Dynamics of soliton cascades in fiber amplifiers

Abstract

We study numerically the formation of cascading solitons when femtosecond optical pulses are launched into a fiber amplifier with less energy than required to form a soliton of equal duration. As the pulse is amplified, cascaded fundamental solitons are created at different distances, without soliton fission, as each fundamental soliton moves outside the gain bandwidth through the Raman-induced spectral shifts. As a result, each input pulse creates multiple, temporally separated, ultrashort pulses of different wavelengths at the amplifier output. The number of pulses depends not only on the total gain of the amplifier but also on the width of the input pulse.

Numerical Study on Supercontinuum Generation in an Active Highly Nonlinear Photonic Crystal Fiber With Anomalous Dispersion

“…Thus, once the effective soliton number has become less than unity, the soliton fission process is eventually terminated [1]. In contrast, when the optical gain is turned on, the dynamics associated with soliton fission becomes substantially different from that of the passive case: The 'pulse remnant' [18], which is the part of the input pulse remaining after the soliton fission or breakup at z = 0.07 m, continues to emit fundamental solitons as shown in Fig. 2(d).…”

“…That is, the rate-equationbased approach utilized in [9] might be no longer appropriate enough for such extremely fast nonlinear interactions in the AD regime. We note that to date only a handful of numerical or theoretical studies have been carried out on analyzing novel characteristic aspects of SCG in active fibers in the AD regime [12], [18]- [20]. In particular, Lei et al reported that SCG in a Yb-doped fiber (YDF) with AD can be modeled by combining the well-known rate equation and the nonlinear Schrödinger equation (NLSE) when excited by ps pulses [12].…”

“…To verify the quantum coherence effects, we analyzed the evolution of a 200-fs soliton pulse in an active fiber with AD by solving the Maxwell-Bloch equations in a direct numerical approach [20]; however, the details of soliton and SCG dynamics in such a condition remained too preliminary. In addition, Arteaga-Sierra et al reported soliton dynamics in fiber amplifiers, using the complex Ginzburg-Landau equation (CGLE) along with a real-valued super-Gaussian gain spectrum [18]. Although this work focused on the soliton generation in a cascade way and the related pulse dynamics during amplification of low soliton number pulses (i.e.…”

Soliton dynamics in photonic-crystal fibers with frequency-dependent Kerr nonlinearity

“…However, fundamental solitons themselves are resistant to fission or any kind of splitting [1,5]. Generally, splitting of a fundamental soliton is only possible if the fiber is tapered [6][7][8] or is doped and pumped to provide amplification [9][10][11][12]. Both of these methods rely on increasing the soliton order to beyond N = 1.5 so that a second-order soliton is formed that splits into two fundamental solitons.…”

Femtosecond fiber Mamyshev oscillator at 1550 nm

“…The experimental results presented below are accompanied by numerical results obtained from our simulation code. Pulse propagation in the fibers is modeled through the scalar generalized nonlinear Schrödinger equation [21] taking into account dispersion up to third order (TOD), the instantaneous Kerr response, the complete delayed Raman response of silica fibers [22], and the spectral gain calculated from the erbium cross sections and the rate equations solved in the steady state [23]. The model does not include ASE.…”