Δβ ≠ 0 can be induced between the waveguides by the application of a
For large m the FWHM bandwidth reduces to λ m / m = λ2m/2ΔnL for both cases. The peak wavelengths are directly proportional to the birefringence.
Hence, the tuning range is given by
where δ(Δn) is the variation of the birefringence induced by an applied field. Consider, as an example, the case of a Pockels cell made with LiNb03.