Femto Seconds Laser Based Efficient THz Generation from Different Temperature Annealed CdTe Thin Films and Effects of Carrier Concentration and Phase Transition on Efficiency of Generation

Abstract

The paper reports the thermal evaporation based growth process of CdTe thin films on glass substrates. These films were annealed between room temperature to 200, 300 and 400 oC, respectively. The XRD characterization of these films revealed the change in crystalline phase from cubic to triclinic above 200 oC. Finally, these films were subjected to 800 nm wavelength of 35fs pulsed obtained from Ti: sapphire amplifier at 1kHz repetition rate. The incident power of the laser was focused and tuned between 150-350 mW range and generated THz signals were recorded using calibrated Pyroelectric detector at 22.5 Hz frequency. The highest power of the THz signal was 80nW for 200 oC annealed film with respect to incident power of 300mW. The highest efficiency of THz signal was of the order of 3.11E-5%. We have also explained the effect of carrier concentration and phase transition with respect to different annealed temperature for efficient generation of THz signal.