Broadband Enhancement of Mid‐Wave Infrared Absorption in a Multi‐Resonant Nanocrystal‐Based Device

Abstract

Light management is one of the main challenges to address when designing a sensor from a nanocrystal (NC) array. Indeed, the carrier diffusion length, limited by hopping mechanism, is much shorter than the absorption depth. Several types of resonators (plasmon, Bragg mirror, guided mode, Fabry–Perot cavity) have been proposed to reduce the volume where light is absorbed. All of them are inherently narrow bands, while imaging applications focus on broadband sensing. Here, an infrared sensor in the short and mid‐wave infrared (SWIR and MWIR) that combines three different photonic modes is proposed to achieve broadband enhancement of the light absorption. Moreover, it is shown that these three modes can be obtained from a simple structure where the NC film is coupled only to a grating and a top metallic layer. The obtained device achieves a high responsivity of >700 mA W–1, a detectivity up to 2 × 1010 Jones at 80 K, and a short response time of 11 µs.

Helmholtz Resonator Applied to Nanocrystal-Based Infrared Sensing

“…It is also worth pointing out that the plasmonic resonance of the grating is expected to appear at n s •p with p = 350 nm the period of the grating, which is expected at ∼800 nm, outside of the spectral window of interest. The dispersion map (Figure S4) shows a very weak dependence of the resonance with the planar wavevector, which can be seen as an improvement compared to similar structures based on plasmonic gratings 30 or guided mode resonators. 16 To experimentally confirm the electric field localization within the gap, we used an infrared scanning near-field optical microscope (SNOM).…”

“…The dispersion map (Figure S4) shows a very weak dependence of the resonance with the planar wavevector, which can be seen as an improvement compared to similar structures based on plasmonic gratings or guided mode resonators …”

“…14−16 Several concepts of photonic structures have been explored, including surface plasmonics, 17 a metal−insulator−metal cavity, 18 optical lens, 19 Fabry−Perot cavity, 20 plasmonic cavity, 21,22 guided-mode resonator, 23−25 epsilon-near-zero resonator, 26,27 electromagnetically induced absorber, 28 distributed Bragg reflector 13,29 and even the combination of some of them. 14,30 In this paper, we explore the design of an optical resonator equivalent to a Helmholtz resonator initially developed for acoustics, 31 see Figure 1a. In this last case, a closed cavity is coupled to the external environment through a small opening in which the acoustic field is dramatically enhanced.…”

“…However, in most devices, the light-matter interaction is dictated by the electronic structure of the material itself. This has raised the need to couple the absorbing/emitting layer to a photonic structure to shape the absorption or enhance its magnitude. − Several concepts of photonic structures have been explored, including surface plasmonics, a metal–insulator–metal cavity, optical lens, Fabry−Perot cavity, plasmonic cavity, , guided-mode resonator, − epsilon-near-zero resonator, , electromagnetically induced absorber, distributed Bragg reflector , and even the combination of some of them. , …”

Vanishing Confinement Regime in Terahertz HgTe Nanocrystals Studied under Extreme Conditions of Temperature and Pressure

“…HgTe nanocrystals , (NCs) have reached a high level of maturity that enables their use in complex devices such as lasers, light-emitting diodes (LEDs), − infrared (IR) sensors with carrier density − light–matter control, − and cameras. − All of these results have been obtained with NCs absorbing in the near- and mid-wave infrared range. Because of the semimetal nature of HgTe, the absorption spectrum of NCs can be tuned up to the terahertz (THz) frequency range, which corresponds to the spectral range in which the NC properties remain underexplored .…”