Experimental properties of injection lasers: VIII. Narrow stripe lasers with induced waveguide

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Abstract
The properties of a type of cw (AlGa)As injection laser whose waveguide is produced or modified by the conditions of operation are studied as a function of current and of delay after the start of a 10-μs square current pulse. They are illustrated by data on a representative unit from a popular structure, the oxide stripe laser, operating in the fundamental spatial mode and with linear power-current characteristic. At the start of the pulse the laser behaves like an oscillator with rigid cavity walls, with mode profiles invariant of current, mode powers linear in junction voltage, and smooth envelope of the spectrum. With delay, all these properties are lost; the beam changes its shape and direction, the shape and position of the coherent near field are changed, and the spectral envelope changes erratically. Since the voltage profile across the facet retains its shape and symmetry and is invariant of delay, the effects are not associated with modifications of the profile of gain or free carriers. They seem to be due to development of a temperature profile beneath the stripe contact. Comparison at fixed current between the changes with delay of the profiles of the modes and the change in propagation constant strengthens the interpretation. Analysis of this laser shows that a 15% increase in free-carrier density is inconsequential to the observed mode confinement, and that spatial hole burning has no role in the modification of its waveguide.