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Quasi-phase-matching and quantum-path control of high-harmonic generation using counterpropagating light

NATURE PHYSICS 2007年第4期3卷 270-275页

作者： Zhang, Xiaoshi Lytle, Amy L. Popmintchev, Tenio Zhou, Xibin Kapteyn, Henry C. Murnane, Margaret M. Cohen, Oren Univ Colorado Joint Inst Lab Astrophys Boulder CO 80309 USA Univ Colorado Dept Phys Boulder CO 80309 USA

High-order harmonic upconversion of femtosecond lasers produces a unique source of short-wavelength light with femtosecond-to-attosecond pulse duration. However, because the involved nonlinear medium is a partially ionized gas, traditional approaches for phase-matching the conversion process are not applicable. This severely limits the flux from this source. Here, we demonstrate the first use of a train of counterpropagating light pulses to enhance high-harmonic emission. This all-optical quasi-phase-matching technique uses interfering beams to scramble the quantum phase of the generated short-wavelength light, to suppress emission from out-of-phase regions. Selective enhancement of more than 300 is observed at photon energies around 70 eV in argon gas. Finally, we show that by adjusting the intensity of the counterpropagating light, different electron quantum trajectories can be selectively enhanced, demonstrating attosecond-timescale coherent control of the radiating electron wavefunction.

关键词： EXTREME-ULTRAVIOLET LIGHT X-RAY GENERATION MULTIPHOTON IONIZATION wave-guides PULSES

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Planar waveguides as high performance sensing platforms for fluorescence-based multiplexed oligonucleotide hybridization assays

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ANALYTICAL CHEMISTRY 1999年第16期71卷 3347-3355页

作者： Budach, W Abel, AP Bruno, AE Neuschäfer, D Novartis Pharma AG DMPK CH-4002 Basel Switzerland

16-Mer and 22-mer oligonucleotide capture probes with an amino function at the 5'-end were covalently immobilized on (3-glycidoxypropyl)trimethoxysilane (GOPTS) silanized planar waveguides in "checkerboard"-style 2-dimensional arrays by means of ink-jet printing in order to demonstrate the potential of multiplexed planar waveguide biosensing. The laser-induced fluorescence was collected by a CCD camera, providing quantitative information regarding the intensity of individual sensing pads. In model hybridization assays with Cy5-labeled complementary oligonucleotides, sample concentrations down to 50 fM were successfully detected within 12 min. The overall spot-to-spot variability of the ink-jet immobilization in combination with amino functionalized oligonucleotides and GOPTS silanized waveguides was found to be about 12% and almost independent of the formation of an equilibrium between the labeled analyte and capture probes. Both pipet-made and ink-jet-made oligonucleotide spots showed comparable assay performances.

关键词： Bioaffinity sensors Single molecules wave-guides Devices Dna

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Design, fabrication and characterization of optical microring sensors on metal substrates

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JOURNAL OF MICROMECHANICS AND MICROENGINEERING 2008年第1期18卷 015025-1-7页

作者： Zhang, Xugang Li, Xiaochun Univ Wisconsin Dept Mech Engn Madison WI 53706 USA

Optical microring sensors can provide measurements with high spatial and temporal resolution along with immunity to electromagnetic interference, multiplexing capabilities and high rates of data collection. If these micro optical sensors can be fabricated on metals, tremendous benefits can be achieved for real industrial applications. In this paper, the principles of the optical microring resonator as temperature sensors were studied. A ring resonator with silicon nitride as the core layer and silica as the cladding layer was designed and fabricated on metal. A nonuniform taper was introduced and optimized to facilitate light coupling. Wafer-scale fabrication processes based on standard microfabrication and electroplating techniques were developed to fabricate the sensors on nickel substrates. Experimental characterization of those microring resonators as temperature sensors was carried out to investigate the feasibility and functionality of optical thin film sensors on metal substrates. The measured thermal sensitivity of microring sensors on the metal substrate was 22.5 pm. degrees C-1, which is much higher than that of those sensors on silicon. This study paves a way to apply optical sensors on metal for manufacturing environments.

