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Articles 1 to 20 of 106 Next Page >>


Time Caliper Method with Enhanced Accuracy using an Arbitrary Waveform Generator and Time Demultiplexer with Fine Clock Offset

  • Hon-Tung Luk and Lian-Kuan Chen
  • received 05/19/2014; accepted 09/19/2014; posted 09/22/2014; Doc. ID 212408
  • [full text: PDF (480) KB)]
  • Abstract: An improved time caliper method has been proposed for measuring a small relative delay of two signals transmitted on different channels. This is achieved by using a new method to generate two periodic pulse trains that have much smaller period difference, over 1000 times smaller than that in the prior scheme. The two pulse trains used for measurement with period difference of 0.1 ps are generated by an arbitrary waveform generator and a time demultiplexer, with a fine clock offset.

Keywords (OCIS):

  • (060.2270) Fiber optics and optical communications : Fiber characterization
  • (060.2300) Fiber optics and optical communications : Fiber measurements

Generation of sub-17 fs vacuum ultraviolet pulses at 133 nm using cascaded four-wave mixing through filamentation in Ne

  • Toshinori Suzuki, Takuya Horio, and Roman Spesyvtsev
  • received 06/27/2014; accepted 09/19/2014; posted 09/22/2014; Doc. ID 214744
  • [full text: PDF (578) KB)]
  • Abstract: The sixth harmonic (6ω, 133 nm) of a Ti:sapphire laser is generated using cascaded four-wave mixing in filamentation propagation of the fundamental (ω) and second harmonic (2ω) pulses through Ne gas. The method provides a pulse energy higher than 5 nJ/pulse at 1 kHz and a pulse duration shorter than 17 fs without dispersion compensation.

Keywords (OCIS):

  • (140.7090) Lasers and laser optics : Ultrafast lasers
  • (140.7240) Lasers and laser optics : UV, EUV, and X-ray lasers
  • (320.7150) Ultrafast optics : Ultrafast spectroscopy

Preparation of two-qubit steady entanglement through driving a single qubit

  • Li-Tuo Shen, Rong-Xin Chen, Zhen Biao Yang, Huai-Zhi Wu, and Shi-Biao Zheng
  • received 06/30/2014; accepted 09/19/2014; posted 09/22/2014; Doc. ID 214980
  • [full text: PDF (432) KB)]
  • Abstract: We propose a novel scheme to generate and stabilize a Bell state of two qubits coupled to a resonator. In the scheme only one qubit is needed to be driven by external classical fields, and the entanglement dynamics is independent of the phases of these fields and insensitive to their amplitude fluctuations. This is a distinct advantage as compared with the previous ones that require each qubit to be addressed by well controlled classical fields. Numerical simulation shows that the steady singlet state with a high fidelity can be obtained with currently available techniques in circuit QED.

Keywords (OCIS):

  • (270.1670) Quantum optics : Coherent optical effects
  • (270.2500) Quantum optics : Fluctuations, relaxations, and noise
  • (270.5580) Quantum optics : Quantum electrodynamics
  • (270.5585) Quantum optics : Quantum information and processing

Dynamic speckle illumination wide-field reflection phase microscopy

  • Youngwoon Choi, Poorya Hosseini, Wonshik Choi, Ramachandra Dasari, Peter So, and Zahid Yaqoob
  • received 07/31/2014; accepted 09/19/2014; posted 09/22/2014; Doc. ID 220156
  • [full text: PDF (1866) KB)]
  • Abstract: We demonstrate a quantitative reflection phase microscope based on time-varying speckle-field illumination. Due to the short spatial coherence length of the speckle-field, it has superior lateral resolution, 520 nm, as well as high depth selectivity, 1.03 μm. Off-axis interferometric detection enables wide-field and single-shot imaging appropriate for high-speed measurements. In addition, the phase sensitivity of this method, which is the smallest measurable axial motion, is several tens of times higher than that available using a transmission system. We demonstrate the utility of our method by successfully distinguishing the motion of the top surface from that of the bottom in red blood cells. The proposed method may facilitate the measurement of membrane dynamics in complex eukaryotic cells.

