Artificial boundary appraoch
A metasurface can be treated as an effective boundary condition, which can be written down as a few parameters. A pair of such can be used to do control guided light.
Maxwell's fish eye and bending: J. Opt. 18, 044015 (2016)
Asymmetric transmission: Nat. Commn 4, 2561 (2013)
External cloak and designer cavities: ACS Photonics 5, 1749 (2018)
2D gauge transformation
An abstract rotation between TE and TM modes behaves like the U(1) gauge transformation in Schrodinger equation. The gauge field corresponds to a splitting of dispersion surfaces. A non-trivial gauge field generates pseudo-magnetic field for cyclotron motion of photon, AB effect and one-way edge states.
Phys. Rev. Lett. 114, 103902 (2015)
A cylindrical cloak and TO with asymmetric functions.
Phys. Rev. B 95, 075157 (2017) (Editor's suggestion)
Roadmap with other scientists in transformation optics:
J. Opt. 20, 063001 (2018)
A pure gauge for the polarization transformation (abstract rotation between TE&TM) can be used for changing impedance and polarization signature.
Example, changing PEC to a PMC with metamaterial
Phys. Rev. Lett. 111, 033901 (2013) (Editor's suggestion)
Wide angle waveplate:
Appl. Phys. Lett. 107, 241106 (2015)
Related experiment from Hao: Sci. Rep. 5, 17532 (2015)
Photonic crystal approach
Photonic crystals, although without effective medium description, can be used manipulate light based on a gardient profile of dispersion surfaces, either elliptical or square-like.
Opt. Exp. 19, 16821 (2011)
Hiding under a carpet is much feasible at optical frequencies than hiding in the middle of air due to a less singular coordiante transformation.
Theory: Phys. Rev. Lett. 101, 203901 (2008) (Editor's suggestion)
Experiment: Nature Materials 8, 568 (2009)
Acoustics: New J. Phys. 10, 115032 (2008)