VCSEL brings fiber closer to home

17 Jun 2002

A new semiconductor laser beats performance records at critical wavelengths.

VCSEL

Researchers at the Walter Schottky Institut in Germany have created a vertical cavity surface emitting laser (VCSEL) that emits at 1.55 µm without the heating problems exhibited by other VCSELs that emit the same wavelength. This, they claim, makes the laser suitable for data transmission over the "last mile" of fiber-optic telecommunication cables.

Commercially available VCSELs have been restricted to a wavelength of 850 nm, but they are not suitable for fiber communications as they can only transmit across distances of a few hundred meters: at 850 nm the damping in the fibers is too high. Light at a wavelength of 1.55 µm, however, experiences minimum absorption and can travel up to 50 km.

Markus Ortseifer and colleagues chose indium phosphide-based materials for the semiconductor substrate, rather than gallium arsenide used for 850 nm VCSELs. They devised a novel shape and new semiconductor structures that exploit quantum-mechanical effects. "At present, [our] device shows record performances in each of the relevant characteristics, such as heat output and reliability, compared with any 1.5 µm VCSELs", says Ortseifer.

Since VCSELs can be mass produced and tested they will offer a commercially viable route to "fiber to the home" if their performance characteristics can be engineered appropriately. The scientists' breakthrough could therefore be an important step in bringing high-speed fiber-optic traffic to our doorsteps.

Plans are under way to commercialize the devices. "Our industrial partners have already been given a number of prototypes so that they can evaluate the potential of our VCSELs," adds Ortseifer. "According to their feedback, our lasers already achieve the required performance and show excellent characteristics. There are plans to increase the high-speed characteristics further and to develop wavelength-tunable VCSELs."

The lasers have other potential applications, including optical data transmission within computers, and gas sensing for environmental analysis.