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The top pane shows the calculated band structure for the design of Ref. 3, the lower laser state is labeled A and the next down stream state is labeled B. The conduction band profile is shown in white and the intensity corresponds electron probability density. Only the eight layers indicated by a brace were allow to change. The lower pane has the resulting modified design, the layer thicknesses for this design starting from the injection barrier are , barriers are shown in bold and wells doped at are shown in italics.
The parameter , as a function of solution number sorted in ascending order. Smaller values of represent a good solution. The red (dashed) line represents the value of for the reference design (4.8). Inset: results from the 1000 best solutions, the sharp dip in for the best solutions demonstrates the quality of the solutions found.
Pulsed ’s taken using a thermopile mounted inside the cryostat at a range of temperatures, the devices were driven at with 1% duty cycle and a slow modulation to match the response of the thermopile. The upper pane shows data from the improved design and the lower pane refers to the reference device. The inset are spectra at a range of currents for each device.
Differential resistance and ’s, taken in cw operation at , for the devices shown in Fig. 3. The discontinuity in the differential resistance at threshold is larger for the improved design on the left hand side.
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