Properties of lasers based on vapors and solutions of complex organic compounds

We present the most important results of investigations of lasers based on vapors and solutions of complex organic compounds. We investigated the effect of a foreign gas, the duration and intensity of the exciting pulse, the temperature of the active medium, and the spectroscopic parameters of the material on the generation characteristics of complex molecules in the gas phase. The special features of generation of radiation by a laser with distributed feedback in transition from a condensed to the gas phase in heating the active medium are considered. It is suggested that the polarization characteristics of the radiation generated by a vapor laser be used to investigate the laws that govern the relaxation of optically induced anisotropy of excited molecules of the active medium. Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 5, pp. 709–720, September–October, 1998.     

Photoprocesses in complex organic compounds

We present the results of investigations of photoprocesses in organic compounds. We have done a theoretical and experimental study of the relationship of photophysical and photochemical processes in organic molecules to the characteristics features of intramolecular and intermolecular interactions and the exciting electromagnetic field. We have developed quantum chemical procedures for theoretical prediction of the structure of organic compounds with specified physicochemical and optical properties. We have designed new active media for lasers with enhanced photostability and increased lifetime. Translated from Izvestiya Vysshkh Uchebnykh Zavedenii, Fizika, No. 8, pp. 76–86, August, 1998.     

Laser prepared organic heterostructures based on star-shaped arylenevinylene compounds

This paper presents some studies about the preparation by matrix-assisted pulsed laser evaporation (MAPLE) technique of organic bulk heterojunctions made from the mixture of a star-shaped arylenevinylene compound, 4,4′,4″-tris[(4′-diphenylamino)styryl] triphenylamine as donor and fullerene derivative, [6, 6]-phenyl C61 butyric acid butyl ester, as acceptor, in the weight ratio 1:2. The mixed layer has been characterized by spectroscopic (UV–Vis, Fourier transform infrared) and microscopic (AFM) methods, and the effects of the deposition conditions (number of pulses) and of a buffer layer of poly(aniline-co-aniline propane sulfonic acid) or poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) have been analyzed. The study of the electrical properties has revealed a typical solar cell behavior for the heterostructure glass/ITO/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/4,4′,4″-tris[(4′-diphenylamino)styryl] triphenylamine: [6, 6]-phenyl C61 butyric acid butyl ester/Al, confirming that MAPLE could be an adequate method for the preparation of active layer based on bulk heterojunction for solar cells.     

Energy yield of fluorescence of complex organic compounds upon electron excitation

With use of electron energy loss spectra for vapors of anthracene, perylene, 1,4[di(2,5-phenyloxazolyl)] benzene, and paratherphenyl the energy yields of fluorescence are calculated for electron collision. It is shown that they are considerably smaller than those for optical excitation conditions. Deceased Institute of Molecular and Atomic Physics of the National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 1, pp. 146–148, January–February, 1998.     

Nonlinear susceptibilities of vapors and solutions of organic dyes

Results of theoretical studies of laser and Kerr nonlinear susceptibilities of vapors and solutions of organic dyes using a series of polycyclic arenes as an example are presented. Nonlinear susceptibilities of the third χ⁽³⁾ (?3ω; ω, ω, ω) and the fifth χ⁽⁵⁾ (?3ω; ω, ω, ω, ω, ?ω) orders of a series of organic dyes responsible for third harmonic generation of Nd:YAG laser radiation are calculated within the context of the free electron model. Results of calculations of their Kerr third-order nonlinear susceptibilities χ⁽³⁾ (?ω; ω, ?ω, ω) and non-linear refractive indices n ₂ are presented. The calculation results are compared with experimental data on third harmonic generation in naphthalene vapors and with χ⁽³⁾ (?ω; ω, ?ω, ω) as well as n ₂ of paraterphenyl and naphthalene solutions.     

Quantum efficiency and thermal stability of organic dye vapors

Organic dyes, POPOP, perylene and pyren, in the vapor phase are excited by a N₂ laser. The quantum efficiency is measures as a function of temperature up to 450°C. Optical properties such as the radiative transition probability are also estimated from the experimental results. It is found that the decrease in the vapor density by the thermal dissociation can be neglected during several tens of hours.     

Lasers based on electrodynamically dispersed media

We demonstrate the possibility of creating a suspension of active-media particles in a discharge tube by using an electrodynamic dispersing system. An electric discharge in an electrodynamically dispersed system of 30-μm Cu particles was studied. The velocity of Cu (30 μm), Al (30 μm), and W (6-μm flakes) particles was measured at atmospheric pressure using a laser Doppler velocimeter. The velocities were found to be in the 0.1−5-m/s range. The electric field strength required to levitate Cu, Al, and W particles was studied as a function of buffer gas (air) pressure in the range from 2 × 10⁻² Torr to 1 atm. It is shown that powders can be suspended with the help of electrodynamic dispersing system at air pressure below 0.1 Torr or above 100 Torr.