Communication And Imaging System Based On Spatial Light-operated Terahertz Modulator

In recent years,Terahertz(THz),known as the “revolution of frontier technology in this century”has become a hot topic of research.Especially,terahertz communication and imaging are the most important parts in the research and application of terahertz technology.Compared with the microwave and millimeter wave,the carrier frequency of THz is higher.As the wireless communication bandwidth requirements of people grow exponentially,terahertz communication will become the key research project of high-speed short distance communication and out space communication.Because terahertz radiation has lots of unique properties,There are broad application prospects of terahertz imaging technology in environmental monitoring,medical diagnosis,non-destructive testing,safety testing and military radar.Especially,in counter-terrorism and security field terahertz imaging technology currently has become one of the most popular cutting-edge technology.At the present stage,terahertz communication is mainly based on the existing microwave communication technology for signal processing,frequency multiplication or through direct control of terahertz source to produce THz wave modulation of which amplitude,phase,frequency is controllable.Terahertz Imaging is mainly based on coherent imaging technology,such as THz time-domain spectroscopy.A communication and imaging system which is based on a set of space type terahertz optical modulators is built in this paper.Different from the way of communication and coherent imaging stated above,the system can be used to modulate the terahertz wave directly in space,so as to realize the spatial direct modulation of terahertz communication and coherent THz continuous wave imaging.Firstly,this paper studies a kind of terahertz space-direct and light-operated amplitude modulator nano based on silicon needles structure.We found that compared to silicon semiconductor the micro nano structures have obvious antireflection effect on the terahertz wave.It can greatly reduce the insertion loss of terahertz.Its transmittance exceeds 85%.We study on black silicon material,made the space-direct and light-operated terahertz modulator of which the modulation depth is above 80%,almost can be “turned off” in static.Then,in the aspect of terahertz communication.The paper uses Labviewprogramming to control the data acquisition board to realizes the A/D signals conversion,the baseband signals generation and reception in the communication process.2ASK scheme is used for modulation and demodulation in communication.In order to improve the anti-jamming ability of communication,Labview is used to realize the codec of signal.The 2ASK modulation and demodulation scheme is adopted to realize a set of terahertz short-range wireless communication system.In order to realize the real-time voice communication,the system has expanded the automatic acquisition,automatic transmission and automatic playing program.In terahertz imaging aspect,this paper builds a terahertz continuous wave scanning imaging system based on the THz communication system.On the found of spatial light modulator,this paper presents a light-operated spatial terahertz amplitude modulator which is based on black silicon.It can control the regulation of distribution of terahertz waves in space,realise the terahertz rapid scanning in space,and acquire the intensity information of terahertz wave.Matlab is used to convert the THz intensity information into images.In the end,a system which can realize the function of THz communication and imaging is set up by sharing common equipments and instruments.The communication function of the system is verified by the transmission of text,pictures and speech signals,and the THz imaging experiments are carried out successfully.