Lev N. Kaporskii

Absorption spectra and optical limiting of the fullerene–polyimide system

Abstract Absorption spectra of the fullerene–polyimide system with various concentrations of fullerene have been investigated. Reverse saturable absorption in this system at different energies of the incident laser beam has been also found.

Holographic recording in thin C70-doped polymer organic films

Abstract The dynamic and static thin holographic gratings have been recorded in C 70 -doped photosensitive polyimide 6B and 2-cyclooctylamino-5-nitropyridine. The drastic change in diffraction efficiency has been observed under the Raman–Nath diffraction condition using the second harmonic of pulse Nd laser. The threshold of the transition from phase grating to amplitude one has been determined. The results obtained have been explained by the absorption spectral peculiarities of the fullerene-doped films and by their thermal properties.

Optical limiting in organic polyimide systems doped with fullerenes and dyes

Optical limiting effect has been investigated in polyimide- fullerene and polyimide-dye-fullerene systems. The second harmonic of a pulsed Nd:YAG laser was applied as an irradiation source. The laser radiation was attenuated at least by an order of magnitude. When fullerenes and dye were simultaneously introduced in polyimide, the most optical limiting effect was observed. It was established the fullerene-doped polyimide systems could be applied for limiting power to more than 4 J cm-2.

Reverse saturable absorption effect in the 2-cyclo-octylamino 5-nitropyridine-fullerene-doped system

Reverse saturable absorption by C60 and C70 fullerenes-doped 2-cyclooctylamino-5-nitropyridine (COANP)- toluene solutions and COANP-polyimide films has been investigated. The fullerene concentration was varied from 0.5 to 5 wt percent. The second harmonic of a pulsed Nd:YAG laser of 532 nm wavelength, overlapping an absorption band of fullerene-doped COANP, was used. For both COANP-fullerene solution and thin films nonlinear transmission was observed. Laser radiation attenuation exceeded at least by a factor of 6-7. The nature of optical limiting effect revealed in COANP-C70 system is discussed. It was established that the COANP-fullerene compounds could be applied for limiting power of about 5-6 J cm-2.

The Effect of Optical Attenuation of Laser Radiation in a Fullerene-Containing COANP-Polyimide System

The optical attenuation of laser radiation was studied in a 2-cyclooctylamino-5-nitropyridine-polyimide (COANP-PI) system with C70 fullerene additives, which is a promising nonlinear optical medium. The experiments were performed using the second-harmonic radiation of a pulsed neodymium laser. Data on the optical attenuation effect observed in the samples with different fullerene content are presented and analyzed proceeding from a qualitative model based on the possible complex formation in the system studied.

Fullerene-doped polymer-dispersed liquid crystals as effective materials for laser modulation and hologram recording

Polymer dispersed liquid crystals are successfully used in display technique because they are of high film-forming capability and photoconductivity inherent in a polymer matrix and of electro-optical and aligning effect in a liquid crystal mesophase. The laser modulation and the holographic recording in the polymer dispersed liquid crystal composites based on some (pi) -conjugate organic compounds doped with fullerenes C60 and C70 have been investigated with a use of cw He-Ne and picosecond pulsed Nd lasers. Both the 80% modulation of laser beams at repetition frequency of 0.2 - 3 Hz and 20% one at 35 Hz have been obtained. The laser induced refractive index in the picosecond range was 0.75 X 10-3 at laser power density of 33 mJ(DOT)cm-2, that was larger than the one for polymer dispersed liquid crystal doped by dyes.

Spectral and nonlinear optical properties of fullerene-doped π-conjugated organic systems

The fullerene-doping effect on spectral and nonlinear optical properties of (pi) -conjugated organic systems based on 2-cyclooctylamino-5-nitropyridine, 2-(n-prolinol)-5- nitropyridine, N-(4-nitrophenyl)-(L)-prolinol, and polyimide 6B has been investigated. Under nanosecond laser irradiation at the wave length of 532 nm, reverse saturable absorption has been examined. To clarify peculiarities of optical laser power limiting, the reverse saturable absorption, the Foerster mechanism, two-photon and free-carrier absorption, as well as the complex formation must be taken into consideration. The compounds investigated have been found to be efficient absorbers and they could be applied to limit the laser irradiation at the energy density of more than 4-5 J/cm-2.

Record of dynamic and static holograms in thin fullerene-doped organic films

Under the Raman-Nath diffraction conditions the thin holographic gratings have been recorded in a promising class of (pi) -conjugate organic materials based on polyimide and 2- cyclooctylamino-5-nitropyridine. The drastic change of refractive index has been observed in the systems doped with fullerene C70. The results have been explained both by laser-induced conformational transformations of organic materials and by their spectral and thermal properties.

Fullerene-doped polyimide systems as effective optical power limiting materials in visible and IR ranges

The optical limiting of the laser radiation over visible and IR ranges in organic material based on polyimide has been studied. The role of the donor-acceptor interaction mechanism in manifestation of organic molecules nonlinear-optical properties has been established. The fullerene-doped photosensitive polyimide structures have been determined to be effective optical limiting materials for attenuating a power density of more than 2 - 4 J(DOT)cm-2.

The optical attenuation of laser radiation in thin fullerene C70-polyimide films. Effect of fullerenes on the transmission of azide films

The phenomenon of optical attenuation of laser radiation in the visible spectral range was studied in a promising photosensitive medium based on fullerene C70-polyimide films. The effect of fullerenes on the transmission of laser radiation in azide-based systems is demonstrated.