Table 1. State-of-the-art near-field intensity enhancement by different nano antennas.

Reference	Resonance wavelength (nm)	Gap size (nm)	Relative intensity enhancement (orders of magnitude)	Antenna structure
Kottmann et al. 200138	329	No gap	5	Irregular triangle
Sundaramurthy et al. 200539	856	16	4	Bowtie
Fischer et al. 200840	820	30	2	Bowtie
	760	30	3	Dipole
Seo et. al 200941	3*106	70	3	Slit
McMahon et al. 200942	900	0.25	5	Dimer
McMahon et al. 20106	570	0.5	5	Bowtie
Feichtner et al. 20127	647	10	3	Split ring + 2 wire antenna
Chen et al. 201243	830	30	2	Bowtie
Palma et al. 201344	75000	Cavity	4	Square patch over a dielectric layer
This work	10600	0.5–1	8	Bowtie
		10	6
		50	4