Interacting Photons

Research in the Interacting Photons group shows that the rules governing how light evolves over time are different from what we might expect. This is not only surprising; its implications could also be significant for the development of energy-efficient information processing systems. The researchers published their findings in the journal Physical Review Letters.

Giel Keijsers Title: Strong light-matter interactions in coherently driven open-access optical cavities Date: November 4 [caption id="" align="alignright" width="290"] Giel Keijsers after defending his thesis[/caption] How can you influence the…

Kevin Peters is the winner of the Ehrenfest-Afanassjewa physics thesis prize 2025. He carried out his research in the group of Said Rodriguez at AMOLF and successfully defended his PhD at Utrecht University on September 4. His thesis, entitled A Symphony of Noise in Nonlinear Optical Resonators, describes his research which combines photonics, nonlinear dynamics, statistical physics, and related fields.

On June 19, AMOLF director Huib Bakker congratulated group leader Said Rodriguez on his honorable and well-deserved recognition as an Outstanding Referee. The honor comes from the American Physical Society (APS), which named Said one of its 2025 Outstanding Referees in recognition of his exceptional contributions to the peer review process in physics.

Halide perovskites are being studied throughout the world as promising materials for harvesting and controlling light, due to their unique optical and electrical properties. Now, for the first time, researchers have observed optical nonlinearity in a halide perovskite crystal under continuous laser illumination. With the discovery of these properties, published in Nature Photonics, researchers at AMOLF expand the possibilities for studies of atomic structure, electronics, and communication technologies.

On Thursday, May 22nd, AMOLF organized the Infomatter Symposium to discuss exciting developments in information processing — ranging from biochemical to mechanical and optical systems. What these systems share is that they do not rely on conventional computers. This is a significant advantage, given that the energy cost of computing is rising much faster than that of energy production. 

We are honored to announce that AMOLF group leader Said Rodriguez has been appointed Professor of ‘Emergence and information in light’ as of 1 April 2025. His Chair by special appointment is embedded in the Debye Institute for Nanomaterials Science of the University of Utrecht.

Scientists at AMOLF and the University of Madrid have observed and described unique and spontaneous symmetry breaking in a metallic grating. By covering the grating with oil, they created a non-linear optical response with memory in the system. This resulted in asymmetric diffraction, even though the grating and illumination were symmetrical. Such behavior opens opportunities for better resolution in imaging and sensing methods with gratings. The scientists published their findings in Physical Review Letters on 27 September 2024.

From monitoring pregnancies to distance detection in cars, light sensors are a workhorse of modern technology. But do we really understand the data they give us? In a surprising find, three AMOLF researchers show evidence of a tendency to detect extreme values more often than average ones, caused by the way our sensors work. This so-called arcsine behavior causes lows and highs to occur much more often than the average in between. The finding may have a great impact on sensing technology, write Vashist Ramesh, Kevin Peters and Said Rodriguez in the prominent scientific journal Physical Review Letters.

For signals barely larger than the noise in a system, measurement is generally a trade-off between speed and precision. Averaging over several measurements reduces the influence of noise but takes (a lot of) time. That could change with a revolutionary new measurement method, devised by AMOLF researchers Kevin Peters and Said Rodriguez. Their idea is based on a non-linear optical resonator, explains Rodriguez: “In this sensor, faster measurement actually produces a stronger signal.” The theoretical elaboration of this new measurement method is published in Physical Review Letters today, June 27, 2022. For an experimental exploration, collaborations are being sought with companies seeking to make fast and precise measurements with light.

In an international collaboration, AMOLF researchers have theoretically described and experimentally observed spontaneous symmetry breaking (SSB) in two laser-driven coupled optical cavities. SSB is a universal phenomenon that occurs in many physical systems. It is at the heart of the laser, superconductivity, and the Higgs mechanism, for example. In the case of laser-driven systems like optical cavities, it was not yet understood how SSB occurs. Because laser-driven systems are always in a state imposed by the laser, the nature and manifestation of SSB is completely different from other systems.

Signals can be amplified by an optimum amount of noise, but this so-called stochastic resonance is a rather fragile phenomenon. Researchers at AMOLF were the first to investigate the role of memory for this phenomenon in an oil-filled optical microcavity. The effects of slow non-linearity (i.e. memory) on stochastic resonance were never considered before, but these experiments suggest that stochastic resonance becomes robust to variations in the signal frequency when systems have memory. This has implications in many fields of physics and energy technology. In particular, the scientists numerically show that introducing slow non-linearity in a mechanical oscillator harvesting energy from noise can increase its efficiency by tenfold. They publish their findings in Physical Review Letters on May 27th.