Experimental Characterization of Particle Swarm Optimized Focusing Non-Uniform Grating Coupler for Multiple SOI Thicknesses

Luca Zagaglia,Peter Oabrien,Francesco Floris

doi:10.1109/jlt.2021.3079575

Luca Zagaglia, Peter Oabrien + Show 1 more

Open Access

https://doi.org/10.1109/jlt.2021.3079575

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Abstract

We report the first experimental characterizations of the coupling efficiencies of a series of e-beam fabricated focusing non-uniform grating couplers interfaced with a horizontal fiber coupling-scheme and designed for multiple Silicon-On-Insulator thicknesses, spanning between the 220 and 340 nm standard platforms. The design of nonuniform grating couplers is tackled either from an engineering perspective focused on to the optimization of the structures for this particular coupling-scheme; and a physics perspective related to the investigation of the scattering process of each structure for a complete comprehension of its performance in support to the experimental findings. Measured coupling efficiencies, up to 83% for the 340 nm platform at 1550 nm, are reported showing to be in excellent agreement with the theoretical findings. The physics behind the scattering process of each structure is investigated taking advantage of the Finite Difference Time Domain method to obtain a deeper understating of the coupling efficiencies. Consequently, a new parameter, the integrated leakage factor, together with the variation of the effective refractive index, across the local pitches, are calculated. Our belief is that any coupling structure for grating coupling can benefit from the proposed designed approach, as a widely applicable technique.

Highlights

S ILICON Photonics has been one of the major topic for more than a decade stimulating the interest of scientists either from a fundamental and an applied researcher prospective [1]
We propose for the first time a complete state-ofthe-art procedure, from the design to the experimental characterization, of optimized focusing non-uniform Grating couplers (GCs) for multiple SOI thicknesses (220 nm, 260 nm, 290 nm, 320 nm, and 340 nm) interfaced with a Horizontal fiber scheme (H-Fb) displaying values of Coupling Efficiency (CE) competitive with the well-established Vertical Fiber coupling-scheme (V-Fb) scheme
It is worthy to highlight that the best CEs of 56% and 83% has been measured respectively for the 220 nm- and the 340 nm-thick standard SOI platforms showing the competitiveness of the H-Fb scheme with the CEs related to the well-established V-Fb scheme [13]–[14]

Summary

Introduction

S ILICON Photonics has been one of the major topic for more than a decade stimulating the interest of scientists either from a fundamental and an applied researcher prospective [1]. In this framework, two different approaches are characterizing the studies: one more oriented on the optimization and the performances of the photonics structures and a second focused on the innovation and the propose of new optical devices. The primary driving force behind Silicon photonics is represented by the combination of the properties of the material and the practical experience of processing high-volume, low-cost electronics over the years.

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