We are developing optical parts made of infrared-transmitting glass, which can be used in various fields of science and in other applications. Herein, spectral dispersers were fabricated from FI-02, which is developed by Nippon Electric Glass Co., Ltd. The radiation test showed that FI-02 is resistant to radiation. Further, a reflection coating to produce an immersion grating made of FI-02 was tested. We designed, manufactured, and evaluated a prototype grating made of FI- 02. The dimensions of the prototype grating were 30 mm × 20 mm, and the pitch of the steps of the grating was 0.217 mm. We observed the microscopic structure of the steps of the prototype grating. The surface roughness values of the wide and narrow surfaces of the steps were 0.084 μm rms (0.070 μm Ra) and 0.082 μm rms (0.064 μm Ra), respectively. The radius of curvature of the edge of the step was also quantified.
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