricated with conventional laser interference lithography. Much deeper resolution down to 19.5 nm is also feasible by decreasing the thickness of PR. Considering that no requirement of expensive EBL or FIB tools are employed, it provides a cost-effective way for large area and nano-scale fabrication. PMID:27466010

  17. Large area and deep sub-wavelength interference lithography employing odd surface plasmon modes.

    PubMed

    Liu, Liqin; Luo, Yunfei; Zhao, Zeyu; Zhang, Wei; Gao, Guohan; Zeng, Bo; Wang, Changtao; Luo, Xiangang

    2016-01-01

    In this paper, large area and deep sub-wavelength interference patterns are realized experimentally by using odd surface plasmon modes in the metal/insulator/metal structure. Theoretical investigation shows that the odd modes possesses much higher transversal wave vector and great inhibition of tangential electric field components, facilitating surface plasmon interference fringes with high resolution and contrast in the measure of electric field intensity. Interference resist patterns with 45 nm (∼λ/8) half-pitch, 50 nm depth, and area size up to 20 mm × 20 mm were obtained by using 20 nm Al/50 nm photo resist/50 nm Al films with greatly reduced surface roughness and 180 nm pitch exciting grating fabricated with conventional laser interference lithography. Much deeper resolution down to 19.5 nm is also feasible by decreasing the thickness of PR. Considering that no requirement of expensive EBL or FIB tools are employed, it provides a cost-effective way for large area and nano-scale fabrication.

  18. Large area and deep sub-wavelength interference lithography employing odd surface plasmon modes

    NASA Astrophysics Data System (ADS)

    Liu, Liqin; Luo, Yunfei; Zhao, Zeyu; Zhang, Wei; Gao, Guohan; Zeng, Bo; Wang, Changtao; Luo, Xiangang

    2016-07-01

    In this paper, large area and deep sub-wavelength interference patterns are realized experimentally by using odd surface plasmon modes in the metal/insulator/metal structure. Theoretical investigation shows that the odd modes possesses much higher transversal wave vector and great inhibition of tangential electric field components, facilitating surface plasmon interference fringes with high resolution and contrast in the measure of electric field intensity. Interference resist patterns with 45 nm (∼λ/8) half-pitch, 50 nm depth, and area size up to 20 mm × 20 mm were obtained by using 20 nm Al/50 nm photo resist/50 nm Al films with greatly reduced surface roughness and 180 nm pitch exciting grating fabricated with conventional laser interference lithography. Much deeper resolution down to 19.5 nm is also feasible by decreasing the thickness of PR. Considering that no requirement of expensive EBL or FIB tools are employed, it provides a cost-effective way for large area and nano-scale fabrication.

  19. Reflector antennas with low sidelobes, low cross polarization, and high aperture efficiency

    NASA Technical Reports Server (NTRS)

    Faigen, I. M.; Reichert, C. F.; Sletten, C. J.; Shore, R. A.

    1984-01-01

    Techniques are presented for computing the horn near field patterns on the subreflectors and for correcting the phase center errors of the horn pattern by shaping the subreflector surface. The diffraction pattern computations for scanned beams are described. The effects of dish aperture diffraction on pattern bandwidth are investigated. A model antenna consisting of a reflector, shaped subreflector, and corrugated feed horn is described.

  20. Properties of Transmission and Leaky Modes in a Plasmonic Waveguide Constructed by Periodic Subwavelength Metallic Hollow Blocks.

    PubMed

    Wu, Jin Jei; Wu, Chien Jang; Shen, Jian Qi; Hou, Da Jun; Lo, Wen Chen

    2015-01-01

    Based on the concept of low-frequency spoof surface plasmon polaritons (spoof SPPs), a kind of leaky mode is proposed in a waveguide made of a subwavelength metal-block array with open slots. Numerical results reveal that a new transmission mode is found in the periodic subwavelength metal open blocks. This modal field is located inside the interior of a hollow block compared with that in a solid metal block array. The dispersion curve shows that such a new SPPs mode has a negative slope, crossing the light line, and then going into a zone of leaky mode at higher frequencies. The leaky mode has a wider frequency bandwidth, and this can lead to a radiation scanning angle of 53° together with high radiation efficiency. Based on the individual characteristics exhibited by a frequency-dependent radiation pattern for the present leaky mode, the waveguide structure can have potential applications such as frequency dividers and demultiplexers. Experimental verification of such a leaky mode at microwave has been performed, and the experimental results are found to be consistent with the theoretical analysis.

  1. Properties of Transmission and Leaky Modes in a Plasmonic Waveguide Constructed by Periodic Subwavelength Metallic Hollow Blocks

    PubMed Central

    Jei Wu, Jin; Jang Wu, Chien; Qi Shen, Jian; Hou, Da Jun; Chen Lo, Wen

    2015-01-01

    Based on the concept of low-frequency spoof surface plasmon polaritons (spoof SPPs), a kind of leaky mode is proposed in a waveguide made of a subwavelength metal-block array with open slots. Numerical results reveal that a new transmission mode is found in the periodic subwavelength metal open blocks. This modal field is located inside the interior of a hollow block compared with that in a solid metal block array. The dispersion curve shows that such a new SPPs mode has a negative slope, crossing the light line, and then going into a zone of leaky mode at higher frequencies. The leaky mode has a wider frequency bandwidth, and this can lead to a radiation scanning angle of 53° together with high radiation efficiency. Based on the individual characteristics exhibited by a frequency-dependent radiation pattern for the present leaky mode, the waveguide structure can have potential applications such as frequency dividers and demultiplexers. Experimental verification of such a leaky mode at microwave has been performed, and the experimental results are found to be consistent with the theoretical analysis. PMID:26403387

  2. Properties of Transmission and Leaky Modes in a Plasmonic Waveguide Constructed by Periodic Subwavelength Metallic Hollow Blocks.

    PubMed

    Wu, Jin Jei; Wu, Chien Jang; Shen, Jian Qi; Hou, Da Jun; Lo, Wen Chen

    2015-01-01

    Based on the concept of low-frequency spoof surface plasmon polaritons (spoof SPPs), a kind of leaky mode is proposed in a waveguide made of a subwavelength metal-block array with open slots. Numerical results reveal that a new transmission mode is found in the periodic subwavelength metal open blocks. This modal field is located inside the interior of a hollow block compared with that in a solid metal block array. The dispersion curve shows that such a new SPPs mode has a negative slope, crossing the light line, and then going into a zone of leaky mode at higher frequencies. The leaky mode has a wider frequency bandwidth, and this can lead to a radiation scanning angle of 53° together with high radiation efficiency. Based on the individual characteristics exhibited by a frequency-dependent radiation pattern for the present leaky mode, the waveguide structure can have potential applications such as frequency dividers and demultiplexers. Experimental verification of such a leaky mode at microwave has been performed, and the experimental results are found to be consistent with the theoretical analysis. PMID:26403387

  3. Diamond turning of high-precision roll-to-roll imprinting molds for fabricating subwavelength gratings

    NASA Astrophysics Data System (ADS)

    Liu, Chun-Wei; Yan, Jiwang; Lin, Shih-Chieh

    2016-06-01

    Diamond turning of high-precision molds is a vital process for the roll-to-roll-based ultraviolet resin imprinting process in fabricating subwavelength gratings. The effects of the grating shape and grating period on diffraction efficiencies and diffraction angles were simulated. Experiments were then conducted to examine the effects of shape design, grating period, and cutting speed on machinability of the mold. According to the optical measurement results, the performance of the subwavelength gratings matched the design well at various incident angles. The results confirm that diamond turning of high-precision molds is a feasible approach for ensuring the continual mass production of subwavelength gratings.

  4. Uniquely identifiable tamper-evident device using coupling between subwavelength gratings

    NASA Astrophysics Data System (ADS)

    Fievre, Ange Marie Patricia

    Reliability and sensitive information protection are critical aspects of integrated circuits. A novel technique using near-field evanescent wave coupling from two subwavelength gratings (SWGs), with the input laser source delivered through an optical fiber is presented for tamper evidence of electronic components. The first grating of the pair of coupled subwavelength gratings (CSWGs) was milled directly on the output facet of the silica fiber using focused ion beam (FIB) etching. The second grating was patterned using e-beam lithography and etched into a glass substrate using reactive ion etching (RIE). The slightest intrusion attempt would separate the CSWGs and eliminate near-field coupling between the gratings. Tampering, therefore, would become evident. Computer simulations guided the design for optimal operation of the security solution. The physical dimensions of the SWGs, i.e. period and thickness, were optimized, for a 650 nm illuminating wavelength. The optimal dimensions resulted in a 560 nm grating period for the first grating etched in the silica optical fiber and 420 nm for the second grating etched in borosilicate glass. The incident light beam had a half-width at half-maximum (HWHM) of at least 7 microm to allow discernible higher transmission orders, and a HWHM of 28 microm for minimum noise. The minimum number of individual grating lines present on the optical fiber facet was identified as 15 lines. Grating rotation due to the cylindrical geometry of the fiber resulted in a rotation of the far-field pattern, corresponding to the rotation angle of moire fringes. With the goal of later adding authentication to tamper evidence, the concept of CSWGs signature was also modeled by introducing random and planned variations in the glass grating. The fiber was placed on a stage supported by a nanomanipulator, which permitted three-dimensional displacement while maintaining the fiber tip normal to the surface of the glass substrate. A 650 nm diode laser was

  5. Wavefront modulation and subwavelength diffractive acoustics with an acoustic metasurface

    NASA Astrophysics Data System (ADS)

    Xie, Yangbo; Wang, Wenqi; Chen, Huanyang; Konneker, Adam; Popa, Bogdan-Ioan; Cummer, Steven A.

    2014-11-01

    Metasurfaces are a family of novel wavefront-shaping devices with planar profile and subwavelength thickness. Acoustic metasurfaces with ultralow profile yet extraordinary wave manipulating properties would be highly desirable for improving the performance of many acoustic wave-based applications. However, designing acoustic metasurfaces with similar functionality to their electromagnetic counterparts remains challenging with traditional metamaterial design approaches. Here we present a design and realization of an acoustic metasurface based on tapered labyrinthine metamaterials. The demonstrated metasurface can not only steer an acoustic beam as expected from the generalized Snell’s law, but also exhibits various unique properties such as conversion from propagating wave to surface mode, extraordinary beam-steering and apparent negative refraction through higher-order diffraction. Such designer acoustic metasurfaces provide a new design methodology for acoustic signal modulation devices and may be useful for applications such as acoustic imaging, beam steering, ultrasound lens design and acoustic surface wave-based applications.

  6. Broadband omnidirectional antireflection coating based on subwavelength surface Mie resonators

    PubMed Central

    Spinelli, P.; Verschuuren, M.A.; Polman, A.

    2012-01-01

    Reflection is a natural phenomenon that occurs when light passes the interface between materials with different refractive index. In many applications, such as solar cells or photodetectors, reflection is an unwanted loss process. Many ways to reduce reflection from a substrate have been investigated so far, including dielectric interference coatings, surface texturing, adiabatic index matching and scattering from plasmonic nanoparticles. Here we present an entirely new concept that suppresses the reflection of light from a silicon surface over a broad spectral range. A two-dimensional periodic array of subwavelength silicon nanocylinders designed to possess strongly substrate-coupled Mie resonances yields almost zero total reflectance over the entire spectral range from the ultraviolet to the near-infrared. This new antireflection concept relies on the strong forward scattering that occurs when a scattering structure is placed in close proximity to a high-index substrate with a high optical density of states. PMID:22353722

  7. Interplay between evanescence and disorder in deep subwavelength photonic structures

    PubMed Central

    Herzig Sheinfux, Hanan; Kaminer, Ido; Genack, Azriel Z.; Segev, Mordechai

    2016-01-01

    Deep subwavelength features are expected to have minimal impact on wave transport. Here we show that in contrast to this common understanding, disorder can have a dramatic effect in a one-dimensional disordered optical system with spatial features a thousand times smaller than the wavelength. We examine a unique regime of Anderson localization where the localization length is shown to scale linearly with the wavelength instead of diverging, because of the role of evanescent waves. In addition, we demonstrate an unusual order of magnitude enhancement of transmission induced due to localization. These results are described for electromagnetic waves, but are directly relevant to other wave systems such as electrons in multi-quantum-well structures. PMID:27708260

  8. Wavefront modulation and subwavelength diffractive acoustics with an acoustic metasurface.

    PubMed

    Xie, Yangbo; Wang, Wenqi; Chen, Huanyang; Konneker, Adam; Popa, Bogdan-Ioan; Cummer, Steven A

    2014-11-24

    Metasurfaces are a family of novel wavefront-shaping devices with planar profile and subwavelength thickness. Acoustic metasurfaces with ultralow profile yet extraordinary wave manipulating properties would be highly desirable for improving the performance of many acoustic wave-based applications. However, designing acoustic metasurfaces with similar functionality to their electromagnetic counterparts remains challenging with traditional metamaterial design approaches. Here we present a design and realization of an acoustic metasurface based on tapered labyrinthine metamaterials. The demonstrated metasurface can not only steer an acoustic beam as expected from the generalized Snell's law, but also exhibits various unique properties such as conversion from propagating wave to surface mode, extraordinary beam-steering and apparent negative refraction through higher-order diffraction. Such designer acoustic metasurfaces provide a new design methodology for acoustic signal modulation devices and may be useful for applications such as acoustic imaging, beam steering, ultrasound lens design and acoustic surface wave-based applications.

  9. Subwavelength alignment mark signal analysis of advanced memory products

    NASA Astrophysics Data System (ADS)

    Yin, Xiaoming; Wong, Alfred K. K.; Wheeler, Donald C.; Williams, Gary; Lehner, Eric A.; Zach, Franz X.; Kim, Byeong Y.; Fukuzaki, Yuzo; Lu, Zhijian G.; Credendino, Santo; Wiltshire, Timothy J.

    2000-06-01

    The impact of alignment mark structure, mark geometry, and stepper alignment optical system on mark signal contrast was investigated using computer simulation. Several sub-wavelength poly silicon recessed film stack alignment targets of advanced memory products were studied. Stimulated alignment mark signals for both dark-field and bright-field systems using the rigorous electromagnetic simulation program TEMPEST showed excellent agreement with experimental data. For a dark-field alignment system, the critical parameters affecting signal contrast were found to be mark size and mark recess depth below silicon surface. On the other hand, film stack thickness and mark recess depth below/above silicon surface are the important parameters for a bright-field alignment system. From observed simulation results optimal process parameters are determined. Based on the simulation results some signal enhancement techniques will be discussed.

  10. Dispersion engineering for vertical microcavities using subwavelength gratings.

    PubMed

    Wang, Zhaorong; Zhang, Bo; Deng, Hui

    2015-02-20

    We show that the energy-momentum dispersion of a vertical semiconductor microcavity can be modified by design using a high-index-contrast subwavelength grating (SWG) as a cavity mirror. We analyze the angular dependence of the reflection phase of the SWG to illustrate the principles of dispersion engineering. We show examples of engineered dispersions such as ones with much reduced or increased energy density of states and one with a double-well-shaped dispersion. This method of dispersion engineering is compatible with maintaining a high cavity quality factor and incorporating fully protected active media inside the cavity, thus enabling the creation of new types of cavity quantum electrodynamics systems. PMID:25763957

  11. Ultrasonic transmission through multiple-sublattice subwavelength holes arrays.

    PubMed

    Estrada, Héctor; Gómez-Lozano, Vicente; Uris, Antonio; Candelas, Pilar; Belmar, Francisco; Meseguer, Francisco

    2012-03-01

    The ultrasonic transmission through plates perforated with 2 × 2 or 3 × 3 square array of subwavelength holes per unit cell are studied by numerical simulations. Calculations are obtained by means of a theoretical model under the rigid-solid assumption. It is demonstrated that when the inter-hole distance within the unit cell is reduced, new transmission dips appear resulting from Wood anomalies that have influence on the second and the third order Fabry-Perot peak. When the inter-hole distance within the unit cell is reduced, the transmission spectrum of the multiple-sublattice holes arrays tends to the transmission spectrum of a plate perforated with only one hole in the unit cell.

  12. Interplay between evanescence and disorder in deep subwavelength photonic structures

    NASA Astrophysics Data System (ADS)

    Herzig Sheinfux, Hanan; Kaminer, Ido; Genack, Azriel Z.; Segev, Mordechai

    2016-10-01

    Deep subwavelength features are expected to have minimal impact on wave transport. Here we show that in contrast to this common understanding, disorder can have a dramatic effect in a one-dimensional disordered optical system with spatial features a thousand times smaller than the wavelength. We examine a unique regime of Anderson localization where the localization length is shown to scale linearly with the wavelength instead of diverging, because of the role of evanescent waves. In addition, we demonstrate an unusual order of magnitude enhancement of transmission induced due to localization. These results are described for electromagnetic waves, but are directly relevant to other wave systems such as electrons in multi-quantum-well structures.

  13. Massively sub-wavelength guiding of electromagnetic waves.

    PubMed

    Hooper, I R; Tremain, B; Dockrey, J A; Hibbins, A P

    2014-01-01

    Recently a new form of ultra-thin flexible waveguide consisting of a conducting comb-like structure with a thickness of the order of 1/600(th) of the operating wavelength was presented. However, whilst the thickness of the guide was massively sub-wavelength, the remaining dimensions (the height and period of the comb) were much longer. In this paper we propose, and experimentally verify, that a modified guiding geometry consisting of a chain of ultra-thin conducting spirals allows guiding of electromagnetic waves with wavelengths that are many times (40+) longer than any characteristic dimension of the guide, enabling super-sub-wavelength guiding and localisation of electromagnetic energy.

  14. Negative refraction, subwavelength focusing and beam formation by photonic crystals

    NASA Astrophysics Data System (ADS)

    Ozbay, Ekmel; Aydin, Koray; Bulu, Irfan; Guven, Kaan

    2007-05-01

    We present a review of our experimental and numerical studies on the negative refraction related phenomena in two-dimensional dielectric photonic crystals (PCs). By employing photonic bands with appropriate dispersion, the propagation of the electromagnetic wave through a PC can be controlled to a large extent, and diverse and completely novel electromagnetic phenomena can be generated. We perform the spectral analysis of the negative refraction arising from a convex TM polarized photonic band of a hexagonal PC. As a consequence of negative refraction, we demonstrate a photonic crystal flat lens, which has the ability to focus electromagnetic waves and provide subwavelength resolution laterally. Finally, a photonic crystal with an embedded source is shown to provide a highly directional beam, which can be utilized in certain antenna applications.

  15. Fabrication of Nanocone Subwavelength Antireflection Structures on Quartz Substrates

    NASA Astrophysics Data System (ADS)

    Tang, Yu-Hsiang; Huang, Mao-Jung; Su, Jien-Yin; Shiao, Ming-Hua

    2012-06-01

    This study combined self-assembled nanosphere lithography (SANL) and inductively coupled plasma reactive ion etching (ICP-RIE) for fabricating orderly arranged quartz nanocone arrays. We reported a simple process for successfully fabricating quartz subwavelength structure (SWS) substrate, achieving broadband antireflection (AR) and increasing the transmittance of incident light across the quartz glass. This combined process arranged a monolayer of nanospheres onto 2×2 cm2 test specimen. In addition, we evaluated various etching times of ICP-RIE for producing SWS surfaces, which resulted in various specific surface areas for the quartz substrates. Consequently, smoothly tapered SWS surfaces with a width of 105 nm and a height of 190 nm could be produced on quartz wafer. This fabricated SWS decreased the surface reflectance to less than 6.75% in the visible light spectrum.

  16. Bio-functional subwavelength optical waveguides for biodetection

    SciTech Connect

    Sirbuly, D J; Fischer, N; Huang, S; Artyukhin, A

    2007-07-10

    We report a versatile biofunctional subwavelength photonic device platform for real-time detection of biological molecules. Our devices contain lipid bilayer membranes fused onto metal oxide nanowire waveguides stretched across polymeric flow channels. The lipid bilayers incorporating target receptors are submersed in the propagating evanescent field of the optical cavity. We show that the lipid bilayers in our devices are continuous, have very high mobile fraction, and are resistant to fouling. We also demonstrate that our platform allows rapid membrane exchange. Finally we use this device for detection of specific DNA sequences in solution by anchoring complementary DNA target strands in the lipid bilayer. This evanescent wave sensing architecture holds great potential for portable, all-optical detection systems.

  17. Subwavelength plasmonics for graded-index optics on a chip.

    PubMed

    Grajower, Meir; Lerman, Gilad M; Goykhman, Ilya; Desiatov, Boris; Yanai, Avner; Smith, David R; Levy, Uriel

    2013-09-15

    Planar plasmonic devices are becoming attractive for myriad applications, owing to their potential compatibility with standard microelectronics technology and the capability for densely integrating a large variety of plasmonic devices on a chip. Mitigating the challenges of using plasmonics in on-chip configurations requires precise control over the properties of plasmonic modes, in particular their shape and size. Here we achieve this goal by demonstrating a planar plasmonic graded-index lens focusing surface plasmons propagating along the device. The plasmonic mode is manipulated by carving subwavelength features into a dielectric layer positioned on top of a uniform metal film, allowing the local effective index of the plasmonic mode to be controlled using a single binary lithographic step. Focusing and divergence of surface plasmons is demonstrated experimentally. The demonstrated approach can be used for manipulating the propagation of surface plasmons, e.g., for beam steering, splitting, cloaking, mode matching, and beam shaping applications.

  18. Complete polarimetry on the asymmetric transmission through subwavelength hole arrays.

    PubMed

    Arteaga, Oriol; Maoz, Ben M; Nichols, Shane; Markovich, Gil; Kahr, Bart

    2014-06-01

    Dissymmetric, periodically nanostructured metal films can show non-reciprocal transmission of polarized light, in apparent violation of the Lorentz reciprocity theorem. The wave vector dependence of the extraordinary optical transmission in gold films with square and oblique subwavelength hole arrays was examined for the full range of polarized light input states. In normal incidence, the oblique lattice, in contrast to square lattice, showed strong asymmetric, non-reciprocal transmission of circularly polarized light. By analyzing the polarization of the input and the output with a complete Mueller matrix polarimeter the mechanisms that permits asymmetric transmission while preserving the requirement of electromagnetic reciprocity is revealed: the coupling of the linear anisotropies induced by misaligned surface plasmons in the film. The square lattice also shows asymmetric transmission at non-normal incidence, whenever the plane of incidence does not coincide with a mirror line.

  19. Encapsulated subwavelength grating as a quasi-monolithic resonant reflector.

    PubMed

    Brückner, Frank; Friedrich, Daniel; Britzger, Michael; Clausnitzer, Tina; Burmeister, Oliver; Kley, Ernst-Bernhard; Danzmann, Karsten; Tünnermann, Andreas; Schnabel, Roman

    2009-12-21

    For a variety of laser interferometric experiments, the thermal noise of high-reflectivity multilayer dielectric coatings limits the measurement sensitivity. Recently, monolithic high-reflection waveguide mirrors with nanostructured surfaces have been proposed to reduce the thermal noise in interferometric measurements. Drawbacks of this approach are a highly complicated fabrication process and the high susceptibility of the nanostructured surfaces to damage and pollution. Here, we propose and demonstrate a novel quasi-monolithic resonant surface reflector that also avoids the thick dielectric stack of conventional mirrors but has a flat and robust surface. Our reflector is an encapsulated subwavelength grating that is based on silicon. We measured a high reflectivity of 93% for a wavelength of lambda = 1.55 microm under normal incidence. Perfect reflectivities are possible in theory.

  20. Active elastic metamaterials for subwavelength wave propagation control

    NASA Astrophysics Data System (ADS)

    Chen, Y. Y.; Huang, G. L.

    2015-06-01

    Recent research activities in elastic metamaterials demonstrate a significant potential for subwavelength wave propagation control owing to their interior locally resonant mechanism. The growing technological developments in electro/magnetomechanical couplings of smart materials have introduced a controlling degree of freedom for passive elastic metamaterials. Active elastic metamaterials could allow for a fine control of material physical behavior and thereby induce new functional properties that cannot be produced by passive approaches. In this paper, two types of active elastic metamaterials with shunted piezoelectric materials and electrorheological elastomers are proposed. Theoretical analyses and numerical validations of the active elastic metamaterials with detailed microstructures are presented for designing adaptive applications in band gap structures and extraordinary waveguides. The active elastic metamaterial could provide a new design methodology for adaptive wave filters, high signal-to-noise sensors, and structural health monitoring applications.

  1. Subwavelength imaging through ion-beam-induced upconversion

    PubMed Central

    Mi, Zhaohong; Zhang, Yuhai; Vanga, Sudheer Kumar; Chen, Ce-Belle; Tan, Hong Qi; Watt, Frank; Liu, Xiaogang; Bettiol, Andrew A.

    2015-01-01

    The combination of an optical microscope and a luminescent probe plays a pivotal role in biological imaging because it allows for probing subcellular structures. However, the optical resolutions are largely constrained by Abbe's diffraction limit, and the common dye probes often suffer from photobleaching. Here we present a new method for subwavelength imaging by combining lanthanide-doped upconversion nanocrystals with the ionoluminescence imaging technique. We experimentally observed that the ion beam can be used as a new form of excitation source to induce photon upconversion in lanthanide-doped nanocrystals. This approach enables luminescence imaging and simultaneous mapping of cellular structures with a spatial resolution of sub-30 nm. PMID:26560858

  2. Development of procedures for programmable proximity aperture lithography

    NASA Astrophysics Data System (ADS)

    Whitlow, H. J.; Gorelick, S.; Puttaraksa, N.; Napari, M.; Hokkanen, M. J.; Norarat, R.

    2013-07-01

    Programmable proximity aperture lithography (PPAL) with MeV ions has been used in Jyväskylä and Chiang Mai universities for a number of years. Here we describe a number of innovations and procedures that have been incorporated into the LabView-based software. The basic operation involves the coordination of the beam blanker and five motor-actuated translators with high accuracy, close to the minimum step size with proper anti-collision algorithms. By using special approaches, such writing calibration patterns, linearisation of position and careful backlash correction the absolute accuracy of the aperture size and position, can be improved beyond the standard afforded by the repeatability of the translator end-point switches. Another area of consideration has been the fluence control procedures. These involve control of the uniformity of the beam where different approaches for fluence measurement such as simultaneous aperture current and the ion current passing through the aperture using a Faraday cup are used. Microfluidic patterns may contain many elements that make-up mixing sections, reaction chambers, separation columns and fluid reservoirs. To facilitate conception and planning we have implemented a .svg file interpreter, that allows the use of scalable vector graphics files produced by standard drawing software for generation of patterns made up of rectangular elements.

  3. SEASAT Synthetic Aperture Radar Data

    NASA Technical Reports Server (NTRS)

    Henderson, F. M.

    1981-01-01

    The potential of radar imagery from space altitudes is discussed and the advantages of radar over passive sensor systems are outlined. Specific reference is made to the SEASAT synthetic aperture radar. Possible applications include oil spill monitoring, snow and ice reconnaissance, mineral exploration, and monitoring phenomena in the urban environment.

  4. Large aperture diffractive space telescope

    DOEpatents

    Hyde, Roderick A.

    2001-01-01

    A large (10's of meters) aperture space telescope including two separate spacecraft--an optical primary objective lens functioning as a magnifying glass and an optical secondary functioning as an eyepiece. The spacecraft are spaced up to several kilometers apart with the eyepiece directly behind the magnifying glass "aiming" at an intended target with their relative orientation determining the optical axis of the telescope and hence the targets being observed. The objective lens includes a very large-aperture, very-thin-membrane, diffractive lens, e.g., a Fresnel lens, which intercepts incoming light over its full aperture and focuses it towards the eyepiece. The eyepiece has a much smaller, meter-scale aperture and is designed to move along the focal surface of the objective lens, gathering up the incoming light and converting it to high quality images. The positions of the two space craft are controlled both to maintain a good optical focus and to point at desired targets which may be either earth bound or celestial.

  5. Code aperture optimization for spectrally agile compressive imaging.

    PubMed

    Arguello, Henry; Arce, Gonzalo R

    2011-11-01

    Coded aperture snapshot spectral imaging (CASSI) provides a mechanism for capturing a 3D spectral cube with a single shot 2D measurement. In many applications selective spectral imaging is sought since relevant information often lies within a subset of spectral bands. Capturing and reconstructing all the spectral bands in the observed image cube, to then throw away a large portion of this data, is inefficient. To this end, this paper extends the concept of CASSI to a system admitting multiple shot measurements, which leads not only to higher quality of reconstruction but also to spectrally selective imaging when the sequence of code aperture patterns is optimized. The aperture code optimization problem is shown to be analogous to the optimization of a constrained multichannel filter bank. The optimal code apertures allow the decomposition of the CASSI measurement into several subsets, each having information from only a few selected spectral bands. The rich theory of compressive sensing is used to effectively reconstruct the spectral bands of interest from the measurements. A number of simulations are developed to illustrate the spectral imaging characteristics attained by optimal aperture codes.

  6. Ultra sub-wavelength surface plasmon confinement using air-gap, sub-wavelength ring resonator arrays

    NASA Astrophysics Data System (ADS)

    Lee, Jaehak; Sung, Sangkeun; Choi, Jun-Hyuk; Eom, Seok Chan; Mortensen, N. Asger; Shin, Jung H.

    2016-02-01

    Arrays of sub-wavelength, sub-10 nm air-gap plasmonic ring resonators are fabricated using nanoimprinting. In near infra-red (NIR) range, the resonator supports a single dipole mode which is excited and identified via simple normal illumination and explored through transmission measurements. By controlling both lateral and vertical confinement via a metal edge, the mode volume is successfully reduced down to 1.3 × 10‑5 λ03. The advantage of such mode confinement is demonstrated by applying the resonators biosensing. Using bovine serum albumin (BSA) molecules, a dramatic enhancement of surface sensitivity up to 69 nm/nm is achieved as the modal height approaches the thickness of the adsorbed molecule layers.

  7. Ultra sub-wavelength surface plasmon confinement using air-gap, sub-wavelength ring resonator arrays

    PubMed Central

    Lee, Jaehak; Sung, Sangkeun; Choi, Jun-Hyuk; Eom, Seok Chan; Mortensen, N. Asger; Shin, Jung H.

    2016-01-01

    Arrays of sub-wavelength, sub-10 nm air-gap plasmonic ring resonators are fabricated using nanoimprinting. In near infra-red (NIR) range, the resonator supports a single dipole mode which is excited and identified via simple normal illumination and explored through transmission measurements. By controlling both lateral and vertical confinement via a metal edge, the mode volume is successfully reduced down to 1.3 × 10−5 λ03. The advantage of such mode confinement is demonstrated by applying the resonators biosensing. Using bovine serum albumin (BSA) molecules, a dramatic enhancement of surface sensitivity up to 69 nm/nm is achieved as the modal height approaches the thickness of the adsorbed molecule layers. PMID:26923610

  8. A 32 × 32 optical phased array using polysilicon sub-wavelength high-contrast-grating mirrors.

    PubMed

    Yoo, Byung-Wook; Megens, Mischa; Sun, Tianbo; Yang, Weijian; Chang-Hasnain, Connie J; Horsley, David A; Wu, Ming C

    2014-08-11

    We report on microelectromechanical systems (MEMS)-actuated 32 × 32 optical phased arrays (OPAs) with high fill-factors and microsecond response time. To reduce the mirror weight and temperature-dependent curvature, we use high-contrast-grating (HCG) mirrors comprising a single layer of sub-wavelength polysilicon gratings with 400 nm thickness, 1250 nm pitch, and 570 nm grating bar width. The mirror has a broad reflection band and a peak reflectivity of 99.9% at 1550 nm wavelength. With 20 × 20 μm2 pixels and 2 μm, the OPA has a total aperture of 702 × 702 μm2 and a fill factor of 85%. The OPA is electrostatically controlled by voltage and has a total field of view of ± 2°, an instantaneous field of view (beam width) of 0.14°, and a response time of 3.8 μs. The latter agrees well with the mechanical resonance frequency of the HCG mirror (0.42 MHz).

  9. Improved Modeling of Open Waveguide Aperture Radiators for use in Conformal Antenna Arrays

    NASA Astrophysics Data System (ADS)

    Nelson, Gregory James

    Open waveguide apertures have been used as radiating elements in conformal arrays. Individual radiating element model patterns are used in constructing overall array models. The existing models for these aperture radiating elements may not accurately predict the array pattern for TEM waves which are not on boresight for each radiating element. In particular, surrounding structures can affect the far field patterns of these apertures, which ultimately affects the overall array pattern. New models of open waveguide apertures are developed here with the goal of accounting for the surrounding structure effects on the aperture far field patterns such that the new models make accurate pattern predictions. These aperture patterns (both E plane and H plane) are measured in an anechoic chamber and the manner in which they deviate from existing model patterns are studied. Using these measurements as a basis, existing models for both E and H planes are updated with new factors and terms which allow the prediction of far field open waveguide aperture patterns with improved accuracy. These new and improved individual radiator models are then used to predict overall conformal array patterns. Arrays of open waveguide apertures are constructed and measured in a similar fashion to the individual aperture measurements. These measured array patterns are compared with the newly modeled array patterns to verify the improved accuracy of the new models as compared with the performance of existing models in making array far field pattern predictions. The array pattern lobe characteristics are then studied for predicting fully circularly conformal arrays of varying radii. The lobe metrics that are tracked are angular location and magnitude as the radii of the conformal arrays are varied. A constructed, measured array that is close to conforming to a circular surface is compared with a fully circularly conformal modeled array pattern prediction, with the predicted lobe angular locations and

  10. Experimental testing of focusing properties of subwavelength photon sieves using exposure method

    NASA Astrophysics Data System (ADS)

    Jiang, Wenbo; Zhang, Xiaohua

    2016-04-01

    An exposure method is proposed to test the focusing properties of subwavelength photon sieves. To solve the problems caused by the subwavelength photon sieves (such as short focal length and small focal spot size), a grating moiré fringe phase detection technique and a microcontact sensor with lead zirconium titanate (PZT) stepping hybrid technique are used in the experimental setup. The focusing properties of the subwavelength photon sieves are tested by this setup. The results show that the focal length and the focal spot size are close to the designed value. Finally, the intensity distribution of the focal spot is proposed. This research result will be beneficial for understanding the focusing properties of subwavelength photon sieves, will help us to improve the imaging quality, and will provide a good experimental basis for practical applications in the nanolithography field.

  11. Alternative aperture stop position designs for SIRTF

    NASA Technical Reports Server (NTRS)

    Davis, Paul K.; Dinger, Ann S.

    1990-01-01

    Three designs of the Space Infrared Telescope Facility (SIRTF) for a 100,000 high earth orbit are considered with particular attention given to the evaluation of the aperture stop position. The choice of aperture stop position will be based on stray light considerations which are being studied concurrently. It is noted that there are advantages in cost, mass, and astronomical aperture to placing the aperture stop at or near the primary mirror, if the stray light circumstances allow.

