Zhengli Han

Thin terahertz-wave phase shifter by flexible film metamaterial with high transmission

Thin terahertz (THz)-wave optical components are fundamentally important for integrated THz-wave spectroscopy and imaging systems, especially for phase manipulation devices. As described herein, a thin THz-wave phase shifter was developed using a flexible film metamaterial with high transmission and polarization independent properties. The metamaterial unit structure employs double-layer un-split ring resonators (USRRs) with a designed distance between the two layers to obtain phase retardance of π/2, thus constituting a THz-wave phase shifter. The metamaterial design keeps the transmission coefficient as high as 0.91. The phase shifter also has polarization independence due to the four-fold symmetry of the USRR structure. Because of the subwavelength feature size of the USRR, this shifter can offer benefits for manipulating the spatial profile for the THz-wave phase through design of a binary optics phase plate by arranging a USRR array. The thickness of 48 μm has benefits for developing integrated THz optics and other applications that demand compactness and flexibility. The developed film size of 5 cm × 5 cm from the device fabrication process is suitable for THz lenses or gratings of large optical components.

Flexible metamaterial device for terahertz-wave imaging system

Metamaterial device with double layers of split ring resonators (SRRs) on flexible substrate is proposed for building a new terahertz (THz)-wave near-field imaging system with real-time performance. The SRRs work as an array of probes that reserve the object near-field information and transfer it to the detection system, which is based on the frequency up-conversion with nonlinear crystal DAST (4-dimethylamino-N-methyl-4-stilbazolium tosylate). A flexible polymer is used for the substrate of the metamaterial device, which finally covers the DAST crystal for the THz wave imaging experiment.

Generation of sub-THz waves with narrow linewidth and wide tunablity by DAST-DFG

Sub-THz waves were generated by DAST-DFG with the pump source of the dual wavelength injection-seeded BBO-OPG. The frequency-tuning of the generated THz wave was obtained in the range from 0.3 THz to 4.0 THz.