The analysis of internal optical loss and internal quantum efficiency in 1.3 μm-range InAlGaAsP/AlGaAs a composite n+-InGaAs/p+-InGaAs/p+-InAlGaAs tunnel junction obtained in the frame of molecular-beam epitaxy and wafer fusion technology. The level of internal optical losses in the lasers under study was varied by depositing a dielectric layer on the surface of the output mirror. It is shown that it is possible in principle to achieve low internal optical loss of less than 0.08% and 0.14% per one pass (round-trip) at temperatures of 20oC and 90oC, respectively. Keywords: vertical-cavity surface-emitting laser, wafer fusion, tunnel junction, superlattice, internal optical loss.

X-ray structural analysis and photoluminescence spectroscopy techniques were used to study heterostructures based on InGaAs/InAlGaAs superlattice for active regions of 1300 nm range lasers grown by molecular beam epitaxy. It is shown that the grown heterostructures have a high crystal quality. The perpendicular lattice mismatch of the average crystal lattice constant of the InGaAs/InAlGaAs superlattice with respect to the crystal lattice constant of the InP substrate is estimated at ~+0.01%. An analysis of the photoluminescence spectra made it possible to conclude that the contribution of Auger recombination is insignificant in the studied range of excitation power density. Studies of vertical-cavity surface-emitting lasers with an active region based on the InGaAs/InAlGaAs superlattice made it possible to estimate the gain coefficient at a level of 650 cm-1 for the standard logarithmic approximation of the dependence of the gain on the current density. The transparency current density of the laser was 400-630 A/cm2, which is comparable to the record low values for the case of highly strained InGaAs-GaAs and InGaAsN-GaAs quantum wells in the spectral ranges of 1300 nm, respectively. Keywords: superlattice, vertical-cavity surface-emitting laser, optical gain.

The impact of transverse optical confinement on the static and spectral characteristics of 1.55 μm vertical-cavity surface-emitting lasers (WF-VCSEL) with a buried tunnel junction (BTJ) n++-InGaAs/p++-InGaAs/p++-InAlGaAs, implemented using molecular-beam epitaxy and wafer fusion. It was found that for VCSELs with a tunnel junction (TJ) etching depth of 15 nm, the single-mode lasing occurs up to 8 μm BTJ mesa size due to a relatively weak lateral optical confinement, while the effect of a saturable absorber (SA) appears when the BTJ mesa size is less than 7 μm. Enhancing lateral optical confinement by increasing the BTJ etching depth up to 20 nm leads to suppression of the SA effect at the BTJ mesa size of 5-6 μm, but simultaneously limits the maximum single-mode optical power. According to obtained results an increase in the spectral mismatch between the maximum of the gain spectrum of the active region and the resonance wavelength of the WF-VCSEL up to ~ 35-50 nm will make it possible to suppress the undesirable SA effect in a wide range of the BTJ mesa sizes maintaining the single-mode lasing. Keywords: vertical-cavity surface-emitting laser, wafer fusion, molecular beam epitaxy, single-mode operation, saturable absorber.