Giant anomalous self-steepening in photonic crystal waveguides

Abstract

Self-steepening of optical pulses arises due the dispersive contribution of the χ (3) (ω) Kerr nonlinearity. In typical structures this response is on the order of a few femtoseconds with a fixed frequency response. In contrast, the effective χ (3) Kerr nonlinearity in photonic crystal waveguides (PhCWGs) is largely determined by the geometrical parameters of the structure and is consequently tunable over a wide range. Here we show self-steepening based on group-velocity (group-index) modulation for the first time, giving rise to a new physical mechanism for generating this effect. Further, we demonstrate that periodic media such as PhCWGS can exhibit self-steepening coefficients two orders of magnitude larger than typical systems. At these magnitudes the self-steepening strongly affects the nonlinear pulse dynamics even for picosecond pulses. Due to interaction with additional higher-order nonlinearities in the semiconductor materials under consideration, we employ a generalized nonlinear Schrödinger equation numerical model to describe the impact of self-steepening on the temporal and spectral properties of the optical pulses in practical systems, including new figures of merit. These results provide a theoretical description for recent experimental results presented in [Scientific Reports 3, 1100) and Phys. Rev. A 87, 041802 (2013]. More generally, these observations apply to all periodic media due to the rapid group-velocity variation characteristic of these structures.

Soliton dynamics in integrated photonic chips

“…The black dashed line indicates simulations with suppressed FCD showing the pulse shifts noticeably less in this case and we conclude that FCD causes the temporal advance. We suspect the remaining shift might be due to strong self-steepening in the photonic crystal [13] or residual pulse chirp. More recently we showed that FCD can induce soliton fission [14].…”

Breaking fundamental noise limitations to supercontinuum generation

“…Two reasons confer on this work the potential to open a new avenue in nonlinear guided optics. First, experimental tests of self-steepening effects predicted theoretically, ranging from MI cancellation and CSC in the long pulse regime, as studied here, to soliton self-frequency shift deceleration [36], on-chip octave-spanning SC generation [37], or even anomalous self-steepening [38], become now feasible using ps sources and more accessible technologies, as silicon-on-insulator (SOI) is, unlike previous approaches [37,38]. Second, these results might also be feasible at telecom [39] or visible wavelenghts [40] where chalcogenides [41] and diamond [42] possess their 2PA resonance.…”

Gradient catastrophe of nonlinear photonic valley-Hall edge pulses

“…Accurate modelling of pulse propagation through photonic crystal waveguides in the slow light regime requires taking into account the dispersion in the effective nonlinearity strength, which can induce effects such as pulse self-steepening and supercontinuum generation [28][29][30][31]. Despite the proven importance of these effects in applications [32][33][34], analysis of nonlinear light propagation in topological photonic structures most often assumes non-dispersive nonlinearities, in both the underlying material response [35][36][37][38][39][40][41][42][43][44][45] and effective models describing the propagation of nonlinear edge states [46][47][48][49][50].…”