Non-destructive shadowgraph imaging of ultracold atoms
  An imaging system is presented that is capable of far-detuned non-destructive imaging of a Bose-Einstein condensate with the signal proportional to the second spatial derivative of the density. Whilst demonstrated with application to $^{85}\text{Rb}$, the technique generalizes to other atomic species and is shown to be capable of a signal to noise of ${\sim}25$ at $1$GHz detuning with $100$ in-trap images showing no observable heating or atom loss. The technique is also applied to the observation of individual trajectories of stochastic dynamics inaccessible to single shot imaging. Coupled with a fast optical phase lock loop, the system is capable of dynamically switching to resonant absorption imaging during the experiment. 
Paul B. Wigley, Patrick J. Everitt, Kyle S. Hardman, Michael R. Hush,   Chunhua Wei, Mahasen A. Sooriyabandara, Manju Perumb...
physics.atom-ph cond-mat.quant-gas quant-ph