Patent ID: 7030993

Claim:
An interferometer comprising: a first polarizing beam splitter configured to direct an input beam in a direction that depends on a polarization state of the input beam; a first retroreflector in optical communication with the first polarizing beam splitter; a second polarizing beam splitter configured to receive an output beam from the first polarizing beam splitter and to direct the received output beam in a direction that depends on a polarization state thereof; and a second retroreflector in optical communication with the second polarizing beam splitter, wherein the first polarizing beam-splitter comprises: a first beam-splitting plane oriented to reflect light having a first polarization toward the second polarizing beam splitter, and a second beam-splitting plane in optical communication with the first beam-splitting plane, the second beam-splitting plane being oriented to transmit light having a second polarization received from the first beam-splitting plane to the first retroreflector and oriented to reflect light received from the first retroreflector and having the first polarization toward the second polarizing beam splitter.