Ping Bai

Plexcitonic strong coupling has ushered in an era of room‐temperature quantum electrodynamics at the nanoscale. Realizing its potential applications from single‐molecule spectroscopy to room‐temperature quantum technologies on an industrial level requires scalable and mass‐producible plasmonic cavities that provide ease of access and control for quantum emitters. Here, a strategy for multidimensional hotspot engineering is proposed via a rational selection of substrates, which facilitates elevation of a gold bowtie nanocavity hotspot to the top of the device and provides a field enhancement of ≈482 (a 1.6‐fold increase compared to a conventional bowtie‐on‐glass cavity at the bottom of the nanogap). The formation mechanism for these antenna modes is discussed from the perspective of charge carrier motion; and their advantages, particularly in view of their dominantly in‐plane polarized near‐fields, are further elaborated in a spatiotemporal study of plexcitonic strong coupling, which reveals ultrafast quantum dynamics and potential for applications related to 2D materials whose excitonic dipoles are typically oriented in‐plane. The conceptual discovery of this substrate‐enabled hotspot nanoengineering could readily be extended to tailor hotspots in other plasmonic platforms, and may inspire a plethora of novel research directions from plasmon‐enhanced spectroscopy and sensing to the design of quantum logic gates and quantum metasurfaces.

Dielectric nanostructures have demonstrated optical antenna effects due to Mie resonances. Previous work has exhibited enhancements in absorption, emission rates and directionality with practical limitations. In this paper, we present a Si mix antenna array to achieve a trifecta enhancement of ∼1200-fold with a Purcell factor of ∼47. The antenna design incorporates ∼10 nm gaps, within which fluorescent molecules strongly absorb the pump laser energy through a resonant mode. In the emission process, the antenna array increases the radiative decay rates of the fluorescence molecules via a Purcell effect and provides directional emission through a separate mode. This work could lead to novel CMOS-compatible platforms to enhance fluorescence for biological and chemical applications.

Development of new detection methodologies and amplification schemes is indispensable for plasmonic biosensors to improve the sensitivity for the detection of trace amounts of analytes. Herein, an ultrasensitive scheme for signal enhancement based on the concept of surface-plasmon-resonance-enhanced light scattering (SP-LS) was validated experimentally and theoretically. The SP-LS of gold nanoparticles’ (AuNPs) tags was employed in a sandwich assay for the detection of cardiac troponin I and provided up to 2 orders of magnitude improved sensitivity over conventional AuNPs-enhanced refractometric measurements and 3 orders of magnitude improvement over label-free SPR. Simulations were also performed to provide insights into the physical mechanisms.