"Vertical cavity surface emitting lasers and LEDs are promising devices for free-space and fibre communication systems. Their advantages include low threshold, single mode operation, a circularly symmetric beam profile and efficient coupling into fibres. Commercially they are attractive because they can be processed readily and tested on wafer. Figure 1 shows an SEM image of a VCSEL structure which has been etched to show the Bragg reflectors and gain region."
Structure of a Vertical Cavity Laser (Source)
Scanning electron micrograph of a vertical cavity surface
emitting laser structure grown by MBE.
bias voltage. The curves correspond to voltage steps of 1 V. The Bragg mirror consists of
(from the substrate):20 x GaAs/AlAs (694A/828A) n-doped, 14 x InGaAs/GaAs (50A/9OA
and 23% In) undoped, 4 x GaAs/AlAs (694A/828A) p doped. (Source)