Selective multi-wavelength infrared emission by stacked gap-plasmon thermal emitters.

Selective multi-wavelength infrared light sources are important elements to achieve precise molecular detection by the usage of their intrinsic vibrational spectra. In this work, we proposed a double-stacked cross-shaped metal-dielectric-metal (MDM) resonator to achieve penta-wavelength mid-infrared thermal emission. Through the optimization of un-symmetric cross-shaped tri-layers incorporated with two sandwiched dielectric materials, four distinct emission bands associated with the magnetic resonances in stacked MDM resonators were realized, which shows nondispersive and polarization-dependent property due to the localized plasmon oscillations of the magnetic resonances. In addition, the phonon emission in the silicon dioxide layer also contributes one radiation peak at λ = 10 μm. Via a simple polarization rotator, the emission wavelengths can be tuned from 4.5 and 7.5 μm to 5.5 and 8.5 μm. This paves the way for simultaneous detection of multi-band molecular absorption fingerprint, and the polarization-tunable emission wavelengths also facilitate the possibility to achieve multi-compound sensing via one compact system.