Quantum-Optical Coherence Microscopy for Bio-imaging Applications

Abstract

Quantum-optical coherence tomography (QOCT) is an optical sectioning modality based on the quantum interference of photon pairs [Nasr et al., Phys. Rev. Lett. 91, 083601 (2003)], obtained from a spontaneous parametric downconversion (SPDC) source. The promise of QOCT derives from two quantumconferred advantages when compared to equivalent classical optical coherence tomography (OCT) systems: a factor of 2 axial resolution enhancement, as well as dispersion cancellation. Despite its promise, the technique is far from being competitive with current OCT devices due to the long required acquisition times, derived from the low photon-pair emission rates. In this work, we on the one hand demonstrate a quantum optical coherence microscopy (QOCM) technique that is designed to overcome some of the limitations of previous QOCT implementations, and on the other hand test it on representative samples, including glass layers with manufactured transverse patterns and metal-coated biological specimens. In an effort to maintain as large a flux as possible, we use a collinear SPDC source, so that the entire emitted photon pair flux may contribute to the measurements, together with a multi-mode detection design. Consistent with the collinear design, we employ a Michelson interferometer with the sample placed as end-mirror in one of the interferometer arms, instead of the more typical Hong-Ou-Mandel used in QOCT implementations. In order to probe biological samples we transition from a Michelson to a Linnik interferometer by placing a microscope objective in the sample arm. In our setup, while the idler photon is collected with a multi-mode fiber, the signal photon is detected by an ICCD camera, leading to full-field transverse reconstruction through a single axial acquisition sequence. Interestingly, our setup permits concurrent OCT and QOCT trace acquisition, the former with greater counts and the latter with the benefit of quantum-conferred advantages. We 1