Single-Tone Optical Frequency Shifting and Nonmagnetic Optical Isolation by Electro-Optical Emulation of a Rotating Half-Wave Plate in a Traveling-Wave Lithium Niobate Waveguide

In this paper, we demonstrate a frequency shifter at 780 nm based on an X-cut Z -propagating lithium niobate waveguide platform with an isotropic orientation. The electro-optic effect modulates the signal with traveling-wave configuration. The frequency-shifting device emulates a rotating half-wave plate when it converts left circular polarized input light to right circular polarized output light and changes the original optical frequency by its modulation frequency. We characterize the device by conducting the polarization conversion experiment and achieve the frequency shift at up to 2 GHz and more than 20 dB extinction ratio. The device needs 30 dBm RF power to perform a frequency shift with high extinction ratio. With the same device, we also demonstrate optical isolation with 18.5 dB extinction ratio.