On using classical light in Quantum Optical Coherence Tomography

TL;DR

This paper explores using classical low-intensity light in Quantum Optical Coherence Tomography, comparing its performance and spectral characteristics to traditional entangled photon-based Q-OCT, through theoretical and experimental analysis.

Contribution

It demonstrates that classical light can mimic some quantum interference effects in Q-OCT but offers limited advantages over entangled photon sources.

Findings

Classical light produces similar joint spectra but with reduced quantum correlations.

Classical approach is easier to implement experimentally.

Limited benefits of classical light compared to entangled photons in Q-OCT.

Abstract

Quantum Optical Coherence Tomography (Q-OCT) presents many advantages over its classical counterpart, Optical Coherence Tomography (OCT): it provides an increased axial resolution and is immune to even orders of dispersion. The core of Q-OCT is quantum interference of negatively correlated entangled photon pairs obtained in a Hong-Ou-Mandel configuration. This two-photon interference can be observed in the time domain in the form of dips or in the Fourier domain by means of a joint spectrum. The latter approach proved to be practical in the sense that it alleviated the requirement posed on light in Q-OCT to exhibit strict negative correlations, since the negative correlations can be easily extracted in the Fourier domain as the main diagonal of the joint spectrum. In this work, we investigate the use of this spectral approach in which quantum interference is obtained with classical low-intensity light pulses. We report theoretical calculations and their experimental validation and show that although such classical light is much easier to launch into an experimental system, it offers limited benefits as compared to Q-OCT based on entangled light. We analyse the differences in the characteristics of the joint spectrum obtained with entangled photons and with classical light and explain the origins of these differences.