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在传统的光学涂层中,实现干涉效应的薄膜厚度至少需要四分之一波长.然而,有报道称利用一种损耗比较高的材料做涂层,可以在薄膜厚度远小于四分之一波长的情况下实现光干涉效应.本文利用一种相变材料Ge_2Sb_2Te_5做涂层材料,发现即使薄膜厚度远小于四分之一入射波长,干涉效应仍然可以实现并且在某些特定波长获得接近100%吸收.吸收波长可以通过薄膜厚度来调节,入射光角度的变化对吸收效果影响不明显.利用相变材料的性质,在Ge_2Sb_2Te_5的非晶和晶体相下,吸收效果会有很大的变化.两种相位下的不同反射率会导致巨大的光学衬度比,实验可获得高达400的光学衬度比,这种衬度比很高的相变器件在光学开关和光学存储上有巨大的应用前景.
In conventional optical coatings, the thickness of the film that achieves the interference effect requires at least a quarter wavelength.However, it has been reported that using a relatively high loss material for coating can be performed at film thicknesses much less than a quarter wavelength .In this paper, a kind of phase change material Ge_2Sb_2Te_5 was used as the coating material and found that the interference effect can be achieved even at film thickness much less than one quarter of the incident wavelength, and it can achieve nearly 100% absorption at certain wavelengths The absorption wavelength can be adjusted by the thickness of the film, and the change of incident light angle has no obvious effect on the absorption effect.Using the properties of phase change material, the absorption effect will be greatly changed under the amorphous and crystalline phases of Ge_2Sb_2Te_5. Different reflectivities in the phase lead to a large optical contrast ratio. Experiments can achieve an optical contrast ratio up to 400. This phase contrast device with high contrast ratio has great application prospects in optical switching and optical storage.