news digest ♦ Lasers
980nm VCSELs Exhibit High Performance at Elevated Temperatures
German researchers have demonstrated that the lasers, produced by IQE, are capable of operating at 25Gbit/s at elevated temperatures. This makes them ideal for very short optical links within high- performance computers.
A team of researchers from the Technical University of Berlin has published work in Applied Physics Journal demonstrating record data transmission rates from an oxide confined 980nm Vertical Cavity Surface Emitting Laser (VCSEL) operating at 85°C.
The VCSEL devices fabricated on wafers produced using Metal Organic Chemical Vapour Deposition (MOCVD), are capable of operating at 25Gbit/s at elevated temperatures, making them ideal for very short optical links within high-performance computers.
“Since temperatures inside computers are as high as 85 °C, or even higher, good temperature stability is indispensable for robust, inexpensive optical links,” says Dieter Bimberg, head of the research team in Berlin.
Most short-reach optical links and local and storage-area networks currently operate at a wavelength of 850nm but Bimberg believes there is a strong case for 980 nm sources in all these applications.
“980 nm has the crucial advantage of transparency of the GaAs substrate, so one can easily realise bottom-emitting devices, increasing and simplifying packaging density. This is very important, for example, in the case of a large number of VCSELs for parallel optical links.”
The epitaxial structure contained 24 pairs of Al0.12Ga0.88As and Al0.90Ga0.10As layers for the bottom mirror, and a further 37 pairs for the top mirror. Sandwiched between these mirrors is an active region with five compressively strained 4.2nm thick In0.21Ga0.79As quantum wells interlaced with 6nm thick GaAs0.88P 0.12tensile strained barriers.
Output from a 10 micron diameter oxide aperture 106
www.compoundsemiconductor.net January / February 2011
VCSEL is 4.3mW at 20 °C and 2.6 mW at 85°C. This relatively small reduction in power stems from an intentional red-shift detuning of 15 nm between the quantum well gain peak and the cavity resonance. The devices have bit error rates at 25 Gbit/s of less than 10-12.
Future targets for the team are to speed the 980 nm VCSELs to 40Gbit/s and maintain this rate at 100°C.
Oclaro VCSELs Power Symmetricom’s First Miniature Atomic Clock
The 795 nm single-mode VCSELs signify a new direction in the industry by enabling the world’s first miniature atomic clocks which are available in volume.
Oclaro, a provider of innovative optical communications and laser solutions, has developed single-mode Vertical Cavity Surface Emitting Lasers (VCSEL) for atomic clocks.
These lasers are being used by Symmetricom, a world leader in the design and manufacturing of frequency standards, in its SA.35m miniaturized rubidium atomic clock. Featuring ultra-high stability, low noise and a wavelength of 795 nm, the Oclaro single-mode VCSELs signify a new direction in the industry by enabling the world’s first miniature atomic clock available in volume.
While atomic clocks are recognized as extremely precise time-keeping devices, they have been limited in size and reliability due to their traditional gas lamp. By replacing the gas lamp with a laser, manufacturers such as Symmetricom can significantly improve the reliability and power consumption of atomic clocks and also begin targeting applications that require smaller devices.
“A core part of Oclaro’s strategy is to expand into adjacent markets where we can leverage our optical technology and solutions to deliver value for customers,” said Yves LeMaitre, Executive VP and Division Manager at Oclaro. “We are pleased to extend our proven laser technology into atomic clock devices which enable Symmetricom
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