Transmission Spectral Characteristics of Photonic Crystals Milled in Annealed Proton-Exchange LiNbO3 Waveguide**Supported by the National Natural Science Foundation of China under Grant Nos 50872089, 61077039 and 61377060, the Research Grants Council of the Hong Kong Special Administrative Region of China under Grant No 11211014, the Key Program for Research on Fundamental to Application and Leading Technology of Tianjin Science and

Abstract

Transmission spectra of triangular lattice photonic crystals milled in the top surface of an annealed proton-exchange waveguide are numerically simulated. The effects of the finite depth, conical shape, trapezoidal shape and hybrid shape of holes are theoretically analyzed. Due to the difficulty of milling high aspect-ratio cylindrical holes in lithium niobate (LiNbO3), a compromised solution is proposed to improve the overlap between shallow holes and the waveguide mode, and useful transmission spectra with strong contrast and sharp band edges are achieved.