Ultra thin high index contrast photonic crystal slabs in lithium niobate

We present for the first time the realization of a free standing photonic crystal slab with a thickness of 450 nm in lithium niobate. The air slot underneath the membrane as well as the air holes, constituting the photonic crystal therein, are realized by the application of ion beam enhanced etching onto bulk lithium niobate. The index difference of 1.2 and the small membrane thickness allow for a very strong vertical confinement of the light and a single mode waveguide behavior (lamda = 1550 nm) at the same time. A photonic crystal structure in a 5 mm long membrane, suspended in air, is shown