Frequency-controlled 2-D focus-scanning terahertz reflectarrays

In this paper, we report the design and realization of 2-D focus scanning of the reflected beam by exploiting the frequency dispersion characteristic of reflectarrays operating at terahertz (THz) frequencies. In the first design, we choose four focal points on a circular path at four different frequencies ranging from 0.225 to 0.3 THz and 2-D beam scanning in the focal plane is achieved as frequency increases. To increase the scanning area, we design a dual-band reflectarray and 1-D scanning is achieved in each of the operating bands with different focal positions along the direction orthogonal to the scanning. The proposed reflectarrays are fabricated and their 2-D focus-scanning abilities are measured and there are good agreements between the simulation results and the measurements. The proposed designs demonstrate and expand further the potential applications of reflectarrays in fast THz imaging and detection.