Single-mode long-wavelength (LW) vertical-cavity surface-emitting lasers (VCSELs) present an inexpensive alternative to DFB-lasers for data communication in next-generation giga data centers, where optical links with large transmission distances are required. Narrow wavelength-division multiplexing systems demand large bit rates and single longitudinal and transverse modes. Spatial division multiplexing transmission through multicore fibers using LW VCSELs is enabling still larger-scale data center networks. This review discusses the requirements for achieving high-speed modulation, as well as the state-of-the-art. The hybrid short-cavity concept allows for the realization of f_3dB frequencies of 17 GHz and 22 GHz for 1300 nm and 1550 nm range VCSELs, respectively. Wafer-fusion (WF) concepts allow the realization of long-time reliable LW VCSELs with a record single-mode output power of more than 6 mW, 13 GHz 3 dB cut-off frequency, and data rates of 37 Gbit/s for non-return-to-zero (NRZ) modulation at 1550 nm.

It is shown that molecular-beam-epitaxy technology can be used to fabricate heterostructures for quantum-cascade lasers of the wavelength range of 7–8 μm with an active region comprising 50 cascades based on a heterojunction of In_0.53Ga_0.47As/Al_0.48In_0.52As solid solutions. The optical emission is obtained using a quantum-cascade design operating on the principle of two-phonon resonance scattering. The properties of heterostructures were studied by the methods of X-ray diffraction and transmission electron microscopy, which showed their high quality with respect to the identical compositions and thicknesses of all 50 cascades. Stripe-geometry lasers made of these heterostructures exhibited lasing with a threshold current density below 1.6 kA/cm² at a temperature of 78 K.

High power single-mode wafer fused 1550 nm VCSELs with an active region based on InGaAs quantum wells are fabricated. An InP-based optical cavity and two AlGaAs/GaAs distributed Bragg reflector heterostructures were grown by molecular-beam epita oy. The current and optical confinements are provided by a lateral-structured buried tunnel junction with $\sim ~6~\mu \text{m}$ diameter and etching depth of ~ 20 nm. The VCSELs demonstrate ~ 3.4 mW single-mode continuous-wave output optical power and a threshold current about 2 mA at 20°C. The output optical power exceeds 1 mW at 70°C. A −3dB modulation bandwidth > 13 GHz is obtained at 20°C. Non-return-to-zero data transmission under back-to-back condition of ~ 37 Gbps is shown.

Room-temperature lasing at a wavelength of 8 μm in multistage quantum-cascade lasers pumped by current pulses is demonstrated. A quantum-cascade laser heterostructure based on the In0.53Ga0.47As/Al0.48...

Single-mode lasing at room temperature in quantum-cascade lasers (QCLs) with arched cavity design has been demonstrated. The output optical power in single-mode lasing regime at ~7.7-μm...

Molecular beam epitaxy techniques were used to grow a quantum-cascade laser (QCL) heterostructure based on an In0.53Ga0.47As/Al0.48In0.52As heteropair lattice-matched with an InP substrate....