All‐Optically Driven Optofluidic Light Modulator

Liquid crystals (LCs) are widely recognized for unique physical and optical properties and remarkable ability to modulate light beams. Traditional methods for actuating LCs by electric fields rely on the use of metallic electrodes, which face limitations in the spatial resolution of LCs actuation and their effective integration into optofluidic devices. In this work, an innovative approach is presented to realize a fully integrated optofluidic light modulator, capable of modifying the optical properties of a light beam propagating through an optical waveguide and coupled with a microfluidic channel. Specifically, the optoelectronic properties of lithium niobate (LN) are leveraged to control the orientation of LCs molecules confined in the microfluidic channel without the need for fixed metallic structures, but solely exploiting light-induced electric fields. It is demonstrated that the light-driven orientation of the LCs can efficiently modulate both the intensity and polarization of the light beam propagating through the waveguide, while the desired amplitude and time-constant of the output optical signal can be achieved by tuning the compositional properties of the LN substrate. The modulation of the guided beam is completely defined and controlled by a pump light source, assuring a high degree of reconfigurability and compatibility of the final optofluidic lab-on-a-chip system.