Light-induced removal of 180° ferroelectric domains in Rh:BaTiO₃

We show that optically-induced photorefractive space-charge fields can remove 180° ferroelectric domains in rhodium-doped barium titanate. The cross section of the domains must be small (less than 100 microns) for this process to occur

Electric field control of diffraction and noise in dye-doped liquid crystals

We present results on permanent gratings in highly dye-doped liquid crystal cells without polymer coatings of the cells' surfaces. The surface-mediated gratings remain in cells for months without degradation of their quality. The peak diffraction efficiency can be controlled, enhanced or decreased, by applying low voltage AC field. At low frequencies, below 1 Hz, the diffracted signal can modulated by the AC field, but the time development of the signal shows a complex response. The enhancement of diffraction can be, however, observed at all frequencies we tested (0.1 Hz – 300 kHz). The permanent gratings cannot be removed by heating above the liquid crystal phase transition temperature as on cooling the diffraction efficiency is restored

Mapping of periodically poled crystals via spontaneous parametric down-conversion

A new method for characterization of periodically poled crystals is developed based on spontaneous parametric down-conversion. The method is demonstrated on crystals of Y:LiNbO3, Mg:Y:LiNbO3 with non-uniform periodically poled structures, obtained directly under Czochralski growth procedure and designed for application of OPO in the mid infrared range. Infrared dispersion of refractive index, effective working periods and wavelengths of OPO were determined by special treatment of frequency-angular spectra of spontaneous parametric down-conversion in the visible range. Two-dimensional mapping via spontaneous parametric down-conversion is proposed for characterizing spatial distribution of bulk quasi-phase matching efficiency across the input window of a periodically poled sample.Comment: 19 pages, 6 figure

Amplification of near-infrared light in a photorefractive ring resonator

We have demonstrated efficient amplification of near-infrared, 0.83-0.7µm and 1.06-1.07µm light, in a photorefractive ring resonator using Rh:BaTiO3. The optical power oscillating inside the ring exceeded the pump power by a factor of up to 2.34. The sensitivity of a ring resonator to nanometer changes in its length was characterised using a piezo-mirror

AC Field Enhancement of Diffraction From Permanent Gratings in Dye-Doped Liquid Crystals

Permanent gratings can be written in doped liquid crystals with high dye concentration without any externally applied electric field, using low intensity, visible light. The gratings are adaptive as their diffraction efficiency can be easily modulated and controlled enhanced by an AC field. The diffracted intensity could also be modulated by a low frequency electric field with the magnitude of modulation decreasing for higher frequencies. The permanent gratings are durable, remaining in the cells for over a year even after application of high temperatures

Near-infrared light amplification in a photorefractive ring resonator

We have demonstrated efficient amplification of near-infrared, 830nm and 1.06µm light, in a photorefractive ring resonator. The oscillating power exceeded the pump power by up to a factor of 2.35

Characterization of periodically poled LiTaO3 crystals by means of spontaneous parametric down-conversion

10.1007/s00340-006-2156-7Applied Physics B: Lasers and Optics832273-278APBO