Robust Higher Harmonic Generation at Exceptional Points

Harmonic generation occurs in driven systems including electronics, acoustics, and photonics. In the frequency conversion process geometrical defects of the medium can alter the coupling between the fundamental frequency and the Second Harmonic and thus it plays a significant role in the phase, and amplitude of the converted frequency. This dependency to the geometrical properties creates a barrier in making precise devices such as upconverted coupled lasers and antenna remoting applications to name a few. Here, we propose a new method to robust Second Harmonic Generation using a class of topological singularities that occurs in non-Hermitian-driven systems which is totally different from Nonlinear Harmonic Generation using kai(2) materials. Specifically, we propose a complex spatiotemporal susceptibility modulation in a slab silicon waveguide. We show the frequency conversion process in such modulated system is governed by a non-Hermitian Hamiltonian. By choosing a equivalent amplitude for real and imaginary part of the modulation, fundamental mode becomes decouple from Second Harmonic which can create a Jordan From Hamiltonian operating at the exceptional point which is independent of geometrical imperfection.