With numerical solution of density matrix motion equations of an open V-type three-level atomic system with spontaneously generated coherence,we analyze transient evolution of gain of lasing without inversion(LWI).It is shown that relative phase(Ф) between probe and driving fields has a significant effect on transient evolution of gain regardless of incoherent pump;Greater transient and steady gains can be obtained by selecting φ;As incoherent pump is absent,longer time is needed to get the greatest transient gain and steady gain.Oscillation amplitude in the evolution process is greater,and gain is also greater;Changing atomic exit rate r₀(ratio of atomic injection rates S) leads to detail of gain transient evolution.In certain range of r₀(S),transient and steady gains increase with S(r₀).

Effects of pulse width on ultrahort laser pulse and spectrum and their carrier-envelope phase(CEP)dependence in a dense V-type three-level atomic medium are investigated with numerical solutions of a full Maxwell-Bloch equation without slowly varying envelope and rotating wave approximations.It is shown that:As pulse width is small,pulse splitting number is less,spectrum is wide,high-frequency part of the spectrum is significant,CEP has great effect on pulse and spectrum,particularly effect on time interval between sub-pulses and strength of high-frequency part is more obvious;As pulse width increasing,pulse splitting number increases,width of spectrum narrows and high-frequency part of the spectrum decreases gradually,effect of CEP on pulse and spectrum weakens gradually.

In one-photon resonance and detuning cases,effect of relative carrier-envelope phase(RCEP) on evolution of two-color sech-type femtosecond pulses and spectrum in a dense V-type three-level atomic medium is investigated with full Maxwell-Bloch equations.Modulation of RCEP on pulse shape and spectral property of two-color pulses in detuning case is more evident than that in single-photon resonance case.And in detuning case we get spectrum broadening much greater than that in resonance case.Supercontinuum with the highest frequency of 18 times of incident frequency appears.

A volume weighting CIC method is developed to compute the node charges and currents in PIC simulation of axial symmetrical plasmas.A set of formulae for computing the node charges and currents is derived.The results given here can be applied to 2(1/2) dimensional electrostatic and electromagnetic PIC simulation of axial symmetrical plasmas.