Interrogation of fibre Bragg grating sensors using an arrayed waveguide grating

We experimentally investigate the use of an arrayed waveguide grating (AWG) to interrogate fibre Bragg grating (FBG) sensors. A broadband light source is used to illuminate the FBG sensors. Reflected spectral information is directed to the AWG containing integral photodetectors providing 40 electrical outputs. Three methods are described to interrogate FBG sensors. The first technique makes use of the wavelength-dependent transmission profile of an AWG channel passband, giving a usable range of 500 με and a dynamic strain resolution of 96 nε Hz-1/2 at 13 Hz. The second approach utilizes wide gratings larger than the channel spacing of the AWG; by monitoring the intensity present in several neighbouring AWG channels an improved range of 1890 με was achieved. The third method improves the dynamic range by utilizing a heterodyne approach based on interferometric wavelength shift detection, providing an improved dynamic strain resolution of 17 nε Hz -1/2 at 30 Hz. © 2005 IOP Publishing Ltd

Interrogation of fibre Bragg grating sensors using an arrayed waveguide grating

We experimentally investigate the use of an arrayed waveguide grating (AWG) to interrogate fibre Bragg grating (FBG) sensors. A broadband light source is used to illuminate the FBG sensors. Reflected spectral information is directed to the AWG containing integral photodetectors providing 40 electrical outputs. Three methods are described to interrogate FBG sensors. The first technique makes use of the wavelength-dependent transmission profile of an AWG channel passband, giving a usable range of 500 με and a dynamic strain resolution of 96 nε Hz-1/2 at 13 Hz. The second approach utilizes wide gratings larger than the channel spacing of the AWG; by monitoring the intensity present in several neighbouring AWG channels an improved range of 1890 με was achieved. The third method improves the dynamic range by utilizing a heterodyne approach based on interferometric wavelength shift detection, providing an improved dynamic strain resolution of 17 nε Hz -1/2 at 30 Hz. © 2005 IOP Publishing Ltd

Interferometric and fibre Bragg grating sensor interrogation using an arrayed waveguide grating

We investigate the use of an arrayed waveguide grating (AWG) to interrogate both fibre Bragg grating (FBG) and interferometric sensors. A broadband light source is used to illuminate both the FBG and interferometric sensors. Reflected spectral information is directed to an AWG with integral photodetectors providing 40 electrical outputs. To interrogate interferometric sensors we investigated the dual wavelength technique to measure the distance of a Fabry-Perot cavity, which produced a maximum unambiguous range of 1440μm with an active sensor. Three methods are described to interrogate FBG sensors. The first technique makes use of the reflected light intensity in an AWG channel passband from a narrow bandwidth grating, giving a usable range of 500με and a dynamic strain resolution of 96nε/√Hz at 30Hz. The second approach utilises wide gratings larger than the channel spacing of the AWG; by monitoring the intensity present in corresponding AWG channels an improved range of 1890με was achieved. The third method improves the dynamic range by utilising a heterodyne approach based on interferometric wavelength shift detection providing a dynamic strain resolution of 17nε/√Hz at 30Hz

Narrow-Band Waveguide Taps Using Photonic Surface Modes Supported by Multilayer Dielectric Stacks

The photonic surface modes supported by multilayer dielectric stacks are highly dispersive. They can therefore be used to design mode-selective taps and narrow-band notch transmission filters for waveguide applications

Theoretical and experimental demonstrations of a microfiber-based flexural disc accelerometer

The proof-of-concept demonstration of a microfiber-based flexural disc accelerometer is presented. The reduced microfiber size and bending radii give rise to high device compactness and responsivity. A flexural disc accelerometer manufactured from a 10mm long microfiber showed a performance of ~2:2 rad/g, with the responsivity expected to increase proportionally with the microfiber lengt

Charge-tunnelling and self-trapping: common origins for blinking, grey-state emission and photoluminescence enhancement in semiconductor quantum dots

Understanding instabilities in the photoluminescence (PL) from light emitting materials is crucial to optimizing their performance for different applications. Semiconductor quantum dots (QDs) offer bright, size tunable emission, properties that are now being exploited in a broad range of developing technologies from displays and solar cells to biomaging and optical storage. However, instabilities such as photoluminescence intermittency, enhancement and bleaching of emission in these materials can be detrimental to their utility. Here, we report dielectric dependent blinking, intensity-“spikes” and low-level, “grey”-state emission, as well as PL enhancement in ZnS capped CdSe QDs; observations that we found consistent with a charge-tunnelling and self-trapping (CTST) description of exciton-dynamics on the QD–host system. In particular, modulation of PL in grey-states and PL enhancement are found to have a common origin in the equilibrium between exciton charge carrier core and surface-states within the CTST framework. Parameterized in terms of size and electrostatic properties of the QD and its nanoenvironment, the CTST offers predictive insight into exciton-dynamics in these nanomaterials

A nanotechnology approach to DNA analysis

This thesis describes the investigation of quantum dots and nano-structured metallic films for use in single genomic DNA analysis. The fluorescence of continuously illuminated core/shell CdSe/ZnS quantum dots (QDs) under various atmospheric conditions is investigated experimentally. Initial enhancement in fluorescence intensity is observed followed by degradation; both are highly dependent on the atmospheric conditions. Following a series of studies theories are put forward to explain these observations.Solution mixtures of DNA strands and QDs are imaged with Atomic Force Microscopy and Fluorescence Microscopy to investigate the binding properties of DNA strands with QDs.Gold nanovoids are fabricated for use as a substrate to provide localised enhanced fluorescence intensity of fluorescently labelled regions of DNA strands stretched and located over nanovoids as a result of resonant coupling with localised surface plasmon polariton modes. The energy and electric field distribution of localised surface plasmon polaritons is considered for various void geometries for use with fluorescently labelled DNA. The experimental fluorescence intensity profile along fluorescently labelled DNA strands stretched over glass, electrochemically grown gold and gold nanovoid substrates is compared and the fluorescence lifetime is measured. Short fluorescence lifetimes and increased intensities over gold nanovoids and a constant lifetime over glass are observed.The results of these biophysical studies are discussed with a view for application as methods for distinguishing different DNA sequences on the nanoscale