254 research outputs found
Dispersionless slow light with 5-pulse-width delay in fibre Bragg grating
No full textThe excitation of gap solitons in a 30 cm fibre Bragg grating using 0.68 ns pulses, which emerge with a tunable delay of up to 3.2 ns, corresponding to almost five pulse widths, and without broadening, are observed. This delay is an improvement by a factor of 2 from previous experiments
Applications for fiber Bragg gratings in communications
No full textThe advent of low insertion-loss, high efficiency gratings photoinduced directly in the core of optical fiber leads to a wide range of applications. Optical fiber Bragg grating (OFBG) technology is now "coining of age", with the likely inclusion of fiber gratings in devices to be incorporated in commercial communication systems
Novel designs of optoacoustic waveguides
No full textWe present two new designs of optoacoustic waveguides supporting nonlinear Brillouin scattering (SBS). The first design, optimized for forward SBS, comprises a rectangular core supporting a low-loss optical mode, suspended in air by a series of transverse ribs. The ribs are engineered to exhibit a complete acoustic stopband and suppress the transverse leakage of acoustic waves. The second design we discuss here is a realization of an Anti-Resonant Reflecting Acoustic Waveguide, which are analogues of optical ARROWs. These waveguides, capable of co-localization and guiding of both the optical and GHz acoustic waves in simple, translationally invariant waveguides, are shown to support backwards SBS
Suspended mid-infrared waveguides for stimulated Brillouin scattering
No full text We theoretically investigate a new class of silicon waveguides for achieving Stimulated Brillouin Scattering (SBS) in the mid-infrared (MIR). The waveguide consists of a rectangular core supporting a low-loss optical mode, suspended in air by a series of transverse ribs. The ribs are patterned to form a finite quasi-one-dimensional phononic crystal, with the complete stopband suppressing the transverse leakage of acoustic waves, confining them to the core of the waveguide. We derive a theoretical formalism that can be used to compute the opto-acoustic interaction in such periodic structures, and find forward intramodal-SBS gains up to 1750 m-1 W-1 , which compares favorably with the proposed MIR SBS designs based on buried germanium waveguides. This large gain is achieved thanks to the nearly complete suppression of acoustic radiative losses. </p
Slow light gap solitons
No full textBook Summary:The exotic effects of slow light have been widely observed in the laboratory. However, current literature fails to explore the wider field of slow light in photonic structures and optical fibers.Reflecting recent research, Slow Light: Science and Applications presents a comprehensive introduction to slow light and its potential applications, including storage, switching, DOD applications, and nonlinear optics. The book covers fundamentals of slow light in various media, including atomic media, semiconductors, fibers, and photonic structures. Leading authorities in such diverse fields as atomic vapor spectroscopy, fiber amplifiers, and integrated optics provide an interdisciplinary perspective. They uncover potential applications in both linear and nonlinear optics.While it is impossible to account for all the captivating developments that have occurred in the last few years, this book provides an exceptional survey of the current state of the slow light field
Ultra-Strong and well-apodized Bragg gratings in chalcogenide rib waveguides
No full text©2005 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.The first ultra-strong, near-perfect, raised-apodised Bragg gratings in As₂S₃ chalcogenide rib waveguides using λ=532 nm light and a modified Sagnac holographic writing setup are demonstrated. Good agreement is achieved between the experimental results and the numerical modelling of the gratings using the transfer matrix analysis for thin film structures.M. Shokooh-Saremi, V.G. Ta’eed , I.C.M. Littler , D.J. Moss, B.J. Eggleton, Y. Ruan and B. Luther-Davie
Broadband Single-polarization Guidance In Hybrid Photonic Crystal Fibers
