We report a novel single-frequency, injection-locked vertical external-cavity surface-emitting laser (VECSEL) for the first time to the best of our knowledge. The wavelength of the injection locked output can be tuned with the master laser. A lower power single-frequency VECSEL served as the master oscillator that provides wavelength tunability with frequency selective elements such as a birefringent filter, and/or an etalon. The master laser is mode-matched to the slave VECSEL ring resonator. By varying the injecting power and wavelength of the master VECSEL oscillator, we investigated the locking ability of the laser. With 200 mW of the injection power, we generated above 4 W of stable output in single frequency. With the ability to provide narrow linewidth, good beam quality, and stable output with sufficient power at specific wavelengths, this kind of laser sources can be useful in many laser applications, such as precision spectroscopy.
The antimonide based vertical external cavity surface emitting lasers (VECSELs) operating in the 1.8 to 2.8 Tm wavelength range are typically based on InGaAsSb/AlGaAsSb quantum wells on AlAsSb/GaSb distributed Bragg reflectors (DBRs) grown lattice-matched on GaSb substrates. The ability to grow such antimonide VECSEL structures on GaAs substrates can take advantage of the superior AlAs based etch-stop layers and mature DBR technology based on GaAs substrates. The growth of such III-Sb VECSELs on GaAs substrates is non-trivial due to the 7.78% lattice mismatch between the antimonide based active region and the GaAs/AlGaAs DBR. The challenge is therefore to reduce the threading dislocation density in the active region without a very thick metamorphic buffer and this is achieved by inducing 90 ° interfacial mist dislocation arrays between the GaSb and GaAs layers. In this presentation we make use of cross section transmission electron microscopy to analyze a variety of approaches to designing and growing III-Sb VECSELs on GaAs substrates to achieve a low threading dislocation density. We shall demonstrate the failure mechanisms in such growths and we analyze the extent to which the threading dislocations are able to permeate a thick active region. Finally, we present growth strategies and supporting results showing low-defect density III-Sb VECSEL active regions on GaAs.
We investigate experimentally and theoretically the influence of non-radiative carrier losses on the performance of
VECSELs under pulsed and CW pumping conditions. These losses are detrimental to the VECSEL performance
not only because they reduce the pump-power to output-power conversion efficiency and lead to increased
thresholds, but also because they are strong sources of heat. This heating reduces the achievable output power
and eventually leads to shut-off due to thermal roll-over. We investigate the two main sources of non-radiative
losses, defect recombination and Auger losses in InGaAs-based VECSELs for the 1010nm-1040nm range as well
as for InGaSb-based devices for operation around 2μm. While defect related losses are found to be rather
insignificant in InGaAs-based devices, they can be severe enough to prevent CW operation for the InGaSb-based
structures. Auger losses are shown to be very significant for both wavelengths regimes and it is discussed how
structural modifications can suppress them. For pulsed operation record output powers are demonstrated and
the influence of the pulse duration and shape is studied.
We demonstrate a novel epitaxial process for the growth of low-dislocation density GaSb on GaAs. The
growth mode involves the formation of large arrays of periodic 90° misfit dislocations at the interface
between the two binary alloys which results in a completely strain relieved III-Sb epi-layer without the
need for thick buffer layers. This epitaxial process is used for the growth of antimonide active regions
directly on GaAs/AlGaAs distributed Bragg Reflectors (DBRs) resulting in 2 μm VECSELs on GaAs