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Fluorescence-based techniques are widely used in bioscience, offering a high sensitivity and versatility. In this work, fluorescence electronic energy migration/ transfer is applied to measure intramolecular distances in two types of systems and under various conditions. The main part of the thesis utilizes the process of donor-acceptor energy transfer to probe distances within the ribosomal protein S16. Proteins are essential to all organisms. Therefore, it is of great interest to study protein structure and function in order to understand and prevent protein malfunction. Moreover, it is also important to try to study the proteins in an environment which resembles its natural habitat. Here two protein homologs were investigated; S16Thermo and S16Meso, isolated from a hyperthemophilic bacterium and a mesophilic bacterium, respectively. It was concluded that the chemically induced unfolded state ensemble of S16Thermo is more compact than the corresponding ensemble of S16Meso. This unfolded state compaction may be one reason for the increased thermal stability of S16Thermo as compared to S16Meso. The unfolded state of S16 was also studied under highly crowded conditions, mimicking the environment found in cells. It appears that a high degree of crowding, induced by 200 mg/mL dextran 20, forces the unfolded state ensemble of S16Thermo to become even more compact. Further, intramolecular distances in the folded state of five S16 mutants were investigated upon increasing amounts of dextran 20. We found that the probed distances in S16Thermo are unaffected by increasing degree of crowding. However, S16Meso shows decreasing intramolecular distances for all three studied variants, up to 100 mg/mL dextran. At higher concentrations, the change in distance becomes anisotropic. This suggests that marginally stable proteins like s16Meso may respond to macromolecular crowding by fine-tuning its structure. More stable proteins like S16Thermo however, show no structural change upon increasing degree of crowding. We also investigated the possibility of local specific interactions between the protein and crowding agent, by means of fluorescence quenching experiments. Upon increasing amounts of a tyrosine labelled dextran, a diverse pattern of fluorescence quantum yield and lifetime suggests that specific, local protein-crowder interactions may occur. In a second studied system, electronic energy migration between two donor-groups, separated by a rigid steroid, was studied by two-photon excitation depolarization experiments. Data were analysed by using recent advances, based on the extended Förster theory, which yield a reasonable value of the distance between the two interacting donor-groups. To the best of our knowledge, this is the first quantitative analysis of energy migration data, obtained from two-photon excited fluorescence.

<p>The advancement in nanotechnology creates a new perspective on future medicine. With more and more understanding on controlling the functional behavior of the nanoplatform, scientists nowadays are aiming to improve the health care system by offering personalized medicine through nanotechnology. Lots of emphasis have been placed on a promising field called theranostics, which integrate imaging and therapeutic functions into one, that not only offers monitoring and imaging of the biological process, but also provides diagnosis and drug delivery simultaneously. Plasmonic gold nanostars, because of its anisotropic geometry and unique plasmonic property, have become one of the most anticipated nanoplatform in the field of nanotheranostics, aiming to achieve superior plasmonic properties for biomedical applications. The work herein will provide an introduction to the related field on plasmonics, nanobiophotonics and nanotheranostics. A facile plasmon-tunable surfactant-free nanostars synthesis method is described followed by an extensive characterization both computationally and experimentally. Its superior plasmon behavior on two-photon photoluminescence imaging and surface-enhanced Raman scattering detection are demonstrated both in cells and in animals. Therapeutic function assessment is carried out both as drug carriers (photodynamic therapy) and as endogenous stimulus responsive agents (photothermal therapy). Finally, the nanostars' cellular uptake mechanism is investigated based on nanostars' endogenous contrast; an enhanced photothermal therapy is achieved using an ultralow irradiance that has ever published. With nanostars being a novel and powerful theranostic agent, the potentials implication lies in the study of their pharmacokinetics, targeted delivery, diagnostic imaging, and toxicity.</p> / Dissertation

