Measurement of mode cut-off wavelength for single mode channel waveguide in LiNbO3

We report a simple but effective experimental technique by utilizing standard off-the-shelf optical fiber cut-off measurement equipment for measuring the second order mode cut-off of channel waveguide in LiNbO₃. The scheme applies multimode excitation of channel waveguide and cut-off wavelength is calculated by comparing guided optical power with respect to modal power in the reference multimode fiber. Typical channel waveguide designs at 1310 and 1550 nm windows are used for experimentation and simulations. Simulations are performed using Optiwave BPM CAD software and the experimental results match well with simulations.