Jin Hui Shi

Method to enhance the accuracy of the retardance measurement of quarter-wave plates

A novel method used for the enhancement of the accuracy of the measurement of the retardance of a quarter-wave plate employing two polaroids and a prism is reported under the condition of knowing the direction of the fast axis of the plate. The theoretical analysis of the principle and the uncertainty formula are given. An application example is also demonstrated. The measured result of the example is verified with an experiment. The main advantages of this method include the accuracy enhancement, simple measuring setup and easy operation.

Theoretical analysis of effects of linear birefringence inside sensing head upon bulk glass current sensors performance

The effects of the linear birefringence inside a bulk glass current sensing element and the incident polarizing angle upon the performance of a bulk glass optical current sensor are derived and analyzed theoretically. The investigation results show that the linear birefringence will modify the scale factor of the system with a sample function; it can also affect the extent of the influence of the incident polarizing angle, at the same time. When the incident polarizing angle has some special values such as 0, 45, or 90 degree, its effect to the system will be zero. These results might provide some useful reference to the researchers and designers of bulk glass optical current sensors.

Method for measuring linear birefringence inside bulk glass current-sensing elements

Linear birefringence is one of the most important parameters of optical (fibre-optic) current-sensing heads, which can obviously affect the performance of optical current sensors. Therefore, it is of great importance to measure the linear birefringence inside the optical current-sensing head to enhance the properties of sensors. A novel method to measure the linear birefringence inside bulk glass current-sensing heads is reported in this paper, which gives a theoretical analysis of the principle, the measurement uncertainty analysis—using the Jones matrix as a mathematical tool—and an applied example. This method overcomes the shortcomings of the two methods reported before which cannot uniquely determine the value of the linear birefringence or introduce large measurement uncertainty. The experimental result shows that this method can certainly enhance the measurement precision.

Research on infrared non-polarizing beam splitters

When used at oblique angles of incidence, the reflectance and transmittance of thin films exhibit strong polarization effects, particularly for the films inside a glass cube, which result from the fact that the tangential components of the electric and magnetic fields are continuous across each layer interface. However, for many applications, the polarization effects are undesirable and should be reduced. Therefore, the concept of non-polarizing beam splitter is proposed. Up to now, however, most of the reports of non-polarizing beam splitters are suitable for visible light. Therefore, it is necessary to find out some methods to reduce the polarization effects for infrared applications. A design method of infrared non-polarizing beam splitter in a cube is proposed, the theoretical analysis is given, designs for different substrates are demonstrated and the simulations of their optical properties are presented in this paper.

Measurement of the linear birefringence inside bulk glass current sensing elements with a retarder

Linear birefringence inside the sensing head can obviously affect the performances of optical (fiber-optic) current transformers. Therefore, it is important to measure the linear birefringence for the design and the property enhancement of optical current transformers. A method employing a retarder to measure the linear birefringence inside the bulk glass current sensing head is reported. The theoretical analyses of the principle and the measurement uncertainty of the method are given using Jones Matrix as a mathematical tool. An applied example is also given. The main advantage of this method is that it can uniquely determine the value of the linear birefringence inside the sensing head, which overcomes the shortcoming of that only a trigonometric function value of the birefringence can be determined by the method reported before. Furthermore, there are some other advantages such as simple structured, practical and that the devices needed are easy to obtain.

Wavelength dependence of the sensitivity of a bulk-glass optical current transformer

The wavelength dependence of the sensitivity of a bulk-glass optical current transformer is theoretically analyzed taking the Jones’ Matrix as a mathematical tool, simulated with a computer and verified with an experiment. The results show that the wavelength dependence will cause obvious sensitivity fluctuation of the system because of the existing of the dispersions of the reflection-induced retardance, Verdet constant and the linear birefringence inside the bulk-glass current transducing head. Therefore, it is necessary to stabilize the driving current and the ambient temperature of the optical source used by some technical means, because these two factors can result in wavelength variation. These results might be useful for the researchers and designers working in the optical current transducing techniques area.