Plasmonic nanorod metamaterials exhibit transversal and longitudinal resonance modes. It is found that the resonance intensity of the transversal modes (T-Modes) excited by the p- polarized wave is obviously larger than the intensity for the s- polarized wave at the wavelength of the transversal resonance, and the resonance intensity of the longitudinal modes (L-Modes) excited by the s- polarized wave is clearly larger than the intensity for the p- polarized wave at the longitudinal resonance wavelength, indicating a distinct polarization characteristics, which results from excitation of the different resonance modes of surface plasmons at different wavelengths. Moreover, the polarization behavior in near field regions for the different resonance modes has been demonstrated by the electric field distributions of the plasmonic nanorods based on FDTD simulation. In addition, the working wavelength of the polarizer can be tuned by the diameter and length of the silver nanorods in the visible spectral range, higher extinction ratios and lower insertion losses can be achieved based on the different resonance modes associated with the different polarizations. The polarizers will be a promising candidate for its potential applications in integration of nanophotonic devices.
Recently, dielectric loaded surface plasmons (SPs) elements are inducing highly interesting in the field of nanooptics, which are composed of dielectric nanostructures fabricated on a metallic thin film. This configuration will provide a route to novel integrated micro-optical devices and components combining photonics and electronics on the same chip. The advantages are easy fabrication, easy integration, and also the potential to realizing active plasmonic devices. In this talk, we will present our recent work in this field. Polymer (PMMA) nano-structures are fabricated on a silver film by the electron beam lithography (EBL) and laser interference lithography. These nano-structures are used to manipulate the behaviors of the SPs, such as converging, diverging, and guiding the propagation of SPs in subwavelength scale. Except for the pure PMMA nano-structures, dye materials (Rhodamine B, RhB) doped PMMA structures are also fabricated on the silver film. The RhB molecules will work as the active medium to excite the SPs or compensation the loss of SPs wave. The dye doped PMMA nanostructure provides a choice to realize active plasmonic elements, such as SPs Bragg gratings. On the other hand, the interaction between the fluorescence molecules and SPs will give rise to some new optical phenomena, such as directional fluorescence emission, anisotropic fluorescence emission. These polymer based plasmonic structures are investigated with a home-built leakage radiation microscopy (LRM).
In this article, two dimensional (2D) metallic gratings of different period and silver nanocubes are fabricated and used as the SERS substrate. The SERS signals of rhodamine6G (R6G) on different substrates are compared. Experimental results show that the SERS signals is much weaker if the R6G molecules are placed on the bare silver film, but the signals will be greatly enhanced if the substrates are composed of both the silver nanocubes and metallic gratings. We attribute this enhancement to the coupling between localized surface plasmons and propagating surface plasmons. Further, we study SERS signals from different parts of the 500nm and 1000nm period 2D metal gratings including the silver nanocubes. The grating of smaller period shows more reproducibility, which arises from the uniformity in the incident laser coverage.
Single quantum dot-cavity system with a deep confinement potential quantum dot is detailedly investigated, with both s- and p-exciton incoherent pump. Through gradually increasing pump rate (about 10-4=ps ∼ 12=ps), the mean photon number shows a linear-dependence on pump power, the photon probability distribution, characterized by g(2)(0), transforms from antibunching to bunching through Poisson, and the spectra go from the doublet to a singlet, the linewidth shows clear reduction in the lasing region. If we increase pump rate further, the mean photon number decreases monotonically to zero, g(2)(0) reaches its maximum value 2, and all the electrons stack at upper lasing level, indicating thermal light generation. The results show, the deep QD-cavity system under s- and p-exciton pump can generate laser although it is not an ideal coherent light, and with only p-exciton pump considered, in spite of the coherent light generated, this pump method is unreasonable to simulate the experimental conditions for the negligible energy spacing between s-exciton and p-exciton.
