Epiwafer foundry and substrate maker IQE plc of Cardiff, Wales, UK has produced epitaxial wafers, combining optical properties of compound semiconductors with electronic properties of silicon, to produce high-power lasers that enable increased storage density for next-gen hard disk drives. In the last 20 years, through research and technological innovation, typical store capacities for consumer disk drives have increased by 100,000 times from around 20 MB to 2 TB, notes IQE. In order to maintain such increases in capacity, while maintaining the same footprint, the next generation of disk drives need to be capable of storing more than 1Tb of data per square inch. Such high-density storage is made possible through HAMR (heat-assist magnetic recording) where the heat source is a semiconductor laser device emitting 10 mW or more of optical power. Work published in the September edition of Nature Photonics volume 6 (2012) p612 (doi:10.1038/nphoton.2012.204) describes the achievement by the Tyndall National Institute (University College Cork), Semprius Inc and Seagate Technology in combining a high-power GaAs (gallium arsenide) laser structure with a silicon substrate using Semprius' proprietary micro-transfer print technology, on epitaxial layers produced by IQE using MOCVD (metal-organic chemical vapour deposition) at its Cardiff manufacturing facility (‘Wafer-scale integration of group III-V lasers on silicon using transfer printing of epitaxial layers', Justice et al). Specifically, the researchers used an elastomeric stamp to selectively release and transfer epitaxial coupons of GaAs to realize III-V lasers on a silicon substrate. Low-threshold cw (continuous wave) lasing at a wavelength of 824nm has been achieved from Fabry-Pérot ridge waveguide lasers operating at temperatures up to 100°C. Single- and multi-transverse mode devices emit total optical powers of >60 mW, support modulation bandwidth of >3 GHz The fabrication strategy opens up a route to the low-cost integration of III-V photonic devices and circuits on silicon and other substrates. In particular, says IQE, they also demonstrated the level of optoelectonic integration that should allow HAMR to meet growing demand in the high-performance, high-capacity and low-cost storage markets. "Programs such as this demonstrate how we successfully combine our high-volume manufacturing capabilities with leading-edge research to support our partners through all stages from development through to production," says Andrew Joel, commercial director for IQE's optoelectronics division. IQE Tyndall National Institute Semprius Inc Seagate Technology
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