A phase feature extraction technique for terahertz reflection spectroscopy

We present a feature extraction technique for identification of explosive and biological materials using terahertz reflection time-domain spectroscopy (RTDS). The absorption signatures of the materials are extracted directly from the second-order derivative of the phase of the sample beam with respect to frequency. This technique provides a straightforward and fast solution to solve the phase-retrieval problem in RTDS and will benefit the future development of a standoff, large-size focal-plane terahertz sensing and imaging system.