Microsphere-based photoexcited efficient terahertz radiation at room temperature enhanced by Ag/PI/PMMA/ZnO circle hollow waveguide resonance

Abstract

The discovery and development of efficient terahertz sources at room temperature could lead to comprehensive application foreground. Here, ZnO mesocrystal microspheres were prepared by hydrothermal method through self-assembly of nanosheets. High-frequency mechanical vibrations of charged nanostructures excited by a continuous 514.5 nm laser at room temperature can lead to radiative emission at 0.36 THz, conversion efficiency of which was only 0.015%. A sandwich-structured Ag/PI/PMMA/ZnO circle hollow terahertz waveguide was fabricated to obtain high-power terahertz radiation source. Nano Ag thin film effectively localized terahertz light in the waveguide and reduced diffusion losses because of high reflection. Then, Optical lenses were placed before and after the waveguide to form a resonant cavity, so that terahertz light was resonantly enhanced at certain length. Meanwhile, the thickness of the PI thin film was designed to enhance the interference of terahertz light. Besides, the incident angle of green laser had a great influence on its reflection path within the waveguide, which in turn affected the number of excitations of ZnO. The above comprehensive reasons have successfully improved the conversion efficiency by 5.5 and 8.3 times when the angle of incident laser was 0° and 30°, respectively. This work revealed a new strategy to design and fabricate terahertz sources with excellent properties simultaneously such as room temperature operation, stable performance, and high power output.