1,720,965 research outputs found
Vertical-cavity surface-emitting lasers: computer-aided modal and polarization engineering
Full text linkL'abstract è presente nell'allegato / the abstract is in the attachmen
Modeling of single-mode high-power VCSEL arrays
Full text linkIn this work we investigate different architectures to realize a single-mode VCSEL array for high power applications. This is done by simulating a large active-area VCSEL with either a metallic or a grating-relief-based patterning at the outcoupling aperture. The investigated designs are compared, highlighting possible strategies to improve the fiber coupling by improving the far field (FF) profile. This contribution also presents a satisfactory match between the simulations and the FF experimental data obtained from the measurements of a VCSEL array structure
Physics-based modeling of AlGaAs tunnel junction VCSELs: a comparative appraisal
Full text linkIn this paper, we adopt our in-house physics-based solver VENUS (Vcsel Electro-optho-thermal NUmerical Simulator) to assess the static output characteristics of an AlGaAs/GaAs TJ-VCSEL emitting at 850 nm. To this aim, VENUS is extended to exploit a combined drift-diffusion model and NEGF formalism, that accurately captures tunneling effects across the TJ. The results are compared to a commercial pin-like VCSEL, at temperatures ranging from 20 to 110°C, to cover a broad set of operations from room temperature to harsh environments
Analytical model of the Ultrabroadband Operation of Transverse-Coupled-Cavity VCSELs
Full text linkThe ultrabroadband operation of transverse-coupled-cavity vertical-cavity-surface-emitting lasers is investigated in this work. Relying on a closed-form expression of the intensity modulation response, our model allows for an extended and fast parametric campaign of the design inputs, as well as an easy interpretation of the bandwidth enhancement
Elliptically polarized light obtained from tilted high-contrast grating VCSELs
No full textWe show that ultrathin elliptically polarized VCSELs can be realized with standard high-contrast gratings (HCGs) whose bars are tilted to the semiconductor crystalline axes on the transverse plane, without relying on any 2D chiral layer. Revisiting orthogonal polarization suppression ratio (OPSR) measurements, we demonstrate that the reduced OPSR for tilted gratings is related to elliptical lasing polarization rather than degraded polarization selectivity. Simulations confirm that the polarization state can be tuned by balancing intrinsic and HCG-induced anisotropies. These devices provide integrated elliptically polarized and wavelength-tunable sources for chip-scale atomic devices
VCSEL Thermal Sources: A Physics-Based Simulation Approach
Full text linkFully-comprehensive physics-based simulations of vertical-cavity surface-emitting lasers (VCSELs) must account for the coupled electrical, optical and thermal problems. While electrical and optical solvers form the foundation of cold-cavity VCSELs modeling, self-heating has the strongest impact during the device operation. In this work, we present the capability of our in-house solver VENUS to model the wavelength redshift induced by temperature variations and show the spatial distribution of the primary thermal sources: Joule effect, free-carrier absorption, non-radiative recombinations and quantumwell capture. The spatial mapping of each source might allow to limit the impact of self-heating on the performance
High-Power Emission via Large-Area VCSELs With Single High-Order Mode Operation
Full text linkIn this work we investigate patterned large-active area AlGaAs vertical-cavity surface-emitting lasers (VCSELs) targeting high-power single-transverse-mode emission. As a first step, our in-house 3D electromagnetic vectorial mode solver VELMS is validated against preliminary experimental data. Then, VELMS is applied to implement single-mode operation on VCSELs featuring large-area rectangular oxide apertures. A comparative appraisal of different mode selection strategies based on patterning the outcoupling facet of the device is presented, providing a number of alternatives for a broad audience of technologists
Modeling carrier transport in mid-infrared VCSELs with type-II superlattices and tunnel junctions
Full text linkVertical-cavity surface-emitting lasers are promising light sources for sensing and spectroscopy applications in the midinfrared 3 - 4 μm spectral region. A type-II superlattice active region is used for carrier injection and confinement, while a buried tunnel junction defines a current aperture, decreasing the series resistivity. Highly nanostructured to optimize device performance, mid-infrared VCSELs pose modeling challenges beyond semiclassical approaches. We propose a quantum-corrected semiclassical approach to device design and optimization, complementing a drift-diffusion solver with a nonequilibrium Green’s function description of band-to-band tunneling in the buried tunnel junction, and a local density of states computed from the solution of the Schrödinger equation in the superlattice active region
AlGaAs Tunnel Junction (TJ)-VCSELs: A NEGF–Drift-Diffusion Approach
Full text linkThis work reports a multiscale physics-based approach aimed at investigating the benefits of introducing a single tunnel junction (TJ) within conventional AlGaAs Vertical-Cavity Surface-Emitting Lasers (VCSELs). Our comprehensive VCSEL solver VENUS is augmented with a non-equilibrium Green's function (NEGF) approach to extract the band-to-band tunneling rate across the TJ. To showcase the NEGF-VENUS features, we apply it to the commercial pin oxide confined AlGaAs VCSEL previously investigated by VENUS, by inserting a TJ with minimal variations to the optical resonator. Besides finding the optimal position of TJ and oxide aperture, we can also compare the different hole injection schemes in the active region. Our results show the potential of doubling the maximum output power with the same threshold current, with perspectives of further enhancement by stacking more tunnel junctions
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