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The results of complex studies of static and dynamic performance of 1550 nm-range VCSELs, which were created by direct bonding (wafer fusion technique) InAlGaAs/InP optical cavity wafers with AlGaAs/GaAs distributed Bragg reflector wafers grown by molecular beam epitaxy, are presented. The VCSELs with a buried tunnel junction diameter less than 7 μm demonstrated a single-mode lasing with a side-mode suppression ratio more than 40 dB; however, at diameters less than 5 μm, a sharp increase in the threshold current is observed. It is associated to the appearance of a saturable absorber due to penetration of optical mode into the non-pumped regions of the active region. The maximum single-mode output optical power and the -3 dB modulation bandwidth reached 4.5 mW and 8 GHz, respectively, at 20oC. The maximum data rate at 20oC under non-return-to-zero on-off keying modulation was 23 Gb/s for a short-reach link based on single-mode fiber SMF-28. As the length of the optical link increased up to 2000 m, the maximum data rate dropped to 18 Gbit/s. The main factors affecting the high-speed operation and data transmission range are defined and discussed, and the further ways to overcome themit are proposed. Keywords: VCSEL, wafer fusion, molecular beam epitaxy, single-mode operation, high-speed performance.

The results of a study of nitrogen-containing active regions based on superlattices grown on GaAs substrates are presented. Active regions based on alternating InAs and GaAsN layers were fabricated by molecular-beam epitaxy using a nitrogen plasma source. Based on the XRD analysis, the thicknesses and average composition of superlattice layers are estimated. The study of dark-field images obtained by transmission electron microscopy showed the presence of interdiffusion of InAs into GaAsN. The results of a study of the photoluminescence and electroluminescence spectra at different pump levels are presented. Efficient electroluminescence is demonstrated near 1150 nm with a full width at half-maximum of about ~90 meV. Keywords: Superlattices, molecular beam epitaxy, gallium arsenide, dilute nitride, GaAsN, InAs.

The possibility of using vertical-emitting lasers with intracavity contacts (IC-VCSEL) and a rhomboidal oxide current aperture for creating a non-zero magnetic field optically pumped atomic magnetometers (OPM) with a 133Cs vapor cell for magnetoencephalographic (MEG) systems were demonstrated. Relative intensity noise (RIN) and polarization resolved RIN of the IC-VCSEL in the 895 nm range with different mirror losses (linewidth) in the frequency range from 1 Hz to 100 kHz were experimentally investigated. Lasers with low mirror loss (narrow linewidth) have polarization resolved RIN comparable to amplitude noise. For IC-VCSEL with an output optical power of 0.8 mW and a linewidth of 55 MHz, the noise level measured is 148 dB/Hz in 1 Hz bandwidth at 40 kHz frequency. The ultimate sensitivity of OPM based on two-beam MZ-scheme with studied VCSELs was estimated as ~ 11 fT/sqrt(Hz)sqrt. Keywords: vertical-cavity surface-emitting laser (VCSEL), magnetoencephalographic (MEG) systems, optically pumped atomic magnetometers (OPAM), relative intensity noise (RIN), polarization-resolved RIN.

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.

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 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.

The possibility of fabrication of 4.6 μm spectral range quantum-cascade laser heterostructures by molecular-beam epitaxy technique with non-selective overgrowth by the metalorganic vapour-phase epitaxy is shown. The active region of the laser was formed on the basis of a heteropair of In0.67Ga0.33As/In0.36Al0.64As solid alloys. The waveguide claddings are formed by indium phosphide. The results of surface defects inspection and X-ray diffraction analysis of quantum-cascade laser heterostructures allow to conclude that the structural quality of the heterostructures is high and the estimated value of the root mean square surface roughness does not exceed 0.7 nm. Lasers with four cleaved facets exhibit lasing at room temperature with a relatively low threshold current density of the order of 1 kA/cm2. Keywords: superlattices, quantum-cascade laser, epitaxy, indium phosphide.

The results of studies of 7.5-8.0 μm range surface-emitting ring quantum-cascade lasers are presented. A second-order diffraction grating with a calculated coupling coefficient of ~9 cm-1 is formed on the entire surface of the ring cavity by focused ion beam milling. Surface-emitting lasing at room temperature near 7.75 μm with a threshold current density of ~8 kA/cm2 and an outer radius of the ring cavity of 202 μm is demonstrated. The results of studying the intensity distribution in the far-field near the normal to the surface showed the presence of two maxima. It is shown that the implemented coupling coefficient is not sufficient to ensure single-mode lasing in the studied ring quantum-cascade lasers. Keywords: superlattices, quantum-cascade laser, epitaxy, indium phosphide, focused ion beam milling.