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Mid-Infrared Sensors and Applications

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A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Optical Sensors".

Deadline for manuscript submissions: closed (25 March 2023) | Viewed by 26591

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Special Issue Editors

Prof. Dr. Kenneth Schepler

E-Mail Website
Guest Editor

University of Central Florida, Orlando, FL, USA
Interests: lasers; mid-infrared fibers; nonlinear optics; infrared sensors and systems; fiber optic sensing

Prof. Dr. Ajoy Kar

*
E-Mail Website
Co-Guest Editor

Institute of Photonics and Quantum Sciences, Heriot Watt University, Riccarton Campus, Edinburgh EH14 4AS, UK
Interests: nonlinear optics; Lasers; amplifiers for telecommunications; ultrafast all-optical switching in novel optical fibres; ultrafast optical nonlinearities in semiconductors; ultrafast laser inscription (ULI) of photonic devices that should result in novel optoelectronic devices and generation of white light continuum from visible to mid-infrared part of the spectrum; novel microfluidic devices for biophotonics applications
* The founder of Optoscribe, who are pioneering 3D photonic integrated circuits.

Special Issue Information

Dear Colleagues,

The mid-infrared (1.5–12 µm) spectral region is of interest for a wide variety of applications, such as environmental sensing, medical diagnostics, industry, agriculture, military defense, and basic spectroscopy. A key component of all of these applications is the sensor. With such a wide variety of applications, mid-infrared sensor requirements also vary considerably, but improvements in sensitivity, spectral coverage, and response time are often needed. At the same time, low cost, reliability, small size, and low power are needed for practical reasons.

The main goal of this Special Issue is to capture the current state-of-the-art and contemporary progress and perspectives of mid-infrared sensor technology. Basic research papers, novel application demonstrations, and review articles will be considered.

Prof. Dr. Kenneth Schepler
Prof. Dr. Ajoy Kar
Guest Editors

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Keywords

mid-infrared sensor
quantum cascade photodetectors
resonantly enhanced detectors
on-chip mid-infrared sensors
avalanche photodiode
mid-infrared sensor arrays/cameras
mid-infrared sensor materials
sensing systems

Published Papers (12 papers)

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Research

12 pages, 10544 KiB

Open AccessArticle

Design of MIR Dispersive Spectrograph System with Uncooled Microbolometer

by Pattarapong Sunongbua, Suwan Aekram and Weerasak Lertsiriyothin

Sensors 2023, 23(4), 2205; https://doi.org/10.3390/s23042205 - 15 Feb 2023

Viewed by 1390

Abstract

To make the mid-infrared (MIR) dispersive spectrograph a practical tool in industrial food processing lines, we designed a dispersive spectrograph system with an uncooled microbolometer focal plane array (FPA) detector for MIR spectral acquisition. To precisely regulate the angle of a rotatable grating to acquire the MIR spectrum, the spectral resolution and spatial resolution of the system were rigorously controlled to improve system performance. In the reflectance operation mode of the MIR dispersive spectrograph, the uncooled microbolometer FPA detector offered a maximum spectral resolution of 12 nm for the MIR, when a 300 grooves/mm blazed grating was used. Utilizing an optical parametric oscillator (OPO) pulse laser source, the wavelengths of the first-order diffraction were validated, and the system’s spectral resolution limit was determined. As a line-scanning source, a Globar broadband source was installed, and the USAF 1951 Resolution Calculator was used to establish the spatial resolution of the imaging spectrograph. Using NI LabView, the logical operational technique for controlling the MIR dispersive spectrograph was encoded into system firmware. The GUI and test results are thoroughly described. Full article

(This article belongs to the Special Issue Mid-Infrared Sensors and Applications)

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14 pages, 4985 KiB

Open AccessArticle

Design of Airborne Large Aperture Infrared Optical System Based on Monocentric Lens

by Jiyan Zhang, Teng Qin, Zhexin Xie, Liting Sun, Zhengyu Lin, Tianhao Cao and Chentao Zhang

