Supercontinuum generation in optical fibers: 40 years of ... generation in optical fibers: ... Supercontinuum instabilities optical rogue waves ... − +=P − HOD perturbation of

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  • Supercontinuum generation in optical fibers: 40 years of nonlinear optics in

    one experiment

    Gory Genty Optics Laboratory, Tampere University of Technology, Finland

    TAMPERE UNIVERSITY OF TECHNOLOGYInstitute of Physics

  • Part I: back to basics

    Optical fibers for supercontinuum generation

    Ultrafast pulse propagation and supercontinuum

    generation Visualizing supercontinuum dynamics

    Coherence properties

  • Part II: recent developments

    New fibers, new materials and new spectral regions

    Supercontinuum instabilities & optical rogue waves

    Bridging the gap between traditional nonlinear optics and supercontinuum generation

    Future steps and challenges

  • A historical note

  • Supercontinuum timeline Supercontinuum generation in bulk silica (R. Alfano)

    1980 1990 2000

    Nonlinearity in silica fiber (R. Stolen & Lin)

    Experimental Fiber solitons (L. Mollenauer)

    1970

    Femtosecond Ti:Sapphire (Sibbett)

    Solid core photonic crystal fiber (P. Russell)

    Supercontinuum generation in photonic crystal fiber (J. Ranka et al.)

    Nobel prize Hall & Hnsch

    Today

    Supercontinuum generation in silica fiber (R. Stolen & Lin)

    Photonics@be

    2005

  • The esthetic slide

  • Why the excitement?

  • Supercontinuum has been around for decades

  • There are some issues though

    Limitations - Walk off - Diffraction - Strong dispersion, limited broadening

    Need very high energy

    - Damage

  • Optical fibers are more convenient

    Pulse propagation in optical fibers No diffraction, long interaction length

    Dispersion/nonlinearity can be controlled: crucial! propagation dynamics depend on pump wavelength relative to

    fiber zero dispersion wavelength (ZDW)

    Small core, high doping Photonic crystal fibers Tapered fibers Non-silica materials

    NEW FIBERS

    Dispersion

    nonlinearity

    Confinement

    PARAMETER CONTROL APPLICATIONS

    Supercontinuum Frequency conversion Pulse compression Regeneration Amplification

  • Optical fibers for nonlinear applications Chemistry and geometry both contribute to the refractive

    index profile Determine modal confinement (nonlinearity) and dispersion

    characteristics Wide range of possibilities

  • Photonic crystal fibers

    Generally single material with a high air-fill fraction

    ZDW displaced to shorter wavelengths: wavelength of

    high-power short pulse sources Large nonlinearity (x100 compared to standard fibers)!

    nonlinear effects dramatically enhanced

  • Taper/microfibers

    Tapering standard fibers: similar properties to photonic crystal fibers

  • Key aspects for supercontinuum

    Micro/nano- structured waveguides: engineered nonlinearity and dispersion

    Dispersion shifts soliton regime to shorter wavelengths Long interaction lengths Light tightly confined very large intensities!

  • Pulse propagation in optical fibers

    E(r, z, t) = F(r)A(z, t)ei0tF(r) modal distributionA(z,t) time variation

    0 =2c0

    carrier frequency

    !

    "

    ###

    $

    ###

    t

    A(z,t)

    Modal distribution does not vary with propagation Consider only the fundamental mode LP01 (Gaussian

    distribution)

    Only temporal effects matters, no diffraction

  • Nonlinear pulse propagation in optical fibers

    ),(),(),(with

    ),(),(1),( 22

    02

    2

    2

    trPtrPtrPttrP

    ttrE

    ctrE

    NLL +=

    =

    +

    ...),(),(),(),( 3)3(02)2(

    0)1(

    0)0(

    0 ++++= trEtrEtrEtrP

    Pulse propagation in optical fiber obeys :

    In silica: (2)=0 (centro-symmetric material)

    Only THIRD-ORDER nonlinear effects

    Dispersion Nonlinearity

  • The Kerr effect

    Light intensity changes the refractive index: n = n0+ n2I = n0 + (n2/Aeff)P

    n2 proportional to (3) : nonlinear refractive index Aeff effective area of the fiber mode

    Important parameter: nonlinear coefficient = n2/cAeff Nonlinear effects scales with $

    In silica, n2 310-20 m2/W: weak nonlinear material! But

    silica has the lowest losses

    Need small Aeff

  • Nonlinear effects in optical fibers

    Pump wavelength is crucial!

