Zhang Chunmin

Refraction of extraordinary rays and ordinary rays in the Savart polariscope

The refraction of rays in the Savart polariscope is different from the isotropic medium. We have analysed and discussed the refraction of rays in the Savart polariscope on the basis of the Snell law. The refraction formulae of the extraordinary rays and ordinary rays were derived. Results obtained may provide theoretical and practical guide lines for studying, developing and engineering of polarization interference imaging spectrometer.

A novel polarization interferometer for measuring upper atmospheric winds

A static polarization interferometer for measuring upper atmospheric winds is presented, based on two Savart plates with their optical axes perpendicular to each other. The principle and characteristics of the interferometer are described. The interferometer with a wide field of view can offer a stable benchmark optical path difference over a specified spectral region of 0.55–0.63 μm because there are no quarter wave plates. Since the instrument employs a straight line common-path configuration but without moving parts and slits, it is very compact, simple, inherently robust and has high throughput. The paper is limited to a theoretical analysis.

Application of Equivalent Air Gap Method in Uniaxial Crystal Plate

The equivalent air gap method is a simple way to trace the ray propagation in an isotropic medium, but it cannot be applied to an anisotropic medium. We present the exact general expressions of the equivalent air gap thicknesses and the displacements for the plane-parallel uniaxial crystal plates. They are also suitable for the isotropic medium. This method is useful when one determines whether certain size plane-parallel plates can be fitted into the available air of an optical system, and also in the prism system design.

Relationship between incident angle and dispersion in static large field of view polarization interference imaging spectrometer

The static large field of the view polarization interference imaging spectrometer is based on the modified Savart polariscope. There appears a dispersion between the ordinary ray and extraordinary ray when light passes through the modified Savart polariscope. The dispersion greatly influences the intensities and the results of the interferogram and target image in the static large field of the view polarization interference imaging spectrometer. At the same time, the incident angle determines the dispersion. When the light goes through the modified Savart polariscope, the dispersion occurs in the left plate, the half-wave plate and the right plate of the modified Savart polariscope. Using the extension of Snells law, the dispersion in the crystal is theoretically calculated and numerically simulated separately. The relationship curve between incident angle and the dispersion is obtained by simulation.

XCO2 satellite retrieval experiments in short-wave and infrared spectra with SCIATRAN model for Sahara Desert

The spectra of O2 A-band (0.76 μm) and CO2 near-infrared emissions (1.6 μm) are simulated by the SCIATRAN radiative transfer model (V3.1.23), and compared with those observed by GOSAT-FTS (Greenhouse gases Observing SATellite-Fourier Transform Spectrometer). Systematic deviations between the observed and simulated spectra are found to exist, especially for the O2 A-band. The discrepancies are characterized by their mean differences averaged over the observed spectral ranges. A correction is applied to the observed GOSAT-FTS L1B (V141.141) spectra by scaling the spectral intensity measured by TANSO-FTS (Thermal and Near infrared Sensor for carbon Observation Fourier Transform Spectrometer) onboard GOSAT. The average columnar CO2 concentrations (XCO2) are retrieved from the observed and the corrected GOSAT-FTS spectra by using the SCIATRAN inversion algorithm. Compared with the GOSAT-FTS L2 XCO2 data products retrieved from the observed spectra of GOSAT-FTS, the SCIATRAN retrievals from the corrected spectra show a much better agreement, with the relative error less than 1%. But the results of GOSAT TANSO-FTS (V161.160) show smaller residuals than GOSAT TANSO-FTS (V141.141) without mean residual correction. The results indicate that the mean residual correction would increase the precision of XCO2 retrieval for spectra with systematic deviations.

Technology of polarization interference imaging spectral based on pupil division and angle shear

With the combination of pupil division, Wollaston prism angle shear and Savart plate lateral shear interference, a new technology that can aquire the message of imaging, polarization and spectrum simultaneously is presented. The system works at the pushing mode with neither mechanical movable nor electrically tunable device, and four quarters of the single charge-coupled device can get four interferograms of different polarization states (two polarization-difference spectral imagings). The device is discussed in detail, and the relationship between azimuth of the prism principal cross section and the output light intensity is analyzed, and then system parameters are optimized In the paper, we derive the interference fringe intensity distribution formula, use computer numerical simulation to verify the feasibility and accuracy of this method, and thus provide an important theory basis and the practice instruction for designing a new type of imaging spectrometer and its engineering applications.

Research on Photoelectric-Precise Monitoring System of Thin-Film Deposition

Existing coating equipments have low precision and automation level about monitoring thin-film thickness. A new photoelectric-control-analysis system had been researched. The proposed system included a double-frequency modulation equipment and a photoelectric dual-light path system. A comprehensive digital processing-controlling system and a dual-lock-phase circuit system were used to process monitoring signals. In the test, all automation-monitoring functions were achieved with a control-analysis system. The experimental results show that the static and dynamic stabilities and the thin-film thickness control precision are extremely increased. The standard deviation of thin-film thickness, which indicates duplication of monitoring thin-film thickness, is less than 0.50%. The display resolving limit on reflectivity is 0.02%. The signal-noise ratio approaches 1300. in the proposed system, the linearity of drift is very high, and the static drift ratio approaches 1.63%/h. It is concluded that the photoelectric-precise monitoring system has advantages of the static and dynamic stabilities, the signal-noise ratio, and the control precision for thin-film thickness.

Nested Bethe Ansatz for Spin Ladder Model with Open Boundary Conditions

The nested Bethe ansatz (BA) method is applied to find the eigenvalues and the eigenvectors of the transfer matrix for spin-ladder model with open boundary conditions. Based on the reflection equation, we find the general diagonal solution, which determines the general boundary interaction in the Hamiltonian. We introduce the spin-ladder model with open boundary conditions. By finding the solution K± of the reflection equation which determines the nontrivial boundary terms in the Hamiltonian, we diagonalize the transfer matrix of the spin-ladder model with open boundary conditions in the framework of nested BA.