Recurrence Quantification Analysis of Rough Surfaces Applied to Optical and Speckle Profiles

In this paper, Recurrence Quantification Analysis (RQA) is set as a practical nonlinear data tool to establish and compare surface roughness (Ra) through percentage parameters of a dynamical system: Recurrence (%REC), Determinism (%DET) and Laminarity (%LAM). Variations in surface roughness of different machining procedures from a typical metallic casting comparator are obtained from scattering intensity of a laser beam and expressed as changes in the statistics of speckle patterns and profiles optical properties. The application of the analysis (RQA) by Recurrence Plots (RPs), allowed to distinguish between machining procedures, highlighting features that other methods are unable to detect.

Close-range optical measurement of aircraft's 3D attitude and accuracy evaluation

A new screen-spot imaging method based on optical measurement is proposed, which is applicable to the close-range measurement of aircraft＇s three-dimensional （3D） attitude parameters. Laser tracker is used to finish the global calibrations of the high-speed cameras and the fixed screens on test site, as well as to establish media-coordinate-frames among various coordinate systems. The laser cooperation object mounted on the aircraft surface projects laser beams on the screens and the high-speed cameras synchronously record the light-spots＇ position changing with aircraft attitude. The recorded image sequences are used to compute the aircraft attitude parameters. Based on the matrix analysis, the error sources of the measurement accuracy are analyzed, and the maximum relative error of this mathematical model is estimated. The experimental result shows that this method effectively makes the change of aircraft position distinguishable, and the error of this method is no more than 3′ while the rotation angles of three axes are within a certain range.

On the stability of multicast flow aggregation in IP over optical network for IPTV delivery

The stable multicast flow aggregation （MFA） problem in internet protocol （IP） over optical network under the dynamical scenario is studied. Given an optical network topology, there is a set of head ends and access touters attached to the optical network, in which each head end can provide a set of programs （IP multicasting flows） and each access router requests a set of programs, we find a set of stable light-trees to accommodate the optimally aggregated multicast IP flows if the requests of access touters changed dynamically. We introduce a program correlation matrix to describe the preference of end users＇ requests. As the original MFA problem is NP-complete, a heuristic approach, named most correlated program first （MCPF）, is presented and compared with the extended least tree first （ELTF） algorithm which is topology- aware. Simulation results show that MCPF can achieve better performance than ELTF in terms of stability with negligible increment of network resource usage.

Optical system and lens design for Blu-ray disc optical pick-up

During the design process of Blu-ray disc optical pick-up （BD OPU）, the optical system and the collimator lens design is especially important. This paper designs an optical system and some lenses for＇the BD OPU, including collimator lens, beam shaping lens for laser beam shaping, and cylinder lens for signal detecting. In this OPU, we use a triplet lens to collimate the laser beam. At the same time, we build a series of assembly jigs to make sure that each lens can be put into the OPU basement properly. At last, we get the reading spot image and S-curve photo of OPU, which can be used to read Blu-ray disc （BD）.

A liquid crystal thermography calibration with true color image processing

Liquid crystal thermography is a high-resolution, non-intrusive optical technique for full-field temperature measurement. We present the detailed calibration data for the thermochromic liquid crystal （TLC） with a useful range of 41-60 ℃. The calibration is done with true color image processing by using an isothermal calibrator. The hue-temperature curve of the TLC is obtained, and the measurement uncertainty is analyzed. Combined with the image noise reduction technique of a 5×5 median filter, the measurement accuracy of the liquid crystal thermography can be significantly improved by approximately 57.1%.

Accurate analysis of ellipsometric data for thick transparent films

Using e-beam evaporation, the ellipsometric parameters of thick transparent films are studied with the modified analysis method for the SiO 2 film samples deposited onto the Si substrate. The ellipsometric parameters are measured at the incidence angles changing from 50 to 70 and in the 3–4.5 eV photon energy range. The error in the conventional method can be significantly reduced by the modified ellipsometric method considering the spatial effect to show good agreement between the theoretical and experimental results. The new method presented in this letter can be applied to other optical measurement of the periodic or non-periodic film structures.

Three-dimensional optical logic devices using spatial multiwaveguide system

Based on the weakly coupled-mode theory, the coupled-mode equations of the spatial multiwaveguide system are presented in general. The intensity distribution in each waveguide is determined by numerical method. Optical logic devices based on spatial multiwaveguide system are proposed. The analysis results show that the spatial multiwaveguide system permits different Boolean logic states obtained by phase modulation. Applications of the logic devices include optical calculation, optical interconnection, and spatial optical signal processing.

Average modulation transfer function of line-array fiber-optic image bundles

The image quality evaluation in fiber-optic image bundles was addressed by the modulation transfer function (MTF). With the definition of the contrast transfer function (CTF), the MTF model of line-array fiber-optic image bundles was established and analyzed numerically. The average MTF was carefully evaluated by considering the influence of phase match on the MTF between input pattern and fiber-optic image bundles. In this paper, the average MTF is mean arithmetical value on the MTFs of eight different phases. The results show that, for certain fiber diameter and spatial frequency, the relationship between the core diameter and the average MTF is inverse proportion; for certain fiber cladding thickness, the relationship between the core diameter and the average MTF is also inverse proportion. And at Nyquist frequencv. the MTF value is near 0.5.

