Integrating infrared lasers onto silicon for future photonic chips

In today’s era of rapid digitalization, the demand for photonic integrated circuits (PICs), which use photons instead of electrons to process information, is increasing significantly, driven by their promising applications in sensing, telecommunications, and environmental care. But PICs are still under active development, and several key challenges remain. A major one is the integration of infrared light sources onto silicon, the primary material used in photonic chips. This step is typically hindered by incompatibilities between silicon and conventional laser materials, limiting device miniaturization and large-scale manufacturing.

Now, ICFO researchers, Hamed Dehghanpour Baruj, Dr. Guy L. Whitworth, Dr. Nima Taghipour, Dr. Mariona Dalmases, Dr. Debranjan Mandal, led by ICREA Prof. Gerasimos Konstantatos, have demonstrated a way to integrate infrared laser sources directly onto a silicon platform. The study, published in Advanced Optical Materials, overcomes this longstanding obstacle by employing solution-processed colloidal quantum dots (CQDs) as light-emitters. The resulting light has a very specific, narrow wavelength that can be tuned across a broad spectral window (1580-1680 nm), covering key telecommunication bands.

“Traditionally, it has been very hard to grow light-emitting materials directly on silicon because their crystal structures don't match, which creates defects that eventually ruin the laser,” explains Hamed Dehghanpour Baruj, first author of the article. “Solution-processed CQDs are essentially a liquid ‘ink’ that can be deposited onto almost any surface, including silicon, without suffering from these crystal problems,” he adds.

To further enhance and control light emission, the researchers introduced a layer made of titanium dioxide (TiO₂) between the silicon substrate and the CQD film, which was patterned periodically, forming a grating. This grating acted as a series of distributed mirrors, which selectively reflect a specific wavelength of light back and forth, giving rise to what is known as a distributed feedback (DFB) laser.

“In our specific design, the pattern is engineered so that the light exits from the edge of the device, making it much easier to connect to other components on a flat chip,” says Dehghanpour. “To the best of our knowledge, this is the first demonstration of an edge-emitting DFB laser based on solution-processed CQDs integrated directly onto a silicon platform.”

This structural design is inherently generalizable, as it can be extended to other types of CQDs, potentially enabling laser emission across a broader spectral range. The technology could thus go beyond on-chip light sources for telecommunications and silicon photonics, paving the way for integrated sensors for biomedical detection or environmental monitoring as well.

Reference:

H. D. Baruj, G. L. Whitworth, N. Taghipour, M. Dalmases, D. Mandal, and G. Konstantatos, “Infrared Colloidal Quantum Dot Edge Emitting Lasers Integrated on Silicon.” Advanced Optical Materials (2026): e03357.

DOI: https://doi.org/10.1002/adom.202503357

Acknowledgements:

The authors acknowledge financial support from the European Union (IRQUAL,101189447). The study also received funding from PDC2023-145903-I00 funded by MCIN/AEI/10.13039/ 501100011033 by the European Union “NextGenerationEU/PRTR”, by MCIN with funding from European Union NextGenerationEU(PRTR-C17.I1), and by Generalitat de Catalunya. The authors were thankful to Johann Osmond for performing cross-sectional SEM characterization.