Ultra-thin midwavelength infrared absorber using bismuth based planar thin film metamaterials

Abstract

We reveal the extraordinary potential of bismuth (Bi) based planar thin film metamaterials in achieving light perfect absorption for midwavelength infrared (MWIR) range from 3 to 6 µm. The proposed absorber is composed of an ultra-thin Bi film and a continuous metallic film separated by a dielectric spacer. Theoretical analyses show that the absorber exhibits narrowband absorption that can continuously span the whole MWIR range by varying the geometric parameters. Furthermore, it is found that the absorber displays wide-angle absorption up to 80° as well as polarization-insensitive properties. Experimental measurements are performed to corroborate the theoretical analyses.

A spectrally selective visible microbolometer based on planar subwavelength thin films

“…1(d) and 1(e). strong absorption, and both the top and bottom gold layers play important roles in the absorption effects, revealing that the remarkable enhancement of light absorption is originated from the strong optical asymmetric Fabry-Perot resonant effect 25 that significantly enhances the free electron contribution. Moreover, it should be noted that for all the cases the energy of incident light is dissipated by the metal and converted to heat eventually.…”

“… 24 At a wavelength of 638 nm ( Fig. 2(d) ), the bare Au thin film has very weak absorption and strong reflection due to the impedance mismatch between the air and the gold film; while, the MIM device structure exhibits strong absorption, and both the top and bottom gold layers play important roles in the absorption effects, revealing that the remarkable enhancement of light absorption originated from the strong optical asymmetric Fabry–Perot resonant effect 25 that significantly enhances the free electron contribution. Moreover, it should be noted that in all the cases the energy of incident light is dissipated by the metal and converted to heat eventually.…”

“…Although our experiment only presents visible MIM microbolometers in this paper, one can modify the thickness of each thin lm layer and alter materials to realize MIM microbolometers operating at any desired wavelength spanning from visible to infrared. 25,33 Moreover, the performance of the microbolometer could be further improved by reducing the active area size and reforming the package of the detector, such as equipping it with a heat-insulating bridge to reduce the thermal conduction. 29 We believe that our proposed planar thin lm-based MIM microbolometer offers a viable way towards the development of miniaturized and inexpensive detectors.…”

Lithography-Free Bismuth Metamaterials for Advanced Light Manipulation

“…Hence, in the investigation of bismuth metamaterial, developing lithography-free fabrication methods are highly desired. So far, the bismuth thin film, the bismuth nanoparticles embedded in a dielectric matrix, and the bismuth nanorod array are applied as the optical metamaterials for absorbers [45,[47][48][49][50][51][52], filters [49,53,54], and analog tuners for intensity and phase [55][56][57], as well as for thermaloptical switching [54,58,59]. Additionally, they can be prepared via lithography-free routes including regular physical vapor deposition (PVD) via magnetron sputter or thermal evaporation [32],pulse laser deposition (PLD) [60], and glazing-angle deposition (GLAD) [57].…”

“…Aside from the bismuth meta-absorber in the Vis-NIR regime, due to the strong Mie resonance in MIR-FIR range, tunable perfect absorption by a sub-λ/100 bismuth nano-film in a fractal phasor resonant cavity was developed and demonstrated angle-insensitive perfect absorption at a variable wavelength from 3 to 20 µm (Figure 7b) [50]. Alternatively, polarization insensitivity can be also enhanced by wide-angle high absorption [51]. The absorber is composed of an ultra-thin Bi film and a continuous metallic film separated by a dielectric spacer, exhibiting narrowband absorption that can continuously span the whole MWIR range from 3 to 6 µm by varying the geometric parameters.…”