Reflective Properties Of One Dimensional Rough Surfaces At Large Incident Angle

Since the reflective properties of random rough surfaces play a crucial role inmilitary and civilian, the effect of surface roughness on the reflective properties hasbeen widely studied in recent years. The methods of studying the scattering propertiescan be divided into two groups: geometry optics approximation and numerical methods.Geometric optics approximation is based on the geometric optics assumptions, and itdoes not apply to study the reflective properties of surface when a large incident angleor the incident wavelength less than the characteristic parameters of the roughenedsurface.While calculating models at large incident angles, the finite difference time domain(FDTD) method needs large computational cost and long computing time to reduce theerrors from the phases matching between the periodic boundary condition and perfectlymatched layer. Our group measuring the bidirectional reflectance distribution function(BRDF) of aluminum rough surface, results show that when incident angle increasingthe reflection energy of specular direction of roughness surface increasing. In fact, therigorous coupled-wave analysis (RCWA) method can accurate the reflective propertiesof surface at large incident angles with sufficient accuracy. Hence, this paper appliedthis method to study the reflective properties of rough surfaces.When studying the reflective properties of surface, this paper verifies theconvergence of parameters of RCWA.Studying the influence of the compute length ofsurface the number of divided layers and orders to the accuracy of calculation results.The FDTD method has been applied to verify the distribution of electric and magneticfield of calculation results of RCWA. The results show that the RCWA method can beused to calculate the reflective properties of rough surfaces with sufficient accuracy.The results show that the specular peak can be observed as the incidence angle atrough surfaces increasing regardless of the TE wave or TM wave. The effect of theincident wavelength, the autocorrelation length, the root-mean-square and the differentthickness of the oxide film on the reflective properties of rough silicon surfaces hasbeen analyzed in detailed. The angle of to the specular peak appeared of TE waves issmaller than the TM waves. The angle of random rough surface appearing specular peakwill be reduced as the wavelength and decreasing root-mean-square increasing.Moreover, increasing autocorrelation length and thickness of the oxide film have littleeffect on the angle of specular peak. The results have been analyzed and discussed indetailed by comparing the results of RCWA with Rayleigh criterion factorg2.