Ultrafast Dynamics of Metal Complexes of Tetrasulfonated Phthalocyanines at Biological Interfaces: Comparison between Photochemistry in Solutions, Films, and Noncancerous and Cancerous Human Breast Tissues

International audienceA promising material in medicine, electronics, opto-electronics, electrochemistry, catalysis, and photophysics, Al(III) phthalocyanine chloride tetrasulfonic acid (AlPcS4) is investigated at biological interfaces of human breast tissue by means of steady-state and time-resolved pump?probe spectroscopies: IR, Raman, UV?vis, fluorescence, and electronic transient absorption by pump?probe spectroscopy. Spectrally resolved pump?probe data were recorded on time scales ranging from femtoseconds to nanoseconds and give insight into molecular interactions and primary events in the interfacial region. The nature of these fast processes and pathways of the competing relaxation processes from the initially excited electronic states in AlPcS4 films and at biological interfaces of human breast cancerous and noncancerous tissues is studied. Comparison between photochemical dynamics in the biological environment of the human breast tissues and that occurring in aqueous solutions is presented. The excited-state absorption (ESA) decays and bleaching recovery of the ground state have been fitted in the time window extending to nanoseconds (0?1 ns). We found that the excited-state dynamics of AlPcS4 at biological interfaces of human breast tissue is extremely sensitive to the biological environment and differs drastically from that observed in solutions and films. We demonstrated that the ultrafast dynamics at biological interfaces is described by three time constants in the ranges of 110?170 fs, 1?7 ps, and 20?60 ps. We were able to ascribe these three time constants to the primary events occurring in phthalocyanine at biological interfaces. The shortest time constants have been assigned to vibrational wavepacket dynamics in the Franck?Condon region down to the local minimum of the excited-state S1. The 1?7 ps components have been assigned to vibrational relaxation in the excited and ground electronic states. In contrast to the dynamics observed in aqueous solutions with the components in the range of 150?500 ps assigned to decay from S1 to the ground electronic state, these slow components have not been recorded in human breast tissue. We have shown that the lifetimes characterizing the first excited-state S1 in the interfacial regions of the breast tissue are markedly shorter than those in solution. It suggests that molecular structures responsible for harvesting of the light energy in biological tissue find their own ways for recovery through some special features of the potential energy surfaces such as conical intersections, which facilitate the rate of radiationless transitions. We found that the dynamics of photosensitizers in normal (noncancerous) breast tissue is markedly faster than that in cancerous tissue

Ultrafast Dynamics of Metal Complexes of Tetrasulphonated Phthalocyanines

International audienceA promising material in medicine, electronics, optoelectronics, electrochemistry, catalysis, and photophysics, tetrasulphonated aluminum phthalocyanine (AlPcS4), is investigated by means of steady-state and time-resolved pump?probe spectroscopies. Absorption and steady-state fluorescence spectroscopy indicate that AlPcS4 is essentially monomeric. Spectrally resolved pump-probe data are recorded on time scales ranging from femtoseconds to nanoseconds. The nature of these fast processes and pathways of the competing relaxation processes from the initially excited electronic states in aqueous and organic (dimethyl sulfoxide) solutions are discussed. The decays and bleaching recovery have been fitted in the ultrafast window (0-10 ps) and later time window extending to nanoseconds (0-1 ns). While the excited-state dynamics have been found to be sensitive to the solvent environment, we were able to show that the fast dynamics is described by three time constants in the ranges of 115-500 fs, 2-25 ps, and 150-500 ps. We were able to ascribe these three time constants to different processes. The shortest time constants have been assigned to vibrational wavepacket dynamics. The few picosecond components have been assigned to vibrational relaxation in the excited electronic states. Finally, the 150-500 ps components represent the decay from S1 to the ground state. The experimental and theoretical treatment proposed in this paper provides a basis for a substantial revision of the commonly accepted interpretation of the Soret transition (B transition) that exists in the literature

Étude d'architectures lasers solides, multiaxes et multipassages, à volumes de gain distribués pompés longitudinalement par diodes lasers fibrées

Le fil conducteur des travaux réalisés, est la recherche d'architectures lasers solides particulières qui permettent de distribuer le pompage dans plusieurs zones du milieu amplificateur afin d'y répartir les charges thermiques responsables d'aberrations dégradant la qualité spatiale des faisceaux émis. La première architecture proposée est une cavité à Transformation de FOURRIER, multiaxe, pompée longitudinalement par N diodes lasers fibrées engendrant N faisceaux uniphases. Le premier chapitre est consacré au couplage en phase de ces N faisceaux par filtrage d'amplitude intracavité. Le filtre est constitué par une grille de fils opaques placé dans l'un des plans de la cavité. En association avec le filtrage volumique par le gain, cette grille assure la sélection d'un mode unique d'ordre élevé. Dans le deuxième chapitre, un élément d'optique diffractive (EOD) placé hors cavité réalise la combinaison cohérente des N faisceaux précédents en un faisceau unique de divergence minimale. Ce même faisceau est ensuite obtenu directement en sortie de cavité, avec un assez bon rendement de conversion opto/optique, en remplaçant le filtre d'amplitude par l'EOD. La seconde architecture que nous étudions au troisième chapitre est constituée par une cavité plan concave repliée comportant une cellule amplificatrice multipassage unique, traversée en plusieurs zones distinctes au cours d'un aller retour. Elle conduit aussi à un faisceau de bonne qualité optique, avec un bon rendement de conversion opto/optique. La quatrième partie de ce manuscrit constitue une prospective comparative des meilleures performances que l'on peut attendre des cavités multiaxe et multipassage optimisées.LIMOGES-BU Sciences (870852109) / SudocSudocFranceF

