| AVS 58th Annual International Symposium and Exhibition | |
| Nanometer-scale Science and Technology Division | Monday Sessions |
| Session NS-MoA |
| Session: | Frontiers in Nanophotonics and Plasmonics |
| Presenter: | Kasey Russell, Harvard University |
| Authors: | E.L. Hu, Harvard University K.J. Russell, Harvard University T.-L. Liu, Harvard University S. Cui, Harvard University K. Yeung, Harvard University |
| Correspondent: | Click to Email |
Optical cavities can tightly confine light in the vicinity of optical emitters, enhancing the interaction of light and matter. The modes or optical states of the cavity can be precisely designed and engineered, and in recent years there has been remarkable progress in demonstrations of ‘cavity quantum electrodynamics (cQED)’ in solid state platforms. Such progress has been primarily for cavities fabricated in dielectric materials, with a steady improvement in cavity quality, with quality factors, Q, in excess of 104 – 106 realized for cavities with coupled emitters [1],[2]. These high Q-coupled emitter systems have demonstrated heralded single photon emission [3], ultra-low threshold lasing [4] and strong light-matter coupling [5],[6].
Metal-based optical cavities would have inherently lower Q’s (and greater loss) than dielectrics; however, metal cavities utilizing surface plasmon polaritons (SPPs) can have sufficiently small mode volume to produce a substantial Q/V, the quantity relevant for high Purcell factors, a measure of the light-matter interaction. This talk will focus on such plasmonic cavities, with optical modes formed within the gap of the two metal layers which defined the cavity [7]. Initial structures comprised silver (Ag) nanowires (NW), 70 nm in diameter and 1 - 3 µm in length, placed into close proximity to a Ag thin film substrate, with the NW axis parallel to the substrate surface. Optically active material was interposed between the nanowire and the Ag substrate: this comprised one to two monolayers of PbS colloidal quantum dots, clad on top and bottom by thin dielectric layers of varying composition and thickness. The fluorescence spectrum of PbS quantum dots within the gap was strongly modified by the cavity mode, with peak position in quantitative agreement with numerical calculations, and demonstrating Q values of ~ 60.
Such plasmonic cavities allow the easy incorporation of a variety of light-emitting active areas, and we have also explored the incorporation of various organic, dye-containing layers within the gap-mode plasmonic cavities. In addition these structures lend themselves to relatively simple modifications of geometry, allowing effective tuning of cavity modes, and also control of modes through the use of photonic crystal geometries, fabricated into metal.
The high Q/V possible for these cavities, and the range of organic and nanocrystalline emitters they can accommodate make these important building blocks for the exploration of light-matter interaction in the solid state.
References
[1] S. Noda, M. Fujita, and T. Asano, Nature Photonics 1 (2007) 449.
[2] B.-S. Song, S.-W. Jeon, and S. Noda, Optics Letter 36 (2011) 91.
[3] P. Michler., et al. Science 290 (2000) 2282.
[4] S. Strauf et al., Phys. Rev. Lett. 96 (2006) 127404.
[5] J. Reithmaier et al.. Nature 432( 2004) 197.
[6] K. Hennessy, A. Badolato, et al. Nature 445 (2007) 896.
[7] K. Russell and E. Hu, Appl. Phys. Lett.97 (2010) 163115.