A simple iterative model is introduced quantifying the interaction of saturable gain and nonlinear loss in a mode-locked laser cavity. The resulting geometrical description of the laser dynamics completely characterizes the generic multi-pulsing instability observed in experiments. The model further shows that the onset of multipulsing can be preceded by periodic and chaotic transitions as recently confirmed in theory and experiment. The results suggest ways to engineer the nonlinear losses in the cavity in order to achieve an enhanced performance.

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(2017) Mid-infrared octave-spanning supercontinuum and frequency comb generation in a suspended germanium-membrane ridge waveguide. Journal of Lightwave Technology, 35 (14 Northumbria University has developed Northumbria Research Link (NRL) to enable users to access the University's research output. Copyright © and moral rights for items on NRL are retained by the individual author(s) and/or other copyright owners. Single copies of full items can be reproduced, displayed or performed, and given to third parties in any format or medium for personal research or study, educational, or not-for-profit purposes without prior permission or charge, provided the authors, title and full bibliographic details are given, as well as a hyperlink and/or URL to the original metadata page. The content must not be changed in any way. Full items must not be sold commercially in any format or medium without formal permission of the copyright holder. The full policy is available online: http://nrl.northumbria.ac.uk/policies.html This document may differ from the final, published version of the research and has been made available online in accordance with publisher policies. To read and/or cite from the published version of the research, please visit the publisher's website (a subscription may be required.) > REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < 1 Abstract-Stable octave-spanning supercontinuum (SC) in the mid-infrared (MIR) region finds extensive applications in spectroscopy, metrology, biochemistry, etc. The absorption of conventional silicon-or silicon oxide-dominated nonlinear media makes SC generation in MIR region technically challenging. In this paper, we propose ultra-broadband MIR-SC generation using a suspended germanium-membrane ridge waveguide. We theoretically showed that when pump pulses centered at 4.8 m with pulse width at 180 fs and peak power at 800 W are injected into a 4-mm long proposed ridge waveguide, the SC generated ranges from 1.96  12 m (about 2.6 octaves), extending deep into the "fingerprint" region. The first-order coherence is calculated to confirm the stability of the generated SC. The performance of the SC-based frequency comb is also investigated by assuming a 100-pulses pump source at a repetition rate of 100 KHz.

We theoretically demonstrate that in a laser cavity mode-locked by a set of waveplates and passive polarizer, the energy performance can be increased by incorporating a second set of waveplates and polarizer in the cavity. The two nonlinear transmission functions acting in combination can be engineered so as to suppress the multi-pulsing instability responsible for limiting the single pulse per round trip energy in a myriad of mode-locked cavities. In a single parameter sweep, the energy is demonstrated to double. It is anticipated that further engineering and optimization of the transmission functions by tuning the eight waveplates, fiber birefringence, two polarizers and two lengths of transmission fiber can lead to further significant increases. Moreover, the analysis suggests a general design and engineering principle that can potentially realize the goal of making fiber based lasers directly competitive with solid state devices. The technique is feasible and easy to implement without requiring a new cavity design paradigm.

Abstract-In this paper, we propose and design a chalcogenide (As2S3) based slot waveguide taper with exponentially decreasing dispersion profile to realize high degree pulse compression of low power chirped solitons. Based on the waveguide taper designed, self-similar pulse compression of fundamental solitons and chirped 2-soliton breather are both investigated numerically. With self-similar pulse compression scheme, a 1 ps input pulse is compressed to 81.5 fs in 6 cm propagation. By using 2-soliton breather pulses, a 1 ps chirped pulse is compressed to 80.3 fs in just 2.54 cm. This is the first demonstration of the feasibility of high degree nonlinear pulse compression in As2S3-based slot waveguide taper.Index Terms-Self-similar pulse compression, fundamental soliton, 2-soliton breather, As2S3-based slot waveguide taper.