The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform
Siddharth Ramachandran - One of the best experts on this subject based on the ideXlab platform.
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intermodal Group Velocity engineering for broadband nonlinear optics
Photonics Research, 2019Co-Authors: Jeff Demas, Lars Rishoj, Xiao Liu, Gautam Prabhakar, Siddharth RamachandranAbstract:Interest in the nonlinear properties of multi-mode optical waveguides has seen a recent resurgence on account of the large dimensionality afforded by the platform. The large volume of modes in these waveguides provides a new spatial degree of freedom for phase matching nonlinear optical processes. However, this spatial dimension is quantized, which narrows the conversion bandwidths of intermodal processes and constrains spectral and temporal tailoring of the light. Here we show that by engineering the relative Group Velocity within the spatial dimension, we can tailor the phase-matching bandwidth of intermodal parametric nonlinearities. We demonstrate Group-Velocity-tailored parametric nonlinear mixing between higher-order modes in a multi-mode fiber with gain bandwidths that are more than an order of magnitude larger than that previously thought possible for intermodal four-wave mixing. As evidence of the technological utility of this methodology, we seed this process to generate the first high-peak-power wavelength-tunable all-fiber quasi-CW laser in the Ti:sapphire wavelength regime. More generally, with the combination of intermodal interactions, which dramatically expand the phase-matching degrees of freedom for nonlinear optics, and intermodal Group-Velocity engineering, which enables tailoring of the bandwidth of such interactions, we showcase a platform for nonlinear optics that can be broadband while being wavelength agnostic.
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intermodal Group Velocity engineering for broadband nonlinear optics
arXiv: Optics, 2018Co-Authors: Jeff Demas, Lars Rishoj, Xiao Liu, Gautam Prabhakar, Siddharth RamachandranAbstract:Interest in the nonlinear properties of multi-mode optical waveguides has seen a recent resurgence on account of the large dimensionality afforded by the platform. However, a perceived fundamental limitation of intermodal parametric interactions - that they are impractically narrowband - has yet to be solved. Here we show that by engineering the relative Group Velocity within the discrete spatial degree of freedom, we can tailor the phase matching bandwidth of intermodal parametric nonlinearities. We demonstrate Group-Velocity-tailored four-wave mixing between the $LP_{0,4}$ and $LP_{0,5}$ modes of a multi-mode fiber with unprecedented gain bandwidths (>60 nm at ~1550 nm). As evidence of the technological utility of this methodology, we seed this process to generate a high-peak-power wavelength-tunable fiber laser in the Ti:Sapphire wavelength regime. More generally, with the combination of intermodal interactions, which dramatically expand the phase matching degrees of freedom for nonlinear optics, and intermodal Group Velocity engineering, which enables tailoring the bandwidth of such interactions, we showcase a platform for nonlinear optics that can be broadband while being wavelength agnostic.
John D. Joannopoulos - One of the best experts on this subject based on the ideXlab platform.
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Zero-Group-Velocity modes in longitudinally uniform waveguides
Applied Physics Letters, 2008Co-Authors: Chun Jiang, Mihai Ibanescu, John D. Joannopoulos, Marin SoljacicAbstract:We present a longitudinally uniform slow light waveguide, which consists of transverse periodic dielectric strips with a few defect layers. The parameters of the proposed waveguide can be tuned to have two anomalous dispersion curves with extreme points which have zero-Group-Velocity frequencies at nonzero wave vector in uniform-index direction. The Group Velocity and Group Velocity dispersion of the two photonic bands are analyzed, and the propagation of the slow mode with a given bandwidth is demonstrated theoretically.
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Distinguishing zero-Group-Velocity modes in photonic crystals
Physical Review A, 2007Co-Authors: Michael Ghebrebrhan, Mihai Ibanescu, Steven G. Johnson, Marin Soljacic, John D. JoannopoulosAbstract:We examine differences between various zero-Group-Velocity modes in photonic crystals, including those that arise from Bragg diffraction, anticrossings, and band repulsion. Zero-Group Velocity occurs at points where the Group Velocity changes sign, and therefore is conceptually related to 'left-handed' media, in which the Group Velocity is opposite to the phase Velocity. We consider this relationship more quantitatively in terms of the Fourier decomposition of the modes, by defining a measure of how much the 'average' phase Velocity is parallel to the Group Velocity--an anomalous region is one in which they are mostly antiparallel. We find that this quantity can be used to qualitatively distinguish different zero-Group-Velocity points. In one dimension, such anomalous regions are found never to occur. In higher dimensions, they are exhibited around certain zero-Group-Velocity points, and lead to unusual enhanced confinement behavior in microcavities.
Kenji Kitamura - One of the best experts on this subject based on the ideXlab platform.
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Group-Velocity control by quadratic nonlinear interactions.
