Researchers achieve multiphoton electronic emission with non-classical light

Strong-field quantum optics is a rapidly emerging research topic, merging elements of nonlinear photoemission rooted in strong-field physics with the well-established field of quantum optics. Although the distribution of light particles (i.e., photons) has been extensively documented in both classical and nonclassical light sources, the impact of such distributions on photoemission processes remains poorly understood.

Researchers from Friedrich-Alexander-University Erlangen-Nürnberg (FAU) and the Max Planck Institute for Light Science recently set out to fill this gap in the literature by exploring the interactions between light and matter with a non-conventional light source. Their article, published in Natural physicsdemonstrates that the photon statistics of the directing light source are imprinted on the statistics of the number of electrons emitted by the tips of metal needles, an observation that could have interesting implications for the future development of optical devices.

“The field of strong field physics is now very developed, as demonstrated by the 2023 Nobel Prize in Physics,” Jonas Heimerl, co-author of the paper and a researcher at FAU, told Phys.org. “This physics is not limited to atoms but also occurs on metallic surfaces like the tips of metal needles. The field of quantum optics is equally developed and even more diverse. One aspect of this field is the generation of light with non-classical light statistics, such as bright pressed vacuum.

The main goal of Heimerl and his collaborators’ latest research has been to understand how quantum light from non-classical light sources interacts with matter. Notably, interactions between quantum light and matter have so far only been explored using classical light sources.

“Our neighbor, Professor Maria Chekhova, is a world-renowned expert in the field of bright vacuum generation, a special form of non-classical light,” said Peter Hommelhoff, co-author of the paper and researcher at the FAU, at Phys. .org. “So we teamed up with her and our long-time partner Ido Kaminer from the Technion in Israel to study electron emission caused by non-classical light.”

Heimerl, Hommelhoff and their research group at FAU conducted their experiments in close collaboration with Chekhova, a researcher with extensive expertise in quantum optics. Chekhova is particularly known for her work on bright compressed vacuum generation, a technique that involves the use of nonlinear optical processes to generate bright compressed vacuum, a non-classical form of light.

“In our experiment, we used this non-classical light source to trigger a photoemission process from a metal needle tip that is only a few tens of nanometers in size,” explained Heimerl. “Think of the well-known photoelectric effect studied by Einstein, but now with a light source that exhibits extreme intensities and fluctuations within each laser pulse.”

For each laser pulse generated, the researchers counted the number of electrons, both for classical and non-classical light sources. Interestingly, they found that the number of electrons can be directly influenced by the high beam.

“Our results could be of great interest, especially for imaging applications with electrons, for example when imaging biological molecules,” said Heimerl.

Biological molecules are known to be very prone to damage and reducing the electron dose used to image these molecules could reduce the risk of such damage. The article by Heimerl et al. suggests that it is possible to modulate the number of electrons to meet the needs of specific applications.

“Before we can solve this problem, however, we need to show that we can also imprint another distribution of photons to electrons, namely one with reduced noise, which might be difficult to achieve,” Hommelhoff said.

The results of this recent work may soon open new research opportunities focused on high-field quantum optics. At the same time, they could provide the basis for new devices, including sensors and strong-field optics that exploit the interaction between quantum light and electrons.

“We believe this is just the beginning of experimental research in this area,” Heimerl added. “Much theoretical work is already underway, some of which is led by our co-author Ido Kaminer. One observable that we have not yet studied but which contains a lot of information is the energy of the electron, which could shed more light on the phenomenon of light-matter.

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