Absorción saturable de Grafeno para Láser mode-locked

Problem: Since the first successful exfoliation of monolayer graphene in 2004 [1] (for which the Nobel prize was awarded in 2008), research interest in this 2D material has surged exponentially. Graphene, consisting of a twodimensional layer of carbon atoms arranged in a hexagonal lattice, behaves distinctly different from regular 3D materials. Not only does graphene have unseen mechanical properties, (one layer of graphene can carry the weight of a cat!) the material also has extraordinary electrical and optical properties, mainly originating from its linear and gapless band structure [2] [3]. A graphene monolayer absorbs 2.3% of the light passing through, in absolute numbers this is small, graphene could thus be an excellent transparent contact. However considering the monolayer thickness, 2.3% is very large and indicates the strong lightmatter interaction, which can be exploited for light detection [4] or modulation [5]. Due to this strong interaction, it has been observed that once optical intensity reaches a certain threshold saturable absorption takes place: band filling at these high optical intensities causes the absorption of graphene to decrease. This phenomenon can be exploited for the modelocking of lasers, a technique used to produce extremely short (ps to even fs, 10^12 of a second!) and coherent light pulses. Graphene has already been successfully used for modelocking fiber lasers, however it can also be used to make chip scale femtosecond lasers by depositing on integrated silicon waveguides. Researchers at UGent have, in close cooperation with imec, been working on the integration of graphene with photonic structures on a SilicononInsulator (SOI) waveguide. On these hybrid grapheneSOI structures, we recently experimentally demonstrated electrically tunable saturable absorption [6]. This principle can potentially be used for realizing integrated spontaneously modelocked lasers with an electrically tunable pulse duration, making the dream of a ultrashort chip scale femtosecond laser almost a reality. Objective: The proposed work extrapolates on the saturable absorption work presented above. The aim will be to further characterize the saturable absorption in hybrid grapheme-SOI or grapheme-SiN waveguides, and to explore the feasibility of mode-locking a fiber laser using graphene, possibly with tunable properties. As the dynamics of a mode-locked laser are highly dependent of the characteristics of the cavity (dispersion, nonlinear effects ¿), as well as the saturable absorber a large part of the project will consist of simulation, design and development. Depending on the progress of the project, the student will have the freedom to elaborate on the work according to his/her own interests. Possible options contain: developing a better understanding of the carrier dynamics in graphene, thoroughly modelling the behavior of a mode-locked laser, fabrication and design of new hybrid SOI-graphene structures, mode-locking of semiconductor lasers using graphene etc.Problema: Desde la primera exfoliación exitosa del grafeno monocapa en 2004 [1] (para la cual el Premio Nobel fue otorgado en 2008), el interés de la investigación en este material 2D ha aumentado exponencialmente. El grafeno, que consiste en una capa de átomos de carbono dispuestos en una red hexagonal, que se comporta claramente diferente de los materiales 3D regulares. El grafeno no sólo tiene propiedades mecánicas insólitas (una capa de grafeno puede soportar el peso de un gato), sino que también tiene extraordinarias propiedades eléctricas y ópticas, originadas principalmente por una estructura con banda lineal y sin ¿gap¿ [2] [3]. Una monocapa de grafeno absorbe el 2,3% de la luz que pasa, en cifras absolutas esto es pequeño, el grafeno podría ser un excelente material transparente. Sin embargo, teniendo en cuenta el grosor de la monocapa, el 2,3% es muy grande, lo que indica una fuerte interacción luz-materia que puede ser explotada para la detección de luz [4] o la modulación [5]. Debido a esta fuerte interacción, se ha observado que una vez que la intensidad óptica alcanza un cierto umbral, tiene lugar la absorción saturable. El llenado de banda a estas altas intensidades ópticas hace que disminuya la absorción de grafeno. Este fenómeno puede ser explotado para láseres con bloqueo de modo, una técnica utilizada para producir pulsos extremadamente cortos (ps a incluso fs) y de luz coherentes. El grafeno ya ha sido utilizado con éxito para el bloqueo de modos de láseres en fibra, sin embargo también puede ser usado para hacer láseres de femtosegundos de escala de chip depositando sobre guías de onda integradas en silicio. Los investigadores de UGent han trabajado en estrecha cooperación con IMEC en la integración del grafeno con estructuras fotónicas de guías en Silicio sobre aislante (SOI). Sobre estas estructuras híbridas de grafeno-SOI, recientemente hemos demostrado experimentalmente una absorción saturable que se puede regular eléctricamente [6]. Este principio puede utilizarse potencialmente para la realización de láseres integrados con bloqueo de modos espontáneo, que genera un pulso de duración sintonizable eléctricamente. Objetivo: El trabajo propuesto emplea el efecto de absorción saturable del grafeno propuesto, con el objetivo de caracterizar la absorción saturable en guías de onda híbridas grafeno-SOI o grafeno-SiN y para explorar la viabilidad de un láser de fibra con bloqueo de modos usando grafeno, posiblemente con propiedades sintonizables. Como la dinámica de láser con bloque de modos es altamente dependiente de las características de la cavidad (dispersión, los efectos no lineales, ... ), así como de la saturación del absorbedor, una gran parte del proyecto consistirá en su simulación, diseño y desarrollo. En función de la evolución del proyecto, el estudiante tendrá la libertad para elaborar más detalles sobre el trabajo en función de sus propios intereses. Las posibles opciones incluyen el desarrollo de una mejor comprensión de la dinámica de cargas en el grafeno, modelado a fondo el comportamiento de un láser con bloqueo de modos, la fabricación y diseño de nuevas estructuras híbridas SOI-grafeno, bloqueo de modos en láser de semiconductor empleando grafeno, etc.Montesinos Ballester, M. (2017). Absorción saturable de Grafeno para Láser mode-locked. http://hdl.handle.net/10251/91809TFG

