Control of light transport by structuring gain and loss

31.10.2012, 16:52

Newsletter 5

 

One of the major achievements in modern optics is the development of novel photonic materials by tailoring the refractive index distribution. But nature also offers the possibility of controlling the flow of light via optical gain and loss.  If parity-time (PT) symmetry is maintained and the gain structure is antisymmetric compared to a symmetric index modulation, materials with new optical properties emerge. By transferring this idea from the spatial to the temporal domain, we have realized the first extended PT-symmetric photonic network. We find that, even when the gain and loss are well-balanced, the optical power is no longer constant but oscillates around a mean value. A phase transition between exponentially exploding and stable optical states is observed for strong gain modulation. We were further able to demonstrate that PT-symmetric elements embedded in a conventional material exhibit unidirectional invisibility (see figure). When illuminated from one side, the PT-symmetric scatterer strongly reflects, the reflected light being even more intense than the incident beam. From the other side, however, it just passes through the scatterer without being reflected – the structure becomes essentially invisible.

 

Contact: alois.regensburger(at)mpl.mpg(dot)de
Group: Leuchs Division (Peschel Group)
Reference: A. Regensburger et al., Nature 488, 167-171 (2012); News & Views article: Nature 488, 163–164 (2012).