Download or read book Mode locking Actif Et Contr le Des Propri t s Spectrales Des Lasers Cascade Quantique T rahertz written by Pierre Gellie and published by . This book was released on 2012 with total page 155 pages. Available in PDF, EPUB and Kindle. Book excerpt: La mise au pint de sources térahertz (THz) dont les propriétés spectrales sont contrôlées est devenu un enjeu important dans plusieurs domaines. Notamment pour des applications comme la spectroscopie de haute résolution, l'imagerie avec haut rapport signal sur bruit ou bien la détection hétérodyne de grande sensibilité. C'est dans ce contexte que se situent mes travaux de thèse. En particulier je me suis penché sur les sources laser à cascade quantique (LCQ) Thz. Dans un premier temps, j'ai montré comment, en modulant un LCQ à une fréquence proche de l'intervalle spectral libre, l'on obtient le verrouillage mutuel des modes du LCQ. Ensuite, j'ai développé une technique de verrouillage de phase du LCQ se basant sur un laser femto-seconde à 1550nm et une détection électro-optique. J'ai ainsi montré que, lorsque la boucle de verrouillage est fermée, la largeur spectrale d'un LCQ à 2.5THZ est inférieure à 1Hz. J'ai ensuite démontré, grâce à une technique optique asynchrone, que l'on peut échantillonner le champ électrique émis par un LCQ fonctionnant en régime de verrouillage de modes. J'ai ainsi pu mesurer une durée impulsion de 10ps pour un LCQ ayant 10 modes longitudinaux au-dessus du seuil, avec un pas d'échantillonnage de 2.3ps. Dans le dernier chapitre de la thèse je me suis intéressé au développement d'une cavité étendue à base d'un LCQ THz. Dans un premier temps, j'ai démontré que la réfléctivité d'une facette d'un LCQ peut être réduite à quelques pourcents en polissant celle-ci à l'angle de Brewster ou bien en déposant une couche antireflet à base de Parylène. Enfin, j'ai développé des LCQ à contre-réaction répartie, afin d'obtenir une émission monomode à haute puissance en régime continu.
Download or read book Mode Locking of Quantum Cascade Lasers written by and published by . This book was released on 2007 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt: A theoretical and experimental study of multimode operation regimes in quantum cascade lasers (QCLs) is presented. It is shown that the fast gain recovery of QCLs promotes two multimode regimes in QCLs: One is spatial hole burning (SHB), and the other one is related to the Risken-Nummedal-Graham-Haken (RNGH) instability predicted in the sixties. A model that can account for coherent phenomena, a saturable absorber and SHB is developed and studied in detail both analytically and numerically. A wide variety of experimental data on multimode regimes is presented. Lasers with narrow active region and/or with metal coating on the sides tend to develop a splitting in the spectrum, approximately equal to twice the Rabi frequency. It is proposed that this behavior stems from the presence of a saturable absorber, which can result from a Kerr lensing effect in the cavity. Lasers with a wide active region, which have weaker saturable absorber, do not exhibit a Rabi splitting, and their multimode regime is governed by SHB. This experimental phenomenology is well explained by our theoretical model.
Download or read book Multimode Dynamics in Quantum Cascade Lasers written by Christine Yi-Ting Wang and published by . This book was released on 2008 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main experimental signature of RNGH instability is a splitting corresponding to twice the Rabi frequency in optical spectrum. In QCLs this coherent instability is enhanced due to the large Rabi frequency compared to the relaxation rates. We have also shown that spatial hole burning, which is not so readily observable in diode lasers, also plays an important role in QCLs. Both experimental data and simulations based on Maxwell-Bloch equations are presented. In the second part of this thesis, we demonstrate active mode-locking in QCLs. The stable mode-locked pulse train was generated by actively modulating the pumping current of a small section on a QCL. Stable mode locking was confirmed by second-order interferometric autocorrelation measurements, and a FWHM of 3 ps and about 0.5 pJ per pulse were deduced from the autocorrelation traces. The system is also simulated using Maxwell-Bloch equations incorporated with a modulation term. We anticipate our results to be a big step toward a compact, electrically-pumped source generating ultrashort pulses in the mid-infrared and terahertz ranges.
