124
5 Recent Advances in Zero-Index Photonics
Fig. 5.4 Zero-index-metamaterial-based all-dielectric nanoantenna proposed by Shankhwar et al.
(a)
(b)
Fig. 5.5 a The original radiation pattern of the emitter. b The radiation pattern of the ZIM nanoantenna. The major radiation lobe is oriented toward +x-direction, indicating that most of the power
is radiated in that direction
boundary, and consequently the former emits a greater amount of radiation than the
latter. We exploited this property to design a zero-index-metamaterial-based highly
directional all-dielectric nanoantenna, which can radiate in a particular direction, the
optical power emitted by an otherwise omnidirectional quantum emitter [65]. The
proposed nanoantenna has been shown in Fig. 5.4. It consists of a ZIM slab made
up of a 7 × 3 array of silicon rods, backed by a Bragg reflector to prevent backward
radiation. Figure 5.5 shows the radiation pattern of the nanoantenna, in which it can
be observed that most of the radiation has been emitted in the +x-direction.
An important parameter called directivity gives the amount of power radiated by
an antenna in a particular direction relative to the power radiated by a omnidirectional
antenna. According to Krasnok et al. [230], Directivity (D) as function of spherical
coordinates θ and φ is given by
5 Recent Advances in Zero-Index Photonics
Fig. 5.4 Zero-index-metamaterial-based all-dielectric nanoantenna proposed by Shankhwar et al.
(a)
(b)
Fig. 5.5 a The original radiation pattern of the emitter. b The radiation pattern of the ZIM nanoantenna. The major radiation lobe is oriented toward +x-direction, indicating that most of the power
is radiated in that direction
boundary, and consequently the former emits a greater amount of radiation than the
latter. We exploited this property to design a zero-index-metamaterial-based highly
directional all-dielectric nanoantenna, which can radiate in a particular direction, the
optical power emitted by an otherwise omnidirectional quantum emitter [65]. The
proposed nanoantenna has been shown in Fig. 5.4. It consists of a ZIM slab made
up of a 7 × 3 array of silicon rods, backed by a Bragg reflector to prevent backward
radiation. Figure 5.5 shows the radiation pattern of the nanoantenna, in which it can
be observed that most of the radiation has been emitted in the +x-direction.
An important parameter called directivity gives the amount of power radiated by
an antenna in a particular direction relative to the power radiated by a omnidirectional
antenna. According to Krasnok et al. [230], Directivity (D) as function of spherical
coordinates θ and φ is given by