Infrared Detectors Research Articles

A Multi-Dimensional Feature Fusion Recognition Method for Space Infrared Dim Targets Based on Fuzzy Comprehensive with Spatio-Temporal Correlation

Space infrared (IR) target recognition has always been a key issue in the field of space technology. The imaging distance is long, the target is weak, and the feature discrimination is low, making it difficult to distinguish between high-threat targets and decoys. However, most existing methods ignore the fuzziness of multi-dimensional features, and their performance mainly depends on the accuracy of feature extraction, with certain limitations in handling uncertainty and noise. This article proposes a space IR dim target fusion recognition method, which is based on fuzzy comprehensive of spatio-temporal correlation. First, we obtained multi-dimensional IR features of the target through multi-time and multi-spectral detectors, then we established and calculated the adaptive fuzzy-membership function of the features. Next, we applied the entropy weight method to ascertain the objective fusion weights of each feature and computed the spatially fuzzified fusion judgments for the targets. Finally, the fuzzy comprehensive function was used to perform temporal recursive judgment, and the ultimate fusion recognition result was obtained by integrating the results of each temporal recursive judgment. The simulation and comparative experimental results indicate that the proposed method improved the accuracy and robustness of IR dim target recognition in complex environments. Under ideal conditions, it can achieve an accuracy of 88.0% and a recall of 97.5% for the real target. In addition, this article also analyzes the impact of fusion feature combinations, fusion frame counts, different feature extraction errors, and feature database size on recognition performance. The research in this article can enable space-based IR detection systems to make more accurate and stable decisions, promoting defense capabilities and ensuring space security.

Research on Packaging Technology of Multi‑Band Infrared Detector Assembly with Integrated Lens

Research on Packaging Technology of Multi‑Band Infrared Detector Assembly with Integrated Lens

Optical up-conversion devices based on organic and inorganic quantum dot materials

Infrared (IR) to visible up-conversion devices made by incorporating IR detectors with visible emitting units are able to directly convert IR light into visible light.

Analysis of the Principle and Applications of Infrared Detectors in Cosmology

Analysis of the Principle and Applications of Infrared Detectors in Cosmology

Optimal design of optomechanical uncooled infrared focal plane array with integrated metalens

Optomechanical uncooled infrared (IR) detectors based on the thermal deformation of bi-material micro-cantilever have proved of significant potential in the IR imaging fields. However, compared to other uncooled infrared detectors, the optomechanical type relies on the mechanical deformation of the thermomechanical cantilevers, which compete for space with the absorbers and isolation beams, resulting in limited sensitivity. By integrating a designed metalens, large deformation, high thermal isolation, and high effective fill factor can be achieved simultaneously. Several pixel designs of optomechanical uncooled IR focal plane array (FPA) with designed integrated metalens are evaluated and optimized through numerical simulation. High thermal conversion efficiency and thermomechanical sensitivity μm K−1 are simultaneously achieved with an inherent noise-equivalent temperature difference(NETD) value of mK at the preset × pixels. Using Figure of Merit(FOM) as a comprehensive evaluation of NETD and response time, the optimized structure can be improved by up to 40% over the original structure.

Practical quantum imaging with undetected photons

Infrared (IR) imaging is invaluable across many scientific disciplines, from material analysis to diagnostic medicine. However, applications are often limited by detector cost, resolution and sensitivity, noise caused by the thermal IR background, and the cost, portability and tunability of infrared sources. Here, we describe a compact, portable, and low-cost system that is able to image objects at IR wavelengths without an IR source or IR detector. This imaging with undetected photons (IUP) approach uses quantum interference and correlations between entangled photon pairs to transfer image information from the IR to a wavelength which can be detected with a standard silicon camera. We also demonstrate a rapid analysis approach to acquire both phase and transmission image information. These developments provide an important step towards making IUP a commercially viable technique.

