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LaRochelle, Sophie

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LaRochelle

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Sophie

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Université Laval. Département de génie électrique et de génie informatique

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ncf10263799

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Résultats de recherche

Voici les éléments 1 - 10 sur 29
  • PublicationAccès libre
    Templated dewetting for self-assembled ultra low-loss chalcogenide integrated photonics
    (OSA Pub., 2021-10-11) Jean, Philippe; LaRochelle, Sophie; Shi, Wei; Messaddeq, Younès; Douaud, Alexandre
    Integrated photonics is of growing interest but relies on complex fabrication methods that have yet to match optical losses of bulkier platforms like optical fibers or whispering gallery mode resonators. Spontaneous matter reorganization phenomenon (e.g. dewetting) in thin-films provides a way for self-assembled structures with atomic scale surface rugosity, potentially alleviating the problems of roughness scattering loss and fabrication complexity. In this article, we study solid-state dewetting in chalcogenide glass thin-films and demonstrate its applicability to the fabrication of high-quality integrated photonics components. Optimal dewetting parameters are derived from a comprehensive experimental study of thin-film properties under high temperature rapid annealing. Atomic scale surface roughness are obtained using dewetting, with RMS values as low as Rq = 0.189 nm. Several integrated photonics components are fabricated using the method and characterized. We show that the use of pre-patterned templates leads to organized, reproducible patterns with large-scale uniformity and demonstrate the record high quality-factor of 4.7 × 106 in compact (R = 50 µm) microdisks, corresponding to 0.08 dB⋅cm−1 waveguide propagation loss. The integrated devices are directly fabricated on standard silicon-on-insulator dice using the micro-trench filling technique and coupled to silicon waveguides, making them readily deployable with existing silicon devices and systems.
  • PublicationAccès libre
    Ultrafast pulse-amplitude modulation with a femtojoule silicon photonic modulator
    (Optical Society of America, 2016-06-09) Dubé-Demers, Raphaël; LaRochelle, Sophie; Shi, Wei
    Ultrahigh-speed optical interconnects are essential to future cloud computing. Further increase in optical transmission speed has been hindered by power consumption and limited bandwidth resources, for which integrated optical transceivers using advanced modulation formats, such as pulse-amplitude modulation (PAM), are a promising solution. We report 80 Gb/s PAM operation of a silicon microring modulator (MRM) with an ultralow power consumption below 7 fJ/bit. We also report the first demonstration of PAM-8 modulation of MRMs in the Gb/s order, achieving error-free capability at 45 Gb/s, using 1 fJ/bit. To the best of our knowledge, these results feature the lowest power consumption, per transmitted bit, ever demonstrated at such high data rates. We further demonstrate PAM data transmission up to 64 Gb/s over 5 km. Simultaneous achievement of ultrafast modulation and ultralow power consumption is a critical step toward next-generation optical interconnects.
  • PublicationAccès libre
    High-efficiency silicon photonic modulator using coupled Bragg grating resonators
    (Institute of Electrical and Electronics Engineers, 2019-02-05) Jafari, Omid; Sepehrian, Hassan; LaRochelle, Sophie; Shi, Wei
    We propose a novel design of a silicon photonic modulator that has a high modulation efficiency and that is tolerant to temperature variations. A series of phase-shifted Bragg gratings are placed in each arm of a Mach-Zehnder interferometer in order to provide enhanced phase modulation. The slow light effect in these ultra-compact coupled resonators improves phase modulation efficiency compared to conventional silicon phase shifters. These Bragg grating cavities are designed such that the optical bandwidth is increased compared to other coupled resonators such as micro-rings. This improved bandwidth reduces the temperature sensitivity of the devices. We present in detail how to optimize these modulators considering properties such as modulation efficiency (Vπ×L), optical modulation amplitude (OMA), and optical bandwidth (𝛥λBW); the latter property determining the operating temperature range (𝛥T). As examples, we present two designs that meet different target specifications for short-reach or long-haul applications. We further provide a model, based on coupled mode theory, to investigate the dynamic response of the proposed modulators. A large signal analysis is performed using finite difference time domain (FDTD) in order to simulate on/off keying (OOK) modulation and eye diagrams up to 110 Gb/s.
  • PublicationAccès libre
    Analytical modeling of silicon microring and microdisk modulators with electrical and optical dynamics
    (Institute of Electrical and Electronics Engineers, 2015-07-29) Bois, Antoine; Dubé-Demers, Raphaël; St-Yves, Jonathan; Zhong, Qiuhang; LaRochelle, Sophie; Caverley, Michael; Shi, Wei; Wang, Yun; Chrostowski, Lukas; Plant, David V.
    We propose an analytical time-domain model for microring and microdisk modulators, which considers both their electrical and optical properties. Theory of the dynamics of microring/microdisk is discussed, and general solutions to the transfer matrix representation are presented. Both static and dynamic predictions from the model are compared to measurement results to demonstrate the accuracy of our model. Static predictions and measurements are presented for power and phase responses, whereas dynamic predictions and measurements are presented for small-signal and large-signal operations. The model verifies that the chirping and modulation bandwidth of the modulators depend on the detuning state. Finally, the accuracy and scalability of several techniques employed in the model are discussed.
