Surface-plasmon resonance of a lollipop near-field transducer integrated in a planar solid immersion mirror for heat-assisted magnetic recording has been studied by a pump-probe photo-thermal measurement without medium coating and by recording on a phase-change medium. The resonant behaviors, including the resonant wavelength, the Q factor, on and off resonance photo-thermal signal, are consistent with our simulations. For lollipops of 190 nm in disk diameter and 20 nm thick, there are two resonant modes in the measured spectroscopic range (710 nm-950 nm). Recording on a phase-change medium shows that the wavelength of the short resonant mode is not sensitive to the presence of the medium while the wavelength of the long resonant mode exhibits significant red-shift. On resonance, the plasmon efficiency enables the pronounced near-field transducer recording.