  12. Algorithm and simulation for analysis of bio-images obtained by aperture diffraction based optical MEMS.

    PubMed

    Zhou, Xiaodong; Poenar, Daniel Puiu; Liu, Kai Yu; Tse, Man Siu; Heng, Chew-Kiat; Tan, Swee Ngin; Zhang, Nan

    2008-08-01

    This paper proposes a novel method to detect transparent living cells in a transparent microfluidic chamber by optical diffraction of an aperture or an aperture array. Through the analysis of the far-field diffraction pattern, one of the parameters of the cells, including the size, refractive index, or position, can be extracted by the analysis software developed in this paper. Calculations are carried out to discuss the key issues of this MEMS device, and our simulation is verified by diffraction patterns of transparent microparticles on fabricated apertures, recorded via a digital camera.

  13. Adaptive millimeter-wave synthetic aperture imaging for compressive sampling of sparse scenes.

    PubMed

    Mrozack, Alex; Heimbeck, Martin; Marks, Daniel L; Richard, Jonathan; Everitt, Henry O; Brady, David J

    2014-06-01

    We apply adaptive sensing techniques to the problem of locating sparse metallic scatterers using high-resolution, frequency modulated continuous wave W-band RADAR. Using a single detector, a frequency stepped source, and a lateral translation stage, inverse synthetic aperture RADAR reconstruction techniques are used to search for one or two wire scatterers within a specified range, while an adaptive algorithm determined successive sampling locations. The two-dimensional location of each scatterer is thereby identified with sub-wavelength accuracy in as few as 1/4 the number of lateral steps required for a simple raster scan. The implications of applying this approach to more complex scattering geometries are explored in light of the various assumptions made.

  14. Enhanced transmission of transverse electric waves through subwavelength slits in a thin metallic film.

    PubMed

    Ye, Yu Qian; Jin, Yi

    2009-09-01

    By adding an array of metallic cut wires, the transmission of transverse electric (TE) waves (the electric field is parallel to the slits) through subwavelength slits in a thin metallic film is significantly enhanced. An 800-fold enhanced transmission is obtained compared to the case without the cut wires. It is demonstrated that a TE incident wave is highly confined by the cut wires, due to the excitation of the electric dipolelike resonance, and then effectively squeezed into and through the subwavelength slits.

  15. Pattern nulling by reflector shaping

    NASA Astrophysics Data System (ADS)

    Havens, D. A.

    1983-12-01

    The applicability of adaptive array concepts to continuous aperture antennas was studied and appropriate aperture field distributions for pattern nulling were found from them. The adaptive array weights were found to be useful as discrete points in a continuous distribution. This distribution could then be used in an aperture integration scheme to produce a nulled pattern. Also studied was the use of geometrical optics to calculate the aperture field distribution of an arbitrarily shaped reflector. Under some restrictions, geometrical optics can provide a useful approximation. Constructing the aperture field of a reflector defined by a discrete grid of points using a numerical ray tracing scheme was also investigated. Certain numerical problems were identified. Finally, an attempt was made to implement the nulled pattern by a well known beam shaping method based on geometrical optics principles. This technique was found to be inadequate. More promising techniques for implementing the aperture distributions were suggested but not pursued in this work.

  16. Electromagnetic Scattering from Arbitrarily Shaped Aperture Backed by Rectangular Cavity Recessed in Infinite Ground Plane

    NASA Technical Reports Server (NTRS)

    Cockrell, C. R.; Beck, Fred B.

    1997-01-01

    The electromagnetic scattering from an arbitrarily shaped aperture backed by a rectangular cavity recessed in an infinite ground plane is analyzed by the integral equation approach. In this approach, the problem is split into two parts: exterior and interior. The electromagnetic fields in the exterior part are obtained from an equivalent magnetic surface current density assumed to be flowing over the aperture and backed by an infinite ground plane. The electromagnetic fields in the interior part are obtained in terms of rectangular cavity modal expansion functions. The modal amplitudes of cavity modes are determined by enforcing the continuity of the electric field across the aperture. The integral equation with the aperture magnetic current density as an unknown is obtained by enforcing the continuity of magnetic fields across the aperture. The integral equation is then solved for the magnetic current density by the method of moments. The electromagnetic scattering properties of an aperture backed by a rectangular cavity are determined from the magnetic current density. Numerical results on the backscatter radar cross-section (RCS) patterns of rectangular apertures backed by rectangular cavities are compared with earlier published results. Also numerical results on the backscatter RCS patterns of a circular aperture backed by a rectangular cavity are presented.

  17. High numerical aperture polymer microstructured fiber with three super-wavelength bridges

    NASA Astrophysics Data System (ADS)

    Gauvreau, Bertrand; Desevedavy, Frederic; Guo, Ning; Khadri, Dhia; Hassani, Alireza; Skorobogatiy, Maksim

    2009-08-01

    The transmission properties of a novel high numerical aperture polymer-based fiber are detailed. The proposed fiber features a large core (520 µm) suspended in air by three bridges of ~3 µm thickness. Unlike existing high NA fibers featuring a large number of subwavelength supports, the bridge size in our fiber is not subwavelength. However, as there are only three such bridges and the core diameter is large, our fiber still confines light efficiently in the inner core. We then detail a modified cutback measurement procedure to study fiber transmission loss. We report an extra ~5 dB m-1 leakage loss from the core through the bridges in addition to the core material absorption loss. We then present a numerical aperture measurement procedure for relatively short fiber pieces guiding in the non-equilibrium mode distribution regime. An NA of over 0.60 was demonstrated for fiber pieces smaller than 30 cm and was shown to decrease gradually for longer fibers. Furthermore, even for fibers as long as 80 cm a relatively high NA of over 0.3 was observed. Finally, we have demonstrated high NA operation of such fibers when the fiber tip was inserted into a highly diffusive aqueous environment (milk). We have also demonstrated a much higher light collection efficiency of our fibers compared to that of a simple rod-in-the-liquid fiber of identical diameter. We believe that the proposed fiber has a strong potential for short range evanescent sensing and light collection applications due to the fiber's simple fabrication methodology, wide unobstructed air channels, relatively low loss and high NA.

  18. Large aperture scanning airborne lidar

    NASA Technical Reports Server (NTRS)

    Smith, J.; Bindschadler, R.; Boers, R.; Bufton, J. L.; Clem, D.; Garvin, J.; Melfi, S. H.

    1988-01-01

    A large aperture scanning airborne lidar facility is being developed to provide important new capabilities for airborne lidar sensor systems. The proposed scanning mechanism allows for a large aperture telescope (25 in. diameter) in front of an elliptical flat (25 x 36 in.) turning mirror positioned at a 45 degree angle with respect to the telescope optical axis. The lidar scanning capability will provide opportunities for acquiring new data sets for atmospheric, earth resources, and oceans communities. This completed facility will also make available the opportunity to acquire simulated EOS lidar data on a near global basis. The design and construction of this unique scanning mechanism presents exciting technological challenges of maintaining the turning mirror optical flatness during scanning while exposed to extreme temperatures, ambient pressures, aircraft vibrations, etc.

  19. Symmetry-broken metamaterial for blocking, cloaking, and supertunneling of sound in a subwavelength scale

    NASA Astrophysics Data System (ADS)

    Xia, Baizhan; Dai, Hongqing; Yu, Dejie

    2016-06-01

    Metamaterials offer extraordinary possibilities for manipulating the propagation of the sound wave in a subwavelength scale. However, the design of acoustic metamaterials remains challenging with traditional strategies, employing two different types of acoustic resonators simultaneously or using specific substructures with multiple resonances. Here we design a symmetry-broken metamaterial comprising of only Helmholtz resonators whose periodical spatial arrangements are broken. The symmetry-broken metamaterials form a hollow hexagonal resonant absorber with two significant resonances. One is the monopolar resonance presenting a collective in-phase pattern motion independent of angle. The other is the dipolar resonance originating from the multiple scattering of symmetry-broken metamaterials. By concentrating the sound energy in peaks of their modes, the hollow hexagonal resonant absorber with extremely small filling ratio can be effectively used to block the propagation of the sound wave in a low-frequency range between monopolar and dipolar resonances. Numerical results also show that the symmetry-broken metamaterials with careful arrangement can be applied to the sound cloaking and the sound supertunneling.

  20. Controlled-aperture wave-equation migration

    SciTech Connect

    Huang, L.; Fehler, Michael C.; Sun, H.; Li, Z.

    2003-01-01

    We present a controlled-aperture wave-equation migration method that no1 only can reduce migration artiracts due to limited recording aperlurcs and determine image weights to balance the efl'ects of limited-aperture illumination, but also can improve thc migration accuracy by reducing the slowness perturbations within thc controlled migration regions. The method consists of two steps: migration aperture scan and controlled-aperture migration. Migration apertures for a sparse distribution of shots arc determined using wave-equation migration, and those for the other shots are obtained by interpolation. During the final controlled-aperture niigration step, we can select a reference slowness in c;ontrollecl regions of the slowness model to reduce slowncss perturbations, and consequently increase the accuracy of wave-equation migration inel hods that makc use of reference slownesses. In addition, the computation in the space domain during wavefield downward continuation is needed to be conducted only within the controlled apertures and therefore, the computational cost of controlled-aperture migration step (without including migration aperture scan) is less than the corresponding uncontrolled-aperture migration. Finally, we can use the efficient split-step Fourier approach for migration-aperture scan, then use other, more accurate though more expensive, wave-equation migration methods to perform thc final controlled-apertio.ee migration to produce the most accurate image.

  1. General Mechanism Involved in Subwavelength Optics of Conducting Microstructures: Charge-Oscillation-Induced Light Emission and Interference

    SciTech Connect

    Huang, X.R.; Peng, Ru-Wen

    2010-03-15

    Interactions between light and conducting microstructures or nanostructures can result in a variety of novel phenomena, but their underlying mechanisms have not been completely understood. From calculations of surface charge density waves on conducting gratings and by comparing them with classical surface plasmons, we revealed a general yet concrete picture regarding the coupling of light to free electron oscillation on structured conducting surfaces that can lead to oscillating subwavelength charge patterns (i.e., structured surface plasmons). New wavelets emitted from these light sources then destructively interfere to form evanescent waves. This principle, usually combined with other mechanisms, is mainly a geometrical effect that can be universally involved in light scattering from all periodic and non-periodic structures containing free electrons. This picture may provide clear guidelines for developing conductor-based nano-optical devices.

  2. Coded aperture imaging with self-supporting uniformly redundant arrays

    DOEpatents

    Fenimore, Edward E.

    1983-01-01

    A self-supporting uniformly redundant array pattern for coded aperture imaging. The present invention utilizes holes which are an integer times smaller in each direction than holes in conventional URA patterns. A balance correlation function is generated where holes are represented by 1's, nonholes are represented by -1's, and supporting area is represented by 0's. The self-supporting array can be used for low energy applications where substrates would greatly reduce throughput. The balance correlation response function for the self-supporting array pattern provides an accurate representation of the source of nonfocusable radiation.

  3. Sub-wavelength nanofluidics in photonic crystal sensors.

    PubMed

    Huang, Min; Yanik, Ahmet Ali; Chang, Tsung-Yao; Altug, Hatice

    2009-12-21

    We introduce a novel sensor scheme combining nano-photonics and nano-fluidics on a single platform through the use of free-standing photonic crystals. By harnessing nano-scale openings, we theoretically and experimentally demonstrate that both fluidics and light can be manipulated at sub-wavelength scales. Compared to the conventional fluidic channels, we actively steer the convective flow through the nanohole openings for effective delivery of the analytes to the sensor surface. We apply our method to detect refractive index changes in aqueous solutions. Bulk measurements indicate that active delivery of the convective flow results in better sensitivities. The sensitivity of the sensor reaches 510 nm/RIU for resonance located around 850 nm with a line-width of approximately 10 nm in solution. Experimental results are matched very well with numerical simulations. We also show that cross-polarization measurements can be employed to further improve the detection limit by increasing the signal-to-noise ratio.

  4. Slow-light enhanced subwavelength plasmonic waveguide refractive index sensors.

    PubMed

    Huang, Yin; Min, Changjun; Dastmalchi, Pouya; Veronis, Georgios

    2015-06-01

    We introduce slow-light enhanced subwavelength scale refractive index sensors which consist of a plasmonic metal-dielectric-metal (MDM) waveguide based slow-light system sandwiched between two conventional MDM waveguides. We first consider a MDM waveguide with small width structrue for comparison, and then consider two MDM waveguide based slow light systems: a MDM waveguide side-coupled to arrays of stub resonators system and a MDM waveguide side-coupled to arrays of double-stub resonators system. We find that, as the group velocity decreases, the sensitivity of the effective index of the waveguide mode to variations of the refractive index of the fluid filling the sensors as well as the sensitivities of the reflection and transmission coefficients of the waveguide mode increase. The sensing characteristics of the slow-light waveguide based sensor structures are systematically analyzed. We show that the slow-light enhanced sensors lead to not only 3.9 and 3.5 times enhancements in the refractive index sensitivity, and therefore in the minimum detectable refractive index change, but also to 2 and 3 times reductions in the required sensing length, respectively, compared to a sensor using a MDM waveguide with small width structure.

  5. Controlling leakage losses in subwavelength grating silicon metamaterial waveguides.

    PubMed

    Sarmiento-Merenguel, J Darío; Ortega-Moñux, Alejandro; Fédéli, Jean-Marc; Wangüemert-Pérez, J Gonzalo; Alonso-Ramos, Carlos; Durán-Valdeiglesias, Elena; Cheben, Pavel; Molina-Fernández, Íñigo; Halir, Robert

    2016-08-01

    Subwavelength gratings (SWG) are photonic structures with a period small enough to suppress diffraction, thereby acting as artificial dielectric materials, also called all-dielectric metamaterials. This property has been exploited in many high-performance photonic integrated devices in the silicon-on-insulator (SOI) platform. While SWG waveguides are theoretically lossless, they may exhibit leakage penalty to the substrate due to a combination of reduced modal confinement and finite thickness of the buried oxide (BOX) layer. In this Letter, for the first time, to the best of our knowledge, we analyze substrate leakage losses in SWG waveguides. We establish a direct relation between the effective index of the waveguide mode and the leakage losses which, remarkably, is independent of the geometric parameters of the SWG waveguide. This universal relation is demonstrated both numerically and experimentally, and it provides practical design guidelines to mitigate leakage losses. For BOX thicknesses of 2 and 3 μm, we find negligible leakage losses when the mode effective index is higher than 1.65 and 1.55, respectively. PMID:27472589

  6. Metallic Strip Gratings in the Sub-Subwavelength Regime

    PubMed Central

    Savin, Adriana; Steigmann, Rozina; Bruma, Alina

    2014-01-01

    Metallic strip gratings (MSG) have different applications, ranging from printed circuits to filters in microwave domains. When they are under the influence of an electromagnetic field, evanescent and/or abnormal modes appear in the region between the traces, their utilization leading to the development of new electromagnetic nondestructive evaluation methods. This paper studies the behavior of MSGs in the sub-subwavelength regime when they are excited with TEz or TMz polarized plane waves and the slits are filled with different dielectrics. The appearance of propagating, evanescent and abnormal modes is emphasized using an electromagnetic sensor with metamaterials lens realized with two conical Swiss rolls, which allows the extraction of the information carried by the guided evanescent waves. The evanescent waves, manipulated by the electromagnetic sensor with metamaterial lenses, improve the electromagnetic images so that a better spatial resolution is obtained, exceeding the limit imposed by diffraction. Their theoretical and experimental confirmation opens the perspective for development of new types of sensors working in radio and microwave frequencies. PMID:24999714

  7. Dispersionless Manipulation of Reflected Acoustic Wavefront by Subwavelength Corrugated Surface

    PubMed Central

    Zhu, Yi-Fan; Zou, Xin-Ye; Li, Rui-Qi; Jiang, Xue; Tu, Juan; Liang, Bin; Cheng, Jian-Chun

    2015-01-01

    Free controls of optic/acoustic waves for bending, focusing or steering the energy of wavefronts are highly desirable in many practical scenarios. However, the dispersive nature of the existing metamaterials/metasurfaces for wavefront manipulation necessarily results in limited bandwidth. Here, we propose the concept of dispersionless wavefront manipulation and report a theoretical, numerical and experimental work on the design of a reflective surface capable of controlling the acoustic wavefront arbitrarily without bandwidth limitation. Analytical analysis predicts the possibility to completely eliminate the frequency dependence with a specific gradient surface which can be implemented by designing a subwavelength corrugated surface. Experimental and numerical results, well consistent with the theoretical predictions, have validated the proposed scheme by demonstrating a distinct phenomenon of extraordinary acoustic reflection within an ultra-broad band. For acquiring a deeper insight into the underlying physics, a simple physical model is developed which helps to interpret this extraordinary phenomenon and predict the upper cutoff frequency precisely. Generations of planar focusing and non-diffractive beam have also been exemplified. With the dispersionless wave-steering capability and deep discrete resolution, our designed structure may open new avenue to fully steer classical waves and offer design possibilities for broadband optical/acoustical devices. PMID:26077772

  8. Sub-wavelength efficient polarization filter (SWEP filter)

    DOEpatents

    Simpson, Marcus L.; Simpson, John T.

    2003-12-09

    A polarization sensitive filter includes a first sub-wavelength resonant grating structure (SWS) for receiving incident light, and a second SWS. The SWS are disposed relative to one another such that incident light which is transmitted by the first SWS passes through the second SWS. The filter has a polarization sensitive resonance, the polarization sensitive resonance substantially reflecting a first polarization component of incident light while substantially transmitting a second polarization component of the incident light, the polarization components being orthogonal to one another. A method for forming polarization filters includes the steps of forming first and second SWS, the first and second SWS disposed relative to one another such that a portion of incident light applied to the first SWS passes through the second SWS. A method for separating polarizations of light, includes the steps of providing a filter formed from a first and second SWS, shining incident light having orthogonal polarization components on the first SWS, and substantially reflecting one of the orthogonal polarization components while substantially transmitting the other orthogonal polarization component. A high Q narrowband filter includes a first and second SWS, the first and second SWS are spaced apart a distance being at least one half an optical wavelength.

  9. Metallic strip gratings in the sub-subwavelength regime.

    PubMed

    Savin, Adriana; Steigmann, Rozina; Bruma, Alina

    2014-07-04

    Metallic strip gratings (MSG) have different applications, ranging from printed circuits to filters in microwave domains. When they are under the influence of an electromagnetic field, evanescent and/or abnormal modes appear in the region between the traces, their utilization leading to the development of new electromagnetic nondestructive evaluation methods. This paper studies the behavior of MSGs in the sub-subwavelength regime when they are excited with TE(z) or TM(z) polarized plane waves and the slits are filled with different dielectrics. The appearance of propagating, evanescent and abnormal modes is emphasized using an electromagnetic sensor with metamaterials lens realized with two conical Swiss rolls, which allows the extraction of the information carried by the guided evanescent waves. The evanescent waves, manipulated by the electromagnetic sensor with metamaterial lenses, improve the electromagnetic images so that a better spatial resolution is obtained, exceeding the limit imposed by diffraction. Their theoretical and experimental confirmation opens the perspective for development of new types of sensors working in radio and microwave frequencies.

  10. Excitonic Lasing in Solution-Processed Subwavelength Nanosphere Assemblies

    NASA Astrophysics Data System (ADS)

    Appavoo, Kannatassen; Liu, Xiaoze; Menon, Vinod; Sfeir, Matthew

    Lasing in solution-processed nanomaterials has gained significant interest because of the potential for low-cost integrated photonic devices. Still, a key challenge is designing low-threshold lasing devices based on a comprehensive understanding of the system's spectral and temporal dynamics. Here we show low-threshold random lasing in sub-wavelength thin films of coupled, highly crystalline zinc oxide nanospheres, with an overall thickness on the order of λ/4. The cavity-free geometry consists of 35nm zinc oxide nanospheres that collectively localize the in-plane emissive light fields while minimizing scattering losses, resulting in excitonic lasing with fluence thresholds at least an order of magnitude lower than previous UV-blue random and quantum-dot lasers. Fluence-dependent effects, as quantified by sub-picosecond transient spectroscopy, highlight the role of phonon-mediated processes in excitonic lasing. Sub-picosecond evolution of distinct lasing modes, together with 3D electromagnetic simulations, indicate a random lasing process - in violation of the commonly cited criteria of strong scattering from individual nanostructures. These results show that coupled nanostructures with high crystallinity can function as building blocks for high-performance optoelectronics. Research is carried out at the Center for Functional Nanomaterials, Brookhaven National Laboratory, which is supported by the U.S.DOE (DE-AC02-98CH10886). This work is supported by the National Science Foundation through Grant No. DMR 1410249.

  11. Dispersionless Manipulation of Reflected Acoustic Wavefront by Subwavelength Corrugated Surface.

    PubMed

    Zhu, Yi-Fan; Zou, Xin-Ye; Li, Rui-Qi; Jiang, Xue; Tu, Juan; Liang, Bin; Cheng, Jian-Chun

    2015-01-01

    Free controls of optic/acoustic waves for bending, focusing or steering the energy of wavefronts are highly desirable in many practical scenarios. However, the dispersive nature of the existing metamaterials/metasurfaces for wavefront manipulation necessarily results in limited bandwidth. Here, we propose the concept of dispersionless wavefront manipulation and report a theoretical, numerical and experimental work on the design of a reflective surface capable of controlling the acoustic wavefront arbitrarily without bandwidth limitation. Analytical analysis predicts the possibility to completely eliminate the frequency dependence with a specific gradient surface which can be implemented by designing a subwavelength corrugated surface. Experimental and numerical results, well consistent with the theoretical predictions, have validated the proposed scheme by demonstrating a distinct phenomenon of extraordinary acoustic reflection within an ultra-broad band. For acquiring a deeper insight into the underlying physics, a simple physical model is developed which helps to interpret this extraordinary phenomenon and predict the upper cutoff frequency precisely. Generations of planar focusing and non-diffractive beam have also been exemplified. With the dispersionless wave-steering capability and deep discrete resolution, our designed structure may open new avenue to fully steer classical waves and offer design possibilities for broadband optical/acoustical devices. PMID:26077772

  12. Dispersionless Manipulation of Reflected Acoustic Wavefront by Subwavelength Corrugated Surface

    NASA Astrophysics Data System (ADS)

    Zhu, Yi-Fan; Zou, Xin-Ye; Li, Rui-Qi; Jiang, Xue; Tu, Juan; Liang, Bin; Cheng, Jian-Chun

    2015-06-01

    Free controls of optic/acoustic waves for bending, focusing or steering the energy of wavefronts are highly desirable in many practical scenarios. However, the dispersive nature of the existing metamaterials/metasurfaces for wavefront manipulation necessarily results in limited bandwidth. Here, we propose the concept of dispersionless wavefront manipulation and report a theoretical, numerical and experimental work on the design of a reflective surface capable of controlling the acoustic wavefront arbitrarily without bandwidth limitation. Analytical analysis predicts the possibility to completely eliminate the frequency dependence with a specific gradient surface which can be implemented by designing a subwavelength corrugated surface. Experimental and numerical results, well consistent with the theoretical predictions, have validated the proposed scheme by demonstrating a distinct phenomenon of extraordinary acoustic reflection within an ultra-broad band. For acquiring a deeper insight into the underlying physics, a simple physical model is developed which helps to interpret this extraordinary phenomenon and predict the upper cutoff frequency precisely. Generations of planar focusing and non-diffractive beam have also been exemplified. With the dispersionless wave-steering capability and deep discrete resolution, our designed structure may open new avenue to fully steer classical waves and offer design possibilities for broadband optical/acoustical devices.

  13. Aperture scanning Fourier ptychographic microscopy

    PubMed Central

    Ou, Xiaoze; Chung, Jaebum; Horstmeyer, Roarke; Yang, Changhuei

    2016-01-01

    Fourier ptychographic microscopy (FPM) is implemented through aperture scanning by an LCOS spatial light modulator at the back focal plane of the objective lens. This FPM configuration enables the capturing of the complex scattered field for a 3D sample both in the transmissive mode and the reflective mode. We further show that by combining with the compressive sensing theory, the reconstructed 2D complex scattered field can be used to recover the 3D sample scattering density. This implementation expands the scope of application for FPM and can be beneficial for areas such as tissue imaging and wafer inspection. PMID:27570705

  14. Dual aperture multispectral Schmidt objective

    NASA Technical Reports Server (NTRS)

    Minott, P. O. (Inventor)

    1984-01-01

    A dual aperture, off-axis catadioptic Schmidt objective is described. It is formed by symmetrically aligning two pairs of Schmidt objectives on opposite sides of a common plane (x,z). Each objective has a spherical primary mirror with a spherical focal plane and center of curvature aligned along an optic axis laterally spaced apart from the common plane. A multiprism beamsplitter with buried dichroic layers and a convex entrance and concave exit surfaces optically concentric to the center of curvature may be positioned at the focal plane. The primary mirrors of each objective may be connected rigidly together and may have equal or unequal focal lengths.

  15. Reconstruction of coded aperture images

    NASA Technical Reports Server (NTRS)

    Bielefeld, Michael J.; Yin, Lo I.

    1987-01-01

    Balanced correlation method and the Maximum Entropy Method (MEM) were implemented to reconstruct a laboratory X-ray source as imaged by a Uniformly Redundant Array (URA) system. Although the MEM method has advantages over the balanced correlation method, it is computationally time consuming because of the iterative nature of its solution. Massively Parallel Processing, with its parallel array structure is ideally suited for such computations. These preliminary results indicate that it is possible to use the MEM method in future coded-aperture experiments with the help of the MPP.

  16. TELESCOPES: Astronomers Overcome 'Aperture Envy'.

    PubMed

    Irion, R

    2000-07-01

    Many users of small telescopes are disturbed by the trend of shutting down smaller instruments in order to help fund bigger and bolder ground-based telescopes. Small telescopes can thrive in the shadow of giant new observatories, they say--but only if they are adapted to specialized projects. Telescopes with apertures of 2 meters or less have unique abilities to monitor broad swaths of the sky and stare at the same objects night after night, sometimes for years; various teams are turning small telescopes into robots, creating networks that span the globe and devoting them to survey projects that big telescopes don't have a prayer of tackling. PMID:17832960

  17. the Large Aperture GRB Observatory

    SciTech Connect

    Bertou, Xavier

    2009-04-30

    The Large Aperture GRB Observatory (LAGO) aims at the detection of high energy photons from Gamma Ray Bursts (GRB) using the single particle technique (SPT) in ground based water Cherenkov detectors (WCD). To reach a reasonable sensitivity, high altitude mountain sites have been selected in Mexico (Sierra Negra, 4550 m a.s.l.), Bolivia (Chacaltaya, 5300 m a.s.l.) and Venezuela (Merida, 4765 m a.s.l.). We report on the project progresses and the first operation at high altitude, search for bursts in 6 months of preliminary data, as well as search for signal at ground level when satellites report a burst.

  18. Design of a coded aperture Compton telescope imaging system (CACTIS)

    NASA Astrophysics Data System (ADS)

    Volkovskii, Alexander; Clajus, Martin; Gottesman, Stephen R.; Malik, Hans; Schwartz, Kenneth; Tumer, Evren; Tumer, Tumay; Yin, Shi

    2010-08-01

    We have developed a prototype of a scalable high-resolution direction and energy sensitive gamma-ray detection system that operates in both coded aperture (CA) and Compton scatter (CS) modes to obtain optimal efficiency and angular resolution over a wide energy range. The design consists of an active coded aperture constructed from 52 individual CZT planar detectors each measuring 3×3×6 mm3 arranged in a MURA pattern on a 10×10 grid, with a monolithic 20×20×5 mm3 pixelated (8×8) CZT array serving as the focal plane. The combined mode is achieved by using the aperture plane array for both Compton scattering of high-energy photons and as a coded mask for low-energy radiation. The prototype instrument was built using two RENA-3 test systems, one each for the aperture and the focal plane, stacked on top of each other at a distance of 130 mm. The test systems were modified to coordinate (synchronize) readout and provide coincidence information of events within a user-adjustable 40-1,280 ns window. The measured angular resolution of the device is <1 deg (17 mrad) in CA mode and is predicted to be approximately 3 deg (54 mrad) in CS mode. The energy resolution of the CZT detectors is approximately 5% FWHM at 120 keV. We will present details of the system design and initial results for the calibration and performance of the prototype.

  19. Direct writing of sub-wavelength ripples on silicon using femtosecond laser at high repetition rate

    NASA Astrophysics Data System (ADS)

    Xie, Changxin; Li, Xiaohong; Liu, Kaijun; Zhu, Min; Qiu, Rong; Zhou, Qiang

    2016-01-01

    The near sub-wavelength and deep sub-wavelength ripples on monocrystalline silicon were formed in air by using linearly polarized and high repetition rate femtosecond laser pulses (f = 76 MHz, λ = 800 nm, τ = 50 fs). The effects of laser pulse energy, direct writing speed and laser polarization on silicon surface morphology are studied. When the laser pulse energy is 2 nJ/pulse and the direct writing speed varies from 10 to 25 mm/s, the near sub-wavelength ripples (NSRs) with orientation perpendicular to the laser polarization are generated. While the direct writing speed reaches 30 mm/s, the direction of the obtained deep sub-wavelength ripples (DSRs) suddenly changes and becomes parallel to the laser polarization, rarely reported so far for femtosecond laser irradiation of silicon. Meanwhile, we extend the Sipe-Drude interference theory by considering the thermal excitation, and numerically calculate the efficacy factor for silicon irradiated by femtosecond laser pulses. The revised Sipe-Drude interference theoretical results show good agreement with the periods and orientations of sub-wavelength ripples.

  20. Improving deep subwavelength imaging through terminal interface design of metallo-dielectric multilayered stacks

    NASA Astrophysics Data System (ADS)

    Hu, Jigang; Zhan, Qiwen; Chen, Junxue; Wang, Xiangxian; Lu, Yonghua; Ming, Hai

    2013-01-01

    Symmetric metallo-dielectric multilayered stacks (MDMS) are investigated to improve the spatial resolution of subwavelength imaging operated in canalization regime. Simulation results revealed that subwavelength imaging capability is very sensitive to the thickness and material of the MDMS terminal layers. Furthermore, the coupling and decoupling of the Bloch modes in MDMS, between the object and image space, strongly depend on the terminal layer parameters which can be tuned to achieve the optimal imaging improvement. In contrast to metal-dielectric periodic MDMS, using MDMS with the developed symmetric surface termination, subwavelength imaging with optimal intensity throughput and improved field spatial resolution (˜20.4%) can be obtained. Moreover, optical singularity, in the form of Poynting vector saddle point, has been found in the free space after lens exit for the two kinds of symmetric MDMS that exhibit improved superresolution imaging performance with 100% energy flux visibility. The improved subwavelength imaging capabilities, offered by this proposed termination design method, may find potential applications in the areas of biological imaging, sensing, and deep subwavelength lithography, and many others.

  1. Advanced Multiple Aperture Seeing Profiler

    NASA Astrophysics Data System (ADS)

    Ren, Deqing; Zhao, Gang

    2016-10-01

    Measurements of the seeing profile of the atmospheric turbulence as a function of altitude are crucial for solar astronomical site characterization, as well as the optimized design and performance estimation of solar Multi-Conjugate Adaptive Optics (MCAO). Knowledge of the seeing distribution, up to 30 km, with a potential new solar observation site, is required for future solar MCAO developments. Current optical seeing profile measurement techniques are limited by the need to use a large facility solar telescope for such seeing profile measurements, which is a serious limitation on characterizing a site's seeing conditions in terms of the seeing profile. Based on our previous work, we propose a compact solar seeing profiler called the Advanced Multiple Aperture Seeing Profile (A-MASP). A-MASP consists of two small telescopes, each with a 100 mm aperture. The two small telescopes can be installed on a commercial computerized tripod to track solar granule structures for seeing profile measurement. A-MASP is extreme simple and portable, which makes it an ideal system to bring to a potential new site for seeing profile measurements.

  2. Buckling-induced retraction of spherical shells: A study on the shape of aperture

    NASA Astrophysics Data System (ADS)

    Lin, Sen; Xie, Yi Min; Li, Qing; Huang, Xiaodong; Zhou, Shiwei

    2015-06-01

    Buckling of soft matter is ubiquitous in nature and has attracted increasing interest recently. This paper studies the retractile behaviors of a spherical shell perforated by sophisticated apertures, attributed to the buckling-induced large deformation. The buckling patterns observed in experiments were reproduced in computational modeling by imposing velocity-controlled loads and eigenmode-affine geometric imperfection. It was found that the buckling behaviors were topologically sensitive with respect to the shape of dimple (aperture). The shell with rounded-square apertures had the maximal volume retraction ratio as well as the lowest energy consumption. An effective experimental procedure was established and the simulation results were validated in this study.

  3. Ion mobility spectrometer with virtual aperture grid

    DOEpatents

    Pfeifer, Kent B.; Rumpf, Arthur N.

    2010-11-23

    An ion mobility spectrometer does not require a physical aperture grid to prevent premature ion detector response. The last electrodes adjacent to the ion collector (typically the last four or five) have an electrode pitch that is less than the width of the ion swarm and each of the adjacent electrodes is connected to a source of free charge, thereby providing a virtual aperture grid at the end of the drift region that shields the ion collector from the mirror current of the approaching ion swarm. The virtual aperture grid is less complex in assembly and function and is less sensitive to vibrations than the physical aperture grid.

  4. Surface-normal emission from subwavelength GaN membrane grating.

    PubMed

    Wang, Yongjin; Shi, Zheng; Li, Xin; He, Shumin; Zhang, Miao; Zhu, Hongbo

    2014-01-13

    We present here the fabrication of subwavelength GaN membrane grating with a double-side process. Controllable GaN membrane thickness is achieved by backside thinning technique, which is essential to realize guided-mode resonant GaN grating in the visible range. Subwavelength GaN grating can serve as an optical resonator and accommodate surface-normal emission coupling. The measured photoluminescence (PL) spectra are sensitive to the parameters and shapes of GaN gratings. Both numerical simulation and reflectivity measurement are in consistent with the PL experimental results. This work opens a promising way to embed GaN-based photon emitter inside subwavelength grating to further produce a surface emitting device with a single layer GaN grating.

  5. Subwavelength nonlinear phase control and anomalous phase matching in plasmonic metasurfaces

    NASA Astrophysics Data System (ADS)

    Almeida, Euclides; Shalem, Guy; Prior, Yehiam

    2016-01-01

    Metasurfaces, and in particular those containing plasmonic-based metallic elements, constitute an attractive set of materials with a potential for replacing standard bulky optical elements. In recent years, increasing attention has been focused on their nonlinear optical properties, particularly in the context of second and third harmonic generation and beam steering by phase gratings. Here, we harness the full phase control enabled by subwavelength plasmonic elements to demonstrate a unique metasurface phase matching that is required for efficient nonlinear processes. We discuss the difference between scattering by a grating and by subwavelength phase-gradient elements. We show that for such interfaces an anomalous phase-matching condition prevails, which is the nonlinear analogue of the generalized Snell's law. The subwavelength phase control of optical nonlinearities paves the way for the design of ultrathin, flat nonlinear optical elements. We demonstrate nonlinear metasurface lenses, which act both as generators and as manipulators of the frequency-converted signal.

