Abstract-Actively tunable broadband terahertz absorption using periodically square-patterned graphene

Longfang Ye, Xin Chen, Jianliang Zhuo, Feng Han,  Qing Huo Liu

http://iopscience.iop.org/article/10.7567/APEX.11.102201/pdf

We propose an actively tunable broadband perfect absorber using a square-patterned graphene–spacer–polysilicon–spacer–metal structure. The simulated results show that the absorber can reach nearly perfect broadband terahertz absorption with over 99.5% (90%) absorbance from 1.52 (1.27) to 2.23 (2.51) THz, corresponding to the normalized bandwidth of 37.5% (65.6%) under normal incidence with the graphene Fermi level of 0.7 eV. The absorption spectra show a clear independence of the polarization and the angle of incidence. By adjusting the graphene Fermi level from 0 to 0.7 eV, the peak absorbance can be continuously tuned from 15 to 100% without shifting the absorption frequency band.

Abstract-Uncertainty in Terahertz Time-Domain Spectroscopy Measurement of Liquids

http://link.springer.com/article/10.1007/s10762-016-0318-1

Terahertz time-domain spectroscopy (THz-TDS) is a significant technique for characterizing materials as it allows fast and broadband measurement of optical constants in the THz regime. The measurement precision of the constants is highly influenced by the complicated measurement procedure and data processing. Taking THz transmission measurement of liquids into account, the sources of error existing in THz-TDS process are identified. The contributions of each source to the uncertainty of optical constants in THz-TDS process are formulated, with particular emphasis on the effect of multilayer reflections and plane wave assumption. As a consequence, an analytical model is proposed for uncertainty evaluation in a THz-TDS measurement of liquids. An actual experiment with a Di 2-Ethyl Hexyl Phthalate (DEHP) sample is carried out to show that the proposed model could be a basis to evaluate the measurement precision of optical constants of liquids.