Fig. 1. (a) 3D schematic view of the proposed low-sidelobe plasmonic antenna. (b) Cross-section view of a uniform plasmonic gap waveguide. (c) E-field distribution of the plasmonic gap mode. The parameters are w=350  nm, g=200  nm, and t=100  nm.

Fig. 2. Schematic views of (a) uniform plasmonic gap waveguide and (b) sinusoidally modulated antenna. (c) Metal absorption loss αc and normalized phase constant versus gap width g0. (d) Average attenuation constant α of the system and leakage factor αr of the antenna as a function of modulation amplitude g1 with g0=600  nm.

Fig. 3. (a) Target Chebyshev amplitude distribution along antenna radiation aperture. (b) Theoretical modulation amplitudes and leakage factors for the 12 radiation periods. The blue symbols represent the fitting points with a quadratic function formula. (c) Simulated far-field patterns on the yoz plane at 1500, 1550, and 1600 nm. (d) Radiation efficiency and directivity of the proposed LWA within the wavelength range of 1500 to 1600 nm.

Fig. 4. (a) Proposed antenna under the coordinate system. (b) 3D radiation pattern of the designed antenna. (c) Radiation patterns in the xoz and yoz planes. (d) Port reflection coefficient S11 as a function of wavelength.

Fig. 5. SEM image of the (a) referenced structure and (b) fabricated array composed of designed SLL antennas. Measured far-field pattern of the (c) referenced array and (d) proposed design. (e) Measured Fourier-space images of the proposed design at wavelengths of 1527, 1550, and 1570 nm.

Fig. 6. (a) Schematic diagram of the operating principle of the proposed leaky-wave antenna. (b) Theoretical normalized radiation pattern in the yoz plane based on the designed Chebyshev amplitude distribution.

Fig. 7. (a) Schematic diagram of a uniform linear array. (b) Radiation patterns in the xoz and yoz planes versus the number of antenna elements. (c) Array realized gain as a function of the number of antenna elements in the array.