We present a design of plasmonic cavities that consists of two sets of 1-D plasmonic crystal reflectors on a plasmonic trench waveguide. A 'reverse image mold' (RIM) technique was developed to pattern high-resolution silver trenches and to embed emitters at the cavity field maximum, and FDTD simulations were performed to analyze the frequency response of the fabricated devices. Distinct cavity modes were observed from the photoluminescence spectra of the organic dye embedded within these cavities. The cavity geometry facilitates tuning of the modes through a change in cavity dimensions. Both the design and the fabrication technique presented could be extended to making trench waveguide-based plasmonic devices and circuits. "Quantum nature of a strongly coupled single quantum dot-cavity system," Nature 445(7130), 896-899 (2007). 4. S. Kühn, U. Håkanson, L. Rogobete, and V. Sandoghdar, "Enhancement of single-molecule fluorescence using a gold nanoparticle as an optical nanoantenna," Phys. between surface plasmon-polaritons and organic molecules in subwavelength hole arrays," Phys. Rev. B 71(3), 035424 (2005). 9. P. Anger, P. Bharadwaj, and L. Novotny, "Enhancement and quenching of single-molecule fluorescence," Phys.

We observed a 32-fold increase in the spontaneous emission rate of InGaN/GaN quantum well ͑QW͒ at 440 nm by employing surface plasmons ͑SPs͒ probed by time-resolved photoluminescence spectroscopy. We explore this remarkable enhancement of the emission rates and intensities resulting from the efficient energy transfer from electron-hole pair recombination in the QW to electron vibrations of SPs at the metal-coated surface of the semiconductor heterostructure. This QW-SP coupling is expected to lead to a new class of super bright and high-speed light-emitting diodes ͑LEDs͒ that offer realistic alternatives to conventional fluorescent tubes. © 2005 American Institute of Physics. ͓DOI: 10.1063/1.2010602͔Currently, InGaN-GaN quantum well ͑QW͒ based lightemitting diodes ͑LEDs͒ have been developed and expected to eventually replace more traditional fluorescent tubes as illumination sources. 1,2 However, the emission efficacy of commercial white LEDs is still substantially lower than that of fluorescent tubes. 3 Recently, we have reported a method for enhancing the light emission efficiency from InGaN QWs by controlling the energy transfer between QW emitters and surface plasmons ͑SPs͒. 4 The idea of SP enhanced light emission was previously described 5-15 and efficient SPenhanced visible light emission has been demonstrated. 4 Moreover, the enhancement of an emission rate is also very important for the development of communication technology and optical computing. However, spontaneous emission rates of InGaN-GaN QWs are usually reduced by the carrier localization effect 16,17 and the quantum confinement Stark effect, 18,19 and very difficult to enhance. There are only a few reports on the enhancement of the emission rates by reducing the piezo-electric field 20 and making photonic crystal structure. 21 We believe that our developed SP coupling technique has the potential to enhance the spontaneous emission rate dramatically. 4 Since the density of states of SP mode is much larger, the QW-SP coupling rate should be very fast, and this new path of a recombination can increase the spontaneous emission rate. However, clear evidence for fast rate of QW-SP coupling has not so far been reported on the SP enhanced emission. We investigate the direct observation of SP coupled spontaneous emission rate by using the timeresolved photoluminescence ͑PL͒ measurements here. Moreover, we consider the mechanisms and dynamics of energy transfer and light extraction. This study should also be very useful for further optimization of the QW-SP coupling condition and for designing even more efficient device structures.InGaN-GaN QW wafers were grown on 0001 oriented sapphire substrates by metal-organic chemical vapor deposition ͑MOCVD͒. The grown structures consist of a GaN ͑4 m͒ buffer layer, an InGaN SQW ͑3 nm͒ followed by a GaN cap layer ͑10 nm͒. A 50 nm thick silver layer was then evaporated on top of the wafer surface. To perform timeresolved PL measurements, the frequency doubled output from a mode-locked Ti: Al 2 O 3 laser was used to...

