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LaRochelle, Sophie

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Université Laval. Département de génie électrique et de génie informatique



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Voici les éléments 1 - 10 sur 66
  • 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
    Optimization criteria and design of few-mode erbium-doped fibers for cladding-pumped amplifiers
    (Optical Society of America, 2023-02-23) Janvier, Pierre-Olivier; Matte-Breton, Charles; Monga, Kaboko Jean-Jacques; Wang, Lixian; Rusch, Leslie; LaRochelle, Sophie
    We propose a novel optimization method that combines two design criteria to reduce the differential modal gain (DMG) in few-mode cladding-pumped erbium-doped fiber amplifiers (FM-EDFAs). In addition to the standard criterion that considers the mode intensity and dopant profile overlap, we introduce a second criterion that ensures that all doped regions have the same saturation behavior. With these two criteria, we define a figure-of-merit (FOM) that allows the design of MM-EDFAs with low DMG without high computational cost. We illustrate this method with the design of six-mode erbium-doped fibers (EDFs) for amplification over the C-Band targeting designs that are compatible with standard fabrication processes. The fibers have either a step-index or a staircase refractive index profile (RIP), with two ring-shaped erbium-doped regions in the core. With a staircase RIP, a fiber length of 29 m and 20 W of pump power injected in the cladding, our best design leads to a minimum gain of 22.6 dB while maintaining a DMGmax under 0.18 dB. We further show that the FOM optimization achieves a robust design with low DMG over a wide range of variations in signal power, pump power and fiber length.
  • PublicationAccès libre
    Integrated optical SSB modulation / frequency shifting using cascaded silicon MZM
    (Institute of electrical and electronics engineers, 2020-08-05) Hasan, Mehedi; Jafari, Omid; Guan, Xun; LaRochelle, Sophie; Rusch, Leslie; Hall, Trevor J.
    A frequency conversion mixer or single side band modulator using two cascaded MZM is proven experimentally. The operation of the circuit is modelled by a transfer matrix approach and verified by simulation in support of the experiment. A 10 GHz shift of the optical carrier in both left and right direction is demonstrated. The residual sideband suppression relative to the enhanced sideband is 22 dB for the best cases. Numerical analysis shows that the circuit has 3-dB optical and 3-dB electrical intrinsic advantage over the functionally equivalent DP-MZM.
  • PublicationAccès libre
    Quantifying the coupling and degeneracy of OAM modes in high-index-contrast ring core fiber
    (Institute of Electrical and Electronics Engineers, 2020-10-14) Banawan, Mai; LaRochelle, Sophie; Wang, Lixian; Rusch, Leslie
    We study orbital angular momentum (OAM) mode coupling in ring-core fibers (RCFs) due to elliptical shape deformation. We introduce a coupling model based on numerical mode solver outputs of perturbation. We show improved predictions in calculating coupling strength compared to the classical modeling approach. Our model captures and quantifies the disparate behaviors of coupling in lower and higher order degenerate OAM modes. The ideal orthogonality of modes is undermined by fiber imperfections. Our model predicts the OAM order at which the orthogonality within OAM mode pair is maintained despite elliptical deformation. We use our coupling model to simulate propagation effects and compare the performance of two fibers (thin and thick RCF) designed under the same constraints. Our numerical propagation results show different performance for the two fibers under the same level of elliptical deformation. This model uncovers distinct digital signal processing requirements for these two types of fiber, and predicts their signal-to-noise ratio penalty. For each fiber, we examine the large number of supported modes and find the optimal subset of mode groups, i.e., the groups with the lowest penalty. We show that this optimal subset is different from that predicted during the fiber design optimization.
  • PublicationAccès libre
    Widely tunable silicon Raman laser
    (Optical Society of America, 2021-05-05) Ahmadi, Mohammad; LaRochelle, Sophie; Shi, Wei
    Stimulated Raman scattering is an effective means of wavelength conversion and can largely extend the operating spectral range of an optical source. We demonstrate a high-performance tunable Raman laser on a sub-micrometer-thick silicon on insulator wafer using a standard foundry process. The key feature to this laser is the use of a tunable coupling mechanism to adjust both pump and signal coupling coefficients in the ring cavity, allowing demonstration of laser emission over a large wavelength tuning range of 83 nm. This Raman laser demonstrates efficient (slope of up to 26% and a maximum pump-to-signal power conversion efficiency of 10%) on-chip nonlinear wavelength conversion. Our results indicate great promise for substantially increasing the optical spectral resources available on a silicon chip.
