MUSHROOM MICROLENSES - OPTIMIZED MICROLENSES BY REFLOW OF MULTIPLE LAYERS OF PHOTORESIST

A novel type of photoresist microlenses is conceived. The characterist ic of these lenses is their mushroom shape: the lens dome is located a t a certain controllable distance from the substrate, and the curvatur e of the lens is larger than that of traditional truncated-sphere lens es. These mushroom microlenses are equilibrium-state, stable products of reflow that are obtained when starting from a multilayer photoresis t stack. Integration on light-emitting diodes results in enhanced outp ut efficiency and directivity: a vertical-to-surface emission enhancem ent of up to a factor of 8 has been achieved.