Construction And Application Of Terahertz Air Ionization Coherent Detection System

In recent years,the study of the generation of THz waves by air plasma has attracted much attention.Unlike the traditional THz source,air has no phonon resonance and damage thresholds as THz sources,and has unparalleled advantages in the production of broadband THz waves,and broadens the field of THz absorption spectroscopy's study for explosive materials.In order to study the physical mechanism of THz wave technology generated by air plasma,this paper summarizes the developmen t of narrowband and broadband THz sources.The advantages and disadvantages of THz sources such as air plasma and photoconductive antenna and electro-optic crystal are compared and analyzed.We used the nonlinear four-wave mixing model and the photocurrent model to analyze and concluded that the THz radiation efficiency is correlated with the intensity and optical phase of the two-color laser pulse.The principle of the THz wave radiated by air plasma is elucidated by the macroscopic and microscopic ways.Based on the theoretical analysis and the influencing factors analysis,the coherent detection optical system of THz wave induced by two-color femtosecond laser was designed and successfully constructed.We studied the effect of different focal length lens on the plasma formation and different angle condition of Zn Te on the THz radiation.Finally,the system debug is completed and we obtained a THz wave from tests whose effective bandwidth is 2.0THz.In the application research,we prepared three explosive material samples for RDX,? / ?-HMX to studied THz absorption spectra and obtained the THz characteristic absorption peak between 0.1THz ~ 2.0Thz.Through the experimental data,the absorption spectrum of the explosive sample is mainly consistent with the results of other research teams,which verifies the correctness and feasibility of the terahertz air ionization coherence detection system.