Normal acoustic modes and Brillouin scattering in single-mode optical fibers

Thomas, Peter J.; Rowell, N. L.; Driel, H. M. van; Stegeman, George I.

doi:10.1103/physrevb.19.4986

Cited by 96 publications

(38 citation statements)

References 21 publications

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“…A waveguide has at least three acoustic modes: one longitudinal (also called compression or dilation) mode and two transverse (shear) modes. If the fiber is thick, there may be additional transverse acoustic modes, and thus be an acoustically multi-mode fiber [35,36]. We assume that one of the acoustic modes is the most important and neglect the others, because the analysis should begin with the most basic acoustic effects and defer to study of multimode and other higher-order effects.…”

Section: Governing Equations and Physical Parametersmentioning

confidence: 99%

Sudden spontaneous acceleration and deceleration of gap-acoustic solitons

2010

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Gap-acoustic solitons (GASs) are stable pulses that exist in nonlinear Bragg waveguides. They are a mathematical generalization of gap solitons, in which the model includes the dependence of the refractive index on the material density. We derive unified dynamical equations for gap solitons along with Brillouin scattering, which also results from the dependence of the refractive index on the material density. We find accurate values of the coefficients for fused silica. The analysis of the GAS conserved quantities-Hamiltonian, momentum, photon energy (or number of photons), and material mass-shows dramatic differences compared to the model neglecting the dependence of the refractive index on the material density. In particular, subsonic GASs in fused silica have far more momentum at low velocities than at high velocities. The dependence of the GAS momentum on velocity due to acoustic effects is dramatic up to approximately 1% of the speed of light. These momentum-connected effects mean that instability of a slow GAS may make it suddenly accelerate to high speeds, and also that an unstable high-speed GAS can abruptly decelerate to close to zero velocity. The predictions are confirmed by a direct numerical simulation.

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Section: Governing Equations and Physical Parametersmentioning

confidence: 99%

Sudden spontaneous acceleration and deceleration of gap-acoustic solitons

2010

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“…The interaction is important, e.g., for Brillouin scattering, diffraction of light by ultrasonic waves [1]. Brillouin scattering in optical fibers-coupling of longitudinal or transverse acoustic modes to optical waves through electrostriction-has been analyzed extensively, though generally not for solitons [2,3,4,5,6]. Sound waves acting on trains of optical solitons in fibers have been studied [7,8], but these interactions were essentially between acoustic continuous waves and their optical counterparts, subject to periodic modulation.…”

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confidence: 99%

“…; in a waveguide, the coefficient may be strongly affected by the modal structure [2,4,5]. The other electrostrictive coefficient, χ es = (ω 0 /c) dn/dw, comes from local changes in the wave vector [k = n(ω 0 , W 0 + w)ω/c], which depends on the index of refraction, which in turn depends on the acoustic field [1,4,8,21].…”

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confidence: 99%

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Optoacoustic Solitons in Bragg Gratings

2007

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Optical gap solitons, which exist due to a balance of nonlinearity and dispersion due to a Bragg grating, can couple to acoustic waves through electrostriction. This gives rise to a new species of "gap-acoustic" solitons (GASs), for which we find exact analytic solutions. The GAS consists of an optical pulse similar to the optical gap soliton, dressed by an accompanying phonon pulse. Close to the speed of sound, the phonon component is large. In subsonic (supersonic) solitons, the phonon pulse is a positive (negative) density variation. Coupling to the acoustic field damps the solitons' oscillatory instability, and gives rise to a distinct instability for supersonic solitons, which may make the GAS decelerate and change direction, ultimately making the soliton subsonic.PACS numbers: 42.81. Dp, 42.70.Qs, 43.25.+y, 72.50.+b Introduction.-Light and sound tend to have widely disparate frequencies, wavelengths, and velocities. As a consequence, interaction between optical and acoustic signals is often weak. The interaction is important, e.g., for Brillouin scattering, diffraction of light by ultrasonic waves [1]. Brillouin scattering in optical fibers-coupling of longitudinal or transverse acoustic modes to optical waves through electrostriction-has been analyzed extensively, though generally not for solitons [2,3,4,5,6]. Sound waves acting on trains of optical solitons in fibers have been studied [7,8], but these interactions were essentially between acoustic continuous waves and their optical counterparts, subject to periodic modulation. Brillouin scattering has been employed in acousto-optic filters, in which light diffracts off an acoustic grating [6]. Brillouin scattering in fibers can lead to pulse compression [9] or formation of trains of very narrow optical solitons [10]. Interaction of phonons with optical nonlinear Schrödinger solitons, with nonlinearity due to electromagnetically-induced transparency, was analyzed in Ref. [11]. Reference [12] considered solitons in Bragg gratings, with electrostriction the only nonlinearity; the correct soliton solution is a limiting case of the results below.In this work, we consider light and acoustic waves in a cubic (χ (3) ) nonlinear medium with a Bragg grating, a fixed spatially periodic variation in the index of refraction [13]. Bragg gratings are typically written in the cladding of an optical fiber, though they have been induced by copropagating continuous waves [14]. Fiber Bragg gratings without electrostriction are known to support optical gap solitons, nonlinear solitary waves with frequencies in the band gap created by the Bragg grating [13,15,16]. Gap solitons can have arbitrarily small velocity, which has motivated great interest in them for stopping light, though creating very slow gap solitons experimentally has been difficult. Early experimental realizations of gap solitons had velocities approximately half the speed of light [16]. Various methods have been proposed for creating slow gap solitons: building up slow gap solitons directly by Raman amplif...

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“…Since the initial theoretical discussions of Thomas et al 1 followed by the experimental observations of Shelby, Levenson, and Bayer demonstrating light scattering from thermally excited acoustic resonant modes in optical fibers, 2,3 little additional phenomenological work has appeared on the subject. These latter authors introduced the acronym ''GAWBS'' ͑guided acoustic-wave Brillouin scattering͒ and presented a comprehensive theory able to explain in detail many aspects of their experimental data.…”

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confidence: 99%

Low-frequency line shapes in guided acoustic-wave Brillouin scattering

Greene

Saeta

1994

Applied Physics Letters

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Guided acoustic-wave Brillouin scattering (GAWBS) measurements were performed on 20-cm lengths of optical fibers with particular attention focused on the lowest lying resonance. In 125-μm-diam silica fibers, this resonance was observed to occur at ∼22 MHz and have a line shape which varied erratically from sample to sample. Significant line shape fluctuations were evident even between sequential samples from the same fiber spool. We speculate that the observed effects are attributable to 0.01–0.1 μm distributed geometric deviations from a perfect cylinder.

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Normal acoustic modes and Brillouin scattering in single-mode optical fibers

Cited by 96 publications

References 21 publications

Sudden spontaneous acceleration and deceleration of gap-acoustic solitons

Sudden spontaneous acceleration and deceleration of gap-acoustic solitons

Optoacoustic Solitons in Bragg Gratings

Low-frequency line shapes in guided acoustic-wave Brillouin scattering

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