Generation of few-cycle laser pulses: Comparison between atomic and molecular gases in a hollow-core fiber

National Natural Science Foundation of China [11204328, 61221064, 61078037, 11127901, 11134010, 61205208]; National Basic Research Program of China [2011CB808101]; Natural Science Foundation of Shanghai, China [13ZR1414800]We numerically study the pulse compression approaches based on atomic or molecular gases in a hollow-core fiber. From the perspective of self-phase modulation (SPM), we give the extensive study of the SPM influence on a probe pulse with molecular phase modulation (MPM) effect. By comparing the two compression methods, we summarize their advantages and drawbacks to obtain the few-cycle pulses with micro- or millijoule energies. It is also shown that the double pump-probe approach can be used as a tunable dual-color source by adjusting the time delay between pump and probe pulses to proper values