Abstract

We describe a broadband and broad angle-of-incidence response antireflectance coating design for multispectral applications. This antireflectance coating has a graded-index profile consisting of a hyperbolic tangent function. We present spectral transmission and reflectance as functions of angle of incidence for both the TE and TM polarizations. We calculate the effect of random index fluctuations, such as are caused by monitoring feedback systems employed in coating fabrication, on the spectral transmission and reflection. This coating design is tolerant of manufacturing errors. We also present transmission calculations as functions of total coating thickness and the steepness parameter of the index profile. For infrared applications, a total physical coating thickness equaling one half the maximum operational wavelength provides nearly optimal transmission. The coating performance is not a strong function of the steepness of the index variation. We compare the performance of the hyperbolic tangent graded-index antireflectance coating to that of a coating having a linear index variation. We show that the hyperbolic tangent graded-index antireflectance coating transmission is significantly better than the transmission of a coating having a linear index variation through the thickness.

© 1991 Optical Society of America