Boosting of the terahertz absorption spectrum based on one-dimensional plastic photonic crystals.

Although terahertz (THz) spectroscopy exhibits a broad application potential in the field of fingerprint sensing and detection, there remain some limitations with the conventional sensing methods for analyzing trace analytes. In this study, a terahertz absorption spectrum boosting method based on the defect one-dimensional (1D) plastic photonic crystal (PPC) structure is proposed to improve the interaction between the terahertz wave and the trace samples. Affected by the Fabry Perot resonance, the local electric field in thin film analytes will be improved. Furthermore, the resonant frequency will be varied by changing the defect width of the 1D PPC. The structure of the uniform planar film sample is easily built and measured. The boosted terahertz absorption spectrum can be obtained by linking the resonant absorption peaks. For the 0.2 μm α-lactose films, a large absorption enhancement factor of about 105 times can be achieved, which has great potential in identifying different analytes. The study performed here gives a novel investigation direction for boosting the broad terahertz absorption spectrum of trace amounts of analytes.