Low-Loss and Broadband Silicon Photonic 3-dB Power Splitter with Enhanced Coupling of Shallow-Etched Rib Waveguides

A silicon photonic 3-dB power splitter is one of the essential components to demonstrate large-scale silicon photonic integrated circuits (PICs), and can be utilized to implement modulators, 1 × 2 switches, and 1 × N power splitters for various PIC applications. In this paper, we reported the design and experimental demonstration of low-loss and broadband silicon photonic 3-dB power splitters. The power splitter was realized by adiabatically tapered rib waveguides with 60-nm shallow etches. The shallow-etched rib waveguides offered strong coupling and relaxed critical dimensions (a taper tip width of 200 nm and gap spacing of 300 nm). The fabricated device exhibited an excess loss as low as 0.06 dB at a 1550-nm wavelength and a broad operating wavelength range from 1470 nm to 1570 nm. The relaxed critical dimensions (≥200 nm) make the power splitter compatible with standard fabrication processes of existing silicon photonics foundries.

Design and performance analysis of integrated focusing grating couplers for the transverse-magnetic TM00 mode in a photonic BiCMOS technology

Focusing grating couplers for the excitation of the fundamental transverse-magnetic (TM) mode in integrated silicon photonic waveguides are designed and characterized under the boundary conditions of a photonic BiCMOS foundry. Two types of waveguide geometries are considered – a nanowire and a rib waveguide. Wafer-scale experimental results for nanowire TM grating couplers are in excellent agreement with numerical investigations and demonstrate a robust behavior on the wafer. The mean coupling loss and the 3σ interval are -3.9 ± 0.3 dB. The on wafer variation is three times lower than for the fundamental transverse-electric (TE) polarization. Similarly, the coupling in rib waveguides is examined as well. The results indicate that the rib waveguides require a modified geometry when designed for TM. In general, the nanowire waveguide type is more suitable for TM coupling, showing a stable and repeatable performance.