Optically Tunable THz Modulator Based On Nanostructures On Silicon Substrate

In recent years,Terahertz(THz)Technology,known as the "revolution of frontier technology in this century ",is widely used in communication,spectroscopy,medical imaging,security inspection and other fields.The backward technology of terahertz modulator limits the development and application of Terahertz Technology.In this paper,an efficient optically tunable terahertz modulator is proposed,which can effectively improve the modulation depth of terahertz modulator at low power.Nanostructures can induce light multireflection,enabling strong light absorption and efficient photocarrier generation.In this paper,we propose an optically tunable THz modulator based on nanostructures on silicon substrate,which includes nanocylinder,nanotip and nanohole structures.Compared with the terahertz modulator based on bare silicon,the optically tunable THz modulator based on nanostructures on silicon substrate has significantly higher terahertz modulation efficiency.1?The nanotip structure based on silicon was etched by acid etching,and then an optically tunable THz modulator was prepared by transferring the graphene.The characterization and test results show that the modulation depth increases with the increase of the pumping power,the modulation depth increases with the increase of the etching time of the nanotip structure,and graphene has a significant effect on the modulation depth of terahertz.Under the 808 nm illumination light of 1200 m W pumping power,the 10 minute etching depth of nanotip structure + graphene modulator can reach a modulation depth of91.63%.The modulation ability is very significant and the modulation effect is excellent.2?We build the model of nanocylinder,nanotip and nanohole structures,and carry out the simulation experiment of THz modulation depth.The simulation results show that under the same conditions,the nanostructure with higher light absorption has a greater THz modulation depth than the bare silicon,and the 808 nm pump beam can obtain a higher THz modulation depth than the 532 nm pump beam.Under the illumination of 808 nm pump beam,when the pumping power is 60mw/mm2,the THz modulation depth of the nanotip structure modulator is 91.63% at 2THz,which has the best THz modulation effect in all models.However,under a shorter wavelength of pump beam(532nm),the modulation performance of THz wave in all models decreases,and the best modulation performance appears in the nanohole structure modulator.3?In order to understand the influence of nanostructures on THz wave,a graded index layer model was established to study the antireflection effect of different nanostructures on THz wave.With a height of 5 ?m,the THz wave reflectivity of nanocylinder,nanotip and nanohole structures are 26.22%,21.04% and 0.63% at 2THz respectively,which are mutual verification with simulation results.The work of this paper may provide a further experimental and theoretical guide for the design of optically tunable THz modulators.