MgO:LiNbO_3与LiNbO_3质子交换光波导光学及结构特征的比较

利用退火的质子交换法在MgO :LiNbO3和LiNbO3两种材料上制作了光波导 ,得到了质子交换的扩散特性以及光波导折射率分布的退火规律 .通过x射线衍射和OH- 红外吸收谱方法研究了MgO :LiNbO3和LiNbO3质子交换光波导的结构特征及其与退火参数的关系 ,对MgO :LiNbO3和LiNbO3光波导光学和结构特征的结果进行了分析和比较     

质子交换MgO:LiNbO3波导的双层结构

本文报导MgO:LiN_bO₃质子交换波导X射线双晶衍射和红外吸收的实验结果。这些结果表明质子交换波导由浅表面层和深表面层构成。浅表面层是一个连续应变层,有着大量随机排列的O—H—O形式的缔合OH^-基团。深表面层是一个均匀应变层,其内H⁺以自由OH^-基团形式出现。质子交换波导折射串不稳定性与双层结构中的结构驰豫密切相关。通过对质子交换过程的分析,提出两条避免双层结构的途径,其一为降低交换剂中的H⁺浓度,另一条是采用有限源工艺。     

质子交换LiNbO3光波导的特性研究

采用X射线衍射谱法和红外吸收光谱法对质子交换和退火质子交换LiNbO3光波导的特性进行了研究.研究结果表明:在LiNbO3晶体衬底X射线衍射主峰的左侧出现质子交换LiNbO3光波导的伴峰,则质子交换使光波导层Li1-xHxNbO3的晶格常数比衬底的晶格常数稍大,产生垂直于表面的应变,波导经过退火后,伴峰向主峰靠近,应变减少.质子交换波导中的OH-基团的红外吸收光谱在3 500和3 300 cm-1处存在特征峰,波导经过退火后,3 300 cm-1处的特征峰基本消失,而3 500 cm-1处的吸收强度基本不变.实验还表明,OH-在3 500 cm-1处吸收带的积分面积基本与交换时间的开方呈正比例关系.     

焦磷酸质子交换LiTaO3光波导

本文首次报道了在低于300℃的焦磷酸中制备质子交换LiTaO_3光波导的方法。通过测量有效扩散系数D给出D_0=3.91×10~6μm~2/h和激活能E_a=0.74eV;并测量了波导参数。实验结果表明:只有非寻常折射率产生增量△n_6,其中TM单模波导的传输损耗低达0.1dB/cm(633mm)。发现,热退火处理后的波导表面非寻常折射率增大了。     

质子交换Y分支光波导弯曲损耗研究

对采用退火质子交换技术(APE)制备的具有正弦型弯曲和余弦型弯曲两种不同的S型弯曲的Y分支光波导,利用宽角有限差分光束传播法,就过渡区长度、波导表面折射率增量、掩模版开口宽度等对波导弯曲损耗的影响进行了研究。结果表明,两种S弯曲下的Y分支波导的弯曲损耗,随波导结构参数的变化基本上是相同的,但二者的表现并不完全一致。数值计算结果为相应波导器件的设计和制备提供了一定的参考。     

质子交换光波导生长动力学研究

分析了质子交换光波导的生长动力学并给出了波导层厚度与生长时间的计算公式。     

质子交换LiTaO3光波导特性及晶格常数变化

采用气相质子交换方法,在Z－切LiTaO3晶体表面制备平面光滑波导层。样品制备采用245℃苯甲酸气体,在LiTaO3晶体在－C和＋C表面交换8－20小时。质子交换层在LiTaO3表面形成,并用棱镜耦合测量波导样品。然后在HF：HNO3酸中用化学方法腐蚀波导层,并用电子显微镜观测光波导层与补底界面的形貌。用X射线衍射法,测量LiTaO3质子交换光波层的晶格常数变化。用双晶X射线测量质子交换（PE）和退火质子交换（APE）波导层晶格常数的变化。样品的X射线衍射曲线表明,PE和APE波导晶格常数的变化不同。实验中,还测量了有无极畴反转LiTaO3晶格常数的改变。     

质子交换光波导生长机理的研究

对质子交换光波导生长机理进行了研究并给出了波导层厚度的计算公式。     

LiNbO3质子交换波导及其退火效应

采用质子交换技术,以苯甲酸为交换源,实验研究X-切LiNbO₃质子交换平面波导及其退火效应。利用棱镜耦合器测出波导模折射率。采用费米函数,由模折射率确定出波导折射率分布随退火时间的变化关系,给出了分布参数和曲线.     

