Research On Optically Controlled Terahertz Modulation Technology Based On Silicon-based Micro-nano Mixed Structures

Terahertz(THz)is an electromagnetic wave band which has not been fully developed.Because of its unique properties and good application prospects,people pay more and more attention to it.THz wave has high frequency and low photon energy,which makes it very useful in communication,medical imaging,biological security,environmental detection and other fields.In recent years,the key technologies of THz emitter and THz detection sensor have been solved,but at the same time,it must be seen that THz-related absorbers,switches,resonators,filters,antennas,modulators and other intermediate devices are still in the research stage.Among them,the THz modulator used in THz communication and THz imaging system is an urgent need to be solved in the research of THz related fields.The problem.In this paper,a THz light-controlled modulator based on silicon micro-nano hybrid structure is proposed.The modulation performance of THz wave under laser irradiation is studied.Silicon-based micro-nano hybrid structure is composed of silicon-based microstructure and silicon nanowires.It has the characteristics of anti-reflection and antireflection of THz wave by silicon-based micro-structure and visible light reduction by silicon nanowires.In the absence of laser,the transmission of THz wave by silicon micronano hybrid structure remains above 75% in the frequency range of 0.4 THz~0.85 THz,up to 85%,which is much higher than that of ordinary high resistance silicon(67%).The reflectivity of visible light band of silicon micro-nano hybrid structure is less than 20%,showing good reflectivity reduction characteristics.The research of silicon micro-nano hybrid structure under 808 nm laser irradiation is carried out.For THz modulation performance,the maximum modulation depth of silicon micro-nano hybrid structure is 42.5% under 1200 mW laser irradiation.At the same time,by comparing the visible light reflectance curves of different sample modulation depth and different length of silicon nanowire samples under the same laser intensity,it is verified that the modulation depth is negatively correlated with visible light reflectance;at the same time,the silicon micronano hybrid junction under 808 nm laser irradiation.The THz spatial modulation performance of the structure is theoretically analyzed and experimentally validated,which proves that the silicon micro-nano hybrid structure can inhibit carrier diffusion and improve THz imaging resolution during THz modulation.Finally,the visible-THz dualband absorber is fabricated based on the silicon micro-nano hybrid structure.The first absorber was prepared by growing the Au layer from the silicon-based micro-nano hybrid structure.The stable absorption bandwidth of the terahertz wave is 0.66 THz,with an absorption rate of more than 74% for the terahertz wave in the frequency range of 0.26 THz~0.92 THz,and 84.5% of the absorption peak at the frequency of 0.75 THz;the second absorber is based on the silicon-based microstructure The doped low-resistance silicon layer has a stable absorption bandwidth of 0.74 THz for the terahertz wave,an absorption ratio of more than 35.2% in the frequency range of 0.16 THz to 0.90 THz,and an absorption peak value of 40.1% at 0.69 THz..