The research described herein is aimed at exploring the thermo-mechanical properties of thiol-ene polymers in bulk form, investigating the ability of thiol-ene polymers to behave desirably as photolithographic media, and providing the first characterization of the mechanical properties of two-photon stereolithography-produced polymer structures. The thiol-ene polymerization reaction itself is well-characterized and described in the literature, but the thermomechanical properties of thiol-ene and thiol-ene/acrylate polymers still require more rigorous study. Understanding the behavior of thiol-ene networks is a crucial step towards their expanded use in bulk form, and particularly in specialized applications such as shape memory devices. Additionally, the thiol-ene polymerization reaction mechanism exhibits unique properties which make these polymers well suited to photolithography, overcoming the typical dichotomy of current materials which either exhibit excellent photolithographic behavior or have controllable properties. Finally, before two-photon stereolithography can create mechanisms and devices which can serve any mechanically functional role, the mechanical properties of the polymers they produce must be quantitatively characterized, which is complicated by the extremely small scale at which these structures are produced. As such, mechanical characterization to date has been strictly qualitative. Fourier transfer infrared spectroscopy revealed functional group conversion information and sol-fraction testing revealed the presence of unconverted monomer and impurities, while dynamic mechanical analysis and tensile testing revealed the thermomechanical responses of the systems. Nanoindentation was employed to characterize the mechanical properties of polymers produced by two-photon stereolithography. Optical and electron microscopy were exploited to provide quantitative and qualitative evaluations of thiol-ene/acrylate performance in small-scale polymerization regimes. The broad objective of the research was to explore thiol-ene polymer behavior both in bulk and at the small scale in an effort to supplement the material library currently used in these fields and to expand the design envelope available to researchers. The significance of the research is the advancement of a more complete and fundamental understanding of thiol-ene polymerization from kinetics to final properties, the quantitative establishment of the mechanical properties of materials created with two-photon stereolithography, and the comprehensive characterization of a supplementary class of photopatternable polymers with greater property tunability than is possible with currently used materials.

The objective of this thesis was to develop novel technologies for measuring the physical characteristics of high-speed pulse trains, for use in performance monitoring applications. This thesis describes the development of three separate techniques that perform measurements in either the time domain, frequency domain or the phase space of the optical signal. The first section investigates phase-sensitive pulse measurement techniques. A high- resolution SHG-FROG apparatus was custom-designed to measure 40GHz RZ pulse trains, from which an operational characterisation of a Mach-Zehnder modulator (MZM) was realised. A numerical model of a nonlinear pulse compressor was developed to compress 40GHz RZ pulses from 8.5ps down to 3.4ps. These pulses were time-division multiplexed to 80GHz, and phase-retrievals of the 80GHz pulse trains were measured. A comparison between the techniques of SHG-FROG and linear spectrogram has been undertaken for 10GHz pulse sources, exposing SHG-FROG's weaknesses at this particular repetition rate. The second section investigates a simple, time-averaged, nonlinear detection technique. Two-photon absorption in a GaAs/InGaAs quantum-well laser diode was used to measure the duty cycle (and by extension, the pulse duration) of a range of pulse sources. This technique was further developed to measure the extinction ratio of NRZ pulse trains. Additionally, the pulse duration of a mode-locked laser source was measured using the nonlinear absorption in a 1-m length of As2Se3 Chalcogenide glass fiber. This demonstrates that the nonlinear properties of this glass may well find application in future instrumentation. The third section investigates the development of an ultra-high resolution swept heterodyne spectrometer. This spectrometer was used to spectrally-distinguish repetitive 8-bit NRZ patterns at 2.5Gbit/s. It was also used to measure the chirp parameter of an X-cut LiNbO3 MZM, revealing a chirp parameter of απ/2 < 0.1 across a modulation band- width of 250-2500MHz. Additionally, the distinctive CW spectrum of a DFB laser diode was measured. Analysis of the measured CW spectrum yielded a linewidth enhancement factor of α≃ 1.8 and also the relative intensity noise of the DFB laser diode.

