ABSTRACT Quantum optical coherence tomography (QOCT) has received significant attention due to its immunity to even‐order dispersion and its ability to double the resolution compared to conventional optical coherence tomography (OCT). However, QOCT typically relies on nonlinear processes to generate frequency‐correlated photon pairs as a probe state. The high‐power pump laser requirement poses a major barrier to practical implementations of QOCT. In this paper, we propose the substitution of spectrally correlated photon pairs in QOCT with the weak multimode coherent state as the input source. Through integration with post‐selective spectral‐domain measurement techniques, we demonstrate that our scheme preserves the advantages of QOCT, including even‐order dispersion cancellation and a two‐fold increase in resolution. The key advantage of our scheme is its removal of the requirement for nonlinear‐process‐generated spectrally correlated photon pairs as the light source. This advancement is particularly beneficial for practical applications of QOCT.
ABSTRACT Quantum optical coherence tomography (QOCT) has received significant attention due to its immunity to even‐order dispersion and its ability to double the resolution compared to conventional optical coherence tomography (OCT). However, QOCT typically relies on nonlinear processes to generate frequency‐correlated photon pairs as a probe state. The high‐power pump laser requirement poses a major barrier to practical implementations of QOCT. In this paper, we propose the substitution of spectrally correlated photon pairs in QOCT with the weak multimode coherent state as the input source. Through integration with post‐selective spectral‐domain measurement techniques, we demonstrate that our scheme preserves the advantages of QOCT, including even‐order dispersion cancellation and a two‐fold increase in resolution. The key advantage of our scheme is its removal of the requirement for nonlinear‐process‐generated spectrally correlated photon pairs as the light source. This advancement is particularly beneficial for practical applications of QOCT.
Quantum optical coherence tomography (QOCT) offers a simple way to cancel dispersion broadening in a sample while also providing twice the resolution compared to classical OCT. However, to achieve these advantages, a bright and broadband source of entangled photon pairs is required. A simple implementation uses collinear spontaneous parametric down-conversion in a Michelson interferometer (MI), yet this autocorrelation scheme suffers from parasitic terms and sensitivity to phase noise. Here, we introduce a cross-correlation MI-based QOCT that overcomes these drawbacks, significantly advancing QOCT toward practical applications.
Optical-coherence tomography (OCT) is a technique that employs light in order to measure the internal structure of semitransparent, e.g. biological, samples. It is based on the interference pattern of low-coherence light. Quantum-OCT (QOCT), instead, employs the correlation properties of entangled photon pairs, for example, generated by the process of spontaneous parametric downconversion (SPDC). The usual QOCT scheme uses photon pairs characterised by a joint-spectral amplitude with strict spectral anti-correlations. It has been shown that, in contrast with its classical counterpart, QOCT provides resolution enhancement and dispersion cancellation. In this paper, we revisit the theory of QOCT and extend the theoretical model so as to include photon pairs with arbitrary spectral correlations. We present experimental results that complement the theory and explain the physical underpinnings appearing in the interference pattern. In our experiment, we utilize a pump for the SPDC process ranging from continuous wave to pulsed in the femtosecond regime, and show that cross-correlation interference effects appearing for each pair of layers may be directly suppressed for a sufficiently large pump bandwidth. Our results provide insights and strategies that could guide practical implementations of QOCT.
Broadband correlated photon pairs (biphotons) are valuable in quantum metrology, but current generation methods either involve complex nonlinear structures or lack sufficient bandwidth and brightness. In this work, we theoretically describe and experimentally demonstrate an alternative technique for generation of a bright collinear biphoton field with a broad spectrum, achieved by using a tightly focused pump in a bulk nonlinear crystal. As the most straightforward application of the source, we employ Michelson interferometer-based quantum optical coherence tomography (QOCT). Utilizing the source enables the demonstration of record resolution and dispersion cancellation for this QOCT scheme.
We propose a technique, called quantum-optical coherence tomography (QOCT), for carrying out tomographic measurements with dispersion-cancelled resolution. The technique can also be used to extract the frequency-dependent refractive index of the medium. QOCT makes use of a two-photon interferometer in which a swept delay permits a coincidence interferogram to be traced. The technique bears a resemblance to classical optical coherence tomography (OCT). However, it makes use of a nonclassical entangled twin-photon light source that permits measurements to be made at depths greater than those accessible via OCT, which suffers from the deleterious effects of sample dispersion. Aside from the dispersion cancellation, QOCT offers higher sensitivity than OCT as well as an enhancement of resolution by a factor of two for the same source bandwidth. QOCT and OCT are compared using an idealized sample.
Quantum optical coherence tomography (QOCT) is the non-classical counterpart of optical coherence tomography (OCT), by which quantum interference of entangled photon pairs is used to show some advantages over classical OCT. Currently, almost all research on the QOCT focuses on the case with two photons and a twofold improvement in axial resolution has been demonstrated. Here, we introduce the multiple reflections strategy into the QOCT scheme, referencing the multi-pass strategy of the sequential scheme in quantum metrology, and provide a theoretical framework for multi-reflection quantum-optical coherence tomography (MQOCT). According to such a scheme, when the incident light interacts with the sample N times, the axial resolution of MQOCT is theoretically enhanced by a factor of N compared to that of QOCT under the same spectral bandwidth while preserving the dispersion cancellation capability of QOCT. Furthermore, we present a classical optical analogy of MQOCT using P -beam correlated multi-mode broadband beams and experimentally validate it. The classical optical analogy of MQOCT theoretically has the same resolution enhancement capability and dispersion cancellation capability as MQOCT while avoiding the fragility issues associated with the quantum light source which is used in MQOCT.
By using entangled photon pairs instead of a laser light, Quantum Optical Coherence Tomography (Q-OCT) outperforms conventional OCT, providing twice better axial resolution and immunity to image-degrading even-order chromatic dispersion. Despite these very sought-after features, its applicability is hindered by long acquisition times, image-scrambling artefacts and chromatic dispersion which reappears in configurations enabling the artefact suppression. Here, we experimentally demonstrate Q-OCT with a Fourier-domain acquisition scheme which allows both fast imaging and immunity to the re-appearance of chromatic dispersion. By delivering two-dimensional joint spectra, our Fourier-domain Q-OCT enables comfortable manipulation of spectral relationships between the photon pairs, and consequently the removal of the dispersion effects. We report attractive acquisition times, accompanied by a demonstration of two joint spectrum pre-processing algorithms, aimed at controlling dispersion effects within the setup. While the first algorithm reverses the effects specific to the joint spectral acquisition, the other one removes the effects leading to the weakening of even-order dispersion cancellation, impossible to be mitigated in other Q-OCT implementations. Contrasted with both the original, time-domain implementation and the conventional OCT, Fourier-domain Q-OCT is shown to be an important step forward towards becoming a practical and competitive solution.