Keywords (OCIS):

  • (110.6150) Imaging systems : Speckle imaging
  • (120.3890) Instrumentation, measurement, and metrology : Medical optics instrumentation
  • (120.5050) Instrumentation, measurement, and metrology : Phase measurement
  • (170.1530) Medical optics and biotechnology : Cell analysis
  • (180.3170) Microscopy : Interference microscopy
  • (090.1995) Holography : Digital holography

Experimental demonstration of 1D crossed gratings for polarization-independent high-Q filtering

  • Antoine Monmayrant, Olivier Gauthier-Lafaye, stephane aouba, Kristel chan-shin-yu, philippe arguel, Anne-Laure Fehrembach, and Anne Sentenac
  • received 07/31/2014; accepted 09/19/2014; posted 09/22/2014; Doc. ID 220203
  • [full text: PDF (798) KB)]
  • Abstract: We demonstrate experimentally a spectral filter with high Q-factor ($\simeq$\expQ), wide accordability range (1500-1600~nm) with respect to the angle of incidence, and record polarization independence. The filter is composed of two 1D crossed gratings engraved on each side of a planar waveguide. We provide a good comparison with theory.

Keywords (OCIS):

  • (050.2770) Diffraction and gratings : Gratings
  • (130.2790) Integrated optics : Guided waves
  • (050.5745) Diffraction and gratings : Resonance domain
  • (050.6624) Diffraction and gratings : Subwavelength structures
  • (130.7408) Integrated optics : Wavelength filtering devices

A time-resolved Multifocal Multiphoton Microscope for High Speed FRET imaging In Vivo

  • Simon Poland, Nikola Krstajic, Simao Coelho, David Tyndall, Richard Walker, Viviane Devauges, Penny Morton, Nicole Nicholas, Justin Richardson, David Li, Klaus Suhling, Claire Wells, Maddy Parsons, Robert Henderson, and Simon Ameer-Beg
  • received 08/29/2014; accepted 09/19/2014; posted 09/22/2014; Doc. ID 221946
  • [full text: PDF (1093) KB)]
  • Abstract: Imaging the spatio-temporal interaction of proteins in vivo is essential to understanding the complexities of biological systems. The highest accuracy monitoring of protein-protein interactions is achieved using FRET measured by fluorescence lifetime imaging, with measurements taking minutes to acquire a single frame, limiting their use in dynamic live cell systems. We present a diffraction limited, massively parallel, time-resolved multifocal multiphoton microscope capable of producing fluorescence lifetime images with 55 ps time-resolution, giving improvements in acquisition speed of a factor of 64. We present demonstrations with FRET imaging in a model cell system and demonstrate in vivo FLIM using a GTPase biosensor in the zebrafish embryo.

Keywords (OCIS):

  • (040.1240) Detectors : Arrays
  • (090.1970) Holography : Diffractive optics
  • (180.0180) Microscopy : Microscopy
  • (180.2520) Microscopy : Fluorescence microscopy
  • (180.4315) Microscopy : Nonlinear microscopy

Stimulated anti-Stokes Raman scattering resonantly enhanced in silica microspheres

  • Silvia Soria, Daniele Farnesi, Franco Cosi, Cosimo Trono, Giancarlo Righini, and Gualtiero Nunzi Conti
  • received 08/08/2014; accepted 09/18/2014; posted 09/22/2014; Doc. ID 220665
  • [full text: PDF (1251) KB)]
  • Abstract: Efficient stimulated anti-Stokes Raman scattering has been observed in silica microspherical resonators pumped by CW laser. This process is observed in the normal dispersion regime. The lack of correlation between stimulated anti-stokes and stokes scattering spectra indicates that the signal has to be resonant with the cavity

Keywords (OCIS):

