Plasmonic–photonic interactions have stimulated significant interdisciplinary interest, leading to rapid innovations in solar design and biosensors. However, the development of an optically pumped plasmonic laser has failed to keep pace due to the difficulty of integrating a plasmonic gain material with a suitable pump source. In the present work, we develop a method for coating high quality factor toroidal optical cavities with gold nanorods, forming a photonic–plasmonic laser. By leveraging the two-photon upconversion capability of the nanorods, lasing at 581 nm with a 20 μW threshold is demonstrated.
Polymer coatings endow ultra-high-Q dielectric resonators with nonlinear properties, impacting numerous applications. However, minimal research combining microcavities with polymer-nanoparticle coatings to tune or tailor the optical properties of the system has been performed. One challenge is maintaining the high performance of the optical device while in the presence of nanoparticles. In the present work, a toroidal microcavity is coated with a polymethylmethacrylate thin film containing thiol-functionalized gold nanoparticles. The thiol-functionalization ensures that the nanoparticles are uniformly distributed throughout the film. The quality factors of these devices are above 5 × 106 and are in good agreement with the theoretical predictions.
Optical microcavities are high sensitivity transducers able to detect single nanoparticles and molecules. However, the specificity of detection is dependent on the availability of an appropriate targeting moiety with minimal cross-reactivity. In the present work, an alternative approach is shown. Namely, using biotin-functionalized toroidal microcavities, the dissociation constant of biotin to two different streptavidin complexes (free and polystyrene bead) is determined. Based on the difference in affinity and in mass transport, the two complexes are identified from a mixture. By leveraging information in the binding site, improved specificity can be achieved.
Optical microcavities provide a sensitive platform for biological and chemical sensing applications. Previous work has focused on optimizing the device performance by increasing the quality factor of the cavity. However, this approach overlooks the impact of the quality factor on the signal to noise ratio of the sensor. Here, our purpose is to show the existence of optimum parameters, both theoretically and experimentally, for achieving maximum signal to noise ratio in the microcavity sensors. Although toroidal cavities are used here, the present work is easily generalizable to any cavity geometry, enabling the performance optimization of a wide range of microcavity sensors.