Generation of Terahertz Radiation under Interaction of Counterpropagating Laser Pulses in Underdense Plasma

Abstract

Generation of terahertz waves under interaction of two counterpropagating laser pulses with different frequencies in underdense plasma is analyzed. Spectral, angular, and energy characteristics of terahertz radiation are investigated as functions of the frequency difference of the laser pulses. It is shown that, due to the frequency difference, in addition to the line at the doubled plasma frequency [L.M. Gorbunov, A.A. Frolov, JETP 98, 527 (2004)], a peak near the plasma frequency appears in the emission spectrum. The total energy of the terahertz signal is calculated, and the condition under which emission at the plasma frequency dominates is found. It is shown that the energy of radiation at the plasma frequency reaches its maximum value when the frequency difference of the laser pulses is close to the plasma frequency.