我利用3维的FDTD solutions 模拟一个石英纳米锥阵列上面多层膜的吸收，表层的光吸收层的吸收效率正常，但石英和光吸收层中间的金属层的吸收异常，在长波长区域吸收达到了2甚至3。如下图：
From Maxwell’s equations, we know that the field component normal to the structure surface will be discontinuous at the interface. Also, it is obvious that interpolating near a discontinuity can lead to errors. In the absorption calculations, the interpolation error typically makes the electric field just inside the absorbing material much larger than it really is. Since absorption is proportional to electric field intensity, this will tend to overestimate the total absorption.
Note that these errors only occur for the mesh cells which cross the material interface. If the absorption in the mesh cells that cross the interface is a small fraction of the total absorption, then the overall error will be small. However, if most of the absorption is concentrated near the surface (as is the case with metals), then the overall error can be significant.