High-density integrated delay line using extreme skin-depth subwavelength grating waveguides

Abstract

Optical delay lines control the flow of light in time, intro-ducing phase and group delays for engineering interferences and ultrashort pulses. Photonic integration of such optical delay lines is essential for chip-scale lightwave signal process-ing and pulse control. However, typical photonic delay lines based on long spiral waveguides require extensively large chip footprints, ranging from mm2 to cm2 scales. Here we present a scalable, high-density integrated delay line using a skin-depth engineered subwavelength grating waveguide, i.e., an extreme skin-depth (eskid) waveguide. The eskid waveguide suppresses the crosstalk between closely spaced waveguides, significantly saving the chip footprint area. Our eskid-based photonic delay line is easily scalable by increas-ing the number of turns and should improve the photonic chip integration density. (c) 2023 Optica Publishing Group