The objective of this thesis was to develop novel technologies for measuring the physical characteristics of high-speed pulse trains, for use in performance monitoring applications. This thesis describes the development of three separate techniques that perform measurements in either the time domain, frequency domain or the phase space of the optical signal. The first section investigates phase-sensitive pulse measurement techniques. A high- resolution SHG-FROG apparatus was custom-designed to measure 40GHz RZ pulse trains, from which an operational characterisation of a Mach-Zehnder modulator (MZM) was realised. A numerical model of a nonlinear pulse compressor was developed to compress 40GHz RZ pulses from 8.5ps down to 3.4ps. These pulses were time-division multiplexed to 80GHz, and phase-retrievals of the 80GHz pulse trains were measured. A comparison between the techniques of SHG-FROG and linear spectrogram has been undertaken for 10GHz pulse sources, exposing SHG-FROG's weaknesses at this particular repetition rate. The second section investigates a simple, time-averaged, nonlinear detection technique. Two-photon absorption in a GaAs/InGaAs quantum-well laser diode was used to measure the duty cycle (and by extension, the pulse duration) of a range of pulse sources. This technique was further developed to measure the extinction ratio of NRZ pulse trains. Additionally, the pulse duration of a mode-locked laser source was measured using the nonlinear absorption in a 1-m length of As2Se3 Chalcogenide glass fiber. This demonstrates that the nonlinear properties of this glass may well find application in future instrumentation. The third section investigates the development of an ultra-high resolution swept heterodyne spectrometer. This spectrometer was used to spectrally-distinguish repetitive 8-bit NRZ patterns at 2.5Gbit/s. It was also used to measure the chirp parameter of an X-cut LiNbO3 MZM, revealing a chirp parameter of απ/2 < 0.1 across a modulation band- width of 250-2500MHz. Additionally, the distinctive CW spectrum of a DFB laser diode was measured. Analysis of the measured CW spectrum yielded a linewidth enhancement factor of α≃ 1.8 and also the relative intensity noise of the DFB laser diode.

The objective of this thesis was to develop novel technologies for measuring the physical characteristics of high-speed pulse trains, for use in performance monitoring applications. This thesis describes the development of three separate techniques that perform measurements in either the time domain, frequency domain or the phase space of the optical signal. The first section investigates phase-sensitive pulse measurement techniques. A high- resolution SHG-FROG apparatus was custom-designed to measure 40GHz RZ pulse trains, from which an operational characterisation of a Mach-Zehnder modulator (MZM) was realised. A numerical model of a nonlinear pulse compressor was developed to compress 40GHz RZ pulses from 8.5ps down to 3.4ps. These pulses were time-division multiplexed to 80GHz, and phase-retrievals of the 80GHz pulse trains were measured. A comparison between the techniques of SHG-FROG and linear spectrogram has been undertaken for 10GHz pulse sources, exposing SHG-FROG's weaknesses at this particular repetition rate. The second section investigates a simple, time-averaged, nonlinear detection technique. Two-photon absorption in a GaAs/InGaAs quantum-well laser diode was used to measure the duty cycle (and by extension, the pulse duration) of a range of pulse sources. This technique was further developed to measure the extinction ratio of NRZ pulse trains. Additionally, the pulse duration of a mode-locked laser source was measured using the nonlinear absorption in a 1-m length of As2Se3 Chalcogenide glass fiber. This demonstrates that the nonlinear properties of this glass may well find application in future instrumentation. The third section investigates the development of an ultra-high resolution swept heterodyne spectrometer. This spectrometer was used to spectrally-distinguish repetitive 8-bit NRZ patterns at 2.5Gbit/s. It was also used to measure the chirp parameter of an X-cut LiNbO3 MZM, revealing a chirp parameter of απ/2 < 0.1 across a modulation band- width of 250-2500MHz. Additionally, the distinctive CW spectrum of a DFB laser diode was measured. Analysis of the measured CW spectrum yielded a linewidth enhancement factor of α≃ 1.8 and also the relative intensity noise of the DFB laser diode.

