Design, Fabrication and Characterization of Si3N4 Photonic Crystal Nanocavities for Diamond-based Quantum Information Processing Applications

摘要

In order to improve the efficiency of quantum emitters, in particular nitrogen-vacancy (NV) color centers in diamond nanocrystals (NCs), it is important to enhance their photon production rate as well as the collection efficiency of the emitted photons. This can be achieved by embedding the emitters within optical cavities. Here we describe the design and fabrication of 1-D photonic crystal nanocavities in an air-bridge silicon nitride (SiN_x) structure. In spite of the low index of SiN_x (n~2), we were able to design optical nanocavities with Quality (Q) factors as high as Q-1 x 10~6. These nanocavities were designed to operate near 637 nm in order to strongly enhance the zero-phonon line (ZPL) emission of an NV center in a diamond NC while suppressing the in-plane emission into the phonon side-band. Simulation results show that a NV center placed near the top of the cavity would experience a reduction of radiative lifetime from ~15ns to ~2ps (Purcell factor -7000), thus significantly improving the photon production rate. Experimental results show a cavity resonance at ~630nm, with a linewidth corresponding to Q-1250, limited by the spectrometer resolution. The presented work is an important step towards the realization of diamond-based single photon devices, including switches.