Abstract:Electro optic (EO) sensor is the core device for free space sampling technique. Conventional EO sensors are fabricated by inorganic crystal, whose EO coefficients are too low. This limits the detecting bandwidth of THz wave. Hostguest polymer possess higher EO coefficient and lower dielectric constant, which becomes the researching focus in related fields. However, phase separation often happens between the host polymer and the guest EO molecules, which leads to the properties decay. In this paper, two kinds of chromophoric groups are introduced into polymer main chains through a combination of chemical and physical methods. Polyphosphazene with double EO molecules, possessing not only high EO coefficient but also fine phasestability, is synthesized successfully and the EO coefficient of the product can be 64.8 pm/V under optimal conditions. Based on our product, a new kind of EO sensor with coplanar electrodes structure is designed and fabricated. On detecting the same THz wave, the amplitude of the new sensor can be enhanced by 50% and the sensibility by 50% compared with the conventional sandwich one. Meanwhile, the effect on detecting sensibility by incident angle can be avoided and the noise interference can be reduced, which makes the sensor with coplanar electrodes structure a more suitable device for THz applications.