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Author : Nor Kamilah Binti Saat
Publisher :
ISBN 13 :
Total Pages : 308 pages
Book Rating : 4.:/5 (89 download)
Download or read book Imaging Using an Electrically Tunable Terahertz Quantum Cascade Laser written by Nor Kamilah Binti Saat and published by . This book was released on 2011 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Nor Kamilah Binti Saat
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (857 download)
Download or read book Imaging Using an Electronically Tunable Terahertz Quantum Cascade Laser written by Nor Kamilah Binti Saat and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis studies THz frequency imaging using different electrically tunable THz QCLs as the source. The THz QCL is based on a three-well resonant phonon active region design and uses a single metal waveguide. Using a heterogeneous cascade scheme, obtained by changing the growth rate of Ga during epitaxial process, the thickness of the GaAs is reduced progressively by 10% throughout the active region. As a result, the emission frequency can be varied from 3.05 to 3.35 THz by switching the bias of the QCL. Two types of imaging system are demonstrated. First, dual frequency imaging is demonstrated by electrically tuning the QCL bias, and a transmission image of the high explosive PETN and other polycrystalline samples (i.e. lactose monohydrate, glucose monohydrate, and sucrose) at frequencies of 3.05 THz and 3.24 THz are obtained in a single raster scan of a sample. By taking the difference of the natural logarithms of the transmission, coefficients obtained at each frequency, difference- attenuation-coefficient images for the samples can be obtained. The difference- intensity imaging may also be found directly by combining amplitude modulation of the QCL bias, and hence output frequency, with lock-in detection. Owing to their unique molecular-specific absorption spectra, the samples measured could be readily distinguished using this methodology. Second, multi-frequency imaging is demonstrated by electrically tuning a heterogeneous active region QCL at five different biases, producing five different output frequencies. Using a scanning resolution target, the imaging system has been shown to be independent of the radiation wavelength, which has been explained through measurement of the far-field emission profile of the QCL. Using the imaging system, the attenuation coefficients of polycrystalline samples have been determined at five frequencies and these results compared with those obtained using THz frequency time-domain spectroscopy and Fourier transform spectroscopy.
Author : Ningren Han
Publisher :
ISBN 13 :
Total Pages : 118 pages
Book Rating : 4.:/5 (868 download)
Download or read book Electrically Tunable Terahertz Quantum Cascade Lasers written by Ningren Han and published by . This book was released on 2013 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, microelectromechanical systems (MEMS) assisted electrically tunable terahertz quantum cascade lasers (THz QCLs) are designed and demonstrated. Two MEMS tuner devices are proposed to achieve electrically tunable THz QCLs. One is the electrostatic comb drive actuated tuner design and the other one is a two-stage flexure design that is actuated by an external piezo nano-positioning actuator. The MEMS tuner devices are all fabricated using standard foundry process SOIMUMPs from MEMSCAP Inc. with some additional in-house post-processings. First order distributed-feedback (DFB) THz wire QCLs with robust mode selectors are designed and fabricated at the MIT Microsystems Technology Laboratories (MTL) using processes developed at our group. By integrating the MEMS tuner chips with the THz QCL chips, broadband electrically tunable THz QCLs are successfully demonstrated. This thesis work provides an important step towards realizing turn-key tunable THz coherent sources for a variety of applications such as THz spectroscopy and THz coherent tomography.
Author : Dan Botez
Publisher : Cambridge University Press
ISBN 13 : 1108570607
Total Pages : 552 pages
Book Rating : 4.1/5 (85 download)
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.
Author : Qi Qin (Ph. D.)
