Tailoring weak-to-strong coupling of a plasmonic-photonic cavity

Control of light–matter interactions is important to a number of advances in quantum communication, information and sensing. Tailoring coupling strength relative to loss rates is central to exert control over the interactions. Recently we have demonstrated we could pin down a high dynamic range of system parameters in a coupled plasmonic-photonic cavity. Embedding the coupled cavity with an index-matching polymer matrix allows plasmonic and photonic modes to be largely overlapped and thus lifts up g to the same order of magnitude as dominant nonradiative loss rate, potentially leading to a strongly coupled cavity. After the coupled cavity is embedded by polydimethylsiloxane (PDMS). Plasmonic resonance of a gold nanorod (AuNR) is red-shifted due to change of local dielectric environment around the AuNR. Decreasing the aspect ratio blue-shifts its plasmon resonance back to our spectral window and then we observe a splitting spectral feature that signifies strong coupling. This demonstration provides an avenue for tailoring weak-to-strong coupling, which foreshadows the potential of entangling multiple plasmonic systems through photonic mode for protection against decoherence in quantum communication.