Femtosecond electro-optic effect in (Cd,Mn)Te single crystals

We present our studies on the femtosecond electro-optic (EO) effect in high quality Cd0.88Mn0.12Te (CMT) single crystals, grown using a modified vertical Bridgman method. Our time-resolved experiments were performed using a coplanar transmission line setup, which incorporated a free-standing, low-temperature-grown GaAs photoconductive switch as a subpicosecond electrical pulse generator and the tested CMT crystal as an active EO transducer. We determined the r-coefficient (r41) of CMT at the high (THz) frequency range to be 29.4 pm/V, an order of magnitude greater than that measured for the same sample at low (MHz) frequencies. The observed suppression of the EO coefficient at low frequencies was due to effective electric field screening by free holes in the crystal volume. Comparison to the standard EO sampling scheme based on the LiTaO3 transducer showed that CMT exhibited the same sub-picosecond temporal resolution with significantly greater voltage sensitivity. We also did not observe, the so-called dielectric loading typical for LiTaO3-based samplers.