  Reflectarrays composed of resonant microstrip gold patches on a dielectric
substrate are demonstrated for operation at terahertz frequencies. Based on the
relation between the patch size and the reflection phase, a progressive phase
distribution is implemented on the patch array to create a reflector able to
deflect an incident beam towards a predefined angle off the specular direction.
In order to confirm the validity of the design, a set of reflectarrays each
with periodically distributed 360*360 patch elements are fabricated and
measured. The experimental results obtained through terahertz time-domain
spectroscopy (THz-TDS) show that up to nearly 80% of the incident amplitude is
deflected into the desired direction at an operation frequency close to 1 THz.
The radiation patterns of the reflectarray in TM and TE polarizations are also
obtained at different frequencies. This work presents an attractive concept for
developing components able to efficiently manipulate terahertz radiation for
emerging terahertz communications.
