Mono and Hybrid integration

Monolithic and hybrid integration

Two main approaches are used for photonic integration: monolithic and hybrid integration.

Monolithic integration implements all the optical functions using one bulk material, typically indium phosphide, but a planar lightwave circuit (PLC) design implementing solely passive components is also a monolithic design.

Hybrid integration uses an alternative philosophy by choosing to integrate several materials onto a common platform.  The idea is that rather than design all the functions using one material, the best materials are used for each. The challenge is assembling the various materials into a working integrated component. An example hybrid circuit is a PLC design, based on silica-on-silicon, implementing such optical functions as waveguides and filters onto which actives – monolithic devices such as lasers and photo-detectors – are coupled using accurate positioning techniques.

Why photonic integration reduces the power consumption compared to discrete optical designs is not immediately obvious.  “There are material developments – novel materials added to indium phosphide – that maintain performance over a wider temperature range,” explains David Smith, CTO at CIP Technologies. “By tolerating a wider temperature range, semi-cooled and even uncooled packages can be used.”

Materials and architecture are also interlinked. “Once components are integrated the next step is traditionally looking for architectural savings to reduce power,” he says.