Measurement accuracy in silicon photonic ring resonator thermometers: identifying and mitigating intrinsic impairments

Silicon photonic ring resonator thermometers have been shown to provide temperature measurements with a 10 mK accuracy. In this work we identify and quantify the intrinsic on-chip impairments that may limit further improvement in temperature measurement accuracy. The impairments arise from optically induced changes in the waveguide effective index, and from back-reflections and scattering at defects and interfaces inside the ring cavity and along the path between light source and detector. These impairments are characterized for 220 × 500 nm Si waveguide rings by experimental measurement in a calibrated temperature bath and by phenomenological models of ring response. At different optical power levels both positive and negative light induced resonance shifts are observed. For a ring with L = 100 µm cavity length, the self-heating induced resonance red shift can alter the temperature reading by 200 mK at 1 mW incident power, while a small blue shift is observed below 100 µW. The effect of self-heating is shown to be effectively suppressed by choosing longer ring cavities. Scattering and back-reflections often produce split and distorted resonance line shapes. Although these distortions can vary with resonance order, they are almost completely invariant with temperature for a given resonance and do not lead to measurement errors in themselves. The effect of line shape distortions can largely be mitigated by tracking only selected resonance orders with negligible shape distortion, and by measuring the resonance minimum wavelength directly, rather than attempting to fit the entire resonance line shape. The results demonstrate the temperature error due to these impairments can be limited to below the 3 mK level through appropriate design choices and measurement procedures.

Optical wavefront phase-tilt measurement using Si-photonic waveguide grating couplers

Silicon photonic wavefront phase-tilt sensors for wavefront monitoring using surface coupling grating arrays are demonstrated. The first design employs the intrinsic angle dependence of the grating coupling efficiency to determine local wavefront tilt, with a measured sensitivity of 7 dB/°. The second design connects four gratings in an interferometric waveguide circuit to determine incident wavefront phase variation across the sensor area. In this device, one fringe spacing corresponds to 2° wavefront tilt change. These sensor elements sample a wavefront incident on the chip surface without the use of bulk optic elements, fiber arrays, or imaging arrays. Both sensor elements are less than 60 µm across and are potential unit cell sensor elements for large arrays that monitor wavefront shape across an image or pupil plane in adaptive optics systems for free-space optical communications, astronomy, and beam pointing applications.

[Effect of "one-stop" outpatient management on the control rate of multiple metabolic disorders patients]

Objective: To explore the effect of "one-stop" outpatient management on the therapeutic schedule and control rate of patients with metabolic disorders. Methods: A total of 332 patients who met the inclusion criteria were enrolled and treated regularly in the "one-stop" outpatient department of the Department of Cardiology of the Third Hospital of Peking University from November 1, 2020 to April 30, 2022. The general information, personal history, family history, drug treatment plan, blood pressure, height, weight, waist circumference, and hip circumference of patients were collected through the outpatient electronic medical record system, and patients were followed up through conducting "one-stop" comprehensive management. The baseline clinical characteristics were analyzed, and the changes of metabolic indexes, treatment conditions and control rate of patients with different metabolic disorders before and after the "one-stop" outpatient management were compared. Results: The time interval between the first visit and the last visit was 44 (26, 60) weeks in 332 patients, whose age was (57.2±13.2) years, including 219 males (66.0%). After the "one-stop" outpatient management, fasting blood glucose (FBG) [ 6.6 (5.6, 7.9) mmol/L vs 6.3 (5.6, 6.9) mmol/L], glycosylated hemoglobin A1c (HbA1c) [ (7.2±1.5) % vs (6.6±0.8) %], low density lipoprotein cholesterol (LDL-C) [ 2.70 (1.97, 3.55) mmol/L vs 2.04 (1.66, 2.63) mmol/L] and blood uric acid (UA) [ (383.7±107.1) μmol/L vs (341.2±90.6) μmol/L] all decreased significantly (all P values<0.05). The control rates of hypertension (19.8% vs 28.2%), diabetes (45.2% vs 66.5%), hyperlipidemia (54.9% vs 87.6%) and hyperuricemia (16.7% vs 49.0%) were significantly improved after the "one-stop" outpatient management (all P values<0.05). Conclusion: The "one-stop" outpatient management of cardiovascular department can significantly improve the metabolic condition and the control rate of patients with multiple metabolic disorders.

