Analytical Study of Sub Terahertz Radiation from Ultrashort Laser Pulse Propagation Streamers
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AIR FORCE RESEARCH LAB KIRTLAND AFB NM DIRECTED ENERGY DIRECTORATE
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A numerical calculation based on Maxwells equations was made to examine the details of this process. The numerical calculation proceeded from Maxwells Curl equations and included the treatment of the of the polarization current by means of a non-linear oscillator model. The oscillator is linear for small displacements but becomes non-linear for large fields where the Kerr Effect is important. The oscillator equations of motion determine a non-linear polarization current that is included as a source term in the Maxwells equation simulation This simulation determines the time dependant dipole moment density of the ionization charge distribution These dipole moments can then be integrated to find the near field and radiation field components of the fields from the standard integrals. The details of these results also show a lower frequency component of the field, but it is still an optical frequency about a factor of 10 lower than the laser frequency. The results do not show the sub terahertz radiation reported in the literature. An interpretation of this is that the measured fields must be very small, coming from second order effects not included.
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