Abstract

The simplest shortwave-pass filter design consists of repetitions of the basic period of the form L/2 H L/2, where L and H refer to quarterwaves of low- and high-index materials at a particular wavelength. Such a filter has a passband limited by the first- and third-order rejection bands. The width of the passband can be extended to shorter wavelengths by further subdividing the basic period using materials of intermediate indices. One such class of design, due to Baumeister,¹ involves intermediate layers of equal optical thickness, except that the layer of lowest index has twice the optical thickness of the other layers. An alternate design with all layers having equal optical thickness requires that the log of the indices of the layers follows a sinusoidal profile between the lowest and highest indices. To provide the best performance over the transmission band, the Herpin-equivalent index of the coating should be close to the index required for an antireflection coating. Various designs are compared for nondispersive indices ranging from 1.38 to 2.25 on a 1.52 index substrate.

© 1987 Optical Society of America