;The preparation of gain medium is extremely important for the study of superfluorescence, that is, different initial conditions will lead to different superfluorescence behavior. The theoretical studies of superfluorescence from the 1970s to 1980s were based on a transversely homogeneous pump or swept-gain pump for the latter an unrealistic δ function conventionally used to describe the ultrashort pump laser pulse. With the development of femtosecond laser technology in recent years, femtosecond laser pulses are used to prepare the gain medium and to generate superfluorescence. Along this line, there are at least two interesting topics: (1) Using X-ray free-electron laser to generate a light source of different wavelengths in noble gas through Raman scattering; (2) Studying Nitrogen-based laser and its origin of population inversion. This article explores the use of femtosecond laser to produce the swept-gain medium in the two systems described above to generate superfluorescence, as well as, the manipulation of the behavior of superfluorescence by the different laser and medium parameters. Through analysis, we find that compared with the conventional δ function used in the past studies, the duration of the femtosecond pulse has a significant effect on the efficiency of the gain medium and the propagation behavior of forward and backward superfluorescence. In the nitrogen laser, we successfully simulated the experimental results of the two-pulse experiments and finally proposed a method to verify the population inversion.
