TM-mode perturbation analysis of dielectric gratings

An improved perturbation procedure that was previously presented for TE modes guided by dielectric gratings is extended here to TM modes. In both cases, the fields are described in terms of a transverse transmission-line network, which lends considerable physical insight into the behavior of dielectric gratings. However, TM modes require equivalent sources of both the voltage and current varieties, in contrast to TE modes which involve only current sources. By comparing with an exact solution, the numerical results obtained by the present perturbation procedure are found to be very accurate. This work was supported by the U.S. Office of Naval Research, under Contract No. N 00014-67-A-0438-0014, and by the U.S. Joint Services Electronics Program, under Contract No. F 44620-69-C-0047.