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.
9 March 2017:
A new publication from CNBP researchers (lead author Jonathan Hall pictured) presents a new model for generating whispering gallery mode spectra for multilayer microspheres.
The work has just been reported in the journal ‘Optics Express’ and is accessible online.
Journal: Optics Express.
Title: Unified theory of whispering gallery multilayer microspheres with single dipole or active layer sources.
Authors: Jonathan M. M. Hall, Tess Reynolds, Matthew R. Henderson, Nicolas Riesen, Tanya M. Monro, and Shahraam Afshar.
Abstract: The development of a fast and reliable whispering gallery mode (WGM) simulator capable of generating spectra that are comparable with experiment is an important step forward for designing microresonators. We present a new model for generating WGM spectra for multilayer microspheres, which allows for an arbitrary number of concentric dielectric layers, and any number of embedded dipole sources or uniform distributions of dipole sources to be modeled. The mode excitation methods model embedded nanoparticles, or fluorescent dye coatings, from which normalized power spectra with accurate representation of the mode coupling efficiencies can be derived. In each case, the emitted power is expressed conveniently as a function of wavelength, with minimal computational load. The model makes use of the transfer-matrix approach, incorporating improvements to its stability, resulting in a reliable, general set of formulae for calculating whispering gallery mode spectra. In the specific cases of the dielectric microsphere and the single-layer coated microsphere, our model simplifies to confirmed formulae in the literature.
30 November 2016:
Exciting translational work by CNBP researchers (project leader Dr Erik Schartner pictured left) has resulted in the development of an optical fibre probe that distinguishes breast cancer tissue from normal tissue – potentially allowing surgeons to be much more precise when removing breast cancer. The work has just been reported in the journal ‘Cancer Research’ and is accessible online.
Journal: Cancer Research.
Title: Cancer Detection in Human Tissue Samples Using a Fiber-Tip pH Probe.
Authors: Erik P. Schartner, Matthew R. Henderson, Malcolm Purdey, Deepak Dhatrak, Tanya M. Monro, P. Grantley Gill and David F. Callen.
Intraoperative detection of tumorous tissue is an important unresolved issue for cancer surgery. Difficulty in differentiating between tissue types commonly results in the requirement for additional surgeries to excise unremoved cancer tissue or alternatively in the removal of excess amounts of healthy tissue. Although pathologic methods exist to determine tissue type during surgery, these methods can compromise postoperative pathology, have a lag of minutes to hours before the surgeon receives the results of the tissue analysis, and are restricted to excised tissue. In this work, we report the development of an optical fiber probe that could potentially find use as an aid for margin detection during surgery. A fluorophore-doped polymer coating is deposited on the tip of an optical fiber, which can then be used to record the pH by monitoring the emission spectra from this dye. By measuring the tissue pH and comparing with the values from regular tissue, the tissue type can be determined quickly and accurately. The use of a novel lift-and-measure technique allows for these measurements to be performed without influence from the inherent autofluorescence that commonly affects fluorescence-based measurements on biological samples. The probe developed here shows strong potential for use during surgery, as the probe design can be readily adapted to a low-cost portable configuration, which could find use in the operating theater. Use of this probe in surgery either on excised or in vivo tissue has the potential to improve success rates for complete removal of cancers.
10 August 2016:
Researchers from the CNBP have published a paper representing the first major study of the stability and compatibility of the major classes of photochromic compounds within the microstructured optical fibre (MOF) environment.
In developing light-responsive surfaces, investigators face several challenges, not only in achieving high photostationary states and fully reversible switching, but also in fluorescence properties and fatigue resistance upon continuous exposure to high intensity light. However, information on the latter two are often lacking as studies on photochromic compounds are often focused on photoswitching, or absorbance and colour changes. To address this gap in literature, the fluorescence and photostability of four major types of photochromic molecules (azobenzene, spiropyran, indolyfulgide and diarylalkene) when dissolved in DMSO, or acetonitrile, or adsorbed to a MOF silica surface were investigated.
Journal: Sensors and Actuators B: Chemical.
Publication title: A Comparative Study of the Fluorescence and Photostability of Common Photoswitches in Microstructured Optical Fibre.
Authors: Daniel B. Stubing (pictured top left), Sabrina Heng, Tanya M. Monro and Andrew D. Abell.
Abstract: The fluorescence spectra and photostability under 532 nm laser excitation of four different common photoswitches (an azobenzene, spiropyran, indolylfulgide, and a diarylperfluorocyclopentene) were investigated in a silica microstructured optical fibre. An example of each photoswitch was examined in solution and physically adsorbed to the silica fibre surface. This comparison was made to define fluorescence behaviour in these two states and to determine which photoswitch has the best performance in this light intense microenvironment. The azobenzene and the spiropyran switches demonstrated the strongest fluorescence response and the least degradation of the fluorescence signal.
The paper is available online.
13 May 2016:
CNBP researchers have created nanoscale biosensors that are capable of sensing Zn2+ ions in biological samples. Such sensors have potential application in disease diagnosis and study, as well as in environmental sensing. The study was published in the journal ACS Applied Materials and Interfaces, May 13th, 2016.
Publication title: Microstructured Optical Fiber-based Biosensors: Reversible and Nanoliter-Scale Measurement of Zinc Ions.
Authors: Sabrina Heng (pictured), Christopher A. McDevitt, Roman Kostecki, Jacqueline R. Morey, Bart A. Eijkelkamp, Heike Ebendorff-Heidepriem, Tanya M. Monro, and Andrew D. Abell.
