Dynamics Of Dispersive Waves Research Articles

Characterization and Manipulation of Temporal Structures of Dispersive Waves in a Soliton Fiber Laser

Dispersive waves (DWs) are ubiquitous in nonlinear optical systems that host optical solitons. In particular, DWs in soliton fiber lasers have attracted continuous interest over the past decades since they are closely related to laser soliton instabilities. Meanwhile, intra-cavity DWs also play important roles in solion interactions. While previous studies mostly focused on their spectral properties, characterizations and manipulations of the intra-cavity DWs in the time domain remain unexplored. Here, we report the experimental studies on temporal structures of intra-cavity DWs, unveiling their exponentially-decaying profiles which can be manipulated by varying cavity parameters, following a simple analytic model. We also studied the evolution dynamics of the intra-cavity DWs under abrupt cavity parameter variations. We observed that both the amplitude and the width of the DW waveform went through variations as the pump power was changed, while their evolution trajectories followed intimately that of the soliton energy. These results provide insights into the DW emission mechanism in mode-locked lasers, and the control methods of intra-cavity DWs may find potential applications in the fields of ultrafast pulse generation and soliton dynamics.

Ultrafast circularly polarized pulses tunable from the vacuum to deep ultraviolet.

We experimentally demonstrate the efficient generation of circularly polarized pulses tunable from the vacuum to deep ultraviolet (160-380 nm) through resonant dispersive wave emission from optical solitons in a gas-filled hollow capillary fiber. In the deep ultraviolet, we measure up to 13 µJ of pulse energy, and from numerical simulations, we estimate the shortest output pulse duration to be 8.5 fs. We also experimentally verify that simply scaling the pulse energy by 3/2 between linearly and circularly polarized pumping closely reproduces the soliton and dispersive wave dynamics. Based on previous results with linearly polarized self-compression and resonant dispersive wave emission, we expect our technique to be extended to produce circularly polarized few-fs pulses further into the vacuum ultraviolet, and few to sub-fs circularly polarized pulses in the near infrared.

Modulations of viscous fluid conduit periodic waves

Modulated periodic interfacial waves along a conduit of viscous liquid are explored using nonlinear wave modulation theory and numerical methods. Large-amplitude periodic-wave modulation (Whitham) theory does not require integrability of the underlying model equation, yet often either integrable equations are studied or the full extent of Whitham theory is not developed. Periodic wave solutions of the nonlinear, dispersive, non-integrable conduit equation are characterized by their wavenumber and amplitude. In the weakly nonlinear regime, both the defocusing and focusing variants of the nonlinear Schrödinger (NLS) equation are derived, depending on the carrier wavenumber. Dark and bright envelope solitons are found to persist in long-time numerical solutions of the conduit equation, providing numerical evidence for the existence of strongly nonlinear, large-amplitude envelope solitons. Due to non-convex dispersion, modulational instability for periodic waves above a critical wavenumber is predicted and observed. In the large-amplitude regime, structural properties of the Whitham modulation equations are computed, including strict hyperbolicity, genuine nonlinearity and linear degeneracy. Bifurcating from the NLS critical wavenumber at zero amplitude is an amplitude-dependent elliptic region for the Whitham equations within which a maximally unstable periodic wave is identified. The viscous fluid conduit system is a mathematically tractable, experimentally viable model system for wide-ranging nonlinear, dispersive wave dynamics.