Chapter 2 - Variational methods in nonlinear fiber optics and related fields

We review the use of hollow-core photonic crystal fibers (PCFs) in the field of ultrafast gas-based nonlinear optics, including recent experiments, numerical modeling, and a discussion of future prospects. Concentrating on broadband guiding kagome-style hollow-core PCF, we describe its potential for moving conventional nonlinear fiber optics both into extreme regimes—such as few-cycle pulse compression and efficient deep ultraviolet wavelength generation—and into regimes hitherto inaccessible, such as single-mode guidance in a photoionized plasma and high-harmonic generation in fiber.

Ultrafast nonlinear optics in gas-filled hollow-core photonic crystal fibers [Invited]

We review supercontinuum generation in optical fibers for particular cases where the nonlinear spectral broadening is induced by pump radiation from fiber-format sources. Based on numerical simulations, our paper is intended to provide experimental design guidelines tailored ytterbium and erbium-based pumps around 1060 and 1550 nm, respectively. In particular, at 1060 nm, we consider conditions under which the generated spectra are phase and intensity stable, and we address the dependence of the supercontinuum coherence on the input pulse parameters and the fiber length. At 1550 nm, special attention is paid to the case of dispersion-flattened dispersion-decreasing fiber, where we revisit the underlying physics in detail and explicitly examine the use of such fiber for supercontinuum generation with pumps of peak power in the range 200-1200 W and sub-10 m fiber lengths. We show that supercontinuum generation under such conditions can be highly coherent and can be applied to nonlinear pulse compression.

Fiber supercontinuum sources (Invited)

We investigate the adiabatic compression of picosecond and subpicosecond soliton pulses from all-fiber, passively mode-locked, erbium-doped fiber soliton lasers operating at 1550 nm in dispersion-decreasing fibers (DDF's). High-quality soliton compression from 630 down to 115 fs in a 100-m DDF and from 3.5 down to 230 fs in a 1.6-km DDF is obtained. The effects of third-order dispersion and Raman self-scattering on the compression process are observed and discussed.

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Soliton pulse compression in dispersion-decreasing fiber

The authors present a method for the generation of high-quality soliton trains at a high repetition rate of gigahertz to terahertz range During nonlinear propagation of a continuous-wave (CW) dual-frequency signal through a fiber with effective amplification, a train of practically noninteracting fundamental solitons is formed It is shown that the effective amplification can be achieved as in usual fibers with an actual amplification as well as in fibers with nonuniform parameters along the fiber axis The method is demonstrated experimentally Dual-frequency 25 ps pulses at lambda =155 mu m are reshaped into 02 THz combs of 049 ps solitons in fiber with slowly decreasing dispersion It is also shown that stimulated Brillouin scattering (SBS) can prevent a CW soliton train transmission through optical fibers, and suggests a method for suppression of SBS >

Generation of fundamental soliton trains for high-bit-rate optical fiber communication lines

The conditions necessary for the amplitude or the temporal width of an N = 1 soliton to increase, remain constant, or decrease with distance on an axially nonuniform optical fiber are derived. Numerical results for a step-index fiber with an axially tapered core are presented. The effects of such a fiber on higher-order solitons are also presented.

H. H. Kuehl

Papers

Solitons on an axially nonuniform optical fiber