No full textWe present hybrid photonic crystal fibers that provide broadband single-polarization guidance based on two different propagation mechanisms, namely, total internal reflection and the photonic bandgap effect. Experimental results demonstrate polarization dependent loss as high as 26:7 dB and the bandwidth of single-polarization behavior over 225 nm. © 2011 Optical Society of America.362133135Cerqueira Jr., A.S., (2010) Rep. Prog. Phys., 73, p. 024401Ortigosa-Blanch, A., Knight, J.C., Wadsworth, W.J., Arriaga, J., Mangan, B.J., Birks, T.A., St. J Russell, P., (2000) Opt. Lett., 25, p. 1325Folkenberg, J.R., Nielsen, M.D., Jakobsen, C., (2005) Opt. Lett., 30, p. 1446Goto, R., Jackson, S.D., Fleming, S., Kuhlmet, B.T., Eggleton, B.J., Himeno, K., (2008) Opt. Express, 16, p. 18752Goto, R., Jackson, S.D., Takenaga, K., (2009) Opt. Express, 34, p. 3119Sun, J., Chan, C.C., (2007) J. Opt. Soc. Am. B, 24, p. 2640Cerqueira Jr., A.S., Luan, F., Cordeiro, C.M.B., George, A.K., Knight, K.C., (2006) Opt. Express, 14, p. 926Xiao, L., Jin, W., Demokan, M.S., (2007) Opt. Express, 15, p. 15637Cerqueira Jr., A.S., Cordeiro, C.M.B., Biancalana, F., Roberts, P.J., Hernandez-Figueroa, H.E., Brito Cruz, C.H., (2008) Opt. Lett., 33, p. 2080Litchinitser, N.M., Dunn, S.C., Usner, B., Eggleton, B.J., White, T.P., McPhedran, R.C., De Sterke, C.M., (2003) Opt. Express, 11, p. 1243Schreiber, T., Roser, F., Schmidt, O., Limpert, J., Iliew, R., Lederer, F., Petersson, A., Tunnermann, A., (2005) Opt. Express, 13, p. 7621Varnham, M.P., Payne, D.N., Barlow, A.J., Tarbox, E.J., (1984) Opt. Lett., 9, p. 30
Second-harmonic generation as characterization tool for Ge/high-k dielectric interfaces
No full textBecause the germanium native oxide constitutes a poor dielectric, building metal oxide semiconductors (MOS) gate stacks on Ge requires passivation of the interface between the dielectric and the Ge channel. Different approaches to perform this passivation are available: GeO2 growth prior to high-k depositing, sulphur passivation, etc. The interface properties of these MOS stacks are important, because they determine the electrical properties of the whole structure. Dangling bonds introduce extra energy levels within the band gap, which results in a loss of efficiency in switching a MOS - field effect transistor on and off. Fixed charges near the interface enlarge the voltage needed for switching between on and off state as well. Hence, characterizing these interfaces is a key challenge in semiconductor fabrication. This can for example be achieved using Second Harmonic Generation (SHG) to probe the interface, because SHG is an inherent surface and interface sensitive technique. In this work, we present SHG as an promising surface and interface characterization tool for semiconductors for passivated germanium samples. Different SHG responses are shown for germanium samples with a sulphur passivated Ge or high-k dielectric on top of Si. We show that the oxide layer as such is not probed by SHG and that different bonds over the Ge/oxide interface result in a difference SHG response.sponsorship: Katholieke Univ Leuven, Dept Chem, B-3001 Louvain, Belgiumstatus: Publishe
Spectral measurements to probe the magneto-optical properties of commonly used organic dyes
No full textMagneto-optically active organic compounds are of great technological interest. In contrast to inorganic materials, used in most current applications, organic materials have the advantages of fast response times, easy processing, low cost and abundant resources of starting materials available. Conjugated organic molecules or polymers have been reported to be eligible candidates for exhibiting magneto-optical responses. As part of an ongoing search in our group for efficient magneto-optical materials, eight organic conjugated dyes were screened for their Faraday rotation responses. Based on the obtained preliminary results, it is expected that planar, efficiently pi-conjugated molecules have a higher chance for exhibiting significant magneto-optical responses. Further research will be undertaken to confirm this hypothesis.sponsorship: Katholieke Univ Leuven, Lab Mol Elect & Photon, Div Mol Imaging & Photon, Dept Chem, B-3001 Leuven, Belgiumstatus: Publishe
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