48 research outputs found
Phase noise characterization of sub-hertz linewidth lasers via digital cross correlation
Phase noise or frequency noise is a key metrics to evaluate the short term
stability of a laser. This property is of a great interest for the applications
but delicate to characterize, especially for narrow line-width lasers. In this
letter, we demonstrate a digital cross correlation scheme to characterize the
absolute phase noise of sub-hertz line-width lasers. Three 1,542 nm
ultra-stable lasers are used in this approach. For each measurement two lasers
act as references to characterize a third one. Phase noise power spectral
density from 0.5 Hz to 0.8 MHz Fourier frequencies can be derived for each
laser by a mere change in the configuration of the lasers. This is the first
time showing the phase noise of sub-hertz line-width lasers with no reference
limitation. We also present an analysis of the laser phase noise performance.Comment: 4 pages, 5 figure
Nanophotonic soliton-based microwave synthesizers
Microwave photonic technologies, which upshift the carrier into the optical
domain to facilitate the generation and processing of ultrawide-band electronic
signals at vastly reduced fractional bandwidths, have the potential to achieve
superior performance compared to conventional electronics for targeted
functions. For microwave photonic applications such as filters, coherent
radars, subnoise detection, optical communications and low-noise microwave
generation, frequency combs are key building blocks. By virtue of soliton
microcombs, frequency combs can now be built using CMOS compatible photonic
integrated circuits, operated with low power and noise, and have already been
employed in system-level demonstrations. Yet, currently developed photonic
integrated microcombs all operate with repetition rates significantly beyond
those that conventional electronics can detect and process, compounding their
use in microwave photonics. Here we demonstrate integrated soliton microcombs
operating in two widely employed microwave bands, X- and K-band. These devices
can produce more than 300 comb lines within the 3-dB-bandwidth, and generate
microwave signals featuring phase noise levels below 105 dBc/Hz (140 dBc/Hz) at
10 kHz (1 MHz) offset frequency, comparable to modern electronic microwave
synthesizers. In addition, the soliton pulse stream can be injection-locked to
a microwave signal, enabling actuator-free repetition rate stabilization,
tuning and microwave spectral purification, at power levels compatible with
silicon-based lasers (<150 mW). Our results establish photonic integrated
soliton microcombs as viable integrated low-noise microwave synthesizers.
Further, the low repetition rates are critical for future dense WDM channel
generation schemes, and can significantly reduce the system complexity of
photonic integrated frequency synthesizers and atomic clocks
Running of Radiative Neutrino Masses: The Scotogenic Model
We study the renormalization group equations of Ma's scotogenic model, which
generates an active neutrino mass at 1-loop level. In addition to other
benefits, the main advantage of the mechanism exploited in this model is to
lead to a natural loop-suppression of the neutrino mass, and therefore to an
explanation for its smallness. However, since the structure of the neutrino
mass matrix is altered compared to the ordinary type I seesaw case, the
corresponding running is altered as well. We have derived the full set of
renormalization group equations for the scotogenic model which, to our
knowledge, had not been presented previously in the literature. This set of
equations reflects some interesting structural properties of the model, and it
is an illustrative example for how the running of neutrino parameters in
radiative models is modified compared to models with tree-level mass
generation. We also study a simplified numerical example to illustrate some
general tendencies of the running. Interestingly, the structure of the RGEs can
be exploited such that a bimaximal leptonic mixing pattern at the high-energy
scale is translated into a valid mixing pattern at low energies, featuring a
large value of \theta_{13}. This suggests very interesting connections to
flavour symmetries.Comment: 35 pages, 10 figures, 2 table
