M. Avazpour

The hyperbolic secant (Sech) shape, as the initial beam profile, is the well-know profile that compensates the diffraction and self-focusing effect during propagation in Kerr medium, and evolves as the bright spatial soliton. The Sech beam can be confined in the Kerr medium andinduces its own waveguide. In this work, two initial beam profiles, rectangular and triangular functions, that are different than Sech profile, are considered, and the propagation of these beam profiles in third-order nonlinear (Kerr) medium is investigated. As a result, the initialbeam-width played an important role in confining the beam profiles in direction of propagation. In addition, the intensity profiles change to the Sech profile after some initial step of propagation. All the calculations and simulations have been done by the Split-Step numericalmethod with MATLAB program.

We report an experimental study of the supercontinuum (SC) generated by molecules of solitons (MS) and noise-like pulses (NLP) and their dependence on pump power in two different types of optical fibers: 500 m of standard fiber (SMF-28, Corning) and 100 m of high-nonlinearity fiber with a zero-dispersion slope (Furukawa HNLF-ZS). Our results show a more complex dependence of the SC spectra on pump power for the MS than for the NLP used for pump. We attribute such differences to soliton fission of MS whereas this process is already done within the NLP. We use a nonlinear optical loop mirror (NOLM) connected to the output of the fiber under test to evaluate the amplitude of ultrashort pulses, which compose SC and found that amplitude is changed strongly throughout the spectrum. The NOLM suppresses pulses with low peak power, this is especially pronounced for wavelengths longer than ∼1750 nm for both fibers, and in the region between 1450 nm–1640 nm for the high-nonlinearity fiber.