Our research focuses on controlling materials at the 100-nanometer scale and investigating their size and shape-dependent properties. We have developed massively parallel, multi-scale nanopatterning tools to generate noble metal (plasmonic) structures that can manipulate visible light at the nanoscale. We are focusing on multi-scale, anisotropic, and 3D plasmonic materials for applications in imaging, sensing, and cancer therapeutics.
Coherent light sources at the nanoscale are important for exploring phenomena in small dimensions and for realizing optical devices with sizes that can beat the diffraction limit of light. Plasmonic lasers can have sub-wavelength sizes because they exploit surface plasmons, collective oscillations of electrons, which have strongly confined electromagnetic fields. We have found a way to manufacture laser devices that are the size of a virus particle and that can operate at room temperature. Our nanolasers are unique because: (1) the 3D bowtie structure provides a well-defined, electromagnetic hot spot in a nano-sized volume; and (2) its discrete structure has only minimal metal "losses". The extreme field compression—and ultra-small mode volume—within the bowtie gaps produced laser oscillations at the LSP gap mode of the 3D bowties. In addition, the 3D bowtie resonators emitted light at specific angles according to the lattice parameters because of the periodic arrangement of the resonators. Transient absorption measurements confirmed that the gain enhancement originated from the ultra-fast resonant energy transfer between the photoexcited dye molecules and gap plasmons.