A grating-based biosensor is disclosed where the biosensor is constructed and arranged such that the grating lines of the sensor align with an optical axis of a birefringent substrate, so as to improve resonance peak uniformity. Methods of manufacturing biosensors to provide alignment of the grating lines with the optical axes of a birefringent substrate are also disclosed. One embodiment uses a grating master wafer to form a grating on a continuous web of substrate material. The grating master wafer is rotated relative to the web until the lines of the grating in the master wafer are in substantial alignment with the optical axis of the web. A UV curable material is applied to the wafer and cured in place to form the grating on the surface of the substrate web. With a web of some preferred materials, such as PET film, one need only determine the optical axis orientation once for a given web since the optical axis orientation is essentially constant along the length of the web.