Excimer laser machining of corner cube structures
K I Jolic; M K Ghantasala; E C Harvey; K I Jolic; IRIS—Industrial Research Institute Swinburne, Swinburne University of Technology, 533-545 Burwood Road, PO Box 218, Hawthorn, Melbourne 3122, Australia; M K Ghantasala; IRIS—Industrial Research Institute Swinburne, Swinburne University of Technology, 533-545 Burwood Road, PO Box 218, Hawthorn, Melbourne 3122, Australia; E C Harvey; IRIS—Industrial Research Institute Swinburne, Swinburne University of Technology, 533-545 Burwood Road, PO Box 218, Hawthorn, Melbourne 3122, Australia
Журнал:
Journal of Micromechanics and Microengineering
Дата:
2004-03-01
Аннотация:
Fabrication of corner cube structures using excimer laser projection has been a challenge for many years due to lack of a suitable machining strategy. This paper presents a new process methodology developed for this purpose, which consists of varying the projection aperture during machining by applying relative motion to two overlapping masks. The effective projection aperture is the two-dimensional area defined by the intersection of the apertures of each mask. During machining the volume of material removed per laser pulse is defined by the etch rate and the effective projection aperture. Using this approach, arrays of corner cubes up to 200 µm in size and 80 µm in depth were laser machined in polycarbonate. Their geometries and surface roughness were characterized using optical and confocal microscopy. The effects of fluence and number of laser shots on the angle and surface roughness of the corner cube facets have been studied. A relatively low cost replication technique has been established by making an electroformed nickel shim using the laser machined corner cube structures in a polycarbonate substrate. Retroreflectance properties of these structures evaluated using ray tracing simulations showed the importance of having near 90° facet angles and low facet roughness for achieving the highest intensity retroreflected signal.
708.8Кб