Measurements of spectral emissivity, reflectance and transmittance at high temperatures using laser heating and auxiliary light source

A multi-wavelength measurement method for the high-temperature radiation properties of semi-transparent materials heated by high power laser and irradiated by the infrared source with alternating spectral distributions is introduced. The method avoids the strong dependence of existing methods on accurate temperature measurements or emissivity model of semi-transparent samples. The spectral emissivity, reflectance, transmittance and temperature of semi-transparent samples can be determined simultaneously. Furthermore, we established the experimental device, including a FTIR spectrometer (spectral range of 2.0∼16 μm), a 500 W 915 nm fiber laser, and an infrared SiC emitter irradiation source. The radiation properties of the oxidized stainless-steel sample (opaque materials) and n-type, phosphorous-doped silicon wafer sample (semi-transparent materials) were investigated experimentally at different temperatures (400∼800 °C). With the increase of laser power, the upper limit of sample temperature can be extended to higher temperatures. The measurement results show that the infrared spectral emissivity of stainless-steel increases with the increase of temperature. The spectral emissivity of semi-transparent n-type, phosphorous-doped silicon wafer increases with the increase of temperature, while the spectral directional-hemispherical reflectance decreases with the increase of temperature. The results of temperature and wavelength dependent emissivity of silicon wafer sample are consistent with the literatures, which verifies the applicability of the device. The research work provides a useful reference for measuring the high-temperature radiation properties of semi-transparent materials.