The polarization direction is marked on all mounted and unmounted polarizers we sell. For a more precise determination, use a laser line beamsplitting polarizer. The transmitted linear polarization direction lies precisely in the plane defined by the incident and reflected laser beams.
If the wavelength difference between the two is greater than 30 to 35% of the lower wavelength, then we recommend a Dual Wavelength Retarder. Please contact your Meadowlark Optics sales engineer for assistance so that we can design for you the required Dual Wavelength Retarder or if you need any help at all.