The energy efficiency of multiwave mixing and geometrical parameters of spatial solitons in photorefractive Bi12TiO20 crystals in conditions of pulsed and continuous-wave laser excitation have been studied experimentally. It has been found that with the use of 532 nm-wavelength laser pulses switching of the photorefractive nonlinearity mechanism requires a time interval in excess of 20 - 50 ns. And saturation is observed when the duration is over 100 ns. The formation dynamics of spatial solitons in photorefractive Bi12TiO20 crystals has been analyzed using radiation of a continuous-wave He-Ne laser. It has been determined that the formation conditions and dynamics are influenced by a number of factors including the radiation input geometry of a crystal, power of the light beam, orientation of its polarization relative to the crystal axes, applied electric field and its direction.
Light-polarizing films are a basis of sheet polarizers, which are used in liquid crystal systems. A light-polarizing film is generally produced by the formation of a uniaxial stretched film made of polyvinyl alcohol (PVA) or its derivatives containing a light-polarizing element like iodine or dichroic dye. Films with iodine are excellent in their initial polarizing performance but poor in resistance to moisture and heat. In order to improve the durability of polarizers more stable dichroic element are used instead of iodine. Films with dichroic organic dyes first of all azodyes are superior in the resistance to moisture and heat as compared with iodine systems. Searching for thermally stable dyes, which do not change their colour under of the influence of high temperature and humidity and are suitable for the manufacturing of effective polarizers is an actual problem. In this paper we show the results of optical investigations of uniaxial PVA-films with iodine (with and without transparent layer) and dichroic azodye.
We present investigations of self-focusing and screening soliton formation processes in photorefractive Bi12TiO20 (BTO) crystals for two different cuts in dependence on both the magnitude of the applied external voltage and additional illumination intensity. We study also temporal behavior of soliton growth and the possibility of stable soliton existence in BTO crystals of the cut .
We present an experimental set-up for the optical detection of condensed vapours or liquids and their refractive indices using photorefractive crystals (e. g. Barium-Calcium-Titanate or Barium-Titanate). Hereby we use a self-pumped phase conjugating mirror along with the effect of total reflection. The modulation of the signal beam in order to avoid background illumination is not necessary due to the phase-conjugated reflection. The detection of different condensed vapours or liquids and their refractive indices is possible by the variation of the input angle of the signal beam.