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Sci Rep. 2016 Jul 26;6:30235. doi: 10.1038/srep30235.

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

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Department of Electrical and Computer Engineering, McGill University, Montréal, Québec H3A 0E9, Canada.
Department of Physics, CEGEP Vanier College, Montréal, Québec H4L 3X9, Canada.
Department of Electronic and Electrical Engineering, University of Strathclyde, Glasgow, G1 1XU, UK.
ITEAM Research Institute, Universitat Politècnica de València, Valencia, 46022, Spain.


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.

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