Tolerant, broadband tunable 2 × 2 coupler circuit.

Area of Science:

• Photonics
• Integrated Optics
• Optical Engineering

Background:

• Waveguide couplers are fundamental components in photonic integrated circuits.
• Tunable couplers are essential for reconfigurable optical networks and signal processing.
• Existing tunable couplers often face limitations in spectral uniformity or fabrication tolerance.

Purpose of the Study:

• To propose and demonstrate a novel circuit design for a broadband tunable 2×2 waveguide coupler.
• To achieve arbitrary coupling ratios with a uniform spectral response.
• To enhance tolerance to fabrication variations.

Main Methods:

• A two-stage Mach-Zehnder interferometer (MZI) configuration was employed.
• Electro-optic phase shifters were integrated into each stage of the MZI.
• The design was analyzed for its spectral response and coupling ratio tunability around 1550 nm.

Main Results:

• The proposed design enables a tunable 2×2 waveguide coupler with arbitrary coupling ratios.
• A uniform spectral response was achieved over a 50-nm bandwidth.
• The design exhibits robustness against fabrication variations impacting directional coupler ratios.

Conclusions:

• The proposed electro-optic tunable MZI offers a versatile solution for broadband photonic applications.
• This design provides a pathway for developing more flexible and reliable integrated optical devices.
• The achieved tunability and fabrication tolerance are significant advancements for optical signal processing.