Personne :
Jafari, Omid

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Jafari
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Omid
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Université Laval. Faculté des sciences et de génie
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ncf11921344
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Résultats de recherche

Voici les éléments 1 - 10 sur 16
  • Publication
    Accès 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.
  • Publication
    Accès 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.
  • Publication
    Accès 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.
  • Publication
    Accès 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.
  • Publication
    Accès libre
    Subwavelength-grating contra-directional couplers for large stopband filters
    (Optical Society of America, 2018-02-14) Jafari, Omid; Charron, Dominique; St-Yves, Jonathan; LaRochelle, Sophie; Shi, Wei
    Manipulating the coupling coefficient at subwavelength scales provides an additional degree of freedom in designing integrated Bragg gratings. We demonstrate asymmetric contradirectional couplers (contra-DCs) using sidewall-corrugated subwavelength grating (SWG) waveguides for broadband add–drop Bragg filters. We show that a SWG can effectively increase the overlap of coupled modes and thus the photonic band gap. The measured spectra show good agreement with the prediction of photonic band structure simulations. A record bandwidth of 4.07 THz (33.4 nm) has been achieved experimentally. A four-port Bragg resonating filter made of a phase-shifted Bragg grating SWG contra-DC is also demonstrated for narrow-band (near 100 GHz) filtering. All these devices are achieved on the 220-nm silicon-on-insulator platform with a compact length of less than 150 μm. These large stopband filters may find important applications such as band splitting, reconfigurable channel band switching, bandwidth-tunable filtering, and dispersion engineering.
  • Publication
    Accès libre
    Mode-conversion-based silicon photonic modulator loaded by a combination of lateral and interleaved p-n junctions
    (Optical Society of America, 2021-03-19) Jafari, Omid; Zhalehpour, Sasan; LaRochelle, Sophie; Shi, Wei
    We experimentally demonstrate a silicon photonic modulator that can be loaded with a combination of lateral and interleaved p-n junctions to enhance its phase modulation. We use an asymmetric Bragg grating to introduce mode conversion in the active area, allowing the modulator to operate in reflection without introducing additional on-chip loss. With a compact footprint (phase shifter length of 290 μm), the modulator demonstrates a modulation speed up to 45 Gb/s with a bit error rate below the 7% forward-error-correction (FEC) threshold (up to 55 Gb/s with 20% FEC), and a low power consumption of 226 fJ/bit.
  • Publication
    Accès 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.
  • Publication
    Restreint
    Mode-conversion-based silicon photonic modulator using asymmetric Bragg grating and Y-branch
    (2019-09-22) Lin, Jiachuan; Jafari, Omid; LaRochelle, Sophie; Shi, Wei
    We experimentally demonstrate a Bragg-grating-based modulator operating in reflection with low loss and without a circulator by using mode conversion and an asymmetric Y-branch. With a compact footprint of 240μm, we demonstrate OOK up to 30 Gbit/s with an estimated switching energy of 150 fJ/bit.
  • Publication
    Restreint
    Silicon photonic modulator loaded by a combination of lateral and interleaved p-n junctions
    (OSA, 2020-07-16) Jafari, Omid; Zhalehpour, Sasan; LaRochelle, Sophie; Shi, Wei
    We experimentally demonstrate a silicon photonic modulator loaded by lateral and interleaved p-n junctions simultaneously. Operated in reflection without a circulator, we demonstrate OOK up to 45Gbit/s with a short phase shifter length of 290µm.
  • Publication
    Accès libre
    A model for electro-optic response of lumped slow-light silicon photonic modulators
    (IEEE, 2020-11-16) Jafari, Omid; LaRochelle, Sophie; Shi, Wei
    We model the electro-optic bandwidth of lumped slow-light modulators. In agreement with experiments, the model shows that modulators speed is determined by the RC constant and the interaction time in the slow light Brag structure.