Focused ion beam lithography for two dimensional array structures for photonic applications

Two dimensional photonic band gap structures on GaAs/AlGaAs, Si3N4 and Si/SiO2 has been fabricated using a 30 keV gallium ion beam. This process is being developed as a viable alternative for fast prototyping of high quality 2D photonic crystal devices. The feasibility of high-resolution (down to 80 nm) unit cell fabrication has been demonstrated as well as the longitudinal depth of the holes (more than 600 nm) over a pattern area of 100 × 100 μm and smaller, using FIB milling as well as FIB gas assisted etching. During milling fluorine gas was added in the sample chamber to control the interior shape of the holes and also to reduce the formation of Ga spherical calotte shaped dots. The in-plane photoluminescence emission of some fabricated devices has been optically characterized by exciting the in plane cavities from the top surface of the device by picosecond laser pulses. As expected, by virtue of its higher back mirror reflectivity leading to lower cavity losses, the 2D photonic crystal cavity showed the occurrence of amplified spontaneous emission.