Conditions have been analyzed for the occurrence for self-sustained pulsations and bistabilities in semiconductor lasers having a saturable absorber region. It is shown that there are three crucial parameters, namely ratios of differential gain and carrier lifetime between amplifying region and absorbing region, and ratio of absorbing magnitude in absorbing region to the cavity loss. Ranges of these three parameters are determined in which bistabilities and self-sustained pulsations take place.
A stripe laser structure called a planar stripe was developed. The edge blurring of the current path is improved by the fact that the current spreads only in the thin p-AlxGa1-xAs layer with relatively high resistance. The planar stripe laser has a small threshold current resulting from the small current spreading effect and a good thermal contact. It also shows finely controlled transverse modes, compared with a usual contact stripe laser, and relatively high external differential quantum efficiency. The threshold current density is comparable to that of the proton bombarded stripe laser. The transverse mode shows an approximate Hermite-Gaussian distribution.
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