Abstract-All-dielectric nanograting for increasing terahertz radiation power of photoconductive antennas

Kemeng Wang, Jianqiang Gu, Wenqiao Shi, Youwen An, Yanfeng Li, Zhen Tian, Chunmei Ouyang, Jiaguang Han, and Weili Zhang

. (a) Schematic diagram of the nanograting-assisted PCA. The width of the coplanar line is 20 µm. Schematic diagram of the unit cells of (b) the Gy and (c) the Gx with the corresponding incidence polarizations, respectively, in which p = 350 nm and the height of the unit cell is 200 nm. The areas of the nanograting in (b) and (c) are 80×80 µm2 and 50×80 µm2 respectively. Electric field distribution of (d) the substrate and (e) an optimized unit cell at the working wavelength (λ∼780 nm) when w = 185 nm. The green dashed line represents the envelops of the bare substrate and the nanograting unit cells, respectively. (f) Simulated anti-reflection effect of the nanogratings with varied w = 245, 230, 215, 200, and 185 nm, respectively. The y-axis is the ratio of the reflectance of the nanograting to its reference.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-28-13-19144

Photoconductive antenna (PCA) is a widely used terahertz (THz) radiation source, but its low radiated power limits the signal-to-noise ratio and bandwidth in THz imaging and spectroscopy applications. Here, we achieved significant PCA power enhancement through etching nanograting directly on the surface of the PCA substrate. The integrated nanograting not only maximizes the generation of photocarriers, but also benefits the bias electric field loaded on the photocarriers. Comparing with the conventional PCA, our PCA realizes a frequency independent THz power enhancement of 3.92 times in the range of 0.05-1.6 THz. Our results reported here not only provide a new method for increasing the THz power of PCAs, but also reveal another way that artificial nanostructures affect the PCAs, which paves the way for the subsequent researches of next-generation PCAs.

© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement