Accelerating terahertz all-optical modulation by hot carriers effects of silver nanorods in PVA film

While the terahertz regime has proved to be a promising solution for wireless big-data transmission, the lack of available functional devices working in this band seriously constrain the wide engineering applications. In this paper, the silver nanorods in polyvinyl alcohol (PVA) film are developed for enhancing and accelerating THz all-optical modulation. The modulation depth can reach 80% under 0.6W/cm², and the speed can reach 3kHz which is much faster than our previous research. It has been attributed to the plasmonic hot carriers' effect of the silver nanorods, which makes the photoexcited electrons more easily jump out of the barrier and assemble in the heterostructure between PVA and silicon. Moreover, the photoelectronic response is proved to be related to the plasmonic absorption of the pumping light, which means the modulation speed is decided by the color of the pump light. This experiment phenomenon provides a way to build color-selective terahertz all-optical modulators. Considering its capability for broadband, efficient, and fast modulation of THz waves, this low-cost and conveniently fabricated device could be broadly applied in polymer related THz devices.