Rhodamine 6G Dye Solution Research Articles

Theory of surface plasmon-polariton amplification in planar structures incorporating dipolar gain media

We investigate theoretically surface plasmon-polariton (SPP) amplification in planar metallic structures taking into account the nonuniformity of the gain medium close to the metal surface due to position-dependent dipole lifetime and pump irradiance. We propose a model that accounts for these nonuniformities and apply it to a physically realizable structure consisting of a thin silver film cladded on one side by a lossless dielectric and on the other by an optically pumped Rhodamine 6G dye solution. We study amplification of the supported long-range SPP mode and show that net amplification is possible at visible wavelengths using reasonable pump power and molecular concentration. It is shown that the gain nonuniformity close to the metal surface must be considered to describe adequately the SPP amplification phenomenon.

High-performance titanium dioxide photocatalyst on ordered mesoporous carbon support

Anatase TiO 2 photocatalysts supported with the ordered mesoporous carbon, CMK-3, were synthesized by the incorporation of TiO 2 into CMK-3 followed by heating at 700 °C. The structural properties of the TiO 2 on CMK-3 were investigated by X-ray diffraction, nitrogen physisorption and electron microscopy techniques. In particular, TiO 2 was observed both inside and the external surface of CMK-3. The photocatalytic activity of TiO 2 on CMK-3 under UV-light exhibited higher efficiency in removing the Rhodamine 6G dye solution than the commercial photocatalyst P25 and TiO 2 on activated carbon. It was attributed to the synergistic effect of large surface area adsorption provided by mesoporous CMK-3 and the distinctive location of TiO 2 on the external surface of CMK-3.

Emission of Au nanoparticles with and without rhodamine 6G dye

We have observed Stokes and anti-Stokes emission of Au nanoparticles suspended in methanol and rhodamine 6G dye solution. Photoluminescence of Au nanoparticles is a three-step process involving single-photon or three-photon excitation of electron-hole pairs, relaxation of excited electrons and holes, and emission from electron-hole recombination, possibly enhanced by surface plasmons. In the presence of dye, the excitation of anti-Stokes emission of gold involves two-photon absorption in rhodamine 6G molecules followed by the energy transfer to Au nanoparticles with simultaneous absorption of one pumping photon by Au. This mechanism significantly enhances anti-Stokes emission of gold nanoparticles in the presence of dye.

Microfiber knot dye laser based on the evanescent-wave-coupled gain

The authors demonstrate a composite microring laser formed by immersing a silica microfiber knot in a rhodamine 6G dye solution. When the dye molecules are evanescently pumped by 532nm wavelength laser pulses guided along a 350μm diameter knot, lasing oscillation occurs inside the evanescently coupled closed-ring microcavity with a linewidth of about 0.06nm. Laser emission around 570 and 580nm wavelengths, which is evanescently coupled back into the microfiber, is observed with a threshold of about 9.2μJ∕pulse. The use of the microfiber knot cavity suggests a convenient and efficient approach to both pumping and collection of the evanescent-wave-coupled dye laser.

Comparative laser performances of pyrromethene 567 and rhodamine 6G dyes in copper vapour laser pumped dye lasers

Narrowband laser performances and photochemical stability of alcoholic solutions of pyrromethene 567 and rhodamine 6G dyes, under high-repetition rate copper vapour laser (at 510 nm), as well as, high-peak intensity Nd:YAG laser (at 532 nm) excitation have been investigated. We have observed that pyrromethene 567 dye solutions offer higher efficiency, wider tuning range, but lower photochemical stability and higher lasing threshold than that of rhodamine 6G dye solutions. An addition of about 100 mM DABCO, as a singlet oxygen quencher, in pyrromethene 567 dye solutions improved its photochemical stability close to that of rhodamine 6G. The observation of higher slope efficiency, in spite of higher threshold pump energy for pyrromethene 567 dye than that of rhodamine 6G dye solutions, was explained by a predictive model on gain characteristics of both dye solutions as a function of pump energy.

A binary solvent of water and propanol for use in high-average power dye lasers

Water is an inherently safe solvent for laser dyes and posses far better photo thermal characteristics in comparison to the commonly used organic solvents in dye lasers. However, water solution of dye needs a suitable deaggregating additive to suppress non-radiative dimers and to achieve similar laser efficiency. We have carried out systematic studies on comparative performances of dye lasers, pumped by low-repetition-rate Nd-YAG, as well as high-repetition-rate copper vapour lasers using Rhodamine 6G dye solutions in ethanol and various binary solvents of water. Among different additives in water, for the first time, the results of our studies on the application of water solvent in dye lasers could clearly establish that binary solvent comprising of normal or heavy water and about 18% to 25% n-propanol has produced similar efficiency, better photochemical stability and superior thermo-optic properties than ethanol solvent in high-repetition rate oscillator-amplifier operation.

Sensitized nonlinear emission of gold nanoparticles

We have studied Stokes and anti-Stokes emission of Au nanoparticles suspended in pure methanol and methanol solution of rhodamine 6G dye. In the presence of dye, excitation of anti-Stokes emission of gold involves two-photon absorption in rhodamine 6G molecules followed by the energy transfer to Au nanoparticles with simultaneous absorption of one pumping photon by Au. The sensitization by dye molecules caused six-fold enhancement of the anti-Stokes emission of gold nanoparticles.

