Affiliation:
1. Xian University of Technology
Abstract
As a novel terahertz (THz) source, a spintronic THz emitter (STE) has become a research hot topic recently due to its ultra-broadband emission, powerful scalability, simple fabrication, and ultrawide pump-wavelength range. To optimize the performance of a STE, its spintronic heterostructure has been extensively investigated and its accessories have been also appropriately improved. In this work, a curved substrate of a STE was proposed and utilized to achieve the modulation of the THz wave front as a new degree of freedom. A STE with a neutral-meniscus substrate was designed and fabricated to attain the focusing function of the emitted THz radiation. Coaxial THz bi-focus with a non-overlapping spatio-temporal distribution were effectively generated and applied in multi-plane imaging by properly using two cascade STEs. Amplitude- and phase-type objects consisting of bilayer structures were measured by the scheme. The focused and defocused regions of the samples were distinguished and analyzed on different cross sections. Furthermore, a STE with a spiral stair substrate was manufactured in this way and the generation of a THz vortex beam was fulfilled. The convenient approach offered more possibilities for developing THz optospintronic devices.
Funder
National Natural Science Foundation of China
National Key Research and Development Program of China
Chinesisch-Deutsche Zentrum für Wissenschaftsförderung
Capacity Building for Science & Technology Innovation-Fundamental Scientific Research Funds