Fabrication of micro-lens array using surface acoustic wave

A technique to form an optical micro-lens array using surface acoustic wave (SAW) was investigated. The lens has no mechanical moving parts, such as gearing systems, and is composed of a simple structure. A viscoelastic transparent silicone gel film with the thickness of 20 μm was formed on a 128°-rotated Y-cut X-propagation LiNbO3 (LN) substrate between two interdigitated transducers (IDTs). The IDT electrodes consisted of 30 finger pairs with the aperture length of 9.1 mm and the periodic pitch of 200 μm were fabricated on the LN substrate. The IDTs was excited with a continuous sine wave with the amplitude of 0 to 15 Vpp at the resonance frequency (20 MHz) to generate the SAW. The leaky SAW propagated into the gel, and the acoustic radiation force acted to the surface of the gel film so that the surface profile of the gel could change and a micro-lens array could be fabricated on the gel. The lens height could be controlled by varying the voltage applied to the IDTs.