  We show that the amplitude, or Higgs mode of a superconductor with strong
spin-orbit coupling and an exchange field, couples linearly to the
electromagnetic field. Furthermore, by coupling such a superconductor to an LC
resonator, we demonstrate that the Higgs resonance becomes a regular mode at
frequencies smaller than the quasiparticle energy threshold $2\Delta$. We
finally propose and discuss a possible experiment based on microwave
spectroscopy for an unequivocal detection of the Higgs mode. Our approach may
allow visualizing Higgs modes also in more complicated multiband
superconductors with a coupling between the charge and other electronic degrees
of freedom.
