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Articles 1 to 20 of 100 Next Page >>


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

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

Enhanced 2.7 and 2.84 μm emissions from diode-pumped Ho3+/ Er3+ -doped fluoride glass

  • Danping Chen, Feifei Huang, Xueqiang Liu, Yu Zhang, and Lili Hu
  • received 08/29/2014; accepted 09/15/2014; posted 09/16/2014; Doc. ID 221927
  • [full text: PDF (1206) KB)]
  • Abstract: This work reports the intense emissions at 2.7 and 2.84 μm in a Ho3+/Er3+ -codoped fluoride glass (ZrF4-BaF2-YF3-AlF3). An extensive transmission spectrum and the absence of strong OH- absorption guarantee the observation of mid-infrared (IR) emissions. For the Ho3+/ Er3+- codoped sample, the 2.7 and 2.84 μm emissions are 5.8 and 3.8 times higher with larger emission cross sections (10.2×10-21 and 9.8×10-21 cm2) , respectively. Meanwhile, other near to middle infrared emissions (1200, 2045 nm emissions from Ho3+ and 980, and 1535 nm emissions from Er3+ ions) are all enhanced. The collective enhanced effect origin from the disappearance of nonradiative decay processes after codping Er3+ and Ho3+ ions. Hence, the advantageous spectroscopic characteristics of Ho3+/Er3+ -codoped ZBYA glass indicate that this kind of fluoride glass may be an attractive host to develop solid-state lasers for 3 μm

Keywords (OCIS):

  • (160.2540) Materials : Fluorescent and luminescent materials
  • (160.4670) Materials : Optical materials
  • (160.5690) Materials : Rare-earth-doped materials
  • (300.6280) Spectroscopy : Spectroscopy, fluorescence and luminescence

Statistics of the Optical Intensity of Chaotic External-Cavity DFB Lasers

  • Nianqiang Li, Byungchil Kim, Alexandre Locquet, Daeyoung Choi, Wei Pan, and David Citrin
  • received 07/30/2014; accepted 09/14/2014; posted 09/15/2014; Doc. ID 220059
  • [full text: PDF (683) KB)]
  • Abstract: We study experimentally and theoretically based on the Lang-Kobayashi model first- and second-order statistical measures of the optical intensity of a chaotic external-cavity semiconductor laser in fully-developed coherence-collapse. The second-order statistic is characterized by the autocorrelation function, for which we achieve consistent experimental and theoretical results over the entire parameter range considered. For the first-order statistic, we find that the experimental probability-density function is significantly more concentrated around the mean optical power and robust to parameter changes than the density functions obtained from the Lang-Kobayashi model.

Keywords (OCIS):

  • (140.3490) Lasers and laser optics : Lasers, distributed-feedback
  • (140.5960) Lasers and laser optics : Semiconductor lasers
  • (190.3100) Nonlinear optics : Instabilities and chaos

Generating and Identifying Optical Orbital Angular Momentum with Silicon Photonic Circuits

  • Jie Sun, Michele Moresco, Gerald Leake, Douglas Coolbaugh, and Michael Watts
  • received 08/11/2014; accepted 09/14/2014; posted 09/18/2014; Doc. ID 220713
  • [full text: PDF (4282) KB)]
  • Abstract: Here, we propose and demonstrate a silicon nanophotonic phased array that is capable of generating light carrying optical orbital angular momentum. Optical beams carrying different orbital angular momenta have been generated. In addition, the generated orbital angular momentum wavefronts are experimentally identified by interfering with another on-chip generated Gaussian beam, opening up opportunities of integrating conventional optical systems and functionalities onto a silicon chip.

Keywords (OCIS):

  • (230.3120) Optical devices : Integrated optics devices
  • (250.3140) Optoelectronics : Integrated optoelectronic circuits

Zero-order suppression for two-photon holographic excitation

  • Marc Guillon, Valentina Emiliani, Eirini Papagiakoumou, and Oscar Hernandez
  • received 08/06/2014; accepted 09/13/2014; posted 09/17/2014; Doc. ID 220486
  • [full text: PDF (496) KB)]
  • Abstract: Wavefront shaping with liquid crystal spatial light modulators (LC-SLMs) is frequently hindered by a remaining fraction of undiffracted light, the so-called "zero-order". This contribution is all the more detrimental in configurations for which the LC-SLM is Fourier conjugated to a sample by a lens, because in these cases this undiffracted light produces a diffraction-limited spot at the image focal plane. In this work we propose to minimize two-photon excitation of the sample resulting from this unmodulated light by introducing optical aberrations to the excitation beam. Aberrations are subsequently compensated by the LC-SLM but only for the modulated part of the beam, and not for the "zero-order" component. In order to experimentally demonstrate the method we use astigmatism as the optical aberration by simply adding one or two cylindrical lenses in the optical path of the beam. A 10⁴ decrease in zero-order-induced two-photon fluorescence intensity is demonstrated. Combining this approach with temporal focusing is shown to decrease zero-order fluorescence by a factor of 4.10⁶.

Keywords (OCIS):

  • (090.1970) Holography : Diffractive optics
  • (230.6120) Optical devices : Spatial light modulators
  • (070.6120) Fourier optics and signal processing : Spatial light modulators

Angle-insensitive and narrow band grating filter with gradient-index layer

  • Gaige Zheng, Jiawei Cong, Linhua Xu, and Wei Su
  • received 08/27/2014; accepted 09/13/2014; posted 09/18/2014; Doc. ID 221737
  • [full text: PDF (624) KB)]
  • Abstract: We demonstrate the design of an efficient angle-insensitive guided mode resonance filter (GMRF) with narrow bandwidth and low sideband reflection for TE-polarized wave. The reflection properties of the multilayer structure have been studied and the results verify that the thin film design of the gradient-index (GRIN) layer is important for the realization of angle-insensitive filter, various gradient coefficients of the thin film have distinct effects on the reflection spectrum. For an increasing incident angle, although the line-shape symmetry becomes less perfect, the positions of the resonant peak remain the same. The GMRF proposed here has many desirable attributes that lends itself to being an excellent platform for devices such as lasers, detectors, filters, and sensors.

