Experimental Observation of Interorbital Coupling.

Abstract

Interorbital coupling refers to the possibility of exciting orbital states by otherwise orthogonal noninteracting modes, a forbidden process in photonic lattices due to intrinsic propagation constant detuning. In this Letter, using a femtosecond (fs) laser writing technique, we experimentally demonstrate that fundamental and excited orbital states can couple each other when located at different spatial positions. We perform a full characterization of an asymmetric double-well-like potential and implement a scan method to effectively map the dynamics along the propagation coordinate. Our fundamental observation also constitutes a direct solution for a spatial mode converter device, which could be located in any position inside a photonic glass chip. By taking advantage of the phase structure of higher-order photonic modes and the effective negative coupling generated, we propose a trimer configuration as a phase beam splitter, which could be of great relevance for multiplexing and interference-based photonic concatenated operations.