The use of semiconductor nano-particles as temperature probes in luminescence chemical sensing applications is addressed. Temperature changes the intensity, the peak wavelength and the spectral width of the quantum dots luminescent emission in a linear and reversible way. Results are presented that show the feasibility of implementing a self-referenced intensity-based sensor to perform temperature measurements independent of the optical power level in the sensing system. A resolution of 0.3 • C was achieved. In addition, it is demonstrated that self-referenced temperature measurements at multiple points could be performed using reflection or transmission based optical fibre configurations.

The potential applications of luminescent semiconductor nanocrystals to optical oxygen sensing are explored. The suitability of quantum dots to provide a reference signal in luminescence-based chemical sensors is addressed. A CdSe-ZnS nanocrystal, with an emission peak at 520 nm, is used to provide a reference signal. Measurements of oxygen concentration, which are based on the dynamic quenching of the luminescence of a ruthenium complex, are performed. Both the dye and the nanocrystal are immobilized in a solgel matrix and are excited by a blue LED. Experimental results show that the ratio between the reference and the sensor signals is highly insensitive to fluctuations of the excitation optical power. The use of CdTe, near-infrared quantum dots with an emission wavelength of 680 nm, in combination with a ruthenium complex to provide a new mechanism for oxygen sensing, is investigated. The possibility of creating oxygen sensitivity in different spectral regions is demonstrated. The results obtained clearly show that this technique can be applied to develop a wavelength division multiplexed system of oxygen sensors.

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A new class of all-fiber beam shaping devices has been realized by inverse etching the end face of single mode and multimode fibers to form a concave cone tip. Concave tip fiber can convert a Gaussian beam profile to a flat top beam profile with a uniform intensity distribution. A flat top beam with intensity variation of approx. 5% and flat top diameter to spot diameter ratio of 67% has been achieved. This device can also change the beam shape from a Gaussian to a donut by moving the observation plane. A flat top multimode fiber beam delivery is attractive for applications which require high power and uniform intensity distribution. In single mode fiber, concave tips could be used to reduce the beam spot size diameter, enabling efficient light coupling from a single mode fiber to an integrated optical waveguide.