Strip Waveguide Directional Coupling Modulator with Equivalent Refractive Index

The equivalent refractive index（ERI） method is employed to analyze the function of the strip waveguide directional coupling modulator（SWM）. Through deducing the diagnostic equation of the Exmn mode of the four-layer media film waveguide equivalent to the SWM,the transmission constant of the symmetrical mode of the positive phase and negative one and the coupling length of powerful transference are obtained. The veracity of ERI is validated with the example of Ex11 basal mode under conditions of comparing the three results of ERI,EIM and Marcatili.

0.05% atropine on control of myopia progression in Chinese school children: a randomized 3-year clinical trial

·AIM:To evaluate the effect of 0.05%atropine on the control of myopia for 2y(phase I)and on spherical equivalent refraction(SER)progression for 1y(phase II)after its withdrawal in Chinese myopic children.·METHODS:Totally 142 children with myopia were randomly assigned to the 0.05%atropine group or to the placebo group.In phase I,children received 1 treatment for each eye daily.In phase II,the patients received no treatment.Axial length(AL),SER,intraocular pressure(IOP)and atropine-related side effects were assessed at 6 months’intervals.·RESULTS:During phase I,the mean change of SER was-0.46±0.30 D in the atropine group,compared to-1.72±1.12 D in the placebo group(P<0.001).The mean change of AL in the atropine group(0.26±0.30 mm)was significantly shorter than that in the placebo group(0.76±0.62 mm,P=0.002).In addition,in phase II(12mo after the withdrawal of atropine),there was no significant difference in AL change from the atropine group,when compared with that from the placebo group(0.31±0.25 mm vs 0.28±0.26 mm,P>0.05).Furthermore,the change in SER from the atropine group was 0.50±0.41 D,which was significantly lower than 0.72±0.60 D from placebo group,(P<0.05).Finally,there were no statistically significant differences in IOP between the treatment and control groups at any stages(all P>0.05).·CONCLUSION:The use of 0.05%atropine for two consecutive years may effectively control elongation of AL and thus progression of myopia,without significant SER progression 1y after atropine withdrawal.Therefore,treatment with 0.05%atropine daily for 2y is effective and safe.

Apodized grating coupler using fully-etched nanostructures

A two-dimensional apodized grating coupler for interfacing between single-mode fiber and photonic circuit is demonstrated in order to bridge the mode gap between the grating coupler and optical fiber. The grating grooves of the grating couplers are realized by columns of fully etched nanostructures, which are utilized to digitally tailor the effective refractive index of each groove in order to obtain the Gaussian-like output diffractive mode and then enhance the coupling efficiency.Compared with that of the uniform grating coupler, the coupling efficiency of the apodized grating coupler is increased by 4.3% and 5.7%, respectively, for the nanoholes and nanorectangles as refractive index tunes layer.