An ultra-broadband, and low loss 3-dB optical power splitter with curved adiabatic taper

Optical power splitter is an essential component for photonics integrated circuits with a variety of applications such as integrated photonic modulators and single-photon detectors. This paper proposes and demonstrates a new design for a 3-dB optical power splitter with curvature optimized adiabatic taper which can achieve ultra-broadband operation, low loss, compact, and fabrication-friendly. The design incorporates a third order Bezier curve to form the adiabatic tapers, with optimized control point positions that effectively enhance waveguide coupling strength while maintaining high transmission efficiency within a compact footprint of and 200 nm minimum feature size. In consequence, simulation results reveal that the design could evenly split the input TE light over an operation bandwidth of 500 nm with an insertion loss (IL) of less than 0.493 dB across 1350 nm to 1850 nm wavelength. A 5-stage cascaded power splitter and a power splitter-based Mach-Zehnder interferometer (MZI) was fabricated for precise measuring. Experimental results demonstrate an average IL of 0.096 dB at 1550 nm, with an IL less than 0.35 dB over the entire measurement range of 1490 nm to 1640 nm. Additionally, the device has a good fabrication tolerance to variations in etching depth, waveguide width, tip width, and sidewall angle.