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12 pages, 1153 KiB

Open AccessArticle

Performance of a High-Speed Pyroelectric Receiver as Cryogen-Free Detector for Terahertz Absorption Spectroscopy Measurements

by Jente R. Wubs, Uwe Macherius, Xiang Lü, Lutz Schrottke, Matthias Budden, Johannes Kunsch, Klaus-Dieter Weltmann and Jean-Pierre H. van Helden

Appl. Sci. 2024, 14(10), 3967; https://doi.org/10.3390/app14103967 - 7 May 2024

Cited by 6 | Viewed by 2258

Abstract

The application of terahertz (THz) radiation in scientific research as well as in applied and commercial technology has expanded rapidly in recent years. One example is the progress in high-resolution THz spectroscopy based on quantum cascade lasers, which has enabled new observations in astronomy, atmospheric research, and plasma diagnostics. However, the lack of easy-to-use and miniaturised detectors has hampered the development of compact THz spectroscopy systems out of the laboratory environment. In this paper, we introduce a new high-speed pyroelectric receiver as a cryogen-free detector for THz absorption spectroscopy. Its performance is characterised by absorption spectroscopy measurements on a reference gas cell (RGC) with ammonia using a tunable THz quantum cascade laser at approximately 4.75 THz as the light source. It is shown that the receiver can record spectra up to 281 Hz without any artefacts to the observed spectral absorption profile, and the results reproduce the known pressure of ammonia in the RGC. This demonstrates that the pyroelectric receiver can be reliably used as an alternative to helium-cooled bolometers for absorption spectroscopy measurements in the THz range, with its main advantages being the high bandwidth, compactness, relatively low cost, and room-temperature operation. Its simplicity and high sensitivity make this receiver a key component for compact THz spectroscopy systems. Full article

(This article belongs to the Special Issue Terahertz Technologies and Applications)

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23 pages, 6520 KiB

Open AccessArticle

Exploiting the PIR Sensor Analog Behavior as Thermoreceptor: Movement Direction Classification Based on Spiking Neurons

by Jose-Maria Guerrero-Rodriguez, Maria-Angeles Cifredo-Chacon, Clemente Cobos Sánchez and Fernando Perez-Peña

Sensors 2023, 23(13), 5816; https://doi.org/10.3390/s23135816 - 22 Jun 2023

Cited by 2 | Viewed by 3906

Abstract

Pyroelectric infrared sensors (PIR) are widely used as infrared (IR) detectors due to their basic implementation, low cost, low power, and performance. Combined with a Fresnel lens, they can be used as a binary detector in applications of presence and motion control. Furthermore, due to their features, they can be used in autonomous intelligent devices or included in robotics applications or sensor networks. In this work, two neural processing architectures are presented: (1) an analog processing approach to achieve the behavior of a presynaptic neuron from a PIR sensor. An analog circuit similar to the leaky integrate and fire model is implemented to be able to generate spiking rates proportional to the IR stimuli received at a PIR sensor. (2) An embedded postsynaptic neuron where a spiking neural network matrix together with an algorithm based on digital processing techniques is introduced. This structure allows connecting a set of sensors to the post-synaptic circuit emulating an optic nerve. As a case study, the entire neural processing approach presented in this paper is applied to optical flow detection considering a four-PIR array as input. The results validate both the spiking approach for an analog sensor presented and the ability to retrieve the analog information sent as spike trains in a simulated optic nerve. Full article

(This article belongs to the Section Electronic Sensors)

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9 pages, 1645 KiB

Open AccessArticle

Photoacoustic Energy Sensor for Nanosecond Optical Pulse Measurement

by Pil Gyu Sang, Junseok Heo, Hui Joon Park and Hyoung Won Baac

Sensors 2018, 18(11), 3879; https://doi.org/10.3390/s18113879 - 11 Nov 2018

Cited by 3 | Viewed by 4146

Abstract

We demonstrate a photoacoustic sensor capable of measuring high-energy nanosecond optical pulses in terms of temporal width and energy fluence per pulse. This was achieved by using a hybrid combination of a carbon nanotube-polydimethylsiloxane (CNT-PDMS)-based photoacoustic transmitter (i.e., light-to-sound converter) and a piezoelectric receiver (i.e., sound detector). In this photoacoustic energy sensor (PES), input pulsed optical energy is heavily absorbed by the CNT-PDMS composite film and then efficiently converted into an ultrasonic output. The output ultrasonic pulse is then measured and analyzed to retrieve the input optical characteristics. We quantitatively compared the PES performance with that of a commercial thermal energy meter. Due to the efficient energy transduction and sensing mechanism of the hybrid structure, the minimum-measurable pulsed optical energy was significantly lowered, ~157 nJ/cm², corresponding to 1/760 of the reference pyroelectric detector. Moreover, despite the limited acoustic frequency bandwidth of the piezoelectric receiver, laser pulse widths over a range of 6–130 ns could be measured with a linear relationship to the ultrasound pulse width of 22–153 ns. As CNT has a wide electromagnetic absorption spectrum, the proposed pulsed sensor system can be extensively applied to high-energy pulse measurement over visible through terahertz spectral ranges. Full article

(This article belongs to the Special Issue Ultrasonic Sensors 2018)

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30 pages, 5158 KiB

Open AccessReview

Piezoelectric Polymer and Paper Substrates: A Review

by Kiran Kumar Sappati and Sharmistha Bhadra

Sensors 2018, 18(11), 3605; https://doi.org/10.3390/s18113605 - 24 Oct 2018

Cited by 273 | Viewed by 25878

Abstract

Polymers and papers, which exhibit piezoelectricity, find a wide range of applications in the industry. Ever since the discovery of PVDF, piezo polymers and papers have been widely used for sensor and actuator design. The direct piezoelectric effect has been used for sensor design, whereas the inverse piezoelectric effect has been applied for actuator design. Piezo polymers and papers have the advantages of mechanical flexibility, lower fabrication cost and faster processing over commonly used piezoelectric materials, such as PZT, BaTiO₃. In addition, many polymer and paper materials are considered biocompatible and can be used in bio applications. In the last 20 years, heterostructural materials, such as polymer composites and hybrid paper, have received a lot of attention since they combine the flexibility of polymer or paper, and excellent pyroelectric and piezoelectric properties of ceramics. This paper gives an overview of piezoelectric polymers and papers based on their operating principle. Main categories of piezoelectric polymers and papers are discussed with a focus on their materials and fabrication techniques. Applications of piezoelectric polymers and papers in different areas are also presented. Full article

(This article belongs to the Section Physical Sensors)

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