Temperature dependence of the reflectivity of silicon with surface oxide at wavelengths of 633 and 1047 nm

We measure the temperature coefficient of the reflectivity of Si at a red wavelength of 633 nm that is much larger than the Si band gap, and at an infrared wavelength of 1047 nm that is close to the band gap. Our reflectivity measurement is done over a temperature range from room temperature to 200 °C, with an accuracy of better than 1 part in $105.$ Our results show that the temperature coefficient for the infrared reflection is over three times larger than that for the red reflection over the temperature range studied. Our results and technique can be useful for remote monitoring of temperatures of Si or other materials.