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Author: Petar Boykov Tzenov
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Author: Petar Boykov Tzenov
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Category :
Languages : en
Pages : 0
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Author: Dan Botez
Publisher: Cambridge University Press
ISBN: 1108570607
Category : Technology & Engineering
Languages : en
Pages : 552
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Book Description
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: Joachim Piprek
Publisher: CRC Press
ISBN: 1498749577
Category : Science
Languages : en
Pages : 887
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Book Description
Provides a comprehensive survey of fundamental concepts and methods for optoelectronic device modeling and simulation. Gives a broad overview of concepts with concise explanations illustrated by real results. Compares different levels of modeling, from simple analytical models to complex numerical models. Discusses practical methods of model validation. Includes an overview of numerical techniques.
Author: Chao Xu
Publisher:
ISBN:
Category : Lasers
Languages : en
Pages : 128
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Recent advances in Terahertz Quantum Cascade Laser (THz QCL) development are pushing this technology ever closer to practical application, particularly within the spectroscopic field. For this reason, optimizing the operation of THz QCL frequency combs, which can potentially provide unprecedented accuracy and stability to the optical spectra in a broad frequency band, is of particular interest to the research community. The THz QCLs frequency comb was only recently realized using two separate techniques: either a broad-gain active region or a group velocity dispersion controlled waveguide. However, due to residual optical dispersion from both the gain medium and the cold waveguide, comb formation in these reported THz QCLs can only sustain a limited current injection region and the observed comb frequency range is much narrower than the bandwidth of the designed gain medium. To overcome these limitations, this thesis targets a new THz QCL frequency comb device design that simultaneously exploits the broadband gain active region and a group velocity dispersion (GVD)-compensated waveguide over an octave frequency band of 2-4 THz. In designing a broadband gain active region, two heterogeneous structures are proposed and simulated, with one combining three different bound-to-continuum (BTC) active regions operating at a temperature of 25 K, and another one consisting of four different resonant-phonon (RP) active regions operating at the liquid nitrogen temperature (77 K) or higher. The simulation results show that both active region designs can provide a broadband and 'flat-top' gain profile covering the frequency range from 2 to 4 THz. To design a group velocity dispersion-compensated waveguide, strategies are explored for simulating chirped Distributed Bragg Reflectors (DBRs) that can serve as THz QCL metal-metal waveguides, and one-dimensional (1D) and three-dimensional (3D) modeling approaches are established and verified. A novel two-section chirped DBR is proposed, which provides substantially-improved group delay compensation over a broadband octave frequency range from 2 to 4 THz. Two THz QCL structures are grown using in-house molecular beam epitaxy and THz QCL devices equipped with a metal-metal waveguides are fabricated in the University of Waterloo Quantum-Nano-Centre clean-room fabrication lab. The experimental results demonstrate that the new THz QCL active region design can operate up to a maximum lasing temperature of 111 K, and with a broad lasing spectrum covering frequencies from 2.36 to 2.86 THz under pulse mode, at temperature of 13 K. The combined theoretical and experimental work would ultimately lead to the demonstration of improved THz QCL frequency comb operation over the broadband range from 2 to 4 THz.