Publisher :
ISBN 13 :
Total Pages : 188 pages
Book Rating : 4.:/5 (832 download)
Download or read book Development of Tunable Terahertz Quantum Cascade Wire Lasers written by Qi Qin (Ph. D.) and published by . This book was released on 2012 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: For a long time, terahertz (THz) radiation has been of great interest to scientific community because of its spectroscopic and imaging applications based on its unique properties, such as the capabilities to penetrate many materials which are opaque in other frequency range (e.g. packaging, plastics, paints and semiconductors), and spectroscopic signatures of many important materials. In this thesis, a continuously tunable THz wire QC laser, which comprises a QC laser with deep sub-wavelength transverse dimensions, and a movable side object, termed as "plunger", is demonstrated. This deep sub-wavelength cross-section results in a large fraction of mode propagating outside of the laser core (GaAs/A10.15Ga0.85As material system). The frequency tuning is achieved by changing the transverse wave vector, using a plunger made by metal (metal plunger) or silicon (dielectric plunger). When nudged close to the wire laser core, the metal plunger can push modes to the opposite side of the waveguide. Confined by a metal-metal waveguide, the mode is squeezed and the transverse wave vector is increased, resulting in a blue-shifted frequency. In contrast, a silicon plunger can suck the mode out due to its similar refractive index to GaAs/Al0.15Ga0.85As material system of laser core. Thus a decreased transverse wave vector results in a redshifted frequency. Although a tuning record of 138GHz (3.6%) was achieved, a discontinuous tuning resulted from a jittering movement of the plungers due to its friction with the guiding system. To solve this problem, an improved plunger based on micro-mechanical system (MEMS) was implemented. This MEMS plunger uses a two-stage folded-beam flexure to isolate the misaligned external actuation. The plunger is attached with the flexure which suspends above a silicon substrate to eliminate friction. Eventually, this MEMS flexure was actuated by a mechanical system which comprised a lever to de-amplify the displacement of a linear mechanical feedthrough. This MEMS plunger enabled a restorable and frictionless movement which led to a continuous tuning range of 330GHz (8.6%) centered at ~3.85 THz. The challenges posted by the weak mode discrimination led to the development of comb-shape connectors which electrically connect the top metal of wire lasers and the side bonding pad. This design can significantly increase the mode discrimination by selectively guiding undesired mode into the lossy bonding pad. This robust design of single mode operation enables the initial lasing at a frequency far below the gain peak, which can potentially increase the tuning range significantly.
Author : Iman Kundu
Publisher :
ISBN 13 :
Total Pages : 192 pages
Book Rating : 4.:/5 (94 download)
Download or read book Frequency Tunable Terahertz Quantum Cascade Lasers written by Iman Kundu and published by . This book was released on 2014 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Tasmim Alam
Publisher : Cuvillier Verlag
ISBN 13 : 3736962975
Total Pages : 132 pages
Book Rating : 4.7/5 (369 download)
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.
Author : Alan Wei Min Lee
Publisher :
ISBN 13 :
Total Pages : 115 pages
Book Rating : 4.:/5 (631 download)
Download or read book Terahertz Imaging and Quantum Cascade Laser Based Devices written by Alan Wei Min Lee and published by . This book was released on 2010 with total page 115 pages. Available in PDF, EPUB and Kindle. Book excerpt: (cont.) The challenges posed by the long THz wavelengths in QCL waveguide design leads to a tradeoff between high temperature operation (
Author : Christopher Curwen
Publisher :
ISBN 13 :
Total Pages : 96 pages
Book Rating : 4.:/5 (97 download)
Download or read book Theory and Design of Tunable Terahertz Metamaterials for Application to Tunable Terahertz Quantum Cascade Lasers written by Christopher Curwen and published by . This book was released on 2014 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: Terahertz quantum cascade lasers are compact, coherent sources of THz power that have drawn considerable attention in the past 10-15 years for their potential use in THz applications such as spectroscopy and imaging. One of the key developments required to further the usefulness of THz QCLs is robust, broadband tenability. In this work, I describe a new technique for tuning THz QCLs by incorporation MEMS fixed-fixed and fixed-free cantilever beams into a THz transmission line metamaterial resonant cavity. An analytic model for such THz transmission line metamaterials is demonstrated using transmission line theory and is supported by 2-D and 3-D finite element simulations. Proposed processes for fabricating tunable THz transmission line metamaterials are outlined and current progress on actual fabrication and device testing is reported.
Author : A. K. Haghi
Publisher : CRC Press
ISBN 13 : 1351659847
Total Pages : 376 pages
Book Rating : 4.3/5 (516 download)
Download or read book Methodologies and Applications for Analytical and Physical Chemistry written by A. K. Haghi and published by CRC Press. This book was released on 2018-07-17 with total page 376 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume presents an up-to-date review of modern materials and concepts, issues, and recent advances in analytical and physical chemistry. Distinguished scientists and engineers from key institutions worldwide have contributed chapters that provide a deep analysis of their particular subjects. The chapters discuss the composition and properties of complex materials as well as mixtures, processes, and the need for new and improved analytical technology.
