Abstract
Multiple quantum well (MQW) structures in conjunction with strained layers (SL) reveal several advantages for semiconductor lasers, as, for example, the reduction of the linewidth enhancement factor and the threshold current density.1 In this paper, we present results from compressively strained InxGa1−xAs/InGaAsP MQW lasers with In-contents ranging from x = 0.5 up to x = 0.78. The active layer consists of five wells with well widths between 4 and 15 nm and quaternary barriers of 8 nm and a quaternary waveguide. The lasers were entirely LP-MOVPE grown 1.55·μm buried heterostructure DFB lasers with semiinsulating (lnP:Fe) and p-n-blocking layers2. Threshold current densities could be reduced by ~50% compared with identical structures with unstrained layers. The light current characteristics for such a laser with 500-μm cavity length is given in Fig. 1. A threshold below 20 mA and a quantum efficiency of >22% have been achieved. The tar-field angle, determined by the special waveguide layer could be reduced to ~20°.
© 1992 Optical Society of America
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