Amplified Spontaneous Emission Characteristics of LD 473 and Coumarin 102 Laser Dyes (original) (raw)
Related papers
Influence of solvent and substituent on excited state characterstics of laser grade coumarin dyes
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2003
Absorption and fluorescence emission of 4 and 7 substituted coumarins viz. C 440, C 490, C 485 and C 311 have been studied in various polar and non-polar organic solvents. These coumarin dyes are substituted with alkyl, amine and fluorine groups at 4-and 7-positions. They give different absorption and emission spectra in different solvents. The study leads to a possible assignment of energy level scheme for such coumarins including the effect on ground state and excited state dipole moments due to substitutions. Excited state dipole moments of these dyes are calculated by solvetochromic data experimentally and theoretically these are calculated by PM 3 method. The dipole moments in excited state, for all molecules investigated here, are higher than the corresponding values in the ground state. The increase in dipole moment has been explained in terms of the nature of excited state and resonance structure. #
Influence of solvents and temperature on the excited state characteristics of coumarin laser dyes
Acta Physica Hungarica, 1991
The present work deals with the effect of solvents and temperature on the photophysical propertJes of 4-methyl-7-aminocoumarin (I), and 4-methyl-7-dimethylaminocoumaxin (II). Change of solvent gives rise to Stokes' shift but due to specific interactions, the excited state dipole moments cannot be calcu]ated. Experimental values of percentage po_ ]axization in different polar solvents indicate the formation of 1:1 solute-solvent exciplexes/intermolecular hydrogen bonding. Further, it is observe(] that the fluorescence intensity decreases with increase in temperature for the compound II, but remains constant for compound I. Tkis difference in behaviour is examined in terms of intramolecular charge transfer (ICT) and twisted intraraolecular charge transfer (TICT) states of the cournarin molecu]e.
Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, 2008
The effect of solvents on the absorption and emission spectra of ergone has been studied in various solvents at 298 K. The bathochromic shift was observed in absorption and fluorescence spectra with the increase of solvents polarity, which implied that transition involved was → *. And the normalized transition energy value E N T showed some scattering when plotted versus . The ground state and excited state dipole moments were calculated by quantum-mechanical second-order perturbation method as a function of the dielectric constant (ε) and refractive index (n). The result was found to be 1.435 D and 2.520 D in ground state and excited state respectively. And also, the density functional calculations were used to obtain the ground state and excited state dipole moments for it has proven to be suitable for calculating electronic excitation energy. And the result is consistent with the experimental.
Photophysics and dynamics of rigidized coumarin laser dyes
Journal of Photochemistry and Photobiology A: Chemistry, 1989
This paper describes some photophysical properties, the results of CNDO molecular orbital (MO) calculations and excited state complex formation for two solvatochromic coumarin laser dyes of the rigidized multichromophoric electron donor-acceptor type (coumarins 314 and 337). Light absorption results in the population of an almost fully fluorescent polar charge transfer singlet state characterized by non-alternate electron density distributions and a remarkable sensitivity to solvent properties. Useful nonlinear, linear and multiparameter relationships between the quantum yield of fluorescence, the emission and absorption maxima and the Stokes shift and some solvent parameters are established. Hydrogen-bonding solvents such as ethanol cause quenching and a bathochromic shift of fluorescence due to ground state complexation. Excited state equilibrium studies reveal the formation of weak (with equilibrium constant of 2 -19 1 mol-') hydrogenbonding complexes with a stoichiometry of 2: 1 (dye:ethanol). The fluorescence polarization behaviour in glycerol at various temperatures shows that the molecular rotational diffusion is controlled by the free volume of the medium. The results point to a possible use of these highly fluorescent dyes as bifunctional fluorescent probes for determining the rigidity and polarity of the surrounding medium of interest. lOlO-6030/89/$3.50 @ Elsevier Sequoia/Printed in*The Netherlands 260 interest to predict and control the properties of fluorescent dyes. In recent years many investigations have focused on the role of the solvent in controlling the intramolecular charge transfer (ICT) process for electron donoracceptor (EDA) dye molecules in solution [4, 6, 7, 15,21 -311, as well as in the gas phase using supersonic jet expansion techniques [32]. Certain dye families of the EDA type are good fluorescers (e.g. the oxazines, rhodamines and coumarins) [4, 331 and they have been used as laser dyes and solar energy concentrators.
Amplified Spontaneous Emission (ASE) Properties of a laser dye (LD-473) in solid state
Journal of the European Optical Society-Rapid Publications
The spectral characteristics of 1,2,3,8-tetrahydro-1,2,3,3,8-pentamethyl-5-(trifluoromethyl)-7H-pyrrolo[3,2-g]quinolin-7one (LD-473) were demonstrated in liquid and solid states. For the liquid state, the absorption and fluorescence spectra of the LD-473 in Methyl Methacrylate showed bands at 385 and 420 nm, respectively. LD-473 in the solid state showed one absorption band at 530 nm, while the fluorescence spectra, under low concentration, showed one band at 615 nm. For higher concentrations, the fluorescence bands are shifted to the red. LD-473 in the solid state under an impulse of Nd: YAG laser showed dual amplified spontaneous emission (ASE) peaks at 605 and 650 nm. The longer wavelength coincided with a fluorescence peak while the shorter wavelength is an abnormal peak.
