Researchers from the HUN-REN Wigner Research Centre for Physics (HUN-REN Wigner RCP), the ELI-ALPS Laser Research Institute in Szeged, and the University of Pécs have developed a completely new principle-based, long-wavelength, light-controlled electron source that could lay the foundation for much faster electronic devices in the near future. Based on experiments, high-speed switches operating at terahertz frequencies can be constructed, making these new findings a significant step towards establishing strong electric field terahertz technology. The study has been published in the prestigious Nature Communications journal.

The electron emission induced by light has long been a known phenomenon, and its study has led to fundamental discoveries. It was the explanation of this phenomenon, and not the theory of relativity, that earned Albert Einstein the Nobel Prize in 1921. The work of Ferenc Krausz, honoured with a Nobel Prize in 2023, has enabled the study of electron motion within atoms on the currently available shortest time scale of attoseconds.

The photoelectric effect - electron emission - is typically achieved using ultraviolet or soft X-ray radiation with wavelengths much shorter than visible light. In such irradiation, the minimum transferable energy allowed by the laws of quantum mechanics is sufficient for liberating electrons within atoms and molecules.

The situation is quite different when it comes to much longer wavelengths, in the millimetre range, known as terahertz radiation. In this case, only extremely strong electric field radiation can liberate electrons from the material, through a phenomenon known as the tunnelling effect.

The latter phenomenon was examined in their recent publication ( by researchers from the ELI-ALPS Laser Research Institute, PTE and HUN-REN Wigner RPC. In their experiment, an extremely strong electric field exceeding 100,000 volts per centimetre was generated in the form of terahertz pulses. Using these, they were the first to successfully experimentally demonstrate surface electron emission induced by terahertz pulses. By reversing the direction of the electric field, they were also able to control the number of emitted electrons.



Illustration by Sámuel Sihombing Fülöp

The switching speed of electronic devices and the data transfer speed in telecommunications have been continuously increasing for decades, and in the near future, we can expect microwave frequencies to be replaced by terahertz waves in our fastest devices. Based on the experiments conducted by Hungarian researchers, high-speed switches operating at terahertz frequencies can be built. The newly published results are thus an important step in establishing this powerful terahertz technology, and also represent a significant milestone in the development of small-sized, intensive electron sources based on surface electron emission, which are essential in various fields of medical science, biology and material science.


Subcycle surface electron emission driven by strong-field terahertz waveforms
Shaoxian Li, Ashutosh Sharma, Zsuzsanna Márton, Priyo S. Nugraha, Csaba Lombosi, Zoltán Ollmann, István Márton, Péter Dombi, János Hebling, József A. Fülöp
Nature Communications 14, 6596 (2023)