Topological photonics, a rapidly developing area of research, focuses on designing photonic lattices whose light behavior is inspired by the topological insulators. Although most of the research in this area focused on photonic systems with linear topological characteristics, recent work has begun to lay the foundations for non-linear topological photosnics.
Researchers from Universite Paris–Saclay CNRS recently reported the nonlinear reaction of a topological structure implementing a driven–dissipative Su-Schrieffer–Heeger model. This famous elementary topological framework describes particles hopping on a 1-D lattice. The team from Universite Paris–Saclay CNRS published their findings in Nature Physics. They found that topological lattices have the potential to exploit coherent driving, which can allow physicists stabilize new nonlinear phases.
"In 2017, our team demonstrated the first topological Laser using a 1D Lattice of Semiconductor Resonator very similar" Jacqueline Bloch and Sylvain Ravets, who were two of the researchers involved in the study, told Phys.org. "In our early work, however we were only using the linear topological characteristics of the system."
Ravets Bloch, their colleagues and others have recently completed a study that builds on their previous research. Their goal is to expand their investigation into non-linear topological Physics, which has been mainly explored within the context of conservative systems. The researchers used a platform that had significant optical nonlinearity and was subject to continuous drive, dissipation, and continuous drive in their experiments.
Ravets & Bloch said that they used nanotechnologies in fabricating a 1D lattice with coupled non-linear resonance resonators. Each resonator is composed of an optical cavity that contains an active medium (a semiconductor quantum well), which provides non-linearity. To implement the Su Schrieffer Heger topological model, the coupling between neighboring cavities has to be staggered.
Ravets and Bloch, along with their colleagues, focused laser beams on certain parts of their 1D lattice to trigger a nonlinear response. They then measured the transmitted intensity in relation to the input laser power.
Ravets & Bloch stated that a particularly important knob in their experiment was the relative phase between excitation beams. This provides a new level control that has not been considered before.
Researchers discovered some interesting and novel results from their experiments. The team discovered that new gap families were formed by the resonant exccitation. These gap solitons are not found in conventional systems such as coupled waveguides in propagative geometries.
These solitons are similar to topological edges states and induce topological edge states for excitations over the nonlinear steady. Ravets & Bloch called this "drive engineering" - the ability to control the system by engineering the laser excitation scheme.
Ravets and Bloch's recent study highlights the potential of coherent driving to stabilize nonlinear topological photonic system phases. The future could see the use of the experimental methods described in their paper to control topology for 1D photonic system and possibly extend them to 2D systems.
Ravets & Bloch said, "In our next research, we plan to expand these ideas to photonic Topological Insulators in 2D Lattices where the aim will be to demonstrate optically control topology of non-linear photonic lactices through the engineering of drive and dissipation."