We replace a commonly used Au film with an Au/Ag bimetallic film working as the sensing
chip in the commercial surface plasmon resonance (SPR) instrument, Biacore 3000. The
bimetallic chip gives out sharper SPR dip than that by the chip made of an Au film which can
improve the sensitivity and accuracy. The applicability and stability of the bimetallic chip on the
Biacore 3000 are tested by real-time monitoring of biological coupling processes between
Sulfamethoxazole (SMX) and anti-SMX. The limit of detection of SMX is 1.8ng/ml.
The general role of the surface plasmons in the transmission of
the metallic grating with narrow slits has been numerical
described using the finite difference time domain method.
Different parameters of grating have been used in the numerical
simulation. It is concluded that whether the transmission peak of
the SP resonance emerges or not does not depend on the SP
travelling on the grating surface. The grating depth and the width
of slit really give a dominant influence on the energy
transmission for the SP resonance.
KEYWORDS: Near field scanning optical microscopy, Near field, Microfluidics, Super resolution, Diffraction, Antimony, Spatial resolution, Near field optics, Optical microscopes, Scattering
A new proposal for biological or microfluidic detection based on super-resolution near-field structure (Super-RENS) proposed by Tominaga is described. The mechanism of the near-field structure we proposed to image microfluid is very similar to near-field scanning optical microscope (NSOM). In this paper, we describe our simulation model and results of the electric field distribution in the near field zone and readout signals from the near-field structure to image microfluid. Calculations have demonstrated that the near-field structure can be applied in biomedicine to detect tracing element or image microfluid etc with a high spatial resolution beyond the diffraction limit.
The SPPs propagation on curved metal-dielectric interface is simulated by FDTD(finite-difference time-domain) method. The propagation loss, the transmittance and the reflection coefficients of SPPs on curved metal-dielectric interface with different radius of curvature is presented. The results shows the radiation loss is the key factor for the SPPs propagation when the propagation area is the same order as the wavelength, and the reflection coefficient is so small that it is ignorable. The critical situation when the radius is zero is also analyzed and the reflection coefficient is much larger than the former situation; for the transmittance, different electronic field components play different roles.
The optical reflector based on two-dimensional photonic crystal constructed by a square lattice of dielectric rods has already been reported in recent years, But the enormous difficulties to fabricate this structure are well-known, because the height of the rods must be finite in a real system so in this case no guided modes appears when air waveguides are created. On the contrary, there is not this inherent limitation for the photonic crystal waveguide made of air holes. In this paper, I will demonstrate an optical reflector based on photonic crystal,which constructed by air holes introduced into high index material. We design a monomode waveguide with even symmetry and discuss the characteristic of the reflector obtained by inserting several defects into the monomode waveguide in FDTD method.This kind of reflectors still have guided mode even if it possess finite thickness. This will make optical reflector based on two-dimensional photonic crystal nearer to practical application.
A novel copolymer optical fiber with high azobenzene concentration is reported (more than 3.2 mol %). The orientation process of the preform was fitted with corrected bi-exponential equation. Compared with the doped one, the photosensitivity of this kind of copolymer optical fiber preform is analyzed. The influence of azobenzene concentrations and write conditions on photosensitivity of copolymerized PMMA was analyzed. Then, long-period of 120um birefringent grating was fabricated in the single mode fiber with core refractive index of 1.485 (at wavelength of 1.5um), and relative index difference delta of 0.008. The duty cycle is 50%, and the refractive index change in the exposed area is about 4*10-4 for the ordinary or extraordinary ray.
Azobenzene polymers show large optical anisotropy, and one can control the optical anisotropy by changing the alignment of the molecules with light. Azo groups fall perpendicularly to the direction of the electric field vector of the linear polarized light by photoisomerization. This reorientation induces anisotropy and the difference of refractive index parallel and perpendicular to the irradiating laser polarization direction. In this paper, the photoinduced birefringence induced with 532 nm light in films of azobenzene polymer has been studied as a function of temperature, light intensity. From the evolution of the birefringence induced by laser, the temperature effects on photochemical trans-cis-trans isomerization cycles have been probed and analyzed. The effect of laser-induced heating has been introduced to the buildup of photoinduced birefringence in azobenzene-side-chain copolymer. The curves for the buildup of birefringence were fitted with a modified function, namely, biexponential curves and Gaussian curves. The relationship of each parameter has been also presented. With the modified fitting function, we obtained better fitting result.