Sensing platforms that allow rapid and efficient detection of metal ions would have applications in disease diagnosis and study, as well as environmental sensing. Here, we report the first microstructured optical fiber-based biosensor for the reversible and nanoliter-scale measurement of metal ions. Specifically, a photoswitchable spiropyran Zn2+ sensor is incorporated within the microenvironment of a liposome attached to microstructured optical fibers (exposed-core and suspended-core microstructured optical fibers). Both fiber-based platforms retains high selectivity of ion binding associated with a small molecule sensor, while also allowing nanoliter volume sampling and on/off switching. We have demonstrated that multiple measurements can be made on a single sample without the need to change the sensor. The ability of the new sensing platform to sense Zn2+ in pleural lavage and nasopharynx of mice was compared to that of established ion sensing methodologies such as inductively coupled plasma mass spectrometry (ICP-MS) and a commercially available fluorophore (Fluozin-3), where the optical-fiber-based sensor provides a significant advantage in that it allows the use of nanoliter (nL) sampling when compared to ICP-MS (mL) and FluoZin-3 (μL). This work paves the way to a generic approach for developing surface-based ion sensors using a range of sensor molecules, which can be attached to a surface without the need for its chemical modification and presents an opportunity for the development of new and highly specific ion sensors for real time sensing applications.
The paper is available online.
14 April 2016:
CNBP Chief Investigator Tanya Monro and senior researcher Heike Ebendorff-Heidepriem are co-authors on a newly published paper in the Journal ‘Optics Express’.
Publication title: Interferometric high temperature sensor using suspended-core optical fibers.
Authors: Linh Viet Nguyen, Stephen C Warren-Smith, Heike Ebendorff-Heidepriem and Tanya M Monro.
Abstract: We propose and experimentally demonstrate, for the first time to our knowledge, high temperature fiber sensing using the multimode interference effect within a suspended-core microstructured optical fiber (SCF). Interference fringes were found to red-shift as the temperature increased and vice versa. Temperature sensing up to 1100°C was performed by measuring the wavelength shifts of the fringes after fast Fourier transform (FFT) filtering of the spectra. In addition, phase monitoring at the dominant spatial frequency in the Fourier spectrum was used as an interrogation method to monitor various temperature-change scenarios over a period of 80 hours. Our proposed high temperature fiber sensor is simple, cost-effective, and can operate at temperatures beyond 1000°C.
The paper is accessible online.
30 March 2016:
CNBP Chief Investigator Prof. Tanya Monro was one of three top tier scientists presenting today, at the Australian National Press Club in Canberra. The topic under discussion, gender inequalities in the scientific workplace and what can be done to best stop the science brain drain that is forcing out some of Australia’s best and most talented minds.
Joining Prof. Tanya Monro in discussion, were Professors Emma Johnston and Nalini Joshi.
You can view the full Press Club address from these three inspiring scientists via this ABC online stream.
14 March 2016:
One of Australia’s favourite outdoor festivals – WOMADelaide -has featured CNBP Advocate and CI Tanya Monro.
Tanya joined internationally celebrated American academic and award winning author, Naomi Oreskes and Australia’s Dr Karl Kruzelnicki, in a panel discussion that examined the theme – ‘Should We Trust Scientists?’
The discussion featured as part of the WOMADelaide Planet Talks 2016 program and can be viewed online in its entirety.
Some of the big questions asked of the panel – Who should we trust and why? When should we accept what scientists say? How is that scientists do not always agree when analyzing the same information? Issues covered – the role of deep empathy, big brains and peer reviewed consideration.
9 March 2016:
CNBP researchers have published a paper in Optics Express, reporting on the fabrication of the first extruded hollow core optical fiber with a single ring of cladding holes. The fibers were used to perform Raman sensing of methanol, demonstrating their potential for future fiber sensing applications.
Title: Single-ring hollow core optical fibers made by glass billet extrusion for Raman sensing.
Authors: G. Tsiminis, K. J. Rowland, E. P. Schartner, N. A. Spooner, T. M. Monro and H. Ebendorff-Heidepriem.
Abstract: We report the fabrication of the first extruded hollow core optical fiber with a single ring of cladding holes, and its use in a chemical sensing application. These single suspended ring structures show antiresonance reflection optical waveguiding (ARROW) features in the visible part of the spectrum. The impact of preform pressurization on the geometry of these fibers is determined by the size of the different hole types in the preform. The fibers are used to perform Raman sensing of methanol, demonstrating their potential for future fiber sensing applications.
The paper is available online.
22 February 2016:
CNBP researchers have published a paper in the journal Scientific Reports. Demonstrated is a novel but simple method for creating transparent conductive reduced graphene oxide film onto microstructured silica fibres for potential optoelectronic applications.
Title: Integration of conductive reduced graphene oxide into microstructured optical fibres for optoelectronics applications.
Authors: Yinlan Ruan, Liyun Ding, Jingjing Duan, Heike Ebendorff-Heidepriem & Tanya M. Monro.
Abstract: Integration of conductive materials into optical fibres can largely expand functions of fibre devices including surface plasmon resonator/metamaterial, modulators/detectors, or biosensors. Some early attempts have been made to incorporate metals such as tin into fibres during the fibre drawing process. Due to the restricted range of materials that have compatible melting temperatures with that of silica glass, the methods to incorporate metals along the length of the fibres are very challenging. Moreover, metals are nontransparent with strong light absorption, which causes high fibre loss. This article demonstrates a novel but simple method for creating transparent conductive reduced graphene oxide film onto microstructured silica fibres for potential optoelectronic applications. The strongly confined evanescent field of the suspended core fibres with only 2 μW average power was creatively used to transform graphene oxide into reduced graphene oxide with negligible additional loss. Existence of reduced graphene oxide was confirmed by their characteristic Raman signals, shifting of their fluorescence peaks as well as largely decreased resistance of the bulk GO film after laser beam exposure.
The paper is open access and available online.