Author : Shuo Tang
Publisher : CRC Press
ISBN 13 : 1498714765
Total Pages : 304 pages
Book Rating : 4.4/5 (987 download)
Download or read book Advances in Imaging and Sensing written by Shuo Tang and published by CRC Press. This book was released on 2016-10-26 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: Includes chapters with up-to-date information from experts in the field. An introductory and in-depth reference book for electronic imaging and sensing research and teaching. Strong practical and application focused chapters. Latest topics such as Nanophotonic Phased Array, Thin-Film Sensors, Label Free DNA Sensor, In Vivo Flow Cytometry etc. are included.
Author : Yifan Jiang (Ph. D. in electrical and computer engineering)
Publisher :
ISBN 13 :
Total Pages : 204 pages
Book Rating : 4.:/5 (111 download)
Download or read book Broadly Tunable Terahertz Difference Frequency Generation in Mid-infrared Quantum Cascade Lasers written by Yifan Jiang (Ph. D. in electrical and computer engineering) and published by . This book was released on 2017 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt: Room-temperature terahertz (THz) sources analogous to diode lasers in the near-infrared/visible or quantum cascade lasers (QCL) in the mid-infrared (mid-IR), i.e., electrically pumped, compact, widely tunable, and suitable for low-cost production, are highly desired for feasible and inexpensive THz systems. This dissertation focuses on demonstrating broadly tunable, room-temperature THz systems based on intra-cavity difference frequency generation (DFG) in mid-IR QCLs with improved spectral capability for versatile applications. Spectral control using an external cavity provides the widest tuning range and is favored for real-world applications. DFG-THz could be spectrally tuned by either tuning one mid-IR pump or by tuning both mid-IR pumps together. I built a Littrow-type, external cavity THz DFG-QCL system that generated spectral tunable THz radiation by fixing one mid-IR pump frequency with an integrated DFB grating on top of the QCL structure and tuning the other mid-IR pump frequency with an external grating, thus demonstrating record broadband narrow linewidth THz frequency tuning from 1.2 to 5.9 THz. A Cherenkov waveguide is used in this system to extract THz radiation through the semi-insulating InP substrate; however, InP has dispersion in 1–6 THz, resulting in steering far field profiles for different THz frequencies. Replacing the InP substrate with high-resistance silicon through an adhesive bonding process solved the beam steering problem of this THz DFG-QCL system. I also built a double-Littrow, external cavity DFG-THz system that tunes both mid-IR pump frequencies using two external diffraction gratings. Such a system allows performing a comprehensive spectroscopic study of the optical nonlinearity and its dependence on the mid-infrared pump frequencies. Our work shows that the terahertz generation efficiency can vary by a factor of two or more, depending on the spectral position of the mid-infrared pumps, even for a fixed THz difference frequency. Using this system, we investigated different active region designs: bound-to-continuum, continuum-to-continuum, three-phonon-resonance, and dual-upper-state active region design. Our studies show THz DFG-QCL based a bound-to-continuum active region with gain centered around 15 μm has an order of magnitude enhancement of mid-IR to THz conversion efficiency, which provides a trend for future improvement of the power performance of THz DFG-QCLs
Author : John M. Chalmers
Publisher : John Wiley & Sons
ISBN 13 : 1119962986
Total Pages : 692 pages
Book Rating : 4.1/5 (199 download)
Download or read book Infrared and Raman Spectroscopy in Forensic Science written by John M. Chalmers and published by John Wiley & Sons. This book was released on 2012-01-03 with total page 692 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book will provide a survey of the major areas in which information derived from vibrational spectroscopy investigations and studies have contributed to the benefit of forensic science, either in a complementary or a unique way. This is highlighted by examples taken from real case studies and analyses of forensic relevance, which provide a focus for current and future applications and developments.
Author : Ioannis Nellas
Publisher :
ISBN 13 :
Total Pages : 33 pages
Book Rating : 4.:/5 (697 download)
Download or read book Terahertz Imaging Via a Microbolometer Camera Under Illumination of a Quantum Cascade Laser written by Ioannis Nellas and published by . This book was released on 2010 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt: The terahertz (THz) region of the electromagnetic spectrum has not been fully utilized due to the lack of compact and efficient sources as well as detectors. This thesis aimed on characterizing a quantum cascade laser (QCL) beam and achieving high quality real-time THz imaging using a 160x120 pixel FLIR A20M microbolometer camera designed to operate in long wave infrared range. The FTIR spectroscopy of the QCL beam revealed that lasing could be achieved at 2.85 and 2.91 THz frequencies depending on the bias current. This behavior was analyzed using the longitudinal modes of the laser and found to correspond well with the experimental observations. Real-time imaging of concealed objects in transmission mode was accomplished using the silicon nitride-based microbolometer camera under illumination via the QCL with average power less than 1 mW. The larger extent of the object required the expansion of the narrow laser beam using a parabolic reflector and refocus on the camera using a second parabolic reflector. The standard Ge lens of the camera was replaced by a Tsurupica lens since the earlier lens was opaque to THz radiation. The real-time imaging can be extended to reflection mode as well as longer standoff distances using higher power THz lasers.
