posted on 2018-01-12, 18:04authored bySu-Hyun Gong, Sejeong Kim, Je-Hyung Kim, Jong-Hoi Cho, Yong-Hoon Cho
Although the study
of single quantum dot (QD) properties without
the background noise and dephasing processes caused by surrounding
carriers is a crucial issue, the spatial-selective excitation of a
single QD is still challenging, due to the diffraction nature of light.
Here, we demonstrate a deep subwavelength excitation of a single QD
using two-photon plasmonic nanofocusing. Self-aligned plasmonic nanofocusing
on a single QD was achieved using metal coated nanopyramid structures.
The highly enhanced local electric field generated by the plasmonic
nanofocusing gives rise to a large increase in the optical nonlinear
effect (i.e., two-photon excitation). As a result of the enhanced
field enhancement on the metal-pyramid hybrid structure, the two-photon
luminescence intensity was enhanced by a factor of 5000, and the selective
excitation of a single QD enabled us to observe InGaN QD emission
at near room temperature, due to the large suppression of the background
emission. Our approach opens promising perspectives for quantum optics
experiments with highly reduced background emissions.