Spontaneous emission within wavelength-scale microstructures

The behaviour of an emitter can be drastically altered by placing it in a structure that is on a scale comparable to the wavelength of the emission. Both the spontaneous emission rate and the spatial distribution of the emitted radiation can be modified in this manner. This modification of the spontaneous emission of an emitter has major applications in devices such as light emitting diodes (LEDs). This thesis focuses on methods for determining the efficiency of emission of light from such devices and methods for increasing this efficiency. Conjugated polymers are frequently used as the emissive material in optical devices such as the LED. As such, we focus our attention on parameters appropriate for organic microcavity LED structures. We investigate how well different microcavity structures perform in controlling emission from sources within them. In particular, we consider the use of either metals or dielectric Bragg stack reflectors as the partially transmitting mirror in a cavity LED. Thin films of emissive polymers often have significant optical birefringence. We establish a suitable model for radiative emission from such birefringent films and successfully compare it with experimental data. The effects of the orientation of the dipole moment and birefringence upon the emission from films of polymer material are thereby calculated. We extend our study beyond the efficiency of emission from planar structures with an assessment of the effectiveness of using periodic corrugation to increase the efficiency of a photoluminescent device. Through measurements and analysis of the emission from these devices we determine that the Bragg scattering of light that is otherwise confined to the fully guided modes of a structure can result in an increase in efficiency. (author)SIGLEAvailable from British Library Document Supply Centre-DSC:DXN043925 / BLDSC - British Library Document Supply CentreGBUnited Kingdo