[Sepsis and acute kidney injury]

Sepsis is a life-threatening multiple organ dysfunction syndrome caused by infection, and kidney is one of the most organs susceptible to injury in sepsis. Critical ill patients with sepsis often suffer from acute kidney injury (AKI) of varying degrees with a high mortality. There are more and more researches on the early identification, pathogenesis, diagnosis and treatment of acute kidney injury in sepsis. In order to improve the understanding and reduce the mortality of acute kidney injury, this review briefly discussed the early identification, physio-pathologic mechanism, treatment, prognosis and follow up.

MiR-363-3p modulates cell growth and invasion in glioma by directly targeting pyruvate dehydrogenase B

OBJECTIVE

This study is designed to investigate the role of miR-363-3p in the cancer development of glioma.

PATIENTS AND METHODS

The expression of miR-363-3p in glioma and adjacent noncancerous tissue was measured using quantitative RT-PCR. The expression of a target gene of miR-363-3p, pyruvate dehydrogenase B (PDHB), was determined by Western blot. The level of miR-363-3p was increased or decreased by transfected with miR-363-3p mimic or miR-363-3p inhibitor, respectively. The impact of miR-363-3p on cell growth, apoptosis and invasion was determined by CCK-8 (Cell Counting Kit) assay, flow cytometry, and transwell assay. The role of PDHB in mediating the oncogenic activities was demonstrated by co-transfected PDHB vector and miR-363-3p mimic.

RESULTS

Our results have shown that miR-3663-3p level was significantly higher in glioma tissue. Furthermore, miR-363-3p functions as onco-miRNA, promotes cell proliferation, protects against apoptosis, and enhances invasion by directly targeting PDHB.

CONCLUSIONS

MiR-363-3p is an onco-miRNA, which can be considered as a potential therapeutic target in glioma.

Fiber-chip grating coupler based on interleaved trenches with directionality exceeding 95

We propose a fiber-chip grating coupler that interleaves the standard full and shallow etch trenches in a 220 nm thick silicon layer to provide a directionality upward exceeding 95%. By adjusting the separation between the two sets of trenches, constructive interference is achieved in the upward direction independent of the bottom oxide thickness and without any bottom reflectors, overlays, or customized etch depths. We implement a transverse subwavelength structure in the first two grating periods to minimize back-reflections. The grating coupler has a calculated coupling efficiency of CE~-1.05 dB with a 1 dB bandwidth of 30 nm and minimum feature size of 100 nm, compatible with deep-UV lithography.

Cloning and expression analysis of Wnt6 and Hox6 during intestinal regeneration in the sea cucumber Apostichopus japonicus

Many developmental genes play important roles in regeneration. Here, we cloned the two developmental genes, Wnt6 and Hox6, from Apostichopus japonicus by rapid amplification of cDNA ends (RACE) polymerase chain reaction (PCR). The Wnt6 full-length cDNA is 1140 bp long with a 1029-bp open reading frame encoding 342 amino acids. The deduced Wnt6 protein contained a 22-amino acid signal peptide and a 274-amino acid mature peptide. The Hox6 (AjHBOX6) full-length cDNA contained 1312 bp with a 966-bp open reading frame encoding 321 amino acids. Its deduced amino acid sequence included one homeodomain (60 amino acids) and three domains with low compositional complexity. Comparison and phylogenetic analysis revealed that Wnt6 and Hox6 in A. japonicus had the nearest relationship to those in sea urchins. Further expression analysis by real-time PCR showed that Wnt6 and Hox6 were apparently upregulated during intestine regeneration, which suggested that they were involved in the intestinal regeneration of sea cucumbers.