  6. Far-field subwavelength imaging with near-field resonant metalens scanning at microwave frequencies

    PubMed Central

    Wang, Ren; Wang, Bing-Zhong; Gong, Zhi-Shuang; Ding, Xiao

    2015-01-01

    A method for far-field subwavelength imaging at microwave frequencies using near-field resonant metalens scanning is proposed. The resonant metalens is composed of switchable split-ring resonators (SRRs). The on-SRR has a strong magnetic coupling ability and can convert evanescent waves into propagating waves using the localized resonant modes. In contrast, the off-SRR cannot achieve an effective conversion. By changing the switch status of each cell, we can obtain position information regarding the subwavelength source targets from the far field. Because the spatial response and Green’s function do not need to be measured and evaluated and only a narrow frequency band is required for the entire imaging process, this method is convenient and adaptable to various environment. This method can be used for many applications, such as subwavelength imaging, detection, and electromagnetic monitoring, in both free space and complex environments. PMID:26053074

  7. Subwavelength nonlinear phase control and anomalous phase matching in plasmonic metasurfaces.

    PubMed

    Almeida, Euclides; Shalem, Guy; Prior, Yehiam

    2016-01-01

    Metasurfaces, and in particular those containing plasmonic-based metallic elements, constitute an attractive set of materials with a potential for replacing standard bulky optical elements. In recent years, increasing attention has been focused on their nonlinear optical properties, particularly in the context of second and third harmonic generation and beam steering by phase gratings. Here, we harness the full phase control enabled by subwavelength plasmonic elements to demonstrate a unique metasurface phase matching that is required for efficient nonlinear processes. We discuss the difference between scattering by a grating and by subwavelength phase-gradient elements. We show that for such interfaces an anomalous phase-matching condition prevails, which is the nonlinear analogue of the generalized Snell's law. The subwavelength phase control of optical nonlinearities paves the way for the design of ultrathin, flat nonlinear optical elements. We demonstrate nonlinear metasurface lenses, which act both as generators and as manipulators of the frequency-converted signal. PMID:26797164

  8. Leaky-Wave Radiations by Modulating Surface Impedance on Subwavelength Corrugated Metal Structures.

    PubMed

    Cai, Ben Geng; Li, Yun Bo; Ma, Hui Feng; Jiang, Wei Xiang; Cheng, Qiang; Cui, Tie Jun

    2016-01-01

    One-dimensional (1D) subwavelength corrugated metal structures has been described to support spoof surface plasmon polaritons (SPPs). Here we demonstrate that a periodically modulated 1D subwavelength corrugated metal structure can convert spoof SPPs to propagating waves. The structure is fed at the center through a slit with a connected waveguide on the input side. The subwavelength corrugated metal structure on the output surface is regarded as metasurface and modulated periodically to realize the leaky-wave radiation at the broadside. The surface impedance of the corrugated metal structure is modulated by using cosine function and triangle-wave function, respectively, to reach the radiation effect. Full wave simulations and measuremental results are presented to validate the proposed design. PMID:27035269

  9. Subwavelength nonlinear phase control and anomalous phase matching in plasmonic metasurfaces

    PubMed Central

    Almeida, Euclides; Shalem, Guy; Prior, Yehiam

    2016-01-01

    Metasurfaces, and in particular those containing plasmonic-based metallic elements, constitute an attractive set of materials with a potential for replacing standard bulky optical elements. In recent years, increasing attention has been focused on their nonlinear optical properties, particularly in the context of second and third harmonic generation and beam steering by phase gratings. Here, we harness the full phase control enabled by subwavelength plasmonic elements to demonstrate a unique metasurface phase matching that is required for efficient nonlinear processes. We discuss the difference between scattering by a grating and by subwavelength phase-gradient elements. We show that for such interfaces an anomalous phase-matching condition prevails, which is the nonlinear analogue of the generalized Snell's law. The subwavelength phase control of optical nonlinearities paves the way for the design of ultrathin, flat nonlinear optical elements. We demonstrate nonlinear metasurface lenses, which act both as generators and as manipulators of the frequency-converted signal. PMID:26797164

  10. Leaky-Wave Radiations by Modulating Surface Impedance on Subwavelength Corrugated Metal Structures

    PubMed Central

    Cai, Ben Geng; Li, Yun Bo; Ma, Hui Feng; Jiang, Wei Xiang; Cheng, Qiang; Cui, Tie Jun

    2016-01-01

    One-dimensional (1D) subwavelength corrugated metal structures has been described to support spoof surface plasmon polaritons (SPPs). Here we demonstrate that a periodically modulated 1D subwavelength corrugated metal structure can convert spoof SPPs to propagating waves. The structure is fed at the center through a slit with a connected waveguide on the input side. The subwavelength corrugated metal structure on the output surface is regarded as metasurface and modulated periodically to realize the leaky-wave radiation at the broadside. The surface impedance of the corrugated metal structure is modulated by using cosine function and triangle-wave function, respectively, to reach the radiation effect. Full wave simulations and measuremental results are presented to validate the proposed design. PMID:27035269

  11. Application of Ruze Equation for Inflatable Aperture Antennas

    NASA Technical Reports Server (NTRS)

    Welch, Bryan W.

    2008-01-01

    Inflatable aperture reflector antennas are an emerging technology that NASA is investigating for potential uses in science and exploration missions. As inflatable aperture antennas have not been proven fully qualified for space missions, they must be characterized properly so that the behavior of the antennas can be known in advance. To properly characterize the inflatable aperture antenna, testing must be performed in a relevant environment, such as a vacuum chamber. Since the capability of having a radiofrequency (RF) test facility inside a vacuum chamber did not exist at NASA Glenn Research Center, a different methodology had to be utilized. The proposal to test an inflatable aperture antenna in a vacuum chamber entailed performing a photogrammetry study of the antenna surface by using laser ranging measurements. A root-mean-square (rms) error term was derived from the photogrammetry study to calculate the antenna surface loss as described by the Ruze equation. However, initial testing showed that problems existed in using the Ruze equation to calculate the loss due to errors on the antenna surface. This study utilized RF measurements obtained in a near-field antenna range and photogrammetry data taken from a laser range scanner to compare the expected performance of the test antenna (via the Ruze equation) with the actual RF patterns and directivity measurements. Results showed that the Ruze equation overstated the degradation in the directivity calculation. Therefore, when the photogrammetry study is performed on the test antennas in the vacuum chamber, a more complex equation must be used in light of the fact that the Ruze theory overstates the loss in directivity for inflatable aperture reflector antennas.

  12. Design of MEMS devices with optical apertures for the detection of transparent biological cells.

    PubMed

    Zhou, Xiaodong; Poenar, Daniel Puiu; Liu, Kai Yu; Tse, Man Siu; Heng, Chew-Kiat; Tan, Swee Ngin

    2008-10-01

    This paper provides a novel technique to detect transparent biological living cells trapped in a microfluidic MEMS device by optical diffraction. The device essentially consists of an optical aperture or an aperture array patterned in metal layer and a microfluidic chamber positioned above the center of the aperture. When the cells in the chamber are illuminated through the aperture, the far-field diffraction pattern can be recorded by a CCD camera or a photodetector array. This diffraction pattern uniquely corresponds to the sizes, positions, and intrinsic optical properties of the aperture, cells, and the microfluidic chamber materials, so any unknown but relevant parameter is able to be extrapolated when all other parameters are fixed or identified. This paper describes in detail the designs of various microfluidic chambers and apertures for this application, and the development of a complete set of software for the analysis of the cells' optical properties. Compared with other currently available methods for the detection of transparent living cells, this method has the advantages of simple device structure, easy to manipulate, able to simultaneously detect several cells of different species, as well as providing accurate and sensitive results. Besides the detection of living cells, this technique can also be used to detect or characterize other transparent or low optical absorption particles, such as polymer spheres or insoluble droplets, inside an aqueous solution.

  13. Synthetic aperture radar target simulator

    NASA Technical Reports Server (NTRS)

    Zebker, H. A.; Held, D. N.; Goldstein, R. M.; Bickler, T. C.

    1984-01-01

    A simulator for simulating the radar return, or echo, from a target seen by a SAR antenna mounted on a platform moving with respect to the target is described. It includes a first-in first-out memory which has digital information clocked in at a rate related to the frequency of a transmitted radar signal and digital information clocked out with a fixed delay defining range between the SAR and the simulated target, and at a rate related to the frequency of the return signal. An RF input signal having a frequency similar to that utilized by a synthetic aperture array radar is mixed with a local oscillator signal to provide a first baseband signal having a frequency considerably lower than that of the RF input signal.

  14. Synthetic aperture interferometry: error analysis

    SciTech Connect

    Biswas, Amiya; Coupland, Jeremy

    2010-07-10

    Synthetic aperture interferometry (SAI) is a novel way of testing aspherics and has a potential for in-process measurement of aspherics [Appl. Opt.42, 701 (2003)].APOPAI0003-693510.1364/AO.42.000701 A method to measure steep aspherics using the SAI technique has been previously reported [Appl. Opt.47, 1705 (2008)].APOPAI0003-693510.1364/AO.47.001705 Here we investigate the computation of surface form using the SAI technique in different configurations and discuss the computational errors. A two-pass measurement strategy is proposed to reduce the computational errors, and a detailed investigation is carried out to determine the effect of alignment errors on the measurement process.

  15. Development of a subwavelength grating vortex coronagraph of topological charge 4 (SGVC4)

    NASA Astrophysics Data System (ADS)

    Delacroix, Christian; Absil, Olivier; Carlomagno, Brunella; Piron, Pierre; Forsberg, Pontus; Karlsson, Mikael; Mawet, Dimitri; Habraken, Serge; Surdej, Jean

    2014-08-01

    One possible solution to achieve high contrast direct imaging at a small inner working angle (IWA) is to use a vector vortex coronagraph (VVC), which provides a continuous helical phase ramp in the focal plane of the telescope with a phase singularity in its center. Such an optical vortex is characterized by its topological charge, i.e., the number of times the phase accumulates 2π radians along a closed path surrounding the singularity. Over the past few years, we have been developing a charge-2 VVC induced by rotationally symmetric subwavelength gratings (SGVC2), also known as the Annular Groove Phase Mask (AGPM). Since 2013, several SGVC2s (or AGPMs) were manufactured using synthetic diamond substrate, then validated on dedicated optical benches, and installed on 10-m class telescopes. Increasing the topological charge seems however mandatory for cancelling the light of bright stars which will be partially resolved by future Extremely Large Telescopes in the near-infrared. In this paper, we first detail our motivations for developing an SGVC4 (charge 4) dedicated to the near-infrared domain. The challenge lies in the design of the pattern which is unrealistic in the theoretically perfect case, due to state-of-the-art manufacturing limitations. Hence, we propose a new realistic design of SGVC4 with minimized discontinuities and optimized phase ramp, showing conclusive improvements over previous works in this field. A preliminary validation of our concept is given based on RCWA simulations, while full 3D finite-difference time-domain simulations (and eventually laboratory tests) will be required for a final validation.

  16. Direct writing of continuous and discontinuous sub-wavelength periodic surface structures on single-crystalline silicon using femtosecond laser

    SciTech Connect

    Kuladeep, Rajamudili; Sahoo, Chakradhar; Narayana Rao, Desai E-mail: dnr-laserlab@yahoo.com

    2014-06-02

    Laser-induced ripples or uniform arrays of continuous near sub-wavelength or discontinuous deep sub-wavelength structures are formed on single-crystalline silicon (Si) by femtosecond (fs) laser direct writing technique. Laser irradiation was performed on Si wafers at normal incidence in air and by immersing them in dimethyl sulfoxide using linearly polarized Ti:sapphire fs laser pulses of ∼110 fs pulse duration and ∼800 nm wavelength. Morphology studies of laser written surfaces reveal that sub-wavelength features are oriented perpendicular to laser polarization, while their morphology and spatial periodicity depend on the surrounding dielectric medium. The formation mechanism of the sub-wavelength features is explained by interference of incident laser with surface plasmon polaritons. This work proves the feasibility of fs laser direct writing technique for the fabrication of sub-wavelength features, which could help in fabrication of advanced electro-optic devices.

  17. Total Internal Reflection Tomography (TIRT) for Three-Dimensional Sub-Wavelength Imaging

    NASA Technical Reports Server (NTRS)

    Fischer, David G.; Carney, P. Scott

    2002-01-01

    We will present a novel new form of near-field microscopy known as total internal reflection tomography (TIRT), which allows for true three-dimensional sub-wavelength imaging. It is based on recent theoretical advances regarding the fundamental interaction of light with sub-wavelength structures, as well as stable algorithms for the near-field inverse problem. We will discuss its theoretical underpinnings, as well describe current efforts at the NASA Glenn Research Center to implement a TIRT system for biofluid research.

  18. A biomimetic projector with high subwavelength directivity based on dolphin biosonar

    NASA Astrophysics Data System (ADS)

    Zhang, Yu; Gao, Xiaowei; Zhang, Sai; Cao, Wenwu; Tang, Liguo; Wang, Ding; Li, Yan

    2014-09-01

    Based on computed tomography of a Yangtze finless porpoise's biosonar system, a biomimetic structure was designed to include air cavity, gradient-index material, and steel outer-structure mimicking air sacs, melon, and skull, respectively. The mainlobe pressure was about three times higher, the angular resolution was one order of magnitude higher, and the effective source size was orders of magnitude larger than those of the subwavelength source without the biomimetic structure. The superior subwavelength directivity over a broad bandwidth suggests potential applications of this biomimetic projector in underwater sonar, medical ultrasonography, and other related applications.

  19. Grating based hybrid plasmonic waveguide for subwavelength optical confinement with low loss

    NASA Astrophysics Data System (ADS)

    Sharma, Tarun; Sharma, Anuj; Kumar, Mukesh

    2016-04-01

    A Grating Based hybrid-Plasmonic-waveguide with subwavelength optical-confinement is proposed which exhibits large-propagation-length with low-modal-propagation-loss. The Grating is formed in Si region by varying the grating period and duty cycle. The thickness of the grating region is 600 nm and the grating period is 700 nm. The mode is confined in the 10 nm SiO2 region. The Si layer below the SiO2 provides the large propagation length of 4 mm with low modal propagation loss of 1 dB/mm with subwavelength mode confinement 0.00079/ μm2 is obtained.

  20. Subwavelength modulation of surface relief and refractive index in preirradiated liquid-crystalline polymer films

    SciTech Connect

    Yu Haifeng; Shishido, Atsushi; Ikeda, Tomiki

    2008-03-10

    We present a simple method to record subwavelength gratings (SWGs) in an azobenzene (AZ)-containing liquid-crystalline polymer by preirradiation. Since the cooperative motions of mesogens are eliminated in a cis-AZ-rich isotropic phase by the pretreatment, the subwavelength modulation of surface relief and refractive index (RI) was obtained. The surface relief of less than 10 nm and the RI modulation were detected by atomic force microscopy. A large phase retardation and formed birefringence were obtained in the recorded SWGs in which a possible schematic illustration of AZ was proposed.

  1. Terahertz imaging of sub-wavelength particles with Zenneck surface waves

    SciTech Connect

    Navarro-Cía, M.; Natrella, M.; Graham, C.; Renaud, C. C.; Seeds, A. J.; Mitrofanov, O.; Dominec, F.; Kužel, P.; Delagnes, J. C.; Mounaix, P.

    2013-11-25

    Impact of sub-wavelength-size dielectric particles on Zenneck surface waves on planar metallic antennas is investigated at terahertz (THz) frequencies with THz near-field probe microscopy. Perturbations of the surface waves show the particle presence, despite its sub-wavelength size. The experimental configuration, which utilizes excitation of surface waves at metallic edges, is suitable for THz imaging of dielectric sub-wavelength size objects. As a proof of concept, the effects of a small strontium titanate rectangular particle and a titanium dioxide sphere on the surface field of a bow-tie antenna are experimentally detected and verified using full-wave simulations.

  2. Total Internal Reflection Tomography (TIRT) for Three-Dimensional Sub-Wavelength Imaging

    NASA Astrophysics Data System (ADS)

    Fischer, David G.; Carney, P. Scott

    2002-11-01

    We will present a novel new form of near-field microscopy known as total internal reflection tomography (TIRT), which allows for true three-dimensional sub-wavelength imaging. It is based on recent theoretical advances regarding the fundamental interaction of light with sub-wavelength structures, as well as stable algorithms for the near-field inverse problem. We will discuss its theoretical underpinnings, as well describe current efforts at the NASA Glenn Research Center to implement a TIRT system for biofluid research.

  3. Subwavelength metrological chracterization by Mueller matrix polarimeter and finite difference time domain method

    NASA Astrophysics Data System (ADS)

    Adhikari, Achyut; Dev, Kapil; Asundi, Anand

    2016-11-01

    Wire grid polarizers (WGP), are sub-wavelength gratings with applications in display projection system due to their compact size, wide field of view and long-term stability. Measurement and testing of these structures are important to optimize their use. This is done by first measuring the Mueller matrix of the WGP using a Mueller matrix polarimeter. Next the finite difference time domain (FDTD) method is used to simulate a similar Mueller matrix thus providing the period and step height of the WGP. This approach may lead to more generic determination of sub-wavelength structures including diffractive optical structures.

  4. Very simple metallic subwavelength cell for constructing left-handed metamaterial

    NASA Astrophysics Data System (ADS)

    Wang, Zhiyu; Wang, Dongxing; Jiang, Tao; Peng, Liang; Huangfu, Jiangtao; Ran, Lixin

    2009-06-01

    In this letter, a very simple metallic subwavelength cell is designed for constructing left-handed metamaterial. The conductive current mode inside the metallic resonator of this cell imitates one reported displacement current mode inside a dielectric subwavelength resonator. We show by simulation and experiments that an artificial metamaterial composed of cells with such kind of current mode can behave simultaneously negative permittivity and permeability. The metallic cell with double negative property obtained in this letter is suitable for the applications in the high frequency band, such as in millimeter or even terahertz bands.

  5. Stripe-shaped apertures in confocal microscopy.

    PubMed

    Shen, Shuhao; Zhu, Bingzhao; Zheng, Yao; Gong, Wei; Si, Ke

    2016-09-20

    We have theoretically verified that, compared with the aperture shapes of previous research, combining two stripe-shaped apertures in a confocal microscope with a finite-sized pinhole improves the axial resolution to a certain extent. Because different stripe shapes cause different effects, we also investigated the relationships among resolution, shapes, pinhole size, and the signal-to-background ratio.

  6. A system model and inversion for synthetic aperture radar imaging.

    PubMed

    Soumekh, M

    1992-01-01

    A system model and its corresponding inversion for synthetic aperture radar (SAR) imaging are presented. The system model incorporates the spherical nature of a radar's radiation pattern at far field. The inverse method based on this model performs a spatial Fourier transform (Doppler processing) on the recorded signals with respect to the available coordinates of a translational radar (SAR) or target (inverse SAR). It is shown that the transformed data provide samples of the spatial Fourier transform of the target's reflectivity function. The inverse method can be modified to incorporate deviations of the radar's motion from its prescribed straight line path. The effects of finite aperture on resolution, reconstruction, and sampling constraints for the imaging problem are discussed.

  7. Vowel aperture and syllable segmentation in French.

    PubMed

    Goslin, Jeremy; Frauenfelder, Ulrich H

    2008-01-01

    The theories of Pulgram (1970) suggest that if the vowel of a French syllable is open then it will induce syllable segmentation responses that result in the syllable being closed, and vice versa. After the empirical verification that our target French-speaking population was capable of distinguishing between mid-vowel aperture, we examined the relationship between vowel and syllable aperture in two segmentation experiments. Initial findings from a metalinguistic repetition task supported the hypothesis, revealing significant segmentation differences due to vowel aperture across a range of bi-syllabic stimuli. These findings were also supported in an additional online experiment, in which a fragment detection task revealed a syllabic cross-over interaction due to vowel aperture. Evidence from these experiments suggest that multiple, independent cues are used in French syllable segmentation, including vowel aperture.

  8. Micro Ring Grating Spectrometer with Adjustable Aperture

    NASA Technical Reports Server (NTRS)

    Park, Yeonjoon (Inventor); King, Glen C. (Inventor); Elliott, James R. (Inventor); Choi, Sang H. (Inventor)

    2012-01-01

    A spectrometer includes a micro-ring grating device having coaxially-aligned ring gratings for diffracting incident light onto a target focal point, a detection device for detecting light intensity, one or more actuators, and an adjustable aperture device defining a circular aperture. The aperture circumscribes a target focal point, and directs a light to the detection device. The aperture device is selectively adjustable using the actuators to select a portion of a frequency band for transmission to the detection device. A method of detecting intensity of a selected band of incident light includes directing incident light onto coaxially-aligned ring gratings of a micro-ring grating device, and diffracting the selected band onto a target focal point using the ring gratings. The method includes using an actuator to adjust an aperture device and pass a selected portion of the frequency band to a detection device for measuring the intensity of the selected portion.

  9. Variable aperture collimator for high energy radiation

    DOEpatents

    Hill, Ronald A.

    1984-05-22

    An apparatus is disclosed providing a variable aperture energy beam collimator. A plurality of beam opaque blocks are in sliding interface edge contact to form a variable aperture. The blocks may be offset at the apex angle to provide a non-equilateral aperture. A plurality of collimator block assemblies may be employed for providing a channel defining a collimated beam. Adjacent assemblies are inverted front-to-back with respect to one another for preventing noncollimated energy from emerging from the apparatus. An adjustment mechanism comprises a cable attached to at least one block and a hand wheel mechanism for operating the cable. The blocks are supported by guide rods engaging slide brackets on the blocks. The guide rods are pivotally connected at each end to intermediate actuators supported on rotatable shafts to change the shape of the aperture. A divergent collimated beam may be obtained by adjusting the apertures of adjacent stages to be unequal.

  10. Performance limits of ion extraction systems with non-circular apertures.

    PubMed

    Shagayda, A; Madeev, S

    2016-04-01

    A three-dimensional computer simulation is used to determine the perveance limitations of ion extraction systems with non-circular apertures. The objective of the study is to analyze the possibilities to improve mechanical strength of the ion optics made of carbon-carbon composite materials. Non-circular grid apertures are better suited to the physical structure of carbon-carbon composite materials, than conventionally used circular holes in a hexagonal pattern, because they allow a fewer number of cut fibers. However, the slit-type accelerating systems, usually regarded as the main alternative to the conventional ion optics, have an intolerably narrow range of operating perveance values at which there is no direct ion impingement on the acceleration grid. This paper presents results of comparative analysis of a number of different ion optical systems with non-circular apertures and conventional ion optical systems with circular apertures. It has been revealed that a relatively wide perveance range without direct ion impingement may be obtained with apertures shaped as a square with rounded corners. Numerical simulations show that this geometry may have equivalent perveance range as the traditional geometry with circular apertures while being more mechanically robust. In addition, such important characteristics, as the effective transparency for both the ions and the neutral atoms, the height of the potential barrier reflecting the downstream plasma electrons and the angular divergence of the beamlet also can be very close to these parameters for the optics with circular apertures. PMID:27131665

  11. Performance limits of ion extraction systems with non-circular apertures

    NASA Astrophysics Data System (ADS)

    Shagayda, A.; Madeev, S.

    2016-04-01

    A three-dimensional computer simulation is used to determine the perveance limitations of ion extraction systems with non-circular apertures. The objective of the study is to analyze the possibilities to improve mechanical strength of the ion optics made of carbon-carbon composite materials. Non-circular grid apertures are better suited to the physical structure of carbon-carbon composite materials, than conventionally used circular holes in a hexagonal pattern, because they allow a fewer number of cut fibers. However, the slit-type accelerating systems, usually regarded as the main alternative to the conventional ion optics, have an intolerably narrow range of operating perveance values at which there is no direct ion impingement on the acceleration grid. This paper presents results of comparative analysis of a number of different ion optical systems with non-circular apertures and conventional ion optical systems with circular apertures. It has been revealed that a relatively wide perveance range without direct ion impingement may be obtained with apertures shaped as a square with rounded corners. Numerical simulations show that this geometry may have equivalent perveance range as the traditional geometry with circular apertures while being more mechanically robust. In addition, such important characteristics, as the effective transparency for both the ions and the neutral atoms, the height of the potential barrier reflecting the downstream plasma electrons and the angular divergence of the beamlet also can be very close to these parameters for the optics with circular apertures.

  12. Ultrafast optical control of terahertz surface plasmon polariton in subwavelength hole-arrays at noon temperature

    SciTech Connect

    Azad, Abul K; Chen, Houtong; Taylor, Antoinette; O' Hara, John F; Kasarla, Satish; Zhang, Weili; Tian, Zhen; Lu, Xinchao

    2008-01-01

    We demonstrate ultrafast optical control of surface plasmon assisted terahertz (THz) transmission in a subwavelength metallic hole array on a semiconductor substrate. The transient photoconductivity of the substrate allows modulation of the THz resonance amplitude via optical excitation with a time scale of {approx}10 ps.

  13. Integrated narrowband optical filter based on embedded subwavelength resonant grating structures

    DOEpatents

    Grann, Eric B.; Sitter, Jr., David N.

    2000-01-01

    A resonant grating structure in a waveguide and methods of tuning the performance of the grating structure are described. An apparatus includes a waveguide; and a subwavelength resonant grating structure embedded in the waveguide. The systems and methods provide advantages including narrowband filtering capabilities, minimal sideband reflections, spatial control, high packing density, and tunability.

  14. Tunable Fabry-Pérot interferometer with subwavelength grating reflectors for MWIR microspectrometers

    NASA Astrophysics Data System (ADS)

    Meinig, Marco; Kurth, Steffen; Seifert, Mario; Hiller, Karla; Wecker, Julia; Ebermann, Martin; Neumann, Norbert; Gessner, Thomas

    2016-04-01

    This report presents recent advances in the design and fabrication of a tunable Fabry-Pérot interferometer (FPI) with subwavelength grating (SWG) reflectors, as well as measurement results and applications. The FPI is designed as wavelength selecting element for highly miniaturized mid-wave infrared spectrometers. The optical resonator of the FPI is built between two highly reflecting mirrors. The mirrors are integrated in a supporting MEMS structure with one electrostatically movable and one fixed mirror carrier. The FPI is fabricated in a bulk micromachining batch process on wafer level from two silicon substrates. The substrates are bonded together with an intermediate SU-8 layer. The reflectors are made of aluminum subwavelength gratings, structured on a thin LP-Si3N4 membrane by nanoimprint lithography. The subwavelength structures build a frequency selective surface with high reflectance and low absorbance in a defined spectral range. Simulations and optimization of the design were done using finite element method with a 3D EM frequency domain solver. Comparison of simulation results and measurements of fabricated reflectors and FPIs are in very good agreement. The FPIs are used in the 5th interference order and can be tuned from 3.5 μm to 2.9 μm electrically. The measured maximum transmittance is between 70 % and 50 % and the measured FWHM bandwidth is lower than 50 nm. The new subwavelength grating reflectors can be integrated in a MEMS batch process more cost-efficient than previously used reflectors of dielectric layer stacks.

  15. Full-Color Subwavelength Printing with Gap-Plasmonic Optical Antennas.

    PubMed

    Miyata, Masashi; Hatada, Hideaki; Takahara, Junichi

    2016-05-11

    Metallic nanostructures can be designed to effectively reflect different colors at deep-subwavelength scales. Such color manipulation is attractive for applications such as subwavelength color printing; however, challenges remain in creating saturated colors with a general and intuitive design rule. Here, we propose a simple design approach based on all-aluminum gap-plasmonic nanoantennas, which is capable of designing colors using knowledge of the optical properties of the individual antennas. We demonstrate that the individual-antenna properties that feature strong light absorption at two distinct frequencies can be encoded into a single subwavelength-pixel, enabling the creation of saturated colors, as well as a dark color in reflection, at the optical diffraction limit. The suitability of the designed color pixels for subwavelength printing applications is demonstrated by showing microscopic letters in color, the incident polarization and angle insensitivity, and color durability. Coupled with the low cost and long-term stability of aluminum, the proposed design strategy could be useful in creating microscale images for security purposes, high-density optical data storage, and nanoscale optical elements.

  16. Optoelectronic metamaterials for sub-wavelength imaging in the mid infra red regime

    NASA Astrophysics Data System (ADS)

    Krishnamurthi, Mahesh; Sparks, Justin; Baril, Neil; He, Rongrui; Sazio, Pier; Badding, John; Gopalan, Venkatraman

    2010-03-01

    The mid infrared (MIR) wavelength range of 4-10μm is critically important to various technologies such as sensing, night vision, nondestructive testing, human health, and scientific research. We have developed a sub-wavelength imaging system in the MIR. The fabrication is based on the high-pressure chemical fluid deposition platform developed in our laboratories to create periodic arrays of waveguides inside the holes of a silica based microstructured optical fiber. Waveguides fabricated within each of these holes, acts as a pixel in the infra red camera. The waveguides in each of the holes of the microstructured optical fiber are tapered down to sub-wavelength dimensions at the input plane. Tapering the microstructured optical fiber down to sub-wavelength dimensions will enable sub-wavelength resolution and, also magnify the image at the output plane. The magnification at the output plane also helps in using the commercially available imaging systems to record the information. The details of numerical modeling, fabrication scheme and characterization of the infrared camera will be discussed. Basic essential features such as optical isolation, magnification and elementary imaging concepts will be presented. In addition, design variations that can be adopted to improve the resolution of the camera will be discussed.

  17. Complex ray analysis of radiation from large apertures with tapered illumination

    NASA Astrophysics Data System (ADS)

    Ghione, G.; Felsen, L. B.; Montrosset, I.

    1984-07-01

    An attempt is made to model the initial distribution of radiation emitted by an antenna feed in terms of a building-block approach. Attention is given to both near and far field calculations for large apertures with tapered illumination. Generalized one-dimensional tapered profiles expressed in terms of the wavenumber and the aperture coordinate are used to handle profiles ranging from gaussian to rectangular. The analysis covers complex ray tracing from the aperture plane to the observer. The inclusion of all relevant rays is assured by a saddle point analysis of the exact field integral. The ray tracing procedure is demonstrated to be effective without reference to an aperture integral. Several field radiation patterns are calculated as examples.

  18. Three dimensional digital holographic aperture synthesis.

    PubMed

    Crouch, Stephen; Kaylor, Brant M; Barber, Zeb W; Reibel, Randy R

    2015-09-01

    Aperture synthesis techniques are applied to temporally and spatially diverse digital holograms recorded with a fast focal-plane array. Because the technique fully resolves the downrange dimension using wide-bandwidth FMCW linear-chirp waveforms, extremely high resolution three dimensional (3D) images can be obtained even at very long standoff ranges. This allows excellent 3D image formation even when targets have significant structure or discontinuities, which are typically poorly rendered with multi-baseline synthetic aperture ladar or multi-wavelength holographic aperture ladar approaches. The background for the system is described and system performance is demonstrated through both simulation and experiments. PMID:26368474

  19. Investigation of transmission enhancement of THz radiation through subwavelength fractal structures of copper foils by FDTD simulation

    NASA Astrophysics Data System (ADS)

    Meng, Wei; Zhao, Guozhong; Meng, Tianhua; Zhang, Cunlin

    2008-12-01

    We present the enhanced transmission spectrum of a copper foil with the sub-wavelength fractal structures by means of the terahertz time domain spectroscopy (THz-TDS) and FDTD simulation. In the view of experimental measurement and finite-difference-time-domain (FDTD) simulations, respectively, we studied the influence of the electric field and magnetic field on the enhanced transmission of THz wave through each level of fractal pattern generated by the repeated affine transformations of an H-shaped mother element on the copper foil. We simulate the incidence and transmission of the THz wave and show the propagation and distribution of the interior electromagnetic field by the software for electromagnetic design named CONCERTO. To compare with the experimental results, we simulate the cases that the certain levels of the pattern are deleted. The results of simulation agree with the experimental one. It is found that the transmission enhancement in the low frequency regime is caused by the radiation of electron resonance in the low fractal levels, and the transmission enhancement in the high frequency regime is caused by the radiation of electron resonance in the high fractal level, that is, the localization resonance of the fractal structures. These results indicate that the flat surface fractal structure like an ideal wave-guide. The vertically incident THz wave is confined on the surface and transmitted along the fractal slits. The controlling ability of fractal structures will offer a powerful tool for the design of THz photonic devices.

  20. Feasibility demonstration of a massively parallelizable optical near-field sensor for sub-wavelength defect detection and imaging

    PubMed Central

    Mostafavi, Mahkamehossadat; Diaz, Rodolfo E.

    2016-01-01

    To detect and resolve sub-wavelength features at optical frequencies, beyond the diffraction limit, requires sensors that interact with the electromagnetic near-field of those features. Most instruments operating in this modality scan a single detector element across the surface under inspection because the scattered signals from a multiplicity of such elements would end up interfering with each other. However, an alternative massively parallelized configuration, capable of interrogating multiple adjacent areas of the surface at the same time, was proposed in 2002. Full physics simulations of the photonic antenna detector element that enables this instrument, show that using conventional red laser light (in the 600 nm range) the detector magnifies the signal from an 8 nm particle by up to 1.5 orders of magnitude. The antenna is a shaped slot element in a 60 nm silver film. The ability of this detector element to resolve λ/78 objects is confirmed experimentally at radio frequencies by fabricating an artificial material structure that mimics the optical permittivity of silver scaled to 2 GHz, and “cutting” into it the slot antenna. The experimental set-up is also used to demonstrate the imaging of a patterned surface in which the critical dimensions of the pattern are λ/22 in size. PMID:27185385

  1. Feasibility demonstration of a massively parallelizable optical near-field sensor for sub-wavelength defect detection and imaging.

    PubMed

    Mostafavi, Mahkamehossadat; Diaz, Rodolfo E

    2016-01-01

    To detect and resolve sub-wavelength features at optical frequencies, beyond the diffraction limit, requires sensors that interact with the electromagnetic near-field of those features. Most instruments operating in this modality scan a single detector element across the surface under inspection because the scattered signals from a multiplicity of such elements would end up interfering with each other. However, an alternative massively parallelized configuration, capable of interrogating multiple adjacent areas of the surface at the same time, was proposed in 2002. Full physics simulations of the photonic antenna detector element that enables this instrument, show that using conventional red laser light (in the 600 nm range) the detector magnifies the signal from an 8 nm particle by up to 1.5 orders of magnitude. The antenna is a shaped slot element in a 60 nm silver film. The ability of this detector element to resolve λ/78 objects is confirmed experimentally at radio frequencies by fabricating an artificial material structure that mimics the optical permittivity of silver scaled to 2 GHz, and "cutting" into it the slot antenna. The experimental set-up is also used to demonstrate the imaging of a patterned surface in which the critical dimensions of the pattern are λ/22 in size. PMID:27185385

  2. Feasibility demonstration of a massively parallelizable optical near-field sensor for sub-wavelength defect detection and imaging

    NASA Astrophysics Data System (ADS)

    Mostafavi, Mahkamehossadat; Diaz, Rodolfo E.

