  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.
