Zhenhong Jia

Immunosensor application based on Raman spectroscopy of porous silicon

Porous silicon (PS) suitable for optical detection of immunoreaction is fabricated. The structure of immunosensor is prepared by the following steps: oxidization, silanization, glutaraldehyde cross-linker, and covalent binding of antibody. When antigen is added into the immunosensor, the Raman intensity is estimated to be linearly reduced according to the concentration of the surface protective antigen protein A (spaA) of below 4.0 ?g·ml?1. The ultimate detection limit is 1.412×10^2 pg.ml^{?1}. Controlled experiments are also presented with non-immune antigen of the spaA, and results show that the immunosensor has high specificity. Compared with the conventional enzyme-linked immuno sorbent assay (ELISA), this method is quick, inexpensive, and label-free.

Preparation and photoluminescence of TiO2/PS composite system

A TiO2/porous silicon (PS) composite system is prepared by chemical vapor deposition. The crystal form with anatase phase of the samples is evaluated by X-ray diffraction and ultraviolet-visible (UV-vis) absorbance spectra, and the morphology with microsphere of TiO2 particles is characterized by scanning electron microscopy. The composite system formed by this technique gives a broad blue luminescence and the mechanism of photoluminescence with TiO2/PS is also discussed.

The effect of argon ion implantation and preanodization argon ion implantation on photoluminescence of porous silicon

Photoluminescence of Ar+ implanted porous silicon and porous structure of Ar+-implanted silicon (porous silicon by preanodization ion implantation) at energy of middle-energy (30keV) are investigated to gain insight into the photoluminescence properties and photoluminescence mechanism. The results show that the photoluminescence intensity of Ar+ implanted porous silicon was reduced, which was attributed to the removal of surface oxygen and creation of defects that act as nonradiative recombination; And whether samples were prepared by p-type or n-type silicon wafers, the photoluminescence intensity of porous structure of Ar+-implanted silicon was enhanced that we attribute these to the enhanced formation of porous silicon microstructure induced by ion implantation and oxygen-related defects were increased.

Study of holographic grating in porous silicon optical waveguides

It was found that the porosity of porous silicon has a maximum value under certain illumination intensity in our experiment. According to the experimental result, the grating was fabricated from porous silicon by controlling illumination intensity. As the refractive index of porous silicon decreases with an increase of the porosity, so the index distributing of porous silicon can be controlled by illumination intensity. A holographic process allows obtaining a mask of light on top layer during fabricating the multilayer porous silicon optical waveguides. The interference of two coherent Ar+ laser beams produces at the sample surface bright parallel lines. The porosity is modulated in the plane. The effective deep of modulation is directly related to the penetration of the illuminating beam. We have developed an experimental setup that allows guide light at 1064nm incidents vertically into the grating in porous silicon optical waveguides. The diffractive efficiency of the first order diffraction light in TE and TM polarization are measured in our experiment respectively.

Formation and characterization of ZnS/CdS nanocomposite materials into porous silicon

ZnS/CdS were deposited by chemical vapor deposition (CVD) technique on porous silicon substrates formed by electrochemical anodization of n-type (100) silicon wafer. The optical properties of ZnS/CdS porous silicon composite materials are studied. The results showed that new luminescence characteristics such as strong and stable visible-light emissions with different colors were observed from the ZnS/CdS-PS nanocomposite materials at room temperature.

Porous silicon-based photonic crystals optical devices for polarization band-pass filtering and sensing applications

We report on the design of porous silicon based polarization band-pass filters, which is not only have excellent optical properties with p-polarization transmittance and s-polarization reflectance in the NIR field, but also can be used for excellent biosensor and gas sensing applications.

Experimental research on radiation induced changes of polymer optical fiber under gamma-ray irradiation

Under the high energy irradiation, the charges (even little) of molecules of polymer can cause the physical and chemical characteristics evident changes of polymer. The physics and chemical mechanisms which are responsible for radiation induced loss was analyzed. The radiation damage of polymethylmethacrylate (PMMA), Polystyrene PS and polycarbonate (PC) optical fiber under γ-ray irradiation was researched experimentally. The visible light transmission of the POF under different irradiation dose was measured. The results indicated that the radiation damage of three kinds of POF was wavelength-dependent. Under lower dose below 1KGy, the transmission rate decreased identical in the whole visible light range. When the irradiation dose exceeded 5KGy, the transmission rate reduced obviously, and the recovery indicated that the visible light transmission rate of the POF in the range of 400nm to 500nm comparing with 600nm to 800nm, decreased seriously under the irradiation dose exceeded 5kGy. The transmission rate of both PMMA and PC have an evident peak value at the range 550nm-650m, and that of PS has a wide band at the range 500-700nm. We also measured the recovery of three kinds of POF under different irradiation dose by measuring several times the POF after stopping irradiating.

Structural and photoluminescence properties of porous silicon with r.f.-sputtered thin films

Thin Sn films in the thickness range 0.3-2nm are deposited by r.f.-sputtering on porous silicon (PS) anodized on p-type silicon. Microstructural features of the samples before and after r.f.-tin-sputtered are investigated with scanning electron microscopy (SEM). The photoluminescence (PL) studies showed that a broad luminescence peak of PS near the 621nm region gets a reduction in intensity, and a new peak at 441nm was produced at first and then disappeared. The FTIR spectra on the PS/Sn structure revealed no major change of the native PS peaks.

The criterions of minimum number of arrayed waveguides for the design of arrayed waveguide gratings

The criterions for determining the minimum number of arrayed waveguides are presented using the design theory of arrayed waveguide gratings (AWGs) and Fraunhofer diffraction principle for the optimal design of AWGs. In addition, some parameters such as the cross section of waveguides and the waveguide separation between adjacent waveguides are chosen to optimize the AWG structure to satisfy the performance specifications and to match the fabrication conditions in our laboratory. As an example to demonstrate the effectiveness of the proposed method, the simulated results of the designed 16 16 AWGs with silica-based sol-gel material were provided using the beam propagation method (BPM). And the effectiveness of optimal parameters, especially to the selection of the minimum number of arrayed waveguides on the performance of the AWG, has been perfectly verified by comparing the transmission spectra of the designed AWGs. The design methodology can serve as a simple and useful tool for the optimal design of AWG multiplexers/demultiplexers.

Study on fabrication of porous silicon and polymer PMMA/DR1 composite films and its optical Properties

We fabricate the porous silicon/ PMMA/DR1 composite films by spin-coating methods in our work. The influence of the rotation speed of spin-coating and solution concentration on inserting of PMMA/DR1 in the porous silicon pores were studied. Micro-Raman spectrometry technique was used to examine the pores filling with PMMA/DR1. The linear and nonlinear refractive index of porous silicon and PMMA/DR1 composite films were studied by Optical reflectivity measurements and Z-scan technique respectively. The luminescence characteristics and stability emission of PMMA/DR1 impregnated samples were also studied in this paper.