    2016-05-01

    To detect and resolve sub-wavelength features at optical frequencies, beyond the diffraction limit, requires sensors that interact with the electromagnetic near-field of those features. Most instruments operating in this modality scan a single detector element across the surface under inspection because the scattered signals from a multiplicity of such elements would end up interfering with each other. However, an alternative massively parallelized configuration, capable of interrogating multiple adjacent areas of the surface at the same time, was proposed in 2002. Full physics simulations of the photonic antenna detector element that enables this instrument, show that using conventional red laser light (in the 600 nm range) the detector magnifies the signal from an 8 nm particle by up to 1.5 orders of magnitude. The antenna is a shaped slot element in a 60 nm silver film. The ability of this detector element to resolve λ/78 objects is confirmed experimentally at radio frequencies by fabricating an artificial material structure that mimics the optical permittivity of silver scaled to 2 GHz, and “cutting” into it the slot antenna. The experimental set-up is also used to demonstrate the imaging of a patterned surface in which the critical dimensions of the pattern are λ/22 in size.

  3. Measuring Spatial Coherence With a Two-Dimensional Aperture Array

    NASA Astrophysics Data System (ADS)

    González, Aura I.; Mejía, Yobani

    2008-04-01

    The complex degree of spatial coherence of the optical fields, in general, is a shift variant quantity. Therefore to characterize it, in addition to knowing how it changes in function of the separation of the two points under analysis, we require knowing how it changes in function of the location of these points. In order to measure the complex degree of spatial coherence of any quasi-monochromatic optical field, we propose a method that uses a mask with a two-dimensional array of apertures (small circular holes) to sample the optical field. The distribution of the apertures in the mask is made so that we get a non redundant array, it means that the classes of aperture pairs of the mask are composed just by one pair. From the Fourier spectrum of the interference pattern in far field generated by the mask we can determine the magnitude and the phase of the complex degree of spatial coherence. The efficiency of the array is verified with experimental results using a partially coherent beam generated following the rotating glass method. Finally, the results obtained in the experiment are compared with those obtained by means of numerical simulations.

  4. Lensless coded aperture imaging with separable doubly Toeplitz masks

    NASA Astrophysics Data System (ADS)

    DeWeert, Michael J.; Farm, Brian P.

    2014-05-01

    In certain imaging applications, conventional lens technology is constrained by the lack of materials which can effectively focus the radiation within reasonable weight and volume. One solution is to use coded apertures -opaque plates perforated with multiple pinhole-like openings. If the openings are arranged in an appropriate pattern, the images can be decoded, and a clear image computed. Recently, computational imaging and the search for means of producing programmable software-defined optics have revived interest in coded apertures. The former state-of-the-art masks, MURAs (Modified Uniformly Redundant Arrays) are effective for compact objects against uniform backgrounds, but have substantial drawbacks for extended scenes: 1) MURAs present an inherently ill-posed inversion problem that is unmanageable for large images, and 2) they are susceptible to diffraction: a diffracted MURA is no longer a MURA. This paper presents a new class of coded apertures, Separable Doubly-Toeplitz masks, which are efficiently decodable, even for very large images -orders of magnitude faster than MURAs, and which remain decodable when diffracted. We implemented the masks using programmable spatial-lightmodulators. Imaging experiments confirmed the effectiveness of Separable Doubly-Toeplitz masks - images collected in natural light of extended outdoor scenes are rendered clearly.

  5. An implementation of synthetic aperture focusing technique in frequency domain.

    PubMed

    Stepinski, Tadeusz

    2007-07-01

    A new implementation of a synthetic aperture focusing technique (SAFT) based on concepts used in synthetic aperture radar and sonar is presented in the paper. The algorithm, based on the convolution model of the imaging system developed in frequency domain, accounts for the beam pattern of the finite-sized transducer used in the synthetic aperture. The 2D fast Fourier transform (FFT) is used for the calculation of a 2D spectrum of the ultrasonic data. The spectrum is then interpolated to convert the polar coordinate system used for the acquisition of ultrasonic signals to the rectangular coordinates used for the presentation of imaging results. After compensating the transducer lobe amplitude profile using a Wiener filter, the transformed spectrum is subjected to the 2D inverse Fourier transform to get the time-domain image again. The algorithm is computationally attractive due to the use of 2D FFT. The performance of the proposed frequency-domain algorithm and the classical time-domain SAFT are compared in the paper using simulated and real ultrasonic data.

  6. Distributed apertures in laminar flow laser turrets

    NASA Astrophysics Data System (ADS)

    Tousley, B. B.

    1981-09-01

    Assume a technology that permits undistorted laser beam propagation from the aft section of a streamlined turret. A comparison of power on a distant airborne target is made between a single aperture in a large scale streamlined turret with a turbulent boundary layer and various arrays of apertures in small scale streamlined turrets with laminar flow. The array performance is mainly limited by the size of each aperture. From an array one might expect, at best, about 40 percent as much power on the target as from a single aperture with equal area. Since the turbulent boundary layer on the large single-turret has negligible effect on beam quality, the array would be preferred (if all development efforts were essentially equal) only if a laminar wake is an operational requirement.

  7. Very Large Aperture Diffractive Space Telescope

    SciTech Connect

    Hyde, Roderick Allen

    1998-04-20

    A very large (10's of meters) aperture space telescope including two separate spacecraft--an optical primary functioning as a magnifying glass and an optical secondary functioning as an eyepiece. The spacecraft are spaced up to several kilometers apart with the eyepiece directly behind the magnifying glass ''aiming'' at an intended target with their relative orientation determining the optical axis of the telescope and hence the targets being observed. The magnifying glass includes a very large-aperture, very-thin-membrane, diffractive lens, e.g., a Fresnel lens, which intercepts incoming light over its full aperture and focuses it towards the eyepiece. The eyepiece has a much smaller, meter-scale aperture and is designed to move along the focal surface of the magnifying glass, gathering up the incoming light and converting it to high quality images. The positions of the two space craft are controlled both to maintain a good optical focus and to point at desired targets.

  8. Shock wave absorber having apertured plate

    DOEpatents

    Shin, Y.W.; Wiedermann, A.H.; Ockert, C.E.

    1983-08-26

    The shock or energy absorber disclosed herein utilizes an apertured plate maintained under the normal level of liquid flowing in a piping system and disposed between the normal liquid flow path and a cavity pressurized with a compressible gas. The degree of openness (or porosity) of the plate is between 0.01 and 0.60. The energy level of a shock wave travelling down the piping system thus is dissipated by some of the liquid being jetted through the apertured plate toward the cavity. The cavity is large compared to the quantity of liquid jetted through the apertured plate, so there is little change in its volume. The porosity of the apertured plate influences the percentage of energy absorbed.

  9. Shock wave absorber having apertured plate

    DOEpatents

    Shin, Yong W.; Wiedermann, Arne H.; Ockert, Carl E.

    1985-01-01

    The shock or energy absorber disclosed herein utilizes an apertured plate maintained under the normal level of liquid flowing in a piping system and disposed between the normal liquid flow path and a cavity pressurized with a compressible gas. The degree of openness (or porosity) of the plate is between 0.01 and 0.60. The energy level of a shock wave travelling down the piping system thus is dissipated by some of the liquid being jetted through the apertured plate toward the cavity. The cavity is large compared to the quantity of liquid jetted through the apertured plate, so there is little change in its volume. The porosity of the apertured plate influences the percentage of energy absorbed.

  10. Synthetic Aperture Radar Missions Study Report

    NASA Technical Reports Server (NTRS)

    Bard, S.

    2000-01-01

    This report reviews the history of the LightSAR project and summarizes actions the agency can undertake to support industry-led efforts to develop an operational synthetic aperture radar (SAR) capability in the United States.

  11. Large aperture ac interferometer for optical testing.

    PubMed

    Moore, D T; Murray, R; Neves, F B

    1978-12-15

    A 20-cm clear aperture modified Twyman-Green interferometer is described. The system measures phase with an AC technique called phase-lock interferometry while scanning the aperture with a dual galvanometer scanning system. Position information and phase are stored in a minicomputer with disk storage. This information is manipulated with associated software, and the wavefront deformation due to a test component is graphically displayed in perspective and contour on a CRT terminal. PMID:20208642

  12. Application of a geocentrifuge and sterolithographically fabricated apertures to multiphase flow in complex fracture apertures.

    SciTech Connect

    Glenn E. McCreery; Robert D. Stedtfeld; Alan T. Stadler; Daphne L. Stoner; Paul Meakin

    2005-09-01

    A geotechnical centrifuge was used to investigate unsaturated multiphase fluid flow in synthetic fracture apertures under a variety of flow conditions. The geocentrifuge subjected the fluids to centrifugal forces allowing the Bond number to be systematically changed without adjusting the fracture aperture of the fluids. The fracture models were based on the concept that surfaces generated by the fracture of brittle geomaterials have a self-affine fractal geometry. The synthetic fracture surfaces were fabricated from a transparent epoxy photopolymer using sterolithography, and fluid flow through the transparent fracture models was monitored by an optical image acquisition system. Aperture widths were chosen to be representative of the wide range of geological fractures in the vesicular basalt that lies beneath the Idaho Nation Laboratory (INL). Transitions between different flow regimes were observed as the acceleration was changed under constant flow conditions. The experiments showed the transition between straight and meandering rivulets in smooth walled apertures (aperture width = 0.508 mm), the dependence of the rivulet width on acceleration in rough walled fracture apertures (average aperture width = 0.25 mm), unstable meandering flow in rough walled apertures at high acceleration (20g) and the narrowing of the wetted region with increasing acceleration during the penetration of water into an aperture filled with wetted particles (0.875 mm diameter glass spheres).

  13. Vector-based synthesis of finite aperiodic diffractive micro-optical elements with subwavelength structures as beam deflectors

    NASA Astrophysics Data System (ADS)

    Feng, Di; Yan, Yingbai; Tan, Qiaofeng

    2003-09-01

    An iterative optimization-based synthesis algorithm has been presented for the design of diffractive micro-optical elements (DMOE's) with subwavelength structures as beam controllers. The DMOE's with subwavelength structures only require single step fabrication, but the subwavelength and aperiodic nature of the DMOE's prevent the use of scalar diffraction theory and the use of coupled-wave theory. We apply the finite-difference time-domain (FDTD) method as the vector model and the iterative plane wave spectrum algorithm (IPWS) as the synthesis algorithm, which can make the design of DMOE's in reasonable time frames. The IPWS, the FDTD method, the plane wave spectrum propagation method have been discussed and a beam deflector with subwavelength structures has been designed.

  14. Modulation of hand aperture during reaching in persons with incomplete cervical spinal cord injury

    PubMed Central

    Stahl, Victoria; Hayes, Heather B; Buetefisch, Cathrin; Wolf, Steven L; Trumbower, Randy D

    2014-01-01

    The intact neuromotor system prepares for object grasp by first opening the hand to an aperture that is scaled according to object size and then closing the hand around the object. After cervical spinal cord injury (SCI), hand function is significantly impaired, but the degree to which object-specific hand aperture scaling is affected remains unknown. Here we hypothesized that persons with incomplete cervical SCI have a reduced maximum hand opening capacity but exhibit novel neuromuscular coordination strategies that permit object-specific hand aperture scaling during reaching. To test this hypothesis, we measured hand kinematics and surface electromyography (EMG) from seven muscles of the hand and wrist during attempts at maximum hand opening as well as reaching for four balls of different diameters. Our results showed that persons with SCI exhibited significantly reduced maximum hand aperture compared to able-bodied (AB) controls. However, persons with SCI preserved the ability to scale peak hand aperture with ball size during reaching. Persons with SCI also used distinct muscle coordination patterns that included increased co-activity of flexors and extensors at the wrist and hand compared to AB controls. These results suggest that motor planning for aperture modulation is preserved even though execution is limited by constraints on hand opening capacity and altered muscle co-activity. Thus, persons with incomplete cervical SCI may benefit from rehabilitation aimed at increasing hand opening capacity and reducing flexor-extensor co-activity at the wrist and hand. PMID:25511164

  15. Deployable Wide-Aperture Array Antennas

    NASA Technical Reports Server (NTRS)

    Fink, Patrick W.; Dobbins, Justin A.; Lin, Greg Y.; Chu, Andrew; Scully, Robert C.

    2005-01-01

    Inexpensive, lightweight array antennas on flexible substrates are under development to satisfy a need for large-aperture antennas that can be stored compactly during transport and deployed to full size in the field. Conceived for use aboard spacecraft, antennas of this type also have potential terrestrial uses . most likely, as means to extend the ranges of cellular telephones in rural settings. Several simple deployment mechanisms are envisioned. One example is shown in the figure, where the deployment mechanism, a springlike material contained in a sleeve around the perimeter of a flexible membrane, is based on a common automobile window shade. The array can be formed of antenna elements that are printed on small sections of semi-flexible laminates, or preferably, elements that are constructed of conducting fabric. Likewise, a distribution network connecting the elements can be created from conventional technologies such as lightweight, flexible coaxial cable and a surface mount power divider, or preferably, from elements formed from conductive fabrics. Conventional technologies may be stitched onto a supporting flexible membrane or contained within pockets that are stitched onto a flexible membrane. Components created from conductive fabrics may be attached by stitching conductive strips to a nonconductive membrane, embroidering conductive threads into a nonconductive membrane, or weaving predetermined patterns directly into the membrane. The deployable antenna may comprise multiple types of antenna elements. For example, thin profile antenna elements above a ground plane, both attached to the supporting flexible membrane, can be used to create a unidirectional boresight radiation pattern. Or, antenna elements without a ground plane, such as bow-tie dipoles, can be attached to the membrane to create a bidirectional array such as that shown in the figure. For either type of antenna element, the dual configuration, i.e., elements formed of slots in a conductive

  16. Programmable Aperture with MEMS Microshutter Arrays

    NASA Technical Reports Server (NTRS)

    Moseley, Samuel; Li, Mary; Kutyrev, Alexander; Kletetschka, Gunther; Fettig, Rainer

    2011-01-01

    A microshutter array (MSA) has been developed for use as an aperture array for multi-object selections in James Webb Space Telescope (JWST) technology. Light shields, molybdenum nitride (MoN) coating on shutters, and aluminum/aluminum oxide coatings on interior walls are put on each shutter for light leak prevention, and to enhance optical contrast. Individual shutters are patterned with a torsion flexure that permits shutters to open 90 deg. with a minimized mechanical stress concentration. The shutters are actuated magnetically, latched, and addressed electrostatically. Also, micromechanical features are tailored onto individual shutters to prevent stiction. An individual shutter consists of a torsion hinge, a shutter blade, a front electrode that is coated on the shutter blade, a backside electrode that is coated on the interior walls, and a magnetic cobalt-iron coating. The magnetic coating is patterned into stripes on microshutters so that shutters can respond to an external magnetic field for the magnetic actuation. A set of column electrodes is placed on top of shutters, and a set of row electrodes on sidewalls is underneath the shutters so that they can be electrostatically latched open. A linear permanent magnet is aligned with the shutter rows and is positioned above a flipped upside-down array, and sweeps across the array in a direction parallel to shutter columns. As the magnet sweeps across the array, sequential rows of shutters are rotated from their natural horizontal orientation to a vertical open position, where they approach vertical electrodes on the sidewalls. When the electrodes are biased with a sufficient electrostatic force to overcome the mechanical restoring force of torsion bars, shutters remain latched to vertical electrodes in their open state. When the bias is removed, or is insufficient, the shutters return to their horizontal, closed positions. To release a shutter, both the electrode on the shutter and the one on the back wall where

  17. Large area, freestanding GaN nanocolumn membrane with bottom subwavelength nanostructure.

    PubMed

    Wang, Yongjin; Hu, Fangren; Kanamori, Yoshiaki; Wu, Tong; Hane, Kazuhiro

    2010-03-15

    We propose, fabricate and characterize the freestanding GaN nanocolumn membrane with bottom subwavelength nanostructures. The GaN nanocolumns are epitaxially grown on freestanding nanostructured silicon substrate that is achieved by a combination of self-assemble technique and silicon-on-insulator (SOI) technology. Optical reflection is greatly suppressed in the visible range due to the graded refractive index effect of subwavelength nanostructures. The freestanding GaN nanocolumn membrane is realized by removing silicon substrate from the backside, eliminating the silicon absorption of the emitted light and leading to a strong blue emission from the bottom side. The obtained structures also demonstrate the potential application for anti-reflective (AR) coating and GaN-Si hybrid microelectromechanical system (MEMS).

  18. Analysis of phase shift of surface plasmon polaritons at metallic subwavelength hole arrays

    NASA Astrophysics Data System (ADS)

    Li, Jiang-Yan; Qiu, Kang-Sheng; Ma, Hai-Qiang

    2014-10-01

    We present the transmission spectra of light transmitting a metallic thin film perforated with differently shaped subwavelength hole arrays, which are calculated by a plane-wave-based transfer matrix method. We analyze the transmission peak positions and the phase-shift angles of different surface plasmon polariton (SPP) modes by using the microscopic theoretical model proposed by Haitao Liu and Philippe Lalanne [Liu Haitao and Lalanne Philippe 2008 Nature 452 728], in which the phase shift properties of the SPPs scattered by the subwavelength hole arrays are considered. The results show that the transmission peak position and the minus phase shift angle of the SPP increase as the hole size increases. On the other hand, the effective dielectric constant of the metallic film can be deduced by the microscopic theoretical model.

  19. Using a Semiconductor-to-Metal Transition to Control Optical Transmission through Subwavelength Hole Arrays

    DOE PAGESBeta

    Donev, E. U.; Suh, J. Y.; Lopez, R.; Feldman, L. C.; Haglund, R. F.

    2008-01-01

    We describe a simple configuration in which the extraordinary optical transmission effect through subwavelength hole arrays in noble-metal films can be switched by the semiconductor-to-metal transition in an underlying thin film of vanadium dioxide. In these experiments, the transition is brought about by thermal heating of the bilayer film. The surprising reverse hysteretic behavior of the transmission through the subwavelength holes in the vanadium oxide suggest that this modulation is accomplished by a dielectric-matching condition rather than plasmon coupling through the bilayer film. The results of this switching, including the wavelength dependence, are qualitatively reproduced by a transfer matrix model.more » The prospects for effecting a similar modulation on a much faster time scale by using ultrafast laser pulses to trigger the semiconductor-to-metal transition are also discussed.« less

  20. Two-path solid-state interferometry using ultra-subwavelength two-dimensional plasmonic waves

    NASA Astrophysics Data System (ADS)

    Yeung, Kitty Y. M.; Yoon, Hosang; Andress, William; West, Ken; Pfeiffer, Loren; Ham, Donhee

    2013-01-01

    We report an on-chip solid-state Mach-Zehnder interferometer operating on two-dimensional (2D) plasmonic waves at microwave frequencies. Two plasmonic paths are defined with GaAs/AlGaAs 2D electron gas 80 nm below a metallic gate. The gated 2D plasmonic waves achieve a velocity of ˜c/300 (c: free-space light speed). Due to this ultra-subwavelength confinement, the resolution of the 2D plasmonic interferometer is two orders of magnitude higher than that of its electromagnetic counterpart at a given frequency. This gigahertz proof-of-concept at cryogenic temperatures can be scaled to the terahertz-infrared range for room temperature operation, while maintaining the benefits of ultra-subwavelength confinement.

  1. Loss and retardation effect on subwavelength imaging by compensated bilayer of anisotropic metamaterials

    NASA Astrophysics Data System (ADS)

    Chen, Yan; Teng, Xiaohua; Huang, Ying; Feng, Yijun

    2006-12-01

    We analyze the subwavelength imaging using compensated bilayer of anisotropic metamaterials and study the material loss and retardation effect on the image properties. Through rigorous analysis of the electromagnetic wave transmission and numerical calculations of the electromagnetic field distribution, we demonstrate that the anisotropic bilayer lens exhibits a decreased sensitivity to material loss and retardation, therefore has a better image with subwavelength resolution than that of the isotropic perfect lens configuration. We find that this is due to the fact that the inhomogeneous evanescent waves that are responsible for image resolution beyond the diffraction limit have been converted to propagating waves in the anisotropic bilayer, resulting in less sensitive to material loss and retardation.

  2. Small divergence substrate emitting quantum cascade laser by subwavelength metallic grating.

    PubMed

    Yao, Dan-Yang; Zhang, Jin-Chuan; Liu, Ying-Hui; Zhuo, Ning; Jia, Zhi-Wei; Liu, Feng-Qi; Wang, Zhan-Guo

    2015-05-01

    Metallic periodic structure in subwavelength scale offers an exciting way to couple light into surface plasmons (SPs), thus manipulating the properties of near-field optics. We show that subwavelength metallic grating (SMG) defined on the substrate side of substrate emitting quantum cascade lasers enables far-field improvement in mid-infrared spectrum. The SMG is designed to tailor the interaction of SPs with single mode transverse magnetic light. The experiment results are in good agreement with the simulated model. A far-field full width at half maximum (FWHM) divergence angle of 3.9 ° in the direction perpendicular to the laser waveguide layers is obtained, improved by a factor of 8.5 compared with traditional surface emitting device.

  3. Polarized thermal radiation by layer-by-layer metallic emitters with sub-wavelength grating.

    PubMed

    Lee, Jae-Hwang; Leung, Wai; Kim, Tae Guen; Constant, Kristen; Ho, Kai-Ming

    2008-06-01

    Metallic thermal emitters consisting of two layers of differently structured nickel gratings on a homogeneous nickel layer are fabricated by soft lithography and studied for polarized thermal radiation. A thermal emitter in combination with a sub-wavelength grating shows a high extinction ratio, with a maximum value close to 5, in a wide mid-infrared range from 3.2 to 7.8 mum, as well as high emissivity up to 0.65 at a wavelength of 3.7 microm. All measurements show good agreement with theoretical predictions. Numerical simulations reveal that a high electric field exists within the localized air space surrounded by the gratings and the intensified electric-field is only observed for the polarizations perpendicular to the top sub-wavelength grating. This result suggests how the emissivity of a metal can be selectively enhanced at a certain range of wavelengths for a given polarization. PMID:18545587

  4. Super-resolution and reconstruction of sparse sub-wavelength images.

    PubMed

    Gazit, Snir; Szameit, Alexander; Eldar, Yonina C; Segev, Mordechai

    2009-12-21

    We show that, in contrast to popular belief, sub-wavelength information can be recovered from the far-field of an optical image, thereby overcoming the loss of information embedded in decaying evanescent waves. The only requirement is that the image is known to be sparse, a specific but very general and wide-spread property of signals which occur almost everywhere in nature. The reconstruction method relies on newly-developed compressed sensing techniques, which we adapt to optical super-resolution and sub-wavelength imaging. Our approach exhibits robustness to noise and imperfections. We provide an experimental proof-of-principle by demonstrating image recovery at a spatial resolution 5-times higher than the finest resolution defined by a spatial filter. The technique is general, and can be extended beyond optical microscopy, for example, to atomic force microscopes, scanning-tunneling microscopes, and other imaging systems.

  5. Surface-wave mechanism of subwavelength imaging by a flat left-handed superlens

    SciTech Connect

    Zharov, A. A.; Zharova, N. A.; Noskov, R. E.

    2009-11-15

    We develop a theory describing the dynamics and interaction of electromagnetic surface waves (ESWs) resonantly excited by an external source in a slab of left-handed material (LHM) with identical negative (equal to -1) values of dielectric permittivity and magnetic permeability that makes up a so-called perfect lens, or a superlens. We show that subwavelength imaging by a superlens is associated with the degeneracy of the spectrum of eigen electromagnetic surface modes at the interfaces of the metamaterial slab, whereas the dynamic response of the superlens is completely determined by the dynamics of these modes and the dispersion properties of the metamaterial. We obtain conditions that enable one to find out when a superlens produces subwavelength images of an external source. We consider the cases of a stationary and a pulse source, as well as of a source that moves with constant velocity or oscillates in space.

  6. MTF analysis for coded aperture imaging in a flat panel display

    NASA Astrophysics Data System (ADS)

    Suh, Sungjoo; Han, Jae-Joon; Park, Dusik

    2014-09-01

    In this paper, we analyze the modulation transfer function (MTF) of coded aperture imaging in a flat panel display. The flat panel display with a sensor panel forms lens-less multi-view cameras through the imaging pattern of the modified redundant arrays (MURA) on the display panel. To analyze the MTF of the coded aperture imaging implemented on the display panel, we first mathematically model the encoding process of coded aperture imaging, where the projected image on the sensor panel is modeled as a convolution of the scaled object and a function of the imaging pattern. Then, system point spread function is determined by incorporating a decoding process which is dependent on the pixel pitch of the display screen and the decoding function. Finally, the MTF of the system is derived by the magnitude of the Fourier transform of the determined system point spread function. To demonstrate the validity of the mathematically derived MTF in the system, we build a coded aperture imaging system that can capture the scene in front of the display, where the system consists of a display screen and a sensor panel. Experimental results show that the derived MTF of coded aperture imaging in a flat panel display system well corresponds to the measured MTF.

  7. Correlated Statistical Uncertainties in Coded-Aperture Imaging

    SciTech Connect

    Fleenor, Matthew C; Blackston, Matthew A; Ziock, Klaus-Peter

    2014-01-01

    In nuclear security applications, coded-aperture imagers provide the opportu- nity for a wealth of information regarding the attributes of both the radioac- tive and non-radioactive components of the objects being imaged. However, for optimum benefit to the community, spatial attributes need to be deter- mined in a quantitative and statistically meaningful manner. To address the deficiency of quantifiable errors in coded-aperture imaging, we present uncer- tainty matrices containing covariance terms between image pixels for MURA mask patterns. We calculated these correlated uncertainties as functions of variation in mask rank, mask pattern over-sampling, and whether or not anti- mask data are included. Utilizing simulated point source data, we found that correlations (and inverse correlations) arose when two or more image pixels were summed. Furthermore, we found that the presence of correlations (and their inverses) was heightened by the process of over-sampling, while correla- tions were suppressed by the inclusion of anti-mask data and with increased mask rank. As an application of this result, we explore how statistics-based alarming in nuclear security is impacted.

  8. Imaging plasmas with coded aperture methods instead of conventional optics

    NASA Astrophysics Data System (ADS)

    Wongwaitayakornkul, Pakorn; Bellan, Paul

    2012-10-01

    The spheromak and astrophysical jet plasma at Caltech emits localized EUV and X-rays associated with magnetic reconnection. However, conventional optics does not work for EUV or X-rays due to their high energy. Coded aperture imaging is an alternative method that will work at these energies. The technique has been used in spacecraft for high-energy radiation and also in nuclear medicine. Coded aperture imaging works by having patterns of materials opaque to various wavelengths block and unblock radiation in a known pattern. The original image can be determined from a numerical procedure that inverts information from the coded shadow on the detector plane. A one-dimensional coded mask has been designed and constructed for visualization of the evolution of a 1-d cross-section image of the Caltech plasmas. The mask is constructed from Hadamard matrices. Arrays of photo-detectors will be assembled to obtain an image of the plasmas in the visible light range. The experiment will ultimately be re-configured to image X-ray and EUV radiation.

  9. Aperture effects in squid jet propulsion.

    PubMed

    Staaf, Danna J; Gilly, William F; Denny, Mark W

    2014-05-01

    Squid are the largest jet propellers in nature as adults, but as paralarvae they are some of the smallest, faced with the inherent inefficiency of jet propulsion at a low Reynolds number. In this study we describe the behavior and kinematics of locomotion in 1 mm paralarvae of Dosidicus gigas, the smallest squid yet studied. They swim with hop-and-sink behavior and can engage in fast jets by reducing the size of the mantle aperture during the contraction phase of a jetting cycle. We go on to explore the general effects of a variable mantle and funnel aperture in a theoretical model of jet propulsion scaled from the smallest (1 mm mantle length) to the largest (3 m) squid. Aperture reduction during mantle contraction increases propulsive efficiency at all squid sizes, although 1 mm squid still suffer from low efficiency (20%) because of a limited speed of contraction. Efficiency increases to a peak of 40% for 1 cm squid, then slowly declines. Squid larger than 6 cm must either reduce contraction speed or increase aperture size to maintain stress within maximal muscle tolerance. Ecological pressure to maintain maximum velocity may lead them to increase aperture size, which reduces efficiency. This effect might be ameliorated by nonaxial flow during the refill phase of the cycle. Our model's predictions highlight areas for future empirical work, and emphasize the existence of complex behavioral options for maximizing efficiency at both very small and large sizes.

  10. Tailorable Zero-Phase Delay of Subwavelength Particles toward Miniaturized Wave Manipulation Devices.

    PubMed

    Zhao, Qian; Xiao, Zongqi; Zhang, Fuli; Ma, Junming; Qiao, Ming; Meng, Yonggang; Lan, Chuwen; Li, Bo; Zhou, Ji; Zhang, Peng; Shen, Nian-Hai; Koschny, Thomas; Soukoulis, Costas M

    2015-10-28

    Adjustable zero-phase delay and equiphase control are demonstrated in single and multilayer dielectric particle arrays with high index and low loss. The polarization-independent near-zero permeability is the origin of the wave control near the first Mie magnetic resonance. The proposed design paves the way for subwavelength devices and opens up new avenues for the miniaturization and integration of THz and optical components.

  11. Ultrafast optical control of terahertz surface plasmons in subwavelength hole-arrays at room temperature

    NASA Astrophysics Data System (ADS)

    Azad, Abul K.; Chen, Hou-Tong; Taylor, Antoinette J.; Zhang, Weili; O'Hara, John F.

    2011-02-01

    Extraordinary optical transmission through subwavelength metallic hole-arrays has been an active research area since its first demonstration. The frequency selective resonance properties of subwavelength metallic hole arrays, generally known as surface plasmon polaritons, have potential use in functional plasmonic devices such as filters, modulators, switches, etc. Such plasmonic devices are also very promising for future terahertz applications. Ultrafast switching or modulation of the resonant behavior of the 2-D metallic arrays in terahertz frequencies is of particular interest for high speed communication and sensing applications. In this paper, we demonstrate ultrafast optical control of surface plasmon enhanced resonant terahertz transmission in two-dimensional subwavelength metallic hole arrays fabricated on gallium arsenide based substrates. Optically pumping the arrays creates a thin conductive layer in the substrate reducing the terahertz transmission amplitude of both the resonant mode and the direct transmission. Under low optical fluence, the terahertz transmission is more greatly affected by resonance damping than by propagation loss in the substrate. An ErAs:GaAs nanoisland superlattice substrate is shown to allow ultrafast control with a switching recovery time of ~10 ps. We also present resonant terahertz transmission in a hybrid plasmonic film comprised of an integrated array of subwavelength metallic islands and semiconductor hole arrays. Optically pumping the semiconductor hole arrays favors excitation of surface plasmon resonance. A large dynamic transition between a dipolar localized surface plasmon mode and a surface plasmon resonance near 0.8 THz is observed under near infrared optical excitation. The reversal in transmission amplitude from a stop-band to a pass-band and up to π/ 2 phase shift achieved in the hybrid plasmonic film make it promising in large dynamic phase modulation, optical changeover switching, and active terahertz

  12. Direct measurement of sub-wavelength interference using thermal light and photon-number-resolved detection

    SciTech Connect

    Zhai, Yanhua E-mail: jfan@nist.gov; Fan, Jingyun E-mail: jfan@nist.gov; Migdall, Alan; Becerra, Francisco E.

    2014-09-08

    We examine thermal light diffracted through a double slit using photon-number-resolved detection to directly measure high-order spatial correlations, and we see sinusoidal modulations of those correlations. The fringe width can, in principal, be made arbitrarily small, and we have experimentally obtained fringe widths as small as 30 nm with 800 nm wavelength light. This extreme sub-wavelength resolution, along with this direct detection technique, offers potential for high precision measurement applications.

  13. Direct measurement of sub-wavelength interference using thermal light and photon-number-resolved detection

    NASA Astrophysics Data System (ADS)

    Zhai, Yanhua; Becerra, Francisco E.; Fan, Jingyun; Migdall, Alan

    2014-09-01

    We examine thermal light diffracted through a double slit using photon-number-resolved detection to directly measure high-order spatial correlations, and we see sinusoidal modulations of those correlations. The fringe width can, in principal, be made arbitrarily small, and we have experimentally obtained fringe widths as small as 30 nm with 800 nm wavelength light. This extreme sub-wavelength resolution, along with this direct detection technique, offers potential for high precision measurement applications.

  14. Ultrafast optical control of terahertz surface plasmons in subwavelength hole-arrays at room temperature

    SciTech Connect

    Azad, Abul Kalam; Chen, Hou - Tong; Taylor, Antoinette; O' Hara, John

    2010-12-10

    Extraordinary optical transmission through subwavelength metallic hole-arrays has been an active research area since its first demonstration. The frequency selective resonance properties of subwavelength metallic hole arrays, generally known as surface plasmon polaritons, have potential use in functional plasmonic devices such as filters, modulators, switches, etc. Such plasmonic devices are also very promising for future terahertz applications. Ultrafast switching or modulation of the resonant behavior of the 2-D metallic arrays in terahertz frequencies is of particular interest for high speed communication and sensing applications. In this paper, we demonstrate optical control of surface plasmon enhanced resonant terahertz transmission in two-dimensional subwavelength metallic hole arrays fabricated on gallium arsenide based substrates. Optically pumping the arrays creates a conductive layer in the substrate reducing the terahertz transmission amplitude of both the resonant mode and the direct transmission. Under low optical fluence, the terahertz transmission is more greatly affected by resonance damping than by propagation loss in the substrate. An ErAs:GaAs nanoisland superlattice substrate is shown to allow ultrafast control with a switching recovery time of {approx}10 ps. We also present resonant terahertz transmission in a hybrid plasmonic film comprised of an integrated array of subwavelength metallic islands and semiconductor holes. A large dynamic transition between a dipolar localized surface plasmon mode and a surface plasmon resonance near 0.8 THz is observed under near infrared optical excitation. The reversal in transmission amplitude from a stopband to a passband and up to {pi}/2 phase shift achieved in the hybrid plasmonic film make it promising in large dynamic phase modulation, optical changeover switching, and active terahertz plasmonics.

  15. Multifunctional bowtie-shaped ridge aperture for overlay alignment in plasmonic direct writing lithography using a contact probe.

    PubMed

    Oh, Seonghyeon; Lee, Taekyong; Hahn, Jae W

    2013-07-01

    We propose a scheme of overlay alignment for plasmonic lithography using a scanning contact probe. Using two resonances of a ridge aperture in a metal film, we introduce the aperture's multifunctional characteristics for patterning and alignment at different wavelengths. To verify this idea, we measure an image of an alignment mark using a scanning ridge aperture and determine the reference point for the alignment. We then analyze the uncertainty of the alignment method with respect to the image data noise and compare the numerical results with the experimental results. The uncertainty of the overlay alignment method is shown to be less than approximately 2 nm.

