We demonstrate all-optical switching in the telecommunication band, in silicon photonic crystals at high speed (similar to 50 ps), with extremely low switching energy (a few 100 fJ), and high switching contrast (simil...
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We demonstrate all-optical switching in the telecommunication band, in silicon photonic crystals at high speed (similar to 50 ps), with extremely low switching energy (a few 100 fJ), and high switching contrast (similar to 10 dB). The devices consist of ultrasmall high-quality factor nanocavities connected to input and output waveguides. Switching is induced by a nonlinear refractive-index change caused by the plasma effect of carriers generated by two-photon absorption in silicon. The high-quality factor and small mode volume led to an extraordinarily large reduction in switching energy. The estimated internal switching energy in the nanocavity is as small as a few tens of fJ, indicating that further reduction on the operating energy is possible. (C) 2005 American Institute of Physics.
Recent theoretical work on exciton-light coupling in waveguide-embedded photonic crystals is reviewed. After a short description of the theory of photonic crystal slabs, the following issues are discussed: (i) a quant...
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Recent theoretical work on exciton-light coupling in waveguide-embedded photonic crystals is reviewed. After a short description of the theory of photonic crystal slabs, the following issues are discussed: (i) a quantum-mechanical formulation of the interaction between photonic modes and quantum-well excitons, leading to a description of photonic crystal polaritons;(ii) calculations of variable-angle reflectance spectra, which show that radiative polaritons can be excited by an optical beam incident on the slab surface;(iii) a description of nanoscale cavities with extremely high Q-factors and low mode volumes in photonic crystal slabs;(iv) a quantum-mechanical model of the interaction between confined nanocavity modes and single quantum-dot transitions, leading again to a strong-coupling regime of light-matter interaction. (c) 2005 WILEYNCH Verlag GmbH & Co. KGaA, Weinheim.
We demonstrate a guided resonance filter based on photonic crystals (PhCs), which are fabricated in a high-permittivity material. The resulting spectra from a three-dimensional analysis of the structure and experiment...
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We demonstrate a guided resonance filter based on photonic crystals (PhCs), which are fabricated in a high-permittivity material. The resulting spectra from a three-dimensional analysis of the structure and experimental measurement results show sharp dips and flattop transmissions. These provide promising properties in constructing sensitive and compact wavelength-selective devices, such as wavelength-division multiplexers. (c) 2005 American Institute of Physics.
The luminescence properties of Eu chelates with different neutral ligands in poly(methyl methacrylate) (PMMA) have been investigated and the influence of the neutral ligand was analyzed. According to the fluorescence ...
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The luminescence properties of Eu chelates with different neutral ligands in poly(methyl methacrylate) (PMMA) have been investigated and the influence of the neutral ligand was analyzed. According to the fluorescence emission spectra, the Judd-Ofelt parameters Omega(2) and Omega(4) of Eu chelates containing PMMA have been calculated and the radiative properties are also presented. (c) 2005 WILEY-VCH Verlag GmbH & Co.
The propagation characteristics of nonlinear TE surface waves at a lateral antiferromagnetic/nonmagnetic superlattices (LANS) substrate and a nonlinear magnetic cover have been investigated. LANS which are linear freq...
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The propagation characteristics of nonlinear TE surface waves at a lateral antiferromagnetic/nonmagnetic superlattices (LANS) substrate and a nonlinear magnetic cover have been investigated. LANS which are linear frequency-dependent gyromagnetic media, are described with an effective medium theory. It is found that the dispersion of the TE waves show the optical bistability behavior. The optical bistability is affected by the magnetic fraction f(1). We also calculate and illustrate the variation of the wave index with the power flow for various values of f(1). We found that the decrease in f(1) makes the power threshold of nonlinear TE surface waves decrease.
We study transport properties of many-mode electron waveguides paying the main attention to the interplay between the amplitude and gradient scattering from rough surfaces. Our analysis shows that the two types of sca...
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We study transport properties of many-mode electron waveguides paying the main attention to the interplay between the amplitude and gradient scattering from rough surfaces. Our analysis shows that the two types of scattering are governed by different control parameters. The first (common) parameter is the ratio of the roughness amplitude to the transverse average width of a waveguide. The second parameter is determined by the squared derivative of a surface profile. We have found that the latter parameter can play the major role in the expression for the inverse mean free path, in contrast to all previous studies where the square-gradient terms were neglected. Our results may be used in experimental realizations of the surface scattering of electron waves, as well as in other applications (e.g., for optical and microwavewaveguides). (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Incorporation of metal alkoxides (Ti.. Zr, etc.) for tuning the optical properties of silica glasses by the sol-gel process is of significant interest for optical applications. In this paper, we report an anhydrous so...
