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This paper considers the scattering of an H-polarized plane wave by a freestanding periodic grating that contains two circular cylinders on each period, one made of silver and the other of dielectric. If such a grating is made of deeply subwavelength wires, the reflection and transmission coefficients demonstrate both plasmon and grating resonances. To clarify them, we also discuss the scattering by similar gratings made of either silver or dielectric wires only. However, the main attention is paid to the associated lasing eigenvalue problem for the dielectric cylinders pumped to become quantum wires, i.e., to obtain a “negative-absorption” complex refractive index. The analysis is done using a meshless analytical-numerical method with guaranteed convergence. The computations show that, in this composite periodic cavity, material thresholds of lasing for the grating modes can be much lower than for the plasmon modes.

The lasing characteristics of a photonic molecule in the form of two optically coupled semiconductor microdisks are investigated. Electromagnetic analysis of the lasing spectra and linear thresholds of the coupled whispering-gallery (WG) modes of four different symmetry classes is presented. Here, Maxwell's equations and accurate boundary and radiation conditions are considered as a specific "cold-cavity-with-gain" eigenvalue problem. Each eigenvalue is a pair of real-valued parameters -frequency and threshold material gain. In the two-dimensional (2-D) approximation, based on the introduction of an effective refractive index, this problem is reduced to a determinant equation with favorable features. A secant-type method is further used to calculate thresholds and lasing frequencies numerically. Results obtained show that optical coupling may lead to a further reduction of the ultralow thresholds of the WG modes, although the opposite, i.e., threshold spoiling, is more common.

An electromagnetic analysis of thin-disk semiconductor resonators with uniform and nonuniform gain regions is presented. A "cold-cavity-with-gain" Maxwellian formulation, including accurate boundary and radiation conditions, is considered as an eigenvalue problem, for the real-valued parameters of frequency and threshold material gain. Although the well-known approximate effective-index method is used to reduce a three-dimensional (3-D) field problem to a two-dimensional (2-D) one, a rigorous formulation of the latter is retained. A quasi-3-D feature is provided through full account of the multiple-wave nature and dispersion of the effective index. Results obtained quantify the ultralow thresholds of the whispering-gallery modes and show the advantage of a ring-shaped gain region.

The nonlinear phenomena accompanying the process of light generation in high-power tapered semiconductor lasers are studied using a combination of simulation and experiment. Optical pumping, electrical overpumping, filamentation, and spatial hole burning are shown to be the key nonlinear phenomena influencing the operation of tapered lasers at high output powers. In the particular tapered laser studied, the optical pumping effect is found to have the largest impact on the output beam quality. The simulation model used in this study employs the wide-angle finite-difference beam propagation method for the analysis of the optical propagation within the cavity. Quasi-three-dimensional (3-D) thermal and electrical models are used for the calculation of the 3-D distributions of the temperature, electrons, holes, and electrical potential. The simulation results reproduce key features and the experimental trends.

A full-vectorial contour integral equation analysis of the natural modes of dielectric waveguides (DW) of arbitrary cross section is presented. The Galerkin method, together with the Analytical Regularization procedure, is applied to discretizing and solving the eigenvalue problem. This ensures the fast convergence and superior accuracy of the numerical algorithms. The waveguide cross section is characterized by a parametrical curve defining its contour, with a limited curvature at each point. This avoids the singularity points at corner regions and provides accurate results, even for waveguides with virtually sharp corners. Both fundamental and higher order mode propagation characteristics are studied in the bound, leaky, and complex regimes. Numerical results consistent with other theories and experimental data are presented for a wide range of practical dielectric waveguides that demonstrate the efficiency, accuracy, and versatility of the method developed. Finally, the technique is applied to model a fused fiber coupler.

An efficient hybrid method has been developed to analyze, for the first time, the three-dimensional problem of fiber-to-chip coupling. The method employs the numerical finite difference beam propagation method to model the fields in the planar chip guide and the semi-analytical free space radiation mode method to model the fields in the fiber guide. The two methods are linked via an iterative algorithm. The results for the transmission, backreflection, and radiation losses are presented for the case of direct butt-coupling and coupling via an antireflection coating. Finally, the effect of the vertical misalignment is analyzed and results are compared with the ones obtained experimentally.

A new approach is presented for calculating the facet reflectivity of semiconductor lasers and waveguides buried at a finite distance below an upper semiconductor-air interface. The full three-dimensional nature of the waveguide is considered, and the effect of the air-semiconductor boundary on the facet reflectivity is fully explored for both TE and TM polarizations, including the use of coated and angled facets. It is clearly shown that the proximity of the semiconductor-air interface cannot be neglected without compromising accuracy, especially in the practically important case of coated facets. Furthermore, the novel method described here is easy to implement, as well as being accurate and fast.

The porosification of silicon can be achieved by the partial electrochemical dissolution (anodization) of the surface of a silicon wafer. The degree of porosity is dependent on the anodization parameters and can generally be controlled within the constraints imposed by substrate dopant type and concentration. Control of porosity leads to control of refractive index, and therein lies the concept of using porous silicon as an optical waveguide. We discuss porous silicon wavegides, for the visible to the infrared, produced by a number of approaches: 1) epitaxial growth onto porous silicon (where the porous layer acts as a substrate for a higher refractive index waveguide epilayer); 2) ion implantation (where either selective areas of high electrical resistivity can be produced, which act as a barrier against porosification, or where the surface of a porosified layer is amorphised to form a waveguide; 3) porous silicon multilayers (where the anodization parameters are periodically varied to produce alternate layers of different porosity and thus refractive index); and 4) oxidation of porous silicon (where a porosified layer is oxidized to form a graded-index, dense or porous, oxide waveguide).