Terahertz bandwidth all-optical Hilbert transformers based on long-period gratings

Area of Science:

• Photonics
• Optical signal processing
• Waveguide technology

Background:

• Implementing real-time Hilbert transformers for terahertz (THz) bandwidth signals presents significant challenges.
• Existing methods may lack the speed or bandwidth required for advanced optical signal processing.

Purpose of the Study:

• To propose and numerically demonstrate a novel, all-optical design for THz bandwidth real-time Hilbert transformers.
• To generalize the design for photonic fractional Hilbert transformers.

Main Methods:

• Utilizing a uniform-period long-period grating (LPG) with a specific amplitude-only apodization profile.
• Incorporating a single π-phase shift in the center of the LPG for basic Hilbert transformers.
• Extending the design with multiple π-phase shifts for fractional Hilbert transformers.

Main Results:

• Numerical simulations confirm the feasibility of the proposed LPG-based all-optical Hilbert transformers.
• The design supports arbitrary optical signals with bandwidths well within the THz range.
• The approach is adaptable for both fiber-optic and integrated-waveguide implementations.

Conclusions:

• The proposed all-optical design offers a practical solution for THz bandwidth real-time Hilbert transformation.
• LPGs with tailored apodization profiles are effective for implementing both Hilbert and fractional Hilbert transformers.
• This work paves the way for advanced optical signal processing at THz frequencies.