Thermographic cameras for thermal comfort applications: simulated and experimental spectral response errors of various long-wave infrared detectors

Modern remote temperature sensing in the form of infrared imaging has become a widely used and important technique, with the ability to measure and characterize important but unseen Radiant heat. As more Long-wave Infrared (LWIR) detectors come to market aiming to meet a wide array of needs and goals, there is a need to differentiate and appraise LWIR detectors based upon the specific needs of thermal comfort research. While most detectors measure in the range of 8-14 μm, only 37.6% of the emitted energy of a blackbody at 300 K is contained in this spectral range. Thus, inherent to the operation of nearly all infrared detectors and cameras is an assumption about the emission curves of the objects sensed. Many materials in the built environment deviate significantly from the blackbody assumption, and the error due to this deviation is one which generic gray-body emissivity corrections are unable to fix — it is akin to taking black-and-white images with only the red channel of a camera, and using exposure compensation to correct the image to attempt a true monochrome rendition: there is simply missing information and the adjusted image will still be very clearly wrong. In this paper, we aim to evaluate by simulation and experiment the potential errors in infrared thermography used to drive thermal comfort heat transfer calculations due to intrinsic spectral assumptions of LWIR detectors.

Numerical study on infrared detectors cooling by multi-stage thermoelectric cooler combined with microchannel heat sink

Lightweight, noiseless, and constant low-temperature refrigeration is crucial for cooled infrared (IR) detectors, especially short-wave-infrared (SWIR) detectors. However, some SWIR detectors, such as HgCdTe photovoltaic detectors are working below 210 K. For this application, multi-stage thermoelectric coolers (TEC) are preferable to single-stage thermoelectric coolers because they can generate larger temperature differences. This paper presents a refrigeration design that integrates SWIR and TEC into a vacuum Dewar package and combines them with a microchannel heat sink (MHS) to improve the detection performance and better responsiveness of SWIR. Two different refrigeration models, SWIR + TEC + AHS (air-cooled heat sink) and SWIR + TEC + MHS, were established to evaluate the refrigeration performance of the proposed SWIR + TEC + MHS scheme using the finite element method. The influences of multi-stage TEC leg length and current, inlet water temperature, and water velocity on the refrigeration performance of the TEC are analyzed. The results show that the SWIR + TEC + MHS design scheme has the best comprehensive performance and minimum volume. The influences of all the factors are obvious while the current has the most important effect on the performance. The temperature of SWIR reached 201.69 K at standard working conditions. It shows that the cooling scheme can not only meet the needs of flexible deployment of SWIR but also provide better thermal security. The proposed cooling design has an excellent prospect for short-wave-infrared detectors.

Plasmon resonance-enhanced graphene nanofilm-based dual-band infrared silicon photodetector

Graphene-based photodetectors have attracted much attention due to their unique properties, such as high-speed and wide-band detection capability. However, they suffer from very low external quantum efficiency in the infrared (IR) region and lack spectral selectivity. Here, we construct a plasmon-enhanced macro-assembled graphene nanofilm (nMAG) based dual-band infrared silicon photodetector. The Au plasmonic nanostructures improve the absorption of long-wavelength photons with energy levels below the Schottky barrier (between metal and Si) and enhance the interface transport of electrons. Combined with the strong photo-thermionic emission (PTI) effect of nMAG, the nMAG–Au–Si heterojunctions show strong dual-band detection capability with responsivities of 52.9 mA/W at 1342 nm and 10.72 mA/W at 1850 nm, outperforming IR detectors without plasmonic nanostructures by 58–4562 times. The synergy between plasmon–exciton resonance enhancement and the PTI effect opens a new avenue for invisible light detection.

