Fourier-optical transverse mode selection in external-cavity broad-area lasers: experimental and numerical results

Dynamic behaviors of a broad-area diode laser with lateral-mode-selected external feedback

“….9) 6000 6500 almost symmetric; curves c) to g) show the far-field profiles from low-order lateral-mode selection to high-order lateralmode selection, the far-field profiles are highly asymmetric and this is normal for BAL with off-axis external feedback [1][2][3][4][5]7 . The results show that high-order lateral-modes, which do not exist without external feedback, are excited by the lateral-mode selected external-cavity feedback, i.e., curves e) to g).…”

“…Different techniques have been developed to improve the beam quality of BALs in the slow axis. Among them, external-cavity feedback with lateral-mode selection is an effective technique to improve the spatial coherence of BALs in lateral direction [1][2][3][4][5] . This external-cavity feedback technique is based on the fact that the output of a gain-guided BAL consists of a set of lateral spatial modes; each high-order mode has a double-lobed far-field in the slow axis, and these modes are distinguished at different angles in the far field 6,7 .…”

“…By this technique, one lobe of a lateral-mode of the BAL at the far-field is selected and reflected back into the BAL, and the other lobe of the same lateral-mode is coupled out of the laser cavity as output beam of the diode laser system. All the other lateral modes are suppressed effectively, thus the spatial beam quality of a BAL in the slow axis is improved significantly [1][2][3][4][5]7 .…”

“…Different dynamic behaviors, such as low frequency fluctuations (LFFs) 14,17 , pulse-package oscillations 16,19 , have been observed in BALs subjected to external feedback. Wolff et al investigated the time-resolved lateral near-and far-field distribution of BAL with lateral-modeselected external-cavity feedback numerically, and a self-Q-switched-like mode was observed in a BAL, which was operated high above the threshold 1 . Pimenov et al studied the dynamical regimes of multistripe laser array with external off-axis feedback theoretically, different periodic and aperiodic oscillations were shown in the study 20 .…”

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

“…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.…”