  • (190.4380) Nonlinear optics : Nonlinear optics, four-wave mixing
  • (230.5750) Optical devices : Resonators
  • (190.4223) Nonlinear optics : Nonlinear wave mixing

WDM optical steganography based on amplified spontaneous emission noise

  • Ben Wu, Alex Tait, Matthew Chang, and Paul Prucnal
  • received 07/09/2014; accepted 09/18/2014; posted 09/18/2014; Doc. ID 214819
  • [full text: PDF (1092) KB)]
  • Abstract: We propose and experimentally demonstrate a wavelength-division multiplexed (WDM) optical stealth transmission system carried by amplified spontaneous emission (ASE) noise. The stealth signal is hidden in both time and frequency domains by using ASE noise as the signal carrier. Each WDM channel uses part of the ASE spectrum, which provides more flexibility to apply stealth transmission in a public network and adds another layer of security to the stealth channel. Multi-channel transmission also increases the overall channel capacity, which is the major limitation of the single stealth channel transmission based on ASE noise. The relations between spectral bandwidth and coherence length of ASE carrier have been theoretically analyzed and experimentally investigated.

Keywords (OCIS):

  • (060.2330) Fiber optics and optical communications : Fiber optics communications
  • (060.4785) Fiber optics and optical communications : Optical security and encryption

Plasmon negative refraction at the heterointerface of two graphene sheet arrays

  • Bing Wang, Peixiang Lu, Huang He, Kai Wang, and Hua Long
  • received 07/24/2014; accepted 09/18/2014; posted 09/18/2014; Doc. ID 217744
  • [full text: PDF (555) KB)]
  • Abstract: We demonstrate negative refraction of surface plasmon porlaritons (SPPs) at the heterointerface of two monolayer graphene sheet arrays (MGSAs) with different periods. The refraction angle is largely related to the period ratio of the two MGSAs. By varying the incident Bloch momentum, the oblique incidence of SPPs could generate refraction in the normal direction and both negative and positive refraction could appear simultaneously. Because of the linear diffraction relation, the incident and refracted SPP beams may experience diffraction-free propagation and good confinement deeply below the diffraction limit. The configuration of the combined MGSAs may find great applications in deep-subwavelength spatial light modulators, optical splitters, and switches.

Keywords (OCIS):

  • (120.5710) Instrumentation, measurement, and metrology : Refraction
  • (240.6680) Optics at surfaces : Surface plasmons
  • (080.1238) Geometric optics : Array waveguide devices

Flexible Frequency Comb Generation in a Periodically Poled Lithium Niobate Waveguide Enabling Optical Multicasting

  • Valeria Vercesi, Sergio Pinna, gianluca meloni, Filippo Scotti, Luca Poti, Antonella Bogoni, and Mirco Scaffardi
  • received 07/28/2014; accepted 09/18/2014; posted 09/18/2014; Doc. ID 219953
  • [full text: PDF (1337) KB)]
  • Abstract: We propose and demonstrate a technique for the generation of a coherent optical comb with tunable line spacing in a periodically-poled lithium niobate waveguide. A single continuous wave laser is modulated to generate three phase locked seed lines which are injected into a periodically poled lithium niobate waveguide to obtain lines multiplication. The line spacing is set acting on the frequency of the electrical signal driving the modulator. The quality of the comb is verified measuring the autocorrelation, the phase noise and the linewidth of the generated lines. With the same scheme, we demonstrate optical multicasting. From a single QPSK signal modulated at 12.5 and 25 GBaud, five replicas are generated with spacing 25GHz and 37.5GHz. The performance of each signal replica is measured after transmission through 80 km of a single mode fiber, demonstrating operation with a BER value lower than the FEC threshold.

