Thin glass micro-dome structure based microlens fabricated by accurate thermal expansion of microcavities

Abstract

We present an efficient fabrication technique for a glass microdome structure (GMDS) based on the microthermal expansion principle, by inflating the microcavities confined between two thin glass slides. This technique allows controlling the height, diameter, and shape of the GMDS with a uniformity under 5%. The GMDS has a high potential for the application of the microlens and lens array. This inflated hollow, thin glass structure is stable at extreme environments such as in strong acid and high temperature conditions. More importantly, the hollow microdome can be filled with liquid substances to further extend its applications. To verify our method, various GMDSs were fabricated under different process conditions, at different temperatures (540 °C-600 °C), microcavity diameters (300 μm-600 μm), glass thicknesses (120 μm-240 μm), and microcavity etching depths (25 μm-70 μm). The optical features of "empty" and "filled" microcavities were investigated. An empty microcavity functioned as a reducing lens (0.61×-0.9×) (meniscus lens), while a filled microcavity functioned as a magnifying lens (1.31×-1.65×) (biconvex lens). In addition, both lenses worked in strong acid (sulfuric acid) and high temperature (over 300 °C) conditions in which other materials of lenses cannot be used.