Infrared Free-electron Laser Operates in Two-color Mode For The First Time

Recently, the Fritz Haber Institute (FHI) of the Max Planck Society in Berlin, Germany, achieved a technological milestone - the first time an infrared free-electron laser operated in two-color mode.
This world-leading technological innovation makes simultaneous two-color laser pulse experiments possible and opens up new possibilities for applications such as the study of time processes in solids and molecules.
Currently, there are about a dozen free-electron lasers available worldwide, which vary widely in size (from a few meters to a few kilometers), wavelength range (from microwaves to hard X-rays), and cost (from millions to more than a billion). However, they share a common feature: they all produce intense and short pulses of radiation.
In recent decades, free-electron lasers have become an important source of radiation and are widely used in basic research and applied science.
It is known that researchers at the Fritz Haber Institute (FHI), together with partners in the United States, have developed a new method which is capable of generating infrared pulses of two different colors simultaneously.
The realization of this technology is ingenious: In a free electron beam stream, the electron beams are first accelerated by an electron gas pedal to reach extremely high kinetic energies close to the speed of light. Subsequently, these high-speed electrons pass through a fluctuator and are forced into a cyclotron-like path by a strong magnetic field with periodic polarity changes.
The oscillating action of the electrons results in the emission of electromagnetic radiation, the wavelength of which can be precisely controlled by adjusting either the electron energy or the strength of the magnetic field. Because of this, free electron lasers (FELs) are capable of generating laser-like radiation in almost all parts of the electromagnetic spectrum, covering a broad range from long terahertz to short X-ray wavelengths.
Since 2012, FHI's FELs have been operating steadily, producing intense pulsed radiation with wavelengths that are continuously tunable in the mid-infrared (MIR) range, from 2.8 microns to 50 microns. In recent years, FHI's scientists and engineers have worked on a two-color extension, successfully installing a second branch of the FEL to produce far-infrared (FIR) radiation at wavelengths between 5 and 170 microns.
This innovation not only expands the range of applications for FELs, but also opens up new avenues for their development in the field of scientific research.