Adaptive Operator-Based Spectral Deconvolution With the Levenberg-Marquardt Algorithm

Spectral distortion often occurs in spectral data due to the influence of the bandpass function of the spectrometer.Spectral deconvolution is an effective restoration method to solve this problem.Based on the theory of the maximum posteriori estimation,this paper transforms the spectral deconvolution problem into a multi-parameter optimization problem,and a novel spectral deconvolution method is proposed on the basis of Levenberg-Marquardt algorithm.Furthermore,a spectral adaptive operator is added to the method,which improves the effect of the regularization term.The proposed methods,Richardson-Lucy(R-L)method and Huber-Markov spectroscopic semi-blind deconvolution(HMSBD)method,are employed to deconvolute the white light-emitting diode(LED)spectra with two different color temperatures,respectively.The correction errors,root mean square errors,noise suppression ability,and the computation speed of above methods are compared.The experimental results prove the superiority of the proposed algorithm.

Tunable multiple plasmon-induced transparency with side-coupled rectangle cavities

The tunable multiple plasmon-induced transparency （PIT） effect is investigated numerically in a metal-insulator-metal （MIM） waveguide with three side-coupled rectangular resonators. The system exhibits dual-mode PIT effects in the visible and near-infrared regions. By adjusting the geometrical parameters of the structure, we can manipulate not only each single PIT window, but also the double PIT windows simulta- neously. Our structures may have potential applications for optical communication, integrated optics, and optical information processing. The finite element method （FEM） illustrates our theoretical design.

Consistency proof of two denoising methods and the parameter selection of PDE f iltering method for ESPI

Electronic speckle pattern interferometry （ESPI） is a nondestructive, whole-field optical measurement technique. The removal of speckle noise is fundamental to extract measurement information accurately. In this letter, two filtering methods based on the oriented feature of ESPI fringes, i.e., the second-order oriented partial differential equation （SOOPDE） and oriented, regularized quadratic-cost function filtering methods, are first proven to be consistent. An important question in solving partial differential equation, i.e., how to select suitable parameters in an adaptive manner, is then discussed. The computer-simulated and experimentally obtained ESPI fringe patterns and phase map are processed by the SOOPDE filtering model with adaptive selective parameters. The qualitative and quantitative analyses demonstrate that the parameters selected by the adaptive method are effective and suitable for the SOOPDE filtering model.

Continuous generation of dissipative spatial solitons in two-dimensional Ginzburg–Landau models with elliptical shaped potentials

We report on the rich dynamics of two-dimensional fundamental solitons coupled and interacting on the top of an elliptical shaped potential in a two-dimensional Ginzburg-Landau model. Under the elliptical shaped poten- tial, the solitons display unique and dynamic properties, such as the generation of straight-line arrays, emission of either one elliptical shaped soliton or several elliptical ring soliton arrays, and soliton decay. When changing the depth and sharpness of the external potential and fixing other parameters of the potential, various scenarios of soliton dynamics are also revealed. These results suggest some possible applications for all-optical data-processing schemes, such as the routing of light signals in optical communication devices.

Properties of the 3D photonic nanojet based on the refractive index of surroundings

We exhibit a three-dimensional （3D） photonic nanojet based on a dielectric microsphere irradiated by a plane wave with the finite-difference time-domain （FDTD） method. We investigate the influence of the refractive index of the surrounding on the properties of the nanojet by simulating the electric field distributions in it. The simulation results show that, by optimally choosing the size of the sphere and the ratio of the refractive indices of the sphere and the surrounding, the focus point can occur just on the surface of the sphere even if the refractive index of the surrounding is changed. Additionally, the peak amplitude of the nanojet increases with increasing the refractive index of the surrounding. However, the decay length and the jet width of the nanojet decrease simultaneously. These effects may have potential applications in observation or manipulation of nano-objects such as antibodies in biology. In nanojet-enabled optical data storage, the photonic nanojet may be also helpful for improving data-storage capacities and retrieval speed by controlling the field amplitude, the decay length, and jet width of the nanojet.

Phase-controlled gain, phase shift, and group velocity using a room-temperature active-Raman-gain medium

A four-level tripod active-Raman-gain scheme is analyzed for obtaining phase-controlled gain, phase shift, and group velocity at room temperature. The scheme can be used to eliminate significant probe field atten- uation or distortion which is unavoidable in the scheme based on electromagnetically induced transparency. It is shown that the intensity gain, phase shift, and group velocity of a probe field can be simultaneously manipulated by changing the relative phase of two pump fields. The scheme is also different from that proposed recently by Deng et al. where a probe-field gain always exists. New features of the scheme presented here raise the possibility of designing rapidly responding optical switches and gates for optical information processing.

Polarization-independent grating coupler based on silicon-on-insulator

A novel and simple polarization independent grating couplers is designed and analyzed here, in which the TE polarization and the TM polarization light can be simultaneously coupled into a silicon waveguide along the same direction with high coupling efficiency. For the polarization-insensitive grating coupler, the coupling effi- ciencies of two orthogonal polarizations light are more than 60% at 1550 nm wavelength based on our optimized design parameters including grating period, etching height, filling factor, and so on. For TE mode the maximum efficiency is ~72% with more than 30 nm i dB bandwidth, simultaneously, for TM mode the maximum efficiency is 75.15% with 40 nm 1 dB bandwidth. Their corresponding wavelength difference between two polarizations＇ coupling peaks is demonstrated to be 35 nm. Polarization independent grating coupler designed here can be widelv used in optical communication and ontical information processing.

Fabrication of air-bridged Kerr nonlinear polymer photonic crystal slab structures in near-infrared region

Fabrication details of air-bridged Kerr nonlinear polymer photonic crystal slab structures are presented. Both the two-dimensional photonic crystal slab and the one-dimensional nanobeam structures are fabricated using direct focused ion beam etching and subsequent wet chemical etching. The scanning electron microscopy images show the uniformity and homogeneity of the cylindrical air holes. The optical measurement in the near-infrared region is implemented using the tapered fiber coupling method, and the results agree with the numerical calculations by using the three-dimensional finite-difference time-domain method.