Novel concepts for injection lasers

Modern trends in the design of semiconductor lasers are ad- dressed. Nanoscale coherent inclusions of a narrower bandgap semi- conductor 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 mm and beyond and improve their device performance. We realize 330-mW cw 1.3-mm single-mode con- tinuous 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 pro- posed. In one concept, high-order mode filtering in structures with peri- odically modulated refractive index containing a ''defect'' enables realiza- tion 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 inci- dence. A ''tilted cavity'' laser (TCL) gives wavelength-stabilized operation in edge and (or) in surface direction and does not require materials hav- ing a high refractive index difference. New generations of semiconductor optical amplifiers, photodetectors, optical fibers, etc. may become a re- ality.