Partner und Internationale Organisationen
(Englisch)
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Trinity College, Dublin (IRL), Ecole Polytechnique Palaiseau-CNRS (F), IMEC, Gand (B), Tampere Institute of Technology (FIN), Glasgow University, Glasgow (UK), Siemens AG, Munich (D), MITEL Semiconductor AB, Stockholm (S)
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Abstract
(Englisch)
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A conceptually new approach for the control of spontaneous emission, that of photon confinement in optical microcavity structures, was pioneered in previous Esprit Project 'SMILES' where extraction efficiencies for planar microcavity light emitting diodes (MCLEDs) in excess of 20 % were demonstrated.
The present project had as objective to establish the ultimate limits of spontaneous light emission in terms of quantum efficiency, directionality, bandwidth, power, brightness and temperature stability, to expand the concepts demonstrated to industrially relevant wavelengths (670 nm, 850 nm, 1300 nm), and to explore the potential of photonic bandgap structures to move beyond the planar microcavity concept.
Some of the major results of the project are:
- full characterization of microcavity devices has been achieved by means of detailed spectrally and angularly resolved measurements of the emission spectra and power as a function of injection current, device geometry and layer composition
- high efficiency red MCLEDs with a peak quantum efficiency of 9.5 %, a maximum power output of 15 mW and transmission speeds up to 500 Mbit/s in a plastic optical fiber have been demonstrated
- high efficiency 1300 nm MCLEDs with a peak quantum efficiency of 9.4 % have been demonstrated, with 250 MHz bandwidth and coupling efficiencies over 11 % in glass multimode fibers
- a simulation tool to model the lateral extraction from a microcavity structure was developed and used to design a novel device in the 850/880 nm wavelength range, achieving efficiencies >20 % for emission into epoxy and an output power of 30 mW
- the introduction of high index contrast AlGaAs/AlOx mirrors has been investigated ; devices with extraction efficiencies over 25 % were demonstrated, pushing the state of the art in surface emitting devices to new levels
- deep etched structures with photonic crystal (PC) patterns were investigated ; a new approach, extracting the guided modes by PC photon sprinklers, appears very promising, with a 22 % extraction efficiency already reached in a non-optimized device.
Overall the project demonstrated the validity of the microcavity concepts for planar high efficiency emitters, with devices based on this work moving into industrial production.
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