Read Books Online and Download eBooks, EPub, PDF, Mobi, Kindle, Text Full Free.
Towards Room Temperature Terahertz Quantum Cascade Lasers
Download Towards Room Temperature Terahertz Quantum Cascade Lasers full books in PDF, epub, and Kindle. Read online Towards Room Temperature Terahertz Quantum Cascade Lasers ebook anywhere anytime directly on your device. Fast Download speed and no annoying ads. We cannot guarantee that every ebooks is available!
Book Synopsis Towards Room-temperature Terahertz Quantum Cascade Lasers by : Chun Wang Ivan Chan
Download or read book Towards Room-temperature Terahertz Quantum Cascade Lasers written by Chun Wang Ivan Chan and published by . This book was released on 2015 with total page 251 pages. Available in PDF, EPUB and Kindle. Book excerpt: Terahertz Quantum Cascade Lasers (THz QCLs) are arguably the most promising technology today for the compact, efficient generation of THz radiation. Their main limitation is that they require cryogenic cooling, which dominates their ownership cost. Therefore, achieving room-temperature operation is essential for the widespread adoption of THz QCLs. This thesis analyzes the limitations of THz QCL maximum lasing temperature (Tmax) and proposes solutions. THz QCL Tmax is hypothesized to be limited by a fundamental trade-off between gain oscillator strength ful and upper-level lifetime [Tau]. This so-called "ful[Tau] tradeoff" is shown to explain the failure of designs which target [Tau] alone. A solution is proposed in the form of highly diagonal (low ful) active region design coupled with increased doping. Experimental results indicate the strategy to be promising, but heavily doped designs are shown to suffer band-bending effects which may deteriorate performance. In order to treat these band-bending effects, which are typically neglected in previous THz QCL designs, a fast transport simulation tool is developed. Scattering integrals are simplified using the assumption of thermalized sub bands. Results comparable to ensemble Monte Carlo are achieved at a fraction of the computational expense. Carrier leakages to continuum states are also investigated, although they are found to have little effect. Other work in this thesis includes the optimization of double-metal THz waveguides to enable Tmax ~ 200 K, a current world record. Furthermore, laser designs to investigate the leakages of carriers to high-energy subbands and continuum states were fabricated and tested; such parasitic leakages are suggested to be small. Finally, the design of gain media for applications is examined, notably the development of 4.7 THz gain media for OI line detection in astrophysics, and the development of broadband heterogeneous gain media for THz comb generation.
Download or read book מסכתות דרך ארץ written by Otzar hahochma and published by . This book was released on 1935 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Characterization and Analysis of Highly Diagonal Terahertz Quantum Cascade Lasers by : Chun Wang Ivan Chan
Download or read book Characterization and Analysis of Highly Diagonal Terahertz Quantum Cascade Lasers written by Chun Wang Ivan Chan and published by . This book was released on 2010 with total page 157 pages. Available in PDF, EPUB and Kindle. Book excerpt: The as yet unattained milestone of room-temperature operation is essential for establishing Terahertz Quantum Cascade Lasers (THz QCLs) as practical sources of THz radiation. Temperature performance is hypothesized to be limited by upper laser level lifetime reduction due to non-radiative scattering, particularly by longitudinal optical phonons. To address this issue, this work studies highly "diagonal" QCLs, where the upper and lower laser level wave functions are spatially separated to preserve upper laser level lifetime, as well as several other issues relevant to high temperature performance. The highly diagonal devices of this work performed poorly, but the analysis herein nevertheless suggest that diagonality as a design strategy cannot yet be ruled out. Other causes of poor performance in the lasers are identified, and suggestions for future designs are made.
Book Synopsis Mid-Infrared and Terahertz Quantum Cascade Lasers by : Dan Botez
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.
Book Synopsis High-Temperature Operating Narrow-Period Terahertz Quantum Cascade Laser Designs by : Li Wang
Download or read book High-Temperature Operating Narrow-Period Terahertz Quantum Cascade Laser Designs written by Li Wang and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presently, terahertz quantum cascade lasers still suffer from operations below room temperature, which prohibits extensive applications in terahertz spectra. The past continuous contributions to improving the operating temperatures were by clarifying the main thermal degradation process and proposing different designs with the optical gain demonstrating higher temperature cut-offs. Recent designs have attempted to employ a narrow period length with a simplified and clean state system, and reach renewed operating temperatures above 200 K. This study reveals how historic designs approach such narrow-period designs, discus the limitations within those designs, and show further possible designs for higher operating temperatures.
Book Synopsis Spectroscopic Applications of Terahertz Quantum-Cascade Lasers by : Tasmim Alam
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.
Book Synopsis Mid-Infrared and Terahertz Quantum Cascade Lasers by : Dan Botez
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.