Infrared Non‐Invasive Exhaled Biomarker Sensing: A Review

AbstractExhaled breath analysis is considered an effective tool for diagnosing the patient's metabolic status because of its non‐invasive nature. Gas chromatography‐mass spectrometry (GC‐MS) and other mass spectrometry techniques are widely used for exhaled breath analysis. Nevertheless, the requirement of a handheld device for real‐time analysis and rapid processing time of multiple samples leads to advancing infrared (IR) based breath gas sensing techniques. Herein, the IR gas sensing technologies are discussed with a focus on non‐dispersive infrared (NDIR), photoacoustic (PAS), and tunable diode laser absorption spectroscopy (TDLAS) gas sensing technologies because of their highly selective gas detection among compound gases (mixture of VOCs), as well as their corresponding sensing mechanisms and characteristics, for real‐time monitoring of exhaled biomarkers. Carbon dioxide, acetone, ammonia, nitric oxide, methane, and ethylene are the significant biomarkers elaborated in this work with their respective clinical applications and the significance of non‐invasive real‐time monitoring using IR detectors. Challenges in selectivity and clinical trials leads to focus on this review. Current market analysis, present status of different techniques to detect specific biomarkers and other challenges with their possible solutions discussed in this review aid in developing highly selective IR‐based handheld breath VOC analyzers for early diagnosis and screening.

Infrared HOT Photodetectors: Status and Outlook.

At the current stage of long-wavelength infrared (LWIR) detector technology development, the only commercially available detectors that operate at room temperature are thermal detectors. However, the efficiency of thermal detectors is modest: they exhibit a slow response time and are not very useful for multispectral detection. On the other hand, in order to reach better performance (higher detectivity, better response speed, and multispectral response), infrared (IR) photon detectors are used, requiring cryogenic cooling. This is a major obstacle to the wider use of IR technology. For this reason, significant efforts have been taken to increase the operating temperature, such as size, weight and power consumption (SWaP) reductions, resulting in lower IR system costs. Currently, efforts are aimed at developing photon-based infrared detectors, with performance being limited by background radiation noise. These requirements are formalized in the Law 19 standard for P-i-N HgCdTe photodiodes. In addition to typical semiconductor materials such as HgCdTe and type-II AIIIBV superlattices, new generations of materials (two-dimensional (2D) materials and colloidal quantum dots (CQDs)) distinguished by the physical properties required for infrared detection are being considered for future high-operating-temperature (HOT) IR devices. Based on the dark current density, responsivity and detectivity considerations, an attempt is made to determine the development of a next-gen IR photodetector in the near future.

Multistep InAs/InAsSb staircase nBn long-wavelength infrared detectors with enhanced charge carrier transport

Gallium-free Type-II superlattices (T2SLs) have emerged as promising candidates for high-performance long-wavelength infrared (LWIR) detectors at a high operating temperature. However, InAs/InAsSb barrier detectors suffer from the limited absorption efficiency, resulting in a trade-off between quantum efficiency (QE) and dark current. Here, a nBn LWIR detector based on multistep strain-balanced InAs/InAs0.5Sb0.5 superlattice staircase configuration is proposed. With this configuration, charge carrier transport and collection can be efficiently improved via the multistep staircase valance band, leading to an increased QE from 19.3% to 20.8% at a bias of −0.20 V. As a result, the device with multistep staircase configuration exhibits an improved performance, including a low dark current density of 4.13 × 10−5 A/cm2, high responsivity of 1.23 A/W and peak detectivity reaching 3.10 × 1011 cm·Hz1/2/W. By optimizing absorbing length of the multistep staircase absorber, the peak QE can be further boosted from 20.8% to 28.4% while maintaining a low dark current level, providing an alternative strategy to improve LWIR T2SL device performance.

Fourier transform IR imaging of primary tumors predicts lymph node metastasis of bladder carcinoma

The process of metastasis is complex and often impossible to be recognized in conventional clinical diagnosis. Lymph node metastasis (LNM) of bladder carcinoma (BC) is often associated with muscle-invasive tumors. To prevent and recognize LNM, the standard treatment includes radical cystectomy with lymph node dissection and histological examination. Here, we propose infrared (IR) microscopy as a tool for the prediction of LNM. For this purpose, IR images of bladder biopsies from patients with diagnosed non-metastatic early (E BC) and advanced (A BC), as well as metastatic advanced (M BC) bladder cancer were first collected. Furthermore, this dataset was complemented with images of the secondary tumors from the lymph nodes (M LN) of the M BC patients. Unsupervised clustering was used to extract tissue structures from IR images to create a data set comprising 382 IR spectra of non-metastatic bladder tumors and 241 metastatic ones. Based on that, we next established discrimination models using PLS-DA with repeated random sampling double cross-validation, and permutation test to perform the classification. The accuracy of BC metastasis prediction from IR bladder biopsies was 83 % and 78 % for early and advanced BC, respectively, herein demonstrating a proof-of-concept IR detection of BC metastasis. The analysis of spectral profiles additionally showed molecular composition similarity between metastatic bladder and lymph node tumors. We also determined spectral biomarkers of LNM that are associated with sugar metabolism, remodeling of extracellular matrix, and morphological features of cancer cells. Our approach can improve clinical decision-making in urological oncology.

