Strong Coupling and Lasing in Solution Processed Semiconductor Microcavity Structures

Solution processed semiconductors have been widely studied for application in display, lighting, electronics and solar energy applications, combining opportunities for high throughput manufacturing and novel device formats.

In the photonics area, the large oscillator strengths typical of molecular systems combined with strong optical gain have attracted interest from the perspective of strong coupling physics and amplification and lasing in dielectric and metallic resonance structures. Professor Bradley and colleagues were the first to show strong coupling with molecular materials and have also published extensively on gain and lasing with these materials.

A new direction of travel in the group has been to use molecular conformation as a vector to control refractive index, thereby allowing the writing of patterns that can provide in-plane optical feedback and control normal-to-plane emission modes.

The project will look to incorporate the recent advances in materials and patterning methods within microcavity structures, with both vacuum and solution deposited DBR mirrors (in collaboration with Dr Paul Stavrinou). Combining in-plane patterning with normal-to-plane mirror structures will allow a reduction of mode volume and achievement of 3-D optical confinement. Others have used harsh processing methods to explore 3-D confinement, for example focused ion beam etching; our approach is much less aggressive and better suited to soft materials.

In relation to the conformational patterning we will also explore copolymers in which the conformation change switches the nature of the excited state from charge-transfer like to bound exciton. This novel approach gives another handle to control the nature of coupling processes and potentially to influence the routes for radiative decay.

In addition, electrically pumped structures will be fabricated for both strongly coupled and resonant cavity (with spatially directed, narrow linewidth emission) LEDs. Again, in-plane patterning will be explored to provide electrical, as well as optical, confinement. Some of these structures are expected to be of interest for so-called Li-Fi data communications, an area in which Professor Dominic O'Brien has a very active programme.

Other collaborators will include researchers in the Chinese Academy of Sciences Changchun Institute of Optics, Fine Mechanics and Physics, Nanjing Tech and the Sumitomo Chemical Company Ltd. This project falls within the EPSRC Photonic Materials & Metamaterials and Optoelectronic Devices & Circuits research areas. It also addresses the optical communications, plasmonics and optical devices and subsystems areas.

It therefore comes under the ICT and Physical Sciences Themes.