Efficient diode-pumped Yb3+:Y2SiO5 and Yb3+:Lu2SiO5 high-power femtosecond laser operation

International audienceWe report the mode-locked operation of two new Yb-doped oxyorthosilicates, Y2SiO5 (YSO) and Lu2SiO5 (LSO), that are longitudinally diode pumped. Yb:YSO supplied pulses as short as 122 fs with 410mW of output power at 1041 nm. More than 2.6W of average output power, for pulse durations of 198 fs at 1044 nm and 260 fs at 1059 nm for Yb:YSO and Yb:LSO, respectively, were provided. These are, to our best knowledge, the highest values ever obtained and the most efficient mode-locked laser in such a classic fibercoupled diode-pumping configuratio

Single-Frequency High-Power Continuous-Wave Oscillation at 1003 nm of an Optically Pumped Semiconductor Laser

This work reports single-frequency laser oscillation at 1003.4 nm of an optically pumped external cavity semiconductor laser. By using a gain structure bonded onto a high conductivity substrate, we demonstrate both theoretically and experimentally the strong reduction of the thermal resistance of the active semiconductor medium, resulting in a high power laser emission. The spectro-temporal dynamics of the laser is also explained. Furthermore, an intracavity frequency-doubling crystal was used to obtain a stable single-mode generation of blue (501.5 nm) with an output power around 60 mW.Comment: 11 page

Sources laser solides pompées par diode, émettant autour de 1000 et 500 nm à base de cristaux dopés ytterbium et de semiconducteurs.

The background of this thesis is the study of new diode-pumped solid-state laser sources emitting a continuous wave single-frequency radiation in the near infrared (1000 nm) and in the blue-green by second harmonic generation, particularly at 501.7 nm. These laser sources aim metrological applications such as ultra-high resolution spectroscopy of molecular iodine (127I2) and the practical application of the meter, fields in which argon lasers are currently used.The first chapter of this work presents the context of this study, through a state of the art of the solid-state laser sources around 500 nm, the adopted and explored solutions, as well as some theoretical elements concerning second harmonic generation. The common principle of these two ways is to produce a single-frequency laser emission at 1000 nm, which is then frequency doubled.The second chapter deals with the solution using ytterbium-doped crystals emitting at 1000 nm, whose emission is intracavity frequency-doubled in a KNbO3 nonlinear crystal. Two laser crystals are used: Yb:YSO and Yb:KYW. In both cases and in single-frequency operation, at 501.7 nm after the frequency doubling process, we demonstrate output powers ranging between 35 and 60 mW for a pump power of 4W at 980 nm.The third chapter relates to the second studied way using a VCSEL type semiconductor amplifying medium with quantum wells. The active structure, composed of a Bragg mirror and quantum wells, is assembled in an extended cavity and optically pumped. The laser emission around 1000 nm is frequency doubled to produce 60 mW in single-frequency operation at 500 nm, from a pump power of 6.5 W at 808 nm.Le cadre général de cette thèse est l'étude de nouvelles sources laser solides, pompées par diode, émettant un rayonnement continu monomode longitudinal dans le proche infrarouge (1000 nm) et dans le bleu-vert par doublement de fréquence, particulièrement à 501,7 nm. Ces sources laser visent des applications métrologiques telles que la spectroscopie de l'iode (127I2) à ultra-haute résolution et la mise en pratique du mètre, domaines dans lesquels les lasers à argon sont actuellement utilisés.Le premier chapitre de ce travail présente le contexte de cette étude, à travers un état de l'art des sources laser autour de 500 nm, les solutions retenues et explorées, ainsi que des éléments théoriques pour la génération de seconde harmonique. Le principe commun des deux voies est de produire une émission laser monomode spectrale à 1000 nm qui est ensuite doublée en fréquence.Le deuxième chapitre traite de la solution utilisant des cristaux dopés ytterbium émettant à 1000 nm, dont l'émission est doublée en fréquence intracavité dans un cristal non linéaire de KNbO3. Deux cristaux laser sont utilisés : le Yb:YSO et le Yb:KYW. Dans les deux cas, à 501,7 nm, nous démontrons des puissances en régime monofréquence comprises entre 35 et 60 mW pour une puissance de pompe de 4W à 980 nm.Le troisième chapitre concerne la seconde voie étudiée utilisant un milieu amplificateur semiconducteur à puits quantiques de type VCSEL. La structure active, formée d'un miroir de Bragg et de puits quantiques, est montée en cavité étendue et pompée optiquement. L'émission autour de 1000 nm est doublée en fréquence pour produire 60 mW en régime monomode spectral à 500 nm, à partir d'une puissance de pompe de 6,5 W à 808 nm

Sources laser solides pompées par diode, émettant autour de 1000 et 500 nm, à base de cristaux dopés ytterbium et de semiconducteurs

