Exploring and understanding the ocean is an important field of scientific study.Acquiring accurate and high-resolution temperature and depth profiles of the oceans over relatively short periods of time is an important...Exploring and understanding the ocean is an important field of scientific study.Acquiring accurate and high-resolution temperature and depth profiles of the oceans over relatively short periods of time is an important basis for understanding ocean currents and other associated physical parameters.Traditional measuring instruments based on piezoelectric ceramics have a low spatial resolution and are not inherently waterproof.Meanwhile,sensing systems based on fiber Bragg grating(FBG)have the advantage of facilitating continuous measurements and allow multi-sensor distributed measurements.Therefore,in this paper,an all-fiber seawater temperature and depth-sensing array is used to obtain seawater temperature and depth profiles.In addition,by studying the encapsulation structure of the FBG sensors,this paper also solves the problem of the measurement error present in traditional FBG sensors when measuring seawater temperature.Through a theoretical analysis and seaborne test in the Yellow Sea of China,the sampling frequency of the all-fiber seawater temperature and depth profile measurement system is 1 Hz,the accuracy of the FBG sensors reaches 0.01℃,and the accuracy of the FBG depth sensors reaches 0.1%of the full scale.The resulting parameters for these sensors are therefore considered to be acceptable for most survey requirements in physical oceanography.展开更多
A novel grating coupler with a stair-step blaze profile is proposed. The coupler is a CMOS process compatible device and can be used for light coupling in optical communication. The blaze profile can be optimized to o...A novel grating coupler with a stair-step blaze profile is proposed. The coupler is a CMOS process compatible device and can be used for light coupling in optical communication. The blaze profile can be optimized to obtain a high efficiency of 66.7% for the out-of-plane coupling at the centre wavelength of 1595 nm with a 1 dB bandwidth of 41 nm. Five key parameters of the stair-step blaze grating and their effects on the coupling are discussed for the application in L band telecommunication.展开更多
Consider the inverse diffraction problem to determine a two-dimensional periodic structure from scattered elastic waves measured above the structure.We formulate the inverse problem as a least squares optimization pro...Consider the inverse diffraction problem to determine a two-dimensional periodic structure from scattered elastic waves measured above the structure.We formulate the inverse problem as a least squares optimization problem,following the two-step algorithm by G.Bruckner and J.Elschner[Inverse Probl.,19(2003),315–329]for electromagnetic diffraction gratings.Such a method is based on the Kirsch-Kress optimization scheme and consists of two parts:a linear severely ill-posed problem and a nonlinear well-posed one.We apply this method to both smooth(C2)and piecewise linear gratings for the Dirichlet boundary value problem of the Navier equation.Numerical reconstructions from exact and noisy data illustrate the feasibility of the method.展开更多
We proposed a method to form a flat transmitted serrated-phase(SP) high-contrast-index subwavelength grating(HCG) beam splitter(HBS) for all dielectric materials, which is to alternately arrange two kinds of grating b...We proposed a method to form a flat transmitted serrated-phase(SP) high-contrast-index subwavelength grating(HCG) beam splitter(HBS) for all dielectric materials, which is to alternately arrange two kinds of grating bars with a phase difference of π. Compared to the typical linear-phase(LP) HBS, which consists of two symmetrical deflecting gratings, the SP-HBS is extensible in size, and can achieve excellent splitting ability regardless of normal incidence or small-angle oblique incidence with large deflection angles, higher diffraction efficiency,lower energy loss, and higher tolerance of fabrication accuracy. Furthermore, the incident light can be split in half at any part of the SP-HBS, and the output beams of light maintain the original shape. In this Letter, we designed an SP-HBS with a 44.8° deflection angle and a 90.28% transmissivity.展开更多
基金We thank for the financial support of the National Natural Science Foundation of China(Grant No.41276094)the Strategic Priority Research Program(Grant No.XDA110-40201)the senior User Project of RV KEXUE(Grant No.KEXUE201XGXX).
文摘Exploring and understanding the ocean is an important field of scientific study.Acquiring accurate and high-resolution temperature and depth profiles of the oceans over relatively short periods of time is an important basis for understanding ocean currents and other associated physical parameters.Traditional measuring instruments based on piezoelectric ceramics have a low spatial resolution and are not inherently waterproof.Meanwhile,sensing systems based on fiber Bragg grating(FBG)have the advantage of facilitating continuous measurements and allow multi-sensor distributed measurements.Therefore,in this paper,an all-fiber seawater temperature and depth-sensing array is used to obtain seawater temperature and depth profiles.In addition,by studying the encapsulation structure of the FBG sensors,this paper also solves the problem of the measurement error present in traditional FBG sensors when measuring seawater temperature.Through a theoretical analysis and seaborne test in the Yellow Sea of China,the sampling frequency of the all-fiber seawater temperature and depth profile measurement system is 1 Hz,the accuracy of the FBG sensors reaches 0.01℃,and the accuracy of the FBG depth sensors reaches 0.1%of the full scale.The resulting parameters for these sensors are therefore considered to be acceptable for most survey requirements in physical oceanography.
基金Project supported by the National Natural Science Foundation of China (Grant No.60877036)the National Basic Research Program of China (Grant Nos.2006CB302803 and 2011CB301701)+1 种基金the State Key Laboratory of Advanced Optical Communication Systems and Networks,China (Grant No.2008SH02)the Knowledge Innovation Program of Institute of Semiconductors,Chinese Academy of Sciences (Grant No.ISCAS2008T10)
文摘A novel grating coupler with a stair-step blaze profile is proposed. The coupler is a CMOS process compatible device and can be used for light coupling in optical communication. The blaze profile can be optimized to obtain a high efficiency of 66.7% for the out-of-plane coupling at the centre wavelength of 1595 nm with a 1 dB bandwidth of 41 nm. Five key parameters of the stair-step blaze grating and their effects on the coupling are discussed for the application in L band telecommunication.
基金the support by the German Research Foundation(DFG)under Grant No.EL 584/1-2.
文摘Consider the inverse diffraction problem to determine a two-dimensional periodic structure from scattered elastic waves measured above the structure.We formulate the inverse problem as a least squares optimization problem,following the two-step algorithm by G.Bruckner and J.Elschner[Inverse Probl.,19(2003),315–329]for electromagnetic diffraction gratings.Such a method is based on the Kirsch-Kress optimization scheme and consists of two parts:a linear severely ill-posed problem and a nonlinear well-posed one.We apply this method to both smooth(C2)and piecewise linear gratings for the Dirichlet boundary value problem of the Navier equation.Numerical reconstructions from exact and noisy data illustrate the feasibility of the method.
基金supported by the National Natural Science Foundation of China (Nos. 61674018,61574019,and 61674020)。
文摘We proposed a method to form a flat transmitted serrated-phase(SP) high-contrast-index subwavelength grating(HCG) beam splitter(HBS) for all dielectric materials, which is to alternately arrange two kinds of grating bars with a phase difference of π. Compared to the typical linear-phase(LP) HBS, which consists of two symmetrical deflecting gratings, the SP-HBS is extensible in size, and can achieve excellent splitting ability regardless of normal incidence or small-angle oblique incidence with large deflection angles, higher diffraction efficiency,lower energy loss, and higher tolerance of fabrication accuracy. Furthermore, the incident light can be split in half at any part of the SP-HBS, and the output beams of light maintain the original shape. In this Letter, we designed an SP-HBS with a 44.8° deflection angle and a 90.28% transmissivity.
