Double phase conjugation with orthogonally polarized beams in a BaTiO(3) crystal

We have demonstrated experimentally the simultaneous self-conjugation of extraordinarily and ordinarily polarized light waves (lambda=514 nm), with the polarization state preserved, in a Ce:BaTiO(3) crystal. Conjugate o waves originate from coupling between o and e waves by means of a circular photogalvanic effect. The conjugator also takes advantage of the Ce:BaTiO(3) crystal, for which it is easy to generate an extraordinary conjugate beam by photorefractive backscattering. This beam of light is necessary for double phase conjugation.     

Optical bistability and hysteresis in phase conjugation by degenerate six-photon mixing

First observation of non-cavity optical bistability and hysteresis in the phase conjugation by degenerate six-photon mixing in CdS crystals together with some analytical consideration is reported.     

Anisotropic selfdiffraction in BaTiO3

A comparison of the operating characteristics of the high-voltage regime of the discharge in a hollow-cathode tube, the hollow-canthode discharge (HCD) and the discharge to a plane cathode are presented. The disappearnce of the hollow-cathode effect and the transition to a high-voltage discharge after inserting several anode rods into the cathode cylinder is exhibited. The similarity between the operating characteristics of such a high-voltage discharge and of a plane cathode discharge is shown. The loss of ions at the anode rods, as well at insulators or floating conductors is believed to be the reason behind the increase of the operating voltage and the disappearance of HCD characteristics. Practical means of increasing the operating voltage are mentioned.On leave from the Institute of Fluid Flow Machines, Polish Academy of Sciences, Gdansk-Wrzeszcz, Fiszera 14, Poland. This work was supported by the Alexander-von-Humboldt Foundation and the Deutsche Forschungsgemeinschaft (DFG)     

An ultra-low hydrolysis sol-gel route for titanosilicate xerogels and their characterization

In this work TiO₂-SiO₂ xerogels were prepared through an ultra low hydrolysis method using titanium and silicon alkoxide. The samples were heat treated to 500°C. The xerogels were characterized using TGA/DTA, FTIR, XRD and TEM. The samples showed the formation of Si–O–Ti bridges by its characteristic vibration within 925–960 cm⁻¹ range. Si–O–Si bond angles were calculated using the central force network model. The TiO₂ in all the samples crystallized on heat treatment to 500°C. The crystallite size calculated using the Scherer formula from the XRD was verified from the Transmission Electron Micrograph. Samples heat treated to 350°C remained amorphous and hence could be used as hosts for biomaterials and organic optical materials.     

Transient energy transfer during hologram formation in LiNbO3 in external electric field

Volume phase hologram recording in pure LiNbO₃ crystals with applied electric field E ≈ 5 kV/cm is accompanied by considerable intensity redistribution of the writing beams by transient energy transfer. Practically the whole intensity of the donor beam may be transferred into the weak acceptor beam with initial intensity 3% from total incident intensity. This effect originates from transient phase mismatch of the recorded phase grating and fringe pattern in the applied electric field when the interacting beams have different intensities.     

Phase conjugation, edge detection and image broadcasting using two-beam coupling configurations in photorefractive KNbO3

Two-beam coupling configurations are employed to obtain the phase conjugate image and edge extraction of an object using photorefractive KNbO₃: Fe. Also, the self-organization of a beam in the material into a hexagonal spot array is utilized to broadcast an input object to the location of each of the spots.