generation, [4][5][6] radiative cooling, [7] and thermophotovoltaics (TPVs). [8] When selective thermal emitters are intended to emit in shorter mid IR range (e.g., an emitter for TPV system), the emitter has to be heated above one thousand kelvin. [9] Refractory metals such as molybdenum (Mo) [10] and tungsten (W) [11] are required in such cases. However, searching for alternative plasmonic materials is essential for reducing the material cost as well as for material research interest.Transition metal nitrides such as titanium nitride (TiN) and zirconium nitride (ZrN) also possess melting point as high as ≈3000 °C, [12][13][14] hence regarded as good candidate materials for thermal emitters. In addition, transition metal nitrides are regarded as alternative plasmonic materials in the visible to infrared region due to their high carrier concentrations up to 10 21 -10 22 cm −3 . [15] Among transition metal nitrides, TiN receives many attentions as an alternative plasmonic material in the past decades. [16][17][18] One of the advantages of using TiN is that it can be used in much higher temperature than other plasmonic materials. [19][20][21] However, there are only limited studies on thermal emitters using TiN so far.To demonstrate wavelength selective thermal emission, nanostructures have been investigated intensively [22,23] rather than microcavity structures which have been studied in 1990's and early 2000's. [24][25][26] Variety of nanostructures have been proposed, such as 1D grating, [27,28] 2D or 3D metallic photonic crystals, [2,29,30] and metal-insulator-metal (MIM) metamaterial structures. [31] Among those nanostructures, MIM metamaterial structures are easy to achieve wavelength selective emissions with single or multibands whose bandwidths and emission wavelengths are adjustable. [32] However, the requirement of nanofabrication, such as e-beam lithography, leads to limitations in large area fabrications.In contrast, thin-film based devices are the candidates for large area samples which do not require nanopatterning. [33,34] One way to optimize 1D thin film structures is via manipulating the phase-shifting layers in Gires-Tournois resonator. [35] Several different multilayer thin-film designs have been explored, which include Fabry-Perot cavity with either distributed Bragg reflectors (DBRs) and/or metallic mirror(s) and Tamm plasmon polaritons (TPPs) structures. For MIM structures (i.e., Fabry-Perot cavity), standing waves exist within the dielectric layer to form a cavity resonator. [36][37][38] In contrast, 1D TPP structure can excite TPP resonance at the interface of a A refractory wavelength selective thermal emitter is experimentally realized by the excitation of Tamm plasmon polaritons (TPPs) between a titanium nitride (TiN) thin film and a distributed Bragg reflector (DBR). The absorptance reaches nearly unity at ≈3.73 μm with the bandwidth of 0.36 μm in the experiment. High temperature stabilities are confirmed up to 500 and 1000 °C in ambient and in vacuum, respectively. When the TiN TPP stru...

Merging photonic structures and optoelectronic sensors into a single chip may yield a sensor‐on‐chip spectroscopic device that can measure the spectrum of matter. In this work, an on‐chip concurrent multiwavelength infrared (IR) sensor, which consists of a set of narrowband wavelength‐selective plasmonic perfect absorbers combined with pyroelectric sensors, where the response of each pyroelectric sensor is boosted only at the resonance of the nanostructured absorber, is proposed and realized. The proposed absorber, which is based on Wood's anomaly absorption from a 2D plasmonic square lattice, shows a narrowband polarization‐independent resonance (quality factor – Q of 73) with a nearly perfect absorptivity as high as 0.99 at normal incidence. The fabricated quad‐wavelength IR sensors exhibit four different narrowband spectral responses at normal incidence following the predesigned resonances in the mid‐wavelength infrared region that corresponds to the atmospheric window. The device can be applied for practical spectroscopic applications such as nondispersive IR sensors, IR chemical imaging devices, pyrometers, and spectroscopic thermography imaging.

We propose and experimentally demonstrate a compact design for membrane-supported wavelength-selective infrared (IR) bolometers. The proposed bolometer device is composed of wavelength-selective absorbers functioning as the efficient spectroscopic IR light-to-heat transducers that make the amorphous silicon (a-Si) bolometers respond at the desired resonance wavelengths. The proposed devices with specific resonances are first numerically simulated to obtain the optimal geometrical parameters and then experimentally realized. The fabricated devices exhibit a wide resonance tunability in the mid-wavelength IR atmospheric window by changing the size of the resonator of the devices. The measured spectral response of the fabricated device wholly follows the pre-designed resonance, which obviously evidences that the concept of the proposed wavelength-selective IR bolometers is realizable. The results obtained in this work provide a new solution for on-chip MEMS-based wavelength-selective a-Si bolometers for practical applications in IR spectroscopic devices.

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Spectrally selective detection is of crucial importance for diverse modern spectroscopic applications such as multi-wavelength pyrometry, non-dispersive infrared gas sensing, biomedical analysis, flame detection, and thermal imaging. This paper reports a quad-wavelength hybrid plasmonic–pyroelectric detector that exhibited spectrally selective infrared detection at four wavelengths—3.3, 3.7, 4.1, and 4.5 μm. The narrowband detection was achieved by coupling the incident infrared light to the resonant modes of the four different plasmonic perfect absorbers based on Al-disk-array placed on a Al2O3–Al bilayer. These absorbers were directly integrated on top of a zinc oxide thin film functioning as a pyroelectric transducer. The device was fabricated using micro-electromechanical system (MEMS) technology to optimize the spectral responsivity. The proposed detector operated at room temperature and exhibited a responsivity of approximately 100–140 mV/W with a full width at half maximum of about 0.9–1.2 μm. The wavelength tunability, high spectral resolution, compactness and robust MEMS-based platform of the hybrid device demonstrated a great advantage over conventional photodetectors with bandpass filters, and exhibited impressive possibilities for miniature multi-wavelength spectroscopic devices.

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The growth of highly crystalline LaB6 films with an excellent optical response and low loss is reported, which will be useful for high‐performance photothermal device applications when combined with their inherent refractory properties. Optimum growth parameters for realizing uniaxial and coherent LaB6 thin films, exhibiting an excellent plasmonic response for near‐ to mid‐infrared device applications, are established. Numerical electromagnetic simulations of the epitaxial LaB6 nanostructures revealed that the electromagnetic field at the LaB6 surface can be as high as that of the Au nanostructures. Furthermore, the LaB6 nanostructures show resonance in the visible (red) to mid‐infrared region comparable to those of Au with the added advantage of improved temperature stability that can withstand harsh photothermal device operations.

Among conductive oxide materials, niobium doped titanium dioxide has recently emerged as a stimulating and promising contestant for numerous applications. With carrier concentration tunability, high thermal stability, mechanical and environmental robustness, this is a material-of-choice for infrared plasmonics, which can substitute indium tin oxide (ITO). In this report, to illustrate great advantages of this material, we describe successful fabrication and characterization of niobium doped titanium oxide nanoantenna arrays aiming at surface-enhanced infrared absorption spectroscopy. The niobium doped titanium oxide film was deposited with co-sputtering method. Then the nanopatterned arrays were prepared by electron beam lithography combined with plasma etching and oxygen plasma ashing processes. The relative transmittance of the nanostrip and nanodisk antenna arrays was evaluated with Fourier transform infrared spectroscopy. Polarization dependence of surface plasmon resonances on incident light was examined confirming good agreements with calculations. Simulated spectra also present red-shift as length, width or diameter of the nanostructures increase, as predicted by classical antenna theory.