Boundary layer effect of light transmission through ionic liquid under electric field

The field strength distribution in the ionic liquid boundary layer under the action of an external electric field is non-uniform. Whether its transmittance (absorption coefficient) spatially varies arouses our interest in exploring the underlying laws. In this paper, with the help of an infrared microscope, a special experimental device was designed and established. The transmittance in the ionic liquid (methyl propyl imidazole iodide, C₃MImI) at different distances from the electrodes (cathode, anode) was measured under electric voltages from 0 V to 0.5 V. Results showed that transmittances of ionic liquid at the boundary layer present nonlinear change with the nonlinear electronic strength under the different applied voltage, and there is a critical threshold (0.2 V) distinguishes the sensitive and non-sensitive responses to the electric field. Our study provides a physical basis for microscale electro-optic regulation and is significant, especially for precise regulation of light field transmittance in micro-nano channels/structures.