Introduction

Several recent developments have resulted in considerable progress in the study of transverse effects and spatial mode dynamics in semiconductor lasers. Demands on higher and higher output powers have led to the development of wide-stripe lasers, coupled laser arrays, integrated master-oscillator power amplifiers (MOPAs), and other more complex laser structures for which spatial dependence of the laser mode becomes important. This is especially true for the vertical-cavity surface-emitting lasers (VCSELs), devices that have recently become commercially available and are being proposed for a multitude of interesting applications. In the case of a VCSEL, the transverse-mode behavior is inherently more complex compared with the traditional edge-emitting lasers because of a large Fresnel number associated with VCSELs. The recent interest in spatio-temporal dynamics of such lasers as an example of well-controlled, spatially extended, self-organizing systems has led to new understanding about patterns, defects, and other coherent and incoherent structures, all being important to large-aperture diode lasers.