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A simplest saturable absorber, in the form of an unpumped section, is introduced into a Fabry-Perot semiconductor laser with a strongly asymmetric broadened waveguide structure incorporating a relatively thick (80 nm) active layer. This allows for suppression of trailing oscillations and a decrease in the optical pulse width compared to the uniformly biased structure. Single optical pulses of ~80 ps full width at half maximum (FWHM) and ~35 W peak power (~3 nJ pulse energy, E(opt)), practically without trailing edge oscillations, were experimentally achieved under room temperature conditions by absorber-assisted gain-switching, using pumping current pulses of ~1.3 ns FWHM and ~17 A amplitude. The laser emission has a narrow (13 degrees FWHM in the transverse direction) far field.

We present a simple semianalytical model for evaluating the free-carrier loss in the waveguide layer of large-cavity semiconductor lasers, which proves that these losses may become an important factor at high bias currents. It is shown that nonbroadened asymmetric waveguide structures can significantly reduce these losses when compared to broadened symmetric waveguides, with little or no degradation in threshold, near- and far-field properties, and are thus a promising configuration for high-power lasers operating high above threshold.