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John Canning

Publications and source records attributed to John Canning.

At least 19 recordsLinked to original sources
arXiv2025

Robot joint characterisation and control using a magneto-optical rotary encoder

A robust and compact magneto-optical rotary encoder for the characterisation of robotic rotary joints is demonstrated. The system employs magnetic field-induced optical attenuation in a double-pass configuration using rotating nonuniform magnets around an optical circulator operating in reflection. The encoder tracks continuous 360{\deg} rotation with rotation sweep rates from {\nu} = 135 {\deg}/s to {\nu} = 370 {\deg}/s, and an angular resolution of {\Delta}{\theta} = 0.3{\deg}. This offers a low-cost and reliable alternative to conventional robot rotation encoders while maintaining competitive performance.

cs.RO↗
arXiv2025

Optically interrogated liquid crystal-based, charge-mode accelerometer telemetry

A hybrid optoelectronic vibration sensing system is presented, combining a conventional charge-mode piezoelectric accelerometer with an optical fiber interface via a liquid crystal-based electrical-to-optical transducer. This configuration allows the accelerometer's electrical output to be converted into an optical signal, enabling remote signal transmission over optical fiber. The same fiber could also be used to supply power to the system, offering a compact and interference-resistant solution suitable for challenging environments such as those with high voltages or explosive risks. Experimental results demonstrate a displacement resolution ranging from \Delta z = 0.015 nm at 0.160 nm displacement, up to \Delta z = 0.720 nm at 351 nm displacement, or equivalently, from \alpha = 0.0005 m/s2 to 0.057 m/s2 in acceleration. Despite undergoing electrical-to-optical and optical-to-electrical signal conversion, the system maintains high sensitivity, low noise levels, and signal integrity. This proof-of-concept optically interrogated accelerometer highlights a path toward reducing sensor infrastructure requirements by eliminating the need for conventional power supplies and electromagnetic shielding, which are typically required in fully electrical accelerometer systems.

physics.optics↗
arXiv2019

Optical Hoovering on Plasmonic Rinks

Excitation of surface waves on conducting materials provides a near resistance-free interface capable of a material glissade either by plasmon forces or optical beam tractors. Analogous to an ice hockey rink, as proof of principle plasmon assisted optical traction, or hoovering, of water drops on a gold surface is demonstrated. Variability in thresholds and movement is observed and can be explained by the presence of significant roughness, measured by SEM. The demonstration opens a path to directly integrate various optical and plasmonic glissade technologies. Ways of improving transport and potential applications spanning configurable microfluidics, antennas, diagnostics,sensing and active devices are discussed.

cond-mat.mes-hall↗
arXiv2017

Water Optical Nonlinearity: Explaining Anomalously Large Electro-Optic Coefficients in Poled Silica Fibres

An explanation is offered for the large anomalous electro-optic (e.o.) effect reported by Fujiwara in 1994. It is based on the large e.o. coefficient of ordered water at an interface measured in recent years. The concept of water-based photonics is introduced, suggesting that liquid states of matter can allow ready shaping and exploitation of many processes in ways not previously considered.

physics.app-ph↗
arXiv2017

Time-Resolved and Temperature Tuneable Measurements of Fluorescent Intensity using a Smartphone Fluorimeter

A smartphone fluorimeter capable of time-based fluorescence intensity measurements at various temperatures is reported. Excitation is provided by an integrated UV LED (370 nm) and detection obtained using the in-built CMOS camera. A Peltier is integrated to allow measurements of the intensity over T = 10 to 40 C with a maximum temperature resolution of DELTA T ~ 0.1 C. All components are controlled using a smartphone battery powered Arduino microcontroller and a customised Android application that allows sequential fluorescence imaging and quantification every DELTA t = 4 seconds. The temperature dependence of fluorescence intensity for four emitters (Rhodamine B, Rhodamine 6G, 5,10,15,20-tetraphenylporphyrin and 6-(1,4,8,11-tetraazacyclotetradecane)2-ethyl-naphthalimide) are characterised. The normalised fluorescence intensity over time of the latter chemosensor dye complex in the presence of Zn ion is observed to accelerate with an increasing rate constant, k = 1.94 min-1 at T = 15 C and k = 3.64 min-1 at T = 30 C, approaching a factor of ~ 2 with only a change in temperature of DELTA T = 15 C. Thermally tuning these twist and bend associated rates to optimise sensor approaches and device applications is proposed.

