High-frequency modulation of twin-stripe semiconductor lasers

Abstract

Generally, the high-speed modulation dynamics ofsemiconductor lasers is determined by a complex interplay of ultrafast light-field and carrier dynamics with characteristic times-scales of inter- or intraband relaxation and scattering. Those determine the relaxation oscillations and set an upper limit to the modulation ofa single-mode semiconductor laser (cut-off frequency). In spatially extended semiconductor lasers, however, the longitudinal and transverse dimensions enable the coexistence ofnumerous longitudinal and transverse modes. With suitable resonator design allowing segmented contact carrier injection and modulation it should thus be possible to directly influence the lateral coupling and transverse mode dynamics ofa given laser structure and modulate the laser with a beat frequency associated with these modes. In this paper, we present results ofsimulations of high-frequency modulation characteristics oftwin-stripe semiconductor lasers. We show that the lateral segmentation of the contact may with proper asymmetric application of the injection current, indeed, lead to a more than five-fold increase of the modulation band-width. Our theory on the basis of multi-mode Maxwell Bloch equations includes propagation effects and spatiotemporally varying mode competition. Numerical simulations show that the increased high-speed modulation is closely associated with the coupled lateral and longitudinal multi-mode dynamics of the laser.