Stanford University engineers built a fingernail-sized photonic chip that separates partially coherent light into incoherent components, as detailed in a study published October 30, 2026, in Nature Photonics.
The research was primarily conducted at Stanford, where Charles Roques-Carmes began the project alongside graduate student Paul-Alexis Mor before establishing his research group at the Institute of Science and Technology Austria (ISTA), with Mor accompanying him to continue the work.
The device, called a partially coherent light analyser (PCLA), uses a network of Mach–Zehnder interferometers and an optimization algorithm to isolate underlying coherence modes from overlapping optical fields.
ISTA Assistant Professor Charles Roques-Carmes noted that while partially coherent light is extremely common, it has frequently been regarded as a drawback in technology.
Co-lead author Paul-Alexis Mor, now at ISTA, said the separated outputs show absolutely no correlation anymore.
Unlike conventional systems built for ordered laser light whose phases align directly, this silicon chip addresses light whose waves align only briefly.
The research team injected two independent infrared lasers operating at a nominal wavelength of 1,534.65 nanometres into the chip to generate a partially coherent mixture.
Stanford electrical engineering professor Shanhui Fan explained that the chip learns the underlying coherence modes of an unknown light field and physically directs them into separate output channels.
During tests on a four-input-port configuration, the researchers achieved eigenvector fidelities of 97.8 percent for layer one and 99.9 percent for layer two, alongside eigenvalue estimation errors of 0.29 percent and 3.11 percent respectively.
A separate rank-three experiment on a fully reconfigurable nine-by-nine photonic circuit verified operation beyond two modes, where three optimized outputs became pairwise mutually incoherent after convergence.
The measured cross-talk between separated beams reached as low as minus 13.0 decibels.
Following these laboratory tests, Stanford professors David Miller and Olav Solgaard are working alongside NASA to explore whether the technology can analyze light originating from distant galaxies.