Vertical-cavity surface-emitting lasers (VCSELs) have become leading light sources in plenty of applications due to their good characteristics and low costs. There are, however, some features that need improvements; therefore, optimized or new designs ideas are necessary. To this aim, an electromagnetic simulation tool, which is fast and precise at the same time, is desirable; to cover all the possible requirements, it should be fully three-dimensional (3-D) and vectorial. A model with such features was first proposed by Bava et al. ("Three-Dimensional Model for Vectorial Fields in Vertical-Cavity Surface-Emitting Lasers", Phys. Rev. A, vol. 63, p. 23816, 2001), based on coupled-mode theory. Here, a review of its applications will be given, related to particular devices: nonperfectly circular VCSELs and phase-coupled arrays. The comparison with the corresponding experimental results turns out to be very satisfactory. Therefore, we were encouraged to use the model for obtaining design criteria of polarization maintaining VCSELs by using a small relief grating. The capability of gratings to pin the VCSEL polarization was already demonstrated; however, the different configurations do not allow one to have a clear overview of this technique. Moreover, to the best of our knowledge, a full simulation of a VCSEL with a grating was never presented, due to the complexity of treating the corresponding fully 3-D and vectorial problem. For the first time, we have the possibility of comparing different configurations on the same footing; in particular, we will evaluate the performances of dielectric and metal gratings. With the design we propose here, single-transverse and single-polarization-mode operation are predicted with a suppression of the other polarization easily in the order of 45 dB.

We present a detailed study of oxide-confined, vertical-cavity surface-emitting lasers (VCSELs), where the reflectivity of the top mirror has been patterned by means of a metal grid, which at the same time acts also as an electrode. Owing to their features, these kind of devices are commonly referred to as phase-coupled VCSEL arrays. The anlaysis is based on a joint experimental and theoretical effort: the former is devoted to a complete characterization of the emission properites, while the latter is based on a comprehensive fully vectorial model for the structure eigenmodes with the details of their complex structure. The detected characteristics make them quite attractive for various applications and the comparison of their modal properties with the model is proven to be essential for a deep understanding of these lasers. In particular we explain for the first time, a characteristic behavior of the lasing array, which displays spatially inhomogeneous polarization characteristics with symmetry properties with respect to the array diagonals. The good matching between theory and experiment opens new perspectives for optimized devices.

We compare the results of different optical vertical-cavity surface-emitting laser models on the position-dependent effects of thin oxide apertures. Both scalar and vectorial models as well as hybrid models are considered. Physical quantities that are compared are resonance wavelength, threshold material gain, and modal stability. For large device diameters and low-order modes, the agreement between the different models is quite good. Larger differences occur when considering smaller devices and higher order modes. It is also observed that the spread in the resonance wavelengths is smaller than that for the threshold material gain.

The electromagnetic problem of modeling vertical-cavity surface-emitting lasers with their full three-dimensional characteristics is analyzed, including oxide confinement, mesa mirrors, metal contacts, and noncircular geometries. The model is based on the mode expansion of the electromagnetic field in the continuous basis of cylindrical TE and TM modes of the cavity medium and on coupled mode theory. The full vectorial treatment of the problem allows a correct analysis of the polarization characteristics of these lasers, which is a topic of great interest both for the device physics and for many applications. A comparison between the fully vectorial treatment and the LP scalar approximation is carried out and polarization resolved results for rectangular and elliptical structures are presented.

An electromagnetic model of Vertical Cavity Surface Emitting Lasers (VCSEL) based on semiconductor compounds is developed; it relies on the rigorous solution of Maxwell equations, including the field confinement due to the gain guiding mechanism which strongly influences the noise properties. The solution of the problem is based on an integral equation of the Fredholm type whose eigenvalues are related to the threshold condition and eigenvectors give the field distributions.

Frequency conversion in Multiple Quantum Well travelling wave amplifiers, when a strong pump is injected in the device and under highly saturated regime, can show longitudinal power fluctuations up to hundreds gigahertz beat frequencies. A model which explains such phenomena is presented.

In this paper a complete model to evalute the nonlinear optical response of a semiconductor quantum-well structure is presented. In these structures, excitonic effects are strong also at room temperature; they arise from coulomb interaction between charged particles, and the corresponding many-body problem is treated in the framework of the second quantization approach, based on the total Hamiltonian of the interacting electron-hole plasma. Moreover Coulomb effects are included, together with a proper description of valence-band states, which accounts for heavy- and light-hole mixing through a variational technique. The computed optical responses, both for TE and TM polarized light, are evaluated by summing up the coupled contributions of the first two transitions; they show a satisfactory agreement with experimental results.

Optically controlled Multiple Quantum Well (MWQ) modulators promise to be of great interest for all optical data processing. In this paper we analyze a device, based on a GaAs/AlAs MQW structure, whose prin­ciple of operation depends on the controlled excitonic absorption by means of free carrier generation. Such a device, experimentally tested in [1,2,3], is able to give a modulation depth close to one; its operation frequency is limited by carrier lifetime up to about some ten megahertz and it can be promising for high speed parallel processing. The numerical results show a good agreement with experimental data reported in [1],