Focused ion beam fabrication of one-dimensional photonic crystals on Si₃N₄/SiO₂ channel waveguides

In this paper we describe a reliable and expedient approach for protyping one-dimensional (1D) photonic crystal (PhC) on optical waveguides using focused ion beam (FIB) lithography (which eliminates the need for photoresist and alignment markers). In particular, we show the detailed fabrication process of three 1D photonic crystal patterns (1) a periodic structure, (2) with micrometre-wide cavity layers, and (3) with one taper element, directly milled onto a silicon nitride/silicon dioxide (Si₃N₄/SiO ₂) channel waveguide. Experimental investigations of the devices obtained using ultra-broadband transmittance spectroscopy in the visible and near-infrared frequency ranges (i.e. wavelengths between 0.4 and 1.7νm) are employed to show photonic band-gap behaviour up to fourth order in the radiative mode region. These results are compared with simulations of both transmission and photonic dispersion behaviour. In addition, we demonstrate the novel effects produced by taper elements on the 1D PhC micro-cavities.