|Title:||Spontaneous Emission Rate is Enhanced by an Optical Antenna|
|Group/Series/Folder:||Record Group 8.15 - Institute for Advanced Study|
Series 3 - Audio-visual Materials
|Notes:||Croucher Advanced Study Institute on New Materials and New Concepts for Controlling Light and Waves. Talk no.13|
Host: HKUST Institute for Advanced Study.
Sponsor: The Croucher Foundation.
Abstract: For over 50 years, stimulated emission has been stronger and far more important than spontaneous emission. Indeed spontaneous emission has been looked down upon, as a weak effect. As an accident of Nature, atoms and quantum dots emit radiation wavelengths that are much larger than the atoms themselves. Molecular sized structures are simply too small to act as efficient antennas. Nonetheless, a molecule is forced to be its own antenna. Thus we live in a world in which spontaneous emission is relatively slow. Therefore the key requirement for speeding up spontaneous emission is to provide the radiating molecule with a proper optical antenna. Size makes a huge difference in antennas. In practice the maximum spontaneous emission speedup requires the molecule to be very close to the metal surfaces. This leads to optical current crowding, which at lower frequencies is often called “spreading resistance”. In addition, the optical resistivity, that is related to the imaginary part of the dielectric constant, ε”, can become more lossy. As molecules approach the surface the skin depth becomes thinner, leading to more frequent surface collisions, (called the “anomalous skin effect”), further adding to Ohmic loss. Thus both “spreading resistance” and the “anomalous skin effect” become more severe as molecules approach the nearby antenna surfaces. There will eventually come a point of diminishing returns from a nanoscale optical antenna. Nonetheless, it appears that a 10[superscript 4] x spontaneous emission rate enhancement should still be possible.
Duration: 39 min.
|Appears in Series:||8.15:3 - Audio-visual Materials|
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