Integrated photonic beamformer employing continuously tunable ring resonator-based delays in CMOS-compatible LPCVD waveguide technology

In this paper a novel CW laser-compatible, squint-free, continuously tunable ring resonator-based optical beamformer mechanism for a phased array receiver system is proposed and partly demonstrated. When the optical delay elements and optical signal processing circuitry are integrated on a chip, a single-chip optical beam forming network (OBFN) is obtained. The optical delay elements are ideally continuously tunable to achieve continuous control of the beam direction, and should have a flat delay and magnitude response over the signal band, to avoid distortion. In the proposed system architecture, filter-based optical single-sideband suppressed-carrier modulation and balanced coherent optical detection are used. Such architecture has significant advantages over a straightforward architecture using optical intensity modulation and direct optical detection, namely reduced complexity of the OBFN chip, and enhanced dynamic range. Measurements on an actual 1×8 OBFN chip and an optical sideband filter chip are presented. Both are realized in CMOS-compatible planar optical waveguide technology (TriPleX).