The free-electron laser (FEL) at Jefferson Lab has produced its first beams at ultraviolet wavelengths. On 31 August, its first day of generating ultraviolet light, the FEL produced more than 50 W of laser light at a wavelength of 372 nm. It was then tuned from 363–438 nm, through many ultraviolet wavelengths and into the visible range.
Jefferson Lab’s FEL, which is based on a superconducting energy-recovery linac, is well known as the most powerful tunable laser in the infrared and also as a powerful source of terahertz light. Its high-power beams of infrared laser light, deliver more than 10 kW in continuous wave operation. Now, a four-year effort has succeeded in extending the spectrum to the shorter wavelengths of the ultraviolet region.
By producing 372 nm at 50 watts in August, the Jefferson Lab team has also demonstrated that it can produce milliwatts of laser light at 124 nm, the third harmonic of the light at 372 nm. So far, the FEL, has produced UV laser light only in the vault, which contains the accelerator and the mirrors that produce the primary wavelength of laser light. Before experiments at the shorter wavelength can begin, the team will need to install a different mirror to extract the 124 nm light and characterize it. In the meantime, the FEL operators plan to test the machine’s capabilities in the ultraviolet region. They expect the FEL to be capable of delivering more than a kilowatt of laser light at 372 nm. This should be ideal for studying many novel materials.