Broadband Mid-IR On-Chip Fourier-Transform Spectrometer

International audienceWe present a new FTS approach that harnesses both spatial heterodyning and thermo-optical path tuning to overcome the resolution-bandwidth tradeoff in conventional counterparts. We experimentally demonstrate a mid-infrared SiGe FTS, with a resolution exceeding 15 cm-1 in a wide bandwidth of 603 cm-1

On-chip fourier-transform spectrometer based on spatial heterodyning tuned by thermo- optic effect

International audienceMiniaturized optical spectrometers providing broadband operation and fine resolution have an immense potential for applications in remote sensing, non-invasive medical diagnostics and astronomy. Indeed, optical spectrometers working in the mid-infrared spectral range have garnered a great interest for their singular capability to monitor the main absorption fingerprints of a wide range of chemical and biological substances. Fourier-transform spectrometers (FTS) are a particularly interesting solution for the on-chip integration due to their superior robustness against fabrication imperfections. However, the performance of current on-chip FTS implementations is limited by tradeoffs in bandwidth and resolution. Here, we propose a new FTS approach that gathers the advantages of spatial heterodyning and optical path tuning by thermo-optic effect to overcome this tradeoff. The high resolution is provided by spatial multiplexing among different interferometers with increasing imbalance length, while the broadband operation is enabled by fine tuning of the optical path delay in each interferometer harnessing the thermo-optic effect. Capitalizing on this concept, we experimentally demonstrate a mid-infrared SiGe FTS, with a resolution better than 15 cm−1 and a bandwidth of 603 cm−1 near 7.7 μm wavelength with a 10 MZI array. This is a resolution comparable to state-of-the-art on-chip mid-infrared spectrometers with a 4-fold bandwidth increase with a footprint divided by a factor two

Optical modulation in Ge-rich SiGe waveguides in the mid-infrared wavelength range up to 11 µm

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Dual-band fiber-chip grating coupler in a 300 mm silicon-on-insulator platform and 193 nm deep-UV lithography

