Achieving precision in measuring birefringence characteristics of a periodically-poled Lithium Niobate waveguide
Researchers developed an accurate, in-situ method using Fourier transformation of light transmission spectra to measure birefringence in a Periodically Poled Lithium Niobate waveguide (PPLN-WG). This technique precisely determined the group index difference ($\Delta n_{gg}$), revealing a birefringence of 0.081(6) and allowing for the prediction of crucial spectral parameters like temporal walk-off and bandwidth for photon-pair generation.