Researchers implement multiphoton emission of electrons with non-classical light

Strong-field quantum optics is a rapidly developing research topic that integrates elements of nonlinear photoemission based on strong-field physics with the established field of quantum optics. While the distribution of light particles (such as photons) has been widely documented in both classical and non-classical light sources, the effect of such distributions on photoemission processes remains poorly understood.

Researchers at Friedrich-Alexander University Erlangen-Nuremberg (FAU) and the Max Planck Institute for Light Science recently set out to fill this gap in the literature by investigating the interaction between light and matter using a non-classical light source. Their paper published in Physics of naturedemonstrates that the photon statistics of a moving light source is reflected in the electron number statistics of electrons emitted by metallic needle tips, an observation that may have interesting implications for future developments in optical devices.

“The field of strong-field physics is now very advanced, as evidenced 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, such as metal needle tips. The field of quantum optics is similarly developed and even more diverse. One aspect of this field is the generation of light with non-classical light statistics, such as bright compressed vacuum”.

The main goal of recent research by Heimerl and his collaborators was to understand how quantum light, which comes from non-classical light sources, interacts with matter. It is noteworthy that the interaction between quantum light and matter has been studied so far only using classical light sources.

“Our neighbor, Professor Maria Chekhova, is the world’s leading expert in the field of bright compressed vacuum generation, a special form of non-classical light,” Peter Hommelhoff, co-author of the paper and a researcher at FAU, told Phys.org. “So we teamed up with her and our longtime partner Ida Kaminer of the Technion in Israel to investigate electron emission induced by non-classical light.”

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

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

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

“Our findings could be very interesting, especially for electron imaging applications, such as when it comes to imaging biological molecules,” Heimerl said.

Biological molecules are known to be highly susceptible to damage, and reducing the dose of electrons used to image these molecules can reduce the risk of such damage. The paper by Heimerl et al. suggests that modulation of the number of electrons to meet the needs of specific applications is possible.

“Before we can do that, we have to show that we can also reflect another distribution of photons in electrons, namely a distribution with reduced noise, which can be difficult to achieve,” Hommelhoff said.

The findings of this recent work may soon open new avenues for research in strong-field quantum optics. At the same time, they can serve as the basis for new devices, including sensors and strong-field optics that use the interaction between quantum light and electrons.

“We believe this is just the beginning of investigating experimental research in this area,” added Heimerl. “A lot of theoretical work is already underway, some of which is being led by our co-author Ida Kaminer. One observable that we haven’t explored yet, but is very informative, is electron energy, which could shed even more light on the interaction of light and matter.” .

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