25 January 2019:
CNBP Associate Investigator Dr Stephen C. Warren-Smith is lead author on a new publication that has demonstrated multi-wavelength third-harmonic generation from an exposed-core microstructured optical fibre.
Journal: Optics Letters.
Publication title: Tunable multi-wavelength third-harmonic generation using exposed-core microstructured optical fiber.
Authors: Stephen C. Warren-Smith, Kay Schaarschmidt, Mario Chemnitz, Erik P. Schartner, Henrik Schneidewind, Heike Ebendorff-Heidepriem, and Markus A. Schmidt.
Abstract: We demonstrate that exposed-core microstructured optical fibers offer multiple degrees of freedom for tailoring third-harmonic generation through the core diameter, input polarization, and nanofilm deposition. Varying these parameters allows control of the phase-matching position between an infrared pump wavelength and the generated visible wavelengths. In this Letter, we show how increasing the core diameter over previous experiments (2.57 μm compared to 1.85 μm) allows the generation of multiple wavelengths, which can be further controlled by rotating the input pump polarization and the deposition of dielectric nanofilms. This can lead to highly tailorable light sources for applications such as spectroscopy or nonlinear microscopy.
10 December 2018:
A proof-of-concept fabrication of a soft-glass imaging microstructured optical fiber has been demonstrated by CNBP scientists in a new research paper published in the journal Optics Express. Lead author of the paper is Dr Stephen C. Warren-Smith, CNBP Associate Investigator at the University of Adelaide who notes that it is envisaged that the glass-based optical fibers will find potential use in applications such as in-vivo white-light and spectroscopic imaging.
Journal: Optics Express.
Publication title: Soft-glass imaging microstructured optical fibers.
Authors: Stephen C. Warren-Smith, Alastair Dowler, and Heike Ebendorff-Heidepriem.
Abstract: We demonstrate the fabrication of multi-core (imaging) microstructured optical fiber via soft-glass preform extrusion through a 3D printed titanium die. The combination of extrusion through 3D printed dies and structured element (capillary) stacking allows for unprecedented control of the optical fiber geometry. We have exploited this to demonstrate a 100 pixel rectangular array imaging microstructured fiber. Due to the high refractive index of the glass used (n = 1.62), such a fiber can theoretically have a pixel pitch as small as 1.8 µm. This opens opportunities for ultra-small, high-resolution imaging fibers fabricated from diverse glass types.
30 April 2018:
A new publication featuring CNBP co-authors (Dr Stephen Warren-Smith pictured left and Prof Heike Ebendorff-Heidepriem) reports on the design and implementation of a novel, high sensitivity Sagnac-interferometer biosensor based on an exposed core microstructured optical fiber (ECF).
Journal: Sensors and Actuators B: Chemical.
Publication title: High-sensitivity Sagnac-interferometer biosensor based on exposed core microstructured optical fiber.
Authors: Xuegang Li, Linh V. Nguyen, Yong Zhao, Heike Ebendorff-Heidepriem, Stephen C. Warren-Smith.
Abstract: A novel, high sensitivity Sagnac-interferometer biosensor based on exposed core microstructured optical fiber (ECF) has been designed and implemented in this paper. The exposed core fiber has noncircular symmetry and thus exhibits birefringence and can form a sensing element within a Sagnac loop interferometer. The exposed-core fiber design provides direct access to the evanescent field, allowing the measurement of bulk refractive index (RI) with a sensitivity of up to −3137 nm/RIU while maintaining the fiber’s robustness. The sensor can also detect the localized refractive index changes at the fiber core’s surface as the result of a biological binding event. We demonstrate the use of this sensor for label-free sensing of biological molecules by immobilizing biotin onto the fiber core as the probe to capture the target molecule streptavidin.
27 April 2017:
Researchers from CNBP and The Institute of Photonic Technology (lead author Stephen Warren-Smith pictured), have just had a paper published on tuning third harmonic light generated within exposed-core fibres.
Journal: Optics Letters.
Publication title: Nanofilm-induced spectral tuning of third harmonic generation.
Authors: Stephen C. Warren-Smith, Mario Chemnitz, Henrik Schneidewind, Roman Kostecki, Heike Ebendorff-Heidepriem, Tanya M. Monro and Markus A. Schmidt.
Abstract: Intermodal third-harmonic generation using waveguides is an effective frequency conversion process due to the combination of long interaction lengths and strong modal confinement. Here we introduce the concept of tuning the third harmonic phase-matching condition via the use of dielectric nanofilms located on an open waveguide core. We experimentally demonstrate that tantalum oxide nanofilms coated onto the core of an exposed core fiber allow tuning the third harmonic wavelength over 30 nm, as confirmed by qualitative simulations. Due to its generic character, the presented tuning scheme can be applied to any form of exposed core waveguide and will find applications in fields including microscopy, biosensing, and quantum optics.
The paper is accessible online.
28 July 2016:
Researchers from CNBP and The Institute of Photonic Technology (IPHT), have had a paper published today on the topic of third harmonic light generation using ECFs.
Journal: Optics Express.
Publication title: Third harmonic generation in exposed-core microstructured optical fibers.
Authors: Stephen C. Warren-Smith, Jingxuan Wie, Mario Chemnitz, Roman Kostecki, Heike Ebendorff-Heidepriem, Tanya M. Monro and Markus A. Schmidt.
