Spectral characteristics of gain-guided semiconductor lasers

A relation for the spectral width of the envelope of lasing emission of gain-guided lasers is derived which contains only parameters that can be easily measured, such as near and far field, gain width, and facet reflectivity. For GaAlAs
V
-groove lasers, one typically obtains for the spectral width
\Delta\lambda
, in relation to the astigmatism factor
K
, a
\Delta\lambda/K \approx 1 ... 2
Å at 5 mW optical power, while GaInAsP
V
-groove lasers at 1.3 μm exhibit a
\Delta\lambda/K \approx 3 ... 5
Å.