Tunable Single-frequency operation of a diode-pumped Vertical-External Cavity Laser at the Caesium D2 line

International audienceWe report on a diode-pumped vertical external-cavity surface-emitting laser emitting around 852 nm for Cesium atomic clocks experiments. We have designed a 7-quantum-well semiconductor structure optimized for low laser threshold. An output power of 330 mW was achieved for 1.1 W of incident pump power. Furthermore a compact setup was built for low-power single-requency emission. We obtained an output power of 17 mW in a single longitudinal mode, exhibiting both broad (9 nm) and continuous (14 GHz) tunability around the Cesium D2 line. The laser frequency has been stabilized on an atomic transition with residual frequency fluctuations ~ 300 kHz. Through a beatnote experiment the -3 dB laser linewidth has been measured to < 500 kHz over 10 ms

COMPACT AND ROBUST SINGLE-FREQUENCY DIODE-PUMPED VECSEL AT THE CESIUM D2 LINE FOR ATOMIC CLOCKS

This work reports on an optically-pumped vertical external-cavity surface­emitting laser emitting around 852 nm dedicated to atomic physics experiments with cold Cs atoms. The design of the semiconductor active structure has been optimized to provide a low threshold. A low-power diode-pumped compact prototype has been developed with improved stability. With this setup, we obtained a 17-mW single frequency emission exhibiting large tunability around the Cesium D2 line. The laser linewidth has been measured to less than 500 kHz on a 10 ms time

Caractérisation et modélisation de lasers accordables à DBR émettant autour de 1.55[micromètres] (étude des bruits d'amplitude et de la largeur de raie)

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Bruit basse et moyenne fréquence des amplificateurs optiques distribués à effet Raman

L'objectif de cette thèse est d'évaluer les contributions en bruit associées aux différents éléments constituant un amplificateur Raman. par A cet effet, nous étudions le bruit associé à la source de pompage dépolarisée, en mettant plus particulièrement l'accent sur l'excès de bruit dû aux deux lasers multimodes qui composent cet étage. Après avoir développé un modèle qualitatif prenant en compte le caractère non-linéaire du gain optique des pompes employées, la source dépolarisée est caractérisée au premier et au second ordre élément par élément puis dans son ensemble. Nous avons alors pu constater qu'outre la contribution du bruit propre aux lasers de pompe, les sources d'alimentation électrique ainsi que divers composants optiques passifs apportaient une contribution non négligeable au bruit total du système de pompage complet. par Parallèlement, nous avons développé un modèle de l'amplificateur Raman à base d'équations de propagation prenant en compte le caractère multimode du système de pompage afin d'évaluer l'impact de l'étalement spectral de la source laser sur la courbe de gain de l'amplificateur. Un ensemble de caractérisations statiques est alors confronté aux résultats de simulation, permettant ainsi de valider le modèle. par Celui-ci est ensuite complété afin d'obtenir la réponse du système en émission spontanée amplifiée, considérée comme le bruit de fond de l'amplificateur, et confronté aux résultats expérimentaux. par Enfin, l'étude des fluctuations vues par le photodétecteur en sortie d'amplificateur est réalisée. La mise en place d'un banc de mesure de bruit d'amplitude permet de valider, par les résultats en bruit obtenus, le développement d'un modèle numérique décrivant efficacement les différents excès de bruit dus à divers phénomènes de battement vus par le photodétecteur en fin de ligne. L'impact de la largeur de raie de la source signal sur le bruit photodétecté ainsi que le report de bruit de pompage sur le signal de sortie sont enfin observésThe main goal of this thesis is to evaluate each Raman amplifier constitutive device noise source contribution in the overall amplifier noise. par We first study the depolarized pumping-system noise, focusing on both included multimode laser excess noise. A qualitative model including the non-linear optical gain contribution of the used pump lasers is developped. Then, static and noise measurements are performed on each depolarized optical source constitutive devices, followed by the overall pumping system study. We observe that, beyond pump lasers excess noise itself, electrical injection systems and passive fibered optical components significantly contribute to the overall system noise. par Moreover, a Raman-amplifier propagation-equation based model is developped. This model includes the pumping system multimode feature, and allows to apprehend the pumping system optical spectrum influence over the full Raman amplifier gain curve as a function of the wavelength. We then notice a good agreement between a set of first order characteristics and the simulation results. par This model is then expanded to predict the amplified spontaneous emission optical power - considered as the amplifier background noise - as a function of the wavelength. Simulation results are once more compared to measurements. par To conclude, the photodetected noise at the amplifier output is investigated. Some noise measurement set-ups were developped in order to corroborate a beat-induced excess-noise numerical model. In addition, the signal laser frequency fluctuations contribution and the pump noise to output signal correlation are observedMONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Pulsed single-mode Yb-doped fibre amplifier around 976 nm: numerical modelling and experimental study

International audienc

Pulsed single-mode Yb-doped fibre amplifier around 976 nm: numerical modelling and experimental study

International audienceDiffraction-limited sources around 976 nm are attractive to build sources around 488 nm, or to pump rare-earth-doped materials. Continuous wave efficient lasers have been obtained with single-mode fibres, in which we demonstrate pulsed laser diode amplification with gains higher than 30 dB. Theoretical studies can predict the amplifier performances versus the input signal characteristics and show the pulse width influence on excited state population. We used a classical timespace two-level model that we solved thanks to a Finite-Difference Time-Domain method. These simulations taking into account both time and space evolutions and a parasitic laser effect describe correctly the experimental results

1/f Noise in DBR-Tunable Lasers

International audienceTunable Lasers are key-components for Wavelength Division Multiplexing optical communication applications at 1.55μm. In this paper, we compare a rate equation model with measurements performed in order to study the Bragg section contribution in the 1/f-optical-beam noise power spectral density

Laser device with a beam carrying controlled orbital angular momentum

A laser device (250) for generating a helical-shaped optical wave and comprising: (i) a gain region (203) located between one first end defined by a first mirror (202) and a second end defined by an exit region, (ii) a second mirror (206) arranged so as to form with the first mirror (202) an optical cavity including the gain region (203) and a gap (207) between the exit region and the second mirror (206), (iii) means for pumping the gain region (203) so as to generate the optical wave, wherein the laser device (250) further comprises at least one means for shaping the light intensity and/or phase profiles of the optical wave and arranged for selecting at least one rotary-symmetrical transverse mode of the optical wave, said rotary-symmetrical transverse mode being chosen between those with a radial index equal to zero and with an azimuthal index being an integer with a module higher or equal to 1