Faraday ellipticity and Faraday rotation of a doped-silicon wafer studied by terahertz time-domain spectroscopy

Free-carrier Faraday ellipticity and Faraday rotation are measured for a moderately doped n-type silicon wafer with the resistivity of 1.1 ohm cm under magnetic fields of +/- 3 T using the terahertz time-domain spectroscopy. From the experimental data, we obtain the time evolution of the electric-field vector of the terahertz radiation pulses. When the magnetic field is applied to the sample, the transmitted radiation has an elliptic polarization with its major axis rotated from the polarization direction of the incident radiation ( Faraday effect ). The Faraday ellipticity and Faraday rotation angle are obtained for the directly transmitted pulse ( first terahertz pulse ) and the pulse reflected twice at the sample surfaces ( second terahertz pulse ) separately. They are compared with the calculations using the Drude model. A slight deviation is observed between the experimental and calculated Faraday ellipticities and Faraday rotation angles probably due to the energy dependence of the carrier scattering time. (c) 2006 American Institute of Physics.