Acousto-optic light deflection in an Al2O3 optical waveguide structure

The total deflection of an optical guided wave by a surface acoustic wave (SAW) in a silicon-based SiO₂/AL₂O₃/SiO₂ optical waveguide structure is reported. The SAW is generated by an interdigital transducer with piezoelectric ZnO deposited on top of the optical waveguide structure.     

Ion synthesis and optical properties of gold nanoparticles in an Al2O3 matrix

Single-crystal Al₂O₃(0001) and Al₂O₃(1120) substrates are implanted by 160-keV Au⁺ ions with doses from 10¹⁵ to 10¹⁷ cm^?2. Some of the implanted samples are air-annealed at 800–1200°C. The properties of the synthesized composite layers are studied by Rutherford backscattering and linear optical reflection measurements, and their nonlinear optical characteristics are examined by RZ-scanning using a picosecond Nd: YAG laser operating at a wavelength of 1064 nm. The Rutherford backscattering spectra indicate that the implanted impurity concentrates near the surface of the Al₂O₃. The formation of gold nanoparticles in the Al₂O₃ can be judged from the characteristic optical plasmon resonance band in the reflectance spectra of the samples irradiated to a dose higher than 6.0 × 10¹⁶ cm^?2. The synthesized particles are shown to be responsible for nonlinear optical refraction in the samples. The nonlinear refractive index, n ₂, and the real part of the third-order susceptibility, Rex⁽³⁾, of the composite layers are determined.     

Theory of waveguide light scattering in an integrated optical waveguide in the presence of noise

We develop a vector theory of waveguide monochromatic light scattering in an integrated optical waveguide with arbitrary three-dimensional irregularities in the presence of noise. The electrodynamical problem of laser radiation scattering in an irregular waveguide is solved by the method of coupled modes with the help of the theory of perturbations. The approximate solution of the inhomogeneous three-dimensional wave equation is derived by the method of modes and the method of Greens functions. The obtained Greens function is analyzed for the cases of propagating and evanescent modes of an irregular asymmetric optical waveguide. Analytical formulas for the near- and far-zone radiation fields are presented. A preliminary analysis of these formulas is given.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 1, pp. 63–75, January 2005.     

Polarization modulation of light in an optical waveguide under lateral compression

It is shown that a lateral pressure applied to a circular single-mode optical waveguide changes the phase difference between two orthogonally polarized modes and thereby modulates the polarization state of light (elastooptic effect). The efficiency of polarization modulation is characterized by a strain-to-phase difference conversion factor as applied to polarization modes of the fiber. An expression relating the phase difference between the modes and the displacement of squeezing plates is obtained and checked in real experiments and numerically. The efficiency of conversion of lateral pressure to phase difference between the polarization modes is shown to be fairly high, on the order of 10⁴ rad/(μm m).     

A numerical analysis of gain characteristics of Er-doped Al2O3 waveguide amplifiers

The gain characteristics of erbium-doped Al₂O₃ waveguide amplifiers are investigated by solving numerically rate equations with upconversion effects and propagation equations. We obtained the dependence of gain of erbium-doped Al₂O₃ waveguide amplifiers on the waveguide length, erbium concentration and pump power at different pumping wavelengths (980 and 1480 nm). The performance of amplifiers pumping at 1480 and 980 nm are compared. It is shown that 980 nm pumping has higher gain and higher pumping efficiency. The parameters of waveguide amplifiers have been optimized. A optical gain of 43 dB can be achieved for a optimum waveguide length of 8.25 cm and 5.8 × 10²⁰ cm^–3 Er concentration pumped with 100 mW at 980 nm, that is a gain of 5.2 dB/cm.     

Asymmetric coherent photon tunneling filter in an optical waveguide structure

Based on the well-known electron coherent tunneling phenomenon, by simulation, a photonic tunneling filter fabricated in an optical waveguide is proposed. The Bragg grating structure is applied as the photonic barrier. Two photonic barriers confine a coherent resonance cavity or photon-quantum-well. We report an asymmetric-barrier structure with opposite phase. In this configuration, the central tunneling wavelength is exactly the same as the Bragg wavelength of the grating, independent of the photon-quantum-well dimension. The photon-quantum-well length can be adjusted to make the tunneling peak interval fall to a desired spacing. The photon barrier length is responsible for the filter bandwidth. As an application, an asymmetric grating photon tunneling filter with International Telecommunication Union grid is demonstrated.     

