Fabrication of low loss two-dimensional InP photonic crystals by inductively coupled plasma etching

Low-loss bidimensional photonic crystals have been fabricated by using an optimized process, consisting of electron beam lithography of a poly(methyl methacrylate) resist, reactive ion etching of an intermediate dielectric layer, and inductively coupled plasma etching of InP-based heterostructures. A depth to diameter aspect ratio as high as 14 has been obtained for hole diameter varying from 260 to 620 nm. As a result of the high aspect ratio and of the almost cylindrical hole shape, very low radiation losses have been obtained. For example, a transmission coefficient in the air band as high as 0.8 has been achieved for eight rows $\mathrm{\Gamma M}$ structure, demonstrating a very low value of the radiation losses.