27 research outputs found
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Realization of a polymer nanowire optical transducer by using the nanoimprint technique
An optical transducer using an integrated optics polymer nanowire is proposed. The nanoimprint technique is used to fabricate an OrmoComp nanowire with 1.0 μm width and 0.5 μm height, but the resulting sidewalls are not perfectly vertical. Maximum sensitivity is achieved by enhancing the evanescent field in the cladding region. The possible mode fields and power confinement of the nanowire are studied with respect to their structural dimensions, the operating wavelength, and the cladding material by using th
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Demonstration of Polarization-Independent Surface Plasmon Resonance Polymer Waveguide for Refractive Index Sensing
The effect of the variation of the refractive index in a gold-coated ormocomp waveguide for sensing application is studied in this paper. The ormocomp waveguide is fabricated by using the nanoimprint method. A waveguide with width and height both equal to 10 μm is coated with 100 nm thick gold using the sputtering technique in order to introduce surface plasmon resonance at the vertical sides and also at the top of the structure. Here, polarization-independent waveguide is achieved by supporting both the plasmonic TE and TM modes and the light confinement in these modes are studied. Supermodes forming from coupling between the fundamental dielectric mode and the plasmonic supermode at the resonance peak are also investigated. This paper presents the numerical simulated results and also their experimental validations. For this structure, there are two dielectric-plasmon supermodes with two resonance peaks separated by 50 nm. A red shift is observed when the refractive index of the cladding material increases. The cladding material includes water (n = 1.333) and iso-propanol solutions with refractive indices of 1.344, 1.351, and 1.365. The gold-coated ormocomp waveguide has sensitivity of about 544.55 nm/RIU with a resolution of 5.3 × 10⁻³ RIU
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Characterization of polymer nanowires fabricated using the nanoimprint method
In this paper, an ormocomp polymer nanowire with possible use in integrated-optics sensing applications is presented. We discuss the structure design, the fabrication process and present results of the simulation and characterization of the optical field profile. Since the nanowires are designed and intended to be used as integrated optics devices, they are attached to tapered and feed waveguides at their ends. The fabrication process in this work is based mainly on the nanoimprint technique. The method assumes a silicon nanowire as an original pattern, and polydimethylsiloxane (PDMS) as thesoft mold. The PDMS mold is directly imprinted on the ormocomp layer and then cured by UV light to form the polymer based nanowire. The ormocomp nanowires are fabricated to have various dimensions of width and length at a fixed 500nm thickness. The length of the nanowires is varied from 250 μm to 2 mm, whereas the width of the structures is varied between 500nm and 1μm. The possible optical mode field profile that occurs in the proposed polymer nanowire design is studied using the H-field finite element method (FEM). In the characterization part, the optical field profile and the intensity at the device output are the main focus of this paper. The various lengths of the nanowires show different characteristics in term of output intensity. An image processing is used to process the image to obtain the intensity of the output signal. A comparison of the optical field and output intensity for each polymer nanowire is also discussed
Hydrography, bacteria and protist communities across the continental shelf and shelf slope of the Andaman Sea (NE Indian Ocean)
Formation of high-carbon abrasion-resistant surface layers when high-energy heating by high-frequency currents
The paper shows the possibility of carburization of low-carbon steel surface layers using high-frequency currents. The mathematical modeling of carburization using high-energy heating by high-frequency currents (HEH HFC) has been carried out, the temperature fields formed during the given processing have been calculated, as well as the structural changes in the surface layers have been simulated. The features of the structure formation in the surface layers of low-carbon steel after carburizing via HEH HFC have been determined by optical and scanning microscopy, which is confirmed by the computational models. The rational mode of fusion via HEH HFC has also been determined (power density of the source q[s]=(1.5...4.0)•10{8} W m{-2}, (the relative travel speed of parts V[p]=5 ... 100 mm /sec), with forming the compressive retained stresses in the surface layer ([sigma][RS]=-300...-400 MPa)
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Surface plasmon resonance-enhanced light interaction in an integrated ormocomp nanowire
An integrated ormocomp nanowire coated with gold metal layer is proposed and its optical characteristics with the effect of surface plasmon resonance (SPR) are studied. The integrated rib-like nanowire has a trapezoidal shape with sidewall angles of 75°. It is coated with 50 nm gold layer to introduce the SPR and enhance the evanescent field in the sensing region located at the dielectric/metal interface. The possible field modes, the normalized power confinement, and the SPR peak position of the nanowire are studied over the wavelength and the metal thickness by using the full-vectorial H-field FEM in quasi-TM mode. The attenuation coefficient of the nanowire, the SPR peak wavelength, and the wavelength shift is experimentally extracted for three different cladding materials. The redshift of the supermode coupling between the dielectric mode and the anti-symmetric supermode is observed with the higher cladding-index and larger metal thickness. The improvement of the power confinement in the sensing region with the SPR effect is ten times (10×) better than a previous similar study
Design of electric-field assisted surface plasmon resonance system for the detection of heavy metal ions in water
Progress towards wafer-scale fabrication based on gel casting technique for 1–3 randomised piezocomposite μUS linear array
Microultrasound (μUS) linear arrays operating at frequencies over 25 MHz have applications in high resolution biomedical imaging. 1–3 connectively piezoceramic – polymer composite (“piezocomposite”) material is attractive for fabrication of these devices due to its high effective electromechanical coupling coefficient and low acoustic impedance for better acoustic matching between transducer and tissue. However, a major concern with this type of material comes from interference between the fundamental thickness-mode resonance and spurious modes, which is usually generated by wave propagation and reflection within the repetitive and symmetrical structure of classical piezocomposite. In general, a fine spatial scale is required of the material structure to suppress the spurious modes; however, the fabrication process is challenging using standard dice-and-fill methods at the fine scales required for high frequencies. A promising way to overcome this challenge is to manipulate the lateral geometry and spacing of the piezoceramic pillars with a random distribution. In this work, gel casting in association with a micromoulding technique has been developed for manufacturing 1–3 randomised piezocomposite active material for μUS linear arrays. 48 vol% solid loading of piezoceramic powder with 30 wt% Hydantoin resin content was employed to prepare a low viscosity aqueous suspension. Through varying powder size, it was found that the suspension with 1.22 µm powder had the highest viscosity, ~ 0.47 Pa.s, and a short gelation time, ~ 10 mins. However, all suspensions had viscosities less than 1 Pa.s at a shear rate of 100 s−1, indicating that they had good flowability. The green body samples showed mean flexural strength 49.7 ± 2.49 MPa. After piezocomposite fabrication with randomised pillars, surface planarisation was used to obtain reliable edge definition of photolithographically-defined electrodes. 20-element arrays with 50-μm element pitch were configured using a bilayer lift-off process. The 1–3 randomised piezocomposite demonstrated its capability to minimise the effects of spurious modes in the thickness mode frequency range, while the thickness resonances provided k33 = 0.67. Without a matching layer, the array produced a − 6 dB bandwidth of 38.4%- and − 20-dB pulse length of 0.26 μs. These results show that 1–3 randomised piezocomposite fabricated from gel-casting associated with a micromoulding technique is feasible for fabrication of μUS linear arrays and may offer a route to small wafer-scale production