Gain spectra in GaInAsP/InP proton-bombarded stripe-geometry DH lasers

We have measured gain spectra for TE polarization in a GaInAsP/InP laser as a function of dc bias current below laser threshold. The measurements were made on a low-threshold device with a stripe geometry defined by proton bombardment. A number of other characteristics of this and similar devices from the same wafer are also reported. These data permit the maximum gain coefficient of the active layer g
max
to be evaluated as a function of nominal current density J
nom
. We obtain the linear relationship
g_{max} = (3.1 \times 10^{-2}/\eta_{r})(J_{nom} - \eta_{r} 5.4 \times 10^{3})
, where η
r
is the radiative quantum efficiency. Our data apply only for large gain (
g \gsim 150
cm
^-1
) and large J
nom
because the active layer of the test device is thin (0.1 μm).