This thesis presents ultrafast photophysical measurements on a number of phosphorescent iridium complexes and establishes relationships between the relaxation rates and the vibrational properties of the material. When ultrafast luminescence is measured on the peak of the phosphorescence spectrum and on its red-side, 230 fs and 3 ps decay time constants were observed in all materials studied, and this was attributed to population redistribution amongst the three electronic substates of the lowest triplet metal-ligand charge transfer (MLCT) state. The observation of luminescence at higher values of energy embodied ultrafast dissipation of excess energy by intramolecular vibrational redistribution (IVR) and it was found that the dissipation channels and rate of IVR could be modified by chemical modification of the emitting molecule. This was tested in two ways. Firstly by adding electronically inactive dendrons to the core, an increase in the preference for dissipation of excess energy by IVR rather than by picosecond cooling to the solvent molecules was found, but this did not change the rate of IVR. The second method of testing was by fusing a phenyl moiety directly onto the ligand, this both increased the rate of IVR and also the preference for dissipation by it rather than by picosecond cooling. Fluorescence was recorded in an iridium complex for the first time and a decay time constant of 65 fs was found, thus allowing a direct observation of intersystem crossing (ISC) to be made. In a deep red emitting iridium complex internal conversion (IC) and ISC were observed and the factors controlling their time constants deduced. IC was found to occur by dissipation of excess energy by IVR. The rate of IC was found to be dependent on the amount of vibrational energy stored in the molecule, with IC fast (< 45 fs) when < 0.6 eV of energy is stored and slower (~ 70 fs) when the value is > 0.6 eV. The rate of ISC agreed with these findings, indicating that the very process of ISC may be thought of as closely analogous to that of IC given the strongly spin-mixed nature of the singlet and triplet MLCT states.

The work of this dissertation has been to prove that the coherence of multiphoton excitation can be studied by an appropriately phased and time delayed sequence of pulses. An application of this fundamental study of coherence has been made for the enhancement of third harmonic generation. The coherent recovery of the energy lost to the two photon absorption process enalled a larger propagation distance for the fundamental than in an interaction which is incoherent or coherent, but not using a 90 degree phase shifted pulse pair. Phase matching over this longer propagation distance gave an enhancement of third harmonic generation.

Many essential processes and interactions on atomic and molecular scales occur at ultrafast timescales. The ability to measure and manipulate ultrashort pulses hold the key to probing and understanding these key processes that physicists, engineers, chemists and biologists study today. Measuring ultrashort pulses means that we measure both the intensity (which is a function of time) and the phase of the pulse in time. Or alternately we might measure spectrum and spectral phase (in the corresponding Fourier domain). In the early 1990's, the invention of FROG opened up the field of ultrashort measurement with it's ability to measure the complete pulse. Since then, there have been a whole host of pulse measurement techniques that have been invented to measure all sorts of ultrashort pulses. However, no variation of FROG nor any other fs pulse measurement technique, for that matter, has yet been able to completely measure arbitrary ultraweak femtosecond light pulses such as those found in nature. In this thesis, we will explore a couple of highly sensitive methods in a quest to measure ultraweak ultrashort pulses. We explore the use of Spectral Interferometry, a known sensitive technique as one possibility. We find that it has certain drawbacks that make it not necessarily suitable to tackle this problem. But in the course of our quest, we find that this technique is highly suitable for measuring 10s of picosecond-long shaped pulses. We discuss a couple of developments which make SI highly practical to use for such shaped pulse-measurements. We also develop a new technique which is a variation of FROG, based on the non-linearity of Difference Frequency Generation and Optical Parametric Amplification, which can amplify pulses as weak as a few hundred attojoules to be able to spectrally resolve them and measure the full intensity and phase of these pulses. This technique offers great potential to measure generalized ultraweak ultrashort pulses.

The objective of the present dissertation is to advance the science and engineering of metal-dielectric thin-film structures for ultrafast all-optical applications. The research presented consists of three parts: first, the linear and nonlinear optical (NLO) properties of Au and Ag/Au bilayer metallic thin films are comprehensively studied; then the design and properties of a novel nonlinear device structure are presented and finally an ultrafast all-optical shutter is developed and applications are discussed. In the first part, this study describes the linear and NLO properties of bilayer metallic films and shows that they can be tuned by controlling the mass-thickness ratio between Au and Ag. The combined properties of these bilayers are attractive for active plasmonic applications and nonlinear optical filters. Detailed physical models describing the linear and NLO response of Au and Ag/Au bilayers are presented and compared with experiments. In the second part, these models are used to optimize the NLO response of a novel Au-based NLO device. With only four layers, this novel device strongly amplifies the NLO response of the component Au thin film. NLO devices with broad spectral and angular bandwidths in the visible spectral region are demonstrated. The narrow band dependent NLO response of the NLO device is shown to lead to all-optical controls of high peak-power optical signal pulses. Finally, the NLO device technology is integrated into a novel ultrafast all-optical shutter, which allows temporal opening windows (the time shutter remains open) as short as a few ps. Ultrafast all-optical shutter potentially can temporally shape high peak-power nanosecond optical pulses, which could benefit biomedical and micromachining applications. Other possible optical applications such as short electron, X-ray pulse generations, ultrafast photography, and biomedical imaging will also be discussed.

