Figure 1: Complex photonic lattice generation with vector-holographic interference in azo-polymer thin films.
From: Observation of exceptional points in reconfigurable non-Hermitian vector-field holographic lattices
(a) Schematic illustration of pump-probe configuration on an azo-polymer thin film. Two coherent incident fields E1 and E2 generate a holographic pump field EP that induces concurrent real and imaginary sub-gratings as results of photo-isomerization-induced molecular migration and reorientation. (b,c) Generated real ΔɛR and imaginary ΔɛI sub-grating profiles along the x axis for two representative combinations of E1 and E2 polarization states. The symbols correspond to the profiles measured by phase-shifting interferometry and the solid curves are theoretical (equations (1) and (2)). Case (b) satisfies precisely the condition for operation at the PT-symmetry breaking threshold, that is, Δɛ*(–x)=Δɛ(x) with identical modulation depths in ΔɛR and ΔɛI.