Sensors 2022, 22(24), 9907; https://doi.org/10.3390/s22249907 - 16 Dec 2022

Cited by 4 | Viewed by 1990

Abstract

Conventional reconnaissance camera systems have been flown on manned aircraft, where the weight, size, and power requirements are not stringent. However, today, these parameters are important for unmanned aerial vehicles (UAVs). This article provides a solution to the design of airborne large aperture infrared optical systems, based on a monocentric lens that can meet the strict criteria of aerial reconnaissance UAVs for a wide field of view (FOV) and lightness of airborne electro-optical pod cameras. A monocentric lens has a curved image plane, consisting of an array of microsensors, which can provide an image with 368 megapixels over a 100° FOV. We obtained the initial structure of a five-glass (5GS) asymmetric monocentric lens with an air gap, using ray-tracing and global optimization algorithms. According to the design results, the ground sampling distance (GSD) of the system is 0.33 m at 3000 m altitude. The full-field modulation transfer function (MTF) value of the system is more than 0.4 at a Nyquist frequency of 70 lp/mm. We present a primary thermal control method, and the image quality was steady throughout the operating temperature range. This compactness and simple structure fulfill the needs of uncrewed airborne lenses. This work may facilitate the practical application of monocentric lens in UAVs. Full article

(This article belongs to the Special Issue Mid-Infrared Sensors and Applications)

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16 pages, 7157 KiB

Open AccessArticle

A High-Precision Mid-Infrared Spectrometer for Ambient HNO₃ Measurements

by Nicolas Sobanski, Béla Tuzson, Philipp Scheidegger, Herbert Looser, Christoph Hüglin and Lukas Emmenegger

Sensors 2022, 22(23), 9158; https://doi.org/10.3390/s22239158 - 25 Nov 2022

Cited by 3 | Viewed by 1370

Abstract

Precise and accurate measurements of ambient HNO₃ are crucial for understanding various atmospheric processes, but its ultra-low trace amounts and the high polarity of HNO₃ have strongly hindered routine, widespread, direct measurements of HNO₃ and restricted field studies to mostly short-term, localized measurement campaigns. Here, we present a custom field-deployable direct absorption laser spectrometer and demonstrate its analytical capabilities for in situ atmospheric HNO₃ measurements. Detailed laboratory characterizations with a particular focus on the instrument response under representative conditions for tropospheric measurements, i.e., the humidity, spectral interference, changing HNO₃ amount fractions, and air-sampling-related artifacts, revealed the key aspects of our method: (i) a good linear response (

R^{2}

> 0.98) between 0 and 25 nmol

\cdot

mol

^{- 1}

in both dry and humid conditions with a limit of detection of 95 pmol

\cdot

mol

^{- 1}

; (ii) a discrepancy of 20% between the spectroscopically derived amount fractions and indirect measurements using liquid trapping and ion chromatography; (iii) a systematic spectral bias due to water vapor. The spectrometer was deployed in a three-week field measurement campaign to continuously monitor the HNO₃ amount fraction in ambient air. The measured values varied between 0.1 ppb and 0.8 ppb and correlated well with the daily total nitrates measured using a filter trapping method. Full article

(This article belongs to the Special Issue Mid-Infrared Sensors and Applications)

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20 pages, 3857 KiB

Open AccessArticle

Design and Optimization of GeSn Waveguide Photodetectors for 2-µm Band Silicon Photonics

by Soumava Ghosh, Radhika Bansal, Greg Sun, Richard A. Soref, Hung-Hsiang Cheng and Guo-En Chang

Sensors 2022, 22(11), 3978; https://doi.org/10.3390/s22113978 - 24 May 2022

Cited by 8 | Viewed by 2157

Abstract

Silicon photonics is emerging as a competitive platform for electronic–photonic integrated circuits (EPICs) in the 2 µm wavelength band where GeSn photodetectors (PDs) have proven to be efficient PDs. In this paper, we present a comprehensive theoretical study of GeSn vertical p–i–n homojunction waveguide photodetectors (WGPDs) that have a strain-free and defect-free GeSn active layer for 2 µm Si-based EPICs. The use of a narrow-gap GeSn alloy as the active layer can fully cover entire the 2 µm wavelength band. The waveguide structure allows for decoupling the photon-absorbing path and the carrier collection path, thereby allowing for the simultaneous achievement of high-responsivity and high-bandwidth (BW) operation at the 2 µm wavelength band. We present the theoretical models to calculate the carrier saturation velocities, optical absorption coefficient, responsivity, 3-dB bandwidth, zero-bias resistance, and detectivity, and optimize this device structure to achieve highest performance at the 2 µm wavelength band. The results indicate that the performance of the GeSn WGPD has a strong dependence on the Sn composition and geometric parameters. The optimally designed GeSn WGPD with a 10% Sn concentration can give responsivity of 1.55 A/W, detectivity of 6.12 × 10¹⁰ cmHz^½W⁻¹ at 2 µm wavelength, and ~97 GHz BW. Therefore, this optimally designed GeSn WGPD is a potential candidate for silicon photonic EPICs offering high-speed optical communications. Full article

