Wavelength-tunable, narrow-band thermal emitter based on moiré patterns

Conventional thermal emitters generate broadband thermal radiation with limited tunability, which are features that limit their application. Guo et al. report on a type of thermal emitter based on the geometric moiré effect that exhibits an ultranarrow linewidth and ultrabroad tuning range.

“Utilizing the geometric effect of moiré patterns, we provide a novel scheme of wavelength-tunable, narrow-band thermal emitters with tunability over a wide wavelength range,” said author Cheng Guo. “It achieves a tuning range-to-bandwidth ratio of 313, which is 68 times larger than the previous record-holding value.”

Current devices tend to suffer from an overly broad bandwidth or too small of a tuning range. The authors proposed a scheme to remedy these limitations involving the superposition of two dielectric gratings that form a moiré pattern, an interference pattern that is produced by overlaying similar but slightly offset templates. Moiré patterns are very sensitive to small variations in the overlaid templates, which leads to the large tunability seen in their unique thermal emitter.

“Our device may find many applications including gas sensing and infrared imaging and in many devices including pyroelectric detectors,” said Guo. “When applied to nondispersive infrared (NDIR) sensing, such emitters can eliminate the need for filters or specially designed spectral selective IR detectors, leading to a scheme of multiplexed NDIR gas sensing that is simple, compact, and cost-effective.”

Their device has a linewidth of 0.0015 electronvolts and a tuning range of 0.47 eV, leading to an impressively large tuning range-to-bandwidth ratio. In terms of future work, the scientists plan to further investigate tailoring the angular and polarization properties of the thermal emitter.

Source: “Wide wavelength-tunable narrow-band thermal radiation from moire patterns,” by Cheng Guo, Yu Guo, Beicheng Lou, and Shanhui Fan, Applied Physics Letters (2021). The article can be accessed at http://doi.org/10.1063/5.0047308 .