[1] BRAUN A, KORN G, LIU X, et al. Self-channeling of high peak power femtosecond laser pulses in air［J］. Optics Letters, 1995, 20(1): 73-75.

[2] XU H L, CHENG Y, CHIN S L, et al. Femtosecond laser ionization and fragmentation of molecules for environmental sensing［J］. Laser & Photonics Reviews, 2015, 9(3): 275-293.

[3] HOU M Y, WANG S Q, YAO D W, et al. Effects of pulse duration and polarization on femtosecond filament-induced fluorescence of combustion intermediates［J］. Chinese Journal of Lasers, 2019, 46(5): 0508024(in Chinese).

[4] LIU Y, DING P J, IBRAKOVIC N, et al. Unexpected sensitivity of nitrogen ions superradiant emission on pump laser wavelength and duration［J］. Physical Review Letters, 2017, 119(20): 203205.

[5] XU H L, LTSTEDT E, IWASAKI A, et al. Sub-10-fs population inversion in N2+ in air lasing through multiple state coupling［J］. Nature Communications, 2015, 6(1): 8347.

[6] LI H L, HOU M Y, ZANG H W, et al. Significant enhancement of N2+ lasing by polarization-modulated ultrashort laser pulses［J］. Physical Review Letters, 2019, 122(1): 013202.

[7] FU Y, LTSTEDT E, LI H L, et al. Optimization of N2+ lasing through population depletion in the X2Σg+ state using elliptically mo-dulated ultrashort intense laser fields［J］. Physical Review Research, 2020, 2(1): 012007.

[8] AZARM A, CORKUM P, POLYNKIN P. Optical gain in rotationally excited nitrogen molecular ions［J］. Physical Review, 2017, A96(5): 051401.

[9] LI G H, JING Ch R, ZENG B, et al. Signature of superradiance from a nitrogen-gas plasma channel produced by strong-field ionization［J］. Physical Review, 2014, A89(3): 033833.

[10] CHEN J M, YAO J P, ZHANG Zh H, et al. Electronic quantum coherence encoded in temporal structures of N2+ lasing［J］. Physical Review, 2021, A103(3): 033105.

[11] KELDYSH L V. Ionization in the field of a strong electromagnetic wave［J］. Soviet Physics JETP, 1965, 20(5): 1307-1314.

[12] BRODEUR A, CHIEN C Y, ILKOV F A, et al. Moving focus in the propagation of ultrashort laser pulses in air［J］. Optics Letters, 1997, 20(5): 304-306.

[13] MITRYUKOVSKIY S, LIU Y, DING P J, et al. Plasma luminescence from femtosecond filaments in air: Evidence for impact excitation with circularly polarized light pulses［J］. Physical Review Le-tters, 2015, 114(6): 063003.

[14] WANG Q J, ZHANG Y H, WANG Zh H, et al. Control of molecular excitation during the plasma generation of a femtosecond laser pulse［J］. Chinese Optics Letters, 2016,14(11): 110201.

[15] ITIKAWA Y. Cross sections for electron collisions with nitrogen mo-lecules［J］. Journal of Physical and Chemical Reference Data, 2006, 35(1): 31-53.

[16] BECKER A, BANDRAUK A D, CHIN S L. S-matrix analysis of non-resonant multiphoton ionisation of inner-valence electrons of the nitrogen molecule［J］. Chemical Physics Letters, 2001, 343(3/4): 345-350.

[17] COUAIRON A, MYSYROWICZ A. Femtosecond filamentation in transparent media［J］. Physics Reports, 2007, 441(2/4): 47-189.

[18] MARBURGER J H. Self-focusing: Theory［J］. Progress in Quantum Electronics, 1975, 4(1): 35-110.

[19] LI S Y, JIN M X. Group velocity dispersion effect on the collapse of femtosecond laser pulses in air : A revised form for Marburger’s law［J］. Chinese Optics Letters, 2015, 13(12): 121901.

[20] HAN S Q, SHEN B, XIONG G, et al. Detection and analysis of photoacoustic signal from gas plasma［J］. Laser & Infrared, 2017,47(4): 428-431(in Chinese).

[21] HAO Z Q. Filamentation nonlinear optics of intense femtosecond laser pulses in air［D］. Beijing: Graduate University of Chinese Academy of Sciences(Institute of Physics CAS), 2007: 31-47(in Chin-ese).