Ultrasensitive beam deflection measurement via interferometric weak value amplification

Phys Rev Lett. 2009 May 1;102(17):173601. doi: 10.1103/PhysRevLett.102.173601. Epub 2009 Apr 27.

Abstract

We report on the use of an interferometric weak value technique to amplify very small transverse deflections of an optical beam. By entangling the beam's transverse degrees of freedom with the which-path states of a Sagnac interferometer, it is possible to realize an optical amplifier for polarization independent deflections. The theory for the interferometric weak value amplification method is presented along with the experimental results, which are in good agreement. Of particular interest, we measured the angular deflection of a mirror down to 400+/-200 frad and the linear travel of a piezo actuator down to 14+/-7 fm.