Fig. 1. Theoretical reflectivity after optimization. (a) Anti-reflection protective film; (b) anti-reflection film

Fig. 2. Sample with film falling off at 140 ℃

Fig. 3. Relationship between thermal stress of germanium material and temperature difference

Fig. 4. Enlarged view of DLC film prepared at 15 Pa

Fig. 5. Raman spectra of DLC film. (a) Comparison; Gaussian fitting diagrams under different pressures of (b) 5 Pa, (c) 10 Pa and (d) 15 Pa

Fig. 6. DLC films prepared at different pressures. (a) Micrograph of DLC film prepared at 10 Pa; (b) sample with DLC film falling off at 5 Pa

Fig. 7. Surface diagram tested by Zygo interferometer. (a) Uncoated chalcogenide glass substrate; (b) DLC film prepared at pressure of 15 Pa; (c) DLC film prepared at pressure of 5 Pa

Fig. 8. DLC film after severe abrasion test. (a) Enlarged view; (b) sample

Fig. 9. Comparison between designed and actual test results. (a) One side reflectivity of anti-reflection protective film; (b) double side transmittance of anti-reflection film and anti-reflection protective film