掺Ce,Fe系列LiNbO3晶体光折变效应光存储特性

研究了系列Ce：Fe掺杂以及不同后处理态(生长态、还原态和氧化态)铌酸锂晶体的透过率光谱和光折变全息存储特性。实验结果表明单掺Ce铌酸锂晶体具有较好的图像存储质量和较宽的透过率光谱范围,二波耦合增益相对较低;高掺杂铌酸锂样品的透过率光谱范围较窄,光折变二波耦合增益较低。晶体的后处理对铌酸锂样品的光折变特性影响明显,双掺Ce:Fe还原态铌酸锂晶体具有较高的二波耦合增益;氧化态样品具有较大的透过率光谱范围;还原态样品具有较大的光折变二波耦合增益特性。实验结果还表明在同种样品中难于同时获得大的二波耦合增益和图像存储质量。     

Ion beam induced modifications in nitroso substituted polyaniline: Spectral and electrical studies

The effects of ion beam irradiation on optical, chemical and electrical properties of nitroso substituted polyaniline, polynitrosoaniline (N-PANI) have been investigated. N-PANI was irradiated with 100 MeV ²⁸Si ions at different ion-fluences. The pristine and irradiated polymer samples were characterized by FT-IR, UV–visible spectroscopic techniques. The electrical conductivity studies were conducted on polymer samples. A significant change in optical band gap and room temperature electrical conductivity was observed in polymer samples after irradiation. The solubility of the polymer samples has also been tested in 1-methyl-2-pyrrolidone (NMP).     

Quasi-one-dimensional photonic lattices and superlattices in lithium niobate: Linear and nonlinear discrete diffraction of light

The effects of linear and nonlinear light propagation in quasi-one-dimensional systems of coupled optical waveguides (photonic lattices and superlattices) obtained by projection optical induction in photorefractive lithium niobate samples have been experimentally studied and numerically simulated.     

How to measure the optical thickness of scattering particles from the phase delay of scattered waves: application to turbid samples

We present a method based on the optical theorem that yields absolute, calibration free estimates of the optical thickness of scattering particles. The thickness is determined from the phase delay of the zero angle scattered wave. It uses a heterodyne scattering scheme operating in the Raman-Nath approximation. The phase is determined by the position of Talbot-like modulations in the two dimensional power spectrum S(qx, qy) of the transmitted beam intensity distribution. The method is quite insensitive to multiple scattering. It is successfully tested to provide quantitative verification of the optical theorem. Exploratory tests on soft matter samples are reported to suggest its wide applicability to turbid samples.     

Optical properties investigation of [nc-Si:SiO2/SiO2]30 periodic multilayer films

The optical properties of 30-layer [nc-Si:SiO₂/SiO₂]₃₀ periodic films have been studied. The films were prepared by alternately evaporating SiO and SiO₂ onto Si(100) substrates, followed by annealing at 1100?^°C. Spectroscopic ellipsometry spectrum analysis was used to determine the optical constants of the samples via the Forouhi?CBloomer model. The optical bandgap of a single periodic film is calculated. The photoluminescence (PL) spectra of three samples with different thicknesses clearly show that there are two physical origins of the PL process.     

近红外波段锑基铋掺杂薄膜厚度对光学常数与光学带隙的影响

采用磁控溅射法制备了不同厚度的锑基铋掺杂薄膜,用X射线衍射(XRD)和透射电子显微镜(TEM)研究了薄膜结构随厚度的变化。利用椭圆偏振法测定了样品薄膜在近红外波段的光学常数与光学带隙,研究了膜厚对样品薄膜光学常数和光学带隙的影响。结果表明,膜厚从7 nm增加至100 nm时,其结构由非晶态转变为晶态。在950～2200 nm波段,不同厚度薄膜样品的折射率在4.6～8.9范围,消光系数在0.6～5.8范围,光学带隙在0.32～0.16 eV范围。随着膜厚的增加,薄膜的折射率和光学带隙减小,而消光系数升高;光学常数在膜厚50 nm时存在临界值,其原因是临界值前后薄膜微观结构变化不同。     

Mapping local retardance in birefringent samples using polarization sensitive optical coherence tomography

We proposed a method to extract depth-resolved local retardance in birefringent samples from conventional polarization-sensitive optical coherence tomography (PSOCT) that uses one circularly polarized incident light. Despite the wide use of such PSOCT systems in characterizing birefringent samples, the measured cumulative retardance does not represent the true cumulative retardance when optical axis varies with depth. A Jones calculus based algorithm was designed to derive the local depth-resolved retardance from conventional cumulative PSOCT results. The algorithm was tested in samples with homogeneous optical axis as well as samples with depth-dependent optical axis.     

Generalised phase contrast: microscopy,manipulation and more

Generalised phase contrast (GPC) not only leads to more accurate phase imaging beyond thin biological samples, but serves as an enabling framework in developing tools over a wide spectrum of contemporary applications in optics and photonics, including optical trapping and micromanipulation, optical phase cryptography, light-efficient image projection and parallel laser beam shaping for optical landscapes. In this review, we discuss the fundamental ideas behind generalised phase contrast and present a survey of its exciting applications.     

