Control Technology Of Terahertz Wave In Silicon Nanowires

T-rays is becoming a hotspot in high-tech fields and has become a favorable tool for human to perceive the material world,while the related generation,emission,reception,detection and control equipment have made great progress.The research on the regulation technology of T-rays is the basis and premise of using this tool.The terahertz(THz)band,with the characteristic of non-ionizing,non-destructive,has a photon energy of 1-100 meV under UV light,which is insufficient to ionize the substance.These features have led to the rapid development and widespread use of T-rays technology from basic science such as biochemical spectroscopy,astronomy and nanomaterial science to environmental science,health care,agriculture and safety.Among them,THz imaging is the most potential and the most commercial application areas of T-rays technology.In the THz imaging system,the spatial terahertz modulator affects the image quality and imaging rate to a large extent,but the lack of related materials is a key factor affecting its performance.In this paper,the silicon nanowires(SiNW),which have good anti-reflective properties in the visible wavelength band,are researched to study their interaction with T-rays and the ability to control T-rays under the motivation of laser.The time domain spectrum of high-resistivity silicon(HR-Si)and SiNW with different length was tested by THz time domain spectroscopy system.It was proved that SiNW had an increasing transmittance on T-rays,and the enhancement effect was proportional to the length of SiNW.The modulation effect of 2.5?m SiNW was the best under the motivation of 915 nm laser,and the modulation effect of 1?m SiNW was the best under the action of 808 nm laser with the change of transmittance from 70% when no laser was added to smaller than 10%,according to the frequency domain spectrum and the transmittance spectrum.Secondly,the THz wave transmission spectrum of HR-Si and SiNW at 0.34 THz was measured on the continuous THz spectrum test platform.Under the motivation of 915 nm laser,the maximum modulation depth is MD5?m=38.8% at the laser power of 900mW;while for 808 nm laser,the maximum modulation depth is MD2.5?m=53.7% at the power of 900 mW.Under the same laser power,the modulation effect of 808 nm laser is more obvious.Based on the analysis of the relationship between the modulation depth and the length of SiNW,it is considered that the distribution of the photodoping carriers on the different lengths of SiNW is the determinant of the nonlinear relationship.Finally,the monolayer and nine-layer films were established for SiNW.The reflectance of different films was compared with the experimental data of reflectance.It was found that the calculated reflectance of nine-layer film system by the transmission matrix theory is more consistent with the experimental results.