A Narrowband Mid-infrared Absorber with Tunable Peak Absorbance and Nearly Unchanged Peak Wavelength Using a Phase Changing Material

A narrowband mid-infrared (MIR) absorber with tunable peak absorbance and nearly unchanged peak wavelength is demonstrated using a phase changing material. The absorber is formed by an Au IR reflector, a SiO₂ dielectric cavity and a 1D photonic crystal that consists of SiO₂ and GeSbTe (GST), which is a phase-transition material and thus controls the absorbance without static power consumption. The dimension of the Au/SiO₂/GST/SiO₂ are optimized for high peak absorbance, high quality factor and low background absorbance. The as-fabricated absorber with amorphous GST shows the peak absorbance of 0.704 at 5.636μm, quality factor of 46.19, and background absorbance less than 0.02. Without significantly changing the absorption peak wavelength and background absorbance, the peak absorbance of the absorber can be tuned up to 4.47 dB by the phase transition of GST. Such tunable narrowband MIR absorber is a promising candidate for low-cost thermal emitter for infrared applications.