Broadband tunable electro-optic switch/power divider as potential building blocks in integrated lithium niobate photonics

We demonstrate an electro-optic (EO) switch or in general, an EO controllable power divider based on a periodically poled lithium niobate (PPLN) polarization mode converter (PMC) and a five-waveguide adiabatic coupler integrated on a Ti:LN photonic circuit chip. In this integrated photonic circuit (IPC) device, the PPLN works as an EO controllable polarization rotator (and therefore a PMC), while the adiabatic coupler functions as a broadband polarization beam splitter (PBS). The 1-cm long PPLN EO PMC of the IPC device is characterized to have a half-wave (or switching) voltage of V_π∼20 V and a conversion bandwidth of ∼2.6 nm. The splitting ratios of the adiabatic coupler PBS in the IPC device are >99% for both polarization modes over a broad spectral range from 1500–1640 nm. The EO mode of the implemented IPC device is activated when the PPLN EO PMC section is driven by an external voltage; the characterized EO switching/power division behavior of the device is in good agreement with the theoretical fit. The tunability of the EO IPC device in the 100-nm experimental spectral range is also demonstrated via the temperature tuning. The featured broad tunability and high integrability of the EO device presented in this study facilitates it to be an advantageous building block for realizing an on-chip photonic system.