Photonic wire biosensor microarray chip and instrumentation with application to serotyping of Escherichia coli isolates

A complete photonic wire molecular biosensor microarray chip architecture and supporting instrumentation is described. Chip layouts with 16 and 128 independent sensors have been fabricated and tested, where each sensor can provide an independent molecular binding curve. Each sensor is 50 μm in diameter, and consists of a millimeter long silicon photonic wire waveguide folded into a spiral ring resonator. An array of 128 sensors occupies a 2 × 2 mm2 area on a 6 × 9 mm2 chip. Microfluidic sample delivery channels are fabricated monolithically on the chip. The size and layout of the sensor array is fully compatible with commercial spotting tools designed to independently functionalize fluorescence based biochips. The sensor chips are interrogated using an instrument that delivers sample fluid to the chip and is capable of acquiring up to 128 optical sensor outputs simultaneously and in real time. Coupling light from the sensor chip is accomplished through arrays of sub-wavelength surface grating couplers, and the signals are collected by a fixed two-dimensional detector array. The chip and instrument are designed so that connection of the fluid delivery system and optical alignment are automated, and can be completed in a few seconds with no active user input. This microarray system is used to demonstrate a multiplexed assay for serotyping E. coli bacteria using serospecific polyclonal antibody probe molecules.

Highly tolerant tunable waveguide polarization rotator scheme

Integrated polarization rotators are known to exhibit stringent fabrication tolerances, which severely handicap their practical application. Here we present a general polarization rotator scheme that enables both the compensation of fabrication errors and wavelength tunability. The scheme is described analytically, and a condition for perfect polarization conversion is established. Simulations of a silicon-on-insulator polarization rotator show polarization extinction ratios in excess of 40  dB even in the presence of large fabrication errors that in a conventional rotator configuration degrade the extinction ratio to below 5  dB. Additionally, wavelength tuning over ±30  nm is shown.

Colorless directional coupler with dispersion engineered sub-wavelength structure

Directional couplers are extensively used devices in integrated optics, but suffer from limited operational wavelength range. Here we use, for the first time, the dispersive properties of sub-wavelength gratings to achieve a fivefold enhancement in the operation bandwidth of a silicon-on-insulator directional coupler. This approach does not compromise the size or the phase response of the device. The sub-wavelength grating based directional coupler we propose covers a 100 nm bandwidth with an imbalance of ≤ 0.6 dB between its outputs, as supported by full 3D FDTD simulations.

All-optical wavelength conversion for 10 Gb/s DPSK signals in a silicon ring resonator

We demonstrate all-optical wavelength conversion at 10 Gb/s for differential phase-shift keyed (DPSK) data signals in the C-band, based on four-wave mixing (FWM) in a silicon ring resonator. Error-free operation with a system penalty of ~4.1 dB at 10⁻⁹ BER is achieved.

All-optical XOR logic gate for 40Gb/s DPSK signals via FWM in a silicon nanowire

We demonstrate an all-optical XOR logic function for 40Gb/s differential phase-shift keyed (DPSK) data signals in the C-band, based on four-wave mixing (FWM) in a silicon nanowire. Error-free operation with a system penalty of ~3.0dB and ~4.3dB at 10⁻⁹ BER is achieved.

Single-etch grating coupler for micrometric silicon rib waveguides

Grating couplers are widely used as an efficient and versatile fiber-chip coupling structure in nanometric silicon wire waveguides. The implementation of efficient grating couplers in micrometric silicon-on-insulator (SOI) rib waveguides is, however, challenging, since the coupler waveguide region is multimode. Here we experimentally demonstrate grating couplers in 1.5 μm-thick SOI rib waveguides with a coupling efficiency of -2.2 dB and a 3 dB bandwidth of 40 nm. An inverse taper is used to adiabatically transform the interconnection waveguide mode to the optimum grating coupler excitation field with negligible higher order Bloch mode excitation. Couplers are fabricated in the same etch step as the waveguides using i-line stepper lithography. The benefits of wafer-scale testing and device characterization without facet preparation are thus attained at no additional cost.

Temperature-independent silicon subwavelength grating waveguides

We demonstrate, by experiment and numerical calculations, temperature-independent subwavelength grating waveguides with a periodic composite core composed of alternating regions of silicon and SU-8 polymer. The polymer has a negative thermo-optic (TO) material coefficient that cancels the large positive TO effect of the silicon. Measurements and Bloch mode calculations were carried out over a range of silicon-polymer duty ratios. The lowest measured TO coefficient at a wavelength of 1550 nm is 1.8×10(-6) K(-1); 2 orders of magnitude smaller than a conventional silicon photonic wire waveguide. Calculations predict the possibility of complete cancellation of the silicon waveguide temperature dependence.

