A novel normal reflection terahertz spectrometer

A method for normal reflection terahertz (THz) spectrometer is proposed. This novel approach makes use of laser induced air plasmas as THz source and receives the normal reflective THz pulses without any THz transceiver and beam splitter. The signal to noise ratio (SNR) of the system is better than 500 and its effective frequency range is 0.2–2.0 THz. For checking the system's validity, we measure the refractive index of a high-resistivity silicon wafer which agrees with the result of the conventional transmission measurement well. The method is useful for the development of reflection THz spectroscopy and makes special advances for the practicability of THz techniques.