(This article belongs to the Special Issue Mid-Infrared Sensors and Applications)

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11 pages, 2501 KiB

Open AccessArticle

Design of a Slab Tamm Plasmon Resonator Coupled to a Multistrip Array Waveguide for the Mid Infrared

by Gerald Pühringer, Cristina Consani, Reyhaneh Jannesari, Clement Fleury, Florian Dubois, Jasmin Spettel, Thang Duy Dao, Gerald Stocker, Thomas Grille and Bernhard Jakoby

Sensors 2022, 22(8), 2968; https://doi.org/10.3390/s22082968 - 13 Apr 2022

Cited by 4 | Viewed by 1607

Abstract

In this work, we present and analyze a design of an absorber–waveguide system combining a highly sensitive waveguide array concept with a resonant selective absorber. The waveguide part is composed of an array of coupled strip waveguides and is therefore called a coupled strip array (CSA). The CSA is then coupled to the end of a slab Tamm plasmon (STP-) resonator, which is composed of a quasicrystal-like reflector formed by the patterning of a silicon slab and an interfacing tungsten slab. The concept describes an emitter–waveguide or waveguide–detector system featuring selective plasmon-enhanced resonant absorption or emission. These are crucial properties for corresponding optical on-chip integrated devices in context with evanescent field absorption sensing in fluids or gases, for example. Thus, the concept comprises a valuable and more cost-effective alternative to quantum cascade lasers. We designed the lateral dimensions of the STP resonator via a simple quasi-crystal approach and achieved strong narrowband resonances (emittance and Q-factors up to 85% and 88, respectively) for different silicon thicknesses and substrate materials (air and silicon oxide). Moreover, we analyze and discuss the sensitivity of the complete emitter–waveguide system in dependence on the slab thickness. This reveals the crucial correlation between the expected sensitivity assigned to the absorber–waveguide system and field confinement within the silicon. Full article

(This article belongs to the Special Issue Mid-Infrared Sensors and Applications)

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15 pages, 6013 KiB

Open AccessArticle

New Results on Small and Dim Infrared Target Detection

by Hao Wang, Zehao Zhao, Chiman Kwan, Geqiang Zhou and Yaohong Chen

Sensors 2021, 21(22), 7746; https://doi.org/10.3390/s21227746 - 21 Nov 2021

Cited by 3 | Viewed by 1935

Abstract

Real-time small infrared (IR) target detection is critical to the performance of the situational awareness system in high-altitude aircraft. However, current IR target detection systems are generally hardware-unfriendly and have difficulty in achieving a robust performance in datasets with clouds occupying a large proportion of the image background. In this paper, we present new results by using an efficient method that extracts the candidate targets in the pre-processing stage and fuses the local scale, blob-based contrast map and gradient map in the detection stage. We also developed mid-wave infrared (MWIR) and long-wave infrared (LWIR) cameras for data collection experiments and algorithm evaluations. Experimental results using both publicly available datasets and image sequences acquired by our cameras clearly demonstrated that the proposed method achieves high detection accuracy with the mean AUC being at least 22.3% higher than comparable methods, and the computational cost beating the other methods by a large margin. Full article

(This article belongs to the Special Issue Mid-Infrared Sensors and Applications)

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11 pages, 2954 KiB

Open AccessArticle

Optical Wireless Link Operated at the Wavelength of 4.0 µm with Commercially Available Interband Cascade Laser

by Janusz Mikołajczyk, Robert Weih and Marcin Motyka

Sensors 2021, 21(12), 4102; https://doi.org/10.3390/s21124102 - 15 Jun 2021

Cited by 6 | Viewed by 2166

Abstract

This paper evaluates the key factors influencing the design of optical wireless communication (OWC) systems operating in the mid-infrared range. The performed analysis has shown that working in this spectral “window”, compared to other wavelengths, is more effective in reducing the attenuation of radiation. The main goal was to verify the capabilities of the “on-shelf” interband cascade (IC) laser in the context of OWC system construction, considering its output power, modulation rate, room temperature operation, and integrated structure. For this purpose, a lab model of a data link with IC laser has been developed. Based on its main parameters, the estimation of signal-to-noise power ratio versus data link range was made. That range was about 2 km for a case of low scintillation and relatively low visibility. In the experimental part of the work, the obtained modulation rate was 70 MHz for NRZ (non-return-to-zero) format coding. It is an outstanding result taking into consideration IC laser operated at room temperature. Full article

