All-Dielectric Silicon Nanogap Antennas To Enhance the Fluorescence of Single Molecules

Plasmonic optical antennas enhance light-matter interactions at the nanoscale, yet this phenomenon is currently limited by the ohmic losses in the metal. Silicon-based nanophotonics is an appealing alternative approach to implement cost-effective CMOS-compatible molecular sensors. So far, the fluorescence experiments with silicon-based antennas did not reach the single molecule level to demonstrate clearly the phenomenon and explore its physical origins. We bridge this gap in a recent Nano Letters publication “All-Dielectric Silicon Nanogap Antennas to Enhance the Fluorescence of Single Molecules”.

Significance:

- This report provides the first experimental evidence that silicon nanoantennas achieve single molecule fluorescence enhancements above 200-fold together with a detection volume of 140 e-21 L that allows the detection of individual molecules at micromolar concentration using dielectric materials only.

- The fluorescence enhancement results from a combination of excitation intensity and radiative rate enhancement within the nanogap region. These effects are quantified in excellent agreement with numerical simulations.

- These results open new routes to implement high sensitivity molecular (bio)sensors with on-chip photonic devices that are CMOS compatible.