A method of increasing the monomolecular recombination and the immunity to
noise of a continuously tunable laser is disclosed. A concentration of
recombination centers in the range of about 1.times.10.sup.16 cm.sup.-3 to
about 1.times.10.sup.18 cm.sup.-3 in the tuning region of the laser device
is achieved by doping the waveguide layer with impurity atoms, by
irradiating the waveguide layer with high energy particles or by varying
the growth conditions of the waveguide layer to introduce native point
defects due to lattice mismatch. This way, the monomolecular recombination
is increased and the radiative recombination over low current ranges is
reduced. By increasing the monomolecular recombination, the immunity to
noise is improved but the tuning efficiency is reduced. Nevertheless, only
a minimal effect on the tuning efficiency is noted over high current
ranges and, therefore, the overall tuning range is only insignificantly
changed.