  • Generalized nonlinear Schrdinger Equation (GNLSE)

    Can include noise, frequency-dependent mode area,

    polarizationetc

    Validity: down to single cycle regime

    Self-Steepening term SPM, FWM, Raman

    Intensity-dependent ref. index

    Raman response

    Dispersion

    Modeling pulse propagation

    Loss

  • Generalized nonlinear Schrdinger Equation (GNLSE)

    Can include noise, frequency-dependent mode area,

    polarizationetc

    Validity: down to single cycle regime

    Self-Steepening term SPM, FWM, Raman

    Intensity-dependent ref. index

    Raman response

    Dispersion

    Modeling pulse propagation

    Loss

    Nonlinear envelope equation modeling ofsub-cycle dynamics and harmonicgeneration in nonlinear waveguides

    G. GentyHelsinki University of Technology, Metrology Research Institute, FIN-02015 HUT, Finland

    P. KinslerImperial College, Blackett Laboratory, Imperial College London, SW7 2BW, United Kingdom.

    B. Kibler and J. M. DudleyInstitut FEMTO-ST, Department of Optics, Universite de Franche-Comte, Besancon, France.

    Abstract: We describe generalized nonlinear envelope equation modelingof sub-cycle dynamics on the underlying electric field carrier duringone-dimensional propagation in fused silica. Generalized envelope equationsimulations are shown to be in excellent quantitative agreement with thenumerical integration of Maxwells equations, even in the presence ofshock dynamics and carrier steepening on a sub-50 attosecond timescale.In addition, by separating the effects of self-phase modulation and thirdharmonic generation, we examine the relative contribution of these effectsin supercontinuum generation in fused silica nanowire waveguides.

    2007 Optical Society of AmericaOCIS codes: 060.7140 Ultrafast processes in fibers, 190.7110 Ultrafast nonlinear optics

    References and links1. J. M. Dudley, G. Genty, and S. Coen, Supercontinuum generation in photonic crystal fiber, Rev. Mod. Phys.78, 11351184 (2006).

    2. M. A. Foster, A. L. Gaeta, Q. Cao, and R. Trebino, Soliton-effect compression of supercontinuum to few-cycledurations in photonic nanowires, Opt. Express 13, 68486855 (2005).

    3. V. P. Kalosha and J. Herrmann, Self-phase modulation and compression of few-optical-cycle pulses, Phys.Rev. A 62, 011804(R) (2000).

    4. N. Karasawa, Computer simulations of nonlinear propagation of an optical pulse using a finite-difference in thefrequency-domain method, IEEE J. Quantum Electron. 38, 626629 (2002).

    5. K. J. Blow and D. Wood, Theoretical description of transient stimulated Raman scattering in optical fibers,IEEE J. Quantum Electron. 25, 26652673 (1989).

    6. T. Brabec and F. Krausz, Nonlinear optical pulse propagation in the single-cycle regime, Phys. Rev. Lett. 78,32823285 (1997).

    7. N. Karasawa, S. Nakamura, N. Nakagawa, M. Shibata, R. Morita, H. Shigekawa, and M. Yamashita, Compari-son between theory and experiment of nonlinear propagation for a-few-cycle and ultrabroadband optical pulsesin a fused-silica fiber, IEEE J. Quantum Electron. 37, 398404 (2001).

    8. P. Kinsler and G.H.C. New, Wideband pulse propagation: single-field and multi-field approaches to Ramaninteractions,Phys.Rev. A 72, 033804 (2005).

    9. A. V. Husakou and J. Herrmann, Supercontinuum generation of higher-order solitons by fission in photoniccrystal fibers, Phys. Rev. Lett. 87, 203901 (2001).

    10. A. V. Husakou and J. Herrmann, Supercontinuum generation, four-wave mixing, and fission of higher-ordersolitons in photonic-crystal fibers, J. Opt. Soc. Am. B 19, 21712182 (2002).

    11. M. Kolesik and J. V. Moloney, Nonlinear optical pulse propagation simulation: From Maxwells to unidirec-tional equations, Phys. Rev. E 70, 036604 (2004).

    #79783 - $15.00 USD Received 5 Feb 2007; accepted 2 Apr 2007; published 18 Apr 2007(C) 2007 OSA 30 Apr 2007 / Vol. 15, No. 9 / OPTICS EXPRESS 5382

  • Generalized nonlinear Schrdinger Equation (GNLSE)

    Important considerations window size (avoid wrapping around) temporal/spectral resolution step size (FWM artifacts) DO NOT use linear Raman model Disp. coeff. must be changed if you change the pump wavelength

    Modeling pulse propagation

  • Good agreement with experimental results

    Success in modeling: physics behind supercontinuum generation now well-understood

    Modeling supercontinuum generation

  • Supercontinuum generation is easy!

    But its dynamics can be rather complex

  • 30 fs, 10 kW input pulses

    Evolution can be divided in 3 stages

    Initial higher-order soliton compression (spectral broadening), soliton fission and dispersive wave generation Raman self-frequency shift

    Deconstructing supercontinuum dynamics

  • Evolution can be divided in 3 stages

    Initial higher-order soliton compression (spectral broadening), soliton fission and dispersive wave generation Raman self-frequency shift

    Better in color Spectral Evolution Temporal Evolution

    SOLITON FISSION

    DISPERSIVE WAVE BACKGROUND

    DIS

    PER

    SIVE

    WAV

    E ED

    GE

    RA

    MA

    N S

    ELF

    FREQ