Fig. 1. Schematic of an electromagnetic wave totally reflected at the interface between two media. The x axis is perpendicular to the interface, and the y axis is parallel to the interface. A metasurface is attached on the upper side of medium 1.

Fig. 2. Critical angles as functions of the phase gradient in the y direction for 30, 40, and 50 THz incident waves. +θc and −θc represent the cases for ‘+’ and ‘−’ in Eq. (7), respectively. The refractive index of medium 1 considered as silicon was set approximately to n1=3.42^[23], and medium 2 was regarded as the vacuum (n2=1).

Fig. 3. GH shifts on the phase-gradient metasurface as functions of the phase gradient at 30, 40, and 50 THz frequencies for the (a) TE and (b) TM polarizations.

Fig. 4. Dip ratios as functions of the phase gradient at 30, 40, and 50 THz frequencies for the (a) TE and (b) TM polarizations.

Fig. 5. GH shifts as functions of the incident angle for the different phase gradients (dφ/dy) of −π/2, −π/4, 0, π/4, and π/2  rad/μm at the frequency of 40 THz. (a) TE polarization; (b) TM polarization.