Temporal pulse shaping based on integrated Bragg gratings is investigated in this work to achieve arbitrary output waveforms. The grating structure is simulated based on the sidewall-etching geometry in an AlGaAs platform. The inverse scattering employin the Gel'fan-Levithan-Marchenko theorem and the layer peeling method provides a tool to determine grating structures from a desired spectral reflection response. Simulations of pulse shaping considered flat-top and triangular pulses as well as one-to-one and one-to-many pulse shaping. The suggested grating profiles revealed a compromise between performance and grating length. The integrated grating, a few hundred microns in length, could generate flat-top pulses with pulse durations as short as 500 fs with rise/fall times of 200 fs; the results are comparable to previous work in free-space optics and fiber optics. The theories and the devised algorithms could serve as a design station for advanced grating devices for, but not restricted to, optical pulse shaping.

Temporal pulse shaping based on integrated Bragg gratings is investigated in this work to achieve arbitrary output waveforms. The grating structure is simulated based on the sidewall-etching geometry in an AlGaAs platform. The inverse scattering employin the Gel'fan-Levithan-Marchenko theorem and the layer peeling method provides a tool to determine grating structures from a desired spectral reflection response. Simulations of pulse shaping considered flat-top and triangular pulses as well as one-to-one and one-to-many pulse shaping. The suggested grating profiles revealed a compromise between performance and grating length. The integrated grating, a few hundred microns in length, could generate flat-top pulses with pulse durations as short as 500 fs with rise/fall times of 200 fs; the results are comparable to previous work in free-space optics and fiber optics. The theories and the devised algorithms could serve as a design station for advanced grating devices for, but not restricted to, optical pulse shaping.

Intensivement étudié depuis son apparition en 1960, le laser est un outil qui a su trouver sa place au-delà du monde académique : ses performances uniques l'ont rendu indispensable dans nombres d'applications de la vie courante. Les particularités les plus attractives du rayonnement laser sont la directivité de son émission, et le caractère quasi-monochromatique de son rayonnement.La première permet de propager un faisceau laser sur des longues distances, et également de concentrer la lumière sur des cibles aux dimensions extrêmement réduites : on parle de cohérence spatiale de l'émission laser. Cette seule propriété trouve de nombreuses applications : les lecteurs de codes-barres, imprimantes laser, pointeurs lasers en sont des exemples très rependus.La seconde permet d'accorder la bande spectrale étroite de l’émission laser aux bandes d'absorption de certains matériaux, ce qui permet de déposer localement de l’énergie de manière contrôlée. Par ailleurs elle confère au rayonnement laser des propriétés de cohérence temporelle uniques, qui peuvent être exploitées notamment en interférométrie, ouvrant la voie à de très nombreuses applications dans le domaine de la mesure, pour la caractérisation de surfaces optiques, dans les capteurs de position à effet Sagnac, en spectrométrie, pour ne pas citer quelques exemples. / ...