Book Synopsis Terahertz Technology by : Ali Rostami
Download or read book Terahertz Technology written by Ali Rostami and published by Springer Science & Business Media. This book was released on 2010-11-25 with total page 256 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book presents information about Terahertz science, Terahertz photodetectors and Terahertz Lasers. A special emphasis is given to room temperature operation of long wavelength photodetectors based on novel quantum dots (Centered Defect Spherical Quantum Dots). Moreover, a complete analysis of systems based on Quantum Cascade structures to detect far infrared wavelengths is provided. Finally, the book presents Terahertz laser principles considering multi-color lasers in this range of wavelengths. Written as a background for graduate students in the Optics field.
Book Synopsis Fundamentals of Terahertz Devices and Applications by : Dimitris Pavlidis
Download or read book Fundamentals of Terahertz Devices and Applications written by Dimitris Pavlidis and published by John Wiley & Sons. This book was released on 2021-08-02 with total page 580 pages. Available in PDF, EPUB and Kindle. Book excerpt: An authoritative and comprehensive guide to the devices and applications of Terahertz technology Terahertz (THz) technology relates to applications that span in frequency from a few hundred GHz to more than 1000 GHz. Fundamentals of Terahertz Devices and Applications offers a comprehensive review of the devices and applications of Terahertz technology. With contributions from a range of experts on the topic, this book contains in a single volume an inclusive review of THz devices for signal generation, detection and treatment. Fundamentals of Terahertz Devices and Applications offers an exploration and addresses key categories and aspects of Terahertz Technology such as: sources, detectors, transmission, electronic considerations and applications, optical (photonic) considerations and applications. Worked examplesbased on the contributors extensive experience highlight the chapter material presented. The text is designed for use by novices and professionals who want a better understanding of device operation and use, and is suitable for instructional purposes This important book: Offers the most relevant up-to-date research information and insight into the future developments in the technology Addresses a wide-range of categories and aspects of Terahertz technology Includes material to support courses on Terahertz Technology and more Contains illustrative worked examples Written for researchers, students, and professional engineers, Fundamentals of Terahertz Devices and Applications offers an in-depth exploration of the topic that is designed for both novices and professionals and can be adopted for instructional purposes.
Book Synopsis Quantum Cascade Lasers by : Jérôme Faist
Download or read book Quantum Cascade Lasers written by Jérôme Faist and published by OUP Oxford. This book was released on 2013-03-14 with total page 321 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides an introduction to quantum cascade lasers, including the basic underlying models used to describe the device. It aims at giving a synthetic view of the topic including the aspects of the physics, the technology, and the use of the device. It should also provide a guide for the application engineer to use this device in systems. The book is based on lecture notes of a class given for Masters and beginning PhD students. The idea is to provide an introduction to the new and exciting developments that intersubband transitions have brought to the use of the mid-infrared and terahertz region of the electromagnetic spectrum. The book provides an introductory part to each topic so that it can be used in a self-contained way, while references to the literature will allow deeper studies for further research.
Book Synopsis Terahertz Generation with Quantum Cascade Lasers by : Karun Vijayraghavan
Download or read book Terahertz Generation with Quantum Cascade Lasers written by Karun Vijayraghavan and published by . This book was released on 2014 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt: The terahertz (THz) spectral range is devoid of commercially feasible radiation sources, detectors, and components. In particular, THz sources are bulky, complex to operate, and cost-prohibitive - more suited for a research laboratory than a commercial setting. Developing compact and mass-producible sources in the 1 to 6 THz spectral range will open up new avenues for this technology to make a mainstream societal impact. The focus of this thesis is the development of compact, room-temperature terahertz sources based on quantum cascade lasers (QCL) and quantum well technology. QCLs are semiconductor lasers that operate with high power at mid-infrared (mid-IR) and THz frequencies. THz QCLs are the only mW-level average power sources with spectral coverage from 0.8 to 5 THz. However they only work at cryogenic temperatures because they cannot maintain population inversion across the lasing transition at elevated temperatures. Cryogenic cooling makes these sources cumbersome to operate and expensive to manufacture. Room-temperature operation significantly enhances their commercial appeal and a portion of this dissertation investigated the improvement in THz QCL temperature performance using GaAs-Al0.15Ga0.85As double-phonon resonant active region designs. These devices worked up to 173 K and were a substantial improvement compared to prior implementations of double-phonon resonant designs. Room-temperature THz sources that do not require population inversion across the lasing transition can be engineered by combining the field of nonlinear optics with intersubband transitions in quantum well structures. One method of creating inversionless THz lasing is based upon the principle of Raman gain in semiconductors and this thesis explores the design of an intersubband Raman laser (IRL) with GaAs-Al0.33Ga0.67As heterostructures. The primary focus of this dissertation is developing room-temperature, broadly-tunable, monolithic THz sources based on difference-frequency generation (DFG) in mid-IR QCLs. The source active region is quantum-engineered to provide lasing at mid-IR frequencies, [omega]1 and [omega]2, and simultaneously have giant second-order optical nonlinearity for THz generation at frequency [omega] [subscript THz]=[omega]1-[omega]2. This dissertation developed a Cherenkov emission scheme that produced devices with a narrow emission linewidth, 0.12 mW peak power and tuning from 1.55 to 5.7 THz - the largest tuning bandwidth compared to semiconductor technology of similar size and cost.
