Fabrication and evaluation of GaN negative and bifocal microlenses

Methods of fabricating negative and bifocal microlens arrays have been demonstrated in this paper. The technique of photoresist molding using a sapphire positive lens template was used for the patterning of negative microlenses, while the bifocal microlens arrays were fabricated using a two-step etch process. In both cases, the lenses were etched using inductively coupled plasma. Microlenses with diameters as small as 10 µm have been demonstrated and were characterized using atomic force microscopy and confocal microscopy. The lens arrays were found to be smooth, uniform, and to have focal lengths consistent with their design and calculated values.