San Francisco -- Researchers at the University of California Santa Barbara (UCSB) have developed a novel quantum dot laser design that not only is grown on silicon but that performs as well as similar lasers grown on their native substrates. This opens up a new generation of low-cost, multi-channel laser devices combined with CMOS driver circuits.
The team’s results, shown March 12 at the Optical Fiber Communications Conference (OFC), use Molecular Beam Epitaxy (MBE) to grow the 1.3μm dots on a silicon substrate using indium and arsenic. The researchers believe the INAS quantum dots represent an important step towards large-scale photonic integration in an ultra low-cost platform for high volume consumer applications, which will lead to the mass adoption of silicon photonics.
The team grew the quantum dots on engineered germanium/silicon substrates and the III-V molecular beam epitaxy (MBE) template growth from IQE. The growth of the quantum dot laser structure and fabrication of the laser components were performed at UCSB and show that the dots can be cost effectively grown in volume on silicon substrates.
This is a step on from Vertical Cavity Surface Emitting Laser (VCSEL) wafers that have been used to produce communications lasers that achieved error-free operation at speeds up to 40 Gb/s with record low energy dissipation (below 100 fJ/bit). The 980nm VCSELs developed at the Technical University of Berlin also demonstrated extreme temperature stability during high-speed operation up to 85°C.
An optical micrograph of the fabricated laser devices (Photo courtesy of Alan Liu, University of California Santa Barbara)
The efficiencies achieved with VCSELs is a critical factor in reducing the overall energy consumption of optical interconnects used in datacenters, and integrated quantum dot devices are seen as the next step in boosting the efficiency.
"Today's energy hungry datacentres are increasingly co-located alongside major industrial power plants,” said Drew Nelson, CEO of IQE. “Data volumes are forecast to continue growing and with more than twenty billion devices being interconnected by 2020, the energy demand is rapidly becoming unsustainable. Data centres are already early adopters of VCSEL technology to help reduce energy demand and are likely to continue to drive the trend for optical communications for industrial and commercial applications."
Professor Dieter Bimberg, Head of the Centre of NanoPhotonics at TU-Berlin, added:
This is the lowest reported value of dissipated energy at error-free operation for any semiconductor laser diode at any wavelength or bit rate. This result is achieved at a low current density of 10kA/cm2, demonstrating the suitability of our devices for application in reliable and sustainable commercial optical interconnects. At 40Gb/s the TU-Berlin/IQE VCSELs dissipate only 108 fJ per transmitted bit, which is at least four times less than any other published result for semiconductor laser diodes.