Enhanced electro-optic property of host-guest polyphosphazene thin film and its application

• A new host-guest polyphosphazene synthetic method was reported.
• Our product possesses not only high EO coefficient but also fine phase stability.
• The maximum value of EO coefficient can be 52.2 pm/v.
• Thin films formed by our product are used to detect terahertz radiation.
• The detecting efficiency and the spectrum sensitivity are enhanced largely.

A new synthetic method by doping two kinds of chromophoric groups into polyphosphazene was reported in this paper. One kind of the chromophoric group (phenol nitro azobenzene) was grafted to the polymer by chemical method for polar improvement of the main chain, and the product was phenol polyphosphazene grafted by paranitroaniline. Then another small nonlinear optical molecule (NOL) was mixed into the polymer by physical method for further improvement of EO property. Here ethyl 4-(dimethylamino) benzoate (EDB) and 4-6-alkoxy-4′-cyano-biphenyl (6OCB) were selected respectively. The effect on EO coefficient by different mixing proportion was investigated and the test of the sample orientation stability was performed. Experimental results show that the material possesses not only high EO coefficient but also fine phase stability. The enhancement of EO property by EDB mixing is more obvious than that by 6OCB and the maximum value of EO coefficient can be 52.2 pm/v. Finally, the polymer thin films were used to detect terahertz (THz) radiation. It is found that the detecting efficiency and the spectrum sensitivity are enhanced largely compared with conventional inorganic crystal.