THz beam shaping based on diffractive transformation for forming patterned simulation lightfields and wavefronts

Abstract

In this paper, the traditional Gerchberg-Saxton (GS) algorithm is used to achieve a key phase recovery in the THz band via common Fourier transformation to realize desired beam manipulation. The main technological process includes a single mask UV-photolithography and a dual-step KOH wet etching, thus enabling a kind of THz diffractive optical element (THz-DOE) with the needed phase-step arrangement. The experimental results about THz beam shaping for generating patterns and wavefronts based on the THz-DOEs are given to demonstrate the feasibility of realizing complex lightfield generation and modulation for THz imaging applications. The developed THz-DOEs exhibit a significant THz amplitude modulation for constructing some particular patterns selected. The non-ideal surface roughness and phase-step configuration of the silicon-based DOEs for both the visible and infrared wavelength ranges is perfectly acceptable in the THz band due to its long wavelength nature. A better imaging exhibition based on the beam modulation of the developed THz-DOEs can be expected since the phase configuration accuracy can be further improved according to the technological and micro-structural parameter optimization.