Numerical study on the modulation of THz wave propagation by collisional microplasma photonic crystal

In order to demonstrate the modulation of terahertz wave propagation in atmospheric pressure microplasmas,in this work,the band structure and the transmission characteristics of a onedimensional collisional microplasma photonic crystal are investigated,using the transfer matrix method.For a lattice constant of 150μm and a plasma width of 100μm,three stopbands of microplasma photonic crystal are observed,in a frequency range of 0.1-5 THz.Firstly,an increase in gas pressure leads to a decrease in the central frequency of the stopband.When the gas pressure increases from 50.5 k Pa to 202 k Pa,the transmission coefficient of the THz wave first increases and then decreases at high frequency,where the wave frequency is much greater than both the plasma frequency and the collision frequency.Secondly,it is interesting to find that the central frequency and the bandwidth of the first THz stopband remain almost unchanged for electron densities of less than 10^15 cm^-3,increasing significantly when the electron density increases up to 10^16 cm^-3.A central frequency shift of 110 GHz,and a bandgap broadening of 200 GHz in the first stopband are observed.In addition,an atmospheric pressure microplasma with the electron density of 1×10^15-6×10^15 cm^-3 is recommended for the modulation of THz wave propagation by plasma photonic crystals.