When optical microscopy meets all-optical analog computing: A brief review

As a revolutionary observation tool in life science, biomedical, and material science, optical microscopy allows imaging of samples with high spatial resolution and a wide field of view. However, conventional microscopy methods are limited to single imaging and cannot accomplish real-time image processing. The edge detection, image enhancement and phase visualization schemes have attracted great interest with the rapid development of optical analog computing. The two main physical mechanisms that enable optical analog computing originate from two geometric phases: the spin-redirection Rytov-Vlasimirskii-Berry (RVB) phase and the Pancharatnam-Berry (PB) phase. Here, we review the basic principles and recent research progress of the RVB phase and PB phase based optical differentiators. Then we focus on the innovative and emerging applications of optical analog computing in microscopic imaging. Optical analog computing is accelerating the transformation of information processing from classical imaging to quantum techniques. Its intersection with optical microscopy opens opportunities for the development of versatile and compact optical microscopy systems.     

Observation of the Fermi-edge singularity in n-doped single asymmetric quantum wells: the influence of residual acceptors

The investigation of the evolution of the photoluminescence spectra, in single asymmetric quantum wells (SAQWs), from a typical emission spectrum to a Fermi-edge singularity, is carried out as a function of both the optical excitation intensity and the temperature. The three samples used here are n-doped, low carrier density (below 5×10¹¹ cm⁻²), GaAs/Al_0.35Ga_0.65As SAQWs grown by molecular beam epitaxy. The strong collective recombination of electrons with different k states up to the Fermi wave vector as well as the optical signature of the Fermi-edge singularity is observed in two samples containing residual acceptors inside the GaAs SAQW. In contrast, a third sample containing no experimental evidence of residual acceptors in the GaAs SAQW shows no optical signature of the Fermi-edge singularity.     

高能Ar离子辐照PET引起的光吸收变化研究

采用紫外–可见光吸收技术分析和研究了35MeV/uAr离子辐照聚酯膜引起的光吸收改性.结果表明,Ar离子轰击聚酯膜时引起了碳键的共轭体系形成,从而导致了紫外–可见光区域中光吸收明显增加,光吸收增加的幅度依赖于离子的照射剂量、离子在样品中的平均电子能量损失以及光的波长,剂量越高,电子能损越大,光吸收增幅越大;而光的波长越长,光吸收的增加则越不明显.利用测量到的光吸收曲线,同时还定量地研究了各种辐照条件下聚酯膜的光能隙和碳原子团的尺寸.     

不同粉料制备Nd∶(Y0.9La0.1)2O3透明陶瓷及其性能

分别采用液相法和固相法制备的纳米粉,制得透明性良好的Nd∶(Y0.9La0.1)2O3透明陶瓷,并测试了各样品的结构,光谱及光学性能.结果表明:该陶瓷具有相同的光谱性能|但液相法复合纳米粉制备的透明陶瓷光学性能优于固相反应法制备的透明陶瓷|固相反应法制备的透明陶瓷,由于有部分La2O3分布不均,易导致晶粒生长不均匀和残留少量气孔|长时间球磨混料,也不利于样品性能的提高.     

利用光镊技术演示光的自旋角动量

阐述了光与物体相互作用时自旋角动量的传递与扭力矩原理.基于光镊光致旋转原理,利用能够悬浮单个粒子的光镊技术并采用具有双折射特性的CaCO3晶体粒子,设计了微粒在不同偏振光场中的旋转运动实验内容,研究光与双折射晶体粒子相互作用产生的光致旋转效应,观察和测量由自旋角动量引起粒子的扭转力矩的大小、方向以及旋转速度等力学效应.     

Impact of composition ratio on the structure and optical properties of (1-x)MnFe2O4/(x)ZnMn2O4 nanocomposite

($1-x$)MnFe$_{2}$O$_{4}$ (MFO)/$x$ZnMn$_{2}$O$_{4}$ (ZMO) ($x=0$, 0.2, 0.5, 0.8, and 1.0) nanocomposite samples were prepared using co-precipitation procedure. The phase percentage, cell parameters, and crystallite size of MFO and ZMO phases in each nanocomposite sample were calculated using Rietveld refinement procedure. The x-ray diffraction (XRD) analysis and Fourier-transform infrared spectroscopy techniques established the variation in the lattice parameters of each phase are due to permutation of all cations among the octahedral and tetrahedral sites of MFO and ZMO. The different oxidation states of different ions in all samples were determined using x-ray photoelectron spectroscopy (XPS) technique. The variation in absorbance of the nanocomposite samples with composition parameter ($x$) is dependent on the wavelength region. The optical bandgap of the nanocomposite samples is decreased as the content of ZMO phase increased. The effect of alloying on the refractive index, extinction coefficient, dielectric constant, optical conductivity, and the nonlinear optical behaviors of all samples were studied in detail. The nanocomposite sample $x=0.5$ disclosed upgraded optical parameters with the highest refractive index, optical conductivity, and PL intensity, which nominate it to be functional in various application fields.     