Author: Michael Riesch
Publisher:
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Category :
Languages : en
Pages : 0
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Author: Dang Bao An Tran
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Category :
Languages : en
Pages : 0
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The thesis consists in developing a high-resolution mid-infrared spectrometer traceable to primary frequency standards and providing a unique combination of resolution, tunability, detection sensitivity and frequency control. A quantum cascade laser (QCL) emitting at 10.3 μm is phase locked to an optical frequency comb stabilized to a remote 1.55 μm ultra-stable reference developed at LNE-SYRTE, monitored against primary frequency standards and transferred to LPL via an active noise compensated fibre link. This results in a 0.1 Hz QCL linewidth, a stability below 10−15 at 1 s and an uncertainty on its absolute frequency below 4 × 10−14. Moreover, the setup allows the QCL to be widely scanned over 1.4 GHz while maintaining the highest stabilities and precision. This QCL was used to carry out saturated absorption spectroscopy of several molecules in a compact multipass cell. We demonstrated statistical uncertaintyon line-center frequencies at the kHz level and sub-10 kHz systematic uncertainty. We have recorded several singular K-doublets and many rovibrational transitions of methanol, in particular weak transitions and weak doublets - unreported so far. Precise parameters modelling trioxaneh ave been determined with only a few tens of rovibrational transitions recorded at unprecedented accuracy. The quadrupole hyperfine structure of an ammonia transition has been resolved for thefirst time. This setup constitutes a key element for the project aiming at the first observation of parity violation in molecules currently held at LPL, and, more generally, for various fields of physics, from atmospheric and interstellar physics to fundamental physics beyond the standard model.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 81
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Author: Benjamin Adams Burnett
Publisher:
ISBN:
Category :
Languages : en
Pages : 223
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The portion of the electromagnetic spectrum between roughly 300 GHz and 10 THz is nicknamed the "THz Gap" because of the enormous difficulty encountered by researchers to devise practical sources covering it. Still, the quantum cascade laser (QCL) has emerged over recent years as the most promising approach to a practical source in the 1-5 THz range. First developed in the higher-frequency mid-IR, where they are now widely available, QCLs were later extended to the THz where a host of greater design challenges awaited. Lasing in QCLs is based on intersubband optical transitions in semiconductor quantum wells, the energy of which can be chosen by design ("bandstructure engineering"). However, simply building a THz optical transition is insufficient; a good design must also produce significant population inversion by the applied cascading electron current, and this requires deep understanding of the transport physics. So far, no THz QCL has operated above the temperature of 200 K, even though the reasons prohibiting high temperature operation are well known. The goal of this Thesis is to put novel ideas for high-temperature operation of THz QCL active regions through rigorous theoretical testing. The central enabling development is a density-matrix-based model of transport and optical properties tailored for use in QCLs, which is general enough that widely varying design concepts can be tested using the same core principles. Importantly, by simulating QCLs more generally, fewer a priori assumptions are required on part of the researcher, allowing for the true physics to emerge on its own. It will be shown that this gives rise to new and useful insights that will help to guide the experimental efforts towards realization of these devices. One specific application is a quantum dot cascade laser (QDCL), a highly ambitious approach in which the electrons cascade through a series of quantum dots rather than wells. Benefits are expected due to the suppression of nonradiative scattering, brought about by the discrete spectrum of electronic states. However, this in turn leads to a highly different physics of transport and effects that are not well understood, even in the case of perfect materials. This work will show that while the benefits are clear, naive scaling of existing QCL designs to the quantum dot limit will not work. An alternative strategy is given based on a revised understanding of the nature of transport, and is put to a test of practicality in which the effects of quantum dot size inhomogeneity are estimated. Another application is to the already existing method of THz difference frequency generation in mid-IR QCLs, which occurs via a difference-frequency susceptibility $\chi^{(2)}$ in the active region itself. For this purpose, the model is extended to enable a coherent and nonperturbative calculation of optical nonlinearities. First, the generality of the method is displayed through the emergence of exotic nonlinear effects, including electromagnetically-induced transparency, in mock quantum-well systems. Then, the modeling concepts are applied to the real devices, where two new and important mechanisms contributing to $\chi^{(2)}$ are identified. Most importantly, it is predicted that the QCL acts as an extremely fast photodetector of itself, giving rise to a current response to the mid-IR beatnote that provides a better path forward to the generation of frequencies below ~2 THz. Finally, the fundamentals of density matrix transport theory for QCLs are revisited to develop a model for conventional THz QCL designs eliminating the usual phenomenological treatment of scattering. The new theory is fully developed from first principles, and in particular sheds light on the effects of scattering-induced electron localization. The versatility of the model is demonstrated by successful simulation of varying active region designs.
Author: Jérôme Faist
Publisher: OUP Oxford
ISBN: 0191663832
Category : Technology & Engineering
Languages : en
Pages : 321
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Book Description
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.
Author: Martin F. Schubert
Publisher:
ISBN:
Category :
Languages : en
Pages : 94
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