Performance evaluation of an Ultra-Fast IR Detector for Astronomy Transients

In this work, we present the design of an ultra-fast IR (InfraRed) detector for the search of astronomical transients. Time-domain astronomy is a field in continuous growth in the last years, with interest in detectors with nanosecond performance, in order to observe potential fast transients with the time scale of GRBs (Gamma Ray Bursts) and FRBs (Fast Radio Bursts). An ultra-fast temporal detector based on HgCdTe photoconductors is under development in Italy, at the Frascati National Laboratory of the National Institute of Nuclear Physics, by tests at SINBAD, the DAFNE infrared beamline. The detector will be used for mid-IR observations together with a ground-based reflecting telescope or launched on a scientific balloon.

Branched Comonomers in LLDPE—Influence of Short Chain Branch Shape on Crystallinity

AbstractThe crystallinity of Linear Low‐Density Polyethylene (LLDPE) is influenced significantly by short‐chain branches (SCBs) present in the backbone of the polymer. Despite the importance of this aspect, with only a few linear comonomers being currently used in the commercial production of LLDPE. It is found that by introducing branched comonomers, the melting point and crystallinity of LLDPE can be influenced to a greater extent than with linear comonomers. Since only a few linear comonomers are currently used in the production of LLDPE, the characterization of LLDPEs with branched comonomer has been often overlooked. By combining High‐Temperature‐Size‐Exclusion Chromatography (HT‐SEC), Nuclear Magnetic Resonance (NMR) spectroscopy, and Infrared (IR) spectroscopy, it is shown that standard HT‐SEC analysis using an IR detector is also applicable to polymers containing branched comonomers.

Ultralow Dark Current Room‐Temperature Infrared Photodetector Based on InSb Nanosheets/MoS2 Van der Waals Heterostructure

As a narrow‐bandgap semiconductor, InSb is widely used in infrared (IR) detection due to its excellent performance and other characteristics such as ultrahigh electron mobility, extremely high quantum efficiency, and robust chemical properties. Herein, an ultralow dark current room‐temperature IR photodetector based on InSb nanosheets (NSs)/MoS2 flakes van der Waals (vdW) heterostructure is presented. Benefiting from a large surface‐to‐volume ratio and phonon scattering suppressed on the nanostructure, InSb NSs devices have high photosensitivity and low dark current density (16.67 A cm−2). To further suppress the dark current, a vdW heterojunction composed of InSb NSs and MoS2 is fabricated. When the InSb NSs/MoS2 vdW heterostructures’ photodetector work on a photovoltaic model (zero‐bias operation), the device shows a dark current density as low as 0.12 A cm−2 at room temperature, exhibiting a high external quantum efficiency (EQE) of 3.6 × 102%, the responsivity of 3.8 A W−1, and detectivity of 1.2 × 109 cm Hz1/2 W−1 under 1310 nm laser illumination. These results demonstrate that InSb NSs vdW heterostructure is a feasible scheme to realize InSb room‐temperature IR detection.

