An electromagnetic undulator for the far infrared at Elbe

Abstract

The first lasing in the mid infrared (IR) at the ELBE FEL [1, 2] allows us to specify the parameters of an additional undulator for longer wavelengths to complement the U27 undulator which is useful up to about 25 microns at most. In the longer wavelength range FELs constitute a unique radiation source with appealing properties. Radiation quanta in this range are appropriate for the lowenergy spectroscopy of various interesting modes in solidstate quantum-structures as well as in complex biological systems (e. g. DNA molecules).<br />We envisage an electromagnetic undulator with a period of roughly 12 cm. Using the electron beam of ELBE, IR light from 15 to 150 microns and beyond can be produced. To keep the transverse beam extension small, the IR beam is to be guided by a partial waveguide. An appropriate bifocal resonator mirror minimizes the mode coupling losses at the exit of the waveguide. Detailed calculations and computer simulations predict an outcoupled laser power of roughly 15W at 150 microns which will be transported to experimental stations. The maximum power is expected to be 35W at wavelengths between 40 and 90 μm.