How do vertical-cavity surface-emitting lasers differ from edge-emitting semiconductor lasers?

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Laser components: cutaway view — laser Basic laser components.

The primary difference between these two types of semiconductor diode lasers lies in the orientation of their resonant cavities and the direction in which light oscillates relative to the p-n junction.1

Edge-emitting semiconductor lasers: These devices feature mirrors positioned on opposite edges of the p-n junction. Consequently, light oscillates within the plane of the junction.1
Vertical-cavity surface-emitting lasers (VCSELs): In these lasers, the mirrors are located above and below the p-n junction. This configuration causes light to resonate in a direction perpendicular to the junction.1

Both types rely on the p-n junction to act as the laser medium, generating stimulated emission when an electric current passes through the interface of the two doped regions.1