Fabrication of sub-wavelength periodic structures upon high-refractive-index glasses by precision glass molding

Mori, Toshiharu; Hasegawa, K.; Hatano, Takuji; Kasa, Haruya; Kintaka, Kenji; Nishii, Junji

doi:10.1117/12.758716

Cited by 4 publications

(1 citation statement)

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“…Previous research has documented the use of GC molds for precision glass molding of microstructures including gratings [8,[12][13], microlens arrays [14] and microfluidic channels [15][16][17][18]. The microstructuring of the GC mold is in the center of focus and was demonstrated with focused ion beam etching [15,18], dicing [16][17], laser machining [17] or O 2 reactive ion etching (RIE) [8,[12][13][14]. Youn et al developed a fabrication process with O 2 /SF 6 RIE offering high quality GC molds with surface roughness Ra below 20nm [19], which is a necessary prerequisite for optics applications.…”

Section: Introductionmentioning

confidence: 99%

Multilevel micro-structuring of glassy carbon molds for precision glass molding

et al. 2015

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Replication techniques for diffractive optical elements (DOEs) in soft materials such as plastic injection molding are state of the art. For precision glass molding in glasses with high transition temperatures, molds with extreme thermal resistivity, low chemical reactivity and high mechanical strength are needed. Glassy Carbon can be operated up to 2000°C making it possible to mold almost all glasses including Fused Silica with a transition temperatures above 1060°C. For the structuring of Glassy Carbon wafers photolithography and a RIE process is used. We have developed a process using Si as a hard mask material. If the flow rates of the etching gases O2 and SF6 are chosen properly, high selectivity of GC to Si 19:1 can be achieved, which provides excellent conditions to realize high resolution elements with feature size down to 1 micron and fulfills requirements for optical applications. We fabricated several multilevel GC molds with 8 levels of structuring. Two different optical functionalities were implemented: 6x6 array beamsplitter and 1x4 linear beamsplitter. The molds were applied for precision glass molding of a low Tg glass L-BAL 42 (from Ohara) with a transition temperature of 565°C. Their optical performance was measured. A more detailed analysis of the impact of mold fabrication defects on optical performance is done. Rigorous coupled wave analysis simulations are performed, where we included fabrication constrains such as duty cycle, edge depth errors, wall verticality and misalignment errors. We will compare the results with the design specifications and discuss the influence of fabrication errors introduced during the different process steps

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