Search Results (6)

Colloidal quantum dots (QDs) have emerged as promising materials for the development of infrared photodetectors owing to their tunable band gaps, cost-effective manufacturing, and ease of processing. This paper provides a comprehensive overview of the fundamental properties of quantum dots and the operating principles of various infrared detectors. We review the latest advancements in short-wave infrared (SWIR), mid-wave infrared (MWIR), and long-wave infrared (LWIR) detectors employing colloidal quantum dots. Despite their potential, these detectors face significant challenges compared to conventional infrared technologies. Current commercial applications are predominantly limited to the near-infrared and short-wave bands, with medium- and long-wave applications still under development. The focus has largely been on lead and mercury-based quantum dots, which pose environmental concerns, underscoring the need for high-performance, non-toxic materials. Looking forward, the development of large array and small pixel detectors and improving compatibility with readout circuits are critical for future progress. This paper discusses these hurdles and offers insight into potential strategies to overcome them, paving the way for next-generation infrared sensing technologies. Full article

The short-wave infrared (SWIR) grating imaging spectrometer based on indium gallium arsenide (InGaAs) material inverts the atmospheric methane concentration by measuring the scattered light signals in the sky. This study proposes spectral and radiometric calibration methods for the characteristics of the spectrometer, such as the small-area array, high signal-to-noise ratio, and high spectral resolution. Four spectral response function models, namely, the Gauss, Lorentz, Voigt and super-Gaussian models, were compared during spectral calibration. With a fitting residual of 0.032, the Gauss model was found to be the most suitable spectral response function for the spectrometer. Based on the spectral response function, the spectral range and spectral resolution of the spectrometer were determined to be 1592.4–1677.2 and 0.1867 nm, respectively. In addition, radiometric calibration of the spectrometer was achieved by combining an integrating sphere and linear measuring instrument. Moreover, absolute and relative radiometric calibrations of the spectrometer were performed. The low signal response problem caused by the quantum efficiency of the detector at long wavelength was corrected, and the uncertainty and non-stability uncertainty of absolute radiometric calibration were calculated to be less than 0.2%. Finally, the calibrated spectrometer was used to accurately measure the solar scattering spectrum in the SWIR band, and the solar spectrum was simulated by the radiative transfer model for verification; the measurement error was found to be 5%. Concurrently, a methane sample gas experiment was performed using the integrating-sphere light source, and the measurement error was less than 4%. This fully proves the effectiveness of the spectral and radiometric calibrations of the SWIR spectrometer and strongly guarantees a subsequent, rapid and accurate inversion of atmospheric methane concentration. Full article

Infrared (IR) sensors are widely used in various applications due to their ability to detect infrared radiation. Currently, infrared detector technology is in its third generation and faces enormous challenges. IR radiation propagation is categorized into distinct transmission windows with the most intriguing aspects of thermal imaging being mid-wave infrared (MWIR) and long-wave infrared (LWIR). Infrared detectors for thermal imaging have many uses in industrial applications, security, search and rescue, surveillance, medical, research, meteorology, climatology, and astronomy. Presently, high-performance infrared imaging technology mostly relies on epitaxially grown structures of the small-bandgap bulk alloy mercury–cadmium–telluride (MCT), indium antimonide (InSb), and GaAs-based quantum well infrared photodetectors (QWIPs), contingent upon the application and wavelength range. Nanostructures and nanomaterials exhibiting appropriate electrical and mechanical properties including two-dimensional materials, graphene, quantum dots (QDs), quantum dot in well (DWELL), and colloidal quantum dot (CQD) will significantly enhance the electronic characteristics of infrared photodetectors, transition metal dichalcogenides, and metal oxides, which are garnering heightened interest. The present manuscript gives an overview of IR sensors, their types, materials commonly used in them, and examples of related applications. Finally, a summary of the manuscript and an outlook on prospects are given. Full article

An anti-reflection coating on a back-illuminated 128 × 128 array Si-based blocked impurity band (BIB) detector in a very-long-wave infrared range was designed in this work. The reflectance and transmittance spectra of ZnS films with different thicknesses on intrinsic Si substrates were studied with a FDTD simulation and experiment. Compared to bare Si substrate, the reflectance of Si coated with 1.5, 2.0, 2.5, and 3.0 μm thick ZnS significantly decreased, while the transmittance increased in the range of 10.0~25.0 μm band. The transmittance enhancement ratio reached approximately 32%, 32%, 28%, and 29%, respectively. It was evidenced that the enhanced transmission at a specific wavelength was caused by the effective interference cancellation effect. Then, a 2.0 μm thick ZnS thin film was deposited on the backside of the 128 × 128 array Si-based BIB detector. The spectral responsivity of the detector increased significantly. Additionally, the blackbody responsivity increased by approximately 36%, suggesting that the ZnS film is an ideal anti-reflection material for VLWIR detectors in the range of 10.0~25.0 μm band. Full article

Circular polarization detection enables a wide range of applications. With the miniaturization of optoelectronic systems, integrated circular polarization detectors with native sensitivity to the spin state of light have become highly sought after. The key issues with this type of device are its low circular polarization extinction ratios (CPERs) and reduced responsivities. Metallic two-dimensional chiral metamaterials have been integrated with detection materials for filterless circular polarization detection. However, the CPERs of such devices are typically below five, and the light absorption in the detection materials is hardly enhanced and is even sometimes reduced. Here, we propose to sandwich multiple quantum wells between a dielectric two-dimensional chiral metamaterial and a metal grating to obtain both a high CPER and a photoresponse enhancement. The dielectric-metal-hybrid chiral metamirror integrated quantum well infrared photodetector (QWIP) exhibits a CPER as high as 100 in the long wave infrared range, exceeding all reported CPERs for integrated circular polarization detectors. The absorption efficiency of this device reaches 54%, which is 17 times higher than that of a standard 45° edge facet coupled device. The circular polarization discrimination is attributed to the interference between the principle-polarization radiation and the cross-polarization radiation of the chiral structure during multiple reflections and the structure-material double polarization selection. The enhanced absorption efficiency is due to the excitation of a surface plasmon polariton wave. The dielectric-metal-hybrid chiral mirror structure is compatible with QWIP focal plane arrays. Full article

The Graphene@PtSe₂ heterostructure is an excellent long-wave infrared detection material. However, the expensive cost of PtSe₂ prevents its widespread use in infrared detection. In this paper, Hf was used to partially replace Pt to form Graphene@(PtSe₂)_n(HfSe₂)_4−n (n = 1, 2, and 3) bidirectional heterostructures consisting of graphene and lateral PtSe₂/HfSe₂ composites based on first-principles calculations. Then, the new bidirectional heterostructures were compared with heterostructures formed by graphene with pure MSe₂ (M = Pt, Hf). It was found that the band gaps of the bidirectional heterostructures were between those of Graphene@PtSe₂ and Graphene@HfSe₂. Among these heterostructures, the Graphene@(PtSe₂)₃(HfSe₂)₁ bidirectional heterostructure has almost the same optical absorption properties in the infrared wavelength region of 1.33~40 µm as the Graphene@PtSe₂ heterostructure, and it improves the absorption in the near-infrared wavelength region of 0.75~1.33 µm. Such a designment may bring the material costs down (since PtSe₂ costs approximately five times more than HfSe₂). This study on the designment of the bidirectional Graphene@(PtSe₂)₃(HfSe₂)₁ heterostructure also illustrates a cost-effective design method for Pt-based IR detectors. Full article