Abstract

A blazed micro-Fresnel lens¹ has useful applications in optical communication and optical processing because of its diffraction-limited focusing characteristics, high diffraction efficiency, thin structure, light weight, and easy reproduction. Especially in a collimating lens of a laser diode,² a N.A. as high as 0.5 is required to obtain a collimated beam with a Gaussian intensity profile and high-power beam without truncating the light output emitted from the laser diode. The difficulties in fabricating such micro-Fresnel lenses with high N.A. by using electron-beam (EB) lithography are that curved lines cannot be drawn in a conventional EB drawing system and also the blazed profile with grating periods of the order of a few micrometers, deviate from the design profile by the influence of the backward scattering.³ A fabrication technique for such a high diffraction efficiency is proposed with a Fresnel lens with 0.5 N.A. that uses EB lithography⁴ applied to the laser diode source.

© 1988 Optical Society of America