Subwavelength grating enabled on-chip ultra-compact optical true time delay line

Junjia Wang, Reza Asharfi, Rhys Adams, Ivan Glesk, Ivana Gasulla, José Capmany, Lawrence R. Chen

Research output: Contribution to journalArticlepeer-review

49 Citations (Scopus)
186 Downloads (Pure)


An optical true time delay line (OTTDL) is a basic photonic building block that enables many microwave photonic and optical processing operations. The conventional design for an integrated OTTDL that is based on spatial diversity uses a length-variable waveguide array to create the optical time delays, which can introduce complexities in the integrated circuit design. Here we report the first ever demonstration of an integrated index-variable OTTDL that exploits spatial diversity in an equal length waveguide array. The approach uses subwavelength grating waveguides in silicon-on-insulator (SOI), which enables the realization of OTTDLs having a simple geometry and that occupy a compact chip area. Moreover, compared to conventional wavelength-variable delay lines with a few THz operation bandwidth, our index-variable OTTDL has an extremely broad operation bandwidth practically exceeding several tens of THz, which supports operation for various input optical signals with broad ranges of central wavelength and bandwidth.
Original languageEnglish
Article number30235
Number of pages10
JournalScientific Reports
Publication statusPublished - 26 Jul 2016


  • SWG waveguide
  • optical delay lines
  • integrated tuneable delay
  • optical true time delay lines
  • chip area
  • subwavelength grating
  • subwavelength grating waveguide
  • silicon-on-insulator
  • photonic

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