A miniaturized plasma source includes a stripline split-ring resonator. The split-ring resonator is sandwiched between two dielectric substrates and two metal ground planes. In order to make the plasma accessible from the outside of the ground planes, a hole is made through the gap between the ends of the split ring. The two ground planes act as an electromagnetic shield, protecting the split-ring resonator from electromagnetic interference due to changes in the electric or dielectric environment surrounding it. The miniaturized plasma source is particularly useful in optogalvanic spectroscopy applications.