Exceptional point generated robust asymmetric high-order harmonics

Using exceptional point dynamics in time and space modulated lattices we propose a new mechanism for generation of asymmetric robust higher harmonics. Specifically we design a metallic-silicon system with a complex optical potential spatiotemporally modulated along the length of the waveguide for this robust higher harmonic generation. In our system the dynamical equations associated with modal field amplitudes are described by a Jordan form Hamiltonian. This ultimately will allow for a unidirectional higher frequency generation which always has a maximum value for a specific length of the waveguide irrespective of the geometrical imperfections in the design of the waveguide. Furthermore, the phase of the generated higher harmonic mode becomes independent of the coupling between the fundamental frequency and higher harmonic one. Unlike other proposed spatiotemporal modulated systems when the system has a Jordan form Hamiltonian, the fundamental mode remains reciprocal while the harmonic generation is non-reciprocal. Consequently, while the proposed device cannot be used as an optical isolator it can be used for many other devices such as laser cavities, interferometry, and holographic processes