Optically pumped wafer fused 1310 nm VECSELs have the advantage of high output power and wavelength agility. Gain mirrors in these lasers are formed by direct bonding of InAlGaAs/InP active cavities to Al(Ga)As/GaAs DBRs. We present for the first time Watt-level 1310 nm wafer-fused VCSELs based on gain mirrors with heat dissipation in the “flip-chip” configuration. Even though output power levels in this approach is lower than with intra-cavity diamond heat-spreaders, the “flip-chip configuration demonstrates higher quality optical emission and is preferable for industrial applications in optical amplifiers, intra-cavity doubled lasers, etc.
Recent developments of wafer-fused long-wavelength VECSELs resulted in reaching record high CW output power of
6.6 W at 1300 nm and a coherence length longer than 5 km in fiber and 1 Watt of output power in single frequency
regime at 1550 nm. First wafer-fused electrically pumped VECSELs emitting at 1470 nm demonstrate maximum CW output power of 6.5 mW which represents more than 10-times improvement compared with previously published results.
The latest achievements of quantum dot based semiconductor disk lasers are reviewed. Several lasers operating at 1040
nm - 1260 nm were studied. All the structures were grown with molecular beam epitaxy on GaAs substrates. The
number of quantum dot layers was varied and the gain was provided either by the ground or the excited state transition of
the quantum dots. Frequency doubling of the lasers was demonstrated and the dual-gain laser geometry was found to be
practical solution for intracavity frequency conversion. Intracavity heat spreader and thinned device heat management
approaches are studied and compared.
We demonstrate a frequency doubled dual-gain quantum dot semiconductor disk laser operating at 590 nm. The
reflective gain element, grown by molecular beam epitaxy, has active region composed of 39 layers of InGaAs Stranski-
Krastanov quantum dots. The gain mirrors produce individually 3 W and 4 W of output power while the laser with both
elements in a single cavity reveals 6 W at 1180 nm with beam quality factor of M<sup>2</sup><1.2. The loss induced by the
nonlinear crystal is compensated by gain boosting in the dual-gain laser and 2.5 W of output power at 590 nm was
achieved after frequency conversion.
1300-nm, 1550-nm and 1480-nm wavelength, optically-pumped VECSELs based on wafer-fused InAlGaAs/InPAlGaAs/
GaAs gain mirrors with intra-cavity diamond heat-spreaders demonstrate very low thermal impedance of 4
K/W. Maximum CW output of devices with5 groups of quantum wells show CW output power of 2.7 W from 180μm
apertures in both 1300-nm and 1550-nm bands. Devices with 3 groups of quantum wells emitting at 1480 nm and with
the same aperture size show CW output of 4.8 W. These devices emit a high quality beam with M² beam parameter
below 1.6 allowing reaching a coupling efficiency into a single mode fiber as high as 70 %. Maximum value of output
power of 6.6 W was reached for 1300nm wavelength devices with 290μm aperture size.
A wafer fusing was applied to integrate an InP-based active medium and a GaAs/AlGaAs distributed Bragg reflector in
an optically pumped semiconductor disk laser. Over 50 mW of output power at room temperature in 1570-1585 nm
spectral range was demonstrated. The results of this study reveal an important finding: the wafer fusion can be used in
emitters with high power. This approach would allow for monolithic integration of lattice-mismatched compounds,
quantum-well and quantum-dot based media and promises substantial wavelength tailoring of semiconductor disk lasers.
We report a passively mode-locked optically pumped semiconductor disk laser with emission at 1220 nm. Both the gain
and the semiconductor saturable absorber mirrors used to build the laser are based on InGaAsN/GaAs quantum wells
fabricated by molecular beam epitaxy. The growth parameters have been optimized to reduce the detrimental effects of
nitrogen on the emission efficiency. Using a gain mirror comprising ten GaInNAs quantum wells with a relatively low
nitrogen content and a saturable absorber mirror incorporating two GaInNAs quantum wells, we demonstrate generation
of pulses with durations of ~5ps and average powers up to 275mW. We describe the fabrication procedure of the
semiconductor structures and the results of laser characterization.
We report an essential progress towards the development of efficient GaInNAs-based semiconductor disk lasers
operating at 1220 nm spectral range. The gain mirrors were fabricated by molecular beam epitaxy using a radio
frequency plasma source for incorporating the nitrogen. The typical structure consisted of a 30-pair GaAs/AlAs
distributed Bragg reflector and 10 GaInNAs quantum wells with relatively low content of nitrogen. The growth
parameters and the composition of the structures have been optimized to reduce the detrimental effect of nitrogen on the
emission efficiency. We have achieved a maximum output power of 3.5 W and a differential efficiency of 20%.
Owing to their good beam quality and high output power, near-infrared semiconductor disk lasers provide an attractive
opportunity for visible light generation via frequency conversion. The typical cavity arrangement of a semiconductor
disk laser, consisting of a semiconductor multiple quantum well gain mirror and one or more external mirror, offers a
convenient configuration for intracavity frequency doubling. Recent progress in the disk laser development has led to
demonstrations of multi-watt green-blue-yellow sources. These achievements have been enabled by the possibility to
integrate high performance InGaAs/GaAs gain media and Al(Ga)As/GaAs Bragg reflectors operating in the 940-1160
nm wavelength range. In order to achieve ~620 nm red emission, a laser emitting near the fundamental wavelength of
1240 nm is needed. To achieve this spectral range we have developed GaInNAs/GaAs gain mirrors and we have
achieved 1 W of output power at 617 nm by frequency doubling in a BBO crystal. This is to our knowledge the highest
power reported to date for intracavity doubled disk laser based on dilute nitride gain material.
We present new approaches for power scaling and tunability in semiconductor disk lasers. The novel concepts allow for
reduced thermal load of the gain material, increasing the threshold of rollover and extending the capability for boosting
the output power without significant degradation in the beam quality. The proposed technique for power scaling of
optically-pumped semiconductor disk lasers is based on the multiple gain scheme. The method allows for significant
power improvement while preserving good beam quality. Total power of over 8 W was achieved in dual-gain
configuration, while one-gain lasers could produce separately about 4 W, limited by the thermal rollover of the output
characteristics. The results show that reduced thermal load to a gain element in a dual-gain cavity allows extending the
range of usable pump powers boosting the laser output.
Tunable Sb-based semiconductor disk laser operating at 2-&mgr;m is demonstrated with nearly 100 nm operation range. The
maximum output is 210 mW and the 3dB tuning range spans from 1946 to 1997 nm. The wavelength tuning is based on
an intracavity birefringent filter. The potential of semiconductor disk lasers for high repetition rate ultrashort pulse
generation using harmonic mode-locking is also discussed. We report on optically-pumped vertical-external-cavity
surface-emitting lasers passively mode-locked with a semiconductor saturable-absorber mirror. The potential of
harmonic mode-locking in producing pulse trains at multigigahertz repetition rates has been explored. The results present
first systematic study of multiple pulse formation in passively mode-locked VECSELs.