Effects of laser pulse shape and carrier envelope phase on pair production

For different fields of supercycle and subcycle laser pulses, the effects of laser pulse shape and carrier envelope phase on pair production are investigated by solving quantum Vlasov equation. By changing the pulse width and shape, the nonlinear behaviors of momentum distribution function and number density of created electron-positron pairs are obtained. It is found that there exist the multiphoton processes and stabilization phenomenon in pair production for supercycle situation. Our study may shed a light on optimizing the form of applied laser field to enhance the created pairs number, for example, when other conditions are fixed, the flat-top super-Gaussian laser pulse has advantage on pairs production.