Towards gamma-ray free-electron lasers

The free-electron laser (FEL), powered by an accelerator and equipped with an undulator, produces intense coherent radiation at ever-shorter wavelengths. Whilst the hard x-ray regime represents the current state of the art, the gamma-ray regime remains the next objective. Gamma-ray lasers, deemed one of the most profound and intriguing challenges in physics by the 2003 Nobel Laureate, hold the key to unlocking the largely unexplored nuclear domain. This article introduces a novel scheme that harnesses FEL harmonics, offering a pathway for existing x-ray FELs to operate as gamma-ray lasers.