The rapid rise of photonic chips, which use light to process data instead of electrons, may offer faster means to transmit data. But scaling such chips has been held back by one stubborn issue: integrating on-chip lasers made from incompatible materials.

Researchers at the University of California have developed a novel method to fabricate a quantum dot laser directly onto a photonic chiplet.

On-chip lasers are essential for photonic circuits to operate effectively. But until now, attempts to integrate laser materials like III-V semiconductors onto silicon often led to structural defects and high signal losses – think of it as trying to weld glass and metal together.

To get around this, the researchers integrated a laser onto a photonic chip by ‘growing’ a crystalline layer of laser material directly onto the hardware.

Detailed in a paper published in the IEEE Journal of Lightwave Technology, the researchers employed a multi-step growth technique, combining metalorganic chemical vapor deposition and molecular beam epitaxy to build a crystalline laser layer directly onto silicon. They also added a polymer gap-fill to minimize optical beam divergence.

Where previously the addition of such a laser would result in coupling losses and poor performance, hardware with the crystalline laser performed efficiently on a single O-band wavelength, which is used to transmit data in high-performance applications in data centers.

Rosalyn Koscica, who led the study, commented: “Photonic integrated circuit (PIC) applications call for on-chip light sources with a small device footprint to permit denser component integration.

“Our integrated quantum dot lasers demonstrated a high temperature lasing up to 105 °C and a life span of 6.2 years while operating at a temperature of 35 °C.”

Photonic hardware’s rapid rise to relevancy coincides with the explosion of global data traffic, with AI, cloud, and 5G fueling the need for more ultra-fast, energy-efficient ways to transfer data.

Where traditional electronic chips struggle to meet that need, photonics can manage massive data rates at far greater bandwidth and lower latency.

Figures from Precedence Research project the global photonic integrated circuit market to rise from $14.85 billion in 2024 to $97.62 billion by 2034, with leading drivers set to be fiber optic cable networks and data centers.

Even the most valuable company in the world is getting in on the act, with Nvidia tapping photonics to power new Spectrum-X networking switches.

To support photonic scale-out, Koscica and the research team contended that their laser integration technique means photonics chips can be manufactured in standard semiconductor foundries, eliminating the need for additional steps in production, like adding laser sources.

“This demonstration of pocket III-V lasers coupled to silicon photonics brings scalable, cost-effective monolithic integration one step closer to practical application,” the researchers wrote.