Ultra-low-loss polymeric waveguide circuits for optical true-time delays in wideband phased-array antennas

The optical true-time-delay line is a key building block for modern broadba nd phased-array antennas, which have become one of the most critical techno logies for both military and civilian wireless communications. We present o ur research results in developing an optical polymer-based waveguide true-t ime-delay module for multilink phased-array antennas by incorporating wavel ength-division multiplexing (WDM) technology. The demonstrated optical poly meric waveguide circuits can provide a large number of optical true-time de lays with a dynamic range of 50 ns and a time resolution of 0.1 ps. Various fabrication techniques are investigated for producing ultralong low-loss ( 0.02 dB/cm) polymeric channel waveguides with tilted waveguide grating outp ut couplers. Fast photodiode arrays are fabricated and rf signals with freq uencies of 10 to 50 GHz are generated through the optical heterodyne techni que. A detailed study of waveguide amplification to achieve loss-less polym eric waveguide is conducted. The optical amplification of 3.8 dB/cm is achi eved at a wavelength of 1064 nm in a Nd3+-doped polymeric waveguide. WDM te chniques are also employed for potential multilink applications. The presen ted methodologies enable hybrid integration with a reduced cost in optoelec tronic packaging and an increased reliability and decreased payload for the next generation of phased-array antennas. (C) 2000 Society of Photo-Optica l instrumentation Engineers. [S0091-3286(00)00603-6].