Modeling and analysis for the position and posture errors of laser focal spot in large-scale fabrication via two photon polymerization

Abstract

The position and posture errors of laser focal spot significantly affect the fabrication quality and functionality of microstructures in two photon polymerization, especially over a large area. These errors can be greatly reduced by using ultra-precision positioning device, such as piezoelectric stage and scanning galvanometer. However, the position and posture errors cannot be neglected in large-scale fabrication using large stroke linear stages which are necessary tools in most instances. In the present work, the relationship between the geometric errors of large stroke positioning platform and the position and posture of laser focal spot were revealed and modeled by homogeneous transformation matrix. Key errors affecting on the position and posture of focal spot were found out by sensitivity analysis and compensated during the construction of machine tool. Proof-of-concept experiments were performed in a millimeter-level (1 mm × 1 mm) fabrication of microfluidic whose surface was measured by an optical profiler. The measuring results showed that arithmetical mean height (Sa) and root mean square height (Sq) of the measured surface were less than 100 nm and maximum height (Sz) of the measured surface was less than 500 nm. The compensated machine tool demonstrated a high precise performance within a large continuous area. This work was expected to provide references for the rational layout of optical components in optical system or error compensation in laser process equipment over a large area.