Exciton-plasmon coupling in hybrids of a monolayer transition metal dichalcogenide and Ag nanoparticles is investigated in the weak and strong coupling regimes. In the weak coupling regime, both absorption enhancement and the Purcell effect collectively modify the photoluminescence properties of the semiconductor. In the strong coupling regime, electromagnetically induced transparency dips are displayed, evidencing coherent energy exchange between excitons and plasmons.

We obtained very bright light emission from CdSe quantum dots (QDs) by using the surface-plasmon (SP) coupling technique. 23-fold enhanced photoluminescence (PL) intensities and two-fold increased PL decay rates are observed when the QDs are located on evaporated gold films. This enhancement is not effective for CdSe cores with ZnS shells ͑ZnS / CdSe͒. The reason for this difference can be explained by using the SP dispersion diagram and by considering the SP coupling mechanism. We discuss the inherent merits and demerits of this technique to increase the emission efficiency. This technique will enable high-speed and efficient light emission for optically as well as electrically pumped light emitters.

This paper describes unique plasmonic characteristics of two dimensional (2D) crystalline sheets composed of homogeneous Ag nanoparticles (AgNPs) fabricated by the Langmuir-Schaefer method at an air-water interface. The localized surface plasmon resonance (LSPR) band of the Ag nanosheet was tuned by changing the interparticle distance of AgNPs via the length of the organic capping molecules. Red shift of the LSPR band of the AgNPs sheet followed an exponential law against the interparticle distance in a similar manner to the previous reports of metal nanodisc pairs. However, the shift was much larger and less dependent on the interparticle separation gap. This phenomenon is reasonably interpreted as the long-range interaction of LSPR in the 2D sheet ('delocalized' LSPR) confirmed by simulation using the finite difference time domain (FDTD) method. The FDTD simulation also revealed additional enhancement of local electric fields on the 2D sheet compared to those on the single or paired particles.

Diffusion coefficients ͑D͒ of various radicals created by the photoinduced hydrogen abstraction reactions from alcohols ͑ethanol and 2-propanol͒ are investigated by using the transient grating ͑TG͒ method. In all the reaction systems, D's of the transient radicals, as well as those of the parent molecules, can be measured simultaneously. The results clearly show slower diffusive motions of the radicals, at least of the radicals in the hydrogen abstraction reaction systems, compared with those of the parent molecules. D's of the parent molecules usually agree well with the calculated values based on the Spernol and Wirtz modification of the Stokes-Einstein ͑SE͒ relation. Although the measured D's of the radicals are closer to the values predicted by the simple SE equation, the agreements and the ratio of D between the radicals and its parent molecules depend on the molecular size. The ratio becomes closer to unity as the molecular size becomes large. Possible origins of this dependence are discussed.

Strain relaxation effect by nanotexturing InGaN/GaN multiple quantum wellEffects of growth interruption on the optical and the structural properties of InGaN/GaN quantum wells grown by metalorganic chemical vapor depositionThe optical properties of InGaN/GaN quantum wells, which were nanopatterned into cylindrical shapes with diameters of 2 m, 1 m, or 500 nm by chemically assisted ion beam etching, were investigated. Photoluminescence ͑PL͒ and time-resolved PL measurements suggest inhomogeneous relaxation of the lattice-mismatch induced strain in the InGaN layers. By comparing to a strain distribution simulation, we found that partial stain relaxation occurs at the free side wall, but strain remains in the middle of the pillar structures. The strain relaxation leads to an enhanced radiative recombination rate by a factor of 4-8. On the other hand, nonradiative recombination processes are not strongly affected, even by postgrowth etching. Those characteristics are clearly reflected in the doughnut-shape emission patterns observed by optical microscopy.

Abstract:We have experimentally verified that the emission of visible light from dye doped polymers can be enhanced with the use of surface plasmon coupling. By matching the plasmon frequency of a thin unpatterned silver film to the emission of a dye doped polymer deposited onto this metal surface, we have observed a eleven-fold enhancement of light emission. By patterning the silver layer, we estimate that the plasmon frequency can be tuned to match dye doped polymer emission frequencies and even larger emission enhancements as well as extraction efficiencies are expected.