Highly efficient dual-level grating couplers for silicon nitride photonics

Vitali, Valerio; Lacava, Cosimo; Bucio, Thalía Domínguez; Gardès, Frédéric; Petropoulos, P.

doi:10.1038/s41598-022-19352-9

Cited by 27 publications

(32 citation statements)

References 46 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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

View full text Add to dashboard Cite

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.

show abstract

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

View full text Add to dashboard Cite

show abstract

“…To solve this problem, several approaches have been proposed. Dual-level or silicon overlay in Si3N4 grating coupler has been reported to improve the directionality, but the complexity is significantly increased [13][14]. And the other approach is using bottom reflectors such as metal mirrors or distributed Bragg reflectors (DBR) to cover the light scattered towards the substrate.…”

Section: Introductionmentioning

confidence: 99%

High-Efficiency focusing grating coupler with distributed Bragg reflector

WEI¹,

Zhang²,

Li³

et al. 2023

Preprint

View full text Add to dashboard Cite

We propose a high-efficiency silicon nitride focusing grating coupler with a bottom reflector. The bottom reflector consists of a distributed Bragg reflector (DBR) with a stack of Si3N4 and SiO2 layers. Moreover, the taperless structure of focusing grating couplers is utilized to further increase the density of integration. The result shows that the reflectivity of the grating coupler with 8-layer DBR reaches 98% at 1550nm, the peak coupling efficiency (CE) is -2.1dB and the 1dB bandwidth is 66nm. Compared to the focusing grating without DBR, the CE is improved by 1.87 dB with slight change in 1dB bandwidth, and the footprint is only 27.1×37.1μm^2.

show abstract

“…These characteristics are attractive for high-volume production of complex photonic integrated circuits using mature CMOScompatible manufacturing and open-access photonic foundries [19]. State-of-the-art surface grating couplers can achieve sub-decibel coupling loss between optical fibers and chips using mature waveguide platforms, mainly high-index contrast silicon-on-insulator (SOI) [13][14][15][16][17][18] and low-index contrast silicon nitride (SiN) [20][21][22][23][24][25]. To this end, grating couplers with bottom reflectors [13][14][15]20,21], interleaved or L-shaped geometries [16][17][18]22,23], multi-layered arrangements [24,25], and waveguide overlayers [26] have been theoretically proposed or experimentally demonstrated.…”

Section: Introductionmentioning

confidence: 99%

“…State-of-the-art surface grating couplers can achieve sub-decibel coupling loss between optical fibers and chips using mature waveguide platforms, mainly high-index contrast silicon-on-insulator (SOI) [13][14][15][16][17][18] and low-index contrast silicon nitride (SiN) [20][21][22][23][24][25]. To this end, grating couplers with bottom reflectors [13][14][15]20,21], interleaved or L-shaped geometries [16][17][18]22,23], multi-layered arrangements [24,25], and waveguide overlayers [26] have been theoretically proposed or experimentally demonstrated. However, complex grating designs call upon customized processes and dedicated fabrication steps, which results either in additional production expenses or optimized processes are offered by open-access foundries.…”

Section: Introductionmentioning

confidence: 99%

Silicon-based surface gratings for efficient fiber-chip and free-space beam coupling

Benedikovič

Fraser

Korcek

et al. 2023

Integrated Optics: Design, Devices, Systems and Applications VII

View full text Add to dashboard Cite

Silicon photonics has established itself as a key integration platform, leveraging high-quality materials and large-scale manufacturing using mastered toolsets of complementary metal-oxide-semiconductor (CMOS) foundries. Chip-scale photonics offer unique promises for dense integration of versatile optical functions through compact and high-performance building blocks. Integrated photonics is now competing technology for many applications, spanning from telecom/datacom and interconnects up to quantum sciences and light detection and ranging (LIDAR) systems, among others. However, the lack of low-loss input/output chip interfaces can be prohibitive to successfully deploy multi-diverse device applications. Low coupling loss is essential in reducing overall power budget in photonic systems, impacting on-chip integration level. The light coupling from an off-chip environment into the planar waveguide platforms has always been a challenging research problem since the early years of integrated photonics. Optical interfaces formed on a photonic chip surface, rather than implemented on a chip edge, have been widely used to access photonic circuits with optical fibers or enabling free-space coupling of light beams. Surface gratings can be positioned at arbitrary locations and/or arranged in pre-defined patterns on the chip, facilitating wafer-scale testing and optical packaging. In this work, we present our recent progress in the development of silicon-based surface gratings for use in fiber-to-chip and free-space beam coupling. In particular, we discuss prospective design approaches to develop low-loss surface grating couplers implemented on silicon-on-insulator (SOI), silicon nitride (SiN), and hybrid silicon-silicon nitride (Si-SiN) platforms, allowing to approach a coupling loss below -1 dB. Among these, we also cover contemporary advances in compact silicon metamaterial nano-antennas for dense optical phased arrays, obtaining high a diffraction performance (> 90%) and wideband operation (> 200 nm) simultaneously.

show abstract

Highly efficient dual-level grating couplers for silicon nitride photonics

Cited by 27 publications

References 46 publications

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

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

High-Efficiency focusing grating coupler with distributed Bragg reflector

Silicon-based surface gratings for efficient fiber-chip and free-space beam coupling

Contact Info

Product

Resources

About