Polarization diffraction element and polarization detector employing the same

Abstract From the Canadian patent

A polarization diffraction element comprising two diffraction gratings formed on both faces of a substrate respectively. Both the diffraction gratings have grating lines which are arranged at the same grating pitch and, whose directions mutually form a predetermined minute angle. The grating lines may also be arranged parallel to each other. In this case, the relationship between grating pitches D1, D2 of the respective diffraction gratings and the wavelength .lambda. of an incident light is expressed as:, 0 < ? .lambda.(1/D1 - 1/D2)(1 - (.lambda./2D1)2) - (1/2) ? ~ 0.35; or 0 < ? .lambda.(1/D1 - 1/D2)(1 - (.lambda./D1 - .lambda./2D2)2) - (1/2) ? ~ 0.35, In a polarization detector …