Strong and weak coupling of a plasmonic resonance with molecular vibrational modes show considerable potential for enabling the creation of extraordinarily narrow band thermal radiation sources. The main prerequisite for that, however, is sufficient thermal stability on behalf of the metasurface structure, and particularly that of the insulator molecular compound. Polyimide is well known for its high thermal stability and heat resistance up to a 350 • C temperature. In our experiments, stable thermal radiation output was successfully measured for heating temperatures ranging from 50 to 250 • C. Some of the emitted radiation spectra are given in Fig. , where they are normalized to respective black-body spectral radiance. Above 300 • C, MIM structure became distorted due to softening and gradual decomposition of polyimide, and its plasmon resonance spectral position shifted, causing corresponding deleterious changes in thermal radiation output. However, when operated in the appropriate temperature range MIM metasurfaces exhibited a marked robustness in the angular dependence of emission upon heating, in contrast to grating-type surface radiators.