physics.ed-ph↗
arXiv2016

Step-index optical fibre drawn from 3D printed preforms

Optical fibre is drawn from a dual-head 3D printer fabricated preform made of two optically transparent plastics with a high index core (NA ~ 0.25, V > 60). The asymmetry observed in the fibre arises from asymmetry in the 3D printing process. The highly multi-mode optical fibre has losses measured by cut-back as low as α ~ 0.44 dB/cm in the near IR.

physics.ins-det↗
arXiv2016

Air-structured optical fibre drawn from a 3D-printed preform

A structured optical fibre is drawn from a 3D-printed structured preform. Preforms containing a single ring of holes around the core are fabricated using filament made from a modified butadiene polymer. More broadly, 3D printers capable of processing soft glasses, silica and other materials are likely to come on line in the not-so distant future. 3D printing of optical preforms signals a new milestone in optical fibre manufacture.

physics.ins-det↗
arXiv2015

Large dynamic range SPR measurements in the visible using a ZnSe prism

Large dynamic index measurement range (n = 1 to n = 1.7) using surface plasmon resonance (SPR) shifts is demonstrated with a ZnSe prism at 632.8 nm, limited by the available high index liquid hosts. In contrast to borosilicate based SPR measurements where angular limitations restrict solvent use to water and requires considerable care dealing with Fresnel reflections, the ZnSe approach allows SPR spectroscopies to be applied to a varied range of solvents An uncertainty in angular resolution between 1.5 and 6 deg, depending on the solvent and SPR angle, was estimated. The refractive index change for a given glucose concentration in water was measured to be n = (0.114 to 0.007) per precentage C6H12O6 conc. Given the transmission properties of ZnSe the processes can be readily extended into the mid infrared.

physics.ins-det↗
arXiv2014

Intelligent smartphone-based portable network diagnostics for water security Case Study realtime pH mapping of tap water

Using a field-portable, smartphone fluorometer to assess water quality based on the pH response of a designer probe, a map of pH of public tap water sites has been obtained. A custom designed Android application digitally processed and mapped the results utilizing the GPS service of the smartphone. The map generated indicates no disruption in pH for all sites measured. All the data are assessed to fall inside the upper limit of local government regulations and are consistent with authority reported measurements. The work demonstrates a new security concept: environmental forensics utilizing the advantage of real-time analysis for the detection of potential water quality disruption at any point in the city. The concept can be extended on national and global scales to a wide variety of analytes.

physics.ins-det↗
arXiv2014

Near orthogonal launch of SPR modes in Au films

We report the excitation of a surface plasmon resonance (SPR) close to the orthogonal axis of a gold (Au) film on borosilicate glass. Direct spectroscopic measurement of SPR shifts using different liquids are made at ~5° incidence within a reflection spectrophotometer. Scattering of light that is able to penetrate across the film at the interfaces is the proposed mechanism by which coupling, and plasmon localization, is established.

physics.optics↗
arXiv2014

Percolation diffusion into self-assembled mesoporous silica microfibres

Percolation diffusion into long (11.5 cm) self-assembled, ordered mesoporous microfibres is studied using optical transmission and laser ablation inductive coupled mass spectrometry (LA-ICP-MS). Optical transmission based diffusion studies reveal rapid penetration (< 5 s, D > 80 um2.s-1) of Rhodamine B with very little percolation of larger molecules such as zinc tetraphenylporphyrin (ZnTPP) observed under similar loading conditions. The failure of ZnTPP to enter the microfibre was confirmed, in higher resolution, using LA-ICP-MS. In the latter case, LA-ICP-MS was used to determine the diffusion of zinc acetate dihydrate, D ~ 3 x 10-4 nm2.s-1. The large differences between the molecules are accounted for by proposing ordered solvent and structure assisted accelerated diffusion of the Rhodamine B based on its hydrophilicity relative to the zinc compounds. The broader implications and applications for filtration, molecular sieves and a range of devices and uses are described.

