Studies of photorefractive crystals of double-doped Ce,Fe:LiNbO3

Two-beam coupling has been studied at red and near-infrared wavelengths in blue Rh:BaTiO3. High amplification, of the order of 20,000–37,000, of a weak signal beam has been measured. The effect of strong intensity-dependent transmission is considered when theoretical plots are fitted to the experimental data.

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Very-high-gain single-pass two-beam coupling in blue Rh:BaTiO(3).

We report what is to our knowledge the first observation of mechanism transformation with wavelength of self-pumped phase conjugation (SPPC) BaTiO3:Ce crystals in the near infrared. in It was found that the SPPC mechanism changed from a backscattering and four-wave-mixing mechanism to a cat mechanism when the pump wavelength was varied from 706 to 770 nm. In addition, SPPC was obtained when the pump beam entered the crystal by the +c face, and a variation with wavelength of optical beam paths in the crystal was also observed.

Mechanism transformation with wavelength of self-pumped phase conjugation in BaTiO(3):Ce.

High-efficiency self-pumped phase-conjugation at 633 nm in cerium-doped barium-titanate crystals

An iron-doped Y-cut lithium niobate (Fe:LN) slab was coated with indium-tin-oxide (ITO) thin films by magnetron sputtering. The electron confinement in a sub-nanometer region at ITO/LN interfaces is resulted from electric screening effect. Consequently, the local plasma frequency in the sub-nanometer metallic-like layer is shifted to the UV regime. This makes it possible to excite surface plasmon polaritons (SPPs) in the visible region with photorefractive phase gratings in the LN slab and to transport SPPs much energy-efficiently. Direct evidence of the excitation of SPPs was demonstrated by the presence of deep transmission spectral valleys in the transmission spectra and striking dark bands in the 2D diffraction patterns while using a white reading beam. Theoretical arguments and confirmation experiments are presented to elucidate all the related findings.

Direct evidence of visible surface plasmon excitation in ITO film coated on LiNbO 3 slabs.

The enhancement of the exponential gain coefficient of two-beam coupling in several thin samples of doped LiNbO3 crystals is reported. The mechanism is analyzed by light crawling that originates from the light-fanning effect. Some experimental results to support the explanation are presented.

Enhancement of the exponential gain coefficient as a result of the light-fanning effect in thin doped LiNbO 3 crystals

We report the self-pumped phase conjugation of an 18°-cut Ce-doped (KyNa1−y)2m(SrxBa1−x)1−m Nb2O6 crystal at a 632.8-nm He–Ne laser wavelength. A maximum phase-conjugation reflectivity of 84.3% has been measured. In addition, its incident angular response and time response are measured.

Self-pumped phase conjugation of 18°-cut Ce-doped KNSBN crystal at 632.8 nm

The largest exponential gain coefficient (Γ = 250 cm-1), to our knowledge, is obtained in thin (d = 0.20 mm) iron-doped LiNbO3 crystal. The dependence of two-beam coupling coefficients on beam crossing angle are measured and compared in two samples fabricated from the same material with different values of thickness. The explanation based on light climbing effect is given.

Shaoping Bian

Papers

Enhancement of the exponential gain coefficient as a result of the light-fanning effect in thin doped LiNbO 3 crystals

Self-pumped phase conjugation of 18°-cut Ce-doped KNSBN crystal at 632.8 nm

Very High Photorefractive Gain in Two-Beam Coupling with Thin Iron-Doped LiNbO 3 Crystal