Field enhancement analysis of an apertureless near field scanning optical microscope probe with finite element method

Plasmonic field enhancement in a fully coated dielectric near field scanning optical microscope (NSOM)probe under radial polarization illumination is analyzed using an axially symmetric three-dimensional (3D)finite element method (FEM) model. The enhancement factor strongly depends on the illumination spot size, taper angle of the probe, and the metal film thickness. The tolerance of the alignment angle is investigated. Probe designs with different metal coatings and their enhancement performance are studied as well. The nanometric spot size at the tip apex and high field enhancement of the apertureless NSOM probe have important potential application in semiconductor metrology.     

Field-enhanced scanning optical microscope

We present experimental results of an imaging technique that uses as a local probe the optical field enhanced at the junction of a scanning tunneling microscope illuminated by a p-polarized laser beam. Images of highly oriented pyrolithic graphite, recorded at a constant height mode, show a lateral optical resolution of as much as 10 nm. Approach curves exhibit sensitivity on a subnanometer scale of the optical signal to the tip-sample distance, yielding the ultrahigh vertical resolution reached in the images.     

Second-harmonic imaging in the scanning optical microscope

A scanning optical microscope in which an image is produced from the generation of optical second harmonics within the specimen has been constructed. Pictures have been obtained from various crystals which show high contrast levels and detail not visible with the conventional microscope.     

Few-electron quantum dot fabricated with layered scanning force microscope lithography

Few-electron quantum dots with integrated charge read-out have been fabricated by layered local anodic oxidation of a Ga[Al]As heterostructure and a thin Titanium top gate. The additional set of gates provided by the metallic film is used to tune the quantum dots into the few-electron regime. Current through the quantum dots and the quantum dot charge have been simultaneously measured for electron numbers varying between zero and two. The singlet–triplet splitting varies in two different samples between 0.5 and 1.5 meV. The Zeeman splitting of the first conductance resonance is observed in parallel magnetic field. The high tunability and straightforward implementation of these structures are promising for future nanostructure design.     

KRIOSBOM101 low-temperature scanning near-field optical microscope

An optical scanning near-field microscope was developed. A cryostat for obtaining low temperatures in the range of 1.8–300 K was designed. The microscope control unit and software were advanced taking into account the temperature range. A room-temperature measurement technique was refined on test aluminum gratings on glass with a period of 4 μm. An optimum size of the scan field, which makes it possible to neglect piezoceramics nonlinearities, was determined.     

A novel phase-sensitive scanning near-field optical microscope

Phase is one of the most important parameters of electromagnetic waves. It is the phase distribution that determines the propagation, reflection, refraction, focusing, divergence, and coupling features of light, and further affects the intensity distribution. In recent years, the designs of surface plasmon polariton(SPP) devices have mostly been based on the phase modulation and manipulation. Here we demonstrate a phase sensitive multi-parameter heterodyne scanning near-field optical microscope(SNOM) with an aperture probe in the visible range, with which the near field optical phase and amplitude distributions can be simultaneously obtained. A novel architecture combining a spatial optical path and a fiber optical path is employed for stability and flexibility. Two kinds of typical nano-photonic devices are tested with the system. With the phase-sensitive SNOM, the phase and amplitude distributions of any nano-optical field and localized field generated with any SPP nano-structures and irregular phase modulation surfaces can be investigated. The phase distribution and the interference pattern will help us to gain a better understanding of how light interacts with SPP structures and how SPP waves generate, localize, convert, and propagate on an SPP surface. This will be a significant guidance on SPP nano-structure design and optimization.     

Electrostatic micromachine scanning mirror for optical coherence tomography

Compact electrostatic micromirror structures for use in the scanning arm of an optical coherence tomography (OCT) system are described. These devices consist of millimeter-scale mirrors resting upon micrometer-scale polyimide hinges that are tilted by a linear micromachine actuator, the integrated force array (IFA). The IFA is a network of deformable capacitor cells that electrostatically contract with an applied voltage. The support structures, hinges, and actuators are fabricated by photolithography from polyimide-upon-silicon wafers. These devices were inserted into the scanning arm of an experimental OCT imaging system to produce in vitro and in vivo images at frame rates of 4 to 8 Hz.     

Optical fibre profiling using a scanning optical microscope

A scanning optical microscope is used to measure directly the refractive-index profile of an optical fibre. The effects of illuminating the fibre end with a highly convergent beam of light are considered.     

Sensitivity analysis of scanning near-field optical microscope probe

In this paper, we study the dynamic modes of a scanning near-field optical microscope (SNOM) which uses an optical fiber probe; and the sensitivity of flexural and axial vibration modes for the probe were derived and the closed-form expressions were obtained. According to the analysis, as expected each mode has a different sensitivity and the first mode is the most sensitive mode of flexural and axial vibration for the SNOM probe. The sensitivities of both flexural and axial modes are greater for a material surface that is compliant with the cantilever probe. As the contact stiffness increases, the high-order vibration modes are more sensitive than the lower-order modes. Furthermore, the axial contact stiffness has a significant effect on the sensitivity of the SNOM probe, and this should be noted when designing new cantilever probes.     

