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.

分别利用氩离子激光,二倍频YAG:Nd 激光泵浦的诺明6G可调谐窄线宽(0.5 cm-1)染料激光和899-21可调谐染料激光作为光源,以单色仪-锁相放大器-光电倍增管-计算机数据采集系统记录光谱,对Y2SiO5:Eu3+晶体进行了光谱和光谱烧孔研究.在常温和液氮温度下测量了晶体的激发光谱、荧光光谱等.在16 K温度下对晶体进行了光谱烧孔研究,得到了孔宽约80 MHz并能保存10 h的永久性光谱孔.

By using an Ar+ ion laser, a tunable Rh 6G dye laser(Linewidth : 0.5 cm(-1)) and a Coherent 899-21 dye laser as light sources and using a monochromator and a phase-locking amplifier, the optical properties of Eu3+ : Y2SiO5 crystal were detected. Persistent spectral hole burning (PSHB) were also observed in (5)Do-(7)Fo transition in the crystal at the temperature of 16 K. For 15 mW dye laser (Wavelength : 579.62 nm) burning the crystal for 0.1 s a spectral hole with about 80 MHz hole width were detected and the hole can been keep for longer than 10 h.

By using an Ar+ ion laser, a tunable Rh 6G dye laser（Linewidth: 0.5 cm -1） and a Coherent 899-21 dye laser as light sources and using a monochromator and a phase-locking amplifier, the optical properties of Eu 3+∶Y 2 SiO 5 crystal were detected. Persistent spectral hole burning （PSHB） were also observed in 5D 0 -7F 0 transition in the crystal at the temperature of 16 K. For 15 mW dye laser （Wavelength: 579.62 nm） burning the crystal for 0.1 s a spectral hole with about 80 MHz hole width were detected and the hole can been keep for longer 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.

CNx nanocrystals and nanotubes were synthesized on Co/Ni-covered Si(100) wafers using a nitrogen-atom-beam-assisted pulsed laser ablation deposition method. Transimission electron microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy showed that nanometer-sized CNx nanocrystals and nanotubes were contained in the as-deposited films. The co-catalyzation by the cobalt and nickel in the synthesis process is considered to play an important role in the formation of CNx nanocrystals and nanotubes. The reasons for the formation of CNx nanocrystals and nanotubes have been analyzed.

It is shown that the cascaded fifth-order nonlinear phase shifts will increase with energy loss in the cascaded processes. Essentially different from the multi-photon absorption accompanied with inherent material nonlinearities, the loss of fundamental wave in a cascaded process is controllable and suppressible. By introducing difference frequencies generated from the reaction between the fundamental and its second harmonic after the cascaded processes, the fundamental wave can be free of energy loss, while the large cascaded fifth-order nonlinear phase shift is maintained.

Carbon nitride nanocrystals were synthesized on Co/Ni-covered Si(100) wafers using a nitrogen-atom-beam-assisted pulsed laser ablation deposition method. Transmission electron miscroscopy, x-ray diffraction, and Raman spectroscopy showed that as-deposited films were constructed primarily from nanometer-sized β-C3N4 and CNx crystallites. The co-catalyzation by the cobalt and nickel in the synthesis process is considered to play an important role in the formation of nanocrystalline β-C3N4. The reasons for the formation of carbon nitride nanocrystals were analyzed.

针对二阶非线性X 2 级联产生等效五阶非线性的过程,研究发现基频光感应到的级联五阶非线性相移会随着其在整个过程中所遭受到的能量损耗的加剧而增大。与材料固有非线性所产生的多光子吸收效应有着本质的区别,该级联非线性过程中所形成的基频光能量损耗是可控的。在数值模拟计算的基础上,提出了在级联五阶非线性过程之后引入倍频光与基频光相互作用的差频过程,最终实现了基频光在感应到大的级联五阶非线性相移的同时无能量损耗效应。

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.

The effect of transverse coupling in a photorefractive oscillator is studied. From the study the condition for stable optical patterns of multimode oscillation is given analytically and verified by numerical simulation. Under the stable condition, the period-doubling route to spatiotemporal chaos is observed.

