Optical Detection and Control of Single Magnetic Ions in Photonic Microcavities

As the density of magnetic information storage scales upwards, the number of magnetic moments in each bit decreases. This pathway ends with the need to manipulate a single spin, a requirement that is also important for nascent information processing schemes including quantum computation. Current demonstrations of coherent single spin control include electron spins in semiconductor quantum dots and nitrogen-vacancy centers in diamond \footnote{R. Hanson and D. D. Awschalom, \textit{ Nature } \textbf{453}, 1043 (2008).} . Single magnetic ions in semiconductors have also emerged as an intriguing spin system due to their surprising ability to be manipulated in zero-field. Manganese (Mn) ions in gallium arsenide (GaAs) are strongly exchange coupled to the charge carriers and can be rapidly controlled either optically or electrically in bandgap- engineered heterostructures. Recently we demonstrated optical control and readout of a small ensemble of Mn ion spins in a GaAs quantum well without magnetic materials or applied magnetic fields\footnote{R. C. Myers, M. H. Mikkelsen, J.-M. Tang, A. C. Gossard, M. E. Flatt\'{e}, and D. D. Awschalom, \textit{ Nature Materials} \textbf{7}, 203 (2008).}. In the limit of low doping levels, their spin lifetimes increase with decreasing concentration as the ions become isolated. Here we describe the spatially-resolved observation and manipulation of isolated Mn spins integrated within photonic microcavities. A single magnetically-doped GaAs quantum well is fabricated within both microdisk and vertical Fabry-Perot cavities in which their respective cavity modes are coupled to the neutral Mn acceptor emission. Scanning micro-photoluminescence measurements reveal cavity-coupled emission and a dramatic increase in the measured signal to noise ratio, thereby allowing direct imaging of narrow linewidth luminescence from the Mn moments. These Mn ion spins are optically polarized at zero-field, exhibit long spin lifetimes, and may be manipulated through a variety of techniques.