Additive analysis of transmission-type all-dielectric encoding supergrating

A transmission-type all-dielectric coded supergrating operating in the terahertz band is designed. The structure uses Si as the dielectric material to realize the change of transmission phase $2\pi$ in the band of $0.06\sim0.15\,$THz. Compared with the conventional gratings, the transmission-type all-dielectric coded supergratings have the advantages of wide operating bandwidth, high transmittance, easy coupling with fiber, and low cost. It represents a new direction of optical coding technology and has a high application prospect and research value. We design a $1$-bit all-dielectric coded supergrating. By changing the width of the grating element structure, two grating basic element structures with high transmission coefficients and continuous transmission phase changes of $180^\circ$ are obtained. Based on the addition theorem of digital coding, the far-field scattering angle of the grating is controlled by encoding the basic unit structure of the grating, changing its arrangement order and physical superposition. Based on the generalized Snell theorem and the far-field scattering principle, the far-field scattering angle of the designed supergrating structure is calculated theoretically, and the characteristics of the simulation results are analyzed.