Keywords (OCIS):

  • (190.4360) Nonlinear optics : Nonlinear optics, devices
  • (190.4223) Nonlinear optics : Nonlinear wave mixing

Design of highly focused fields that remain unpolarized on axis

  • Artur Carnicer, Rosario Martinez-Herrero, and Ignasi Juvells
  • received 07/23/2014; accepted 09/17/2014; posted 09/22/2014; Doc. ID 217633
  • [full text: PDF (418) KB)]
  • Abstract: Research on the properties of highly focused fields mainly involved fully polarized light whereas partially polarized waves received less attention. The aim of this work is to provide an appropriate framework for designing some features of the focused field when dealing with incoming partially polarized beams. In particular, in this letter we describe how to get an unpolarized field on the axis of a high numerical aperture objective lens. Some numerical results that corroborate theoretical predictions are provided.

Keywords (OCIS):

  • (260.0260) Physical optics : Physical optics
  • (260.2110) Physical optics : Electromagnetic optics
  • (260.5430) Physical optics : Polarization

Elementary polarization properties in the backscattering configuration

  • Oriol Arteaga, Razvigor Ossikovski, and Enric Garcia-Caurel
  • received 07/11/2014; accepted 09/17/2014; posted 09/22/2014; Doc. ID 216860
  • [full text: PDF (284) KB)]
  • Abstract: In the backscattering configuration a polarimetric measurement always preserves the reciprocal symmetry. For a reciprocal Jones matrix the number of elementary polarization properties is reduced from six to four. In this work the physical interpretation of these properties is examined and they are compared with the equivalent polarization properties in transmission. It is found that, with exception of natural optical activity, a polarimetric backreflection experiment can essentially provide the same type of information about the anisotropy of a medium that a transmission analysis, although transmission and backreflection information comes in a completely different form. Experimental examples are provided to illustrate the discussion.

Keywords (OCIS):

  • (120.2130) Instrumentation, measurement, and metrology : Ellipsometry and polarimetry
  • (260.1440) Physical optics : Birefringence
  • (260.2130) Physical optics : Ellipsometry and polarimetry
  • (260.5430) Physical optics : Polarization

Active FTIR-based stand-off spectroscopy using a femtosecond optical parametric oscillator

  • Zhaowei Zhang, Rhea Clewes, Christopher Howle, and Derryck Reid
  • received 08/25/2014; accepted 09/17/2014; posted 09/18/2014; Doc. ID 221689
  • [full text: PDF (619) KB)]
  • Abstract: We present the first demonstration of stand-off Fourier transform infrared (FTIR) spectroscopy using a broadband mid-infrared optical parametric oscillator, with spectral coverage over 2700–3200 cm-1. For vapor-phase water and nitromethane (NM), stand-off spectra recorded using a concrete target at 1-m to 2-m range showed good agreement with reference spectra, and in NM a normalized detection sensitivity of 15 ppm•m•Hz−1∕2 was obtained. Spectra from 50-µL droplets of liquid thiodiglycol were detected at a stand-off distance of 2 m from aluminum, concrete and painted metal surfaces. Our results imply that OPO-based active FTIR stand-off spectroscopy is a promising new technique for the detection of industrial pollutants and the identification of chemical agents, explosives or other hazardous materials.

Keywords (OCIS):

  • (120.0280) Instrumentation, measurement, and metrology : Remote sensing and sensors
  • (120.6200) Instrumentation, measurement, and metrology : Spectrometers and spectroscopic instrumentation
  • (190.4970) Nonlinear optics : Parametric oscillators and amplifiers
  • (300.6300) Spectroscopy : Spectroscopy, Fourier transforms

Resonant mode conversion in the waveguides with an unbroken and broken PT-symmetry

  • Victor Vysloukh and Yaroslav Kartashov
  • received 07/30/2014; accepted 09/16/2014; posted 09/18/2014; Doc. ID 220108
  • [full text: PDF (2111) KB)]
  • Abstract: We study resonant mode conversion in the PT-symmetric multimode waveguides, where symmetry breaking manifests itself in sequential destabilization (appearance of the complex eigenvalues) of the pairs of adjacent guided modes. We show that the efficient mode conversion is possible even in the presence of the resonant longitudinal modulation of the complex refractive index. The distinguishing feature of the resonant mode conversion in the PT-symmetric structure is a drastic growth of the width of the resonance curve when the gain/losses coefficient approaches a critical value, at which symmetry breaking occurs. We found that in the system with broken symmetry the resonant coupling between exponentially growing mode with stable higher-order one effectively stabilizes dynamically coupled pair of modes and remarkably diminishes the average rate of the total power growth.

