Optical device for beam combination in heterodyne interferometers and polarimeters and its use

A method of making a laser beam combiner comprising:

• providing a modulator configured to receive laser light having a combination of both a vertical polarization component and a horizontal polarization component, wherein the modulator shifts a frequency of one of the vertical polarization component and the horizontal polarization component relative to the other;
• and
• providing a wedge combiner having an index of refraction and comprising:
• a first surface coating on one side of the wedge combiner comprising a mirror coating, and
• a second surface coating on other side of the wedge combiner comprising a transmissive coating producing total transmission of a P-polarization component at Brewster's angle of incidence and producing total reflection of an S-polarization component at a different angle of incidence;
• wherein said laser light having the P-polarization component on the second surface coating is reflected by the first surface coating on the one side;
• wherein said laser light having S-polarization component on the second surface coating is reflected by the second surface coating on the other side;
• and
• wherein said laser light having P polarization component as incident on the second surface coating combines with said laser light having S polarization component as said laser light having P polarization component as incident on the second surface coating and said laser light having S polarization component departs said wedge combiner.