  16. Extraordinary light transmission through opaque thin metal film with subwavelength holes blocked by metal disks.

    PubMed

    Li, Wen-Di; Hu, Jonathan; Chou, Stephen Y

    2011-10-10

    We observed that when subwavelength-sized holes in an optically opaque metal film are completely covered by opaque metal disks larger than the holes, the light transmission through the holes is not reduced, but rather enhanced. Particularly we report (i) the observation of light transmission through the holes blocked by the metal disks up to 70% larger than the unblocked holes; (ii) the observation of tuning the light transmission by varying the coupling strength between the blocking disks and the hole array, or by changing the size of the disks and holes; (iii) the observation and simulation that the metal disk blocker can improve light coupling from free space to a subwavelength hole; and (iv) the simulation that shows the light transmission through subwavelength holes can be enhanced, even though the gap between the disk and the metal film is partially connected with a metal. We believe these finding should have broad and significant impacts and applications to optical systems in many fields.

  17. Exploiting spatiotemporal degrees of freedom for far-field subwavelength focusing using time reversal in fractals

    NASA Astrophysics Data System (ADS)

    Dupré, Matthieu; Lemoult, Fabrice; Fink, Mathias; Lerosey, Geoffroy

    2016-05-01

    Materials which possess a high local density of states varying at a subwavelength scale theoretically permit the focusing of waves onto focal spots much smaller than the free space wavelength. To do so, metamaterials—manmade composite media exhibiting properties not available in nature—are usually considered. However, this approach is limited to narrow bandwidths due to their resonant nature. Here, we prove that it is possible to use a fractal resonator alongside time reversal to focus microwaves onto λ /15 subwavelength focal spots from the far field, on extremely wide bandwidths. We first numerically prove that this approach can be realized using a multiple-channel time reversal mirror that utilizes all the degrees of freedom offered by the fractal resonator. Then, we experimentally demonstrate that this approach can be drastically simplified by coupling the fractal resonator to a complex medium, here a cavity, that efficiently converts its spatial degrees of freedom into temporal ones. This makes it possible to achieve deep subwavelength focusing of microwave radiation by time reversing a single channel. Our method can be generalized to other systems coupling complex media and fractal resonators.

  18. Evolutionary optimization of compact dielectric lens for farfield sub-wavelength imaging

    PubMed Central

    Zhang, Jingjing

    2015-01-01

    The resolution of conventional optical lenses is limited by diffraction. For decades researchers have made various attempts to beat the diffraction limit and realize subwavelength imaging. Here we present the approach to design modified solid immersion lenses that deliver the subwavelength information of objects into the far field, yielding magnified images. The lens is composed of an isotropic dielectric core and anisotropic or isotropic dielectric matching layers. It is designed by combining a transformation optics forward design with an inverse design scheme, where an evolutionary optimization procedure is applied to find the material parameters for the matching layers. Notably, the total radius of the lens is only 2.5 wavelengths and the resolution can reach λ/6. Compared to previous approaches based on the simple discretized approximation of a coordinate transformation design, our method allows for much more precise recovery of the information of objects, especially for those with asymmetric shapes. It allows for the far-field subwavelength imaging at optical frequencies with compact dielectric devices. PMID:26017657

  19. Subwavelength silicon through-hole arrays as an all-dielectric broadband terahertz gradient index metamaterial

    SciTech Connect

    Park, Sang-Gil; Jeong, Ki-Hun; Lee, Kanghee; Han, Daehoon; Ahn, Jaewook

    2014-09-01

    Structuring at subwavelength scales brings out artificial media with anomalous optical features called metamaterials. All-dielectric metamaterials have high potential for practical applications over the whole electromagnetic spectrum owing to low loss and optical isotropy. Here, we report subwavelength silicon through-hole arrays as an all-dielectric gradient index metamaterial with broadband THz operation. The unit cell consists of a single subwavelength through-hole on highly resistive monocrystalline silicon. Depending on the fill-factor and period, the effective index was linearly modulated at 0.3–1.6 THz. The experimental results also demonstrate silicon gradient refractive index (Si-GRIN) lenses with parabolic index profiles through the spatial modification of a single unit cell along the radial direction. Si-GRIN lenses either focus 0.4–1.6 THz beam to the diffraction-limit or serve as a flat and thin solid immersion lens on the backside of THz photoconductive antenna for highly efficient pulse extraction. This all-dielectric gradient index metamaterial opens up opportunities for integrated THz GRIN optics.

  20. Class of near-perfect coded apertures

    NASA Technical Reports Server (NTRS)

    Cannon, T. M.; Fenimore, E. E.

    1977-01-01

    Coded aperture imaging of gamma ray sources has long promised an improvement in the sensitivity of various detector systems. The promise has remained largely unfulfilled, however, for either one of two reasons. First, the encoding/decoding method produces artifacts, which even in the absence of quantum noise, restrict the quality of the reconstructed image. This is true of most correlation-type methods. Second, if the decoding procedure is of the deconvolution variety, small terms in the transfer function of the aperture can lead to excessive noise in the reconstructed image. It is proposed to circumvent both of these problems by use of a uniformly redundant array (URA) as the coded aperture in conjunction with a special correlation decoding method.

  1. Solar energy apparatus with apertured shield

    NASA Technical Reports Server (NTRS)

    Collings, Roger J. (Inventor); Bannon, David G. (Inventor)

    1989-01-01

    A protective apertured shield for use about an inlet to a solar apparatus which includesd a cavity receiver for absorbing concentrated solar energy. A rigid support truss assembly is fixed to the periphery of the inlet and projects radially inwardly therefrom to define a generally central aperture area through which solar radiation can pass into the cavity receiver. A non-structural, laminated blanket is spread over the rigid support truss in such a manner as to define an outer surface area and an inner surface area diverging radially outwardly from the central aperture area toward the periphery of the inlet. The outer surface area faces away from the inlet and the inner surface area faces toward the cavity receiver. The laminated blanket includes at least one layer of material, such as ceramic fiber fabric, having high infra-red emittance and low solar absorption properties, and another layer, such as metallic foil, of low infra-red emittance properties.

  2. Axial superresolution by synthetic aperture generation

    NASA Astrophysics Data System (ADS)

    Micó, V.; García, J.; Zalevsky, Z.

    2008-12-01

    The use of tilted illumination onto the input object in combination with time multiplexing is a useful technique to overcome the Abbe diffraction limit in imaging systems. It is based on the generation of an expanded synthetic aperture that improves the cutoff frequency (and thus the resolution limit) of the imaging system. In this paper we present an experimental validation of the fact that the generation of a synthetic aperture improves not only the lateral resolution but also the axial one. Thus, it is possible to achieve higher optical sectioning of three-dimensional (3D) objects than that defined by the theoretical resolution limit imposed by diffraction. Experimental results are provided for two different cases: a synthetic object (micrometer slide) imaged by a 0.14 numerical aperture (NA) microscope lens, and a biosample (swine sperm cells) imaged by a 0.42 NA objective.

  3. Near-field to far-field characterization of speckle patterns generated by disordered nanomaterials.

    PubMed

    Parigi, Valentina; Perros, Elodie; Binard, Guillaume; Bourdillon, Céline; Maître, Agnès; Carminati, Rémi; Krachmalnicoff, Valentina; De Wilde, Yannick

    2016-04-01

    We study the intensity spatial correlation function of optical speckle patterns above a disordered dielectric medium in the multiple scattering regime. The intensity distributions are recorded by scanning near-field optical microscopy (SNOM) with sub-wavelength spatial resolution at variable distances from the surface in a range which spans continuously from the near-field (distance ≪ λ) to the far-field regime (distance ≫ λ). The non-universal behavior at sub-wavelength distances reveals the connection between the near-field speckle pattern and the internal structure of the medium. PMID:27136995

  4. Micro-fabrication considerations for MEMS-based reconfigurable antenna apertures: with emphasis on DC bias network

    NASA Astrophysics Data System (ADS)

    Moghadas, Hamid; Mousavi, Pedram; Daneshmand, Mojgan

    2016-11-01

    This note addresses the main challenges involved in monolithic micro-fabrication of large capacitive-MEMS-based reconfigurable electromagnetic apertures in antenna applications. The fabrication of a large DC bias line network, and also the metallic features in such apertures, requires special attention and optimization. It is shown that the choice of DC bias network material can impact DC and RF performance of the structure, and a trade-off between switching time and radiation pattern integrity should be considered.

  5. Large-Aperture Wide-Bandwidth Anti-Reflection-Coated Silicon Lenses for Millimeter Wavelengths

    NASA Technical Reports Server (NTRS)

    Datta, R.; Munson, C. D.; Niemack, M. D.; McMahon, J. J.; Britton, J.; Wollack, E. J.; Beall, J.; Devlin, M. J.; Fowler, J.; Gallardo, P.; Hubmayr, J.; Irwin, K.; Newburgh, L.; Nibarger, J. P.; Page, L.; Quijada, M. A.; Schmitt, B. L.; Staggs, S. T.; Thornton, R.; Zhang, L.

    2013-01-01

    The increasing scale of cryogenic detector arrays for sub-millimeter and millimeter wavelength astrophysics has led to the need for large aperture, high index of refraction, low loss, cryogenic refracting optics. Silicon with n = 3.4, low loss, and relatively high thermal conductivity is a nearly optimal material for these purposes, but requires an antireflection (AR) coating with broad bandwidth, low loss, low reflectance, and a matched coffecient of thermal expansion. We present an AR coating for curved silicon optics comprised of subwavelength features cut into the lens surface with a custom three axis silicon dicing saw. These features constitute a metamaterial that behaves as a simple dielectric coating. We have fabricated and coated silicon lenses as large as 33.4 cm in diameter with coatings optimized for use between 125-165 GHz. Our design reduces average reflections to a few tenths of a percent for angles of incidence up to 30 deg. with low cross-polarization. We describe the design, tolerance, manufacture, and measurements of these coatings and present measurements of the optical properties of silicon at millimeter wavelengths at cryogenic and room temperatures. This coating and lens fabrication approach is applicable from centimeter to sub-millimeter wavelengths and can be used to fabricate coatings with greater than octave bandwidth.

  6. Large-aperture Wide-bandwidth Antireflection-coated Silicon Lenses for Millimeter Wavelengths

    NASA Technical Reports Server (NTRS)

    Datta, R.; Munson, C. D.; Niemack, M. D.; McMahon, J. J.; Britton, J.; Wollack, Edward J.; Beall, J.; Devlin, M. J.; Fowler, J.; Gallardo, P.; Hubmayr, J.; Irwin, K.; Newburgh, L.; Nibarger, J. P.; Page, L.; Quijada, Manuel A.; Schmitt, B. L.; Staggs, S. T.; Thornton, R.; Zhang, L.

    2013-01-01

    The increasing scale of cryogenic detector arrays for submillimeter and millimeter wavelength astrophysics has led to the need for large aperture, high index of refraction, low loss, cryogenic refracting optics. Silicon with n 3.4, low loss, and high thermal conductivity is a nearly optimal material for these purposes but requires an antireflection (AR) coating with broad bandwidth, low loss, low reflectance, and a matched coefficient of thermal expansion. We present an AR coating for curved silicon optics comprised of subwavelength features cut into the lens surface with a custom three-axis silicon dicing saw. These features constitute a metamaterial that behaves as a simple dielectric coating.We have fabricated silicon lenses as large as 33.4 cm in diameter with micromachined layers optimized for use between 125 and 165 GHz. Our design reduces average reflections to a few tenths of a percent for angles of incidence up to 30deg with low cross polarization.We describe the design, tolerance, manufacture, and measurements of these coatings and present measurements of the optical properties of silicon at millimeter wavelengths at cryogenic and room temperatures. This coating and lens fabrication approach is applicable from centimeter to submillimeter wavelengths and can be used to fabricate coatings with greater than octave bandwidth.

  7. PDII- Additional discussion of the dynamic aperture

    SciTech Connect

    Norman M. Gelfand

    2002-07-23

    This note is in the nature of an addition to the dynamic aperture calculations found in the report on the Proton Driver, FERMILAB-TM-2169. A extensive discussion of the Proton Driver lattice, as well as the nomenclature used to describe it can be found in TM-2169. Basically the proposed lattice is a racetrack design with the two arcs joined by two long straight sections. The straight sections are dispersion free. Tracking studies were undertaken with the objective of computing the dynamic aperture for the lattice and some of the results have been incorporated into TM-2169. This note is a more extensive report of those calculations.

  8. Synthetic aperture radar capabilities in development

    SciTech Connect

    Miller, M.

    1994-11-15

    The Imaging and Detection Program (IDP) within the Laser Program is currently developing an X-band Synthetic Aperture Radar (SAR) to support the Joint US/UK Radar Ocean Imaging Program. The radar system will be mounted in the program`s Airborne Experimental Test-Bed (AETB), where the initial mission is to image ocean surfaces and better understand the physics of low grazing angle backscatter. The Synthetic Aperture Radar presentation will discuss its overall functionality and a brief discussion on the AETB`s capabilities. Vital subsystems including radar, computer, navigation, antenna stabilization, and SAR focusing algorithms will be examined in more detail.

  9. Synthesis aperture femtosecond-pulsed digital holography

    NASA Astrophysics Data System (ADS)

    Zhu, Linwei; Sun, Meiyu; Chen, Jiannong; Yu, Yongjiang; Zhou, Changhe

    2013-09-01

    A new aperture-synthesis approach in femtosecond-pulse digital holography for obtaining a high-resolution and a whole field of view of the reconstructed image is proposed. The subholograms are recorded only by delay scanning holograms that have different delay times between the object and reference beams. In addition, by using image processing techniques, the synthesis aperture digital hologram can be superposed accurately. Analysis and experimental results show that the walk-off in femtosecond off-axis digital holography caused by low coherent can be well eliminated. The resolution and the field of view of the reconstructed image can be improved effectively.

  10. Optical binary image encryption using aperture-key and dual wavelengths.

    PubMed

    Wang, Xiaogang; Chen, Wen; Chen, Xudong

    2014-11-17

    We described a method where the secret binary image that has been encoded into a single amplitude pattern in Fresnel domain can be recovered based on phase retrieval with an aperture-key and wavelength keys, and no holographic recording is needed in the encryption. The predesigned aperture-key not only realizes the intensity modulation of the encrypted image, but also helps to retrieve the secret image with high quality. All the necessary decryption keys can be kept in digital form that facilitates data transmission and loading in image retrieval process. Numerical simulation results are given for testing the validity and security of the proposed approach.

  11. Coded aperture imaging with self-supporting uniformly redundant arrays. [Patent application

    DOEpatents

    Fenimore, E.E.

    1980-09-26

    A self-supporting uniformly redundant array pattern for coded aperture imaging. The invention utilizes holes which are an integer times smaller in each direction than holes in conventional URA patterns. A balance correlation function is generated where holes are represented by 1's, nonholes are represented by -1's, and supporting area is represented by 0's. The self-supporting array can be used for low energy applications where substrates would greatly reduce throughput.

  12. Radiation safety considerations in proton aperture disposal.

    PubMed

    Walker, Priscilla K; Edwards, Andrew C; Das, Indra J; Johnstone, Peter A S

    2014-04-01

    Beam shaping in scattered and uniform scanned proton beam therapy (PBT) is made commonly by brass apertures. Due to proton interactions, these devices become radioactive and could pose safety issues and radiation hazards. Nearly 2,000 patient-specific devices per year are used at Indiana University Cyclotron Operations (IUCO) and IU Health Proton Therapy Center (IUHPTC); these devices require proper guidelines for disposal. IUCO practice has been to store these apertures for at least 4 mo to allow for safe transfer to recycling contractors. The devices require decay in two staged secure locations, including at least 4 mo in a separate building, at which point half are ready for disposal. At 6 mo, 20-30% of apertures require further storage. This process requires significant space and manpower and should be considered in the design process for new clinical facilities. More widespread adoption of pencil beam or spot scanning nozzles may obviate this issue, as apertures then will no longer be necessary.

  13. Aperture synthesis imaging from the moon

    NASA Technical Reports Server (NTRS)

    Burns, Jack O.

    1991-01-01

    Four candidate imaging aperture synthesis concepts are described for possible emplacement on the moon beginning in the next decade. These include an optical interferometer with 10 microarcsec resolution, a submillimeter array with 6 milliarcsec resolution, a moon-earth VLBI experiment, and a very low frequency interferometer in lunar orbit.

  14. Perceiving Affordances for Fitting through Apertures

    ERIC Educational Resources Information Center

    Ishak, Shaziela; Adolph, Karen E.; Lin, Grace C.

    2008-01-01

    Affordances--possibilities for action--are constrained by the match between actors and their environments. For motor decisions to be adaptive, affordances must be detected accurately. Three experiments examined the correspondence between motor decisions and affordances as participants reached through apertures of varying size. A psychophysical…

  15. Clutter free synthetic aperture radar correlator

    NASA Technical Reports Server (NTRS)

    Jain, A.

    1977-01-01

    A synthetic aperture radar correlation system including a moving diffuser located at the image plane of a radar processor is described. The output of the moving diffuser is supplied to a lens whose impulse response is at least as wide as that of the overall processing system. A significant reduction in clutter results is given.

  16. A modular approach toward extremely large apertures

    NASA Astrophysics Data System (ADS)

    Woods, A. A., Jr.

    1981-02-01

    Modular antenna construction can provide a significant increase in reflector aperture size over deployable reflectors. The modular approach allows reflective mesh surfaces to be supported by a minimum of structure. The kinematics of the selected deployable design approach were validated by the subscale demonstration model. Further design refinements on the module structural/joints and design optimization on intermodule joints are needed.

  17. Depolarization by high-aperture focusing

    NASA Astrophysics Data System (ADS)

    Bahlmann, Karsten; Hell, Stefan W.

    2002-05-01

    We propose and demonstrate a method employing ferroelectric monomolecular layers, by which it is possible to precisely measure the planar light field polarization in the focus of a lens. This method allowed us to establish for the first time to our knowledge, the perpendicularly oriented field that is anticipated at high apertures. For a numerical aperture 1.4 oil immersion lens illuminated with linearly polarized plane waves, the integral of the modulus square of the perpendicular component amounts to (1.51r0.2) % of that of the initial polarization. It is experimentally proven that depolarization decreases with decreasing aperture angle and increases when using annular apertures. Annuli formed by a central obstruction with a diameter of 89 % of that of the entrance pupil raise the integral to 5.5 %. This compares well with the value of 5.8% predicted by electromagnetic focusing theory; however, the depolarization is also due to imperfections connected with focusing by refraction. Besides fluorescence microscopy and single molecule spectroscopy, the measured intensity of the depolarized component in the focal plane is relevant to all forms of light spectroscopy combining strong focusing with polarization analysis.

  18. Agile multiple aperture imager receiver development

    NASA Astrophysics Data System (ADS)

    Lees, David E. B.; Dillon, Robert F.

    1990-02-01

    A variety of unconventional imaging schemes have been investigated in recent years that rely on small, unphased optical apertures (subaperture) to measure properties of an incoming optical wavefront and recover images of distant objects without using precisely figured, large aperture optical elements. Such schemes offer several attractive features. They provide the potential to create very lare effective aperture that are expandable over time and can be launched into space in small pieces. Since the subapertures are identical in construction, they may be mass producible at potentially low cost. A preliminary design for a practical low cost optical receiver is presented. The multiple aperture design has high sensitivity, wide field-of-view, and is lightweight. A combination of spectral, temporal, and spatial background suppression are used to achieve daytime operation at low signal levels. Modular packaging to make the number of receiver subapertures conveniently scalable is also presented. The design is appropriate to a ground-base proof-of-concept experiment for long range active speckle imaging.

  19. Interdisciplinary science with large aperture detectors

    NASA Astrophysics Data System (ADS)

    Wiencke, Lawrence

    2013-06-01

    Large aperture detector systems to measure high energy cosmic rays also offer unique opportunities in other areas of science. Disciplines include geophysics such as seismic and volcanic activity, and atmospheric science ranging from clouds to lightning to aerosols to optical transients. This paper will discuss potential opportunities based on the ongoing experience of the Pierre Auger Observatory.

  20. Radiation safety considerations in proton aperture disposal.

    PubMed

    Walker, Priscilla K; Edwards, Andrew C; Das, Indra J; Johnstone, Peter A S

    2014-04-01

    Beam shaping in scattered and uniform scanned proton beam therapy (PBT) is made commonly by brass apertures. Due to proton interactions, these devices become radioactive and could pose safety issues and radiation hazards. Nearly 2,000 patient-specific devices per year are used at Indiana University Cyclotron Operations (IUCO) and IU Health Proton Therapy Center (IUHPTC); these devices require proper guidelines for disposal. IUCO practice has been to store these apertures for at least 4 mo to allow for safe transfer to recycling contractors. The devices require decay in two staged secure locations, including at least 4 mo in a separate building, at which point half are ready for disposal. At 6 mo, 20-30% of apertures require further storage. This process requires significant space and manpower and should be considered in the design process for new clinical facilities. More widespread adoption of pencil beam or spot scanning nozzles may obviate this issue, as apertures then will no longer be necessary. PMID:24562073

  1. An Electroactive, Tunable, and Frequency Selective Surface Utilizing Highly Stretchable Dielectric Elastomer Actuators Based on Functionally Antagonistic Aperture Control.

    PubMed

    Choi, Jun-Ho; Ahn, Jaeho; Kim, Jin-Bong; Kim, Young-Cheol; Lee, Jung-Yong; Oh, Il-Kwon

    2016-04-13

    An active, frequency selective surface utilizing a silver-nanowire-coated dielectric elastomer with a butterfly-shaped aperture pattern is realized by properly exploiting the electroactive control of two antagonistic functions (stretching vs compression) on a patterned dielectric elastomer actuator. PMID:26864249

  2. Sub-wavelength Laser Nanopatterning using Droplet Lenses

    NASA Astrophysics Data System (ADS)

    Duocastella, Martí; Florian, Camilo; Serra, Pere; Diaspro, Alberto

    2015-11-01

    When a drop of liquid falls onto a screen, e.g. a cell phone, the pixels lying underneath appear magnified. This lensing effect is a combination of the curvature and refractive index of the liquid droplet. Here, the spontaneous formation of such lenses is exploited to overcome the diffraction limit of a conventional laser direct-writing system. In particular, micro-droplets are first laser-printed at user-defined locations on a surface and they are later used as lenses to focus the same laser beam. Under conditions described herein, nanopatterns can be obtained with a reduction in spot size primarily limited by the refractive index of the liquid. This all-optics approach is demonstrated by writing arbitrary patterns with a feature size around 280 nm, about one fourth of the processing wavelength.

  3. Sub-wavelength Laser Nanopatterning using Droplet Lenses

    PubMed Central

    Duocastella, Martí; Florian, Camilo; Serra, Pere; Diaspro, Alberto

    2015-01-01

    When a drop of liquid falls onto a screen, e.g. a cell phone, the pixels lying underneath appear magnified. This lensing effect is a combination of the curvature and refractive index of the liquid droplet. Here, the spontaneous formation of such lenses is exploited to overcome the diffraction limit of a conventional laser direct-writing system. In particular, micro-droplets are first laser-printed at user-defined locations on a surface and they are later used as lenses to focus the same laser beam. Under conditions described herein, nanopatterns can be obtained with a reduction in spot size primarily limited by the refractive index of the liquid. This all-optics approach is demonstrated by writing arbitrary patterns with a feature size around 280 nm, about one fourth of the processing wavelength. PMID:26541765

  4. Buckling-induced retraction of spherical shells: A study on the shape of aperture

    PubMed Central

    Lin, Sen; Xie, Yi Min; Li, Qing; Huang, Xiaodong; Zhou, Shiwei

    2015-01-01

    Buckling of soft matter is ubiquitous in nature and has attracted increasing interest recently. This paper studies the retractile behaviors of a spherical shell perforated by sophisticated apertures, attributed to the buckling-induced large deformation. The buckling patterns observed in experiments were reproduced in computational modeling by imposing velocity-controlled loads and eigenmode-affine geometric imperfection. It was found that the buckling behaviors were topologically sensitive with respect to the shape of dimple (aperture). The shell with rounded-square apertures had the maximal volume retraction ratio as well as the lowest energy consumption. An effective experimental procedure was established and the simulation results were validated in this study. PMID:26096171

  5. High power 808 nm vertical cavity surface emitting laser with multi-ring-shaped-aperture structure

    NASA Astrophysics Data System (ADS)

    Hao, Y. Q.; Shang, C. Y.; Feng, Y.; Yan, C. L.; Zhao, Y. J.; Wang, Y. X.; Wang, X. H.; Liu, G. J.

    2011-02-01

    The carrier conglomeration effect has been one of the main problems in developing electrically pumped high power vertical cavity surface emitting laser (VCSEL) with large aperture. We demonstrate a high power 808 nm VCSEL with multi-ring-shaped-aperture (MRSA) to weaken the carrier conglomeration effect. Compared with typical VCSEL with single large aperture (SLA), the 300-μm-diameter VCSEL with MRSA has more uniform near field and far field patterns. Moreover, MRSA laser exhibits maximal CW light output power 0.3 W which is about 3 times that of SLA laser. And the maximal wall-plug efficiency of 17.4% is achieved, higher than that of SLA laser by 10%.

  6. RF Performance of Membrane Aperture Shells

    NASA Technical Reports Server (NTRS)

    Flint, Eirc M.; Lindler, Jason E.; Thomas, David L.; Romanofsky, Robert

    2007-01-01

    This paper provides an overview of recent results establishing the suitability of Membrane Aperture Shell Technology (MAST) for Radio Frequency (RF) applications. These single surface shells are capable of maintaining their figure with no preload or pressurization and minimal boundary support, yet can be compactly roll stowed and passively self deploy. As such, they are a promising technology for enabling a future generation of RF apertures. In this paper, we review recent experimental and numerical results quantifying suitable RF performance. It is shown that candidate materials possess metallic coatings with sufficiently low surface roughness and that these materials can be efficiently fabricated into RF relevant doubly curved shapes. A numerical justification for using a reflectivity metric, as opposed to the more standard RF designer metric of skin depth, is presented and the resulting ability to use relatively thin coating thickness is experimentally validated with material sample tests. The validity of these independent film sample measurements are then confirmed through experimental results measuring RF performance for reasonable sized doubly curved apertures. Currently available best results are 22 dBi gain at 3 GHz (S-Band) for a 0.5m aperture tested in prime focus mode, 28dBi gain for the same antenna in the C-Band (4 to 6 GHz), and 36.8dBi for a smaller 0.25m antenna tested at 32 GHz in the Ka-Band. RF range test results for a segmented aperture (one possible scaling approach) are shown as well. Measured antenna system actual efficiencies (relative to the unachievable) ideal for these on axis tests are generally quite good, typically ranging from 50 to 90%.

  7. SU-8 microcantilever with an aperture, fluidic channel, and sensing mechanisms for biological and other applications

    PubMed Central

    Gaitas, Angelo; Hower, Robert W.

    2014-01-01

    We describe a method for fabricating an aperture on a fluidic cantilever device using SU-8 as a structural material. The device can ultimately be used for patch clamping, microinjections, fluidic delivery, fluidic deposition, and micromaterial removal. In the first generation of this device, the initial aperture diameter is 10 μm and is fabricated on a silicon-on-insulator (SOI) wafer that is structurally used to define the aperture. The aperture can be reduced in size through mask design. This self-aligned process allows for patterning on the sharp tip projecting out of the fluidic plane on the cantilever and is batch fabricated, reducing the cost and time for manufacture. The initial mask, SOI device layer thickness, and the width of the base of the tip define the size of the aperture. The SU-8 micromachined cantilever includes an electrode and a force sensing mechanism. The cantilever can be easily integrated with an atomic force microscope or an optical microscope. PMID:25544864

  8. Metallic Nanomesh with Disordered Dual-Size Apertures As Wide-Viewing-Angle Transparent Conductive Electrode.

    PubMed

    Qiu, Tengfei; Luo, Bin; Ali, Fawad; Jaatinen, Esa; Wang, Lianzhou; Wang, Hongxia

    2016-09-01

    With the rapid development of display-related markets, transparent conductive films (TCFs) with wide viewing angles, high transmittance and low sheet resistance are in high demand. However, as a promising TCF material, metallic membranes with a submicrometer-sized periodicity pattern fabricated by currently available techniques always reveal the angle-dependent structure color which can be a major issue in the development of wide-angle viewing display-related applications. In this work, we demonstrate an Au nanomesh with disordered dual-size apertures as a novel TCF with wide viewing angles which is made via a modified nanosphere lithography technique. The as-prepared Au nanomesh film shows good optoelectronic properties (Rs = 160 Ω sq(-1), T = 80%; Rs = 8 Ω sq(-1), T = 57%) that are similar to the Au nanomesh with single size apertures, while the former exhibits excellent wide-angle viewing performance. There is no obvious change in the film when the viewing angle, the light incidence angle or the orientation of substrate vary in the range of 0-90°. In contrast, a rainbow color is observed with the film with ordered single-size apertures. Electrochromic devices based on the novel metallic film show more uniform color distribution than the devices based on metallic film with ordered single-size apertures under indoor natural light irradiation. These findings demonstrate the applicability of the Au nanomesh film with dual-size apertures in enhancing display quality of high-performance optoelectronic devices.

  9. Metallic Nanomesh with Disordered Dual-Size Apertures As Wide-Viewing-Angle Transparent Conductive Electrode.

    PubMed

    Qiu, Tengfei; Luo, Bin; Ali, Fawad; Jaatinen, Esa; Wang, Lianzhou; Wang, Hongxia

    2016-09-01

    With the rapid development of display-related markets, transparent conductive films (TCFs) with wide viewing angles, high transmittance and low sheet resistance are in high demand. However, as a promising TCF material, metallic membranes with a submicrometer-sized periodicity pattern fabricated by currently available techniques always reveal the angle-dependent structure color which can be a major issue in the development of wide-angle viewing display-related applications. In this work, we demonstrate an Au nanomesh with disordered dual-size apertures as a novel TCF with wide viewing angles which is made via a modified nanosphere lithography technique. The as-prepared Au nanomesh film shows good optoelectronic properties (Rs = 160 Ω sq(-1), T = 80%; Rs = 8 Ω sq(-1), T = 57%) that are similar to the Au nanomesh with single size apertures, while the former exhibits excellent wide-angle viewing performance. There is no obvious change in the film when the viewing angle, the light incidence angle or the orientation of substrate vary in the range of 0-90°. In contrast, a rainbow color is observed with the film with ordered single-size apertures. Electrochromic devices based on the novel metallic film show more uniform color distribution than the devices based on metallic film with ordered single-size apertures under indoor natural light irradiation. These findings demonstrate the applicability of the Au nanomesh film with dual-size apertures in enhancing display quality of high-performance optoelectronic devices. PMID:27541186

  10. Sparse aperture mask for low order wavefront sensing

    NASA Astrophysics Data System (ADS)

    Subedi, Hari; Zimmerman, Neil T.; Kasdin, N. Jeremy; Cavanagh, Kathleen; Riggs, A. J. E.

    2015-09-01

    A high contrast is required for direct imaging of exoplanets. Ideally, the level of contrast required for direct imaging of exoplanets can be achieved by coronagraphic imaging, but in practice, the contrast is degraded by wavefront aberrations. To achieve the required contrast, low-order wavefront aberrations such as tip-tilt, defocus and coma must be determined and corrected. In this paper, we present a technique that integrates a sparse- aperture mask (SAM) with a shaped pupil coronagraph (SPC) to make precise estimates of these low-order aberrations. Starlight rejected by the coronagraph's focal plane stop is collimated to a relay pupil, where the mask forms an interference fringe pattern on a detector. Using numerical simulations, we show that the SAM can estimate rapidly varying tip-tilt errors in space telescopes arising from line-of-sight pointing oscillations as well as other higher-order modes. We also show that a Kalman filter can be used with the SAM to improve the estimation. At Princetons High Contrast Imaging Laboratory, we have recently created a testbed devoted to low-order wavefront sensing experiments. The testbed incorporates custom-fabricated masks (shaped pupil, focal plane, and sparse aperture) with a deformable mirror and a CCD camera to demonstrate the estimation and correction of low-order aberrations. Our first experiments aim to replicate the results of the SAM wavefront sensor (SAM WFS) Fourier propagation models.

  11. Simultaneous beam sampling and aperture shape optimization for SPORT

    SciTech Connect

    Zarepisheh, Masoud; Li, Ruijiang; Xing, Lei; Ye, Yinyu

    2015-02-15

    Purpose: Station parameter optimized radiation therapy (SPORT) was recently proposed to fully utilize the technical capability of emerging digital linear accelerators, in which the station parameters of a delivery system, such as aperture shape and weight, couch position/angle, gantry/collimator angle, can be optimized simultaneously. SPORT promises to deliver remarkable radiation dose distributions in an efficient manner, yet there exists no optimization algorithm for its implementation. The purpose of this work is to develop an algorithm to simultaneously optimize the beam sampling and aperture shapes. Methods: The authors build a mathematical model with the fundamental station point parameters as the decision variables. To solve the resulting large-scale optimization problem, the authors devise an effective algorithm by integrating three advanced optimization techniques: column generation, subgradient method, and pattern search. Column generation adds the most beneficial stations sequentially until the plan quality improvement saturates and provides a good starting point for the subsequent optimization. It also adds the new stations during the algorithm if beneficial. For each update resulted from column generation, the subgradient method improves the selected stations locally by reshaping the apertures and updating the beam angles toward a descent subgradient direction. The algorithm continues to improve the selected stations locally and globally by a pattern search algorithm to explore the part of search space not reachable by the subgradient method. By combining these three techniques together, all plausible combinations of station parameters are searched efficiently to yield the optimal solution. Results: A SPORT optimization framework with seamlessly integration of three complementary algorithms, column generation, subgradient method, and pattern search, was established. The proposed technique was applied to two previously treated clinical cases: a head and

  12. Fraunhofer diffraction of a slit aperture between a knife-edge and a metal cylinder.

    PubMed

    Fukaya, J; Sasaki, A; Matsuda, Y; Aoyama, H

    1995-12-01

    The Fraunhofer diffraction pattern of a slit aperture formed between a reference knife-edge and a metal-cylinder surface is different from that of an ideal slit aperture. This pattern should include reflected light coming from both the front and rear sides of a cylinder surface. To investigate the influence of light reflected from the cylinder surface, we discuss the theoretical consideration based on the simple model of the reflected light on the surface. The experimental setup is designed and constructed to measure the actual diffraction pattern produced by the slit between the knife-edge and the cylinder surface. As a result it is obvious that the reflection of diffracted light on the rear side is dominant in both the simulation and the experiment.