Optical frequency comb based ultralow phase noise photonic microwave generation
Les meilleurs oscillateurs dans le domaine micro-onde sont souvent des systĂšmes encombrants ou requĂ©rant une maintenance fastidieuse ce qui freine leur utilisation pour des applications mobiles ou dans des environnements aux conditions difficiles. L'avĂšnement des peignes de frĂ©quences optiques, rĂ©compensĂ©s par un prix Nobel en 2005, a ouvert de nouvelles perspectives en permettant un transfert des qualitĂ©s inĂ©galĂ©es des sources optiques vers le domaine micro-onde. Dans la technique utilisĂ©e au LNE-SYRTE, la division de frĂ©quence optique, un signal micro-onde peut ĂȘtre extrait d'un laser ultra-stable dans l'infrarouge proche par photodĂ©tection, ce qui s'accompagne d'une rĂ©duction du bruit Ă©gale au carrĂ© du rapport des frĂ©quences initiale et finale, soit plus de 8 ordres de grandeurs. Ce bĂ©nĂ©fice est cependant rĂ©duit par diffĂ©rents processus collatĂ©raux qui augmentent le niveau de bruit final. Le travail dĂ©crit dans cette thĂšse est la gĂ©nĂ©ration et la caractĂ©risation du signal micro-onde le plus pur gĂ©nĂ©rĂ© jusqu'Ă prĂ©sent. Les diffĂ©rents processus introduisant un excĂšs de bruit lors de la conversion opto-Ă©lĂ©ctronique sont Ă©tudiĂ©s et en partie surmontĂ©s. En particulier la conversion du bruit d'amplitude du laser femtoseconde vers la porteuse micro-onde est analysĂ©e en dĂ©tail et son effet grandement rĂ©duit. Les rĂ©sultats obtenus laissent penser que les techniques optiques de gĂ©nĂ©ration de micro-ondes vont bouleverser l'Ă©tat de l'art. Les niveaux de puretĂ© atteints et les techniques dĂ©veloppĂ©es peuvent bĂ©nĂ©ficier un vaste Ă©ventail de domaines comme les radars mobiles, la mĂ©trologie temps-frĂ©quence ou les prochaines gĂ©nĂ©rations de tĂ©lĂ©communications Ă ultra-haut dĂ©bit.State-of-the-art microwave oscillators are typically bulky systems requiring tedious maintenance which is hindering their use in mobile applications or in demanding environments. The invention of the optical frequency combs, which was awarded a Nobel prize in 2005, was a game-changer as it enabled a high-fidelity transfer of the unrivalled properties of optical oscillators to the microwave domain. In the technique used at SYRTE, the optical frequency division, a microwave signal can be extracted from a near-infrared ultra-stable laser using photodetection. The transfer is accompanied by a reduction of phase noise equal to the microwave-to-optical frequency ratio squared, i.e. more than eight order of magnitudes. This benefit is however reduced by several processes producing excess noise during the transfer. The work described in this thesis is the generation of the lowest phase noise microwave signal ever reported. The different processes inducing excess noise are analyzed and, in part, overcome. Specifically, the conversion of the femtosecond laser intensity noise to the microwave phase noise is studied thoroughly and its effect significantly reduced. The results augur that the optical approaches in microwave generation are on the verge to disrupt the state-of-the-art. The noise levels demonstrated and the techniques developed can benefit a large range of applications such as mobile radars, time and frequency metrology or the next generation of ultrafast telecommunication networks
Génération photonique de signaux micro-ondes trÚs bas bruit de phase par peignes de fréquences optiques
State-of-the-art microwave oscillators are typically bulky systems requiring tedious maintenance which is hindering their use in mobile applications or in demanding environments. The invention of the optical frequency combs, which was awarded a Nobel prize in 2005, was a game-changer as it enabled a high-fidelity transfer of the unrivalled properties of optical oscillators to the microwave domain. In the technique used at SYRTE, the optical frequency division, a microwave signal can be extracted from a near-infrared ultra-stable laser using photodetection. The transfer is accompanied by a reduction of phase noise equal to the microwave-to-optical frequency ratio squared, i.e. more than eight order of magnitudes. This benefit is however reduced by several processes producing excess noise during the transfer. The work described in this thesis is the generation of the