Phan Ngoc MINH^1,*, Takahito ONO¹, Yoichi HAGA¹, Kazumi INOUE¹, Minoru SASAKI¹, Kazuhiro HANE¹ and Masayoshi ESASHI²

¹Graduate School of Engineering, Tohoku University Aza-Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan
²New Industry Creation Hatchery Center, Tohoku University Aza-Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan

(Received November 8, 2002; Accepted March 11, 2003)

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 170^°C for 1 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 SF₆ 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 μm, numerical aperture (NA) of 0.285 and a depth of focus of 16 μm.

Key words: Microlens, array, optical fiber, bundle, self-photolithography

^*Author to whom correspondence should be addressed. On leave from Institute of Materials Science, Vietnam National Center for Natural Science and Technology, HoangQuocViet Road, Caugiay, Hanoi, Vietnam. E-mail address: minh@mems.mech.tohoku.ac.jp