Transformation optics with pseudomagnetic field

A real-space gauge field provides an alternative way in bending light by shifting the local dispersion surfaces instead of changing their shapes or sizes in conventional gradient index media. Here, we show that such gauge field can be realized by anisotropic metamaterials. A metamaterial structure with balanced electric and magnetic responses is designed to materialize such gauge field. By combining with transformation optics, it allows us to design spin-dependent optical devices. A unidirectional retroreflector is demonstrated as an example.