690 research outputs found
Nonlinear self-flipping of polarization states in asymmetric waveguides
Waveguides of subwavelength dimensions with asymmetric geometries, such as
rib waveguides, can display nonlinear polarization effects in which the
nonlinear phase difference dominates the linear contribution, provided the
birefringence is sufficiently small. We demonstrate that self-flipping
polarization states can appear in such rib waveguides at low (mW) power levels.
We describe an optical power limiting device with optimized rib waveguide
parameters that can operate at low powers with switching properties
Dynamic self-referencing approach to whispering gallery mode biosensing and its application to measurement within undiluted serum
Biosensing within complex biological samples requires a sensor that can compensate for fluctuations in the signal due to changing environmental conditions and nonspecific binding events. To achieve this, we developed a novel self-referenced biosensor consisting of two almost identically sized dye-doped polystyrene microspheres placed on adjacent holes at the tip of a microstructured optical fiber (MOF). Here self-referenced biosensing is demonstrated with the detection of Neutravidin in undiluted, immunoglobulin-deprived human serum samples. The MOF allows remote excitation and collection of the whispering gallery modes (WGMs) of the microspheres while also providing a robust and easy to manipulate dip-sensing platform. By taking advantage of surface functionalization techniques, one microsphere acts as a dynamic reference, compensating for nonspecific binding events and changes in the environment (such as refractive index and temperature), while the other microsphere is functionalized to detect a specific interaction. The almost identical size allows the two spheres to have virtually identical refractive index sensitivity and surface area, while still having discernible WGM spectra. This ensures their responses to nonspecific binding and environmental changes are almost identical, whereby any specific changes, such as binding events, can be monitored via the relative movement between the two sets of WGM peaks.Tess Reynolds, Alexandre Franc, ois, Nicolas Riesen, Michelle E. Turvey, Stephen J. Nicholls, Peter Hoffmann, and Tanya M. Monr
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Machine learning approach for computing optical properties of a photonic crystal fiber
Photonic crystal fibers (PCFs) are the specialized optical waveguides that led to many interesting applications ranging from nonlinear optical signal processing to high-power fiber amplifiers. In this paper, machine learning techniques are used to compute various optical properties including effective index, effective mode area, dispersion and confinement loss for a solid-core PCF. These machine learning algorithms based on artificial neural networks are able to make accurate predictions of above-mentioned optical properties for usual parameter space of wavelength ranging from 0.5-1.8 µm, pitch from 0.8-2.0 µm, diameter by pitch from 0.6-0.9 and number of rings as 4 or 5 in a silica solid-core PCF. We demonstrate the use of simple and fast-training feed-forward artificial neural networks that predicts the output for unknown device parameters faster than conventional numerical simulation techniques. Computation runtimes required with neural networks (for training and testing) and Lumerical MODE solutions are also compared
Optimization of whispering gallery mode sensor design for applications in biosensing
Abstract not availableT. Reynolds, A. François, M.R. Henderson, S.J. Nicholls, T.M Monr
Q-factor limits for far-field detection of whispering gallery modes in active microspheres
Abstract not availableNicolas Riesen,Tess Reynolds, Alexandre François, Matthew R. Henderson, and Tanya M. Monr
An quantum approach of measurement based on the Zurek's triple model
In a close form without referring the time-dependent Hamiltonian to the total
system, a consistent approach for quantum measurement is proposed based on
Zurek's triple model of quantum decoherence [W.Zurek, Phys. Rev. D 24, 1516
(1981)]. An exactly-solvable model based on the intracavity system is dealt
with in details to demonstrate the central idea in our approach: by peeling off
one collective variable of the measuring apparatus from its many degrees of
freedom, as the pointer of the apparatus, the collective variable de-couples
with the internal environment formed by the effective internal variables, but
still interacts with the measured system to form a triple entanglement among
the measured system, the pointer and the internal environment. As another
mechanism to cause decoherence, the uncertainty of relative phase and its
