Multi-type quantum well semiconductor membrane external-cavity surface-emitting lasers (MECSELs) for widely tunable continuous wave operation

Membrane external-cavity surface-emitting lasers (MECSELs) are at the forefront of pushing the performance limits of vertically emitting semiconductor lasers. Their simple idea of using just a very thin (hundreds of nanometers to few microns) gain membrane opens up new possibilities through uniform double side optical pumping and superior heat extraction from the active area. Moreover, these advantages of MECSELs enable more complex band gap engineering possibilities for the active region by the introduction of multiple types of quantum wells (QWs) to a single laser gain structure. In this paper, we present a new design strategy for laser gain structures with several types of QWs. The aim is to achieve broadband gain with relatively high power operation and potentially a flat spectral tuning range. The emphasis in our design is on ensuring sufficient gain over a wide wavelength range, having uniform pump absorption, and restricted carrier mobility between the different quantum wells during laser operation. A full-width half-maximum tuning range of > 70 nm (> 21.7 THz) with more than 125 mW of power through the entire tuning range at room temperature is demonstrated.