Comparative analysis of multi-wave mixing and measurements of the higher-order nonlinearities in resonant media

The features of degenerate multi-wave mixing in resonant media (dye solutions) have been studied theoretically and experimentally. It has been demonstrated that thermal nonlinearity due to the induced absorption from the excited level contributes significantly to the efficiency of four-wave mixing, but results in lower efficiency of higher-order interactions. The measurement results obtained for the energy efficiency of four-, six- and eight-wave mixing enable calculations of the third-, fifth- and seventh-order nonlinear optical susceptibilities, respectively. Experimentally, the method proposed for measurements of the higher-order nonlinearities has been realized with the use of the multi-wave mixing at second harmonic λ=532nm of monopulse YAG:Nd3+ laser radiation in a Rhodamine 6G dye solution. The ratios ∣χ(5)∣/∣χ(3)∣ and ∣χ(7)∣/∣χ(5)∣ are determined to be of the order of 10−5cm3/erg.

Fabrication of dye-infiltrated macroporous silica for laser amplification

We have fabricated a dielectrically disordered medium based on monolithic silica (SiO2) with interconnected macropores by a sol–gel method. Macroporous SiO2 is obtained in a system containing tetramethoxysilane, poly(ethylene glycol), acetic acid, and water. The macroporous structure is formed when the transient structure of phase separation developed during the hydrolysis and polycondensation of alkoxysilane is frozen by the sol–gel transition. An active disordered medium is prepared by infiltrating a methanol solution of rhodamine 6G (R6G) dye into the macropores of the monolithic SiO2. When R6G dye molecules filled in the interconnected macropores are pumped by a frequency-doubled Nd:YAG laser, a drastic narrowing of dye emission accompanied by an increase in the peak intensity is observed. The large optical gain is ascribed to the increase in residence time of emitted photons in the active region due to multiple scattering.

A distributed feedback dye laser based on higher order Bragg scattering

A distributed feedback dye laser based on second order Bragg scattering due to a sinusoidal susceptibility modulation is reported. Rhodamine 6G dye solution in three different solvents; methanol, ethanol and benzyl alcohol is pumped by interference fringes produced by two beams from the second harmonic of Nd:YAG laser. Output power is plotted as a function of the pump power. The spectrum of dye laser shows a new type of modulation.

Suppression of stimulated Raman scattering from microdroplets by seeding with nanometer-sized latex particles

Stimulated Raman scattering (SRS) in laser-irradiated microdroplets is suppressed by the addition of nanometersized latex particles. The microdroplets consist of either pure ethanol or a solution of Rhodamine 6G dye in ethanol, seeded with latex particles having diameters of 50 < d < 500 nm. SRS emission occurs at droplet morphology-dependent resonances (MDR's) after either direct pumping by the incident 532-nm laser or indirectly whereby the pump laser first initiates dye lasing, which in turn pumps SRS. For large latex, we observe SRS suppression at a near-coincident threshold concentration independent of the presence of dye, whereas, for small latex, adding dye reduces the threshold concentration by more than an order of magnitude. These findings are consistent with the interpretation that for large latex ~1 particle must occupy the MDR mode volume at threshold, whereas for small latex the addition of particles facilitates Förster-assisted annihilation of both 532-nm and dye-lasing MDR pump photons.

Theoretical and experimental study on the profile of pump—probe time-resolved intensity correlation spectroscopy with incoherent light beams

An expression for the time profile of pump—probe two-photon intensity correlation spectroscopy with incoherent light beams is derived by using the perturbative density matrix method. Profiles of pump—probe time-resolved stimulated emission from a rhodamine 6G dye solution excited by incoherent light beams are measured. Origins of rising as well as decaying components of the profile are discussed by using the derived expression. Effects of the intensity correlation time on the time profile of vibronic states coherently excited by incoherent light beams are theoretically investigated.

Rayonnement panoramique d'un train d'impulsions brèves par un laser à Rhodamine 6G dont le résonateur est fermé en géométrie cylindrique

A "halo" type laser system is presented whose radiation is characterized by a propagation planar beam rather than a unidirectional beam. A doubled Nd:glass laser mode-locked picosecond pulse train is used to pump a Rhodamine 6G dye solution filling a cylindrical closed resonator. The laser short pulse train propagates in a plane across 360°, with mrad divergence transversely to the propagation plane.

Deterioration of rhodamine 6G dye solution in methanol

The mechanism of the deterioration process of a Rhodamine 6G dye solution in methanol is studied. It is found that oxygen plays an important role in the fading of the Rhodamine 6G solution and during this fading oxygen is spent in the photochemical reaction of methanol. The fading of a Rhodamine 6G solution without oxygen becomes 70 ± 20 times as rapid as that of a Rhodamine 6G solution with a sufficient amount of oxygen.

On anti-stokes luminescence from Rhodamine 6G in ethanol solutions

Anti-Stokes luminescence form Rhodamine 6G ethanol solutions excited by a He-Ne laser is observed to be strongly temperature dependent. A theoretical model is proposed for the absorption line shape on the long wavelength side of the pure electronic transition which fits the absorption and luminescence data. Vavilov's law is found to hold even when the absorption coefficient is 10 -6 times the peak absorption coefficient for the Rhodamine 6G dye solution. Another luminescence peak at 6650 Å is observed which is attributed to impurity fluorescence. It could not be related to photochemical products.