Optical inspection and characterization of microoptics using confocal microscopy

With the growing demand for microoptics in different areas the importance of the characterization increases. Methods for a fast defect detection in microlens arrays are developed. We present a technique where the confocal principle is applied for determining the variation and the absolute value of the focal length. Additionally, using a self–filtering method the deviation of the periodic structure of microlens arrays is investigated theoretically and experimentally. Point-like defects as well as aberrations have been detected. The introduced methods allow the fast, parallel characterization of microlens arrays.     

Imprinting by hot embossing in polymer substrates using a template of silica glass surface-structured by the ablation of LIBWE method

Laser-induced backside wet etching (LIBWE) of silica glass plates was performed to fabricate an imprinting template for hot embossing in polymer substrates such as polystyrene and silicone resin. Well-defined inverse surface-micropatterns of gratings and grid arrays on the substrates were produced by the hot embossing using a surface-structured silica glass as the template. These results indicate that the LIBWE method allows us to generate robust glass molding tools that exhibit the inverse shapes of the intended microstructures. PACS 52.38.Mf; 68.47.Mn; 81.05.Kf; 81.05.Lg; 83.50.Uv     

Comparative research on the optical properties of three surface patterning ZnO ordered arrays

We fabricate three surface patterning zinc oxide(ZnO) ordered arrays on glass substrates by using nanosphere lithography technique and dc magnetron sputtering technique. The crescent, tube and honeycomb surface morphologies of the samples are observed by scanning electron microscopy. The transmittance, fluorescence and confocal Raman spectra of the sample are measured. Obviously, when the angle between the plume and the substrate is 90?, the honeycomb arrays have a better transmission. Additionally, the PL intensity of honeycomb arrays is superior. With the increasing of the angle between the substrate and the sputtering plume, the fluorescence peak shows blue shift. The Raman peak located at438 cm-1belongs to ZnO E2(high) mode, which corresponds to the characteristic band of the hexagonal wurtzite phase.The tube arrays have the best Raman spectrum intensity.     

Sol–gel concave micro-lens arrays fabricated by combining the replicated PDMS soft mold with UV-cured imprint process

Photosensitive TiO₂/organically modified silane organic–inorganic hybrid thin films were synthesized by combining a low-temperature sol–gel process with a spin-coating method. Optical transmittance properties and the photochemical activities of the planar hybrid films were characterized by UV–Visible spectroscopy and Fourier transform infrared spectroscopy. Advantages for fabrication of the concave micro-lens arrays (MLAs) based on the photosensitive hybrid films were demonstrated by using the replicated polydimethylsiloxane (PDMS) soft mold as the imprint mold and a UV soft imprint technique. Morphological and surface profile properties of the master, the PDMS soft molds and the as-fabricated sol–gel concave MLAs were observed by scanning electron microscopy and laser confocal scanning microscopy. Contact angles of water on the PDMS soft molds baked at different temperatures were studied. Optical imaging properties of the as-fabricated concave MLAs were confirmed by a self-made optical test system. Results indicate that the as-prepared photo-patternable hybrid materials have great applicability for the fabrication of photonic components, thus providing an effective method to fabricate concave MLAs based on the as-synthesized hybrid films by combining the UV-cured imprint technique with the replicated PDMS soft mold, which has advantages of simplicity, cost-effective and mass production and potential application in industry production.     

Nanoscale metal pillar arrays on elastomeric substrates for surface-enhanced Raman spectroscopy platform

The nanostructures found in nature sometimes have elaborate, three-dimensional structures that consist of soft and flexible constituents, and which exhibit diverse mechanical and optical functions. Here, we introduce a facile, low-cost and scalable nanofabrication approach based on a hot embossing process that can replicate sub-micron to nanoscale features on elastomeric substrates. We have further developed this technique to achieve polymer/metal heterostructure nanopillar arrays via conformal coating of Au films on polymeric templates. Each nanopillar displays a smooth surface and a constant diameter along the vertical direction. Raman spectroscopy studies revealed that the metallic nanostructures decorated with methylene blue exhibited a dominant Raman peak at 1624 cm⁻¹ that was enhanced more than 3000 times and seven times relative to bare planar Si and Au-coated planar polystyrene substrates, respectively. These results indicate that our nanopillar array can be exploited as a flexible, large area platform for surface-enhanced Raman spectroscopy.     

Confocal diffraction phase microscopy of live cells

We present a new quantitative phase microscopy technique, confocal diffraction phase microscopy, which provides quantitative phase measurements from localized sites on a sample with high sensitivity. The technique combines common-path interferometry with confocal microscopy in a transmission geometry. The capability of the technique for static imaging is demonstrated by imaging polystyrene microspheres and live HT29 cells, while dynamic imaging is demonstrated by quantifying the nanometer scale fluctuations of red blood cell membranes.     

