Optical soliton formation controlled by angle twisting in photonic moiré lattices (2010.15294v1)

Abstract: Exploration of the impact of synthetic material landscapes featuring tunable geometrical properties on physical processes is a research direction that is currently of great interest because of the outstanding phenomena that are continually being uncovered. Twistronics and the properties of wave excitations in moir\'e lattices are salient examples. Moir\'e patterns bridge the gap between aperiodic structures and perfect crystals, thus opening the door to the exploration of effects accompanying the transition from commensurate to incommensurate phases. Moir\'e patterns have revealed profound effects in graphene-based systems1,2,3,4,5, they are used to manipulate ultracold atoms6,7 and to create gauge potentials8, and are observed in colloidal clusters9. Recently, it was shown that photonic moir\'e lattices enable observation of the two-dimensional localization-to-delocalization transition of light in purely linear systems10,11. Here, we employ moir\'e lattices optically induced in photorefractive nonlinear media12,13,14 to elucidate the formation of optical solitons under different geometrical conditions controlled by the twisting angle between the constitutive sublattices. We observe the formation of solitons in lattices that smoothly transition from fully periodic geometries to aperiodic ones, with threshold properties that are a pristine direct manifestation of flat-band physics11.

Optical Soliton Formation Controlled by Angle-Twisting in Photonic Moiré Lattices

The paper "Optical Soliton Formation Controlled by Angle-Twisting in Photonic Moiré Lattices" presents an intricate paper of optical solitons within moiré lattices, employing the twist angle between sublattices of different geometrical configurations. The primary focus of the research lies in examining the threshold conditions for soliton excitation and the distinct properties exhibited by solitons in commensurate and incommensurate lattice geometries.

Key Contributions and Findings

• Moiré Lattices: The paper utilizes moiré patterns generated by the interference of two twisted periodic square sublattices in a photorefractive nonlinear medium to facilitate the transition from commensurate (periodic) to incommensurate (aperiodic) lattice structures. These patterns exhibit flat-band physics, influencing light localization and diffusion properties.
• Soliton Formation: The paper explores two-dimensional localized soliton formations under varying twist angles and amplitudes between sublattices. It employs a nonlinear Schrödinger equation model, demonstrating the dependency of soliton characteristics and thresholds on the lattice's geometrical properties.
• Threshold Properties: The paper provides evidence for the existence or absence of soliton power thresholds in different lattice configurations. For incommensurate lattices (non-Pythagorean angles), linear modes are localized, eliminating the threshold for soliton creation. Contrastingly, commensurate lattices (Pythagorean angles) always impose a power threshold for soliton existence, irrespective of sublattice depths.

Implications

The findings suggest profound implications for photonic systems where lattice geometry manipulation can lead to controlled soliton dynamics integral to the development of advanced optical devices. The observation of threshold behaviors offers potential pathways to engineer systems with tunable nonlinear responses, practical for applications in optical communications and integrated photonics.

Theoretical Advancements

The paper deepens theoretical insights by linking lattice geometry, specifically the twist angle, with band structure alterations. This relationship dictates the localization properties of optical waves, providing a basis for manipulating light transport in artificial photonic structures.

Future Directions

Future studies could explore soliton formation in moiré patterns with varying crystallographic symmetries, such as honeycomb lattices, expanding the application domain of this research. Additionally, a deeper investigation into soliton dynamics under different nonlinear regimes, possibly with other photonic materials or experimental configurations, may yield further novel applications in optical and quantum computing systems.

In conclusion, the paper significantly contributes to understanding the intricate interplay between geometrical tuning and nonlinear optical phenomena, offering valuable insights into the development of advanced spatial-light modulators and photonic circuitry.