A novel photosensitive fluorinated poly(arylene ether) containing chalcone units was synthesized from decafluorinated chalcone and fluorinated bisphenol at low temperature. Upon UV irradiation, the refractive indices of the polymer film were decreased because of the reduction of electronic polarizability in the chalocone moiety. The decrease was more significant in the in-plane direction than in the out-of-plane direction, and consequently, zero birefringence (at 632.8 nm) was obtained after 90 s of exposure.