Demonstration of Fourier-domain Quantum Optical Coherence Tomography for a fast tomographic quantum imaging

TL;DR

This paper demonstrates a faster Fourier-domain Quantum Optical Coherence Tomography (Q-OCT) technique that enhances resolution and dispersion cancellation, advancing quantum imaging towards practical, real-time applications.

Contribution

The authors experimentally implement Fourier-domain Q-OCT with novel spectrum pre-processing algorithms, overcoming speed limitations of time-domain Q-OCT and improving imaging performance.

Findings

Achieved faster imaging with fixed reference mirror and spectral acquisition.

Implemented algorithms to compensate fibre dispersion and enhance dispersion cancellation.

Demonstrated superior axial resolution and imaging capabilities compared to classical OCT.

Abstract

Using spectrally correlated photon pairs instead of classical laser light and coincidence detection instead of light intensity detection, Quantum Optical Coherence Tomography (Q-OCT) outperforms classical OCT in several experimental terms. It provides twice better axial resolution with the same spectral bandwidth and it is immune to even-order chromatic dispersion, including Group Velocity Dispersion responsible for the bulk of axial resolution degradation in the OCT images. Q-OCT has been performed in the time domain configuration, where one line of the two-dimensional image is acquired by axially translating the mirror in the interferometer's reference arm and measuring the coincidence rate of photons arriving at two single-photon-sensitive detectors. Although successful at producing resolution-doubled and dispersion-cancelled images, it is still relatively slow and cannot compete with its classical counterpart. Here, we experimentally demonstrate Q-OCT in a much faster Fourier-domain configuration, theoretically proposed in 2020, where the reference mirror is fixed and the joint spectrum is acquired by inserting long fibre spools in front of the detectors. We propose two joint spectrum pre-processing algorithms, aimed at compensating resolution-degrading effects within the setup. While the first one targets fibre spool dispersion, an effect specific to this configuration, the other one removes the effects leading to the weakening of even-order dispersion cancellation, the latter impossible to be mitigated in the time-domain alternative. Being additionally contrasted with both the time-domain approach and the conventional OCT in terms of axial resolution, imaging range and multilayer-object imaging, Fourier-domain Q-OCT is shown to be a significant step forward towards a practical and competitive solution in the OCT arena.