Download or read book THz Quantum Cascade Lasers for Standoff Molecule Detection written by and published by . This book was released on 2007 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt: Remote optical detection of molecules, agents, and energetic materials has many applications to national security interests. Currently there is significant interest in determining under what circumstances THz frequency coverage will aid in a complete sensing package. Sources of coherent THz frequency (i.e. 0.1 to 10 THz) electromagnetic radiation with requisite power levels, frequency agility, compactness and reliability represent the single greatest obstacle in establishing a THz technology base, but recent advances in semiconductor-based quantum cascade lasers (QCLs) offer huge improvements towards the ultimate THz source goals. This project advanced the development of narrow-linewidth THz quantum cascade lasers. We developed theoretical tools to guide the improvement of standard THz quantum cascade lasers, the investigation of nonlinear optics employing infrared QCLs, and the exploration of quantum coherence to improve QCL performance. The latter was aimed especially towards achieving high temperature operation. In addition we developed a computer algorithm capable of shifting the frequencies of an existing THz QCL to a different frequency and invented a new type of laser that may enable room temperature THz generation in a electrically driven solid-state source.
Download or read book Spectroscopic Applications of Terahertz Quantum Cascade Lasers written by Tasmim Alam and published by Cuvillier Verlag. This book was released on 2020-10-29 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum cascade lasers (QCLs) are attractive for high-resolution spectroscopy because they can provide high power and a narrow linewidth. They are particularly promising in the terahertz (THz) range since they can be used as local oscillators for heterodyne detection as well as transmitters for direct detection. However, THz QCL-based technologies are still under development and are limited by the lack of frequency tunability as well as the frequency and output power stability for free-running operation. In this dissertation, frequency tuning and linewidth of THz QCLs are studied in detail by using rotational spectroscopic features of molecular species. In molecular spectroscopy, the Doppler eff ect broadens the spectral lines of molecules in the gas phase at thermal equilibrium. Saturated absorption spectroscopy has been performed that allows for sub-Doppler resolution of the spectral features. One possible application is QCL frequency stabilization based on the Lamb dip. Since the tunability of the emission frequency is an essential requirement to use THz QCL for high-resolution spectroscopy, a new method has been developed that relies on near-infrared (NIR) optical excitation of the QCL rear-facet. A wide tuning range has been achieved by using this approach. The scheme is straightforward to implement, and the approach can be readily applied to a large class of THz QCLs. The frequency and output stability of the local oscillator has a direct impact on the performance and consistency of the heterodyne spectroscopy. A technique has been developed for a simultaneous stabilization of the frequency and output power by taking advantage of the frequency and power regulation by NIR excitation. The results presented in this thesis will enable the routine use of THz QCLs for spectroscopic applications in the near future.
Download or read book High Power Mid infrared Quantum Cascade Laser Array for Standoff Photoacoustic Chemical Detection written by Xing Chen and published by . This book was released on 2013 with total page 364 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum cascade lasers (QCLs) are compact, portable, powerful semiconductor laser sources with emission wavelengths from mid-infrared (mid-IR) to terahertz (THz) regions of the electromagnetic spectrum. Mid-IR (i.e. wavelengths from 3 to 20 μm) QCLs are of great importance in a wide range of applications such as trace gas sensing, environmental monitoring, free space communication, medical diagnosis and so on. High power QCLs are particularly important to applications such as infrared counter measure (IRCM) and standoff chemical detections. In such applications, the system performances critically depend on the amount of power a QCL can produce. This dissertation includes two major studies: the first part of the dissertation includes design, fabrication and characterization of high power mid-IR QCL arrays; the second part involves standoff chemical detection using QCLs as laser sources and photoacoustic effect as sensing technologies.
Download or read book Mid Infrared and Terahertz Quantum Cascade Lasers written by Dan Botez and published by Cambridge University Press. This book was released on 2023-09-14 with total page 552 pages. Available in PDF, EPUB and Kindle. Book excerpt: Learn how the rapidly expanding area of mid-infrared and terahertz photonics has been revolutionized in this comprehensive overview. State-of-the-art practical applications are supported by real-life examples and expert guidance. Also featuring fundamental theory enabling you to improve performance of both existing and future devices.
Download or read book Towards Terahertz Dual comb Spectroscopy Based on Quantum Cascade Lasers written by and published by . This book was released on 2015 with total page 99 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, terahertz (THz) laser frequency combs are improved and THz dual-comb spectroscopy method is demonstrated. To achieve better performance of THz quantum cascade laser (QCL) frequency combs, several broadband homogeneous and heterogeneous gain media are characterized, and corresponding dispersion compensators are designed. All THz QCL frequency combs are fabricated in Microsystems Technology Laboratories at MIT using our group's standard process. By utilizing the broad spectral coverage of THz QCL frequency combs and the multiheterodyne detection method, a prototype of the THz dual-comb spectrometer is demonstrated. This thesis work provides an important step towards realizing laser-based broadband THz spectroscopy system for chemical identification and explosive detection.
