| Recent vertical-cavity surface-emitting semiconductor laser structures exhibit complex features, such as the presence of an intracavity index-guide, which complicates the electromagnetics problem. Yet, determining the optical characteristics of the cold-cavity is essential to correctly interpret the physical behavior of these devices and generate accurate simulations. To this end, an efficient vector optical solver combining the numerical mode-matching method and Krylov subspace techniques has been developed. In particular, a new formulation for the modal quality factor and the effective cavity length is presented. Scalar and vector modeling results are directly compared for the first time and the limits of the scalar approximation are investigated. It is found that the scalar approximation leads to significant errors for small, strongly index-guiding apertures.; Calculated spectral and spatial characteristics are confirmed by experimental measurements for different structures. Near-field scanning optical microscopy is used to obtain a direct measurement of the beam-waist.; It is experimentally and theoretically shown that there is a correlation between the spatial and spectral characteristics of VCSELs. A universal diagram relating the normalized beam-waist to a normalized wavelength parameter is developed and simple analytical formulas are derived for the different asymptotic cases.; Finally, the optical model is combined with a multimode, spatially dependent, non-linear rate-equation model to determine the modal light power versus current (L-I) characteristics. Thermal effects, multi-quantum-well gain, carrier leakage, and recombination mechanisms are included in the model. A detailed investigation of ion-implanted index-guided VCSELs is then carried out. For the first time, theoretical and experimental modally resolved L-I characteristics are compared and agreement is very good. It is found that modal competition and spatial hole burning have a significant effect on the multimode behavior of these devices.; It is shown that the multimode behavior can be controlled by changing the relative sizes of the current confinement aperture and the index-guide aperture. This is true even in the limit of devices with very large apertures, for which the cold-cavity resonant wave-lengths and losses are the same for all modes. This concept is used to design optimized structures for high-power single-mode operation. |
