Zinc selenide Middle Window (CF/DN old style/CCC) Zinc selenide is a reliable cryogenic window for the mid IR. Care should be taken with handling as it is toxic and scratches easily. The transmission data is for a 2 mm thick window. Measuring 20mm diameter x 2mm thick.
Zinc selenide optical windows are often used as protective windows in both forward looking infrared (FLIR) and thermal imaging applications. Often these protective windows would have a BBAR coating to reduce the reflection back into the system and maximise the transmission.