Inter-modal phase-matched third harmonic generation has been demonstrated in an
exposed-core microstructured optical fiber. Our fiber, with a partially open core having a
diameter of just 1.85 µm, shows efficient multi-peak third-harmonic generation between 500nm and 530 nm, with a maximum visible-wavelength output of 0.96 μW. Mode images and simulations show strong agreement, confirming the phase-matching process and polarization dependence. We anticipate this work will lead to tailorable and tunable visible light sources by exploiting the open access to the optical fiber core, such as depositing thin-film coatings in order to shift the phase matching conditions.
The paper is available online.
27 June 2016:
Dr Stephen Warren-Smith, currently working at the Leibniz Institute of Photonic Technology (IPHT), Jena, Germany will return to the University of Adelaide in October this year, to take-up a four-year 2016 Ramsay Fellowship.
In exciting news for the Centre, and in conjunction with this Fellowship commencement, Stephen will also be granted official CNBP Associate Investigator status.
A University of Adelaide graduate, Stephen will be looking to develop very fine optical fibres with a range of potential industrial and diagnostic imaging applications, including bronchoscopy, where very thin endoscopes are required to reach the periphery of the lung.
We look forward to working closely with Stephen in this exciting area of research!
For further information on this story, please visit the University of Adelaide news site.
9 February 2016:
Associate Investigator Dr Stephen Warren-Smith at the Institute of Photonic Technology (Jena, Germany) has just published work on a new fabrication technique for creating micro-optical sensors in CNBP optical fibres.
Citation: S. C. Warren-Smith, R. M. André, C. Perrella, J. Dellith, H. Bartelt, “Direct core structuring of microstructured optical fibers using focused ion beam milling,” Optics Express 24 (1), 378-387 (2016).
We demonstrate the use of focused ion beam milling to machine optical structures directly into the core of microstructured optical fibers. The particular fiber used was exposed-core microstructured optical fiber, which allowed direct access to the optically guiding core. Two different designs of Fabry-Perot cavity were fabricated and optically characterized. The first cavity was formed by completely removing a section of the fiber core, while the second cavity consisted of a shallow slot milled into the core, leaving the majority of the core intact. This work highlights the possibility of machining complex optical devices directly onto the core of microstructured optical fibers using focused ion beam milling for applications including environmental, chemical, and biological sensing.
5 August 2015:
Optical fibers provided to international partner IPHT Jena, by the Adelaide node of the Centre for Nanoscale BioPhotonics, will be the subject of a presentation by Stephen Warren-Smith at the ‘Workshop on Speciality Optical Fibres’, Hong Kong, 2015.
The presentation will be based on the paper “Focused Ion Beam Structuring of Exposed-Core Microstructured Optical Fibers” : Authors: Stephen C. Warren-Smith, Ricardo M. André, Jan Dellith, Manfred Rothhardt and Hartmut Bartelt.
Focused ion beam milling has been employed to create micro-structured features onto an exposed-core microstructured optical fiber. Here we detail results for fabricating and characterizing Fabry-Perot cavities using this method.
15 December 2014: Congratulations to Dr Stephen Warren Smith
Congratulations to Dr Stephen Warren Smith who was awarded the University of Adelaide Faculty of sciences Daniel Walker Medial awarded annually to the best Early Career Researcher in the Faculty
3 December 2014: Publication
Recently published paper from CNBP researchers using optical fibres to monitor the evolution of processes relating to ischaemic stroke by measuring the activation of a fluorescent photosensitive dye inside the brain of living mice in real time.
Researchers from the ARC Centre of Excellence for Nanoscale BioPhotonics (CNBP) have demonstrated that measurements of fluorescent chemicals can be made deep inside the brain of living mice in a project hoping to expand our understanding of the events unravelling during a stroke event. The research was published at Biomedical Optics Express.
Dr Georgios Tsiminis, Dr Erik Schartner, Dr Stephen Warren-Smith and Prof. Tanya Monro from the CNBP, along with Dr Thomas Klaric and Dr Martin Lewis from the Stroke Research Programme led by Prof. Simon Koblar at the South Australian Health and Medical Research Institution (SAHMRI) and the University of Adelaide put together a transdisciplinary research programme, funded by a pilot project grant provided by the Institute for Photonics and Advanced Sensing (IPAS).
This project aimed to extend understanding of what happens during the photochemical stroke model, a rodent stroke model that creates stroke infarcts using a photosensitive organic dye, allowing biomedical researchers to investigate how stroke events occur and what they can do to aid recovery. The existing photochemical stroke model creates stroke infarcts on the surface of the brain as it uses external illumination and any information on what has occurred in the brain can only be determined by post-mortem biopsy.
In this work CNBP researchers used an optical fibre to deliver laser light deep inside the brain at the hippocampus, allowing the controlled creation of stroke infarcts anywhere in the brain. In addition, the same fibre collects the signal from the stroke-inducing dye, allowing the estimation of the dye concentration at the site of the stroke event and the monitoring of the evolution of the dye breakdown in real time.
This is the first time that such measurements have been performed inside the brain of a living animal, highlighting the capabilities of photonics technologies applied to biomedical problems and the novel results they create for researchers in the field.
The original publication can be found at http://dx.doi.org/10.1364/BOE.5.003975.