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

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 (H₂O₂) 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 H₂O₂ production without adversely affect the development of the embryo. Here we report studies on such a fibre-based sensor for the detection of H₂O₂ 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 H₂O₂ 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 H₂O₂. Using this method, biologically relevant concentrations of H₂O₂ 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