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Photoinduced birefringence with large optical nonlinearity in a bacteriorhodopsin/polymer composite film is observed. A high refractive index change of 8.5 ? 10?5 photoinduced by 476 nm pumping beam is reached at the low intensity of 6.5 mW/cm2. Based on it, a broadband all-optical photonic switch is realized with an optical controlling switch system. Because of controlling beam's selectivity in switching, the transporting beams of different wavelengths with different intensities and shapes can be modulated by adjusting the wavelength and intensity of the controlling beam.

We perform a comparative study on the electroluminescence (EL) and photoluminescence (PL) of Si nanocrystal-doped SiO2 (nc-Si:SiO2) and SiO2, and clarify whether the contribution from Si nanocrystals in the EL of nc-Si:SiO2 truly exists. The results unambiguously indicate the presence of EL of Si nanocrystals. The difference of peak positions between the EL and PL spectra are discussed. It is found that the normal method of passivation to enhance the PL of Si nanocrystals is not equally effective for the EL, hence new methods need to be explored to promote the EL of Si nanocrystals.

By using an Ar+ ion laser, a tunable Rh 6 G dye laser (linewidth 0.5 cm−1) pumped by the second harmonic of a YAG:Nd laser and a Coherent 899-21 dye laser as light sources and using a monochromator, a phase-locking amplifier and a computer as the data detecting system, we detect the optical properties of Eu3+-doped Y2SiO5 crystal. Persistent spectral hole burning (PSHB) are observed in the Eu3+ ions spectral lines (5D0−7F0 transition) in the crystal at the temperature of 16 K. For 15 mW dye laser burning the crystal for 0.1 s spectral holes with hole width about 80 MHz both at 579.62 nm and at 579.82 nm are detected and the holes can remain for a long time, more than 10 h.

We developed a novel photorefractive (PR) polymer PVK-PBA:DR1:TNF, and its film sample was prepared with outstanding performance by using the method of combination of vacuum saturated vapour resolving with vacuum hot-pressing. The sample exhibits distinctive PR properties with the two-beam coupling coefficient up to 140 cm−1 and four-wave mixing (FWM) diffraction efficiency above 1.5% in the absence of applied external electric field. The designed experiments, including measurements of the second-order nonlinear coefficient and birefringence as well as the relationship between the diffraction efficiencies of the FWM and the external bias field, were performed to understand the underlying mechanism, because this phenomenon cannot be explained by the conventional PR theories. It is presented that because of its high orientational mobility and large dipole moment, the polymer produces the photovoltaic effect under the irradiation of laser to induce a space-charge field so as to engender the PR effect under zero or low external fields. A model based on the assumption was established and the simulation agrees well with the experimental results.

Nonlinear absorption of the organic material Zn-tetrabenzoporphin-crotonicacid-phenoxy resin (ZnTBP-CA-PhR) in the donor-acceptor energy-transfer (DA-ET) system is investigated by the irradiation of Ar+ laser on its solid film. A reverse saturable absorption and an enhanced second reverse saturable absorption called the rereverse saturable absorption are observed in a visible wavelength range. The high performance of optical limiting of the sample possessing low input threshold and an over 95% linear transmission ratio are observed. The physical mechanism of rereverse saturable absorption is analysed by a five-level rate-equation simulating. According to the Huygens wave diffraction principle and the combination of Kerr effect, thermo-optic effect and optical absorption variation, a mathematical model for the optical limiting of ZnTBP-CA-PhR film limiter is established and the theoretical simulating gives a good agreement with the experimental results.

We study photoluminescence (PL) of SiOx (0

A theoretical model was assumed to describe the kinetic processes of light-driven proton pump and motion. The calculation shows that the photovoltage signals are greatly affected by experimental conditions including pulse width of excitation and impedance of measurement system. At the same excitation, only a negative photovoltage signal can be observed with small impedance and both the negative and positive signals can be observed with large impedance. With the same impedance, shorter response time of the pulsed photoelectric signals is responsible for shorter pulsed excitation. All these phenomena are in good agreement with the experimental results.

More than 300% anisotropic persistent spectral holes were written in and read out in some materials such as THP/PMMA and TMP/PMMA with high signal-to-noise ratio by CW linearly polarized light. The effect of probe angle and modulation field on the hole depth and hole shape were also interpreted by using polarisation spectra hole burning theory.

We describe a PVK-based photorefractive polymer composite doped with disperse red 1, poly-butylacrylate and TNF. Using the two-beam coupling experiment, we investigate its photorefractive properties as well as the dynamic process of the index gratings in the sample. We observe the photorefractive effect in the absence of an applied external electric field. The two-beam coupling gain coefficient was measured to reach a value as high as 140 cm-1 in the absence of an external applied electric field and a value of 470 cm-1 at a poling dc electric field of 25V/µm.