Coupling strategies for silicon photonics integrated chips [Invited]

Abstract

Over the last 20 years, silicon photonics has revolutionized the field of integrated optics, providing a novel and powerful platform to build mass-producible optical circuits. One of the most attractive aspects of silicon photonics is its ability to provide extremely small optical components, whose typical dimensions are an order of magnitude smaller than those of optical fiber devices. This dimension difference makes the design of fiberto-chip interfaces challenging and, over the years, has stimulated considerable technical and research efforts in the field. Fiber-to-silicon photonic chip interfaces can be broadly divided into two principle categories: in-plane and out-of-plane couplers. Devices falling into the first category typically offer relatively high coupling efficiency, broad coupling bandwidth (in wavelength), and low polarization dependence but require relatively complex fabrication and assembly procedures that are not directly compatible with wafer-scale testing. Conversely, out-of-plane coupling devices offer lower efficiency, narrower bandwidth, and are usually polarization dependent. However, they are often more compatible with high-volume fabrication and packaging processes and allow for on-wafer access to any part of the optical circuit. In this paper, we review the current state-of-the-art of optical couplers for photonic integrated circuits, aiming to give to the reader a comprehensive and broad view of the field, identifying advantages and disadvantages of each solution. As fiber-to-chip couplers are inherently related to packaging technologies and the co-design of optical packages has become essential, we also review the main solutions currently used to package and assemble optical fibers with silicon-photonic integrated circuits.

A modular laboratory curriculum for teaching integrated photonics to students with diverse backgrounds

“…Coupling a fiber to a chip is a crucial skill that is required in all PIC characterizations [5]. Both edge-coupling as well as grating coupling are presented.…”

Silicon chip-integrated fiber couplers with sub-decibel loss

“…Direct butt-coupling is largely inefficient, with losses in excess of -30 dB. The coupling is particularly difficult due to the mismatch in mode sizes between Si waveguides and standard single-mode optical fibers [11][12][13][14] . This is a serious obstacle for many nanophotonic applications in areas such as communications, interconnects, or quantum information sciences, amongst other.…”

“…This is a serious obstacle for many nanophotonic applications in areas such as communications, interconnects, or quantum information sciences, amongst other. The quest for low-loss light coupling in and out of the chip drives the development in SOI nanophotonics for many years and definitely remains a very active research area [12][13][14] . In this buoyant field, edgecoupled [15][16][17][18][19][20] and grating-coupled optical interfaces are leading solutions.…”

Nonvertical Sidewall Angle Influence on the Efficiency of Diamond‐on‐Insulator Grating Couplers

“…The aim of this work is to estimate the limitations imposed by our RIE technological processes on the efficiency of diamond‐on‐insulator grating coupler. Grating couplers are diffractive structures for coupling light between planar IOCs and vertical optical fibers . They are preferable to tapers because they have a much smaller footprint on the chip and allow wafer‐scale testing and dense device packaging on chip .…”