Download or read book Laser Based Optical Detection of Explosives written by Paul M. Pellegrino and published by CRC Press. This book was released on 2018-09-03 with total page 409 pages. Available in PDF, EPUB and Kindle. Book excerpt: Laser-Based Optical Detection of Explosives offers a comprehensive review of past, present, and emerging laser-based methods for the detection of a variety of explosives. This book: Considers laser propagation safety and explains standard test material preparation for standoff optical-based detection system evaluation Explores explosives detection using deep ultraviolet native fluorescence, Raman spectroscopy, laser-induced breakdown spectroscopy, reflectometry, and hyperspectral imaging Examines photodissociation followed by laser-induced fluorescence, photothermal methods, cavity-enhanced absorption spectrometry, and short-pulse laser-based techniques Describes the detection and recognition of explosives using terahertz-frequency spectroscopic techniques Each chapter is authored by a leading expert on the respective technology, and is structured to supply historical perspective, address current advantages and challenges, and discuss novel research and applications. Readers are left with an in-depth understanding and appreciation of each technology’s capabilities and potential for standoff hazard detection.
Download or read book Quantum Cascade Lasers written by Jérôme Faist and published by Oxford University Press. This book was released on 2013-03-14 with total page 321 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book describes the physics, fabrication technology, and applications of the quantum cascade laser.
Download or read book New Frontiers in THz Quantum Cascade Lasers written by Ali Khalatpour and published by . This book was released on 2020 with total page 113 pages. Available in PDF, EPUB and Kindle. Book excerpt: Terahertz (THz) frequencies (0.5-10 THz) are among the most underdeveloped electromagnetic spectra, even though their application potentials are great in imaging, sensing, and communications. This underdevelopment is primarily due to the lack of compact and powerful THz sources. The invention of THz quantum cascade lasers (QCL) held great promise to bridge the gap between semiconductor electronic and photonic devices. However, the demanding cooling requirements for THz QCL have been a hard brake in the race for achieving compact and portable systems, and they have confined THz QCL systems to a laboratory environment. Therefore, raising the maximum operating temperature to above that of a compact cooler (>/= 235 K for single-stage thermoelectric coolers), has been a paramount long-term goal in the THz field. In this thesis, THz QCLs (at ~~ 4 THz) with a maximum operating temperature T[subscript max]= 250 K has been developed. This operating temperature enabled the construction of coherent THz radiation sources using cheap commercial single-and multi-stage thermoelectric coolers, yet with power levels sufficient for real-time imaging of beam pattern and fast spectral measurements without requiring expensive cryogenically cooled detectors. The combination of TEC-cooled THz QCLs with room-temperature cameras and detectors enables portable systems that are operable outside the laboratory environment. Furthermore, and perhaps more importantly, the demonstrated significant increase in T[subscript max] and the preservation of room-temperature NDR pave a clear path toward further increases in T[subscript max]: designing clean n-level systems based on the direct-phonon scheme with tall barriers.
Download or read book Existing and Potential Standoff Explosives Detection Techniques written by National Research Council and published by National Academies Press. This book was released on 2004-05-14 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: Existing and Potential Standoff Explosives Detection Techniques examines the scientific techniques currently used as the basis for explosives detection and determines whether other techniques might provide promising research avenues with possible pathways to new detection protocols. This report describe the characteristics of explosives, bombs, and their components that are or might be used to provide a signature for exploitation in detection technology; considers scientific techniques for exploiting these characteristics to detect explosives and explosive devices; discusses the potential for integrating such techniques into detection systems that would have sufficient sensitivity without an unacceptable false-positive rate; and proposes areas for research that might be expected to yield significant advances in practical explosives and bomb detection technology in the near, mid, and long term.
Download or read book Photonics for THz Quantum Cascade Lasers written by Maria Ines Amanti and published by . This book was released on 2010 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mid Infrared and Terahertz Quantum Cascade Lasers written by Dan Botez and published by Cambridge University Press. This book was released on 2023-06-30 with total page 551 pages. Available in PDF, EPUB and Kindle. Book excerpt: A state-of-the-art overview of this rapidly expanding field, featuring fundamental theory, practical applications, and real-life examples.