  13. Metallic nanorods array for magnified subwavelength imaging (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Ohashi, Yoshiro; Ranjan, Bikas; Saito, Yuika; Verma, Prabhat

    2015-08-01

    Earlier, our group proposed a lens made of metallic nanorods, stacked in 3D arrays tapered in a conical shape. This nanolens could theoretically realize super-resolution color imaging in the visible range. The image could be magnified and transferred through metallic nanorods array. Lithography or self-assembly are common ways to fabricate such nanostructured devices. However, to precisely arrange nanorods is challenging due to the limitations to scale down components, and to increase accuracy of assembling particles in large area. Here we experimentally demonstrated 2D nanolens with long chains of metallic nanorods placed at tapered angles in a fan-like shape to magnify images. In the fabrication, we chemically synthesized gold nanorods coated with CTAB surfactant to ensure a 10 nm gap between the rods for the resonance control of nanolens. And we prepared trenches patterned by FIB lithography on a PMMA coated glass substrate. The different hydrophobicity of PMMA and CTAB coats enabled to optimize capillary force in gold nanorod solution and selectively assemble nanorods into hydrophilic trenches. Finally, we obtained 2D nanolens after lift-off of the PMMA layer. We numerically estimated the resonance property of nanorods chain and found a broad peak in the visible range located at a wavelength of 727 nm. The broadness of this peak (~178 nm) confirms that a broad range of wavelength can be resonant with this structure. This phenomenon was also confirmed experimentally by optical measurements. These results show that the combination of lithography and self-assembly has the potential to realize plasmonic nanolens.

  14. Subwavelength Gold Grating as Polarizers Integrated with InP-Based InGaAs Sensors.

    PubMed

    Wang, Rui; Li, Tao; Shao, Xiumei; Li, Xue; Huang, Xiaqi; Shao, Jinhai; Chen, Yifang; Gong, Haimei

    2015-07-01

    There are currently growing needs for polarimetric imaging in infrared wavelengths for broad applications in bioscience, communications and agriculture, etc. Subwavelength metallic gratings are capable of separating transverse magnetic (TM) mode from transverse electric (TE) mode to form polarized light, offering a reliable approach for the detection in polarization way. This work aims to design and fabricate subwavelength gold gratings as polarizers for InP-based InGaAs sensors in 1.0-1.6 μm. The polarization capability of gold gratings on InP substrate with pitches in the range of 200-1200 nm (fixed duty cycle of 0.5) has been systematically studied by both theoretical modeling with a finite-difference time-domain (FDTD) simulator and spectral measurements. Gratings with 200 nm lines/space in 100-nm-thick gold have been fabricated by electron beam lithography (EBL). It was found that subwavelength gold gratings directly integrated on InP cannot be applied as good polarizers, because of the existence of SPP modes in the detection wavelengths. An effective solution has been found by sandwiching the Au/InP bilayer using a 200 nm SiO2 layer, leading to significant improvement in both TM transmission and extinction ratio. At 1.35 μm, the improvement factors are 8 and 10, respectively. Therefore, it is concluded that the Au/SiO2/InP trilayer should be a promising candidate of near-infrared polarizers for the InP-based InGaAs sensors.

  15. Spectral characterization of porous dielectric subwavelength THz fibers fabricated using a microstructured molding technique.

    PubMed

    Dupuis, Alexandre; Mazhorova, Anna; Désévédavy, Frédéric; Rozé, Mathieu; Skorobogatiy, Maksim

    2010-06-21

    We report two novel fabrication techniques, as well as THz spectral transmission and propagation loss measurements of subwavelength plastic wires with highly porous (up to 86%) and non-porous transverse geometries. The two fabrication techniques we describe are based on the microstructured molding approach. In one technique the mold is made completely from silica by stacking and fusing silica capillaries to the bottom of a silica ampoule. The melted material is then poured into the silica mold to cast the microstructured preform. Another approach uses a microstructured mold made of a sacrificial plastic which is co-drawn with a cast preform. Material from the sacrificial mold is then dissolved after fi ber drawing. We also describe a novel THz-TDS setup with an easily adjustable optical path length, designed to perform cutback measurements using THz fibers of up to 50 cm in length. We fi nd that while both porous and non-porous subwavelength fibers of the same outside diameter have low propagation losses (alpha subwavelengths fibers can be very well explained by the onset of material absorption loss at higher frequencies, due to strong confinement of the modal fields in the material region of the fi ber, as well as strong coupling loss at lower frequencies, due to mismatch between the modal field diameter and the size of the gaussian-like beam of a THz source.

  16. Vacuum aperture isolator for retroreflection from laser-irradiated target

    DOEpatents

    Benjamin, Robert F.; Mitchell, Kenneth B.

    1980-01-01

    The disclosure is directed to a vacuum aperture isolator for retroreflection of a laser-irradiated target. Within a vacuum chamber are disposed a beam focusing element, a disc having an aperture and a recollimating element. The edge of the focused beam impinges on the edge of the aperture to produce a plasma which refracts any retroreflected light from the laser's target.

  17. Dual aperture dipole magnet with second harmonic component

    DOEpatents

    Praeg, Walter F.

    1985-01-01

    An improved dual aperture dipole electromagnet includes a second-harmonic frequency magnetic guide field winding which surrounds first harmonic frequency magnetic guide field windings associated with each aperture. The second harmonic winding and the first harmonic windings cooperate to produce resultant magnetic waveforms in the apertures which have extended acceleration and shortened reset portions of electromagnet operation.

  18. Dual aperture dipole magnet with second harmonic component

    DOEpatents

    Praeg, W.F.

    1983-08-31

    An improved dual aperture dipole electromagnet includes a second-harmonic frequency magnetic guide field winding which surrounds first harmonic frequency magnetic guide field windings associated with each aperture. The second harmonic winding and the first harmonic windings cooperate to produce resultant magnetic waveforms in the apertures which have extended acceleration and shortened reset portions of electromagnet operation.

  19. Charge-oscillation-induced light transmission through subwavelength slits and holes

    NASA Astrophysics Data System (ADS)

    Huang, X. R.; Peng, R. W.; Wang, Z.; Gao, F.; Jiang, S. S.

    2007-09-01

    We present a concrete picture of spoof surface plasmons (SSPs) combined with cavity resonance to clarify the basic mechanism underlying extraordinary light transmission through metal films with subwavelength slits or holes. This picture may indicate a general mechanism of metallic nanostructure optics: When light is incident on a nonplanar conducting surface, the free electrons cannot move homogeneously in response to the incident electric field, i.e., their movement can be impeded at the rough parts, forming inhomogeneous charge distributions. The oscillating charges and dipoles then emit photons (similar to Thomson scattering of x rays by oscillating electrons), and the interference between the photons may give rise to anomalous transmission, reflection, or scattering.

  20. High speed low power optical detection of sub-wavelength scatterer

    NASA Astrophysics Data System (ADS)

    Roy, S.; Bouwens, Maryse; Wei, Lei; Pereira, S. F.; Urbach, H. P.; van der Walle, P.

    2015-12-01

    Optical detection of scatterers on a flat substrate, generally done using dark field microscopy technique, is challenging since it requires high power illumination to obtain sufficient SNR (Signal to Noise Ratio) to be able to detect sub-wavelength particles. We developed a bright field technique, based on Fourier scatterometry, with special illumination and detection control to achieve this goal with a power level that can be sustained by most substrates including polymers. The performance of the system in a roll-to-roll line in production environment and strict throughput requirement is shown.

  1. Slot plasmonic waveguide based on doped-GaAs for terahertz deep-subwavelength applications.

    PubMed

    Amarloo, Hadi; Safavi-Naeini, Safieddin

    2015-11-01

    A new plasmonic waveguide for deep-subwavelength field localization at the terahertz (THz) range of frequency is proposed. GaAs with optimum doping level is used as the plasmonic material. The waveguide structure is a narrow slot in a thin GaAs film on top of the quartz substrate. The waveguide characteristics are analyzed, and its dimensions are optimized to minimize the losses. It is shown that the mode size of the proposed waveguide is less than λ/16 by λ/16. The proposed plasmonic waveguide can be a platform for numerous THz plasmonic-based integrated devices, such as integrated sensors and imagers.

  2. High speed low power optical detection of sub-wavelength scatterer.

    PubMed

    Roy, S; Bouwens, Maryse; Wei, Lei; Pereira, S F; Urbach, H P; van der Walle, P

    2015-12-01

    Optical detection of scatterers on a flat substrate, generally done using dark field microscopy technique, is challenging since it requires high power illumination to obtain sufficient SNR (Signal to Noise Ratio) to be able to detect sub-wavelength particles. We developed a bright field technique, based on Fourier scatterometry, with special illumination and detection control to achieve this goal with a power level that can be sustained by most substrates including polymers. The performance of the system in a roll-to-roll line in production environment and strict throughput requirement is shown. PMID:26724010

  3. ZnO subwavelength wires for fast-response mid-infrared detection.

    PubMed

    Dai, Wei; Yang, Qing; Gu, Fuxing; Tong, Limin

    2009-11-23

    Room temperature operating thermal detection for mid-infrared light based on ZnO subwavelength wires has been demonstrated. Electric resistance in ZnO wires increases linearly with the intensity of incident light. Noise equivalent power (NEP) of 5.8 microW/Hz(1/2) (at 1 kHz) with typical response times as fast as 1.3 ms is obtained at 10.6-microm wavelength. The sensitivity and response time of the detector are also found to be insensitive to the ambient.

  4. Sub-wavelength imaging with a left-handed material flat lens

    NASA Astrophysics Data System (ADS)

    Feise, Michael W.; Kivshar, Yuri S.

    2005-01-01

    We study numerically, by means of the pseudospectral time-domain method, the unique features of imaging by a flat lens made of a left-handed metamaterial that possesses the property of negative refraction. We confirm the earlier finding that a left-handed flat lens can provide near-perfect imaging of a point source and a pair of point sources with clear evidence of sub-wavelength resolution. We illustrate the limitation of the resolution in the time-integrated image due to the presence of surface waves.

  5. Enhanced absorption of graphene strips with a multilayer subwavelength grating structure

    SciTech Connect

    Hu, Jin-Hua; Huang, Yong-Qing Duan, Xiao-Feng; Wang, Qi; Zhang, Xia; Wang, Jun; Ren, Xiao-Min

    2014-12-01

    The optical absorption of graphene strips covered on a multilayer subwavelength grating (MSG) surface is theoretically investigated. The absorption of graphene strips with MSG is enhanced in the wavelength range of 1500 nm to 1600 nm by critical coupling, which is associated with the combined effects of a guided resonance of MSG and its photonic band gap effect. The critical coupling of the graphene strips can be controlled by adjusting the incident angle without changing the structural parameters of MSG. The absorption of graphene strips can also be tuned by varying key parameters, such as grating period, strip width, and incident angle.

  6. Plasmonic-dielectric systems for high-order dispersionless slow or stopped subwavelength light.

    PubMed

    Karalis, Aristeidis; Joannopoulos, J D; Soljacić, Marin

    2009-07-24

    A material platform of multilayered surface-plasmon-dielectric-polariton systems is introduced, along with a new physical mechanism enabling simultaneous cancellation of group-velocity and attenuation dispersion to extremely high orders for subwavelength light of any small positive, negative, or zero group velocity. These dispersion-free systems could have significant impact on the development of nanophotonics, e.g., in the design of efficient and very compact delay lines and active devices. The same dispersion-manipulation mechanism can be employed to tailor at will exotic slow-light dispersion relations.

  7. Experimental Realization of Two Decoupled Directional Couplers in a Subwavelength Packing by Adiabatic Elimination.

    PubMed

    Mrejen, Michael; Suchowski, Haim; Hatakeyama, Taiki; Wang, Yuan; Zhang, Xiang

    2015-11-11

    On-chip optical data processing and photonic quantum integrated circuits require the integration of densely packed directional couplers at the nanoscale. However, the inherent evanescent coupling at this length scale severely limits the compactness of such on-chip photonic circuits. Here, inspired by the adiabatic elimination in a N-level atomic system, we report an experimental realization of a pair of directional couplers that are effectively isolated from each other despite their subwavelength packing. This approach opens the way to ultradense arrays of waveguide couplers for integrated optical and quantum logic gates. PMID:26421374

  8. Object Motion with Structured Optical Illumination as a Basis for Far-Subwavelength Resolution

    NASA Astrophysics Data System (ADS)

    Webb, Kevin J.; Chen, Yulu; Smith, Trevor A.

    2016-08-01

    An imaging method based on object motion with structured light illumination and far-field measurement data that results in far-subwavelength image information is proposed. Simulations with realistic noisy data show that this approach will lead to the ability to distinguish object features on the nanometer scale using visible light, without the need for fluorophores. The principle is that far-field measurements with controlled motion in a spatially varying incident field add information about nanometer-scale dimensions and material properties.

  9. Magneto-exciton-polariton condensation in a sub-wavelength high contrast grating based vertical microcavity

    SciTech Connect

    Fischer, J.; Brodbeck, S.; Worschech, L.; Kamp, M.; Schneider, C.; Höfling, S.; Zhang, B.; Wang, Z.; Deng, H.

    2014-03-03

    We comparably investigate the diamagnetic shift of an uncoupled quantum well exciton with a microcavity exciton-polariton condensate on the same device. The sample is composed of multiple GaAs quantum wells in an AlAs microcavity, surrounded by a Bragg reflector and a sub-wavelength high contrast grating reflector. Our study introduces an independent and easily applicable technique, namely, the measurement of the condensate diamagnetic shift, which directly probes matter contributions in polariton condensates and hence discriminates it from a conventional photon laser.

  10. Deep-Subwavelength-Scale Directional Sensing Based on Highly Localized Dipolar Mie Resonances

    NASA Astrophysics Data System (ADS)

    Zhu, Xuefeng; Liang, Bin; Kan, Weiwei; Peng, Yugui; Cheng, Jianchun

    2016-05-01

    This paper reports the formation of highly localized Mie resonances on a closed metasurface encapsulating a rigid core and the realization of directional sensing at deep-subwavelength scale (diameter ˜λ /8 ) with the proposed physical model. Based on modal-expansion and mode-matching methods, it is theoretically shown that the extremely anisotropic metasurface shell can support varied orders of Mie resonances around the rigid core. We further experimentally demonstrate that the Mie resonance with a dipolelike profile is strongly excited under the illumination of a plane wave at low frequencies, enabling the sensitive directional sensing due to the intensified and azimuthally dependent pressure field.

  11. Steering light by a sub-wavelength metallic grating from transformation optics

    PubMed Central

    Xu, Yadong; Fu, Yangyang; Chen, Huanyang

    2015-01-01

    Transformation optics has shown great ability in designing devices with novel functionalities, such as invisibility cloaking. A recent work shows that it can also be used to design metasurfaces which usually come from the concept of phase discontinuities. However, metasurfaces from transformation optics have very complicated material parameters. Here in this work, we propose a practical design, a sub-wavelength metallic grating with discrete and gradient index materials. Such a design not only inherits some functionalities of metasurfaces from phase discontinuities, but also shows richer physics. Our work will also provide a guidance to recent activities of acoustic metasurfaces, especially for those made of extremely anisotropic metamaterials. PMID:26183391

  12. Lensless focusing with subwavelength resolution by direct synthesis of the angular spectrum

    NASA Astrophysics Data System (ADS)

    Hong, Stanley S.; Horn, Berthold K. P.; Freeman, Dennis M.; Mermelstein, Michael S.

    2006-06-01

    We consider the coherent superposition of unfocused wave fronts for lensless focusing of electromagnetic waves with subwavelength resolution. Near the focal point, intensity distributions generated using the approach approximate those generated using lenses. Far from the focal point, discretization of spatial frequencies results in a trade-off between the number of wave fronts and the accuracy of the approximation. We experimentally demonstrate the feasibility of the approach by generating an approximation of an azimuthally polarized Bessel beam with a focal spot diameter (full width at half maximum intensity) of 0.37λ.

  13. Tunable plasmonic enhancement of light scattering and absorption in graphene-coated subwavelength wires

    NASA Astrophysics Data System (ADS)

    Riso, Máximo; Cuevas, Mauro; Depine, Ricardo A.

    2015-07-01

    The electromagnetic response of subwavelength wires coated with a graphene monolayer illuminated by a linearly polarized plane waves is investigated. The results show that the scattering and extinction cross-sections of the coated wire can be dramatically enhanced when the incident radiation resonantly excites localized surface plasmons. The enhancements occur for p-polarized incident waves and for excitation frequencies that correspond to complex poles in the coefficients of the multipole expansion for the scattered field. By dynamically tuning the chemical potential of graphene, the spectral position of the enhancements can be chosen over a wide range.

  14. Triangular lattice of carbon nanotube arrays for negative index of refraction and subwavelength lensing effect

    SciTech Connect

    Wang, Y.; Wang, X.; Rybczynski, J.; Wang, D.Z.; Kempa, K.; Ren, Z.F.

    2005-04-11

    Self-assembly of polystyrene microspheres has been utilized in a two-step masking technique to prepare triangular lattices of catalytic nanodots at low cost. Subsequent triangular lattices of aligned carbon nanotubes on a silicon substrate are achieved by plasma-enhanced chemical vapor deposition. Nickel is used both in the nanodots and in the secondary mask. The triangular lattices of carbon nanotube arrays as two-dimensional photonic crystals show higher geometrical symmetry than the hexagonal lattices previously reported, enabling broader applications including negative index of refraction and subwavelength lensing effect.

  15. Enhanced light coupling in sub-wavelength single-mode silicon on insulator waveguides.

    PubMed

    Pang, C; Gesuele, F; Bruyant, A; Blaize, S; Lérondel, G; Royer, P

    2009-04-27

    We report on NIR efficient end-coupling in single-mode silicon on insulator waveguides. Efficient coupling has been achieved using Polymer-Tipped Optical Fibers (PTOF) of adaptable radius of curvature (ROC). When compared with commercial micro lenses, systematic studies as a function of PTOF ROC, lead for subwavelength PTOF to a coupling factor enhancement as high as 2.5. This experimental behavior is clearly corroborated by radial FDTD simulations and an absolute coupling efficiency of about 50% is also estimated.

  16. Evanescent wave amplification and subwavelength imaging by ultrathin uniaxial μ-near-zero material

    SciTech Connect

    Zhao, Yan

    2014-02-15

    We demonstrate strong evanescent wave amplification by a thin slab of uniaxial μ-near-zero (UMNZ) material. It is found that while retaining the same amplification effect, the slab can be made arbitrarily thin when the negative permeability along the axis of anisotropy approaches zero. Numerical results show that using a single layer of split-ring resonators (SRRs) with its thickness equal three thousandth of the incident wavelength (λ/3000), a subwavelength source distribution with λ/4 resolution can be transferred to a distance of λ/3.

  17. Steering light by a sub-wavelength metallic grating from transformation optics

    NASA Astrophysics Data System (ADS)

    Xu, Yadong; Fu, Yangyang; Chen, Huanyang

    2015-07-01

    Transformation optics has shown great ability in designing devices with novel functionalities, such as invisibility cloaking. A recent work shows that it can also be used to design metasurfaces which usually come from the concept of phase discontinuities. However, metasurfaces from transformation optics have very complicated material parameters. Here in this work, we propose a practical design, a sub-wavelength metallic grating with discrete and gradient index materials. Such a design not only inherits some functionalities of metasurfaces from phase discontinuities, but also shows richer physics. Our work will also provide a guidance to recent activities of acoustic metasurfaces, especially for those made of extremely anisotropic metamaterials.

  18. Improved optical transmission and current matching of a triple-junction solar cell utilizing sub-wavelength structures.

    PubMed

    Chiu, M-Y; Chang, C-H; Tsai, M-A; Chang, F-Y; Yu, Peichen

    2010-09-13

    Sub-wavelength antireflective structures are fabricated on a silicon nitride passivation layer of a Ga₀.₅In₀.₅P/GaAs/Ge triple-junction solar cell using polystyrene nanosphere lithography followed by anisotropic etching. The fabricated structures enhance optical transmission in the ultraviolet wavelength range, compared to a conventional single-layer antireflective coating (ARC). The transmission improvement contributes to an enhanced photocurrent, which is also verified by the external quantum efficiency characterization of the fabricated solar cells. Under one-sun illumination, the short-circuit current of a cell with sub-wavelength structures is enhanced by 46.1% and 3.4% due to much improved optical transmission and current matching, compared to cells without an ARC and with a conventional SiN(x) ARC, respectively. Further optimizations of the sub-wavelength structures including the periodicity and etching depth are conducted by performing comprehensive calculations based on a rigorous couple-wave analysis method.

  19. Adjustment of ablation shapes and subwavelength ripples based on electron dynamics control by designing femtosecond laser pulse trains

    SciTech Connect

    Yuan Yanping; Jiang Lan; Li Xin; Wang Cong

    2012-11-15

    A quantum model is proposed to investigate femtosecond laser pulse trains processing of dielectrics by including the plasma model with the consideration of laser particle-wave duality. Central wavelengths (400 nm and 800 nm) strongly impact the surface plasmon field distribution, the coupling field intensity distribution (between the absorbed intensity and the surface plasma), and the distribution of transient localized free electron density in the material. This, in turn, significantly changes the localized transient optical/thermal properties during laser materials processing. The effects of central wavelengths on ablation shapes and subwavelength ripples are discussed. The simulation results show that: (1) ablation shapes and the spacing of subwavelength ripples can be adjusted by localized transient electron dynamics control using femtosecond laser pulse trains; (2) the adjustment of the radii of ablation shapes is stronger than that of the periods of subwavelength ripples.

  20. Moving receive beam method and apparatus for synthetic aperture radar

    DOEpatents

    Kare, Jordin T.

    2001-01-01

    A method and apparatus for improving the performance of Synthetic Aperture Radar (SAR) systems by reducing the effect of "edge losses" associated with nonuniform receiver antenna gain. By moving the receiver antenna pattern in synchrony with the apparent motion of the transmitted pulse along the ground, the maximum available receiver antenna gain can be used at all times. Also, the receiver antenna gain for range-ambiguous return signals may be reduced, in some cases, by a large factor. The beam motion can be implemented by real-time adjustment of phase shifters in an electronically-steered phased-array antenna or by electronic switching of feed horns in a reflector antenna system.

  1. Wigner analysis of three dimensional pupil with finite lateral aperture

    PubMed Central

    Chen, Hsi-Hsun; Oh, Se Baek; Zhai, Xiaomin; Tsai, Jui-Chang; Cao, Liang-Cai; Barbastathis, George; Luo, Yuan

    2015-01-01

    A three dimensional (3D) pupil is an optical element, most commonly implemented on a volume hologram, that processes the incident optical field on a 3D fashion. Here we analyze the diffraction properties of a 3D pupil with finite lateral aperture in the 4-f imaging system configuration, using the Wigner Distribution Function (WDF) formulation. Since 3D imaging pupil is finite in both lateral and longitudinal directions, the WDF of the volume holographic 4-f imager theoretically predicts distinct Bragg diffraction patterns in phase space. These result in asymmetric profiles of diffracted coherent point spread function between degenerate diffraction and Bragg diffraction, elucidating the fundamental performance of volume holographic imaging. Experimental measurements are also presented, confirming the theoretical predictions. PMID:25836443

  2. Development of a resettable, flexible aperture cover

    NASA Technical Reports Server (NTRS)

    Christiansen, Scott

    1992-01-01

    A flexible aperture cover and latch were developed for the Thermal Ion Detection Experiment (TIDE). The latch utilized a high-output paraffin (HOP) linear motor to supply the force to operate the latch. The initial approach for the cover was to use a heat-treated, coiled strip of 0.05 mm (.002-inch)-thick beryllium-copper as the cover. Development test results showed that one end of the cover developed a trajectory during release that threatened to impact against adjacent instruments. An alternative design utilizing constant force springs and a flexible, metallized Kapton cover was then tested. Results from development tests, microgravity tests, and lessons learned during the development of the aperture cover are discussed.

  3. Compact high precision adjustable beam defining aperture

    DOEpatents

    Morton, Simon A; Dickert, Jeffrey

    2013-07-02

    The present invention provides an adjustable aperture for limiting the dimension of a beam of energy. In an exemplary embodiment, the aperture includes (1) at least one piezoelectric bender, where a fixed end of the bender is attached to a common support structure via a first attachment and where a movable end of the bender is movable in response to an actuating voltage applied to the bender and (2) at least one blade attached to the movable end of the bender via a second attachment such that the blade is capable of impinging upon the beam. In an exemplary embodiment, the beam of energy is electromagnetic radiation. In an exemplary embodiment, the beam of energy is X-rays.

  4. Performance limits for Synthetic Aperture Radar.

    SciTech Connect

    Doerry, Armin Walter

    2006-02-01

    The performance of a Synthetic Aperture Radar (SAR) system depends on a variety of factors, many which are interdependent in some manner. It is often difficult to ''get your arms around'' the problem of ascertaining achievable performance limits, and yet those limits exist and are dictated by physics, no matter how bright the engineer tasked to generate a system design. This report identifies and explores those limits, and how they depend on hardware system parameters and environmental conditions. Ultimately, this leads to a characterization of parameters that offer optimum performance for the overall SAR system. For example, there are definite optimum frequency bands that depend on weather conditions and range, and minimum radar PRF for a fixed real antenna aperture dimension is independent of frequency. While the information herein is not new to the literature, its collection into a single report hopes to offer some value in reducing the ''seek time''.

  5. Complex synthetic aperture radar data compression

    NASA Astrophysics Data System (ADS)

    Cirillo, Francis R.; Poehler, Paul L.; Schwartz, Debra S.; Rais, Houra

    2002-08-01

    Existing compression algorithms, primarily designed for visible electro-optical (EO) imagery, do not work well for Synthetic Aperture Radar (SAR) data. The best compression ratios achieved to date are less than 10:1 with minimal degradation to the phase data. Previously, phase data has been discarded with only magnitude data saved for analysis. Now that the importance of phase has been recognized for Interferometric Synthetic Aperture Radar (IFSAR), Coherent Change Detection (CCD), and polarimetry, requirements exist to preserve, transmit, and archive the both components. Bandwidth and storage limitations on existing and future platforms make compression of this data a top priority. This paper presents results obtained using a new compression algorithm designed specifically to compress SAR imagery, while preserving both magnitude and phase information at compression ratios of 20:1 and better.

  6. CRTF Real-Time Aperture Flux system

    SciTech Connect

    Davis, D.B.

    1980-01-01

    The Real-Time Aperture Flux system (TRAF) is a test measurement system designed to determine the input power/unit area (flux density) during solar experiments conducted at the Central Receiver Test Facility, Sandia National Laboratories, Albuquerque, New Mexico. The RTAF is capable of using both thermal sensors and photon sensors to determine the flux densities in the RTAF measuring plane. These data are manipulated in various ways to derive input power and flux density distribution to solar experiments.

  7. Aperture modulated, translating bed total body irradiation

    SciTech Connect

    Hussain, Amjad; Villarreal-Barajas, Jose Eduardo; Dunscombe, Peter; Brown, Derek W.

    2011-02-15

    Purpose: Total body irradiation (TBI) techniques aim to deliver a uniform radiation dose to a patient with an irregular body contour and a heterogeneous density distribution to within {+-}10% of the prescribed dose. In the current article, the authors present a novel, aperture modulated, translating bed TBI (AMTBI) technique that produces a high degree of dose uniformity throughout the entire patient. Methods: The radiation beam is dynamically shaped in two dimensions using a multileaf collimator (MLC). The irregular surface compensation algorithm in the Eclipse treatment planning system is used for fluence optimization, which is performed based on penetration depth and internal inhomogeneities. Two optimal fluence maps (AP and PA) are generated and beam apertures are created to deliver these optimal fluences. During treatment, the patient/phantom is translated on a motorized bed close to the floor (source to bed distance: 204.5 cm) under a stationary radiation beam with 0 deg. gantry angle. The bed motion and dynamic beam apertures are synchronized. Results: The AMTBI technique produces a more homogeneous dose distribution than fixed open beam translating bed TBI. In phantom studies, the dose deviation along the midline is reduced from 10% to less than 5% of the prescribed dose in the longitudinal direction. Dose to the lung is reduced by more than 15% compared to the unshielded fixed open beam technique. At the lateral body edges, the dose received from the open beam technique was 20% higher than that prescribed at umbilicus midplane. With AMTBI the dose deviation in this same region is reduced to less than 3% of the prescribed dose. Validation of the technique was performed using thermoluminescent dosimeters in a Rando phantom. Agreement between calculation and measurement was better than 3% in all cases. Conclusions: A novel, translating bed, aperture modulated TBI technique that employs dynamically shaped MLC defined beams is shown to improve dose uniformity

  8. Variable-Aperture Reciprocating Reed Valve

    NASA Technical Reports Server (NTRS)

    Lindner, Jeffrey L. (Inventor); Myers, W. Neill (Inventor); Kelley, Anthony R. (Inventor); Yang, Hong Q. (Inventor)

    2015-01-01

    A variable-aperture reciprocating reed valve includes a valve body defining a through hole region having a contoured-profile portion. A semi-rigid plate is affixed on one side thereof to the valve body to define a cantilever extending across the through hole region. At least one free edge of the cantilever opposes the contoured-profile portion of the through hole region in a non-contact relationship.

  9. Effective wavelength scaling of rectangular aperture antennas.

    PubMed

    Chen, Yuanyuan; Yu, Li; Zhang, Jiasen; Gordon, Reuven

    2015-04-20

    We investigate the resonances of aperture antennas from the visible to the terahertz regime, with comparison to comprehensive simulations. Simple piecewise analytic behavior is found for the wavelength scaling over the entire spectrum, with a linear regime through the visible and near-IR. This theory will serve as a useful and simple design tool for applications including biosensors, nonlinear plasmonics and surface enhanced spectroscopies. PMID:25969079

  10. Exploiting Decorrelations In Synthetic-Aperture Radar

    NASA Technical Reports Server (NTRS)

    Zebker, Howard A.; Villasenor, John D.

    1994-01-01

    Temporal decorrelation between synthetic-aperture-radar data acquired on subsequent passes along same or nearly same trajectory serves as measure of change in target scene. Based partly on mathematical models of statistics of correlations between first- and second-pass radar echoes. Also based partly on Fourier-transform relations between radar-system impulse response and decorrelation functions particularly those expressing decorrelation effects of rotation and horizontal shift of trajectories between two passes.

  11. Large-Aperture Membrane Active Phased-Array Antennas

    NASA Technical Reports Server (NTRS)

    Karasik, Boris; McGrath, William; Leduc, Henry

    2009-01-01

    Large-aperture phased-array microwave antennas supported by membranes are being developed for use in spaceborne interferometric synthetic aperture radar systems. There may also be terrestrial uses for such antennas supported on stationary membranes, large balloons, and blimps. These antennas are expected to have areal mass densities of about 2 kg/sq m, satisfying a need for lightweight alternatives to conventional rigid phased-array antennas, which have typical areal mass densities between 8 and 15 kg/sq m. The differences in areal mass densities translate to substantial differences in total mass in contemplated applications involving aperture areas as large as 400 sq m. A membrane phased-array antenna includes patch antenna elements in a repeating pattern. All previously reported membrane antennas were passive antennas; this is the first active membrane antenna that includes transmitting/receiving (T/R) electronic circuits as integral parts. Other integral parts of the antenna include a network of radio-frequency (RF) feed lines (more specifically, a corporate feed network) and of bias and control lines, all in the form of flexible copper strip conductors on flexible polymeric membranes. Each unit cell of a prototype antenna (see Figure 1) contains a patch antenna element and a compact T/R module that is compatible with flexible membrane circuitry. There are two membrane layers separated by a 12.7-mm air gap. Each membrane layer is made from a commercially available flexible circuit material that, as supplied, comprises a 127-micron-thick polyimide dielectric layer clad on both sides with 17.5-micron-thick copper layers. The copper layers are patterned into RF, bias, and control conductors. The T/R module is located on the back side of the ground plane and is RF-coupled to the patch element via a slot. The T/R module is a hybrid multilayer module assembled and packaged independently and attached to the membrane array. At the time of reporting the information for

  12. Rapid production of large-area deep sub-wavelength hybrid structures by femtosecond laser light-field tailoring

    SciTech Connect

    Wang, Lei; Chen, Qi-Dai E-mail: hbsun@jlu.edu.cn; Yang, Rui; Xu, Bin-Bin; Wang, Hai-Yu; Yang, Hai; Huo, Cheng-Song; Tu, Hai-Ling; Sun, Hong-Bo E-mail: hbsun@jlu.edu.cn

    2014-01-20

    The goal of creation of large-area deep sub-wavelength nanostructures by femtosecond laser irradiation onto various materials is being hindered by the limited coherence length. Here, we report solution of the problem by light field tailoring of the incident beam with a phase mask, which serves generation of wavelets. Direct interference between the wavelets, here the first-order diffracted beams, and interference between a wavelet and its induced waves such as surface plasmon polariton are responsible for creation of microgratings and superimposed nanogratings, respectively. The principle of wavelets interference enables extension of uniformly induced hybrid structures containing deep sub-wavelength nanofeatures to macro-dimension.

  13. Formation of subwavelength grating on molybdenum mirrors using a femtosecond Ti:sapphire laser system operating at 10 Hz.

    PubMed

    Sharma, Avnish Kumar; Smedley, John; Tsang, Thomas; Rao, Triveni

    2011-03-01

    We report formation of subwavelength surface grating over large surface area of molybdenum mirror by multiple irradiation of amplified femtosecond laser pulses from a homemade Ti:sapphire oscillator-amplifier laser system in a raster scan configuration. The laser system delivered 2 mJ, 80 fs duration laser pulses at a pulse repetition rate of 10 Hz. Various parameters such as pulse fluence, number of pulses, laser polarization, scan speed, and scan steps were optimized to obtain uniform subwavelength gratings. Energy dispersive x-ray spectroscopy measurements were conducted to analyze the elemental composition of mirror surfaces before and after laser treatment.

  14. Large aperture adaptive optics for intense lasers

    NASA Astrophysics Data System (ADS)

    Deneuville, François; Ropert, Laurent; Sauvageot, Paul; Theis, Sébastien

    2015-05-01

    ISP SYSTEM has developed a range of large aperture electro-mechanical deformable mirrors (DM) suitable for ultra short pulsed intense lasers. The design of the MD-AME deformable mirror is based on force application on numerous locations thanks to electromechanical actuators driven by stepper motors. DM design and assembly method have been adapted to large aperture beams and the performances were evaluated on a first application for a beam with a diameter of 250mm at 45° angle of incidence. A Strehl ratio above 0.9 was reached for this application. Simulations were correlated with measurements on optical bench and the design has been validated by calculation for very large aperture (up to Ø550mm). Optical aberrations up to Zernike order 5 can be corrected with a very low residual error as for actual MD-AME mirror. Amplitude can reach up to several hundreds of μm for low order corrections. Hysteresis is lower than 0.1% and linearity better than 99%. Contrary to piezo-electric actuators, the μ-AME actuators avoid print-through effects and they permit to keep the mirror shape stable even unpowered, providing a high resistance to electro-magnetic pulses. The MD-AME mirrors can be adapted to circular, square or elliptical beams and they are compatible with all dielectric or metallic coatings.

  15. The radiation from apertures in curved surfaces

    NASA Technical Reports Server (NTRS)

    Pathak, P. H.; Kouyoumjian, R. G.