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Incorporation of metal alkoxides (Ti.. Zr, etc.) for tuning the optical properties of silica glasses by the sol-gel process is of significant interest for optical applications. In this paper, we report an anhydrous sol-gel process for preparation of photosensitive titania-doped hybrid glassy polymer with good homogeneity and high doping concentration (TiO2 up to 40mol%). The process, consists of two steps: in the first step methacryloxypropyltrimethoxysilane (MPS) is hydrolyzed by boric acid through ligand exchange reaction (OH <----> OR) under anhydrous conditions;and in the second step dimethyldimethoxysilane (DMDMS), diphenyidimethoxysilane (DPhDMS) and titanium ethoxide (TET) were added to condense with the silanols formed in the first step. The optical properties of the synthesized hybrid polymer were studied, and results showed that the hybrid material has low OH absorption, low optical losses (0.45dB/cm at 1550nm and 0.16dB/cm at 1310nm respectively), and good thermo-optical linearity with tuneable refractive index. The effect of TiO2 doping in reducing the OH concentration of the hybrid material was observed. and the mechanism for this effect is discussed. (C) 2004 Elsevier B.V. All rights reserved.
We report on refractive index measurements of guiding and non-guiding films synthesized by the sol-gel technique. An experimental setup has been developed in our laboratory based on both m-line and Brewster angle meth...
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We report on refractive index measurements of guiding and non-guiding films synthesized by the sol-gel technique. An experimental setup has been developed in our laboratory based on both m-line and Brewster angle methods. The main feature of the setup is the ability to perform both m-line and Brewster angle measurements on the same sample allowing a more accurate measurement of the refractive index. Moreover, using laser sources at different wavelengths, we are able to measure refractive index as a function of wavelength in the visible and near infrared spectral range. We have tested our experimental setup performing measurements on many guiding and non-guiding sol-gel films deposited by the spin-coating technique on glass substrates. Estimation of refractive indices for non-absorbing thin films with an accuracy and reproducibility to within 0.1%, in a spectral region from 532 nm to 780 nm, has been achieved. (c) 2005 Elsevier B.V. All rights reserved.
A photoinduced decrease of refractive index has been demonstrated in SiO2:SnO2 (15 mol%) optical-grade glass ceramic, exposed to a 780 nm wavelength, focused femtosecond laser radiation at 1 kHz repetition rate. Expos...
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A photoinduced decrease of refractive index has been demonstrated in SiO2:SnO2 (15 mol%) optical-grade glass ceramic, exposed to a 780 nm wavelength, focused femtosecond laser radiation at 1 kHz repetition rate. Exposition have been performed translating the sample perpendicularly to the laser beam at a constant velocity of 17 mu m/s, with energies ranging between 2 and 5 mu J per pulse. The samples were fabricated by the sol-gel method, from 85 mol% tetraetoxysilane and 15 mol% dibutyl tin-diacetate, adding water to a solution of the precursors. Xerogel was produced by slowly evaporating the solvent for 2 weeks at 35 degrees C. The final material was obtained heating in O-2 the xerogel samples by a thermal ramp (4 degrees C/h) up to 1050 degrees C. Samples were then cut from the blocks with a diamond saw to 10 x 10 x 1 mm(3) and all the faces polished. A negative variation of the refractive index has been demonstrated in the irradiated zone (-3 x 10(-4)) measured by the prism coupling technique. Multimode waveguides at 633 nm have been obtained exploiting a positive refractive index change at the boundaries of the irradiated zone. Raman spectra have been measured showing several broad bands centered at about 430, 800 and 1100 cm(-1), and with two peaks at 490 and 610 cm(-1), when exciting at 488 nm. Strong red luminescence has also been observed when exciting at 633 nm suggesting the creation of non-bridging oxygen defects in the silica-based glass. We proposed that the negative refractive index change in the irradiated zone is due to the amorphization of the nanocrystals, while further investigation is needed to fully understand the origin of the positive index change at the boundaries. (c) 2005 Elsevier B.V. All rights reserved.
Features of the behavior of light beams in one-dimensional photonic lattices in iron-doped lithium niobate have been experimentally studied. It is demonstrated that bright discrete spatial solitons and bright gap soli...
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Features of the behavior of light beams in one-dimensional photonic lattices in iron-doped lithium niobate have been experimentally studied. It is demonstrated that bright discrete spatial solitons and bright gap solitons can be formed in this system using 633 nm radiation on a microwatt power level. (C) 2005 Pleiades Publishing, Inc.
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