Introduction

The study of nonlinearity has been a central part of optics research since the invention of the laser, but a host of developments in materials and source technologies are currently allowing the study of nonlinear light-matter interactions in previously inaccessible regimes. Surprisingly, however, much current research in the field is fragmented, being carried out by distinct communities of specialised researchers in non-overlapping technical areas. An unfortunate consequence of this circumstance is that specialists in one area cannot adequately follow technical advances in other areas, and possibilities for important synergies are being lost.

This Focus Serial aims to address this problem by assembling a number of invited papers in key areas of the field to both survey the current state-of-the-art and identify new directions for future research. Papers will include both condensed reviews of areas that have achieved relative maturity as well as contributions that describe the latest progress in several exciting hot topics.

In selecting the invited papers for the Focus Serial, we have attempted to strike a balance between research efforts focused on fundamental physics and those carried out with more of an applications-potential in mind. The topics that will be covered are therefore very diverse, including nonlinear optical effects in novel nonlinear materials, novel localization phenomena, nonlinear propagation in engineered structures and waveguides, device applications, high field nonlinearities, and the development of new theoretical techniques.

Researchers in nonlinear optics can look back at contributions spanning two generations which have resulted in a tremendous number of advances influenced by both academic and commercial factors. It seems likely that future milestones and developments in the field will similarly need to build on multidisciplinary activities, and combine expertise from various technical sub-disciplines. It is therefore our hope that the invited papers published as part of this Focus Serial will provide a stimulating overview of this area and be of wide interest to researchers spanning all fields of optics and photonics.