Intensity correlation OCT is a classical mimic of quantum OCT providing up to twofold resolution improvement

Sylwia M Kolenderska,Piotr Kolenderski

doi:10.1038/s41598-021-90837-9

Abstract

Quantum Optical Coherence Tomography (Q-OCT) uses quantum properties of light to provide several advantages over its classical counterpart, OCT: it achieves a twice better axial resolution with the same spectral bandwidth and it is immune to even orders of dispersion. Since these features are very sought-after in OCT imaging, many hardware and software techniques have been created to mimic the quantum behaviour of light and achieve these features using traditional OCT systems. The most recent, purely algorithmic scheme—an improved version of Intensity Correlation Spectral Domain OCT named ICA-SD-OCT—showed even-order dispersion cancellation and reduction of artefacts. The true capabilities of this method were unfortunately severely undermined, both in terms of its relation to Q-OCT and its main performance parameters. In this work, we provide experimental demonstrations as well as numerical and analytical arguments to show that ICA-SD-OCT is a true classical equivalent of Q-OCT, more specifically its Fourier domain version, and therefore it enables a true two-fold axial resolution improvement. We believe that clarification of all the misconceptions about this very promising algorithm will highlight the great value of this method for OCT and consequently lead to its practical applications for resolution- and quality-enhanced OCT imaging.

Highlights

Optical Coherence Tomography (OCT) has become an indispensable tool in medicine[1] due to its ability to visualise internal structures of biomedical objects on a micrometre scale and in a non-contact and non-invasive way
Abouraddy et al.[17] reached to quantum optics to realize the first-ever Quantum OCT (Q-OCT)— did this method intrinsically provide a two-fold resolution increase, and it is free of even-order dispersion effects, which contribute most to the resolution degradation
We show that the method of Jensen et al called intensity correlation spectral domain OCT (ICA-SD-OCT) is a true classical equivalent of Q-OCT. We prove that this approach is able to recreate the signal of Fd-Q-OCT and all that such signal entails: dispersion cancellation, artefacts and most importantly—what was tried to be debunked by Jensen et al.—almost two-fold axial resolution improvement

Summary

Introduction

Optical Coherence Tomography (OCT) has become an indispensable tool in medicine[1] due to its ability to visualise internal structures of biomedical objects on a micrometre scale and in a non-contact and non-invasive way. It was shown that the practical limit for axial resolution—one which weighs in the bandwidth-dispersion trade-off during imaging of bulk objects such as the eye—is 1 μm[10] and this limit has already been achieved in OCT in both v isible[11,12,13] and Because of this trade-off, further development of OCT in terms of resolution seems no longer possible through traditional means. An A-scan is obtained by Fourier transforming the main diagonal of the joint spectrum Both Q-OCT modalities require sources of entangled photon pairs, which are inefficient and pose significant experimental challenges. Due to low intensity levels, data acquisition time extends from at least tens of minutes to even hours and the imaging itself can only be performed for simple highly reflective objects, which excludes biomedical samples

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Results

Conclusion