One-dimensional polarization-hybrid photonic crystal molecules

TL;DR

This paper introduces a new class of one-dimensional photonic molecules that utilize polarization as the primary dimension, enabling novel device functionalities in integrated photonics.

Contribution

The work demonstrates polarization-based photonic molecules in 1D waveguides, expanding beyond traditional geometries and enabling new topological and nonlinear photonic applications.

Findings

Successfully engineered Bragg gratings for polarization coupling.

Realized devices supporting Fano resonances and resonance-splitting.

Experimental validation in lithium niobate platforms.

Abstract

Photonic molecules, i.e. artificial structures composed of coherently coupled optical cavities, are paradigmatic systems for investigating fundamental phenomena across photonics, quantum optics and topological physics. In recent years, photonic integrated circuits have emerged as a particularly powerful platform for their realization, exploiting also additional synthetic dimensions afforded by the degrees of freedom of light. To date, however, photonic molecule implementations have relied almost entirely on geometries defined by spatial coupling and lattice symmetries rather than polarization. Here, we introduce a fundamentally new class of photonic molecules in which polarization is exploited as the primary dimension in the device response. By harnessing fundamental guided-mode couplings sustained by engineered Bragg gratings in photonic waveguides, we establish a new paradigm to access in 1D formats the coupled-resonator physics traditionally associated with higher-dimensional or free-space systems, demonstrating prototypical devices which can support Fano resonances or resonance-splitting for signals in the telecom band. Besides corroborating the theoretical predictions, experimental realizations in thin film lithium niobate open new prospects for the further exploration of novel reconfigurable topological, non-Hermitian and quantum photonic circuits, relying on the intrinsic nonlinear and electro-optic functionalities of this platform.