Chapter 9.6: Edge-Emitting Diode Lasers

9.6 EDGE-EMITTING DIODE LASERS

Diode laser resonators can be constructed in a number of ways. A logical way to group the various types of laser resonators is by their orientation relative to the active layer where the stimulated emission is generated.

Early diode lasers resonated in the plane of the junction layer, as shown in Figures 9-7 and 9-11. These lasers are called edge emitters because their output comes from the active layer at the edge of the laser chip. Their advantage is that they can extract laser gain from the length of the laser chip, typically a few hundred micrometers, to produce relatively high power. They take a few different forms.

An important alternative is the surface-emitting laser, in which the beam emerges from the surface of the chip. Surface emitters have other advantages in beam quality and come in two basic variations: vertical-cavity lasers that oscillate perpendicular to the junction layer, and hybrid lasers that oscillate in the junction plane but direct output through the surface. You will learn more about these types in Section 9.7.