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

Area of Science:

• Photonics and Optical Engineering
• Integrated Optics
• Microwave Photonics

Background:

• Optical true time delay lines (OTTDLs) are fundamental components in microwave photonics and optical processing.
• Conventional integrated OTTDLs often rely on length-variable waveguides, leading to complex circuit designs.
• Existing wavelength-variable delay lines have limited operational bandwidths.

Purpose of the Study:

• To demonstrate the first integrated index-variable OTTDL.
• To present a novel approach utilizing spatial diversity in an equal length waveguide array.
• To achieve a compact and simply designed OTTDL with significantly enhanced bandwidth.

Main Methods:

• Employed subwavelength grating waveguides fabricated on silicon-on-insulator (SOI).
• Exploited spatial diversity within an array of equal length waveguides.
• Demonstrated an index-variable approach to control optical true time delays.

Main Results:

• Successfully realized an integrated index-variable OTTDL with a simple geometry.
• Achieved a compact chip footprint for the developed OTTDL.
• Exhibited an ultra-broad operation bandwidth, exceeding several tens of THz, far surpassing conventional designs.

Conclusions:

• The proposed index-variable OTTDL offers a significant advancement over conventional designs.
• Subwavelength grating waveguides enable a simplified and compact integrated photonic solution.
• The ultra-broad bandwidth makes this technology suitable for diverse optical signal processing applications.