Jingjing Ai

Multiple frequency bands of square split resonant rings and metal wire metamaterial

This work presents experimental measurements of two square split resonant ring and metal wire (SSRR-MW) samples with different cell sizes at microwave frequencies. The geometrical sizes of the metamaterial cells are found to play an important role in the resonant frequency. Cells with different geometrical sizes are chosen to stack into a two-layer or three-layer metamaterial unit to realize the multiple negative passbands. The effective parameters of three separate SSRR-MW models (a one-layer unit, a two-layer unit, and a three-layer unit) are retrieved from the simulation data. The composed models exhibit two or three negative bands by overlapping the passbands of original cells and broadening the overall bandwidth. The recovered parameters show good agreement with the theoretical analysis.

The design concept of a static wide field-of-view polarization Michelson interferometer for Mars atmosphere survey

Passive optical remote sensing is one of the effective methods to measure the composition of the Martian atmosphere. A static wide field-of-view polarization Michelson interferometer is intended to be used to measure winds in the atmosphere of Mars. The highlight of the instrument is the application of a thin lens array and a polarizer array to obtain four interferograms simultaneously without moving parts; then the velocity and temperature can be deduced from the four interferograms. The thin lens array is used to divide the pupil, and this makes the optical system small and lightweight. Moreover, there is no influence on the recovered temperature and velocity when the lens array is misaligned. A fully compensation technology is applied to widen the field-of-view and fulfill achromatic and thermal compensation, and simulations show that the designed scheme responds well to theoretical expectation.

Optical throughput of the Sagnac interferometer with a modified large optical path difference

The basic principle of Sagnac interferometer with modified large optical path difference is expounded on in this paper. According to the Fresnel formula, electromagnetic field energy, and energy flux, the transmittance and reflectance of each interface of a Sagnac interferometer are calculated, respectively, and then the exact expressions of the optical throughput changing with the incident angle, the angle of the incident plane, and paper plane (the bottom plane of Sagnac interferometer) and Sagnac interferometer acute angles are given. Furthermore, we analyze the effects of various parameters on the optical throughput by computer simulation, and some important conclusions are obtained. This work is of great scientific significance to the static, real-time simultaneous detection of upper atmospheric wind field.

Modulation transfer function of a modified spatially modulated imaging interferometer

The modulation transfer function (MTF) is one of the main criteria for judging the image quality of an imaging system. Together with the well-known optical transfer function, the MTF can be regarded as an objective basis reflecting the comprehensive performance of an imaging interferometer. In order to improve the imaging quality of a modified spatially modulated imaging interferometer (MSMII) with large optical path difference, the boundary conditions of an incident ray, at full field of view, along the x and y directions, respectively, are first calculated by the method of prism expansion, and then the exact expression of the pupil function of the MSMII is given. The two-dimensional MTF of the MSMII is obtained by the Fourier transform. Compared with previous studies, this work gives the two-dimensional MTF for the MSMII, and analyzes the effects of various parameters on the MTF. The optimal values of the incident angle i together with the acute angels and are chosen as and , respectively. If so, a high MTF is obtained, i.e. the imaging quality of the MSMII can satisfy the need of detecting upper atmospheric wind fields.

Metamaterial composed of different cells exhibiting a negative refraction property over multiple frequency bands

Experimental measurements are presented of the SSRR-MW (square split resonant ring and metal wire) and CSRR-MW (C split resonant ring and metal wire) samples at microwave frequencies. The geometrical shapes of the metamaterial samples are found to play an important role in determining the resonant frequency. Different cells are chosen to stack into a two-layer or a three-layer metamaterial unit to realize multiple negative passbands. The effective parameters of three one-layer models, a two-layer unit, and a three-layer unit are retrieved from the simulation data. The composed models exhibit two or more negative bands by overlapping the passbands of the original cells, and broaden the negative refraction. The recovered parameters show good agreement with theoretical analysis.

Metamaterial with negative refraction over wide frequency band

Abstract This work presents the measurements of square split resonant rings and metal wires (MWs) and C split resonant rings and MW samples through a prism refraction experiment. Negative refraction properties are observed in both models, and the cell shapes are found to play an important role in resonant frequency of the metamaterial samples. A new method is proposed to strictly broaden the negative refraction passband through overlapping the bandwidths using mixed split resonant rings and MWs. The broadened negative refraction bandwidth over a range of 8–12 GHz wider than the other models is proved by both simulative and experimental results, and provided a good metamaterial property.

Optical path difference and lateral displacement of Sagnac lateral shearing interferometer

The basic principle of the Sagnac lateral shearing interferometer with a large optical path difference (OPD) is explained. Using the method of prism expansion, the exact expressions of the OPD and the lateral displacement as a function of different parameters are obtained. In order to analyze and discuss the influences of the incident angle, , the angle between the incident plane and the bottom plane of the Sagnac lateral shearing interferometer, along with the acute angles and on the OPD and the lateral displacement, computer simulations were carried out. To ensure a large OPD and lateral displacement, the incident angle is controlled in the range while the angle has minimal impact on the OPD and the lateral displacement. Moreover, if the relative error of the OPD is required to be less than 2%, the deviations of and relative to the ideal situation ( ) must be in the ranges and , respectively. The result provides a theoretical and practical guidance for improving the spectral resolution of the Sagnac lateral shearing interferometer together with its engineering realization.

Modulation depth of static four-phase-divided wind imaging interferometer

The static four-phase-divided imaging interferometry is a new technology of passive detection for the upper atmospheric wind field. It is featured with real-time detection, no moving parts, stability, and so on. In this paper, its basic theory is discussed, and its characteristics are briefly introduced. Furthermore, its key technical parameter, modulation depth, is analyzed. The relationships of modulation depth with the incident angle and temperature of the working environment are derived by using computer simulation. It is shown that the modulation depth decreases with the increase of the temperature and incident angle. The study provides a theoretical basis to increase the modulation depth of the interferometer, and it is of significance for the development of the upper atmosphere detection technique and theory.