Characterization of (Cd,Mn)Te and (Cd,Mg)Te single crystals in the THz frequency range using integrated photoconductive and electro-optic effects

We present THz frequency range characterization of highly resistive (Cd,Mg)Te and (Cd,Mn)Te single crystals, using an "experiment-on-chip" configuration. We have demonstrated that both of these single crystals exhibit simultaneously strong photoconductive (PC) and electro-optic (EO) effects by performing measurements on a given single platelet with a deposited Au coplanar transmission line. We optically generated a subpicosecond electrical transient by focusing an ultraviolet 100-fs-wide pump pulse between the electrodes of a dc-biased coplanar line (PC effect) and, subsequently, time resolved it with a subpicosecond resolution along the transmission line using an internal EO effect by passing infrared, 100-fs-wide probe pulses through the crystal between the coplanar strips. Transients sampled at different distances from the generation site allowed us to calculate the complex propagation factor γ(f) of our transmission lines and the corresponding THz bandwidth attenuation and phase velocity. The latter parameters enabled us to reconstruct the original ∼600-fs-in-duration, PC-generated transient by "back-propagating" a signal to the excitation point. Furthermore, we have also determined the THz-bandwidth EO coefficients of our (Cd,Mn)Te and (Cd,Mg)Te crystals to be 6 pm/V and 1.2 pm/V, respectively.