Search

A semiconductor-laser design is proposed in which parasitic recombination in the waveguide region is suppressed by means of double asymmetric barriers adjacent to the active region. Double asymmetric barriers block the undesirable transport of one type of charge carrier while allowing the transport of the other type of carrier. The spacer in the double asymmetric barrier can serve to compensate the elastic strain introduced by the barrier layers as well as to control the energy spectrum of charge carriers and, thus, the transmission coefficient. By the example of a laser with Al0.2Ga0.8As waveguide layers, it is shown that the design with double asymmetric barriers makes it possible to suppress undesirable electron transport by a factor of 4 in comparison to the design using single asymmetric barriers.

The spatial distribution of the intensity of the emission caused by recombination appearing at a high injection level (up to 30 kA/cm2) in the waveguide layer of a GaAs/AlGaAs laser structure with GaInP and AlGaInAs asymmetric barrier layers is studied by means of near-field scanning optical microscopy. It is found that the waveguide luminescence in such a laser, which is on the whole less intense as compared to that observed in a similar laser without asymmetric barriers, is non-uniformly distributed in the waveguide, so that the distribution maximum is shifted closer to the p-type cladding layer. This can be attributed to the ability of the GaInP barrier adjoining the quantum well on the side of the n-type cladding layer to suppress the hole transport.

The structural and optical properties of GaP and GaPN layers synthesized by molecular-beam epitaxy on Si(100) substrates misoriented by 4° are studied. The possibility of producing GaP buffer layers that exhibit a high degree of heterointerface planarity and an outcropping dislocation density of no higher than ~2 × 108 cm–2 is shown. Emission from the Si/GaP/GaPN structure in the spectral range of 630–640 nm at room temperature is observed. Annealing during growth of the Si/GaP/GaPN structure makes it possible to enhance the room-temperature photoluminescence intensity by a factor of 2.6, with no shift of the maximum of the emission line.

The spectral, threshold, and power characteristics of a microdisk laser 31 μm in diameter with an active region based on InAs/InGaAs quantum dots, operating in the continuous-wave (cw) mode at room temperature are studied. The minimum threshold current density is 0.58 kA/cm2, the subthreshold linewidth of the whispering-gallery mode is 50 pm at a wavelength lying in the range of 1.26–1.27 μm. The total power emitted into free space reaches ~0.1 mW in the cw mode, whereas the radiation power of the whispering-gallery modes is ~2.8%.

In this work we report, to the best of our knowledge, the first quantum well electrically-pumped microdisk lasers monolithically deposited on (001)-oriented Si substrate. The III-V laser structure was epitaxially grown by MOCVD on silicon with an intermediate MBE-grown Ge buffer. Microlasers with an InGaAs/GaAs quantum well active region were tested at room temperature. Under pulsed injection, lasing is achieved in microlasers with diameters of 23, 27, and 31 µm with a minimal threshold current density of 28 kA/cm2. Lasing spectrum is predominantly single-mode with a dominant mode linewidth as narrow as 35 pm.

We analyze the optical forces acting on a nanoparticle placed in the vicinity of a plasmonic interface. We show that the under oblique plane wave excitation the nanoparticle excites surface plasmon polariton propagating along the plasmonic interface. The momentum conservation law in the plane of the interface results in appearance of optical recoil force attracting the particle to the source of light. The analyzed recoil force could increase the radiation pressure force by an order of magnitude.

We report on microdisk lasers based on GaInNAs(Sb)/GaAs(N) quantum well active region. Their characteristics were studied under electrical and optical pumping. Small-sized microdisks (minimal diameter 2.3 μm) with unprotected sidewalls show lasing only at temperatures below 220 K. Sulfide passivation followed by SiNx encapsulation allowed us achieving room temperature lasing at 1270 nm in 3 μm GaInNAs/GaAs microdisk and at 1550 nm in 2.3 μm GaInNAsSb/GaAsN microdisk under optical pumping. Injection microdisk with a diameter of 31 μm based on three GaInNAs/GaAs quantum wells and fabricated without passivation show lasing up to 170 K with a characteristic temperature of T0 = 60 K. publishedVersion

