Investigation of point-defect cavity formed in two-dimensional photonic crystal slab with one-sided dielectric cladding

Three-missing-hole point-defect cavities formed in a two-dimensional photonic crystal slab with a silicon-on-insulator structure are investigated. It is theoretically revealed that radiation loss to the SiO2-cladding side is four times higher than that to the air-cladding side due to the smaller refractive index contrast. In addition, in-plane radiation due to transverse electric-transverse magnetic (TE-TM) coupling occurs due to the vertical structural asymmetry. The amount of TE-TM coupling loss is comparable with that of radiation loss to the SiO2 cladding. Experimental results agreed well with theoretical predictions. This treatment can be applied to point-defect cavities in one-sided dielectric cladding structures and in three-dimensional configurations.