LE CADRE GENERAL DE CETTE THESE EST L'ETUDE DE NOUVELLES SOURCES LASER SOLIDES, POMPEES PAR DIODE, EMETTANT UN RAYONNEMENT CONTINU MONOMODE LONGITUDINAL DANS LE PROCHE INFRAROUGE (1000 NM) ET DANS LE BLEU-VERT PAR DOUBLEMENT DE FREQUENCE, PARTICULIEREMENT A 501,7 NM. CES SOURCES LASER VISENT DES APPLICATIONS METROLOGIQUES TELLES QUE LA SPECTROSCOPIE DE L'IODE (127I2) A ULTRA-HAUTE RESOLUTION ET LA MISE EN PRATIQUE DU METRE, DOMAINES DANS LESQUELS LES LASERS A ARGON SONT ACTUELLEMENT UTILISES.LE PREMIER CHAPITRE DE CE TRAVAIL PRESENTE LE CONTEXTE DE CETTE ETUDE, A TRAVERS UN ETAT DE L'ART DES SOURCES LASER AUTOUR DE 500 NM, LES SOLUTIONS RETENUES ET EXPLOREES, AINSI QUE DES ELEMENTS THEORIQUES POUR LA GENERATION DE SECONDE HARMONIQUE. LE PRINCIPE COMMUN DES DEUX VOIES EST DE PRODUIRE UNE EMISSION LASER MONOMODE SPECTRALE A 1000 NM QUI EST ENSUITE DOUBLEE EN FREQUENCE.LE DEUXIEME CHAPITRE TRAITE DE LA SOLUTION UTILISANT DES CRISTAUX DOPES YTTERBIUM EMETTANT A 1000 NM, DONT L'EMISSION EST DOUBLEE EN FREQUENCE INTRACAVITE DANS UN CRISTAL NON LINEAIRE DE KNBO3. DEUX CRISTAUX LASER SONT UTILISES : LE YB:YSO ET LE YB:KYW. DANS LES DEUX CAS, A 501,7 NM, NOUS DEMONTRONS DES PUISSANCES COMPRISES ENTRE 35 ET 60 MW POUR UNE PUISSANCE DE POMPE DE 4W A 980 NM.LE TROISIEME CHAPITRE CONCERNE LA SECONDE VOIE ETUDIEE UTILISANT UN MILIEU AMPLIFICATEUR SEMICONDUCTEUR A PUITS QUANTIQUES DE TYPE VCSEL. LA STRUCTURE ACTIVE, FORMEE D'UN MIROIR DE BRAGG ET DE PUITS QUANTIQUES, EST MONTEE EN CAVITE EXTERNE ET POMPEE OPTIQUEMENT. L'EMISSION AUTOUR DE 1000 NM EST DOUBLEE EN FREQUENCE POUR PRODUIRE 60 MW EN REGIME MONOMODE SPECTRALA 500 NM, A PARTIR D'UNE PUISSANCE DE POMPE DE 6,5 W A 808 NM.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Single-frequency operation of diode-pumped Yb:KYW at 1003.4 nm and 501.7 nm by intracavity second harmonic generation

International audienc

Blue-green single-frequency laser based on the intracavity SHG of a diode-pumped Ytterbium-doped laser

International audienceSingle-frequency lasers in the blue-green (500 nm) visible spectrum are important for many applications including iodine precision spectroscopy, optical frequency standards or ionized argon lasers substitution. To the best of our knowledge, we report in this paper the first single-frequency diode-pumped Ytterbium-doped solid-state laser operating at 501.7 nm by intracavity second harmonic generation (SHG). The singlefrequency fundamental infrared laser light is generated by a diode-pumped Yb3+:Y2SiO5 crystal in a ring oscillator. Intracavity SHG with a KNbO3 nonlinear crystal produced more than 50 mW of single-frequency bluegreen radiatio

Activity Level of an Atrial Ectopic Focus Observed Through the Equivalent Dipole: a Biophysical Model

Quantifying the role of atrial ectopic foci in the initiation and the maintenance of atrial fibrillation (AF) is a relevant clinical problem. This study aims at assessing the relation between the activity level of an ectopic focus and the complexity of the resulting AF dynamics. Eight different episodes of focal AF were simulated in a 3D model of human atria based on Courtemanche atrial kinetics. Focal sources were introduced as a group of cells firing at a fixed rate. To create various AF dynamics, the episodes differed by the location of their focal source. Clinically relevant sites were selected in the left and right atrium. Their activity level was quantified by the number of propagating focal fronts originating from the source within a 10-s time window. The dynamic complexity was evaluated through the time course of the atrial equivalent dipole orientation. The 3rd eigenvalue (smallest) of the covariance matrix of the normalized dipole vector was used to characterize the spread of spatial distribution of the atrial dipole. Different degrees of dynamic complexity were observed in the 8 episodes, from broad wavelets/stable macroreentries to multiple wavelets/spirals. The number of focal fronts within 10 s ranged from 21 to 43 (30.9±7.2). The 3rd eigenvalue varied between 0.13 and 0.23 (0.19±0.03). The maximum of the dipole’s spatial distribution consistently pointed toward the location of the source when the dynamic complexity was low. A negative correlation (-0.93) was found between the 3rd eigenvalue and the number of focal fronts. An outlier was observed, which was characterized by the lowest dynamic complexity (3rd eigenvalue of 0.13) in spite of a non-extreme number of focal fronts (28) caused by a stable macroreentry masking the focal source. Analyzing the spatial distribution of the atrial dipole, possibly estimated from non-invasive data, could provide information about the activity level of atrial ectopic foci and the complexity of AF dynamics