CMOS Compatible Reconfigurable Silicon Photonic Lattice Filters Using Cascaded Unit Cells for RF-Photonic Processing

This paper presents an overview of a complementary metal-oxide-semiconductor-compatible, programmable, analog optical lattice filter based on silicon unit cells arrayed in large-scale photonic integrated circuits. The unit cell employs a combination of a ring resonator and a Mach-Zehnder interferometer with tunable phase elements in both of the paths. Each proposed unit cell contributes a separately controllable pole and zero pair. Under various configurations, we experimentally achieved >60-dB two-tone spurious-free dynamic range. For more sophisticated signal processing, we experimentally demonstrated an optical lattice filter with four cascaded unit cells capable of dynamically reconfiguring between a bandpass filter and a notch filter. The reconfiguration of the unit-cell and four-cell silicon lattice filter is based on a recursive algorithm, which brings new possibilities to RF photonic processing and a wide range of applications with design scalability to a large number of poles and zeros. The experimental results and the recursive algorithms show potentials for scaling to higher order filter designs.