High sensitivity two-frequency paired polarized interferometer in Faraday rotation angle measurement of ambient air with single-traveling configuration

High sensitivity detection on Faraday rotation and Verdet constant of ambient air under weak applied magnet field and single-pass configuration specimen is setup in which a two-frequency paired linear polarized interferometer (TPPI) coupled with balanced detector shown at shot-noise-limited detection is demonstrated. The Verdet constant of ambient air at 1.3×10−6 rad/mT m and its sensitivity at 4.3×10−8 rad/mT m were measured. Additionally, this method also is able to extend into a broad spectral range on Faraday rotation angle or Verdet constant measurement. Finally, the enhancement on detection sensitivity by integrating a Fabry–Perot cavity into TPPI is discussed.