ZnO：LiNbO3质子交换光波导层内应变的测定

报道了利用Ｘ射线双晶衍射法精确确定ＺｎＯ：ＬｉＮｂＯ３质子交换光波导的晶格常数变化，结果表明，波导层内含有均匀分布的三维应变场，晶格常数的变化随着波导取向的不同而呈现各向异性特点。     

Surface acoustic wave distribution and acousto-optic interaction in proton exchanged LiNbO3 waveguides

The efficiency of acoustooptic (AO) interaction in YZ-cut proton exchanged (PE) LiNbO₃ waveguides is theoretically analysed by determining the overlap between the optical and acoustic field distributions. The present analysis takes into account the perturbed SAW field distribution due to the presence of the PE layer on the LiNbO₃ substrate determined by the rigorous layered medium approach. The overlap is found to be significant upto very high acoustic frequencies of the order of 5 GHz, whereas in the earlier analysis by vonHelmolt and Schaffer [6] for diffused waveguides, it was shown that the overlap integral rolls down to nearly zero at this high frequency range.     

Characterization of Annealed, Proton Exchange Optical Waveguides in Y-cut MgO:LiNbO3 Crystal

It is reported the results of a systematic study on planar waveguides fabricated in Y-cut MgO:LiNbO3 crystal. The index profile of the as-exchanged waveguide can be modeled as a step-like one. It is deduced the diffusion coefficient and the activation energy for the proton exchange process. The surface index increases Δne of around 0.127 after proton exchange can be reduced by post thermal annealing. The effects of the annealing on the index profile and guide depth were found not as fast as it does on a pure LiNbO3 crystal.     

Design and demonstration of interferometric integrated-optic sensors in Ti:LiNbO3 waveguides

The design of an integrated optic Michelson interferometer sensor for stress, temperature, and microdisplacement measurements consisting of a semi-asymmetric X-junction made by Ti in-diffused LiNbO₃ waveguides is reported. The possibility of performing simultaneous measurements of strain and temperature is investigated, and different calibration schemes are proposed. Experimental results of displacement-only measurements show a 64% intensity modulation with 33-dB optical loss.     

Optical waveguides in LiNbO<Subscript>3</Subscript> and stoichiometric LiNbO<Subscript>3</Subscript> crystals by proton exchange

The formation of optical planar waveguides in LiNbO₃ and stoichiometric LiNbO₃ crystals by proton exchange was reported. The prism-coupling method was used to characterize the dark-line spectroscopy at the wavelength of 633 and 1539 nm, respectively. The mode optical near-field outputs from proton-exchanged LiNbO₃ and SLN waveguides at 633 nm were presented. The mode field from stoichiometric LiNbO₃ (SLN) waveguide is lighter and more uniform than that from LiNbO₃ waveguide, which means the quality of the waveguide in SLN crystal is better than that of the LiNbO₃ waveguide. For proton-exchanged LiNbO₃ waveguides, the evolution of the refractive index profile with annealing was presented. The disorder profiles of Nb atoms in proton-exchanged LiNbO₃ waveguides were obtained by Rutherford backscattering/channeling technique. It is shown that the longer the exchange time, the larger the displacement of Nb atoms. Supported by the National Natural Science Foundation of China (Grant No. 10475052) and the Scientific Research Start-up Financing of Qufu Normal University     

Substitution and proton doping effect on SrZrO3 behaviour: high‐pressure Raman study

The high‐pressure Raman studies of pure, Yb‐modified, protonated and non‐protonated SrZrO₃ dense ceramics were performed between 0.1 and 40 GPa using a diamond anvil cell. Lanthanide‐modified, protonated SrZrO₃ perovskites are potential materials for electrolytic membrane in fuel cells and electrolysers working at medium temperature. The comparison of the Raman spectra shows important differences in the pressure behaviour between the pure and Yb‐modified SrZrO₃ ceramics. SrZrO₃ exhibits a rigid structure without any structural modification, whereas for both SrZr_0.93 Yb_0.07 O_2.965 and SrZr_0.93 Yb_0.07 O_2.962 H_0.003 a sequence of structural modifications at 10, 20 and 35 GPa is revealed. The character of these structural modifications is very similar to that observed as a function of the temperature (orthorhombic Pnma 750 °C → pseudo‐tetragonal Imma 840 °C → tetragonal I4/mcm 1070 °C → cubic Pm3m), which suggests that they can be considered as the phase transitions. Despite the low level of proton content (0.3% mole/mole), significant difference between protonated and non‐protonated compounds is observed for the 700–750 cm⁻¹ doublet assigned to the Zr O octahedron stretching mode, perturbed by an oxygen atom vacancy and/or neighbouring Yb ion. The location of proton is discussed. Copyright © 2011 John Wiley & Sons, Ltd.     

