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Proceedings Paper

Angular emission profiles and coherence length measurements of highly efficient,low-voltage resonant-cavity light-emitting diodes operating around 650 nm
Author(s): Jonathan W. Gray; Rupert F. Oulton; Paul N. Stavrinou; Mark Whitehead; Gareth Parry; Geoff Duggan; Ricardo C. Coutinho; David R. Selviah
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Paper Abstract

We present results on Resonant Cavity Light Emitting Diodes (RCLEDs) emitting at 650 nm, which have high efficiencies and low voltages. In particular, we report on the angular properties of these devices, and highlight the observation that overall spectral linewidth increases with collection angle. This unusual property of RCLEDs is largely a consequence of employing a microcavity in the design. An additional contributing factor is the relative distribution of gain amongst the cavity modes (i.e. the level of tuning or detuning of the underlying emission, defined with respect to the longitudinal cavity mode). We have used measurement techniques which spectrally resolve angular radiation profiles to determine the (de)tuning directly. Moreover, these profiles demonstrate how the overall spectral linewidth increases with collection angle. To this end, we have developed a semi- empirical method for determining the overall linewidth as a function of emission numerical aperture (NA). A 4 nm detuned device has been investigated and linewidths have been found to increase from 3.1 nm to 13.6 nm over a range of NA approximately equals 0 to NA equals 1, an increase by a factor of around 4. Obviously, a variable linewidth also implies a variable coherence length with NA. Consequently, the coherence length was found to decrease from 30 micrometer to 9 micrometer over the same range. Independent coherence length measurements were carried out by direct interferometric measurements, and confirmed the expected trends.

Paper Details

Date Published: 14 May 2001
PDF: 9 pages
Proc. SPIE 4278, Light-Emitting Diodes: Research, Manufacturing, and Applications V, (14 May 2001); doi: 10.1117/12.426836
Show Author Affiliations
Jonathan W. Gray, Imperial College of Science, Technology and Medicine (United Kingdom)
Rupert F. Oulton, Imperial College of Science, Technology and Medicine (United Kingdom)
Paul N. Stavrinou, Imperial College of Science, Technology and Medicine (United Kingdom)
Mark Whitehead, Imperial College of Science, Technology and Medicine (United Kingdom)
Gareth Parry, Imperial College of Science, Technology and Medicine (United Kingdom)
Geoff Duggan, IQE plc (United Kingdom)
Ricardo C. Coutinho, Univ. College London (Brazil)
David R. Selviah, Univ. College London (United Kingdom)


Published in SPIE Proceedings Vol. 4278:
Light-Emitting Diodes: Research, Manufacturing, and Applications V
H. Walter Yao; E. Fred Schubert, Editor(s)

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