Emerging nanostructured infrared absorbers enabling cost-effective image sensing: a review

Abstract

Image sensing has entered a new era with advancements in quantum mechanics. The infrared (IR) absorbers are the heart of this new era of image sensing. Within the IR spectra, the shortwave to mid-wave (MWIR) radiations are absorbed by IR photodetectors, whereas the MWIR to very-long wave spectrum is absorbed by IR thermal detectors. Both of these categories of image sensing cover the complete IR spectrum utilized by the applications ranging from biosensing in healthcare sector to autonomous vehicle navigation in military and space purposes. Despite having high-cost semiconductor technology with group-II–VI (mercury–cadmium–telluride) and group-III–V (indium–gallium–arsenide) dominating this IR absorbance industry for many decades, the need to have a cost-effective solution has led to an explosion in the exploration of potential materials. Two-dimensional (graphene, dichalcogenides of transition metals, and black-phosphorous) antimonite-based and group-IV/IV alloys have been found to show unprecedented absorption yield and detector properties comparable to traditional dominators with flexible fabrication methods. At the same time, the photon upconversion phenomenon that upconverts low-energy light to high-energy light has emerged as an exceptionally rich area of research in image sensing. The principle behind this concept lies in different energy transfer mechanisms (two photon absorption, triplet–triplet annihilation, cooperative energy pooling, etc.). The advancements that took place most recently in the development of IR absorbers have been reviewed in a concise way. Furthermore, the advancements in upconversion-based detection focusing on how this is evolving as a low-cost alternative for image sensing have been reviewed. Further discussion on how to anticipate a low-power, cost-effective, and light-weight image sensing system has been presented while mentioning some recent research as a proof-of-concept. We finally suggest a possible approach that could come up by synergizing the two simultaneous technologies to foresee the realization of an all-optical, low-power, and light-weight broad-range IR absorber for various applications.