SMALL FARADAY-ROTATION MEASUREMENT WITH A FABRY-PEROT CAVITY

The eigenstates of a high-finesse Fabry-Perot (FP) cavity was demonstrated to be very sensitive probes of circular birefringences. This allowed for the refinement of the sensitivity of small Faraday rotation measurements by several orders of magnitude. A table-top experiment with relatively small magnetic fields yielded a rotation sensitivity of 100 picoradians. This method could be used to test magneto-optic Kerr anisotropies in magnetic coatings by employing a FP ended with a magnetic mirror. The high sensitivity of the passive FP eigenstates could also be used in high resolution magnetic field measurements as shown by an active FP. Lastly, all the reported results could be transposed to solid-state or fiber-optic FP and could lead to new compact sensors.