Download or read book Laser Mode locking and Pulse Propagation written by Frederick Roggeman Faxvog and published by . This book was released on 1971 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Modelocking of THz Quantum Cascade Lasers written by Valentino Pistore and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: THz QCLs are nowadays considered a promising platform for the generation of intense and ultrashort THz pulses. Owing to their fast gain recovery time, passive modelocking of THz QCLs has so far proved to be difficult. On the contrary, active modelocking with a microwave modulation has been successfully applied. The pulse duration, however, has been arduous to reduce despite years of research. In 2017, THz pulses as short as 4ps have been generated by our group with the application of an integrated structure (a GTI) aiming to reduce the chromatic dispersion. The research in this thesis starts from this point.In particular, I present dispersion engineering in THz QCLs in order to obtain very short pulses even from relatively narrow-band devices. This is achieved using proven active modulation methods that can tune the QCL emission from high to low dispersion regimes. I also show that THz QCLs can present a strong amplitude modulation of their emission profile and that they can spontaneously emit pulses as a result of a self-locking mechanism, contrary to the expected frequency modulated response. As a consequence, this indicates that the fast gain recovery time is not a limiting factor for the generation of pulses. I also show this passive self-locking scheme for passive pulse generation in the framework of the first demonstrations of harmonic modelocking of THz QCLs. Finally, a new phenomenon is presented where the modes of a free running THz QCL can beat together to generate free space microwave emission.
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 320 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 Design and Fabrication of Quantum Cascade Lasers written by Giuseppe Scarpa and published by . This book was released on 2003 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experimental and Numerical Study on Active Mode Locking with Hybrid Lasers written by Bo Guo and published by . This book was released on 2001 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Solid state Laser Mode Locking and Ultrafast Studies in Quantum Semiconductor Structures PHD written by Paulo Tiago Ferraz de Meira Guerreiro and published by . This book was released on 1997 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Studies in Laser Stabilities and Mode locking written by and published by . This book was released on 1986 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mode Locking Experiments with GaAlAs Semiconductor Lasers written by A. Elmeland-Ygge and published by . This book was released on 1981 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Passive Mode locking and Millimeter wave Modulation of Quantum Well Lasers written by Steven Sanders and published by . This book was released on 1992 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mid infrared Quantum Cascade Lasers for Chaos Secure Communications written by Olivier Spitz and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The mid-infrared domain is a promising optical domain because it holds two transparency atmospheric windows, as well as the fingerprint of many chemical compounds. Quantum cascade lasers (QCLs) are one of the available sources in this domain and have already been proven useful for spectroscopic applications and free-space communications. This thesis demonstrates how to implement a private free-space communication relying on mid-infrared optical chaos and this requires an accurate cartography of non-linear phenomena in quantum cascade lasers. This private transmission is made possible by the chaos synchronization of two twin QCLs. Chaos in QCLs can be generated under optical injection or external optical feedback. Depending on the parameters of the optical feedback, QCLs can exhibit several non-linear phenomena in addition to chaos. Similarities exist between QCLs and laser diodes when the chaotic dropouts are synchronized with an external modulation, and this effect is known as the entrainment phenomenon. With a cross-polarization reinjection technique, QCLs can generate all-optical square-waves. Eventually, it is possible to trigger optical extreme events in QCLs with tilted optical feedback. All these experimental results allow a better understanding of the non-linear dynamics of QCLs and will extend the potential applications of this kind of semiconductor lasers.
Download or read book Stabilization of Mode locked Lasers written by Steven T. Cundiff and published by . This book was released on 2003 with total page 133 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Passive Mode Locking of Lasers with the Optical Kerr Effect Modulator written by Sala, K. L. C. (Kenneth Leonard Charles) and published by University of Waterloo. This book was released on 1976 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Stabilized Mode locking of the Figure Eight Laser written by V. V. Prasad Dasika and published by . This book was released on 1993 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Laser Mode Locking by External Modulation written by Kristine Marie Garner and published by . This book was released on 1991 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:
