Windows into Non-Euclidean Spaces

Two microlens arrays that are separated by the sum of their focal lengths form arrays of micro-telescopes. Parallel light rays that pass through corresponding lenses remain parallel, but the direction of the transmitted light rays is different. This remains true if corresponding lenses do not share an optical axis (i.e. if the two microlens arrays are shifted with respect to each other). The arrays described above are examples of generalized confocal lenslet arrays, and the light-ray-direction change in these devices is well understood [Oxburgh et al., Opt. Commun. 313, 119 (2014)]. Here we show that such micro-telescope arrays change light-ray direction like the interface between spaces with different metrics. To physicists, the concept of metrics is perhaps most familiar from General Relativity (where it is applied to spacetime, not only space, like it is here) and Transformation Optics [Pendry et al., Science 312, 1780 (2006)], where different materials are treated like spaces with different optical metrics. We illustrate the similarities between micro-telescope arrays and metric interfaces with raytracing simulations. Our results suggest the possibility of realising transformation-optics devices with micro-telescope arrays, which we investigate elsewhere

Improved solid state electron-charge-storage device

Storage device is applicable in memory systems and in high-resolution arrays for light-responsive image sensing. The device offers high yield in multiple arrays and allows charge release with light striking only the edge of a metal electrode

Light Bullets in Nonlinear Periodically Curved Waveguide Arrays

We predict that stable mobile spatio-temporal solitons can exist in arrays of periodically curved optical waveguides. We find two-dimensional light bullets in one-dimensional arrays with harmonic waveguide bending and three-dimensional bullets in square lattices with helical waveguide bending using variational formalism. Stability of the light bullet solutions is confirmed by the direct numerical simulations which show that the light bullets can freely move across the curved arrays. This mobility property is a distinguishing characteristic compared to previously considered discrete light bullets which were trapped to a specific lattice site. These results suggest new possibilities for flexible spatio-temporal manipulation of optical pulses in photonic lattices.Comment: 7 pages, 4 figure

Light propagation in nanorod arrays

We study propagation of TM- and TE-polarized light in two-dimensional arrays of silver nanorods of various diameters in a gelatin background. We calculate the transmittance, reflectance and absorption of arranged and disordered nanorod arrays and compare the exact numerical results with the predictions of the Maxwell-Garnett effective-medium theory. We show that interactions between nanorods, multipole contributions and formations of photonic gaps affect strongly the transmittance spectra that cannot be accounted for in terms of the conventional effective-medium theory. We also demonstrate and explain the degradation of the transmittance in arrays with randomly located rods as well as weak influence of their fluctuating diameter. For TM modes we outline the importance of skin-effect, which causes the full reflection of the incoming light. We then illustrate the possibility of using periodic arrays of nanorods as high-quality polarizers.Comment: 6 pages, 7 figure

Arrays of Light: Betsy Schramm CD Release Concert, April 15, 2015

This is the concert program of the Arrays of Light: Betsy Schramm CD Release Concert on Wednesday, April 15, 2015 at 8:00 p.m., at the Tsai Performance Center, 685 Commonwealth Avenue. Works performed were the following by Betsy Schramm: Arrays of Light, Restless Airs, Light Excelleth Darkness, I. Prisms and IV. Dance from Suite for Flugelhorn, Luminous Duo, and Transformations. Digitization for Boston University Concert Programs was supported by the Boston University Humanities Library Endowed Fund

Enhancement of Visible-Light-Induced Photocurrent and Photocatalytic Activity of V and N Codoped TiO2 Nanotube Array Films

Highly ordered TiO2 nanotube arrays (TNAs) codoped with V and N were synthesized by electrochemical anodization in association with hydrothermal treatment. The samples were characterized by field emission scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The photocurrent and photocatalytic activity of codoped TiO2 nanotube arrays were investigated under visible light irradiation. Moreover, the production of hydroxyl radicals on the surface of visible light-irradiated samples is detected by a photoluminescence technique using terephthalic acid (TA) as a probe molecule. It was found that the V+N co-doped TiO2 nanotube arrays showed remarkably enhanced photocurrent and photocatalytic activity than undoped sample due to the V and N codoping.Comment: 15 Pages, 6 figure

Simulations of detector arrays and the impact of atmospheric parameters

In Monte-Carlo simulations of gamma-ray or cosmic-ray detector arrays on the ground (here mainly arrays of imaging atmospheric Cherenkov telescopes), the atmosphere enters in several ways: in the development of the particle showers, in the emission of light by shower particles, and in the propagation of Cherenkov light (or fluorescence light or of particles) down to ground level. Relevant parameters and their typical impact on energy scale and so on are discussed here.Comment: 4 pages, 5 figures. Proceedings of the Atmospheric Monitoring for High-Energy Astroparticle Detectors (AtmoHEAD) Conference, Saclay (France), June 10-12, 201