Investigation of aspherical microlens based on reflow technique

Abstract

In this paper, the key parameters including radius of curvature (ROC) and conic of aspherical microlens based on silicon material are calculated. Moreover, aspherical microlens was fabricated by utilizing UV lithography followed by the thermal reflow method. During preparation, the photoresist microlens was successfully transferred to the silicon substrate by precisely controlling the etching selection ratio. The anti-reflective film for air is prepared by an optical coater after chemical mechanical polishing. Finally, high-precision microlens was successfully fabricated and the key surface parameter of the radius of curvature, clear Aperture, surface profile deviation (SPD), and coupling efficiency were characterized by the white-light interferometer. The curvature tolerance can be controlled to ±3%, conic tolerance can be controlled to ±0.5, and surface profile deviation is below 25 nm. Furthermore, the surface reflectivity is below 0.3% between 1260 to 1620 nm. In addition, a coupling test system is developed by utilizing lasers, lenses, single-mode fibers (SMF) and other mechanical parts, and 78% of coupling efficiency is obtained by this system.