  We performed a Laser angle-resolved photoemission spectroscopy (ARPES) study
on a wide doping range of Ba1-xKxFe2As2 (BaK) iron-based superconductor. We
observed a robust low-binding energy (BE) kink structure in the dispersion
which is doping dependent where its energy peaks at the optimally-doped (OP)
level (x~0.4) and decreases towards the underdoped (UD) and overdoped (OD)
sides. It is also temperature-dependent and survives up to ~90K. We attribute
this kink to electron-mode coupling in good agreement with the inelastic
neutron scattering (INS) and scanning tunneling microscopy (STM) results on the
same compound which observed a similar bosonic mode associated with spin
excitations. The relation between the mode energy ({\Omega}) and the SC
transition temperature (Tc) deduced from our Laser ARPES data follow the
universal relation deduced from INS and STM. In addition, we could resolve
another kink at higher BE showing less doping and temperature dependence and
may thus be of different origin.
