Simple narrow-linewidth 1.5 ?m InGaAsP DFB external-cavity laser

An external-cavity laser consisting of a 1.5 ?m-wavelength antireflection-coated DFB laser chip, a microscope objective and a mirror provides a stable, single-frequency, narrow-linewidth (?f=40 kHz) output. Because the laser operates in the strong feedback regime, it is immune to external optical perturbations. Single-longitudinal-mode operation is maintained by the DFB grating, and the linewidth is reduced by the extended passive cavity.     

Prediction of the frost formation on a cold flat surface

A mathematical model is presented to predict the behavior of frost formation by simultaneously considering the air flow and the frost layer. The present model is validated by comparing with several other analytical models and our experiments. It is found that most of the previous models cause considerable errors depending on the working conditions or the correlations used in predicting the frost thickness growth, whereas the model in this work estimates the thickness, density, and surface temperature of the frost layer more accurately within an error of 10% except the early stage of frosting in comparison with the experimental data. Numerical results are presented for the variations of heat and mass transfer during the frost formation and for the behavior of frost layer growth along the direction of air flow. Also, a correlation between the convective heat and mass transfer is obtained as Le⁽¹⁻ⁿ⁾=0.905±0.005 in this work.     

Avalanche buildup time of InP/InGaAsP/InGaAs avalanche photodiodes with separate absorption, grading, and multiplication regions

The avalanche buildup time of an avalanche photodiode can be determined from the frequency response of the noise power as a function of the dc multiplication M0. In this paper we report on the first measurements of the avalanche buildup time of InP/InGaAsP/ InGaAs avalanche photodiodes with separate absorption, grading, and multiplication regions (SAGM-APD's). Measurements on several different device structures reveal that the avalanche buildup time (gain-bandwidth product) decreases (increases) with increasing carrier concentration in the multiplication region. The shortest buildup time that we have observed wasM_{0} times 4.2ps which corresponds to a gain-bandwidth Product of 38 GHz.     

Fabrication of LiNbO3 channel waveguides using water

A channel waveguide formed in LiNbO₃ was fabricated by using distilled water instead of acids for proton exchange and a self-aligned SiO₂ cap for diffusion. It was demonstrated that the water reaction is an important reaction to cause the index change in proton exchange     

Linewidth reduction of cleaved-coupled-cavity lasers by optical feedback from a single-mode polarisation-preserving fibre external cavity

Linewidth characteristics of a cleaved-coupled-cavity laser with a single-mode polarisation-preserving fibre external cavity have been investigated as a function of feedback power level and side-mode suppression ratio. The optimum power feedback ratio is near 2×10?4 for a minimum linewidth of about 30 kHz. A weak dependence of linewidth on side-mode suppression ratio is observed as long as the suppression ratio is greater than 500:1.     

Effect of surface treatments on the frosting/defrosting behavior of a fin-tube heat exchanger

The effects of the heat exchanger surface treatment on the frosting/defrosting behavior in a fin-tube heat exchanger are investigated experimentally. It is found that the hydrophilic surface mainly influences the frosting behavior, while the hydrophobic surface has some influence on the defrosting behavior. In view of the frosting, a surface-treated heat exchanger with either hydrophilic or hydrophobic characteristic shows little improvement in the thermal performance rather than the bare aluminum heat exchanger. The results reveal that the heat exchanger with a hydrophobic surface treatment is more effective in view of the defrosting efficiency and time. The amount of residual water on the surface-treated heat exchangers is shown to be smaller than that of the bare heat exchanger. Therefore further improvements on the performance of re-operations are expected.

Résumé

The effects of the heat exchanger surface treatment on the frosting/defrosting behavior in a fin-tube heat exchanger are investigated experimentally. It is found that the hydrophilic surface mainly influences the frosting behavior, while the hydrophobic surface has some influence on the defrosting behavior. In view of the frosting, a surface-treated heat exchanger with either hydrophilic or hydrophobic characteristic shows little improvement in the thermal performance rather than the bare aluminum heat exchanger. The results reveal that the heat exchanger with a hydrophobic surface treatment is more effective in view of the defrosting efficiency and time. The amount of residual water on the surface-treated heat exchangers is shown to be smaller than that of the bare heat exchanger. Therefore further improvements on the performance of re-operations are expected.     

Equilibration of plain carbon and alloy steels with endothermic carburizing atmospheres: Part I. Activity of carbon in plain carbon steels

Experimental data on the activity of carbon in commercial plain carbon steel, AISI type 1010, common shim-stock material, at 871 °C, 927 °C, 1000 °C, and 1038 °C, equilibrated with common endothermic carburizing atmospheres, were found to be generally in agreement at relatively high carbon concentrations with previously published data on pure iron equilibrated with CO-CO₂ mixtures. However, noticeable differences were found at low carbon concentrations. The carbon contents of type 1010 steel were generally higher compared to those of previously published data regarding pure iron except at very high activities of carbon. The carbon contents of type 1010 steel foil specimens by weight gain were generally higher than or equal to those chemically analyzed; however, they corresponded with each other within 0.02 wt.% except at very low carbon potentials.     

Y-cut LiNbO3 directional coupler with a self-alignedelectrode

A 2×2 Y-cut LiNbO₃ directional coupler switch using a self-aligned uniform Δβ electrode is fabricated by the proton diffusion method. Our design method makes it possible to form the electrode without the delicate alignment of the electrode pattern mask and optical waveguide. The switching voltage is also reduced due to the enhanced electro-optic efficiency by using the self-aligned electrode. To achieve the initial cross state of the uniform Δβ switch that is essential for low crosstalk, we control the proton diffusion time successively after the proton exchange. The measured crosstalk level of the directional coupler switch is -23 dB~-29 dB and its voltage-length product is as small as 9.6 Vmm     

Inhibitory effect of Zizania latifolia chloroform fraction on allergy-related mediator production in RBL-2H3 cells

Food Science and Biotechnology - Zizania latifolia exhibits anti-inflammatory and anti-allergic effects; however, the mechanisms behind these effects are unknown. Here the ethanol extract of Z....     

The effect of nonuniform gain on the multiplication noise of InP/InGaAsP/ InGaAs avalanche photodiodes

We have investigated the effect of spatial gain uniformity on the multiplication noise of InP/InGaAsP/InGaAs avalanche photodiodes (APD's) with separate absorption, "grading," and multiplication regions. APD's with localized regions of high gain exhibit higher excess noise factors and poorer Performance in lightwave receivers than those with uniform gain.