All-fiber tunable mode converter for a mini-two-arm Mach-Zehnder interferometer

Area of Science:

• Photonics
• Optical Engineering
• Fiber Optics

Background:

• Mach-Zehnder interferometers (MZIs) are crucial optical devices.
• Controlling light modes in optical fibers is essential for advanced applications.
• Existing mode converters often lack all-fiber integration and tunability.

Purpose of the Study:

• To propose and realize the first all-fiber tunable mode converter.
• To develop a compact device based on a mini-two-arm Mach-Zehnder interferometer (MTA-MZI).
• To demonstrate real-time detection of optical mode properties.

Main Methods:

• Fabrication of a centimeter-scale MTA-MZI using electric arc discharge to fuse multi-mode fiber (MMF) and single-mode fiber (SMF).
• Exploiting the differential sensitivity of fiber modes to bending-induced mode leakage.
• Monitoring interference fringe patterns to analyze mode properties in real-time.
• Conducting a verification experiment using a 'peanut structure' to excite higher-order modes.

Main Results:

• Successfully realized an all-fiber tunable mode converter with centimeter-scale arms.
• Demonstrated that bending-induced mode leakage alters the MZI's interference fringe pattern.
• Verified the device's ability to detect mode properties by observing fringe pattern changes.
• Showcased mode conversion by reverting the fringe pattern to its initial state upon curvature modification.

Conclusions:

• The developed MTA-MZI functions effectively as an all-fiber tunable mode converter.
• The device enables real-time monitoring of optical field mode properties.
• This work paves the way for all-fiber optical field mode conversion technologies.