Recent Developments on MECSELs: Multi-type Quantum Well Gain Structures for Widely Tunable Continuous Wave Operation and a Non-Resonant Sub-Cavity Design

Membrane external-cavity surface-emitting lasers (MECSELs [1], [2]) are 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 and no monolithically integrated distributed Bragg reflector (DBR) opens up new possibilities through efficient double-side optical pumping and superior heat extraction [3] from the active area. One such possibility is the introduction of multiple types of quantum wells (QWs) to a single laser gain structure. We present this new design strategy and demonstrate how it can be used to create broadband, high power membrane external-cavity surface-emitting laser gain structures that can potentially generate a flat emission power spectrum. The emphasis in this strategy is on ensuring sufficient gain over a wide wavelength range, having efficient pump absorption, and restricted carrier mobility between the different QWs during laser operation. Latest results show > 86 nm (> 26 THz) tuning range (see Fig. 1a), but still 70 nm (> 21 THz) FWHM tuning range (see Fig. 1b) with more than 125 mW of power through the whole tuning range at room temperature operation.