Real-time cancellation of temperature induced resonance shifts in SOI wire waveguide ring resonator label-free biosensor arrays

A comprehensive investigation of real-time temperature-induced resonance shift cancellation for silicon wire based biosensor arrays is reported for the first time. A reference resonator, protected by either a SU8 or SiO(2) cladding layer, is used to track temperature changes. The temperature dependence of resonators in aqueous solutions, pertinent to biosensing applications, is measured under steady-state conditions and the operating parameters influencing these properties are discussed. Real-time measurements show that the reference resonator resonances reflect the temperature changes without noticeable time delay, enabling effective cancellation of temperature-induced shifts. Binding between complementary IgG protein pairs is monitored over 4 orders of magnitude dynamic range down to a concentration of 20 pM, demonstrating a resolvable mass of 40 attograms. Reactions are measured over time periods as long as 3 hours with high stability, showing a scatter corresponding to a fluid refractive index fluctuation of ± 4 × 10(-6) in the baseline data. Sensor arrays with a SU8 protective cladding are easy to fabricate, while oxide cladding is found to provide superior stability for measurements involving long time scales.

Continuously apodized fiber-to-chip surface grating coupler with refractive index engineered subwavelength structure

We demonstrate a fully etched, continuously apodized fiber-to-chip surface grating coupler for the first time (to our knowledge). The device is fabricated in a single-etch step and operates with TM-polarized light, achieving a coupling efficiency of 3.7 dB and a 3 dB bandwidth of 60 nm. A subwavelength microstructure is employed to generate an effective medium engineered to vary the strength of the grating and thereby maximize coupling efficiency, while mitigating backreflections at the same time. Minimum feature size is 100 nm for compatibility with deep-UV 193 nm lithography.

Label-free biosensor array based on silicon-on-insulator ring resonators addressed using a WDM approach

We report a silicon-on-insulator ring resonator biosensor array with one output port, using wavelength division multiplexing as the addressing scheme. With the use of on-chip referencing for environmental drift cancellation, simultaneous monitoring of multiplexed molecular bindings is demonstrated, with a resolution of 0.3 pg/mm(2) (40 ag of total mass) for protein concentrations over 4 orders of magnitude down to 20 pM. Reactions are measured over time periods as long as 3 h with high stability.

Error-free all-optical demultiplexing at 160Gb/s via FWM in a silicon nanowire

We demonstrate all-optical time division demultiplexing from 160Gb/s to 10Gb/s in the C-band, based on four-wave mixing (FWM) in a silicon nanowire. We achieve error-free operation with a system penalty of approximately 3.9dB at 10(-9) BER.

Silicon photonic wire biosensor array for multiplexed real-time and label-free molecular detection

We demonstrate a silicon photonic wire waveguide biosensor array chip for the simultaneous monitoring of different molecular binding reactions. The chip is compatible with automated commercial spotting tools and contains a monolithically integrated microfluidic channel for sample delivery. Each array sensor element is a 1.8-mm-long spiral waveguide folded within a 130 microm diameter spot and is incorporated in a balanced Mach-Zehnder interferometer with a near temperature independent response. The sensors are arranged in a 400 microm spacing grid pattern and are addressed through cascaded 1x2 optical power splitters using light from a single input fiber. We demonstrate the real-time monitoring of antibody-antigen reactions using complementary and mismatched immunoglobulin G receptor-analyte pairs and bovine serum albumin. The measured level of detection for each sensor element corresponds to a surface coverage of less than 0.3 pg/mm(2).

Extracting coupling and loss coefficients from a ring resonator

A method is developed for extracting the coupling and loss coefficients of ring resonators from the peak widths, depths, and spacings of the resonances of a single resonator. Although the formulas used do not distinguish which coefficient is coupling and which is loss, it is shown how these coefficients can be disentangled based on how they vary with wavelength or device parameters.

Silicon-on-insulator guided mode resonant grating for evanescent field molecular sensing

We present experimental and theoretical results of label-free molecular sensing using the transverse magnetic mode of a 0.22 mum thick silicon slab waveguide with a surface grating implemented in a guided mode resonance configuration. Due to the strong overlap of the evanescent field of the waveguide mode with a molecular layer attached to the surface, these sensors exhibit high sensitivity, while their fabrication and packaging requirements are modest. Experimentally, we demonstrate a resonance wavelength shift of approximately 1 nm when a monolayer of the protein streptavidin is attached to the surface, in good agreement with calculations based on rigorous coupled wave analysis. In our current optical setup this shift corresponds to an estimated limit of detection of 0.2% of a monolayer of streptavidin.

