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

Spatial modulation of terahertz waves 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 modulators. 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. Through a comparison test, it is found that gold nanoparticle coated small silicon arrays have improved contrast and resolution for terahertz imaging over the uncoated and coated large pieces of silicon, respectively.