Simple technique for producing a 1D periodic intensity profile with a desired open fraction for optical sensor applications

The interference contrast in a near-field diffraction pattern can be improved using an asymmetric grating with a small grating window. However, commercial asymmetrically shaped gratings are not available. Here, we report a method that overlaps two gratings to produce an arbitrary open fraction in the combination grating. Both theoretical simulation and experimental observations of the near-field Talbot effect are provided to validate this concept. A characterization of optical vortices is also used as a demonstration of potential applications. This method is simple and can improve the resolution in metrology with optical sensors.