Synthetic photonic lattices: new routes towards all-optical photonic   devices
  All-optical photonic devices are crucial for many important photonic technology and applications, ranging from optical communication to quantum information processing. Conventional design of all-optical devices is based on photon propagation and interference in real space, which may reply on large numbers of optical elements and are challenging for precise control. Here we propose a new route for engineering all-optical devices using photon internal degrees of freedom, which form photonic crystals in such synthetic dimensions for photon propagation and interference. We demonstrate this new design concept by showing how important optical devices such as quantum memory and optical filter can be realized using synthetic orbital angular momentum (OAM) lattices in a single main degenerate cavity. The new designing route utilizing synthetic photonic lattices may significantly reduce the requirement for numerous optical elements and their fine tuning in conventional design, paving the way for realistic all-optical photonic devices with novel functionalities. 
Xi-Wang Luo, Xingxiang Zhou, Jin-Shi Xu, Chuan-Feng Li, Guang-Can Guo,   Chuanwei Zhang, and Zheng-Wei Zhou
quant-ph