Measurement method for high-temperature infrared optical constants of ZnS crystal materials in a multi-layer structure

• Measurement method of optical constants in a multi-layer structure was investigated.
• Establish radiative transfer model in a multi-layer semi-transparent structure.
• Effects of two side layers on radiation properties of the structure were analyzed.
• Establish inverse method of optical constants based on angle transmittances.
• Inverse accuracy of optical constants of ZnS sample was numerically verified.

An inverse method was used to calculate the optical constants of high-temperature semi-transparent materials in the infrared spectra based on the angle dependent transmittances of multi-layer structure. The radiative transfer model for the multi-layer semi-transparent structure was established. A three-layer structure composed by zinc sulfide (ZnS) infrared optical materials was investigated with a numerical analysis of the radiation characteristics to analyze the effects of the two side layers (defined as optical windows) on the radiation properties of the three-layer structure. The inverse calculations of the optical constants of ZnS materials were carried out based on the total transmittances of the three-layer structure at different incidence angles using the Levenberg–Marquardt algorithm. The inverse accuracy for the optical constants was numerically verified. This research works provides a reference for measurements of high-temperature radiation properties of semi-transparent materials in multi-layer structure.