Design and Optimization of High Reflectance Graded Index Optical Filter with Quintic Apodization

摘要

Rugate filters are a special kind of graded-index films that may provide advantages in both, optical performance and mechanical properties of the optical coatings. In this work, design and optimization of a high reflection rugate filter having reflection peak at 540nm has been presented which has been further optimized for side-lobe suppression. A suitable number of apodization and matching layers, generated through Quintic function, were added to the basic sinusoidal refractive index profile to achieve high reflectance of around 80% in the rejection window for normal incidence. Smaller index contrast between successive layers in the present design leads to less residual stress in the thin-film stack which enhances the adhesion and mechanical strength of the filter. The optimized results show excellent side lobe suppression achieved around the stopband.