higher order FDTD methods in modeling of dielectric interface

hi.
Is there anyone who is familiar with higher order FDTD methods in dielectric interface modeling in one dimensional or more?
If there is,please reply.I have one question about dielectric interface modeling...

why when I use from one sided difference formula in boundaries (exactly same as my reference papers), my answers become divergent?
is there anyone who is familiar with higher order FDTD schemes?