Superresolved optical imaging through higher-order spatial frequency harmonic generation without beating the diffraction limit of light

TL;DR

This paper introduces a novel superresolution optical imaging technique that magnifies spatial frequency components without surpassing the diffraction limit, demonstrated through a proof-of-principle experiment using frequency doubling/tripling in a modified $4f$ system.

Contribution

The paper presents a new method for superresolution imaging based on higher-order spatial frequency generation, distinct from existing superresolution techniques.

Findings

Spatial frequency of a two-line source was doubled or tripled.

Unresolvable images became resolvable after frequency enhancement.

Method does not require beating the diffraction limit.

Abstract

We proposed a method to achieve superresolved optical imaging without beating the diffraction limit of light. This is achieved by magnifying the ideal optical image of the object through higher-order spatial frequency generation while keeping the size of the effective point spread function of the optical imaging system unchanged. A proof-of-principle experiment was demonstrated in a modified $4f$-imaging system, where the spatial frequency of a two-line source was doubled or tripled on the confocal Fourier plane of the $4f$-imaging system through a light pulse storage and retrieval process based on the electromagnetically induced transparency effect in a Pr$^{3+}$:$\rm Y_2SiO_5$ crystal, and an originally unresolvable image of the two line sources in the conventional $4f$-imaging system became resolvable with the spatial frequency doubling or tripling. Our results offer an original way towards improving optical imaging resolution without beating the diffraction limit of light, which is totally different from the existing superresolution methods to overcome the diffraction limit.