  Fibonacci or bifocal terahertz (THz) imaging is demonstrated experimentally
employing silicon diffractive zone plate (SDZP) in a continuous wave mode.
Images simultaneously recorded in two different planes are exhibited at 0.6 THz
frequency with the spatial resolution of wavelength. Multi-focus imaging
operation of the Fibonacci lens is compared with a performance of the
conventional silicon phase zone plate. Spatial profiles and focal depth
features are discussed varying the frequency from 0.3 THz to 0.6 THz. Good
agreement between experimental results and simulation data is revealed.