cond-mat.mtrl-sci↗
arXiv2013

The viscosity of silica fibres

The viscosity of an optical fibre over 1000 to 1150 °C is studied by inscribing an optical fibre Bragg grating that can withstand temperatures up to 1200 °C and monitoring fibre elongation under load through the Bragg wavelength shift. This optical interrogation offers high accuracy and reliability compared to direct measurements of elongation, particularly at lower temperatures, thus avoiding significant experimental error. An excellent Arrhenius fit is obtained from which an activation energy for viscous flow of Ea = 450 kJ/mol is extracted; addition of an additional temperature dependent pre-exponential does not change this value. This value is less than that idealised by some literature but consistent with other literature. The log plot of viscosity is overall found to be consistent with that reported in the literature for silica measurements on rod and beams, but substantially higher to past work reported for optical fibres. The discrepancy from an idealised activation energy Ea ~ 700 kJ/mol may be explained by noting the higher fictive temperature of the fibre. On the other hand, past optical fibre results obtained by beam bending with much lower values leave questions regarding the method of viscosity measurement and the time taken for structural equilibration. We note that because regenerated gratings already involve post-annealing to stabilise their operation at higher temperature, the structures are much more relaxed compared to normal fibres. This work highlights the need to stabilize components for operation in harsh environments before their application, despite some mechanical compromise. Given the increasing expectation of all-optical waveguide technologies operating above 1000 °C, the need to study the behaviour of glass over the long term brings added significance to the basic understanding of glass in this regime.

cond-mat.mtrl-sci↗
arXiv2012

Temperature and strain characterization of regenerated gratings

Both temperature and strain characterization of seed and regenerated gratings with and without post-annealing is reported. The high temperature regeneration has significant impact to thermal characterization and mechanical strength of gratings whilst the post annealing has little effect. The observed difference is evidence of viscoelastic changes in glass structure.

cond-mat.mtrl-sci↗
arXiv2012

Tailoring surface interactions, contact angles, drop topologies and self-assembly using laser irradiation

UV laser irradiation (lambda = 193 nm), below and above damage thresholds, is used to both alter and pattern the surface properties of borosilicate slides to tune and control the contact angle of a water drop over the surface. Large variation exceeding 25 deg using laser processing alone, spanning across both sides of the original contact angle of the surface, is reported. An asymmetric contact angle distribution, giving rise to an analogous ellipsoidal-like drop caplet, is shown to improve convective self-assembly of silica nanoparticles into straighter microwires over a spherical caplet.

cond-mat.mtrl-sci↗
arXiv2012

Room temperature self-assembly of mixed nanoparticles into complex material systems and devices

The ability to manufacture nanomaterials with complex and structured composition using otherwise incompatible materials increasingly underpins the next generation of technologies. This is translating into growing efforts integrating a wider range of materials onto key technology platforms1 - in photonics, one such platform is silica, a passive, low loss and robust medium crucial for efficient optical transport2. Active functionalisation, either through added gain or nonlinearity, is mostly possible through the integration of active materials3, 4. The high temperatures used in manufacturing of silica waveguides, unfortunately, make it impossible to presently integrate many organic and inorganic species critical to achieving this extended functionality. Here, we demonstrate the fabrication of novel waveguides and devices made up of complex silica based materials using the self-assembly of nanoparticles. In particular, the room temperature fabrication of silica microwires integrated with organic dyes (Rhodamine B) and single photon emitting nanodiamonds is presented.

cond-mat.mtrl-sci↗
arXiv2011

New theory of femtosecond induced changes and nanopore formation

Recent results confirm the presence of molecular oxygen proving that recombination of dissociated silica bonds does not occur. This combined with the observation of nanopores within the nanograting structure in silica, leads to a new interpretation of femtosecond processing based on the unusual characteristics of quenching of tetrahedral silica compared to other glasses. This new approach suggests very different directions and implications for devices, including sensors, based on femtosecond laser processing of glasses.

cond-mat.mtrl-sci↗