  • PublicationRestreint
    Characterization of Giles parameters for extended L-band Erbium-doped fibers
    (Optical Society of America, 2022-06-13) Maes, Frédéric; Jalilpiran, Saber; Feng, Hanlin; LaRochelle, Sophie; Wang, Lixian
    In this study, we present theoretical and experimental uncertainty analysis of erbium-doped fiber (EDF) characterization to improve performance prediction of erbium-doped fiber amplifiers (EDFAs) in the extended L-band. Through this uncertainty analysis, the optimal EDF lengths for absorption coefficient and emission coefficient characterization are determined to improve precision with a limited number of experimental steps. The uncertainty in the measured clustering ratio is also evaluated based on the uncertainty analysis of absorption and emission coefficients. To verify the accuracy of the Giles parameters determined from the EDF characterization, we compare simulation results, with calculated upper and lower uncertainties for the gain and noise figure (NF), to experimental measurements. The results show that the measured spectral gain and NF match well with the calculated value.
  • PublicationAccès libre
    Silicon photonic modulator using mode conversion with asymmetric sidewall bragg gratings
    (IEEE, 2018-10-04) Jafari, Omid; LaRochelle, Sophie; Shi, Wei
    An asymmetric sidewall grating allows to operate a Bragg modulator in reflection without circulator and with less than 1.5 dB on-chip loss. An asymmetric Y-branch directs the incident TE0 mode to the grating, while the reflected TE1 mode is guided to the drop port.
  • PublicationAccès libre
    Demonstration of an erbium-doped fiber with annular doping for low gain compression in cladding-pumped amplifiers
    (The Optical Society, 2018-10-01) Essiambre, René-Jean.; Chen, Haoshuo; Matte-Breton, Charles; Fontaine, Nicolas K.; Jin, Cang; Ryf, Roland; LaRochelle, Sophie; Messaddeq, Younès; Kelly, C.
    We present the design and characterization of a cladding-pumped amplifier with erbium doping located in an annular region near the core. This erbium-doped fiber is proposed to reduce gain saturation, leading to smaller gain compression when compared to uniform core doping. Through numerical simulations, we first compare the performance of three fibers with different erbium doping profiles in the core or the cladding. When the doped fibers are operated at the optimum length, results show that the smaller overlap of the signal mode field with the annular erbium doping region leads to higher gain and lower saturation of the amplifier. A single-core erbium-doped fiber with an annular doping and a D-shaped cladding was fabricated. Measurements demonstrate less than 4 dB of gain compression over the C-band for input power ranging from −40 dBm to 3 dBm. Small gain compression EDFAs are of interest for applications that require input channel reconfiguration. Higher gain and saturation output power are also key issues in cladding-pumped multi-core amplifiers.
  • PublicationRestreint
    DAC-less PAM-4 slow-light silicon photonic modulator providing high efficiency and stability
    (Institute of Electrical and Electronics Engineers, 2021-05-25) Jafari, Omid; Zhalehpour, Sasan; LaRochelle, Sophie; Shi, Wei
    We report a slow-light silicon modulator that enables high-speed PAM operation without using an electrical digital-to-analogue converter (DAC). Bragg grating resonators, integrated into each arm of a Mach-Zehnder modulator, enhance the phase modulation through the slow light effect. The optical 4-level PAM signal is generated by driving directly the segmented phase shifter design with two binary signals. This modulator presents an ultra-compact footprint (LSL-MZM = 570 m), low energy consumption (73 fJ/bit), large electro-optic bandwidth (> 40 GHz). Up to 90 Gb/s is achieved over an nm-range spectral operation bandwidth (= 2 nm). Compared to other low-energy resonator-based modulators, such as micro-rings, this operating bandwidth confers higher stability with a potential operating temperature range of T = 50 C. We further examine the robustness of the proposed design to fabrication variations by measurements of spectral properties across the wafer. This modulator is of particular interest for applications, such as short-range data communications that require multiple compact and energy-efficient modulators on a single chip
  • PublicationAccès libre
    Slow light in subwavelength grating waveguides
    (IEEE, 2019-08-07) Jean, Philippe; Gervais, Antoine; LaRochelle, Sophie; Shi, Wei
    Structural slow light is the dispersion engineering process by which the group velocity of light can be drastically reduced in a periodic waveguide structure. Enabling large group delay and enhancing the light-matter interaction on a subwave- length scale, on-chip slow light is of great interest in a vast array of fields such as non-linear optic, sensing, laser physics, telecommunication and computing. In this work, we experimen- tally demonstrate, for the first time, slow light in subwavelength grating waveguides on the silicon-on-insulator platform. We present a comprehensive numerical study in analytical modelling and 3D FDTD. Multiple waveguides variations were fabricated using an electron-beam lithography process. Figures of merit such as group index, bandwidth and loss-per-delay are examined in both theory and experiment. A maximum measured group index of 47.74 with a loss-per-delay of 103.37 dB/ns has been achieved near the wavelength of 1550 nm. A broad bandwidth of 8.82 nm was measured, in which the group index remains larger than 10. We also show that the region of slow light operation can be shifted over a large wavelength span by controlling a single design parameter.