Abstract
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.
Highlights
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
All the applications depend on the vivid development of the THz components, where tremendous progress has been made on sources and detectors[10,11,12,13] and there is an urgent need for functional devices, such as modulators,[14–17] lens,[18] isolators[19] and polarizers[20,21] for building complex THz apparatus system
The silver nano-rods were synthetized in the polyvinyl alcohol (PVA) film on top of the silicon substrate in the following steps. 2g PVA powders were added into 25 ml deionized water and the mixed solution was heated at 60 degrees centigrade in a water bath with magnetic stirring
Summary
Terahertz (THz) technology plays more and more important roles in our modern life: security apparatus based on millimeter waves in airports,[1] imaging or spectrum system for physical,[2] chemical and biomedical detection,[3,4,5,6,7] THz communication system for big-data transmission.[8,9] All the applications depend on the vivid development of the THz components, where tremendous progress has been made on sources and detectors[10,11,12,13] and there is an urgent need for functional devices, such as modulators,[14–17] lens,[18] isolators[19] and polarizers[20,21] for building complex THz apparatus system. With the purpose to achieve both low insertion loss and large modulation depth, the conductivity needs be a lower value at the primary state and higher value at the modulation state, which requires a huge dynamic electronic response Intrinsic semiconductors, such as silicon and GaAs, have low electronic conductivity and play an important role in THz artificial microstructure devices.[23–25]. Plasmonics[26] and metamaterials[27] have been introduced to enhance the interaction between the electromagnetic waves and materials.[28,29] Metamaterial-based modulator[30–32] was reported to achieve a large modulation and quick response due to its ability on slowing down
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