Infrared free‐electron laser uses electrostatic accelerator

From the near ultraviolet to the near infrared—2000 Å to 25 microns—we have access to an abundance of coherent sources, some of them tunable over limited ranges. For the outer reaches of the optical spectrum—the far ultraviolet and the far infrared, where conventional laser sources offer very little—free‐electron lasers present a unique opportunity. The preceding story describes the promise of FEL harmonic frequency multiplication for the vacuum ultraviolet and extreme ultraviolet. At the other end of the spectrum, a novel, electrostatic‐accelerator‐based, broadly tunable, far‐infrared FEL at the University of California, Santa Barbara, began lasing at 400 microns two months ago.