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.
Highlights
Lasers operated with multiple colors have been developed over the last half century with a number of applications in physics research
The two-color free-electron laser (FEL) lasing has been realized using a pair of dual-band high-reflectivity FEL mirrors with two different undulator configurations
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
Summary
Lasers operated with multiple colors have been developed over the last half century with a number of applications in physics research. Oscillator FELs mainly operate in the spectral region from IR to vacuum UV Another FEL configuration, the high-gain single-pass FEL, is mainly driven by linacs and does not use an optical cavity. In these FELs, the amplification of the FEL beam is realized in a single pass via the interaction between the electron beam and its radiation in a long undulator array [25,26] or with an external laser [27,28]. This difficulty can be overcome by using mirrors with very high reflectivity in multiple wavelength bands. We have confirmed the simultaneousness of two-color lasing at the time scale of FEL micropulses with power modulation at a larger time scale, displaying a temporal structure of macropulses in the two-color laser beams
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