Er3＋ ion concentration effect on transient and steady-state behavior in Er3＋ ：YAG crystal

The effect of Er3＋ ion concentration on transient and steady-state behavior in 45-nm Er3＋ ：YAG crystal is investigated. It is shown that by changing the signal field, the coherent field and the concentration of Er3＋ ions in the crystal, the absorption, dispersion, and group index of the weak probe field can be adjusted. Also, it is found that the probe absorption occurs in the presence of population inversion and probe amplification is obtained in the absence of population inversion.     

The effect of benzo‐annelation on intermolecular hydrogen bond and proton transfer of 2‐methyl‐3‐hydroxy‐4(1H)‐quinolone in methanol: A TD‐DFT study

Excited‐state intermolecular or intramolecular proton transfer (ESIPT) reaction has important potential applications in biological probes. In this paper, the effect of benzo‐annelation on intermolecular hydrogen bond and proton transfer reaction of the 2‐methyl‐3‐hydroxy‐4(1H)‐quinolone (MQ) dye in methanol solvent is investigated by the density functional theory and time‐dependent density functional theory approaches. Both the primary structure parameters and infrared vibrational spectra analysis of MQ and its benzo‐analogue 2‐methyl‐3‐hydroxy‐4(1H)‐benzo‐quinolone (MBQ) show that the intermolecular hydrogen bond O₁―H₂?O₃ significantly strengthens in the excited state, whereas another intermolecular hydrogen bond O₃―H₄?O₅ weakens slightly. Simulated electron absorption and fluorescence spectra are agreement with the experimental data. The noncovalent interaction analysis displays that the intermolecular hydrogen bonds of MQ are obviously stronger than that of MBQ. Additionally, the energy profile analysis via the proton transfer reaction pathway illustrates that the ESIPT reaction of MBQ is relatively harder than that of MQ. Therefore, the effect of benzo‐annelation of the MQ dye weakens the intermolecular hydrogen bond and relatively inhibits the proton transfer reaction.     

Theoretical studies of the optical and EPR spectra for Fe ion in the MF3:Fe (M=Al, Ga) systems

By analyzing the EPR spectra of Fe³⁺ ion in the fluorinde glasses, the local lattice structures around impurity Fe³⁺ ion in MF₃:Fe³⁺ (M=Al, Ga) systems have been studied by means of diagonalizing the complete energy matrices of the electron-electron repulsion, the ligand-field and the spin-orbit coupling for a d⁵ configuration ion in a trigonal ligand-field. Both the second-order and fourth-order EPR parameters D and (a−F) are taken simultaneously in the structural investigation. The results indicate that the local lattice structure around octahedral Fe³⁺ center has an expansion distortion for Fe³⁺ in MF₃:Fe³⁺ (M=Al, Ga). The expansion distortion may be ascribed to the fact that the radius of Fe³⁺ ion is larger than that of Al³⁺ ion and Ga³⁺ ion, and the Fe³⁺ ion will push the fluoride ligands upwards and downwards, respectively. The local lattice structure parameters R=1.927 A, θ=55.538° for Fe³⁺ in AlF₃:Fe³⁺ and R=1.931 A, θ=56.09° for Fe³⁺ in GaF₃:Fe³⁺ are determined, respectively, and the EPR spectra of the MF₃:Fe³⁺ (M=Al, Ga) systems are satisfactorily explained.     

Local defect structures and EPR studies on (FeO6)9− and (FeO4)5− clusters in YGG: Fe3+ system

The octahedral (FeO₆)^9? and tetrahedral (FeO₄)^5? clusters in yttrium gallium garnet (YGG): Fe³⁺ system are investigated based on the 252 × 252 complete energy matrices for d⁵ configuration ions in trigonal and tetragonal ligand fields, moreover, the EPR and optical spectra are made unified calculation. The results indicate that the defect structures around Fe³⁺ centres display expansion effects at different temperatures 4.2 and 295 K, and which are close to those in YIG garnet, respectively. Simultaneously, the defect structure parameters for Fe³⁺ centres in YGG are determined, and the relationship between the defect structure and the temperature has been discussed.