Dynamics of an optical signal in a multimode waveguide structure

A mathematical model of linear dynamic distortions of average signal power in a planar optical waveguide stemming from the intermodal coupling and dispersion of waveguide modes caused by macroscopic bends and irregularities of the optical waveguide surface has been developed on the basis of pulse intermodal scattering matrix. It is shown that the elements of this matrix are determined at a waveguide segment whose length greatly exceeds the correlation scale of the field of irregularities but is much smaller than the normalization length of waveguide modes and are described by rectangular functions with a duration proportional to the relative velocity of the corresponding modes. The dependences of the pulse intermodal scattering matrix on the intensities of absorption, Rayleigh scattering, and optical signal scattering from waveguide irregularities have been established. It is shown that, at waveguide lengths exceeding the normalization length, the optical signal shape becomes almost stable and can be expressed in terms of the pulse characteristic of an integrating circuit. It has been established that irregularities of the film in a bent optical waveguide lead not only to additional attenuation but also to enhancement of multimode distortion. A matrix method is proposed for taking into account these distortions, which is based on the effect of equalization (scrambling) of the signal energy over the spectrum of the bent waveguide modes. The model developed was used to process the experimental data on the dynamics of a signal in a weakly guiding multimode polymer optical fiber in order to estimate the parameters of attenuation and irregularities of the waveguide surface.     

Acousto-optic mode coupling of partially coherent light in two-mode optical fibers

An acoustic pulse propagating on a two-mode fiber can act as a beam splitter in a scanning interferometer. When this device is employed in white-light interferometry, the effects of distributed coupling and dispersive interferometer arms need to be considered. A theory suitable for treating acousto-optic interaction of partially coherent light in a moving interaction region was developed. It was found that differential optical dispersion should be negligible and the acoustic pulse length short. Also the coherence time should be short but long compared to the intermodal group delay difference over a pulse length. Experiments with long acoustic pulses were performed, and fairly good agreement with theory was obtained.     

Radiation-induced electrical and optical processes in materials based on Al2O3

The irradiation of dielectrics induces electric charging of microscopic regions in the bulk, which is associated with concentration inhomogeneities in the system of traps and the differences in characteristic diffusion lengths of free electrons and holes that are produced in ion tracks and collision cascades. Experimental data on radiation-induced luminescence (RIL) give evidence of the existence of three states of oxygen vacancies in Al₂O₃: an optically inactive (electrically neutral) vacancy, its excited state (known as F ⁺ center), and a negatively charged vacancy (F center). The formation of negatively charged regions under irradiation increases the intensity of the 415-nm band of F centers of RIL of Al₂O₃ single crystals. In Al₂O₃:Cr³⁺ ceramics, a radiation-induced negative charging of grain boundaries with respect to the bulk of grains takes place, which manifests itself as an increase in the intensity of the 690-nm band of RIL of Cr³⁺ ions, whereas the intensity of this band in Al₂O₃:Cr³⁺ single crystals remains unchanged. Using data on RIL, the local-charge density in grains of Al₂O₃:Cr³⁺ ceramics and the field produced by this charge are estimated.     

冲击压缩下蓝宝石光学性质的晶向效应

本文基于第一性原理计算方法,研究了a向、c向和r向蓝宝石理想晶体和含氧离子空位点缺陷晶体在0-180 GPa冲击压力范围内的光学性质.波长在1550 nm处理想晶体的折射率数据表明,在蓝宝石Corundum、Rh2O3以及CalrO_3相区,其折射率分别表现出强、弱以及强的晶向效应.波长在0-250 nm范围内理想晶体的能量损失谱结果指明,在Corundum和Rh_2O_3结构相区,其晶向效应不明显;在CalrO_3结构相,主峰附近的波段范围内,蓝宝石的能量损失谱有一定的晶向效应:c和r向的主峰强度基本相同,但a向主峰强度明显高于c和r向主峰强度.缺陷晶体数据表明:氧离子空位点缺陷对蓝宝石折射率和能量损失谱晶向效应的影响较微弱.     

Highly efficient, low-threshold monolithic distributed-Bragg-reflector channel waveguide laser in Al2O3:Yb3+

We report the fabrication and performance of a highly efficient, monolithic distributed-Bragg-reflector channel waveguide laser in ytterbium-doped aluminum oxide. The 1?cm long device was fabricated on a standard thermally oxidized silicon substrate and was optically pumped with a 976?nm laser diode. Single-longitudinal-mode and single-polarization operation was achieved at a wavelength of 1021.2?nm. Continuous-wave output powers of up to 47?mW and a launched pump power threshold of 10?mW resulted in a slope efficiency of 67%.     

Electronic structure and optical properties of Nb doped Al2O3 on Si by atomic layer deposition

Nb₂O₅ and Nb doped Al₂O₃ have proved to be good candidates as resistive switch materials or optical materials. In this letter, we focus on the complex electronic structure and optical properties of Nb doped Al₂O₃ to give chemical physical images of the films. With the help of SE, XPS and XPS valence band spectra, the detailed electronic structure with atomic bonding structure and optical properties are given. The band gap of a thin oxide film is determined to be 5.05 eV, and the evolution of VBO and CBO of the film on Si are also discussed.     

