LP01–LP11 Cross-Mode Interference in a Chirped Grating Inscribed in Two-Mode Fiber

We have demonstrated LP
₀₁
-LP
₁₁
cross-mode interference in a single chirped grating (CG) inscribed in a two-mode fiber (TMF). With the aid of a binary phase plate, LP
₀₁
mode and LP
₁₁
mode can be selectively excited in the CG. By offsetting the position of the phase plate from the center of the input beam, we can simultaneously excite both the spatial modes at different LP
₀₁
:LP
₁₁
intensity ratios in the TMF. The excited modes lead to the formation of different interference patterns in the output spectra. The measured output spectra are found to be in good agreement with the simulation based on a coupled mode theory.