Bach fabrication of microlens at the end of optical fiber using self-photolithgraphy and etching techniques

This paper describes a simple batch process for fabrication of microlens and microlens array at the end of an optical fiber or an optical fiber bundle using self-photolithography and etching techniques. A photoresist micro-cylinder was exactly formed at the core of the fiber end by exposing an UV light from the other end of the fiber and conventional development, rinse processes. A photoresist microlens was formed by thermal reflowing of the fiber at 170degreesC for I h. A measurement of transmissivity showed that the fabricated photoresist microlens is applicable for a wavelength that is longer than 450 nm. Alternatively, a glass microlens was fabricated at the core of the fiber by dry etching with an SF(6) gas using the photoresist microlens as a mask. The focusing of the lensed fiber was confirmed and simulation work showed that the lensed fiber could focus the light with a beam spot of 2 mum, numerical aperture (NA) of 0.285 and a depth of focus of 16 mum.