关键词： THIN-FILM THERMOCOUPLES wave-guides RESONATORS LOSSES

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UV-Vis, FT-IR and EPR investigation on multi-component germano-silicate glasses for photonics

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JOURNAL OF NON-CRYSTALLINE SOLIDS 2004年第1-3期347卷 246-253页

作者： Ferraris, M Milanese, D Contardi, C Chen, Q Menke, Y Politecn Torino Dept Mat Sci & Chem Engn I-10129 Turin Italy

Photosensitive multi-component germano-silicate glasses, with or without sodium and boron ions in their composition, were studied by means of UV-Vis, FT-IR, and EPR spectroscopy in order to assess the structural changes occurring in the glasses under UV laser irradiation at 248 nm (KrF excimer UV laser). A new absorption band at 285 nm was found for high sodium containing germano-silicate glasses;this band is bleached after UV laser irradiation at 248 nm. (C) 2004 Elsevier B.V. All rights reserved.

关键词： BRAGG GRATING INSCRIPTION OPTICAL-FIBER PHOTOSENSITIVE GLASS GEO2-SIO2GLASSES EXCIMER-LASER wave-guides CENTERS IRRADIATION GENERATION ABSORPTION

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Ultrafast Kikuchi Diffraction: Nanoscale Stress-Strain Dynamics of wave-Guiding Structures

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NANO LETTERS 2012年第7期12卷 3772-3777页

作者： Yurtsever, Aycan Schaefer, Sascha Zewail, Ahmed H. CALTECH Arthur Amos Noyes Lab Chem Phys Phys Biol Ctr Ultrafast Sci & Technol Pasadena CA 91125 USA

Complex structural dynamics at the nanoscale requires sufficiently small probes to be visualized. In conventional imaging using electron microscopy, the dimension of the probe is large enough to cause averaging over the structures present. However, by converging ultrafast electron bunches, it is possible to select a single nanoscale structure and study the dynamics, either in the image or using electron diffraction. Moreover, the span of incident wave vectors in a convergent beam enables sensitivity levels and information contents beyond those of parallel-beam illumination with a single wave vector Bragg diffraction. Here, we report the observation of propagating strain waves using ultrafast Kikuchi diffraction from nanoscale volumes within a wedge-shaped silicon single crystal. It is found that the heterogeneity of the strain in the lateral direction is only 100 nm. The transient elastic wave gives rise to a coherent oscillation with a period of 30 ps and with an envelope that has a width of 140 ps. The origin of this elastic deformation is theoretically examined using finite element analysis;it is identified as propagating shear waves. The wedge-shaped structure, unlike parallel-plate structure, is the key behind the traveling nature of the waves as its angle permits "transverse" propagation;the parallel-plate structure only exhibits the "longitudinal" motion. The studies reported suggest extension to a range of applications for nanostructures of different shapes and for exploring their ultrafast eigen-modes of stress strain profiles.

关键词： UEM convergent electron beams electron diffraction elastic waves wave-guides

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GRAPHICAL DEPICTION OF THE ELECTROMAGNETIC-FIELDS OF HERMITE-GAUSSIAN MODES

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IEE PROCEEDINGS-H MICROwaveS ANTENNAS AND PROPAGATION 1992年第4期139卷 369-375页

作者： ARORA, RK LU, Z FLORIDA STATE UNIV COLL ENGNDEPT ELECT ENGNTALLAHASSEEFL 32306

The theory of Hermite-Gaussian beam waveguide modes is briefly reviewed, leading to expressions for the paraxial vector electric and magnetic fields for wave modes of arbitrary order. The variation of field amplitude in the transverse xy-plane is depicted by three-dimensional graphs, and constant-amplitude contour plots are derived. Also, the electric and magnetic field lines in longitudinal xz- and yz-planes are plotted for transverse modal orders ranging from (0,0) to (2,2).

