Beam divergence measurements of InGaN/GaN micro-array light-emitting diodes using confocal microscopy

C. Griffin a) , E. Gu, H.W. Choi, C. W. Jeon, J.M. Girkin, and M.D. Dawson Institute of Photonics, University of Strathclyde, 106 Rottenrow, Glasgow G4 0NW, United Kingdom G. McConnell, Centre for Biophotonics, University of Strathclyde 27 Taylor Street, Glasgow G4 0NR, United Kingdom Abstract The recent development of high-density, two-dimensional arrays of micrometer-sized InGaN/GaN light-emitting diodes (micro-LEDs) with potential applications from scientific instrumentation to micro-displays has created an urgent need for controlled manipulation of the light output from these devices. With directed light output these devices can be used in situations where collimated beams or light focussed onto several thousand matrix points is desired. In order to do this effectively, the emission characteristics of the devices must be fully understood and characterised. Here we utilise confocal microscopy to directly determine the emission characteristics and angular beam divergences from the individual micro-LED elements. The technique is applied to both top (into air) and bottom (through substrate) emission in arrays of green (540nm), blue (470nm), and UV (370nm) micro-LED devices, at distances of up to 50μm from the emission plane. The results are consistent with simple optical modelling of the expected beam profiles. a) Author to whom correspondence should be addressed; electronic mail: [email protected]