Fully-integrated optofluidic device on lithium niobate for liquid crystals actuation

International audienceDuring the last years Optofluidic has attracted the interest of the scientific community due to its widerange of applications, from optics to biochemistry. In this field, one of the most exploited tool is thetechnology based on liquid crystals, due to their liquid nature, their optical properties and the highbiocompatibility.In this work we report our latest results on the realization of an optofluidic platform which is fullyintegrated on a lithium niobate (LiNbO3, LN) cell and allows actuating and monitoring liquid crystalsby means of light [1]. The device consists of two part: the microfluidic channel which has beenengraved on a Ti-doped LN substrate and the cover realized with a Fe-doped LN crystal. The Fe:LNcover allows reorienting liquid crystal molecules by means of the strong charge accumulations andelectric fields which can be easily created at the surface of the material by light via the photovoltaiceffect [2]. The diffused Ti:LN waveguides which cross the microfluidic channel are exploited tomonitor the time evolution of the liquid crystals reorientation, thanks to the fact that this latter inducesa change of polarization on the incoming light from the waveguide.In this way the chip is able at the same time to optically control the liquid crystals alignment inside themicrochannel and it reads the consequent light polarization alteration via an integrated waveguidessystem, thus increasing the level of integration and the full optical control of this system, paving theway for new interesting Lab-on-a-Chip and optical applications