Fabricating THz spiral zone plate by high throughput femtosecond laser air filament direct writing

Zhi Zhang,Chunyue Chu,Weiwei Liu,Olga Kosareva,Nan Zhang,Zijie Dai,Yunfei Wang,Lie Lin,Qiang Su

doi:10.1038/s41598-020-70997-w

Abstract

The sixth-generation wireless communication will exploit the radio band with frequencies higher than 90 GHz, reaching terahertz (THz) band, to achieve huge signal bandwidths. However, the cost-effective fabrication methods of the key components in THz band, which can compromise large scale, high precision, and high efficiency, remain great challenges at present. In this work, we have developed a high throughput fabrication method based on the femtosecond laser filament direct writing. The ability of fabricating large-scale THz elements with high precision and fast speed has been demonstrated by fabricating 100 × 100 mm2 spiral zone plates (SZPs), which can convert the Gaussian THz beam into vortex beam. The performance of the obtained THz vortex beam is in good agreement with the theoretical predictions. The fabrication method reported here has promising applications in fabricating various kinds of THz elements on substrates with both flat and curved surfaces.

Highlights

The sixth-generation wireless communication will exploit the radio band with frequencies higher than 90 GHz, reaching terahertz (THz) band, to achieve huge signal bandwidths
The orbital angular momentum (OAM) of the vortex optical beam provides a new informational degree of freedom due to its infinite number of eigenstates characterized by the topological c harges[11]
THz vortex beams obtained by spiral zone plates (SZPs)

Summary

Introduction

The sixth-generation wireless communication will exploit the radio band with frequencies higher than 90 GHz, reaching terahertz (THz) band, to achieve huge signal bandwidths. Significant improvements on beam controlling has been made in optics, which mainly relies on the skillful design of micro-/nano-structuring e lements[5,6,7] and the state of art fabrication technology such as electron beam lithography[8], extreme ultraviolet lithography[9] and ion beam e tching[10] These advanced optical beam controlling methods and concepts can be directly transferred to the THz band. We develop a high throughput direct writing method using the femtosecond laser air filament, which can fabricate large scale THz elements with a lateral resolution of ~ 100 μm, i.e. In the filamentation the pulsed laser beam propagates with a constant diameter (~ 100 μm) over a distance much

Methods

Results

Conclusion