posted on 2018-01-25, 00:00authored byClaire Deeb, Zhi Guo, Ankun Yang, Libai Huang, Teri W. Odom
Excited-state interactions
between nanoscale cavities and photoactive
molecules are critical in plasmonic nanolasing, although the underlying
details are less-resolved. This paper reports direct visualization
of the energy-transfer dynamics between two-dimensional arrays of
plasmonic gold bowtie nanocavities and dye molecules. Transient absorption
microscopy measurements of single bowties within the array surrounded
by gain molecules showed fast excited-state quenching (2.6 ±
1 ps) characteristic of individual nanocavities. Upon optical pumping
at powers above threshold, lasing action emerged depending on the
spacing of the array. By correlating ultrafast microscopy and far-field
light emission characteristics, we found that bowtie nanoparticles
acted as isolated cavities when the diffractive modes of the array
did not couple to the plasmonic gap mode. These results demonstrate
how ultrafast microscopy can provide insight into energy relaxation
pathways and, specifically, how nanocavities in arrays can show single-unit
nanolaser properties.