All-Fiberized Top-Hat Beam Shaper by Mode Content Control and Multimode Interference Suppression

A new method of all-fiberized top-hat beam shaper based on controlling mode content and suppressing multimode interference is proposed both numerically and experimentally. The sample is fabricated by fusion splicing a predetermined tapered multimode fiber to a nearly single mode fiber. A 2D simulation model to calculate the mode content weight with different taper ratio and taper shape is established, and the output intensity profile in multimode fiber is investigated. Based on the simulation results, we fabricated an all-fiberized beam shaper, achieving a top-hat beam at a taper ratio of 0.51 with parabolic taper shape. The flatness factor of the top-hat beam is measured to be about 0.6. These theoretical results show a good agreement with the experimental results.