Fabrication of large-scale infrared diffractive lens arrays on chalcogenide glass by means of step-and-repeat hot imprinting and non-isothermal glass molding

Abstract

In this study, a new cost-effective and high-precision process chain for the fabrication of large-scale diffractive lens arrays on chalcogenide glass is proposed. First, a positive diffractive lens array is fabricated on a PMMA master substrate by employing a step-and-repeat hot imprinting process. The direct hot imprinting can transfer the microstructures from a heated mold to the polymer substrate accurately. Repeating the hot imprinting process according to a predetermined path, the desired diffractive lens array is obtained. Unlike photolithography and electron-beam writing, which are expensive technologies with sophisticated process, the hot imprinting is an easier, cheaper and more eco-friendly method for fabricating diffractive features with continuous pro le. Afterwards a casting process is applied to create a PDMS mold with the negative features. The diffractive lens array with continuous pro le is successfully transferred from the master substrate to the PDMS elastomer, which is used as a mold for subsequent precision glass molding. Finally, the microstructures of PDMS mold are replicated to the chalcogenide glass by non-isothermal glass molding. In this process, the mold and workpiece are set at different temperatures. The PDMS mold at low temperature maintains enough rigidity, so as to press the features into the softened chalcogenide glass more easily, which is at relatively higher temperature, resulting in a positive high-delity diffractive lens array on the chalcogenide glass. Surface pro les and optical performance of the fabricated components are characterized quantitatively. Results showed that large-scale diffractive lens array with continuous pro le can be successfully fabricated on Chalcogenide glass by this proposed process chain with high quality and integrity.

Fabrication of anti-reflective structure array on chalcogenide glass by compression molding with polydimethylsiloxane mold

“…Such nonisothermal compression molding process has been adopted in previous chalcogenide glass molding research. 10 However, since the feature size of AR microstructure was small and deep, to obtain a satisfactory filling rate of the glass material during molding, especially in vertical direction, a high molding force and molding temperature were required. After both top and bottom heaters reached the given temperature, the system was kept in this stable situation for around 20 min to ensure that the glass preform was soft enough.…”

“…5 Up to now, various infrared optical elements were fabricated by compression molding, including infrared Shack-Hartmann sensor, 6 infrared compound eye microlens array imaging system, 7 infrared waveguides, 8 infrared photonic crystal surface, 9 and diffractive microlens arrays. 10 Considering the geometry of the fabricated structures in these research activities, previous studies were focused on surface features with low aspect ratio (ratio between height/depth and width of the feature), negative slope (feature with cone or pyramid shapes), and large/moderate size (around several microns to tens of microns). Some studies investigated embossing of microstrip arrays on chalcogenide glass surfaces with moderate aspect ratio (around 1:1.5).…”

“…Recently, research on nanoimprinting lithography using polydimethylsiloxane (PDMS), a relatively soft mold than conventional mold materials, has been proposed. 10,[27][28][29] PDMS mold is easy to obtain from master mold substrates with high replication accuracy, has low surface energy which is convenient to separate from workpieces, and is less sensitive to surface defects and contamination. 30 At room temperature, hardness of PDMS is about 43 HA.…”

“…31 At high temperature during molding, previous experiment has shown that PDMS is a good candidate in compression molding with sufficient rigidity and hardness around the glass transition temperature of chalcogenide glass. 10 However, this reported research only studied structures with low aspect ratio in surface structure replication process. In this reported research, the height of the feature was around 1.2 μm but the width of the feature varied from 15 to 130 μm, which indicated that the lowest aspect ratio was around 1:100 and highest aspect ratio was around 1:10.…”

Development of an Epoxy-Based Rapid Tool with Low Vulcanization Energy Consumption Channels for Liquid Silicone Rubber Injection Molding

“…Generally, the more uniform the mold temperature, the shorter the cross-linking time of LSR. According to practical experience in the fabrication of LSR parts using injection molding [ 6 , 7 ], one major drawback is that the uniformity of the vulcanization temperature of LSR can be improved when a cartridge heater [ 8 ] is incorporated in the conventional mold steel. Thus, improving the uniformity of the vulcanization temperature of LSR is an important research issue.…”