A review on the recent developments in the field of long-wavelength (λ > 1.2 μm) high-brightness opticallypumped semiconductor disk lasers (OPSDLs) is presented. As thermal effects have such a crucial impact on the laser performance particular emphasis is given to modelling the thermal behaviour and optimisation of the heat-sinking. Selected OPSDL devices, realized in different III-V and IV-VI semiconductor material systems, with corresponding emission wavelengths between 1.2 μm and 5.3 μm are presented. Specific applications in this broad spectral range are addressed and methods to obtain high output power are discussed in terms of the underlying material properties and device operating principles.Schematic OPSDL setup, two-dimensional far-field profile of an emitted beam and typical emission spectrum of an (AlGaIn)(AsSb)-based OPSDL.

The semiconductor heterostructure design and lasing characteristics of an optically in-well pumped (AlGaIn)(AsSb)-based vertical-external-cavity surface-emitting laser (VECSEL) emitting at 2.35μm are presented. The pump absorption in the active quantum wells at 1.96μm has been enhanced by a higher-order microcavity resonance. VECSEL operation in-well pumped by a thulium-doped fiber laser has been demonstrated. Compared to a VECSEL barrier pumped at 1μm, the in-well pumped device reaches a significantly higher power efficiency, and thus a higher output power at a given pump power, due to the smaller quantum deficit and hence reduced internal heat generation. Using an intracavity SiC heat spreader, a cw output power in excess of 3W has been achieved at a heat sink temperature of −15°C, and still more than 2W at +15°C.

We report on GaSb-based 2.Xμm diode lasers with an improved waveguide design, leading to a reduced beam divergence in the fast axis of 44° full width at half maximum (FWHM), compared to 67° FWHM of a conventional broadened waveguide design. 2.3μm ridge-waveguide lasers with the improved epitaxial design showed, besides the narrow beam profile in the fast axis, an excellent slow axis beam quality [M2<1.1 up to 70mW, continuous wave (cw)]. 2.0μm broad-area lasers with the improved waveguide too, exhibit a maximum cw-output power of 1.96W.

We report a high-power (AlGaIn)(AsSb) semiconductor disk laser emitting around 2 microm. With a diamond heat spreader used for thermal management, a maximum output power of just over 5 W and slope efficiencies of over 25% were demonstrated. The output wavelength was tunable over an 80 nm range centered at 1.98 microm. The beam propagation parameter (M2) was measured to be in the range of 1.1 to 1.4 for output powers up to 3 W.

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