Production of aspheric microlens arrays by a combination of selective laser induced etching and laser polishing

We present a process with the potential for the production of aspherical micro lens arrays in glass with an individual lens diameter as low as 100 μm and a surface roughness of under λ/10 the visible spectrum. This development paves the way for innovative applications such as fluorescence microscopy in a microtiter plate with 500 μm or smaller diameter wells, while concurrently ensuring the mitigation of light pollution in adjacent wells. The proposed method facilitates the fabrication of micro lens arrays without the requirement for inter-element spacing, while ensuring shape consistency. In order to manufacture lenses with a diameter down to 100 μm, a two-step process is utilized. This process involves the implementation of selective laser induced etching (SLE) and is subsequently followed by laser polishing. In the context of the SLE process, the focus is on two distinct spot sizes, with the objective of ascertaining their potential for achieving optimal resolution and process times. In the subsequent stage of the process, the residual surface roughness, which is measured in a range of a few hundred nanometers, is subjected to a polishing procedure utilizing pulsed CO2 laser radiation with a wavelength of 9.4 μm. The absorption of the laser in the outer layers of the glass enables the production of aspherical lenses and other free form shapes. This work marks another step towards the production of custom shape micro lens arrays for illumination applications.