Tapered multi-core fiber for lensless endoscopes
Citation
El Moussawi, F., Hofer, M., Labat, D., Cassez, A., Bouwmans, G., Sivankutty, S., ... & Andresen, E. R. (2022). Tapered multi-core fiber for lensless endoscopes. arXiv preprint arXiv:2204.03320.
Keywords
- tapered multi-core fiber (MCF)
- lensless endoscopes
- two-photon imaging
- memory effect
- point-scanning
- power delivery
- coupled-mode theory (CMT)
- cross-talk
- Strehl ratio
- fabrication
- characterization
Brief
A new tapered multi-core fiber (MCF) component is designed to address low power delivery in MCF-based lensless endoscopes, resulting in a two-photon signal yield increase by a factor of 6.0 while keeping the point-scanning ability of the memory effect, and a factor of 8.9 when sacrificing it.
Summary
This article presents a novel fiber-optic component called a "tapered multi-core fiber (MCF)" for use in ultra-miniaturized endoscopes. The tapered MCF improves upon existing MCF-based lensless endoscopes by addressing the issue of power delivery, which is crucial for two-photon imaging.
The authors outline the design, fabrication, and application of a tapered MCF optimized for two-photon imaging with 920 nm pulsed excitation. The tapered MCF aims to address the conflicting requirements of lensless endoscopes for both dense and sparse core layouts by incorporating three segments: injection, transport, and imaging. The segments are joined by conical tapers.
Key Findings:
- A six-fold increase in two-photon signal yield was achieved experimentally by using a tapered MCF with optimal design parameters. This design maintained the ability to point-scan using the memory effect.
- Sacrificing the memory effect allowed the researchers to further enhance the two-photon signal yield by a factor of 8.9.
- The researchers developed a fast numerical model based on coupled-mode theory (CMT) to predict the essential properties of an arbitrarily tapered MCF from its structural parameters.
- They validated the CMT model with a finite-element beam propagation method (FE-BPM) model.
- The study demonstrated the fabrication of the target tapered MCF designs using a CO2 laser-based glass processing and splicing system.
- The researchers characterized the optical properties of the fabricated tapered MCFs using a filtered super-continuum laser source.
The article highlights the potential of tapered MCFs to improve two-photon lensless endoscopy by significantly increasing two-photon yield, offering a promising avenue for minimally invasive, high-resolution imaging in biological tissues.