Faraday optical isolator in the 9.2 $mu$m range for QCL applications

We have fabricated and characterized a n-doped InSb Faraday isolator in the mid-IR range (9.2 $mu$m). A high isolation ratio of $approx$30 dB with a transmission over 80% (polarizer losses not included) is obtained at room temperature. Further possible improvements are discussed. A similar design can be used to cover a wide wavelength range (lambda ~ 7.5-30 $mu$m).