Remerciez-le!

Remerciez @Admin pour avoir partagé cet document gratuitement, de la manière la plus simple, en partageant sur les réseaux sociaux.

See discussions, stats, and author profiles for this publication at: https://ww

See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/283081246 Static and dynamic characteristics of InGaN-based laser diodes Article · January 2014 CITATIONS 2 READS 1,576 1 author: Luca Sulmoni Technische Universität Berlin 47 PUBLICATIONS 645 CITATIONS SEE PROFILE All content following this page was uploaded by Luca Sulmoni on 24 October 2017. The user has requested enhancement of the downloaded file. POUR L'OBTENTION DU GRADE DE DOCTEUR ÈS SCIENCES acceptée sur proposition du jury: Prof. C. Moser, président du jury Prof. N. Grandjean, Dr J.-F. Carlin, directeurs de thèse Prof. B. Deveaud-Plédran, rapporteur Dr J. Heffernan, rapporteur Prof. M. Kneissl, rapporteur STATIC AND DYNAMIC CHARACTERISTICS OF INGAN-BASED LASER DIODES THÈSE NO 6083 (2014) ÉCOLE POLYTECHNIQUE FÉDÉRALE DE LAUSANNE PRÉSENTÉE LE 24 JANVIER 2014 À LA FACULTÉ DES SCIENCES DE BASE LABORATOIRE EN SEMICONDUCTEURS AVANCÉS POUR LA PHOTONIQUE ET L'ÉLECTRONIQUE PROGRAMME DOCTORAL EN PHOTONIQUE Suisse 2014 PAR Luca Alex Milo SULMONI If you can meet with Triumph and Disaster And treat those two impostors just the same — Rudyard Kipling, If Ai miei genitori, per tutto. . . A mio nonno, per assomigliarti. . . Remerciements En premier lieu, je veux remercier un professeur de thèse extraordinaire, Nicolas Grand- jean. Nicolas, grâce à ta curiosité contagieuse et ta disponibilité sans faille, ces quatre années de thèse ont été un véritable plaisir. Tu n’as jamais manqué de m’apporter ton soutien et je t’en suis reconnaissant. Dans l’avenir, j’espère mettre à proﬁt ton incroyable capacité à toujours trouver de nouvelles voies à poursuivre dans le cadre de la recherche scientiﬁque (ou non), une attitude que tu m’as transmise sans cesse au cours de ma thèse. Je m’excuse d’avance pour ma soutenance publique. Je voudrais ensuite remercier le Prof. Christophe Moser pour avoir présidé mon jury de thèse ainsi que tous les membres qui ont accepté de lire et de juger le présent travail: mon co-directeur de thèse, le Dr. Jean-François Carlin, les Profs. Benoît Deveaud, Michael Kneissl et Jon Heﬀernan. Merci à tous les membres du LASPE qui ont rendu cette expérience très agréable et enrichissante (du nord au sud du couloir): Jacques, Georg, Nils, Gatien, Marcel, Lorenzo, Marlene, Christian, Marco M., Guillaume, Raphaël, Amélie, Alexei, Noelia, Jean-Michel, Lise, Etienne, Munise, Eric, Julien, Nino, Marco R., Jean-François, Denis et Aline. Avant tout un grand merci à Gatien, Nino, Julien et Jean-Michel pour l’inestimable formation à l’utilisation des salles blanches et aux techniques et procédés de microfabrication ainsi que pour les profondes discussions concernant l’interprétation de nombreuses données. Merci à Raphaël W. Butté (le W c’est pour wikipedia) pour son incroyable disponibilité à répondre à la moindre question avec laquelle invariablement je l’importunais et pour m’avoir appris la rigueur de la rédaction scientiﬁque à coups de rouge. Je lui suis énormément reconnaissant pour toutes ses nombreuses corrections de l’anglais ainsi que du français qui ont caractérisées mes écrits, y compri ces lignes que vous lisés, mersi Raph! Merci à Jean-François pour son aide concernant la croissance épitaxiale de tous les échantillons étudiés. Merci à Mehran et Gwénolé pour toutes les mesures résolues en temps que nous avons eﬀectuées sur mes dispositifs ainsi qu’à Benoît Deveaud pour toutes les précieuses discussions scientiﬁques sur les sujets délicats de la superradiance et de la superﬂuorescence. Merci à Marlene et Christian pour toute l’assistance fournie au cours des mesures d’électroréﬂectance. Un grand merci aussi à tous les membres du projet européen Femtoblue avec lesquels j’ai eu le plaisir de collaborer pendant ces années de thèse. Merci en particulier à Thomas et Ulrich pour l’opportunité qu’ils m’ont oﬀerte d’eﬀectuer des mesures dynamiques en régime de self-pulsation et de mode-locking sur les MS-LDs. v Remerciements Un grazie speciale agli amici che mi hanno accompagnato (indirettamente) in questi anni di dottorato all’EPFL. Sebastiano, per un’amicizia che prosegue da tempo immemorabile e per tutti i ﬁlm in seconda serata (dobbiamo smetterla di vederci così!), grazie dal profondo del cuore! Mirco, per il tuo sostegno incondizionato nei momenti peggiori e per il Morra declinato. Mitica grande Sluts! Stefano, per tutti i pranzi, partite, birre e serate in cui hai cercato disperatamente di avere ragione. Diego, una delle persone più entusiaste che abbia mai conosciuto, grazie per tutti i preziosi consigli. Vai Doggy! Mariano, per esserci sempre stato in ogni momento e per essere il miglior complice che si possa desiderare. Michele, ci perseguitiamo ﬁn dall’asilo ma grazie per tutte le partite a squash e le inﬁnite afterdiscussions. Ferro, la tua pazzia mi ha tenuto vivo in questi anni, pregevole Bolla! Et, last but not