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Sökning: L773:1094 4087 > Chalmers tekniska högskola

  • Resultat 1-10 av 161
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1.
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2.
  • Andrekson, Peter, 1960, et al. (författare)
  • Ultrafast, atto-Joule switch using fiber-optic parametric amplifier operated in saturation
  • 2008
  • Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 16:15, s. 10956-10961
  • Tidskriftsartikel (refereegranskat)abstract
    • ll-optical manipulation of signals carried by lightwaves is attractive because controlling the light directly can be more efficient, allows a multitude of signal formats, and can also prove most cost effective. We implemented a novel scheme for ultrafast optical switching using very small control energy that relies on the use of a saturated fiber-optic parametric amplifier. Approximately 19 aJ (150 photons) of control pulse energy was needed for 50% extinction of the signal which is three to four orders of magnitude smaller than in other all-optical switching demonstrations. This allows the consideration of novel practical approaches to implement all-optical switching devices and all-optical subsystems for telecommunications and other applications.
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3.
  • Antosiewicz, Tomasz, 1981, et al. (författare)
  • A simple model for the resonance shift of localized plasmons due to dielectric particle adhesion
  • 2012
  • Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 20:1, s. 524-533
  • Tidskriftsartikel (refereegranskat)abstract
    • Ultrasensitive detectors based on localized surface plasmonresonance refractive index sensing are capable of detecting very lownumbers of molecules for biochemical analysis. It is well known that thesensitivity of such sensors crucially depend on the spatial distribution ofthe electromagnetic field around the metal surface. However, the preciseconnection between local field enhancement and resonance shift is seldomdiscussed. Using the quasistatic approximation, we developed a model thatrelates the sensitivity of a nanoplasmonic resonator to the local field inwhich the analyte is placed. The model, corroborated by finite-differencetime-domain simulations, may be used to estimate the magnitude of theshift as a function of the properties of the sensed object – permittivity andvolume – and its location on the surface of the resonator. It requires onlya computation of the resonant field induced by the metal structure and istherefore suitable for numerical optimization of nanoplasmonic sensors.
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4.
  • Antosiewicz, Tomasz, 1981, et al. (författare)
  • Plasmonic glasses: Optical properties of amorphous metal-dielectric composites
  • 2014
  • Ingår i: Optics Express. - : The Optical Society. - 1094-4087 .- 1094-4087. ; 22:2, s. 2032-2043
  • Tidskriftsartikel (refereegranskat)abstract
    • Plasmonic glasses composed of metallic inclusions in a host dielectric medium are investigated for their optical properties. Such structures characterized by short-range order can be easily fabricated using bottom-up, self-organization methods and may be utilized in a number of applications, thus, quantification of their properties is important. We show, using T-Matrix calculations of 1D, 2D, and 3D plasmonic glasses, that their plasmon resonance position oscillates as a function of the particle spacing yielding blue-and redshifts up to 0.3 eV in the visible range with respect to the single particle surface plasmon. Their properties are discussed in light of an analytical model of an average particle's polarizability that originates from a coupled dipole methodology.
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5.
  • Arafin, S., et al. (författare)
  • Comprehensive analysis of electrically-pumped GaSb-based VCSELs
  • 2011
  • Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 19:18, s. 17267-17282
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper discusses several performance-related aspects of electrically-pumped GaSb-based buried tunnel junction VCSELs with an emission wavelength of 2.6 mu m based on theoretical and experimental results. These results allow a deeper insight into the internal device physics, such as radial diffusion of carriers, maximum continuous-wave operating temperature, diffraction loss, internal temperature, gain and loss parameters, internal quantum efficiency of the active region etc. These parameters can be taken into account while designing mid-infrared lasers which leads to an improved device performance. A simple thermal model of the devices based on the two-dimensional (2-D) finite element method using the material data from the literature is also presented. In addition, an application-based result utilizing these lasers for the measurement of absolute water vapor concentration by wavelength modulation spectroscopy (WMS) method are also described, hinting that devices are well-suited for the targeted sensing applications.
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6.
  • Astra, E., et al. (författare)
  • Dispersion management for nonlinearity mitigation in two-span 28 GBaud QPSK phase-sensitive amplifier links
  • 2017
  • Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 25:12, s. 13163-13173
  • Tidskriftsartikel (refereegranskat)abstract
    • We present an investigation of dispersion map optimization for-span single channel 28 GBaud QPSK transmission systems with phase-sensitive amplifiers (PSAs). In experiments, when the PSA link is operated in a highly nonlinear regime, a 1.4 dB error vector magnitude (EVM) improvement is achieved compared to a one-span optimized dispersion map link due to improved nonlinearity mitigation. The two-span optimized dispersion map of a link differs from the optimized dispersion map of a dispersion managed phase-insensitive amplifier (PIA) link, Simulations show that the performance of the two-span dispersion map optimized PSA link does not improve by residual dispersion optimization. Further, by using the two-span optimized dispersion maps repeatedly in a long-haul PSA link instead of one-span optimized maps, the maximum transmission reach can he improved 1,5 times, (C) 2017 Optical Society of America
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7.
