Research On Terahertz Modulator Based On Graphene-loaded Metal Wire Grating

Terahertz wave usually refers to the electromagnetic wave in the 0.1-10 THz frequency band.It is in a special position in the electromagnetic spectrum,and its special frequency makes it have a broad application prospect in the field of medical imaging.Compared with the existing medical imaging technology,terahertz imaging technology has many irreplaceable advantages.For example: Its non-ionizing radiation characteristics are safe and non-destructive for medical personnel and examiners,compared with X-ray imaging technology.At the same time,non-contact measurement can also be achieved.Compared with ultrasonic detection technology,terahertz imaging technology has higher resolution(~ 100 ?m),which can determine the edge information of the diseased tissue more clearly.Compared with MRI technology,the terahertz imaging system is small in size,more convenient to operate,lower in cost,and does not use contrast agents.It is not harmful to human health.Most traditional raster-scanned terahertz imaging systems are naturally slow due to the limitation of the imaging mechanism.Most available THz imaging systems can speed up the imaging speed but require expensive detector array.In order to overcome this shortcoming,a terahertz imaging system based on compressed sensing technology is used,where only one detector and one spatial light modulator array are needed to reconstruct the image signal quickly.The key technology of this method is to produce a high-performance terahertz modulator.We report a high-performance terahertz modulator design by exploiting Fabry-Perot cavity coupled to graphene-loaded metal wire grating.In this paper,finite element simulation software(COMSOL)is used to simulate the device performance,and the theoretical formula is used to calculate the reflectivity of the device model.Based on the simulation and theoretical formula results,we have produced asingle-point modulator.Finally,the simulation results,theoretical calculation results and experimental results achieved good agreement.We achieve a modulation depth close to 100% at the resonance frequency in the range of 0.2-1 THz,which is superior to the reported terahertz modulators in both the modulation depth and the number of device operating frequencies.The modulation frequency can also be flexibly adjusted according to the angle of incidence,substrate thickness and refractive index.The research work in this paper has made important contributions to solving the core hardware problems in the terahertz high-speed imaging system based on compressed sensing,and is expected to realize a high-speed imaging technology based on terahertz compressed sensing.