Narrow gap IV-VI (lead chalcogenide) compounds are employed since long time as mid-IR-detectors and -lasers. IV-VIs are tolerant to structural defects (dislocations). This allows lattice mismatched MBE-growth on foreign substrates like Si which offers significant advantages with respect to size, costs and thermal conductivities. In addition, IV-VIs are unique as regards design of Bragg mirrors because of the very high index contrast between IV-VI materials (nH = 4-5) and BaF2 (nL=1.43). A few pairs of quarter wavelength nH/nL-stacks suffice to obtain very high reflectivities R>99%. We review some of our results for different devices: Infrared sensor arrays for thermal imaging on active Si read-out chips, RCEDs (resonant cavity enhanced IR detectors), optically pumped PbSe/Pb1-xEuxSe edge emitting DH (double heterostructure) or QW (quantum well) lasers on Si substrates and “wavelength transformers”, VCSEL (vertical cavity surface emitting laser) structures operated in sub-threshold.