1. Terahertz generation by the beating of two laser beams in collisional plasmas Ram Kishor Singh and R. P. Sharma Centre for Energy Studies, Indian Institute of Technology Delhi, India Terahertz generation by the beating of two laser beams in collisional plasmas Ram Kishor Singh and R. P. Sharma Centre for Energy Studies, Indian Institute of Technology Delhi, India... The wave equations for the laser beams can be written as Considering the solution as follows The spatial profile of intensity distribution of laser beams can be written as, The dielectric function can be written as, In the steady state: the thermal pressure induced by the laser beams is balanced by the space charge force. From the equation of motion The energy balance equation The electron temperature at beat wave frequency The THz wave propagation equation The nonlinear current density THz amplitude variation with respect to propagation direction From the equation of motion The energy balance equation The electron temperature at beat wave frequency The THz wave propagation equation The nonlinear current density THz amplitude variation with respect to propagation direction,,,, Abstract The role of two cross-focused spatial-Gaussian laser beams has been studied for the high power and efficient terahertz (THz) radiation generation in the collisional plasma. The nonlinear current at THz frequency arises on account of temperature dependent collision frequency of electrons with ions in the plasma and the presence of a static electric field (applied externally in the plasma) and density ripple. Optimisation of laser-plasma parameters gives the radiated THz power of the order of Abstract The role of two cross-focused spatial-Gaussian laser beams has been studied for the high power and efficient terahertz (THz) radiation generation in the collisional plasma. The nonlinear current at THz frequency arises on account of temperature dependent collision frequency of electrons with ions in the plasma and the presence of a static electric field (applied externally in the plasma) and density ripple. Optimisation of laser-plasma parameters gives the radiated THz power of the order of Conclusions:  The cross focused laser beams in collisional plasmas are able to enhance the generation of THz radiation in the presence of external transverse static electric field.  The maximum amplitude of THz radiation generation can be achieved by the suitable phase matching condition with the employment of ripple density.  Amplitude of the generated THz radiation increased by factor of two to three in the case of cross-focusing of two Gaussian beams as compared to the case without cross-focusing. Acknowledgement: University Grant Commission (UGC), India. Conclusions:  The cross focused laser beams in collisional plasmas are able to enhance the generation of THz radiation in the presence of external transverse static electric field.  The maximum amplitude of THz radiation generation can be achieved by the suitable phase matching condition with the employment of ripple density.  Amplitude of the generated THz radiation increased by factor of two to three in the case of cross-focusing of two Gaussian beams as compared to the case without cross-focusing. Acknowledgement: University Grant Commission (UGC), India. References:  R. P. Sharma and R. K. Singh, Phys. Plasmas, 21, 073101 (2014).  A. Houard, Y. Liu, B. Prade, V. T. Tikhonchuk, and A. Mysyrowicz, Phys. Rev. Lett., 100, 255006 (2008).  M. S. Sodha, A. K. Ghatak, and V. K. Tripathi, Prog. Opt., 13, 169 (1976)  S. A. Akhmanov, A. P. Sukhorukov, and R. V. Khokhlov, Sov. Phys. Usp., 10, 609(1968).