Strong Coupling and Lasing in Solution Processed Semiconductor Microcavity Structures

Lead Research Organisation: University of Oxford
Department Name: Oxford Physics


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.


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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509711/1 01/10/2016 30/09/2021
1734341 Studentship EP/N509711/1 01/10/2016 31/03/2020 Florian Le Roux
Description Through the research funded on this grant, Prof. Donal Bradley and I main interest was to understand how changing the conformation (i.e. the geometry) of a light-emitting polymer would impact its interaction with light. In order to probe this experimentally, we sandwiched the polymer layer between two mirrors, effectively trapping a light mode in between them and therefore making it interact with the polymer. We observed that the resulting interaction yielded novel properties for the wavelength of the light emitted from the whole structure (colour and colour purity) and that this could for example be applied to high purity organic LEDs in the future or more fundamental research.

In a subsequent work, the alignment of polymer chains inside microcavity structures allowed to reach unprecendented strength for the light-matter interaction and polarization-dependent applications.
Exploitation Route What we learned can be used at the nanoscale and for more efficient lasing applications.
Sectors Electronics,Manufacturing, including Industrial Biotechology