High-efficiency grating coupler for an ultralow-loss Si<sub>3</sub>N<sub>4</sub>-based platform

Chmielak, Bartos; Suckow, Stephan; Parra, Jorge; Duarte, Vanessa C.; Mengual, T.; Piqueras, M.A.; Giesecke, Anna Lena; Kilders, Pablo Sanchis

doi:10.1364/ol.455078

Cited by 20 publications

(13 citation statements)

References 16 publications

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“…The bidirectional grating coupler, as the beam splitter/ combiner of the hybrid electro-optic modulator, greatly affects the performance of the whole device [31][32][33]. The main parameters of the grating coupler include grating pitches, waveguide height, etching depth, duty cycles.…”

Section: Grating Couplermentioning

confidence: 99%

Simulation of hybrid silicon nitride/polymer Mach-Zehnder optical modulator beyond 170 GHz

Huang

Zhang²,

Li³

et al. 2022

Front. Phys.

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In this paper, a hybrid Mach-Zehnder optical modulator is proposed based on silicon nitride/organic polymer waveguides, which is expected to break through the performance bottleneck of the silicon-based optical modulator by exploiting the low-loss optical transmission property of silicon nitride waveguides and the excellent modulation performance of organic polymers. For reduction of the optical loss and ease of photonic packaging, perfectly vertical silicon nitride bidirectional grating couplers are utilized for both input/output optical coupling and power splitting/combining. Thus, a Mach-Zehnder interferometer can be constructed with a back-to-back configuration of such grating couplers. With grating apodization, the coupler can achieve a simulated coupling efficiency of 70%. To bridge the silicon nitride waveguides and the polymer waveguides, a longitudinal adiabatic mode-spot converter with a transmission efficiency of 99.2% was designed. In this paper, high-β donor-π bridge-accepter molecule YLD-124 combined with HD-BB-OH as the host polymer is utilized for a design example. The polymer waveguides with inverted ridge structure can be realized through the processes of silica cladding etching, spin coating or microfluidic trench filling of polymer. Following this design, we numerically demonstrate a hybrid silicon nitride-polymer Mach-Zehnder modulator with modulation efficiency of 1.57 Vcm and Electric-Optical bandwidth of 174 GHz. The total insertion loss is less than 5.74 dB, including two grating coupler losses of about 3.08 dB.

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Section: Grating Couplermentioning

confidence: 99%

Simulation of hybrid silicon nitride/polymer Mach-Zehnder optical modulator beyond 170 GHz

Huang

Zhang²,

Li³

et al. 2022

Front. Phys.

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“…Different strategies have been proposed over the years to improve the efficiency of SiN grating couplers. These include L-shaped gratings with multi-level etching [6], bottom reflectors [7][8][9], or multi-layer waveguide stacks [10,11]. In this work, we present the design of an efficient grating coupler for silicon nitride photonic integrated circuits based on a hybrid α-Si/SiN architecture.…”

Section: Introductionmentioning

confidence: 99%

Design of subwavelength-engineered surface grating couplers on a hybrid α-Si/SiN photonic platform

Fraser,

Benedikovic,

Korcek

et al. 2024

Integrated Optics: Devices, Materials, and Technologies XXVIII

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The design of a high-efficiency grating coupler for silicon nitride (SiN) photonic integrated circuits is presented. Our devices use a high-index amorphous silicon (α-Si) overlay and subwavelength metamaterial apodization to achieve superior coupling efficiency compared to SiN-only gratings. The high index contrast of the α-Si layer results in increased grating strength, making it possible to radiate more power off-chip within the mode field diameter (MFD) of a standard single mode optical fiber. Simultaneously, through the use of subwavelength grating (SWG) apodization, we shape the radiated field to optimize the overlap with the Gaussian-like profile of the fiber mode at an operating wavelength of 1.31 µm. The overlap is further improved by considering a focalizing scheme, wherein the grating is designed to couple to a fiber placed a certain distance away from the chip. In this configuration, the constraint imposed on the length of the grating by the MFD of the fiber mode is relaxed, allowing for a longer structure that will diffract more power off-chip. By combining the use of an α-Si overlay with SWG apodization and beam focalization, we achieve a coupling efficiency of -1.3 dB.

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“…Dual-layer gratings composed of such hybrid stacks have already been demonstrated on the SiN-on-SOI platform [12,13]. However, grating coupling to 𝑇 𝐹𝑆𝑖𝑁 waveguides are emerging to appear [14,15]. A critical limiting factor in fabricating dual-layer designs is the need for precise layer alignment and surface planarization.…”

Section: Introductionmentioning

confidence: 99%

Embedded Silicon Gratings for High-efficiency Light-Chip Coupling to Thin Film Silicon Nitride Waveguides

Rawat¹,

Nambiar²,

Venkatachalam³

et al. 2023

Preprint

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Thin film silicon nitride (<150 nm) waveguide has emerged as a dominant ultra-low-loss platform for many loss-critical applications. While thin-film silicon nitride propagation loss is a crucial characteristic, coupling light between an optical fiber and the waveguide is still challenging. While the larger mode size of the decoupled thin waveguide offers better coupling than a highly-confined waveguide, the coupling efficiency is still sub-optimal. The poor diffraction efficiency of such thin films limits the scope of implementing standalone surface gratings. We demonstrate an efficient way to couple into thin film silicon nitride waveguides using amorphous silicon strip gratings. The high contrast gratings provide an efficient means to boost the directionality from thin films leading to an enhanced coupling performance. In addition, we incorporate a bottom reflector to further improve the coupling. We present an optimal design for uniform strip gratings with a maximum coupling efficiency of -1.7 dB/coupler. We achieved a maximum coupling efficiency of -0.28 dB/coupler by engineering the scattering strength along the grating through apodization. We experimentally demonstrate the highest coupling efficiency reported yet of -2.22 dB/coupler and -1.84 dB/coupler for uniform and apodized grating couplers in the C-L band, offering $>75 nm$ of 3dB bandwidth. We present a detailed design strategy, simulation, fabrication and characterization data on the effect of various parameters on the coupling.

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High-efficiency grating coupler for an ultralow-loss Si₃N₄-based platform

Cited by 20 publications

References 16 publications

Simulation of hybrid silicon nitride/polymer Mach-Zehnder optical modulator beyond 170 GHz

Simulation of hybrid silicon nitride/polymer Mach-Zehnder optical modulator beyond 170 GHz

Design of subwavelength-engineered surface grating couplers on a hybrid α-Si/SiN photonic platform

Embedded Silicon Gratings for High-efficiency Light-Chip Coupling to Thin Film Silicon Nitride Waveguides

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High-efficiency grating coupler for an ultralow-loss Si3N4-based platform

Cited by 20 publications

References 16 publications

Simulation of hybrid silicon nitride/polymer Mach-Zehnder optical modulator beyond 170 GHz

Simulation of hybrid silicon nitride/polymer Mach-Zehnder optical modulator beyond 170 GHz

Design of subwavelength-engineered surface grating couplers on a hybrid α-Si/SiN photonic platform

Embedded Silicon Gratings for High-efficiency Light-Chip Coupling to Thin Film Silicon Nitride Waveguides

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High-efficiency grating coupler for an ultralow-loss Si₃N₄-based platform