Use of a scanning near-field optical microscope architecture to study fluorescence and energy transfer near a metal

Fluorescence intensity depends strongly on the distance between the emitting molecule and a metallic interface. We show that a scanning near-field optical microscope (SNOM) is a simple and versatile tool for studying such an effect. The fluorescent molecules are embedded in a layer upon a silica substrate, and metal is coated on the SNOM tip. We present variations of fluorescence intensity versus tip-sample distance from 800 to ~80 nm . A simple model is used to explain the experimental results. The proposed setup could be used to study nonradiative transfer at a nanometric scale. It could also yield to a new type of optical near-field profiler that uses fluorescent signal.     

Local magneto-optical Kerr effect imaging by scanning near-field optical microscope in reflection-mode

<正>A method for local magneto-optical Kerr effect imaging based on a home-made scanning near-field optical microscope working in reflection mode is presented.Shear force detection is carried out by using a symmetric piezoelectric bimorph sensor,which provides an easy way not only for probe-surface distance control but also for imaging.Polarization-preserving fiber probes used as a local optical detector are fabricated with a heating-pulling technique and the probes' polarization properties are measured.Shear force topographic and near-field magneto-optical images of magneto-optical disk taken with the proposed method are shown.     

Gold-bead scanning near-field optical microscope with laser-force position control

We have developed a scanning near-field optical microscope with an optically trapped metallic particle that has a small diameter compared to the wavelength of visible light. In this microscope we employed spot illumination to enhance the intensity of light scattered from a probe particle so we could reduce the diameter of the probe particle to 40nm. We detected slight irregularities of the surface of the cover glass near 10-nm depth. Also, we observed gold colloidal particles on the surface of the cover glass.     

微波模拟近场光学显微镜实验

介绍了近场光学显微镜的基本原理，并利用微波代替可见光模拟了近场光学显微镜实验．     

Near-field optical microscope with a multiheight scanning imaging mode

A near-field scanning optical microscope has been developed to yield optical images with various gap distances between the probe and the sample surface. The microscope uses an apertureless metallic probe, the position of which is controlled by regulation of the tunneling-electron current from the probe to the sample and by computer-generated bias voltage. Experimental results of near-field optical imaging with the developed microscope at different gap distances are shown. Thirteen images at gap distances of 0 to 500nm demonstrate that the near-field image depends strongly on the gap distance. The imaging characteristics of a near-field imaging system are shown with the spatial-frequency spectra of images. Future investigation of the developed microscope is also discussed.     

Micromachining of diamond with a near-field scanning optical microscope

Direct-write laser micromachining of diamond on a submicrometer scale with a near-field scanning optical microscope with an uncoated tapered fiber tip has been demonstrated. Micromachined structures can be imaged in situ immediately after modification of the sample. An early stage of the ablation process, which is believed to be conversion of diamond into graphite, has been visualized.     

Differential amplitude contrast imaging in the scanning optical microscope

A split detector is used in a scanning optical microscope to produce high-quality differential amplitude contrast images. A slight lateral offset in the detector position is shown to introduce information about object height variations to the image. These results are compared with images obtained by electrical differentiation.     

Electroless silver plating for metallization of near-field optical fiber probes

By using mercaptopropyltrimethoxysilane (MPTS) self-assembled monolayers (SAMs), electroless silver plating is developed for the metallization of near-field optical fiber probes.     

Cloaked near-field scanning optical microscope tip for noninvasive near-field imaging

Near-field imaging is a well-established technique in biomedical measurements, since closer to the detail of interest it is possible to resolve subwavelength details otherwise unresolved by regular lenses. A near-field scanning optical microscope (NSOM) tip may indeed overcome the resolution limits of far-field optics, but its proximity inherently perturbs the measurement. Here, we apply the recent concept of a "cloaked sensor" to an NSOM device in collection mode, showing theoretically how a proper plasmonic cover applied to an NSOM tip may drastically improve its overall measurement capabilities.     

激光扫描声学显微镜光学系统的设计

半导体激光器具有半导体和固体器件的许多优点：结构紧凑、效率高、价格便宜、长寿命，在许多方面优于气体激光器，因此在一些测量领域有较好的应用前景。本文基于棱镜对光的一维压缩及新型半导体激光器，对激光扫描声学显微镜的光学系统进行了新的设计，给出了相关数据及具体技术指标，实验证实其光学性能满足要求。整个光学系统具有结构紧凑、可靠性高、使用方便等特点，现已用于激光扫描声学显微镜定型设计。     

Spatially defined silver mirror reaction on a micropatterned aldehyde-terminated self-assembled monolayer

A simple microfabrication technique for silver (Ag) based on spatially defined silver mirror reaction using a photolithographically micropatterned aldehyde (CHO)-terminated self-assembled monolayer (SAM) is proposed. First, both a Si substrate covered with native oxide and a quartz glass plate were exposed to a vapor of triethoxysilylundecanal (TESUD) diluted with absolute toluene for 3 h at 403 K. This vapor phase treatment produced a 1.2-nm-thick TESUD-SAM with a flat, homogeneous surface. Several samples were then photolithographically micropatterned using an excimer lamp radiating 172 nm vacuum ultraviolet light, and subsequently employed as templates for area-selective electroless Ag plating. Optical microscopy, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) confirmed that Ag metal was preferentially deposited on the CHO-terminated regions, resulting in the formation of well-ordered Ag microstructures composed of rectangular 5 μm × 25 μm features. The CHO terminal groups of the TESUD-SAM were found to be effective in reducing Ag ionic species at the solid/liquid interface.