Book Synopsis New Widely Tunable Room-Temperature Terahertz Coherent Sources by :
Download or read book New Widely Tunable Room-Temperature Terahertz Coherent Sources written by and published by . This book was released on 2008 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this proposal was to develop a new type of THz semiconductor sources that are injection-pumped, efficient, compact, narrowband, tunable, and can operate at room temperature. The proposed device was a mid-infrared InGaAs/AlInAs Quantum Cascade Laser (QCLs) with the waveguide core containing a multi-functional coupled-quantum-well active region that supports both laser action in the mid-infrared and THz generation due to resonant coherent beating of two laser modes. During the course of the work a path was also found to substantially improve the temperature performance and directionality of conventional THz QCLs in which an electronic transition is used for the direct generation of THz radiation. The following was accomplished: first room temperature operation of an elctrically pumped quantum cascade laser based THz source, using intra-cavity nonlinear optics; record operating temperature (180K) of a conventional THz Quantum Cascade Laser, using a copper double metal waveguide for low loss; surface emitting THz QCLs with low beam divergence.
Book Synopsis Room Temperature Operation of Quantum Cascade Lasers Monolithically Integrated Onto a Lattice-mismatched Substrate by : Rowel Canaon Go
Download or read book Room Temperature Operation of Quantum Cascade Lasers Monolithically Integrated Onto a Lattice-mismatched Substrate written by Rowel Canaon Go and published by . This book was released on 2018 with total page 35 pages. Available in PDF, EPUB and Kindle. Book excerpt: A small sample of 2 cm2 size was taken from a 6-inch wafer and processed into ridge-waveguide chips 3 mm x 30 [micrometer] in size. Lateral current injection scheme was utilized due to an insulating M-buffer layer. Preliminary reliability testing up to 200 minutes of runtime showed no sign of power degradation. Laser chips with high reflection (HR) coating showed optical power over 200 mW of total peak power at cryogenic temperature (78 K), with lasing seen up to 230 K. In this temperature range, the measured characteristic temperatures of T0 ≈ 460 K and T1 ≈ 210 K describes the temperature dependence for threshold current and slope efficiency. Adding a partial HR coating (56%) on the front facet extended the lasing range above room temperature (303 K). This thesis will also discuss the preliminary cryogenic temperature result of the first InP-based QCL grown on latticemismatched silicon (Si) substrate.
Download or read book Zinc & Nitride Based QCL written by and published by . This book was released on 2014 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Widely Tunable Terahertz Semiconductor Laser Sources by : Aiting Jiang
Download or read book Widely Tunable Terahertz Semiconductor Laser Sources written by Aiting Jiang and published by . This book was released on 2015 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt: Terahertz Quantum Cascade Lasers (THz QCLs) and Terahertz Difference Frequency Generation Quantum Cascade Laser sources (DFG-QCLs) are two types of semiconductor THz radiation sources that are compact and amenable to production in mass quantities. THz QCL can generate over 1W of power under cryogenic temperatures, while THz DFG-QCL can be operated under room temperature over 1mW level output. For either case, widely tunable solution is highly desired for spectroscopy applications. For THz QCLs, operation is still limited to cryogenic temperature and broad tuning is not available. Our experimental study shows that using variable barriers is a viable approach to enhance the design space for THz QCLs. We also propose to tune the spectral output of these devices using an optically projected variable distributed feedback grating. Tuning will be achieved by changing the projected grating period. Preliminary experimental results support the idea but higher pumping light intensity is required for this method to work. For THz DFG-QCLs, very broad tuning in 1-6 THz range has been demonstrated using rotating diffraction grating in an external cavity setup. Similar tuning range can also be achieved in a monolithic configuration. Based on the previous work which demonstrated an electrical monolithic tuner with 580 GHz tuning range, we design and test in this dissertation a linear array of 10 DFG-QCL devices to cover a 2 THz tuning range. An independent gain control scheme is developed to achieve high yield (~100%) of individual device. It is implemented via independent current pumping of two electrically isolated sections. Surface DFB grating and independent current pumping scheme used in our DFG QCLs is found to be useful for mid-IR QCL array sources. We propose a longitudinal integration scheme of multiple grating sections. It enables a single ridge to emit single mode radiation at different wavelengths upon selection. This helps to reduce mid-IR QCL array far field span. We demonstrated single ridge devices that can emit 2 or 3 different wavelengths upon selection.
Book Synopsis New Frontiers in THz Quantum Cascade Lasers by : Ali Khalatpour
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.
Book Synopsis Physics and Applications of Terahertz Radiation by : Matteo Perenzoni
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.
