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Vcsels Vertical-Cavity Surface-Emitting Lasers

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Vcsels Vertical-Cavity Surface-Emitting Lasers

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  • Author: Robin Mcdonald
As the name suggests, a Vertical-Cavity Surface-Emitting Laser, (pronounced vixel), emits laser light from the surface of a wafer, as opposed to an edge, as found with standard semi-conductor lasers. A common problem associated with edge-emitting lasers is that the light output is highly astigmatic, making it difficult to effectively couple light into a single-mode fibre. The VCSEL provides significant advantages in that the light emerges without this astigmatism, allowing for much more efficient coupling. VCSELs are constructed with resonating mirrors both above and below an "active gain region". In the case of the VCSEL, the bottom mirror, called a high reflector, is 100% reflective. The top mirror, or output coupler, is almost completely reflective (99%), and allows a small amount of light leakage. Laser light is generated in the active region and reflects back and forth between these mirrors, amplifying the light on each pass. The leakage through the output coupler forms the laser output.

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