From a technological point of view, MECSELs are a descendant of VECSELs, which in turn evolved from VCSELs. At the same time, VECSELs and MECSELs represent a cross between semiconductor lasers and solid-state thin disk lasers. Major advances, such as radical design simplification, double-sided pumping, and performance scaling through multi-pass in-well pumping, have played a pivotal role in the evolution of MECSELs. Critical aspects of active region membrane design will be discussed, particularly the flexible pumping capabilities made possible by the absence of a monolithically integrated distributed Bragg reflector (DBR) and substrate. A specific focus will be placed on optical pumping of relatively thick membranes, and recent results will be presented from newly designed broadband structures optimized for ultra-wide tunability, achieved using two different types of quantum wells. All this could only be realized due to the unique possibility of excellent thermal management, which in turn was only enabled by the fabrication of the laser structure as a membrane sandwiched between transparent heat spreaders. This seminar talk on MECSELs will conclude with an overview of ongoing research at UNM in this still relatively young field of research.

Hermann Kahle received his PhD in Physics at the University of Stuttgart, Germany, in 2016. The thesis was performed on the detailed investigation and optimization of red emitting semiconductor disk laser structures. He developed a novel concept - the membrane external-cavity surface-emitting laser with the first double-side diamond cooling implementation. After PhD graduation he moved to Tampere, Finland, where he joined the Optoelectronics Research Centre (ORC) at the Tampere University in 2017. He was leading a research team further investigating this novel category of heat spreader sandwiched membrane structures as laser gain elements. After a short research stay in 2022 at Kassel University, Germany, he was with the Paderborn University, Institute for Photonic Quantum Systems (PhoQS) in 2023. In 2024 he moved to the US and joined The University of New Mexico at the Department for Physics and Astronomy continuing research on MECSELs in the NIR spectral range and for high-power applications.