Professor Robert Taylor

Abstract:

Color modulation has been a topic of longstanding interest in science and engineering given its multiple applications in display technology, smart glass, security marks and active optical components.[1,2] Passive elements such as optical coatings employing a wide range of materials, multilayer configurations or structured films have been extensively used in optical systems to obtain a full range of colors and spectral windows in both reflective and transmissive devices.[1–6] Moreover, active materials with unique physical or chemical properties such as electrochromism,[7–9] piezochromism,[10] plasmonic effect,[11] photoluminescence[12,13] and volatile phase-change materials[14] have been exploited for color modulation purposes. The dynamic modulation of optical properties by such materials has given rise to remarkable resolution, low dimensionality and low energy operation of displays.[15] However, a combination of both, i.e. a device with high resolution featuring offline color retention while still allowing full-gamut modulation, had been elusive or had required external chemical agents[16] until recently, when an optoelectronic framework using nonvolatile nucleation dominated phase-change materials (PCMs) was proposed to fill this gap by employing Ge2Sb2Te5 (GST) as the active bistable component.[17]

Abstract:

The lasing behavior of solution-based colloidal quantum dots within an open microcavity is reported. The small size and wide tunability of the cavity provide single mode lasing over a wavelength range in excess of 25 nm. By extracting the lasing threshold and differential gain for the fundamental cavity mode over this spectral range, gain spectroscopy of the quantum dot solution is demonstrated. This new approach could help in the optimization of laser gain media and provides a way of constructing miniature laser arrays for on-chip integration.

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.