(This article belongs to the Special Issue Mid-Infrared Sensors and Applications)

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13 pages, 21500 KiB

Open AccessCommunication

Data Link with a High-Power Pulsed Quantum Cascade Laser Operating at the Wavelength of 4.5 µm

by Janusz Mikołajczyk

Sensors 2021, 21(9), 3231; https://doi.org/10.3390/s21093231 - 07 May 2021

Cited by 5 | Viewed by 2073

Abstract

This article is a short study of the application of high-power quantum cascade lasers and photodetectors in medium-infrared optical wireless communications (OWC). The link range is mainly determined by the transmitted beam parameters and the performance of the light sensor. The light power and the photodetector noise directly determine the signal-to-noise power ratio. This ratio could be maximized in the case of minimizing the radiation losses caused by atmospheric attenuation. It can be obtained by applying both radiation sources and sensors operated in the medium infrared range decreasing the effects of absorption, scattering or scintillation, beam spreading, and beam wandering. The development of a new class of laser sources based on quantum cascade structures becomes a prospective alternative. Regarding the literature, there are descriptions of some preliminary research applying these lasers in data transmission. To provide a high data transfer rate, continuous wave (cw) lasers are commonly used. However, they are characterized by low power (a few tens of mWatts) limiting their link range. Also, only a few high-power pulsed lasers (a few hundreds of mWatts) were tested. Due to their limited pulse duty cycle, the obtained modulation bandwidth was lower than 1 MHz. The main goal of this study is to experimentally determine the capabilities of the currently developed state-of-the-art high-power pulsed quantum cascade (QC) lasers and photodetectors in OWC systems. Finally, the data link range using optical pulses of a QC laser of ~2 W, operated at the wavelength of ~4.5 µm, is discussed. Full article

(This article belongs to the Special Issue Mid-Infrared Sensors and Applications)

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15 pages, 6961 KiB

Open AccessCommunication

Designing Mid-Infrared Gold-Based Plasmonic Slot Waveguides for CO₂-Sensing Applications

by Parviz Saeidi, Bernhard Jakoby, Gerald Pühringer, Andreas Tortschanoff, Gerald Stocker, Florian Dubois, Jasmin Spettel, Thomas Grille and Reyhaneh Jannesari

Sensors 2021, 21(8), 2669; https://doi.org/10.3390/s21082669 - 10 Apr 2021

Cited by 9 | Viewed by 2350

Abstract

Plasmonic slot waveguides have attracted much attention due to the possibility of high light confinement, although they suffer from relatively high propagation loss originating from the presence of a metal. Although the tightly confined light in a small gap leads to a high confinement factor, which is crucial for sensing applications, the use of plasmonic guiding at the same time results in a low propagation length. Therefore, the consideration of a trade-off between the confinement factor and the propagation length is essential to optimize the waveguide geometries. Using silicon nitride as a platform as one of the most common material systems, we have investigated free-standing and asymmetric gold-based plasmonic slot waveguides designed for sensing applications. A new figure of merit (FOM) is introduced to optimize the waveguide geometries for a wavelength of 4.26 µm corresponding to the absorption peak of CO₂, aiming at the enhancement of the confinement factor and propagation length simultaneously. For the free-standing structure, the achieved FOM is 274.6 corresponding to approximately 42% and 868 µm for confinement factor and propagation length, respectively. The FOM for the asymmetric structure shows a value of 70.1 which corresponds to 36% and 264 µm for confinement factor and propagation length, respectively. Full article

(This article belongs to the Special Issue Mid-Infrared Sensors and Applications)