The interference of the surface plasmons polaritons (SPPs),
localized SPPs, has been numerical analyzed by 2D finite
difference time domain (FDTD) method. The near-field distributions
of the localized SPPs have been presented. It is found that the
quality of the output is not always good with strong interaction
of the SPPs in super-RENS. It is also found that the near-field
distribution and the output are almost changeless when the regions
of the dark stripes have been adjusted.
KEYWORDS: Polymers, Near field scanning optical microscopy, Near field optics, Polymer thin films, Anisotropy, Data storage, Near field, Optical microscopy, Physics, Polarization
We report the near-field investigation on azobenzene contained polymer films using scanning near-field optical microscopy. Nanometer scale dots and lines were inscribed on these films, and the topographies and transmitting images of these patterns could be obtained at the same time. The transmitting images were in agreements with the topographies, and it proved that trans-cis isomerization of the azobenzene moieties in the illuminated area induced both surface relief and anisotropy. The experimental results helped to discover the mechanism of the photo induced surface relief and anisotropy, and the agreement between the transmitting images and the topographies could be applied in pure optical writing/reading in high-density data storage.
In this paper, an off-axis holographic lens with the focal length of about 70mm is recorded in the azobenzene liquid crystal polymer film (azo-LCP) by 532nm YbVO4 double-frequency lasers and is reconstructed by a 633nm He-Ne laser. The particularity and main advantage of the work consists in writing and reading out the hologram at the same place, without moving, post-exposure adjusting or chemical processing. The converging and imaging property of the holographic lens is measured and analyzed.
KEYWORDS: Near field optics, Near field, Silver, Finite-difference time-domain method, Nonlinear optics, Super resolution, Particles, Surface plasmons, Optical storage, Near field scanning optical microscopy
In this paper, modified finite differential time domain (FDTD) method is used to investigate super resolution near-field structure (Super-RENS). The random distributed Ag particles, which is responsible for the localization and the enhancement of the surface plasmon within the Super-RENS, is included in this simulation. The near-field optical distribution when recording mark is just beneath the nonlinear aperture is achieved. And the transmitted readout signal is also simulated.
With the increasing demand of optical storage capacity, multi-level (ML) optical storage based on multi-level-amplitude modulation is receiving more and more attention, for it transmits more information ove a fixed bandwidth channel by using the available SNR more efficiently. We proposed an ML optical storage technology in azo LCP film based on polarization angle division. In this paper, the write strategy is developed by a ML write-compensation system that corrects for non-linearities of the data signal. The dynamic transmittance range is extended with the full monotonic range of angle and the varaition of each amplitude level relative to our dynamic range is improved. The experiments of imroved linear and nonlinear 16-level storage in azo LCP are demonstrated. The effects of thickness non-uniformity on linear and nonlinear 16-level storage are discussed.
Third-order nonlinear optical properties of cover glass coated with different metal films are studied by using a focused pulse laser (λ=532 nm, pulse width 0.7ns, repetition rate 15.79kHz) with a Z-scan system. The results of open-aperture mode Z-scan shows high transmittance in the AgOx sample. The enhanced third-order nonlinear coefficients were examined by close-aperture mode Z-scan. The plasmon excitation and thermal relaxation were discussed for experimental results.
KEYWORDS: Near field scanning optical microscopy, Optical fibers, Channel waveguides, Near field, Silica, Telecommunications, Near field optics, Aluminum, Physics, Optical testing
Construction of a tapping-mode tuning fork with a short fiber probe as the force sensing element for near-field scanning optical microscopy is reported. This type of near-field scanning optical microscopy provides stable and high Q factor at the tapping frequency of the tuning fork, and thus gives high quality NSOM and AFM images of samples.We present results obtained by using the short tip tapping-mode tuning fork near-field scanning optical microscopy measurements performed on a single mode telecommunication optical fiber and a silica based buried channel waveguide.
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