Stabilization of chaotic spatiotemporal filamentation in large broad area lasers by spatially structured optical feedback

Abstract

In large high-power broad-area lasers the spatiotemporal filamentation processes and instabilities occur macroscopic as well as on microscopic scales. Numerical simulations on the basis of Maxwell- Bloch equations for large longitudinally and transversely extended semiconductor lasers reveal the internal spatial and temporal processes, providing the relevant scales on which control for stabilization consequently has to occur. It is demonstrated that the combined longitudinal instabilities, filamentation, and propagation effects may be controlled by suitable spatially structured delayed optical feedback allowing, in particular, the control of coherent regimes in originally temporally and spatially chaotic states.

Stabilization of flat-mirror vertical-external-cavity surface-emitting lasers by spatiotemporal modulation of the pump profile

“…As a result, the output power of these lasers is severely restricted, limiting their applications. Current approaches for the stabilization of output beam's spatial structure commonly rely on an external forcing techniques such as optical injection [7] and optical feedback in various configurations spatially structured feedback [8,9] and feedback from external cavities [10,11]. All these techniques reduce the main advantage of VCSEL lasers: their compactness, and thus limit their applicability.…”

Fundamental Transverse Mode Selection (TMS#0) of Broad Area Semiconductor Lasers with Integrated Twice-Retracted 4f Set-Up and Film-Waveguide Lens

“…of several millimeters, considering the properties of the 1D spatial Fourier-transform, vacuum wavelength 0 , and (effective) refractive index (eff) [9], but for best differential quantum efficiency a semiconductor laser resonator should rather be short [26]. Thus, currently, that is, for this contribution, we have retracted the branches (once more) so that they spatially coincide, giving a compact linear 2f geometry (1f plus the path after reflection, the resonator thus called "retracted twice"), as sketched in Figure 2.…”

“…In most cases either the BAL facets or the lateral (effective) refractive index or pump current distributions are modified [1][2][3][4][5][6][7][8] (if so including transverse Bragg gratings [7,8]) or an external cavity is used [7][8][9][10][11][12][13][14] to achieve the desired transverse mode selection (TMS) (and if applicable also to stabilize a longitudinal mode [7,8]). In all these cases eventually spatial frequency filtering is performed.…”

Monolithic integration of transverse mode selectors with antimonide broad area lasers

“…The large width of the active region leads to the emission of many transverse modes. Moreover the high BAL power causes strong non-linear optical coupling between the field and the gain medium and results in an uncontrolled filamentation of the gain profile, which destabilizes the transverse modes on a 10 ps time scale [5]. The emission of BALs can be controlled e.g.…”

“…The emission of BALs can be controlled e.g. using a grating integrated in the semiconductor chip [2][3][4] or by external cavities [5][6][7][8]. It was found that the feedback strength has a strong influence on the characteristics of the BAL's dynamics.…”