Fabrication of diffractive micro-optical lens for integration with optoelectronic devices by direct laser writing

The optical performances of fabricated diffractive micro-optical lens are determined by some fabrication process parameters. These key fabrication parameters are found to be the laser intensity, the speed of the movable stages, the distance from the top surface of the photoresist to the W objective lens, the starting laser intensity, the laser intensity variation step and the overlap of the adjacent patterns. In order to get the continuous-relief profile, a method was used to fabricate diffractive optical lens with any surface relief profile. Each zone of the diffractive micro-optical lens is divided into a different number of spiral lines according to the zone radius requirement. Control of each adjacent pattern thickness and linewidth is achieved by changing the fabrication parameters. A computer control program has been developed to optimize the key fabrication parameters for fabricating the high quality continuous-relief diffractive micro-optical lens matched with designed parameters. The fabricated lens has a focal length of 1.1 cm which is very close to the design value of 1.0 cm.