A Liquid Crystal Tunable Wavelength-Interleaved Isolator With Flat Spectral Response

A liquid crystal tunable bidirectional isolator is proposed. A wave plate is employed to realize a wavelength interleaving function. If it works as a full wave plate, the corresponding light only may pass along a specific direction while the opposite way is isolated. However, for wavelengths that the light experiences a half wave plate, the isolator´s passing direction is reversed. A liquid crystal cell is utilized to tune the isolator so that both the isolated wavelength and direction could be reconfigured. A 100-GHz channel-interleaved tunable bidirectional isolator is demonstrated with 30 dB isolation in both directions. The spectral response at ITU grids are further flattened by using a wave plate stacking technique.