Integrated plasmonic circuitry on a vertical-cavity surface-emitting semiconductor laser platform

Integrated plasmonic sources and detectors are imperative in the practical development of plasmonic circuitry for bio- and chemical sensing, nanoscale optical information processing, as well as transducers for high-density optical data storage. Here we show that vertical-cavity surface-emitting lasers (VCSELs) can be employed as an on-chip, electrically pumped source or detector of plasmonic signals, when operated in forward or reverse bias, respectively. To this end, we experimentally demonstrate surface plasmon polariton excitation, waveguiding, frequency conversion and detection on a VCSEL-based plasmonic platform. The coupling efficiency of the VCSEL emission to waveguided surface plasmon polariton modes has been optimized using asymmetric plasmonic nanostructures. The plasmonic VCSEL platform validated here is a viable solution for practical realizations of plasmonic functionalities for various applications, such as those requiring sub-wavelength field confinement, refractive index sensitivity or optical near-field transduction with electrically driven sources, thus enabling the realization of on-chip optical communication and lab-on-a-chip devices

Persistent near-infrared photoconductivity of ZnO nanoparticles based on plasmonic hot charge carriers

We report on the coupling of ZnO nanoparticles with plasmonic gold nanoislands in a solution processed photodetector, which results in a clear enhancement in the optical absorption and the electrical responsivity of ZnO nanoparticles to cover the visible and the near-IR (NIR) spectral range, well beyond its intrinsic optical absorption. This enhancement, which arises from the coupling between ZnO nanoparticles and the plasmonically mediated hot electron generation in the Au plasmonic nanoislands, results in a significant plasmonically driven photoresponse in the NIR of 2.5×10-5 A/W. The recorded photocurrent exhibits a persistent behaviour, which is attributed to surface defect states in the ZnO nanoparticles. This study provides a route to solution processed, low-cost device fabrication schemes with important implications on low processing temperature optoelectronics technology to enhance the performance of photovoltaic devices over a wide solar spectrum. Additionally, this unusual behaviour paves the way towards harnessing plasmonic resonances to probe and examine the surface defects of metal oxide semiconductors

Synthesis of super bright indium phosphide colloidal quantum dots through thermal diffusion

Indium phosphide based quantum dots have emerged in recent years as alternatives to traditional heavy metal (cadmium, lead) based materials suitable for biomedical application due to their non-toxic nature. The major barrier to this application, is their low photoluminescent quantum yield in aqueous environments (typically < 5%). Here we present a synthetic method for InP/ZnS quantum dots, utilizing a controlled cooling step for equilibration of zinc sulfide across the core, resulting in a photoluminescent quantum yield as high as 85% in organic solvent and 57% in aqueous media. To the best of our knowledge, this is the highest reported for indium phosphide quantum dots. DFT calculations reveal the enhancement in quantum yield is achieved by redistribution of zinc sulfide across the indium phosphide core through thermal diffusion. By eliminating the need for a glove box and relying on Schlenk line techniques, we introduce a widely accessible method for quantum dots with a realistic potential for improved biomedical applications