The Pure-Quartic Soliton Laser

Temporal optical solitons are a class of optical pulses arising from the interplay between anomalous dispersion and self-phase modulation (SPM). These pulses can propagate across long distances while maintaining their spectral and temporal shapes, with applications in telecommunications, lasers and optical memories [1-4]. Historically, only solitons balancing SPM and negative second-order dispersion have been studied and used in photonic application. In 2016, solitons arising from fourth-order dispersion and SPM were observed for the first time in silicon photonic crystals [5]. Subsequent theoretical and numerical studies showed that these pulses, pure-quartic solitons (PQSs), have the potential to overcome the intrinsically low-energy limit of conventional solitons [6,7]. This work also suggested that modifying the linear properties can significantly enhance the nonlinear properties of these systems [7]. In this project we built and demonstrated the first laser system operating in PQS regime and we experimentally confirm their physical properties [8]. We then extended this initial work and demonstrated that solitons can arise with any negative even order of dispersion [9]. Finally, by advanced tailoring of the linear dispersion we generated a novel a family of high complex pulses consisting of several, equally spaced spectral components that are nonlinearly bound and propagate as a single unit [10]. The associated theory that we developed shows that this leads to enhancement of the effective nonlinear parameter that increases with the number of spectral components. Therefore, this novel technique allows for the generation of ultrashort pulses with low pump energy.