Fig. 2. Experimentally measured optical response of the fabricated device.

a The configuration for measuring the optical transfer function. A linear polariser selects the required polarisation direction relative to the direction of the grating stripes. The output lens produces a Fourier plane image. b The experimentally measured normalised two-dimensional modulation transfer function ${∣\mathcal{M}\left(k_x,k_y\right)∣}^2$ for incident light polarised parallel (y-pol) and perpendicular to the silver grating stripes (x-pol). The measurement wavelength was λ = 637 nm. c Profiles along the dashed lines in b (red lines) highlighting the suppression of the direct beam. The corresponding simulated profile for s-polarisation is given for comparison (blue) with the spatial-frequency content of the incident beam (grey). d The normalised modulation transfer function $∣\mathcal{M}\left(k_x,k_y\right)∣$ in the vicinity of k_x/k₀ = 0.04. A small tilt in the incident beam relative to the surface normal of the NEC shifts the spatial-frequency origin (dashed line) introducing an asymmetry into the optical transfer function