  • PublicationAccès libre
    Mach-Zehnder silicon photonic modulator assisted by phase-shifted Bragg gratings
    (Institute of Electrical and Electronics Engineers, 2020-03-05) Jafari, Omid; LaRochelle, Sophie; Shi, Wei
    We experimentally demonstrate a silicon photonic Mach-Zehnder modulator (MZM) assisted by phase-shifted Bragg gratings. Coupled resonators are inserted in the Bragg grating structure to significantly enhance the phase modulation efficiency, while maintaining a wide optical bandwidth compared to other resonator-based modulators. Fabricated using a CMOS-compatible foundry process, the device achieved a small-signal Vπ× L of 0.18 V.cm, which is seven times lower than a conventional silicon MZM fabricated with the same process. The device has a compact footprint, with a length of only 162 μm , and shows a modulation bandwidth of 28 GHz at a reverse bias of 1 V. Non-return-to-zero modulation is demonstrated at 30 Gb/s with a bit-error-rate (BER) below the 7%-overhead forward error correction (FEC) threshold over a bandwidth of 3.5 nm. This bandwidth should translate into an operating temperature range greater than 40 0 C.
  • PublicationAccès libre
    Tunable slow-light in silicon photonics subwavelength grating waveguides
    (IEEE, 2019-12-09) Jean, Philippe; Gervais, Antoine; LaRochelle, Sophie; Shi, Wei
    Slow-light is experimentally demonstrated in subwavelength grating waveguides integrated on a silicon photonic chip. At the band-edge, a group index up to 30 is measured. We show that the band-edge wavelength varies linearly with the subwavelength grating period and can be shifted by thermal tuning.
  • PublicationAccès libre
    Silicon photonic modulator loaded by NPN junctions
    (Institute of electrical and electronics engineers, 2020-08-17) Jafari, Omid; LaRochelle, Sophie; Shi, Wei
    We experimentally demonstrate an asymmetric Bragg grating modulator with a phase shifter length of 240 μm, loaded by p-n junctions. The mode conversion by the asymmetric sidewall grating allows us to operate a Bragg modulator in reflection without a circulator. Simulation results show that there is room for improving the modulator efficiency and footprint by exploiting NPN junctions instead of p-n junctions.
  • PublicationAccès libre
    Sulfur-rich chalcogenide claddings for athermal and high-Q silicon microring resonators
    (OSA Pub., 2021-02-26) Jean, Philippe; LaRochelle, Sophie; Thibault, Tristan; Shi, Wei; Messaddeq, Younès; Douaud, Alexandre
    Heterogeneous integration of materials with a negative thermo-optic coefficient is a simple and efficient way to compensate the strong detrimental thermal dependence of silicon-on-insulator devices. Yet, the list of materials that are both amenable for photonics fabrication and exhibit a negative TOC is very short and often requires sacrificing loss performance. In this work, we demonstrate that As20S80 chalcogenide glass thin-films can be used to compensate silicon thermal effects in microring resonators while retaining excellent loss figures. We present an experimental characterization of the glass thin-film and of fabricated hybrid microring resonators at telecommunication wavelengths. Nearly athermal operation is demonstrated for the TM polarization with an absolute minimum measured resonance shift of 5.25 pm K−1, corresponding to a waveguide effective index thermal dependence of 4.28×10-6 RIU/K. We show that the thermal dependence can be controlled by changing the cladding thickness and a negative thermal dependence is obtained for the TM polarization. All configurations exhibit unprecedented low loss figures with a maximum measured intrinsic quality factor exceeding 3.9 × 105, corresponding to waveguide propagation loss of 1.37 dB cm−1. A value of−4.75(75)×10-5 RIU/K is measured for the thermo-optic coefficient of As20S80 thin-films.
  • PublicationAccès libre
    Silicon photonic modulator based on coupled Bragg grating resonators used as phase shifters
    (Optical Society of America, 2018-03-11) Jafari, Omid; Sepehrian, Hassan; LaRochelle, Sophie; Shi, Wei
    Bragg gratings with phase-shifts are inserted in a Mach-Zehnder modulator to enhance phase modulation, reduce device length and improve efficiency (Vπ×L=0.28 Vcm). Simulations show 3 nm optical bandwidth corresponding to 50 K operating temperature range.
  • PublicationAccès libre
    Integrated flexible-grid WDM transmitter using an optical frequency comb in microring modulators
    (OSA Publishing, 2018-04-01) Lin, Jiachuan; Xu, Yelong; Dubé-Demers, Raphaël; LaRochelle, Sophie; Shi, Wei; Rusch, Leslie
    Advanced optical interconnects require high-speed links, which can be achieved by combining high channel rates with wavelength-division multiplexing (WDM). We report a multi-channel transmitter using cascaded microring modulators (MRMs) in silicon photonics. One MRM works as a flexible-grid optical comb generator, while the others work as channel modulators. With a single-wavelength laser input, we achieve flexible channel spacing (up to 25 GHz) with a tone-to-noise ratio (TNR) above 54 dB, all at low power consumption (less than 4.6 mW). We examine experimentally multichannel transmission modulating data onto adjacent comb lines without significant signal crosstalk. This single-laser, flexible-grid WDM transmitter is a scalable solution: more comb lines can be obtained using uncoupled MRMs in series. This is the first demonstration of monolithic integration of a comb generator and multi-channel modulators for ultracompact, power-efficient WDM photonic interconnects.