Interfacial structure of sub-micron Al2O3 particles in aluminum matrix

The surfaces of ellipsoidal Al₂O₃ particles with average size of 0.15 μm and the interfaces between the Al₂O₃ particles and 1070Al were investigated by transmission electron microscopy (TEM) and high resolution electron microscopy (HREM).The results show that the surfaces of Al₂O₃ particles appear to be polyhedrons consisting of crystal planes with small angle, while every plane of the polyhedrons could be considered as a stepped structure composed of close-packed planes along the close-packed direction. The interfaces of the 0.15 μm Al₂O₃p/1070Al composite bond well, without any interfacial reaction products. It is proposed that there are several kinds of crystallographic orientation relationships between the aluminum matrix and Al₂O₃particles due to the polyhedral structure. In our study, such orientation relationships are found to be {110} _Al ||{1100} _Al2O3 and ?110? _Al ||?1126? _Al2O3 .     

Comparison of optical properties of Cu-Al2O3 and Ag-Al2O3 nano-array composite structure

Cu-Al2O3 (Ag-Al2O3) nano-array composite structures were obtained by alternating current (AC) electrodeposition Cu (Ag) into the pores of anodic alumina.     

The probabilities of optical transitions in an Al2O3 crystal in the 9–30 eV range

The spectra of elementary oscillators of optical transitions in corundum in the region of 8–30 eV are determined for the first time. The parameters of the oscillators are calculated using experimental reflection spectra taken from four different papers. The main features of the spectra are established.     

纳米集成光路中的光源、光波导和光增强

使用近场光学显微术(scanning near-field optical microscopy, SNOM)研究了ZnO亚微米线端面出射性质,不同空间形貌Ⅱ-Ⅵ族半导体荧光器件光波导特性,二维光子晶体、准晶光子晶体对LED的出射增强作用以及表面等离激元(surface plasmon polariton, SPP)与半导体纳米荧光器件的相互作用,对纳米集成光路中的光源、光波导、光增强三个重要问题做了实验和理论上的分析.研究发现半导体微纳米线端面出射光束的质量与样品的直径有密切关系.通过合理地设计其直径和 关键词： 纳米集成光路 扫描近场光学显微术 光波导 光增强     

纳米集成光路中的光源、光波导和光增强

使用近场光学显微术(scanning near-field optical microscopy, SNOM)研究了ZnO亚微米线端面出射性质，不同空间形貌Ⅱ-Ⅵ族半导体荧光器件光波导特性，二维光子晶体、准晶光子晶体对LED的出射增强作用以及表面等离激元(surface plasmon polariton, SPP)与半导体纳米荧光器件的相互作用，对纳米集成光路中的光源、光波导、光增强三个重要问题做了实验和理论上的分析.研究发现半导体微纳米线端面出射光束的质量与样品的直径有密切关系.通过合理地设计其直径和     

High-pressure optical studies on R-line fluorescence lifetime in Al2O3:V2+

The effect of high hydrostatic pressure (up to 10.3?GPa) at room temperature on fluorescence lifetime τ for R line (²E→⁴A₂ transition) in ruby Al₂O₃:V²⁺ was studied. The performed studies show the linear increase of τ with increasing pressure. At 10.3?GPa, τ is about 1.36 times higher than at ambient pressure. The obtained trend was explained by a model which considered the effect of pressure on τ through an induced change of line position, inter-ionic distance, compressibility, and molecular polarizability. A good agreement between the calculated and experimental values for τ was obtained.     

Optical properties of Co/Al2O3 nano-array composite structure

Co/Al₂O₃ nano-array composite structure assemblies with Co grown in the pores of an anodic alumina membrane (AAM) were obtained by alternating current electrodeposition. X-ray diffraction pattern results show that a mixture of face-centred cubic and hexagonal-close-packed structures, with a preferred (100) direction, co-exists in the Co nanowires. The transmission electron microscopy image reveals that the nanowires are both very regular and uniform, with an average diameter of about 20 nm. The transmission ratio of Co/Al₂O₃ composite in the near-IR and mid-IR wavebands decreases with the increasing of the electrodeposition time, while it rises with the increasing of the pore-widening time. The Co/Al₂O₃ composite has good polarization in the near-IR waveband, and its extinction ratio increases significantly when extending the electrodeposition time. With the expanding of pores in the AAM, the extinction ratio first decreases and then rises. PACS 78.67.-n; 81.05.-t; 81.05.Rm; 81.40.Tv; 82.80.Fk