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This thesis looks at fluorescence techniques and their use for nanometrology applications. It has been primarily industrially linked with scientific instrument vendors Horiba Scientific IBH and Horiba Scientific ISA and examines the state of the art instrumentation taking the reader from grounds up from simple steady-state and time-resolved fluorescence spectroscopy techniques that are routinely used and newer more advanced techniques made possible but rapid developments in technology. Secondary industrial links are to NPL allowing the examination of the state of the art instrument in fluorescence microscopy an extension of fluorescence spectroscopy and this thesis likewise builds from simple to advanced microscopy techniques. In the case of nanometrology well-established techniques in particular time-resolved fluorescence anisotropy, which overcomes the diffraction barrier by use of low concentrations and infers the average particle size of a homogeneous distribution by use of polarized light and Brownian motion are discussed. These applications are examined in conjunction to high concentration microscopy techniques such as direct Stochastic Optical Reconstruction Microscopy (dSTORM) High concentration heterogeneous techniques are better suited to most biological applications which involve the measurement of highly packed nanostructures. dSTORM requires use of specific chemical conditions and high laser power to enable stochastic blinking. A video of these stochastic blinks by use of a fast capture imaging CCD allows one to temporally resolve each single-molecule blinks and construct a single super-resolution image. The implication of these chemical conditions, high laser power and limitations even in today’s state of the art CCDs need to be properly understood and any development in either but preferably all three will make this advanced microscopy technique more feasible. This work looks at the properties of some new probes for nanometrology however, the strict criteria required for successful dSTORM applications in particular leaves this work an open investigation.

Experimental investigation of the optical properties of single InGaN/GaN quantum dots (QDs) is presented. The results are compared to a theoretical model based on an atomistic semi-empirical tightbinding approach. Nonlinear excitation is investigated by micro-photoluminescence (micro-PL), time-resolved PL and PL excitation (PLE) spectroscopy. It is found to produce almost total suppression of the background emission arising from the underlying quantum well. This is explained qualitatively by the enhancement of the nonlinear absorption due to the zero-dimensional confinement in the QDs. PLE spectra show clear evidence for the existence of excited states. We present direct evidence of the control of the oscillator strength of the exciton state in the QD by an applied vertical electric field. This is achieved through the study of the radiative lifetime of the QD embedded in a p-i-ll diode structure. The effect is explained by the increase in the overlap between the electron and the hole wavefunctions due to the partial compensation of the internal piezoelectric field and was found to be accompanied by a large blue shift of the transition energy. The results are found to be in good quantitative agreement with theoretical predictions arising from the theoretical model extended to take into account the effect of the applied field. The induced increase in the overlap between the wavefunctions of the carriers is shown experimentally to enhance the attractive Coulomb interaction leading to the change of the sign of the biexcitonic binding energy. The electroluminescence observed from the structure under forward bias showed clear indication of single QD emission which persists up to ',,85 K. The generation of single photons in the blue spectral region from a single QD is demonstrated. The collection efficiency was enhanced by embedding the QD layer in a low-Q microcavity. The single QD emission is observed to be ',,10 times stronger than typical emission without a cavity. Nonlinear excitation spectroscopy proved essential in these measurements since any background emission would mask the signature of single-photon emission. This result provides a clear evidence of the quantum nature of the emission.

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