Micro-combs: a novel generation of optical sources

The quest towards the integration of ultra-fast, high-precision optical clocks is reflected in the large number of high-impact papers on the topic published in the last few years. This interest has been catalysed by the impact that high-precision optical frequency combs (OFCs) have had on metrology and spectroscopy in the last decade [1–5]. OFCs are often referred to as optical rulers: their spectra consist of a precise sequence of discrete and equally-spaced spectral lines that represent precise marks in frequency. Their importance was recognised worldwide with the 2005 Nobel Prize being awarded to T.W. Hänsch and J. Hall for their breakthrough in OFC science [5]. They demonstrated that a coherent OFC source with a large spectrum – covering at least one octave – can be stabilised with a self-referenced approach, where the frequency and the phase do not vary and are completely determined by the source physical parameters. These fully stabilised OFCs solved the challenge of directly measuring optical frequencies and are now exploited as the most accurate time references available, ready to replace the current standard for time. Very recent advancements in the fabrication technology of optical micro-cavities [6] are contributing to the development of OFC sources. These efforts may open up the way to realise ultra-fast and stable optical clocks and pulsed sources with extremely high repetition-rates, in the form of compact and integrated devices. Indeed, the fabrication of high-quality factor (high-Q) micro-resonators, capable of dramatically amplifying the optical field, can be considered a photonics breakthrough that has boosted not only the scientific investigation of OFC sources [7–13] but also of optical sensors and compact light modulators [6,14]

Bifurcation Structure of Dissipative Solitons

8 pages.-- Final full-text version of the paper available at: http://dx.doi.org/10.1016/j.physd.2006.12.008.In this paper we analyse in detail the structure of the phase space of a reversible dynamical system describing the stationary solutions of a model for a nonlinear optical cavity. We compare our results with the general picture described in [P.D. Woods and A.R. Champneys, Physica D {f 129} (1999) 147 ; P. Coullet, C. Riera and C. Tresser, Phys. Rev. Lett. {f 84} (2000) 3069] and find that the stable and unstable manifolds of homogeneous and pattern solutions present a much higher level of complexity than predicted, including the existence of additional localized solutions and fronts. This extra complexity arises due to homoclinic and heteroclinic intersections of the invariant manifolds of low-amplitude periodic solutions, and to the fact that these periodic solutions together with the high-amplitude ones constitute a one-parameter family generating a closed line on the symmetry plane.We acknowledge financial support from FunFACS and EPSRC (Grant No. GR/S28600/01)

Stable droplets and dark-ring cavity solitons in nonlinear optical devices

7 pages, 11 figures.Two kinds of cavity solitons, stable circular domain walls (droplets) and dark ring cavity solitons, are presented in models of vectorial Kerr resonators and degenerate optical parametric oscillators. These structures are universal in systems with two equivalent homogeneous states and are found for parameter values close to those of a modulational instability of a flat front. We show that stable droplets nucleate out of dark ring cavity solitons and that in some systems there are regimes in which they coexist.This work was supported by the EC Networks QSTRUCT (FMRXCT960077) and QUANTIM (IST-2000-26019), and by the European Science Foundation network PHASE. The work of D. Gomlia, P. Colet, and M. San Miguel was supported by MCyT, Spain, under Project PB97-0141-C02-02 and Project BFM2000-1108. The work of A. J. Scroggie and G.-L. Oppo was supported by the EPSRC under Grant M19727, Grant M31880, and Grant R04096. The work of G.-L. Oppo was supported in part by SGI.Peer reviewe

Sensitivity to noise in synchronously pumped optical parametric oscillators

We give numerical evidence that a singly resonant optical parametric oscillator is sensitive to noise in the single-pulse regime throughout the evolution of the fields. The noise induces pulse jitter that can be eliminated by use of either a small-amplitude injected field or an additional feedback cavity