Investigations were made of the spectral, fluorescence, and lasing characteristics of 2-iminocoumarin derivatives. It was established that proton donor solvents have the strongest influence on these characteristics. The structure factor also has a substantial effect. In specific interactions of the molecule the attachment of the diethylamino group in position 7 results in changes in the nonradiative deactivation of its electronic excitation. The characteristics of the solvate effects of iminocoumarins identified can not only increase the spectral tuning range of an active medium utilizing these coumarins, but can also enhance appreciably the efficiency of flashlamp-pumped lasers.

Influence of solvent on spectral and stimulated emission characteristics of iminocoumarin laser dyes

We synthesized a series of sol–gel silica matrices doped with laser dyes DCM, LK678, LD1, and LD2 which alcohol solutions have efficient lasing in the red spectral region and Rh800–in the near infrared (NIR) one. Absorption, fluorescence, and laser properties of the dyes in silica samples prepared by sol–gel process were investigated. It has found some peculiarities in preparation process of the laser matrices and in spectral characteristics of the dyes in these matrices.

Spectral and Lasing Characteristics of Some Red and Nir Laser Dyes in Silica Matrices

Spectral, luminescent, and lasing characteristics of chromene dyes and their julolidine analogs emitting in the red spectral range are investigated experimentally and theoretically. It is shown that the cause for a low lasing efficiency of oxochromene compared with iminochromene is a high intersystem crossing to the T
 1 state and the presence of the induced T
 1→T
 n
 absorption in the region of the luminescence band.

Stimulated Emission of Active Media in the Red Spectral Range

The spectroscopic and laser characteristics of two benzopyrane derivatives for 600–670 nm spectrum region of lasing in preliminarily annealed silica xerogel matrices in non-selective cavity under laser pumping at 551 nm have been measured and analysed. The influence of molecular structure of the dyes on their non-radiating losses has been revealed. The specific output laser energy of the studied matrices was approximately equal to the ones for corresponding methanol solutions under the same pumping conditions. The laser spectra of the matrices were displaced to the red region from the fluorescence maximum by about 1000–1500 cm−1 in a nonselective cavity. Such spectral displacement may improve the characteristics of biosensors made on the basis of these matrices because it shifts their emission spectrum to the range of deeper penetration into biological tissues.

Characteristics of BENZOPYRAN Laser Dyes in Annealed Silica XEROGEL

An experimental investigation was made of the spatioangular and spectral?energy characteristics of high-power tunable repetitively pulsed flashlamp-pumped dye lasers. A high directionality of the output radiation was attained in a wide range of the concentrations of the active molecules when aqueous solutions of dyes, in particular an inclusion complex of coumarin-120 and ?-cyclodextrin, were used. Such high directionality was obtained for alcohol and water?alcohol solutions only when the concentrations of these molecules were low. Continuous variation of the tuning range of lasers of this class should be possible by the use of suitable mixtures of efficient donor and acceptor dyes.

Tunable repetitively pulsed flashlamp-pumped dye lasers

An investigation was made of the spectral, fluorescence, and lasing characteristics of two compounds of benzopyran derivatives with a condensed benzimidazole ring that emit in the 610–660 nm range under flashlamp excitation. The efficiency and photostability of the synthesized derivatives were several times better than those of the known xanthene dyes rhodamine C and rhodamine 101. Quantum chemical calculations using the π electron approximation were used to estimate the localization of the electronic excitations in molecular fragments.

A. I. Novikov

Papers

New efficient dyes for the red part of the lasing spectrum