Effect of polarization on the structure of electromagnetic field and spatiotemporal distribution of $e^+e^-$ pairs by colliding laser pulses

摘要

Electron-positron pair production by means of vacuum polarization in thepresence of strong electromagnetic (EM) field of two counterpropagating laserpulses is studied. A 3-dimensional model of the focused laser pulses based onthe solution of the Maxwell's equations proposed by Narozhny and Fofanov isused to find the structure of EM field of the circularly polarizedcounterpropagating pulses. Analytical calculations show that the electric andmagnetic fields are almost parallel to each other in the focal region whenpulses are completely transverse either in electric (e-wave) or magnetic(h-wave) field. On the other hand the electric and magnetic fields are almostorthogonal when the counterpropagating pulses are made up of equal mixture ofe- and h- polarized waves. It is found that while the latter configuration ofthe colliding pulses has much larger threshold for pair production it canprovide much shorter electron/positron pulses compared to the former case. Thedependence of pair production and its spatiotemporal distribution onpolarization of the laser pulses is analyzed using the structure of the EMfield.