Finite element simulation-based prediction of CMOS-compatible pyroelectric material in MEMS IR detectors

Aluminum nitride (AlN) and zinc oxide (ZnO) have immensely drawn the interest of researchers as lead-free and CMOS-compatible materials for pyroelectric applications to replace the existing hazardous materials, namely lead zirconate titanate (PZT), lithium niobate (LiNbO3), and lithium tantalate (LiTaO3) in infrared (IR) detectors applications. This article uses the finite element method (FEM) to conduct a systemic investigation of a micro-electromechanical system (MEMS)-based pyroelectric IR detector using AlN or ZnO as the sensing material. The IR detector is designed over a 1 μm thin silicon dioxide diaphragm with a trapezoidal-shaped cavity of 300 μm depth in the silicon substrate to lower the detector's thermal mass and to increase the rate of change of temperature (dT/dt). The thickness and area of the pyroelectric layer were varied in the ranges of 0.5 to 5 μm and 0.16 to 3.24 mm2, respectively. The studies indicate that the AlN-based IR detector shows better performance than that of ZnO, with dT/dt ∼ 15.65 K/s, voltage responsivity (Rv) ∼ 62.52 V/W, noise equivalent power (NEP) ∼ 4.41 ×10−8 W/√Hz and specific detectivity (D*) ∼ 9.06 × 105 cm√Hz/W for a 0.16 mm2 area and 5 μm thick sensing layer.

Lead‐free pyroelectric infrared detector based on (Bi1/2Na1/2)TiO3‐BaTiO3 ferroelectric ceramics

AbstractIn this paper, we theoretically and experimentally reported a lead‐free pyroelectric infrared (PIR) detector using (Bi1/2Na1/2TiO3)‐BaTiO3(BNT‐BT) ferroelectric ceramics as the sensitive material. The variation of noise density, voltage response rate (RV), and specific detection rate (D*) with the modulation frequency under the current mode amplification circuit was investigated, and it was found that the lead‐free PIR detector showed high RV in the low frequency band. The RV and D* reached 1.51 × 105 V/W and 2.02 × 108 cmHz1/2W−1 at 10 Hz, respectively. The results were much superior to the PIR based on traditional commercial pyroelectric ceramics, indicating that BNT‐BT lead‐free ceramics have great potential in application to PIR detectors.

HOTCOLD Block: Fooling Thermal Infrared Detectors with a Novel Wearable Design

Adversarial attacks on thermal infrared imaging expose the risk of related applications. Estimating the security of these systems is essential for safely deploying them in the real world. In many cases, realizing the attacks in the physical space requires elaborate special perturbations. These solutions are often impractical and attention-grabbing. To address the need for a physically practical and stealthy adversarial attack, we introduce HotCold Block, a novel physical attack for infrared detectors that hide persons utilizing the wearable Warming Paste and Cooling Paste. By attaching these readily available temperature-controlled materials to the body, HotCold Block evades human eyes efficiently. Moreover, unlike existing methods that build adversarial patches with complex texture and structure features, HotCold Block utilizes an SSP-oriented adversarial optimization algorithm that enables attacks with pure color blocks and explores the influence of size, shape, and position on attack performance. Extensive experimental results in both digital and physical environments demonstrate the performance of our proposed HotCold Block. Code is available: https://github.com/weihui1308/HOTCOLDBlock.

Understanding the growth mechanisms of ultrasmall silver selenide quantum dots for short-wave infrared detectors

Colloidal quantum dots (CQDs) allow for wavelength-tunable, economic, and elegant access to the infrared (IR) spectrum by utilizing inter- and intraband excitonic transitions in narrow bandgap semiconductors. With the emergence of new applications for IR detection, developing competitive non-toxic and environmentally benign alternatives to heavy metal-containing semiconductors is of increasing importance. Over the last decade, silver selenide (Ag2Se) has emerged as an alternative to lead- and mercury-based QDs, especially with large, intraband Ag2Se CQDs showing promising performance in the mid-wave IR. Herein we explored the critical nucleation and growth mechanisms of ultrasmall (2.5–3.5 nm) interband absorbing Ag2Se CQDs operating in the near to short-wave IR. Classical nucleation and growth was observed at most reaction conditions, with a growth temperature of 140 °C and a Ag:Se precursor molar ratio of 1:2 providing the most robust control over the IR absorption spectrum. We proceeded to perform an in-depth study of the impact of surface ligand chemistry of CQD thin-films on resulting optoelectronic properties. By tuning the functional groups and optimizing ligand exchange parameters, we obtained IR responsivity values of ∼25 mA/W in photoconductor devices and ∼1.8 mA/W in photodiode devices in the range 800 – 1250 nm.