Multitype Quantum Well Semiconductor Membrane External-Cavity Surface-Emitting Lasers for Widely Tunable Continuous Wave Operation

Membrane external-cavity surface-emitting lasers (MECSELs) represent a cutting-edge approach in pushing the performance boundaries of vertically emitting semiconductor lasers. The fundamental concept of employing an extremely thin gain membrane, spanning from hundreds of nanometers to a few micrometers in thickness and sandwiched between transparent heat spreaders, introduces novel opportunities through uniform double-sided optical pumping and enhanced heat dissipation from the active region. Additionally, these advantages of MECSELs facilitate more intricate band gap engineering possibilities for the active region by integrating multiple types of quantum wells (QWs) into a single laser gain structure. This work introduces a novel design strategy for laser gain structures incorporating various QW types. The objective is to achieve broad-spectrum gain with relatively high-power operation and potentially a flat spectral tuning range. Our design focuses on ensuring sufficient gain across a wide wavelength span, achieving uniform pump absorption, and limiting carrier mobility between different quantum well types during laser operation. We demonstrate a full-width half-maximum (FWHM) tuning range exceeding 70 nm (equivalent to more than 21.7 THz) with over 125 mW of output power across this entire tuning range at room temperature.