Design and implementation of silicon-based optical nanostructures for integrated photonic circuit applications using Deep Reactive Ion Etching (DRIE) technique

In this paper, we present the fabrication of nano optical elements by means of deep reactive ion etching technique (Bosch process) on a silicon-on-insulator substrate. The nano structures are fabricated in a two step process. The first step consists of direct-writing nanoscale patterns on PMMA polymer by electron beam lithography. These nano patterns are then transferred to the silicon surface by a low temperature and low pressure deep reactive ion etching (DRIE) process using PMMA as a mask. The low temperature and low pressure conditions in the DRIE process minimize scalloping in the nanoscale features. We found that the etch rate is highly dependent on the aspect ratio of the structure. We have used the DRIE method to fabricate a negative-index photonic crystal flat lens and demonstrated the focusing properties of this flat lens using a near-field scanning optical microscope.