Low power four wave mixing in an integrated, micro-ring resonator with Q = 1.2 million

We demonstrate efficient, low power, continuous-wave four-wave mixing in the C-band, using a high index doped silica glass micro ring resonator having a Q-factor of 1.2 million. A record high conversion efficiency for this kind of device is achieved over a bandwidth of 20 nm. We show theoretically that the characteristic low dispersion enables phase-matching over a tuning range > 160 nm.

High reflectivity gratings on silicon-on-insulator waveguide facets

We demonstrate by numerical simulations and experiments that highly reflective (HR) facets can be formed on silicon waveguides with high reflectivity diffraction gratings. We use an HR grating with a plane wave reflectivity exceeding 99.99%, as calculated by rigorous coupled wave analysis. Experimentally, we demonstrate the HR effect for silicon-on-insulator waveguide facets patterned lithographically with grating structures. Due to a strong mode size dependence, the maximum facet reflectivity for 1.5 microm thick waveguide is 77%, but finite difference time-domain simulations show that modal reflectivies larger than 90% can be achieved for silicon waveguides with thicknesses of 4 microm or more.

Folded cavity SOI microring sensors for high sensitivity and real time measurement of biomolecular binding

We demonstrate folded waveguide ring resonators for biomolecular sensing. We show that extending the ring cavity length increases the resonator quality factor, and thereby enhances the sensor resolution and minimum level of detection, while at the same time relaxing the tolerance on the coupling conditions to provide stable and large resonance contrast. The folded spiral path geometry allows a 1.2 mm long ring waveguide to be enclosed in a 150 microm diameter sensor area. The spiral cavity resonator is used to monitor the streptavidin protein binding with a detection limit of approximately 3 pg/mm(2), or a total mass of approximately 5 fg. The real time measurements are used to analyze the kinetics of biotin-streptavidin binding.

Interference effect in scattering loss of high-index-contrast planar waveguides caused by boundary reflections

We present theoretical and experimental results on an interference effect caused by boundary reflections on the optical scattering loss in high-index-contrast planar waveguides. Analytical expressions for the polarization-dependent scattering loss are derived using a surface Green's function. For high-index-contrast waveguides of submicrometer dimensions a significant deviation from accepted theory arises, including scattering loss suppression owing to a thin-film interference effect. Our theoretical predictions are confirmed by loss measurements on silicon-on-insulator channel waveguides.

Spiral-path high-sensitivity silicon photonic wire molecular sensor with temperature-independent response

We demonstrate a new silicon photonic wire waveguide evanescent field (PWEF) sensor that exploits the strong evanescent field of the transverse magnetic mode of this high-index-contrast, submicrometer-dimension waveguide. High sensitivity is achieved by using a 2 mm long double-spiral waveguide structure that fits within a compact circular area of 150 microm diameter, facilitating compatibility with commercial spotting apparatus and the fabrication of densely spaced sensor arrays. By incorporating the PWEF sensor element into a balanced waveguide Mach-Zehnder interferometer circuit, a minimum detectable mass of approximately 10 fg of streptavidin protein is demonstrated with near temperature-independent response.

Fresnel diffraction effects in Fourier-transform arrayed waveguide grating spectrometer

We present an analysis of Fourier-transform arrayed waveguide gratings in the Fresnel diffraction regime. We report a distinct spatial modulation of the interference pattern referred to as the Moiré-Talbot effect. The effect and its influence in a FT AWG device is explained by deriving an original analytical expression for the modulated field, and is also confirmed by numerical simulations using the angular spectrum method to solve the Fresnel diffraction integral. We illustrate the retrieval of spectral information in a waveguide Fourier-transform spectrometer in the presence of the Moiré-Talbot effect. The simulated device comprises two interleaved waveguide arrays each with 180 waveguides and the interference order of 40. It is designed with a Rayleigh spectral resolution of 0.1 nm and 8 nm bandwidth at wavelength lambda approximately 1.5 mum. We also demonstrate by numerical simulations that the spectrometer crosstalk is reduced from -20 dB to -40 dB by Gaussian apodization.