关键词： HERMITE-GAUSSIAN MODES wave-guides

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ANALYSIS OF DISCONTINUITIES IN wave-GUIDING STRUCTURES BY MAB METHOD

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IEE PROCEEDINGS-H MICROwaveS ANTENNAS AND PROPAGATION 1992年第4期139卷 351-357页

作者： MACHAC, J Faculty of Electrical Engineering Czech Technical University Prague Czechoslovakia

The method of minimal autonomous blocks is briefly described. A universal code computing reflectivity and transmissivity of discontinuities in waveguide structures was developed on the basis of the MAB method. This technique is applied to the solution of dielectric cylinders, metal ridges and bandpass filters in a rectangular waveguide, as well as on shunt posts in a microstrip line. Special attention was given to E-plane tee junctions in rectangular waveguides;scattering matrices are evaluated and approximated by the proper function with dependence on frequency and branch waveguide height.

关键词： MICROSTRIP wave-guides ELECTROMAGNETICS

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FREQUENCY DOUBLING OF DIODE-LASERS WITH POLED POLYMERS

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PHILIPS JOURNAL OF RESEARCH 1992年第4-5期46卷 215-230页

作者： RIKKEN, GLJA SEPPEN, CJE VENHUIZEN, AHJ NIJHUIS, S STARING, EGJ Netherlands

In this contribution we describe molecular, material and technological aspects of using poled polymers in frequency doubling devices. This includes the trade-off between transparency and nonlinearity of the active moiety, characterization of the polymer material and principles and implementations of polymer waveguide frequency doublers.

关键词： HARMONIC GENERATION INTEGRATED OPTICAL DEVICES NONLINEAR OPTICS PHASE MATCHING POLYMERS wave-guides

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Controllable branching of optical beams by quasi-two-dimensional dark spatial solitons

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 1997年第11期14卷 2869-2876页

作者： Neshev, D Dreischuh, A Dinev, S Windholz, L UNIV SOFIA DEPT QUANTUM ELECTBG-1164 SOFIABULGARIA

A variable number of quasi-two-dimensional dark spatial solitons of adjustable transverse velocities could be generated by a proper choice of the initial phase profile (odd or even) and the width of the crossed dark stripes and the background-beam intensity. The possibility of branching a single input probe beam into ordered structures of subbeams is demonstrated numerically in a bulk self-induced-defocusing Kerr nonlinear media. The energy-density branching efficiency for each subbeam is evaluated and discussed. (C) 1997 Optical Society of America.

关键词： KERR NONLINEAR MEDIA VORTEX SOLITONS wave-guides Y-JUNCTIONS PULSES PROPAGATION INSTABILITY STRIPES FIBERS COMPRESSION Fiber Solitons light beams waveguide Device Component branches compression Y junction darkness

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EXPERIMENTAL AND THEORETICAL-STUDY OF TURNING MIRRORS AND BEAM-SPLITTERS WITH OPTIMIZED wave-GUIDE STRUCTURES

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OPTICAL AND QUANTUM ELECTRONICS 1995年第5期27卷 395-403页

作者： CHUNG, Y DAGLI, N UNIV CALIF SANTA BARBARA DEPT ELECT & COMP ENGNSANTA BARBARACA 93106

Integrated waveguide turning mirrors (IWTM) based on total internal reflection are investigated theoretically and experimentally. The effects of the mirror surface displacement, the rotation, and the roughness are studied. The loss due to the various spectral components of the roughness is comprehensively analysed. A wide waveguide turning mirror is more influenced by the low-frequency component, which is the major component of the actually fabricated mirror surface, resulting in high radiation loss of an IWTM with long taper, contrary to expectation. The excess radiation loss is about 0.8 dB/mirror and 1.0 dB/mirror for quasi-TE and quasi-TM modes, respectively, in the optimum design, which could be reduced by further minimizing the displacement error of the mirror position. We also designed and fabricated a low-loss beam splitter with modal interference region, the measured excess losses being about 1.2 dB and 1.8 dB for quasi-TE and quasi-TM modes, respectively, which are believed to be the lowest in this kind of beam splitter.

关键词： Propagation method Guide structure wave-guides displacement error RADIATION LOSSES beam splitters roughness Mirrors waveguide Device Component Theoretical Study Optimal design mirror surface TM mode Spectral composition

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