Keywords (OCIS):

  • (050.1940) Diffraction and gratings : Diffraction
  • (260.2710) Physical optics : Inhomogeneous optical media

Terahertz-field-induced second harmonic generation through Pockels effect in Zinc Telluride crystal

  • Eric Freysz, Emmanuel Abraham, marion cornet, and Jérôme Degert
  • received 09/01/2014; accepted 09/16/2014; posted 09/16/2014; Doc. ID 222284
  • [full text: PDF (372) KB)]
  • Abstract: We report on the second harmonic generation of a near-infrared pulse in a Zinc Telluride crystal through the Pockels effect induced by an intense terahertz pulse. The temporal and angular behaviors of the second harmonic generation have been measured and agree well with theoretical predictions. This phenomenon, so far overlooked, makes it possible to generate second harmonic through cascading of two second-order nonlinear phenomena in the near-infrared and terahertz range. We also show how this cascading process can be used to sample terahertz pulses.

Keywords (OCIS):

  • (190.0190) Nonlinear optics : Nonlinear optics
  • (190.7110) Nonlinear optics : Ultrafast nonlinear optics
  • (320.7110) Ultrafast optics : Ultrafast nonlinear optics

The interplay between photo- and radio-darkening in ytterbium-doped fibres

  • Jean-Bernard DUCHEZ, Franck MADY, Yasmine MEBROUK, Nadège Ollier, and Mourad BENABDESSELAM
  • received 07/23/2014; accepted 09/16/2014; posted 09/17/2014; Doc. ID 217671
  • [full text: PDF (1386) KB)]
  • Abstract: This letter demonstrates a remarkable interplay between photo- and radio-induced darkening of ytterbium-doped alumino-silica optical fibres operated in amplifying conditions and harsh environments (as e.g. in space-based applications). Influences of the pump power, ionizing dose and dose rate on this interaction are characterized. The pump is capable of accelerating or slowing-down the radio-darkening build-up depending on the ionizing dose. The steady state photo-radio-darkening level is independent of the dose and at least equal to the equilibrium level of pure photo-darkening. This lower limit is notably reached at low dose rates, including those encountered in space. We therefore argue that photo-resistant ytterbium-doped fibres will resist against a space mission, whatever the dose.

Keywords (OCIS):

  • (140.3510) Lasers and laser optics : Lasers, fiber
  • (160.2750) Materials : Glass and other amorphous materials
  • (160.5690) Materials : Rare-earth-doped materials
  • (260.5210) Physical optics : Photoionization
  • (350.5610) Other areas of optics : Radiation
  • (140.3615) Lasers and laser optics : Lasers, ytterbium

Correction of Rotational Distortion for Catheter-based en face OCT and OCT Angiography

  • James Fujimoto, Osman Ahsen, Hsiang-Chieh Lee, Michael Giacomelli, Zhao Wang, Kaicheng Liang, Tsung-Han Tsai, Benjamin Potsaid, and Hiroshi Mashimo
  • received 07/24/2014; accepted 09/16/2014; posted 09/17/2014; Doc. ID 217711
  • [full text: PDF (565) KB)]
  • Abstract: We demonstrate a computationally efficient method for correcting the nonuniform rotational distortion (NURD) encountered in catheter-based imaging systems to improve en face Optical Coherence Tomography (OCT) imaging and endoscopic OCT angiography. The method performs a non-rigid registration based on the position of fiducial markers located on the catheter to correct the variations in the rotational speed. Performance of the correction algorithm is verified with an ultrahigh speed endoscopic OCT system and a micromotor imaging catheter. Scan nonuniformity is quantitatively characterized and artifacts from variations in rotational speed are significantly reduced with the correction algorithm. Furthermore, we present en face OCT and endoscopic OCT angiography images of human gastrointestinal tract in vivo to demonstrate the improvement in the image quality using the correction algorithm.

