Abstract: A system for characterising a material is provided. The system includes an optical sensor including an optical waveguide, the optical waveguide having first and second ends and being characterised by having a numerical aperture greater than or equal to 0.2, and a microresonator including an optically active material, the microresonator being positioned in an optical near field of an end face of the first end of the optical waveguide such that the optically active material is excitable by light. The system further includes a light source for exciting the optically active material of the microresonator so as to generate whispering gallery modes (WGMs) in the microresonator and a light collector for collecting an intensity of light that is associated with the WGMs excited in the microresonator.

Abstract: The present disclosure provides a method of characterising a dielectric material. The method comprises the step of providing a light source, a light collector and a sensor. The sensor is arranged so that an evanescent field of light penetrates through a surface of the sensor and surface plasmons are generated at the surface of the sensor when suitable light is directed along at least a portion of the sensor. The method also includes the step of exposing the surface of the sensor to the dielectric material so that an interface is formed between the surface and the dielectric material. Further, the method comprises guiding light along at least a portion of the sensor to generate the surface plasmons. In addition, the method comprises the step of collecting an intensity of light from the interface as a function of a spectral parameter of the light. Further, the present disclosure provides an apparatus for characterising the dielectric material in accordance with the method.

Abstract: The present disclosure provides an optical detector for detecting radiation. The optical detector includes an optical light guide that incorporates a sensing region. The sensing region includes a sensing material that emits luminescence light when the sensing material is exposed to suitable ionizing radiation and accrues trapped charge which is released and produces optically stimulated luminescence (OSL) when the sensing material is optically stimulated. The optical detector also includes a light source for optically stimulating the sensing material and a light detector for detecting the OSL. The optical light guide is arranged to guide light through the sensing region and between the sensing region and the luminescence light detector.

Abstract: To overcome problems of fabricating conventional core-clad optical fibre from non-silica based (compound) glass, it is proposed to fabricate non-silica based (compound) glass optical fibre as holey fibre i.e. one contining Longitudinal holes in the cladding. This removes the conventional problems associated with mismatch of the physical properties of the core and clad compound glasses, since a holey fibre can be made of a single glass composition. With a holey fibre, it is not necessary to have different glasses for the core and cladding, since the necessary refractive index modulation between core and cladding is provided by the microstructure of the clad, i.e. its holes, rather than by a difference in materials properties between the clad and core glasses. Specifically, the conventional thermal mismatch problems between core and clad are circumvented.

Abstract: An optical fibre device based on the Raman effect comprises a first optical source to provide light at a first wavelength, and a holey optical fibre which receives the light from the first optical source such that optical gain or loss is provided at a second wavelength by the effect of Raman scattering within the fibre. For optical gain, the second wavelength is longer than the first wavelength, and the device can be operated as an amplifier, or as a laser if optical feedback is provided. For optical loss, the second wavelength is shorter than the first, and the device may be used as an optical modulator. The fibre may be fabricated from pure silica, although other undoped or doped materials may alternatively be used to tailor properties of the fibre such as gain spectrum, bandwidth, power handling capability and mode propagation.

Abstract: An optical fibre is provided with dispersion tuning holes (510) arranged in the wings of the modal field distribution (512). These dispersion tuning holes can be used in a holey or conventional fibre geometry to tune the fibre dispersion independently from the other modal properties, such as the mode shape, to generate birefringence and for other dispersion tuning applications. These holes contrast from the usual “holey fibre” holes in that they are generally carefully placed laterally offset from the geometrical axis of the optical fibre by a distance of the same order as the mode field radius. The placement and size of the proposed “dispersion tuning holes” ensures that they affect the dispersion of the mode in a desired manner.

Abstract: To overcome problems of fabricating conventional core-clad optical fibre from non-silica based (compound) glass, it is proposed to fabricate non-silica based (compound) glass optical fibre as holey fibre i.e. one contining Longitudinal holes in the cladding. This removes the conventional problems associated with mismatch of the physical properties of the core and clad compound glasses, since a holey fibre can be made of a single glass composition. With a holey fibre, it is not necessary to have different glasses for the core and cladding, since the necessary refractive index modulation between core and cladding is provided by the microstructure of the clad, i.e. its holes, rather than by a difference in materials properties between the clad and core glasses. Specifically, the conventional thermal mismatch problems between core and clad are circumvented.

Abstract: The percentage fraction of fundamental mode power located in the cladding holes of different holey fibers (PFholes) is shown as a function of wavelength in microns of the fundamental mode (&lgr;). Properties of two groups of holey fibers are shown. The upper group of three curves shows embodiments of the invention with &Lgr;=0.75 &mgr;m and d/&Lgr;=0.6, 0.7 & 0.8 respectively, where d is the hole diameter and &Lgr; the hole spacing or pitch. The lower group of curves, which are almost superimposed on each other, show properties of holey fibers representative of the prior art with &Lgr;=3.2 &mgr;m and d/&Lgr;=0.6, 0.7 & 0.8 respectively. A huge improvement in the mode power present in the holes is evident. In the prior art curves, the mode power fraction is generally less than 1%, whereas with the illustrated embodiments of the invention, holey fibers with 10-40% of the fundamental mode power in the holes are achieved.

Abstract: The percentage fraction of fundamental mode power located in the cladding holes of different holey fibers (PFholes) is shown as a function of wavelength in microns of the fundamental mode (&lgr;). Properties of two groups of holey fibers are shown. The upper group of three curves shows embodiments of the invention with &Lgr;=0.75 &mgr;m and d/&Lgr;=0.6, 0.7 & 0.8 respectively, where d is the hole diameter and &Lgr; the hole spacing or pitch. The lower group of curves, which are almost superimposed on each other, show properties of holey fibers representative of the prior art with &Lgr;=3.2 &mgr;m and d/&Lgr;=0.6, 0.7 & 0.8 respectively. A huge improvement in the mode power present in the holes is evident. In the prior art curves, the mode power fraction is generally less than 1%, whereas with the illustrated embodiments of the invention, holey fibers with 10-40% of the fundamental mode power in the holes are achieved.