Storage ring two-color free-electron laser

Abstract

We report a systematic experimental study of a storage ring two-color free-electron laser (FEL) operating simultaneously in the infrared (IR) and ultraviolet (UV) wavelength regions. The two-color FEL lasing has been realized using a pair of dual-band high-reflectivity FEL mirrors with two different undulator configurations. We have demonstrated independent wavelength tuning in a wide range for each lasing color, as well as harmonically locked wavelength tuning when the UV lasing occurs at the second harmonic of the IR lasing. Precise power control of two-color lasing with good power stability has also been achieved. In addition, the impact of the degradation of FEL mirrors on the two-color FEL operation is reported. Furthermore, we have investigated the temporal structures of the two-color FEL beams, showing simultaneous two-color micropulses with their intensity modulations displayed as FEL macropulses.

International workshop on next generation gamma-ray source

“…The oscillator FEL is well-known for its wavelength flexibility (e.g., the Duke storage ring FEL can be operated from 2.1 μm to 188 nm). More recently, the storage ring FEL has been developed to demonstrate several new capabilities which can have an important impact for a CGS, including simultaneous two-color lasing [380,381] and the use of an 'optics-free' method to rapidly control and manipulate the laser beam (and γ-ray beam) polarization with an unprecedented level of precision [269,382].…”

International Workshop on the Next Generation Gamma-ray Sources

“…The oscillator FEL is well-known for its wavelength flexibility (e.g., the Duke storage ring FEL can be operated from 2.1 µm to 188 nm). More recently, the storage ring FEL has been developed to demonstrate several new capabilities which can have an important impact for a CGS, including simultaneous two-color lasing [161,162] and the use of an "optics-free" method to rapidly control and manipulate the laser beam (and γ-ray beam) polarization with an unprecedented level of precision [50,163].…”

Gain cascading scheme of a free-electron-laser oscillator

“…An accelerator driven electron bunch passes through an undulator, co-propagating with a light pulse trapped in an optical cavity. The light pulse is amplified in the undulator and reflected back and forth by a set (typically a pair) of cavity mirrors so that at the entrance of undulator it meets the electron bunch (either a new bunch from a linac or the same bunch circulating in a storage ring [35]) again. With g is the single-pass gain (relative increase of the optical intensity per pass) and r is the cavity round-trip reflectivity related to the active output coupling and passive cavity loss, if (1 + g)r > 1, the light pulse would evolve from the initial incoherent spontaneous emission to a coherent pulse.…”