Abstract In pursuing cheap and effective oxygen reduction catalysts, the Fe/N/C system emerges as a promising candidate. Nevertheless, structural transformations of starting materials into Fe- N-doped carbon catalysts remains poorly characterized under pyrolytic conditions. Here, we explore evolution Fe species track formation Fe–N 4 site development by employing diverse in-situ diagnostic techniques. In-situ heating microscopy reveals initial FeO x nanoparticles subsequent internal...

We report the long-term reliability measurement on uncoated Al-free InGaAsP/GaAs (λ=808 nm) lasers at high-power and high-temperature operation. No degradation in laser performance has been observed for over 30 000 h of lifetime testing any randomly selected several 100-μm-wide operated 60 °C with 1 W continuous wave output power. This is first most conclusive evidence ever reported that directly shows high lasers.

A compressively strained InAsSb/InAs multiple quantum-well (MQW) structure was grown by low-pressure metal-organic chemical vapor deposition. Maximum output power (from two facets) up to 1 W with differential efficiency about 70% obtained from a MQW laser stripe width of 100 μm and cavity length 700 for emitting wavelength 3.65 at 90 K in pulse mode operation. About 2 times lower threshold current density the lasers temperature range 140 compared double heterostructure on same growth conditions.

InAsSb-InAsSbP double heterostructure diode lasers have been grown by metal-organic chemical vapor deposition on (100) InAs substrates. High-output powers of 660 mW in pulse mode and 300 continuous wave operation with 400-μm cavity length 100-μm-wide aperture at 78 K obtained. These devices showed low threshold current density 40 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , internal loss 3.0 cm/sup -1/, far-field /spl...

Photoluminescence has been measured for double- and separate-confinement InAsSb/InAsSbP heterostructures grown by low-pressure metalorganic vapor deposition. A measurement of the integrated luminescence intensity at temperature range 77–300 K shows that over a wide excitation level (1–5×102 W/cm2) radiative transitions are dominant mechanism below T∼170 K. Auger recombination coefficient C=C0 exp(−Ea/kT) with C0≊5×10−27 cm6/s Ea≊40 meV estimated.

The optimized structure for the InGaAsP/GaAs quaternary material lasers (λ=0.808 μm) is investigated most efficient high-power operation through an experiment and theoretical study. A comparative study performed of threshold current density Jth differential efficiency ηd dependence on cavity length (L) two different laser structures with active layer thickness (150 300 Å) as well multiple quantum structures. model a more accurate formulation minority leakage phenomenon provides explanation...

We report metal–organic chemical-vapor deposition-grown double heterostructure InAsSbP/InAsSb/InAs diode lasers emitting at 3.2 μm operating temperatures up to 220 K with threshold current density of 40 A/cm2 77 and characteristic temperature 42 K. Output powers as high 260 mW in pulse mode 60 continuous wave operation have been obtained from an uncoated 100 stripe-width broad-area laser Comparison theory shows that there is no significant nonradiative recombination mechanism for these

We demonstrate high-power InAsSb/InPAsSb laser bars (λ≈3.2 μm) consisting of three 100-μm-wide stripes 700 μm cavity length, with peak output power up to 3 W at 90 K, and far-fields for the direction perpendicular junction as narrow 12° full width half maximum. Spectra far-field patterns are shown have excellent characteristics a wide range operating conditions, suggesting possibility even higher light emission good beam quality. Joule heating is be major factor limiting operation.

In this work, we study the origin of optical losses in Al-free InGaAsP/GaAs (λ=0.808 μm) and InGaAs/GaAs/InGaP (λ=0.980 lasers. Theoretical modeling experimental results indicate that scattering laser beam by refractive index fluctuation alloys is dominant loss our lasers, due to free-carrier absorption interface roughness are negligible.

An experimental and theoretical study on temperature dependence of the threshold current density Jth differential efficiency ηd for InGaAsP/GaAs laser diodes emitting at λ=0.8 μm was performed. Threshold increases decreases as is increased mainly because thermal broadening gain spectrum. However, measured could not be explained when only this effect considered. In letter, momentum relaxation rate ℏ/τ carriers investigated by performing photoluminescence study. At high temperature, increase...

The reliability of uncoated InGaAsP/GaAs high-power diode lasers emitting at 808 nm wavelength has been studied. 47 W quasicontinuous wave output power (pulse width 200 μs, frequency 20 Hz) have obtained from a 1-cm-wide laser bar. A single-stripe without mirror coating life tested 40 °C for 800 mW continuous (cw) and showed no noticeable degradation change the lasing after 6000 h operation.

