Narrowband Thermal Emission Realized through the Coupling of Cavity and Tamm Plasmon Resonances

A hybrid structure that supports the coupling of a cavity mode and a Tamm plasmon (TP) mode is demonstrated as a spectrally selective thermal emitter for the mid-infrared spectral range. Unlike conventional TP structures, the presented hybrid structure contains an optical cavity sandwiched between the distributed Bragg reflector (DBR) and the metallic mirror of a typical TP structure. In simulation, the TP-cavity hybrid structure exhibits a strong peak (absorptance = 0.993) in the absorption spectrum with a high quality factor (Q = 135), and this absorptance peak can exist over a wide range of resonance wavelengths by adjusting the cavity thickness. Moreover, the hybrid structure shows a small polarization dependence (for incident angles less than 30°, the resonance wavelength of TM and TE differ by less than 2 nm) and a shift of less than 20 nm in the absorptance peak wavelength for incident angles between 0° and 8°. The absorptance peak of the hybrid structure is stronger and sharper than that of a pure TP structure made from the same materials, which has a maximum absorptance of 0.898 and Q-factor of 28, and a Fabry–Perot cavity structure topped with a 5 nm Au layer, which has a maximum absorptance of 0.899 and Q-factor of 25. Upon heating, a strong and narrow bandwidth thermal emittance peak is observed with a maximum emittance value of 0.90 and a Q-factor of 88 at a wavelength of 4.731 μm. This easy-to-fabricate and high-performance infrared thermal emitter is ideal for applications where narrowband infrared light sources are required.