  The property of the FEL polarization is of great importance to the user
community. FEL pulses with ultra-high intensity and flexible polarization
control ability will absolutely open up new scientific realms. In this paper,
several polarization control approaches are presented to investigate the great
potential on Dalian coherent light source, which is a government-approved novel
FEL user facility with the capability of wavelength continuously tunable in the
EUV regime of 50-150 nm. The numerical simulations show that both circularly
polarized FELs with highly modulating frequency and 100 microjoule level pulse
energy could be generated at Dalian coherent light source.
