Tunable coupling of chip-scale photonic molecules via thermal actuation

Photonic molecules (PMs) are of great interest for, e.g., optical filters/sensors or topological and exceptional-point photonics. A key requirement for their versatile application is the tunability of the PM's coupling strength. This important feature is realized in the here introduced widely and precisely tunable PM on an all-polymeric chip-scale platform. The PM consists of two disk-shaped whispering gallery mode cavities on a liquid crystal elastomer (LCE) substrate. The coupling strength of the PM is controlled via the contraction of the LCE under an external stimulus like local heating. We reveal the reversible (de)coupling via the analysis of laser supermodes emitted from a dye-doped PM. The tunability of the PM's coupling strength is apparent from the pronounced mode splittings observed in single-fiber transmission spectra and is consistent with coupled-mode theory. Finally, we demonstrate the applicability of the PM as an add-drop filter with a highly controllable intensity transfer. In this light, our PM on an LCE substrate represents a novel platform system for tunably coupled photonic resonators.

Automated summary

Photonic molecules with tunable coupling strength are demonstrated on a liquid crystal elastomer substrate, allowing for various applications and highly controllable intensity transfer. The tunability of the coupling strength is evident from observed mode splittings in single-fiber transmission spectra and is consistent with coupled-mode theory. Additionally, the photonic molecules can be utilized as add-drop filters with a highly controllable intensity transfer.