Coherent-interaction effects in the amplification of short optical pulses in neon

Власов Антон Юрьевич

Ivan P. Christov

N. C. Wong

Ашурбеков Назир Ашурбекович, К. О. Иминов, M. B. Kurbangadzhieva +1 more

The interaction of polychromatic radiation of a dye laser with a neon gas-discharge plasma in shielded cylindrical tubes at medium gas pressures (1-30 Torr) near atomic spectral absorption lines of NeI atoms with wavelengths 650.6 and 656.2 nm was experimentally studied. Along the direction of propagation of the laser radiation, a shift in the central frequency of absorption is observed in the presence of inhomogeneities in the plasma column. The character of the optical transmission spectrum near narrow resonances was empirically shown to substantially depend on the density of absorbing atoms in a plasma; if this density exceeds 1012 cm-3, the contour of the transmission spectrum near the absorption resonance acquires a dispersive form. The general laws of the formation of nonstationary plasma transmission spectra depending on the laser power, the density of absorbing atoms, the nature of plasma inhomogeneities along the direction of propagation of laser radiation are examined in detail. The role of nonlinear and coherent effects and phase self-modulation during resonant interaction of short pulses of polychromatic laser radiation with gas-discharge plasma in narrow shielded tubes is discussed.

Andrei I. Maimistov, Yu. M. Sklyarov

Fumihiko Kannari, Minoru Obara

Coherent amplification of short-pulse XeCl lasers is studied theoretically by using multilevel Maxwell–Bloch equations in which the vibrational–rotational structures of a XeCl gain spectrum are included. The model used considers 100 transitions each in the P and R branches for six different vibrational transitions of XeCl(B, υ = 0) → XeCl(X, υ′ = 0–5). Coherence components between sublevels in the B and X states are also properly calculated. The model can successfully predict coherent effects such as a quantum beat caused by the spectrum overlap of the several vibrational–rotational transitions involved in a short-pulse laser spectrum. During amplification, laser pulses experience some nonlinear effects caused by the complex gain spectrum structure and by the coherent interactions; thus a considerable change in the laser pulse shape and a substantial reduction in the duration of the amplified laser pulse are predicted. The Frantz–Nodvik equation in the rate-equation limit and even single-level Maxwell–Bloch equations are not applicable for short-pulse propagation analyses in inhomogeneously broadened gain media.