P. S. Shirshnev

Nonlinear optical effects in glasses containing copper chloride nanocrystals

Nonlinear optical properties of various glasses containing copper chloride nanocrystals have been studied at wavelengths of 532 and 1064 nm. It is established that the nonlinear optical response is manifested by the optical limiting of transmitted radiation and consists of two, low- and high-threshold parts. The low-threshold response is related to a self-defocusing of the radiation, while the high-threshold response is related to the phenomena of two-photon absorption, color center photogeneration, and thermal lens formation.

Precipitation of Nanosized Crystals CuBr and CuCl in Potassium Aluminoborate Glasses

The precipitation of nanosized crystals CuBr and CuCl in potassium aluminoborate glasses containing additives of jointly introduced Cu and Br, as well as Cu and Cl, respectively, has been studied by the methods of small-angle X-ray scattering (SAXS) and X-ray powder diffraction (XRPD) analysis. It has been found that, upon thermal treatments at temperatures close to the glass transition temperature Tg, halide phases precipitate in the form of liquid drops containing CuBr and KBr or CuCl and KCl. The presence of nanocrystals CuBr or CuCl, respectively, has been established in the samples at room temperature by the XRPD method. Liquidus, solidus, and crystallization onset temperatures in the regions of precipitated halide phases in heat treated glass samples have been determined from the temperature dependences of SAXS intensity. The liquid released upon the heat treatment inside a matrix of potassium aluminoborate glass remains in the state of a supercooled liquid at temperatures essentially below the solidus temperature. At the drop sizes of the order of 10 nm, crystallization processes in them start at temperatures of 40–85°C.

Luminescent glass fiber sensors for ultraviolet radiation detection by the spectral conversion

Abstract. It is shown that glass fibers doped with luminescent molecular clusters of silver, cadmium and lead chalcogenides, or copper (I) can be used for the efficient radiation conversion of ultraviolet (UV) radiation to the visible spectral region. The advantages of radiation trapping in fibers by the luminescent centers and of spectral conversion are discussed. The excitation and luminescence spectra of luminescent fibers are presented. Analysis of application areas of the luminescent glasses and fibers is performed. The construction of the sensitive element for sensor models for electrical spark and UV radiation detection is described. The characteristics of the models of sensors for electrical spark and UV radiation detection are presented.

The effect of temperature on the exciton absorption of copper chloride and copper bromide nanocrystals in potassium-aluminum-borate glass

The absorption spectra of nanosized crystals of copper (I) halides distributed in the potassium-aluminum borate glass system were investigated in the region of the exciton absorption band in the temperature range from 20 to 300°C. The temperature dependences of the exciton absorption band of CuHal (Hal = Cl, Br) nanocrystals, which were obtained upon the heating and cooling of the sample, have a form of hysteresis. The melting (140–240°C) and crystallization (35–105°C) temperatures of copper (I) halide nanocrystals contained in the potassium-aluminum borate glass were determined by the optical spectroscopy method.

Luminescence properties of potassium aluminoborate glasses with copper(I) ions at cryogenic temperatures

Luminescence spectra of potassium aluminoborate glasses with copper(I) ions have been recorded in the temperature range from +20 to −196°C. It is shown that a decrease in the glass temperature gives rise to thermochromic luminescence, which manifests itself as a red shift of the luminescence band, a value of which reaches 95 nm. This spectral shift is accompanied by a decrease in the luminescence-band amplitude by 30%.

The effect of temperature on the luminescence spectra of potassium-aluminum borate and silicate glasses with copper(I) and silver ions

Luminescence and luminescence-excitation spectra of potassium-aluminum borate glasses containing copper(I) and silver ions have been investigated in the temperature range of 20–300°C. It is shown that the luminescence thermochromic effect, which manifests itself in a blue spectral shift of the luminescence bands with an increase in temperature, occurs in glasses of all types, reaching a value of 100 nm. Heating leads to a red shift of luminescence-excitation bands by 20 nm and their broadening. Luminescence quenching occurs in glasses exhibiting photochromic effect at room temperature. An increase in temperature leads to weakening and, finally, disappearance of the photochromic effect in these glasses with subsequent occurrence of the luminescence thermochromic effect.

Spectral properties of copper halide nanocrystals in glasses of fluorine-phosphate matrix

The absorption spectra of glasses of fluorine-phosphate matrix in the near-UV spectral region have been investigated in the temperature range from 20 to 420°C. It is shown that the absorption bands in this spectral region are exciton absorption bands of copper chloride(I) nanocrystals. Results of X-ray diffraction analysis of the glasses are presented. It is shown that the temperature dependences of the exciton absorption bands of CuCl nanocrystals, obtained upon heating and cooling samples, have a a form of hysteresis.

Effect of the size of CuBr nanocrystals formed in potassium-aluminum-borate glass on the phase transformation temperature

At thermal treatment of samples of potassium-aluminum-borate glass containing Cu and Br, a heterogeneous nanophase is formed as drops of the liquid containing CuBr and KBr. At room temperature, the phase contains CuBr and K2CuBr3 nanocrystals. The effect of sizes of nanophase areas on the temperatures of phase transformations (liquidus, solidus, and crystallization) at heating and cooling has been investigated. At the sizes of CuBr crystals equal to 10 nm, the solidus temperature is close to that shown on the state diagram of the KBr-CuBr system. The decrease of the sizes of CuBr crystals from 10 to 4.5 nm results in the decrease of the solidus temperature from 170 to 95°C and the liquidus temperature from 208 to 120°C: in other words, the dimensional effect is manifested almost identically on the values of the solidus and liquiddus temperatures. The decrease of the sizes of the liquid drops from 19 to 7 nm results in the decrease of the crystallization temperature from 100 to 70°C.

Specific features of the optical properties of potassium–aluminum borate glasses with copper chloride nanocrystals at high temperatures

It is shown that heating of potassium–aluminum borate glasses with CuCl nanocrystals above 80°C leads to the disappearance of exciton absorption peaks, whereas cooling below 50°C gives rise to these peaks. These effects are related, respectively, to the melting of nanocrystals and crystallization of nanophase.

The formation of vanadium oxide microcrystals in potassium aluminoborate glasses

This paper presents the results of a study of how the synthesis conditions affect the formation of the crystalline phase in potassium aluminoborate glasses with vanadium ions. It is shown that, when the glass is synthesized under oxidizing conditions, needlelike microcrystals of vanadium pentoxide are formed in it. When the glass is synthesized under reducing conditions, needlelike microcrystals of vanadium dioxide are formed.