Light Splitting Function of Branched Chains of Microspheres Fabricated by Self-Assembly Process

2012 ◽  
Vol 1392 ◽  
Author(s):  
Tadashi Mitsui ◽  
Yutaka Wakayama ◽  
Tsunenobu Onodera ◽  
Takeru Hayashi ◽  
Naoki Ikeda ◽  
...  
Keyword(s):  
Self Assembly ◽  
Optical Waveguides ◽  
Near Field ◽  
Fdtd Simulation ◽  
Splitting Function ◽  
Assembly Process ◽  
Selective Filter ◽  
Scanning Optical Microscopy ◽  
Branching Chains ◽  
Branched Chains

ABSTRACTUsing a self-assembly process, we fabricated ordered chains of transparent polystyrene microspheres that have 30°- and 60°-branched structures and that act as coupled-resonator optical waveguides (CROWs). We then observed the optical properties of propagation light through the CROWs. The light spectra were directly measured by guide-collection-mode near-field scanning optical microscopy (NSOM) techniques. The spectrum of light propagating to the 60°-branch shows some sharp peaks, which seem to be associated with whispering gallery modes (WGMs). On the other hand, the spectrum of light propagating to the 30°-branch shows rather broad peaks. Moreover, we observed the detailed structures of the CROWs by high-resolution scanning electron microscopy (HR-SEM), and performed a finite-difference time-domain (FDTD) simulation to explain the NSOM spectra. The results suggest that the microspheres’ branching chains themselves have a light-splitting function, which is a kind of wavelength-selective filter.

A molecular yarn: Near-Field optical studies of self-assembled, flexible fluorescent fibers

1996 ◽  
Vol 54 ◽  
pp. 202-203
Author(s):  
D. A. Higgins ◽  
J. Kerimo ◽  
D. A. Vanden Bout ◽  
P. F. Barbara
Keyword(s):  
Thin Films ◽  
Self Assembly ◽  
Liquid Crystalline ◽  
Near Field ◽  
Spectral Characteristics ◽  
Van Der Waals Interactions ◽  
Cross Linking ◽  
Aqueous Mixtures ◽  
Scanning Optical Microscopy ◽  
Gel Forming Ability

The formation of flexible molecular fibers via the solution-phase self-assembly of the pseudoisocyanine dye (PIC) 1,1’-diethyl-2,2’-cyanine and poly(vinyl sulfate) (PVS) is reported. The physical and electronic properties of these fibers spin coated into thin films on fused-quartz substrates are studied by fluorescence and topographic imaging with near-field scanning optical microscopy (NSOM) and also by atomic force microscopy (AFM). The scanned-probe images demonstrate that fibers with lengths in the hundred micron range, widths of hundreds of nanometers, and thicknesses of a few tens of nanometers, are readily formed in aqueous mixtures of PVS and PIC. Unprecedented flexibility in these fibers is exemplified by the formation of numerous curved and looped structures in the spin-coated thin films. A sandwich-like composite structure of alternating anionic PVS and cationic PIC layers is proposed as a model for the assembly of the dye and polymer in these fibers. The alternating layers in this model are held tightly together via the cooperative “cross-linking” of the PVS and PIC layers by electrostatic dye/polymer interactions, and by hydrophobic van der Waals interactions between the PIC molecules. The intermolecular interactions in the PIC layer result in the formation of a liquid-crystalline-like, well-ordered layer of the PIC, which exhibits the spectral characteristics of J-aggregates. The proposed layered structure apparently possess “reactive” surfaces which link individual fibers into a yam-like assembly. This cross-linking effect is supported by the presence of continuous circular fibers and by the gel-forming ability of the solutions from which these fibers are grown.

Simulation of Electromagnetic Field Distribution at a Nanowire Probe for Near Field Scanning Optical Microscopy

2008 ◽  
Author(s):  
Nathan P. Malcolm ◽  
Alex J. Heltzel ◽  
Li Shi ◽  
John R. Howell
Keyword(s):  
Optical Microscopy ◽  
Signal To Noise Ratio ◽  
Near Field ◽  
Three Dimensional ◽  
Field Enhancement ◽  
Fdtd Simulation ◽  
Plasmonic Nanoparticle ◽  
Excitation Laser ◽  
Scanning Optical Microscopy ◽  
Near Field Scanning

This work studies a new design of a near field scanning optical microscopy (NSOM) probe based on a ZnO nanowire sub-wavelength waveguide terminated with a plasmonic gold nanoparticle. Three-dimensional finite difference time domain (FDTD) simulation is used to visualize light guiding in the nanowire and near field coupling between the plasmonic nanoparticle and the substrate. The simulation results reveal local field enhancement at the gap between the nanoparticle and a gold substrate when the nanowire axis is tilted from the substrate normal by a small angle. The enhancement occurs only along the cross section plane that is parallel to the polarization of the excitation laser beam. The regime of field enhancement is much smaller than the diameter of the 100 nm plasmonic particle, making the nanowire probe well suited for NSOM with superior spatial resolution and signal to noise ratio compared to the state of the art.

