Recent progresses of SOI-based photonic devices - art. no. 60201R

SOI (Silicon on Insulator) based photonic devices, including stimulated emission from Si diode, RCE (Resonant Cavity Enhanced) photodiode with quantum structure, MOS (Metal Oxide Semiconductor) optical modulator with high frequency, SOI optical matrix switch and wavelength tunable filter are reviewed in the paper. The emphasis will be played on our recent results of SOI-based thermo-optic waveguide matrix switch with low insertion loss and fast response. A folding re-arrangeable non-blocking 4x4 matrix switch with total internal reflection (TIR) mirrors and a first blocking 16 x 16 matrix were fabricated on SOI wafer. The extinction ratio and the crosstalk are better. The insertion loss and the polarization dependent loss (PDL) at 1.55 mu m increase slightly with longer device length and more bend and intersecting waveguides. The insertion losses are expected to decrease 2-3 dB when anti-reflection films are added in the ends of the devices. The rise and fall times of the devices are 2.1 mu s and 2.3 mu s, respectively.

High-Q and High-extinction-ratio Microdisk Add-drop Filter with Grating Couplers in Silicon-on-Insulator

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Adaptive fading Kalman filter with an application

A new adaptive state estimation algorithm, namely adaptive fading Kalman filter (AFKF), is proposed to solve the divergence problem of Kalman filter. A criterion function is constructed to measure the optimality of Kalman filter. The forgetting factor in AFKF is adaptively adjusted by minimizing the defined criterion function using measured outputs. The algorithm remains convergent and tends to be optimal in the presence of model errors. It has been successfully applied to the headbox of a paper-making machine for state estimation.

Ultra-narrow dual-channel filter based on symmetrical sampled fibre Bragg grating

A kind of ultra-narrow dual-channel filter is proposed in principle and demonstrated experimentally. This filter is designed by means of two sampled fibre Bragg gratings (SFBGs), where one is periodic 0-pi sampling and the other is symmetrical spatial sampling. The former can create two stopbands in the transmission spectra and the latter can produce two ultra-riarrow passbands. Our filter has the 3-dB bandwidth of about 1 pm, whose value is two orders of magnitude less than the bandwidth of the traditional SFBG filters. The proposed filter has a merit that the channel spacing remains unchanged when tuning the filter.

Preparation and optical property of a novel hydrophobic anti-reflection coating for KDP crystal

A novel inorganic-organic hybrid hydrophobic anti-reflection silica film used for laser crystal was obtained by sol-gel process. The film consisted of silica sols mixed with a small amount of polymethyl methacrylate (PMMA) or polystyrene (PS). The optical transparency, hydrophobic property and surface morphology of the film were characterized by UV-VIS-NIR spectrophotometer; contact angle instrument and Scanning Electron Microscopy (SEM), respectively. The results showed that the anti-reflection coating had good hydrophobility and optical transparency from 400 nm to 1200 nm. The contact angle reached to 130-140 degrees. SEM images indicated the hydrophobic films modified with PMMA or PS had compact structure compared to the pure silica sol film. (C) 2008 Elsevier B.V. All rights reserved.

Construction of 2-D directional filter bank by cascading checkerboard-shaped filter pair and CMFB

In this paper, we propose a new approach to construct a 2-dimensional (2-D) directional filter bank (DFB) by cascading a 2-D nonseparable checkerboard-shaped filter pair and 2-D separable cosine modulated filter bank (CMFB). Similar to diagonal subbands in 2-D separable wavelets, most of the subbands in 2-D separable CMFBs, tensor products of two 1-D CMFBs, are poor in directional selectivity due to the fact that the frequency supports of most of the subband filters are concentrated along two different directions. To improve the directional selectivity, we propose a new DFB to realize the subband decomposition. First, a checkerboard-shaped filter pair is used to decompose an input image into two images containing different directional information of the original image. Next, a 2-D separable CMFB is applied to each of the two images for directional decomposition. The new DFB is easy in design and has merits: low redundancy ratio and fine directional-frequency tiling. As its application, the BLS-GSM algorithm for image denoising is extended to use the new DFBs. Experimental results show that the proposed DFB achieves better denoising performance than the methods using other DFBs for images of abundant textures. (C) 2008 Elsevier B.V. All rights reserved.

Recombinant protein of heptad-repeat HR212, a stable fusion inhibitor with potent anti-HIV action in vitro

HR212, a recombinant protein expressed in Escherichia coli, has been previously reported to inhibit HIV-1 membrane fusion at low nanomolar level. Here we report that HR212 is effective in blocking laboratory strain HIV-1IIIB entry and replication with EC50 values of 3.92±0.62 and 6.59±1.74 nM, respectively, and inhibiting infection by clinic isolate HIV-1KM018 with EC50 values of 44.44±10.20 nM, as well as suppressing HIV-1- induced cytopathic effect with an EC50 value of 3.04±1.20 nM. It also inhibited HIV-2ROD and HIV-2CBL-20 entry and replication in the μM range. Notably, HR212 was highly effective against T20-resistant strains with EC50 values ranging from 5.09 to 7.75 nM. Unlike T20, HR212 showed stability sufficient to inhibit syncytia formation in a time-of-addition assay, and was insensitive to proteinase K digestion. These results suggest that HR212 has great potential to be further developed as novel HIV-1 fusion inhibitor for treatment of HIV/ AIDS patients, particularly for those infected by T20-resistant variants.