2000
Out of thousands of organic dyes synthesized over the last hundred years only a few show laser action when excited by Q-switched laser or a pulsed nitrogen laser and still fewer under flash lamp excitation. Organic dyes that show laser action are selected by trial and error. For an efficient working of a laser material it is important to select dyes which have high quantum yield and low lasing threshold. Coumarins or -benzopyrones are known for their strong lasing effect. It is a class of laser dyes emitting in the blue green region of the spectrum and derived from coumarin-the parent molecule on substitution with auxochromic (OH, NH2, CH3, etc.) groups at various carbon positions. Depending on the location and direction of the singlet-singlet (S-S) relative to triplet-triplet (T-T) oscillators within the molecular frame, substitution by the hydroxy auxochromic group may cause T-T absorption bands to move in or out of fluorescence region, or they may be left unchanged. An attempt is made to study the spectroscopic characteristics of 4hydroxycoumarin molecule. Electronic absorption spectra of 4-hydroxycoumarin are measured in the wavelength region 200 700 nm in liquid solvents and solgel. Fluorescence spectrum is measured on exciting 4-hydroxycoumarin doped in solgel by varying the excitation wavelengths. Electronic transitions observed experimentally, are interpreted using the optimized geometries and CNDO/S-CI method. Assignments of observed electronic transitions are made on the basis of singlet-triplet electronic transitions. Further, effect of hydroxy substituent on the spectral properties of the parent aromatic molecule are investigated on the basis of molecular structure and spectral predictions for 4-hydroxycoumarin as a potential dye laser material are made. These predictions supported by theoretical results are presented graphically with possible arrangements of low energy S-S oscillators relative to T-T oscillators located in the fluorescence region. Depending on short or long axis substitution, the redshifts of the S-S and T-T absorption bands are observed and the importance of these red shifts, as related to the laser action properties are discussed. We found a good agreement between the experimental and calculated results. Further more, 4-hydroxy coumarin doped in solgel is found to be a potential dye laser material.
Journal of the Korean Chemical Society
The photophysical properties of 7-diethylaminocoumarin (DEAC) laser dye have been measured in different solvents. The emission spectrum of DEAC has also been measured in cationic (CTAC) and anionic (SDS) micelles. The laser parameters have been calculated in different solvents namely acetone, dioxane, ethanol and dimethylforamide(DMF). The photoreactivity of DEAC has been studied in solvent using 366 nm light. The values of photochemical yield () and rate constant (k) are determined. The interaction of organic acceptors such as picric acid (PA), tetracyanoethylene (TCNE) and 7,7,8,8-tetracynoquinonedimethane (TCNQ) with DEAC are also studied using fluorescence measurements in acetonitrile (). The electrochemical investigation of (DEAC) has been carried out using cyclic voltammetry and convolutive voltammetry combined with digital simulation technique at a platinum electrode in 0.1 mol tetrabutyl ammonium perchlorate (TBAP) in solvent. The electrochemical parameters of the investigat...
Effect of 1,4-diazabicyclo-[2,2,2]-octane on the laser properties of 7-amino coumarin dyes
Journal of Photochemistry and Photobiology A: Chemistry, 1991
1,4-Diazabicyclo-[2,2,2]-octane (Dabco), a tertiary amine, was found to quench the fluorescence of two 7-amino coumarin dyes Cl and (302. The quenching was monitored in solvents of varying polarity. In non-polar and polar aprotic solvents the quenching is very efficient and the rate constants for quenching are within diffusion-controlled limits, whereas in protic solvents the quenching efficiency is very low. An attempt has also been made to delineate the mechanism for the stabilization of a dye laser by Dabco, following the reactions of the triplets of Cl with Dabco and also by monitoring the photodegradation of Cl in the presence of Dabco.
Photophysical parameters and fluorescence quenching of 7-diethylaminocoumarin (DEAC) laser dye
Optics & Laser Technology, 2011
The optical properties including electronic absorption spectrum, emission spectrum, fluorescence quantum yield, and dipole moment of electronic transition of 7-diethylaminocoumarin (DEAC) laser dye have been measured in different solvents. Both electronic absorption and fluorescence spectra are red shifted as the polarity of the medium increases, indicating that the dipole moment of molecule increases on excitation. The fluorescence quantum yield of DEAC decreases as the polarity of solvent increases, a result of the role of solvent polarity in stabilization of the twisting of the intramolecular charge transfer (TICT) in excited state, which is a non-emissive state, as well as hydrogen bonding with the hetero-atom of dye. The emission spectrum of DEAC has also been measured in cationic (CTAC) and anionic (SDS) micelles, the intensity increases as the concentration of surfactant increases, and an abrupt change in emission intensity is observed at critical micelle concentration (CMC) of surfactant. 2 Â 10 À 3 mol dm À 3 of DEAC gives laser emission in the blue region on pumping with nitrogen laser (l ex ¼ 337.1 nm). The laser parameters such as tuning range, gain coefficient (a), emission cross section (s e ), and half-life energy have been calculated in different solvents, namely acetone, dioxane , ethanol, and dimethyforamide (DMF). The photoreactivity of DEAC has been studied in CCl 4 at a wavelength of 366 nm. The values of photochemical yield (f c ) and rate constant (k) are determined. The interaction of organic acceptors such as picric acid (PA), tetracyanoethylene (TCNE), and 7,7,8,8-tetracynoquinonedimethane (TCNQ) with DEAC is also studied using fluorescence measurements in acetonitrile (CH 3 CN); from fluorescence quenching study we assume the possible electron transfer from excited donor DEAC to organic acceptor forming non-emissive exciplex.