Fast M2 measurement for fiber beams based on modal analysis

Area of Science:

• Optics and Photonics
• Optical Fiber Technology
• Metrology

Background:

• Accurate measurement of beam quality is crucial for optical fiber applications.
• Traditional methods for measuring the beam propagation ratio M(2) can be complex and time-consuming.
• Characterizing light propagation within optical fibers requires precise determination of modal properties.

Purpose of the Study:

• To introduce a fast and experimentally straightforward technique for measuring the beam propagation ratio M(2) in optical fibers.
• To enable accurate reconstruction of the optical field within the fiber by determining modal amplitudes and phases.
• To validate the proposed method against established ISO standards for beam propagation measurements.

Main Methods:

• Utilized a holographic filter to precisely measure the amplitudes and phases of excited fiber eigenmodes.
• Employed coherent superposition of the determined modes to reconstruct the complete optical field.
• Simulated the free-space propagation of the reconstructed optical field to perform a virtual caustic measurement.

Main Results:

• Successfully demonstrated a rapid and easy-to-implement experimental technique for M(2) measurement.
• The method accurately determines the amplitudes and phases of all excited fiber modes.
• Calculated beam propagation ratios M(2) showed excellent agreement with results from standard ISO-compliant measurements.

Conclusions:

• The presented holographic filter-based technique offers an efficient and accurate approach for characterizing optical fiber beam quality.
• This method simplifies the virtual caustic measurement by enabling precise optical field reconstruction.
• The technique provides a reliable alternative for M(2) determination, meeting industry standards.