Thin ferroelectric films: Preparation and prospects of integration

The properties of (Ba,Sr)TiO₃ and BiFeO₃ thin films and related nanostructures have been considered. The films have been prepared by rf sputtering in an oxygen atmosphere at an elevated pressure, and the nanostructures have been produced using focused ion-beam etching. The electric field has been applied across a planar interdigital structure of electrodes. The structure, dielectric, electro-optical, and nonlinear optical properties of the prepared samples have been investigated over wide ranges of thicknesses and electric field frequencies. The high efficiency of the planar switching and its influence on the optical properties of the produced structures have been demonstrated. The nanostructuring makes it possible to change the dielectric and optical properties of the materials under investigation, thus increasing the range of switching of functional parameters.     

Comment on: “growth,spectroscopic studies,and third order non-linear optical analysis of an organic dicarboxylic acid based single crystal: urea oxalic acid” [Chin. J. Phys., 56 (2018) 1449–1466]

In a recent paper [Chin. J. Phys., 56 (2018) 1449–1466] Jeeva et al. have studied the physical properties of the Urea Oxalic acid (UOA) Crystals. The authors have used a wrong approach to calculate the reflectance spectra of the samples and obtained values of this parameter are incorrect. Consequently, other reported optical parameters in the commented paper that are calculated based on the reflectance such as refractive index, real and imaginary parts of the optical dielectric constant, optical and electrical conductivity and electrical susceptibility are incorrect.     

Determination of optical properties of tissues

Recent results and used way of tissue optical properties measurements in vitro with laser goniophotometer are presented. The optical properties were obtained on the basis of an indirect technique using solution of the radiative transfer equation, which relate the optical parameters of tissue with the measured parameters of reflected and transmitted radiation. The angular patterns of reflected and transmitted radiation by optically thick saline-soaked samples of tumor tissue, namely, mammary fibroadenoma, were measured at the wavelength of 0.63 μm, and the measurement data were inverted to find the absorption and extinction coefficients and the parameters of the phase function of these tumor samples. Obtained values of the optical parameters have been found to be of the same order of magnitude as the earlier reported data for similar tumor samples.     

Poly(N-vinyl carbazole)-grafted multiwalled carbon nanotubes: Synthesis via direct free radical reaction and optical limiting properties

In this work, samples of poly(N-vinyl carbazole) (PVK)-grafted multiwalled carbon nanotubes (MWCNTs) were synthesized via free radical reaction. The ready-made PVK was allowed to react directly with MWCNTs at 70 °C in the presence of azo-bis-isobutyronitrile (AIBN). The purified deep grey products, which can dissolve in common organic solvents such as chloroform and 1,2-dichlorobenzene (DCB), were then characterized by FTIR spectra, TEM, TGA, elemental analysis, XPS, UV-vis spectra and Raman spectra. It was confirmed that PVK chains were grafted onto the surface of the carbon nanotubes (CNTs). The optical limiting properties of these PVK-grafted MWCNTs samples were investigated by open-aperture z-scan method. All of the samples of PVK-modified carbon nanotubes in chloroform showed optical limiting behavior better than that of C₆₀ in toluene.     

Optical and nonlinear optical properties of copper nanocomposite glasses annealed near the glass softening temperature

Copper nanocomposite glasses have been prepared by the ion-exchange method, and annealed at different temperatures up to and above the glass softening temperature. The absorption spectra, fluorescence spectra, and nonlinear optical transmission of the samples at 532 nm for nanosecond laser pulses, have been investigated. The optical and nonlinear optical properties of the glasses are found to be distinctly different below and above the glass softening temperature. For instance, thermal annealing up to the glass softening temperature makes the samples behave like saturable absorbers, while annealing at higher temperatures makes them behave like optical limiters. Such flexibility in controlling the optical nonlinearity in these materials makes them potential candidates for photonic applications.     

Study on the optical limiting properties of the mixed liquid of carbon black suspensions and green tea solution by multi-pulse laser

The optical limiting properties of the mixed liquid of carbon black suspensions (CBS) and green tea solution were studied by using an 8 ns laser pulse at 532\,nm. The optical limiting effects of the CBS and mixed liquid have been compared between 5 and 10\,Hz repetition frequencies with nanosecond laser pulse. The experimental results indicate that the optical limiting threshold of the sample with the incidence laser at 10\,Hz repetition frequency is lower than at 5\,Hz repetition frequency. The possible reasons for the influence of the repetition frequency on the samples are discussed. And by observing the optical radiant distributions when the laser pulse passing through different samples, a possible mechanism for the observed effects is suggested. At the same time, the result shows that the optical limiting of CBS is the dominant factor to optical limiting of the mixed liquid.