Transmission halographic polymer dispersed liquid crsytal grating with high spatial frequencies (3000 lp/mm)

abbrivrated as HF-THPDLC

was fabricated

and the material system was investigated. In order to get the HF-THPDLC grating with high diffraction efficiency and perfect surface morphology

the average functionality of the reaction system was determined first. Therefore

the diffusion time of the pre-polymer monomer and the liquid crystal

the nucleation time of the liquid crystal and the gelation time of the polymer are on the same order. Consequently

the perfect surface morphology was obtained and the scattering loss of the grating was reduced. Secondly

small monomer NVP was added into the reaction system of fabricating grating

and the optimum concentration was found. The addition of NVP enhanced the degree of phase separation and got perfect surface morphology as well as higher refractive index modulation. And accordingly the diffraction efficiency of HF-THPDLC grating was remarkably improved. Experimental results indicated that when the average functionality was 3.2 and NVP concentration was 10%

the optical properties of the HF-THPDLC grating were the best and the diffraction efficiency reached 78.3%.