The project "Design of nonlinear silicon devices incorporating graphene and using the Parity-Time symmetry concept" (MIS 5047874) has as primary goal the analysis and design of novel integrated photonic devices for applications in the near infrared spectral window, with focus on the fiber-optic telecom band at 1550 nm. The host platform is silicon-on-insulator (SOI) with the inclusion of 2D materials and novel technologies, such as graphene. The theoretical foundation of this approach is the framework of Parity-Time (PT) symmetry, exhibited in structures with balanced gain and loss, and the broader class of Non-Herminitian (NH) devices which exhibit asymmetric losses. All these devices can be analyzed and designed with respect to the so-called Exceptional Points (EPs), which result in stark thresholds to the device response, e.g., operating-power thresholds that mark an abrupt switching between maximum and minimum transmission.

The project builds upon the group's longtime experience with nonlinear effects in nanophotonics and aims to uncover novel aspects of light-matter interaction in these PT-symmetric and NH devices. Analytical tools such as the coupled mode theory (CMT) and the nonlinear Schrödinger equations (NLSE), complemented with full-wave numerical tools, namely the finite element method (FEM) and the beam propagation method (BPM), will be used. The focus is on guided-wave photonic devices, such as directional couplers, photonic lattices, and waveguide arrays. These devices can exhibit loss-induced transparency and non-reciprocal (NR) response, which in turn can be exploited for developing isolators and circulators. The key element to access the NR regime is the structural asymmetry in the loss properties of the device together with the presence of an optical nonlinearity, enabled by operation above a certain power threshold. 

It is a 15-month project, launched in December 2019, involving two postdoctoral researchers and two faculty members. The project is co-financed by Greece and the European Union (European Social Fund- ESF) through the Operational Program “Human Resources Development, Education and Lifelong Learning 2014-2020”.