La tenue au flux des traitements de surfaces optiques constitue aujourd'hui un enjeu majeur pour le développement des lasers de puissance à courtes durées d'impulsion. L’étude des interactions laser-matière en régime sub-picoseconde a montré que l’initiation de l'endommagement laser est le résultat de processus d’excitation fortement non-linéaires (photoionisation, ionisation par impact et avalanche électronique). Dans cette thèse, un dispositif de tests multiparamétriques a été développé pour l’étude de la tenue au flux des composants optiques. Différentes études expérimentales ont été menées sur des matériaux diélectriques, en couche mince ou en matériau massif, afin d’apporter des données nouvelles sur les matériaux couches minces assez peu étudiés dans la littérature. L’étude de l’influence de la longueur d’onde a révélé différentes phases de prédominance des processus d’ionisation. L’influence du nombre de tirs à différentes longueurs d’ondes aussi a été étudiée, en considérant différentes techniques de dépôt de couches minces. L’interprétation de ces résultats expérimentaux est soutenue par un modèle de simulation numérique que nous présentons en détail dans le manuscrit. Une place, non moins importante, a été accordée dans notre travail à la métrologie de l’endommagement. Nous avons proposé et appliqué l’utilisation d’un dispositif original de mesure quantitative de phase pour l’analyse des processus d’endommagement. Et pour terminer nous avons développé un système de microscopie pompe-sonde afin de pousser les investigations sur les processus en jeu lors de l’interaction laser-matière en régime sub-picoseconde. / Laser fluence resistance of optical surfaces is a major challenge for the development of high power and short duration pulse lasers. Studies on laser matter interactions show that the damage initiation is the result of highly nonlinear excitation process such as photoionization, impact ionization and electronic avalanche. In this PhD thesis we focused on the study of the damage and the response of materials after this initiation and their dependence with laser parameters, this in order to better understand the complex mechanisms of damage, identify laws of relevant scales for applications, and enable new optical design with higher laser resistance and lifetimes. A multi parametric experimental testing setup was developed for studying laser resistance of optical components. To collect new data on thin film materials damage dependences, which have been less studied in the literature, different experimental studies have been conducted on dielectrics, in coating or bulk form. The study of the dependency of damage with laser wavelength reveals different ranges characterized by the electronic processes occurring during the interaction. We have considered also the effect of multiple pulse irradiations, with different wavelengths and on coatings realized by different technologies. All these experimental results have been discussed with the help of a numerical simulation model we have developed and presented in this thesis. We have also proposed an original method based on optical phase difference measurement for damage characterization and study. We finished with some experiments on the time resolved microscopy measurements and investigations of damage processes.

Je rapporte dans ce manuscrit une étude théorique et expérimentale d’une source compacte, fiable et bas coût d’ondes électromagnétiques continues et cohérentes de 30 Hz de largeur de raie, accordables de 1 GHz à 500 GHz par pas de 1 GHz. Ces ondes sont générées par un photo-mélange de deux diodes lasers DFB (Distributed Feedback) très accordables autour de 1550 nm, stabilisées avec des polarisations orthogonales sur une même cavité Fabry-Perot optique fibrée. J’ai conçue des électroniques de correction très rapides pour chaque laser permettant d’avoir une bande passante d’asservissement de 7 MHz limitée par la longueur de la boucle. Je démontre des suppressions de bruit de phase jusqu’à -60 dBc/ Hz à 1 kHz et de -90 dBc/Hz à 100 kHz d’écart d’une porteuse électrique à 92 GHz. Je mesure aussi une dérive de fréquence de ~170 kHz d’un battement à 10 GHz à long terme sur 7,5 heures de verrouillage continu. Je montre une conception optimisée d’une boucle d’asservissement intégrée de quelques dizaines de cm de longueur qui réduit le bruit de phase de 18 dB à 1 MHz d’écart à la porteuse optique et des couplages phase-amplitude réduits dans la cavité d’un facteur 50 par rapport à ceux estimés expérimentalement. L’ajout d’un troisième laser DFB stabilisé en phase sur un oscillateur local permettrait d’avoir une source continûment accordable sur 1 THz. La source d’ondes continues permettrait également de générer à partir de fibres hautement non linéaires et dispersives des impulsions pico- ou femtosecondes à un taux de répétition fixe en remplacement les lasers DFB par des lasers plus stables. Je calcule par simulation une gigue temporelle de 7,2 fs sur un temps d’intégration de 1 ms à 40 GHz de taux de répétition. / I report in this manuscript a theoretical and experimental study of a compact, reliable and low cost source of 30 Hz linewidth, continuous and coherent electromagnetic waves tunable from 1 GHz to 500 GHz in steps of 1 GHz. These waves are generated by photomixing two distributed feedback (DFB) laser diodes at 1550 nm which are frequency stabilized with orthogonal polarizations on the same optical fibered Fabry-Perot cavity. I have designed very fast electronic control filters for each laser allowing a 7 MHz servo bandwidth limited by the loop length. I demonstrate phase noise suppressions down to -60 dBc/Hz at 1 kHz and -90 dBc/Hz at 100 kHz offset frequencies from a 92 GHz electrical carrier. I also measure a ~170 kHz frequency drift of the beat note at 10 GHz on the long term over a continuous 7.5 hour locking period. I show an optimized design of an integrated servo loop of few tens of cm length which reduces the phase noise by 18 dB at 1 MHz optical carrier offset frequency and the phase-amplitude couplings in the cavity by a factor of 50 compared to the experimental one. The addition of a third DFB laser phase stabilized on a local oscillator allows the possibility to have continuously tunable source over 1 THz. The continuous wave source also makes it possible to generate fixed repetition rate pico- or femtosecond pulses from highly non-linear and dispersive fibers, replacing the DFB lasers by further stable lasers. I have calculated by simulation 7.2 fs temporal jitter at 40 GHz repetition rate over a 1 ms integration time.