Fig. 1 The matched nanoantenna. (a) A general view with a typical far-field pattern. The chain is excited by a quantum emitter modeled as a short dipole, generating a guided mode that propagates in the (allowed) $+\widehat{z}$ direction. Back reflections at the remote end cannot take place, hence the mode is converted to radiation. This end is a matched local antenna. (b) The near E-field. Energy is transmitted from the port to the remote end with minimal loss (4dB, due to material), and is emitted essentially from particles near the end. (Media 1 0.5Mb) (c) Due to the one-way property, if the port is located on the other end the chain excitation is marginal and the radiation is directly from the port. (d) Normalized fields at the center of each particle in Figs. 1(b-c). Dashed [solid] lines– corresponds to Fig. 1(b) [1(c)], source at $z=0$ ($z=103d$).

Fig. 2 Antenna matching in Tx. (a) A DFT of the chain response. (b) reflection (transmission) coefficient - solid lines (dashed lines) vs. frequency for two levels of magnetization. (c) Radiation efficiency of the entire structure.

Fig. 3 Antenna Tx and Rx gain in the plane. (a) One way is on. (b) One way is off. The beam is conical; hence gain in plane is the same.

Fig. 4 Dynamic control of the optical beam by the bias magnetic field. (a) Tx gain. (b) Rx gain.