least, un grand merci à tous les collègues du babyfoot: Gabriel, Dimitri, Adrien, Daniel, Ben, Michael, Hienhien, Diego, Nicola, Marc, Cyril, Yann,... Merci les gars! Ça n’aurait jamais été pareil sans vous... Inﬁne, vorrei ringraziare la mia famiglia per il loro sostegno durante tutti questi lunghi anni di studio. Ai miei genitori in particolare per non avermi mai fatto mancare niente. A mia sorella, la migliore che un fratellino pestifero possa mai desiderare. Grande Iaia! A mia zia un grazie particolare, senza tutti i tuoi libri tutto sarebbe stato un po’ più diﬃcile da capire. E un pensiero speciale a mio nonno che avrebbe sempre voluto vedermi laureare ﬁnalmente in chimica. Un grazie dal profondo del cuore a Nina che con cipiglio severo ha supervisionato questi miei anni di dottorato. Quando ti accorgi che vuoi passare il resto della vita con qualcuno, vuoi che il resto della vita cominci il più presto possibile. Beh la tesi l’ho ﬁnita, gufa, ora tocca a noi. . . sei pronta a partire? ⊙ Lausanne, janvier 2014 L. S. vi Abstract III-nitride-based laser diodes (LDs) are compact and eﬃcient source of highly coher- ent continuous wave light for optoelectronic applications in the short-wavelength range (λ ∼400 nm). High peak-power and short-pulse generation in this spectral range has not yet been attempted and is of particular interest for applications such as, e.g., the next-generation of high-density optical data storage systems, ultraprecise nanoprocessing and ﬂuorescence bio-imaging. More sophisticated devices like electrically-driven multi- section LDs (MS-LDs) with a monolithically integrated saturable absorber section (AS) would lay the foundation for miniature portable femtosecond lasers combining the well known advantages of semiconductor LDs such as their easy manufacturing, the absence of mechanical alignments, their low cost, compactness and high potential for integrability. MS-LDs are fabricated by simply deﬁning an electrically separated p-contact section that acts as a saturable absorber along the waveguide of a standard laser resonator. This way, the multiple-contacted sections on the laser cavity share the same active region and are therefore optically coupled. Additionally, the particular design of a MS-LD allows to modulate a posteriori the internal absorption of the device, aﬀecting both its static and dynamic regimes, as it will be shown in this thesis. Under appropriate modulation conditions for the AS, the induced variations in the absorption coeﬃcient can develop non-linearities in the system. Accordingly, the MS-LD can then be operated in stable and, more importantly, controllable dynamic regimes of self-pulsation (SP), Q-switching and active/passive mode-locking. The goal of the present study is to provide a detailed analysis of the system properties ac- counting for nitride speciﬁcities, to describe the static and dynamic mechanisms governing a GaN-based MS-LD and to present exhaustive interpretations of the experimental results and of the physical processes aﬀecting the device performance. First, we design and grow high quality heterostructures with low defect density on free-standing GaN substrates. Achieving a high structural quality during the growth of InGaN multiple-quantum-well (MQW) is critical for the device performance. Using standard photolithography and dry etching techniques, we fabricate the MS-LDs with careful metallic deposition to deﬁne the cavity sections. Then, the LD structures are cleaved and tested on a probe station to deﬁne the optical emission characteristics. In particular, the trends of the main diﬀerent observables (e.g., optical gain and loss distributions, lasing threshold current, absorption coeﬃcient, pulsating frequency,...) and their respective issues are identiﬁed and commented. These measurements provide an important feedback for optimizing vii Abstract the heterostructures and will be used as inputs for modeling the cavity and improving the design. For this purpose, several simulation approaches are carefully developed to support the qualitative understanding of the physical processes. The methods ﬁrstly developed in the case of a standard single-section LD are then generalized to the case of MS-LDs and the impact on the diﬀerent dynamic operating regimes is discussed in regards to the driving conditions for a stable pulsating emission. In this thesis we report detailed investigations on multi-contacted InGaN MQW LDs grown on c-plane freestanding GaN substrate consisting of an AS and an ampliﬁer gain section. As a result of the interplay between external bias applied to the AS and the internal piezoelectric and spontaneous polarization ﬁelds inherent to c-plane InGaN MQWs, the devices exhibit non-linear non-monotonic variations in the threshold current due to the quantum-conﬁned Stark eﬀect that takes place in the AS MQWs. We report on how this eﬀect governs the lasing characteristics and lasing dynamics, from steady-state cw lasing regime for unbiased AS uploads/Science et Technologie/ static-and-dynamic-characteristics-of-ingan-based.pdf