THz-near IR hyper-Raman surface spectroscopy of silicon wafer surface

We recorded the hyper-Raman spectra resulting from the interaction of picosecond visible and ultrashort THz pulses at the surface of (111) silicon wafer. It reveals the signature of the Si lattice phonon and SiO2 mode centered at ~610 cm -1 and ~1100 cm - 1 , respectively. This technique also evidences the growing of the SiO2 layer at the surface of the silicon wafer exposed to ambient ai

Second Harmonic and Hyper-Rayleigh Generation of (111) silicon wafer

Ultrafast time-resolved THz-induced SHG, also named hyper-Rayleigh generation, is performed at the surface of a (111) silicon wafer upon its excitation by a 50 fs IR optical pulse. The evolution of the SHG spectrum is recorded delaying in time the optical pulse with respect to the THz pulse. Upon excitation, we record a broad Stokes and anti-Stokes bands centered around the Si lattice phonon at ~610 cm -1 . The spectral evolution of the SHG signal versus the delay between optical and THz pulses makes it possible to evidence the interference between volume and surface contributions as well as the ultrafast evolution of the hyper-Rayleigh susceptibility upon hot carrier generatio

Coherent combination of four laser beams in a multi-axis Fourier cavity using a diffractive optical element

International audienceThermal aberrations in diode-pumped solid-state laser media are well known. To avoid these effects we propose to end-pump separated zones of a laser crystal with elementary beams of moderate power. We present a multi-axis laser cavity with a single-gain medium longitudinally pumped by four fibre-coupled laser diodes. The four elementary laser beams are coherently combined inside the cavity by a diffractive optical element. 82% of the laser power is focused in a single diffraction limited beam

Tuning and focusing THz pulses by shaping the pump laser beam profile in a nonlinear crystal

Spatially shaped femtosecond laser pulses are used to generate and to focus tunable terahertz (THz) pulses by Optical Rectification in a Zinc Telluride (ZnTe) crystal. It is shown analytically and experimentally that the focusing position and spectrum of the emitted THz pulse can be changed, in the intermediate field zone, by controlling the spatial shape of the near-infrared (NIR) femtosecond (fs) laser pump. In particular, if the pump consists of concentric circles, the emitted THz radiation is confined around the propagation axis, producing a THz pulse train, and focusing position and spectrum can be controlled by changing the number of circles and their diameter

Time resolved hyper-Raman surface spectroscopy of (111) silicon

We performed a time-resolved Hyper-Raman spectroscopy of a (111) silicon wafer upon its excitation by a near IR optical pulse. Upon excitation of the silicon wafer by the optical pulse, we record the broadening and increase of the Stokes and anti-Stokes bands centered around the Si lattice phonon and SiO2 mode centered at ~610 cm -1 and ~1100 cm -1 , respectively. This unique technic makes it possible to reveal the electron-phonon scattering which thermalize the hot carriers with the lattice on time scale of 100 to 300 f

Kinetics and wavelength dependence of thermal and gain lens induced in Nd:YAG rod amplifier

Using a wavefront sensor, we have measured the temporal evolution of the lens induced in a Nd:YAG rod amplifier under side pumping by laser diode bars centered around 808 nm in a quasi-continuous wave regime. The evolution of the induced lens is drastically different when measured with a probe pulse centered at 532 nm or 1064.5 nm. To explain this evolution, we developed a model that accounts for both the excited state population of the Nd3+ ions and the thermal contribution to the refractive index of the amplifier. This model, which takes into account amplification and wavelength shift of the probe pulse at 1064.5 nm, makes it possible to quantitatively describe the spectral and temporal evolution of the amplifier focal length. It also shows that the excited state population contribution is more important around 1064.5 nm and can partly compensate for the thermal lens induced in the amplifier

Impact of dispersion, free carriers, and two-photon absorption on the generation of intense terahertz pulses in ZnTe crystals

We study the evolution of the energy and the spectrum of a terahertz wave generated by optical rectification of an ultrashort laser pulse in ZnTe crystals with different thicknesses. As the pump intensity increases, we observe a shift in the terahertz spectrum toward lower frequencies. Moreover, at high pump intensities, in disagreement with common sense, thin crystals have a better conversion efficiency than thicker ones. These phenomena are accounted for by the pump depletion induced by two-photon absorption, pulse broadening and the impact of the photoinduced free carriers on the complex refractive index of the crystal in the terahertz range