Abstract-Semiconductor terahertz spatial modulators with high modulation depth and resolution for imaging applications

Tianlong Wen, Jing Tong, Dai-nan Zhang, Yunqiao Zhu, Qi-Ye Wen, Yuanpeng Li, Huai-Wu Zhang, Yu-Lan Jing,  Zhi-Yong Zhong

https://iopscience.iop.org/article/10.1088/1361-6463/ab146d/pdf

Spatial modulation of terahertz wave enabled by the charge carrier generation-recombination dynamics in semiconductor is promising for terahertz compressive sensing imaging since the modulation is broadband, low-loss and of enough speed (tens of thousands of Hertz). However their performance in terahertz compressive sensing imaging is significantly limited by their inferior modulation depth and resolution. Here silicon was cut into small pieces and packed closely in arrays to shut off the charge carrier diffusion between them and increase the resolution of the terahertz spatial modulator. A monolayer of gold nanoparticles was coated on the silicon surface to enhance the terahertz modulation depth through the enhanced generation of charge carriers by surface plasma. By comparison test, it is found that the gold nanoparticle coated small silicon arrays have improved contrast and resolution for terahertz imaging over the uncoated and coated large pieces of silicon respectively.

Abstract-Semiconductor terahertz modulator arrays: the size and edge effect

Tianlong Wen, Chong Zhang, Xiaochen Zhang, Yulong Liao, Quanjun Xiang, Qiye Wen, Dainan Zhang, Yuanpeng Li, Huaiwu Zhang, Yulan Jing, and Zhiyong Zhong

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-43-13-3021

A terahertz spatial modulator is the critical component for active terahertz imaging using compressive sensing. Here small silicon pieces were put in arrays on flexible polymer substrate to fabricate semiconductor terahertz spatial modulators. By doing this, the inter-diffusion of photo-generated charge carriers is prevented for better resolution, and flexibility is achieved. Since the size of silicon is comparable to the wavelength of the terahertz wave, and the dielectric properties of the gap are very different from silicon, the optical modulation of each element is very different from the large silicon. In this Letter, the terahertz wave interaction and optical modulation of the small silicon are systematically studied by time domain spectroscopy. Notably, a strong resonance-like absorption peak was observed in a transmittance spectrum for the small silicon due to the size and edge effect. The spatial modulation of the terahertz wave was also compared between the silicon array and the large silicon samples.

© 2018 Optical Society of America

Abstract-Enhanced Optical Modulation Depth of Terahertz Waves by Self-Assembled Monolayer of Plasmonic Gold Nanoparticles

http://onlinelibrary.wiley.com/doi/10.1002/adom.201600248/abstract

Ultra-large-area self-assembled mono­layers of gold nanoparticles are coated on the intrinsic silicon to boost the generation of electron–hole pairs upon laser illumination. As a result, larger optical modulation depth of terahertz wave can be obtained by the monolayer coated silicon in comparison with the bare silicon.