    1973-01-01

    The geometrical theory of diffraction is extended to treat the radiation from apertures or slots in convex, perfectly-conducting surfaces. It is assumed that the tangential electric field in the aperture is known so that an equivalent, infinitesimal source can be defined at each point in the aperture. Surface rays emanate from this source which is a caustic of the ray system. A launching coefficient is introduced to describe the excitation of the surface ray modes. If the field radiated from the surface is desired, the ordinary diffraction coefficients are used to determine the field of the rays shed tangentially from the surface rays. The field of the surface ray modes is not the field on the surface; hence if the mutual coupling between slots is of interest, a second coefficient related to the launching coefficient must be employed. In the region adjacent to the shadow boundary, the component of the field directly radiated from the source is presented by Fock-type functions. In the illuminated region the incident radiation from the source (this does not include the diffracted field components) is treated by geometrical optics. This extension of the geometrical theory of diffraction is applied to calculate the radiation from slots on elliptic cylinders, spheres and spheroids.

  16. Restoring Aperture Profile At Sample Plane

    SciTech Connect

    Jackson, J L; Hackel, R P; Lungershausen, A W

    2003-08-03

    Off-line conditioning of full-size optics for the National Ignition Facility required a beam delivery system to allow conditioning lasers to rapidly raster scan samples while achieving several technical goals. The main purpose of the optical system designed was to reconstruct at the sample plane the flat beam profile found at the laser aperture with significant reductions in beam wander to improve scan times. Another design goal was the ability to vary the beam size at the sample to scan at different fluences while utilizing all of the laser power and minimizing processing time. An optical solution was developed using commercial off-the-shelf lenses. The system incorporates a six meter relay telescope and two sets of focusing optics. The spacing of the focusing optics is changed to allow the fluence on the sample to vary from 2 to 14 Joules per square centimeter in discrete steps. More importantly, these optics use the special properties of image relaying to image the aperture plane onto the sample to form a pupil relay with a beam profile corresponding almost exactly to the flat profile found at the aperture. A flat beam profile speeds scanning by providing a uniform intensity across a larger area on the sample. The relayed pupil plane is more stable with regards to jitter and beam wander. Image relaying also reduces other perturbations from diffraction, scatter, and focus conditions. Image relaying, laser conditioning, and the optical system designed to accomplish the stated goals are discussed.

  17. Synthetic aperture radar processing with tiered subapertures

    SciTech Connect

    Doerry, A.W.

    1994-06-01

    Synthetic Aperture Radar (SAR) is used to form images that are maps of radar reflectivity of some scene of interest, from range soundings taken over some spatial aperture. Additionally, the range soundings are typically synthesized from a sampled frequency aperture. Efficient processing of the collected data necessitates using efficient digital signal processing techniques such as vector multiplies and fast implementations of the Discrete Fourier Transform. Inherent in image formation algorithms that use these is a trade-off between the size of the scene that can be acceptably imaged, and the resolution with which the image can be made. These limits arise from migration errors and spatially variant phase errors, and different algorithms mitigate these to varying degrees. Two fairly successful algorithms for airborne SARs are Polar Format processing, and Overlapped Subaperture (OSA) processing. This report introduces and summarizes the analysis of generalized Tiered Subaperture (TSA) techniques that are a superset of both Polar Format processing and OSA processing. It is shown how tiers of subapertures in both azimuth and range can effectively mitigate both migration errors and spatially variant phase errors to allow virtually arbitrary scene sizes, even in a dynamic motion environment.

  18. Coded-aperture imaging in nuclear medicine

    NASA Astrophysics Data System (ADS)

    Smith, Warren E.; Barrett, Harrison H.; Aarsvold, John N.

    1989-11-01

    Coded-aperture imaging is a technique for imaging sources that emit high-energy radiation. This type of imaging involves shadow casting and not reflection or refraction. High-energy sources exist in x ray and gamma-ray astronomy, nuclear reactor fuel-rod imaging, and nuclear medicine. Of these three areas nuclear medicine is perhaps the most challenging because of the limited amount of radiation available and because a three-dimensional source distribution is to be determined. In nuclear medicine a radioactive pharmaceutical is administered to a patient. The pharmaceutical is designed to be taken up by a particular organ of interest, and its distribution provides clinical information about the function of the organ, or the presence of lesions within the organ. This distribution is determined from spatial measurements of the radiation emitted by the radiopharmaceutical. The principles of imaging radiopharmaceutical distributions with coded apertures are reviewed. Included is a discussion of linear shift-variant projection operators and the associated inverse problem. A system developed at the University of Arizona in Tucson consisting of small modular gamma-ray cameras fitted with coded apertures is described.

  19. Biomineral repair of abalone shell apertures.

    PubMed

    Cusack, Maggie; Guo, Dujiao; Chung, Peter; Kamenos, Nicholas A

    2013-08-01

    The shell of the gastropod mollusc, abalone, is comprised of nacre with an outer prismatic layer that is composed of either calcite or aragonite or both, depending on the species. A striking characteristic of the abalone shell is the row of apertures along the dorsal margin. As the organism and shell grow, new apertures are formed and the preceding ones are filled in. Detailed investigations, using electron backscatter diffraction, of the infill in three species of abalone: Haliotis asinina, Haliotis gigantea and Haliotis rufescens reveals that, like the shell, the infill is composed mainly of nacre with an outer prismatic layer. The infill prismatic layer has identical mineralogy as the original shell prismatic layer. In H. asinina and H. gigantea, the prismatic layer of the shell and infill are made of aragonite while in H. rufescens both are composed of calcite. Abalone builds the infill material with the same high level of biological control, replicating the structure, mineralogy and crystallographic orientation as for the shell. The infill of abalone apertures presents us with insight into what is, effectively, shell repair.

  20. Coded-aperture imaging in nuclear medicine

    NASA Technical Reports Server (NTRS)

    Smith, Warren E.; Barrett, Harrison H.; Aarsvold, John N.

    1989-01-01

    Coded-aperture imaging is a technique for imaging sources that emit high-energy radiation. This type of imaging involves shadow casting and not reflection or refraction. High-energy sources exist in x ray and gamma-ray astronomy, nuclear reactor fuel-rod imaging, and nuclear medicine. Of these three areas nuclear medicine is perhaps the most challenging because of the limited amount of radiation available and because a three-dimensional source distribution is to be determined. In nuclear medicine a radioactive pharmaceutical is administered to a patient. The pharmaceutical is designed to be taken up by a particular organ of interest, and its distribution provides clinical information about the function of the organ, or the presence of lesions within the organ. This distribution is determined from spatial measurements of the radiation emitted by the radiopharmaceutical. The principles of imaging radiopharmaceutical distributions with coded apertures are reviewed. Included is a discussion of linear shift-variant projection operators and the associated inverse problem. A system developed at the University of Arizona in Tucson consisting of small modular gamma-ray cameras fitted with coded apertures is described.

  1. Vortex characteristics of Fraunhofer diffractions of a plane wave by a spiral phase plate limited by pseudoring polygonal apertures.

    PubMed

    Tang, Huiqin; Wang, Taofen; Zhu, Kaicheng

    2008-08-15

    We introduce a multilevel spiral phase plate (SPP) limited by a pseudoring polygonal aperture (PRPA). Such an SPP has the advantages of easier fabrication and greater suppression of the sidelobes of the diffraction field over that generated with a polygonal aperture (PA). The Fraunhofer diffraction fields generated by an SPP with a PRPA or with a PA have the same topological charge features and a similar diffraction pattern. Numerical evaluations show that the maximum bright annular-intensity difference between the diffraction patterns for the SPP with a PRPA and that of a PA does not exceed 3% under optimal design parameters.

  2. Imaging performance of annular apertures. II - Line spread functions

    NASA Technical Reports Server (NTRS)

    Tschunko, H. F. A.

    1978-01-01

    Line images formed by aberration-free optical systems with annular apertures are investigated in the whole range of central obstruction ratios. Annular apertures form lines images with central and side line groups. The number of lines in each line group is given by the ratio of the outer diameter of the annular aperture divided by the width of the annulus. The theoretical energy fraction of 0.889 in the central line of the image formed by an unobstructed aperture increases for centrally obstructed apertures to 0.932 for the central line group. Energy fractions for the central and side line groups are practically constant for all obstruction ratios and for each line group. The illumination of rectangular secondary apertures of various length/width ratios by apertures of various obstruction ratios is discussed.

  3. Near-field radiative heat transfer between parallel structures in the deep subwavelength regime.

    PubMed

    St-Gelais, Raphael; Zhu, Linxiao; Fan, Shanhui; Lipson, Michal

    2016-06-01

    Thermal radiation between parallel objects separated by deep subwavelength distances and subject to large thermal gradients (>100 K) can reach very high magnitudes, while being concentrated on a narrow frequency distribution. These unique characteristics could enable breakthrough technologies for thermal transport control and electricity generation (for example, by radiating heat exactly at the bandgap frequency of a photovoltaic cell). However, thermal transport in this regime has never been achieved experimentally due to the difficulty of maintaining large thermal gradients over nanometre-scale distances while avoiding other heat transfer mechanisms, namely conduction. Here, we show near-field radiative heat transfer between parallel SiC nanobeams in the deep subwavelength regime. The distance between the beams is controlled by a high-precision micro-electromechanical system (MEMS). We exploit the mechanical stability of nanobeams under high tensile stress to minimize thermal buckling effects, therefore keeping control of the nanometre-scale separation even at large thermal gradients. We achieve an enhancement of heat transfer of almost two orders of magnitude with respect to the far-field limit (corresponding to a 42 nm separation) and show that we can maintain a temperature gradient of 260 K between the cold and hot surfaces at ∼100 nm distance.

  4. Electromagnetic wave transmission through a subwavelength nano-hole in a two-dimensional plasmonic layer.

    PubMed

    Horing, Norman J M; Miessein, Désiré; Gumbs, Godfrey

    2015-06-01

    An integral equation is formulated to describe electromagnetic wave transmission through a subwavelength nano-hole in a thin plasmonic sheet in terms of the dyadic Green's function for the associated Helmholtz problem. Taking the subwavelength radius of the nano-hole to be the smallest length of the system, we have obtained an exact solution of the integral equation for the dyadic Green's function analytically and in closed form. This dyadic Green's function is then employed in the numerical analysis of electromagnetic wave transmission through the nano-hole for normal incidence of the incoming wave train. The electromagnetic transmission involves two distinct contributions; one emanates from the nano-hole, and the other is directly transmitted through the thin plasmonic layer itself (which would not occur in the case of a perfect metal screen). The transmitted radiation exhibits interference fringes in the vicinity of the nano-hole, and they tend to flatten as a function of increasing lateral separation from the hole, reaching the uniform value of transmission through the sheet alone at large separations.

  5. Electromagnetic diffraction radiation of a subwavelength-hole array excited by an electron beam.

    PubMed

    Liu, Shenggang; Hu, Min; Zhang, Yaxin; Li, Yuebao; Zhong, Renbin

    2009-09-01

    This paper explores the physics of the electromagnetic diffraction radiation of a subwavelength holes array excited by a set of evanescent waves generated by a line charge of electron beam moving parallel to the array. Activated by a uniformly moving line charge, numerous physical phenomena occur such as the diffraction radiation on both sides of the array as well as the electromagnetic penetration or transmission below or above the cut-off through the holes. As a result the subwavelength holes array becomes a radiation array. Making use of the integral equation with relevant Green's functions, an analytical theory for such a radiation system is built up. The results of the numerical calculations based on the theory agree well with that obtained by the computer simulation. The relation among the effective surface plasmon wave, the electromagnetic penetration or transmission of the holes and the diffraction radiation is revealed. The energy dependence of and the influence of the hole thickness on the diffraction radiation and the electromagnetic penetration or transmission are investigated in detail. Therefore, a distinct diffraction radiation phenomenon is discovered.

  6. Highly efficient and ultra-broadband graphene oxide ultrathin lenses with three-dimensional subwavelength focusing

    PubMed Central

    Zheng, Xiaorui; Jia, Baohua; Lin, Han; Qiu, Ling; Li, Dan; Gu, Min

    2015-01-01

    Nanometric flat lenses with three-dimensional subwavelength focusing are indispensable in miniaturized optical systems. However, they are fundamentally challenging to achieve because of the difficulties in accurately controlling the optical wavefront by a film with nanometric thickness. Based on the unique and giant refractive index and absorption modulations of the sprayable graphene oxide thin film during its laser reduction process, we demonstrate a graphene oxide ultrathin (∼200 nm) flat lens that shows far-field three-dimensional subwavelength focusing (λ3/5) with an absolute focusing efficiency of >32% for a broad wavelength range from 400 to 1,500 nm. Our flexible graphene oxide lenses are mechanically robust and maintain excellent focusing properties under high stress. The simple and scalable fabrication approach enables wide potential applications in on-chip nanophotonics. The wavefront shaping concept opens up new avenues for easily accessible, highly precise and efficient optical beam manipulations with a flexible and integratable planar graphene oxide ultrathin film. PMID:26391504

  7. Organized chromophoric assemblies for nonlinear optical materials: towards (sub)wavelength scale architectures.

    PubMed

    Xu, Jialiang; Semin, Sergey; Rasing, Theo; Rowan, Alan E

    2015-03-01

    Photonic circuits are expected to greatly contribute to the next generation of integrated chips, as electronic integrated circuits become confronted with bottlenecks such as heat generation and bandwidth limitations. One of the main challenges for the state-of-the-art photonic circuits lies in the development of optical materials with high nonlinear optical (NLO) susceptibilities, in particular in the wavelength and subwavelength dimensions which are compatible with on-chip technologies. In this review, the varied approaches to micro-/nanosized NLO materials based on building blocks of bio- and biomimetic molecules, as well as synthetic D-π-A chromophores, have been categorized as supramolecular self-assemblies, molecular scaffolds, and external force directed assemblies. Such molecular and supramolecular NLO materials have intrinsic advantages, such as structural diversities, high NLO susceptibilities, and clear structure-property relationships. These "bottom-up" fabrication approaches are proposed to be combined with the "top-down" techniques such as lithography, etc., to generate multifunctionality by coupling light and matter on the (sub)wavelength scale.

  8. Near-field radiative heat transfer between parallel structures in the deep subwavelength regime

    NASA Astrophysics Data System (ADS)

    St-Gelais, Raphael; Zhu, Linxiao; Fan, Shanhui; Lipson, Michal

    2016-06-01

    Thermal radiation between parallel objects separated by deep subwavelength distances and subject to large thermal gradients (>100 K) can reach very high magnitudes, while being concentrated on a narrow frequency distribution. These unique characteristics could enable breakthrough technologies for thermal transport control and electricity generation (for example, by radiating heat exactly at the bandgap frequency of a photovoltaic cell). However, thermal transport in this regime has never been achieved experimentally due to the difficulty of maintaining large thermal gradients over nanometre-scale distances while avoiding other heat transfer mechanisms, namely conduction. Here, we show near-field radiative heat transfer between parallel SiC nanobeams in the deep subwavelength regime. The distance between the beams is controlled by a high-precision micro-electromechanical system (MEMS). We exploit the mechanical stability of nanobeams under high tensile stress to minimize thermal buckling effects, therefore keeping control of the nanometre-scale separation even at large thermal gradients. We achieve an enhancement of heat transfer of almost two orders of magnitude with respect to the far-field limit (corresponding to a 42 nm separation) and show that we can maintain a temperature gradient of 260 K between the cold and hot surfaces at ∼100 nm distance.

  9. Near-field radiative heat transfer between parallel structures in the deep subwavelength regime.

    PubMed

    St-Gelais, Raphael; Zhu, Linxiao; Fan, Shanhui; Lipson, Michal

    2016-06-01

    Thermal radiation between parallel objects separated by deep subwavelength distances and subject to large thermal gradients (>100 K) can reach very high magnitudes, while being concentrated on a narrow frequency distribution. These unique characteristics could enable breakthrough technologies for thermal transport control and electricity generation (for example, by radiating heat exactly at the bandgap frequency of a photovoltaic cell). However, thermal transport in this regime has never been achieved experimentally due to the difficulty of maintaining large thermal gradients over nanometre-scale distances while avoiding other heat transfer mechanisms, namely conduction. Here, we show near-field radiative heat transfer between parallel SiC nanobeams in the deep subwavelength regime. The distance between the beams is controlled by a high-precision micro-electromechanical system (MEMS). We exploit the mechanical stability of nanobeams under high tensile stress to minimize thermal buckling effects, therefore keeping control of the nanometre-scale separation even at large thermal gradients. We achieve an enhancement of heat transfer of almost two orders of magnitude with respect to the far-field limit (corresponding to a 42 nm separation) and show that we can maintain a temperature gradient of 260 K between the cold and hot surfaces at ∼100 nm distance. PMID:26950243

  10. Highly efficient and ultra-broadband graphene oxide ultrathin lenses with three-dimensional subwavelength focusing.

    PubMed

    Zheng, Xiaorui; Jia, Baohua; Lin, Han; Qiu, Ling; Li, Dan; Gu, Min

    2015-01-01

    Nanometric flat lenses with three-dimensional subwavelength focusing are indispensable in miniaturized optical systems. However, they are fundamentally challenging to achieve because of the difficulties in accurately controlling the optical wavefront by a film with nanometric thickness. Based on the unique and giant refractive index and absorption modulations of the sprayable graphene oxide thin film during its laser reduction process, we demonstrate a graphene oxide ultrathin (∼200 nm) flat lens that shows far-field three-dimensional subwavelength focusing (λ(3)/5) with an absolute focusing efficiency of >32% for a broad wavelength range from 400 to 1,500 nm. Our flexible graphene oxide lenses are mechanically robust and maintain excellent focusing properties under high stress. The simple and scalable fabrication approach enables wide potential applications in on-chip nanophotonics. The wavefront shaping concept opens up new avenues for easily accessible, highly precise and efficient optical beam manipulations with a flexible and integratable planar graphene oxide ultrathin film. PMID:26391504

  11. Three-dimensional all-dielectric metamaterial solid immersion lens for subwavelength imaging at visible frequencies.

    PubMed

    Fan, Wen; Yan, Bing; Wang, Zengbo; Wu, Limin

    2016-08-01

    Although all-dielectric metamaterials offer a low-loss alternative to current metal-based metamaterials to manipulate light at the nanoscale and may have important applications, very few have been reported to date owing to the current nanofabrication technologies. We develop a new "nano-solid-fluid assembly" method using 15-nm TiO2 nanoparticles as building blocks to fabricate the first three-dimensional (3D) all-dielectric metamaterial at visible frequencies. Because of its optical transparency, high refractive index, and deep-subwavelength structures, this 3D all-dielectric metamaterial-based solid immersion lens (mSIL) can produce a sharp image with a super-resolution of at least 45 nm under a white-light optical microscope, significantly exceeding the classical diffraction limit and previous near-field imaging techniques. Theoretical analysis reveals that electric field enhancement can be formed between contacting TiO2 nanoparticles, which causes effective confinement and propagation of visible light at the deep-subwavelength scale. This endows the mSIL with unusual abilities to illuminate object surfaces with large-area nanoscale near-field evanescent spots and to collect and convert the evanescent information into propagating waves. Our all-dielectric metamaterial design strategy demonstrates the potential to develop low-loss nanophotonic devices at visible frequencies. PMID:27536727

  12. Wideband antireflection coatings combining interference multilayers and subwavelength structures prepared by reactive ion etching

    NASA Astrophysics Data System (ADS)

    Bruynooghe, S.; Helgert, M.; Challier, M.; Tonova, D.; Sundermann, M.; Koch, T.; Gatto, A.; Schulze, M.; Kley, E.-B.

    2015-08-01

    To further reduce the intensity of the Fresnel reflections of optical components, subwavelength structures prepared by reactive ion etching of SiO2 thin films are combined as outermost layer with a multilayer system made of conventional thin film materials and prepared by magnetron sputtering. In this approach, a hybrid coating is realized in which the nanoscaled structured outermost layer is expected to further improve the antireflection properties of common interference stacks. The subwavelength structures are examined by spectroscopic ellipsometry, spectral photometry and scanning electron microscopy. The microscopic and optical spectroscopic analysis revealed that pillar-shaped nanostructures are formed during etching which exhibit low-index properties and have a depth-dependent refractive index. To take into account the index gradient in the coating design, the optical properties of the nanostructures are modeled using the effective medium approximation. The calculated average effective refractive index is 1.11 at 500 nm wavelength. A hybrid coating was designed to minimize the residual reflectance in the 400 - 900 nm spectral range for BK7 glass substrate. Experimental results showed that the hybrid coating achieves a low residual reflectance with very good omni-directional properties, owing to the properties of its nanostructured surface. The residual reflection of the hybrid coating is found to be two times smaller than the reflection obtained by applying a common interference multilayer system which demonstrates the benefit of the use of hybrid systems for the realization of broadband antireflective coatings with wide-angle properties.

  13. Three-dimensional all-dielectric metamaterial solid immersion lens for subwavelength imaging at visible frequencies

    PubMed Central

    Fan, Wen; Yan, Bing; Wang, Zengbo; Wu, Limin

    2016-01-01

    Although all-dielectric metamaterials offer a low-loss alternative to current metal-based metamaterials to manipulate light at the nanoscale and may have important applications, very few have been reported to date owing to the current nanofabrication technologies. We develop a new “nano–solid-fluid assembly” method using 15-nm TiO2 nanoparticles as building blocks to fabricate the first three-dimensional (3D) all-dielectric metamaterial at visible frequencies. Because of its optical transparency, high refractive index, and deep-subwavelength structures, this 3D all-dielectric metamaterial-based solid immersion lens (mSIL) can produce a sharp image with a super-resolution of at least 45 nm under a white-light optical microscope, significantly exceeding the classical diffraction limit and previous near-field imaging techniques. Theoretical analysis reveals that electric field enhancement can be formed between contacting TiO2 nanoparticles, which causes effective confinement and propagation of visible light at the deep-subwavelength scale. This endows the mSIL with unusual abilities to illuminate object surfaces with large-area nanoscale near-field evanescent spots and to collect and convert the evanescent information into propagating waves. Our all-dielectric metamaterial design strategy demonstrates the potential to develop low-loss nanophotonic devices at visible frequencies. PMID:27536727

  14. Strong localization of an acoustic wave in a sub-wavelength slot between two plates.

    PubMed

    Cai, Feiyan; Li, Fei; Meng, Long; Wu, Junru; Zheng, Hairong

    2015-03-01

    The dispersion relation of the acoustic field in a sub-wavelength slot (its width is smaller than the acoustic wavelength) between two identical plates immersed in an inviscid liquid is theoretically analyzed. Each plate has a phononic crystal structure consisting of periodical grooves drilled in one of outer sides of each plate. It is found that highly localization of acoustic energy can be achieved in the sub-wavelength slot when a traveling acoustic wave is incident upon the slots. The associate physical principle is as follows: The lowest anti-symmetric non-leaky A0 mode of the Lamb wave of each individual thin plate propagating as an evanescent wave extends to the liquid from opposite direction; when the width of the slot is much smaller than the characteristic decay length of the evanescent wave in the liquid, the constructive interference of evanescent waves of the both plates takes place, leading to a strong acoustic field in the slot. This system has potential to serve as an excellent candidate for the ultrasensitive microscopic chemical/biological stimulators and sensors.

  15. Design of a silicon polarization grating with a sub-wavelength anisotropic structure

    NASA Astrophysics Data System (ADS)

    Anju, Koji; Tsuda, Hiroyuki; Uetsuka, Hisato

    2016-02-01

    Polarization gratings, which have the important properties of being highly efficient for first order diffraction and having high polarization sensitivity, can be applied to beam splitters, displays, spectro-polarimeters, and so on. Usually, polarization gratings are fabricated utilizing the periodic anisotropy of liquid crystal molecules. However, high tolerance to light, heat, and humidity is required, in particular, for optical communication applications. Therefore, a polarization grating based on an inorganic material is more suitable than one based on an organic one. We propose a silicon polarization grating with form birefringence induced by an anisotropic surface microstructure with features shorter than the wavelength of light (sub-wavelength anisotropic structure), allowing the birefringence to be controlled through selection of the dimensions of the periodic structure. In this paper, we describe the design of sub-wavelength structures of half wave plates using a thin film of silicon. By optimizing the line width, the line spacing, and the thickness of the film, a transmittance of more than 99% at an incident wavelength of 1550 nm was obtained. A polarization grating based on this half wave plate was designed. The orientation of the half wave plate structure was rotated in a particular direction. Furthermore, we evaluated the wavelength dependence and incident angle dependence of the diffraction efficiency using a finite-difference time-domain method.

  16. Application of holographic sub-wavelength diffraction gratings for monitoring of kinetics of bioprocesses

    NASA Astrophysics Data System (ADS)

    Tamulevičius, Tomas; Šeperys, Rimas; Andrulevičius, Mindaugas; Kopustinskas, Vitoldas; Meškinis, Šarūnas; Tamulevičius, Sigitas; Mikalayeva, Valeryia; Daugelavičius, Rimantas

    2012-09-01

    In this work we present a refractive index (RI) sensor based on a sub-wavelength holographic diffraction grating. The sensor chip was fabricated by dry etching of the finely spaced (d = 428 nm) diffraction grating in SiOx doped diamond like carbon (DLC) film. It is shown that employing a fabricated sensor chip, and using the proposed method of analysis of data, one can inspect kinetics of processes in liquids occurring in the vicinity of the grating surface. The method is based on the spectral composition analysis of polarized polychromatic light reflected from the sub-wavelength diffraction grating. The RI measurement system was tested with different model liquid analytes including 25 wt.%, 50 wt.% sugar water solutions, 10 °C, 50 °C distilled water, also Gram-positive bacteria Bacillus subtilis interaction with ion-permeable channels forming antibiotic gramicidin D and a murolytic enzyme lysozyme. Analysis of the data set of specular reflection spectra enabled us to follow the kinetics of the RI changes in the analyte with millisecond resolution. Detectable changes in the effective RI were not worse than Δn = 10-4.

  17. Two-Dimensional Synthetic-Aperture Radiometer

    NASA Technical Reports Server (NTRS)

    LeVine, David M.

    2010-01-01

    A two-dimensional synthetic-aperture radiometer, now undergoing development, serves as a test bed for demonstrating the potential of aperture synthesis for remote sensing of the Earth, particularly for measuring spatial distributions of soil moisture and ocean-surface salinity. The goal is to use the technology for remote sensing aboard a spacecraft in orbit, but the basic principles of design and operation are applicable to remote sensing from aboard an aircraft, and the prototype of the system under development is designed for operation aboard an aircraft. In aperture synthesis, one utilizes several small antennas in combination with a signal processing in order to obtain resolution that otherwise would require the use of an antenna with a larger aperture (and, hence, potentially more difficult to deploy in space). The principle upon which this system is based is similar to that of Earth-rotation aperture synthesis employed in radio astronomy. In this technology the coherent products (correlations) of signals from pairs of antennas are obtained at different antenna-pair spacings (baselines). The correlation for each baseline yields a sample point in a Fourier transform of the brightness-temperature map of the scene. An image of the scene itself is then reconstructed by inverting the sampled transform. The predecessor of the present two-dimensional synthetic-aperture radiometer is a one-dimensional one, named the Electrically Scanned Thinned Array Radiometer (ESTAR). Operating in the L band, the ESTAR employs aperture synthesis in the cross-track dimension only, while using a conventional antenna for resolution in the along-track dimension. The two-dimensional instrument also operates in the L band to be precise, at a frequency of 1.413 GHz in the frequency band restricted for passive use (no transmission) only. The L band was chosen because (1) the L band represents the long-wavelength end of the remote- sensing spectrum, where the problem of achieving adequate

  18. Construction of a 56 mm aperture high-field twin-aperture superconducting dipole model magnet

    SciTech Connect

    Ahlbaeck, J; Leroy, D.; Oberli, L.; Perini, D.; Salminen, J.; Savelainen, M.; Soini, J.; Spigo, G.

    1996-07-01

    A twin-aperture superconducting dipole model has been designed in collaboration with Finnish and Swedish Scientific Institutions within the framework of the LHC R and D program and has been built at CERN. Principal features of the magnet are 56 mm aperture, separate stainless steel collared coils, yoke closed after assembly at room temperature, and longitudinal prestressing of the coil ends. This paper recalls the main dipole design characteristics and presents some details of its fabrication including geometrical and mechanical measurements of the collared coil assembly.

  19. Planar dielectric resonator stabilized HEMT oscillator integrated with CPW/aperture coupled patch antenna

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Lee, Richard Q.

    1992-01-01

    A design of an active antenna with a dielectric resonator stabilized high-electron-mobility transistor (HEMT) oscillator (DRO) and an aperture-coupled patch antenna is reported. The circuit is fabricated using coplanar waveguide (CPW) with the oscillator and the antenna on opposite sides of the substrate. The active antenna was demonstrated at 7.6 GHz; however, the design can be scaled to higher frequencies. Excellent oscillator characteristics and radiation patterns were obtained.

  20. Planar dielectric resonator stabilized HEMT oscillator integrated with CPW/aperture coupled patch antenna

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Lee, Richard Q.

    1992-01-01

    A new design of an active antenna with a dielectric resonator stabilized high electron mobility transistor (HEMT) oscillator (DRO) and an aperture-coupled patch antenna is reported. The circuit is fabricated using coplanar waveguide (CPW) with the oscillator and the antenna on opposite sides of the substrate. The active antenna was demonstrated at 7.6 GHz; however, the design can be scaled to higher frequencies. Excellent oscillator characteristics and radiation patterns were obtained.

  1. Optimization of synthetic aperture image quality

    NASA Astrophysics Data System (ADS)

    Moshavegh, Ramin; Jensen, Jonas; Villagomez-Hoyos, Carlos A.; Stuart, Matthias B.; Hemmsen, Martin Christian; Jensen, Jørgen Arendt

    2016-04-01

    Synthetic Aperture (SA) imaging produces high-quality images and velocity estimates of both slow and fast flow at high frame rates. However, grating lobe artifacts can appear both in transmission and reception. These affect the image quality and the frame rate. Therefore optimization of parameters effecting the image quality of SA is of great importance, and this paper proposes an advanced procedure for optimizing the parameters essential for acquiring an optimal image quality, while generating high resolution SA images. Optimization of the image quality is mainly performed based on measures such as F-number, number of emissions and the aperture size. They are considered to be the most contributing acquisition factors in the quality of the high resolution images in SA. Therefore, the performance of image quality is quantified in terms of full-width at half maximum (FWHM) and the cystic resolution (CTR). The results of the study showed that SA imaging with only 32 emissions and maximum sweep angle of 22 degrees yields a very good image quality compared with using 256 emissions and the full aperture size. Therefore the number of emissions and the maximum sweep angle in the SA can be optimized to reach a reasonably good performance, and to increase the frame rate by lowering the required number of emissions. All the measurements are performed using the experimental SARUS scanner connected to a λ/2-pitch transducer. A wire phantom and a tissue mimicking phantom containing anechoic cysts are scanned using the optimized parameters for the transducer. Measurements coincide with simulations.

  2. The Configurable Aperture Space Telescope (CAST)

    NASA Astrophysics Data System (ADS)

    Ennico, Kimberly; Bendek, Eduardo A.; Lynch, Dana H.; Vassigh, Kenny K.; Young, Zion

    2016-07-01

    The Configurable Aperture Space Telescope, CAST, is a concept that provides access to a UV/visible-infrared wavelength sub-arcsecond imaging platform from space, something that will be in high demand after the retirement of the astronomy workhorse, the 2.4 meter diameter Hubble Space Telescope. CAST allows building large aperture telescopes based on small, compatible and low-cost segments mounted on autonomous cube-sized satellites. The concept merges existing technology (segmented telescope architecture) with emerging technology (smartly interconnected modular spacecraft, active optics, deployable structures). Requiring identical mirror segments, CAST's optical design is a spherical primary and secondary mirror telescope with modular multi-mirror correctors placed at the system focal plane. The design enables wide fields of view, up to as much as three degrees, while maintaining aperture growth and image performance requirements. We present a point design for the CAST concept based on a 0.6 meter diameter (3 x 3 segments) growing to a 2.6 meter diameter (13 x 13 segments) primary, with a fixed Rp=13,000 and Rs=8,750 mm curvature, f/22.4 and f/5.6, respectively. Its diffraction limited design uses a two arcminute field of view corrector with a 7.4 arcsec/mm platescale, and can support a range of platescales as fine as 0.01 arcsec/mm. Our paper summarizes CAST, presents a strawman optical design and requirements for the underlying modular spacecraft, highlights design flexibilities, and illustrates applications enabled by this new method in building space observatories.

  3. Dual-sided coded-aperture imager

    DOEpatents

    Ziock, Klaus-Peter

    2009-09-22

    In a vehicle, a single detector plane simultaneously measures radiation coming through two coded-aperture masks, one on either side of the detector. To determine which side of the vehicle a source is, the two shadow masks are inverses of each other, i.e., one is a mask and the other is the anti-mask. All of the data that is collected is processed through two versions of an image reconstruction algorithm. One treats the data as if it were obtained through the mask, the other as though the data is obtained through the anti-mask.

  4. Digital exploitation of synthetic aperture radar

    NASA Technical Reports Server (NTRS)

    Wagner, H. L.; Shuchman, R. A.

    1977-01-01

    A digital processing and analysis scheme for use with digitized synthetic aperture radar data was developed. Using data from a four channel system, the imagery is preprocessed using specially designed software and then analyzed using preexisting facilities originally intended for use with MSS type data. Geometric and radiometric correction may be performed if desired, as well as classification analysis, Fast Fourier transform, filtering and level slice and display functions. The system provides low cost output in real time, permitting interactive imagery analysis. System information flow diagrams as well as sample output products are shown.

  5. Lossless compression of synthetic aperture radar images

    SciTech Connect

    Ives, R.W.; Magotra, N.; Mandyam, G.D.

    1996-02-01

    Synthetic Aperture Radar (SAR) has been proven an effective sensor in a wide variety of applications. Many of these uses require transmission and/or processing of the image data in a lossless manner. With the current state of SAR technology, the amount of data contained in a single image may be massive, whether the application requires the entire complex image or magnitude data only. In either case, some type of compression may be required to losslessly transmit this data in a given bandwidth or store it in a reasonable volume. This paper provides the results of applying several lossless compression schemes to SAR imagery.

  6. Cancellation of singularities for synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Caday, Peter

    2015-01-01

    In a basic model for synthetic aperture radar (SAR) imaging, one wishes to recover a function or distribution f from line integrals over circles whose centers lie on a given curve γ. In this paper, we consider the problem of recovering the singularities (wavefront set) of f given its SAR data, and specifically whether it is possible to choose a singular f whose singularities are hidden from γ, meaning that its SAR data is smooth. We show that f 's singularities can be hidden to leading order if a certain discrete reflection map is the identity, and give examples where this is the case. Finally, numerical experiments illustrate the hiding of singularities.

  7. Synthetic aperture radar autofocus via semidefinite relaxation.

    PubMed

    Liu, Kuang-Hung; Wiesel, Ami; Munson, David C

    2013-06-01

    The autofocus problem in synthetic aperture radar imaging amounts to estimating unknown phase errors caused by unknown platform or target motion. At the heart of three state-of-the-art autofocus algorithms, namely, phase gradient autofocus, multichannel autofocus (MCA), and Fourier-domain multichannel autofocus (FMCA), is the solution of a constant modulus quadratic program (CMQP). Currently, these algorithms solve a CMQP by using an eigenvalue relaxation approach. We propose an alternative relaxation approach based on semidefinite programming, which has recently attracted considerable attention in other signal processing problems. Experimental results show that our proposed methods provide promising performance improvements for MCA and FMCA through an increase in computational complexity.

  8. Sparse synthetic aperture with Fresnel elements (S-SAFE) using digital incoherent holograms

    PubMed Central

    Kashter, Yuval; Rivenson, Yair; Stern, Adrian; Rosen, Joseph

    2015-01-01

    Creating a large-scale synthetic aperture makes it possible to break the resolution boundaries dictated by the wave nature of light of common optical systems. However, their implementation is challenging, since the generation of a large size continuous mosaic synthetic aperture composed of many patterns is complicated in terms of both phase matching and time-multiplexing duration. In this study we present an advanced configuration for an incoherent holographic imaging system with super resolution qualities that creates a partial synthetic aperture. The new system, termed sparse synthetic aperture with Fresnel elements (S-SAFE), enables significantly decreasing the number of the recorded elements, and it is free from positional constrains on their location. Additionally, in order to obtain the best image quality we propose an optimal mosaicking structure derived on the basis of physical and numerical considerations, and introduce three reconstruction approaches which are compared and discussed. The super-resolution capabilities of the proposed scheme and its limitations are analyzed, numerically simulated and experimentally demonstrated. PMID:26367947

  9. Aperture Effects and Mismatch Oscillations in an Intense Electron Beam

    SciTech Connect

    Harris, J R; O'Shea, P G

    2008-05-12

    When an electron beam is apertured, the transmitted beam current is the product of the incident beam current density and the aperture area. Space charge forces generally cause an increase in incident beam current to result in an increase in incident beam spot size. Under certain circumstances, the spot size will increase faster than the current, resulting in a decrease in current extracted from the aperture. When using a gridded electron gun, this can give rise to negative transconductance. In this paper, we explore this effect in the case of an intense beam propagating in a uniform focusing channel. We show that proper placement of the aperture can decouple the current extracted from the aperture from fluctuations in the source current, and that apertures can serve to alter longitudinal space charge wave propagation by changing the relative contribution of velocity and current modulation present in the beam.

  10. Development of large aperture composite adaptive optics

    NASA Astrophysics Data System (ADS)

    Kmetik, Viliam; Vitovec, Bohumil; Jiran, Lukas; Nemcova, Sarka; Zicha, Josef; Inneman, Adolf; Mikulickova, Lenka; Pavlica, Richard

    2015-01-01

    Large aperture composite adaptive optics for laser applications is investigated in cooperation of Institute of Plasma Physic, Department of Instrumentation and Control Engineering FME CTU and 5M Ltd. We are exploring opportunity of a large-size high-power-laser deformable-mirror production using a lightweight bimorph actuated structure with a composite core. In order to produce a sufficiently large operational free aperture we are developing new technologies for production of flexible core, bimorph actuator and deformable mirror reflector. Full simulation of a deformable-mirrors structure was prepared and validated by complex testing. A deformable mirror actuation and a response of a complicated structure are investigated for an accurate control of the adaptive optics. An original adaptive optics control system and a bimorph deformable mirror driver were developed. Tests of material samples, components and sub-assemblies were completed. A subscale 120 mm bimorph deformable mirror prototype was designed, fabricated and thoroughly tested. A large-size 300 mm composite-core bimorph deformable mirror was simulated and optimized, fabrication of a prototype is carried on. A measurement and testing facility is modified to accommodate large sizes optics.

  11. Multi-mission, autonomous, synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Walls, Thomas J.; Wilson, Michael L.; Madsen, David; Jensen, Mark; Sullivan, Stephanie; Addario, Michael; Hally, Iain

    2014-05-01

    Unmanned aerial systems (UASs) have become a critical asset in current battlespaces and continue to play an increasing role for intelligence, surveillance and reconnaissance (ISR) missions. With the development of medium-to-low altitude, rapidly deployable aircraft platforms, the ISR community has seen an increasing push to develop ISR sensors and systems with real-time mission support capabilities. This paper describes recent flight demonstrations and test results of the RASAR (Real-time, Autonomous, Synthetic Aperture Radar) sensor system. RASAR is a modular, multi-band (L and X) synthetic aperture radar (SAR) imaging sensor designed for self-contained, autonomous, real-time operation with mission flexibility to support a wide range of ISR needs within the size, weight and power constraints of Group III UASs. The sensor command and control and real-time image formation processing are designed to allow integration of RASAR into a larger, multi-intelligence system of systems. The multi-intelligence architecture and a demonstration of real-time autonomous cross-cueing of a separate optical sensor will be presented.

  12. KAOS: kilo-aperture optical spectrograph

    NASA Astrophysics Data System (ADS)

    Barden, Samuel C.; Dey, Arjun; Boyle, Brian; Glazebrook, Karl

    2004-09-01

    A design is described for a potential new facility capable of taking detailed spectroscopy of millions of objects in the Universe to explore the complexity of the Universe and to answer fundamental questions relating to the equation of state of dark energy and to how the Milky Way galaxy formed. The specific design described is envisioned for implementation on the Gemini 8-meter telescopes. It utilizes a 1.5° field of view and samples that field with up to ~5000 apertures. This Kilo-Aperture Optical Spectrograph (KAOS) is mounted at prime focus with a 4-element corrector, atmospheric dispersion compensator (ADC), and an Echidna-style fiber optic positioner. The ADC doubles as a wobble plate, allowing fast guiding that cancels out the wind buffeting of the telescope. The fibers, which can be reconfigured in less than 10 minutes, feed to an array of 12 spectrographs located in the pier of the telescope. The spectrographs are capable of provided spectral resolving powers of a few thousand up to about 40,000.

  13. The SKA New Instrumentation: Aperture Arrays

    NASA Astrophysics Data System (ADS)

    van Ardenne, A.; Faulkner, A. J.; de Vaate, J. G. bij

    The radio frequency window of the Square Kilometre Array is planned to cover the wavelength regime from cm up to a few meters. For this range to be optimally covered, different antenna concepts are considered enabling many science cases. At the lowest frequency range, up to a few GHz, it is expected that multi-beam techniques will be used, increasing the effective field-of-view to a level that allows very efficient detailed and sensitive exploration of the complete sky. Although sparse narrow band phased arrays are as old as radio astronomy, multi-octave sparse and dense arrays now being considered for the SKA, requiring new low noise design, signal processing and calibration techniques. These new array techniques have already been successfully introduced as phased array feeds upgrading existing reflecting telescopes and for new telescopes to enhance the aperture efficiency as well as greatly increasing their field-of-view (van Ardenne et al., Proc IEEE 97(8):2009) by [1]. Aperture arrays use phased arrays without any additional reflectors; the phased array elements are small enough to see most of the sky intrinsically offering a large field of view.

  14. Sparse aperture mask wavefront sensor testbed results

    NASA Astrophysics Data System (ADS)

    Subedi, Hari; Zimmerman, Neil T.; Kasdin, N. Jeremy; Riggs, A. J. E.

    2016-07-01

    Coronagraphic exoplanet detection at very high contrast requires the estimation and control of low-order wave- front aberrations. At Princeton High Contrast Imaging Lab (PHCIL), we are working on a new technique that integrates a sparse-aperture mask (SAM) with a shaped pupil coronagraph (SPC) to make precise estimates of these low-order aberrations. We collect the starlight rejected from the coronagraphic image plane and interfere it using a sparse aperture mask (SAM) at the relay pupil to estimate the low-order aberrations. In our previous work we numerically demonstrated the efficacy of the technique, and proposed a method to sense and control these differential aberrations in broadband light. We also presented early testbed results in which the SAM was used to sense pointing errors. In this paper, we will briefly overview the SAM wavefront sensor technique, explain the design of the completed testbed, and report the experimental estimation results of the dominant low-order aberrations such as tip/tit, astigmatism and focus.

  15. Statistically normalized coherent change detection for synthetic aperture sonar imagery

    NASA Astrophysics Data System (ADS)

    G-Michael, Tesfaye; Tucker, J. D.; Roberts, Rodney G.

    2016-05-01

    Coherent Change Detection (CCD) is a process of highlighting an area of activity in scenes (seafloor) under survey and generated from pairs of synthetic aperture sonar (SAS) images of approximately the same location observed at two different time instances. The problem of CCD and subsequent anomaly feature extraction/detection is complicated due to several factors such as the presence of random speckle pattern in the images, changing environmental conditions, and platform instabilities. These complications make the detection of weak target activities even more difficult. Typically, the degree of similarity between two images measured at each pixel locations is the coherence between the complex pixel values in the two images. Higher coherence indicates little change in the scene represented by the pixel and lower coherence indicates change activity in the scene. Such coherence estimation scheme based on the pixel intensity correlation is an ad-hoc procedure where the effectiveness of the change detection is determined by the choice of threshold which can lead to high false alarm rates. In this paper, we propose a novel approach for anomalous change pattern detection using the statistical normalized coherence and multi-pass coherent processing. This method may be used to mitigate shadows by reducing the false alarms resulting in the coherent map due to speckles and shadows. Test results of the proposed methods on a data set of SAS images will be presented, illustrating the effectiveness of the normalized coherence in terms statistics from multi-pass survey of the same scene.

  16. Target discrimination in synthetic aperture radar using artificial neural networks.

    PubMed

    Principe, J C; Kim, M; Fisher, M

    1998-01-01

    This paper addresses target discrimination in synthetic aperture radar (SAR) imagery using linear and nonlinear adaptive networks. Neural networks are extensively used for pattern classification but here the goal is discrimination. We show that the two applications require different cost functions. We start by analyzing with a pattern recognition perspective the two-parameter constant false alarm rate (CFAR) detector which is widely utilized as a target detector in SAR. Then we generalize its principle to construct the quadratic gamma discriminator (QGD), a nonparametrically trained classifier based on local image intensity. The linear processing element of the QCD is further extended with nonlinearities yielding a multilayer perceptron (MLP) which we call the NL-QGD (nonlinear QGD). MLPs are normally trained based on the L(2) norm. We experimentally show that the L(2) norm is not recommended to train MLPs for discriminating targets in SAR. Inspired by the Neyman-Pearson criterion, we create a cost function based on a mixed norm to weight the false alarms and the missed detections differently. Mixed norms can easily be incorporated into the backpropagation algorithm, and lead to better performance. Several other norms (L(8), cross-entropy) are applied to train the NL-QGD and all outperformed the L(2) norm when validated by receiver operating characteristics (ROC) curves. The data sets are constructed from TABILS 24 ISAR targets embedded in 7 km(2) of SAR imagery (MIT/LL mission 90).

  17. Optical nanolithography with λ/15 resolution using bowtie aperture array

    NASA Astrophysics Data System (ADS)

    Wen, Xiaolei; Traverso, Luis M.; Srisungsitthisunti, Pornsak; Xu, Xianfan; Moon, Euclid E.

    2014-10-01

    We report optical parallel nanolithography using bowtie apertures with the help of the interferometric-spatial-phase-imaging (ISPI) technique. The ISPI system can detect and control the distance between the bowtie aperture, and photoresist with a resolution of sub-nanometer level. It overcomes the difficulties brought by the light divergence of bowtie apertures. Parallel nanolithography with feature size of 22 ± 5 nm is achieved. This technique combines high resolution, parallel throughput, and low cost, which is promising for practical applications.

  18. Acoustic one-way metasurfaces: Asymmetric Phase Modulation of Sound by Subwavelength Layer

    NASA Astrophysics Data System (ADS)

    Jiang, Xue; Liang, Bin; Zou, Xin-Ye; Yang, Jing; Yin, Lei-Lei; Yang, Jun; Cheng, Jian-Chun

    2016-06-01

    We theoretically design and numerically demonstrate an acoustic one-way metasurface, which is a planar and acoustically subwavelength layer behaving like a nearly-reflectionless surface with arbitrary wave-steering capability for incident wave impinging on one side, while virtually blocking the reversed wave. The underlying mechanism is based on an asymmetric phase modulation by coupling a phase array and a near-zero-index medium. We exemplify a metastructure-based implementation by combining the hybrid metastuctures and labyrinthine structures. Moreover, the performance of the proposed implementation is demonstrated via three distinct phenomena of anomalous refraction, wave splitting and conversion of propagation wave to surface wave. Our findings may offer more possibilities for sound manipulation and improve the application potential of acoustic artificial devices in situations such as ultrasonic imaging and therapy.

  19. Influence of grating thickness in low-contrast subwavelength grating concentrating lenses

    NASA Astrophysics Data System (ADS)

    Ye, Mao; Yi, Ya Sha

    2016-07-01

    Conventional subwavelength grating concentrating lenses are designed based on calculated phase overlap, wherein the phase change is fixed by the grating thickness, bar-width, and airgap, and therefore the focus. We found that certain concentration effects can still be maintained by changing the grating thickness with the same bar-widths and airgap dimensions. Following that, we discovered the existence of the grating thickness threshold; light concentration intensity spikes upon exceeding this limit. However, the light concentration property does not change continuously with respect to a steady increase in grating thickness. This observation indicates that there exists a concentration mode self-interference effect along the light propagation direction inside the gratings. Our results may provide guidance in designing and fabricating microlenses in a potentially more easy and controllable manner. Such approaches can be utilized in various integrated nanophotonics applications ranging from optical cavities and read/write heads to concentrating photovoltaics.

  20. Self-assembly of subwavelength nanostructures with symmetry breaking in solution

    NASA Astrophysics Data System (ADS)

    Tian, Xiang-Dong; Chen, Shu; Zhang, Yue-Jiao; Dong, Jin-Chao; Panneerselvam, Rajapandiyan; Zhang, Yun; Yang, Zhi-Lin; Li, Jian-Feng; Tian, Zhong-Qun

    2016-01-01

    Nanostructures with symmetry breaking can allow the coupling between dark and bright plasmon modes to induce strong Fano resonance. However, it is still a daunting challenge to prepare bottom-up self-assembled subwavelength asymmetric nanostructures with appropriate gaps between the nanostructures especially below 5 nm in solution. Here we present a viable self-assembly method to prepare symmetry-breaking nanostructures consisting of Ag nanocubes and Au nanospheres both with tunable size (90-250 nm for Au nanospheres; 100-160 nm for Ag nanocubes) and meanwhile control the nanogaps through ultrathin silica shells of 1-5 nm thickness. The Raman tag of 4-mercaptobenzoic acid (MBA) assists the self-assembly process and endows the subwavelength asymmetric nanostructures with surface-enhanced Raman scattering (SERS) activity. Moreover, thick silica shells (above 50 nm thickness) can be coated on the self-assembled nanostructures in situ to stabilize the whole nanostructures, paving the way toward bioapplications. Single particle scattering spectroscopy with a 360° polarization resolution is performed on individual Ag nanocube and Au nanosphere dimers, correlated with high-resolution TEM characterization. The asymmetric dimers exhibit strong configuration and polarization dependence Fano resonance properties. Overall, the solution-based self-assembly method reported here is opening up new opportunities to prepare diverse multicomponent nanomaterials with optimal performance.Nanostructures with symmetry breaking can allow the coupling between dark and bright plasmon modes to induce strong Fano resonance. However, it is still a daunting challenge to prepare bottom-up self-assembled subwavelength asymmetric nanostructures with appropriate gaps between the nanostructures especially below 5 nm in solution. Here we present a viable self-assembly method to prepare symmetry-breaking nanostructures consisting of Ag nanocubes and Au nanospheres both with tunable size (90-250 nm

  1. Hybrid plasmonic-photonic mode in a subwavelength fiber for enhanced single-nanoparticle detection

    NASA Astrophysics Data System (ADS)

    Chen, You-Ling; Gong, Qihuang

    2015-01-01

    We study a hybrid mode in a composite system consisting of a localized metal nanosphere on a subwavelength fiber. It is found that the hybrid mode resulting from coupling of the fiber propagating mode and the plasmonic resonance is promising for strongly enhanced interaction between light and matter. We then propose a single-nanoparticle detection scheme by monitoring the nanofiber transmission change induced by the plasmonic-enhanced target scattering. The detection limit can be as low as 18 nm in target diameter, showing great potential for sensing single viruses or biomolecules. In the hybrid system, the resonant wavelength is tunable from visible to near-infrared spectral range by employing a metal nanoshell instead of the nanosphere, while the low detection limit of a few tens of nanometers can still remain.

  2. Strong coupling in the sub-wavelength limit using metamaterial nanocavities

    PubMed Central

    Benz, A.; Campione, S.; Liu, S.; Montaño, I.; Klem, J.F.; Allerman, A; Wendt, J.R.; Sinclair, M.B.; Capolino, F.; Brener, I.

    2013-01-01

    The interaction between cavity modes and optical transitions leads to new coupled light-matter states in which the energy is periodically exchanged between the matter states and the optical mode. Here we present experimental evidence of optical strong coupling between modes of individual sub-wavelength metamaterial nanocavities and engineered optical transitions in semiconductor heterostructures. We show that this behaviour is generic by extending the results from the mid-infrared (~10 μm) to the near-infrared (~1.5 μm). Using mid-infrared structures, we demonstrate that the light-matter coupling occurs at the single resonator level and with extremely small interaction volumes. We calculate a mode volume of 4.9 × 10−4 (λ/n)3 from which we infer that only ~2,400 electrons per resonator participate in this energy exchange process. PMID:24287692

  3. Funneling light into subwavelength grooves in metal/dielectric multilayer films.

    PubMed

    Zhu, Peng; Jin, Peng; Shi, Haofei; Guo, L Jay

    2013-02-11

    Light funneling in metal/dielectric multilayer films with subwavelength grooves is numerically and experimentally demonstrated. Incident light at the resonant wavelength can be completely funneled into dielectric layers through a narrow groove that only covers 12.5% of the surface area within one period and absorbed by a resonant cavity composed of metal/dielectric multilayer films. A narrower resonant dip is observed than that produced by bulk metals with the same thickness and grooves. The mechanism and influencing factors of the reflection spectrum, including groove widths, layer numbers, and the profile of the groove side wall are comprehensively analyzed. Coupling between adjacent grooves with different depths are also discussed. Our study can be applied in the applications of biological sensing and infrared detectors.

  4. Plasmon-enhanced Kerr nonlinearity via subwavelength-confined anisotropic Purcell factors

    NASA Astrophysics Data System (ADS)

    Ren, Juanjuan; Chen, Hongyi; Gu, Ying; Zhao, Dongxing; Zhou, Haitao; Zhang, Junxiang; Gong, Qihuang

    2016-10-01

    We theoretically investigate the enhancement of Kerr nonlinearity through anisotropic Purcell factors provided by plasmon nanostructures. In a three-level atomic system with crossing damping, larger anisotropism of Purcell factors leads to more enhanced Kerr nonlinearity in electromagnetically induced transparency windows. While for fixed anisotropic Purcell factors, Kerr nonlinearity with orthogonal dipole moments increases with the decrease of its crossing damping, and Kerr nonlinearity with nonorthogonal dipole moments is very sensitive to both the value of crossing damping and the orientation of the dipole moments. We design the non-resonant gold nanorods array, which only provides subwavelength-confined anisotropic Purcell factors, and demonstrate that the Kerr nonlinearity of cesium atoms close to the nanorods array can be modulated at the nanoscale. These findings should have potential application in ultracompact quantum logic devices.

  5. Achieving selective interrogation and sub-wavelength resolution in thin plates with embedded metamaterial acoustic lenses

    SciTech Connect

    Semperlotti, F. Zhu, H.

    2014-08-07

    In this study, we present an approach to ultrasonic beam-forming and high resolution identification of acoustic sources having critical implications for applications such as structural health monitoring. The proposed concept is based on the design of dynamically tailored structural elements via embedded acoustic metamaterial lenses. This approach provides a completely new alternative to conventional phased-array technology enabling the formation of steerable and collimated (or focused) ultrasonic beams by exploiting a single transducer. Numerical results show that the ultrasonic beam can be steered by simply tuning the frequency of the excitation. Also, the embedded lens can be designed to achieve sub-wavelength resolution to clustered acoustic sources, which is a typical scenario encountered in incipient structural damage.

  6. Acoustic one-way metasurfaces: Asymmetric Phase Modulation of Sound by Subwavelength Layer.

    PubMed

    Jiang, Xue; Liang, Bin; Zou, Xin-Ye; Yang, Jing; Yin, Lei-Lei; Yang, Jun; Cheng, Jian-Chun

    2016-06-16

    We theoretically design and numerically demonstrate an acoustic one-way metasurface, which is a planar and acoustically subwavelength layer behaving like a nearly-reflectionless surface with arbitrary wave-steering capability for incident wave impinging on one side, while virtually blocking the reversed wave. The underlying mechanism is based on an asymmetric phase modulation by coupling a phase array and a near-zero-index medium. We exemplify a metastructure-based implementation by combining the hybrid metastuctures and labyrinthine structures. Moreover, the performance of the proposed implementation is demonstrated via three distinct phenomena of anomalous refraction, wave splitting and conversion of propagation wave to surface wave. Our findings may offer more possibilities for sound manipulation and improve the application potential of acoustic artificial devices in situations such as ultrasonic imaging and therapy.

  7. Responsivity improvements for a vanadium oxide microbolometer using subwavelength resonant absorbers

    NASA Astrophysics Data System (ADS)

    Smith, Evan M.; Nath, Janardan; Ginn, James; Peale, Robert E.; Shelton, David

    2016-05-01

    Subwavelength resonant structures designed for long-wave infrared (LWIR) absorption have been integrated with a standard vanadium-oxide microbolometer. Dispersion of the dielectric refractive index provides for multiple overlapping resonances that span the 8-12 μm LWIR wavelength band, a broader range than can be achieved using the usual quarter-wave resonant cavity engineered into the air-bridge structures. Experimental measurements show a 49% increase in responsivity for LWIR and a 71% increase across a full waveband as compared to a similar device designed for only LWIR absorption, using a 300°C blackbody at 35 Hz chopping rate. Increased thermal time constant due to additional mass is shown to lessen this enhancement at higher chopping rates.

  8. Numerical analysis of the sub-wavelength fabrication of MTMO grayscale photomasks by direct laser writing.

    PubMed

    Xia, Feng; Zhang, Xinzheng; Wang, Meng; Yi, Sanming; Liu, Qian; Xu, Jingjun

    2014-07-14

    Metal-transparent-metallic-oxide (MTMO) grayscale photomasks fabricated by direct laser writing have been proposed in recent years. The fabrication mechanism is attributed to light-induced melt-oxidization. The temporal-spatial distribution of temperature fields of indium film-glass samples under a laser pulse have been calculated by the Finite-Difference Time-Domain method. The laser action area of the indium film is studied based on the oxidation theories and the absorbed laser power density distribution in molten indium films. The calculated average sub-wavelength fabrication diameter of 302 nm is consistent with the experimental fabrication size under a laser power of 6.0 - 8.0 mW. PMID:25090505

  9. Sub-wavelength imaging using silver-dielectric metamaterial layered prism

    NASA Astrophysics Data System (ADS)

    Stolarek, Marcin; Pastuszczak, Anna; Pniewski, Jacek; Kotyński, Rafał

    2010-12-01

    In this paper we study the propagation of light through silver-dielectric metamaterial layered prism which operates in the canalization regime. The prism is illuminated with TM-polarized light and is designed using the effective medium theory as strongly anisotropic and impedance matched to air. The structure has an infinite value of the effective permittivity in the direction perpendicular to layer surfaces. Therefore it is able to couple a broad spectrum of incident spatial frequencies, including evanescent waves, into propagating modes. As a result, subwavelength resolution at the output interface of the structure is observed. Further the device is characterised with the transfer matrix method (TMM), and investigated with Finite Difference Time Domain method (FDTD). Two parameters of the prism are studied, namely the angle of incidence and the apex angle, to obtain the best resolution.

  10. Coherent perfect absorption in deeply subwavelength films in the single-photon regime.

    PubMed

    Roger, Thomas; Vezzoli, Stefano; Bolduc, Eliot; Valente, Joao; Heitz, Julius J F; Jeffers, John; Soci, Cesare; Leach, Jonathan; Couteau, Christophe; Zheludev, Nikolay I; Faccio, Daniele

    2015-05-05

    The technologies of heating, photovoltaics, water photocatalysis and artificial photosynthesis depend on the absorption of light and novel approaches such as coherent absorption from a standing wave promise total dissipation of energy. Extending the control of absorption down to very low light levels and eventually to the single-photon regime is of great interest and yet remains largely unexplored. Here we demonstrate the coherent absorption of single photons in a deeply subwavelength 50% absorber. We show that while the absorption of photons from a travelling wave is probabilistic, standing wave absorption can be observed deterministically, with nearly unitary probability of coupling a photon into a mode of the material, for example, a localized plasmon when this is a metamaterial excited at the plasmon resonance. These results bring a better understanding of the coherent absorption process, which is of central importance for light harvesting, detection, sensing and photonic data processing applications.

  11. Coherent perfect absorption in deeply subwavelength films in the single-photon regime

    PubMed Central

    Roger, Thomas; Vezzoli, Stefano; Bolduc, Eliot; Valente, Joao; Heitz, Julius J. F.; Jeffers, John; Soci, Cesare; Leach, Jonathan; Couteau, Christophe; Zheludev, Nikolay I.; Faccio, Daniele

    2015-01-01

    The technologies of heating, photovoltaics, water photocatalysis and artificial photosynthesis depend on the absorption of light and novel approaches such as coherent absorption from a standing wave promise total dissipation of energy. Extending the control of absorption down to very low light levels and eventually to the single-photon regime is of great interest and yet remains largely unexplored. Here we demonstrate the coherent absorption of single photons in a deeply subwavelength 50% absorber. We show that while the absorption of photons from a travelling wave is probabilistic, standing wave absorption can be observed deterministically, with nearly unitary probability of coupling a photon into a mode of the material, for example, a localized plasmon when this is a metamaterial excited at the plasmon resonance. These results bring a better understanding of the coherent absorption process, which is of central importance for light harvesting, detection, sensing and photonic data processing applications. PMID:25991584

  12. Dielectric inspired scaling of polarization conversion subwavelength resonances in open ultrathin chiral structures

    NASA Astrophysics Data System (ADS)

    Serebryannikov, Andriy E.; Mutlu, Mehmet; Ozbay, E.

    2015-11-01

    It is shown that the scaling of subwavelength resonances in open ultrathin chiral structures can be obtained by varying only the permittivity of dielectric spacers, while multiband one-way polarization conversion and related asymmetric transmission remain possible. These features are quite general and obtainable in a wide range of parameter variation. Surprisingly, the difference in the power of ɛ for the classical ɛ-1/2 scaling rule and the empirical rules obtained in the present letter does not exceed 22%, giving an important entry point for future theoretical studies and design strategies. Both spectral scaling and conservation of the polarization characteristics can be achieved by using either tunneling or real-index impedance matching. The scaled structures with strong polarization and directional selectivity may have thickness of λ/100 and smaller.

  13. Plasmon-enhanced Kerr nonlinearity via subwavelength-confined anisotropic Purcell factors.

    PubMed

    Ren, Juanjuan; Chen, Hongyi; Gu, Ying; Zhao, Dongxing; Zhou, Haitao; Zhang, Junxiang; Gong, Qihuang

    2016-10-21

    We theoretically investigate the enhancement of Kerr nonlinearity through anisotropic Purcell factors provided by plasmon nanostructures. In a three-level atomic system with crossing damping, larger anisotropism of Purcell factors leads to more enhanced Kerr nonlinearity in electromagnetically induced transparency windows. While for fixed anisotropic Purcell factors, Kerr nonlinearity with orthogonal dipole moments increases with the decrease of its crossing damping, and Kerr nonlinearity with nonorthogonal dipole moments is very sensitive to both the value of crossing damping and the orientation of the dipole moments. We design the non-resonant gold nanorods array, which only provides subwavelength-confined anisotropic Purcell factors, and demonstrate that the Kerr nonlinearity of cesium atoms close to the nanorods array can be modulated at the nanoscale. These findings should have potential application in ultracompact quantum logic devices. PMID:27632352

  14. Efficiency enhancement in Cu2ZnSnS4 solar cells with subwavelength grating nanostructures.

    PubMed

    Kuo, Shou-Yi; Hsieh, Ming-Yang

    2014-07-01

    In the article, a study of sub-wavelength grating (SWG) nanostructures for broadband and omni-directional anti-reflection coatings (ARCs) on Cu2ZnSnS4 (CZTS) solar cells using the rigorous coupled-wave analysis (RCWA) method is presented. Various SWG nanostructures of different shapes and periodic geometry on CZTS solar cells are discussed in detail. The optimized reflectance decreased to 1.67%, and efficiency increased to 13.74%, accordingly. The omni-directional and broadband antireflections of the SWG nanostructures are also investigated. Under a simulated 1-sun condition and with the light incident angle increased to 80°, cells with SWG nanostructures enhanced the short-circuit current density by 16.5%. This considerable enhancement in light harvesting is attributed to the linearly graded effective refractive index profile from the air to the device surface. PMID:24890020

  15. Brillouin light scattering from surface acoustic waves in a subwavelength-diameter optical fibre

    PubMed Central

    Beugnot, Jean-Charles; Lebrun, Sylvie; Pauliat, Gilles; Maillotte, Hervé; Laude, Vincent; Sylvestre, Thibaut

    2014-01-01

    Brillouin scattering in optical fibres is a fundamental interaction between light and sound with important implications ranging from optical sensors to slow and fast light. In usual optical fibres, light both excites and feels shear and longitudinal bulk elastic waves, giving rise to forward-guided acoustic wave Brillouin scattering and backward-stimulated Brillouin scattering. In a subwavelength-diameter optical fibre, the situation changes dramatically, as we here report with the first experimental observation of Brillouin light scattering from surface acoustic waves. These Rayleigh-type surface waves travel the wire surface at a specific velocity of 3,400 m s−1 and backscatter the light with a Doppler shift of about 6 GHz. As these acoustic resonances are sensitive to surface defects or features, surface acoustic wave Brillouin scattering opens new opportunities for various sensing applications, but also in other domains such as microwave photonics and nonlinear plasmonics. PMID:25341638

  16. Efficient bending and focusing of light beam with all-dielectric subwavelength structures

    NASA Astrophysics Data System (ADS)

    Shen, Yue; Luo, Xiangang

    2016-05-01

    In this paper, all-dielectric subwavelength structures are proposed to construct beam deflectors and lenses that modulate the light fields efficiently. These devices are composed of planar array of silicon pyramids with spatially varying geometric shapes, thereby introducing arbitrary phase shift to the propagating light. Meanwhile, owing to the intrinsic low-reflection property, average reflectance as low as 10% is accomplished. The lenses were rigorously designed in both one-dimensional (1D) and two-dimensional (2D) cases. Due to the symmetry of the unit cell, there is no limitation on the polarization state of the incident light. Since no plasmonic loss is incorporated, this design could meet the requirement of wavefront manipulation for laser beams.

  17. Subwavelength film sensing based on terahertz anti-resonant reflecting hollow waveguides.

    PubMed

    You, Borwen; Lu, Ja-Yu; Liou, Jia-Hong; Yu, Chin-Ping; Chen, Hao-Zai; Liu, Tze-An; Peng, Jin-Long

    2010-08-30

    A simple dielectric hollow-tube has been experimentally demonstrated at terahertz range for bio-molecular layer sensing based on the anti-resonant reflecting wave-guidance mechanism. We experimentally study the dependence of thin-film detection sensitivity on the optical geometrical parameters of tubes, different thicknesses and tube wall refractive indices, and on different resonant frequencies. A polypropylene hollow-tube with optimized sensitivity of 0.003 mm/μm is used to sense a subwavelength-thick (λ/225) carboxypolymethylene molecular overlayer on the tube's inner surface, and the minimum detectable quantity of molecules could be down to 1.22 picomole/mm(2). A double-layered Fabry-Pérot model is proposed for calculating the overlayer thicknesses, which agrees well with the experimental results.

  18. Acoustic one-way metasurfaces: Asymmetric Phase Modulation of Sound by Subwavelength Layer

    PubMed Central

    Jiang, Xue; Liang, Bin; Zou, Xin-ye; Yang, Jing; Yin, Lei-lei; Yang, Jun; Cheng, Jian-chun

    2016-01-01

    We theoretically design and numerically demonstrate an acoustic one-way metasurface, which is a planar and acoustically subwavelength layer behaving like a nearly-reflectionless surface with arbitrary wave-steering capability for incident wave impinging on one side, while virtually blocking the reversed wave. The underlying mechanism is based on an asymmetric phase modulation by coupling a phase array and a near-zero-index medium. We exemplify a metastructure-based implementation by combining the hybrid metastuctures and labyrinthine structures. Moreover, the performance of the proposed implementation is demonstrated via three distinct phenomena of anomalous refraction, wave splitting and conversion of propagation wave to surface wave. Our findings may offer more possibilities for sound manipulation and improve the application potential of acoustic artificial devices in situations such as ultrasonic imaging and therapy. PMID:27305973

  19. Super-transmission from a finite subwavelength arrangement of slits in a metal film.

    PubMed

    Chen, Shuwen; Jin, Shilong; Gordon, Reuven

    2014-06-01

    A theory is presented for the transmission of transverse magnetic waves through a finite number of subwavelength slits in metal film. While a single slit achieves the single channel limit on resonance, multiple slits show super-transmission exceeding the single channel limit. The phenomenon of super-transmission is revealed as a result of cross-coupling of modes and confirmed by simulations. The influence of finite permittivity in the IR and microwave regime is included by perturbative corrections to the theory. The theory agrees quantitatively with past experiments and finite-difference time-domain simulations. By considering two or more modes in the slit region, our theory provides an approach to the analysis of cross-coupling among slits, which allows for super-transmission and features of a Fano resonance.

  20. Millimeter-wave broadband antireflection coatings using laser ablation of subwavelength structures.

    PubMed

    Matsumura, Tomotake; Young, Karl; Wen, Qi; Hanany, Shaul; Ishino, Hirokazu; Inoue, Yuki; Hazumi, Masashi; Koch, Jürgen; Suttman, Oliver; Schütz, Viktor

    2016-05-01

    We report on the first use of laser ablation to make submillimeter, broadband, antireflection coatings (ARCs) based on subwavelength structures (SWSs) on alumina and sapphire. We used a 515 nm laser to produce pyramid-shaped structures with a pitch of about 320 μm and a total height of near 800 μm. Transmission measurements between 70 and 140 GHz are in agreement with simulations using electromagnetic propagation software. The simulations indicate that SWS-ARCs with the fabricated shape should have a fractional bandwidth response of Δν/νcenter=0.55 centered on 235 GHz for which reflections are below 3%. Extension of the bandwidth to both lower and higher frequencies, between a few tens of gigahertz and a few terahertz, should be straightforward with appropriate adjustment of laser ablation parameters.