News: Optoelectronics
29 March 2021
KAIROS delivers commercial-grade single-mode 894nm VCSELs
Running from November 2018 to September 2021 and part-funded by the UK National Quantum Technologies Challenge via UK Research and Innovation (UKRI) to develop a miniaturized atomic clock platform for precision timing, GPS-free navigation and primary time standard applications, the £4.4m KAIROS project has delivered single-mode vertical-cavity surface-emitting lasers (VCSELs) with ultra-high mode-stability operating at 894nm, the wavelength corresponding to the D1 transition line of Cs used in high accuracy (10e-13) clocks.
Led by Teledyne e2v (UK) Ltd with partners Compound Semiconductor Centre Ltd (CSC), the UK National Physical Laboratory (NPL), Leonardo, Altran, ICS, HCD Research, Optocap, University of York and Cardiff University, the KAIROS consortium was targeted at developing a pre-production prototype of a miniature atomic clock for providing precise timing to critical infrastructure services such as reliable energy supply, safe transport links, mobile communications data networks and electronic financial transactions.
Capabilities demonstrated by the project consortium’s laser design, epitaxial materials and device fabrication partners includes:
- a suite of proprietary laser design and simulation models at Cardiff University and Institute for Compound Semiconductors (ICS) Ltd;
- high-uniformity epitaxial layer structures realized at CSC - a joint venture founded in 2015 between Cardiff University and epiwafer foundry and substrate maker IQE plc of Cardiff, Wales, UK – with <3nm centre wavelength tolerance;
- polarization-insensitive, single-mode VCSEL performance with a linewidth of ~30MHz and side-mode suppression ratio (SMSR) of 28dB, fabricated by ICS Ltd; and
- novel VCSEL characterization processes specifically developed for quantum applications at the National Physical Laboratory (NPL).
Having met stringent target performance specifications required for atomic clock applications, the supply-chain partners are preparing to service future opportunities for high-specification VCSELs through several parallel activities, one of which is the QFoundry project to upscale the manufacturability and reliability of quantum photonic components (QPCs), also part-funded by the UK National Quantum Technologies Challenge.
The recent achievement at the Institute for Compound Semiconductors at Cardiff University in establishing a multi-wafer 6” VCSEL fabrication pilot-line further supports the partners’ collective capability in high-performance VCSEL design, fabrication and testing.
“Whilst high-stability, single-mode VCSEL operation is required for numerous emerging applications, the concern over reliability and cost is forcing system integrators to compromise on performance,” says CSC director Wyn Meredith. “Following solid groundwork on uniformity improvements for Kairos VCSEL structures, we are confident that our collective capabilities across the VCSEL supply chain will provide a pathway towards high-end VCSEL solutions for new applications in quantum, sensing and industrial markets,” he adds.
“We are extremely pleased to deliver a manufacturing capability for high-specification single-mode VCSELs to complement our existing product lines in avalanche photodiodes, Hall-effect sensors and resonant tunnelling diodes (RTDs),” states ICS chief technology officer professor Mohamed Missous.
“VCSEL technologies are a key focus area for Cardiff University and we are in a position to support industry with prototyping novel VCSEL devices to complement our device simulation and design expertise for highly specialized structures,” comments ICS director professor Peter Smowton.
