Nanocouplers for Infrared and Visible Light

Table 1

Comparison of various nanocoupling approaches.

Approach	Coupling efficiency: low (<10%), medium (10–50%), high (>50%)	Size: compact (<10 𝜇m) or large (>10 𝜇m)	Subwavelength coupling or focusing	Lateral or vertical coupling	References
4.1. Tapered dielectric	High	Both	No	Lateral	[18–25]
4.2. Tapered metal	Medium and large	Compact	Yes	Lateral	[26–39]
4.3. Tapered metamaterial	Low and medium	Compact	Yes	Lateral	[40–42]
5.1. Next to another	High	Both	Yes	Lateral	[43–53]
5.2. End-fire	High	Compact	No	Lateral	[54–60]
5.3. Resonant stub	High	Compact	Yes	Lateral	[11, 61–64]
6.1. Dielectric lens	High	Large	No	Lateral	[66, 67, 69, 70]
6.2. Plasmonic lens	Medium	Compact	Yes	Lateral	[71–78]
6.3. Negative index lens	N/a	N/a	Yes	Lateral	[79, 80, 84, 100]
6.4. Photonic crystal lens	N/a	Compact	Yes	Lateral	[101–105]
6.5. Hyperlens	Low or medium	Compact	Yes	Lateral	[107–122]
7.1. Antenna	Medium	Compact	Yes	Both	[125–131]
7.2. Grating	High	Large	No	Vertical	[132–140]
7.3. Random scatterers	Low	N/a	Yes	Both	[141]