lowest phase noise microwave signal ever reported. The different processes inducing excess noise are analyzed and, in part, overcome. Specifically, the conversion of the femtosecond laser intensity noise to the microwave phase noise is studied thoroughly and its effect significantly reduced. The results augur that the optical approaches in microwave generation are on the verge to disrupt the state-of-the-art. The noise levels demonstrated and the techniques developed can benefit a large range of applications such as mobile radars, time and frequency metrology or the next generation of ultrafast telecommunication networks.Les meilleurs oscillateurs dans le domaine micro-onde sont souvent des systĂšmes encombrants ou requĂ©rant une maintenance fastidieuse ce qui freine leur utilisation pour des applications mobiles ou dans des environnements aux conditions difficiles. L'avĂšnement des peignes de frĂ©quences optiques, rĂ©compensĂ©s par un prix Nobel en 2005, a ouvert de nouvelles perspectives en permettant un transfert des qualitĂ©s inĂ©galĂ©es des sources optiques vers le domaine micro-onde. Dans la technique utilisĂ©e au LNE-SYRTE, la division de frĂ©quence optique, un signal micro-onde peut ĂȘtre extrait d'un laser ultra-stable dans l'infrarouge proche par photodĂ©tection, ce qui s'accompagne d'une rĂ©duction du bruit Ă©gale au carrĂ© du rapport des frĂ©quences initiale et finale, soit plus de 8 ordres de grandeurs. Ce bĂ©nĂ©fice est cependant rĂ©duit par diffĂ©rents processus collatĂ©raux qui augmentent le niveau de bruit final. Le travail dĂ©crit dans cette thĂšse est la gĂ©nĂ©ration et la caractĂ©risation du signal micro-onde le plus pur gĂ©nĂ©rĂ© jusqu'Ă prĂ©sent. Les diffĂ©rents processus introduisant un excĂšs de bruit lors de la conversion opto-Ă©lĂ©ctronique sont Ă©tudiĂ©s et en partie surmontĂ©s. En particulier la conversion du bruit d'amplitude du laser femtoseconde vers la porteuse micro-onde est analysĂ©e en dĂ©tail et son effet grandement rĂ©duit. Les rĂ©sultats obtenus laissent penser que les techniques optiques de gĂ©nĂ©ration de micro-ondes vont bouleverser l'Ă©tat de l'art. Les niveaux de puretĂ© atteints et les techniques dĂ©veloppĂ©es peuvent bĂ©nĂ©ficier un vaste Ă©ventail de domaines comme les radars mobiles, la mĂ©trologie temps-frĂ©quence ou les prochaines gĂ©nĂ©rations de tĂ©lĂ©communications Ă ultra-haut dĂ©bit
Multistability-Enabled Complex Soliton Dynamics in a Bichromatically Driven Optical Microresonator
We enter a bichromatically-pumped multistability regime in a microresonator to observe the emergence of complex dynamics of dissipative Kerr soliton interactions, including short-range soliton binding and periodic soliton collision. (C) 2020 The Author(s
Formation and Collision of Multistability-Enabled Composite Dissipative Kerr Solitons
Multistability in Kerr resonators which are driven by continuous or modulated optical waves gives rise to the superposition of distinct nonlinear states, yielding a unique platform for studying complex soliton dynamics. Here, by pumping a crystalline microresonator with two lasers that are frequency detuned from each other by one or multiple cavity free spectral ranges, we go beyond the traditional bichromatic pumping framework and enter an unexplored multistability regime that allows observing novel dynamics including composite solitons and successive soliton collisions. We generate complex frequency comb patterns, observing the velocity mismatch between the solitons and the dual-pumping-induced lattice traps and showing the synchronization of the repetition rates of constituent distinct solitons under the influence of index-barrier-induced intersoliton repulsion. We also demonstrate soliton collisions and observe transient soliton response with spectral analysis and ultrafast imaging, highlighting the eigenfrequency of dissipative soliton dynamics that coincides the "soliton (S) resonance." Furthermore, we exploit the higher-order dispersion effect to manipulate the intrinsic group velocity mismatch between distinct solitons and demonstrate reversible switching between the composite soliton state and the soliton collisional state. Our findings bring to light the rich physics of the Kerr multistability and may equally be useful in microcomb-based spectroscopy and metrology