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Solid line: Optical mode intensity profile in an waveguide structure. The solid line is the mode computed assuming the current is injected by a two-dimensional electron gas (2DEG). For comparison, the mode computed assuming an heavily doped buried contact layer is also shown (dashed line). The growth, on a semi-insulating InP substrate, starts by a two-dimensional electron gas formed successively of period of a superlattice, a -thick undoped layer, a -thick doped layer, an undoped -thick spacer layer, and finishing by an undoped -thick layer. The growth follows by 70 periods of the active region, and followed by an undoped, -thick layer. The latter consists of an undoped -thick layer, an undoped, -thick layer, a -thick heavily doped contact layer. In the simulations above, free carrier loss in the undoped InP substrate was neglected and loss inside the 2DEG was generally considered using the bulk Drude model.
Computed conduction band profile at of one stage of the structure under an average applied electric field of . The layer sequence of one period of the active layers starting from the injection barrier is as follows: / where the layers are in bold, and is the Roman underlined number that corresponds to a Si-doped layer with .
Emission spectra measured as a function of current for a -wide and -long device (solid line). The blueshift of the emission with current increase is consistent with the stark shift of the diagonal laser transition. For comparison, the same measurement performed from the side of a device that has been cleaved along the length of the stripe is shown (dashed line). Inset: High-resolution spectra of the same laser taken above threshold. The spectra are vertically displaced for clarity.
(a) Peak optical output power vs injected current in pulsed mode at a duty cycle of 0.008% at various temperatures, as indicated. The sample is processed into a -long and -wide waveguide. (b) Pulsed threshold current as a function of inverse laser length measured at .
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