  We report on the investigation on harmonic-seeded remote laser emissions at
391 nm wavelength from strong-field ionized nitrogen molecules in three
different gas mixtures, i.e., N2-Ar, N2-Xe and N2-Ne. We observed a decrease in
the remote laser intensity in the N2-Xe mixture because of the decreased
clamped intensity in the filament; whereas in the N2-Ne mixture, the remote
laser intensity slightly increases because of the increased clamped intensity
within the filament. Remarkably, although the clamped intensity in the filament
remains nearly unchanged in the N2-Ar mixture because of the similar ionization
potentials of N2 and Ar, a significant enhancement of the lasing emission is
realized in the N2-Ar mixture. The enhancement is attributed to the stronger
third harmonic seed, and longer gain medium due to the extended filament.
