Semiconductor laser diodes, particularly high power AlGaAs-based
ridge-waveguide laser diodes, are often used in opto-electronics as
so-called pump laser diodes for fiber amplifiers in optical communication
lines. To provide the desired high power output and stability of such a
laser diode and avoid degradation during use, the present invention
concerns an improved design of such a device, the improvement in
particular significantly minimizing or avoiding (front) end section
degradation of such a laser diode and significantly increasing long-term
stability compared to prior art designs. This is achieved by establishing
one or two "unpumped end sections" of the laser diode. One preferred way
of providing such an unpumped end section at one of the laser facets (10,
12) is to insert an isolation layer (11, 13) of predetermined position,
size, and shape between the laser diode's semiconductor material and the
usually existing metallization (6). A further embodiment shows separate,
further isolation layers (5) extending along the laser diode, potentially
abutting the ridge waveguide of the laser.