Membrane external-cavity surface-emitting lasers (MECSELs) are a new kind of vertically emitting semiconductor laser with enormous potential and versatility for tailoring the laser parameters. Part of their benefits is related to the fact that they do not need to employ integrated distributed Bragg reflectors (DBRs), which are known to hamper the heat transfer and limit wavelength versatility via strain and band-gap engineering constrains. Furthermore, the substrate on which the active region is grown on is removed and the resulting thin active region membrane is sandwiched between transparent intra cavity heat spreaders for improved thermal management.
In recent years, MECSELs have experienced a rapid progress. With all their benefits, where an intrinsically excellent beam quality is just one of it, new dynamics were brought into the field of vertically emitting semiconductor lasers. The most important advances, like the radical design simplification, double-side pumping and power scaling capabilities play a major role. Also, wavelengths not yet covered by classical vertical emitters like VCSELs and VECSELs (vertical-cavity surface-emitting lasers and vertical-external-cavity surface-emitting lasers) have been reached as growth related limitations or difficulties introduced by the DBR do not play a role anymore. The latest developments on continuous wave broadband tunable MECSELs (> 25 THz) will be discussed as well as the relevance of non-resonant designs of semiconductor gain membranes sandwiched between transparent heat spreaders.
|