Transverse pattern morphogenesis in a CO_2 laser

Abstract

Irregular and nonrepetitive transverse intensity distributions were measured in the near field during the gain-switch pulse (60-ns width) of a transversely excited atmospheric CO(2) laser. Transverse patterns are regular and repetitive in the long-pulse (1-micros width) mode and in ensemble average in the short-pulse mode, and in both cases symmetry is imposed by the boundary conditions. Short-pulse transverse patterns formed by lasing domains appear with a mean size of 0.8 mm. The prediction of domain size based on a model of population inversion filamentation agrees with the experimental result.

Transverse Patterns in Nonlinear Optical Resonators

“…The predicted laser TW patterns have been observed in experiments with large-Fresnel-number cavities [126][127][128]. The TW solutions are also found in passive resonators described by the same order parameter equation, such as nondegenerate optical parametric oscillators (OPOs) [35,129].…”

Probabilistic approach to pattern selection

“…Especially accurate and thorough experimental studies for CO 2 and Dye lasers have been accomplished in Refs. [25][26][27][28][29][30]. The independence of turbulent optical filamentation of boundary conditions and, hence, its purely self-organized nature are confirmed by the observation of this effect in the resonatorless discharge-tube superluminescent samples, such as lasers on Ne, Tl, Pb, N 2 , and N + 2 vapors [31][32][33][34][35].…”

“…Contrary to the regime of small F , when the regular spatial structures are prescribed by the geometry and boundary conditions imposing their symmetry constraints, the turbulent optical filamentation is strictly self-organized, with its organization emerging from intrinsic properties of the medium [20,24]. This kind of optical turbulence has been observed in both photorefractive crystals [18][19][20] and lasers [21][22][23][25][26][27][28][29][30]. Especially accurate and thorough experimental studies for CO 2 and Dye lasers have been accomplished in Refs.…”

“…This suggests to look for a solution of Eqs. (30) in the form of a bunch of filaments aligned along the cylinder axis. Let us imagine that the radiation field inside the sample is stratified into N f photon filaments stretched along the axis z.…”

“…The above discussion explains why it is reasonable to try to find the solutions of Eqs. (30) in the form of expansions…”