Nanocrystalline carbon nitride films were synthesized on cobalt-covered Si(111) wafers using a nitrogen-atom-beam-assisted pulsed laser ablation method. Raman spectroscopy and other analyses showed that as-synthesized films were constructed primarily from nanometer-sized β-C3N4 and CNx crystallites. Catalyzation by the cobalt in the synthesis process is considered to play an important role in the formation of nanocrystalline β-C3N4. The effect of the experimental conditions on the characters of the as-synthesized films has been discussed.

We demonstrated the feasibility of the growth of GaN thin films from polycrystalline GaAs using reactive pulsed laser deposition. The films were grown on Si (100) substrates at temperatures lower than 80 degreesC. A bulk of polycrystalline GaAs was used as target. Reactive nitrogen plasma was provided by electron cyclotron resonance (ECR) microwave discharge in pure nitrogen gas to assist the film growth. Composition analysis showed that the grown films are slightly N-rich, and arsenic can hardly be detected. A strong absorption peak corresponding to Ga-N stretching vibration in the hexagonal-type GaN crystals is clearly resolved from the IR absorption spectrum. The films exhibit transparency in the visible and near-IR regions. The band gap of the films was determined to be about 3.4 eV. When excited by 325-nm light at 10.2 K, the grown films luminesce in the blue region.

We have prepared carbon nitride thin films by using plasma assisted pulsed laser deposition. In this method, a graphite target was ablated by laser pulses in the environment of a nitrogen plasma generated from electron cyclotron resonance microwave discharge in pure nitrogen gas, while the growing film was simultaneously bombarded by the plasma stream. The deposited films were characterized by Rutherford backscattering spectroscopy (RBS), Fourier transform infrared (FTIR) spectroscopy, and Raman Spectroscopy. Films consisting purely of carbon and nitrogen with nitrogen content over at.50% were obtained on Si (100) substrates at low deposition temperatures (<80 degree(s)C). N atoms in the as-prepared films were found to be bound to C atoms through hybridized sp2 and sp3 configurations. A strong influence of substrate bias voltage on the composition and bonding configuration in the films as well as on the deposition rate was observed.

光折变振荡器中存在复杂多样的时空现象. 从理论上研究了弱场条件下横向耦合在其中的影响, 并结合数值模拟的方法系统地研究了多个横向模式在不同情况下光学斑图稳定的条件, 以及模式处于简并或准简并时, 系统从周期变化进入时空混沌的途径.

Oxygen-free nanosized InN was synthesized by pulse discharge. NH3/N2 mixture and bulk indium were used as nitrogen source and discharge cathode, respectively. Optical emission spectra show that N2 and NH3 were highly dissociated in the discharge and oxygen could be eliminated effectively. A comparison was made among samples produced in the discharge of N2, NH3 and N2/NH3, respectively. The XPS was used to determine the composition of the synthesized materials. Only In-N was produced when N2/NH3 was used as the discharge gas, whereas indium oxide was found in the case using N2 or NH3 as the discharge gas. The size of the produced InN was between 5 and 200 nm. A broad band with a blue shift of 150 nm from that of bulk InN was detected in the photoluminescence of the produced nanosized InN.

We have used optical emission spectroscopy to characterize the high-voltage pulsed discharge of ammonia. Ammonia was highly dissociated in the discharge at low pressures. More atomic nitrogen was generated as compared to the discharge of nitrogen gas at the same pressure of 0.8kPa. We discuss the elimination of the oxygen impurity in the ammonia discharge and we estimate the time-dependent atomic excitation temperature and the electron density from the measured spectra.

We report on the preparation of boron carbon nitride (BCN) thin films by pulsed laser ablation of a sintered B4C target and the compositional and structural characterization of the films. The film preparation was performed with assistance of nitrogen ion beam from a Kaufman source. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) were used for compositional analysis and structural characterization. The results showed that the prepared films contain several chemical bonds such as B-N and C-N. The BCN films were found to show good adhesion to the substrates and have a high transparency from visible to near-infrared region. WE also grew films in nitrogen background without ion beam assistance and in vacuum. The atomic ratio of boron, carbon and nitrogen and the chemical bonds are strongly dependent on the deposition conditions. The ion beam assistance, i.e. the reactive nitrogen environment and the bombardment of the growing films by the energetic species in the nitrogen ion beam, is beneficial to the incorporation of nitrogen.