Ultrabright Bowtie Nanoaperture Antenna Probes Studied by Single Molecule Fluorescence

We report on a novel design for the fabrication of ultrabright bowtie nanoaperture antenna (BNA) probes to breach the intrinsic trade-off between power transmission and field confinement of circular nanoapertures as in near-field scanning optical microscopy (NSOM) or planar zero mode waveguides. The approach relies on the nanofabrication of BNAs at the apex of tapered optical fibers tuned to diameters close to their cutoff region, resulting in 103× total improvement in throughput over conventional NSOM probes of similar confinement area. By using individual fluorescence molecules as optical nanosensors, we show for the first time nanoimaging of single molecules using BNA probes with an optical confinement of 80 nm, measured the 3D near-field emanating from these nanostructures and determined a ∼6-fold enhancement on the single molecule signal. The broadband field enhancement, nanoscale confinement, and background free illumination provided by these nanostructures offer excellent perspectives as ultrabright optical nanosources for a full range of applications, including cellular nanoimaging, spectroscopy, and biosensing.