A non-contact technique for determining the depth of zero-order gratings

In this work we present a simple, non-contact method for characterizing the depth of deep zero-order diffraction gratings using standard visible optic s. Form birefringence exhibited by zero-order structures alters the polariz ation state of light transmitted through them. The amount of change is depe ndent on several factors including the depth of the grating grooves. By rec ording the polarization changes of laser light transmitted through the samp le we demonstrate how the depth of any grating with a known pitch may be de termined. Results for many different gratings have been analysed and show g ood agreement with groove depths measured from scanning electron micrograph s. From these results a universal relationship between the amount of polari zation change and the depth of the grating grooves has been determined.