Download or read book Terahertz THz Mid Infrared MIR and Near Infrared NIR Technologies for Protection of Critical Infrastructures Against Explosives and CBRN written by Mauro Fernandes Pereira and published by Springer Nature. This book was released on 2021-04-30 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt: Critical infrastructures are targets for terrorism and deliver a valuable vector through which the proliferation of CBRN and explosive precursors can be detected. Recent technological breakthroughs, notably in the field of near infrared (NIR), mid infrared (MIR), Terahertz (THz) and Gigahertz (GHz) sources and detectors, have led to rugged commercial devices, capable of standoff sensing a range of these dangerous substances. However, at the same time criminal and terrorist organizations have also benefited from the availability of technologies to increase the threat they pose to the security of citizens and a concerted effort is needed to improve early detection measures to identify activities, such as the production of homemade explosives or CBRN that can be potentially dangerous to society. The key global technological bottleneck to be overcome is the current lack of integration and networking of mature detection technology into early warning systems for critical infrastructures. Thus, this book brings together complementary information connecting the research of leading teams working on critical Infrastructure protection with academic developers and industrial producers of state of the art sensors.
Download or read book Terahertz Imaging for Biomedical Applications written by Xiaoxia Yin and published by Springer Science & Business Media. This book was released on 2012-03-23 with total page 321 pages. Available in PDF, EPUB and Kindle. Book excerpt: Terahertz biomedical imaging has become an area of interest due to its ability to simultaneously acquire both image and spectral information. Terahertz imaging systems are being commercialized, with increasing trials performed in a biomedical setting. As a result, advanced digital image processing algorithms are needed to assist screening, diagnosis, and treatment. "Pattern Recognition and Tomographic Reconstruction" presents these necessary algorithms, which will play a critical role in the accurate detection of abnormalities present in biomedical imaging. Terhazertz tomographic imaging and detection technology contributes to the ability to identify opaque objects with clear boundaries, and would be useful to both in vivo and ex vivo environments, making this book a must-read for anyone in the field of biomedical engineering and digital imaging.
Download or read book Quantum Cascade Laser Based Absorption Spectrometer for Trace Gas Molecular Detection and Nonlinear Optics written by Michael Telfer McCulloch and published by . This book was released on 2006 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Frequency Stabilization of a Single Mode Terahertz Quantum Cascade Laser to the Kilohertz Level written by and published by . This book was released on 2009 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: A simple analog locking circuit was shown to stabilize the beat signal between a 2.408 THz quantum cascade laser and a CH2DOH THz CO2 optically pumped molecular laser to 3-4 kHz (FWHM). This is approximately a tenth of the observed long-term (t ~ sec) linewidth of the optically pumped laser showing that the feedback loop corrects for much of the mechanical and acoustic-induced frequency jitter of the gas laser. The achieved stability should be sufficient to enable the use of THz quantum cascade lasers as transmitters in short-range coherent transceivers.
Download or read book Laser Spectroscopy for Sensing written by Matthieu Baudelet and published by Elsevier. This book was released on 2014-02-15 with total page 601 pages. Available in PDF, EPUB and Kindle. Book excerpt: Laser spectroscopy is a valuable tool for sensing and chemical analysis. Developments in lasers, detectors and mathematical analytical tools have led to improvements in the sensitivity and selectivity of spectroscopic techniques and extended their fields of application. Laser Spectroscopy for Sensing examines these advances and how laser spectroscopy can be used in a diverse range of industrial, medical, and environmental applications. Part one reviews basic concepts of atomic and molecular processes and presents the fundamentals of laser technology for controlling the spectral and temporal aspects of laser excitation. In addition, it explains the selectivity, sensitivity, and stability of the measurements, the construction of databases, and the automation of data analysis by machine learning. Part two explores laser spectroscopy techniques, including cavity-based absorption spectroscopy and the use of photo-acoustic spectroscopy to acquire absorption spectra of gases and condensed media. These chapters discuss imaging methods using laser-induced fluorescence and phosphorescence spectroscopies before focusing on light detection and ranging, photothermal spectroscopy and terahertz spectroscopy. Part three covers a variety of applications of these techniques, particularly the detection of chemical, biological, and explosive threats, as well as their use in medicine and forensic science. Finally, the book examines spectroscopic analysis of industrial materials and their applications in nuclear research and industry. The text provides readers with a broad overview of the techniques and applications of laser spectroscopy for sensing. It is of great interest to laser scientists and engineers, as well as professionals using lasers for medical applications, environmental applications, military applications, and material processing. Presents the fundamentals of laser technology for controlling the spectral and temporal aspects of laser excitation Explores laser spectroscopy techniques, including cavity-based absorption spectroscopy and the use of photo-acoustic spectroscopy to acquire absorption spectra of gases and condensed media Considers spectroscopic analysis of industrial materials and their applications in nuclear research and industry
Download or read book THz Quantum Cascade Lasers written by and published by . This book was released on 2012 with total page 35 pages. Available in PDF, EPUB and Kindle. Book excerpt:
