Laser Scanning Confocal Microscopy for Analyzing Optical Characteristics and Morphology of an Aspherical Microlens Array

Abstract

Aspherical microlenses and microlens arrays allow increasing efficiency of various optical devices. However, it is technologically challenging to produce these items. The problem arises from impossibility of making microlenses with an arbitrary profile in a characteristic size region of several tens of micrometers using traditional technologies like single-point diamond milling and thermal reflow. In this work, a precisely aligned combination of an aspherical microlens and a microlens array produced by the two-photon polymerization direct laser writing (2PP-DLW) is presented. This structure is designed and optimized using computer simulation methods. A unique photosensitive composition based on the methacrylate dye (derivative of benzylidene cyclopentanone) is used to produce the structures. A specific feature of the chosen composition is dependence of its mechanical and optical properties on the femtosecond radiation dose which could widely vary during the fabrication. The produced structures are investigated using laser scanning confocal microscopy, which allows reconstruction of the 3D image of the structures and detailed analysis of their morphological properties. The aspherical microlens aligned with the microlens array has a wide range of applications in production of complicated optical devices, optimized microobjective lenses for high-precision wave front sensing, and refractive X-ray lenses.