| Terahertz(THz)has a unique spectral location and electromagnetic characteristics.At present,the difficulties and research hotspots of terahertz technology mainly focused on the fields of sources,detectors,and functional devices.As for functional devices,many commonly used devices with high performance for the microwave or optical field are no longer suitable in the terahertz field.Therefore,the preparation of low-cost and high-performance functional devices is a key point in the practical process of THz technology.The discovery and application of metasurface provide an effective method for the fabrication of terahertz functional devices.Here,this work focuses on the requirements of high-performance THz functional devices.We combine low-cost novel nanomaterials and classical semiconductor with metasurface to design multifunctional tunable devices,including terahertz frequency and amplitude modulator,terahertz slow light devices based on plasmon-induced transparency.Furthermore,the deep learning neural network is used to design the metasurface structure.The main content and innovation points are as follows:1.Terahertz frequency and amplitude modulation devices and plasmon-induced transparency modulation devices were fabricated by combining nanocrystals with traditional metal metamaterials.The first work combines the core-shell Cd Se/Cd S quantum rods with the coupled SRRs metasurface,achieving the effective modulation of the resonance frequency and transmittance amplitude of the metasurface.In the second work,Cs Pb Br3 quantum dots were combined with plasmon-induced transparency metasurface to realize the optical control of the transparent window.The experimental results show that the normalized modulation depth of the transparent window can reach 74%.At the same time,it has better phase advance and group delay characteristics.This device can be used as an efficient slow light device in terahertz communication and modulation fields.The combination of nanomaterials and metasurfaces provides an effective method for the dynamic modulation of terahertz metasurface devices.2.Two types of multifunctional metasurfaces are designed.The one demonstrates a dual-mode controllable terahertz metasurface based on complementary plasmon-induced reflection structure.Both photosensitive silicon and monolayer graphene are integrated into the unit cell to realize the active control of the EIT-like reflection window and the whole resonance,modulated by optical pumping and extra electrical voltage,respectively.The excellent properties of the modulation depth and the group delay highlight these metasurfaces in the applications of terahertz modulators and slow light devices.The other combines the vanadium dioxide phase change material with the metasurface,achieving the flexibly switch between narrowband absorption and slow light modulation.The design of multifunctional metasurface provides a good way for the preparation of compact multifunctional control devices,which can enhance the practicability of terahertz modulation devices.3.Deep learning neural network is used to realize the fast,efficient and intelligent design of high Q metasurface sensors.This work builds a neural network based on the deep learning method.By using the transmission spectrum of the Fano structure as the input sample,the neural network can be trained to correlate the metasurface structure parameters with the electromagnetic resonance characteristics of the Fano structure.The relationship between the parameters of the metasurface structure and its electromagnetic response characteristics can be excavated by the trained neural network,and the structure of the terahertz sensor with both high Q and sensitivity can be obtained. |
