H-pulsing: A transient effect in GaAs/GaxAl1-xAs injection lasers

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H
-shape" light pulses, i.e., short light pulses superimposed on the beginning and end of a steady laser emission, are observed from pulsed single-heterostructure lasers operated at particular temperatures and currents. At a slightly higher current the steady laser emission is extinguished leaving the two peaks. The effect, observed in single-heterostructure lasers fabricated on low doped n-type substrates, was studied for various driving currents and laser temperatures. A theoretical study involving computations with standard laser parameters has resulted in light-output curves having a similar form. The rate equations computed contained a superlinear carrier-concentration-dependent loss term as well as the term for the emission of spontaneous photons into the laser mode. Loss of optical confinement due to carrier-induced changes in refractive index is proposed as an explanation for the superlinear carrier-dependent loss.