Nickolai V. Kukhtarev

SELF-ORGANIZATION OF SCATTERING IN PHOTOREFRACTIVE KNBO3 INTO A RECONFIGURABLE HEXAGONAL SPOT ARRAY

The scattering cone (~2 degrees ) from an Ar laser beam (514 nm) in photorefractive KNbO(3):Fe has been observed to transform into a reconfigurable hexagonal spot array. This phenomenon can be explained through the creation of laser-induced transmission and reflection grating arrays.

Optical characterization of Mn:YAlO 3 : material for holographic recording and data storage

Photoinduced coloration and the holographic grating recording associated with it are experimentally studied in Mn-doped yttrium orthoaluminate (Mn:YAlO3). High diffraction efficiency is demonstrated in visible and in infrared light. The diffraction efficiency at 514.5 nm exceeds 50%. The strong energy exchange between the writing beams observed in a two-wave mixing experiment suggests that diffraction in Mn:YAlO3 is due to mainly nonlocal holographic effect and an electro-optical effect. Mn:YAlO3 is shown to be a promising material for holographic recording and optical storage.

Generation of focused electron beam by pyroelectric and photogalvanic crystals

We have developed a model to explain the phenomena of electron focusing by pyroelectric crystals. The pyroelectric crystals used to compare the experiments with theory were the Fe-doped and undoped LiNbO3. The crystals were either heated from the +z end or illuminated with a laser. Heating the crystals by passing a current through a resistor attached to the +z end produced the pyroelectric effect, a change in polarization in response to a change in temperature. The crystal illumination with a cw solid-state diode-pumped laser (532 nm and 100 mW) produces the photogalvanic current, which creates charges on polar surface of the LiNbO3:Fe. In both cases, the polar ends of the crystal becomes electrically charged and produced self-focusing electron beams that were imaged on a ZnS screen. In addition, we have demonstrated x-ray imaging using the pyroelectric effect.

Broadband Dynamic, Holographically Self-Recorded, and Static Hexagonal Scattering Patterns in Photorefractive KNbO3:Fe

We have observed and explained three types of hexagon pattern formation in photorefractive crystal KNbO 3 :Fe. These are: (1) dynamic (laser induced), (2) semipermanent (holographically stored), (3) permanent (induced by a static domain grid) over a wide wavelength range.

Holographic surface gratings in iron-doped lithium niobate

Surface gratings associated with holographic volume gratings in photorefractive crystals of iron-doped lithium niobate have been studied using diffraction of a reflected probe beam and high-resolution phase-shifted interferometric profilometry. Both techniques show that the surface gratings exist in the form of periodical corrugations of the same period as that of the volume grating. The maximum amplitude of the periodical surface relief measured by both techniques is close to 6.5 nm. We also demonstrated that the periodical electric forces on the surface were capable of assembling polystyrene microspheres along the fringes of the grating. Large amplitude of the periodic electric field (1.6×104 V/cm) is associated with the photogalvanic effect.

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

Abstract 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.

Phase conjugation by the degenerate six-photon mixing in semiconductors

Abstract The first observation is reported of phase conjugation (PC) with two times gain in six-photon mixing realized in a semi- conductor ZnSe crystal during two-photon absorption. Compensation of the influence of self-action effects on PC by the pump waves misalignment is demonstrated. A theory of six-photon mixing with illustration by scattering diagrams is developed.

Optical, photoelectric, and photorefractive properties of Ti-doped CdTe crystals

The photorefractive characteristics of Ti-doped CdTe semi-insulating crystals were measured. Additional optical and photoelectric measurement confirmed that titanium has advantages over other dopants and that this material has better characteristics for potential applications. The high optical holographic gain coefficient, Γ≈0.60 cm−1, low background absorption, kb≈0.2 cm−1, high optical quality and homogeneity, and almost monopolar (electronic) photoconductivity show that these materials can be effectively used for both optical and photoelectric applications in the near infrared region. Studies of the optical absorption and photodiffusion current made it possible to determine the nature and energy structure of impurity and intrinsic defects as well as to establish their role in the photorefractive effect. It is shown that the excited impurity 4T1(F) state is in resonance with the conduction band. As a result, autoionization of electrons to the conduction band under laser excitation takes place. An energy...

Determination of model airplane attitudes using dynamic holographic interferometry.

We demonstrate how real-time holographic interferometry yielding two-dimensional fringes can be recorded and used to determine changes in three-dimensional attitude of a model airplane through digital image processing. A simple bench-top experiment with a model airplane as a test object is conducted to demonstrate interference fringes superposed on the image due to changes in attitudes (pitch, yaw, and roll) as well as distortion. A novel second-generation thermoplastic camera suitable for dynamic multiple reversible registration of thin-phase holograms using thermoplastic and semiconductor film on glass substrate is used for in situ recording and readout during real-time holographic interferometry. Thin-phase holograms also offer the advantage of exact image reconstruction from forward-phase conjugation.

Polarization-multiplexed volume holograms in LiNbO3 with 90-deg geometry

We propose and demonstrate a novel holographic multiplexing technique, polarization multiplexing, in LiNbO 3 with a 90-deg geometric scheme. The technique provides the possibility for storing the index fringes by two waves with the polarization state orthogonal to each other.