Nanoscale Photonic Circuit Near Development (2009.5.25)
Professor Moon-Ho Jo (Department of Materials Science and Engineering) and his group, in a joint study with a Harvard University team, have materialized a new all-electrical surface plasmon polaritons (SPPs) detection technique based on the near-field coupling between guided plasmons and a nanowire field-effect transistor.
Photonic circuits can be much faster than their electronic counterparts, but it is difficult to miniaturize them below the optical wavelength scale. Nanoscale photonic circuits based on SPPs are a promising solution to this problem because they can localize light below the diffraction limit. However, there is a general trade-off between the localization of an SPP and the efficiency with which it can be detected with conventional far-field optics.
The new detectors developed by Professor Jo’s research group are both nanoscale and highly efficient (~0.1 electrons per plasmon), and a plasmonic gating effect can be used to amplify the signal even higher (up to 50 electrons per plasmon). The researchers used the technique to electrically detect the Plasmon emission from an individual colloidal quantum dot coupled to an SPP wavelength.
These results may open up several directions for further research. New on-chip optical sensing applications may be enabled. The achievement also marks a key step towards ‘dark’ optoplasmonic nanocircuits in which SPPs can be generated, manipulated and detected without involving far-field radiation.
The plasmon-detection sensitivity could be improved by using a nanoscale avalanche photodiode as the SPP detector, potentially enabling efficient electrical detection of individual plasmons. Electrical plasmon detectors could lead to new applications for optical sensing without collection optics, including the measurement of plasmon states in which coupling to the far-field is suppressed by symmetry. Finally, the strong near-field coupling between single-plasmon emitters and plasmonic nanocircuits could lead to completely new capabilities that are not available with conventional photonics, such as nonlinear switches, single-photon transistors and quantum non-demolition detectors.
The study results were published in the May 24 online edition of Nature Physics.
Professor Moon-Ho Jo
Department of Materials Science and Engineering