Silicon photonics boosted with UK fabrication research

Silicon photonics is one of the industry's hottest research fields, because it holds out the promise of accelerating on-chip communications without the extra heat that faster copper-based comms generate.

One of the big challenges is fabrication, and that's the subject of research announced by University College London, Cardiff University, the University of Sheffield and the UK's Engineering and Physical Sciences Research Council (EPSRC).

The group reckons they've cracked one of the big fabrication challenges: growing a 1,300-nanometre quantum dot laser directly on a silicon substrate.

The key characteristics of the device, according to this UCL press release, are that it can stand high temperatures (operating at up to 120°C (248°F)) but works with a low threshold current.

The hard part about growing lasers directly on the substrate, the university says, is that the different crystal structures involved often result in the laser having a short lifetime.

As UCL researcher Huiyun Liu told optics.org, the interface between the silicon substrate and the laser (what's known as a III-V because they're compounds of elements in columns III and V of the periodic table) has a “high defect density.”

The trick, according to the group's paper in Nature Photonics, was to deposit a nucleation layer between the substrate and the laser.

They reckon that operating at 105 mW, the laser could have a lifetime in the order of 100,000 hours (or more than 11 years), which is plenty to survive the typical obsolescence cycle in the IT industry.

Next on the research list is to integrate the lasers with waveguides and drive electronics. ®