Soft lithography processing of fresnel lens for on-chip applications

Soft lithography and UV-NIL are important technologies for micro- and nano- structures replication [1]. It is possible to adapt surface structures preparation for many applications regarding e.g. opto-fluidic on-chip microscopy, wetting or reflection properties [2]. Light microscopy has been one of the most common tools in biological research, because of its high resolution and non-invasive nature of the light. Fresnel lens can be used in passive and active high quality polymer-based on-chip components for integrated photonics circuits [3]. In presented soft lithography technique the various materials were used for Fresnel lens replication: PDMS, h-PDMS and thiol-ene-epoxy resin. Mentioned polymers are characterized by high flexibility and transparency with minimal color. The silicon matrices replication process involves two main steps: anti-adhesive layer preparation and polymer deposition. The influence of structures geometry on the optical properties Fresnel lens has been investigated. The topography of obtained replicas was characterized using the atomic force microscopy (AFM) and scanning electron microscopy (SEM). The efficiency of light focus of the selected wavelength has been checked by intensity measurement using a standard optical microscope. As a result of replication 10□m diameter Fresnel lenses have been prepared.