Development of thermally stable and moldable chalcogenide glass for flexible infrared lenses
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In this study, the ternary Ge–Sb–Se chalcogenide glass was fabricated by a standard meltquenching technique for flexible infrared lenses. Chalcogenide glass should have unique thermal and mechanical properties to be applied to precision glass molding (PGM) process. Therefore, the relations between thermal properties and the moldability were investigated for (35–20)Ge–(5–20) Sb–60Se glass systems. The thermal and thermos-mechanical properties were characterized by the differential scanning calorimeter and thermos-mechanical analysis, respectively. Preceding experiments using a pressing tester were conducted before PGM process to evaluate the moldability. The surface condition of both chalcogenide glass disks and Tungsten Carbide (WC) molds were characterized by using an optical microscopy and an interferometer. The preferential compositions in (35–20)Ge–(5–20)Sb–60Se glass systems were selected to produce molded lenses. Finally, the molded chalcogenide lens was successfully fabricated using the preferential compositions and the processing conditions from the preceding experiments using a pressing tester.
I. INTRODUCTION
The needs of aspherical optical lenses have been increased because of their extensive usage in photonic applications. One of the most attractive applications of infrared aspheric lenses is for the infrared thermographic camera. Aspheric lenses lead to superior optical performance such as reduction of optical aberrations. Furthermore, due to its widespread applications and merits, the companies like Umicore and Lightpath are successfully commercializing molded chalcogenide glasses for last ten years. The conventional techniques for manufacturing aspheric lenses for infrared optics are the single point diamond turning and polishing methods, which can be applied to crystalline materials such as Ge and ZnSe etc. However, the main drawback of these methods is timeconsuming process and difficulty in mass production with high accuracy. Therefore, the use of precision glass molding (PGM) method has recently became more attractive to fabricate aspheric glass lens in infrared optics since it is simple and cost effective which can lead to the mass production.1,2 In case of amorphous materials for infrared optical lenses, the ternary Ge–Sb–Se glass systems have attracted researchers’ attention since these materials have a unique optical transmittance in the wave length region from ;2 to 16 lm.3–5 Therefore, there have Contributing Editor: Himanshu Jain a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.199 1674
J. Mater. Res., Vol. 31, No. 12, Jun 28, 2016
http://journals.cambridge.org
Downloaded: 17 Aug 2016
been intensive studies for the Ge–Sb–Se glass systems for photonics applications.6–9 It has been proved that special chalcogenide glasses had the feasibility of infrared optical lenses with aspherical optical geometries using PGM process.1,2 However, all commercial chalcogenide glasses cannot always satisfy the requirement for PGM process in making aspherical opt
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