Collective Mie Resonances for Directional On-Chip Nanolasers.

A highly efficient nanocavity formed by optically coupled nanostructures is achieved by optimization of the collective Mie resonances in a one-dimensional array of semiconductor nanoparticles. Analysis of quasi-normal multipole modes enables us to reveal the close relation between the collective Mie resonances and Van Hove singularities. On the basis of these concepts, we experimentally demonstrate a directional GaAs nanolaser at cryogenic temperatures with well-defined, in-plane emission, which, moreover, can be controlled by selective excitation. The lasing threshold is shown to be significantly reduced by optimizing the interparticle gap such that the optimal near-field confinement is achieved at a resonant wavelength corresponding to the highest gain of GaAs. We show that the lasing performance of this nanolaser is orders of magnitude better than a nanowire-based laser of the same dimensions. The present work provides design guidelines for high performance in-plane emission nanolasers, which may find applications in future photonic integrated circuits.

Highly efficient tunable and localized on-chip electrical plasmon source using protruded metal-insulator-metal structure.

A compact and highly efficient tunable and localized source of propagating surface plasmon-polaritons is proposed based on a protruded metal-insulator-metal (pMIM) structure. The protrusion along a segment of the pMIM forms a nanometer gap and allows a low voltage bias to generate a localized tunneling current. The tunneling current excited plasmons can be fully coupled to the metal-insulator-metal (MIM) waveguiding segment of the pMIM without leakage and propagate a long distance as the gap in the MIM waveguiding segment is much larger than the gap in the protruded segment of the pMIM. Eigenmode and numerical analyses show that by using MIM structures as a benchmark, the pMIM structure enhances the total amount of average power that is transferred from the tunneling current into the excitation of intrinsic eigenmodes of the MIM waveguiding segment. Depending on the magnitude of the applied voltage bias, the pMIM structure supports single, dual and multi modes for a typical Au-SiO2-Au design with a 500 nm-thick SiO2. Among all excited modes, the single mode operation allows highly efficient excitation of long travelling surface plasmon-polaritons (SPPs) of up to 30 µm. The electrical excitation of SPPs using pMIM structures opens up the possibility of integrating plasmon sources into nanoscale optoelectronic circuits to facilitate on-chip data communications.