Near-Field Scanning Optical Microscopy: Single Channel Imaging of Selected Gold Nanoparticles through Two Photon Induced Photoluminescence

2014 ◽  
Vol 938 ◽  
pp. 118-122 ◽  
Author(s):  
Mohammad Kamal Hossain ◽  
Masahiro Kitajima ◽  
Kohei Imura ◽  
Hiromi Okamoto
Keyword(s):  
Gold Nanoparticles ◽  
Optical Microscopy ◽  
Near Field ◽  
Fdtd Simulation ◽  
Local Geometry ◽  
Optical Confinement ◽  
Two Photon ◽  
Em Field ◽  
Scanning Optical Microscopy ◽  
Near Field Scanning

Near-field scanning optical microscopy (NSOM) is known to be a technique of choice to investigate nanometric materials and their properties beyond far-field diffraction limit resulting high spatial, spectral and temporal resolution. Here in this report, a state of art facility, aperture-NSOM was used to probe single nanoparticle, dimer, trimer and small nanoaggregate of gold nanoparticles. Shear force topography and two photon induced photoluminescence (TPI-PL) images captured simultaneously by the system facilitated to clarify the correlation between the local geometry and the emitted photon of TPI-PL. Small gold aggregates including trimer showed strong optical confinement of TPI-PL with reference to that of single gold nanoparticles. It was also evident that the interparticle gap does have a great influence in localized electromagnetic (EM) field mediated optical confinement of TPI-PL. Such observations were also supported by finite different time domain (FDTD) analysis keeping the simulation parameter nearly identical to that of experiment. FDTD simulation demonstrated that incident excitation parallel to the interparticle axis induces strong near-field distribution at the interstitials whereas out of plane excitation modifies such confinement depending on the nanometric geometry of the nanoaggregates. Such an observation is indispensable to understand the localized EM field-mediated optical confinement in surface-enhanced spectroscopy.

Internal Spatial Modes and Local Propagation Properties in Optical Waveguides Measured Using Near-Field Scanning Pptical Microscopy

1999 ◽  
Vol 588 ◽  
Author(s):  
Bennett B Goldberg ◽  
M. Selim Ünlü ◽  
Greg Vander Rhodes
Keyword(s):  
Optical Waveguides ◽  
Near Field ◽  
Rate Of Change ◽  
Modal Shape ◽  
Optical Wave ◽  
Local Propagation ◽  
Spatial Modes ◽  
Dielectric Interfaces ◽  
Scanning Optical Microscopy ◽  
Near Field Scanning

AbstractNear-field scanning optical microscopy has been used to measure the internal spatial modes and local properties controlling optical wave propagation in glass/silica buried waveguides. The period of the observed standing modes provides a direct measure of the effective index, which combined with the measured transverse modal shape and decay constants, determines the values of all spatial components of the wave vector.Typically, small fluctuations in the material properties of structures can prevent proper operation as well as accurate diagnostic device modeling. The NSOM local probe measurements provide a means of detailed characterization, and defects in processing and their affects on performance are readily identified. We have also developed a technique that can obtain information about the locations of remote dielectric interfaces based upon the rate of change in the phase of the standing wave as a function of wavelength. Finally, experimental results addressing the issue of perturbation of the NSOM probe on the measurement of the local field shows a weak but measurable perturbation, and the dependence on aperture and material parameters will be discussed.

Near-field scanning optical microscopy

1986 ◽  
Vol 44 ◽  
pp. 642-643
Author(s):  
E. Betzig ◽  
A. Harootunian ◽  
M. Isaacson ◽  
A. Lewis
Keyword(s):  
Near Field ◽  
Optical Microscope ◽  
Visible Radiation ◽  
Field Methods ◽  
Optical Elements ◽  
Optical Region ◽  
Order Of Magnitude ◽  
Nondestructive Imaging ◽  
Scanning Optical Microscopy ◽  
Near Field Scanning

In general, conventional methods of optical imaging are limited in spatial resolution by either the wavelength of the radiation used or by the aberrations of the optical elements. This is true whether one uses a scanning probe or a fixed beam method. The reason for the wavelength limit of resolution is due to the far field methods of producing or detecting the radiation. If one resorts to restricting our probes to the near field optical region, then the possibility exists of obtaining spatial resolutions more than an order of magnitude smaller than the optical wavelength of the radiation used. In this paper, we will describe the principles underlying such "near field" imaging and present some preliminary results from a near field scanning optical microscope (NS0M) that uses visible radiation and is capable of resolutions comparable to an SEM. The advantage of such a technique is the possibility of completely nondestructive imaging in air at spatial resolutions of about 50nm.

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