many-particle amplification can be summed up to an ideal entanglement or an
Shmidt decomposition with respect to the preferred basis.Comment: 22pages,3figure
Enhancing the radiation efficiency of dye doped whispering gallery mode microresonators
We present a novel form of a Whispering Gallery Mode (WGM) sensor that exploits dye doped polystyrene microspheres, as active resonators, positioned onto the tip of a Microstructured Optical Fiber (MOF) as a means of overcoming the limited Q-factors for small resonators. We show that it is possible to substantially enhance the fluorescence emission of selected WGMs of the microspheres, resulting in an increase of the signal-to-noise ratio of the modes and of the effective Q-factor. This is done by positioning the resonator into one of the holes of a suspended core MOF and matching the resonator diameter with the hole diameter where it sits, effectively breaking the symmetry of the environment surrounding the sphere. Furthermore we demonstrate that using this experimental configuration, the lasing efficiency of the dye-doped microspheres is also significantly enhanced, which also contributes to an enhancement in the observed Q-factor.Alexandre François, Kristopher J. Rowland, Shahraam Afshar V., Matthew R. Henderson, and Tanya M. Monr
Localised hydrogen peroxide sensing for reproductive health
Session 10 - Chemical Sensors and Biosensors IIThe production of reactive oxygen species (ROS) is known to affect the developmental competence of embryos. Hydrogen peroxide (Hâ‚‚Oâ‚‚) an important reactive oxygen species, is also known to causes DNA damage and defective sperm function. Current techniques require incubating a developing embryo with an organic fluorophore which is potentially hazardous for the embryo. What we need is a localised ROS sensor which does not require fluorophores in solution and hence will allow continuous monitoring of Hâ‚‚Oâ‚‚ production without adversely affect the development of the embryo. Here we report studies on such a fibre-based sensor for the detection of Hâ‚‚Oâ‚‚ that uses a surface-bound aryl boronate fluorophore carboxyperoxyfluor-1(CPF1). Optical fibres present a unique platform due to desirable characteristics as dip sensors in biological solutions. Attempts to functionalise the fibre tips using polyelectrolyte layers and (3-aminopropyl)triethoxysilane (APTES) coatings resulted in a limited signal and poor fluorescent response to Hâ‚‚Oâ‚‚ due to a low tip surface density of the fluorophore. To increase the surface density, CPF1 was integrated into a polymer matrix formed on the fibre tip by a UV-catalysed polymerisation process of acrylamide onto a methacrylate silane layer. The polyacrylamide containing CPF1 gave a much higher surface density than previous surface attachment methods and the sensor was found to effectively detect Hâ‚‚Oâ‚‚. Using this method, biologically relevant concentrations of Hâ‚‚Oâ‚‚ were detected, enabling remote sensing studies into ROS releases from embryos throughout early development.Malcolm S Purdey, Erik P Schartner, Melanie L Sutton-McDowall, Lesley J Ritter, Jeremy G Thompson, Tanya M Monro, and Andrew D Abel
Full vectorial analysis of polarization effects in optical nanowires
We develop a full theoretical analysis of the nonlinear interactions of the
two polarizations of a waveguide by means of a vectorial model of pulse
propagation which applies to high index subwavelength waveguides. In such
waveguides there is an anisotropy in the nonlinear behavior of the two
polarizations that originates entirely from the waveguide structure, and leads
to switching properties. We determine the stability properties of the steady
state solutions by means of a Lagrangian formulation. We find all static
solutions of the nonlinear system, including those that are periodic with
respect to the optical fiber length as well as nonperiodic soliton solutions,
and analyze these solutions by means of a Hamiltonian formulation. We discuss
in particular the switching solutions which lie near the unstable steady
states, since they lead to self-polarization flipping which can in principle be
employed to construct fast optical switches and optical logic gates
Advances in high power short pulse fiber laser systems and technology
We review recent advances in Yb fiber lasers and amplifiers for high power short pulse systems. We go on to describe associated recent developments in fiber components for use in such systems. Examples include microstructured optical fibers for pulse compression and supercontinuum generation, and advanced fiber grating technology for chirped-pulse amplifier systems
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