Lipopolysaccharide (LPS) Up-Regulates the Expression of Haem Oxygenase-1 in Mouse Placenta

Haem oxygenase-1 (HO-1) is an inducible enzyme that catalyses the rate-limiting step in the degradation of haem to biliverdin, carbon monoxide and iron. There is increasing evidence that HO plays important roles in the cellular defence against oxidative stress and the deleterious effects of pro-inflammatory cytokines. In the present study, we investigated the effects of lipopolysaccharide (LPS) on the expression of HO-1 in mouse placenta. When a single dose of LPS (75 microg/kg, i.p.) was administered to the pregnant mice, the expression of HO-1 in mouse placenta was markedly increased at 12 h after LPS treatment and remained elevated up to 48 h after LPS administration. The expression of HO-2, the constitutive form, did not change at the various time points observed. LPS-induced up-regulation of placental HO-1 was blocked after the pregnant mice were pre-treated with alpha-phenyl-N-t-butylnitrone (PBN), a free radical spin trapping agent. Correspondingly, PBN pre-treatment significantly inhibited LPS-induced lipid peroxidation and glutathione (GSH) depletion in mouse placenta. Furthermore, pentoxifylline (PTX), an inhibitor of tumour necrosis factor alpha (TNF-alpha) synthesis, also significantly attenuated LPS-induced up-regulation of placental HO-1. However, aminoguanidine (AG), a selective inhibitor of inducible nitric oxide synthase (iNOS), had little effect on LPS-induced up-regulation of HO-1 in mouse placenta. Taken together, these results indicate that LPS up-regulates the expression of HO-1 in mouse placenta. LPS-induced up-regulation of placental HO-1 is probably mediated, at least in part, by reactive oxygen species (ROS) and TNF-alpha, rather than nitric oxide.

Gradient-index antireflective subwavelength structures for planar waveguide facets

We demonstrate the use of subwavelength gratings etched into the facets of silicon-on-insulator ridge waveguides as a means of reducing facet reflectivity by the gradient-index effect. Reflectivities as low as 2.0% and 2.4% for the fundamental TE and TM modes, respectively, are demonstrated experimentally for light of 1.55 microm wavelength, in agreement with both effective medium theory and finite-difference time domain calculations. Simulations show that facet reflectivites can be further reduced to less than 1% by increasing the grating modulation depth.

A high-resolution silicon-on-insulator arrayed waveguide grating microspectrometer with sub-micrometer aperture waveguides

We demonstrate a 50-channel high-resolution arrayed waveguide grating microspectrometer with a 0.2 nm channel spacing on a silicon-on-insulator (SOI) platform. The chip size is 8 mm x 8 mm. High channel density and spectral resolution are achieved using high aspect ratio 0.6 mum x 1.5 mum waveguide apertures to inject the light into the input combiner and to intercept different spectral channels at the output combiner focal region. The measured crosstalk is <-10 dB, the 3 dB channel bandwidth is 0.15 nm, and the insertion loss is -17 dB near the central wavelength of lambda = 1.545 mum.

Subwavelength waveguide grating for mode conversion and light coupling in integrated optics

We propose a new method for mode conversion and coupling between an optical fiber and a sub-micrometer waveguide using a subwavelength grating (SWG) with a period less than the 1st order Bragg period. The coupler principle is based on gradual modification of the waveguide mode effective index by the SWG effect that at the same time frustrates diffraction and minimizes reflection loss. We demonstrate the proposed principle by two-dimensional Finite Difference Time Domain (FDTD) calculations of various SWG structures designed for the silicon-on-insulator (SOI) platform with a Si core thickness of 0.3 microm. We found a coupling loss as small as 0.9 dB for a 50 microm-long SWG device and low excess loss due to fiber misalignment, namely 0.07 dB for a transverse misalignment of +/-1 microm, and 0.24 dB for an angular misalignment of +/-2 degrees. Scaling of the SWG coupler length down to 10 microm is also reported on an example of a 2D slab waveguide coupling structure including aspect ratio dependent etching and micro-loading effects. Finally, advantages of the proposed coupling principle for fabricating 3D coupling structures are discussed.

