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Author: Sajjad Mahdizadeh
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Author: Sajjad Mahdizadeh
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Author:
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Category :
Languages : en
Pages : 9
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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.
Author: Andriy Danylov
Publisher:
ISBN:
Category : Lasers
Languages : en
Pages : 266
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Author: Dan Botez
Publisher: Cambridge University Press
ISBN: 1108427936
Category : Science
Languages : en
Pages : 551
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A state-of-the-art overview of this rapidly expanding field, featuring fundamental theory, practical applications, and real-life examples.
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:
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Category :
Languages : en
Pages : 11
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In this study, we have performed frequency locking of a dual, forward reverse emitting third-order distributed feedback quantum cascade laser (QCL) at 3.5 THz. By using both directions of THz emission in combination with two gas cells and two power detectors, we can for the first time perform frequency stabilization, while monitor the frequency locking quality independently. We also characterize how the use of a less sensitive pyroelectric detector can influence the quality of frequency locking, illustrating experimentally that the sensitivity of the detectors is crucial. Using both directions of terahertz (THz) radiation has a particular advantage for the application of a QCL as a local oscillator, where radiation from one side can be used for frequency/phase stabilization, leaving the other side to be fully utilized as a local oscillator to pump a mixer.
Author: Tasmim Alam
Publisher: Cuvillier Verlag
ISBN: 3736962975
Category : Science
Languages : en
Pages : 132
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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: Federico Capasso
Publisher: Walter de Gruyter GmbH & Co KG
ISBN: 3110710684
Category : Technology & Engineering
Languages : en
Pages : 783
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Book Description
This book provides a cutting-edge research overview on the latest developments in the field of Optics and Photonics. All chapters are authored by the pioneers in their field and will cover the developments in Quantum Photonics, Optical properties of 2D Materials, Optical Sensors, Organic Opto-electronics, Nanophotonics, Metamaterials, Plasmonics, Quantum Cascade lasers, LEDs, Biophotonics and biomedical photonics and spectroscopy.
Author: Chao Xu
Publisher:
ISBN:
Category : Lasers
Languages : en
Pages : 128
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Book Description
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: Marc Ruben Mertens
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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