Photonic crystals are more commonly referred as photonic band gapped materials with the ability to stop and confine light. In this talk, I am going to extend the applications of photonic crystals to achieve some intriguing EM properties:
We can realize extreme effective medium properties, presumably very difficult to be achieved by metamaterial designs by engineering photonic band diagrams. Utilizing the scaling property of Maxwell’s Equation, we realized a complementary medium by stacking two photonic crystal slabs scaled uniformly . An Ultratransparent medium, with all angle impedance matching to vacuum, is also possible by using pure dielectric photonic crystals . A new design of invisibility cloak is also proposed and demonstrated using zero-index photonic crystal and metasurface .
Studying the analogy between electronic wave and light, novel ideas to optical devices can be motivated by condensed matter physics theories. By mapping photonic band gaps to electronic Zak phase, multiple methods to realize the deterministic interface states were demonstrated experimentally in two-dimensional photonic crystals . We target at achieving unidirectional optical waveguides without external magnetic field. We show experimentally an optical analogy of quantum spin Hall effect of light using deformed honeycomb lattices of dielectrics . The valley degrees of freedom in two-dimensional photonic crystals are exploited and future optical devices such as valley filter and valley coupler are proposed.
 T. Xu, A. Fang, Z. Jia, L. Ji and Z. H. Hang*, Opt. Lett. 42, 4902 (2017).
 J. Luo, Y. Yang, Z. Yao, W. Lu, B. Hou, Z. H. Hang*, C. T. Chan and Y. Lai*, Phys. Rev. Lett. 117, 223901 (2016).
 H. Chu, Q. Li, B. Liu, J. Luo, S. Sun*, Z. H. Hang*, L. Zhou and Y. Lai*, Light: Science & Applications, 7, 50 (2018)
 Y. Yang, X. Q. Huang, and Z. H. Hang*, Phys. Rev. Applied 5, 034009 (2016).
 Y. Yang, Y. F. Xu, T. Xu, H.-X. Wang, J.-H. Jiang, X. Hu*, and Z. H. Hang*, Phys. Rev. Lett. 120, 217401 (2018).