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Several characteristics of In$\sb{x}$Ga$\sb{1-x}$As-GaAs-Al$\sb{y}$Ga$\sb{1-y}$As separate confinement heterostructure strained-layer quantum well lasers are investigated in this work. The main implications of strain are examined briefly, including the importance of a critical layer thickness, strain-induced changes of the band structure, and their effects on laser performance. Experimental characterization of various aspects of both single-stripe devices and laser arrays is described.
The laser gain coefficient is measured in separate confinement heterostructure In$\sb{x}$Ga$\sb{1-x}$As-GaAs-Al$\sb{y}$Ga$\sb{1-y}$As strained-layer quantum well lasers with 70 A In$\sb{x}$Ga$\sb{1-x}$As ($0.08<x<0.33$) quantum wells. An increase of 93% is measured in going from x = 0.16 to x = 0.33. For narrow-stripe devices, the strong carrier-induced antiguiding present in InGaAs-GaAs-AlGaAs lasers is studied. A value of K = 12.9 for the astigmatism factor and a corresponding antiguiding factor of b = 6.4 are measured. In all cases, the antiguiding is much stronger than reported for similar GaAs-AlGaAs lasers.
Current-controlled wavelength switching between the first and second bound quantum well state transitions is observed. For a narrow current range, the wavelength also switches during the current pulse. The order of this temporal switching is opposite to that observed for GaAs QW lasers, and this is explained in terms of the strong antiguiding in the InGaAs-GaAs-AlGaAs lasers and the temperature dependence of the gain vs. carrier density characteristic.
Two different types of laser arrays are also investigated. The far-field intensity patterns of oxide-stripe arrays are shown to depend on the element spacing, with wider spacings operating in the highest array mode, while closer spacings result in operation in the fundamental array mode. Ridge-waveguide laser arrays covering a range of effective index steps are studied. The devices span the range from gain-guided to strongly index-guided elements.
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