Abstract
In the past decade numerous efforts have been concentrated to achieve optical imaging resolution beyond the diffraction limit. In this letter a thin microcavity theory of near-field optics is proposed by using the power flow theorem firstly. According to this theory, the near-field optical diffraction from a tiny aperture whose diameter is less than one-tenth incident wavelength embedded in a thin conducting film is investigated by considering this tiny aperture as a thin nanocavity. It is very surprising that there exists a kind of novel super-resolution diffraction patterns showing resolution better than λ/80 (λ is the incident wavelength), which is revealed for the first time to our knowledge in this letter. The mechanism that has allowed the imaging with this kind of super-resolution patterns is due to the interaction between the incident wave and the thin nanocavity with a complex wavenumber. More precisely, these super-resolution patterns with discontinuous upright peaks are formed by one or three items of the integration series about the cylindrical waves according to our simulation results. This novel optical super-resolution with upright edges by using the thin microcavity theory presented in the study could have potential applications in the future semiconductor lithography process, nano-size laser-drilling technology, microscopy, optical storage, optical switch, and optical information processing.
Highlights
The past decade has seen numerous efforts to achieve optical imaging resolution beyond the diffraction limit
By considering the subwavelength aperture within a thin film as a thin microcavity, this paper first presents a thin microcavity theory to describe this kind of near-field optical diffraction and a novel optical superresolution pattern with upright edges is revealed
For the near-field optical diffraction from a subwavelength aperture in a thin conducting film, the subwavelength aperture within the thin film could be considered as a thin microcavity
Summary
The past decade has seen numerous efforts to achieve optical imaging resolution beyond the diffraction limit. The evanescent waves containing fine detail of the electromagnetic field distribution were exploited to form subwavelength hotspots, such as near-field scanning optical microscope [1,2,3], various field concentrators [4,5,6,7], and negative index superlens [8,9,10,11,12,13]. Instead of using evanescent waves in these works, the super-oscillatory phenomenon was found [14] and a super-oscillatory lens with a high-throughput binary masks was exploited for subwavelength imaging showing resolution better than λ/6 [15]. In our previous paper [3], a theoretical model of near-field optics diffracted from a subwavelength aperture in a thin conducting film was proposed. By considering the subwavelength aperture within a thin film as a thin microcavity, this paper first presents a thin microcavity theory to describe this kind of near-field optical diffraction and a novel optical superresolution pattern with upright edges is revealed
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