Fig. 1. Light ray tracing for a conformal carpet cloak with minimized lateral shift. The carpet cloak covers the top of a curved PEC bump, making it reflect light as a virtual flat plane denoted by the blue dashed line. The blue and black solid arrows indicate the trajectories of light reflected by the virtual plane and the cloak, respectively. The contour plot represents the refractive index distribution for the cloak. The cloak is designed with a conformal transformation with a=0.005, b=0.005, and t=3.7.

Fig. 2. Minimization of the lateral shift. Analytically calculated lateral shift and simulated reflection coefficients (for TE and TM polarizations) at the interface between the background and the cloak as a function of (a) the periodicity p and (b) the cloak height H.

Fig. 3. Numerical verification of the polarization-insensitive performance. Simulated electric field distributions of a bumped surface (a) without the cloak and (b) with the cloak when a TE-polarized Gaussian beam is incident at an angle 32° with respect to the horizontal direction. Simulated electric field distributions of a bumped surface (c) without the cloak and (d) with the cloak when a TE-polarized Gaussian beam is incident at an angle 42° with respect to the horizontal direction. Simulated magnetic field distributions of a bumped surface (e) without the cloak and (f) with the cloak when a TM-polarized Gaussian beam is incident at an angle 32° with respect to the horizontal direction. Simulated magnetic field distributions of a bumped surface (g) without the cloak and (h) with the cloak when a TM-polarized Gaussian beam is incident at an angle 42° with respect to the horizontal direction.

Fig. 4. Blueprint of the mid-IR carpet cloak designed at a wavelength λ=10.6  μm. (a) Schematic of the practical implementation of the cloak. Light is incident upon a triangular background drilled with homogenous holes. The cloak is built by drilling spatially gradient holes into an SOI wafer. Magnetic field distributions when a TM-polarized Gaussian beam is incident at an angle 45° onto (b) a bare bump and (c) a bumped surface covered with the cloak.

Fig. 5. Demonstration of the robust cloaking performance over a broad frequency range from 24 to 29 THz. (a) Intensity profile versus the different positions along the white dashed line in Fig. 4(b) when the incident laser beam illuminates the bare bump. (b) Intensity profile versus the different positions along the white dashed line in Fig. 4(c) when the incident laser beam illuminates the bump covered with the cloak.