Silicon nitride microdisks in the visible range

We fabricate microdisks from Silicon Nitride (Si₃N₄) on a silica (SiO₂) substrate using a simple e-beam lithography and inductively coupled plasma (ICP) etching process. The method results in production of a large number of resonators in a quick and reproducible fashion. The Si₃N₄ exhibits an intrinsic broad defect emission across the visible range. We use this luminescence to probe the resonance structure of the microdisks using micro-photoluminescence (PL) spectroscopy. Together this provides a quick method to fabricate and characterise the microdisk structures. We are interested in small disks with diameters ranging 1 - 10 μm. These disks exhibit modes of reasonable quality factor (Q) dominated by radiative loss. This fabrication process will allow a fast method to study coupling in photonic molecule systems in the visible range. In this paper we demonstrate the feasibility of this method to produce adequately size matched microdisks for mode coupling experiments. We determine the optimum disk size and examine the variation of FSR and Q factor with disk diameter.