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Schematic diagram of the tapered laser investigated and the reference system used.
SE intensity maps for different currents (0.4–2 A) concentrating on the flared region in order to maintain a high spatial resolution. The dotted white line (0.4 A) indicates the resonator axis. The SE is not uniform below threshold with a maximum close to the narrow taper section. Above threshold, the onset of the lateral hole burning is indicated by a nonuniform carrier depletion by the stimulated emission. The blue curved lines are bonding wires partly crossing the device while vertical dark line at is due to a metal stripe in the -substrate.
(a) Lateral SE intensity distributions at the position from the output facet for different currents starting from below threshold. The shaded area indicates the stripe width while the legend in the picture (b) is valid for (a), (c), and (d) too. (b) Logarithm of the near field intensity as function of current reimaged with a 4 mm focal distance lens with 0.5 numerical aperture. (c) SE intensity along the resonator axis (see white dotted line in Fig. 2) for positions from for different current values. The black curves indicate the fits obtained by applying Eq. (1). The drop at and the peak at in the intensity are due to an obscuring metal line on the substrate and to a scattering defect in the substrate, respectively. (d) Integrated SE intensity along the lateral as function of . Above threshold the reduces the SE intensity close to the output facet due to the high carriers recombination rate. The perturbations of the curves in the range are due to partial obscuration by the bonding wires.
(a) SE intensity as function of the current for different positions along the resonator axis and net gain (left triangles) calculated by fitting the SE curves of Fig. 3(c). A logarithmic fit to the net gain is shown (solid line). The carrier density clamping takes place around 1.2 A compared with a threshold current of 0.75 A and is similar for all the points along the axis. (b) Voltage/power vs current characteristic showing a linear behavior above threshold with a small kink between and . The slope efficiency is 0.43 W/A.
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