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Sailing He

Publications and source records attributed to Sailing He.

At least 19 recordsLinked to original sources
PubMed2007

Strong resonant coupling of surface plasmon polaritons to radiation modes through a thin metal slab with dielectric gratings.

Strong resonant coupling of surface plasmon polaritons to radiation modes by means of a dielectric grating deposited on top of a metal slab is numerically analyzed, and some novel properties of this configuration are discussed. The dielectric grating is not only responsible for coupling of incident light to surface plasmon polaritons but also for outcoupling of the surface plasmon polaritons to radiation modes. A key advantage of the configuration presented is that it is not based on conventional attenuated total reflection using a prism with high refractive index.

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PubMed2006

Optical low-coherence reflectometry based on long-period grating Mach-Zehnder interferometers.

The optical low-coherent interferometric technology for long-period grating (LPG) Mach-Zehnder interferometers is described. By including the coupling and recoupling behaviors of a LPG pair, a numerical model is developed to analyze the output reflectogram of the system. The effects of the grating interval, grating length, grating strength, and light source on the output reflectogram have been comprehensively discussed, which reveals that the low-coherence reflectometry offers the capability of interrogating the multiplexed sensors based on LPG pairs. A comparison of the calculated and experimental results is presented, and an excellent agreement between the simulation and the measurement is shown.

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PubMed2006

Characteristic analysis of nanosilicon rectangular waveguides for planar light-wave circuits of high integration.

When a full-vectorial finite-difference method is used, rectangular Si waveguides can be characterized for planar light-wave circuits of high integration. The single-mode condition for a rectangular Si waveguide is obtained first. The birefringence, which can be adjusted by modifying the thickness of the cladding layer, is also studied. For a nano-Si rectangular waveguide the pure bending loss is very small even for an ultrasmall bending radius (e.g., a few micrometers), and the transition loss becomes dominant. The width and height are optimized to minimize the bending radius for the requirement that the bending loss is smaller than 0.1 dB. Finally the coupling between two parallel straight waveguides is analyzed, and it is shown that there is an optimal width for the maximal coupling length.

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PubMed2006

Design of a polarization-insensitive arrayed waveguide grating demultiplexer based on silicon photonic wires.

The polarization dependence of an arrayed waveguide grating demultiplexer based on Si photonic wires is analyzed. The height and width of the arrayed waveguides are optimized to make the channel spacing polarization insensitive. To make the central wavelength polarization insensitive, different diffraction orders are chosen for TE and TM polarizations, and the remaining polarization-dependent wavelength is compensated with a noncentral input. A detailed design procedure is presented and numerical simulation results are given.

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PubMed2006

Average intensity and spreading of an elliptical gaussian beam propagating in a turbulent atmosphere.

An analytical formula for the average intensity of an elliptical Gaussian beam (EGB) propagating in a turbulent atmosphere is derived. The spreading properties of an EGB in a turbulent atmosphere are studied. It is found that an EGB will eventually become a circular Gaussian beam in a turbulent atmosphere. This interesting phenomenon is quite different from the propagation of an EGB in free space. The evolution properties are closely related to the parameters of the beam and the turbulent atmosphere.

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PubMed2006

Effects of surface roughness on the performance of an etched diffraction grating demultiplexer.

The fabrication tolerance of surface roughness on the performance [such as the insertion loss, the polarization-dependent loss (PDL), and the chromatic dispersion] of an etched diffraction grating demultiplexer is analyzed by using an accurate method of moments. The results show that both the insertion loss and the chromatic dispersion rapidly increase as the roughness of the grating facets increases. Appropriate residual roughness of the shaded facets can reduce the PDL of the demultiplexer, and the mechanism for the existence of an optimal residual roughness is explained.

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PubMed2006

Propagation of hollow Gaussian beams through apertured paraxial optical systems.

On the basis of the generalized Collins formula and the expansion of the hard-aperture function into a finite sum of complex Gaussian functions, an approximate analytical formula for a hollow Gaussian beam propagating through an apertured paraxial stigmatic (ST) ABCD optical system is derived. Some numerical examples are given. Furthermore, by using a tensor method, we derive approximate analytical formulas for a hollow elliptical Gaussian beam propagating through an apertured paraxial general astigmatic ABCD optical system and an apertured paraxial misaligned ST ABCD optical system. Our results provide a convenient way for studying the propagation and transformation of a hollow Gaussian beam and a hollow elliptical Gaussian beam through an apertured general optical system.

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PubMed2006

Partially coherent flattened Gaussian beam and its paraxial propagation properties.

