Eli Yariv

Efficiency and photostability of dye-doped solid-state lasers in different hosts

Abstract We survey the preparation procedures of pyrromethene (PM) and rhodamine dyes in silica, silica–zirconia, organically modified silicate (ormosil) and organic polymer matrices. Absorption and luminescence spectra, as well as decay time fluorescence of pyrromethene dyes are given. The solid-state laser samples were tested and their efficiencies and photostabilities at transversal pumping configuration, are given. Pyrromethene 597 had the best laser dye performance with slope efficiency of 43.3% when doped in ormosil glass and high photostability when doped in poly(methyl methacrylate) (PMMA) . Analysis and explanations for the results are given.

Laser properties of pyrromethene dyes in sol-gel glasses

Abstract Solid-state dye lasers were made by incorporating pyrromethene dyes in organically modified silicate (ormosil) and composite glass matrices. Three different types of pyrromethene (PM) were used: PM 567, PM 580 and PM 597. The ormosil glass samples were prepared by a one-step process at room temperature sol–gel technology which led to the formation of hybrid organic/inorganic materials. The composite glass samples are made by a biphase process: (a) preparation of porous silica gel, (b) impregnation of the dye dissolved in methylmethacrylate (MMA) into the silica gel. A number of various glass compositions were tested and their efficiencies and half output energy lifetimes were measured. The optimal slope efficiency for the lasers pumped transversally, by frequency doubled Nd-Yag laser, approaches 42%. Fluorescence lifetimes, excitation and emission spectra were also measured. In addition, significant dependency of these dyes on pH was found. These dyes lose their lasing ability in acidic (pH

New developments in solid state lasers

Abstract Solid state dye lasers emitting in the range 540–615 nm were prepared by incorporating perylimide and pyrromethene dyes into glasses prepared by a biphase process and by a one step process. A number of various glass compositions were tested and their efficiencies were measured. The optimal efficiency for the lasers pumped transversally approaches 30%.

Photostability of luminescent dyes in solid-state dye lasers

Abstract Fluorescence photobleaching was measured in dye-impregnated sol–gel/polymer composite glasses. These fluorescent glasses were used as the gain medium in a transverse-pumped solid-state dye laser. In this configuration, the fluorescent glass was excited by a pulsed Nd:YAG laser (about 6 mJ/pulse) either while placed in an optical cavity (i.e., functioning as a pulsed laser) or with the optical cavity blocked, so that lasing did not occur. The decay of the fluorescence signal versus cumulative excitation energy was recorded. We found that the rate of photobleaching decreased when the glass was lasing, as compared to the case where the optical cavity was blocked. This paper presents these results, and suggests a simple kinetic model that may explain this phenomenon.

Optimization of tunable laser glasses with the aid of dielectric relaxation and adsorption measurements

Abstract The recently developed tunable dye lasers in the visible are obtained by incorporation of stable laser dyes into glasses prepared by the sol–gel method. In order that the lasers be photostable and more efficient it is essential that the dye molecules penetrate into the glass matrices in a unimolecular form and be protected from the surroundings. In this respect, the size of the pores and their distribution in the glass are of major importance. In this paper the influence of the various catalysts on the porosity of the glasses is presented. The pore sizes, their surface area, pore volume, pore size distribution and glass effective density are presented, and the solid state tunable lasers prepared under the optimal conditions are demonstrated. The results obtained by the conventional adsorption methods (water, nitrogen adsorption) and mercury porosimetry are compared with dielectric measurements and the conclusion is that the latter provide information about charge movement in glasses with the smallest pores. The water vapor from the atmosphere is adsorbed within the smallest pores in a monolayer resulting in the formation of dipoles, that can be detected by dielectric measurements.

Solid state dye lasers: Rhodamines in silica–zirconia materials

Silica-zirconia materials as well as silica-zirconia ormosils prepared by the sol-gel technique were doped with the laser dyes Rhodamine B and Rhodamine 6G and used as solid state dye lasers. The photostability and efficiency of the solid state laser samples were measured in a transverse pumping configuration by either a nitrogen laser or the second harmonic of a Nd-YAG laser. Under the excitation of a nitrogen laser the photostability of Rhodamine B in silica-zirconia materials was low and decreased with a growing amount of zirconia. The photophysical properties of the incorporated dyes were studied by time-resolved fluorescence spectroscopy. The fluorescence lifetimes of both dyes increased when the matrix was modified by organic compounds Furthermore, the threshold energy of Rhodamine 6G in two ormosils containing 3 and 50% methylsilica was measured. The results revealed that the threshold energy was lower for the matrix with a higher amount of ormosil while the slope efficiency was higher in the matrix containing 30% ormosil.

Solid lasers tunable in the visible range

A new type of solid state lasers tunable in the visible rang has been developed recently. Incorporation of perylimide and pyrromethene dyes into glasses prepared by the sol gel method allows to design new types of visible, stable solid lasers. These can be prepared either in the form of slabs or rods or as waveguiding active media deposited on glass or polymer supports. The bulk lasers are prepared by two methods: (1) By one phase procedure by preparation of dye- ORMOSIL samples including the photostable laser dyes. (2) By incorporation of the laser photostable dyes into pre- prepared porous glasses by the sol gel method followed by polymerization in situ in the glass. We summarize her the laser properties obtained by different methods and when possible compare the performance of the solid laser with the solutions of corresponding laser dyes.

Optical nonlinearities of methyl red in various solid matrices

An azo dye, methyl red (MR), was introduced into glass films and bulks and into polymer films. The glasses were either pure silicate or composed of a silicate network with the addition of long chain organic molecules. Some glasses were composites of silicate and methyl methacrylate (MMA) or poly(vinyl acetate) (PVAc). The polymer films, which consisted of PVAc or poly(vinyl alcohol) (PVA), were deposited on glass plates. The induced transparency of the samples was measured by a pump and probe method, using the 488 nm line of an argon- ion laser for both the pump and probe beams. The nonlinear effect was observed with the neutral and basic forms of MR (orange and yellow, respectively). The magnitude of the effect decreased with increasing density of the host as follows: polymer matrices, composite glass, sol-gel glass. These results, as well as measurements of the excited state spectra, are consistent with the hypothesis that the observed nonlinearities are the result of a trans-cis isomerization of MR, for optical excitation in the milliwatt range.