  We investigate the propagation modes of gauge fields in an infinite
Randall-Sundrum scenario. In this model a sine-Gordon soliton represents our
thick four-dimensional braneworld while an exponentially coupled scalar acts
for the dilaton field. For the gauge-field motion we find a differential
equation which can be transformed into a confluent Heun equation. By means of
another change of variables we obtain a related Schrodinger equation with a
family of symmetric rational (\gamma-\omega z^2)/(1-z^2)^2 potential functions.
We discuss both results and present the infinite spectrum of analytical
solutions for the gauge field. Finally, we assess the existence and the
relative weights of Kaluza-Klein modes in the present setup.