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12 pages, 4510 KiB

Open AccessCommunication

Reflectometers for Absolute and Relative Reflectance Measurements in the Mid-IR Region at Vacuum

by Jinhwa Gene, Min Yong Jeon and Sun Do Lim

Sensors 2021, 21(4), 1169; https://doi.org/10.3390/s21041169 - 07 Feb 2021

Cited by 4 | Viewed by 2408

Abstract

We demonstrated spectral reflectometers for two types of reflectances, absolute and relative, of diffusely reflecting surfaces in directional-hemispherical geometry. Both are built based on the integrating sphere method with a Fourier-transform infrared spectrometer operating in a vacuum. The third Taylor method is dedicated to the reflectometer for absolute reflectance, by which absolute spectral diffuse reflectance scales of homemade reference plates are realized. With the reflectometer for relative reflectance, we achieved spectral diffuse reflectance scales of various samples including concrete, polystyrene, and salt plates by comparing against the reference standards. We conducted ray-tracing simulations to quantify systematic uncertainties and evaluated the overall standard uncertainty to be 2.18% (k = 1) and 2.99% (k = 1) for the absolute and relative reflectance measurements, respectively. Full article

(This article belongs to the Special Issue Mid-Infrared Sensors and Applications)

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19 pages, 5362 KiB

Open AccessArticle

Interband Cascade Photonic Integrated Circuits on Native III-V Chip

by Jerry R. Meyer, Chul Soo Kim, Mijin Kim, Chadwick L. Canedy, Charles D. Merritt, William W. Bewley and Igor Vurgaftman

Sensors 2021, 21(2), 599; https://doi.org/10.3390/s21020599 - 16 Jan 2021

Cited by 13 | Viewed by 2682

Abstract

We describe how a midwave infrared photonic integrated circuit (PIC) that combines lasers, detectors, passive waveguides, and other optical elements may be constructed on the native GaSb substrate of an interband cascade laser (ICL) structure. The active and passive building blocks may be used, for example, to fabricate an on-chip chemical detection system with a passive sensing waveguide that evanescently couples to an ambient sample gas. A variety of highly compact architectures are described, some of which incorporate both the sensing waveguide and detector into a laser cavity defined by two high-reflectivity cleaved facets. We also describe an edge-emitting laser configuration that optimizes stability by minimizing parasitic feedback from external optical elements, and which can potentially operate with lower drive power than any mid-IR laser now available. While ICL-based PICs processed on GaSb serve to illustrate the various configurations, many of the proposed concepts apply equally to quantum-cascade-laser (QCL)-based PICs processed on InP, and PICs that integrate III-V lasers and detectors on silicon. With mature processing, it should become possible to mass-produce hundreds of individual PICs on the same chip which, when singulated, will realize chemical sensing by an extremely compact and inexpensive package. Full article

(This article belongs to the Special Issue Mid-Infrared Sensors and Applications)

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14 pages, 3867 KiB

Open AccessArticle

Impact of Different Metals on the Performance of Slab Tamm Plasmon Resonators

by Gerald Pühringer, Cristina Consani and Bernhard Jakoby

Sensors 2020, 20(23), 6804; https://doi.org/10.3390/s20236804 - 28 Nov 2020

Cited by 4 | Viewed by 1757

Abstract

We investigate the concept of slab Tamm plasmons (STP) in regard to their properties as resonant absorber or emitter structures in the mid-infrared spectral region. In particular, we compare the selective absorption characteristics resulting from different choices of absorbing material, namely Ag, W, Mo or highly doped Si. We devised a simplified optimization procedure using finite element simulations for the calculation of the absorption together with the application of micro-genetic algorithm (GA) optimization. As characteristic for plasmonic structures, the specific choice of the metallic absorber material strongly determines the achievable quality factor (Q). We show that STP absorbers are able to mitigate the degradation of Q for less reflective metals or even non-metals such as doped silicon as plasmonic absorber material. Moreover, our results strongly indicate that the maximum achievable plasmon-enhanced absorption does not depend on the choice of the plasmonic material presuming an optimized configuration is obtained via the GA process. As a result, absorptances in the order of 50–80% could be achieved for any absorber material depending on the slab thickness (up to 1.1 µm) and a target resonance wavelength of 4.26 µm (CO₂ absorption line). The proposed structures are compatible with modern semiconductor mass fabrication processes. At the same time, the optimization procedure allows us to choose the best plasmonic material for the corresponding application of the STP structure. Therefore, we believe that our results represent crucial advances towards corresponding integrated resonant absorber and thermal emitter components. Full article

(This article belongs to the Special Issue Mid-Infrared Sensors and Applications)

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