High-power operation of 3 W in pulse mode, 750 mW quasi-continuous wave and 650 continuous per uncoated facet from 100-μm aperture has been demonstrated for 1-mm-long cavity InGaAsP/GaAs 808-nm laser diodes prepared by low-pressure metalorganic chemical vapor deposition. Threshold current density 300 A/cm2, differential efficiency 1.1 W/A, T0=155 °C, transverse beam divergence 27°, less than 2-nm linewidth at 808 nm have measured. No degradation observed after 1000 h a regime.

We report a theoretical model that accurately describes the effects of minority carrier leakage from InGaAsP waveguide into InGaP cladding layers in high-power aluminum-free 0.8 μm InGaAsP/InGaP/GaAs separate confinement heterostructure lasers. Current due to relatively low band-gap discontinuity between active region and barrier can be eliminated by employing laser diodes with cavity length longer than 500 μm. Experimental results for lasers grown low-pressure metalorganic chemical vapor...

InAs x Sb 1−x /InP 1−x−y As y double heterostructures have been grown on substrates by metal-organic chemical vapor deposition. The minority carrier leakage to the cladding layers was studied with photoluminescence measurements InAsSb/InPAsSb heterostructures. A model is used extract parameters related current (diffusion-coefficient and length) from experimental results. Using obtained parameters, temperature dependence of threshold density heterostructure lasers predicted compared

We investigated the quantum-size effects of quantum well (QW) on gain and threshold current density for InGaAsP/GaAs (λ=808 nm) laser diodes. In this work, a comparison is made lasers with different QW thickness while keeping optical confinement factors constant. found that differential efficiency were not affected by narrowing thickness. The theoretical model taking into account mixing valence bands momentum relaxation spontaneous emission (optically pumped) measurement shows absence...

Special double- and separate-confinement InGaAsP/GaAs heterostructures intended for photoluminescence measurements have been grown by low-pressure metal-organic chemical-vapor deposition. The band gap of the active region quaternary material was close to 1.5 eV, waveguide structures near 1.8 eV. Measurement integrated luminescence efficiency at 300 K has shown that over a wide range excitation level (10–103 W/cm2) radiative transitions are dominant mechanism excess carrier recombination in...

Far fields in perpendicular direction to the junction are investigated double heterostructure (DH) and multiple quantum well (MQW) midwave-infrared InAsSb/InPAsSb/InAs lasers (λ=3.2–3.6 μm). Strong broadening of far DH was observed with increases temperature and/or current. On contrary, MQW otherwise identical structure exhibit very stable as narrow 23° for all operating conditions investigated. Our experiment theoretical modeling suggest that these different behaviors attributed refractive...

We present a generalized $\mathbf{k}\ensuremath{\cdot}\mathbf{p}$ perturbation method that is applicable for atomic-scale superlattices. The model in good quantitative agreement with full band theories local-density approximation, and approaches results of the conventional (i.e., Kane's Hamiltonian) envelope function approximation superlattices large periods. indirect gap AlAs/GaAs short periods observed experiments explained using this method.

InGaAsP/GaAs aluminum-free laser diodes are currently attracting attention as an emerging competitor for widely used AlGaAs-based lasers emitting at 0.87-0.75 /spl mu/m, especially Nd-YAG pumping (/spl lambda/=0.808 mu/m). These have already demonstrated such advantages narrow transverse far-field pattern, absence of uncoated mirror facet oxidation under high-power operation, low series resistance and processing ease offer a strong promise longer lifetime. In recent paper the authors studied...

The InGaAsP high power laser emitting at 808 nm with /spl eta//sub d/=1.1 W/A, J/sub th/=200 A/cm/sup 2/, and T/sub o/=155/spl deg/C have been grown by LP-MOCVD. Far field divergence of 27/spl deg/, output 3 W in the pulse-regime, 1.5 quasi-CW-regime 1 CW-mode per uncoated facet obtained for mm long diodes.

InGaAsP/GaAs materials are currently attracting attention for potentially reliable high-power SCH-SQW laser fabrication 0.98 and 0.8 /spl mu/m range. Scattered points show experimental results variation of J/sub th/ eta//sub d/ vs. cavity length respectively, lasers with different thicknesses quantum well active layer. These features were evidenced high reproducibility more than 40 structures. characteristics anomalously strong dependence the short that cannot be explained by theoretical...