Vertical-cavity surface-emitting lasers emitting at the spectral range of 1.55 µm based on heterostructures with a buried tunnel junction (BTJ) with a height step of 15 nm are studied. The devices are realized using wafer fusion technique of heterostructures grown by molecular beam epitaxy and demonstrate a single-mode lasing regime at the 8 μm BTJ-diameter. With a decrease in the BTJ-diameter, a sharp increase in the threshold current, accompanied by an abrupt increase in the output optical power and resonance frequency at the lasing threshold are observed. Stable single-mode lasing is due to the smoothing of the boundary of the overgrown surface relief, which leads to a smooth change in the profile of the effective refractive index in the lateral direction, while maintaining effective current confinement, which makes it possible to significantly reduce the transverse optical confinement factor for high-order modes even at large BTJ-diameter. However, at small BTJ-diameter, it also leads to the formation of a saturable absorber in the non-pumped parts of the active region.
The design of the n++-InGaAs/р++-InGaAs/р++-InAlGaAs tunnel junction (TJ) for 1.55 μm range vertical-cavity surface-emitting lasers (VCSELs), developed by wafer fusion technique of InAlGaAsP/InP optical cavity with AlGaAs/GaAs distributed Bragg reflectors is proposed and realized. The presence of oxidation-resistant InGaAs layers allows the use of molecular-beam epitaxy at all stages of the heterostructure fabrication, including for regrowth of the TJ surface relief. In the case of using the n++-InGaAs/р++-InGaAs/р++-InAlGaAs TJ, a noticeable increase in the internal optical losses compared to the n++/р++-InAlGaAs TJ design was not obtained. The increase in internal optical loss in lasers can be avoided due to Burshtein-Moss effect in n++-InGaAs layers and thickness minimization of р++-InGaAs layer. As a result, the characteristics of fabricated lasers are comparable with characteristics of VCSELs with n++/p++-InAlGaAs TJ with a similar level of mirror losses.
The characteristics of a 23-μm in diameter microdisk laser are studied under high-frequency modulation with a heatsink stabilized at 18оC. It is shown that the minimum consumption of electrical energy is 1.6 pJ/bit as achieved at modulation frequency of 4.2 GHz. The maximum modulation frequency reaches 6.7 GHz with energy consumption of 3.3 pJ/bit.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.