Two-wave mixing in photorefractive BaTiO3:Rh at 1,06 µm in the nanosecond regime

International audienceWe present two-beam coupling experiments in the nanosecond regime at 1.06 mm, using photorefractive BaTiO3:Rh. The maximum observed exponential gain coefficient is 14.2 cm-1. No intensity-dependent electron-hole competition and no strong saturation of the photoionized charge carriers are observed for intensities of less than 20 MW cm-2. The energy required for recording the photorefractive grating is not significantly different in the nanosecond and the cw regimes

Characterization and optimization of a ring self-pumped phase conjugate mirror at 1.06 Μm with BaTiO3:Rh

International audienceWe optimize the ring self-pumped phase-conjugate mirror at 1.06 mm. With cw as well as nanosecond illumination the photorefractive efficiency is higher than 90%. Therefore the reflectivity (79%) is limited only by the transmission of the loop. Another relevant characteristic is the time needed to increase the reflectivity from 10% to 90% of its maximum value, which is as little as 12 s at 5 W cm22 in the cw regime. In the nanosecond regime, 90 J cm22 is needed. We study the response to an abrupt change in the incident wave front, taking into account the three-prism system inserted in the loop

Dielectric and Piezoelectric Properties of K(Ta0.51Nb0.49)O3 Single Crystal

Dielectric and piezoelectric properties of K(Ta0.51Nb0.49)O3 [KTN] single crystals along [100], [001] and [011] pseudo-cubic crystallographic orientations are reported and discussed. Temperature dependencies of dielectric permittivity in tetragonal phase of monodomain and polydomain crystals of these orientations are compared. Strong dielectric anisotropy is found in the tetragonal phase, with ε[100] / ε[001] ratio equal 16 at 300 K. Room temperature piezoelectric coefficients for the monodomain state of KTN are reported

Frequency Doubling Nanocrystals for Cancer Theranostics

A novel bio-photonics approach based on the nonlinear optical process of second harmonic generation by non-centrosymmetric nanoparticles is presented and demonstrated on malignant human cell lines. The proposed method allows to directly interact with DNA in absence of photosensitizing molecules, to enable independent imaging and therapeutic modalities switching between the two modes of operation by simply tuning the excitation laser wavelength, and to avoid any risk of spontaneous activation by any natural or artificial light source.Comment: 16 pages, 7 figure

Structural origins of relaxor behavior in a 0.96(Bi1/2Na1/2)TiO3-0.04BaTiO(3) single crystal under electric field

Diffuse x-ray scattering intensities from a single crystal of 0.96(Bi1/2Na1/2TiO3)-0.04(BaTiO3) have been collected at room temperature with and without application of an electric field along the [100] direction. Distinct features in the diffuse scattering intensities indicate correlations on a nanometer length scale. It is shown that locally correlated planar-like structures and octahedral tilt-domains within the room temperature rhombohedral R3c phase are both electrically active and are irreversibly affected by application of an electric field of 4.3 kV/mm. The field dependence of these nanoscale structures is correlated with the relaxor behavior of the material by macroscopic permittivity measurementsopen221

Twins in YAl_3(BO_3)_4 and K_2Al_2B_2O_7 Crystals as Revealed by Changes in Optical Activity

Many borate crystals feature nonlinear optical properties that allow for efficient frequency conversion of common lasers down into the ultraviolet spectrum. Twinning may degrade crystal quality and affect nonlinear optical properties, in particular if crystals are composed of twin domains with opposing polarities. Here, we use measurements of optical activity to demonstrate the existence of inversion twins within single crystals of YAl_3(BO_3)_4 (YAB) and K_2 Al_2 B_2 O_7 (KABO). We determine the optical rotatory dispersion of YAB and KABO throughout the visible spectrum using a spectrophotometer with rotatable polarizers. Space-resolved measurements of the optical rotation can be related to the twin structure and give estimates on the extent of twinning. The reported dispersion relations for the rotatory power of YAB and KABO may be used to assess crystal quality and to select twin-free specimens

Twins in YAl_3(BO_3)_4 and K_2Al_2B_2O_7 Crystals as Revealed by Changes in Optical Activity

Many borate crystals feature nonlinear optical properties that allow for efficient frequency conversion of common lasers down into the ultraviolet spectrum. Twinning may degrade crystal quality and affect nonlinear optical properties, in particular if crystals are composed of twin domains with opposing polarities. Here, we use measurements of optical activity to demonstrate the existence of inversion twins within single crystals of YAl_3(BO_3)_4 (YAB) and K_2 Al_2 B_2 O_7 (KABO). We determine the optical rotatory dispersion of YAB and KABO throughout the visible spectrum using a spectrophotometer with rotatable polarizers. Space-resolved measurements of the optical rotation can be related to the twin structure and give estimates on the extent of twinning. The reported dispersion relations for the rotatory power of YAB and KABO may be used to assess crystal quality and to select twin-free specimens