SEM images of different antenna structures. (a) Gold trimer antenna consisting of nanoparticles supported by a dielectric tip (Figure reproduced with permission from ref. 9, ©2011 NPG.). (b) Bowtie aperture antennas fabricated by FIB milling of an aluminum coated fiber probe (Reprinted with permission from Nano Lett., 2012, 12, 5972. Copyright 2012 American Chemical Society.). (c) Tapered plasmonic waveguide on top of a photonic crystal cavity for efficient photonic plasmonic coupling (Figure reproduced with permission from ref. 80, ©2010 NPG.). (d) Template-stripped 200 nm thick gold tips fabricated in anisotropically etched pyramidal molds on a Si wafer (Reprinted with permission from ACS Nano, 2012, 6, 9168. Copyright 2012 American Chemical Society.). (e) Coaxial antenna incorporated on the end of a scanning probe tip (Reprinted with permission from Nano Lett., 2011, 11, 1201. Copyright 2011 American Chemical Society.). (f) Etched gold wire tip with grating structure for SPP coupling and plasmonic nanofocusing (Reprinted with permission from J. Phys. Chem. Lett., 2012, 3, 945. Copyright 2012 American Chemical Society.).