Monolithically integrated asymmetric graded and step-index couplers for microphotonic waveguides

A monolithically integrated asymmetric graded index (GRIN) or step-index (GRIN) mode converters for microphotonic waveguides are proposed and described. The design parameters and tolerances are calculated for amorphous silicon (a-Si) couplers integrated with silicon-on-insulator waveguides. The GRIN and step-index couplers operate over a wide wavelength range with low polarization dependence, and the lithographic resolution needed is only +/-1 microm. Finally, experimental results are presented for a single layer 3 microm thick step-index a-Si coupler integrated on a 0.8 microm thick SOI waveguide. The measured variation of coupling efficiency with coupler length is in agreement with theory, with an optimal coupling length of 15 microm for this device.

Eliminating the birefringence in silicon-on-insulator ridge waveguides by use of cladding stress

We propose and demonstrate the use of the cladding stress-induced photoelastic effect to eliminate modal birefringence in silicon-on-insulator (SOI) ridge waveguides. Birefringence-free operation was achieved for waveguides with otherwise large birefringence by use of properly chosen thickness and stress of the upper cladding layer. With the stress levels typically found in cladding materials such as SiO2, the birefringence modification range can be as large as 10(-3). In arrayed waveguide grating demultiplexers that were fabricated in a SOI platform, we demonstrated the reduction of the birefringence from 1.2 x 10(-3) (without the upper cladding) to 4.5 x 10(-5) when a 0.8-microm oxide upper cladding with a stress of -320 MPa (compressive) was used. Because the index changes induced by the stress are orders of magnitude smaller than the waveguide core-cladding index contrast, the associated mode mismatch loss is negligible.

[An experimental and comparative study of chemical method for etching metal frameworks in adhesive bridge]

Authors studied the best dispensing and the time of nickel base alloy etching gel by using orthogonal design and the scanning electron microscope (SEM) evaluation. Shear bond strengths were compared after treating with metal etching gel, electro-etching, painting KH-570 on the surface of Ni-Cr alloy after treating with the gel. The results showed that the gel was found to be an aqua regia solute gel. The optimum time was 90 mins. Shear stress tests revealed that the highest shear bond strength can be obtained by synthetic methods.

[Studies on cell surface fibronectin of transformed Syrian hamster lung cells induced by butyric acid]

In this paper, Fn was analysed qualitatively and quantitatively in three Syrian hamster cell lines, ie, nontransformed baby hamster lung fibroblasts cell line (BHL), a transformed cell line (BHLB4) and a butyric acid-induced phenotypically reversed cell line (ButB4) respectively. Fn was visualized on cell surface by means of indirect immunofluorescence technique. Immunofluorescence of Fn on the surface of BHL was bright with a stripe-like distribution, while that on the surface of BHLB4 was very dim or dispersed. On ButB4 cell surface, the intensity and distribution of immunofluorescence was similar to that on BHLB4 cells. Fn was isolated by affinity chromatography from the cell surface of the three cell lines. Its molecular weight was 250 kDa on SDS-polyacrylamide electrophoresis. The quantity of Fn isolated from surface of ButB4 was a bit lower than that from BHL, but was much higher than that from BHLB4. The result offers us a useful criterion for transformation and reverse transformation.

[Establishment of a human colonic carcinoma xenograft in nude mice and its chief biological characteristics]

A human colonic cancer specimen cut into 1-2 mm3 pieces under aseptic condition was heterotransplanted hypodermically by trocar to the inguinal region of BALB/cATcL nude mice bred in our laboratory. 53 days later, a 10 X 9 X 11 mm3 tumor was obtained. The take rate was 100% (48/48). The take rate of liquid nitrogen frozen and recovered tissue pieces was also 100% (13/13). Grossly, the tumor was rich in blood supply and well encapsulated. Within the tumor, the tissue was cream-colored. G-banded chromosome analysis revealed a human chromosome pattern with the mode 70-90. Pathologic diagnosis was signet-ring cell cancer, which was identical to the surgical specimen. No change was found after maintaining 13 passages in nude mice. It was named the human colonic carcinoma xenograft XHCn/w. It provides an ideal tumor model for in vivo or in vitro experiments.