Disclosed is a battery pack including guide recesses inside a case. The polarization splitter has an ultra thin substrate whose thickness is chosen so that the depth of focus of the projection lens in imager space is greater than the astigmatism produced by the splitter at its tilted angle. The deposition method may be used to fill recesses in a substrate and smoothen out reentrant cavities in a silicon nitride liner, in the fabrication of polysilicon gates in a substrate. When light is incident from the first major surface side, light polarized in a direction parallel to the specific direction is absorbed, and light polarized in a direction perpendicular to the specific direction is transmitted.