From fundamental physics to the clinic

Film-coupled nanocube cavities enhance the emission rate of embedded emitters more than a thousandfold while keeping the light bright and directional. This work identified the mechanisms behind the enhancement and established the platform that underlies everything the group does.

A single colloidal quantum dot in a nanogap cavity emits single photons at 1550 nm with a lifetime of a few picoseconds — a radiative rate enhanced more than 10,000-fold while keeping half its quantum efficiency — at room temperature and made entirely from solution-processed components.

Diamond is centrosymmetric and has no bulk second-order nonlinearity. Inside nanogap cavities, a diamond film only 12 nanometers thick becomes a bright source of second-harmonic light, enhanced ten-million-fold, while several nonlinear processes run in the same cavity at once — a nanoscale frequency converter in a material that should not be one.

Pyroelectric detectors are limited by how fast heat can move. By structuring the absorber as a metasurface only nanometers thick, we made a pyroelectric photodetector with sub-nanosecond response and built-in spectral selectivity — and have since pushed the same idea to gigahertz speeds.

Silver nanocube metasurfaces patterned into micrometer-scale pixels, with six resonances spanning the visible and near-infrared, can be combined into 9,261 colors — enough to reconstruct a photograph in absorption at 560 dpi. The bird above is 2 mm across and made entirely of nanoscale cavities.

An inkjet-printed immunoassay for the cardiac biomarker BNP, built directly inside nanogap cavities: antibodies on a nanometer-thin polymer brush over gold, capped with silver nanocubes. The cavity brightens the fluorescence more than a hundredfold, so inexpensive point-of-care readers can do the job of a laboratory scanner. With Ashutosh Chilkoti’s group; supported by an NIH R01.