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Concept

Supercontinuum

Résumé

Un supercontinuum est un phénomène d'optique non linéaire qui correspond à un élargissement de spectre très prononcé à partir d'une onde électromagnétique. Typiquement, on peut créer un supercontinuum en dirigeant un faisceau laser sur un matériau non linéaire : les effets non linéaires élargissent le spectre du faisceau de départ au cours de sa traversée dans le matériau. Historique Les premières générations de supercontinuum ont eu lieu en 1970 dans des matériaux massifs, à l’aide de lasers impulsionnels. En effet, l’exploitation d’effets non linéaires nécessitait plus d’énergie que n’en pouvaient fournir les lasers continus. L’utilisation d’impulsions plus courtes, en augmentant la puissance crête disponible, permettait de créer plus de longueurs d’onde. Si des élargissements spectraux notables ont été observés dès 1963, l’expérience d’Alfano et Shapiro en 1970 crée un spectre dix fois plus large : des impulsions picosecondes (de l'ordre de 10-12 s) de 5 mJ à 530

Source officielle

https://fr.wikipedia.org/wiki/Supercontinuum

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Publications associées (25)

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Personnes associées (10)

Personnes associées

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Unités associées (4)

Unités associées

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Concepts associés (3)

Concepts associés

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Cours associés (3)

Presentation of the different sources of optical nonlinearities in an optical fibre

This course provides the fundamental knowledge and theoretical tools needed to treat nonlinear optical interactions, covering both classical and quantum theory of nonlinear optics. It presents applications such as nonclassical state generation and coherent frequency conversion.

This course proposes a selection of different facets of modern optics and photonics.

Cours associés

Chargement

Séances de cours associées (7)

Séances de cours associées

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The middle-infrared (mid-IR) spectral range hosts the most intense roto-vibrational absorption lines of many important molecules. Particularly, mid-IR spectroscopy constitutes a unique tool for identifying and quantifying molecular species through their mid-IR spectral fingerprints. Exploiting efficient ways to access the mid-IR is of supreme importance for spectroscopic applications and environmental monitoring. Supercontinuum (SC) sources have been a common way to access this spectral region, using femtosecond fiber lasers and optical fibers as the broadening medium. However, emphasis has recently shifted towards compact SC sources based on integrated platforms. Among the different materials studied for the integration of SC, stoichiometric silicon nitride,

\mathrm{Si_3N_4}

, is one of the most promising. With a transparency window extending from the visible to mid-IR, CMOS compatibility, and a mature fabrication technology combined with flexibility in design,

\mathrm{Si_3N_4}

waveguides represent an attractive solution for on-chip SC generation. The thesis's main aim is to develop a tunable mid-IR SC source based on

\mathrm{Si_3N_4}

waveguides that can efficiently reach the spectral region between 3 - 4

\mathrm{\mu m}

, enabling mid-IR spectroscopy experiments. Towards this goal, nonlinear SC dynamics based on anomalous and all-normal-dispersion (ANDi) pumping regimes are explored in different waveguide designs. In the first part of the thesis, the development of a tunable mid-IR source is presented. Starting from a tunable turn-key femtosecond 2

\mathrm{\mu m}

fiber laser located in the anomalous dispersion regime of cladded waveguides, mid-IR soliton-induced dispersive waves (DWs) are generated. A synergy of proper waveguide geometry and pump positioning enables favorable dispersion profiles towards the mid-IR while suppressing the generation into the visible. Moreover, by switching to a waveguide with different dimensions, the DW can be tuned between the entire 3 - 4

\mathrm{\mu m}

spectral region, reaching record efficiencies up to 35%. The milliwatt output powers of the mid-IR DWs guarantee their utilization in gas spectroscopy. In the second part, the application of the on-chip generated mid-IR source in direct absorption spectroscopy is demonstrated for the first time. The most efficient DW generated at 3.0

\mathrm{\mu m}

is used to detect acetylene in a proof-of-principle spectroscopic experiment. However, due to DWs' limited bandwidth, parallel gas detection is not possible. By leveraging a waveguide that generates a DW centered at 3.5

\mathrm{\mu m}

and fine-tuning the pump wavelength, a larger bandwidth of the DW source is achieved, enabling simultaneous detection of multiple gas-phase species. Using the broad mid-IR DW from a single

\mathrm{Si_3N_4}

waveguide, detection of acetylene, methane, and ethane is successfully demonstrated, with hundreds of ppm detection limit. Finally, a polarization-sensitive SC source based on an un-cladded

\mathrm{Si_3N_4}

waveguide is studied. The waveguide is engineered to yield ANDi at 2

\mathrm{\mu m}

for the TM mode and anomalous dispersion regime for TE mode excitation. A flat and highly coherent ANDi SC or an octave-spanning soliton fission-driven SC source can be selectively generated by simply switching between the pump's polarization states. As a result, the SC has the potential for versatile applications, from broadband on-chip sensing to pulse compression.

EPFL2021

Chargement

Extreme polarization-dependent supercontinuum generation in an uncladded silicon nitride waveguide

Caroline Gaëlle Amiot, Camille Sophie Brès, Eirini Tagkoudi

We experimentally demonstrate the generation of a short-wave infrared supercontinuum in an uncladded silicon nitride (Si3N4) waveguide with extreme polarization sensitivity at the pumping wavelength of 2.1 µm. The air-clad waveguide is specifically designed to yield anomalous dispersion regime for transverse electric (TE) mode excitation and all-normal-dispersion (ANDi) at near-infrared wavelengths for the transverse magnetic (TM) mode. Dispersion engineering of the polarization modes allows for switching via simple adjustment of the input polarization state from an octave-spanning soliton fission-driven supercontinuum with fine spectral structure to a flat and smooth ANDi supercontinuum dominated by a self-phase modulation mechanism (SPM). Such a polarization sensitive supercontinuum source offers versatile applications such as broadband on-chip sensing to pulse compression and few-cycle pulse generation. Our experimental results are in very good agreement with numerical simulations.

2021

Chargement

1.3 Octave Supercontinuum Generation in Highly Ge-doped Photonic Crystal Fiber

Deniz Aydin, Camille Sophie Brès, Thibault Emmanuel North

We present a flat, visible 1.3-octave supercontinuum generated in a GeO2-doped photonic crystal fiber owing to an overlap of the modulation instability and Raman gain regions resulting in efficient energy transfer to new frequency components

Optical Society of America2016

Chargement

\mathrm{Si_3N_4}

, is one of the most promising. With a transparency window extending from the visible to mid-IR, CMOS compatibility, and a mature fabrication technology combined with flexibility in design,

\mathrm{Si_3N_4}

waveguides represent an attractive solution for on-chip SC generation. The thesis's main aim is to develop a tunable mid-IR SC source based on

\mathrm{Si_3N_4}

waveguides that can efficiently reach the spectral region between 3 - 4

\mathrm{\mu m}

\mathrm{\mu m}

\mathrm{\mu m}

\mathrm{\mu m}

\mathrm{\mu m}

and fine-tuning the pump wavelength, a larger bandwidth of the DW source is achieved, enabling simultaneous detection of multiple gas-phase species. Using the broad mid-IR DW from a single

\mathrm{Si_3N_4}

waveguide, detection of acetylene, methane, and ethane is successfully demonstrated, with hundreds of ppm detection limit. Finally, a polarization-sensitive SC source based on an un-cladded

\mathrm{Si_3N_4}

waveguide is studied. The waveguide is engineered to yield ANDi at 2

\mathrm{\mu m}

EPFL2021