Quantum Optoelectronics

Abstract:

The ability of individual nanocube patch antennas, consisting of a silver nanocube separated from an Ag sheet by a thin fluoropolymer spacer, to act as subwavelength sensing elements is demonstrated. An increase in relative humidity (RH) causes the spacer to expand, which alters the resonance of the plasmon cavity mode formed between the cube and the sheet. Using bottom-up fabrication techniques, sensitivities up to 0.57 nm/% RH are recorded, and a resolution of better than 1% RH achieved with a rapid response time, making this the most effective single nanoparticle plasmonic humidity sensor to date. Finite-difference time–domain simulations are conducted to understand the effects of particle geometry on the sensitivity. This platform could be utilized to detect a variety of gases with an appropriate choice of spacer material, and could be scaled up to create a large-area metamaterial sensor, or used as a subwavelength sensing element with the potential for integration into plasmonic circuitry.

Abstract:

We experimentally demonstrate fine tuning of the mode splitting of a photonic molecule based on a local perturbation of a photonic crystal waveguide and propose a scheme to achieve parity exchange of the ground state.

Abstract:

The lasing threshold of the fundamental cavity mode is measured as a function of wavelength and single mode lasing is demonstrated for colloidal CdSe/CdS quantum dots and nanoplaletes using tunable open microcavities.

Abstract:

Semiconducting single-walled carbon nanotubes are one-dimensional materials with great prospects for applications such as optoelectronic and quantum information devices. Yet, their optical performance is hindered by low fluorescent yield. Highly mobile excitons interacting with quenching sites are attributed to be one of the main non-radiative decay mechanisms that shortens the exciton lifetime. In this paper we report on time-integrated photoluminescence measurements on individual polymer wrapped semiconducting carbon nanotubes. An ultra narrow linewidth we observed demonstrates intrinsic exciton dynamics. Furthermore, we identify a state filling effect in individual carbon nanotubes at cryogenic temperatures as previously observed in quantum dots. We propose that each of the CNTs is segmented into a chain of zero-dimensional states confined by a varying local potential along the CNT, determined by local environmental factors such as the amount of polymer wrapping. Spectral diffusion is also observed, which is consistent with the tunneling of excitons between these confined states.