25  W continuous wave output at 665  nm from a multipass and quantum-well-pumped AlGaInP vertical-external-cavity surface-emitting laser

Abstract

An output power of 2.5 W at a wavelength of 665 nm was obtained from a quantum-well (QW) and multipass-pumped AlGaInP-based vertical-external-cavity surface-emitting laser operated at a heat sink temperature of 10°C. Intracavity frequency doubling resulted in an output power of 820 mW at a wavelength of 333 nm. To the best of our knowledge, these are the highest continuous wave output powers from this type of laser both at the fundamental wavelength and in frequency-doubled operation. In fundamental wavelength operation, further power scaling by increasing the pump-spot size increased the output power to 3.3 W. However, at this power level, the laser was highly unstable. When the laser was operated at 50% pump duty cycle, a reproducible and stable peak output power of 3.6 W was obtained. These results demonstrate the potential of optical QW pumping combined with multipass pumping for the operation of AlGaInP-based semiconductor disk lasers.

Quantum dot membrane external-cavity surface-emitting laser at 1.5 μm

“…To optically pump the gain membrane under small pump incident angles below 15 • with an almost circular pump spot, a 90 • off-axis parabolic mirror was integrated in the pump optics. In the future, this pump approach could be extended by a second set of pump optics, positioned on the opposite side of the MECSEL for double-side pumping 11 or pump recycling 31 by reflecting the transmitted pump beam back to the MECSEL structure to increase the pump efficiency. Additionally, a high DOP larger than 99 % was obtained where the s-polarized modes were far more prominent than the p-polarized ones which was reproducible across the sample.…”

Optically pumped VECSELs: review of technology and progress

“…However, due to the short light-matter interaction length, it is difficult to absorb the pump light effectively even in a double-pass configuration; the typical QW is only a few nanometers thick, so the total absorptive path length is rather small in a typical VECSEL gain mirror having 5-15 QWs. To some extent, the pump absorption can be improved by adding more QWs into the structure, but usually a resonant pumping scheme [60] or external pump recirculation optics are required to attain high output powers [61]. In addition, the selection of the pump laser (wavelength) for in-well pumping is more critical (and possibly more expensive) than for spacer pumped lasers, where low-cost 808 nm diodes can be used for pumping gain mirrors covering wavelengths in the 900 nm to 2 µm range.…”

“…The gain structures for 620-700 nm red emission are based on a GaAs material system using (Al)GaInP QWs [61] or InP QDs [94]. The longer wavelengths in the 700-800 nm band can be reached using GaAsP and AlGaInAs QWs [95] (although, to our knowledge they are not yet used successfully as VECSEL gain mirrors) or InP QDs [96].…”

“…These issues were recently addressed in two new VECSEL configurations. In the first approach, the thermal load of the VECSEL was reduced via in-well pumping with a multipass pumping scheme (as illustrated in figure 10), generating 2.5 W at 665 nm [61]. In the second approach, the constraints regarding the DBR were circumvented using a double-side cooled 'DBR-free' gain membrane [74].…”

Novel semiconductor membrane external-cavity surface-emitting laser

“…For instance, large-scale bonding processes 21 can be applied to the device. Furthermore, it may be possible to achieve in-well and multipass pumping 22,23 in a transmission configuration (where the pump light is recycled and folded several times through the active region). We are also investigating how these processes can be adapted for classical solid-state thin-disk lasers (i.e., to better optimize their thermal management).…”