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Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE

Superresolving optical microscope by means of two-photon entanglement

Naoki Fukutake

Published Mar 10, 2006• 0 citations
Publisher

Abstract

We propose a two-photon imaging system and formulate the property of the system into an image-formation formulae. The idea of two-photon image-formation, in which the entangled photon pairs are utilized, unveils the possibility of the advancement in resolution. We show that the two-photon microscopy beats the diffraction limit and discuss the resolution of this high-resolving optical system.

DOI
10.1117/12.655428

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We propose a two-photon imaging system and formulate the property of the system into an image-formation formulae. The idea of two-photon image-formation, in which the entangled photon pairs are utilized, unveils the possibility of the advancement in resolution. We show that the two-photon microscopy beats the diffraction limit and discuss the resolution of this high-resolving optical system.
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We formulate an image-forming optical theory of quantum lithography in which Entangled-photon pairs generated by spontaneous parametric down-conversion play an important role. Our optical system consists of an image-forming system, an illumination system with a second-order nonlinear medium, and two-photon absorbing materials. We evaluate the resolution of the quantum lithography system by using the optical transfer function and show a super-resolving condition which is, however, difficult to achieve.
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We use entangled photons as the light source in a normal microscope. Using this quantum illumination improves both the resolution and noise rejection in the image. The resolution of any classical imaging system is limited by the diffraction created by the finite size of the imaging lens. By using a light source that emits pairs of entangled photons and carefully controlling a camera that is capable of detecting single photons it is possible to observe these photons arriving two-by-two. Applying camera analysis software to log only these two-by-two events one can form an image from the mid-point (bisector) of each of these pair events. The image formed from the sum of all these bisectors has an improved resolution that surpasses the classical limit. Another advantage of using a quantum illumination is that it allows the two-by-two events from entangled photon pairs to be distinguished from background (classical) light and sensor noise. When processed in this way the resulting image is free of camera noise and any background light may be eliminated. The use of a quantum illumination protocol such as that used here results in the elimination of background light and therefore allows the development of the optical equivalent of quantum radar – a quantum enhanced LIDAR scheme. Using quantum illumination, combined with commercially available cameras that are sensitive to single photons creates a new approach to super-resolution and low noise microscopy. Imaging through noise with quantum illumination, T Gregory, P-A Moreau, E Toninelli, and M J Padgett, Science Advances 6, eaay2652 (2020) Resolution-enhanced quantum imaging by centroid estimation of biphotons, E Toninelli, P-A Moreau, T Gregory, A Mihalyi, M Edgar, N Radwell, and M J Padgett, Optica 6, 347-353 (2019)
The resolution of optical scanning microscopes is limited by the spot size of the scanning beam. It has been proposed by Boto1 et al. and Nasr2 et al. that momentum entangled photons can be focused more tightly than classical light. Thus they should enable one to break the di ractive resolution limit. We report experiments measuring the spatial distribution of strong focussed momentum entangled photon pairs at a center wavelength of 812 nm from a spontaneous parametric down conversion source. Using a single gold stripe deposited on a glass surface as test object we observe a two-photon spot size as small as 194 nm, thereby beating the di raction limit even for conventional two-photon microscopy.