Do P A, Touaibia M, Haché A
Appl Opt. 2013 Aug 20;52(24):5979-84. doi: 10.1364/AO.52.005979.
The thickness change of a film is measured optically using self-interference of a single laser beam incident at the edge of the film. Theory suggests that when a half-plane phase shift is applied to a Gaussian laser beam, interference fringes appear in the near and far field, in which position varies with the amount of phase shift. By measuring fringe pattern displacement, we demonstrate detection of thickness changes in chitosan films induced by temperature rises of a few degrees centigrade. With a laser at 543 nm, the minimum detectable thickness change is 0.8 nm in ideal conditions (quarter wave films), corresponding with a phase shift of 0.02 rad, and the minimum detectable film thickness is ∼30 nm. Potential use for surface temperature measurements is discussed.
利用入射在薄膜边缘的单束激光的自干涉，通过光学方法测量薄膜的厚度变化。理论表明，当对高斯激光束施加半平面相移时，在近场和远场会出现干涉条纹，其中条纹位置会随相移量而变化。通过测量条纹图案的位移，我们展示了对几摄氏度温度升高引起的壳聚糖薄膜厚度变化的检测。在使用543nm激光时，理想条件下（四分之一波长薄膜）的最小可检测厚度变化为0.8nm，对应于0.02rad的相移，最小可检测薄膜厚度约为30nm。还讨论了其在表面温度测量方面的潜在用途。
