Fabrication of micro lens array using low cost, one step electrochemical discharge processing

Micro lens arrays (MLA) are the important optical component in a variety of optics related applications. The different micro-fabrication techniques were adopted for formation of MLAs in glass such as laser assisted wet etching, hot embossing. The factors such as mold requirement, slow processing, use of toxic chemicals, process complexity limit the usage of these techniques for MLA formation. Hence, in the present work, an efficient, one-step, flexible, scalable and cost-effective method based on the electro-chemical discharge processing (ECDP) is presented to form the MLAs in glass. ECD processing is used to form the concave MLAs in glass by the subtractive fabrication route. The ECD processing involves generation of EC discharges through the arrayed tool electrode in an electro-chemical cell where glass workpiece placed underneath of tool electrode. Material patterning by combined action of high temperature melting and evaporation and localized chemical etching. The fabrication of arrayed tool electrode is carried out using wire-tool electric discharge cutting. The effect of key parameters such as applied voltage, tool-workpiece distance, and alkaline electrolyte (KOH) concentration on the micro lens geometric features such as size, depth as well as the surface quality have been studied. An array of MLAs has been formed with range of size and depth of ~200-300 µm and 100 to 150 µm respectively with the fabrication time of 10 to 20 s. The Fabricated MLAs exhibit good dimensional control and higher sidewall surface quality. Moreover, the optical performance of the formed MLAs has been evaluated. This study demonstrates the capability of a low-cost, efficient ECD processing for scalable production of MLAs as a potential alternative to existing methods for the application in the field of 3D optical sensing/imaging, shaping of beams etc.