Pavel Polykin is an Associate Research Professor of Optical Sciences at the University of Arizona in Tucson. He received his PhD degree from Texas A&M University in 2000. His current research interests lie in the fields of femtosecond laser science and ultra-intense nonlinear optics. He has co-authored over 60 peer-reviewed research articles, holds 11 US patents, and has delivered numerous invited talks at international conferences on laser physics and optics.Ya Cheng is a professor at the Shanghai Institute of Optics and Fine Mechanics (SIOM), Chinese Academy of Sciences, and the deputy director of the State Key Laboratory of High Field Laser Physics, SIOM. He received his B.S. degree from Fudan University in 1993, and Ph.D degree from SIOM in 1998. Since 1995, he has been working in the ultrafast photonics related fields. His current research interests include femtosecond laser micromachining, ultrafast nonlinear optics, and strong field laser physics. He has published morethan 100 papers in peer-reviewed journals, and given more than 100 invited talks at international conferences.

• Preface.- 1 Diagnostic properties of two-photon pumped stimulated emission in atmospheric species.- 2 High-gain air lasing by multi-photon pumping of atomic species.- 3 The role of electron collisions in lasing in neutral and singly ionized molecular nitrogen.- 4 Molecular rotational effects in free-space N_2^+ lasers induced by strong-field ionization.- 5 Filament-initiated lasing in neutral molecular nitrogen.- 6 Filament-assisted impulsive Raman spectroscopy.- Index.

Pavel Polykin is an Associate Research Professor of Optical Sciences at the University of Arizona in Tucson. He received his PhD degree from Texas A&M University in 2000. His current research interests lie in the fields of femtosecond laser science and ultra-intense nonlinear optics. He has co-authored over 60 peer-reviewed research articles, holds 11 US patents, and has delivered numerous invited talks at international conferences on laser physics and optics.Ya Cheng is a professor at the Shanghai Institute of Optics and Fine Mechanics (SIOM), Chinese Academy of Sciences, and the deputy director of the State Key Laboratory of High Field Laser Physics, SIOM. He received his B.S. degree from Fudan University in 1993, and Ph.D degree from SIOM in 1998. Since 1995, he has been working in the ultrafast photonics related fields. His current research interests include femtosecond laser micromachining, ultrafast nonlinear optics, and strong field laser physics. He has published morethan 100 papers in peer-reviewed journals, and given more than 100 invited talks at international conferences.

• Preface.- 1 Diagnostic properties of two-photon pumped stimulated emission in atmospheric species.- 2 High-gain air lasing by multi-photon pumping of atomic species.- 3 The role of electron collisions in lasing in neutral and singly ionized molecular nitrogen.- 4 Molecular rotational effects in free-space N_2^+ lasers induced by strong-field ionization.- 5 Filament-initiated lasing in neutral molecular nitrogen.- 6 Filament-assisted impulsive Raman spectroscopy.- Index.

Pavel Polykin is an Associate Research Professor of Optical Sciences at the University of Arizona in Tucson. He received his PhD degree from Texas A&M University in 2000. His current research interests lie in the fields of femtosecond laser science and ultra-intense nonlinear optics. He has co-authored over 60 peer-reviewed research articles, holds 11 US patents, and has delivered numerous invited talks at international conferences on laser physics and optics.Ya Cheng is a professor at the Shanghai Institute of Optics and Fine Mechanics (SIOM), Chinese Academy of Sciences, and the deputy director of the State Key Laboratory of High Field Laser Physics, SIOM. He received his B.S. degree from Fudan University in 1993, and Ph.D degree from SIOM in 1998. Since 1995, he has been working in the ultrafast photonics related fields. His current research interests include femtosecond laser micromachining, ultrafast nonlinear optics, and strong field laser physics. He has published morethan 100 papers in peer-reviewed journals, and given more than 100 invited talks at international conferences.

• Preface.- 1 Diagnostic properties of two-photon pumped stimulated emission in atmospheric species.- 2 High-gain air lasing by multi-photon pumping of atomic species.- 3 The role of electron collisions in lasing in neutral and singly ionized molecular nitrogen.- 4 Molecular rotational effects in free-space N_2^+ lasers induced by strong-field ionization.- 5 Filament-initiated lasing in neutral molecular nitrogen.- 6 Filament-assisted impulsive Raman spectroscopy.- Index.