Surface Plasmonic Nanodisk/Nanopan Lasers

We report the demonstration of subwavelength plasmonic lasers from a semiconductor nanodisk with a silver nanopan cavity. Full 3-D surface-plasmon-polariton (SPP) lasing was achieved because the nanodisk/nanopan structure enables excitation of high-quality SPP modes with subwavelength mode volumes. The optical properties of all possible resonant modes including SPP and optical modes excited in the nanodisk/nanopan were calculated and analyzed systematically using the finite-difference time-domain method. To fabricate the nanodisk/nanopan structure with an ultra-smooth silver surface, conformal deposition of silver was performed on the nanodisk. Rich SPP lasing actions were demonstrated through optical pumping of the fabricated structures. The observed SPP lasing modes were indentified unambiguously from measurements of the spectrum, mode image, and polarization state. These measurements compared well with the simulation results. In particular, the significant temperature-dependent threshold of the SPP lasers, which distinguishes SPP modes from conventional optical modes, was measured. This subwavelength SPP laser is a significant step toward the further miniaturization of a coherent light source in ultra-compact photonic integrated circuits.