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

Wang, Junjia and Asharfi, Reza and Adams, Rhys and Glesk, Ivan and Gasulla, Ivana and Capmany, José and Chen, Lawrence R. (2016) Subwavelength grating enabled on-chip ultra-compact optical true time delay line. Scientific Reports, 6. 30235. ISSN 2045-2322

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    Abstract

    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.