Electrode-free photonic electric field sensor on thin film lithium niobate with high sensitivity

A high-sensitivity electrode-free photonic electric field (E-field) sensor is introduced on a thin film lithium niobate (TFLN) platform. An integrated Michelson interferometer, constructed by low-loss etched lithium niobite (LN) waveguide structures, is implemented as the sensing element. The sensing arms are designed in a spiral shape, which facilities a long interaction length with the external E-field in a small chip area. A minimal detectable E-field amplitude of 8.43 mV/m/Hz^1/2 is experimentally obtained. The metal-electrode-free design of the proposed device avoids affecting the E-field to be measured and enables a vectorial response with a measured extinction ratio (ER) of 38 dB.