利用Pb1-xGexTe材料的折射率异常性质改善红外光学薄膜的低温性能

红外薄膜干涉滤光片性能在低温下的变化是空间遥感系统中的一个关键性问题。经研究表明IV-VI族半导体PbTe和GeTe的赝二元合金Pb1-xGexTe在铁电相变点具有折射率异常—相应于铁电相变,Pb1-xGexTe薄膜呈现出最大折射率值。用Pb0.94Ge0.06Te材料代替PbTe材料,制作了一个红外薄膜干涉滤光片。测试结果表明:其中心波长漂移从0.48nm/K改进到0.23nm/K,在所测量的80K～300K的温度范围,用Pb0.94Ge0.06Te材料制作的滤光片的峰透过率高于用PbTe材料制作的滤光片约3%,从而极大地改善了光学薄膜器件在深低温环境下的稳定性和可靠性。

Improving low-temperature performance of infrared optical coatings utilizing the abnormal refractive index of Pb1-xGexTe

The deterioration in the performances of the infrared thin-film interference filters at low-temperature is crucial to the spaceborne remote sensing instruments. Pb_(1-x)Ge_xTe is the pseudobinary alloy of IV-VI narrow gap semiconductor PbTe and GeTe. The research carried out by us shows that the maximum refractive index occurs corresponding to the ferroelectric phase transition in Pb_(1-x)Ge_xTe thin films. Therefore, the phenomenon that the temperature coefficient of refractive index of Pb_(1-x)Ge_xTe can be tuned by means of changing Ge composition can be theoretically explained. An interference filter was fabricated substituting Pb_(0.94)Ge_(0.06)Te for PbTe, of which the shift of center wavelength is improved from 0.48nm/K to 0.23nm/K. Meanwhile, the peak transmittance of filter fabricated with Pb_(0.94)Ge_(0.06)Te has a 3% advantage over that fabricated with PbTe in the temperature range of 80K to 300K.