Ultra-Broadband Coherence-Domain Imaging Using Parametric Downconversion and Superconducting Single-Photon Detectors at 1064 nm

TL;DR

This paper demonstrates an ultra-broadband coherence-domain imaging system using parametric downconversion and superconducting single-photon detectors at 1064 nm, achieving high resolution and deep tissue penetration.

Contribution

It introduces a novel method for generating adjustable broadband SPDC light near 1064 nm using chirped-PPSLT structures, combined with superconducting detectors for enhanced imaging.

Findings

Achieved axial resolution suitable for biological tissue imaging.

Extended the wavelength sensitivity from 700 to 1500 nm.

Successfully imaged complex biological samples.

Abstract

Coherence-domain imaging systems can be operated in a single-photon counting mode, offering low detector noise; this in turn leads to increased sensitivity for weak light sources and weakly reflecting samples. We have demonstrated that excellent axial resolution can be obtained in a photon-counting coherence domain imaging (CDI) system that uses light generated via spontaneous parametric down-conversion (SPDC) in a chirped periodically poled stoichiometric lithium tantalate (chirped-PPSLT) structure, in conjunction with a niobium nitride superconducting single-photon detector (SSPD). The bandwidth of the light generated via SPDC, as well as the bandwidth over which the SSPD is sensitive, can extend over a wavelength region that stretches from 700 to 1500 nm. This ultra-broad wavelength band offers a near-ideal combination of deep penetration and ultra-high axial resolution for the imaging of biological tissue. The generation of SPDC light of adjustable bandwidth in the vicinity of 1064 nm, via the use of chirped-PPSLT structures, had not been previously achieved. To demonstrate the usefulness of this technique, we have constructed images for a hierarchy of samples of increasing complexity: a mirror, a nitrocellulose membrane, and a biological sample comprising onion-skin cells.