Subwavelength Plasmonic Lasing from a Semiconductor Nanodisk with Silver Nanopan Cavity Soon-Hong Kwon, † Ju-Hyung Kang, ‡ Christian Seassal, § Sun-Kyung Kim, † Philippe Regreny, § Yong-Hee Lee, ‡ Charles M. Lieber,* ,|,⊥ and Hong-Gyu Park* ,† † Department of Physics, Korea University, Seoul 136-701, Korea, ‡ Department of Physics, KAIST, Daejeon 305-701, Korea, § Universite´ de Lyon, Institut des Nanotechnologies de Lyon INL-UMR 5270, CNRS, Ecole Centrale de Lyon, 36 Avenue Guy de Collongue, F-69134 Ecully Cedex, France, | Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, and ⊥ School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138 ABSTRACT We report the experimental demonstration of an optically pumped silver-nanopan plasmonic laser with a subwavelength mode volume of 0.56(λ/2n) 3 . The lasing mode is clearly identified as a whispering-gallery plasmonic mode confined at the bottom of the silver nanopan from measurements of the spectrum, mode image, and polarization state, as well as agreement with numerical simulations. In addition, the significant temperature-dependent lasing threshold of the plasmonic mode contrasts and distinguishes them from optical modes. Our demonstration and understanding of these subwavelength plasmonic lasers represent a significant step toward faster, smaller coherent light sources. KEYWORDS Surface plasmons, active plasmonics, nanolasers, subwavelength mode volumes I nvestigations of ultrasmall light sources have opened up the possibilities of demonstrating low-threshold lasers, 1 efficient single photon sources, 2 and ultrafast modulation sources 3 aswellasstudyingstronglight-matterinteractions. 4,5 Wavelength-scale lasers with mode volumes approaching a cubic half-wavelength in material, (λ/2n) 3 , have been dem- onstrated in dielectric cavities such as photonic crystals 6 and semiconductor nanowires. 7,8 In addition, lasers operating with optical modes excited in metal-clad cavities 1,9,10 showed mode volumes slightly smaller than (λ/2n) 3 . More recently, plasmonic cavities capable of reducing mode volumes below the diffraction limit of conventional optics have been proposed, 11-16 and reports have successfully demonstrated lasing in several structures. 17-19 However, most plasmonic cavities still show wavelength-scale or marginally subwave- length-scale mode volumes, 13,17,18 and thus the full three- dimensional (3D) confinement of surface plasmons in a subwavelength volume remains a challenge. Furthermore, plasmonic and optical modes have been simultaneously excited in such wavelength-scale cavities, 13,17 making it difficult to identify clearly observed resonant modes as plasmonic versus optical. To address these issues and demonstrate unambiguously subwavelength plasmonic la- sers, we have designed and characterized the optical proper- ties and temperature-dependent lasing thresholds of semi- conductor nanodisks with 3D confinement imposed by a silver-nanopan cavity. Our plasmonic laser structure consists of a 235 nm thick InP disk with four InAsP quantum wells (QWs) in the middle * Corresponding authors, cml@cmliris.harvard.edu and hgpark@korea.ac.kr. Received for review: 06/20/2010 Published on Web: 08/12/2010 FIGURE 1. Structure of the plasmonic nanopan cavity. (A) Schematic diagram of the nanodisk/nanopan structure. The top of the InP disk was bonded to a transparent glass substrate, and the bottom and sidewall of the disk were coated with silver. Four InAsP QWs were embedded in the middle of the disk. d is the diameter of the disk. (B) Schematic diagram of the removal of the silver nanopan. The blue, magenta, and gray colors correspond to the glass, InP disk, and silver, respectively. (C) SEM image of the InP disk on glass prior to silver deposition. (D) SEM image of the silver film separated from the disk. The white arrow indicates damage by the separation process. Scale bars in C and D are 400 nm. pubs.acs.org/NanoLett © 2010 American Chemical Society 3679 DOI: 10.1021/nl1021706 | Nano Lett. 2010, 10, 3679–3683