Instrumentation and Application of THz time-domain spectroscopy (THz-TDS)

 Terahertz time-domain spectroscopy (THz-TDS) has been a powerful and important technique that benefits a variety of research fields, such as material characterization, spectral fingerprints identification, biomedical imaging and non-destructive inspection in a broad THz band (0.1~10THz).Using photoconductive antenna (PCA) as THz source and detector, we have built a free-space THz-TDS system, and are exploring its capabilities in various applications. For example, we are working on a THz near-field imager for photonic and phononic metamaterial and devices research. Different from existing methods, this near-field imager can realize sub-wavelength resolution at high signal-to-noise ratio in THz band without commonly used tip or aperture.Beyond that, we are also working on the design of novel PCA aiming at enhanced output THz power and optics-to-THz efficiency, so that the performance of the THz-TDS (such as signal-to-noise ratio and dynamic range) can be further improved. To achiveing this, we have developed a simulation tool by finite-difference-time-domain (FDTD) method based on full-wave model. Implemented on Matlab platform, this simulation tool involves multi-physical phenomena that happen in the PCA so that almost all of the related parameters (such as light-matter interaction, photo-excited carrier dynamics, and electromagnetic wave propagation) can be simulated and optimized in a comprehensive way.

Terahertz Time-domain Spectrometer
Modeling of the Terahertz Photoconductive Antenna by 3D Fnite-Difference Time-Domain Method