Yudong Jia

A Generally Optimized FDTD Model for Simulating Arbitrary Dispersion Based on the Maclaurin Series Expansion

An optimized solution to the discrete numerical model for simulating arbitrary dispersion by the finite-difference time-domain (FDTD) method is derived for both the single-pole and two-pole frequency responses of dispersive media. Based on the method of Maclaurin series expansion, the derivation is aimed to suppress the redundant truncation errors into minimum levels by eliminating the first several series terms of difference between the numerical and theoretical solutions to a modeled susceptibility. The accuracy of numerical approximation to theoretical dielectric functions based on our proposed approach is shown to be exactly equivalent to the bilinear transformation model for the single-pole dispersion response of the modeled dispersive material, but higher than those of other two previously reported models for a two-pole dispersion response of a modeled dispersive material. The explicit coefficients of the proposed model for several classical types of dispersive materials are derived and their corresponding dominant truncation errors are given as well. Both the analytical and simulation results obtained from the FDTD modeling of an exemplified material, silver, demonstrate that the new model outperforms the other models when they are incorporated into the fourth-order accurate FDTD algorithm with small numerical dispersion error rather than in the second-order one with large numerical dispersion error.

Narrow-linewidth single-polarization frequency-modulated Er-doped fiber ring laser

We demonstrate a 1550-nm narrow-linewidth fiber ring laser with stable single polarization by using single-mode Er-doped fiber as active fiber and saturable absorber. A polarization-maintaining circulator is used to acquire single-polarization laser light with the degree of polarization of 99.8%-99.9%. The linewidth measured using a delayed self-heterodyne method is less than 0.5 kHz. Frequency of the fiber laser can be modulated by driving the waveguide phase modulator with proper voltage. A Mach-Zehnder interferometer with the optical path difference between two arms of about 36 km is used to study the long-distance coherent detection of the fiber laser for frequency-modulated continuous-wave application.

A Highly Accurate FDTD Model for Simulating Lorentz Dielectric Dispersion

A highly accurate and numerically stable model of Lorentz dielectric dispersion for the finite-difference time-domain (FDTD) method is presented. The coefficients of the proposed model are optimally derived based on the Maclaurin series expansion (MSE) method and it is shown that the model is much better than the other four reported models in implementing the Lorentz dielectric dispersion with error of relative permittivity several orders lower. The models stability and performance are also analyzed when it is incorporated into the practical second- and fourth-order accurate FDTD algorithms for an exemplified Lorentz medium. Interestingly, we find that all the mentioned models show nearly the same performance in the second-order algorithm due to its large intrinsic numerical dispersion and the superiority of the proposed MSE model begins to be manifested in the higher-order, say, fourth-order FDTD algorithms as implied by the governing numerical dispersion equations.

A Full-Spectrum Numerical-Dispersion Compensation Technique for the Pseudospectral Time-Domain Method

In the standard pseudospectral time-domain (PSTD) method, the approximation of temporal derivatives based on the central difference formula is only of second-order accuracy, which results in large numerical dispersion errors when the simulated structures are of electrically large size. In this letter, a numerical technique according to the principle of finite impulse response digital filtering is applied to reduce the errors by numerically modifying the material parameters, and therefore the updating equations, for the constitutive relations of arbitrarily materials. It is not only shown to be simple and stable, but also efficient in the reduction of numerical dispersion errors as demonstrated by the results obtained from both the theoretical derivation and the PSTD simulations of numerical examples.

Using Translation Invariant Discrete Wavelet Transform to Improve Bias Stability of Fiber Gyroscope

The method using translation invariant discrete wavelet transform arithmetic to improve gyroscope bias stability is described. On the basis analyzing the noise characteristic of fiber gyroscope signal, the suitable wavelet vector was selected to extract the noise from signal. The TIDWT, which can avoid the Pseudo-Gibbs phenomena, had be adopted to construct the denosing arithmetic, then the arithmetic was used to filter the real gyroscope signal, the result indicated that the bias stability was improved about 0.6% effectively.