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BTG acquires exclusive rights to commercialize Strain-Compensated Multiple Quantum Well VCSELs from the Cornell Research Foundation
November 20, 2003
LONDON -- BTG (LSE: BGC), the global technology commercialisation company, announced today that it has acquired the exclusive rights to commercialise Strain-Compensated Multiple Quantum Well VCSELs from the Cornell Research Foundation (Ithaca, NY). The lasers, which emit light perpendicular to the surface of the laser chip, are a relatively new class of semiconductor lasers known as VCSELs (vertical cavity surface emitting lasers), and offer communications companies a lower cost alternative to traditional edge-emitting lasers.
VCSELs are extremely attractive for telecom and datacom applications due to the lower power consumption of the technology, as well as high-volume manufacturability, simple two-dimensional array fabrication, superior beam quality, and less complex testing and manufacturing. Because of these advantages, VCSEL-based transceivers operating at 850 nm have become the dominant laser communications solution for high-speed, very short-reach (VSR) optical interconnects applications, such as Gigabit Ethernet and Fibre Channel. With the advent of longer wavelength VCSELs operating at 1300 nm and 1550 nm, VCSELs will increasingly appeal to transceiver products required for short and intermediate reach SONET/SDH and Fibre to the Home (FTTH) applications. Parallel VCSEL transceivers are particularly attractive for back-plane interconnect applications.
VCSELs are constructed by sandwiching the laser gain medium, or active layer, between two stacks of alternating high and low refractive index mirrors, known as Distributed Bragg Reflector (DBR) mirrors. Multiple quantum wells (MQW), extremely thin layers of Group III-V materials, are used as the gain medium in VCSELs and can be strained to improve VCSEL performance. Prior to this invention, it was not possible to employ a sufficient number of strained quantum wells to achieve the gain desired for long wavelength VCSELs due to so-called "critical thickness" constraint. When the thickness of the strained quantum wells exceeds this critical thickness, dislocations and other defects are formed between the quantum well layers, and the performance of the device is significantly compromised.
The Strain-Compensated Multiple Quantum Well technology overcomes the critical thickness constraint by employing strain-compensated quantum wells, allowing many quantum wells to be stacked to form the gain medium without undue strain buildup. This dramatically improves the performance of the VCSEL.
"The telecoms market is looking for a next generation technology that will replace costly, low yield devices, such as Distributed Feedback (DFB) lasers at 1300 nm and 1550 nm wavelengths," said Jay Kshatri, Vice President of BTG's Semiconductors & Optoelectronics Business Unit. "We believe that the strain-compensated VCSEL is that technology, and we are actively seeking licensees who are interested in integrating this technology into their commercial products."
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