Active sub-Rayleigh alignment of parallel or antiparallel laser beams.
We measure and stabilize the relative angle of parallel and antiparallel laser beams to 5 nrad/(square root of)Hz resolution by comparing the phases of radio frequency beat notes on a quadrant photodetector. The absolute accuracy is 5.1 and 2.1 microrad for antiparallel and parallel beams, respectively, which is more than 6 and 16 times below the Rayleigh criterion.
Müller
Holger
H
Physics Department, Stanford University, Stanford, California 94305, USA. holgerm@stanford.edu
Chiow
Sheng-Wey
SW
Long
Quan
Q
Vo
Christoph
C
Chu
Steven
S