A new balanced-path heterodyne I/Q-interferometer scheme for low environmental noise, high sensitivity phase...

A new heterodyne interferometer scheme which has open accesses to both the geometrically balanced probe beam (PB) and reference beam (RB) paths, for which, depending on the nature of a specific sensing mechanism, a transmission geometry or a reflection geometry can be employed, is presented. We will show that, because of a small separation between the short length PB and RB running parallel to each other our newly proposed optical arrangement allows high rejection of unlocalized environmental perturbations. In fact, the geometrically balanced optical arrangement provides 19 dB rejection of any vibrations parallel to the direction of beam propagation, which cannot be achieved in a conventional interferometer scheme. Applications of this new interferometer scheme are discussed. As an example, we will show that our newly proposed interferometer scheme can be applied for high sensitivity measurements of concentration dependent refractive indexes in various solutions.