Grating-Assisted Fiber to Chip Coupling for SOI Photonic Circuits

Nambiar, Siddharth; Sethi, Purnima; Selvaraja, Shankar Kumar

doi:10.3390/app8071142

Cited by 45 publications

(32 citation statements)

References 64 publications

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“…Since the modal field diameter of edge couplers is comparable to this value, a small deviation in the aligning fiber with the edge coupler facet can bring about a sharp decrease in coupling efficiency. Secondly, the packaging of edge coupling usually applies optical fiber pigtailing combined with laser welding [121]. The fiber requires cleaving, dicing, and tapering to lensed fiber in some cases.…”

Section: Packaging Issue Of Optical Couplersmentioning

confidence: 99%

“…From the industrial point of view, non-contact probing and the testing of packaged circuits is critical for flexible measurement and tests at low cost. Grating couplers have much larger mode spot sizes than edge couplers, which is suitable for coupling with SMF [121]. It is worthwhile to mention that edge coupling can suit for some particular photonic applications, including scenarios requiring high power transmission such as nonlinear silicon photonics and situations where broad bandwidth is needed to enable integrated devices with high optical input/output (I/O) counts and high-frequency characteristics [39].…”

Section: Packaging Issue Of Optical Couplersmentioning

confidence: 99%

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Edge Couplers in Silicon Photonic Integrated Circuits: A Review

Cheng

et al. 2020

Applied Sciences

161

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Silicon photonics has drawn increasing attention in the past few decades and is a promising key technology for future daily applications due to its various merits including ultra-low cost, high integration density owing to the high refractive index of silicon, and compatibility with current semiconductor fabrication process. Optical interconnects is an important issue in silicon photonic integrated circuits for transmitting light, and fiber-to-chip optical interconnects is vital in application scenarios such as data centers and optical transmission systems. There are mainly two categories of fiber-to-chip optical coupling: off-plane coupling and in-plane coupling. Grating couplers work under the former category, while edge couplers function as in-plane coupling. In this paper, we mainly focus on edge couplers in silicon photonic integrated circuits. We deliver an introduction to the research background, operation mechanisms, and design principles of silicon photonic edge couplers. The state-of-the-art of edge couplers is reviewed according to the different structural configurations of the device, while identifying the performance, fabrication feasibility, and applications. In addition, a brief comparison between edge couplers and grating couplers is conducted. Packaging issues are also discussed, and several prospective techniques for further improvements of edge couplers are proposed.

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Section: Packaging Issue Of Optical Couplersmentioning

confidence: 99%

Section: Packaging Issue Of Optical Couplersmentioning

confidence: 99%

Edge Couplers in Silicon Photonic Integrated Circuits: A Review

Cheng

et al. 2020

Applied Sciences

161

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“…The two main coupling strategies being investigated are grating couplers [11] and edge couplers [12]- [19]. The latter approach (also called in-plane coupling) generally offers the best optical performance in terms of coupling efficiency, spectral transmission bandwidth and polarization independency [20], [21].…”

Section: Introductionmentioning

confidence: 99%

Mode-field Matching Down-Tapers on Single-Mode Optical Fibers for Edge Coupling Towards Generic Photonic Integrated Circuit Platforms

Vanmol

Saurav²,

Panapakkam³

et al. 2020

J. Lightwave Technol.

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Connections between standard single-mode fibers and waveguides in photonic integrated circuits tend to have relatively high coupling losses due to a difference in mode size and mode profile between both light guiding media. Edge coupling strategies involving specialty fibers are frequently used to obtain the best performance in terms of coupling efficiency, bandwidth and polarization independence. We propose the fabrication of free-standing down-taper structures on top of cleaved fiber facets by two-photon direct laser writing and show their performance for silicon, silicon nitride and indium phosphide generic chip platforms. We present a comprehensive analysis of the design of such taper structures that show unprecedented flexibility. We demonstrate their fabrication and fully characterize them in terms of output modal fields and coupling efficiencies. Furthermore, we experimentally compare the fabricated down-tapers with commercially available lensed fibers and demonstrate equal or better coupling efficiency for four out of the five investigated photonic integrated circuit platforms, with a measured improvement in coupling efficiency up to 1.43 dB.

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“…Conventional grating couplers couple light from tilted fiber to avoid second-order reflection [10,11]. Fiber angle tuning and polishing are always needed in optical tests and packaging of silicon PICs, which are disadvantageous for rapid wafer-scale tests and low-cost photonic packaging [12,13]. Therefore, perfectly vertical grating couplers with high CE would be very attractive as they can further lower the cost of photonic packaging.…”

Section: Introductionmentioning

confidence: 99%

Efficiency Enhanced Grating Coupler for Perfectly Vertical Fiber-to-Chip Coupling

et al. 2020

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In this work, a bidirectional grating coupler for perfectly vertical coupling is proposed. The coupling efficiency is enhanced using a silicon nitride (Si3N4) layer above a uniform grating. In the presence of Si3N4 layer, the back-reflected optical power into the fiber is diminished and coupling into the waveguide is increased. Genetic algorithm (GA) is used to optimize the grating and Si3N4 layer simultaneously. The optimal design obtained from GA shows that the average in-plane coupling efficiency is enhanced from about 57.5% (−2.5 dB) to 68.5% (−1.65 dB), meanwhile the average back-reflection in the C band is reduced from 17.6% (−7.5 dB) to 7.4% (−11.3 dB). With the help of a backside metal mirror, the average coupling efficiency and peak coupling efficiency are further increased to 87% (−0.6 dB) and 89.4% (−0.49 dB). The minimum feature size of the designed device is 266 nm, which makes our design easy to fabricate through 193 nm deep-UV lithography and lowers the fabrication cost. In addition, the coupler proposed here shows a wide-band character with a 1-dB bandwidth of 64 nm and 3-dB bandwidth of 96 nm. Such a grating coupler design can provide an efficient and cost-effective solution for vertical fiber-to-chip optical coupling of a Wavelength Division Multiplexing (WDM) application.

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Grating-Assisted Fiber to Chip Coupling for SOI Photonic Circuits

Cited by 45 publications

References 64 publications

Edge Couplers in Silicon Photonic Integrated Circuits: A Review

Edge Couplers in Silicon Photonic Integrated Circuits: A Review

Mode-field Matching Down-Tapers on Single-Mode Optical Fibers for Edge Coupling Towards Generic Photonic Integrated Circuit Platforms

Efficiency Enhanced Grating Coupler for Perfectly Vertical Fiber-to-Chip Coupling

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