Confined optical fields [
1,
2], always appeared in the metallic plasmonic configurations [
3–
5] and optical cavities [
6–
8], can possibly produce strong interaction between photons and matters [
9] due to the localized photons distributions. When the coupling interaction strengths between cavities photons with resonant excitons are larger than the losses [
10], the exciton polaritons can be probably formed. Attributed polaritons condensations and strong nonlinearities inherited from their exciton polaritons, exciton polaritons have exhibited enormous potentials [
11] in the field of low-threshold lasers [
12–
14], all-optical logic devices [
15–
18] and quantum devices [
19–
21]. In recent years, many research groups have developed the exciton polaritons nanostructures utilizing the strong coupling between material excitons and confined optical fields in metallic configurations or vertical Fabry Perot cavity and distributed Bragg reflectors (DBRs) [
22,
23]. The metallic nanostructures [
24] are ultracompact but suffer from inherent ohmic losses. Nanostructure DBRs-type exciton polaritons [
22,
25] are difficult to fabricate and easy to destroy the excitonic material layer. So it is essential to explore novel nanostructures with low losses and flexible structural design and fabrications this field. Last year, Long Zhang et al. [
26] have already demonstrated exciton polaritons in silicon nitride half-etching photonic crystals coupled with WSe
2 materials. But due to relative weak optical confinement fields, there are rare exciton polaritons reports directly established on dielectric cavity nanostructures. Therefore, it is still necessary to explore a planar dielectric nanostructure to demonstrate the exciton polaritons.