ON CALCULATING THE REFLECTANCE AND TRANSMITTANCE OF LIGHT FOR A SIMPLE THICK GRATING STRUCTURE

This paper presents a formulation for calculating the reflectance and transmittance of classical light for a simple structure that contains a rectangularly shaped line grating layer that lies atop a thick trans parent or weakly absorbing substrate layer. It is assumed that the sub strate thickness is sufficiently large and non-uniform that when the l ight traverses it is averaged over a large surface area, the averaged field is considered as losing phase coherence and intensities can be a dded. It is assumed that the optical properties of the media in the va rious homogeneous regions of the structure are complex, local, linear, isotropic, and non-magnetic. This kind of structure has important app lications in the metrology of linewidths for the semiconductor integra ted circuit industry.