We demonstrate that quantum dot microdisk lasers are able to operate under continuous wave current injection at 100 °C. We also present a novel method for increasing a side mode suppression ratio in microdisk lasers. publishedVersion

High-index dielectric (Si) nanoantennas providing outcoupling of light from InAs/Ga(Al)As quantum dot (QD) microdisk lasers have been designed. The spatial distribution of light emitted from optically pumped QD microdisk lasers with a single Si spherical nanoantenna placed on the top surface of the microdisk was studied experimentally by confocal optical microscopy. Dependences of the emission intensity on the size and position of the Si nanoantenna were investigated. It was found that the laser mode to be outcoupled can be selected by choosing the nanosphere position with respect to the mode electromagnetic field maximum. Optimization of the Si nanoantenna parameters resulted in a 23-fold increase of the emission intensity at the location of the Si nanoantenna (whereas the total intensity enhanced 4 times) compared to the emission intensity from the initial microdisk laser without significant deterioration of the resonator quality factor.

We probe the resonance properties of complex plasmonic structures by Scanning Near-field Optical Microscopy (SNOM). Groups of three differently arranged silver nanoparticles covered with Surface-Enhanced Raman Scattering (SERS) analyte Rhodamine 6G were chosen to visualize electric field distribution nearby the nanostructures. The particles were grown on the surface of a silver-ion-exchanged glass using thermal poling and annealing of the processed glass substrate in hydrogen atmosphere. The morphology of the nanoparticles and their arrangement in the groups were characterized with Atomic Force Microscopy (AFM). The near-field SERS maps superimposed on the AFM scans of the studied groups of nanoparticles visualize the Raman hotspots with 100 nm resolution.

In this paper a probe of an atomic force microscope (AFM) served as a detector of optical radiation. We investigated absorption of optical radiation in the visible range by commercially available Si and Si3N4 probes. It has been shown that the radiation in the far field is mainly absorbed in the probe tip. By scanning a laser beam with a diameter of ~ 0.7 microns by the AFM probe, a lateral resolution of ~ 1.5 microns was demonstrated. Numerical modeling of evanescent wave absorption by AFM probes showed enhancement of the absorption in the probes as compared with a flat surface. A Si3N4 probe more effectively absorbs the evanescent radiation.

We present detailed studies of optically pumped InAs/InGaAs quantum dot based racetrack microlasers with 3.5-μm bend radius operating at room temperature. Q factor over 8000 and room temperature threshold power in the mW-range were achieved in the racetrack microlasers with straight section length ranging from 0 to 4 μm. A systematic investigation of the influence of the racetrack straight section length on spatial distribution of optical modes is presented. The microcavity eigenmodes and electromagnetic field distribution calculated by means of three-dimensional numerical simulation demonstrate a good agreement with the experimental results obtained by micro-photoluminescence and scanning near-field optical microscopy. The racetracks demonstrate zigzagging behavior of the modes inside the cavity and the energy switching between the radial maxima in second-order modes. Higher-order modes are found to be suppressed in micro-photoluminescence spectra.

Electrically driven microdisk lasers with top contacts made of a semitransparent conducting pyrolytic carbon film are developed. Electrical properties of the pyrolytic carbon contact to a p-type doped GaAs epitaxial layer are studied. Room temperature electroluminescence spectra from an array of the microdisk lasers and a single 27 μm in diameter microdisk laser are demonstrated.

Far field emission of optically pumped QD microdisk lasers with spherical Si nanoantenna placed on the top surface of microdisk is studied theoretically and experimentally. The interaction of the whispering gallery mode microdisk resonator with properly designed and positioned Si nanospheres results in improvement of light outcoupling and directed emission.

Optically pumped 3-6μm in diameters microdisk lasers with InGaAsN/GaAs quantum well active region has been studied. Single-mode CW lasing at 78K temperature in microdisk laser with 3 μm diameter is demonstrated.