Hybrid Multiphase Fresnel Lenses on Silicon Wafers for Terahertz Frequencies

Abstract

The hybrid multi-phase Fresnel lenses (H-MPFLs) were developed on silicon (Si) wafer at the selected frequency of 585 GHz. For this reason, the design of a standard MPFL was modified thoroughly in various outer zone areas in order to reduce complexity and manufacturing time of the diffractive optical elements (DOEs) by employing the direct laser ablation (DLA) processes. The phase offset was found by a precise control over the phase shift of incoming radiation in steps of /12, revealing its optimal value to be of +/4 independently on the hybridization order of the lens, the focusing gain of which was found to be up to 10 % higher than that achieved with a standard design MPFL. The numerical modeling data were confirmed by experiments demonstrating the effective THz beam focusing with H-MPFL samples to the diffraction limited spot size. Proposed development procedure can be further modified by scaling the hybrid lens design to other frequencies with different zone numbers and/or by employing other materials suitable for THz photonics integration on-chip with the semiconductor devices.

High-Gain Circularly Polarized 500–750 GHz Lens Antenna Enabled by Silicon Micromachining

“…However, these designs often involve intricate fabrication processes and suffer from limitations in aperture efficiency and limited bandwidth. Another approach in recent literature involved Fresnel lens antennas with multistep phase compensation components [18], but these faced challenges related to restricted bandwidth and gain. These existing studies emphasize the need for a new solution that simplifies fabrication, improves aperture efficiency, and expands the operational bandwidth and gain of silicon lens antennas.…”