Optical EngineeringNovel concepts for injection lasers
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Modern trends in the design of semiconductor lasers are addressed. Nanoscale coherent inclusions of a narrower bandgap semiconductor in a wider gap semiconductor matrix, or quantum dots (QDs), are designed as a new type of active medium for injection lasers. QDs provide a possibility to extend the wavelength range of heterostructure lasers on GaAs substrates to 1.3 μm and beyond and improve their device performance. We realize 330-mW cw 1.3-μm single-mode continuous wave edge emitters and 1.2-mW cw vertical-cavity surface-emitting lasers (VCSELs). Long operation lifetimes and other competitive device parameters are demonstrated. Novel device designs are proposed. In one concept, high-order mode filtering in structures with periodically modulated refractive index containing a "defect" enables realization of stable narrow-beam divergence fundamental mode lasing in both edge emitters and VCSELs. In a different novel design, light propagates at some angle with respect to multilayer interference reflectors (MIRs), and the MIRs and the cavity are calculated for the tilted photon incidence. A "tilted cavity" laser (TCL) gives wavelength-stabilized operation in edge and (or) in surface direction and does not require materials having a high refractive index difference. New generations of semiconductor optical amplifiers, photodetectors, optical fibers, etc. may become a reality.