Geometrical characterization techniques for microlens made by thermal reflow of photoresist cylinder

Microlens characterization is a prerequisite for improving fabrication process, and for satisfying the end user needs. In this paper we explore techniques to characterize geometrical properties of microlens made by thermal reflow: viz. microlens profile; radius of curvature; microlens height; contact angle and focal length. The geometrical characterization is done using techniques such as contact profilometry, scanning electron microscopy (SEM), optical microscopy, white light confocal microscopy and fluorescence confocal microscopy. All the above techniques are studied and compared, keeping in mind the characterization requirements of polymer microlens made by thermal reflow technique.     

Deconvolution of local surface response from topography in nanometer profilometry with a dual-scan method

In profilometric measurements, by scanning the sample twice with a fixed vertical offset, one can separate the signal that comes from surface heterogeneity from the topographic signal. Using differential confocal microscopy, a newly developed open-loop nanometer profilometric technique, we demonstrated this dual-scan method on composite samples and obtained 10-nm depth resolution. This technique can also be applied to other profilometric techniques such as atomic force microscopy and scanning tunneling microscopy.     

One-step synthesis of CdTe branched nanowires and nanorod arrays

Single crystalline CdTe branched nanowires and well-aligned nanorod arrays were simultaneously synthesized by a simple chemical vapor deposition (CVD) technique. X-ray diffraction (XRD), scanning electronic microscopy (SEM), transmission electronic microscopy (TEM) and selected area electronic diffraction (SAED) were used to study the crystalline structure, composition and morphology of different samples. Vapor-liquid-solid (VLS) and vapor-solid (VS) processes were proposed for the formation of the CdTe branched nanowires and nanorod arrays, respectively. As-grown CdTe nanorod arrays show a strong red emission band centered at about 620 nm, which can be well fitted by two Gaussian curves centered at 610 nm and 635 nm, respectively.     

Improvement of confocal microscope performance by shaped annular beam and heterodyne confocal techniques

In order to further improve the performance of a confocal microscope (CM) used for measurement of surface profiles and 3D microstructures, a shaped annular beam heterodyne confocal measurement method based on annular pupil filter technique and reflection confocal microscopy, is proposed to expand the measurement range and to improve the defocused property of CM. The approach proposed uses a confocal dual-receiving light path arrangement and a heterodyne subtraction of two signals received from detectors with axial offset to enable CM to be used for bipolar absolute measurement and to improve the defocused property of CM, and it uses the annular pupil filter technique to produce a binary optical shaped annular beam, which expands the measurement range by expanding the full-width at half-maximum of intensity curve received from two detectors in a heterodyne confocal microscopy system. Theoretical analyses and experimental results indicate that a shaped annular beam heterodyne microscope has a measurement range expanded from 4 to 14 μm, achieved an axial resolution of 2 nm and improved the defocused property, when ε=0.5 and NA=0.65. It can be therefore concluded that the shaped annular beam heterodyne confocal measuring method proposed is a new approach to ultraprecision measurement of surface profiles and 3D microstructures.     

Investigation of the Doughnut Effect in Cy3-Labeled Protein Microarrays using Scanning Near-Field Optical Microscope

We demonstrate the fluorescence mapping of protein microarrays by the technique of scanning near-field optical microscopy (SNOM) and confocal microscopy. Micron sized spots (300 μm) of human Immunoglobulin G (hIgG) protein with and without a Cy3 dye labeling have been fabricated on glass substrates by an immobilization method which makes use of calixcrown derivatives termed Prolinker. We have also tried to probe into the well-known “doughnut effect” observed in fluorescence images of proteins using the SNOM technique. The topographic and fluorescence SNOM images revealed that the number of proteins at the boundary of the spot were more than at the center in the case of the microarray spot which showed brighter luminescence at the edge than at the center in the confocal image.     

Bi2Te3/Sb超晶格纳米线的外延生长和热电测量

通过脉冲电沉积,外延生长出小单元长度的Bi₂Te₃/Sb超晶格纳米线.借助哈曼方法,测量了超晶格纳米线阵列的热电性能,330 K时的ZT值可达0.15.研究了Bi₂Te₃/Sb超晶格纳米线阵列器件的制冷或者加热能力,发现器件的上下表面的最大温差可以达到6.6 K.     

