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Abstract

We study the transverse mode selection of a weakly index-guided vertical-cavity surface-emitting laser (VCSEL), based on an extension of the model of Valle et al. [Opt. Commun. 115 (1995) 297]. In the model we incorporate carrier capture and escape processes between the separate confinement heterostructure (SCH) layer and the quantum well (QW) active region of a VCSEL. These effects are characterized with phenomenological capture and escape times, τcap,τesc. We show analytically and by numerical simulations that when the carrier loss in the SCH region is taken into account, carrier capture and escape critically affects the transverse-mode selection of a VCSEL. A large ratio between τcap and τesc diminishes the number of photons in the QWs, leading to a decrease of the spatial-hole burning, which in turn benefits emission on the fundamental transverse mode. On the contrary, a small ratio between τcap and τesc increases the number of photons in the QWs, leading to a large spatial-hole burning which in turn favors higher-order transverse modes. If the carrier loss in the SCH region is neglected the total number of photons in the QW region is independent of τcap and τesc. In this case carrier capture and escape play no fundamental role in the transverse-mode selection of the VCSEL, but modify the transient dynamics of the relaxation oscillations.