Extremely high transmission of light through a nanohole inside a photonic crystal

The transmission of light through single nanoholes with diameters considerably smaller than the wavelength of light (smaller than lambda/10) is experimentally studied. The nanoholes were made in a gold film, which is a part of a photonic crystal forming a microcavity with the quality factor Q a parts per thousand 100. A 28-fold increase in the transmission of light through a nanohole inside the microcavity compared to transmission through a nanohole in a gold film is demonstrated. The high spectral selectivity of light transmission through a nanohole is discovered, which is characterized by two features: (i) the transmission maximum is located at the resonance wavelength of the microcavity and (ii) the peak full width at half-maximum is about lambda/90.