On-chip optical true time delay lines based on subwavelength grating waveguides

An optical true time delay line (OTTDL) is a fundamental building block for signal processing applications in microwave photonics (MWP) and optical communications. Here, we experimentally demonstrate an index-variable OTTDL based on an array of forty subwavelength grating (SWG) waveguides on silicon-on-insulator (SOI). Each SWG waveguide in the array is 34 mm long and arranged in a serpentine manner; the average incremental delay between waveguides is about 4.7 ps and the total delay between the first and last waveguides is approximately 181.9 ps. The waveguide array occupies a chip area of ~ 6.5 × 8.7 = 56.55 . The proposed OTTDLs bring potential advantages in terms of compactness as well as operation versatility to a variety of microwave signal processing applications