Author : Larry A. Coldren
Publisher : John Wiley & Sons
ISBN 13 : 1118148185
Total Pages : 752 pages
Book Rating : 4.1/5 (181 download)
Download or read book Diode Lasers and Photonic Integrated Circuits written by Larry A. Coldren and published by John Wiley & Sons. This book was released on 2012-03-02 with total page 752 pages. Available in PDF, EPUB and Kindle. Book excerpt: Diode Lasers and Photonic Integrated Circuits, Second Edition provides a comprehensive treatment of optical communication technology, its principles and theory, treating students as well as experienced engineers to an in-depth exploration of this field. Diode lasers are still of significant importance in the areas of optical communication, storage, and sensing. Using the the same well received theoretical foundations of the first edition, the Second Edition now introduces timely updates in the technology and in focus of the book. After 15 years of development in the field, this book will offer brand new and updated material on GaN-based and quantum-dot lasers, photonic IC technology, detectors, modulators and SOAs, DVDs and storage, eye diagrams and BER concepts, and DFB lasers. Appendices will also be expanded to include quantum-dot issues and more on the relation between spontaneous emission and gain.
Author :
Publisher :
ISBN 13 :
Total Pages : 81 pages
Book Rating : 4.:/5 (244 download)
Download or read book Real-Time Terahertz Imaging Using a Quantum Cascade Laser and Uncooled Microbolometer Focal Plane Array written by and published by . This book was released on 2008 with total page 81 pages. Available in PDF, EPUB and Kindle. Book excerpt: Real-time imaging in the terahertz (THz) spectral range was achieved using an uncooled, 160 120 pixel infrared microbolometer camera and a milliwatt-scale quantum cascade laser (QCL). By replacing the camera's original focusing optics with a Tsurupica-based lens and minimizing diffraction effects incurred by the QCL output beam, an imaging scheme was developed in which the camera's focal plane array successfully detected wavelengths that are more than an order of magnitude longer than those for which the system is designed. Moreover, the incorporation of parabolic reflecting optics yielded a capability to produce high-resolution images of objects placed within the beam path. Despite the low laser powers employed, this scheme allows high-contrast imaging of various objects concealed by a wide range of nonmetallic materials confirming the suitability of this technology for homeland security screening applications. Furthermore, the identification of relatively obscure security features in British currency notes suggests that Terahertz imaging could serve a future role as a detection mechanism against assorted counterfeiting practices. An extensive comparative analysis of experimental data produced using two QCLs (resonating at 2.8 and 3.6 THz) provides additional insight into the physics underlying these results, and suggests methods by which this imaging technology could be further improved.
Author : Matteo Perenzoni
Publisher : Springer
ISBN 13 : 9400738374
Total Pages : 257 pages
Book Rating : 4.4/5 (7 download)
Download or read book Physics and Applications of Terahertz Radiation written by Matteo Perenzoni and published by Springer. This book was released on 2013-10-16 with total page 257 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book covers the latest advances in the techniques employed to manage the THz radiation and its potential uses. It has been subdivided in three sections: THz Detectors, THz Sources, Systems and Applications. These three sections will allow the reader to be introduced in a logical way to the physics problems of sensing and generation of the terahertz radiation, the implementation of these devices into systems including other components and finally the exploitation of the equipment for real applications in some different field. All of the sections and chapters can be individually addressed in order to deepen the understanding of a single topic without the need to read the whole book. The THz Detectors section will address the latest developments in detection devices based on three different physical principles: photodetection, thermal power detection, rectification. The THz Sources section will describe three completely different generation methods, operating in three separate scales: quantum cascade lasers, free electron lasers and non-linear optical generation. The Systems and Applications section will take care of introducing many of the aspects needed to move from a device to an equipment perspective: control of terahertz radiation, its use in imaging or in spectroscopy, potential uses in security, and will address also safety issues. The text book is at a level appropriate to graduate level courses up to researchers in the field who require a reference book covering all aspects of terahertz technology.
