Ion beam etching of high resolution structures in Ta2O5 for grating-assisted directional coupler applications

An investigation on thin Ta2O5 films patterning using argon ion beam etching (IBE) is presented. The etch rates are characterised by varying the angle of incidence of the beam onto the substrate. Ta2O5 gratings with a period of 2.2 mm (1.1 mm linewidth) and 0.25 mm thickness are fabricated using an angle of incidence of 08. The resulting Ta2O5 grating cross sectional profiles are analysed using AFM and SEM imaging. A fabrication method is thus demonstrated which could be used to implement wavelength selective gratings in applications such as grating-assisted directional couplers (GADCs).