Abstract
In this paper we demonstrate the enhancement of the sensing capabilities of glass capillaries. We exploit their properties as optical and acoustic waveguides to transform them potentially into high resolution minimally invasive endoscopic devices. We show two possible applications of silica capillary waveguides demonstrating fluorescence and optical-resolution photoacoustic imaging using a single 330 μm-thick silica capillary. A nanosecond pulsed laser is focused and scanned in front of a capillary by digital phase conjugation through the silica annular ring of the capillary, used as an optical waveguide. We demonstrate optical-resolution photoacoustic images of a 30 μm-thick nylon thread using the water-filled core of the same capillary as an acoustic waveguide, resulting in a fully passive endoscopic device. Moreover, fluorescence images of 1.5 μm beads are obtained collecting the fluorescence signal through the optical waveguide. This kind of silica-capillary waveguide together with wavefront shaping techniques such as digital phase conjugation, paves the way to minimally invasive multi-modal endoscopy.
Highlights
Glass capillaries, referred to as capillary waveguides (CWGs) in the photonics community due to their ability to support the propagation of waveguiding modes in the annular glass ring, have been consistently exploited by researchers as sensors [1] or as biosensors in lab on a chip platforms [2]
In this paper we demonstrate two new possible applications: using digital phase conjugation (DPC [6]), a 330 μm-thick silica capillary can be used as a fluorescence and optical resolution photoacoustic endoscope
We first demonstrated that the CWG is used as a fluorescence endoscopic device
Summary
Glass capillaries, referred to as capillary waveguides (CWGs) in the photonics community due to their ability to support the propagation of waveguiding modes in the annular glass ring, have been consistently exploited by researchers as sensors [1] or as biosensors in lab on a chip platforms [2]. No application was demonstrated showing their use as an imaging device per se. Optical fibers are widely used in endoscopy, at first glance the use of a CWG for endoscopic purposes does not bring advantages. The presence of a physical access to the sample side, enabled by the presence of the hollow core at the center, adds a degree of freedom to the endoscopic device, which can be used for many applications. For example an endoscopic device can be used to deliver high-energy light for ablation purposes, so the hollow core could be used for eliminating gases formed during the ablation process. An endoscope based on CWGs can be used to check in vivo the effect of drugs that can be injected using the same device
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