Demolding behavior of oxide glasses from molds was experimentally analyzed using a specially developed molding set up equipped with highly sensitive load cell and servomotor. The demolding point and the demolding force were apt to increase with the tensile force applied to the pressing axis, and also to the cooling rate. Especially the demolding force was strongly affected by the cooling rate when the demolding point was located near the glass transition temperature region. These results offer a useful direction for highly accurate glass-molding and glass-imprint processes. (C) 2013 Elsevier B.V. All rights reserved
Surface-relief gratings with high spatial frequencies were first fabricated using a direct imprinting process with a glassy carbon mold at the softening temperature of phosphate glass. A grating with maximum height of 730 nm and 500 nm period was formed on the glass surface by the pressing at the softening temperature of glass under constant pressure of 0.4 kN/cm(2). Phase retardation of 0.1 lambda was observed between TE-polarized and TM-polarized light at 600 nm wavelength.
For the first time, an antireflective structure (ARS) on a convex spherical glass surface was fabricated using an imprinting process. The inverted pattern of the ARS with a 250-nm period was fabricated on a SiC mold with a concave surface using electron beam (EB) direct writing and reactive ion etching. The sample surface height was adjusted to the EB focal position along the mold curvature during the step-and-repeat EB lithography. The imprinted lens with the ARS exhibited surface reflectance of 0.2% at a wavelength of 530 nm and a spherical error magnitude of less than 500 nm.
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