Keywords (OCIS):

  • (130.2790) Integrated optics : Guided waves
  • (230.0230) Optical devices : Optical devices
  • (050.5745) Diffraction and gratings : Resonance domain

Revisiting the which-way experiment with twisted light beams

  • Lixiang Chen, Wuhong Zhang, Kai Cai, Yuanying Zhang, and Qianqian Qi
  • received 07/15/2014; accepted 09/13/2014; posted 09/15/2014; Doc. ID 216884
  • [full text: PDF (1689) KB)]
  • Abstract: We report an experiment of which-way information and quantum eraser based on polarization-controlled interference of two twisted light beams carrying high orbital angular momentum (OAM) up to $\ell=\pm 50$ and $\pm 100$, respectively. By changing the polarization plane of one OAM beam from $0^\circ$ to $90^\circ$ with respect to that of the other OAM beam, we observe the gradual disappearance of the interference petal-like patterns into the noninterference single bright rings. Subsequently, we use the eraser of a diagonal polarizer to retrieve the characteristic petal-like interference. The experimental results can be well explained in the frame of single-photon Greenberger-Horne-Zeilinger-like (GHZ-like) entanglement. Our work may be beneficial to understanding the wave-particle duality of light.

Keywords (OCIS):

  • (260.3160) Physical optics : Interference
  • (260.5430) Physical optics : Polarization
  • (100.3175) Image processing : Interferometric imaging
  • (050.4865) Diffraction and gratings : Optical vortices

Spectroscopic properties and continuous-wave laser operation of Yb:LuPO4 crystal

  • Junhai Liu, Wenjuan Han, Xiaowen Chen, Degao Zhong, Bing Teng, Chao Wang, and Yuyi Li
  • received 07/04/2014; accepted 09/12/2014; posted 09/15/2014; Doc. ID 216305
  • [full text: PDF (1245) KB)]
  • Abstract: We report, for the first time, on continuous-wave (cw) laser operation of Yb:LuPO4 crystal, demonstrated at room-temperature in a compact plano-concave resonator end pumped by a diode laser. With 2.40 W of pump power at 976 nm being absorbed in a 0.3 mm thick crystal, 1.61 W of cw output power around 1039 nm was generated, leading to an optical-to-optical efficiency of 67%, while the slope efficiency being 75%. The polarized absorption and emission cross section spectra were also presented and discussed in detail.

Keywords (OCIS):

  • (140.3380) Lasers and laser optics : Laser materials
  • (140.3580) Lasers and laser optics : Lasers, solid-state
  • (140.3615) Lasers and laser optics : Lasers, ytterbium

32-fs Kerr-lens mode-locked Yb:CALGO oscillator optically pumped by a bright fiber laser

  • Pierre Sevillano, Patrick Georges, Frederic Druon, Dominique Descamps, and Eric Cormier
  • received 08/07/2014; accepted 09/12/2014; posted 09/15/2014; Doc. ID 220411
  • [full text: PDF (453) KB)]
  • Abstract: In this study, we report on pure Kerr-lens mode-locked Yb:CALGO oscillator optically pumped by a diffraction limited fiber laser. At the repetition rate of 96 MHz, several configurations have been studied to achieve either pulse duration of 40 fs with average powers up to the watt level or shorter pulse duration down to 32 fs. To the best of our knowledge, this represents the shortest pulse duration ever achieved with an Yb-doped materials and the highest average power for sub-40 fs Kerr-lens mode-locked Yb-bulk oscillator.

Keywords (OCIS):

  • (140.3580) Lasers and laser optics : Lasers, solid-state
  • (140.7090) Lasers and laser optics : Ultrafast lasers
  • (190.3270) Nonlinear optics : Kerr effect
  • (140.3615) Lasers and laser optics : Lasers, ytterbium

Ultra-long Phase-sensitive OTDR with Hybrid Distributed Amplification

  • Zinan Wang, Yi Zhou, Jiajia Zeng, Li Zhang, Jin Li, Fei Peng, Yun-Jiang Rao, Mengqiu Fan, and Han Wu
  • received 07/25/2014; accepted 09/12/2014; posted 09/15/2014; Doc. ID 217773
  • [full text: PDF (1131) KB)]
  • Abstract: A phase-sensitive optical time-domain reflectometry with 175km sensing range is demonstrated, using the combination of co-pumping 2nd-order Raman amplification based on random fiber lasing, counter-pumping 1st-order Raman amplification, and counter-pumping Brillouin amplification. With elaborate arrangements, each pumping scheme is responsible for the signal amplification in one particular segment of the all three. To the best of our knowledge, this is the first time that distributed vibration sensing is realized over such a long distance without inserting repeaters. The novel hybrid amplification scheme in this work can also be incorporated in other fiber-optic sensing systems for extension of sensing distance.

Keywords (OCIS):

  • (060.2370) Fiber optics and optical communications : Fiber optics sensors
  • (190.4370) Nonlinear optics : Nonlinear optics, fibers
  • (290.5870) Scattering : Scattering, Rayleigh
  • (290.5900) Scattering : Scattering, stimulated Brillouin
  • (290.5910) Scattering : Scattering, stimulated Raman

Articles 1 to 20 of 100 Next Page >>

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