Pulsed-laser deposition and characterization of ZnO nanowires with regular lateral arrangement

We report on the high-pressure pulsed-laser deposition growth of periodic arrays of free-standing single zinc oxide nanowires with uniform hexagonal arrangement and cross-section with thickness of less than 100 nm. In order to achieve the wire alignment, we prepared an ordered array of catalytic gold seed particles by a nanosphere lithography mask transfer technique using monodisperse spherical polystyrol nanoparticles. These templates were investigated by scanning electron microscopy and atomic force microscopy prior to nanowire growth. X-ray diffraction revealed the epitaxial relationships between the nanostructures and the a-plane sapphire substrate and excellent crystal quality. The optical properties of the ZnO nanowire arrays were measured by cathodoluminescence. PACS 61.82.Rx; 81.05.-t; 81.05.Dz; 81.10.-h     

Diameter-dependent electrical transport properties of bismuth nanowire arrays

Single-crystalline bismuth nanowire arrays with different diameters were fabricated within porous anodic alumina membranes with the same pore size using the pulsed electro-deposition technique. X-ray diffraction measurements show that the as-synthesized nanowires have a highly preferential orientation. Scanning electron microscopy, transmission electron microscopy and high-resolution transmission electron microscopy analyses indicate that bismuth nanowire arrays are high filling, ordered and single-crystalline. Electrical resistance measurements show that the bismuth nanowires have a metal-semiconductor transition when the diameters decrease from 90 to 50 nm, and the resistance behaviors are explained on the basis of the quantum confinement effect and Matthiessen’s rule.     

Hot embossing of PTFE: Towards superhydrophobic surfaces

Three types of reusable stamps with features in the form of 2D arrays of pits having lateral dimensions in the range of 2-80 μm and heights of 1.5-15 μm were successfully employed for the hot embossing of PTFE at temperatures up to 50 °C above the glass transition temperature of PTFE amorphous phase. Due to the softening of PTFE at the temperatures used in this study, we were able to decrease imprint pressure significantly when comparing with the imprint conditions reported by other authors. Impact of the imprint temperature, pressure and time on the fidelity of pattern transfer as well as on water repellency was tested. The best results of embossing were achieved by applying pressure of 10 kg/cm² for 2 min at 170 °C. In this case, flattening of a natural PTFE roughness and pretty accurate deep replicas of the stamp patterns were observable on the whole imprinted area. Improvement in water repellency was largest for the samples imprinted by Ni stamp patterned with a 2D array of 2 μm square pits spaced by the same dimension and having a depth of 1.5 μm. Cassie-Baxter wetting regime was observed for the deepest imprints with water contact angles up to the superhydrophobic limit.     

Mercury in archeological hair samples from Xiongnu burials (Noin‐Ula,Mongolia): SR XRF and CXRM analysis

A technique has been developed for determining mercury content in the concentration range of 1–1000 μg/g in hair samples by X‐ray fluorescence analysis using synchrotron radiation (synchrotron radiation X‐ray fluorescence, Siberian Synchrotron and Terahertz Radiation Center, Budker Institute of Nuclear Physics SB RAS). The mercury content was identified in archeological hair samples from an ancient burial of Xiongnu nobility (Mongolia, mound 22, 1^st century BC–1^st century AD); the content values were elevated (up to 1100 μg/g) in all the samples (n = 41). An X‐ray microanalysis using polycapillary lenses in a confocal scheme (confocal X‐ray microscopy station) was developed at the Synchrotron radiation X‐ray fluorescence to establish mercury distribution in a cross section of hair shaft with a spatial resolution of 5 μm. The findings of the study make it possible to assume exogenous income of mercury (from the burial environment) to the hair.     

横向面积分割法及其在二维/三维模压全息图中的应用

本文提出制造二维/三维模压全息图(又称分层模压全息图)的一种新方法——横向面积分割法,详细介绍了基本原理,设计思想和计算公式.此外,还提出了应用色序双循环或多循环技术增大垂直方向视角、应用定向散斑屏增大水平方向视角的新方法.成功地制造了质量满意的二维/三维模压全息图.     

Cross-talk reduction in confocal images of dual fluorescence labelled cell spheroids.

Dual fluorescence labelling is an advanced method to separate two individual specimens in a biological system using confocal microscopy. An inherent problem of this method is fluorescence channel cross-talk, which causes problems for the exact spatial determination and separation of the specimens. Using a parallel fluorescence detection and an image processing technique, based on an image subtraction method, we have developed a very straight forward method for correcting the dual channel fluorescence images. We successfully applied this method to a 3-dimensional cancer spheroid invasion assay and controlled the cross-talk compensation efficiency by a quality parameter.     

Simultaneous process of embossing and poling at elevated temperatures: a simple technique for nonlinear grating formation in polymer films

A simple technique for fabrication of nonlinear gratings in polymer films, based on simultaneous embossing and poling, is proposed and demonstrated. A master grating consisting of a metal electrode with a dielectric die was fabricated and used for repeated embossing of the grating structures into nonlinear optical polymers at elevated temperatures. At the same time, we applied high voltage to the polymer films to induce second-order nonlinearity. The grating profile and the nonlinearity were estimated, as well as the mass productivity of nonlinear gratings.