4 pags., 5 figs., 1 tab.Surface grating couplers are fundamental building blocks for coupling the light between optical fibers and integrated photonic devices. However, the operational bandwidth of conventional grating couplers is intrinsically limited by their wavelength-dependent radiation angle. The few dual-band grating couplers that have been experimentally demonstrated exhibit low coupling efficiencies and rely on complex fabrication processes. Here we demonstrate for the first time, to the best of our knowledge, the realization of an efficient dual-band grating coupler fabricated using 193 nm deep-ultraviolet lithography for 10 Gbit symmetric passive optical networks. The footprint of the device is 17 × 10 µm. We measured coupling efficiencies of −4.9 and −5.2 dB with a 3-dB bandwidth of 27 and 56 nm at the wavelengths of 1270 and 1577 nm, corresponding to the upstream and downstream channels, respectively.Spanish Ministry of Science, Innovation and Universities (MICINN) (RTI2018-097957-B-C33, TEC2015-71127-C2-1-R with FPI Scholarship BES-2016-077798); Community of Madrid - FEDER funds (S2018/NMT-4326); Horizon 2020 Research and Innovation Program (Marie Sklodowska-Curie 734331); H2020 European Research Council (ERC POPSTAR 647342); European Commission (H2020- ICT-26127-2017 COSMICC 688516); French Industry Ministry (Nano2022 project under IPCEI program); Agence Nationale de la Recherche (ANR-MIRSPEC-17-CE09-0041)

1 GHz electro-optical silicon-germanium modulator in the 5-9 µm wavelength range

: Spectroscopy in the mid-infrared (mid-IR) wavelength range is a key technique to detect and identify chemical and biological substances. In this context, the development of integrated optics systems paves the way for the realization of compact and cost-effective sensing systems. Among the required devices, an integrated electro-optical modulator (EOM) is a key element for advanced sensing circuits exploiting dual comb spectroscopy. In this paper, we have experimentally demonstrated an integrated EOM operating in a wide wavelength range, i.e. from 5 to 9 µm at radio frequency (RF) as high as 1 GHz. The modulator exploits the variation of free carrier absorption in a Schottky diode embedded in a graded silicon germanium (SiGe) photonic waveguide

Room Temperature‐Integrated Photodetector between 5 μm and 8 μm Wavelength

Mid-infrared (mid-IR) optics has a great importance for a large number of applications in sensing, imaging, or even telecommunication. However, high-speed and room-temperature-integrated photodetector (PD) operating in a wide spectrum of the mid-IR is a critical device that is currently missing for the development of compact and efficient spectroscopic systems exploiting synchronous detection. Herein, a waveguide-integrated PD based on a Schottky diode embedded in a graded silicon germanium waveguide is demonstrated. Photodetection is obtained in a wide spectral range from 5 to 8 μm wavelength, with responsivity reaching up to 0.1 mA W−1. Photodetection performed in pulsed regime with laser pulse width between 50 and 200 ns indicates an operation beyond 20 MHz. Interestingly, the achieved performances indicate that this device is already suitable for on-chip signal monitoring, while further improvement can pave the way toward advanced compact and fully integrated spectroscopic systems operating in long-wave infrared regions

Ahora / Ara

La cinquena edició del microrelatari per l’eradicació de la violència contra les dones de l’Institut Universitari d’Estudis Feministes i de Gènere «Purificación Escribano» de la Universitat Jaume I vol ser una declaració d’esperança. Aquest és el moment en el qual les dones (i els homes) hem de fer un pas endavant i eliminar la violència sistèmica contra les dones. Ara és el moment de denunciar el masclisme i els micromasclismes començant a construir una societat més igualitària. Cadascun dels relats del llibre és una denúncia i una declaració que ens encamina cap a un món millor

Fabricación Niobato de Litio

El objetivo de este trabajo es el desarrollo del proceso de fabricación de guías a canal de bajas pérdidas en niobato de litio para dispositivos ópticos integrados mediante el método de Annealed Proton ExChange. Además se desarrollará un montaje de caracterización propio basado en la técnica de Prism Coupling, el cual será controlado por un software en Python. Este trabajo se llevará a cabo en la empresa DAS Photonics, S.L.Montesinos Ballester, M. (2015). Fabricación Niobato de Litio. http://hdl.handle.net/10251/79524.Archivo delegad