Quick and Easy Measurements of the Inherent Optical Property of Water by Laser

To compare properties of different waters we measured the reflectance of the second harmonic of Nd: YAG laser light through different water samples in the laboratory. To generate realistic images of natural waters one must consider in some details the interaction of light with the water body. The diagrams have been utilized to represent effective parameters in the water's reflectivity such as: the angle of incidence or the bottom conditions, height of the laser from water surface, wavelength of the laser light, radiant intensities, depth of water and also the impurities of water. The reflectance of the bottom from a mirror at the bottom of an aquarium with different depths of water will depend on the bottom slope relative to the direction of incidence of the laser light and the coating to prevent damaging the mirror against the laser light so it is necessary to change the mirror after several experiments.El presente trabajo muestra las mediciones hechas en diferentes líquidos para comparar sus propiedades, tomando como referencia la reflectancia de la segunda armónica de un laser Nd. YAG, esto a través de diferentes muestras de líquidos en el laboratorio. Para poder generar imágenes realistas se debe de considerar algunos detalles de interacción de la luz con el cuerpo líquido. Los diagramas fueron utilizados para representar parámetros efectivos de la reflexión del liquido como puede ser el ángulo de incidencia y las condiciones de fondo, la altura del laser respecto a la superficie del liquido, la longitud de onda de la luz laser, la intensidades de radiación la profundidad del líquido y las impurezas que pudieran existir. La reflexión de la profundidad utilizando un espejo a diferentes profundidades depende de la inclinación relativa a la dirección de incidencia del laser y de la protección del espejo para que no se dañe, por lo que es necesario cambiar el espejo después de varios experimentos

Effect of gold nanoparticles on the optical properties of Rhodamine 6G

Gold nanoparticles are synthesized by the laser ablation method and characterized by transmission electron microscopy and UV-visible absorption spectroscopy. The absorption and emission spectra and powers of Rhodamine 6G in the absence and presence of 27 nm diameter gold nanoparticles were studied. Empirical measurements represented that presence of gold nanoparticles lead to decrease the fluorescence power and fluorescence quantum yield, and increase the absorbance and absorbed power of Rhodamine 6G. Also, Stern-Volmer quenching constant of dye in proximity of nanoparticles shows high value which implies efficient quenching of the dye fluorescence by gold nanoparticles. Fluorescence quantum yield, radiative and nonradiative decay rate of Rhodamine 6G-gold nanoparticles assembly, in parallel orientation, as a function of dye’s dipole moment distance from gold nanoparticle’s surface, based on Gersten-Nitzan model, are calculated. Calculations show variations of the fluorescence quenching is strongly depended on the distance between the dye molecules and the Nps’ surface. Also, calculated radiative decay rate indicates good agreement with the experimental value, and results of the ratio of the nonradiative to the radiative decay rate of Rhodamine 6G-gold nanoparticles mixture show nonradiative energy transfer is better explained in terms of NSET rather than FRET mechanism