Keywords (OCIS):

  • (100.6890) Image processing : Three-dimensional image processing
  • (110.4500) Imaging systems : Optical coherence tomography
  • (170.2680) Medical optics and biotechnology : Gastrointestinal
  • (170.3880) Medical optics and biotechnology : Medical and biological imaging
  • (170.4500) Medical optics and biotechnology : Optical coherence tomography

Silica Microspheres Array Strain Sensor

  • Marta Ferreira, Jose Luis Santos, and Orlando Frazao
  • received 07/25/2014; accepted 09/16/2014; posted 09/16/2014; Doc. ID 217768
  • [full text: PDF (584) KB)]
  • Abstract: An optical fiber sensor based on arrays of silica microspheres is proposed. The microspheres are produced separately using a fusion splicer and then connected in series also by fusion splicing. Three different sensors are presented, differing on the number of microspheres. Due to the geometry of the structures, different behaviors are obtained in strain measurements. Sensors with an odd number of microspheres are more sensitive to strain than the ones with an even number of microspheres. Besides, the sensing heads are subjected to temperature where a sensitivity of 20.3 pm/ºC is obtained in a range of 200 ºC.

Keywords (OCIS):

  • (060.2310) Fiber optics and optical communications : Fiber optics
  • (060.2370) Fiber optics and optical communications : Fiber optics sensors
  • (060.2430) Fiber optics and optical communications : Fibers, single-mode

Cherenkov second-harmonic Talbot effect in one-dimension nonlinear photonic crystal

  • Xianfeng Chen, Xiaohui Zhao, Yuanlin Zheng, Huaijin Ren, and Ning An
  • received 07/25/2014; accepted 09/15/2014; posted 09/16/2014; Doc. ID 217798
  • [full text: PDF (1761) KB)]
  • Abstract: We demonstrate a new method to generate second-harmonic Talbot effect through degenerate Cherenkov radiation in one-dimension anomalous-dispersion-like nonlinear photonic crystals. In anomalous-dispersion-like medium, the degenerated nonlinear Cherenkov radiation can be achieved and is parallel to domain walls, of which the intensity is adjusted by the second nonlinear coefficient. In this system the one-dimension nonlinear photonic crystal can be regarded as a nonlinear grating, which is necessary for nonlinear Talbot effect. This is a new method to generate enhanced nonlinear Talbot effect in addition to the quasi-phase-matching technique reported previously.

Keywords (OCIS):

  • (070.6760) Fourier optics and signal processing : Talbot and self-imaging effects
  • (190.0190) Nonlinear optics : Nonlinear optics
  • (190.2620) Nonlinear optics : Harmonic generation and mixing

Observer dependent sign inversions of polarization singularities

  • Isaac Freund
  • received 07/28/2014; accepted 09/15/2014; posted 09/16/2014; Doc. ID 219897
  • [full text: PDF (776) KB)]
  • Abstract: We describe observer dependent sign inversions of the topological charges of vector field polarization singularities: C points (points of circular polarization), L points (points of linear polarization), and two previously unknown singularities we call gamma-C and αlpha-L points. In all cases the sign of the charge seen by an observer can change as she changes the direction from which she views the singularity. Analytic formulas are given for all C and all L point sign inversions.

Keywords (OCIS):

  • (260.0260) Physical optics : Physical optics
  • (260.5430) Physical optics : Polarization
  • (260.6042) Physical optics : Singular optics

Articles 1 to 20 of 106 Next Page >>

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