A simple model called partially coherent flattened Gaussian beam (FGB) is proposed to describe a partially coherent beam with a flat-topped spatial profile. An explicit and analytical formula is derived for the cross-spectral density of a partially coherent FGB propagating through a paraxial ABCD optical system. The propagation factor and propagation properties of a partially coherent FGB in free space are studied in detail and found to be closely related to its coherence and beam order.

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PubMed2006

Sidelobe suppression design of etched diffraction grating demultiplexers using optimized air trenches in front of each output waveguide.

An etched diffraction grating (EDG) demultiplexer with high sidelobe suppression is designed. Sidelobes resulting from two adjacent wavelengths are suppressed by etching two optimized rectangular air trenches in front of each output waveguide that can induce large resonance loss in the adjacent wavelength but have little influence on the operational wavelength. The designed EDG demultiplexer can suppress crosstalk to less than 50 dB in theory.

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PubMed2006

Analytical method for the identification of a thin-strip defect in a planar waveguide.

Nondestructive reconstruction of the location and width of a thin-strip defect in a strongly confined planar waveguide is considered. Explicit reconstruction formulas are given for a quick reconstruction of a thin-strip defect whose width is small by measuring the scattered fields at the two end faces of the planar waveguide for two frequencies. Numerical results are given, and the analytical reconstruction method is shown to be reliable regardless of the location of the defect.

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PubMed2005

Compact silicon-on-insulator-based multimode interference coupler with bilevel taper structure.

A novel compact silicon-on-insulator- (SOI-)based multimode interference (MMI) coupler with bilevel taper structures was designed. The MMI section and the S-bend sections of the input-output waveguides are deeply etched. The input-output waveguides connecting to single-mode fibers or other photonic light circuits are etched shallowly to yield single-mode operation. A bilevel taper is introduced in the transition region between the shallowly and deeply etched regions. It is predicted theoretically that this design will not only improve the quality of the self-imaging in the MMI section but will also make the structure compact. Both the excess loss and the nonuniformity of the MMI coupler are reduced. By use of a three-dimensional beam propagation method, the performance of a 1 x 4 MMI coupler based on a SOI is simulated as a numerical example of the novel design. The simulated nonuniformity and the excess loss are approximately 0.0285 and 0.2 dB, respectively.

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PubMed2005

Design of metal-cladded near-field fiber probes with a dispersive body-of-revolution finite-difference time-domain method.

A dispersive body-of-revolution finite-difference time-domain method is developed to simulate metal-cladded near-field scanning optical microscope (NSOM) probes. Two types of NSOM probe (aperture and plasmon NSOM probes) are analyzed and designed with this fast method. The influence of the metal-cladding thickness and the excitation mode on the performance of the NSOM probes is studied. We introduce a new scheme of illumination-mode NSOM by employing the plasmon NSOM probe with the TM01 mode excitation. Such a NSOM probe is designed, and we demonstrate its advantages over the conventional aperture NSOM probe by scanning across a metallic object.

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PubMed2005

Assembly of silica nanowires on silica aerogels for microphotonic devices.

We report on the assembly of low-loss silica nanowires into functional microphotonics devices on a low-index nondissipative silica aerogel substrate. Using this all-silica technique, we fabricated linear waveguides, waveguide bends, and branch couplers. The devices are significantly smaller than existing comparable devices and have low optical loss, indicating that the all-silica technique presented here has great potential for future applications in optical communication, optical sensing, and high-density optical integration.

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PubMed2005

Explicit formulas for the identification of a small defect in a planar waveguide.

Nondestructive testing of a small defect (a dust particle or air void) in a strongly confined planar waveguide is considered. Explicit formulas are given for a quick identification of the small defect by use of the distorted fields measured at the two end faces of the planar waveguide for two frequencies. The explicit identification scheme is verified numerically.

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PubMed2005

Analysis of the loss resulting from point defects for an etched diffraction grating demultiplexer by using the method of moments.

An effective method for analyzing the effect of point defects (e.g., dust grains and air bubbles) on an etched diffraction grating demultiplexer is presented by using the method of moments. This method leads to a deep insight into the influence of point defects on the loss of the demultiplexer. Numerical results show that strong resonance losses can be produced at some special point defects and incident light.

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PubMed2005

Fast analysis method for polarization-dependent performance of a concave diffraction grating with total-internal-reflection facets.

A fast simulation method for a waveguide-based concave grating with total-internal-reflection (TIR) facets is presented using the Kirchhoff-Huygens principle. Unlike the conventional scalar method, modifications are made to take into account the influence of the Goos-Hänchen (GH) shift. The simple method is in good agreement with a numerical method based on rigorous coupled-wave analysis for a wide range of practical device parameters and can provide an insightful physical explanation for the numerical results. It is shown that the GH shift is a main contributing factor for the loss and the polarization-dependent loss of an etched diffraction grating demultiplexer with TIR facets.

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