M. M. Kulagina

High external differential efficiency and high optical gain of long-wavelength quantum dot diode laser

Abstract Long-wavelength (1.29 μm ) lasers grown on GaAs and based on several planes of self-organized quantum dots in an external quantum well demonstrate significant improvement of the external differential efficiency (88%) and the characteristic temperature (150 K ) . This is due to suppression of carrier pile-up in the waveguide region in combination with extended range of optical loss in which the ground-state lasing survives.

Control of emission spectra in quantum dot microdisk/microring lasers

Focused ion beam is applied to quantum dot based microresonators to form pits or groove on their surface. The emission spectra of the resonators based lasers are significantly thinned out after the ion beam milling, and one or two modes become dominant instead of a group of modes having comparable intensities. The linewidth of the lasing mode is kept unchanged, whereas the lasing threshold demonstrates an insignificant growth.

Transverse single-mode edge-emitting lasers based on coupled waveguides.

We report on the transverse single-mode emission from InGaAs/GaAs quantum well edge-emitting lasers with broadened waveguide. The lasers are based on coupled large optical cavity (CLOC) structures where high-order vertical modes of the broad active waveguide are suppressed due to their resonant tunneling into a coupled single-mode passive waveguide. The CLOC lasers have shown stable Gaussian-shaped vertical far-field profiles with a reduced divergence of ∼22° FWHM (full width at half-maximum) in CW (continuous-wave) operation.

Mode selection in InAs quantum dot microdisk lasers using focused ion beam technique

Optically pumped InAs quantum dot microdisk lasers with grooves etched on their surface by a focused ion beam are studied. It is shown that the radial grooves, depending on their length, suppress the lasing of specific radial modes of the microdisk. Total suppression of all radial modes, except for the fundamental radial one, is also demonstrated. The comparison of laser spectra measured at 78 K before and after ion beam etching for a microdisk of 8 μm in diameter shows a sixfold increase of mode spacing, from 2.5 to 15.5 nm, without a significant decrease of the dominant mode quality factor. Numerical simulations are in good agreement with experimental results.

Highly efficient photovoltaic cells based on In{sub 0.53}Ga{sub 0.47} as alloys with isovalent doping

The effect of isovalent doping with P on the surface and bulk properties of the In0.53Ga0.47As alloy (below, InGaAs) was evaluated from variations in the photoluminescence and transmission spectra. It is established that isovalent doping decreases the nonradiative recombination rate in the bulk and on the surface of doped layers. The use of additional isovalent doping provided an improvement of parameters of the narrow-gap InGaAs-based solar cell used for the conversion of the concentrated solar radiation. The maximum efficiency of photovoltaic conversion in a spectral range of 900–1840 nm was 7.4–7.35% at a ratio of concentration of the solar radiation of 500–1000 for the AM1.5D Low AOD spectrum.

Electrically pumped InGaAs/GaAs quantum well microdisk lasers directly grown on Si(100) with Ge/GaAs buffer

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.

Microdisk lasers based on GaInNAs(Sb)/GaAs(N) quantum wells

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 2.3u2009μm) with unprotected sidewalls show lasing only at temperatures below 220u2009K. Sulfide passivation followed by SiNx encapsulation allowed us achieving room temperature lasing at 1270u2009nm in 3u2009μm GaInNAs/GaAs microdisk and at 1550u2009nm in 2.3u2009μm GaInNAsSb/GaAsN microdisk under optical pumping. Injection microdisk with a diameter of 31u2009μm based on three GaInNAs/GaAs quantum wells and fabricated without passivation show lasing up to 170u2009K with a characteristic temperature of T0u2009=u200960u2009K.

In0.53Ga0.47As/InP conventional and inverted thermophotovoltaic cells with back surface reflector

Characteristics of conventional and inverted InGaAs/InP thermophotovoltaic (TPV) cells with a back surface reflector (BSR) fabricated on electrically active n‐type InP substrates are presented. Thermophotovoltaic cells based on lattice matched InP‐In0.53Ga0.47As heterostructures were fabricated with the use of LPE and Zn,P diffusion technologies.In the p‐n TPV cells (conventional type, spectral range 600÷1800 nm) with a frontal p‐InGaAs layer, BSR was made on a n‐InP substrate. In the n‐p structure (inverted type, spectral range1000–1800 nm) with a frontal bulk n‐InP‐window‐substrate, BSR was formed on a p‐InGaAs layer. Antireflection coating (ARC) on the frontal cell surface consists of ZnS/MgF2 layers.Results of investigation of sub‐bangap photons reflection from InP substrates with a backside MgF2/Au mirror in the range of 1800÷2000nm are described. The reflection of BSR for InP samples with the doping level in the range of 1×1017÷6×1018cm−3 evidenced a weak dependence on their thickness and doping lev...

Effect of modulation p-doping level on multi-state lasing in InAs/InGaAs quantum dot lasers having different external loss

The influence of the modulation p-doping level on multi-state lasing in InAs/InGaAs quantum dot (QD) lasers is studied experimentally for devices having various external losses. It is shown that in the case of short cavities (high external loss), there is an increase in the lasing power component corresponding to the ground-state optical transitions of QDs as the p-doping level grows. However, in the case of long cavities (small external loss), higher dopant concentrations may have an opposite effect on the output power. Based on these observations, an optimal design of laser geometry and an optimal doping level are discussed.

Microdisk Injection Lasers for the 1.27-μm Spectral Range

Microdisk injection lasers on GaAs substrates, with a minimum diameter of 15 μm and an active region based on InAs/InGaAs quantum dots, are fabricated. The lasers operate in the continuous-wave mode at room temperature without external cooling. The lasing wavelength is around 1.27 μm at a minimum threshold current of 1.6 mA. The specific thermal resistance is estimated to be 5 × 10–3 °C cm2/W.