Robust frequency conversion at the exceptional points

Frequency conversion occurs in driven systems including electronics, acoustics, and photonics. In the frequency conversion process geometrical properties of the medium mandate the coupling between the fundamental frequency and the converted frequency and thus it plays a significant role in the efficiency, phase, and amplitude of the converted frequency. This sensitivity 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 approach to robust frequency conversion using a class of topological singularities that occurs in non-Hermitian-driven systems. Specifically, we propose a spatiotemporal equitable real and imaginary refractive index modulation in a planar optical waveguide. We show the frequency conversion process in such modulated system is governed by a Hamiltonian like matrix that has a Jordan From matrix operating at the exceptional point which is independent of geometrical imperfection.