Recent Advances in Power Scaling of GaSb-Based Semiconductor Disk Lasers

Optically pumped VECSELs: review of technology and progress

“…Consequently, the output power of a VECSEL exhibits a thermal roll-over with increased pump power. As a general strategy for achieving high power operation, one should seek to maximize the heat transfer away from the gain region and, at the same time, minimize the heat generation by reducing the quantum-defect and non-radiative processes [37,38].…”

“…To maximize output power, one should also optimize heat conduction in the material boundaries and ensure appropriate geometry of the heat sink and cooling elements. Furthermore, heat generation can be minimized by reducing the quantumdefect [37] and by using high crystalline quality epitaxial material that has a low number of defects and high internal quantum efficiency [38].…”

“…On the other hand, at wavelengths > 1.8 µm, GaSb/AlAsSb DBRs offer a high refractive index contrast and can be fabricated using just 20-25 layer pairs. However, the thermal conductance of these DBRs is low and the increased thickness of the λ/4 layers reduces the heat flow even further [37].…”

“…Second, increasing the pump absorption in the active region via recirculating the residual pump absorption has already been shown to enhance VECSEL performance (when using pump-transparent DBRs) [149,150]. Third, the benefits of reducing the number of DBR layers by using metal reflectors become more obvious with increasing wavelength, because the thickness of the λ/4 DBR layers increases with the emission wavelength [20,21,37]. The most common wafer bonding methods are schematically summarized in figure 7, as adapted from [151][152][153][154][155].…”

Novel semiconductor membrane external-cavity surface-emitting laser

“…To overcome the heat flow problems and to improve the performance of VECSELs, numerous thermal management strategies have been previously proposed. Such approaches include changes to the heat spreader arrangement, 8 removing the substrate, 1 flip-chip processes, 9 or the insertion of compound mirrors. 10 According to the natural progression of these developments, all semiconductor components of a VECSEL that are not essential for building a whole laser could eventually be abandoned.…”