Multi-scale polarisation phenomena

Multi-scale methods that separate different time or spatial scales are among the most powerful techniques in physics, especially in applications that study nonlinear systems with noise. When the time scales (noise and perturbation) are of the same order, the scales separation becomes impossible. Thus, the multi-scale approach has to be modified to characterise a variety of noise-induced phenomena. Here, based on stochastic modelling and analytical study, we demonstrate in terms of the fluctuation-induced phenomena and Hurst R/S analysis metrics that the matching scales of random birefringence and pump–signal states of polarisation interaction in a fibre Raman amplifier results in a new random birefringence-mediated phenomenon, which is similar to stochastic anti-resonance. The observed phenomenon, apart from the fundamental interest, provides a base for advancing multi-scale methods with application to different coupled nonlinear systems ranging from lasers (multimode, mode-locked, random, etc.) to nanostructures (light-mediated conformation of molecules and chemical reactions, Brownian motors, etc.)

Stokes solitons in optical microcavities

Solitons are wave packets that resist dispersion through a self-induced potential well. They are studied in many fields, but are especially well known in optics on account of the relative ease of their formation and control in optical fibre waveguides. Besides their many interesting properties, solitons are important to optical continuum generation, in mode-locked lasers, and have been considered as a natural way to convey data over great distances. Recently, solitons have been realized in microcavities, thereby bringing the power of microfabrication methods to future applications. This work reports a soliton not previously observed in optical systems, the Stokes soliton. The Stokes soliton forms and regenerates by optimizing its Raman interaction in space and time within an optical potential well shared with another soliton. The Stokes and the initial soliton belong to distinct transverse mode families and benefit from a form of soliton trapping that is new to microcavities and soliton lasers in general. The discovery of a new optical soliton can impact work in other areas of photonics, including nonlinear optics and spectroscopy

Coherent master equation for laser modelocking

Modelocked lasers constitute the fundamental source of optically-coherent ultrashort-pulsed radiation, with huge impact in science and technology. Their modeling largely rests on the master equation (ME) approach introduced in 1975 by Hermann A. Haus. However, that description fails when the medium dynamics is fast and, ultimately, when light-matter quantum coherence is relevant. Here we set a rigorous and general ME framework, the coherent ME (CME), that overcomes both limitations. The CME predicts strong deviations from Haus ME, which we substantiate through an amplitude-modulated semiconductor laser experiment. Accounting for coherent effects, like the Risken-Nummedal-Graham-Haken multimode instability, we envisage the usefulness of the CME for describing self-modelocking and spontaneous frequency comb formation in quantum-cascade and quantum-dot lasers. Furthermore, the CME paves the way for exploiting the rich phenomenology of coherent effects in laser design, which has been hampered so far by the lack of a coherent ME formalism

SIMILARITY REDUCTION AND PERTURBATION SOLUTION OF THE STIMULATED-RAMAN-SCATTERING EQUATIONS IN THE PRESENCE OF DISSIPATION

Similarity and other group-invariant solutions of stimulated Raman scattering (SRS) in the presence of dissipation are studied. The group-theoretical analysis reduces the SRS equations to ordinary differential equations which in the most interesting cases, i.e., in the case of the self-similar and soliton solutions, are studied perturbatively to derive the effect of dissipation

SELF-SIMILARITY IN TRANSIENT STIMULATED RAMAN-SCATTERING

Stimulated Raman scattering in the transient limit is an integrable system. In contrast, however, to the usual behavior in integrable systems, solitons are transient and the behavior of the system at long distances is dominated by self-similar solutions which may be found by symmetry reduction. It is shown for fairly general initial conditions precisely which self-similar solution the system tends toward at long distances, and the system evolution is studied numerically. It is argued that this behavior in which self-similar solutions dominate the long-distance evolution should often appear in nonlinear optical systems with memory. A possible experiment is proposed

EXACT-SOLUTIONS OF THE STIMULATED-RAMAN-SCATTERING EQUATIONS

Exact analytic solutions of the stimulated-Raman-scattering equations are obtained using group-theoretical methods. Special attention is devoted to a self-similar solution in terms of the fifth Painleve transcendent P(v). Its asymptotic behavior is established and shown to agree with experimental data and with earlier numerical calculations

Influence of the model for random birefringence on the differential group delay of periodically spun fibers

We consider the two Wai-Menyuk models of birefringence in periodically spun fibers, and we show that the differential group delay differs significantly for the two models when the spin period approaches or exceeds the fiber beat length. When the fiber correlation length is large, we explain this difference quantitatively, and we explain it qualitatively for any fiber correlation length

Analytical treatment of randomly birefringent periodically spun fibers

Spun fibers are increasingly used in telecommunication systems because their polarization-mode dispersion (PMD) is lower than that in unspun fibers. In this paper, we investigate the effects of a periodic spin on the PMD of fibers with randomly varying birefringence. Numerical simulations show that when the spin period is of the same order as or larger than the beat length, the mean differential group delay of a spun fiber depends on the model used for the random birefringence. We then carry out a general theoretical analysis using the second Wai-Menyuk model, which is the only model of fiber birefringence to date that is consistent with polarization optical time domain reflectometry data. Finally, we consider some particular regimes by means of a perturbative approach

Polarization mode dispersion of spun fibers with randomly varying birefringence

The polarization mode dispersion of spun fibers with randomly varying birefringence was investigated. The effects of periodic spinning on the polarization mode dispersion were determined by the values of the beat length, the birefringence correlation length and the spin period. The limits were determined in which the spin is effective in reducing the mean differential group delay

Design of a dual-channel modelocked fiber laser that avoids multi-pulsing

CLEO: Applications and Technology 2018, San Jose, California United States, 13-18 May 2018202209 bcvcAccepted ManuscriptRGCPublishe