Research On The Electromagnetic Stealth Effect Of Femtosecond Plasma Filament Array

The research and application of the interaction between femtosecond plasma filaments and electromagnetic wave has always been one of the important directions in scientific research.Based on the Maxwell equations,the propagation constants and decay constants of the electromagnetic wave propagating in the optical fiber are deduced.The interaction model between the femtosecond plasma filaments array and the electromagnetic wave is established.The finite element software COSMSOL is used to establish the simulation model to study the reflection coefficient,transmission coefficient and absorption coefficient of electromagnetic wave when there is no target and when the target exists,respectively.When there is no target,the influence of femtosecond plasma filaments array on electromagnetic wave only once.The smaller angle between the polarization direction of the electromagnetic wave and the plasma filaments,the greater the influence of the array on the electromagnetic wave.When increasing the electron density,reducing the electron temperature,increasing the diameter of the plasma filaments and reducing the distance of the plasma filaments,the reflection coefficient of the electromagnetic wave increases,and the transmission coefficient decreases.Femtosecond plasma filaments array can absorb the energy of electromagnetic wave,when the skin depth of electromagnetic wave is slightly larger than the diameter of plasma filament,the absorption coefficient is maximum,for example,when the electromagnetic wave frequency is 10 GHz,the plasma filaments diameter is 200 ?m,the distance is 4 mm,and the skin depth is 208 ?m,the maximum absorption coefficient is 0.46.The maximum absorption coefficient is more than 0.45,when diameter of the plasma filaments is 150?m,the frequency of electromagnetic wave is 10GHz,and the projection direction perpendicular to the incident direction is 1.65 mm.With the increase of the number of array layers,the reflection coefficient is almost invariable,the absorption coefficient increases and the transmission coefficient decreases.When the target exists,the electromagnetic wave was reflected and absorbed by the plasma filaments array,transmission wave incident to the target will occur reflection,diffraction,and then the target reflection wave again passed through the femtosecond plasma filaments array and was once again reflected,absorbed,and transmitted.There will be great changes,and eventually only less than 20%of the energy reaches the receiving end.Considering the two conditions,it can be concluded that it is feasible to apply the femtosecond plasma filaments array to the target stealth.By using the femtosecond plasma filaments control technology,one or more plasma filaments array are formed in front of the target and by controlling the parameters of the array,while ensuring that the array has a high absorption coefficient for the radar wave,the electromagnetic wave is reflected in other directions so that the receiving point cannot receive information of target,then the target is stealthy.The above conclusions provide some references for the.military applications of femtosecond plasma filaments array,and the next,we will study the influence of single-layer array structure on the electromagnetic transmission characteristics,and the impact of array structure shielding target on radar echo transmission characteristics.