High-Sensitivity Detection of IgG Operating near the Dispersion Turning Point in Tapered Two-Mode Fibers

The conventional methods for monitoring IgG levels suffer from some apparent problems such as long assay time, multistep processing, and high overall cost. An effective and suitable optical platform for label-free biosensing was investigated by the implementation of antibody/antigen immunoassays. The ultrasensitive detection of IgG levels could be achieved by exploiting the dispersion turning point (DTP) existing in the tapered two-mode fibers (TTMFs) because the sensitivity will reach ±∞ on either side of the DTP. Tracking the resonant wavelength shift, it was found that the fabricated TTMF device exhibited limits of detection (LOD) down to concentrations of 10 fg/mL of IgG in PBS solution. Such immunosensors based on DTP have great significance on trace detection of IgG due to simple detection scheme, quick response time, and miniaturization.

Response Characteristics of Silicon Microring Resonator Hydrogen Sensor

A silicon microring-resonator (MRR) hydrogen sensor which utilizes platinum-loaded tungsten oxide (Pt/WO3) thin film was fabricated and evaluated. The uniform film was deposited on MRR portion by using sol-gel technique. By the exposure to pure hydrogen gas, the sensor devise showed the large resonant wavelength shift at room temperature. It is suggested that the change in the optical properties of hydrogen sensitive layer results in this response.

The Influence of Glucose Concentration to Resonant Wavelength Shift of Polymer-Based Microring Resonators

Microring resonators (MRRs) is a compact and multi-functioned device which is mainly characterized by free spectral range (FSR) and quality factor (Q-factor). In this paper, the influence of glucose concentration to the resonant wavelength shift of MRRs is presented. The calculation was carried out using semi-numerical method for different values of FSR and Q-factor. The parameters used in the calculation including incident wavelength, ring radii of circular waveguide, gap sizes between circular and straight waveguides, the dimension of both waveguides, and refractive index of polymer, SiO2 and glucoce solution. The results show that glucose affects the resonant wavelength shift for each values of FSR and Q-factor. The increase of the glucose concentration causes the increase of the resonant wavelength shift, therefore this polymer-based MRR’s can be used for glucose sensing application.

Nanocomposite with Very Large Electro-optic Effect and Widely Tunable Refractive Index

ABSTRACTVery large electro-optic effect has been observed in relaxor ferroelectric poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) ( P(VDF-TrFE-CFE) ) terpolymer. By adding small amount of zinc sulfide (ZnS) nanoparticles, the refractive index of the nanocomposites can be tuned between about 1.4 and 1.5 while retaining large electro-optic effect and high transparency. Tunable long-period fiber gratings have been fabricated with the nanocomposite as the second cladding, and over 50nm of resonant wavelength shift has been achieved under a change of electric field of 30V/μm, which is much larger than other reported E-O tuning ranges. This corresponds to a pure refractive index change of the nanocomposite of Δn/n ∼ 0.4%.