Jinfa Ho

A Nanowire-Based Plasmonic Quantum Dot Laser

Quantum dots enable strong carrier confinement and exhibit a delta-function like density of states, offering significant improvements to laser performance and high-temperature stability when used as a gain medium. However, quantum dot lasers have been limited to photonic cavities that are diffraction-limited and further miniaturization to meet the demands of nanophotonic-electronic integration applications is challenging based on existing designs. Here we introduce the first quantum dot-based plasmonic laser to reduce the cross-sectional area of nanowire quantum dot lasers below the cutoff limit of photonic modes while maintaining the length in the order of the lasing wavelength. Metal organic chemical vapor deposition grown GaAs-AlGaAs core-shell nanowires containing InGaAs quantum dot stacks are placed directly on a silver film, and lasing was observed from single nanowires originating from the InGaAs quantum dot emission into the low-loss higher order plasmonic mode. Lasing threshold pump fluences as low as ∼120 μJ/cm(2) was observed at 7 K, and lasing was observed up to 125 K. Temperature stability from the quantum dot gain, leading to a high characteristic temperature was demonstrated. These results indicate that high-performance, miniaturized quantum dot lasers can be realized with plasmonics.

Design of efficient surface plasmon polariton modulator using graphene

We numerically investigate graphene based surface plasmon polariton (SPP) waveguide modulators. We demonstrate that SPP waveguides with metal-air-metal structure can have a two times improvement in the figure of merit, defined by the ratio of extinction ratio to the voltage-off propagation loss, compared to indium-tin oxide based SPP electroabsorption modulators.

Demonstration of lasing oscillation in a plasmonic microring resonator containing quantum dots fabricated by transfer printing

We demonstrate room-temperature lasing oscillation in a plasmonic microring resonator containing InAs/GaAs self-assembled quantum dots. The resonator is composed of a GaAs microring placed on an atomically flat silver surface. Such a structure was fabricated by transfer printing, through which we can pick the dielectric microring and place it on the silver surface at will, hence maintaining a high-quality metal surface without introducing any complex fabrication process. Our result will be important in the development of nanoscale light sources in future densely integrated plasmonic circuits.

Lasing Oscillation in Multi-stacked InGaAs/GaAs Quantum Dots with a Single GaAs Nanowire Cavity

We report a demonstration of infrared lasing oscillation in multi-stacked In0.22Ga0.78As/GaAs quantum dots (QDs) with a single GaAs nanowire (NW) Fabry-Pèrot cavity. Micro photoluminescence spectra at 6 K of the NW cavity containing 50 stacked QDs exhibits lasing behavior at a peak wavelength of 864 nm with a threshold pump power density of 5.35 kW/cm2, which originates from the higher-order subband of the multi-stacked QDs. This is the first demonstration of lasing oscillation in a QD-NW cavity system.

Demonstration of a plasmonic laser using quantum dot gain medium

Summary form only given. Plasmonic nanolasers have made rapid progress in recent years, with room temperature lasing being achieved in the ultra-violet to visible wavelength range using ZnO, GaN and CdS semiconductors. However, the binding energy of excitons for semiconductors such as GaAs that emit in the technologically important near infrared region is insufficient to be stable at room temperature. Quantum dots act as traps for carriers and allow for efficient radiative recombination even at higher temperatures, and is a promising solution to this problem. Here, we demonstrate a plasmonic nanowire laser using quantum dots as the gain medium. We observed lasing up to 125 K, with a low threshold pump pulse fluence of 120 μJ/cm2 at 7 K. A decreased temperature dependence of the lasing threshold with a high characteristic temperature of ~309 K was achieved. This is promising for the future realization of room temperature plasmonic lasing in the near-infrared region.

Room-temperature lasing in GaAs nanowires embedding multi-stacked InGaAs/GaAs quantum dots

We report the demonstration of room-temperature lasing in a single GaAs nanowire embedding 50-stacked In_0.22Ga_0.78As/GaAs quantum dots at a lasing emission energy of 1.37 eV with a threshold pump pulse fluence of 138 μm/cm².