Asymmetric Bragg mirrors for the reduction of emission wavelength dependence on the viewing angle in organic microcavity light emitting diodes

Organic microcavity light emitting diodes typically exhibit a blue shift of the emitting wavelength with increasing viewing angle. While the wavelength shift can be reduced with the appropriate choice of organic materials and metal mirrors, for further reduction of the emission wavelength shift it is necessary to consider a mirror whose phase shift can partly compensate the effect of the change of optical path within the cavity. In this work, we used a genetic algorithm (GA) to design an asymmetric Bragg mirror in order to minimize the emission wavelength shift with viewing angle. Based on simulation results, the use of asymmetric Bragg mirrors represents a promising way to reduce the emission wavelength shift. Detailed comparison between GA optimized and conventional Bragg mirrors in terms of resonant wavelength dependence on the viewing angle, spectral narrowing, and brightness enhancement is given. (C) 2004 Elsevier B.V. All rights reserved.

The development of self-recognition in mirrors and live videos

By 24-months of age most children show mirror self-recognition. When surreptitiously marked on their forehead and then presented with a mirror, they explore their own head for the unexpected mark. Here we demonstrate that self-recognition in mirrors does not generalize to other visual feedback. We tested 80 children on mirror and live video versions of the task. Whereas 90% of 24-month olds passed the mirror version, only 35% passed the video version. Seventy percent of 30-month olds showed video selfrecognition and only by age 36-months did the pass rate on the video version reach 90%. It remains to be y 24-months of age most children show mirror self-recognition. When surreptitiously marked on their forehead and then presented with a mirror, they explore their own head for the unexpected mark. Here we demonstrate that self-recognition in mirrors does not generalize to other visual feedback. We tested 80 children on mirror and live video versions of the task. Whereas 90% of 24-month olds passed the mirror version, only 35% passed the video version. Seventy percent of 30-month olds showed video selfrecognition and only by age 36-months did the pass rate on the video version reach 90%. It remains to be