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Title: Optical antenna enhanced spontaneous emission

Atoms and molecules are too small to act as efficient antennas for their own emission wavelengths. By providing an external optical antenna, the balance can be shifted; spontaneous emission could become faster than stimulated emission, which is handicapped by practically achievable pump intensities. In our experiments, InGaAsP nanorods emitting at ~200 THz optical frequency show a spontaneous emission intensity enhancement of 35 × corresponding to a spontaneous emission rate speedup ~115 ×, for antenna gap spacing, d = 40 nm. Classical antenna theory predicts ~2,500 × spontaneous emission speedup at d ~10 nm, proportional to 1/d2. Unfortunately, at d < 10 nm, antenna efficiency drops below 50%, owing to optical spreading resistance, exacerbated by the anomalous skin effect (electron surface collisions). Quantum dipole oscillations in the emitter excited state produce an optical ac equivalent circuit current, I(o) = qω|x(o)|/d, feeding the antenna-enhanced spontaneous emission, where q|x(o)| is the dipole matrix element. Despite the quantum-mechanical origin of the drive current, antenna theory makes no reference to the Purcell effect nor to local density of states models. Additionally, plasmonic effects are minor at 200 THz, producing only a small shift of antenna resonance frequency.
Authors:
 [1] ;  [1] ;  [2] ;  [1] ;  [1]
  1. Univ. of California, Berkeley, CA (United States). Dept. of Electrical Engineering and Computer Sciences
  2. Bell Labs, Alcatel-Lucent, Holmdel, NJ (United States)
Publication Date:
OSTI Identifier:
1235502
Grant/Contract Number:
AC02-05CH11231
Type:
Published Article
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 112; Journal Issue: 6; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Research Org:
Univ. of California, Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; 77 NANOSCIENCE AND NANOTECHNOLOGY; metal optics; nanophotonics; plasmonics; ultrafast devices