Light Controlled Tunable Grating Based On Self-assembly Effect Of Liquid Crystal Microfluidics

Grating is an optical device composed of a large number of parallel slits with equal width and spacing,which is widely used in spectrum measurement,optical calculation and optical information processing.However,the traditional grating master plate is not only expensive,but also needs mechanical engraving,and the periodic phase angle is fixed and single,which can not achieve high-precision beam deflection.In recent years,liquid crystal grating has become a research hotspot of grating devices because of its incomparable advantages such as low driving voltage,low power consumption,light weight,small volume and adjustable diffraction characteristics.Based on the self-assembly effect of microfluidics,the liquid crystal gratings which can be adjusted in various controllable fields such as light field,electric field,chiral concentration field and thermal field are fabricated by using the photoalignment technology.The micro morphology of this kind of multi field adjustable liquid crystal grating was observed and recorded by orthogonal polarized light microscope and CCD,and its diffraction effect was observed and analyzed by grating diffraction light path.Firstly,we set up two 457 nm laser interference holographic optical paths with orthogonal circular polarization to expose the liquid crystal cell with optical orientation layer.A phase periodic orientation film is formed on the inner surface of liquid crystal cell by a kind of light orientation material called bright yellow dye.Secondly,we use rod-shaped liquid crystal 1008 and chiral material S811 to dope with different concentration,and prepare mixed liquid crystal materials with different concentration field,and fill the mixed liquid crystal with different concentration into the light oriented liquid crystal cell.Finally,the liquid crystal grating is formed in the liquid crystal cell by using the self-assembly characteristics of the liquid crystal material.By controlling a single variable,we analyzed and studied the microstructure morphology and diffraction characteristics of the liquid crystal grating driven to thethreshold under different frequency AC electric field,the difference of the grating structure under different light field configuration,the change of the microstructure morphology and diffraction characteristics under different concentration field.It is found that this kind of liquid crystal grating follows the optical field induced self-assembly periodic structure,but also produces the electric field driven micro periodic domain structure.Moreover,with the adjustment of chirality and temperature to the pitch P0 of the liquid crystal,the micro periodic domain will have an angle of nearly 180 °.The multi field tunable grating based on the self-assembly effect of microfluidics has stable and controllable conditions,and its grating morphology is also flexible in the external field,which is expected to have more applications in the fields of optical communication and optical information processing.Through the study and analysis of the external field conditions,it will lay a solid foundation for the better preparation and improvement of the liquid crystal grating device in the future.