Polarization insensitive low-loss coupling technique between SOI waveguides and high mode field diameter single-mode fibers

Abstract

A polarization insensitive technique for highly efficient coupling between SOI waveguides and high mode field diameter single-mode fibers is reported. The proposed coupling structure is based on an inverted taper structure coupled to a fiber-adapted waveguide. The fiber-adapted waveguide is made by using the SiO(2) layer under the Si waveguiding layer of the SOI wafer thus avoiding the use of extra materials such as polymers. The proposed coupling structure is aimed for being integrated with V-groove auto-alignment techniques. Coupling losses of 3.5dB and 3.7dB to 8mum mode field diameter single-mode fibers have been estimated by means of 3D-BPM simulations for TE and TM polarizations respectively and a 1550nm input signal wavelength.

Embedded parabolic fiber lens for efficient fiber-to-waveguide coupling fabricated by focused ion beam

“…Within the same range of lens heights, the working distance varies from 20 to 1.6 μm, as shown in figure 3(b). Since a spot size of m 2.5 m is optimal for coupling into our input test waveguide (in this work, defined as an inverted taper in silicon, with a cross-section of200 nm 220 nm at the edge) [26], we use the curve of figure 3(a) to determine the corresponding lens height of m 5 m (indicated by the red circle in the figure), and then use that lens height to find the adequate working distance of m 6.5 m, from figure 3(b) (also indicated by the red circle in the figure). A similar procedure can be used to estimate the working distance and spot size for any other waveguide cross-section requiring a lens spot size different than m 2.5 m. As a result, an embedding depth of m 6.5 m was selected for the fabricated lens, in accordance with the numerical simulations.…”

Photonic Packaging: Transforming Silicon Photonic Integrated Circuits into Photonic Devices

“…Adding an edge-coupler onto a Si-PIC also increases post-fabrication processing costs, because it calls for either accurate dicing and polishing of the PIC edges, or an additional deep-etch (>60 μm) lithography to create a high-quality facet for low insertion-losses [6]. Deep etching techniques can even be taken further, to simultaneously create a facet and v-grove in which the fiber can be passively aligned with respect to the on-PIC waveguides [20]. The principle draw-back of this approach is that the v-grooves can occupy a significant fraction the Si-PIC footprint that would otherwise be available for the active part of the photonic device.…”

“…High-speed SMA (18)(19)(20)(21)(22)(23)(24)(25) and SMK (46 GHz) connectors have a ≈1 cm 2 footprint on the PCB, while the pitch of the electrical bond-pads on a PIC is typically 100 μm. Therefore, the pitch of the high-speed 50 Ω transmission lines must be reduced by two orders-of-magnitude between the connector and the PIC, while maintaining the path-length of different electrical-channels to preserve signal timings.…”

Suspended Spot‐Size Converters for Scalable Single‐Photon Devices

“…The width of the GaAs waveguide () is gradually reduced to enlarge the area of its fundamental transverse electric (TE 00 ) mode (see inset of Figure a), which is transferred to the overlay polymer waveguide with a size matched to the focal spot of a lensed fiber. Unlike tapers without polymers, the adiabatic condition is easier to fulfill, resulting in virtually perfect spot‐size conversion. Here, we focus on the TE modes only, since the QD dipole is exclusively in‐plane and thus does not couple to transverse magnetic modes .…”