The objective of this thesis was to develop novel technologies for measuring the physical characteristics of high-speed pulse trains, for use in performance monitoring applications. This thesis describes the development of three separate techniques that perform measurements in either the time domain, frequency domain or the phase space of the optical signal. The first section investigates phase-sensitive pulse measurement techniques. A high- resolution SHG-FROG apparatus was custom-designed to measure 40GHz RZ pulse trains, from which an operational characterisation of a Mach-Zehnder modulator (MZM) was realised. A numerical model of a nonlinear pulse compressor was developed to compress 40GHz RZ pulses from 8.5ps down to 3.4ps. These pulses were time-division multiplexed to 80GHz, and phase-retrievals of the 80GHz pulse trains were measured. A comparison between the techniques of SHG-FROG and linear spectrogram has been undertaken for 10GHz pulse sources, exposing SHG-FROG's weaknesses at this particular repetition rate. The second section investigates a simple, time-averaged, nonlinear detection technique. Two-photon absorption in a GaAs/InGaAs quantum-well laser diode was used to measure the duty cycle (and by extension, the pulse duration) of a range of pulse sources. This technique was further developed to measure the extinction ratio of NRZ pulse trains. Additionally, the pulse duration of a mode-locked laser source was measured using the nonlinear absorption in a 1-m length of As2Se3 Chalcogenide glass fiber. This demonstrates that the nonlinear properties of this glass may well find application in future instrumentation. The third section investigates the development of an ultra-high resolution swept heterodyne spectrometer. This spectrometer was used to spectrally-distinguish repetitive 8-bit NRZ patterns at 2.5Gbit/s. It was also used to measure the chirp parameter of an X-cut LiNbO3 MZM, revealing a chirp parameter of απ/2 < 0.1 across a modulation band- width of 250-2500MHz. Additionally, the distinctive CW spectrum of a DFB laser diode was measured. Analysis of the measured CW spectrum yielded a linewidth enhancement factor of α≃ 1.8 and also the relative intensity noise of the DFB laser diode.

The objective of this thesis was to develop novel technologies for measuring the physical characteristics of high-speed pulse trains, for use in performance monitoring applications. This thesis describes the development of three separate techniques that perform measurements in either the time domain, frequency domain or the phase space of the optical signal. The first section investigates phase-sensitive pulse measurement techniques. A high- resolution SHG-FROG apparatus was custom-designed to measure 40GHz RZ pulse trains, from which an operational characterisation of a Mach-Zehnder modulator (MZM) was realised. A numerical model of a nonlinear pulse compressor was developed to compress 40GHz RZ pulses from 8.5ps down to 3.4ps. These pulses were time-division multiplexed to 80GHz, and phase-retrievals of the 80GHz pulse trains were measured. A comparison between the techniques of SHG-FROG and linear spectrogram has been undertaken for 10GHz pulse sources, exposing SHG-FROG's weaknesses at this particular repetition rate. The second section investigates a simple, time-averaged, nonlinear detection technique. Two-photon absorption in a GaAs/InGaAs quantum-well laser diode was used to measure the duty cycle (and by extension, the pulse duration) of a range of pulse sources. This technique was further developed to measure the extinction ratio of NRZ pulse trains. Additionally, the pulse duration of a mode-locked laser source was measured using the nonlinear absorption in a 1-m length of As2Se3 Chalcogenide glass fiber. This demonstrates that the nonlinear properties of this glass may well find application in future instrumentation. The third section investigates the development of an ultra-high resolution swept heterodyne spectrometer. This spectrometer was used to spectrally-distinguish repetitive 8-bit NRZ patterns at 2.5Gbit/s. It was also used to measure the chirp parameter of an X-cut LiNbO3 MZM, revealing a chirp parameter of απ/2 < 0.1 across a modulation band- width of 250-2500MHz. Additionally, the distinctive CW spectrum of a DFB laser diode was measured. Analysis of the measured CW spectrum yielded a linewidth enhancement factor of α≃ 1.8 and also the relative intensity noise of the DFB laser diode.

A high resolution photoconductivity investigation of two 13 -3 photon magneto-absorption (TPMA) in n-InSb (n - 9 x 10 cm ) has been performed. This is the first time that two-photon absorption in a semiconductor has been studied with cw lasers only. With a stable cw CC>2 laser and a highly sensitive sampling and magnetic field modulation technique, a minimum of 4 2 transitions in the TPMA photoconductivity spectra can be observed. Most of these transitions are a result of the usual spherical approximation TPMA selections rules (An =0, ±2; As = 0 for e ⊥ B and Δn = 0; Δs = 0 for e || B) . However, some transitions, in particular several near the TPMA band edge, are not explained by these rules. The TPMA spectra have been found to depend upon crystallographic orientation. This has not been previously observed. The temperature variation of the fundamental energy gap Eg between 2 and 100° K is also obtained from TPMA experiments.