Dissipatively coupled waveguide networks for coherent diffusive photonics

Abstract

A photonic circuit is generally described as a structure in which light propagates by unitary exchange and transfers reversibly between channels. In contrast, the term ‘diffusive’ is more akin to a chaotic propagation in scattering media, where light is driven out of coherence towards a thermal mixture. Based on the dynamics of open quantum systems, the combination of these two opposites can result in novel techniques for coherent light control. The crucial feature of these photonic structures is dissipative coupling between modes, via an interaction with a common reservoir. Here, we demonstrate experimentally that such systems can perform optical equalisation to smooth multimode light, or act as a distributor, guiding it into selected channels. Quantum thermodynamically, these systems can act as catalytic coherent reservoirs by performing perfect non-Landauer erasure. For lattice structures, localised stationary states can be supported in the continuum, similar to compacton-like states in conventional flat-band lattices.

Floquet topological transition by unpolarized light

“…Traditional bulk-boundary correspondence was extended to Floquet topological systems taking into account the periodicity of the Floquet spectrum 20,21 . Experimental verification of such states has already been achieved using both time and angle resolved photoemission spectroscopy(PES) 22,23 and also in photonic systems 24,25 .…”

Coherent Diffusive Photon Gun for Generating Nonclassical States

“…Let us take coupling parameters as used in the CDP circuits in Ref. [14], g a ≈ 200m −1 . The decay rate of the c 0 mode Fig.…”

“…These new experimental advances gave rise to recently introduced concept of "coherent diffusive photonics" (CDP): light-processing in a specifically designed system of single-mode waveguides coupled by common loss reservoirs, as realized in practice in [14]. Even with linear glass, dissipative coupling enables, for example, light equalization in a waveguide chain: any input state tends to a completely symmetrized state over all the (3) nonlinearity and nonlinear coherent loss (NCL).…”

“…In contrast to the common unitary coupling schemes, CDP schemes are quite robust with respect to variations in the coupling length and strength. Further, CDP allows one to realize an optical router directing light in different arms of the structure by selective excitation of the central control nodes, and CDP can even allow light to be localized in a perfect lattice of dissipatively coupled modes [14].…”

Flat bands in lattices with non-Hermitian coupling

“…Thus, the effective gain (loss) is sensitive to the relative phase between neighboring waveguides. Non-Hermitian couplings can also be realized by periodically modulating the on-site gain/loss 28 , or as an effective description of larger waveguide networks 46,47 .…”