Coherent amplification of high-power laser radiation in multicore fibers from a rectangular array of cores

Abstract

The coherent propagation and amplification of high-power laser radiation in a multicore fiber consisting of a square array of weakly bound cores are studied. Exact stable analytical solutions are found for the out-of-phase mode, which describes the coherent propagation of wave beams in such fibers. The analytical results are confirmed by direct numerical simulation of the wave equation. The stability conditions of the out-of-phase mode in the active medium are found.

Controlled Excitation of Supermodes in a Multicore Fiber with a 5 × 5 Square Array of Strongly Coupled Cores

“…In an MCF with single-mode cores, the light propagation can be described by a discrete set of onedimensional nonlinear coupled Schrödinger equations. For a square array of N × N cores with allowance for coupling of each core with its four nearest neighbors, we obtain [36] i…”

“…It was predicted theoretically [33][34][35][36][37] and then shown in an experiment that in the MCFs with N cores arranged in a ring close to each other, the light with transversal structure of the out-of-phase supermode can propagate and be amplified [38]. In this supermode the intensity is equal in all cores, whereas the phase of the light in neighboring cores differs by π.…”

“…Moreover, the MCFs with coupled cores are attractive for exploration of many nonlinear and laser phenomena, including selective mode amplification [22], Raman lasing [23,24], spatiotemporal pulse compression [25,26], light bullet and soliton formation [27][28][29], supercontinuum generation [30], radiation trapping, and pulse cleaning [31,32]. Recent studies have shown that in the MCFs with coupled cores there are regimes of light propagation that are stable at high power and maintain coherency between the channels [33][34][35][36]. Such regimes are promising for designing novel high-power laser systems.…”

“…Better scaling of the number of cores with the linear size of the fiber is achieved in MCFs with a square array of cores. Recently, it was predicted theoretically and numerically that with such an arrangement of cores there exists an out-of-phase supermode, too, where the light phase in the cores is 0 and π following the chessboard pattern [36]. It was shown theoretically that, in principle, the power carried in this mode can be N times higher than the limiting power of a single core.…”

“…It was shown theoretically that, in principle, the power carried in this mode can be N times higher than the limiting power of a single core. According to the theory, the intensity distribution is nonuniform at low powers (it is higher in the central core and lower at the peripheral), however, it equalizes with increasing power [36]. Besides, it was shown in a recent work [40] that radiation with a transverse structure of such a supermode can be easily coherently combined with high efficiency.…”