1. Project Summary

We aim to break new ground in the science and technology of semiconductor light emitters. We focus on Gallium Nitride (GaN) based semiconductor microcavities (MCs) in which excitons and photons are strongly coupled to form exciton-polariton coupled modes, to fabricate coherent light emitters and parametric amplifiers (OPA), with major advantages over present technologies. The particular goals are:

Design, fabricate and test the first polariton laser - the demonstration of this new coherent light source would represent a major breakthrough with implications for both pure and applied science. We target both optically and electrically pumped devices at room temperature.

In very similar structures demonstrate ultrafast optical parametric amplifier (OPA) operation in compact micron size devices.

Polaritons have a number of novel properties including scattering stimulated by final state occupancy, very light mass and new dispersions. Many new fundamental and applied opportunities arise from these properties, and form the basis of our proposal. The high exciton binding energy and large oscillator strength of GaN provide the materials properties to achieve our goals. At the same time GaN MC technology is in its infancy and poses a number of challenges we are well placed to overcome.

Although GaN devices are efficient light emitters, they have high thresholds for inversion due to the high carrier densities of states. MCs in the strong coupling regime overcome this intrinsic limitation, with up to 4 orders of magnitude lower density of states. Stimulation is thus much easier to attain, with the promise of low thresholds for coherent emission, an order of magnitude lower than present blue or ultra-violet semiconductor lasers.

Our goals require advanced crystal growth, device fabrication, ultrafast and continuous wave spectroscopy, theory and device modelling, beyond the capabilities of any one laboratory. We have assembled a collaboration from leading laboratories around Europe, with the necessary expertise. Success will enable EU scientists, many of whom have pioneered the field, to achieve a real lead on the international scale. Our findings will also have applicability to other GaN-devices e.g. resonant cavity LEDs and VCSELs.

The project will begin on 1 September 2005 and will end 1 September 2008.

2. Project Objectives

Stimscat aims to realise two new forms of opto-electronic device, the polariton laser and polariton-based micron-size optical parametric amplifier, both operating at room temperature and above. We focus on Gallium Nitride (GaN) based semiconductor microcavities (MCs) in which excitons and photons are strongly coupled together to form exciton-polariton coupled modes, to fabricate new forms of coherent light emitters and compact optical parametric amplifiers, with major potential advantages over present-day technologies. These radically new device concepts have major potential advantages over present day technologies, in terms of low threshold, short wavelength coherent emission and low power operation.