  • Astra, Egon, et al. (författare)
  • Improved mitigation of self-phase modulation induced impairments in 28 GBaud phase-sensitive amplified links
  • 2019
  • Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 27:4, s. 4304-4316
  • Tidskriftsartikel (refereegranskat)abstract
    • The improved mitigation of self-phase modulation (SPM) induced nonlinear impairments by the use of a multi-span dispersion map optimization in 28 GBaud phase-sensitive amplifier (PSA) links is numerically investigated. We show that a four-span dispersion map optimized PSA link provides 2.1 times reach improvement over a single-span optimized PSA link with a total nonlinear phase shift tolerance increase from 2.1 radians to 8.8 radians. Furthermore, the optimized PSA link increases the maximum transmission reach by 6.9 times compared to a single-span optimized in-line dispersion managed phase-insensitive amplifier (PIA) link and 4.3 times reach extension is achieved compared to a dispersion unmanaged PIA link. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
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8.
  • Baveja, P. P., et al. (författare)
  • Assessment of VCSEL thermal rollover mechanisms from measurements and empirical modeling
  • 2011
  • Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 19:16, s. 15490-15505
  • Tidskriftsartikel (refereegranskat)abstract
    • We use an empirical model together with experimental measurements for studying mechanisms contributing to thermal rollover in vertical-cavity surface-emitting lasers (VCSELs). The model is based on extraction of the temperature dependence of threshold current, internal quantum efficiency, internal optical loss, series resistance and thermal impedance from measurements of output power, voltage and lasing wavelength as a function of bias current over an ambient temperature range of 15-100 degrees C. We apply the model to an oxide-confined, 850-nm VCSEL, fabricated with a 9-mu m inner-aperture diameter and optimized for highspeed operation, and show for this specific device that power dissipation due to linear power dissipation (sum total of optical absorption, carrier thermalization, carrier leakage and spontaneous carrier recombination) exceeds power dissipation across the series resistance (quadratic power dissipation) at any ambient temperature and bias current. We further show that the dominant contributors to self-heating for this particular VCSEL are quadratic power dissipation, internal optical loss, and carrier leakage. A rapid reduction of the internal quantum efficiency at high bias currents (resulting in high temperatures) is identified as being the major cause of thermal rollover. Our method is applicable to any VCSEL and is useful for identifying the mechanisms limiting the thermal performance of the device and to formulate design strategies to ameliorate them.
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9.
  • Berrocal, Edouard, et al. (författare)
  • Laser light scattering in turbid media Part II: Spatial and temporal analysis of individual scattering orders via Monte Carlo simulation.
  • 2009
  • Ingår i: Optics Express. - 1094-4087. ; 17:16, s. 13792-13809
  • Tidskriftsartikel (refereegranskat)abstract
    • In Part I of this study [1], good agreement between experimental measurements and results from Monte Carlo simulations were obtained for the spatial intensity distribution of a laser beam propagating within a turbid environment. In this second part, the validated Monte Carlo model is used to investigate spatial and temporal effects from distinct scattering orders on image formation. The contribution of ballistic photons and the first twelve scattering orders are analyzed individually by filtering the appropriate data from simulation results. Side-scattering and forward-scattering detection geometries are investigated and compared. We demonstrate that the distribution of positions for the final scattering events is independent of particle concentration when considering a given scattering order in forward detection. From this observation, it follows that the normalized intensity distribution of each order, in both space and time, is independent of the number density of particles. As a result, the amount of transmitted information is constant for a given scattering order and is directly related to the phase function in association with the detection acceptance angle. Finally, a contrast analysis is performed in order to quantify this information at the image plane.
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10.
  • Beygi, Lotfollah, 1977, et al. (författare)
  • On nonlinearly-induced noise in single-channel optical links with digital backpropagation
  • 2013
  • Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 21:22, s. 26376-26386
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, we investigate the performance limits of electronic chromatic dispersion compensation (EDC) and digital backpropagation (DBP) for a single-channel non-dispersion-managed fiber-optical link. A known analytical method to derive the performance of the system with EDC is extended to derive a first-order approximation for the performance of the system with DBP. In contrast to the cubic growth of the variance of the nonlinear noise-like interference, often called nonlinear noise, with input power for EDC, a quadratic growth is observed with DBP using this approximation. Finally, we provide numerical results to verify the accuracy of the proposed approach and compare it with existing analytical models.
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