Optics letters, 2006Co-Authors: Marco Marangoni, Federico Baronio, Cristian Manzoni, Roberta Ramponi, Giulio Cerullo, Costantino De Angelis, Kenji KitamuraAbstract:We give direct experimental evidence that the Group Velocity of ultrashort pulses can be controlled through chi(2)-cascaded interactions, under the condition of large Group-Velocity mismatch. The Group Velocity can be finely tuned by acting on pulse intensity and phase mismatch. Group-delay shifts up to 50 fs are achieved by propagating 40 fs pulses around 1400 nm in a 25 mm long periodically poled stoichiometric lithium tantalate crystal.
Mihai Ibanescu - One of the best experts on this subject based on the ideXlab platform.
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Zero-Group-Velocity modes in longitudinally uniform waveguides
Applied Physics Letters, 2008Co-Authors: Chun Jiang, Mihai Ibanescu, John D. Joannopoulos, Marin SoljacicAbstract:We present a longitudinally uniform slow light waveguide, which consists of transverse periodic dielectric strips with a few defect layers. The parameters of the proposed waveguide can be tuned to have two anomalous dispersion curves with extreme points which have zero-Group-Velocity frequencies at nonzero wave vector in uniform-index direction. The Group Velocity and Group Velocity dispersion of the two photonic bands are analyzed, and the propagation of the slow mode with a given bandwidth is demonstrated theoretically.
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Distinguishing zero-Group-Velocity modes in photonic crystals
Physical Review A, 2007Co-Authors: Michael Ghebrebrhan, Mihai Ibanescu, Steven G. Johnson, Marin Soljacic, John D. JoannopoulosAbstract:We examine differences between various zero-Group-Velocity modes in photonic crystals, including those that arise from Bragg diffraction, anticrossings, and band repulsion. Zero-Group Velocity occurs at points where the Group Velocity changes sign, and therefore is conceptually related to 'left-handed' media, in which the Group Velocity is opposite to the phase Velocity. We consider this relationship more quantitatively in terms of the Fourier decomposition of the modes, by defining a measure of how much the 'average' phase Velocity is parallel to the Group Velocity--an anomalous region is one in which they are mostly antiparallel. We find that this quantity can be used to qualitatively distinguish different zero-Group-Velocity points. In one dimension, such anomalous regions are found never to occur. In higher dimensions, they are exhibited around certain zero-Group-Velocity points, and lead to unusual enhanced confinement behavior in microcavities.
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microcavity confinement based on an anomalous zero Group Velocity waveguide mode
Optics Letters, 2005Co-Authors: Mihai Ibanescu, Steven G. Johnson, David Roundy, Yoel Fink, J D JoannopoulosAbstract:We propose and demonstrate a mechanism for small-modal-volume high-Q cavities based on an anomalous uniform waveguide mode that has zero Group Velocity at a nonzero wave vector. In a short piece of a uniform waveguide with a specially designed cross section, light is confined longitudinally by small Group-Velocity propagation and transversely by a reflective cladding. The quality factor Q is greatly enhanced by the small Group Velocity for a set of cavity lengths that are separated by approximately ?/k0, where k0 is the longitudinal wave vector for which the Group Velocity is zero.
Marin Soljacic - One of the best experts on this subject based on the ideXlab platform.
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Zero-Group-Velocity modes in longitudinally uniform waveguides
Applied Physics Letters, 2008Co-Authors: Chun Jiang, Mihai Ibanescu, John D. Joannopoulos, Marin SoljacicAbstract:We present a longitudinally uniform slow light waveguide, which consists of transverse periodic dielectric strips with a few defect layers. The parameters of the proposed waveguide can be tuned to have two anomalous dispersion curves with extreme points which have zero-Group-Velocity frequencies at nonzero wave vector in uniform-index direction. The Group Velocity and Group Velocity dispersion of the two photonic bands are analyzed, and the propagation of the slow mode with a given bandwidth is demonstrated theoretically.
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Distinguishing zero-Group-Velocity modes in photonic crystals
Physical Review A, 2007Co-Authors: Michael Ghebrebrhan, Mihai Ibanescu, Steven G. Johnson, Marin Soljacic, John D. JoannopoulosAbstract:We examine differences between various zero-Group-Velocity modes in photonic crystals, including those that arise from Bragg diffraction, anticrossings, and band repulsion. Zero-Group Velocity occurs at points where the Group Velocity changes sign, and therefore is conceptually related to 'left-handed' media, in which the Group Velocity is opposite to the phase Velocity. We consider this relationship more quantitatively in terms of the Fourier decomposition of the modes, by defining a measure of how much the 'average' phase Velocity is parallel to the Group Velocity--an anomalous region is one in which they are mostly antiparallel. We find that this quantity can be used to qualitatively distinguish different zero-Group-Velocity points. In one dimension, such anomalous regions are found never to occur. In higher dimensions, they are exhibited around certain zero-Group-Velocity points, and lead to unusual enhanced confinement behavior in microcavities.
